The Ordovician graptolite sequence of Australasia

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The Ordovician graptolite sequence of Australasia a

A.H.M. Vandenberg & R.A. Cooper

b

a

Department of Industry, Geological Survey of Victoria, P.O. Box 173, East Melbourne, 3002, Victoria b

DSIR Geology and Geophysics, P.O. Box 30368, Lower Hutt, New Zealand Available online: 27 Nov 2008

To cite this article: A.H.M. Vandenberg & R.A. Cooper (1992): The Ordovician graptolite sequence of Australasia, Alcheringa: An Australasian Journal of Palaeontology, 16:1, 33-85 To link to this article: http://dx.doi.org/10.1080/03115519208619032

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The Ordovician graptolite sequence of Australasia A. H. M. V A N D E N B E R G A N D R. A. C O O P E R

Downloaded by [Museum of Victoria], [Alfons VandenBerg] at 17:13 29 August 2011

VANDENBERG,A. H. M., & Cooplm, R. A., 1992:03:30. The Ordovician grsptolite sequence of Australasia. Alcheringa 16, 33-85. ISSN 0311-551. The classical Ordovician grsptolite succession of Victoria has long been taken as standard for the region and widely used for subdivision and correlation of Ord~clcian sequences around the world. We review the Victorian succession and incorporate other Australian and New Zealand graptolitlc sequences into an Australasian set of zones and stages. Thirty zones are recognlz~d and defined, of which one (Ca4, lsograptus victoriae maximodivepgens) is new and two (l..al, Da4) each comprise two subzones. Several zones are redefined, but the previous zone notation has been retained. Nine stages are recognized (as previously) and defined, six (Lancefieldian,Bendigonian, Chewtonian, Castlemainian, Yapeenian, Darriwilian) in the Early Ordovieian and three (Gishornian, Eastonian, Bollndian) in the Late Ordoviclan; reference sections for each are nominated. The Bolindlan stage contains 5 zones, here designated Bol-5. The Australasian stages are correlated internationally. A census of Australasian graptoiite taxa lists the currently recognized 313 species and subspecies, with references. A range chart showsthe zonal distribution of all species, and reveals an average duration of 2.46 zones per species, approximately equivalentto 5 Ida. Th© pattern of diversity change shows maxima during the Bendigonian-Chawtonian (peaking in Bel with 55 taxa), late Castlemainian-mid Darriwilian, and late Gisbornian-early Eastonian. Sl~cies originations peak in Bel and Da3 and are high throughout much of the Late Ordovician. Extinctions peak in the Da3 and are high towards the end of the Ordovician. A. H. M. VandenBerg, Geological Survey of Victoria, Department of Industry, P.O. Box 173, East Melbourne, 3002, Victoria. R. A. Cooper, DSIR Geology and Geophysics, P.O. Box 30368, Lower Hutt, New Zealand; received 24 September 1990.

Keywords: Australia, biostratigraphy, correlation, graptolites, New Zealand, Ordovician, stages, Victoria, zones.

AUSTRALASIhZS Ordovician graptolite sequence is one o f the richest and most freely zoned in the world. It has long been regarded as the standard for the Pacific Province; the zones and/or stages have been directly used for sequences in N W Canada (Lenz, 1988) and Newfoundland (Kindle & Whittington, 1958), and as the framework for w o d d wide correlation (Cooper & Lindholm, 1990). It is now 30 years since publication o f the review o f the Australian graptolite sequence by Thomas (1960). His paper, which owes a great deal to the work o f M r G. Bell, has been widely used and quoted, and gives the most convenient access to the zonal distribution o f Australian species and to literature on the Australian suecession. A considerable number o f papers on 0311155181921010000-53 $3.00 ©AAP

Australasian graptolites has b e e n published since; many taxa have been revised or have had their ranges modified. The U p p e r Ordovician zones have been extensively revised. It is therefore timely to review the overall succession and this is the purpose o f the present paper. We present an updated zonal distribution chart and species census, incorporating the N e w Zealand succession. The current zonal scheme is further modified and refined and w e attempt to put the stages on a more formal basis, although designation o f boundary stratotypes will have to await documentation o f the various candidate seedons. It is to be hoped that future w o r k will b e directed toward this end. The Australasian Ordovician is here divided into U p p e r and Lower parts, with the boundary placed at the base o f the N e m a g r a p t u s gracilis Zone, following Cas & VandenBerg (1988).

34

A.H.M.

V A N D E N B E R G & R. A. C O O P E R

This differs from the division used by Thomas (1960), who had a three-part subdivision, with a ' M i d d l e Ordovician' consisting o f a single stage, the Darriwilian. This subdivision, although long-standing (it was introduced by Harris & Thomas, 1938c), was rejected by Cas &

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VandenBerg (1988) because the Victorian ' M i d dle Ordovician' differs in concept from that used in any other region, and because it represents only a relatively short time interval. The base o f the Ordovieian, which lies below the base o f the lowest Australasian graptolit¢ 130


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zone (Lal), is taken at the base of the Tremadoc, 'at or just below the lowest beds with Dictyonema flabelliforme s.l.' in North Wales (Rushton, 1982), consistent with the (1986) resolution of the Cambrian-Ordovician Boundary Working Group (Norford, 1988). Following the decision of the Ordovician/Silurian Working Group of the I.U.G.S. Commission on Stratigraphy, the top of the Ordovician is taken at the appearance of Parakidograptus acuminatus (i. e. top of Normalograptus? persculptus Zone), found in the Darraweit Guim area of central Victoria (VandenBerg et al., 1984; VandenBerg & Webby, 1988). Localities in Victoria are defined by the Australian metric grid (AMG), those in New Zealand by the New Zealand national grid (GR). Most Victorian localities are listed in the Museum of Victoria fossil locality register and are then prefixed PL. New Zealand graptolite localities are listed in the New Zealand Fossil Record File and are listed under their File number, e.g. M28/ff/552.

Distribution and setting Ordovician graptolites are distributed widely throughout the Tasman Orogenic Zone, which lay along the Pacific margin of the Australian/Antarctic segment of Gondwana in the Early Palaeozoic (Embleton, 1984). Early Ordovician graptolites are most abundant and diverse in the quartz-rich turbidite and black shale sequence of the Bendigo-Ballarat belt and Mornington Peninsula (central Victoria), in similar quartz-rich turbidites and black shales in the Buller Terrane of New Zealand (Cooper, 1979b), and in volcaniclastics in the Mt W'mdsor Subprovince in northern Queensland (Henderson, 1983). They are rare and less diverse in the extensive quartz-rich turbidite sequence of eastern Victoria and New South Wales (Tabberabbera, Omeo, Mallacoota structural belts and the Molong-South Coast Anticlinorial Zone). Late Ordovician graptolites are abundant and diverse in the turbidite and black shale facies of the Melbourne Trough (central Victoria) and in the black shale facies of eastern Victoria; in SE New South Wales they are largely confined to E of the Wagga Anticlinorial Zone (VandenBerg, in Webby & Nicoll, 1989), where they

ORDOVICIAN GRAPTOLITE ZONAHON

35

occur in shallow marine andesitic volcanichstics, and farther east in deep marine black shale. In New Zealand, Late Ordovician graptolites are poorly preserved but quite abundant and a r e found in black shales and siltstones in both the Buller and Takaka terranes. Elsewhere in Australasia, graptolites a r e found more sparsely. There are a few records of both Early and Late Ordovician graptolites from Tasmania (Banks & Burrett, 1980; Riekards & Stait, 1984; Baillie et al., 1978). The shallow water epieratonie basin shale-carbonate sequence of the Canning Basin in West Australia contains a reasonably diverse Tremadoe to Darriwil graptolite sequence. A small graptolite fauna of Early Ordovician age occurs in the Horn Valley Siltstone, in the Amadeus Basin, (Bagas, 1988). The Australasian region of Gondwana lay in low latitudes in the Ordovician (Scotese et aL, 1979) and its graptolite faunas characterize the low latitude Pacific Province (Bulman, 1971a; Skevington, 1969, 1974). In terms of the depth zone model of Cooper et al. (1991), the relatively shallow water Canning Basin sequence contains graptolites of the epipelagie and inshore biotopes only (didymograptid biofaeies) including Didymograptus (Didymograptus) artus -- a species typical of the restricted inshore biotope and absent from SE Australia. The deep water (below shelf/slope break) turbidite-black shale facies of SE Australia and New Zealand contains the isograptid biofaeies (Fortey, 1984), with a more diverse graptolite fauna representing the epipelagic and deep water biotopes (Cooper et al., 1991).

Overview of graptolite sequence The sequence of graptolite assemblages, or 'faunas', of Australia was outlined by Harris & Thomas (1938c) and Thomas (1960). In upward succession through the Eady Ordovician are the anisograptid, dichograptid, isograptid and glossograptid faunas. The diplograptid fauna commences in the late Early Ordovician (Darriwilian) and ranges to the end of the Late Ordovician; the dicranograptid (Dicellograptus and Dicranograptus) fauna ranges through the Late Ordovician.

36

A . H . M . VANDENBERG & R. A. COOPER


Faunal dynamics With 313 taxa (not including the 26 or so undescribed taxa -- see census footnote), the Australasian Ordovician graptolite fauna is relatively rich. The ranges of species as shown in the range chart (Fig. 12) are found to be remarkably complete when compared with the ranges of the same species in other sections around the world (Cooper & Lindholm, 1990). Thus the Australasian record of first and last appearances of species can be taken as a reasonable estimate of the real (evolutionary) ranges of taxa in the Pacific Province and permits a good approximation of evolutionary rates (origination, extinction, diversity change, etc.) to be made. However, until the graptolite zones are calibrated to a time scale, these rates can be measured in terms of the zonal sequence only. If we take the Ordovician Period to have lasted for 71 Ma (Harland et al., 1990) mean zone duration is 2 Ma. Ordovician graptolite species average 2.5 zones each in duration (Fig. 1D), approximately equivalent to 5 Ma each. For comparison, the average duration of a Silurian graptolite zone is 0.86 Ma (35 zones for 30 Ma) and the average duration of a Silurian graptolite species is 1.63 Ma (recalculated from the data of Rickards, 1977). The zone diversity histogram (Fig. 1A) shows three broad peaks. The first, in the Bendigonian and Chewtonian, corresponds to the initial radiation of the Order Graptoloidea (planktic graptolites) and diversification of the dichograptids. The second, in the late Castlemainian, Yapeenian and early Darriwilian marks the diversification of the isograptids and the glossograptids (including Pseudisograptus), with a late and short-lived flowering of the dichograptids in Da3. The third broad peak, in the Gisbornian to early Bolindian, corresponds to the expansion of the dicranograptids and diplograptids. The waning of this last group in the late Bolindian brings about the almost complete demise of the graptolites near the end of the Ordovician; only 2 species in the Australian sequence (Normalograptus angustus and N. normalis) range into the Silurian. The origination/extinction rate diagrams (Figs 1B, 1C) show the fluctuating but generally high rate of faunal turnover that contributes to the biostratigraphic utility of the group. The

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origination and extinction spikes in Be 1 and Da3 are conspicuous (Fig. 1B), though less so when expressed as a percentage of the zone fauna (Fig. 1C). With the exception of these spikes, faunal turnover is generally more rapid in the Late Ordovician than in the Early Ordovician, reflected in the higher origination and extinction rates (in terms of zones) in diplograptids and dicranograptids, than in dichograptids, isograptids and glossograptids. In Fig. 1C the high origination and extinction rates in the Early Lancefieldian result from the very low diversity (inevitable at the beginning of the group) and short duration of the few species that are present. The progressive drop off in diversity and near-demise of the graptolites towards the end of the Ordovician is not due to a slowdown in origination rate of species (the origination rates were lower for much of the Bendigonian, Chewtonian and Castlemainian), but rather to a high extinction rate with a particularly 'vicious' peak at the end of Bo3, where 93 % of all species became extinct. The cause of this peak is generally ascribed, either directly or indirectly, to the Late Ordovician glaciation (Skevington, 1974).

Zones General comments on Australasian graptolite zones

Thirty zones, two of which are divided into subzones, are here recognized in the Ordovician System of Australasia. The nature of the zones was described by Cooper (1979a) and the Vietorian zones have been summarized by VandenBerg (1981a, and in Cas & VandenBerg, 1988). The zones are defined in terms o f the stratigraphic ranges of selected species; zone boundaries are defined by the successive horizons of appearance of the defining species, the zones being the stratal intervals between the horizons. The only exceptions to this rule are the Be2 and Be4 zones, whose bases are defined by the disappearance of taxa. The nature of the zones has been described by Cooper (1979a) and the Victorian zones have been summarized by VandenBerg (1981a, and in Cas & VandenBerg, 1988). The present zonal scheme has its origins in the early detailed mapping of the Bendigo,


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ORDOVICIAN GRAPTOLITE ZONATION

37

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Fig. 2. Two large Lancefieldian (l.,a2) graptolites. A, Araneograptus macgillivrayt, ×0.5. B, Teranograptus magniflcus, xO.3.

Castlemaine, Steiglitz and Daylesford goldfields at the turn of the century. Because of their lithologicallymonotonous character and tight folding, the turbiditie sandstones and siltstones could be subdivided and mapped only on the basis of their contained graptolite faunas. An early scheme of zones and series (now stages) was established by T.S. Hall (1895, 1899a, 1912, 1914b) and later refined and revised by Harris (1916, 1933, 1935), Harris & Keble (1932) and Harris & Thomas (1938c). The Gisbornian, Eastonian and Bolindian stages and their zones were not established until the 1930s and relied, at least in part, on the known stratigraphic distribution of species in Britain (VandenBerg, 1981a). The zonal scheme of Thomas (1935), slightly modified by Harris & Thomas (1938c) and Thomas (1960), was revised by VandenBerg (1981a and in Cas & VandenBerg, 1988), based on re-examination of the largely undescribed Wellington River

collections of Harris & Thomas and on additional surveys in the Bolinda-Darraweit Guim region, the Mount Easton Belt and the BonangDelegate region in eastern Victoria. The zonal scheme outlined below differs significantly in concept from that of Thomas (1960) only in the Lal and Ca4 zones of the Lower Ordovician, but in many of the zones of the upper Ordovician. The convention of numbering zones within stages has worked successfully for many years because zone boundaries have proved to be highly homotaxial (see discussion of stages). Although the convention is inflexible and thus inconvenient for revisions such as those of this paper, it is so well established that we retain it here. Zone Lal, Rhabdinopora scitulum and Anisograptus The base of the oldest zone in the Victorian succession is defined by the appearance of


38

A.H.M.

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L Fig. 3. Lancefieldian graptolites. A, Rhabdinopora scitulum, x 1.5. B, Adelograptus delicatulus. 12, A. compactus. D, Psigraptusjacksoni. E, Ctonograptus sp. 1. F, G, Adelograptus victoriae. H, Clonograptua tenellus. I, Teranograptus aft. irregularis, x 1. J, Tetragraptus? bulmani. K, M, Paradelograptus antiquus. L, P. pHtchardi. N, Tetragraptua? decipiens, 4 and 3-stiped forms. O, Tetragraptus acclinans, ×1.5. P, T. appra~imatus, × 1"5. Magnifications x2-5 unless indicated otherwise.

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R. scitulum. It comprises upper and lower parts with completely different assemblages and which could be regarded as distinct zones (Cooper & Stewart, 1979). However, because the assemblage and the number of fossil localities for each part is small, the two parts are here regarded as subzones.


Subzone Lala, R. scitulum and Anisograptus, the lower subzone, is the L a l zone of Thomas (1960) and earlier authors, and contains R. scitulum, Anisograptus compactus and A. delicatulus together with R? enigma. The subzone is known only from two localities at Lancefield (Cooper & Stewart, 1979; VandenBerg, in press) and at Mt Patriarch, New Zealand (Cooper & Wright, unpublished).

Subzone Lalb, Psigraptus, the upper subzone, is the Lal.5 zone of Cooper & Stewart (1979). P.jacksoni together with various indeterminate species of "Clonograptus' and Adelograptus constitute the subzone fauna. The subzone has been found outside its original locality (in Stauro Gully) only at one locality, in Tasmania (Rickards & Stait, 1984). Zone La2, Adelograptus victoriae The zone base is defined by the appearance of

A. victoriae (an abundant form), which is accompanied by Paradelograptus antiquus (also abundant), Temnograptus sp., Tetragraptus decipiens and T. bulmani. Making their appearance higher up are Araneograptus pulchellum, A. macgillivrayi, Temnograptus magnificus and 'Didymograptus' taylori (all confined to the zone), and Paradelograptus pritchardi, Clonograptus flexilis, C. rigidus and C. tenellus. The zone marks the appearance of a diverse anisograptid fauna. Most La2 species are characterized by a particularly wide range ofmorphologic variation. The zone is known from numerous localities in Victoria and New Zealand and the zone fauna has been widely recognized around the world. It is readily recognized by the abundance ofanisograptids and lack of didymograptids.

Zone La3 , Tetragraptus approximatus The zone base is marked by the appearance of the worldwide zone fossil, T. approximatus. The zone marks, to a large extent, the end of


39

the anisograptids as a major element of the fauna; Araneograptus pulchellum, Paradelograptus antiquus, and seven others all make their last appearance. Tetragraptus approximatus and 8 others first appear in the zone. The zone marks the appearance of the first undoubted didymograptinids in the sequence and is widely reeognisable throughout eastern Australia and New Zealand and around the world.

Zone Bel, Pendeograptus fruficosus + Tetragraptus approximatus Base of the zone is marked by the appearance of P. fruticosus and the zone spans the overlap in ranges of this species and T. approximates. It also marks the most spectacular burst of new forms in the entire Australasian Ordovieian succession, making it very easy to detect. No fewer than 47 species make their appearance in the zone, including three of Trochograptus, two of Schizograptus, three of Sigmagraptus, five of Goniograptus, three of Pendeograptus and eight extensiform didymograptids. Fifteen forms are restricted to the zone, and 21 make their last appearance. The large number of multistiped forms is noteworthy. The zone marks the appearance of a diverse dichograptid fauna that dominates the graptolite assemblages of the Bendigonian and Cbewtonian stages. P. fruticosus (4-stiped) is relatively abundant throughout the zone; the species is used widely around the world as a zone fossil.

Zone Be2, Pendeograptus fruticosus (4-st) Base of the zone is defined by the disappearance of T. approximatus. Although this level is not always easily detected, 10 new forms make their appearance, five of which are confined to the zone, making it more readily recognisable. Pendeograptus fruticosus (4-stiped) is abundant. Eleven species make their last appearance.

Zone Be3, Pendeograptus fruticosus (3 + 4st) Base of the zone is def'med by the incoming of the 3-stiped morph ofP. fruticosus and the zone extends through the overlap in range of 3- and 4-stiped morphs of this species. Five species make their first appearance, and five make their last. In practice, this has proved to be the most


40

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A. H. M. VANDENBERG & R. A. COOPER

E

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Fig. 4. Bendigonian graptolites. A, Pel~ograptus fruticosus 4-st. B, P. frulicosus 3-st. C, Pseudophyllograptus angustifolius. D, Didymograptus (semu Into) hemicyclus, x 2.5. E, Pendeograptus pendens. F, Dichograptus maccoyl densus. G, Trichograptus fergusoni, x2.5. H, Etagraptus harti, x2-5. I, Didymograptus (s.I.) eocaduceus, ×2.5. J, D. (Expat~ograptus) iatus. K, D. (F_~pansograptus) elongatus. L, D. (E.) ensjoensis. M, D. (E.) dilatans. N, D. (E.) asperus, x 1, proximal detail x2. O, D. (Corymbograptus) vicinus. P, D. (E.) similis. Q, R, Gordograptus macer, Q x2.5. Magnification x I unless otherwise indicated.



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41

/" j f

Fig. 5. Chewtoniangraptolites. A, Didymograptus (Expansograptus) constrictus, x 1.5. B, Mimograptus mutabili$, × 1. C, Perissograptus trygmaeus, x5 (right). D, Zygograptusjunori. E, Acrograptus gracilis, x 1-5. F, D. (DidymograpteUus) protobifidus. G, D. (19.)bidens. H, Kinnegraptus kinnekullensis, x 3. I, lsograptus prlmulus. J, Tetragraptus sen'a, × 1.5. K, Sigmagraptus praecursor. L, Phyllograptus anna, x 1.5. M, Etagraptus tenuissimus, × I "5. Magnifieatioa×2.5 unless

indicatedotherwise.

easily recognized zone in the Bendigonian.

species appear in the zone, and seven make their last appearance.

Zone Be4, Pendeograptus fruticosus (3-sO

Base of the zone is marked by the disappearance of the 4-stiped morph ofP. fruticosus, an event that is not always easy to detect (Byrne, 1985; Willman, 1988). However, the zone boundaries are marked by distinctive faunal change; six

Zone C h l , Didymograptus (Didymograptel-

lus) protobifidus The zone base is detrmed by the appearance of D. (D.)protobi.fidus, a conspicuous event, and

the species is prominent throughout the zone.

42


Twelve species make their first appearance and 8 make their last. Although the zone is readily recognized and used for mapping in Victoria, it is not separated from the following zone in New Zealand where a single D. protobifidus zone represents a short stratigraphie interval and comprises the entire Chewtonian stage.


Zone Ch2, Isograptus primulus Base of the zone is here defined at the app e a r a n c e o f the e a r l i e s t ' i s o g r a p t i d ' , I. primulus, differing slightly from that of Thomas (1960) and earlier workers, who defined the base as the horizon of disappearance of Pendeograptus fruticosus. Detailed mapping in the Bendigo district (Willman, 1988; Byrne, 1985) has shown that the disappearance of P. fruticosus is difficult to detect as the species becomes rare towards the top of its range. Isograptus primulus is never abundant but it has proved an easier species to use, and was adopted as zonal indicator by VandenBerg (1981a). D. protobifidus populations in New Zealand include forms larger and broader-stiped than in Chl; a population analysis of this species may provide a good quantitative basis for the zone. Five species are conf'med to the zone, 7 make their first appearance, and 18 species make their last. The zone represents the waning of the diverse Bendigonian-Chewtonian dichograptid fauna. It is widely recognized in central Victoria. Zone Ca1, Isograptus victoriae lunatus The zone spans the range of L v. lunatus and is terminated by the appearance of its descendant, L v. victoriae. The zone species is relatively abundant, making the zone easy to recognize, but it marks little other faunal change; only two other species make their first appearance and only three make their last. The L v. lunatus datum is recognized widely around the world. The zone, in Australasia, marks the appearance of the isograptid fauna. Zone Ca2, Isograptus victoriae victoriae The zone spans the range of L v. victoriae, which is relatively abundant allowing the zone to be readily recognized. The only other first appearance is Dichograptus octonarius, also conf'med to Ca2. However, 10 species make their last appearance; most are holdovers from

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the Chewtonian. The L v. victoriae datum is recognized widely around the wodd. Zone Ca3, Isograptus victoriae maximus Base of the zone is defined by the appearance ofL v. maximus which is particularly abundant, and the zone spans the range of this fossil. The L victoriae lineage populations show extreme morphological variability at this and the immediately preceding level, where its two descendant clades, L caduceus and Pseudisograptus originate. The two successive subspecies, victoriae and maximus, are distinguished generally only on the basis of populations as they overlap in morphology (Cooper, 1973). Both are recognized widely around the world. Six species, including the first pseudisograptid, P. hastatus, make their appearance. Zone Ca4, Isograptus victoriae rnaximodivergens This zone is here erected for the distinctive assemblage in the upper part of the Ca3 zone of Thomas (1960) and earlier authors -- it is equivalent to the L v. maximodivergens Zone of Cooper (1979a). Base of the zone is defined by the appearance of the eponymous fossil, which ranges beyond the top of the zone. Twelve forms make their first appearance of which 5 are confined to the zone; 10 make their last appearance. The zone marks the expansion of the isograptid-pseudisograptid complex. Zone Yal, Oncograptus upsilon The zone base is marked by the appearance of Oncograptus upsilon. This species is seldom abundant in collections and no species is confined to the zone, but it is readily recognized by the influx of new forms -- 13 taxa, including many members of the isograptid-pseudisograptid complex, which reaches its greatest diversity. DMymograptus (C.) v-deflexus, a robust Pseudotrigonograptus (= Graptoloid Gen. 1 of Cooper, 1979a) and L v. maximodivergens are particularly prominent. Oncograptus is a usefill correlation fossil in the Pacific (low latitude) province, reported from North and South America, W Ireland, N Siberia, Kazakhstan (Bulman, 1936; Lenz & Jackson, 1986; Tsay, 1974). Note. At Aorangi Mine in New Zealand, Car-


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Fig. 6. Castlcmainian and Yape~nian graptolltes. A, Didymograpu~s (Expansograptus) extensus. 13, D. (~nsu lato) distinctus. C, Pseudotrigonograptus minor. D, Phyllograptus typus. E, [sograptus victoriae l~matu~. F, L v. victoriae. G, L v. maximus. H, L v. marimodivergens. I, Psel~lisograptus dumosus form A. J, R hastams. K, P. gracilis. L, L caduceue australis. M, Oncograptus upsilon. N, Paracardiograpnls sp. O, Cardiograptus morsus (wide form). P, Pseudotrigonosraptus er~iformis. Q, P el. ensiformis, R, Skiagraptt~s gnomonicus. S, L v. divergens. T, L 8ubtili$. U, Pseudisograptus tau. V, P. dumosus B. W, R jiangxiensis. X, R manubruams manubriatus. Y, R m. koi. Z, R m. janua. AA, D. (Corymbograptus) v-deflexus. BB, Apiograptus cnMus. A-L first appear in the Castlemainlan, the remainder in Ih¢ Yapeenian. All x 1-5 except proximal detail of/). distinctus = x3.

44

diograptus and Apiograptus appear, in the lower


ALCHERINGA


part of Slaty Creek, at a horizon apparently below that of the appearance of Oncograptus. However, this apparent inversion is more probably due to undetected structural and stratigraphic complexity in the northern part of the mapped area (Cooper 1979a), where exposure is limited to stream sections; the late Yapeenian to early Darriwilian stratigraphic interval in this area is probably excluded, to the south of Golden Ridge fault, by faulting.

Zone Ya2, Cardiograptus morsus The zone base is defined by the appearance of Cardiograptus morsus. Only three others make their appearance here, including Apiograptus crudus and Paracardiograptus. The latter is so far only recorded from New Zealand - - it is likely to be more common in Australasia, but not yet detected in the indifferently preserved Victorian material. Fifteen species make their last appearance in the zone. The appearance of Apiograptus in the upper part of the zone was used as the basis of a third Yapeenian zone, Ya3 by McLaurin (1976). However, there is no other faunal change marking the zone base and the recognition of a separate zone does not seem warranted. Other, now obsolete, subdivisions of the Yapeenian are summarized by VandenBerg (1981a).

Zone Dal, Undulograptus austrodentatus The zone base is defined by the appearance of U. austrodentatus, which is very common throughout the zone. Six others make their first appearance at this level, including Glossograptus acanthus and Paraglossograptus tentaculatus. Six forms make a last appearance. Undulograptus austrodentatus is a good correlation fossil, with subspecies in Britain, North America and Scandinavia (Bulman, 1963).

Zone Da2, Undulograptus? intersitus The zone base is here defined by the appearance of Undulograptus? inters#us, as opposed to the level where U..? intersitus becomes abundant (Harris, 1935). Harris claimed that U. ? intersitus is uncommon in the basal part of the zone but we know of no single section where this interval is sufficiently well exposed for the fauna to be assessed. Nine other species make their first appearance, of which 4 are confined

to this zone. pearance.

Thirteen make their last ap-

Zone Da3, Pseudoclimacograptus? decoratus The zone base is here def'med by the appearance o f Pseudoclimacograptus? decoratus rather than at the level where P. ? decoratus becomes abundant (Harris, 1935). The robust index species is very abundant in almost all Da.3 collections. The zone contains a most diverse assemblage, and reflects an extraordinary faunal revolution. Twenty-one species make their first appearance; 17 of these, plus an additional 16 longer-ranging species, disappear by the end of the zone making this the greatest extinction event (in numbers of species m Fig. 1B) in the Ordovician.

Zone Da4, Pseudoclimaeograptus (Archiclimacograptus) riddellensis This zone is known from only a handful of localities and therefore still poorly documented. Its base is provisionally def'med by the appearance of the distinctive Pseudoclimacograp-

tus (Archiclimacograptus) riddellensis, apparently coincidental with the appearance of Glyptograptus n. sp. A (wrongly identified in many faunal lists and figures as both G. teretiusculus and G. euglyphus). The zone is equivalent to the G. teretiusculus zone of earlier authors, including Thomas (1960). The zone is here divided into two subzones:

Subzone Da4a, without Dicellograptus and Dicranograptus, marks the appearance of 11 forms, four of which are restricted to it. Seven species make their last appearance.

Subzone Da4b, w i t h Dicellograptus and Dicranograptus, is only recognized in New Zealand; it is defined by the appearance of

Dicellograptus, which comes in with a burst of small forms, including D. of. vagus (Cooper, 1979a). In Victoria, if present, the subzone is most likely to be found in the important Ba67 section on Jackson Creek, where a typical Da4a assemblage is followed in the upper beds with a Gil fauna with Nemagraptus gracilis.

Zone Gil, Nemagraptus gracilis The base of this zone is defined by the entry of

Nemagraptus gracilis -- which is reasonably



ALCHER1NGA

45

g

o

J

T

Q

R

$

¥ r

Z

AA ~~

BS

Fig. 7. Darrlwiliangraptolites. A, 13,Acrograptus cognatus. C, D, Atopograptus woodwardi (C is type of 'D. dubitatus'. E, D. (E.) cuspidatus. F, Holmograptus spinosus. G, Bractu'ograpms etaformis. H, Bergstroemograpw.s crawfordi. I, l~erograptgs paraUelus. J, P. elegans. K, Glossograptus acanthus, ×1. L, Paraglossograpw.s tentaculatus, ×1. M, Kcdpinograptus ovazus. N, Reteograptus speciosus. O, Pseudophyllograptus? nobills. P, Isograptus subtilis. Q, Undulograptus austrodenta2us. R, U. ? intersims. S, Cryptograptus circinus. T, C. sclmeferi. U, DiceUograptus ¢f. vagu~. V,D. (Didymograpms) arcus. W, Pseudoclimacograpms modicellus. X, Glyptograptus n. sp. A.. Y, Z, Pseudoclimacograptus (Archiclimacograptus) riddellensis. AA, 'Amplexograptus' differtus. BB, CC, Pseudoclimacograplus (sensu faro) decorazus, BB with characteristic nematulafium. Magnification x2.5, proximal details at B and D X5, rest as indicated otherwise.

46

A.H.M.

s


ALCHERINGA

VANDENBERG & R. A. COOPER

e

K

I.I

M

Fig. 8. Gisbornian graptolites. A, B, Nemagraptus gracilis, A, x 1, B, juvenile, x2.5. C, Dicellograptus sextana. D, 1:). divaricatus. E, Reteograptus geinitzianus. F, Didymograptus (s.l.) superstes. G, Lasiograptus costatua. H, Glossograptus eiliatus. I, Climacograptus bicomis bicomis. J, C. b. tridentatus. K, Pseudoclimacograptus (lq.) scharenbergt. L, Corynoidea australis. M, Orthograptus calcaratus vulgatus. N, O. c. acuuts. Magnification x2-5 unless otherwise indicated.

Fig. 9. Early Eastonian (Ea I-2) graptolites. A, Ensigraptus caudatus. B, Diplacanthograptus lanceolatus. C, D. spiniferus. D, Climucograptus baragwanathi. E, Cryptograptus eL insect?formis. F, Neurograprus margaritatus. G, Hallograptua bimucronatus. H, Dicranograptus nicholsord. I, D. ramosus spinifer. J, Orthograptus n. sp. A. K, O. q. quadrimucronatua. L, Amplexograptus ingens ingens. M, Dicranograptus hians. N, O. q. cf. cornutus. O, A. tardus. P, Pseudoclimacograptua n. sp. A. Q, Climacograptus? a~O~nis. R, Orthograpms ex gr. amplexicaulis. S, T, O. vuedemannL U, DiceUograptus flexuosus. "%I,D. caduceus. W, Corynoides amedcaruts. X, C. ultimus. Y, Orthograptus pageanus splnosus. All x 2.5.


ALCHERINGA

ORDOVICIAN GRAPTOLITE ZONATION 47

O

I

P

TII

v

48



common throughout its zone. The DarriwilianGisbornian boundary appears to be fully exposed in the Ba67 section on Jackson Creek near Riddell, but has not been investigated in any detail. Thirteen species appearin Gil, ofwhich 4 are confined to the zone. Nine forms, including the last dichograptid, make their last appearance.

ALCHERINGA

tus lanceolatus and Orthograptus ruedemanni are confined to the basal part of the zone. Zone Ea3, Dicranograptus kirki The zone is defined by the appearance of

Dicranograptus ldrki (a direct descendant of D. hians but with a helical rhabdosome) which is common throughout the zone. Leptograptus

The zone base is defined by the appearance of

reappears after a complete absence in the lower Eastonian, and 13 other forms make their ftrst appearance. Five make their last appearance.

the Orthograptus calcaratus group, especially O. c. acutus and O. c. vulgatus. Thirteen other

Zone Ea4, Dicellograptus gravis

Zone Gi2, Orthograptus calcaratus

species make their first appearance including the first Corynoides, and 6 are confined to it. The last species of Glossograptus disappear in this zone, along with 16 other forms including Nemagraptus gracilis Oow in the zone). Just below the top ofGi2, Neurograptus margaritatus, Amplexograptus tardus ( s e n i o r s y n o n y m o f A. praetypicalis Riva) and Climacograptus caudatus m a k e t h e i r appearance. These are part of a varied assemblage that is more characteristic of the lower Eastertian (Eal-Ea2).

Zone Eal, Diplacanthograptus lanceolatus The zone base is defined by the appearance of Eighteen other species appear within the zone, of which 6 are confined to it. Eight forms make their last appearance. The zone is remarkable for the complete absence of any species of Dicellograptus and Leptograpl//s.

Diplacanthograptus lanceolatus.

Zone Ea2, Diplacanthograptus spiniferus Previously called 'Climacograptus baragwanathi Zone' (Thomas, 1960; VandenBerg, 1981a; Cas & VandenBerg, 1988), the zone name is here changed to D. spiniferus Zone, after the characteristic and abundant zone index species, whose appearance defines the zone base (Cas & VandenBerg, 1988). Climacograptus baragwanathi, although confined to Ea2, is rare. Dicellograptus reappears in Ea2 but Leptograptus is still absent. Ten species make their first appearance, of which 6 are conf'med to the zone. Twenty forms, including most of the species characteristic of the early Eastonian, make their last appearance. Diplacanthograp-

The zone base is defined by the appearance of Dicellograptus gravis (senior synonym o f D. alector Carter), a species with very robust stipes and prominently protruding free ventral walls. Four others make their first appearance here and 13 make their last.

Zone Bo l , Climacograptus? uncinatus The zone base is defined by the appearance of Climacograptus? uncinatus, an u n u s u a l climacograptid with septal 'spines' which are formed by the split ends of the nema. Four other forms make their first appearance, including two climacograptids which characterize the 'classic' Bolindian (Bol-Bo3), Euclimacograptus and Appendispinograptus. Pleurograptus linearis simplex appears to be restricted to Be l, but is very rare in Australasia (known from only a single locality). Five taxa make their last appearance.

Zone Be2, unnamed pre-pacificus interval Following the end of the Bol zone fossil, C. uncinatus, and prior to the appearance of Paraorthograptus paeificus which marks the base of the Be3 zone, is an interval (Be2 zone) that is still poorly documented. First appearing in this interval are nine taxa, four of which do not range beyond the zone, including Dicellograptus anceps -- only known, within Australasia, from New South Wales. Six taxa make their last appearance.

Zone Be3, Paraorthograptus pacificus The zone base is defined by the appearance of Paraorthograptus pacificus. The only other species appearing within (and conf'med to) Be3 are Dicellograptus complexus and Orthograptus

ALCHERINGA


fastigatus. The top of Bo3 marks a drastic reduction in diversity of the graptolite fauna with the disappearance of 13 taxa (93 % of the fauna). Thus, of the Bo3 fauna, Normalograptus angustus is the only species that persists into the next zone. Zone Bo4, Normalograptus? extraordinarius The zone base is detrmed by the appearance of Normalograptus ? extraordinarius, although, in a practical sense, it is the wholesale disappearance of the Bo3 fauna that forms the most striking feature of this zone boundary. Zone Bo4 contains a very impoverished assemblage consisting of N. ? extraordinarius, N. angustus and 'Glyptograptus" cf. acceptus -- of which only N. angustus survives into the next zone. Zone Bo5, Normalograptus? persculptus The zone base is defined by the appearance of N. ? persculptus. Again the assemblage is extremely impoverished, consisting only of N. persculptus and N. normalis, together with N. angustus, the sole survivor from Bo4.

Stages Concept and use The Lancefieldian, Bendigonian, Castlemainian and Darriwilian stages were originally proposed (as 'series') by T.S. Hall (1899a). They were refined and revised by Harris (1916) and again by Harris & Keble (1932) who described the faunal characteristics of the stages and their correlation with Great Britain and New York. The Chewtonian and Yapeenian stages were added by Harris & Thomas (1938c) who also revised the whole (Lower Ordovician) sequence. The Harris & Thomas scheme is essentially that used today, with only minor modifications by later workers, as described below. The three Upper Ordovician stages -Gisbornian, Eastonian, Bolindian -- were erected by Thomas & Keble (1933) and Thomas (1935), based on the Gisborne-Sunbury area north of Melbourne, and Mount Easton, 117 km E of Melbourne. Although Hall originally named the stages after specific areas, they have never been tied to type sections. They are, in effect, groupings of graptolite zones, or 'superzones'. Stage


49

boundaries are defined by the first appearance of key species (VandenBerg, 1981a) and thus are, in terms of the International Stratigraphie Guide (Hedberg, 1976), biostratigraphic rather than chronostratigraphic in nature. However, the full sequence of 9 stages has functioned satisfactorily, without ambiguity, in the absence of type sections for over 50 years, both in Victoria and in New Zealand. This may, inpart, be due to the fact that until recently only graptolites were available for correlation and subdivision in the 'graptolite facies' i.e., there has been no other fossil group that might have given alternative correlations. But it is also because the graptolite zones on which they are based have proved to be remarkably good correlation units, the stratigraphic ranges of individual graptolite species being highly accordant in widely scattered localities, both nationally and internationally. The stages have survived, almost unchanged, during halfa century of intensive and detailed use and are considered to be good approximations of ehronostratigraphic units. Confusion about the precise definition and correlation of the stages has therefore not arisen and the need for type sections or boundary stratotypes has never been felt.

Stratotypes For several reasons it now seems desirable to nominate boundary stratotypes for the stage boundaries. Conodonts are now known to be widely present in graptolite-bearing rocks of Victoria (Stewart, in Cas & VandenBerg, 1988) and offer hope of an independent means of correlation. Also, physical (e.g. palaeomagnetic), chemical and event stratigraphy techniques now being used world-wide relate local sequences to global isochronous events, again offering an independent means of correlation. Further, the Victorian stages are increasingly being used for international correlation of Ordovician sequences (Webby et al., 1981; Webby & Nicoll, 1989; Cooper & Lindholm, 1990). Because the stages were established in Vietoria, and because Victoria has the richest graptolite sequence in Australasia, the stratotypes should ideally be based on Victorian sections. Unfortunately, most of central Victoria is deeply weathered and of low relief so that good outcrops are rare. Generally graptolites are confined to thin beds within the thick, rapidly


50


r

ALCHERINGA

"/ O

i

Y

U

X

Fig. 10. Late t~.stoaian (~3-4) (at left, A-I) and l~lindian graptolites. A, Normalograptus tubuliferus tubuliferua. 13, iV. t. nevadensis. 12, O. quadrimucronatus spinigerus. D, Leptograptus eastonensis. E, Dicranograptus kirld. F, Dicellograptus purailus. G, D. elegans. H, I, D. gravis. J, Climacograptus uncinatus. K, 1). ornatus. L, DiceUograptus n. ~p. el. 1). minor. M, Normalograptus angustus. N, Orthograptus thorsteinssoni. O, Euclimacograptua hastatua. P, O. pul¢herrimua. Q, Amplexograptus latus. R, Appendispinograptus longispimts. S, A. supernus. T, Orthoretiograptua dew ticulatus. U, V, Normalograptus? extraordinarius. W, X, IV. ? persculptus. Y, Paraorthograptus pacificus. All × 2"5.


ALCHERINGA

deposited turbidites and the whole sequence is tightly folded and disrupted by numerous faults. Stratigraphie sections spanning the boundaries separating the six Lower Ordovician stages are rare. The three Upper Ordovician stages on the other hand, are represented by black shale sequences in the higher relief region of eastern Victoria, and outcrops and sections are more common. However, the detailed section measuring and collecting has yet to be done. We are able to nominate a stratotype for the lower boundary of only the Lancefieldian stage, but reference sections are nominated for all stages. We hope that future work on the documentation of these sections will enable the designation of boundary stratotypes for all stages.

Lancefieldian

ORDOVICIAN GRAPTOLITE ZONAl'ION

51

ticularly fossiliferous at the site of a disused quarry (Lancefield Quarry, PLl144) near Lancefield (Hall, 1899a; Erdtmann & VandenBerg, 1985).

Faunal characteristics. The fauna of Lal and La2 is dominated by anisograptids, particularly

Rhabdinopora, Anisograptus, Adelograptus, Paradelograptus, Clonograptus, Temnograptus and Araneograptus (Figs 2, 3). The La3 zone marks the appearance of the first dichograptids, one of which is the world-wide zone fossil, Tetragraptus approximatus. This coincides with a waning of the anisograptus fauna. The conodonts Cordylodus proavus and C. intermedius occur in Lancefieldian ribbon cherts in a fault melange in eastern Victoria, and C. intermedius also occurs at Lancefield in the Bryo Gully Shale.

Definition. The stage extends from the first appearance of Rhabdinopora scitulum in the

Bendigonian

boundary stratotype up to the base of the Bendigonian. The name was introduced by Hall (1899a) for graptolite-bearing shales at Lancefield. Subsequent revisions or important descriptions are by Harris & Keble (1932), Harris & Thomas (1938c), Thomas (1960), Cooper & Stewart, 1979), VandenBerg (1981 a) and Erdtmann & VandenBerg (1985).

Definition. The stage extends from the first appearance of Pendeograptus fruticosus to the

Lower boundary stratotype (designated herein). Stauro Gully, Romsey, 532 m (479 m in straight line) upstream from its junction with Deep Creek, AMG 0460-6638, i.e. at the lower boundary of the Lal zone (Cooper & Stewart, 1979) in the Stauro Gully Shale (VandenBerg, in press).

Reference section. The lower boundary of the stage is exposed in Bryo Gully, 800 m NW of the same horizon in Stauro Gully. In these two gullies the stage is represented by Stauro Gully Shale, Split Hill Sandstone, Bryo Gully Shale and Angry Hill Sandstone, containing graptolites of Lal, La2 and La3 zone age. The upper part of the stage (La2-La3) is exposed at Aorangi Mine, in Anthill Creek from locality M25/f6712 (GR 62655515) up to locality M25/f6590 (GR 62735515) at the base of the Bendigonian (Cooper, 1979a), and at Cape Providence and Chalky Inlet coastal sections of Fiordland (Benson & Keble, 1935). It is par-

base of the Chewtonian. The name was introduced by Hall (1899a) for the graptolite-bearing slates, shales and sandstones of the Bendigo goldfield. Subsequent revision, redefinition, or important descriptions are given in Harris & Keble (1932), Harris & Thomas (1938e) and VandenBerg (1981a). No stratotype has yet been designated for the lower boundary.

Reference sections. The best sections across the lower boundary, outside Victoria, are exposed in Anthill Creek, Aorangi Mine, where it is placed at the first appearance ofP. fruticosus at locality M25/f6580 (GR 62755515) (Cooper, 1979a), and at Cape Providence, Fiordland, where it is placed at the same fossil horizon at locality 6 ofBenson & Keble (1935). The stage is well exposed in cuttings in the ChewtonCastlemaine railway near Chewton (Harris, 1916; C. Willman, pets comm.), and in numerous mine shafts and exposures in the Bendigo goldfield (Harris & Keble, 1932; Willman, 1988). It is widely distributed in central Victoria and has been recognized in sequences around the world (e.g. Lenz & Jackson, 1986).

Faunal characteristics. The graptolite faunas of the Be 1-Be4 zones represent the rapid diver-

52


sification of the dichograptid fauna, Bel containing the greatest diversity reached by any Australasian zone (Fig. 1B). Pendeograptus fruticosus is the characteristic species throughout the stage. Clonograptids are common in the lower beds, and other multistiped forms such as


Schizograptus, Loganograptus, Goniograptus, Dichograptus and Sigmagraptus are common throughout (Fig. 4). Reclined tetragraptids, particularly T. serra and T. bigsbyi, Phyllograptus angustifolius and extensiform didymograptids are also common. Stewart (in Cas & VandenBerg, 1988) noted that there is an important association of the conodonts Paraois-

todus proteus, Oepikodus communis, Prioniodus elegans and Paracordylodus gracilis with Bel graptolites at Dargo. Higher up, in Be3, this is replaced by an association of Oepik-

odus evae, Bergstroemognathus extensus, Protoprioniodus aranda and Scolopodus rex. Chewtonian Definition.

The stage extends from the appearance of Didymograptus protobifidus to the base of the Castlemainian. The name was introduced by Harris & Thomas (1938c) for rocks of the Chewton district and the stage has since been redefined by VandenBerg (1981a). No stratotype has yet been designated for the lower boundary.

Reference section. The lower boundary, and the stage itself, is best exposed in stream sections at Aorangi Mine (Cooper, 1979a) where it is placed at the appearance ofD. protobifidus; in Anthill Creek, at locality M25/f6564 (GR 62785515), in Bottle Creek at locality M25/f6606 (GR 62695498), in Sandhills Creek, North Branch, at locality M25/f6625 (GR 62895339), and on the North shore of Coal Island, Preservation Inlet, at locality 32 of Benson & Keble (1935). The stage is well exposed in railway cuttings at Castlemaine, on the Chewton-Castlemaine line (Harris, 1916), and at Devilbend Quarry, Mornington Peninsula (VandenBerg & Stewart, 1983).

Faunal characteristics. The graptolite fauna of the Chl-Ch2 zones represents the waning of the diverse dichograptid fauna of the Bendigonian. Reclined tetragraptids, Phyllograptus

ilicifolius, Pseudophyllograptus angustifolius

ALCHERINGA

and extensiform didymograptids are common (Fig. 5). D. protobifutus is very common throughout, passing, in the youngest beds, into forms transitional to D. bifidus.

Castlemainian Definition.

The stage extends from the appearance of L v. lunatus to the base of the Yapeenian. The name was introduced by T.S. Hall (1899a) for the graptolite-bearing beds at Castlemaine, and has since been revised or redescribed by Harris (1916), Harris & Keble (1932), Harris & Thomas (1938c) and VandenBerg (1981 a). No stratotype has yet been designated for the lower boundary.

Reference sections. The lower boundary is best exposed in Bottle Creek at Aorangi Mine, locality M25/f6603 (GR 62715498), and in Sandhills Creek at locality M25/f6755 (GR 62895339). The stage is also well exposed in railway cuttings on the Chewton-Castlemaine line (Harris, 1916) and at numerous localities in the Castlemaine and Bendigo districts.

Faunal characteristics.

Isograptids dominate most assemblages. The first members of the isograptid complex appear at the base (Cal-Ca2 zones) of the stage and the complex begins to diversify at the top (Ca3-4 zones) (Fig. 6). The appearance of Pseudotrigonograptus, represented by P. minor, is a conspicuous event in Ca2. Goniograptus macer, tetragraptids (particularly reclined forms), Dichograptus (octonarius, octobrachiatus) are prominent, especially in the upper part of the stage and phyllograptids (P. typus, P. anna) are prominent in the lower part.

Yapeenian Definition.

The stage extends from the appearance of Oncograptus to the base of the Darriwilian. The name was introduced by Harris & Thomas (1938c), and derived from Yapeen, SW of Castlemaine, where 'Oncograptus and Cardiograptus beds are well developed'. The stage is further described by McLaurin (I976) and VandenBerg (198Ia). A lower boundary stratotype has not yet been designated.

ALCHERINGA

Reference section. The stage is well exposed in


railway cuttings and outcrops west of Castlemaine (Harris, 1916; C. Willman, pers. comm.) and in Slaty Creek, Jimmy Creek, and Sandhills Creek in the Aorangi Mine area where, however, it is largely represented by quartz sandstone and graptolites are confined to a few thin shale bands.


The Yapeenian graptolite fauna represents the maximum diversity reached by the isograptid fauna. Species of the lineages of Isograptus victoriae (particularly

L v. maximodivergens), L caduceus (L c. australis) and Pseudisograptus (P. manubriatus subspecies, P. dumosus form B, P. fianxiensis) dominate Yapeenian assemblages (Fig. 6). Oncograptus is seldom abundant, but ranges through and beyond the stage; Cardiograptus and Apiograptus appear in the upper part (Ya2). Large reclined tetragraptids (T. aff. serra), Didymograptus v-deflexus, Goniograptus speciosus and Pseudotrigonograptus ensiformis are the most common forms that are not part of the complex.

Darriwilian Definition. The stage extends from the first appearance of Undulograptus austrodentatus to the base of the Gisbornian. It was one of Hall's original 'series' (Hall, 1899a), based on what later became the Da3 zone. The concept of the Darriwil has undergone several changes, reviewed by VandenBerg (1981a), the main revisors being Harris (1916, 1935), Harris & Keble (1932) and Harris & Thomas (1938c) who proposed abandoning the name in favour of Middle Ordovician. However, the retention of the name by Victorian geologists was eventually acknowledged by Thomas (1960), and has been used since. No stratotype has yet been designated for the lower boundary.

Reference sections. The Darriwilian in Victoria is dominated by soft siltstone and shale which weather easily. Its most extensive outcrop area east of the Whitelaw Fault near Bendigo is thus one of very low relief, with fossil localities largely conf'med to small, often ephemeral exposures. No section across the lower boundary has yet been located, although sections in the Lerderderg River Gorge hold some promise


53

(R.A. Cas, pers. comm.). No continuous section spanning Da3 and Da4 exists in the Bendigo-Ballarat Zone, and the known Da4 localities within the Melbourne Trough do not extend down into Da3. A single possible exception occurs at the head of Eight Mile Creek in the Howqua River (see below), where Da2, Da4 and Gi 1 fossils have been located in a small area. There are few Darriwilian localities east of the Bendigo-Ballarat Zone. Isolated Da3 and Da4 localities occur in the Mount Easton Shale along the Mount Wellington Fault Zone and on Mornington Peninsula. In eastern Victoria, Da3 graptolites occur with conodonts (Periodon aculeatus, Polonodus sp., Spinodus spinatus, 'Cordylodus' horridus) at Tabberabbera (Stewart, in Cas & VandenBerg, 1988). The pre-Da3 rocks of eastern Victoria consist of turbidites without black shale, and there are no known pre-Da3 Darriwilian graptolite localities. A section extending from Dal to Gisbornian is well exposed in Slaty Creek and its eastern tributary, in the Aorangi Mine district of New Zealand (Cooper, 1979a), and in the main ridge south of Chaffey Creek, on the south side of Cobb Valley (Da3-Gil, Cooper, unpublished). Contact between the Yapeenian and Darriwil stages is complicated by the Comas Creek shear zone at Aorangi Mine, and by the Fenella fault zone in Cobb Valley.

Faunal characteristics. The Darriwilian marks the incoming of diplograptids in Australasia; U.

austrodentatus is abundant in the lower (DalDa2) part, and large diplograptids, particularly

PseudocIimacograptus decoratus, P. riddellensis and Glyptograptus n. sp. A, in the upper (Da3-Da4) part (Fig. 7). It also encompasses the full range of the distinctive Glossograptus acanthus (replaced by G. ciliatus in Da4) and Cryptograptus schaeferi (replaced by C. tricornis in Da4). Dichograptids, after their late burst in the Da3 zone, are reduced to a minor element of the fauna. The Da3 zone is quite remarkable; it has the highest diversity (39 taxa) of any zone after the Chewtonian, the second highest number of zonally restricted taxa (17), and marks the greatest extermination event (33 taxa) of any zone. Of the few species that remain, most do

54


not extend beyond the top of the Darriwilian. Many new genera and unusual species make a brief appearance: Pseudobryograptus,


Brachiograptus , Pterograptus , Trichograptus (?= Thamnograptus), Atopograptus, together with the sinograptids -- Holmograptus and Nicholsonograptus, the isograptid Bergstroemograptus, the glossograptid Kalpinograptus? and the abrograptid, Reteograptus (Fig. 7). This is also the highest level at which phyllocarid crustacea are abundant. By the end of Darriwilian time, total zonal diversity has been reduced to just 18 species, the lowest level since the Lancefieldian.

Gisbornian Definition.

The stage extends from the first appearance of Nemagraptus gracilis to the base of the Eastonian. The name was introduced by Thomas & Keble (1933), from the township of Gisborne 48 km NW of Melbourne, and based on localities near Gisborne and north of Sunbury. Thomas (1935) proposed the first zonal subdivision, and subsequent revision, redefinition or important descriptions are by Harris & Thomas (1938c), Thomas (1960), VandenBerg (1981a) and Cas & VandenBerg (1988). No stratotype has yet been designated for the lower boundary.

Reference sections. The best Victorian section across the lower boundary is exposed at the old GSV loc. Ba67 at the junction of Riddells Creek and Jackson Creek (AMG 9742-4892), in very soft weathered coarse-grained siltstone. The graptolites, however, are generally poorly preserved. A possibly incomplete boundary section is exposed at the head of Eight Mile Creek on the Howqua-Jamieson Divide, 38 km SE of Mansfield (see map in Harris & Thomas, 1938b). The Wellington River section is complicated by faulting but the Gisbornian fossils are better preserved. In eastern Victoria, the Gisbornian spans the boundary between the cherty Sunlight Creek Formation and the black Warbisco Shale. In New Zealand, the lower boundary is exposed in the main ridge south of Chaffey Creek, on the S side of Cobb Valley (Cooper, unpublished) and on the N side of Cobb Valley (Skwarko, 1962); preservation of the fossils, however, is generally poor.

ALCHERINGA

Faunal characteristics. The Gisbornian is characterized by the presence of Nemagraptus gracilis, Dicellograptus sextans, D. divaricatus and D. intortus, and especially Climacograptus bicornis bicornis, which is extremely abundant in the upper part (Fig. 8). Glossograptus ciliatus is also present and easily reeognisable. The distinctive large platform element of the conodont Pygodus anserinus is quite commonly found pyritized in the siliceous lower Gisbornian.

Eastonian Definition.

The stage extends from the first appearance of Diplacanthograptus lanceolatus up to the base of the Bolindian. The name was introduced by Thomas & Keble (1933), and based principally on the faunas from Mount Easton identified and partly described by Keble & Harris (1925). A two-zone subdivision was proposed by Thomas (1935), but this was extensively revised by VandenBerg (1981a) who established the subdivision used here. The very diverse early Eastonian assemblage of Enoch's Point was partly illustrated by VandenBerg & Stewart (1983), and other important species were illustrated in Cas & VandenBerg (1988).

Reference sections. The lower boundary of the stage is best exposed in a low roadside cutting at Concordia Gully, a tributary of MeLauchlans Creek, 17 km west of Delegate in eastern Victoria (AMG Bendoc 5503-9981). Here, the appearance of Diplacanthograptus lanceolatus a few metres above the disappearance of Climacograptus bicornis bicornis has been documented in a closely sampled interval by VandenBerg (1986). Higher in this section the Eastonian is disrupted by faulting along a major fault zone, but a complete Eastonian section is exposed in the same region in the type section of Warbisco Shale in Mountain Creek, 39 km WSW of Delegate (AMG Bendoc 3435-8682 to 3480-8750) (VandenBerg, 1981b). The Eastonian section consists almost entirely of siliceous black shale and is several hundred metres thick. Large-scale thrusting within the Warbisco Shale has introduced a great deal of structural complexity, but the Eastonian grap-tolite succession is reasonably well sampled with over 100 Eastonian graptolite localities spread over all zones.


ALCHERINGA


55

An excellent Eastonian section occurs in the Mount Easton Shale northeast of Melbourne. The two best-known successions are one at Enoch's Point, in bleached shale extending from Eal to Ea4 but not beyond the stage limits (see VandenBerg & Stewart, 1983 for the Eal-Ea2 portion), and the other at Wellington RiverDolodrook River, where the entire stage is represented in fresh black shale, albeit with fault disruptions. Abriefaccount of this section is given in Harris & Thomas (1954). In southeastern New South Wales, Zones Ea2-Ea4 are well represented in the/errawa beds of the Bungonia area, and in equivalent age black shale in the Cooma region.

lower zone of Pleurograptus linearis, and a n upper zone of Dicellograptus el. complanatus (Harris & Thomas, 1938c; Thomas, 1960). Neither is satisfactory: Pleurograptus is far too rare to be of use as zone index fossil, makes its first appearance much lower than was thought and has a long range (from Ea3 to Be3), and the 'D. cf. complanatus Zone' was based on several misidentified forms, partly Eastonian, partly Bolindian. VandenBerg (1981a) substituted two new zones, but since then the Bolindiaa has been much extended due to redefinition of the Ordovician-Silurian boundary (Cocks, 1985). The present concept of the Bolindian has been summarized in Cas & VandenBerg (1988).


Reference section.

The Eastonian is dominated by diplograptids (Figs 9, 10). It encompasses the full range of the D. spiniferus group. The lower and upper Eastonian assemblages are quite different: the lower (Eal and Ea2) typically consists of Dicranograptus

nicholsoni, D. hians, D. ramosus spinifer, Neurograptus margaritatus and Climacograptus caudatus (Fig. 9), all of which are quite common throughout this interval, and all of which are absent from the upper Eastonian. Amplexograptus tardus is often very abundant and Climacograptus ? affinis is also common. The two respective zone index species are common throughout their zones. The upper Eastonian, Ea3 and Ea4 (Fig. 10), typically contains abundant Normalograptus tubuliferus and Orthograptus quadrimucronatus (and O. q. spinigerus). The Ea3 index D. kirki is common throughout its zone. Dicellograptus gravis, the Ea4 index, is not common but is present in most Ea4 collections.

Bolindian Definition.

The stage extends from the appearance of Climacograptus uncinatus, to the base of the Silurian System. The name was introduced by Thomas & Keble (1933), for the sequence exposed in the parish of Bollinda north of Melbourne. Until recently, the Bolindian has remained the least well known of the Victorian stages - - the older part, on which the stage was initially based, is very poorly exposed, and the fauna of the much better exposed upper portion (Belinda Shale) has never been documented. The original concept involved two zones: a

No single section incorporating the entire Bolindian exists in Victoria. The lower part (Bol to Be3) is best represented in the Warbisco Shale of eastern Victoria, especially in its type section where the EastonianBolindian boundary has been located in a continuous outcrop section that extends into Be3 (VandenBerg, 1981b). The upper Bolindian zones Be4 and Be5 are only known from the Darraweit Guim area northwest of Melbourne, where they are continuous with Be3 (VandenBerg et al., 1984). At Wellington River, Bol and Be3 occur but only along faults; similarly Be3 occurs in a fault zone in Mount Easton Shale at Mount Matloek, and in isolated localities at Abbeyard and near Walwa.

Faunal characteristics. The Bolindian consists of two entirely contrasting portions: a lower portion e n c o m p a s s i n g B o l - B o 3 with a reasonably diverse fauna, and an upper portion (Bo4-Bo5) with an extremely impoverished fauna (Fig. 10). The lower fauna contains the last of the Ordovician diplograptids (i.e. families Orthograptidae and Diplograptidae of Mitchell, 1987), and is characterized by Appen-

dispinograptus and Euclimacograptus, both occurring

in a b u n d a n c e ,

together

with

Dicellograptus ornatus and a suite of other species. The zone fossils of each of the zones are not present at all levels but no doubt this must be due, at least in part, to the very high sedimentation rate (the Belinda Shale, entirely within Be3, is fully 400 m thick! - - at Dob's Linn, the same interval is covered by between 2 and 4.5 m; Williams, 1982b). In the upper two zones, graptolites are extremely rare and

56


even when found, the assemblage only consists of two or three species of Normalograptus. This paucity clearly reflects the world wide crisis in graptolite diversity, and the end Ordovician mass extinction (Skevington, 1974; Brenchley, 1984).


World correlation of stages International correlation of the Australasian sequence is shown in Fig. 11. Correlation of the Early Ordovician has been discussed in detail by Cooper & Lindholm (1990) and is not considered further here. The following comments apply to correlation of the Late Ordovician. The appearance of Nemagraptus gracilis at the base of the Upper Ordovician is one of the best correlation tools at this level -- it marks the base of the N. gracilis Zone which is recognized around the world. Above this datum, there is increased provincialism up to the Paraorthograptus pacificus Zone, from which level most species are once again globally distributed.

Britain The Scottish sequence has graptolites extending down to at least as low as the N. gracilis Zone (Williams et al., 1972), but only the Hartfell Shale has been documented, and this only extends down into the upper Dicranograptus clingani Zone. Above the N. gracilis Zone is the Climacograptus wiIsoni Zone which contains Climacograptus bicornis and therefore correlates (at least approximately) with Gi2. The D. clingani Zone has several species in common with the early Eastonian (Corynoides

calicularis, Neurograptus margaritatus, Dicranograptus ramosus, Dicellograptus flexuosus). The (rather misnamed) Pleurograptus linearis Zone has a few species in common with Ea3: P. linearis, Leptograptus capillaris, Dicellograptus elegans, Normalograptus tubuliferus, and Orthograptus quadrimucronatus spinigerus; other species of the P. linearis Zone such as D. pumilus and D. morrisi do not appear, in Victoria, until Ea4. The Dicellograptus complanatus Zone contains Dicellograptus gravis (figured under its junior s y n o n y m D. alector in Williams, 1987), D. minor and Orthograptus pulcherrimus -sufficient to provide precise correlation with

ALCHERINGA

Ea4 (Williams, 1987). There appears to be no correlative of Bol in Scotland, and the succeeding DiceUograptus anceps Zone correlates with Be2 and Be3. Be2 probably correlates with the Dicellograptus complexus Subzone (Williams, 1982b) although D. complexus has not yet been found in Be2. Be3 certainly correlates with the P. pacificus Subzone -- they have almost identical assemblages (Williams, 1982b). The two upper Bolindian zones are recognized by the same criteria as their respective correlates in Scotland (williams, 1986). In Wales and Shropshire, which occupied an Ordovician high latitude position (Cocks & Fortey, 1982), the Diplograptus multidens Zone contains Gi2 species such as Dicranograptus

ramosus spinifer, Climacograptus bicornis and Orthograptus calcaratus and is eorrelated accordingly.

Scandinavia Correlation with the Upper Ordovician of Scandinavia is difficult due to the largely endemic Scandinavian assemblages, and the scarcity of modern taxonomic studies. Whilst early authors (e.g. Hadding, 1915) used local zone fossils, modem workers use the British zonation so that correlation is done indirectly, by reference to Scotland. Furthermore, there is a dearth of taxonomic information in the Scandinavian literature. Few authors provide identifications, most preferring to identify only the zone to which an assemblage might belong.

North America: St Lawrence Lowlands Riva (1969, 1974a) has provided large faunal lists for the entire Upper Ordovieian. The N. gracilis Zone is recognized by the same criterion as that in Victoria, but contains a much more d i v e r s e fauna. The s u c c e e d i n g Diplograptus multidens Zone correlates with the upper part of Gi2 only: the Gi2 index O. calcaratus makes its appearance in America below the base of the D. multidens Zone. The succeeding Corynoides americanus Zone correlates reasonably precisely with Eal, judging from the Enoch's Point sequence (VandenBerg & Stewart, 1983). The Orthograptus ruedemanni Zone cannot be recognized as such in Victoria because O. ruedemanni is very rare. Its range at Enoch's Point extends from the

ALCHERINGA

ORDOVICIAN GRAPTOLITE

uppermost E a l into b a s a l E a 2 . The North A m e r i c a n 'C.' spiniferus Z o n e is t h e r e f o r e +

+

.I

II II -,4

I~

o ~


2__+

1 x

1

'

1

Ii.~ I

"~'~ I ~~,i ~: ' , °°'"~,~

',° i

A

II

~0 .o'0

~

,

o

~o ~'O OO

.p

0 ~ ,.-i

.9.

mu 0 II

I • I

i

~',

p r o b a b l y n o t p r e c i s e l y e q u i v a l e n t to t h e E a 2

D. sptniferus Z o n e , a l t h o u g h b o t h a r e d e f i n e d

0

'~:

•

~i°,,

i

~.~~

~

~

~.2 ~

~

u

o~

~,

,

o

,.'.

~,~

~.~

,1= I

,,

- - +

~

r

|

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y ~ ~ ~ .~= g ~

.~ ', "~ ~,,

,~ ~, ~

~ '~',

i

i

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~.~ ol I

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57

I

H..4

o

ZONATION

"~

I

t

8 1 I

I

-7. -,4

~ -,.,I

.! ,,..;

x

I

"

~ • ', .! ~,~ ,, o ..',~ ~.',

~, .~ ~ ,~

g

÷

~ "

,

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?

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i

i

s

+ - - +

)

.---+

I i

I I e

Fig. 11. Correlation of Australasian zones with other important Ordovician graptolite se.quences. Sources for ]Early Ordovician columns and correlations are given in Cooper & Lindholm (1990). Additional sources for the Later Ordovician ate: Texas column from Berry (1960), Finney (1982); NE North America from Riva (1974a, 1988); NW Canada column from Lenz (1977, 1988), Lenz & McCracken (1982), Ler~ & Chen (1985) and Lenz & Jackson, 1986; Scandinavia and E. Baltic column from Jaanusson (1982); Central China column from Mu (1974) and Wang (I 980); Britain column from Rushton, 1982; Williams, 1982a,b, 1987. Note that the Britain column is a composite of the Welsh (Atlantic Province) and Scottish (Pacific Province) columns.

58


by the appearance of Diplacanthograpms

spiniferus.


The interval above the 'C.' spiniferus Zone in North America contains faunas of low diversity and with mostly endemic zone indices, and is therefore difficult to correlate. The 'C. 'pygmaeus Zone may broadly correlate with Ea3: it has a few species in common, although all are long-ranging: Pleurograptus linearis, Or-

thograptus amplexicaulis and O. quadrimucronatus. The Climacograptus manitoulinensis Zone contains no species that can be used for correlation with Victoria, but the succeeding D. complanatus Zone probably correlates with Ea4 assuming that it correlates with the Scottish D. complanatus Zone. The Climacograptus prominens-elongatus Zone of Riva (1974a) was renamed Amplexograptus inuiti Zone by Riva (in Rickards & Riva, 1981). All three name-givers are here considered to belong to Amplexograptus latus (see also Riva, 1987, 1988). However A. latus in Victoria has a long range, from Bol to Bo3. There are no other species in the '.4. inuiti Zone' that afford more precise correlation. The highest zone in northeastern America is the Normalograptus persculptus Zone, recognized, as in Victoria, by the presence of its name-giver. -

-

Central North America Correlation with the sequence of central North America has been facilitated considerably by the publication of excellent figures by Finney (1986). The N. gracilis and C. bicornis subzones of Finney correlate with the lower part of Gil, and uppermost Gil plus Gi2, respectively. The succeeding O. amplexicaulis Zone (sensu Firmey, 1986) correlates with both Eal and Ea2: it contains such typical early Eastonian forms as Diplacanthograptus (figured as Climacograptus spiniferus, although all are tiny specimens that could equally belong to D. lan-

ceolatus), Corynoides americanus, C. ultimus (Finney, 1986 figs 8A, 9I), Dicranograptus hians (figured as D. clingani in Finney, 1986), Amplexograptus ingens (figured as A. aff. A. maxwelli, Finney, 1986 fig. 3C), Climacograptus caudatus and Neurograptus marFig. 12. Rangechart of Australasiangraptolites.

ALCHERINGA

garitatus. The succeeding Climacograptus tubuliferus Zone correlates with the upper Eastonian (Ea3 plus Ea4), on the basis of Normalograptus tubuliferus and Dicellograptus elegans. Canadian Cordillera and northwestern USA Lenz and co-workers have gradually refined the Ordovician zonation in northwestern Canada (summarized in Lenz, 1988), and Carter (1989) has recently described part of the sequence in Washington, USA. The Cordilleran G/yptograptus euglyphus Zone contains Pseudo-

climacograptus riddellensis, Glossograptus ciliatus and Reteograptus geinitzianus and clearly correlates with Da4. The same applies to the (misnamed) D. ? decoratus Zone of Washington (Carter, 1989), whose assemblage is identical with that of Da4. The N. gracilis Zone and C. bicornis Zone span the Gisbornian -- the base of the C. bicornis Zone is well below the base of Gi2. It seems that there is a complete absence of early Eastonian (Ea 1-Ea2) elements in the Cordilleran sequence. The fauna o f the Dicranograptus clingant?. Zone is virtually identical with that of the C. bicornis Zone below, and lacks any of the diplograptines and corynoidids that permit fine subdivision of the late Gisbornian and early Eastonian. Specimens identified as D. clingam9. (I..enz & Chen, 1985, pl. 2 figs 21, 22) probably do not belong to D. clingani, so that correlation with the Scottish D. cIingani Zone is also doubtful. Most likely, the D. clingam~. Zone correlates, at least in part, with the upper Gisbornian. The presence of Orthograptus quadrimucronatus (figured as O. pageanus abnormispinosus in Lenz & Chen, 1985, pl. 3 fig. 27) however suggests that the D. clingam~ Zone may extend well into the Eastonian. This is further supported by the fauna of the succeeding O. quadrimucronatus Zone, which contains typically Ea3 elements such as Pleurograptus, Dicel-

lograptus elegans, Climacograptus tubuliferus and Orthograptus pulcherrimus. Early Eastonian (Ea2) species are well represented however in the C. spiniferus Zone in Washington, from which Carter (1989) has

ALCHERINGA

?


RANGE CHART OF AUSTRALASIAN GRAPTOLITES = range def'mite; note that tiffs indicates presence in zone, not range within zone = specific identification doubtful; * = zone uncertain (WA and N T occurrences)

LOWER


Z*Ali'CS]*ZI~JD

ANISOGRAPTIDAE

Adelograptus victoriae Anisograptus compactll,s delicatulus Araneograptus macgillivrayi pulcheUus Clonograptus fle:dlis kingi pervelatus persistens ramulosu$ rarus rigidu~ smithi tenellus tenellus problematicus timidus trochograptoides sp.l sp. 2 sp. 3

Kiaerograptus sp. Paradelograptus

I.

anfiqul~ pritchardi Psigraptus jacksoni Rhabdinopora enigma scitulum DICHOGRAPTIDAE

Dichograptus expansus changshanensis

maccoyi maccoyi maccoyi densus norvegicus octobrachiatus octonarius solidus Didymograptus (Corymbograptus) mundus vicinus v-deflexus Didymograptus (Didymograptus) artus stabilis stavu3

.

• .

I

° °

ORD B]WDZG~I'.

~ .

OVI

CJUJ~WJkZI~.

C IAN Y / ~ I[1~

~_m_°_l"llZZ,ZAII

59

60

A.H.M.


ALCHERINGA

L O W E R LAMC~FZ ELD


la *

lb *

2 •

O R D 0 V I C I A N

BZNDZGON.

3 t

1 t

2 *

3 *

~iJJL]mQ~N.

~ .

4 *

1 *

2 *

"

"

1 *

2 t

3 *

3[~Pu'I~J

4 ff

1 t

2 *

"

"

UPPER

DARRII~I~ 1 *

2 *

3 *

4s *

GIJB. 4]0 t

1 *

Didymograptus (Didymograptus) bidens bifidus protobifidus Didymograptus (Expansograptus) abnormis acriculus adamantinus asperus al~reus balticus constrictus cu~pidatus dilatans ellesae elongatus ensjoensis latu$ latus aequalis nicholsoni nitidus perditus procumbens similis cf suecicus suecicus robustus validus communis Didymograptus sensu lato bartrumi distinctus eocaduceus hemicyclus superstes taylori Loganograptus logani logani logani pertenuis rectus Mimograptus mutabilis Orthodichograptus robbinsi Pendeograptus cra$su~

dependulus fruticosus 2-st fruticosus 3-st fruticosus 4-st pendens cf pendens Pseudobryograptus incertus parallelus Pseudophyllograptus angustifolius angust, elongatus nobilis

.

.

.

.

I

.

.

.

.

I

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.

.

.

.

|

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.

.

.

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2 *


ALCHERINGA

LOWER

O R D O V I C I A N

.T~IrZlLTaD

ls *

lb ,

2 *

B]OIDZOON.

$ *

1 *

2 #

3 *

{ ~ .

4 *

YAIPII~

~73B~ZN.

1 *

2 *

1 *

2 *

3 *

4 t

1 *

2 t

I

"

*

t

"

i~lULVl~ld~ll 1 *

2 t

3 *

"

°

"

Temnograptus (Teranograptus)


rnagnCicus regutaris Teranograptus (Schizograptus) incompositus spectabilis

waddickorum Temnograptus (Trochograptus) australis

diffusus indignus Tetragraptus (Tetragraptus) acclinans amii approximatus bigsbyi headi reclinatus Serrd

of. serra Tetragraptus sensu lato bulmani decipiens 4-st decipiens 3-st decipiens bipatens insuetus otagoensis quadribrachiatus taraxacum Triaenograptus neglectus Zygograptus abnormis ferrarius junori

.

.

.

.

I

.

.

.

.

t

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°

|

.

.

.

.

.

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.

.

.

I

.

.

.

.

I

°

°

!

.

.

I

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.

.

.

.

SIGMAGRAPTIDAE

Acrograptus gracilis cognatus compressus Brachiograptus etaformis Etagraptus harti tenuissimus triograptoides Goniograptus alternans macer sculptus speciosus thureaui thureaui clonograptoides thureaui inaequalis tumidus velatus

°

"

- - I

]

4a *

4b *

61

62


ALCHERINGA

L O W E R mnmZGCU.


1 *

2 *

3 *

•

°

0 R D 0 V

C~'yr/.

4 *

r.AJZ,llmt..~l.

1 t

2 t

1 t

l

"

•

I

.

t

-

°

i

•

2 *

3 *

I C I A N

YJtJ, l U ~

4, *

1 ,

2 *

"

*

DJULLIl~LZAg

1 #

2 *

3 *

*

" - -

Kinne graptus chapmani kinnekullensis Laxograptus irregularis

shell: Pterograptus elegans Pterograptu$? sp. nov.

Sigmagraptus crinitus

praecursor yandoitensis Trichograptus fergusoni immotus New genuW sedecimus whitelawi

D

SINOGRAPTIDAE Cymatograpt~ sp. Holmograptus spinosus Nicholsonograptus fasciculatus

t

.

.

.

.

.

.

.

I

PHYLLOGRAZrIDAE Phyllograptus anna ilicifolius typus Perissograptus pygmaeus

i

.

.

I .

.

.

.

ISOGRAPTIDAE

Bergstroemograptus crawfordi

Cardiograptus inorsu5

morsus (narrow form) lsograptus caduceus australis caduceus imitatus caduceus aff. imitatus forcipOrormis horridus primulus spinifer subtilis tenuis victoriae lunatus victoriae victoriae victoriae maxiraus vict.maximodivergens victoriae divergens

i' i

.

.

•

•

- -

I

&s t

~PER 8ZIB.

4b t

1 k

2 #

[


ALCHERINGA

LOWER


CI~IT.

Oncograptus upsilon Paracardiograptus sp. Skiagraptus gnomonicus

1 t

2 *

•

"

ORDOVZCZ~

~ZilQ~13t.

1 t

I

.

2 t

.

.

3 *

.

y~t.lm

4 t

J. t

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UPPER ORDOV

DA2RZltZL.~&II

1 *

2 •

3 t

4 a 411= t t

GZ82°

1 •

2 •

t.~ITgi".Mi

1 *

2 =

3 *

4 *

" ~ !

GLOSSOGRAPTIDAE

Apiosraptus crudus Corynoides americanus australis calicularis curtu$

serpens ultimus Cryptograptus circinus inutilis scl~.feri tricornis sp, A cf insectiformis Glossograptus acanthus ciliatus fimbriatus pilosus Kalpinograptus? ovatu$ Paraglossograptus tentaculatus aft. tentaculatus proteus Pseudisograptus manubriatus manubriatus manubriatus harrisi manubriatus koi manubriatus janus dumosus form A dumosus form B gracilis hastatus jiangxiensis tau Pseudisograptus? aggestus

i •

•

PSEUIN)TRIGONOGRAPTIDAE

Pseudotrigonograptus ensilormis minor ABROGRAPTIDAE

Reteograptus geinitzianus speciosus FAMILY UNCERTAIN

Atopograptus woodwardi N. gen.?

defensus

w

63

64

A.H.M.

ALCHERlNGA

VANDENBERG & R. A. COOPER

QR00V. ~l~rJ~G~l

t)~iPJt ~n,

i~olf~4i

G[tl)0VZCZ~II 31c~TalO~

1 2 3 4 a ~ 1 2 1 2 3 4 1 2 3 4 s * * t t t t t ~ t t i t t t t t

DICRANOGRAPTIDAE

D/cranograplus h/arts k/rki


nicholsoni r a m o $ ~ ramo$1~

ramosus longicaulis r~raos~ spinifer JianFd graptus sp. nov.?

Dicellograptus anceps caduceus complexl~

divaricatus divaricatus divaricatus rigidus elegans elegans rigens flexllD sv~

gravis intortus minor morrisi ornatus pumilus sexlall$ seYda$1$

sextans exilis cf vagus n. sp. A

Nemagraptus gracilis Leptograptus capillaris eastonensis flaccidus arcuatus sp.A Pleurograptus linearis linearis linearis simplex DIPLOGRAFIIDAE and ORTHOGRAPTIDAE

Amplexograptus differtus ingens ingens weUingtonensis latus tardus n. sp. A

Appendispinograptus longispinus supernus Climacograptus

a~

baragwanathi bicornis bicornis tridentatus cruci/ormis missilis uncinatus n. sp. A

Diplacanthograptus dorotheus lanceolatus spiniferus

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GZIII.

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Ensi&raptus caudatus Euclimacograptus hastatus


cf tr/fidus

HaUograptus bimucronatus hirtus l.,asiograptus

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.

¢o$latl~

Neuro&raptus margaritatus Nymphograptus halli Orthograptus amplexicaulis calcaratus calcaratus acutus calcaratus vulgatus fastigatus pageanus pageanus spiaosus pulcherrirt~ quadr, quadrimucronatus quadr, cf cornutus quadr, spini&erus ruedemanni thorsteinssoni

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.

.

.

.

,

,

.

.

.

.

•

.

.

°

_

?

n. sp. A

Orthoretiograptus denticulatus Paraorthograptus

pacilicus Pseudoclimacograptus decoratus

I °

I

fus~ormis modicellus primus riddetlensis scharenbergi subminimus

.

.

.

.

.

I - -

n. sp. A n. sp. B n. sp. C

Sinoretiograptus mirabilis MONOGRAPTIDAE

Glyptograptus acceptus brevis brevis strictus

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o

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n. s p . A

Normalograptus angustus extraordinarius normalis persculptus

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tubutgerus tubul~feru$ nevadenai$ Undulograptus austrodentatus intersitus situlus

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65

66

described Dicranograptus hians, Dicellograp-

tus flexuosus, Diplacanthograptus spiniferus, Climacograptus baragwanathi, C. caudatus, Neurograptus margaritatus and others. The D. ornatus Zone in the Cordillera contains typically early Bolindian elements such as

Climacograptus uncinatus, Amplexograptus Downloaded by [Museum of Victoria], [Alfons VandenBerg] at 17:13 29 August 2011

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lotus and Appendispinograptus longispinus. It correlates with Bol, and probably Bo2. The P. pacificus Zone is recognized by the same criteria in NW Canada and Victoria. Both contain Paraorthograptus pacificus, and Orthoretiograptus denticulatus (described as Reteograptus pulcherrimus in Lenz, 1977). The Normalograptus extraordinarius Zone has not yet been discovered in NW Canada, and the last zone is the N. persculptus Zone, tentatively identified by the appearance ofN. normalis and Diplograptus modestus below the appearance of Parakidograptus acuminatus. N. normalis appears at the same level in Victoria. Ch/na It is still difficult to make precise correlation of much of the Late Ordovician with any part of China. Whilst the Wufeng Shale faunas have been documented in minute detail, there is very little information on faunas below this. Thus the correlation suggested here (Fig. 11) is based on the zone names and correlations indicated by Chinese workers, not on on comparison of zonal content. The very finely subdivided Wufengian correlates with most of the Bolindian -- excluding perhaps Bol. There are many species in common, although this similarity is somewhat obscured by the abundance of junior synonyms in the Chinese literature. The A. disjunctus yangtzensis Zone contains Dicellograptus cornplexus (as D. szechuansis), A. latus (as A. disjunctus yangtzensis and other synonyms) and A. supernus (as C. belluIus and C. supernus), indicating correlation probably with Bo2. The Bo3 index Paraorthograptus pacificus first appears in the succeeding D. 'szechuanensis' Zone and continues through the Tangyagraptus typicus and Paraorthograptus 'uniformis' Zones (Mu & Lin, 1984; Chen& Lenz, 1984b).

Acknowledgements We thank David Holloway and Tom Darragh

of the MtLseum of Victoria for the loan of type specimens, and Clive Willman and Eric Wilkinson for unpublished information on the Bendigo district. Avi Olshina helped with the statistics. The participation of AHMV is by permission of R. Dalgarno, Director of the Victorian Geological Survey.

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