Journal of the Royal Society of New Zealand Early ...

This article was downloaded by: [121.75.216.62] On: 12 October 2014, At: 02:37 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

Journal of the Royal Society of New Zealand Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/tnzr20

Early Miocene flora of the Manuherikia Group, New Zealand. 10. Paleoecology and stratigraphy Mike Pole

a

a

Department of Geology , University of Otago , P.O. Box 56, Dunedin , New Zealand Published online: 14 Jun 2013.

To cite this article: Mike Pole (1993) Early Miocene flora of the Manuherikia Group, New Zealand. 10. Paleoecology and stratigraphy, Journal of the Royal Society of New Zealand, 23:4, 393-426, DOI: 10.1080/03036758.1993.10721232 To link to this article: http://dx.doi.org/10.1080/03036758.1993.10721232

PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions

©Journal of The Royal Society of New Zealand, Volume 23, Number 4, December 1993, pp 393--426

Early Miocene flora of the Manuherikia Group, New Zealand. 10. Paleoecology and stratigraphy

Downloaded by [121.75.216.62] at 02:37 12 October 2014

Mike Pole*

A stratigraphic sequence of vegetation is recognised from macrofossil assemblages in Lower-Mid Miocene fluvial-lacustrine sediments of the Manuherikia Group, New Zealand. Temperature, water-level, drainage, fire and rainfall were probably the factors that divided the distribution of plant taxa into several distinct communities.These communities are compared with structural vegetation types presently recognised in eastern Australia, including notophyll vine forest (sometimes with podocarp conifers), microphyll forest, araucarian notophyll vine forest, tall open-forest (at times probably closed forest with sclerophyll emergents), notophyll feather palm vine forest, and fern fields. The earliest assemblage in the Cromwell region represents Nothofagus forest (microphyll fern forest or microphyll vine forest), or at least a forest in which Nothofagus was probably an important element. Rainfall was high, but the associated presence of Allocasuarina indicates forest edge conditions, or perhaps disturbance by fire, which removed the canopy long enough for this genus to have a temporary advantage. Temperature may have been cooler than that required for subtropical rainforest, or alternatively, soil nutrients may have been low. The succeeding Araucarian zone may indicate lower rainfall (and probably warmer conditions than when Nothofagus dominated the vegetation), allowing the araucarians to compete with the rainforest trees and the Allocasuarina to persist, but not low enough to result in a high frequency of fires. Vegetation was araucarian notophyll vine forest. The Eucalyptus zone suggests that rainfall continued to decrease, or become more seasonal, to the point at which the frequency of fires rose to at least once every 350 years, and a tall-open forest developed. The part of this zone in which Allocasuarina was absent may represent the peak frequency of fires, which were detrimental to Allocasuarina. A dramatic increase in rainfall and possibly soil-nutrients seems to have eliminated fire and caused the local replacement of Eucalyptus and Allocasuarina by a podocarp notophyll evergreen vine forest, including Elaeocarpaceae, Lauraceae, Myrtaceae, Podocarpaceae and, in areas of impeded drainage, palms. A return to drier conditions, or a large fire, heralded the regrowth of Eucalyptus - Allocasuarina woodland or open forest. Rainforest conditions are probably represented in the highest part of the sequence. At various times there were wide expanses of raised peat bog with a generally treeless cover. Climate was microthermal to mesothermial. Keywords: paleobotany, paleoclimatology, Eucalyptus, Nothofagus, Casuarinaceae

INTRODUCTION The plant-bearing Manuherikia Group was deposited during the Miocene as a complex of fluvial, lacustrine, and associated facies on top of a deeply weathered, and possibly peneplained,

*Department of Geology, University of Otago, P.O. Box 56, Dunedin, New Zealand. Present address: Department of Plant Science, University of Tasmania, G.P.O. Box 252C, Hobart, 7001 Australia.

155


394

Journal of The Royal Society of New Zealand, Volume 23, 1993

schist basement. Douglas ( 1986) has produced a detailed analysis of Manuherikia Group sedimentology, stratigraphy and paleogeography. The final record of sedimentation records a single lake, Lake Manuherikia (Douglas, 1986), which spread from at least Mt Pisa in the west to the Maniatoto Valley in the east, and from the Nevis Valley and Roxburgh in the south, to St Bathans and perhaps even the Waitaki Valley in the north (B.J. Douglas, pers. comm., 1987). Palynological evidence (Mildenhall, 1989; Mildenhall and Pocknall, 1989) does not constrain the age of the plant fossils in the lower Manuherikia Group closer than to Early to Middle Miocene (Otaian to Lillburnian local stages). This paper attempts to summarise and synthesise the distribution of plant fossils within the Manuherikia Group and to make a contribution towards our understanding the present flora of New Zealand. Taxonomic investigation (Pole, 1992,a, b, c, d; 1993 a, b, c, d, e, f) leads to the conclusion that most of the fossil taxa from the Manuherikia Group are now extinct in New Zealand. This precludes the possibility of a floristic approach, proceeding easily from identification to ecology, and deducing the characters of an ancient flora from living representatives' known requirements. In this study, conclusions about ecology must often be based on other criteria, such as the origin of the sediment enclosing the fossil or the physiognomy of the specimens. Fortunately, some fossil taxa found in the Manuherikia Group can, with confidence, be assigned to extant genera with known ecology. These taxa greatly assist in the formation of ecological conclusions about the whole set of fossils. Other fossils can be placed into broad, extant categories, such as conifers and palms, also having reasonably well-defined characters. Before advancing into paleoecology, some stage-setting is necessary. It has long been believed that the topography of New Zealand in the mid-Tertiary was very subdued. Although relief was starting to increase in response to movement associated with the Alpine Fault system (Kamp, 1986), there were no mountains that might have produced an altitudinal zonation of plant communities. There were no significant rain-shadows, and aspect differences between plants growing on northern and southern slopes were minimal or absent. Douglas ( 1986) has indicated that only locally was there a maximum relief of 500 m. This suggests that the range of macroenvironments was limited. The land area was also less than that of the present (Fig. 1). This paper is divided into six sections, dealing with (l) Taphonomy; (2) Community composition, physiognomy, and forest structure- an attempt to relate the Manuherikia Group fossil communities to extant plant communities in Australasia; (3) Stratigraphic relationships between the localities; (4) Climate; (5) Ecological factors which may have been responsible for producing the variety of plant associations found; (6) Ecological synthesis. 1. TAPHONOMY Several recent studies on the effects of taphonomic processes on potential fossil communities are directly relevant to the Manuherikia Group. Some of these, for instance, Drake and Burrows ( 1980), Hill and Gibson ( 1986) and Carpenter and Horwitz ( 1988), report that most species in the extant vegetation surrounding their study areas (lakes and streams) were recovered as potential leaf fossils from the sediments. However, species representation in the living community and after the effects of taphonomic processes vary a great deal. Species representation of potential fossils also varies widely between samples. This was shown to be partly dependent on the effects of leaf buoyancy and breakdown. In particular, Eucalyptus leaves were shown to have a low chance of fossilisation because they sank and decomposed quickly, and conversely, Nothofagus leaves, with opposite behaviour, stood a high chance of fossilisation (Hill and Gibson, 1986; Carpenter and Horwitz, 1988). All studies indicate a minor amount of long-distance (sometimes over one kilometre) transport. Burnham ( 1989) and Greenwood ( 1992) showed that leaves most likely to enter the fossil record were overwhelmingly those of canopy trees. Greenwood cautioned that although

156

Pole -Miocene ecology and stratigraphy, Manuherikia Group

·-1\-~~\.\\. 1\:.

395

.· ·; ·--··- -·

'\'

.'


Minimum Extent of Ute

- J - - i - - - Manuherlkla Group

..•'

~ ~

,.,.

'•

.;

.~'

Early Miocene

Late Miocene

Fig. I -New Zealand paleogeography in the Miocene, from various sources, including Kamp (1986), Hayward (1979 and pers. comm. 1988), Carter (1974), Norris and Carter (1980), Lindqvist (pers. comm. 1989) and Douglas (pers. comm. 1989). Present shoreline is shown as dotted lines. Minimum extent of the Manuherikia Group is shown as a stipple. In the early Miocene the stippled area was fluvially dominated with probably large areas of floodbasin lakes, while in the Late Miocene it represents open-lake (Douglas pers. comm. 1989).

forest litter preserves a characteristic physiognomic signature, taphonomic factors significantly affect this. Wilson ( 1980,1988) also presented evidence that the distance from shore has a dramatic effect on the composition of fossil communities. Off-shore associations had relatively more dicotyledonous leaves and woody parts, while in-shore associations had relatively more needles or taxodiaceous leaves. Roth and Dilcher ( 1978), Spicer ( 1980, 1981) and Ferguson ( 1985) all reported a decrease in average leaf size with distance from shore. Scheihing and Pfefferkorn (1984) discuss a model for incorporation of plant parts into a fluvial-deltaic system. Taphonomy in a lower delta plain is shown to be strongly tidally influenced, but Lake Manuherikia is not thought to have had any marine connections (Douglas, pers. comm., 1989). However, Scheihing and Pfefferkorn make generalisations about deposition in an upper delta plain which are applicable to the Manuherikia Group. Levees, which are not sites of plant preservation, form physical barriers between the floodbasins which preserve lake perimeter vegetation, and channel and channel-margin facies preserve the vegetation growing on the levees. In the data presented below, several separate communities are shown to have existed during the deposition of the Manuherikia Group. Based on the work reviewed above, I accept that: (1) the original communities probably grew in a relatively narrow riparian habitat; and (2) the fossil taxa from each locality might be well represent what grew in the locality, but the 157

396


relative frequency of occurrence of the fossil taxa is likely to have been different from that in the original community. However, I maintain that the fossil communities do represent discrete original communities, and that that there has been little pre-depositional mixing, i.e. the distinct fossil assemblages represent distinct original communities or fragments of them. My view is based on the presence of several taxonomically distinct (as distinct from species-proportion) communities.


2. COMMUNITY COMPOSITION, PHYSIOGNOMY, AND FOREST STRUCTURE Introduction Physiognomy, from the foliar level to a more general level of the "life-form", has been used to classify plant associations as an alternative to using floristics. Webb and Tracey (1981b) state that "In floristically complex vegetation such as tropical rainforest, structural typology is certainly more feasible and rapid than using floristics, and provides a convenient reference framework". We can apply this approach to the fossil record by substituting "floristically poorly known" for "floristically complex vegetation". This method allows us to use the physiognomy of fossils to identify areas of extant vegetation which may resemble the fossil community; that may in turn suggest the soil, rainfall, and/or temperature conditions preferred by the extinct species. It may identify an area where the extant relatives of unidentified fossils are most likely to be located (J.G. Tracey, pers. comm., 1988), i.e. it introduces a predictive element whereby the closest living relatives of fossil species can be looked for in equivalent extant physiognomic types. A large amount of work on the physiognomy of forests and their environmental relationships has been carried out in Australia (e.g Webb, 1959, 1968, 1978; Tracey, 1987). Fortunately the dominant fossil taxa so far identified from the Manuherikia Group appear to be similar to those which are important in the forests of Australia, and furthermore many important contemporary New Zealand taxa appear to be lacking, or at least not prominent, in the fossil communities. I contend that the extant forests of Australia may provide good analogues for the vegetation represented in the Manuherikia Group. The approach I have adopted follows a simplistic interpretation of the various fossil communities in terms of published Australian physiognomic vegetation types, but with reference to local New Zealand vegetation where this is obviously more relevant. I will use a combination of floristic and physiognomic evidence. The most important limitation of this approach is that it provides no means to assess communities which certainly existed in the past but which have no parallel today. The widely disjunct present distribution of, for instance, Nothofagus and Phyllocladus in south-eastern Australia and Papua New Guinea, separated by areas in which, from palynological evidence. we know that these species once lived but are now extinct, clearly indicate that the rainforest communities of the region in between are taxonomically fragmented- that is, they have had important taxa removed, probably by what Tracey (1987) terms "climatic sifting," as well as by fire. Until the value of the approach used here is better known, such problems will have tc be dealt with individually. For instance, in the terminology of Webb (1959), I have taken the liberty of substituting "podocarp" for "araucarian" in the structural nomenclature when suitable. Araucaria (A. bidwillii Hook. and A. cunninghamii Ait. ex D. Don in Lamb.) is thf emergent conifer genus of some eastern Australian forests, while in New Zealand this role is often filled by species of the Podocarpaceae. Structural vegetation types of Australia The structural nomenclature used here follows Webb (1959, 1968, 1978) for rainforests. Tracey (1987) for further subdivision of rainforest, and refers to Groves (1981) for othe1 vegetation. Webb's rainforest types are based on the predominant leaf size (nanophyll

158



397

microphyll, notophyll, mesophyll), the presence of various life-forms (for instance palms, araucarians, vines, ferns, moss), categories of deciduousness, and of the canopy. In fern forest, lianes are "generally wiry and slender and tree ferns and terrestrial ferns rather than epiphytic mosses are conspicuous features", and leaf size is "predominantly microphyll" (Webb, 1968: 298). In moss forest, leaf size is predominantly nanophyll and there is a predominance of mossy epiphytes rather than lianes. In vine forest, there is a predominance of robust woody lianes, and leaf size may be microphyll, notophyll or mesophyll. One problem is that in Webb's scheme, understorey shrubs are not considered. Webb also considered only mature, exposed (sun) leaves of evergreen species and avoided shade leaves. There is no solution to this problem at present, but Webb (1959: 556) stated "The general impression of leaf size of tall trees may be confirmed by inspection of fallen leaves on the forest floor, allowing for some larger sizes due to shading or understorey and vine species", a situation analogous to a fossil assemblage. No taxa from the Manuherikia Group are known to be robust woody lianes; the only Iiane taxa to be identified, Ripogonum scandens J.R. et G. Forst. and Muehlenbeckia aff. M. australis Meissn. are of the "wiry and slender" form. All forest types where notophyll and microphyll leaves are most common (and this was the situation in the Manuherikia Group), were termed "vine forest" by Webb. Composition and interpretation of Manuherikia Group fossil localities The composition of individual Manuherikia Group localities is summarised in Fig. 2. For discussion and interpretation, localities are grouped into "suites" which are taxonomically, stratigraphically, or otherwise conceptually convenient. The suites are named after one of the localities, and the localities included in each suite follow in brackets. Two stratigraphic "sequences", the Kawarau and Bannockburn (Fig.3), refer to measured sections along the Kawarau River and the Bannockburn respectively (Figs 8, 9). The H41/f045 suite (H41/f047, H41/f048, H41/f053, H41/f054) St Bathans Geology These localities all have "mummified" leaf remains and lie within the St Bathans Member of Douglas ( 1986). They are essentially lenses of carbonaceous mud within a sequence which is dominated by cross-bedded and channelised quartz gravels. The crosscutting nature of the fluvial bedforms has obscured the finer stratigraphic relationships of these units so their relative age is not known. Botany H4l/f045 is dominated by Nothofagus azureus Pole (Pole 1993e) and Podocarpus alwyniae Pole (Pole, 1992c) which are both absent in the other localities of this suite. P. alwyniae leaves are abundant and hundreds may be obtained by breaking down blocks of sediment. In situ most are found as isolated leaves, but there are also occasional shoots. Dacrycarpus dacrydioides (A. Rich.) de Laubenf. is also frequent (Pole, 1992c), as well as broad-leaved angiosperms and a variety of fruits or nuts. H41/f048 appears to contain only large amounts of the podocarp Retrophyllum vulcanense Pole (Pole, l992c) and infrequent remains of an undescribed angiosperm leaf. H4llf047 and H41/f053 both contain only angiosperm leaves. Their compositions have not been investigated in detail, but the two localities appear to differ at least in the proportions of taxa. Laurophyllum sp. (MANU-1) is frequent in H41/f053. The leaves in H41/f047 are thinly dispersed throughout a carbonaceous mud, whereas H41/f053 consists of at least 20 em of little other than compressed leaves. Such a thickness, without coniferous remains, may have resulted from concentration of floating leaves by drift. H41/f054 is rather similar to H4llf047 but contains coniferous shoots, probably Retrophyllum. A preliminary examination of cuticle indicates the majority of the broadleaved taxa are of the Lauraceae. Allocasuarina and Eucalyptus have not been found from any of these localities. Discussion The present day forests and braided river environments of Westland are potentially suitable analogues for these localities. Structural Type Podocarp notophyll vine forest. 159

398


SUITE H41/f045 F41/f208 F41/f214 F411f225 F411f220 F411f235 F41/f237 F41/f245 F41/f228 H411f042 H41/f046 F42/f008

Journal of The Royal Society of New Zealand, Volume 23, 1993 SUITE IH41/f045 F41/f208 F41/f214 F411f225 F41/f220 F41/f235 F41/f237 F41/f245 F41/f228 H41/f042 H41/f046 F42/f008

SUITE H41/f045 F41/f208 F41/f214 F41/f225 F411f220 F41/f235 F41/f237 F41/f245 F41/1228 H41/f042 H41/f046 F42/f008

SUITE H41/f045 F41/f208 F41/f214 F41/1225 F41/1220 F41/f235 F41/1237 F41/f245 F411f228 H41/f042 H41/1046 F42/f008

SUITE H41/f045 F41/f208 F41/f214 F41/f225 F411f220 F411f235 F41/f237 F41/f245 F41/f228 H41/f042 H41/f046 F42/f008

SUITE H41/f045 F41/f208 F41/f214 F41/f225 F41/f220 F41/1235 F41/1237 F41/1245 F41/f228 H41/1042 H41/1046 F421f008

SUITE H41/f045 F41/f208 F411f214 F41/f225 F411f220 F41/1235 F41/f237 F41/f245 F41/f228 H41/f042 H41/f046 F42/f008

lndet. MANU-31

Cryp. long. Cryp. sp. Cryp.d.m Muehlen. MANU-3 MANU-4 MANU-1 MANU-2 X

X X

X X

X

Elaeocarp. Nolhofag. Eucalypt. MANU-S MANU~ MANU-7 X X X X X X

X

Metrosid.

MANU-8

Myrt. MANU-9

Rip n. MANU·10

X X X X X X

? X

X

X X

? ?

X

lndel. MANU-11

lndel. lndel. MANU-12 MANU-13

X X X

X

lndel. MANU-21

lndet. lndel. lndel. lndel. MANU-14 MANU-15 MANU-16 MANU-17 X X

X

lndel. lndel. MANU-22 MANU-23

X

lndet. MANU-24

lndel. MANU-18

X lndet. lndel. MANU-19 MANU-20

X

lndel. lndet. lndet. MANU-25 MANU-26 MANU-27

X

X

X

lndet. MANU-28

lndet. MANU-29

lndel. MANU·30

X

X

X

X

X lndet. MANU-32

X

X

Legumes

X

X

X

X

Allocasu.

X

Palms

Araucaria

X X X

X

X

Podocarpus

Dacrycarpus

Retrophyllum

X

X

X

X

X

X

X

X X

X

X

Fig. 2 - Distribution of taxa among the locality suites of the Manuherikia Group.

The F41/f208 suite (F41/f221, F41/f233, F42/f005) Bannockburn Geology The sedimentological associations of these localities, including their position above stream channel gravel units, shaley nature, absence of rooting, and presence of fresh water mussels, indicates that deposition was probably in a flood-basin lake (Douglas, 1986 and pers. comm.). Leaves are often fragmentary, which may indicate damage during transport, although an interpretation according to Scheihing and Pfefferkorn ( 1984) suggests that this community was growing around the floodbasin perimeter rather than along the channel levees. Most leaves are small (microphyll), indicating either distance-from-shore size sorting, or that the original community was dominated by small-leaved taxa. Botany By far the most numerous specimens are leaves of Nothofagus novaezealandiae (Oliver) Holden emend. Pole and cones of Allocasuarina avenacea (Campbell). Other taxa present include myrtacean leaves and fructifications. Discussion Hill and Gibson ( 1986) make it clear that Nothofagus should not automatically be

160



399

NEW ZEALAND

45S

) 170E

0

2

3

Fig. 3 - Locality map.

assumed to have been a dominant. However, Mildenhall's palynological study showed that a Nothofagus forest was present at this time, and it is difficult to avoid the conclusion that these localities contain the evidence of a forest in which Nothofagus was either dominant or at least very important. Allocasuarina was probably growing along the forest-edge/stream interface, or perhaps within fire-initiated breaks in the canopy. The distribution of Allocasuarina avenacea macrofossils throughout the Manuherikia Group suggests it did not grow on, or bordering the swamps, though its cones may have dropped directly into a watercourse. Areas of bare sediment suitable for colonisation of Allocasuarina are likely to have been continually accreting on the stream point bars. Structural Type Microphyll fern forest if the Nothofagus tended to be dominant and tree ferns were prominent; otherwise microphyll vine forest. The F41/f214 suite (F41/f264, F41/f265) Bannockburn Geology This locality extends over at least a metre thickness of shaley material. The strata were exposed by road-cutting operations, and the beds dip steeply, so the material is continually eroding onto the road. Since the plant remains are quite dispersed, and a large proportion of the material has been collected as displaced slabs lying on the road, it has been convenient to consider the whole thickness as one locality. Douglas (1986) interprets this locality as containing both poorly- and well-drained interdistributary bay sediments. Botany Nothofagus novaezealandiae leaves and Allocasuarina avenacea cones are both frequent, but do not dominate the assemblage. Eucalyptus has not been recorded. The most distinctive specimens in this suite are remains, including shoots, female-cone scales, and a possible male-cone, of Araucaria sp. sect. Eutacta (Pole, 1992c). Legume pods, cf.

161


400


Parvileguminophylum Herendeen & Dilcher, considered to belong to the Mimosoideae, are present (Pole et al, 1989; Pole, 1992a). Discussion All three localities at the same stratigraphic level along 400 m of outcrop have produced araucarian remains. As araucarian seed dispersal is limited to a few tens of metres (Havel, 1971; personal observation), this suggests that the original forest may have been of regional importance. I know of no studies of the behaviour of araucarian remains in water, but it seems likely that the foliage would act like that of the Athrotaxis cupressoides D. Don. reported by Hill and Gibson ( 1986) - most leaves sank quickly and congregated close to shore, and only a few remains floated for as much as 200 m. Hill and Gibson ( 1986) warned that the amounts of material present even 15m from shore would have predicted a partly A. cupressoides-dominated canopy, which would have been an incorrect interpretation for most of the area around their study lake. Araucaria species are canopy emergents and sometimes form a pure emergent layer (Johns, 1982). Havel (1971) reports that Auraucaria is not very competitive with other rainforest taxa, and survives as a normal component only in forests with a canopy reduced in height and density (due to "less favourable climatic or edaphic conditions") where it can regenerate adequately. It can also act as a seral taxon, "invading later stages of secondary succession" after a disturbance; but in an area where secondary succession is prevented, Araucaria could not compete and the stocking level dropped off. I surmise that many Araucaria trees were emergent along the shore of the interdistributary bay, interdispersed with Nothofagus novaezealandiae, Allocasuarina avenacea, and probably several other canopy trees. Structural Type Araucarian notophyll vine forest.

The F41/f225 suite (F41/f224, F41/f226, F41/f238, F41/f244, F41/f262) Bannockburn and Kawarau River Geology Localities F41/f224, F41/f225, F41/f226, are in interdistributary bay sediments of the Kawarau Member (Douglas, 1986). Depositional environments of the other localities are not yet clear; possibilities are either interdistributary bays or well-drained swamps. Botany These localities are discussed together because they all contain, and are dominated by, Eucalyptus s.l. (Pole, 1993 d). Discussion From both Hill and Gibson (1986) and Carpenter and Horwitz (1988) we may deduce that the original vegetation of these communities was a Eucalyptus forest/woodland. Both of these studies suggest that Eucalyptus would not be expected to dominate in a fossil community unless it was the dominant in the original vegetation, and that the trees were growing very close to, or overhanging, the basin of deposition. Reverse reasoning would also suggest that Nothofagus was rare in the original community, although sporadic leaves in F41 I f225 show that it was there. Allocasuarina avenacea is present in localities F41/f224 and F41/f226 but is surprisingly absent throughout the whole Eucalyptus-bearing stratigraphic interval of F41/f225. The association of the two "sclerophyllous" and "open-canopied" genera Eucalyptus and Allocasuarina is certainly frequent today. Due to their totally different fire response, there are places in Australia where Allocasuarina is replacing Eucalyptus, apparently as part of a long post-fire secondary succession (Withers and Ashton, 1977). Structural Type Tall open-forest, at times probably closed forest with sclerophyll emergents. The F41/f220 suite (F41/f216 F41/f239 F41/f246) Bannockburn and Kawarau River Geology The F41/f220, F41/f216 and F41/f239localities gradationally overlie lignite or very carbonaceous mud and silt, and were probably deposited close to the swampy edge of an interdistributary bay. F41/f246 was deposited in a "mudswamp" marginal to an interdistributary bay (Douglas, 1986). Botany F41!f220 is the most diverse assemblage (containing at least 12 "broad-leaved" angiosperms) and yet Eucalyptus, Nothofagus, Allocasuarina, and conifers are apparently absent. Most taxa are present in approximately equal amounts, and include Ripogonum 162

Pole- Miocene ecology and stratigraphy, Manuherikia Group

401


scandens, Muehlenbeckia aff. M. australis, Elaeocarpaceae (aff. Sloanea/Elaeocarpus) (Pole, 1993 b), and Metrosideros sp. (Pole, 1993 d). Other taxa remain unidentified. Discussion The presence of at least two lianes, R. scandens and M. aff. M. australis and the diversity and often large size of the leaves, suggest rich growth similar to some of the subtropical vine forests of Australia today. F41/f239 is composed almost entirely of Elaeocarpaceae (aff. Sloanea/Elaeocarpus) and Myrtaceae (Metrosideros sp.), and I consider it to be an impoverished version of the same community. In the pollen record, high values for Myrtaceae and Elaeocarpaceae and very low values for Nothofagus are related to the presence of lowland subtropical rainforest (Kershaw and Sluiter, 1982). F41/f246 is gradational with the palm-dominated locality of F41/f245. It is floristically similar, if not identical, with F41/f220. Structural Type Simple notophyll evergreen vine forest. The F41/f235 suite (F41/f236 F41/f247) Bannockburn Geology These localities, which are probably stratigraphically equivalent, gradationally overlie lignite or very carbonaceous mud and silt and were probably deposited very close to the swampy edge of an interdistributary bay. The sequence is capped by a crevasse-splay sandstone unit. The geological setting appears to be similar to that of the previous F41/f220 series of localities. Botany The taxonomic assemblage is quite different from that of F41/f220. Eucalyptus, Nothofagus, and Allocasuarina are also absent, but at least two conifers, Dacrycarpus dacrydioides and Retrophyllum vulcanense are common. A different suite of angiosperm leaves is present. Discussion The occurrence of D. dacrydioides brings to mind the "swamp-forest" or "floating forest" associations in which the living tree is often found. D. dacrydioides tends to be a colonising plant of fluvial flood-plains where there is a good supply of nutrients and soils too young to be leached or likely to be rejuvenated by further flooding. Dacrycarpus can tolerate a high water-table on which it is able to compete against understorey hardwoods, and the interlocking root systems of adjacent trees can form a platform over "peaty ooze" or even flowing water (Smith 1987a, 1987b; Wardle, 1974). The mycorrhizal conifer roots found at F41/f247 provide evidence for in situ growth of podocarp trees. Although no unequivocal growth-position roots were found, they are dispersed throughout the matrix and it is unlikely that they have been redeposited. Cantrill and Douglas ( 1988) reviewed the occurrence of mycorrhizal conifer roots, reporting that their development could be inhibited by waterlogging. However the very preservation of the roots at F41/f247 would seem to indicate anaerobic conditions, probably as a result of a high water table. Cantrill and Douglas conclude that their mycorrhizal conifer roots grew on a "levee adjacent to a channel". However Scheihing and Pfefferkorn (1984) generalised that "levees are not sites of preservation of plant material due to oxidising conditions in the soil during the dry season". I surmise that the F41/f235 suite of localities accumulated in an interdistributary bay, as channel-margin deposits. Proximity to a channel may explain the differences in the community between this suite and the F41/f220 suite. Structural Type Podocarp notophyll vine forest. Locality F41/f245 Kawarau River Geology The sediments accumulated in a mud swamp (rather than a peat-accumulating swamp) of the Kawarau Member (Douglas, 1986). The high density of palm fronds, fruits, and occasional flower-heads is closely comparable with the floor beneath extant nikau (Rhopalostylis sapida Wendl. et Drude) palm-dominated forest in New Zealand, and I surmise that the fossil assemblage is virtually in situ, having accumulated directly beneath a canopy of palm trees. It was probably a relatively stagnant portion of a backswamp. Botany This assemblage is dominated by remains of the palm Phoenicites zeelandica (Ett.) Pole (Pole, 1993 a).

163

402


Discussion Tracey ( 1987) records vine forest dominated by palms in areas of north Queensland with impeded drainage. Through loss of the palm material and increase of the "broadleaved" component, F41/f245 passes up into F41/f246. Structural Type Notophyll feather palm vine forest.


Locality F41/f237 Bannockburn Geology F41/f237 is a very small outcrop of heavy clay at the top of the Bannockburn sequence; it probably accumulated in a mudswamp. Botany Dominated by Laurophyllum sp. with some Ripogonum scandens and Blechnum sp .. Structural Type Not clear, probably simple notophyll evergreen vine forest. The H41/f042 suite (H41/f043) Vinegar Hill Geology Both localities were deposited in shallow nearshore lacustrine sediments of the Lauder Member of the Bannockburn Formation (Douglas, 1986). Botany Fossils are sparse but the assemblage is dominated by Nothofagus novaezealandiae (Pole, 1993 e) and Myrtaceae are also present. Discussion These fossils are the only ones collected in the Manuherikia Group from fully lacustrine sediments. They come from less than a metre below sediments of the Ewing Submember of the Kawarau Member, which at this locality was, according to Douglas, deposited in a marginal lacustrine mudflat, periodically desiccated. On the whole, Douglas interprets the beds of the Ewing Submember to have been deposited in a more agitated lake margin than the Cromwell Submember, which formed part of the marginal facies in the Bannockburn-Cromwell area. The presence of Nothofagus in these sediments, in contrast with their absence in lakeward sediments at Bannockburn, may have something to do with this difference in lake-shore type. Structural Type Possibly microphyll fern forest if the Nothofagus tended to be dominant and tree ferns were prominent; otherwise microphyll vine forest. Locality H41/f046 Lauder Station Geology The geological setting of this locality has not been investigated in detail, but sedimentation appears to have been in an interdistributary bay. Botany The assemblage is similar to the F41/f220 suite in its lack of Eucalyptus, Allocasuarina, Nothofagus (one or two leaves may be present) and conifers, and in the diversity and often large size of its leaves. Taxonomically it is completely distinct, dominated by MANU-23 and with Ripogonum and Muehlenbeckia absent. A single Cunoniaceae inflorescence has been identified (Pole, 1993 f). Structural Type Simple notophyll evergreen vine forest. The F42/f008 suite (F42/f006 F42/f007) Nevis Valley Geology These localities all lie in the Nevis Basin within the Nevis Oil Shale Member of the Bannockburn Formation (Douglas, 1986), but strong tectonism in the area has disrupted their stratigraphic position relative to each other (Douglas, pers. comm.). Douglas concluded that these sediments were deposited "in a semi-restricted to stagnant bay of Lake Manuherikia". Botany F41/f007 has only sporadic and poorly preserved leaves. F41/f008 is similar, but includes two Nothofagus novaezealandiae leaves. F42/f006 is entirely different, resembling F41/f220 and H41/f046 in the diverse, well preserved, sometimes large-leaved assemblage, with no Nothofagus or Eucalyptus, but differing in the presence of Allocasuarina avenacea (a single cone) and of conifers (a single cladode of Phyllocladus sp.) and in the taxa of broadleaved angiosperms. The most distinctive feature of the assemblage is the quantity of remains of Leguminosae (cf. Parvileguminophyllum) including both fruits and foliage (Pole et al, 1989; Pole, 1992a). Discussion The original community is difficult to reconstruct. Phyllocladus is a component of rainforest throughout its range, whereas the small-leaved legumes suggest more open 164


403


conditions (perhaps the forest-water interface, the large pods almost certainly dropped directly into the water) or forest clearings (Acacia melanoxylon R. Br. may be found occasionally in Tasmanian rainforest alongside with Phyllocladus aspleniifolius (Labill.) Hook. f. after disturbance (personal observation). Carpenter and Horwitz (1988) concluded that the robust Phyllocladus cladodes could be over-represented in fossil communities, but that they apparently sank quickly. Like the pods, they probably also came from trees growing at the water's edge. Structural Type Simple notophyll evergreen vine forest. The F41/f228 suite (F41/f218, F41/f227, F41/f234) Bannockburn and Kawarau River Geology These localities are all in units of near-lignite, and only a few leaf remains have been preserved among the otherwise decomposed plant matter. The units appear to have been initiated in interdistributary bays after the water-level dropped low enough for wide-spread peat growth to begin over the floor of the basin. Large areas (several square kilometres) could have been exposed quickly during these events, and subsequently submerged after a small rise in water-level. Botany The broad-leaved communities growing on this peat were distinct, probably adapted for low nutrient conditions and representing a series of successions beginning with each drop in water level. However because the fossils are few and scattered, little attention has yet been paid to them. Preliminary work (on these as well as some unrecorded localities) suggests an association between Laurophyllum sp. (MANU-I) and this kind of environment. Some times bedding surfaces are covered with fronds of the fern Pneumatopteris sp. (Pole, 1992b ), and these I surmise to be the remains of an in situ bed of fern growing directly on the peat swamp surface, which was overwhelmed by a rise in water depth and/or an incursion of sediment. F41/f234 contains large numbers of fern "fiddle heads", which presumably would not be preserved without sudden burial. Discussion The pakihi bogs of Westland are potentially an extant analogue of this situation. These are generally raised peat bogs where drainage is outwards towards the lower perimeter. This makes them extremely nutrient deficient, and it is unlikely that forest would ever develop on them (K. Smith, pers comm., 1989). However, forest/scrubland abuts the bogs along the margin where there is flowing water (personal observation). Structural Type Unclear. J.G. Tracey (pers. comm. 1989) notes that "Fern fields are a disturbance expression of Simple Microphyll Vine-fern Thicket on north Queensland mountains. In such environments fern fields could develop on shallow peat on rock outcrops." The G43/f004 suite (H41/f055) Roxburgh and Idaburn Geology G43/f004 and H41/f055 are general locality numbers and refer to the lignite of the McPherson seam in Harliwich's open-cast mine at Roxburgh, and the Oturehua Seam in the ldaburn Coal Mine. Both localities contain much wood, some of it apparently in situ. Leaves are not preserved in the lignite. Botany Study of this wood is beyond the scope of this paper, but descriptions have been published by Evans (1931, 1934, 1936, 1937). He recorded wood of Agathis (compared with A. australis Salish.), Podocarpus (compared with P. totara D. Don in Lamb.), Nothofagus, and either Phyllocladus or Dacrydium s.l. and reported that a chemical analysis of the resin "tears" common in the lower part of the lignite seam proved their relationship with Agathis. H411055, in addition to wood similar to G43/f004, contains large quantities of small, branching twigs or rhizomes. Their affinities are unknown. Structural Type J.G. Tracey (pers. comm., 1989) suggests that it may have been Simple Notophyll Evergreen Vine Forest type 9. "e.g. Mt Spurgeon. Here Agathis atropurpurea B.P.M. Hyland and Prumnopitys ladei (Bailey) de Laubenfels occur together over SNEVF. Canopy trees in this type of forest have masses of small branching twigs".

165

404

Journal of The Royal Society of New Zealand, Volume 23, 1993 MAORI BOITOM GROUP

MANUHERIKIA GROUP

IANNOCKIUaN SEQUENCI

NEVIS IAIIN FWfiDISUtn.

KAWAUU HQUENCE

I L •· i .• .· ~ ·.

STU.1HANS

UUDEil STAT10N

HttlfDISSUm

Ht11fCNI VINICAaHIU

HtllfiHtsum


BANNOCKBURN FORMATION

SCALE I -J"m

·:.:.·:~-~··_:,

.....

Fig. 4- Restored stratigraphy of the Manuherikia Group (modified from Douglas 1986) showing plant fossil localities.

3. STRATIGRAPHIC RELATIONS The broad stratigraphic relationships of the localities and suites of localities are shown in Fig. 4, modified from Douglas (1986). The oldest localities are the H41/f045 suite, found in St Bathans Member sediments of the incised St Bathans paleovalley. Their detailed relationships have been obscured by channel erosion, but all lie within a 40-75 m zone above the basement. The H41/f042 suite overlies these sediments, 5 km to the west, at Vinegar Hill. H41/f046 lies 6.5 km to the south, in sediments of the Kawarau Member and within a few metres of the schist basement. Detailed sedimentological work on the Kawarau River sequence has been presented by Douglas, but this did not extend to the Bannockburn sequence. The following discussion of the Bannockburn sequence and its relationship to the Kawarau sequence is based on my own work, assisted by discussions with B.J. Douglas. The Kawarau River sequence and the Bannockburn sequence are lateral equivalents, but there are still difficulties in correlating individual beds over the 2.5 km which separates them. Many of the key units of the Kawarau sequence disappear beneath the Kawarau River (some of them are visible at very low river levels, Douglas, pers. comm., 1987) and near the mouth of the Bannockburn there is evidence of tectonic disturbance. Both sequences include around 90 m of Fiddlers and Kawarau Member sediment above schist basement with prominent lignite, or very carbonaceous, horizons continuing for over a kilometre before disappearing from view. There is nothing to suggest that there was a significant difference (i.e. more than 10m) in basement topography between the two sequences, and nothing to prevent my use of the level of basement as a general datum line (a 100m deep incised valley existed a few kilometers to the west at Ripponvale (Douglas, pers. comm., 1987}). However the main zone of lignite development in the Kawarau sequence lies 34-44 m above basement, while in the Bannockburn sequence it is 60-70 m above basement. 166



405

Both sequences have 4-10 m of Fiddlers Member channel quartz gravel or sand at or near the base, unfossiliferous except for wood fragments. The channel deposits are overlain by Fiddlers levee and floodbasin sediments, which grade upwards into interdistributary bay sediments alternating with peat swamp deposits of the Kawarau Member. Field surveys suggest that a single body of water overlay this area shortly after deposition of the quartz gravel. The communities represented always contain Nothofagus novaezealandiae and MANU14, and frequently Allocasuarina avenacea. This series includes locality F42/f005 ofthe F411 f208 suite, lying 3 km south of the Bannockburn sequence. The Eucalyptus -bearing sediments of the F41/f225 suite within the Kawarau sequence span at least 12m of section, including several, important, non-fossiliferous lignite horizons. The lower localities of this zone have yielded both Eucalyptus and Allocasuarina; intensive collection throughout the 2 m of locality F41/f225 has yielded many Eucalyptus leaves but no Allocasuarina. This "Eucalyptus zone" can be traced for over a kilometre along the Kawarau River towards Bannockburn, but the corresponding portion of the Bannockburn sequence is barren. The absence of any leaves may be real, not just due to poor preservation. If all that existed in the area was a Eucalyptus woodland, the low transport potential of Eucalyptus leaves would have ensured that any area distant from the shore would have received little detritus. The corresponding portion of the Bannockburn sequence may be the offshore equivalent of the Eucalyptus zone. The uppermost Eucalyptus zone locality in the Kawarau sequence (F41/f226, with a single Allocasuarina specimen) is at 47 m above basement. Eucalyptus and Allocasuarina remains are found in locality F41/f238, at the top of the Bannockburn sequence barren zone, 59 m above the basement. Localities ofthe F41/f220 suite lie 60 m above basement in the Bannockburn and 70 m in the Kawarau sequence. I regard them as possible time-correlatives. Alternatively, the thin, very carbonaceous localities F41/f227 and F41/f228, lying respectively 61 m and 68 m above basement in the Kawarau sequence, could represent more distal, lakeward equivalents of the series of lignites and very carbonaceous horizons developed between 60 m and 70 m in the Bannockburn sequence. Communities 60 m - 77 m above basement in both columns are dominated by apparent rainforest taxa with no Eucalyptus or Allocasuarina. Eucalyptus and A. avenacea are present in F41/f262, 76 m above basement in the Bannockburn sequence, but fossils have not been found in the corresponding portion of the Kawarau sequence. The localities of the F42/f006 suite in the Nevis Valley, 15 km to the south, potentially contain the youngest leaf fossils examined in the Manuherikia Group. Douglas' reconstructed stratigraphy shows the bulk of the Nevis Oil Shale lying above the limits of the Kawarau sequence; however Douglas (pers. comm., 1988) regards the localities of the F41/f214 suite as being a lateral correlative of the Nevis Oil Shale. Fossil legume remains are present in both suites.

4. CLIMATE Miocene climate of New Zealand deduced from non-paleobotanical evidence The evidence of marine paleontology has generally indicated that Early Miocene temperatures in New Zealand were warmer than today. Molluscs (Beu and Maxwell, 1968) suggest marginally tropical conditions, and planktonic foraminifera (Jenkins, 1968) warm temperate to possibly tropical. Calcareous nannoplankton (Edwards, 1968), however, suggest temperatures similar to, or only 1-2·c higher than, those of today. The most recent isotopic evidence (Nelson and Bums, 1982) recalibrates data from Devereux (1967) to give a curve which is 4•c lower. This again suggests temperatures similar to or only 2-3·c higher than today. However, they indicated that "some of Devereux' data may represent only portions of a few more rapid, cyclical, isotopic fluctuations" (pp. 7980). They further warned that these "shorter term temperature fluctuations may be of similar 167




407

not hold. Pocknall' s ( 1989: 15-16) statement that "The main difference between the distribution of N. brassii in New Zealand during the Late Eocene to Early Miocene and the present day distribution in New Guinea is that all New Guinean species are restricted to montane regions, whereas in New Zealand they grew predominantly in the lowlands." leads one to wonder why the lowlands of New Caledonia were not postulated as a more suitable analogue. Van Steenis ( 1979) made the observation that, while nutrient deficient soils are widespread in Australia, they are "rare and local" in New Guinea and tend to be found in the mountains. This led van Steenis to an explanation of the distribution of several Australian genera (p. 169) "which are not mountain plants in their homeland - [but] are represented by montane or subalpine species in New Guinea." The restriction of Nothofagus to the montane regions in New Guinea may be a similar soil-related phenomenon. Baumann-Bodenheim ( 1953) reported that all Nothofagus in New Caledonia were confined to the extremely low-nutrient ultramafic bedrock. Wardle (1984) notes this could explain the presence there of some Nothofagus in lowland areas which would otherwise be dominated by more typical subtropical forest. Wardle also records the tendency for Nothofagus, in parts of its range, to be concentrated on ridges and spurs. Both of these observations suggest that when assessing presence of Nothofagus in the fossil record, soil nutrient status, as well as climate, should be considered. Foliar physiognomy and climate Introduction Foliar physiognomy has evolved as a method for estimating paleoclimates using the size and margin characters of fossil broad-leaved angiosperm leaves. It has developed largely as an alternative to the floristic method. Its advantages over the latter are that it does not require identification of fossils, and that it makes no extrapolations back in time concerning the climatic constraints of extant taxa. Conclusions are based on percentages, so that a large number of taxa is required in order to give statistically valid results. The method is somewhat controversial and has been widely discussed by both proponents and opponents: e.g. Axelrod and Bailey (1969), Bailey and Sinnott (1916), Dilcher (1973), Dolph (1971, 1978, 1979), Dolph and Dilcher (1979), Raunkiaer (1934), Webb (1959), Wolfe (1971, 1979, 1981), Wolfe and Hopkins (1967). The present position on in this on-going debate is that there is certainly something in the method, but the caution that must be exercised when interpreting the data is best illustrated by two quotes: Wolfe (1978: 696) stated that "Compilations of leaf margin data of secondary vegetation -vegetation on disturbed sites that has not yet reached a climax ... [does] not display such a correlation [with climate]". This is of extreme interest in Australia, where many forested regions can be shown to have fire-deflected climaxes. In fact the trend of opinion in Australia now is that undisturbed sites may not exist. For instance Webb and Tracey (1981a: 68) write that "All rainforests, especially the most complex tropical ones, are composed of a mixture of species representing different stages of succession following different kinds of disturbance". A physiognomic interpretation of some Australian Tertiary plant fossil assemblages hasbeen attempted by Christophel and Blackburn (1978) and Christophel and Greenwood ( 1987). The foliar physiognomy of the Manuherikia Group In describing climatic regimes, many paleobotanists conclude that a paleocommunity was "cool temperate", "subtropical", etc. without citing any definition of what these terms stand for. The distinctions between them have generally been based on mean annual temperature, but several different categories have been used. The most recent discussion on this topic is by Wolfe (1979), and here I will use his system. The usual terms themselves are unfortunate in that they have misleading latitudinal implications. The system of Nix ( 1982), reflecting mean air temperature only, is more appropriate for discussing paleoclimates and vegetation types. Fig. 5 compares various schemes.

169

408

00

w

a:

:::»

!cc a:

w

D.

:::E

w


1-


30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0

--

-----

WOLFE

WEBB

POCKNALL

NIX

1979

1968

1989

1982

TROPICAL

TROPICAL

PARATROPICAL

TROPICAL

MEGATHERM

SUBTROPICAL

MESO/MEGA

WARM TEMP.

MESOTHERM

SUBTROPICAL SUBTROPICAL

MARGINAL WARM TEMP.

MICRO/MESO

TEMPERATE PARATEMPERATI

COOL TEMPERATE

COOL TEMPERATE

MICROTHERM

SUBTEMPERATE

Fig. 5 - Comparison of climatic schemes used by four authors. Pocknall ( 1989) follows Devereux (1967) and Nelson and Bums (1982).

a) The Number of taxa Wolfe (1979, 1981) has stressed that, to be statistically significant and stable, foliar physiognomic data should be based on as many species as possible. From his experience Wolfe suggested that "percentages based on 30 or more species are probably reproducible with further collecting or revision to ±5%, percentages based on 20--29 species are probably reproducable to ±10%, and percentages based on less than 20 species should be regarded as highly tentative". My own results so far bear this out (see below). Wolfe (1971) analysed 12 localities in the western United States with an average number of taxa per locality of 44. No single locality within the Manuherikia Group has provided more than 20 taxa. Therefore all localities have been grouped to form a "regional" community with total number of species 32. There are several possible reasons for the low number of taxa per New Zealand locality (the highest is F41/f220 with 12 broadleaved angiosperm taxa) compared with Wolfe's criteria: (1) I used a more restricted definition for my localities. I defined them lithologically, and some are only the thickness of a single bed. (2) Entire-margined leaves, more common in the Southern Hemisphere, are the hardest to separate taxonomically, as they provide fewer characters than non-entire margins, and therefore the proportion of species they represent may be underestimated. (3) Small sample size. Even in the north Queensland rainforests, where diversity is high, the same, relatively small group of taxa, seem to dominate over large areas, and the diversity is produced by the many taxa that co-exist with them in low numbers. (4) Taphonomic effects. The number of taxa I identified is quite comparable with forested localities in New Zealand today. However, one would predict that the the fossil record preserves only a fraction of the original regional community, and then only those species living in a restricted riparian habitat (Drake and Burrows ( 1980) reported that most forest taxa surrounding a small lake in Westland found entered the lake sediments, and thus potentially, the fossil record). The original regional diversity of the Manuherikia Group was 170


409

therefore probably higher than in the fossil record, but not as high as those Australian fossil communities interpreted to be tropical or subtropical, such as Maslin Bay with about 200 taxa (Christophel and Blackburn, 1978); Anglesea with 100+ taxa from 6 localities, 70 from one of them (Christophel et al., 1987); Golden Grove with 30--35 taxa (Christophel and Greenwood, 1987); and Nerriga with a similar number (Hill, 1982).


b) Margin Proportions Of the 32 Manuherikia Group broad-leaved taxa recognised in this study, 66% (see Fig. 6) have entire margins (Pole, 1989, recorded 68% entire margins from 25 taxa). According to Wolfe (1979), this would indicate a mean annual temperature of about 20•c and a mean annual range of temperature of w·c or less -i.e., subtropical according to Webb (1968), but paratropical in Wolfe's terminology. However, an entire leaf margin percentage of 66% is similar to that found in the extant New Zealand forest community, both in the south and far north of the country, although at the upper end of the range (Pole, unpublished data). c) Sizes of Teeth Teeth on Manuherikia Group leaves are mostly quite small. On one of the non-entire specimens the teeth are little more than marginal glands. Teeth are mostly much broader than they are high, and are recumbent, with their axis at a low angle to the tangent to the margin. Indentations of Manuherikia Group taxa are all less than I 0% of the distance of the margin to the midrib. The tallest tooth (perpendicular to the margin) is 4 mm, most teeth are less than I mm high. d) Leaf area The areas of individual Manuherikia Group taxa range from nanophyll to mesophyll, but most (60%) are either microphyll or notophyll or range across the boundary. Leaf specimens smaller than microphyll are not abundant. Only two taxa are consistently within nanophyll range. The same dominance of microphylls and notophylls is found in the extant rainforest community in New Zealand (see data in Dawson, 1986), but not the low numbers of nanophylls and leptophylls. The Tasmanian forest flora is radically different from New Zealand in that notophyll leaves are rare and mesophylls absent, the majority of the leaves being microphyll or smaller. e) Drip Tips The striking frequency of drip-tips in warmer rainforest areas is well-established, and they are widely assumed to be an adaptation for ridding the lamina surface of excess water. Drip-tips are not a feature of the Manuherikia Group community. Most apices are acute; only MANU-4 (Muehlenbeckia aff. M. australis), MANU-10 (Ripogonum scandens ), and some MANU-3 (Lauraceae), MANU-8 (Metrosideros sp.), and MANU-16 (indet.), could be categorised this way, but even then only marginally. Climate change within the Manuherikia Group Some evidence of climatic change during the deposition of the Manuherikia Group strata may be provided by leaves of Nothofagus. Differences between populations within the Manuherikia Group, and also between other Miocene localities in East Otago, include consistent variation in the form of the marginal teeth (Pole, 1993 e). N. novaezealandiae var. obtusus has teeth which are very small, recumbent, and irregularly formed, while N. azureus has teeth which are very thin, erect and clearly defined. The differences may reflect climate change, the former variety living in a slightly warmer, or more equable climate than the latter variety, with larger, more sharply defined teeth.

171


410


TAXON Cryptocarya longfordiensis Cryptocarya sp. Cryptocarya cf. macrocarpa Muehlenbeckia sp. Sloanea/Eiaeocarpus Nothofagus novaezealandiae Nothofagus azureus Eucalyptus sp. Metrosideros sp. Myrtaceae indet. Ripogonum scandens indet. indet. indet. indet. indet. indet. indet. indet. indet. indet. indet. indet. indet. indet. indet. indet. indet. indet. indet. indet. indet. indet.

PARATAXON MANU-1 MANU-2 MANU-3 MANU-4 MANU-5 MANU-6a MANU-6b MANU-7 MANU-8 MANU-9 MANU-10 MANU-11 MANU-12 MANU-13 MANU-14 MANU-15 MANU-16 MANU-17 MANU-18 MANU-19 MANU-20 MANU-21 MANU-22 MANU-23 MANU-24 MANU-25 MANU-26 MANU-27 MANU-28 MANU-29 MANU-30 MANU-31 MANU-32

MARGIN E E E E N.E. N.E. N.E. E E E E E E E N.E. N.E. N.E. N.E. E E E E E N.E. E E N.E. N.E. E N.E. N.E. E N.E.

SIZE micro/noto micro no to micro/noto micro/noto nano/noto nano/noto micro micro micro/noto micro/meso micro/noto micro/noto micro/meso micro micro/noto nano/noto micro/noto macro micro micro/noto micro no to noto/macro micro nano micro no to no to no to no to no to micro

Fig. 6 - Margin types (E = entire, N.E. = non-entire), and lamina areas (nanophyll, notophyll, mesophyll, macrophyll) of Manuherikia Group taxa.

Discussion of physiognomy The high proportion of entire-margined leaves in the Australasian forests makes them an important exception to the model of Wolfe ( 1979). A separate scale could be constructed for Australasia but it does not restore confidence in the theory. Wolfe does not disagree with the hypothesis of Bailey and Sinnott ( 1916), that the higher proportion of entire-margined leaves in Australasia is due to the general absence of broad-leaved deciduous forests (in which most 172


411


species are non-entire). However, if the relationship between climate and margin is geographically variable today, presumably it can change in one area over time. Does the same proportion of entire-margins in Miocene communities of New Zealand and in the extant community really indicate that the mean average temperature was the same in both ? Axelrod and Bailey ( 1969), considered that vegetation with a high proportion of entire-margined leaves had more to do with "equability" than warmth. New Zealand today was cited as an example of a region with a high equability, a condition which would have prevailed to at least an equal extent in the Miocene. Regarding leaf size, why should Tasmania, with a climate roughly similar to that of New Zealand, have a spectrum of radically smaller leaf sizes ? Hill and Read ( 1987) provide data indicating that the smaller Tasmanian leaves are, compared with equivalent mainland species, genetically fixed, not phenotypic variants. Compared with New Zealand, however, Tasmania cannot be considered as isolated from mainland Australia. Physiognomy is a challenging subject and many questions remain to be answered. Future study of past and present Australasian communities will certainly, uncover a complex story. Conclusions Any climatic conclusions based on leaf margin percentages in the Australasian region should be viewed cautiously. The Manuherikia Group provides data suggesting that the climate could have been similar to that of forested areas of New Zealand today (ranging from microtherm to mesotherm), but no cooler. The proportion of entire-margined leaves is high (66 % ), even for New Zealand, but so far does not seem to follow an expected pattern over the country. I suspect that the value of 66 % is a minimum, due to difficulties in distinguishing some entire-margined taxa. Structural analogues for the Manuherikia Group communities are found associated today in north-eastern New South Wales and south-eastern Queensland, in Australia (Webb, 1959; Floyd, 1990) and this region may provide a close climatic match for Central Otago in the Early - Middle Miocene. Brisbane lies at sea level and has a mean annual temperature of just over 20 ·c (Wolfe, 1979). Simple Notophyll Vine Forest, sometimes with Araucaria, growing in this area, probably indicate a maximum for the range of temperature experienced by the Manuherikia Group. Nothofagus dominated forests grow in a microthermal climate of about 10-12 ·c mean annual temperature, inland at higher altitudes (personal observation).

5. ECOLOGICAL CONTROLS Effect of temperature The species diversity of individual communities within the Manuherikia Group is unfortunately too small to allow study of climate change within the Group from leaf physiognomy. However, Nelson and Bums ( 1982) have shown that there were changes in climate within the Miocene as dramatic as those once thought to have been more gradually spread over the whole of the Tertiary (Devereux, 1967). Any suggestions of climatic change within the Manuherikia Group should therefore be taken seriously. Mildenhall (1987), on palynological evidence, equates dominance of genera such as Phyllocladus and Podocarpus with periods of a cool temperate (probably microtherm) climate in the Manuherikia Group. The locality H4l/fD45, dominated by leaves of Podocarpus alwyniae (possibly of the section Australis ), may represent one of these periods. The Nothofagus-dominated F41/f208 suite probably represents the coolest phase of the Bannockburn and Kawarau sequences. Effect of soil Studies on the recent deposition of leaves in sedimentary systems have all indicated that the leaves which become incorporated as fossils are all derived from plants growing in riparian 173


412

Journal ofThe Royal Society of New Zealand, Volume 23, 1993

communities. This implies that none of the fossils of the Manuherikia Group came from plants growing in the poor soils of the old land surface, the highly weathered schist, but rather were growing in young soils on fresh sedimentary deposits, or on peat accumulations*. Holden (1981) has commented on soil fertility with respect to the communities of the Gore Lignite Measures. Beadle ( 1981) has concluded that phosphorus is the limiting nutrient that most often controls the distribution of vegetation in Australia. Phosphorus tends to have a low concentration in granites and in the sands derived from them, but Beadle noted that "the lighter soil particles, with which plant nutrients are associated, are likely to be removed and the coarser particles left behind ... However, the finer fractions are in some cases deposited as alluvium, particularly along the main river systems ... where soils of relatively high fertility occur." Beadle cited data indicating that "in general, clays have a higher phosphorus content than sands" (p. 22). Some of the vegetation changes within the Manuherikia Group could result from an overall trend from relatively poorer soils associated with the weathered schist at the base of the Group compared with the more clay and nutrient-rich soils higher up. Effect of the water-table and drainage A short section just upstream of the Bannockburn Bridge provides an example of what might be a hydrosere. The cycle starts with growth of peat on a green clay base. This clay was probably deposited in the final stages of filling up of a small pond or lake. When the water depth was shallow enough, peat-forming plants began to grow. Macrofossil remains of these plants are not preserved within the peat itself. After peat had accumulated for some time, the swamp was inundated again. The first 43 mm of silt (F4l/f240) deposited on top of the flooded peat contains the remains of plants probably growing nearby on a higher, unflooded portion of the peat swamp and washed in, or perhaps sometimes growing in-situ in very shallow water. Four different associations of plant remains can be recognised and they alternate throughout this thickness. (l) The lowest type especially consists of the finely fragmented remains of fern fronds, perhaps washed off the peat swamp by an initial flood event. (2) Criss-crossing fern fronds, perhaps in situ growth. At another locality (F4l/f247) similar remains include many fiddle-heads. These probably represent ferns growing directly on a saturated, slightly raised swamp surface, commonly seen in New Zealand today. (3) Stems, often lined-up. (4) Large numbers of parallel veined leaves, probably some kind of reed (at another locality in Bannockburn, this kind of association overlies that of another kind of unidentified, reed-like plant or perhaps the jointed roots of an aquatic plant). There are no leaves of dicotyledonous plants amongst these four associations at this general locality. However, the 30 em or more of silt overlying this sequence contains large numbers of dicotyledonous leaves, and little else (F4l/f239). This may record the first establishment of woody vegetation on the swamp surface, or perhaps a narrowing of the swamp area allowing established forests around the swamp margin to grow closer together. These represent associations which could be thought of as forming some part of a hydroseral succession, controlled by level of the water-table. Communities dominated by palms are almo~t certainly a result of a high water-table.

* Soils developed on, or from the schist, would have been poor relative to those developed on a basaltic substrate (J.G. Tracey, pers. comm. 1987) and it would be interesting to compare Manuherikia Group floras with those fossil floras which grew on the possibly partly contemporaneous Dunedin Volcanic Complex. 174



413

The effect of tire Pole ( 1983) produced a model of community relationships for the plants of the Manuherikia Group. The more extensive data now available calls for some changes to this model, but one basic conclusion remains - that two fundamentally different vegetation types were present: Open-canopy vegetation typified by Eucalyptus sp. and Allocasuarina avenacea, and closedcanopy vegetation typified by Nothofagus novaezealandiae and other varieties of rain-forest plant. Open-canopy vegetation cannot regenerate under closed-canopy vegetation. This is partially because the light levels are too low, but R.S Hill (pers. comm. 1989) points out that seedlings die for many other reasons, including that a closed-canopy environment may be too wet. Pole ( 1983) assumed that this meant that the two forest types would be spatially separated, and that, if elements of both communities were found together in one locality, they must have been mixed at the depositional stage. It is now apparent that the key factor is fire (Pole, 1988a). Fire is overwhelmingly important in the Australian environment. For instance it explains the distribution of much of the open-canopy vegetation in Tasmania, particularly in those areas which would otherwise (due to the high rainfall) be covered with closed-canopy rainforest. Repeated burning of rainforest in these regions produces natural open-canopy vegetation dominance, but with closed-canopy taxa regenerating as undergrowth. If there is no further fire, the vegetation reverts to closed-canopy. Most eucalypts mature in about 350 years, so fires of at least this frequency are needed to maintain eucalypts in any area with a rainfall capable of supporting rainforest. Any longer than 350 years between fires would allow the local extinction of eucalypts (Jackson, 1968). Eucalypts appear not only to be firetolerant, but fire-promoting (Jackson, pers. comm., 1988). The taxa of the Manuherikia Group may be classified on whether they indicate opencanopy, closed-canopy, periodic fires, or absence of fire, as follows: Nothofagus indicates closed-canopy rainforest conditions and an absence of fire, or a relatively low frequency of fires. Eucalyptus growing in areas which would normally be in closed-canopy rainforest (due to high rainfall and rich soils) indicate recurrent fires with an interval less than 350 years but probably more than around 50 years, which would tend to eliminate eucalypts. Note that the Eucalyptus leaves found in the Manuherikia Group are falcate and probably amphisophyll. This makes them quite different from the few species which are truly fire-sensitive rainforest taxa and are probably an "ancestral" eucalypt type, such as E. deglupta BI. from Papua New Guinea. Allocasuarina cones are well known from the Manuherikia Group. In Tasmania Allocasuarina thrives in areas where burning has been frequent, co-existing with Nothofagus at Cradle Mountain in a situation which is certainly fire-related (pers. obs.). The presence of both together in Manuherikia Group communities but without Eucalyptus suggests forestedge conditions, or perhaps a low level of disturbance by fire distant from a source of Eucalyptus seed. Complete absence of Allocasuarina from an otherwise typical rainforest flora may indicate long periods without disturbance, while its absence from Eucalyptus woodland may indicate a high frequency of fires. Conifers imply an absence of fire or at the most a fire frequency of 300-600 years. They are usually emergent rainforest trees, although in Tasmania they may form a dwarf shrub land. Conifers in the Manuherikia Group include Podocarpus alwyniae, Retrophyllum vulcanense, Dacrycarpus dacrydioides, and Araucaria sp. sect. Eutacta. Large-leaved angiosperms record the presence of closed-canopy rainforest. "Large" leaves are defined here as leaves of mesophyll size or larger. However their absence does not necessarily imply open-canopy conditions; in Tasmania, notophyllous leaves are virtually absent, even in the rainforest, where leaves are mostly microphyllous. Eucalyptus globulus Labill., with leaves of notophyll size and above, provides an awkward exception to this generalisation. Taxa with large leaves in the Manuherikia Group include BAN-31 and MANU-23.

175

414

Journal of The Royal Society of New Zealand, Volume 23, 1993 VEGETATION

90

80 F4U246

j 70

F4tn24s

--F4tn22B

- - F4tn227

60

_}F41n22s

50


_F4U225

~

40

? ~? ? 9 ~®'t

~F41n224 \

F4U244

30

lF4tn223

20 F4tn222

~-F4tn2ss

10

.. .

?+ {® { ® ?~~ ?~ ~?

FIRE FREQUENCY

Closed Canopy Rain Forest

Low

Palm Swamp

Low

Closed Canopy Rain Forest growing on peat

Low

Closed Canopy Rain Forest growing on peat

Low

Open Canopy Forest/Swamp

Mostly Opon Canopy Forost with some mixing

Open Canopy Forest

Open Canopy Forest

Medium Medium

Medium

Medium

Mixed Forest

Low

Mixed Forest

Low

Closed Canopy Rain Forest

Low

0 scale in metres

KAWARAU SEQUENCE

KEY No Fire

Not Indic.

Fire

~ ~ Open

Canopy

~' (j) Closed Canopy

Ecological Indicators in Dry-Land Environments

Interval Between Successive Fires.

$

Nothofagus

;

\Conifers

~Palms ~ A/locasuarina [

Medium Low

Sand Silt Gravel

Eucalyptus

(J) Large-Leaves

?

Small Leaves

Jl[ Reeds Fig. 7 - Key explaining the symbols used in Figs 8 and 9 and the interpretation of various floristic elements with respect to forest canopy type and a fire-regime.

VFem'beds' High

~l~te

Fig. 8- Interpretation ofthe Kawarau Sequence with respect to a fireregime.

< 25 Years

25-350 Years > 350 Years

176


F41n237

90

80

Jc~.,

(?

r®

-!Jt~" \CD? 7 F4tn247

70

--F41~234

,.

¥

~F41n21a ~~?

60

,.,~


F4tn2t9

50 F41/l238

40

CD?

~~ 'f 'f

30

20

--F4tn214

10

--F41n2oa

~\~? ~~?\

VEGETATION

415

FIRE FREQUENCY

Closed Canopy Forest

Low

Open Canopy Forest

Medium

Peat Swamp


Low

Peat Swamp

Peat Swamp

Low

with Palms Closed Canopy Forest

Low


Low

growing on peat Open Canopy Forest

Reed Swamp Reed Swamp

Mixed Forest

Mixed Forest

Medium

Low Low

Low

Low

0 scale

in metres

BANNOCKBURN SEQUENCE Fig. 9 - Interpretation of the Bannockburn Sequence with respect to a fire-regime.

The distribution of these key elements in the Kawarau and Bannockburn sequences has been plotted in Figs 8 and 9 to show their distribution through time. Associations including both closed and open canopy elements are inferred to have been mixed forests produced by fire. Interpretation of them depends on the time-resolution of the sedimentary unit. They could imply either that the frequency of fires was about 100-350 years throughout the deposition of the unit, or that the entire unit was deposited within that space of time. No conclusions have yet been reached yet on the deposition rates of the Manuherikia Group, but for now I will assume the former, which implies that sedimentation was too slow to resolve individual fires. There is probably little hope of relating macrocommunity assemblages directly with concentrations of charcoal or fusinite from individual fires, but the search may not be futile. Mildenhall ( 1989) reports the rather unexpected observation that charcoal in the Manuherikia Group "is found predominantly in samples in which Nothofagus is the dominant pollen type". Stronger evidence for (or against) the importance of fire could follow if we could 177



417


AN AUSTRALASIAN PERSPECTIVE: SYNTHESIS AND SUMMARY Conclusions drawn by earlier students of New Zealand macrofossils Ettingshausen, a proponent of the "Cosmopolitan Flora" theory, maintained (Ettingshausen, 1891: 238) that "The Tertiary flora of New Zealand is a part of that universal original flora from which all living floras of the globe descend ... In New Zealand only one part of its Tertiary flora has changed into its living flora; the other has become extinct". This theory was summarised by Deane (1900: 464) " ... the Tertiary floras of different countries contained the same types and were closely allied and resembled one another much more than the Tertiary flora of any particular country resembles its existing flora. In the recent period the floras of different regions have acquired their distinctive characters, due to climatic influences, and the old types which at one time were universally distributed have disappeared in some regions and not in others". Deane went on to soundly criticise the "Cosmopolitan Flora" theory, mainly on the basis of Ettingshausen's rather tenuous identifications of Australian fossil material as extant Northern Hemisphere genera. Deane expressed the opinion that there was no need for this as "each fossil type possessed representatives in the existing flora of Australia" (p. 463). Oliver ( 1955) reviewed the history of the flora of New Zealand as represented by both macro and microfossils. He concluded that from early Cretaceous times until the end of the Oligocene New Zealand's flora consisted of" ... Asiatic and deciduous types such as Acer, Cinnamomum, Ginkgo and large-leaved species of Nothofagus, and plants, probably all evergreen, related to present day New Zealand species ... About the end of the Oligocene a good many of the early types of angiosperms in the New Zealand flora had died out and so there arose in the Miocene the third main type of New Zealand flora, namely, the one which we know today". Holden ( 1980, 1981, 1983a, 1983b) emphasised the effect of prolonged weathering producing low-nutrient soils and poor vegetation, and mentioned the possible presence of Eucalyptus in the Manuherikia Group. She described Nothofagus and Lauraceae and Proteaceae from the Longford Formation (Holden, 1982a, 1982b). Conclusions drawn from palynology Palynology has so far provided the bulk of the data supporting conclusions on New Zealand's paleobotany. Mildenhall (1980) stated that Miocene floras in New Zealand contained "a rich variety of taxa which was never exceeded even in the Quaternary." A number of these taxa have been identified with extant genera and some environmental scenarios have been produced. Mildenhall (1980: 219) summarised contemporary knowledge of New Zealand's Miocene floras as follows, "During the Early Miocene a wide range of vegetational assemblages occurred even in the same locality as ephemeral lakes appeared and disappeared. Assemblages are dominated by pollen of [Nothofagus subgenus Brassospora ]. Myrtaceae (including ? Eucalyptus), [Casuarinaceae], Podocarpaceae, Palmae, Macaranga-Mallotus ... , Sparganiaceae and occasionally fern spores, especially tree ferns (Cyathaceae) ... Both in the south of the South Island and the north of the North Island flat low-lying swampy areas were common in which Sparganium was abundant ... and Palmae pollen either common or abundant. These possibly large shallow swamps were surrounded by dense subtropical forests." Mildenhall ( 1987) concluded that the spore/pollen assemblages of the Central Otago Miocene "are highly diverse and are dominated by many different taxa. Composition changed as the local environment changed with time. Nothofagus [subgenera Brassospora and Fuscospora], [Casuarinaceae], Myrtaceae, Chenopodiaceae, Palmae, Liliaceae, Araucariaceae, Podocarpaceae, Sparganiaceae, and several taxa of unknown botanical affinities all dominate the assemblages at different stages. Charcoal is abundant in some samples indicating an incidence of fire. Some samples are dominated by cool temperate taxa (e.g. Phyllocladus, [Nothofagus subgenus Fuscospora], Podocarpus)." Mildenhall (1977) provided a summary 179

418



of his work on the Kawarau Sequence. He stated "The pollen reflects a broad change in the vegetation during the Altonian from a [Nothofagus subgenus Brassospora]/Casuarinaceae forest to a Palmae/Metrosideros swamp forest back to she-oak forest in response to an increase and subsequent decrease in water levels." Mildenhall and Pocknall ( 1984) note that Myrtaceae in the Kawarau River sequence includes Eucalyptus and Acmena. ". Mildenhall ( 1989: 19) provided further data from which he deduced that the palynological assemblages from localities in the Manuherikia Group reflected "a dynamic, constantly changing, local environment caused by a combination of tectonic activity, changing climatic patterns, fire, soil material and sedimentary sources." Patterns in time, past and present: where the Manuherikia Group floras tit in Beginning with Oliver ( 1955), botanists have realised that, even as late as the Miocene, New Zealand floras were dominated by taxa different from the present. Both micro and macropaleobotanists have shown that elements were present, sometimes abundant, which today are restricted to Australia or New Caledonia. The composition of local floras within New Zealand varied considerably. Fluctuating rainfall, temperature, and water-levels have all been invoked to account for this variation. Evidence of fires has been noted, and also the possible effect on the vegetation of prolonged leaching during Tertiary peneplanation. In this paper an attempt is made to interpret the macrofossil remains and so to test the current views. The advantages of macrofossils over pollen rest on the fact that the dispersal of large fragments is limited, and there is no reworking between widely different periods. In contrast the rain of pollen largely represents a selection of the regional flora and may include reworked material, so there are obvious problems of resolution of pollen data. Macro remains are much more likely to represent discrete, contemporary floras. Macropaleobotany therefore offers a good chance of answering questions on how many communities existed, and where they existed within the physical environment. Macrofossils also have a better chance of being identified to low taxonomic rank. In this study the presence of several taxa reported as fossils by earlier workers, including palynologists, is confirmed. These include Araucaria, Dacrycarpus, Eucalyptus, Metrosideros, Nothofagus, Ripogonum, Cunoniaceae and Lauraceae. Pneumatopteris, Retrophyllum, Sloanea /Elaeocarpus and Muehlenbeckia are recorded for the first time. The Tertiary floral history of Australia records a general drying-out, with intermittent wetter phases. In the Early Tertiary, rainforest probably covered most of the continent; now the country's centre is arid, surrounded mostly by open Eucalyptus forest. Rainforest is restricted to isolated pockets which today in total would fill a circle of 70 km radius on the mainland, and less than 40 km in Tasmania (Winter eta/., 1987). Reduction and fragmentation of the rainforest has led to the extinction of a large number of taxa, by processes including "climatic sifting" (Tracey, 1987). Many of those which remain have very restricted or disjunct distribution. Some "refugia" contain a high proportion of primitive angiosperms, and this suggests that the refugia are "of great antiquity, extending back to the Cretaceous or earlier" (Webb and Tracey, 1981 b: 661 ), presumably because their microclimate has remained relatively unchanged and the effects of climatic sifting has been minimised (J.G. Tracey, pers. comm., 1988). The subject of Late Cenozoic plant extinctions has been reviewed by Kershaw (1984 ), largely in terms of increasing aridity and climatic variability. In New Zealand there has also been progressive climatic deterioration and forest fragmentation, in the Pliocene-Pleistocene at least. Many plant taxa which were prominent in the Tertiary (e.g. Nothofagus subgenus Brassospora, Eucalyptus and Allocasuarina) made their last appearance at that time (Mildenhall, 1980). Additional coniferous elements, present in New Zealand's Tertiary flora but now extinct, are exemplified by Retrophyllum, Araucaria, and broad-leaved Podocarpus (Pole, 1992c). This is similar to Australia (e.g. Bigwood and Hill, 1985; Wells and Hill, 1989; Hill and Carpenter, 1991; Hill and Pole, 1992; Pole, 1992e). The present distribution of conifers in circum-Tasman lands appears to be relictual.

180



419

While the absence of certain Tertiary taxa from contemporary New Zealand (e.g. Eucalyptus, and I offer the suggestion that an absence of fire for more than 300 years in an otherwise rainforest situation would have eliminated the genus from perhaps already isolated patches) is relatively easy to explain, it is their presence that is the more perplexing problem. Eucalyptus must certainly be regarded as a typical, if not the typical Australian tree. Its poor representation in Australian fossil localities is surprising, but its discovery in the Miocene of New Zealand is wholly unexpected. Lange ( 1978) and Ambrose et al ( 1979) record Eucalyptus remains from undated silicified deposits in the South Australian arid zone. Lange ( 1980) discusses the theory that while most of the well-investigated sites in Australia are nearcoastal and were in mesophytic rainforest vegetation in the mid-late Tertiary, Eucalyptus was more likely to have been developing in a drier central zone, but wetter than the present. As the Australian climate tended towards increased aridity, the eucalypts moved towards the coast and rainforest vegetation retreated north and to isolated regions with a higher rainfall and less chance of fire (Holmes et at (1982) described Eucalyptus leaves and fruits from a Middle Miocene locality in northwestern New South Wales, providing a time tag for the change in this region). Under this scenario, it is hard to imagine why Miocene New Zealand, with a probably overall maritime climate judging by its small size and lack of relief, would have been experiencing a drying-out. Alternatively, Bowler's (1982) model of northwardmigrating Sub Tropical High Pressure belts resulting in a change from summer to winter rainfall in the late Tertiary of southern Australia, is probably also applicable to New Zealand. The presence in the Manuherikia Group flora of Eucalyptus, Allocasuarina, Acacia, and no doubt a large range of other taxa now more commonly regarded as being "Australian" suggests that New Zealand's Tertiary flora may have had much more in common with other Australasian floras than it has now. Whether this common feature goes back to a "pre-drift" time, or results from Trans-Tasman dispersal (which may then have been easier than is generally assumed), may be answered by future paleobotanical study. The important common elements included Nothofagus, Myrtaceae, Elaeocarpaceae, Cunoniaceae, Podocarpaceae and Araucariaceae. The fragmented remnants of this more cosmopolitan flora are apparently scattered, not only over the Australian continent, but also from near sea-level in Tasmania and the southern Australian mainland to the montane regions of Papua New Guinea. Mildenhall (1980) and Martin ( 1982) have both commented on the similarity of the Cainozoic palynological record of New Zealand and Australia; several taxa appeared at about the same time in both countries, or a little later in New Zealand. This is further confirmation of the cosmopolitan nature of the original flora, and raises the possibility that direct comparison between New Zealand Tertiary macrofo~sils and those in Australia may be fruitful. The Manuherikia Group fossils can be envisaged as being a part of this widespread flora. New Zealand's present flora seems particularly depauperate. A large proportion of genera are monospecific or nearly so (Dawson, 1986), while other genera seem to have radiated recently (e.g. Pittosporum and Pseudopanax ). Climatic sifting and fire are likely to have been important agents guiding the evolution ofthe flora the Tertiary to the present. Macphail and Hill (1983: 186) state that "As aforest type, all modem Tasmanian rainforest is young: less than 12,000 years old. It is the product of the present interglacial climate, but comprises taxa which have had to survive long periods of cold conditions either in small, isolated stands or mixed within other, non-forest communities." They stress that this bottleneck effect also applies to the evolution of temperate rainforest in New Zealand. McGlone ( 1985) suggests that the disruption of large areas of nutrient-poor soils, so characteristic of the Tertiary, by tectonic uplift also extinguished many Tertiary species. In contrast to earlier explanations of New Zealand plant distributions which stressed the disruptive effect of ice and of severe climate during the Last Glaciation, followed by Recent migration from glacial refugia (e.g. Wardle, 1963; Burrows, 1965), McGlone introduced the "tectonic hypothesis." This places emphasis on the effects of post-Oligocene (Kaikoura Orogeny) tectonism on long-established endemic, vicariant, and disjunct plant distribution, which, in some cases date back to the Late Miocene. With the onset of tectonic activity there was (p. 743) "a general depauperisation of 181

420


the lowland and montane forest and tall shrub flora, a process which was only to a limited extent counteracted by the evolution of new tree and shrub species. It is the conservatism of the lowland and montane forest flora which ensures that it shows so clearly the imprint of post-Miocene events." (McGlone, 1985). If the tectonic hypothesis is correct, many of our present forest species became established in at least the Late Miocene, and have survived the rigours of repeated glacial episodes. The fossil evidence from the Manuherikia Group suggests that such species were not present earlier, in the Early - Middle Miocene. The implication is that the bulk of our forest species evolved, or arrived, late in the Miocene. The various contributions of palynology and macropaleobotany have thus narrowed down the period in which we must search for the real origins of the present New Zealand flora. If it was not the Late Miocene, then certainly it was towards the end of the Tertiary.


ACKNOWLEDGEMENTS I thank my supervisor, J.D. Campbell, and also R.S. Hill, J.D. Lovis and M.E. Dettmann who reviewed the manuscript at various stages. Special thanks also to J.G. Tracey. This work was financed by a UGC scholarship and University of Otago Bridging Finance, and completed with ARC funding at the Department of Plant Science, University of Tasmania.

REFERENCES Ambrose, G.J., Callen, R.A., and Flint, R.B., 1979. Eucalyptus fruits in stratigraphic context in Australia. Nature 280: 387-389. Axelrod, D.l., and Bailey, H.P., 1969. Paleotemperature analysis of Tertiary floras. Palaeogeography, Palaeoclimatology, Palaeoecology 6: 163-195. Bailey, I.W. and Sinnott, E.W., 1916. The climatic distribution of certain types of angiosperm leaves. American Journal of Botany 3: 24-39. Baumann-Bodenheim, G., 1953. Fagacees de Ia Nouvelle Caledonie. Bulletin du Museum National d'Histoire Naturelle, Paris 25: 419-421. Beadle, N.C. W ., 1966. Soil phosphate and its role in moulding segments of the Australian flora and vegetation, with special reference to xeromorphy and sclerophylly. Ecology 47: 992-1007. Beadle, N.C.W., 1968. Some aspects of the ecology and physiology of Australian xeromorphic plants. Australian Journal of Science 30: 348-355. Beadle, N.C. W ., 1981. The vegetation of Australia. Gustav Fischer Verlag, Stuttgart, New York. Beu, A.G., and Maxwell, P.A., 1968. Molluscan evidence for Tertiary sea temperatures in New Zealand: a reconsideration. Tuatara 16: 68-74. Bigwood, A.J ., and Hill, R.S., 1985. Tertiary araucarian macrofossils from Tasmania. Australian Journal of Botany 33: 645-656. Bowler, J.M., 1982. Aridity in the late Tertiary and Quaternary of Australia. In W.R. Barker and P.J.M. Greenslade (Eds): Evolution of the flora and fauna of arid Australia, pp. 35-45. Peacock Publications, Adelaide. Burnham, R.J., 1989. Relationships between standing vegetation and leaf litter in a paratropical forest: implications for paleobotany. Review of Palaeobotany and Palynology 58: 5-32. Burrows, C.J ., 1965. Some discontinuous distributions of plants within New Zealand and their ecological significance. 2: disjunctions between Otago-Southland and Nelson-Marlborough and related distribution patterns. Tuatara 13: 9-29. Campbell, J.D., 1985. Casuarinaceae, Fagaceae, and other plant megafossils from Kaikorai Leaf Beds (Miocene) Kaikorai Valley, Dunedin, New Zealand. N.Z. Journal of Botany 23: 311-320. Campbell, J.D., and Holden, A.M., 1984. Miocene casuarinacean fossils from Southland and Central Otago, New Zealand. N.Z. Journal of Botany 22: 159-167. Cantrill, D.J., and Douglas, J.G., 1988. Mycorrhizal conifer roots from the Lower Cretaceous of the Otway Basin, Victoria. Australian Journal of Botany 36: 257-272. Carpenter, R.J ., and Horwitz, P., 1988. Leaf litter in two southern Tasmanian creeks and its relevance to palaeobotany. Papers and Proceedings of the Royal Society of Tasmania 122: 39-45. Carter, R.M., 1974. The moulding of the landscape (3). New Zealand's Nature Heritage 2: 211-217. Christophel, D.C., and Blackburn, D.T., 1978. Tertiary megafossil flora of Maslin Bay, South Australia: a preliminary report. Alcheringa 2: 311-319.

182



421

Christophel, D.C., and Greenwood, D.C., 1987. A megafossil flora from the Eocene of Golden Grove, South Australia. Transactions of the Royal Society of South Australia III: 155-162. Christophel, D.C., Harris, W.K., and Syber, A.K., 1987. The Eocene flora of the Anglesea locality, Victoria. Alcheringa II: 303-323. Cookson, I. C., and Pike, K.M., 1953a. The Tertiary occurrence and distribution of Podocarpus (section Dacrycarpus) in Australia and Tasmania. Australian Journal of Botany I: 71-82. Cookson, I. C., and Pike, K.M., 1953b. A contribution to the Tertiary occurrence of the genus Dacrydium in the Australian region. Australian Journal of Botany l: 474-484. Dawson, J.W., 1986. Floristic relationships of lowland rainforest phanerogams of New Zealand. Telopea 2: 681--695. Deane, H., 1900a. Observations on the Tertiary flora of Australia, with special reference to Ettingshausen's theory of the Tertiary Cosmopolitan flora. Part I. Proceedings of the Linnean Society of New South Wales 25: 463-475. Deane, H., 1900b. Observations on the Tertiary flora of Australia, with special reference to Ettingshausen's theory of the Tertiary Cosmopolitan flora. Part 2. Proceedings of the Linnean Society of New South Wales 25: 581-590. Devereux, I., 1967. Oxygen isotope paleotemperature measurements on New Zealand Tertiary fossils. N.Z. Journal of Science 10: 988-1011.. Dilcher, D.L., 1973. A paleoclimatic interpretation of the Eocene floras of southwestern North America. In A. Graham (Ed.): Vegetation and vegetational history of northern Latin America, pp. 39-59. Elsevier, Amsterdam. Dilcher, D.L., 1974. Approaches to the identification of angiosperm leaf remains. The Botanical Review 40: 1-85. Dolph, G., 1971. A comparison of local and regional leaf characteristics in Indiana. Proceedings of the Indiana Academy of Science 80: 99-103. Dolph, G., 1975. A statistical analysis of Apocynophyllum mississippiensis. Palaeontographica Abt B 151: 1-51. Dolph, G., 1976a. Taxometric partitioning of leaf collections. Palaeontographica Abt. B 156: 65-86. Dolph, G., 1976b. Interrelationships among the gross morphological features of angiosperm leaves. Bulletin of the Torrey Botanical Club 103: 29-34. Dolph, G., 1977. The effect of different calculational techniques on the estimation of leaf area and the construction of leaf size distributions. Bulletin of the Torrey Botanical Club 104: 264-269. Dolph, G., 1978. Variation in leaf size and margin type with respect to climate. Courier Forschungsinstitut Senckenberg 30: 153-158. Dolph, G., 1979. Variation in leaf margin with respect to climate in Costa Rica. Bulletin of the Torrey Botanical Club 106: 104-109. Dolph, G.E., and Dilcher, D.C., 1979. Foliar physiognomy as an aid in determining palaeoclimate. Palaeontographica B 170: 151-172. Douglas, B.J., 1986. Lignite resources of Central Otago. New Zealand Energy Research and Development Committee. Publication PI04. Doyle, J.A., and Hickey, L.J., 1976. Pollen and leaves from the Mid-Cretaceous Potomac Group and their bearing on early Angiosperm evolution. In C.B. Beck (Ed.): Origin and early evolution of angiosperms, pp. 139-206. Columbia University Press, New York and London Drake, H., and Burrows, C.J., 1980. The influx of potential macrofossils into Lady Lake, north Westland, New Zealand. N.Z. Journal of Botany 18: 257-274. Edwards, A.R., 1968. The calcareous nannoplankton evidence for New Zealand Tertiary marine climate. Tuatara 16: 26-31. Ettingshausen, C. von, 1887. Beitrage zur Kenntniss der Fossilen Flora Neuseelands. Denkschriften der Akademie der Wissenschaften, Wien 53: 143-194. Ettingshausen, C. von, 1891. Contributions to the knowledge of the fossil flora of New Zealand. Transactions of the N.Z. Institute 23: 237-310. Evans, W.P., 1931. A fossil Nothofagus (Nothofagoxylon ?) from the Central Otago coal-measures. Transactions of the N.Z. Institute 62: 98. Evans, W.P., 1934. Microstructure of New Zealand lignites. Part 3: Lignites apparently not altered by igneous action. A: Coal Creek Flat, Roxburgh, Central Otago. N.Z. Journal of Science and Technology 15: 365-385. Evans, W.P., 1936. Microstructure of New Zealand lignites. Part 3: Lignites apparently not altered by igneous action. A: Coal Creek Flat, Roxburgh, Central Otago. N.Z. Journal of Science and Technology 17: 649--658.

183


422


Evans, W.P., 1937. Note on the flora which yielded the Tertiary lignites of Canterbury, Otago and Southland. N.Z. Journal of Science and Technology 19: 188-193. Ferguson, D.K., 1985. The origin of leaf assemblages - new light on an old problem. Review of Palaeobotany and Palynology 46: 117-188. Florin, R., 1940. The Tertiary fossil conifers of south Chile and their phytogeographical significance, with a review of the fossil conifers of southern lands. Kungl. Svenska Vetenskapsakademiens Handlingar, tredje serien.19. Floyd, A.G., 1990. Australian Rainforest in New South Wales. Vol. I. Surrey Beattie & Sons, Chipping Norton. Greenwood, D.R., 1987. Early Tertiary Podocarpaceae: megafossils from the Eocene Anglesea locality, Victoria, Australia. Australian Journal of Botany 35: 111-133. Greenwood, D.R., 1992. Taphonomic constraints on foliar physiognomic interpretations of Late Cretaceous and Tertiary palaeoclimates. Review of Palaeobotany and Palynology 71: 149-190. Gregg, D.R., 1975. Type and figured specimens of fossil plants in the Canterbury Museum. Records of the Canterbury Museum 9: 259-276. Groves, R.H. (Ed.), 1981. Australian vegetation. Cambridge University Press, Cambridge. Havel, J.J ., 1971. The Araucaria forests of New Guinea and their regenerative capacity. Journal of Ecology 59: 203-214. Hayward, B.W., 1979. Eruptive history of the Early to Mid Miocene Waitakere Volcanic Arc, and palaeogeography of the Waitemata Basin, northern New Zealand. Journal of the Royal Society of N.Z. 9: 297-320. Hickey, L.J., 1973. Classification of the architecture of dicotyledonous leaves. American Journal of Botany 60: 17-33. Hickey, L.J., 1977. Stratigraphy and paleobotany of the Golden Valley Formation (Early Tertiary) of western North Dakota. Geological Society of America, Memoir 150. Hickey, L.J., 1979. A revised classification of the architecture of dicotyledonous leaves. In C.R. Metcalfe and L. Chalk (Eds): Anatomy of the Dicotyledons. Vol. I. second edition, pp. 25-39. Clarendon Press, Oxford. Hickey, L.J., and Wolfe, J.A., 1975. The bases of angiosperm phylogeny: vegetative morphology. Annals of the Missouri Botanical Garden 62: 538-589. Hill, R.S., 1980. A numerical taxonomic approach to the study of angiosperm leaves. Botanical Gazette 142: 213-229. Hill, R.S., 1982. The Eocene megafossil flora of Nerriga, New South Wales, Australia. Palaeontographica Abt. B 181:44-77. Hill, R.S., 1984. History of rainforest - evidence from plant macrofossils. In G.L. Werren and A.P. Kershaw (Eds): Australian National Rainforest Study Report to the World Wildlife Fund (Australia) Vol. I. Proceedings of a workshop on the past, present and future of Australian rainforests, pp. 478487. Griffith University, Dec. 1983. Hill, R.S., 1984. Tertiary Nothofagus macrofossils from Cethana, Tasmania. Alcheringa 8: 81-86. Hill, R.S., 1986. Lauraceous leaves from the Eocene of Nerriga, New South Wales. Alcheringa 10: 327-351. Hill, R.S., and Carpenter, R.J., 1991. Extensive past distribution for major gondwanic floral elements: macrofossil evidence. In Aspects of Tasmanian Botany, a tribute to Winifred Curtis, pp. 239-247. Royal Society of Tasmania, Hobart. Hill, R.S., and Gibson, N., 1986. Distribution of potential macrofossils in Lake Dobson, Tasmania. Journal of Ecology 74: 373-384. Hill, R.S., and Pole, M.S. 1992: Leaf and shoot morphology of extant Afrocarpus, Nageia and Retrophyllum (Podocarpaceae) species, and species with similar leaf arrangement, from Tertiary sediments in Australia. Australian Systematic Botany 5: 337-358. Hill, R.S., and Read, J., 1987. Endemism in Tasmanian cool temperate rainforest: alternative hypotheses. Botanical Journal of the Linnean Society 95: 113-124. Holden, A.M., 1980. A beech-laurel forest from the Miocene of South-East Nelson. Abstracts, Geological Society of New Zealand, Christchurch Conference, 1980: 52. Holden, A.M., 1981. The flora and environment of the Gore Lignite Measures: Evidence from plant macrofossils. Abstracts, Geological Society of New Zealand, Hamilton Conference, 1981: 51. Holden, A.M., 1982a. Fossil Nothofagus from the Longford Formation, Murchison, New Zealand. Journal of the Royal Society of N.Z. 12: 65-77. Holden, A.M., 1982b. Fossil Lauraceae and Proteaceae from the Longford Formation, Murchison, New Zealand. Journal of the Royal Society of N.Z. 12: 79-80.

184



423

Holden, A.M., 1983a. Eucalyptus -like leaves from Miocene rocks in Central Otago. Abstracts, Pacific Science Association, 15th Congress: 103. Holden, A.M., 1983b. Megafossil evidence on non-uniformity in New Zealand Miocene vegetation. Abstracts, Pacific Science Association 15th Congress: 103. Holmes, W.B.K., Holmes, F.M., and Martin, H.A., 1982. Fossil Eucalyptus remains from the Middle Miocene Chalk Mountain Formation, Warrumbungle Mountains, New South Wales. Proceedings of the Linnean Society of New South Wales I 06: 299-310. Jackson, W.O., 1968. Fire, air, water and earth- an elemental ecology of Tasmania. Proceedings of the Ecological Society of Australia 3: 9-16. Jenkins, D.G., 1968. Planktonic foraminifera as indicators of New Zealand Tertiary paleotemperatures. Tuatara 16: 32-37. Johns, R.J., 1982. Plant zonation. In J.L. Gressitt (Ed.): Ecological biogeography of New Guinea, pp. 309-330. Dr W. Junk Publishers, The Hague. Johnston, R.D., and Lacey, C.J., 1984. A proposal for the classification oftree-dominated vegetation in Australia. Australian Journal of Botany 32: 529-549. Kamp, P.J.J., 1986. The mid-Cenozoic Challenger Rift System of western New Zealand and its implications for the age of Alpine fault inception. Geological Society of America, Bulletin 97: 255281. Kemp, E.M., 1978. Tertiary climatic evolution and vegetation history in the southeast Indian Ocean region. Paleogeography, Palaeoclimatology, Palaeoecology 24: 169-208. Kershaw, A.P., 1984. Late Cenozoic plant extinctions in Australia. In P.S. Martin and R.G. Klein (Eds): Quaternary extinctions: a prehistoric revolution, pp. 691-707. University of Arizona Press. Kershaw, A.P., 1976. A Late Pleistocene and Holocene pollen diagram from Lynch's Crater, northeastern Queensland, Australia. New Phytologist 77: 469-498. Kershaw. A.P., and Sluiter, I.R., 1982. The application of pollen analysis to the elucidation of Latrobe Valley brown coal depositional environments and stratigraphy. Australian Coal Geology 4: 169186. Kovar, J.B., Campbell, J.D., and Hill, R.S., 1987. Nothofagus ninnisiana (Unger) Oliver from Waikato Coal Measures (Eocene-Oligocene) at Drury, Auckland, New Zealand. N.Z. Journal of Botany 25: 79-85. Lange, R.T., 1978. Carpological evidence for fossil Eucalyptus and other Leptospermeae (subfamily Leptospermoideae ofMyrtaceae) from a Tertiary deposit in the South Australian arid zone. Australian Journal of Botany 26: 221-233. Lange, R.T., 1980. Evidence of lid-cells and host-specific microfungi in the search for Tertiary Eucalyptus. Review of Paleobotany and Palynology 29: 29-33. Laubenfels, D.J. de, 1969. A revision of the Malaysian and Pacific rainforest conifers. I. Podocarpaceae. Journal of the Arnold Arboretum 50: 274-369. Luly, J ., Sluiter, I.R., and Kershaw, A.P., 1980. Pollen studies of Tertiary brown coals: preliminary analyses of lithotypes within the Latrobe valley, Victoria. Monash Publications in Geography 23. Macphail, M.K., and Hill, R.S., 1983. Cool temperate rainforest in Tasmania: a reply. Search 14: 186187. Martin, H.A., 1982. Changing Cenozoic barriers and the Australian paleobotanical record. Annals of the Missouri Botanical Garden 69: 625-667. McGlone, M.S., 1985. Plant biogeography and the late Cenozoic history of New Zealand. N.Z. Journal of Botany 23: 723-749. McQueen, D.R., 1954. Fossil leaves, fruits and seeds from the Wanganui Series (Plio-Pleistocene) of New Zealand. Transactions of the Royal Society of N.Z. 82: 667-676. Meyerhoff, A.A., 1952. A study of leaf venation in the Betulaceae, with its application to paleobotany. Unpublished PhD thesis, Stanford University. Mildenhall, D.C., 1970. Checklist of valid and invalid plant macrofossils from New Zealand. Transactions of the Royal Society of N.Z.: Earth Sciences 8: 77-89. Mildenhall, D.C., 1972. Fossil pollen of Acacia type from New Zealand. N.Z. Journal of Botany I0: 485-494. Mildenhall, D.C., 1977. Preliminary palynological thoughts on the Lower Miocene, Kawarau River, Central Otago [abstract]. p. 44. Geological Society of New Zealand Conference, Queenstown, Programme and abstracts. Mildenhall, D.C., 1980. New Zealand Late Cretaceous and Cenozoic plant biogeography: a contribution. Palaeogeography, Palaeoclimatology. Palaeoecology 31: 197-233.

185


424


Mildenhall, D.C., 1982. Pollen and spores. In Hoskins, R.H. (Ed): Stages of the New Zealand marine Cenozoic: a synopsis, pp. 45-46. New Zealand Geological Survey Report 107. Mildenhall, D.C., 1987. Palynology and paleoenvironments of Miocene sediments, Central Otago, New Zealand. Abstracts, Time, change and the vegetation of New Zealand, conference. 24-26 November, 1987. Botany Division, DSIR, Christchurch. Mildenhall, D.C., 1989. Summary of the age and paleoecology of the Miocene Manuherikia Group, Central Otago, New Zealand. Journal of the Royal Society of N.Z. 19: 19-29. Mildenhall, D.C., and Pocknall, D.T., 1984. Palaeobotanical evidence for changes in Miocene and Pliocene climates in New Zealand. In Vogel, J.C. (Ed): South African Society for Quaternary Research, International Symposium, Swaziland,I983, pp 159-171. A.A. Balkema, Rotterdam. Mildenhall, D.C., and Pocknall, D.T., 1989. Miocene-Pliocene spores and pollen from Central Otago, South Island, New Zealand. New Zealand Geological Survey, Paleontological Bulletin 59. Nelson, C.S., and Bums, D.A., 1982. Effect of sampling interval on the resolution of oxygen isotopic paleotemperature trends - an example from the New Zealand Early Miocene. N.Z. Journal of Geology and Geophysics 25: 77-81. Nix, H., 1982. Environmental determinants of biogeography and evolution in Terra Australis. In W.R. Barker and P.J.M. Greenslade (Eds): Evolution of the flora and fauna of arid Australia, pp. 47-66. Peacock Publications, Frewville, South Australia. Norris, R.J., and Carter, R.M., 1980. Offshore sedimentary basins at the southern end of the Alpine Fault, New Zealand. Special Publications of the International Association of Sedimentologists 4: 237-265. Oliver, W.R.B., 1928. The flora of the Waipaoa Series (Later Pliocene) of New Zealand. Transactions of the N.Z. Institute 59: 287-303. Oliver, W.R.B .• 1936. The Tertiary flora of the Kaikorai Valley, Otago, New Zealand. Transactions of the Royal Society of N.Z. 66: 284-304. Oliver, W.R.B., 1950. The fossil flora of New Zealand. Tuatara 3: 1-11. Oliver, W.R.B., 1955. History of the flora of New Zealand. Svensk Botanisk Tidskrift 49: 11-18. Pocknall, D.T., 1989. Late Eocene to Early Miocene vegetation and climatic history of New Zealand. Journal of the Royal Society of N.Z. 19: 1-18. Pocknall, D.T., and Mildenhall, D.C., 1984. Late Oligocene-Early Miocene spores and pollen from Southland, New Zealand. N.Z. Geological Survey Paleontological Bulletin 5! . Pole, M.S., 1983. Paleoecology and stratigraphy of Miocene floras. Unpublished BSc hons thesis. Department of Geology, University of Otago. Pole, M.S., 1987a. Fagacean-like leaves from the Miocene of Otago. Geological Society of New Zealand Miscellaneous Publication 37 A . Pole, M.S., 1987b. Early Miocene floras from Central Otago. Abstracts, Time, change and the vegetation of New Zealand symposium. 24-26 November 1987. Botany Division, DSIR, Christchurch. Pole, M.S., 1988. The ecology of early Miocene plants of Central Otago. Botanical Society of Otago Newsletter 8: 2-3. Pole, M.S., 1989. Early Miocene floras from Central Otago, New Zealand. Journal of the Royal Society ofN.Z. 19: 121-125. Pole, M.S., 1992a. Fossils of Leguminosae from the Miocene Manuherikia Group of New Zealand. In P.S. Herendeen and D.L. Dilcher (Eds): Advances in legume systematics: Part 4. The fossil record, pp. 251-258. The Royal Botanic Gardens, Kew. Pole, M.S., I992b. Early Miocene flora of the Manuherikia Group, New Zealand. I. Ferns. Journal of the Royal Society of N.Z. 22: 279-286. Pole, M.S., 1992c. Early Miocene flora of the Manuherikia Group, New Zealand. 2. Conifers. Journal of the Royal Society of N.Z. 22: 287-302. Pole, M.S., 1992d. Early Miocene flora of the Manuherikia Group, New Zealand. 3. Possible cycad. Journal of the Royal Society of N.Z. 22: 303-306. Pole, M.S., 1992e. Eocene vegetation from Hasties, north-eastern Tasmania. Australian Systematic Botany 5:431-475. Pole, M.S., 1993. Early Miocene flora of the Manuherikia Group, New Zealand. 4. Palm fossils. Journal of the Royal Society of N.Z. 23: 283-288. Pole, M.S.,1993 b. Early Miocene flora of the Manuherikia Group, New Zealand. 5. Smilacaceae, Polygonaceae, and Elaeocarpaceae. Journal of the Royal Society of N.Z. 23: 289-302. Pole, M.S., 1993c. Early Miocene flora of the Manuherikia Group, New Zealand. 6. Lauraceae. Journal of the Royal Society of N.Z. 23: 303-312

186



425

Pole, M.S., 1993d. Early Miocene flora of the Manuherikia Group, New Zealand. 7. Myrtaceae, including Eucalyptus. Journal of the Royal Society of N.Z. 23: 313-328 Pole, M.S., 1993e. Early Miocene flora of the Manuherikia Group, New Zealand. 8. Nothofagus. Journal of the Royal Society of N.Z. 23:329-344. Pole, M.S., 1993 f. Early Miocene flora of the Manuherikia Group, New Zealand. 9. Miscellaneous leaf fossils and reproductive structures. Journal of the Royal Society of N.Z. 23:345-391. Pole, M.S., Holden, A.M., and Campbell, J.D., 1987. Fossil legumes from Manuherikia Group sediments (Miocene), Central Otago. Abstracts, Time, change and the vegetation of New Zealand symposium. 24-26 November 1987. Botany Division, DSIR, Christchurch. Pole, M.S., Holden, A.M., and Campbell, J.D., 1989. Fossil legumes from the Manuherikia Group (Miocene), Central Otago, New Zealand. Journal of the Royal Society of N.Z. 19: 225-228. Raunkiaer, C., 1934. The life forms of plants and statistical plant geography. Clarendon Press, Oxford. Romero, E.J., and Dibbern, M.C., 1985. A review of the species described as Fagus and Nothofagus by Dusen. Palaeontographica Abt B 197: 123-138. Roth, J.L., and Dilcher, D.L., 1978. Some considerations in leaf size and leaf margin analysis of fossil leaves. Courier Forschungsinstitut Senckenberg (West Germany) 30: 165-171. Rury, P.M., and Dickison, W.C., 1977. Leaf venation patterns of the genus Hibbertia (Dilleniaceae). Journal of the Arnold Arboretum 58: 209-256. Scheihing, M.H., and Pfefferkorn, H. W ., 1984. The taphonomy of land plants in the Orinoco delta: a model for the incorporation of plant parts in clastic sediments of late Carboniferous age in Euramerica. Review of Palaeobotany and Palynology 41: 205-240. Selling, O.H., 1950. Some Tertiary plants from Australia. Svensk. Botansk Tidskrift 44: 551-561. Smith, K., 1987a. Rainforests of the south-west. In G. Hutching and C. Potton (Eds): Forests, fiords and glaciers. New Zealand's World Heritage, pp. 49-61. Royal Forest and Bird Protection Society, Wellington. Smith, K., 1987b. Kahikatea. The feathers ofTawhaitari. Forest and Bird 18:4-9. Sneath, P.H.A., and Sokal, R.R., 1973. Numerical taxonomy. W.H. Freeman and Co., San Francisco. Specht, R.L., 1981. Heathlands. In R.H. Groves (Ed): Australian Vegetation, pp. 253-275. Cambridge University Press, Cambridge. Spicer, R.A., 1980. The importance of depositional sorting to the biostratigraphy of plant megafossils. In D.L. Dilcher and T.N. Taylor (Eds): Biostratigraphy of fossil plants -successional and paleoecological analyses, pp. 171-183. Dowden, Hutchinson and Ross. Inc., Stroudsberg. Spicer, R.A., 1981. The sorting and deposition of allochtonous plant material in a modem environment at Silwood Lake, Silwood Park, Berkshire, England. United States Geological Survey Professional Paper 1143. Spicer, R.A., 1986a. Pectinal veins: a new concept in terminology for the description of dicotyledonous leaf venation patterns. Botanical Journal of the Linnean Society 93: 379-388. Spicer, R.A., 1986b. Computerised paleobotanical data bases: the way forward? In R.A. Spicer and B.A. Thomas (Eds): Systematic and taxonomic approaches in paleobotany, pp. 283-296. Systematics Association, Special Volume 31. Steenis, C.G.G.J. van, 1953. Results of the Archbold expeditions. Papuan Nothofagus. Journal of the Arnold Arboretum 34: 301-373. Steenis, C.G.G.J. van, 1971. Nothofagus, key genus of plant geography, in time and space, living and fossil, ecology and phylogeny. Blumea !9: 65-98. Steenis, C.G.G.J. van, 1979. Plant-geography of east Malesia. Botanical Journal of the Linnean Society 79: 97-178. Sturm, M., 1971. Die Eozane Flora von Messel bei Darmstadt. I. Lauraceae. Palaeontographica Abt B 134: 1-60. Thompson, D'Arcy W., 1942. On growth and form. Cambridge University Press, Cambridge. Tracey, J .G., 1987. The vegetation of the humid tropical region ofnorth Queensland. CSIRO, Melbourne. Unger, F., 1864. Fossile Pflanzenreste aus Neu-Seeland. Palaeontologie von Neu-Seeland, NovaraExpedition. Th. 1. Bd. 2. Vienna. Wardle, J.A., 1984. The New Zealand beeches. Ecology, utilisation and management. New Zealand Forest Service, Caxton Press, Christchurch. Wardle, P., 1963. Evolution and distribution of the New Zealand flora, as affected by Quaternary climates. N.Z. Journal of Botany I: 3-17. Wardle, P., 1974. The Kahikatea (Dacrycarpus dacrydioides) forest of south Westland. Proceedings of the N .Z. Ecological Society 21 : 62-71.

187


426


Webb, L.J., 1959. Physiognomic classification of Australian rain forests. Journal of Ecology 47: 551570. Webb, L.J., 1968. Environmental relationships of the structural types of Australian rain forest vegetation. Ecology 49: 296-311. Webb, L.J., 1978. A general classification of Australian rainforests. Australian Plants 9: 349-363. Webb, L.J., 1978. A structural comparison of New Zealand and south-east Australian rain forests and their tropical affinities. Australian Journal of Ecology 3: 7-21. Webb, L.J., and Tracey, J.G., 1981a. The rainforests of northern Australia. In R.H. Groves (Ed.): Australian vegetation, pp. 67-101. Cambridge University Press, Cambridge. Webb, L.J., and Tracey, J.G., 1981 b. Australian rainforests: patterns and change. In A. Keast (Ed.): Ecological biogeography of Australia, pp. 607-694. Dr W. Junk, The Hague. Webb, L.J., Tracey, J.G., and Williams, W.T., 1984. A floristic framework of Australian rainforests. Australian Journal of Ecology 9: 169-198. Wells, P.M., and Hill, R.S., 1989. Fossil imbricate-leaved Podocarpaceae from Tertiary sediments in Tasmania. Australian Systematic Botany 2: 387--423. Whitmore, T.C., 1986. Tropical rainforests of the Far East. English Language Book Society, Oxford University Press. Wilde, M.H., and Eames, A.J., 1952. The ovule and seed of Araucaria bidwillii with discussion of the taxonomy of the genus. 2. Taxonomy. Annals of Botany n.s. 16: 27--47. Wilson, M.V.H., 1980. Eocene lake environments: depth and distance-from-shore variation in fish, insect, and plant assemblages. Palaeogeography, Palaeoclimatology, Palaeoecology 32: 21--44. Wilson, M. V .H., 1988. Reconstruction of ancient lake environments using both autochthonous and allochthonous fossils. Palaeogeography, Palaeoclimatology, Palaeoecology 62: 609-623. Wing, S.L., 1984. Relation of paleovegetation to geometry and cyclicity of some fluvial carbonaceous deposits. Journal of Sedimentary Petrology 54: 52-66. Winter, J.W., Atherton, R.G., Bell, F.C., and Pahl, L.I. 1987. An introduction to Australian rainforests. In Werren, G.L., and Kershaw, A.P. (Eds): The rainforest legacy. Australian National Rainforests study, volume I, pp. 1-7. Special Australian Heritage Publication Series 7( I). Australian Government Publishing, Canberra. Withers, J., and Ashton, D.H., 1977. Studies on the status of unburnt Eucalyptus woodland at Ocean Grove, Victoria. I. The structure and regeneration. Australian Journal of Botany 25: 623-637. Wolfe, J.A., 1971. Tertiary climatic fluctuations and methods of analysis of Tertiary floras. Palaeogeography, Palaeoclimatology, Palaeoecology 9: 25-57. Wolfe, J.A., 1973. Fossil forms of Amentiferae. Brittonia 25: 334-355. Wolfe, J .A., 1977. Paleogene floras from the Gulf of Alaska region. Geological Survey Professional Paper997. Wolfe, J.A., 1978. A paleobotanical interpretation of Tertiary climates in the Northern Hemisphere. American Scientist 66: 694-703. Wolfe, J.A., 1979. Temperature parameters of humid to mesic forests of eastern Asia and relation to forests of other regions of the Northern Hemisphere and Australasia. U.S. Geological Survey Professional Paper II 06. Wolfe, J.A., 1981. Paleoclimatic significance of the Oligocene and Neogene floras of the northwestern United States. In K.J. Niklas (Ed): Paleobotany, paleoecology and evolution, pp. 79-101. Praeger, New York. Wolfe, J .A., and Hopkins, D.M., 1967. Climatic changes recorded by Tertiary land floras in northwestern North America. In K. Hatai (Ed.): Tertiary correlation and climatic changes in the Pacific. Pacific Science Congress1966, pp. 67-76. Sasaki, Sendai. Wolfe, J.A., and Upchurch, G.R., 1987. North American nonmarine climates and vegetation during the Late Cretaceous. Palaeogeography, Palaeoclimatology, Palaeoecology 61: 33-77.

Received 25 November 1991; accepted 23 February 1993.

188