Shallow water benthic foraminifera from the Polonez Cove Formation (lower Oligocene) of King George Island, West Antarctica

    Shallow water benthic foraminifera from the Polonez Cove Formation (lower Oligocene) of King George Island, West Antarctica Wojciech Majewski, Andrzej Ga´zdzicki PII: DOI: Reference:

S0377-8398(14)00046-2 doi: 10.1016/j.marmicro.2014.05.003 MARMIC 1525

To appear in:

Marine Micropaleontology

Received date: Revised date: Accepted date:

17 December 2013 7 May 2014 13 May 2014

Please cite this article as: Majewski, Wojciech, Ga´zdzicki, Andrzej, Shallow water benthic foraminifera from the Polonez Cove Formation (lower Oligocene) of King George Island, West Antarctica, Marine Micropaleontology (2014), doi: 10.1016/j.marmicro.2014.05.003

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT Shallow water benthic foraminifera from the Polonez Cove Formation (lower Oligocene) of King George Island, West Antarctica

Institute of Paleobiology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warszawa,

IP

1

1

T

Wojciech Majewski1

* [email protected], (48 22) 625 88 53

SC R

Poland

NU

Keywords: microfossils, foraminifera, Cenozoic, South Shetlands, Antarctica.

AC

CE P

TE

D

MA

Abstract: We present the first description of benthic foraminifera from the lower Oligocene of the Antarctic Peninsula sector (South Shetlands) of West Antarctica. The single assemblage was collected at several sites and has no modern Antarctic analogue. It is dominated by robust calcareous species and represents a fan-delta front system. The assemblage includes a group of the most morphologically conservative Antarctic foraminifera known from other Cenozoic neritic sites around Antarctica, indicating their presence since at least the Eocene. Despite including some characteristic taxa, e.g., sp., it is difficult to correlate this assemblage with any particular interval of the Ross Sea record, mainly because of a strong taxonomic imprint of a shallow water environment.

ACCEPTED MANUSCRIPT Shallow water benthic foraminifera from the Polonez Cove Formation (lower Oligocene) of King George Island, West Antarctica

IP

T

Keywords: microfossils, foraminifera, Cenozoic, South Shetlands, Antarctica.

Abstract: We present the first description of benthic foraminifera from the lower Oligocene

SC R

of the Antarctic Peninsula sector (South Shetlands) of West Antarctica. The single assemblage was collected at several sites and has no modern Antarctic analogue. It is dominated by robust calcareous species and represents a fan-delta front system. The assemblage includes a group

NU

of the most morphologically conservative Antarctic foraminifera known from other Cenozoic neritic sites around Antarctica, indicating their presence since at least the Eocene. Despite sp., it is difficult to correlate this

MA

including some characteristic taxa, e.g.,

assemblage with any particular interval of the Ross Sea record, mainly because of a strong

D

taxonomic imprint of a shallow water environment.

TE

1. Introduction

1.1. Fossil benthic foraminifera from the Cenozoic of West Antarctica

CE P

Despite the level of scientific activity in the area, there is still surprisingly little known about pre-Holocene foraminifera from the Antarctic Peninsula sector of West Antarctica, and most of what is known comes from natural outcrops. Substantial gaps in the foraminiferal

AC

record of the Antarctic Peninsula prevent thorough stratigraphic and evolutionary studies, and comparisons with records from the Ross Sea sector, which are far more complete thanks to several drilling campaigns (Leckie and Webb 1986; Webb 1988, 1989; Coccioni and Galeotti 1997; Galeotti et al. 2000; Strong and Webb 2000, 2001; Webb and Strong 2000, 2006; Patterson and Ishman 2012). In the Antarctic Peninsula sector, early Paleocene foraminiferal assemblages have been reported from the James Ross Island region, where Upper Cretaceous to Paleocene assemblages were investigated by Huber (1988). The second report on Paleogene benthic foraminifera has been published only recently, on lower Eocene assemblages from the La Meseta Formation of Seymour Island foraminifera are only slightly better studied. Miocene benthic foraminifera from the Cape Melville Formation, exposed on the far east of King George Island, were described by . Some more detailed reports on

and

ACCEPTED MANUSCRIPT

benthic foraminiferal assemblage was reported from a SHALDRIL core from the Weddell Sea, located ~120 km off Joinville Island (Majewski et al. 2012). Although the host sediment , thus

T

was dated at ~12.5 Ma (Anderson et al. 2011), the assemblage seems to be not

IP

probably slightly older in age. The only stratigraphically younger, pre-Holocene benthic assemblages were described from Miocene-Pliocene strata of James Ross Island (Jonkers et

SC R

al. 2002), Pliocene of Cockburn Island

Vega Island (Carames and Concheyro 2013); all located east of the Antarctic Peninsula.

NU

1.2. The Polonez Cove Formation

The benthic foraminiferal assemblage described in this work occurs in the glaciomarine strata of the Polonez Cove Formation (PC Fm.), best exposed in coastal cliffs and

MA

ledges on the Bransfield Strait side of King George Island (South Shetlands) between Low Head and Lions Rump, as well as on Magda and Conglomerate nunataks (Fig. 1). The

D

sediments of the PC Fm. were deposited during the Oligocene Polonez Glaciation

TE

largest Cenozoic glaciations in West Antarctica, with the continental ice-sheet present on King George Island (Birkenmajer 1983; Troedson and Smellie 2002).

CE P

The PC Fm. is ~60-m thick and comprises of six lithostratigraphic members (Fig. 2). The lowest, Krakowiak Glacier Member (Mb.) includes continental tillites, while the succeeding Bayview Mb., Low Head Mb., Siklawa Mb., Oberek Cliff Mb., and Chlamys

AC

Ledge Mb. are coastal glacio-marine strata composed of conglomerates and sandstones interbedded with mudstones. These strata were initially considered to be Pliocene in age (e.g.,

2002) proved the Oligocene age of this formation. The Low Head Member of the PC Fm. was finally dated as early Oligocene based on a suite of planktonic foraminifera including and nannoplankton

and

1985; Birkenmajer et al. 1988, 1991), as well as Sr isotope stratigraphy yielding an age of 28.5-29.8 Ma for the PC Fm. (Dingle et al. 1997; Dingle and Lavelle 1998; Troedson and Smellie 2008). The Low Head Mb. is up to 20-m thick and is the most fossiliferous one. The best exposure of this sequence is at site I, located at the foot of a prominent cliff at the base of

ACCEPTED MANUSCRIPT Chopin Ridge in Polonez Cove (Figs 1 and 2). It comprises glacio-marine strata formed in a shallow-water marine setting controlled by calving ice-sheets and hosting a cold-water -

T

rafted dropstones are common. The occurrence of the bivalve beds (Figs 4-5) with numerous

IP

(Jonkers, 2003; also see Beu and Taviani 2013), interbedded with

SC R

shales and fine-grained sandstones, indicates deposition in a fan-

(Quaglio et al. in press).

The strata of the PC Fm. are especially rich in both sessile and vagile benthic fossils,

NU

including foraminifera. In fact, the existence of a benthic foraminiferal assemblage in the Low

MA

reported the occurrence of scarce planktonic foraminifera (13 specimens belonging to 3 genera:

and

TE

D

1989a). Other studies documented fossils, including algal microfossil

and Rhynchonellida (Bitner and Pisera 1984; Bitner et al. 2009),

CE P

wska 1984; Quaglio et al. 2008, in

press), echinoids (Jesionek2008).

AC

2. Methods

cki in the austral summers of

1978/79, 1980/81 and 2006/07. Nine rock samples of approximately 1 kg in weight were collected at sites I V from the Low Head Mb. and one sample at site VI from the Chlamys Ledge Mb. in the area of Low Head

Lions Rump (Fig. 1). Two more samples, collected by

K. Birkenmajer, came from the Magda (A-682) and Conglomerate (A-688) nunataks located on Kraków Icefield (Fig. 1). In total, twelve samples were investigated. It is important to note that sites II and III (Fig. 1 and p accessible as they are completely covered by rock debris, which accumulated in the lower part of the cliff over the last decades. Foraminiferal specimens were extracted after mechanical crushing and treatment of the rock fragments with Glauber salt. Disintegrated sediments were washed through a set of sieves. The >125 m fraction of the residue was studied under a light microscope. All

ACCEPTED MANUSCRIPT foraminiferal specimens isolated from this fraction were picked and mounted on micropaleontological slides. Selected specimens of each species were studied under SEM. Generic classification was based on Loeblich and Tappan (1987). The investigated collection

T

is housed at the Institute of Paleobiology of the Polish Academy of Sciences (Warszawa)

IP

under the catalogue number ZPAL F.66.

SC R

3. Results

All twelve samples examined contain benthic foraminifera. In 7 samples, more than 100 specimens have been collected, and 3 samples contained more than 1000 specimens

NU

(Table 1). All of these richly fossiliferous samples came from the Low Head Mb. of the PC Fm., from the coastal shell beds with numerous pectenid

. The

MA

benthic foraminiferal assemblages are strongly dominated by calcareous benthic taxa, while agglutinated foraminifera are nearly absent. More than 60 foraminiferal species were recognized, numbering 6683 specimens in total. The most abundant taxon,

,

,

,

,

,

,

TE

species of

D

s.l., accounts for more than a half of this number. Other common taxa, including

, as well as miliolids and unilocular calcareous foraminifera, are significantly less

,

CE P

abundant. Planktonic foraminifera are very sparse. The 13 specimens belonging to , and

, came from the single sample I/11

AC

Taxonomical notes

sp. (Fig. 9.13-15). Our specimens resemble specimens pictured by Leckie

and Webb (1986: plate 10.1-10, 21.1-7), however the specimens from the PC Fm. show the exterior completely covered by pustules and less trochospiral coiling than the specimens of Leckie and Webb (1986). ?

sp. (Fig. 9.11-12). Although poor preservation makes it difficult to

recognize morphological details, e.g., presence of pustules typical for

, this

taxon shows the general characteristics of this genus. It seems to be associated with sp., and shows similar opaque test walls. sp. (Fig. 9.4). It is represented by a single, poorly preserved specimen. There appear to be remnants of the sutural plates, which outline resembles that of Kennett, 1967.

ACCEPTED MANUSCRIPT sp. (Fig. 8.18). This taxon resembles

(Reuss, 1850), but it appears wider

and more ornamented. cf.

Cushman and Parker, 1937 (Fig. 8.15). It shows less developed

sp. (Fig. 11.9). Our specimen shows general shape and lenticular section of this

IP

?

T

spines, but the same chamber shape as the typical form.

genus. However, it lacks an umbilical apertural flap, which may be missing because of

SC R

incomplete preservation. A very similar specimen was pictured by Quilty (2001: plate 3, figs 21-22) and classified as

. However, the smooth wall surface

of our specimen without pustules indicates that it is a benthic species.

NU

sp.1 (Fig. 10.9-11). This seems to be a polyphyletic taxon, grouping forms of uncertain classification and considerable morphologic variability.

MA

sp. 2 (Fig. 10.12). The characteristic coarse perforation resembles that of (Karrer, 1864), especially the specimen pictured by Hornibrook et al. (1989). Nevertheless, it differs from the latter species by the less pronouncedly biconvex profile and

D

the more pronounced two last chambers, compared to the earlier ones.

TE

s.l. Vella, 1957 (Fig. 10.1-6). This is the most abundant and morphologically diverse species in our samples. Its morphological plasticity was also noted

CE P

for late Oligocene - early Miocene Ross Sea populations described by Leckie and Webb (1986).

sp. (Fig. 10.13) is analogous with

from recent sediments of

AC

Patagonian fiords, as used by Hromic et al. (2006). It is significantly different from ngly curved sutures, as opposed to the weakly

curved to nearly radial sutures in our specimens. (Fichtel and Moll, 1798) (Fig. 9.1). We dispose of a single, strongly

recrystallized specimen. It shows all characteristics of this morphologically diverse taxon, presented by Pillet et al. (2012). (Brady, 1884) (Fig. 11.12-13) shows, characteristic for this species, single aperture perpendicular to the basal suture of the last chamber. However, in Recent Antarctic settings,

is typical for deep-water environments, where it is

represented by smaller specimens with less massive test walls than the majority of the specimens from the PC Fm. Recent Antarctic shallow-water settings are dominated by more strongly built (Majewski and Pawlowski 2010).

, showing a double aperture in adult specimens

ACCEPTED MANUSCRIPT ?

sp. (Fig. 11.18-19). Its early chambers are clearly biserial and only slightly

coiled, much like in

, however, more matured globular specimens show

overlapping chambers typical for Cassidulininae. sp. (Fig. 11.6). An imperfect preservation, obscuring morphological structures,

T

?

IP

prevents explicite taxonomic determination of our specimens. cf.

Galloway and Hemingway, 1941 (Fig. 6.10). Our specimens show

SC R

fewer costae than the holotype but seem similar to specimens pictured by Boltovskoy and Watambe (1993) from DSDP Site 525.

spp. (Fig. 8.5-10). This is a morphologically diverse group, which might

NU

include more than one species. Large specimens show massive, thick outer walls and a completely recrystallized interior, leaving little morphological details for precise

?

MA

classification.

sp. (Fig. 8.4). The poor preservation of our single specimen makes a more

precise systematic determination speculative.

(Linnaeus, 1758) (Fig. 7.6). This taxon shows similarity to (e.g., Jones 1994; Hayward et al. 1999) by its

TE

some specimens described as

D

cf.

overall chamber shape and the somehow angular profile. It differs from the holotype

CE P

illustrated by Linnaeus by the much narrower final chamber, especially in the apertural area. cf.

Cushman, 1921 (Fig. 7.7). This taxon differs from the

holotype only by the more depressed sutures and narrower chambers as viewed in profile (Fig. 7.7b)

AC

sp. (Fig. 11.5). The classification of our single specimen is based on the very

characteristic wall of the umbilical side ornamented with radically oriented striate and pustules.

4. Discussion 4.1. Foraminiferal preservation Only three agglutinated tests were found among the nearly 6700 isolated specimens. This surprisingly low contribution may be due to environmental conditions, post-depositional processes e.g., reworking and diagenesis, and/or sample treatment, but most likely due to a combination of these factors. It seems probable that agglutinated forms were more abundant within the original, living assemblages, especially in view of the disintegration of numerous

ACCEPTED MANUSCRIPT modern agglutinated taxa during early diagenesis, which is well known from Holocene sediments (e.g., Schröder 1988). Relatively high abundances of

, along with

and other

T

species with rather massive tests, underline the strong dominance of robust foraminifera in the

before,

IP

analyzed material. This seems to result from a combination of the same factors as mentioned the composition of the original assemblage and an enrichment in resistant

SC R

specimens after deposition. It appears that the latter could take place through remobilization and sorting of the sediment (e.g., Murray et al. 1982), winnowing due to current activity (e.g.,

NU

Hromic et al. 2006; Majewski and Anderson 2009), or selective dissolution of more fragile

-delta

MA

environment, with winnowing by tidal currents being the mechanism responsible for macrofossil concentration within the Low Head Mb. (Quaglio et al. in press). This mechanism could also explain very well the composition of the benthic foraminiferal assemblages from

D

the PC Fm., with a strong presence of robust forms. The rather violent sample treatment could

TE

strengthen this aspect by further enriching the fossil assemblage in more resistant taxa. Despite this potential bias, the foraminifera from the PC Fm. represent unique, diverse, and

CE P

abundant assemblage, extremely rarely reported from marine and glacio-marine Paleogene sediments throughout the Antarctic Peninsula sector of West Antarctica.

4.2. Benthic foraminiferal assemblage and its paleoenvironmental interpretation

AC

To analyze the variability among the foraminiferal populations reported from the twelve analyzed samples (Table 1), a matrix with the Renkonen's similarity indices ( calculated according to the formula

) was

, p ), where p1i is the frequency of species

in sample (Wolda 1981). The Renkonen's similarity index is considered one of the best similarity coefficients because it is not heavily influenced by sample size and species number. The

matrix presented in Table 2 shows values between 17.0% and 89.6% of similarity

with the average calculated for all coefficients at 69.1 %, indicating very high similarity between the samples. Samples showing lower values than the average, e.g., VI, A-682, and I/10, have low numbers of specimens, so that their analysis based on the statistical treatment is problematic. Consequently, our statistical results do not support the presence of a substantial variability between the populations extracted from different samples reported in this study. Instead, they suggest the presence of a single foraminiferal assemblage in all the samples that were analyzed for foraminifera.

ACCEPTED MANUSCRIPT As discussed above, it is possible that the population structure and taxonomic composition of the original assemblage might have been modified by depositional processes and sample treatment. Irrespective of this potential bias, ,

,

,

,

, and

,

T

,

along with

IP

as well as miliolids and unilocular calcareous foraminifera, dominate the fossil assemblage and had to constitute an essential part of the original assemblage. Although many of these

SC R

taxa could be present in mid-neritic to upper bathyal environments (e.g., Leckie and Webb 1986), the strong variability in foraminiferal abundances, combined with high scores of robust tests, and very low numbers of planktonic forms indicate shallow-water, near-shore and rather

NU

turbid conditions. This assessment agrees with sedimentological analyses supporting a prograding fan delta system for the Low Head Mb., located in a shallow-water marine

MA

environment, in large part at depths affected by winnowing due to tidal currents (Quaglio et al. in press).

The taxonomic composition of the lower Oligocene assemblage from PC Fm. does not

D

correspond strictly to any assemblages reported from modern Antarctic environments. One of

TE

the reasons is evolutionary change over the last almost 30 million years, being expressed for ranging only until the Pliocene (Webb 1974; Leckie and Webb

and

CE P

example in

, as well as less abundant

are still fairly common

throughout Antarctic shelf waters (e.g., Violanti 1996; Igarashi et al. 2001; Majewski 2013) and around King George Island itself (Majewski 2005, 2010), they do not represent the same

AC

species in the early Oligocene and in the modern assemblages. Other genera such as and

are fairly common in the assemblage from the PC Fm., but are only

occasionally reported from the present day Antarctic shelf (e.g., Majewski 2005, 2013). They are very minor components in these recent assemblages. Their modern abundances cannot match those reported from the PC Fm. Moreover, other genera, also common in our samples, including

and

, appear to be absent in the present day Antarctica, but they

do inhabit fjords of Patagonia (Hromic et al. 2006), which are characterized by much milder climatic conditions than West Antarctica. Considering these observations, the overall benthic foraminifera assemblage from the PC Fm. does not seem to be out of place and corresponds to a rather shallow-water environment with elevated water energy, interpreted for the Low Head Mb. sediments. The taxonomic differences between the fauna from PC Fm. and modern Antarctica are not surprising, considering the Oligocene age of the fossil material. However, the association of

ACCEPTED MANUSCRIPT the most abundant fossil genera does not correspond to any communities known from present day Antarctica, but the fossil assemblage shows similarieties with present day temperate faunas from across the Drake Passage, arguing for less severe climates during the late early

IP

T

Oligocen

4.3. Shallow-water Cenozoic foraminiferal assemblages from Antarctic Peninsula

SC R

The known Cenozoic foraminiferal record from the Antarctic Peninsula region remains fragmentary. The assemblage described from the PC Fm. is the first benthic foraminiferal record from Oligocene strata, therefore a direct comparison with other

NU

contemporaneous faunas from the area is impossible. The taxonomy of the early Paleocene outer neritic assemblage from the James Ross Island region described by Huber (1988) is very

MA

different from taxa reported in this paper. Although the Eocene assemblages of the La Meseta -water

environment, the stratigraphical difference of over 20 million years, including the major

D

Eocene/Oligocene climatic cooling (DeConto and Pollard 2003; Francis et al. 2009; Liu et al.

sections are limited to

(

, sister species of

and

,

, and

CE P

,

TE

2009), explains strong faunal differences. Species found both in the Oligocene and Eocene

. Otherwise, the dominant elements of the Eocene and

Oligocene assemblages are markedly different, in case of the Eocene La Meseta Fm. showing

AC

than the assemblage from the PC Fm. The lower Miocene benthic foraminiferal assemblages from Cape Melville Fm.

22.6 Ma (Dingle and Lavelle 1998) and are significantly younger. Moreover, they are rich in agglutinated species and represent a markedly deeper-water outer-shelf environment (Birkenmajer 1995; study. It is not surprising that the number of shared species is even smaller than in the case of the fauna from the La Meseta Fm. It appears that only , and

,

,

occur both in assemblages from the Polonez Cove and Cape

Melville formations. However, the poor quality of photographic documentation of the Miocene assemblage prevents conclusive comparisons. In fact, the foraminiferal assemblage from the PC Fm. shows more simmilarity with even younger, Miocene-

ACCEPTED MANUSCRIPT Webb 1996) and James Ross (Jonkers et al. 2002) islands, located on the opposite side of the Antarctic Peninsula. This may be explained by the similar shallow-water paleoenvironment of the two records, which are both dominated by calcareous species. The species shared with the ,

,

,

, and

. All but the latter

T

PC Fm. are

IP

taxon are also noted from the shallow-water assemblage of the lower Eocene La Meseta Fm.

SC R

2013). Thus, they appear to constitute a group of morphologically very conservative neritic Antarctic foraminifera that have been present in the area since at least the early Eocene. The presence of several long-ranging and morphologically conservative species in

NU

West Antarctica throughout well over 50 million years, inferred from the paleontological data only, is not that straightforward. For example, recent

appears to be a deep-

MA

water species, which in shallow waters has been replaced by the evolutionally younger (e.g., Fillon 1974). In some cases, specimens of these two species may be distinguished only using molecular analysis (Majewski and Pawlowski 2010), which

D

is unfortunately not applicable for fossil material. Despite a likelihood of similar

TE

complications also in case of other species, the possibility of a continuous presence in shallow-water Antarctic settings of benthic foraminiferal taxa such as ,

, and

is remarkable.

CE P

,

,

4.4. Cenozoic record from Ross Sea and biostratigraphic position of the PC Fm. foraminiferal assemblage

AC

The record of Cenozoic evolution of benthic foraminifera is much better understood in the Ross Sea area thanks to several drilling campaigns: DVDP and DSDP (Leckie and Webb 1986; Webb 1988), CIROS (Webb 1989; Coccioni and Galeotti 1997), CRP (Galeotti et al. 2000; Strong and Webb 2000, 2001; Webb and Strong 2000, 2006), and ANDRIL (Patterson and Ishman 2012). All these efforts have led to a solid benthic foraminiferal record reaching back to the late Eocene (Coccioni and Galeotti 1997). Unfortunately, its relevance for our new record is limited, as the records from the Ross Sea represent considerably deeper water paleoenvironments than that of the PC Fm. However, the record from the Ross Sea does include data corresponding with the PC Fm. stratigraphically, i.e. from the lower Oligocene. Some upper Eocene to lower Oligocene assemblages were reported from lower part of the CIROS-1 drillhole (Webb 1989; Coccioni and Galeotti 1997) and lower Oligocene faunas were described from the CRP-3 drillhole (Strong and Webb 2001). However, these records, despite being of the same age, do not show

ACCEPTED MANUSCRIPT a stronger faunal affinity with the PC Fm. than the Eocene and Miocene-Pliocene shallowwater faunas from the Antarctic Peninsula. In fact, the long-ranging Antarctic foraminifera mentioned above are also present among fossil assemblages from the Ross Sea throughout the

T

Cenozoic (e.g., Leckie and Webb 1986; Webb 1989; Coccioni and Galeotti 1997), as well as

IP

in modern faunas (Webb 1988; Violanti 1996). It appears that the environmental influences on the foraminiferal assemblages from the Ross Sea, related to the apparent bathymetrical

SC R

differences, strongly overprints evolutionary changes to the point where a straightforward biostratigraphical correlation of the PC Fm. with the Ross Sea Cenozoic record is difficult to establish.

NU

Nevertheless, the assemblage from the PC Fm. seems to bear the most resemblance to the lower part (lithologic units 2I and 2H) of the upper Oligocene G-C-T Assemblage Zone ) from DSDP Site 270 (Leckie and

MA

(

Webb 1983, 1986). The similarity is expressed most of all by high abundances of spp., accounting for ~30% of the total assemblage and including spp., including

D

increasing abundances of

s.l.,

(

) spp. The

TE

appearance and percentage increase of

, and a sudden

problem is, however, that at DSDP Site 270, these three taxa, which are also the most

CE P

prominent in the PC Fm. assemblage, were not contemporaneous, i.e. the appearance of and

increase in other foraminifera, like

coincided with sharp decline in

and an

, that are practically absent in our samples.

Some of these discrepancies, which hamper a firm correlation, may result from a

AC

deeper bathymetrical setting of the G-C-T Assemblage Zone of Lecke and Webb (1983, 1986) as compared to the Low Head Mb. of the PC Fm. In the upper Oligocene part of the DSDP Site 270, no abundant macrofossil shells similar to the pectenids from PC Fm. were found (Leckie, personal communication), which, together with a common presence of planktonic foraminifera, confirms the deeper water setting of Site 270 in the Ross Sea. The differences may also result from a younger age of the G-C-T Assemblage Zone from Site 270 dated at less than 26 Ma (Lecke and Webb 1983 and references herein) compared to the Low Head Mb. of the PC Fm., dated at ~29 Ma (Dingle and Lavelle 1998). Another problem is the poor resolution of the stratigraphic ranges of the foraminiferal species constituting the PC Fm. assemblage. This is well illustrated by the two most characteristic species from the PC Fm. record.

sp. and the most common

s.l. are both present among foraminifera from the upper Oligocene - lower Miocene glacio-marine section of DSDP Site 270 (Leckie and Webb 1986).

is

ACCEPTED MANUSCRIPT potentially important stratigraphically, as it belongs to a relatively rapidly evolving genus (Leckie and Webb 1986), but to-date its evolution remains poorly understood. s.l. is a morphologically variable taxon with a long range, spanning from late

T

Eocene to the Recent in New Zealand (Hornibrook 1961), and in Antarctica being common

IP

throughout most of upper Oligocene - lower Miocene (Leckie and Webb 1986). In fact, similar correlation problems have been evoked by Strong and Webb (2001), who concluded

SC R

that species from the early Oligocene section of CRP-3 were either long-ranging or had poorly resolved ranges, and therefore they were of no use for external correlations,

NU

necessitating further investigations.

5. Conclusions

MA

Abundant and diverse benthic foraminifera are described for the first time from Oligocene strata of the Antarctic Peninsula sector of West Antarctica. They come predominantly from a prograding fan-delta front facies of the upper lower Oligocene Low Head Mb. of the Polonez

D

Cove Fm. on King George Island. Despite being collected from eight different sites they

along with

,

,

,

,

,

, as well as miliolids and unilocular calcareous foraminifera. The

CE P

, and

TE

constitute a single assemblage strongly dominated by calcareous species, belonging to

faunas are clearly enriched in foraminifera with robust tests. This assemblage does not correspond to any known modern Antarctic foraminiferal community, but it shows some links with Patagonian assemblages, suggesting different environmental conditions during the early

AC

Oligocene than in Recent Antarctica. The benthic foraminiferal assemblage from the Polonez Cove Fm. shares a group of common species with other Cenozoic neritic sites from the Antarctic Peninsula and Ross Sea region, including ,

, , and

, (

. These species form a group of morphologically very conservative Antarctic foraminifera, that seem to be present continuously in neritic Antarctic settings since the Eocene. Despite also including some endemic Antarctic taxa, for example species of the extinct

, the assemblage from the Polonez Cove Fm. is difficult to correlate

biostratigraphically with the foraminiferal record from the Ross Sea that is characterized by deeper-water assemblages. Apparently, a strong environmental imprint on the foraminiferal assemblages overshadows their long-term evolutionary changes, complicating biostratigraphical correlations.

ACCEPTED MANUSCRIPT Acknowledgements We would like to thank Ewa Hara for support with sample processing. The latest stages of this study were supported by a grant of the National Science Centre, Poland No.

T

2011/01/B/ST10/06956. R. Mark Leckie and an anonymous reviewer provided helpful

IP

comments for improving this manuscript.

SC R

References

Anderson J.B., Warny S., Askin R.A., Wellner J.S., Bohaty S.M., Kirshner A.E., Livsey D.N., Simms A.R., Smith T.R., Ehrmann W., Lawver L.A., Barbeau D., Wise S.W.,

NU

Kulhanek D.K., Weaver F.M., Majewski W. 2011. Progressive Cenozoic cooling and

MA

108, 11356-11360.

Barton C.M. 1965. The geology of the South Shetland Islands. III. The stratigraphy of King George Island.

44, 1-33.

D

Beu A. and Taviani M. In press. Early Miocene Mollusca from McMurdo Sound, Antarctica

(Bivalvia).

TE

(Andrill 2A drill core), with a review of Antarctic Oligocene and Neogene Pectinida .

CE P

Birkenmajer K. 1982. Pliocene tilite-bearing succession of King George island (South Shetland Islands, Antarctica).

74, 7-22.

Birkenmajer K. 1983. Extent and course of the Pliocene glaciations in West Antarctica. 30, 9-20.

AC

Birkenmajer K. 1995. The Cape Melville Formation (Lower Miocene glacio-marine deposits on King George Island, South Shetland Islands (West Antarctica): its basal and top strata.

43, 113-122.

Birkenmajer K. 2001. Mesozoic and Cenozoic stratigraphic units in parts of the South Shetland Islands and Northern Antarctic Peninsula (as used by the Polish Antarctic Programmes). Birkenmajer K. and

118, 5-188. Conglomerate on King

George Island, West Antarctica.

34, 219-

226. ne age of glaciomarine and related strata, Moby Dick Group, King George Island (South Shetland Islands, Antarctica).

90, 81 123.

ACCEPTED MANUSCRIPT Birkenmajer K., Dudziak J., Tokarski A.K. 1988. Paleogene calcareous nanoplankton from a neptunian dyke in the Low Head Member: its bering on the age of the Polonez Glaciation in West Antarctica.

95, 7-21.

T

Birkenmajer K.,

IP

Origin and age of pectinid-bearing conglomerate (Tertiary) on King George Island, West Antarctica. 663 665. In: Thomson M.R.A., Crame J.A. and Thomson J.W. (eds).

SC R

. Cambridge University Press, Cambridge, viii + 722 p

B. 2009. Brachiopods from the Chlamys Ledge

NU

Member (Polonez Cove Formation, Oligocene) of King George Island, West Antarctica.

30, 277-290.

MA

Boltovskoy E. and Watambe S. 1993. Cenozoic monothalamous foraminifers from DSDP Site 525 (southern Atlantic).

39, 1-27

Carames A. and Concheyro A. 2013. Lace Cenozoic foraminifera from diamictites of Cape 50, 114-135.

D

Lamb, Vega Island, Antarctic Peninsula.

TE

Coccioni R. and Galeotti S. 1997. Foraminiferal biostratigraphy and palaeoecology of the CIROS-1 core from McMurdo Sound (Ross Sea, Antarctica).

CE P

117.

4, 103-

DeConto R.M and Pollard D. 2003. Rapid Cenozoic glaciation of Antarctica induced by declining atmospheric CO2

421, 245-249.

Dingle R.V. and Lavelle M. 1998. Antarctic Peninsular cryosphere: Early Oligocene ( . 30

AC

Ma) initial and a revised glacial chronology. 155, 433-437.

Dingle R.V., McArthur J.M., Vroon P. 1997. Oligocene and Pliocene interglacial events in the Antarctic Peninsula dated using strontium isotope stratigraphy. 154, 257-264. Fillon R.H. 1974. Late Cenozoic foraminiferal paleoecology of the Ross Sea, Antarctica. 20, 129 151. Francis J.E., Marenssi S., Levy R., Hambrey M., Thorn V.C., Mohr B., Brinkhuis H., Warnaar J., Zachos J., Bohaty S., DeConto R. 2009. From greenhouse to icehouse the Eocene-Oligocene in Antarctica. In: Developments in Earth and Environmental Sciences 8, Elsevier, Amsterdam

(eds. F. Florindo and M. Siegert): 309 368.

ACCEPTED MANUSCRIPT Galeotti S., Cita M.B., Coccioni R. 2000. Foraminiferal biostratigraphy and paleoecology from two intervals of the CRP-2/2A drillhole, Victoria Land Basin, Antarctica. 7, 473 478.

T

Oligocene coccoliths of the Pecten Conglomerate, West 12, 727-735.

IP

Antarctica.

coquinas in glacio-marine sediments (Pliocene) of King 10, 145-152.

SC R

George Island, West Antarctica.

Planktonic foraminifera from the Oligocene Polonez Cove Formation of King George Island. West Antarctica.

(Chrysophyta) from Tertiary glacio-marine

NU

1989b. Microfossil

10, 47-55.

sediments of King George Island, West Antarctica.

MA

586.

10, 581-

2008. Provenance of recycled stromatolites from the Polonez Cove Formation (Oligocene) of King George Island, West Antarctica.

Cooper A.K., P.J. Barrett , H.

D

Stagg, B. Storey, E. Stump, W. Wise and the 10th ISAES editorial team, eds. (2008).

TE

Proceedings of the 10th International

Symposium on Antarctic Earth Sciences. Washington, DC: The National Academies

CE P

Press. EA 143, 1-3.

Foraminifera from the Eocene La Meseta Formation of

Isla Marambio (Seymour Island), Antarctic Peninsula. G

24, 408-416.

A. and Pugaczewska H. 1984.

AC

Formation, Pliocene) of King George Island (South Shetland Islands, Antarctica). 79, 59-120. 1992. An Oligocene rekord of the coral

Antarctica. G

from

13, 265-272..

A. and Webb P.−N. 1996. Foraminifera from the

Conglomerate (Pliocene)

of Cockburn Island, Antarctic Peninsula.

55, 147–174.

Hara U. 1992. Cyclostomatous Bryozoa from the Polonez Cove Formation of King George Island, West Antarctica.

13, 255-263..

Hayward B.W., Grenfell H.R., Reid C.M. and Hayward K.A. 1999. Recent New Zealand shallow-water benthic foraminifera: Taxonomy, ecologic distribution, biogeography, and use in paleoenvironmental assessment 21, 258 p.

ACCEPTED MANUSCRIPT Hornibrook N. de B. 1961. Tertiary foraminifera from Oamaru District (N.Z.). Part I Systematics and Distribution. 34, 192 p.

T

Hornibrook N. de B., Brazier R.C., Strong C.P. 1989 Manual of New Zealand Permian to

IP

Pleistocene foraminiferal biostratigraphy. 56, 175 p.

SC R

Hromic T., Ishman S., Silva N. 2006. Benthic. foraminiferal distributions in Chilean fjords: 47ºS to 54ºS.

59, 115 134.

Huber B.T. 1988. Upper Campanian–Paleocene foraminifera from the James Ross Island : Feldmann R.M. and Woodburne M.O. (eds) Geology

NU

region, Antarctic Peninsula.

and paleontology of Seymour Island, Antarctic Peninsula.

MA

169, 163–252.

Igarashi A., Numanami H., Tsuchiya Y., Fukuchi M. 2001. Bathymetric distribution of fossil foraminifera within marine sediment cores from the eastern part of Lutzow−Holm

D

Bay, East Antarctica, and its paleoceanographic implications.

TE

42, 125–162. Jones R.W. 1994.

. Oxford: Oxford University Press, 149 pp.

CE P

Jonkers H.A., Lirio J.M., Del Valle R.A., Kelley S.P. 2002. Age and environment of Miocene–Pliocene glaciomarine deposits, James Ross Island, Antarctica. 139, 577–594.

AC

Leckie R.M. and Webb P.N. 1983 Late Oligocene Early Miocene glacial record of the Ross Sea. Antarctica: evidence from DSDP Site 270.

11, 578-82.

Leckie R.M. and Webb P.N. 1986. Late Paleogene and early Neogene foraminifers of DSDP Site 270, Ross Sea, Antarctica.

90, 1093 1142.

Liu Z.H., Pagani M., Zinniker D., DeConto R., Huber M., Brinkhuis H., Shah S.R., Leckie R.M., Pearson A. 2009. Global cooling during the Eocene-Oligocene climate transition.

323, 1187 1190.

Loeblich Jr A.R. and Tappan H. 1987.

. Van

Nostrand Reinhold, New York: 970 pp. Majewski W. 2005. Benthic foraminiferal communities: distribution and ecology in Admiralty Bay, King George Island, West Antarctica. 214.

26, 159-

ACCEPTED MANUSCRIPT Majewski W. 2010. Benthic foraminifera from West Antarctic fiord environments: An overview.

31, 61-82.

Majewski W. 2013. Benthic foraminifera from Pine Island and Ferrero bays, Amundsen Sea.

T

34, 169-200.

Tay, Antarctic Peninsula: Paleoclimate implications.

73,

SC R

135-147.

IP

Majewski W. and Anderson J.B. 2009. Holocene foraminiferal assemblages from Firth of

Majewski W. and Pawlowski J. 2010. Morphologic and molecular diversity of the foraminiferal genus Globocassidulina in Admiralty Bay, West Antarctica.

NU

22, 271-281.

Majewski W., Olempska E., Kaim A., Anderson J.A. 2012. Rare calcareous microfossils from

MA

Middle Miocene strata, Weddell Sea off Antarctic Peninsula. 33, 245-257.

Murray J.W., Sturrock S., Weston J. 1982. Suspended load transport of foraminiferal tests in a 12, 51-65.

D

tide- and wave-swept sea.

TE

Patterson M.O. and Ishman S.E. 2012. Neogene benthic foraminiferal assemblage zones and paleoenvironmental record for McMurdo Sound, Antarctica.

CE P

1341.

8, 1331-

Pillet L., Fontaine D., Pawlowski J. 2012. Intra−genomic ribosomal RNA polymorphism and morphological variation in

AC

in foraminifera.

suggests inter−specific hybridization 7, e32373. Depositional history of the Polonez Cove Formation

(Oligocene), King George Island, West Antarctica: a record of continental glaciation, shallow-marine sedimentation and contemporaneous volcanism. 93, 7-62. Quaglio F., Anelli L.E., dos Santos P.R., Rocha-Campos A. C. 2008. Invertebrates from the Low Head Member (Polonez Cove Formation, Oligocene) at Vaureal Peak, King George Island, West Antarctica.

20, 149-168.

Quaglio F., Warren L.V., Anelli L.E., dos Santos P.R., RochaStrikis P.C., Ghilardi R.P., Tiossi A.B. In press. Shell beds from the Low Head Member (Polonez Cove Formation, Early Oligocene) at King George Island, West Antarctica: new insights on facies analysis, taphonomy and environmental significance.

. DOI: 10.1017/S0954102013000783

ACCEPTED MANUSCRIPT Quilty P.G. 2001. Reworked Paleocene and Eocene foraminifera, Mac. Robertson Shelf, East Antarctica: paleoenvironmental implications.

31,

369 384.

T

Quilty P.G., Gillieson D., Burgess J., Gardiner G., Spate A., Pigeon R. 1990.

IP

from the Pliocene of Larsemann Hills, East Antarctica. 20, 1 7.

SC R

Schröder C.J. 1988. Subsurface preservation of agglutinated foraminifera in the northwest Atlantic Ocean.

41, 325-336.

Strong C.P. and Webb P.-N., 2000. Oligocene and Miocene foraminifera from CRP-2/2A, 7, 461 472.

NU

Victoria Land Basin, Antarctica.

Strong C.P. and Webb P.-N., 2001. Lower Oligocene foraminiferal fauna from CRP-3 8, 347 358.

MA

drillhole, Victoria Land Basin, Antarctica.

Troedson A.L. and Smellie J.L. 2002. The Polonez Cove Formation on King George Island, Antarctica: stratigraphy, facies and implications for mid-Cenozoic cryosphere 49, 277-301.

TE

D

development.

sp. nov. and other trace

fossils from the Cape Melville Formation (Lower Miocene) of King George Island, 31, 83-99.

CE P

Antarctica.

Violanti D. 1996. Taxonomy and distribution of recent benthic foraminifers from Terra Nova Bay (Ross Sea, Antarctica), Oceanographic Campaign 1987/1988.

AC

83, 25–71.

Webb P.-N. 1988. Upper Oligocene Holocene foraminifera of the Ross Sea region. Special Volume 2, 589 603.

Webb P.-N. 1989. Benthic foraminifera.

Barrett, P.J. (Ed.)

. Bulletin vol. 245. Department of Scientific and Industrial Research, Wellington, New Zealand, pp. 99 118. Webb P.-N. and Strong C.P. 2000. Pliocene benthic foraminifera from CRP-2 (Lithostratigraphic Unit 2.2), Victoria Land Basin, Antarctica.

7(4),

453-459. Webb P-N. and Strong C.P. 2006 Foraminiferal biostratigraphy and palaeoecology in Upper Oligocene-Lower Miocene glacial marine sequences 9, 10, and 11, CRP-2/2A drill hole, Victoria Land Basin, Antarctica. 231, 71-100. Wolda H. 1981. Similarity indices, sample size and diversity.

50, 296-302.

ACCEPTED MANUSCRIPT

Table 1. Foraminiferal counts.

T

Table 2. Renkonen's similarity indices calculated based on foraminiferal percentages from all

IP

12 samples analyzed. Note total numbers of specimens collected from each samples indicated

SC R

for assessing reliability of the percentages used for the calculations.

Fig. 1. Location of the study area.

NU

Fig. 2. Lithostratigraphic scheme of the Polonez Cove and neighboring formations after Birkenmajer (

MA

Smeillie (2002). The Low Head Member is rich in benthic foraminifera and is marked in gray. Radiometric ages of the lithostratigraphic units are after Dingle et al. (1997) and Dingle and

D

Lavelle (1998).

TE

Fig. 3. Polonez Cove and Chopin Ridge as seen from Low Head. Prominent cliffs in the lower

CE P

part of slope formed by the Polonez Cove Formation (arrowed). Photo by A.G. 1979.

Fig. 4. The photograph shows a vertical section and the sedimentary structure of the lower part of the Low Head Member of the Polonez Cove Formation (site I). The shell bed shown in the upper part of the photograph is composed mostly of shells of

AC

(Jonkers, 2003). Photo by A.G. 1979.

Fig. 5. Vertical section showing shells of the pelecypod (A) and

and a few intraclasts

(Jonkers, 2003) (B).

Fig. 6. Agglutinated and unilocular calcareous foraminifera from Polonez Cove Fm. 1. Höglund, 1947, IV; 2. ? Hornibrook, 1961, II/3; 4-5. Tappan, 1953), IV, III; 8. (Jeffreys, 1848), II/3; 10. 17-21. IV; 22.

sp., II/1; 3.

spp., IV, II/3; 6-7.

(Loeblich

Parr, 1950, III; 9. cf.

Galloway and Hemingway, 1941, II/2; 11-12,

spp., IV, I/12, II/2, II/3, II/2, II/2, II/2; 13-16. (Wiesner, 1931), II/3.

spp., II/2, II/2, I/12,

ACCEPTED MANUSCRIPT Fig. 7. Some miliolid foraminifera from Polonez Cove Fm. 1. ? sp. 1, III; 3.

sp. 2, IV; 4. cf.

sp. 3, I/11; 5.

(Linnaeus, 1758), II/2; 7.

sp. 5, II/2; 11.

Fig. 8. 1-2. ? ?

sp. 6, II/3.

sp., S-new 11, I/11; 3. ? sp., II/2; 5-10.

SC R

10.

sp. 1, I/11; 9.

var.

cf.

(Fichtel

Moll, 1798), I/12; 2. ?

D

Fig. 9. 1.

MA

(Parr, 1950), II/3; 18.

Howe, 1939, A/11.

(Reuss, 1851), II/3; 7.

(Fichtel

CE P

9-10.

s.l. Vella, 1957, IV, II/3, II/2, IV, II/2, II/3; 7-8.

AC

sp., II/3; 14.

Fig. 11. 1-2.

sp. 1, I/12, II/3, I/11; 12. sp., IV.

(Parker, 1953), II/3, II/3; 3.

1934), II/3; 4. IV; 6. ?

Moll, 1798), II/2; 8.

sp., II/3, II/3, IV.

(Walker et Jacob, 1798), IV, II/3; 9-11. sp. 2, I/11; 13.

sp., I/11; 3.

Finlay, 1939, II/3, I/11; 11-12.

sp., II/3, II/2; 13-15.

Fig. 10. 1-6.

sp., I/11; 19.

(Reuss, 1851), II/3; 6.

TE

sp., I/11; 5.

?

Cushman and

Cushman and Parker 1937, I/11; 16.

sp., II/3; 17.

sp., II/2; 4.

sp., II/3; 12.

NU

sp. 2, II/3; 14.

Wickenden, 1929, II/2; 15. ?

sp. 2, 688; 4.

spp. all specimens from II/3, Fig. 8.8 shows

dissected specimen with strongly recrystallized interior; 11. sp. 1, I/11; 13.

sp. 4, I/11;

T

Cushman, 1921, II/3; 8. ?

cf.

IP

sp., IV; 6.

sp., I/11; 2.

(Earland,

(Leckie and Webb, 1985), II/3; 5. sp., II/2; 7.

(Cushman, 1915), IV; 9. ?

sp.,

sp., II/3; 8. sp., III; 10-11.

1932, I/11, IV; 12-13.

Heron-Allen and Earland, (Brady, 1884), II/2, IV; 14-15.

(Heron-Allen and Earland, 1932), II/2, II/3; 16-17. gny, 1826, II/2, II/2; 18-19. ?

sp., IV, IV.

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

CE P

TE

Figure 1

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

AC

CE P

Figure 2

AC

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

Figure 3

AC

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

Figure 5

AC

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

Figure 6

AC

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

Figure 7

AC

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

Figure 8

AC

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

Figure 9

AC

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

Figure 10

AC

CE P

TE

D

MA

NU

SC R

IP

T

ACCEPTED MANUSCRIPT

Figure 11

ACCEPTED MANUSCRIPT Table 1. Foraminiferal counts. I/11

CE P AC

I/12

II/1

II/2

II/3

III

IV

V

1

T

1

1 35

2

1

4

1 7

1 1

MA

1 2 7

2

3 16 47

7 27 46 1 2 94 3 2

1 15

31 9

1

D

1 1

6 14 22

13 10 37

19

1 1 1

46 2

4

SC R

1 3 13

NU

1 1 4

IP

1

TE

I/10 agglutinated Ammodiscus planorbis Siphotextularia finlayi ?Trochammina sp. calcareous Lagena spp. Oolina spp. Fissurina spp. Parafissurina spp. ?Triloculinella sp. Triloculina spp. Quinqueloculina spp. Quinqueloculina cf. Q. seminula Other miliolids 1 ?Pseudotriloculina sp. Polymorhina spp. 2 Bulimina sp. 1 Bulimina sp. 2 Bulimina patagonica Bulimina cf. B. subulata Bolivina huneri

1 1

1

VI

A-682 A-688