foraminifera from late pliocene sediments of ...

FORAMINIFERA FROM LATE PLIOCENE SEDIMENTS OF HEIDEMANN VALLEY, VESTFOLD HILLS, EAST ANTARCTICA PATRICK G. QUILTY School of Earth Sciences, University of Tasmania, Private Bag 79, Hobart, Tasmania, 7001, Australia; Email: [email protected]

Journal of Foraminiferal Research, v. 40, no. 2, p. 193–205, April 2010

FORAMINIFERA FROM LATE PLIOCENE SEDIMENTS OF HEIDEMANN VALLEY, VESTFOLD HILLS, EAST ANTARCTICA PATRICK G. QUILTY School of Earth Sciences, University of Tasmania, Private Bag 79, Hobart, Tasmania, 7001, Australia; Email: [email protected]

dated as .300 Ka with diatom biostratigraphy and .1Ma by amino-acid racemization. Concerns about the interpretation of the sequence in the pits led to the early 1997 excavation of a significantly larger pit nearby (Fig. 2) that is ,20 m long and also bottoms at basement. The results of that excavation are detailed by Colhoun and others (2010), who recognized four major till units and 16 sedimentary subdivisions in the sequence. They also showed, using diatom and amino-acid racemization stratigraphy that the sediments are 3.5–2.6 Ma in age, corresponding with the Gauss Normal magnetic epoch and the last major glacial episode in the region. Both Hirvas and others (1993) and Colhoun and others (2010) referred to a meager but significant calcareous foraminiferal fauna that is predominantly benthic but they did not discuss it in detail. The present study documents the fauna recovered from the pits excavated by Hirvas and others (1993) and from each of the sedimentary units sampled by Colhoun and others (2010). The Neogene sedimentary rocks of Heidemann Valley are essentially in situ and the section is one of the very few in the onshore Antarctic for which this is true. Recognition of the details of the Heidemann Valley sequence adds to the value of the region as a source of information on the evolution of the Antarctic during the Late Neogene.

ABSTRACT

The foraminiferal fauna in Pliocene (3.5–2.6 Ma) sediments excavated in a trench 4 m deep, in Heidemann Valley, Vestfold Hills, East Antarctica is examined and described. Sediments accumulated in shallow, fully marine conditions in a glacial valley during the last major glacial event in the Vestfold Hills. The section correlates well with the Cockburn Island Formation (Pecten Conglomerate), sediments of Wright Valley, Dry Valleys, and marine event M10 recognized as far south as Amery Oasis, 500 km to the southwest of Heidemann Valley. The foraminiferal fauna generally is dominated by infaunal cassidulinid and elphidiid species. Assemblages vary dramatically, even between samples collected very close to each other, and no simple relationship with the position in sections or the valley can be determined. It is a shallow-water, fully marine fauna virtually free of agglutinated forms and with a low planktonic component Planoglabratella webbi is described as new. INTRODUCTION The Pliocene is becoming of successively greater international significance as scientists search for an analog for the environment into which the world seems to be evolving. Recent papers such as Raymo and others (2009) highlight the need for more research into specific time intervals, such as 3.3–2.9 Ma, where the mid-Pliocene climate optimum is within the Gauss Normal magnetic epoch. Heidemann Valley in the Vestfold Hills of East Antarctica appears to hold a marine sequence relevant to this issue. Heidemann Valley (Fig. 1) is narrow, approximately flatfloored, immediately south of the Australian station of Davis, oriented ENE-WSW, typically about 0.5 km wide, and about 3 km long where it meets Lake Dingle or 5 km long if extended to Lake Stinear. It was described in detail by Quilty and Franklin (1997) who summarized all known survey maps with contours at 0.5 m intervals. The valley is crossed by a few ridges and in summer may be swampy or with small ponds. Its floor is mainly Quaternary sand about 1 m thick (Quilty and Franklin, 1997). The Pliocene section underlies the young sand. The flanks of the valley are up to ,45 m above the floor and consist of Precambrian gneiss and a series of metamorphosed basaltic intrusions (Collerson and Sheraton, 1986). Below the Holocene sediment, Hirvas and others (1993) described a three-meter section of glacial sediment in a series of pits excavated to basement at depths of 4.0–4.5 m. They also provided some information on the faunas recovered from those pits and proposed that the sequence represents two episodes of sedimentation separated by a thin marine unit that reflects a distinct interval they named the Davis Interglacial. The sediments could only be age-

MATERIALS AND METHODS A total of 27 samples was collected during the austral summer seasons of 1989/90 and 1996/97 of the Australian National Antarctic Research Expeditions (ANARE). During the first season, four pits were excavated to basement and they provided the material that was examined by Hirvas and others (1993). These pits are 55/VFH/89, 56/ VFH/89, 60/VFH/89, 70/VFH/89 and they yielded a total of 11 samples (Table 1). In the second field season, a 20-mlong trench, the subject of Colhoun and others (2010), was excavated and provided an additional 16 samples (HBP116; Table 1). Locations of both the 1989/90 and 1996/97 sites are shown on Figure 1. All samples were disaggregated in water, some with the aid of Calgon (Na6O18P6). Each sediment sample was then washed over 63-, 125-, and 250-mm sieves. The foraminiferal study focused on those specimens retained by the 125-mm and coarser screens. The biogenic component of the sediment generally is very minor and, in addition to the foraminifera recorded here, consists of fragments of three bivalve species (i.e., Laternula elliptica King and Broderip, an inderminate pectenid, and a hiatellid). Their fragments dominate the washed residue. There are a few ostracodes, broken sponge spicules, and fragments of echinoid spines. Although Hirvas and others (1993) recorded the hiatellid as Hiatella arctica (Linne´), it

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FIGURE 1. Locality map of pits .(e.g., 55/VFH/89) excavated in 1989 and discussed by Hirvas and others (1993). Detail increases from A to C. The 1997 trench (shaded) is the subject of Colhoun and others (2010). M.P. 5 Marine Plain, CI 5 Cockburn Island, DV 5 Dry Valleys.

might belong to the undescribed genus of hiatellid that Harding (2005) recorded from the nearby Marine Plain. For Hirvas and others (1993), large samples (up to 300 gm) were processed but only a small portion of each was examined. In the present investigation, each entire sample was analyzed and the data are recorded in Table 1. Preservation generally is good but a few samples have suffered minor diagenesis rendering identification difficult. The taxa identified in this study are assigned to genera included in Loeblich and Tappan (1987), and their suprageneric classification is followed. Synonymies consist of original descriptions and, for the most part, Pliocene Antarctic records. Samples and figured specimens are curated in the Commonwealth Palaeontological Collection (CPC) of Geoscience Australia (GA) in Canberra, Australian Capital Territory. Catalog numbers are included in the captions for the figures showing the taxa. SYSTEMATIC PALEONTOLOGY Class FORAMINIFERA Loeblich and Tappan, 1992

Family HORMOSINIDAE Haeckel, 1894 Genus Reophax de Montfort, 1808 Reophax sp. Fig. 3.1

Material. A single tubular specimen, broken and open at each end, 0.6 3 0.27 mm with uniformly very fine-grained wall with no obvious sutures. Discussion. The generic name is applied tentatively. It is the only agglutinated specimen recovered during this study. Family HAUERINIDAE Schwager, 1876 Genus Quinqueloculina d’Orbigny, 1826 Quinqueloculina triangularis (d’Orbigny, 1846) Fig. 3.2 Quinqueloculina triangularis d’Orbigny 1826, p. 36, mode`les no. 34 (nomen nudum). d’Orbigny, 1846, p. 288, pl. 18, figs. 7–9. Quinqueloculina triangularis (d’Orbigny). Hirvas and others, 1993, pl. 1, fig. 2.

Discussion. This species is similar to Q. seminulum d’Orbigny but is relatively shorter and more inflated. It occurs in two samples and is the only miliolid encountered in this study.

LATE PLIOCENE FORAMINIFERA, EAST ANTARCTICA

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FIGURE 2. Stratigraphy of the five sections excavated, after Hirvas and others (1993) and Colhoun and others (2010). Lithological correlation is speculative.

Family NODOSARIIDAE Ehrenberg, 1838 Genus Nodosaria Lamarck, 1812 Nodosaria sp.

Material. A single, thin-walled, fragile specimen, perhaps partly dissolved. It is unidentifiable and not illustrated. Genus Dentalina Risso, 1826 Dentalina subemaciata Parr, 1950 Fig. 3.3 Dentalina subemaciata Parr, 1950, p. 329, pl. 12, fig. 1.

Discussion. The single specimen recorded by Hirvas and others (1993), on re-examination, is closer to F. subcircularis than to F. submarginata. The expected clear area on the lumen is not obvious, but degree of inflation and characters of the aperture and rim seem identical. The entosolenian tube was not seen as the wall is opaque. Family GLOBOROTALIIDAE Cushman, 1927 Genus Neogloboquadrina Bandy, Frerichs and Vincent, 1967 Neogloboquadrina pachyderma (Ehrenberg, 1861) Fig. 3.5

Material. A single robust specimen of five chambers, 2.25 mm long, circular in section with basal spine broken. Apertural end broken, exposing slightly eccentric, circular aperture with raised rim; not radiate. Discussion. This is the early quarter of the species described by Parr. The lack of radial features on the aperture might be due to an ontogenetic change as later chambers were added.

Aristerospira pachyderma Ehrenberg, 1861, p. 303 Neogloboquadrina pachyderma (Ehrenberg). Leckie and Webb, 1986, p. 1117, pl. 16, figs 1, 2; Ishman and Webb, 1988, p. 536, pl. 4, figs. 3, 4; Hirvas and others, 1993, pl. 1, fig. 1.

Family ELLIPSOLAGENIDAE A. Silvestri, 1923 Genus Fissurina Reuss, 1850 Fissurina subcircularis Parr, 1950 Fig. 3.4

Family GLOBIGERINIDAE Carpenter, Parker and Jones, 1862 Genus Globigerina d’Orbigny, 1826 Globigerina bulloides d’Orbigny, 1826 Fig. 3.6

Fissurina subcircularis Parr, 1950, p. 311, pl. 8, fig. 15; pl. 9, fig. 1. Fissurina submarginata (Boomgart). Hirvas and others, 1993, pl. 1, fig. 3.

Discussion. This species occurs only in one sample that yielded abundant planktonic foraminifera and where it constitutes 12% of the assemblage. All are sinistral and the compact form described by Be´ (1960).

Globigerina bulloides d’Orbigny, 1826, p. 277, mode`les no. 1. Banner and Blow, 1960, p. 3, pl. 1, figs. 1–4.

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TABLE 1. Species distribution, dominance, and diversity of foraminiferal assemblages recovered from excavations in Heidemann Valley. Numbers are specimen counts. Shaded areas indicate samples were barren of foraminifera. For non-foraminiferal components, x indicates presence.

Material. A single typical sinistral specimen is present in one sample. Family CASSIDULINIDAE d’Orbigny, 1839 Genus Globocassidulina Voloshinova, 1960 Globocassidulina crassa (d’Orbigny, 1839) sensu lato Fig. 3.7

subspecies occur in the Heidemann Valley samples but G. c. biora dominates and G. c. crassa s.s. was not identified. Some specimens on which apertural details are unavailable are placed here as G. crassa s.l. Leckie and Webb (1986) synonymized Globocassidulina crassa rossensis with G. crassa s.l. but that approach is not followed here and both subspecies are recognized.

Cassidulina crassa d’Orbigny, 1839, p. 56, pl. 7, figs. 18–20. Globocassidulina crassa (d’Orbigny). Leckie and Webb, 1986, p. 1115, pl. 12, figs. 7–9; Quilty and others, 1990, p. 3, pl. 1, fig. 9.

Globocassidulina crassa biora (Crespin, 1960) Figs. 3.8–3.10

Discussion. As elsewhere (e.g., Quilty, 2004), three subspecies are recognized—G. crassa crassa (d’Orbigny), G. c. biora (Crespin) and G. c. rossensis Kennett. Two

Cassidulina biora Crespin, 1960, p. 28, pl. 3, figs. 1–10. Globocassidulina biora (Crespin). Fillon, 1974, p. 139, pl. 1, figs. 9–12, 14, 15; Leckie and Webb, 1986, p. 1115, pl. 12, fig. 10; Hirvas and others, 1993, pl. 1, fig. 4.


Discussion. If, as suggested by Fillon (1974), this form was the immediate ancestor of G. c. rossensis Kennett, biostratigraphic value has been achieved from documenting this lineage. Fillon (1974) speculated that Crespin’s (1960) specimens from Deep Lake in the Vestfold Hills were redeposited from older (Pleistocene–Holocene) sediments. This might be true, but the redeposition is most likely to have been only from Holocene sediments that are widespread in the Vestfold Hills (Adamson and Pickard, 1986). The Deep Lake sediments are very close to being in situ (Quilty, 1988). At the time of Fillon’s (1974) paper, G. crassa biora was not known from the modern environment. That has now changed (e.g., Finger and Lipps, 1981; Nomura, 1984; Ishman and Domack, 1994; Igarashi and others, 2001) and its range now extends from the late Pliocene (Gauss) to the Recent. A modern specimen from sediments in Prydz Bay is illustrated. G. crassa biora specimens are typically compact (Figs. 3.8–3.9), but some are very laterally compressed (Fig. 3.10) Globocassidulina crassa rossensis Kennett, 1967 Fig. 3.11 Globocassidulina crassa rossensis Kennett, 1967, p. 133, pl. 11, figs. 4, 6; Fillon, 1974, p. 140, pl. 1, figs. 1–7.

Discussion. Fillon (1974) regarded this form as more typical of Brunhes Polarity Epoch sediments and G. c. biora as more typical of the Gauss and taking the role of rootstock from which G. c. rossensis evolved. G. c. rossensis is identified tentatively as rare specimens in three samples where preservation is not ideal but the aperture appears to divide. Thus Fillon’s generalization seems to hold, although not perfectly. Globocassidulina subglobosa (Brady, 1881) Fig. 3.12 Cassidulina subglobosa Brady, 1881, p. 60, pl. 54, fig. 17. Globocassidulina subglobosa (Brady). Fillon, 1974, p. 140; Leckie and Webb, 1986, p. 1115, pl. 12, figs. 4–6; Birkenmajer and Luczkowska, 1987, p. 117, pl. 6, fig. 6; Ishman and Webb, 1988, p. 537, pl. 6, figs. 2, 4; Hirvas and others, 1993, pl. 1, fig. 6.

Discussion. A common form with distinctly commashaped aperture roughly perpendicular to the suture from which it arises. It is the dominant species in 56/VFH/89, 50– 100 cm, where it is accompanied by slightly fewer G. crassa biora. It is likely that some of the specimens represent the neanic stage of G. crassa biora as postulated by Nomura (1984). Genus Cassidulinoides Cushman, 1927 Cassidulinoides parkerianus (Brady, 1884) Fig. 3.13 Cassidulina parkeriana Brady, 1884, p. 432, pl. 54, figs. 11–16. Cassidulinoides parkerianus (Brady). Parr, 1950, p. 344, pl. 12, fig. 25; Webb and others, 1986, p. 117; Ishman and Webb, 1988, p. 534, pl. 6, fig. 1; Hirvas and others, 1993, pl. 1, fig. 7; Gazdzicki and Webb, 1996, p. 161, pl. 35, figs. 4–6. Ehrenbergina parva Earland, 1934, p. 139, pl. 6, figs. 28–32. Cassidulinoides parvus (Earland). Nomura, 1984, p. 498, pl. 90, fig. 10, pl. 91, figs. 1–5; Igarashi and others, 2001, p. 156, pl. 10, fig. 12.

Description. Test distinctly curved, circular in section, typically 0.55 mm long, 0.22 mm wide in straight portion of

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test that has 3–4 pairs of biserial chambers. Sutures distinctly depressed, forming simple zigzag pattern on inner and outer aspects of unrolled biserial section. Early cassidulinid portion small and not prominent. Aperture oval, with imperforate rim, isolated from suture. Discussion. This is the smaller of the two species of Cassidulinoides in the Heidemann Valley faunas. It is the same form recorded from Recent sediments by Nomura (1984) and Igarashi and others (2001) as C. parvus (Earland), but C. parkerianus has priority and is by far the most widely used name. In contrast with Parr’s (1950) recording of this species as rare on the Antarctic continental shelf off Enderby Land, it is the most abundant Cassidulinoides in the Heidemann Valley faunas. Sample 70/VFH/ 89, 220–260 cm has a high proportion of forms morphologically very similar to, but much smaller than, Globocassidulina subglobosa (Brady). They are taken to be immature or fragmentary specimens of C. parkerianus. This species has a significantly smaller diameter than that of C. porrectus (Heron-Allen and Earland) and generally has more chambers in the unrolled biserial portion. Its test appears delicate compared to the robust C. porrectus, probably reflecting its thinner and more translucent wall. Cassidulinoides porrectus (Heron-Allen and Earland, 1932) Fig. 3.14 Cassidulina crassa porrecta Heron-Allen and Earland, 1932, p. 358, pl. 9, figs 34–37. Cassidulinoides porrectus (Heron-Allen and Earland, 1932). Webb and others, 1986, 117; Ishman and Webb, 1988, p. 534, pl. 6, fig. 16; Quilty and others, 1990, p. 3, pl. 1, fig.10; Hirvas and others, 1993, pl. 1, fig. 8.

Description. Test typically 0.8-mm long, 0.37-mm across in straight biserial portion of 2–3 chamber pairs, circular in cross-section. Its early cassidulinid portion is prominent and laterally compressed. Aperture comma-shaped and in contact with suture. Discussion. This species is larger and more robust than C. parkerianus. Re-examination of Cassidulinoides cf. C. parkerianus specimens recorded by Quilty and others (1990) suggests that they were misidentified and should be referred to this species. Genus Ehrenbergina Reuss, 1850 Ehrenbergina glabra Heron-Allen and Earland, 1922 Fig. 3.15 Ehrenbergina hystrix Brady var. glabra Heron-Allen and Earland, 1922, p. 140, pl. 5, figs. 1–6. Ehrenbergina glabra Heron-Allen and Earland. Fillon, 1974, p. 139, pl. 5, figs. 9, 10; Leckie and Webb, 1986, p. 1115, pl. 12, figs. 11, 12; Ishman and Webb, 1988, p. 537, pl. 4, fig. 17; Quilty and others, 1990, p. 3, pl. 1, fig. 11; Hirvas and others, 1993, pl. 1, fig. 9.

Discussion. This is the form described by Heron-Allen and Earland (1922). Its concave test has a smooth surface and short peripheral spines, whereas Ehrenbergina hystrix Brady, 1881 differs by having complex ridged keel-like structures on the ventral (concave) side of the test. Fillon (1974) recorded both E. glabra and E. pupa (d’Orbigny, 1839) from the Gauss Polarity Epoch and E. glabra from the younger Brunhes Epoch with the implication that they have discrete biostratigraphic ranges. The material studied here belongs to the Gauss Polarity Epoch, but no specimens of E. pupa are present. The form illustrated by Igarashi and

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FIGURE 3. Late Pliocene foraminifera, Heidemann Valley, East Antarctica. 1 Reophax sp., CPC39955. 2 Quinqueloculina triangularis (d’Orbigny, 1846), CPC39956. 3 Dentalina subemaciata Parr, 1950, CPC39957. 4 Fissurina subcircularis Parr, 1950, CPC39958. 5 Neogloboquadrina pachyderma (Ehrenberg, 1861), CPC39959. 6 Globigerina bulloides d’Orbigny, 1826, CPC39960. 7 Globocassidulina crassa crassa sensu lato (d’Orbigny, 1839), CPC39961, 8–10 Globocassidulina crassa biora (Crespin, 1960): 8, CPC39962; 9, CPC39963; 10, CPC39964. 11 Globocassidulina crassa rossensis Kennett, 1967, CPC39965. 12 Globocassidulina subglobosa (Brady, 1881), CPC39966. 13 Cassidulinoides parkerianus (Brady, 1884), CPC39967. 14 Cassidulinoides porrectus (Parr, 1950), CPC39968. 15 Ehrenbergina glabra Heron-Allen and Earland, 1922, CPC39969. 16 Rosalina globularis


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others (2001) as E. glabra more closely resembles E. pupa as it is laterally compressed and lacks many peripheral spines. Family ROSALINIDAE Reiss, 1963 Genus Rosalina d’Orbigny, 1826 Rosalina globularis d’Orbigny, 1826 Figs. 3.16 Rosalina globularis d’Orbigny 1826, p. 271, pl. 13, figs. 1–4; Fillon, 1974, p. 140, figs. 11, 12; Webb and others, 1986, p. 117; Jones, 1994, p. 93, pl. 86, fig. 13.

Discussion. A few specimens were found in one sample. They have slightly raised sutures in the center of the dorsal surface and gently depressed sutures in the final whorl, as illustrated by Jones (1994). Family PARALLELOIDIDAE Hofker, 1956 Genus Alabaminoides Gudina and Saidova, 1967 Alabaminoides exiguus (Brady, 1884) Fig. 3.17 Pulvinulina exigua Brady 1884, p. 696, pl. 103, figs 13, 14. Epistominella exigua (Brady, 1884). Echols, 1971, pl. 15, fig. 4; Fillon, 1974, p.139, pl. 4, figs. 9, 10; Webb and others, 1986, p. 117; Schro¨der-Adams, 1991, p. 625. Alabaminoides exiguus (Brady, 1884). Jones, 1994, p. 103, pl. 103, figs 13, 14.

Discussion. This species is represented by a few specimens in two samples. Preservation generally is poor. Jones (1994) transferred the species to Alabaminoides. Family GLABRATELLIDAE Loeblich and Tappan, 1964 Genus Planoglabratella Seiglie and Bermu´dez, 1965 Planoglabratella webbi Quilty, new species Figs. 3.18–3.23, 5.1–5.3 Pileolina cf. P. opercularis (d’Orbigny). Hirvas and others, 1993, pl. 1 figs. 10, 11.

Etymology. Named for Professor Peter-Noel Webb, Ohio State University, Columbus, who has done much to advance our knowledge of Antarctic Cenozoic foraminifera and history. Diagnosis. Final whorl of 7–8 chambers; dorsal surface with prominent proloculus and abundant fine papillae concentrated near sutures; ventral surface flat with two types of abundant and widely distributed fine papillae and coarse papillae concentrated in the umbilicus. No radial striae or evidence of plastogamy. Description. Test circular, very low planoconvex varying from a dome to scale-like. Final whorl with 7–8 strongly recurved chambers visible on evolute dorsal surface and emphasized by abundant small papillae. Small papillae widespread but concentrated at sutures and less abundant on proloculus. Proloculus large (40–70 mm) and prominent. Ventral surface flat with generally flush sutures that can be slightly depressed in last 1 or 2 chambers or accentuated by small papillae; coarse papillae concentrated near center, fine papillae very numerous and widespread; no radial striae. Aperture a narrow slit roughly paralleling periphery

FIGURE 4. n. sp.

Maximum diameter variation in Planoglabratella webbi,

and with flap but no lip or rim; secondary aperture occasionally on suture along posterior of ultimate chamber. Plastogamy not seen but ventral surface sporadically with a few coarse pores near umbilicus; no evidence of broodpouch. Maximum diameter 0.15–0.45 mm (Fig. 4). Discussion. This is one of the most abundant species in the study. Quilty (1977) and Hayward and others (1999) used the name Pileolina Bermu´dez, 1952 (regarded by Loeblich and Tappan, 1964, 1987 as an unrecognizable genus) for forms similar to this species, all of which are characterized by an evolute dorsal surface and populations that include plastogamic pairs. Introduction of the name Planoglabratella seemed to clear up confusion over possible allocation of species within this group. Despite the statement in Loeblich and Tappan (1987) that plastogamy is normal in the family Glabratellidae, no plastogamic pairs were recovered and no evidence of the expected broodpouch was seen. Thus, there is possible need to re-examine generic concepts within this group further in order to recognize species-groups lacking evidence of plastogamy and its attendant modification to the ventral surface. The most similar species appears to be Pileolina zelandica Vella, 1957. Family DISCORBINELLIDAE Sigal, 1952 Genus Discorbinella Cushman and Martin, 1935 Discorbinella umbonifer (Parr, 1950) Figs. 5.4 Discorbis umbonifer Parr, 1950, p. 353, pl. 13, fig. 22. Discorbinella umbonifer (Parr). Quilty and others 1990, p. 3, pl. 1, figs. 14, 15; Hirvas and others, 1993, pl. 1, figs. 12, 13.

Discussion. A few specimens in one sample, marked by the presence of the typical ventral boss. Discorbinella cf. D. araucana (d’Orbigny, 1839) Figs. 5.5

Discussion. This species, occurring in two samples, has a slightly more involute dorsal surface than D. araucana as

r d’Orbigny, 1826, CPC39970. 17 Alabaminoides exiguus (Brady, 1884), CPC39971. 18–23 Planoglabratella webbi Quilty, n. sp.: 18, holotype CPC39972; 19, paratype CPC39973; 20, paratype CPC39974. 21 paratype CPC39975. 22 paratype CPC39976. 23 paratype CPC39977. LocalITIES of figured specimens: 1, 3, 13, 18–23 from 70/VFH/89, 2.2–2.6 m; 2, 5–9, 12, 14–16 from 56/VFH/89, 0.5–1.0 m; 4, 17 from 55/VFH/89, 2.8–4.0 m. 10, modern, Prydz Bay station 1982/8; 11 from 55/VFH/89, 0–1.9 m. Scale bar is 500 mm for all figures, except Fig. 4.3 where it is 1.0 mm and Figs. 4.18–4.19 where it is 0.25 mm.

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FIGURE 5. Late Pliocene foraminifera, Heidemann Valley, East Antarctica. 1–3 Planoglabratella webbi Quilty, n. sp.: 1, paratype CPC39978. 2, paratype CPC39979; 3, paratype CPC39980. 4 Discorbinella umbonifer Parr, CPC39981. 5 Discorbinella cf. D. araucana (d’Orbigny), CPC39982. 6–7 Discorbinella sp. 1, 6 CPC39982. 7 CPC39984. 8 Discorbinella sp. 2, CPC39985. 9, 10 Cibicides refulgens de Montfort, CPC39986. 11 Cibicides sp., CPC39987. 12 Astrononion antarcticus Parr, CPC39988. 13 Astrononion echolsi Kennett, CPC39989. 14 Gyroidella sp., CPC39990. 15 Elphidium (Cribrononion) sp. 1, CPC39992. 16 Elphidium (Cribroelphidium) sp., CPC39991. 17–18 Elphidium (Cribrononion) sp. 2, 17 CPC39993. 18 CPC39994, to show asymmetry.

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illustrated by Jones (1994, pl. 86, figs. 10, 11) and, while the ventral surface normally is identical, a few specimens have a small, discrete umbonal boss. Discorbinella sp. 1 Figs. 5.6–5.7 Rosalina globularis d’Orbigny, 1826. Igarashi and others, 2001, p. 159 pl. 11, fig. 13.

Description. Dorsal surface virtually identical to that of D. araucana (d’Orbigny 1839) in being convex and evolute, with final whorl of 7–8 clearly perforate chambers and imperforate intercameral sutures that are very slightly elevated (inconsistently between specimens) and uniformly gently recurved. Ventral surface flat to slightly concave, involute, with or without umbilical plug. Ventral sutures straight proximally and becoming more sharply curved near periphery; proximal ends of sutures depressed to form central stellate pattern. Aperture multiple; primary aperture a peripheral, small, high arch with rim; one or two smaller apertures at base of apertural face. Size 0.17–0.42 mm, most ,0.37 mm in diameter. Discussion. This appears to be the species recorded as R. globularis d’Orbigny by Igarashi and others (2001). The R. globularis specimen illustrated by Jones (1994, pl. 86, fig. 13) is a different form with simple ventral surface in contrast to the form recorded here that has depressed proximal ends of ventral sutures producing a stellate central feature. The dorsal surface has perforate chamber walls but imperforate sutures that are very slightly raised and are similar to those seen in Rosalina australis (Parr) of Jones (1994, pl. 87, figs. 5–7). It has 7–8 chambers in the final whorl and the ratio of sinistral vs. dextral coiling is approximately 3:2. It occurs in only one sample (70/VFH/ 89, 220–260 cm) from which 18 specimens were recovered. The species is similar to Discorbinella umbonifer (Parr, 1950) but is much larger with fewer chambers and a lessprominent or no umbilical plug. ‘Discorbinella’ sp. 2 Figs. 5.8a, b

Description. Eight chambers in final whorl; dorsal surface smooth, evolute with gently depressed spiral suture for latter half of last whorl. Periphery bluntly rounded. Ventral surface with deeply depressed intercameral sutures and deep cavity surrounding ventral umbonal boss for last five chambers; boss attached to proximal ends of earlier chambers. Ventral ends of each chamber with small folium that does not cover umbilicus in the last half whorl. Primary aperture a high arch at peripheral end of apertural face but not passing over periphery; secondary apertures continuous under folia. Discussion. The single specimen recovered is tentatively assigned to Discorbinella from which it differs only in having a bluntly rounded periphery. It has much in common with Valvulineria polita Parr, 1950 but has a more open umbilicus with the primary aperture limited to close to the periphery.

Family CIBICIDIDAE Cushman, 1927 Genus Cibicides de Montfort, 1808 Cibicides refulgens de Montfort, 1808 Figs. 5. 9, 10 Cibicides refulgens de Montfort, 1808, p. 123, pl. 92, figs. 7–9; Leckie and Webb, 1986, p. 1115, pl. 11, figs. 13–15; Birkenmajer and Luczkowska, 1987, p. 117, pl. 6, figs. 3a–c; Quilty and others, 1990, p. 3, pl. 1, fig. 17; Gazdzicki and Webb, 1996, p. 162, pl. 36, figs. 4– 6.

Discussion. Distribution is irregular, but it is the dominant form in 70/VFH/89, 2.2–2.6 m. There is no indication that it intergrades with any specimens that could be identified as C. lobatulus as suggested by Gazdzicki and Webb (1996). Twenty specimens were selected 13C/12C and 18 O/16O analysis. Cibicides sp. Fig. 5.11

Discussion. A single large specimen with irregular growth occurs in the sample from 56/VFH/89, 50–100 cm. It has a high spire and is composed of globular chambers with a rough, coarsely perforate surface. The final chamber protrudes over the ventral surface that shows signs of having been attached. Family NONIONIDAE Schultze, 1854 Genus Astrononion Cushman and Edwards, 1937 Astrononion antarcticus Parr, 1950 Fig. 5.12 Astrononion antarcticus Parr, 1950, p. 371, pl. 15, figs. 13, 14; Fillon, 1974, p. 139, pl. 6, figs. 4–6.

Discussion. Occurs only in 56/VFH/89, 50–100 cm. Rare. Astrononion echolsi Kennett, 1967 Fig. 5.13 Astrononion echolsi Kennett, 1967, p. 133, pl. 11, figs. 7, 8; Fillon, 1974, p. 139, pl. 6, figs. 1–3; Leckie and Webb, 1986, p. 1115, pl. 13, figs. 1, 2; Ishman and Webb, 1988, p. 538, pl. 6, fig. 5 Schro¨der-Adams, 1991, p. 624.

Discussion. Two specimens recovered from 70/VFH/89, 2.2–2.6 m, one poorly preserved but showing the characteristic sutural pores. A third specimen of Astrononion, from HBP6A and also broken, probably belongs to this species. Family GAVELLINELLIDAE Hofker, 1956 Genus Gyroidella Saidova, 1975 Gyroidella sp. Figs. 5.14

Material. A single specimen in each of two samples. Description. Test 0.22 mm in diameter, uniformly biconvex with bluntly rounded periphery, smooth and gently domed on the dorsal surface and evolute with about 3K whorls visible, increasing slowly in height; nine chambers in the final whorl. Dorsal sutures flush; intercameral sutures straight and directed posteriorly toward periphery. Ventral surface completely involute, with weakly depressed umbilicus but no umbilical boss; sutures initially radiate straight but become gently directed posteriorly near periphery. Aperture interiomarginal, along base of final

r Localities of figured specimens: 1–3, 5–7, 9, 10, 13, 15, 16 from 70/VFH/89 2.2–2.8 m. 4, 8, 11–12, 14, 17 from 56/VFH/89 0.5–1.0 m. 18 from 55/ VFH/89 2.8–4.0 m. Scale bar is 500 mm for all figures except Figs. 5.11 where it is 1.0 mm and Fig. 5.18 where it is 0.25 mm.

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chamber and extending at periphery in depressed equatorial slit. Discussion. The species seems to be closely related to Epistominella cassidulinoides Hornibrook, 1961 but has a more bluntly rounded periphery, is considerably larger, and its ventral intercameral sutures are less recurved. Family ELPHIDIIDAE Galloway, 1933 Genus Elphidium de Montfort, 1808

Hayward and others (1997) used Elphidium in a broad sense to include species otherwise ascribed to Elphidium, Cribroelphidium, and Cribrononion. Elphidium sensu stricto is said to have an angular periphery, but the three species found here all have rounded peripheries characteristic of Criboelphidium and Cribrononion. I have opted to regard the three forms as subgenera of Elphidium until they have been subject to a comprehensive review, as called for by Hayward and others (1997). Subgenus Cribroelphidium Cushman and Bro¨nnimann, 1948 Elphidium (Cribroelphidium) sp. Fig. 5.16 ?Cribroelphidium cf. bartletti (Cushman, 1933). Ward and Webb, 1986, p. 194, pl. 6, figs. 4, 5; pl. 9, fig. 7.

Discussion. This species is uncommon and is distinguished from Elphidium (Cribroelphidium) sp. 1 in being large (0.6 mm) with 10–11 chambers and almost flush sutures in the final whorl. It occurs in 70/VFH/89/2.2–2.6 m and 70/VFH/89/300 cm. Ward and Webb (1986) figured Cribroelphidium cf. bartletti from young sediments on Ross Island, noting that their specimens had only nine chambers in the final whorl compared with the original description of 10–12. The specimen found here has 10–11 and the surface around the sutures is covered with small papillae that are not evident in the specimen figure provided by Ward and Webb. The apertural face has about six pores at the base and an additional pore near the periphery. Subgenus Cribrononion Thalmann, 1947 Elphidium (Cribrononion) sp. 1 Fig. 5.15 Elphidium magellanicum Heron-Allen and Earland. Leckie and Webb, 1986, p. 1113, pl. 7, figs. 1–4, 6, 8; Quilty and others, 1990, p. 9, pl. 1 figs. 22, 23; Hirvas and others 1993, pl. 1, fig. 14. Cribroelphidium magellanicum Heron-Allen and Earland. Webb and others, 1986, p. 117. ? Cribrononion vulgare (Voloshinova). Birkenmajer and Luczkowska, 1987, p. 115, pl. 3, fig. 18, pl. 5, fig. 15.

Discussion. This species is smaller than Elphidium sp. 2. It is a common species in a few samples. Its final whorl has six smooth, inflated chambers and slightly but clearly depressed radial sutures. Sutures vary greatly within a population but most are finely papillate. There is no umbo. Maximum diameter normally is ,0.3 mm. This species has been identified as Elphidium magellanicum Heron-Allen and Earland, 1932 by several authors but the type description of E. magellanicum refers to a compressed form and with dimensions (0.35 3 0.12 mm) that suggest a maximum diameter/thickness ratio of ,3. The Heidemann Valley specimens are more robust with their maximum diameter of ,0.35 mm and maximum

diameter/thickness ratio of 1.3–1.45, and resemble the specimens figured by Leckie and Webb (1986) as E. magellanicum. The generic assignment of this species is questionable, as it varies from strictly planispiral to slightly asymmetrical. The asymmetry is not apparent in lateral view but when viewed in profile, the apertural face often appears slightly twisted and the plane of symmetry is slightly off center. The asymmetry, absence of any indication of a carinate periphery, and low number of chambers in the final whorl would exclude it from Elphidium according to Loeblich and Tappan (1987). Of the elphidiid genera recognized by Loeblich and Tappan (1987), Cribrononion is the most appropriate for this species, but that genus is umbonate and bilaterally symmetrical. Although Elphidium (Cribrononion) sp. 1 has the number of chambers consistent with Cribrononion, Loeblich and Tappan restrict the range of Cribrononion as Eocene–Miocene. Elphidium (Cribrononion) sp. 2 Figs. 5.17a–18 Cribrononion sp. Gazdzicki and Webb, 1996, p. 163, pl. 37, figs. 3, 4.

Discussion. A few specimens of this form were recovered. It differs from Elphidium (Cribrononion) sp. 1 by its larger size and its distribution of much larger pustules. Slightly asymmetrical forms are also common. The two species have comparable maximum diameters, but this one has a much lower maximum diameter/thickness ratio of 1.3–2.2 (average 5 1.61). This is a much more robust species than E. magellanicum s.s. Elphidium (Cribrononion) sp. typically has its pustules restricted to proximal parts of sutures on both sides of the test, producing a stellate arrangement, but with age the pustulose zone becomes more distal and crosses the periphery of the last chamber, perhaps a result of overlapping chambers. Pustules along the base of the ultimate chamber are better developed at the anterior end, and broken specimens reveal that those on the anterior face are concentrated proximal of the ultimate chamber. About six widely spaced septal foramina are visible on each suture on both sides of the test, more prominently on earlier chambers of the final whorl. An illustration of this species by Gazdzicki and Webb (1996) appears to show asymmetrical ornamentation on opposite sides of the same specimen, but this might be an consequence of preservation. The pustules near retral processes on all but the last chamber of their specimen are arranged in pairs giving a more Ammoelphidiella-like appearance than the retral processes characteristic of Elphidium or Cribrononion. Among the large variety of Elphidium species (including what could also be referred to Cribrononion) figured by Hayward and others (1997), very few species have a ‘sutural ornament’ similar to that typical of most species of Ammoelphidiella. The similarities between Elphidium (Cribrononion) sp. 2 and Ammoelphidiella, however, suggest that this form might be a descendant from some element of the Ammoelphidiella lineage and that Cribrononion, as currently defined, is polyphyletic. Leckie and Webb (1986) discussed Trochoelphidiella sp. (now Ammoelphidiella sp.), which is virtually planispiral but more compressed than this species.


Unidentified Foraminifera Discussion. Most material is preserved well enough for identification. In the surface sample from 70/VFH/89, there is a broken fragment that could be of Globocassidulina. Those fragments from HBP16 are too poorly preserved for identification. DISCUSSION The distribution of foraminifera in this study is very patchy. The lower section of the 1997 trench, below sample HBP6 is essentially devoid of foraminifera and even sponge spicules and echinoid spines are less evident. This is perhaps unexpected from the sampled section in the center of the valley, which has yielded the most samples. The richest faunas, although meager, are from 56/VFH/89 (near the valley margin) and 70/VFH/89 (central and close to the 1997 trench site), but it is impossible to relate abundance to position in the valley, or to identify consistent geographic patterns of distribution. The Heidemann Valley faunas, with the exception of a specimen identified as Reophax sp., lack agglutinated taxa, and planktonic species occur in only one sample where they account for a small proportion of the total fauna. The faunas are highly dominated by a diverse assemblage of cassidulinid (Globocassidulina, Cassidulinoides, Ehrenbergina) species, all compatible with a predominantly infaunal lifestyle in a sandy substrate under fully marine conditions (Corliss and Chen, 1988, Murray, 1991). The occasional presence of Cibicides refulgens in significant numbers adds an attached epifaunal element to the fauna. While the dominance of infaunal species is noteworthy, the virtual absence of agglutinated species (normal in the Antarctic Pliocene but not the Recent) and elongate buliminid and bolivinid infaunal forms is striking and might be related to the absence of clay minerals and dominance, even in the very fine fraction, by freshly broken non-clay minerals. As defined by Walton (1964), dominance is high and diversity low (Table 1). This patchy distribution might reflect the dynamic character of the seafloor and regular gouging of the valley floor by ice that redistributes sediment and biota, even on the scale of a few meters. Nutrient or sediment flux must have varied rapidly to account for differences between faunas. Deposition occurred in a narrow valley under glacial conditions (Colhoun and others, 2010) during a marine incursion onto the continent, and thus water temperature was close to the freezing point of sea water, possibly in the range 21u to +1u or 2uC. The fauna, including the echinoid fragments and sponge spicules, indicates fully marine conditions, and the rarity and low diversity of planktonic species are consistent both with low temperature and shallow water in a narrow embayment. It is very similar to that recorded from raised beaches and modern sediments in Lu¨tzow-Holm Bay well to the west of this locality (Nomura, 1984). It is no surprise that new species were found in the material from Heidemann Valley because very few Pliocene foraminiferal faunas have been documented from the Antarctic. In addition, even though it has been generally

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assumed that the Antarctic fauna has not changed from the Late Neogene to the present, there is some evidence suggesting milder climate and higher sea level (20–35 m) in the Late Neogene (Haq and others, 1987). Fillon (1974) recorded Pliocene faunas from USNS Eltanin cores in the Ross Sea, relating them specifically to the Gauss Polarity Epoch, which also correlates with the Heidemann Valley sequence (Colhoun and others, 2010). Much of Fillon’s fauna represents a deeper water facies with some elongate buliminid and bolivinid infaunal forms and a few agglutinated species; thus, many of the species he recorded were not found in the Heidemann Valley study. Webb (1972, 1974) documented the Pliocene faunas from Wright Valley in the Dry Valleys region, Ross Sea region and they obtained a radiometric age of 3.8–2.5 Ma from the subjacent rocks, which indicates that the Wright Vally section is nearly coeval with the Heidemann Valley section. The faunas from Wright Valley have been shown by Webb and Wrenn (1982) to be coeval with those from the Pecten Conglomerate of Cockburn Island. Webb and Wrenn (1982) divided Dry Valleys Drilling Project sections into a series of zones of which Zone II (3.4–2.5 Ma) is most similar to the Heidemann Valley section. Zone II contains Ammoelphidiella antarctica Conato and Segre, has the lowest occurrence of Globocassidulina crassa rossensis recorded in that study, lacks planktonic species, and has most other species in common with the adjacent zones. Quilty and others (1990) described a small foraminiferal fauna from the Larsemann Hills, about 100 km south of Heidemann Valley, which initially was thought to be comparable in age with the Heidemann Valley fauna, but later analysis of the associated diatom flora indicated an age of 4.5–4.0 Ma (McMinn and Harwood, 1995; Harwood and others, 2000). The Larsemann Hills fauna was collected in poorly consolidated sediment and is dominated by cassidulinids, but the presence of Ammoelphidiella antarctica is noteworthy. A few foraminifera were identified in thin sections of concretions from Marine Plain (Quilty and others, 2000) that are coeval with the Larsemann Hills sediments, but they did not yield enough information to comment on faunal structure. Gazdzicki and Webb (1996) described the foraminiferal fauna from the Pecten Conglomerate of the Cockburn Island Formation on Cockburn Island. They reported that the basalts immediately above and below that unit have KAr ages of 2.0 and 2.8 Ma. Diatoms from the formation (Harwood, 1986) indicate an age of 3.0–2.8 Ma (Jonkers and Kelley, 1998). The concurrent age of 2.8 Ma for the Cockburn Island Formation suggests that the Heidemann Valley sediments are coeval and both deposits are related to a marine incursion upon Antarctica that in turn reflects a warmer climate. Both the Heidemann Valley and Cockburn Island faunas are dominated by cassidulinids. The Cockburn Island fauna differs by the presence of Ammoelphidiella and a few elongate infaunal species. The spatial distribution of samples is much smaller on Cockburn Island than in Heidemann Valley. Whitehead and others (2006) summarized the history of Cenozoic sedimentation in the Lambert Graben-Prydz Bay region and recognized a series of marine incursions referred to as M events. The Heidemann Valley sediments correlate

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best with M10, which was dated at 3.2–2.5 Ma and includes marine sediments recognized at Amery Oasis (,500 km SW) as part of a major marine incursion onto the East Antarctic craton. CONCLUSIONS Marine sediments excavated in Heidemann Valley, Vestfold Hills, are 3.5–2.6 Ma in age and yield a meager fauna of foraminifera, at least three species of bivalves, sponge spicules, echinoid spines, and ostracodes. As expected in the shallow, glaciomarine bay setting, foraminiferal dominance is high and diversity is low. Most samples studied were barren of foraminifera and the recovered fauna is predominantly from three samples. There is no evidence to link abundance, diversity, or dominance to geographic position within the valley or stratigraphic level in the sequence examined. Planoglabratella webbi, is described as a new species and questions remain concerning the identity and affiliation of several forms of Elphidium. The Vestfold Hills is now known to be host to two in situ marine Pliocene sections, at Marine Plain (4.5–4.0 Ma) and Heidemann Valley (3.5–2.6 Ma). The latter coincides with the high sea-level event recorded during the Gauss Normal Magnetic Epoch and known as the mid-Pliocene Climate Optimum. Holocene sediment is widespread (Adamson and Pickard, 1986) and forms a veneer containing a few foraminifera and other marine constituents (Gore and others, 1994). Most of this study has concentrated on a relatively small area in the southern part of the Vestfold Hills, but Quilty and Franklin (1997) showed that there are other sedimentary outcrops scattered in the eastern and northern part of the region. Future studies of those units will further enhance our understanding of the paleoenvironmental evolution of the Vestfold Hills region, in the context of global paleoclimatic change in the Late Neogene. ACKNOWLEDGMENTS I thank many who have been involved in a related project over many years. The support staff of the Australian Antarctic Division; Prof. Eric Colhoun, University of Newcastle was a major influence, as was Dr. Heikki Hirvas of the Geological Survey of Finland. Gerry Nash, Australian Antarctic Division helped (again) with the electron microscopy. Dr. Ken Finger, University of California Museum of Paleontology, Berkeley helped with advice on format. I thank Drs. S. Ishman, M. Katz, and an anonymous reviewer for making comments that have improved this paper. REFERENCES ADAMSON, D. A., and PICKARD, J., 1986, Cainozoic history of the Vestfold Hills, in Pickard, J. (ed.), Antarctic Oasis: Terrestrial Environments and History of the Vestfold Hills: Academic Press, Sydney, p. 63–97. BANNER, F. T., and BLOW, W. H., 1960, Some primary types of species belonging to the superfamily Globigerinacea: Contributions from the Cushman Foundation for Foraminiferal Research, v. 11, p. 1–41.

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