Palaeogene Macrofossils from CRP-3 Drillhole, Victoria Land Basin, Antarctica
Istituto cli Gcologia Marina. Consiglio Na~ionale(Idle Ricerche. via Gobclli 101. 1-40129 Bologna - Italy ~nstitutcof Geological & Nuclear Sciences. P.O. Box 30 308. Lower Hutt - New Zealand
Received 5 March 200 1 : accf,p/ec/ in rcri.sed form 3 July 2001
Abstract - CRP-3 cored Palaeogene strata to 823 metres below the sea floor (mbsf). before passing through Devonian bedrock (Beacon Siipcrgroup) to a depth of 939 mbsf. Palaeogene body fossils have been identified at 239 horizons in the core. The best preserved macrofossils from the core help elucidate the taxonomy. chronology and biogeography of Cenozoic ecosystems of Antarctica. although poor preservation prevents identification to species level in most cases. The lithostratigraphic unit (LSU) of the core top (LSU I. I) contains an almost inonospecific modiolid assemblage, similar to mussel beds recovered in the bottom part of the CRP-212A core. These semi-infauna1 mussels appear to be conspecific, apparently indicating the same age (Early Oligocene) and environment, i.e., a deep muddy shelf characterized by high turbidity and dysoxiclanoxic bottom conditions (high H,S sediment content). LSU 1.2 contains reasonably diverse assemblages representing innerlmiddle shelf environments dominated by epifa~inal suspension feeders. LSU 2.1 contains low-diversity assemblages of suspension feeders (bivalves. brachiopods and bryzoans), probably indicating innerlmiddle shelf environments. LSU 3.1 contains assemblages including infaunal and epifaunal suspension feeders (bivalves, including a scallop, ?Ada/71;(ssiumn.sp.. and solitary corals) and infaunal deposit-feeders, possibly indicating deposition on a deep muddy shelf. Both the coral and the scallop previously have been recorded from Oligocene to Miocene rocks in Antarctica. Inner to middle shelf environments are suggested by macrofossils in LSU 5.1. mostly infaunal and epifaunal suspension-feeding bivalves. A similar environment is suggested for LSU 6.1, which contains epifaunal scallops and gastropods and infaunal bivalves. LSU 8.1 contains a relatively diverse macrofa~inaof infauna1 suspension feeding bivalves and semi-infaunal/epifaunal gastropods, probably indicating middle shelf environments. ?Aclc~m~~,~siumn.sp. occurs lowest in LSU 8.1, establishing an Oligocene age for CRP-3 down to 320.43 mbsf. One poorly preserved gastropod at 359.07 mbsf indicates marine deposition for LSU 9.1. The only ~nacrofossilbelow this is one modiolid mussel in LSU 13.2. The species apparently is different from that observed in the top of CRP-3. An Eocene age for this mussel is possible but uncertain. The presence of relatively warm-water taxa in the diamicton-dominated part of the CRP-3 core indicates that these taxa did not become extinct abruptly with the onset of Antarctic glaciation, but progressively decreased in diversity as sea-temperatures gradually decreased.
INTRODUCTION Project core repository facility in Bremerhaven (Germany). Macrofossils suitable for more detailed CRP-3 hole, drilled at 77.011° and 163.640°E palaeontological study were cleaned at the Crary about 12 km east of Cape Roberts, in the Ross Sea, Science & Engineering Center at McMurdo Station reached 939 metres below sea floor (mbsf). wit using dental tools and delicate specimens hardened recovered a thick Palaeogene (Oligocene-?Eocene) using a solution of water and dilute PVA glue. succession capping Palaeozoic (Devonian) rocks of This report is based on a selection of the best the Beacon Supergroup (Cape Roberts Science Team. preserved and most identifiable body macrofossils. 2000). Even so, most fossils are minute, highly fragmented 239 macrofossiliferous horizons have been andlor highly decalcified, and their poor preservation identified in core from CRP-3. Horizons initially state made their identification challenging. As in identified at the Cape Roberts Laboratory were previous reports on CRP macropalaeontology, many inspected in the Crary Science & Engineering Center taxa from CRP-3 have not been identified to specific at McMurdo Station. Macrofossil material not suitable or even generic level. The collection is temporarily for further palaeontological investigation was either retained as a discrete entity in the Institute of sampled for geochemical (oxygen and carbon stable Geological and Nuclear Sciences, Lower Hutt. isotope composition, Ss-chronology) and diagenetic Macrofossils are common in the Oligocene section studies or stored to be shipped to the Cape Roberts of the core, providing further palaeontological
"Correspondiq author ([email protected]) doc~imentationof marine macroinvertebrates for this environment low in the core (LSU 9.1 and l .\.?), epoch in Antarctica. The CRP-3 drill core adds new Uicse may prove to be of diagnostic v;iI~it,, data to the growing palaeobiological information for considering the overall scarcity of palaeontoloi~ic~al the Oligocene epoch in Antarctica, which combines information in the lower past of the core. results from previous drilling operations in the Ross Sea region: DSDP Leg 28 (Dell & Fleming, 1975). CIROS-1 (Beu & Dell, 1989). and CRP-212A (Taviani TAPHONOMY et al., 2000) and from erratics at McMurdo Sound (l Iarwood & Levy, 2000: Stilwell & Feldmann, 2000). Dia~pnesis.Most carbonate is in an advancril A few CRP-3 macrofossils, however, originated from stage of dissolution (Cape Roberts Science 'l'i-iiii~. sedin~entaryunits of uncertain age and depositional 2000). In general, only calcitic fossils of peelini(1
Sill sand travel
. . . .
. .:. -...... ---P--****. -: $SO-'.. .:. 1, -:; :*:L- -...... : ...... - - L.'....-+ -...... -.-. .. . jOOÑ .' . . " KEY
""'7 Clam 6.-,.A Br>ozoan 7>. ~eaf
0 ,F-, :;, Plant . Scrpuiid ^' Echinoid . Cirripcd 'CG fiagment
Fig. 1 - Litliostratigraphical summary of the CRP-3 drill core showing-. position and composition of the major macrofossil assemblages (slightly modified from Cape Roberts Science Team. 2000). I'c~lacopcn~'Mcicrolossi Is from ('RP-.! Drillholr 425
bivalves (i.e.. ?Aclamussiuni n.sp. ). worms (scrpiil id 8.1 as uni~len~ii'ieclbivalves (Cape Roberts Science polycliaetes) and ecliinoids are well preserved. Most 'I'eani, 2000). Barnacles (('irripedia) have only rarely aragonitic bivalves and gastropods show advancecl been reported from the CXeno/.oicof Antarctica (Zullo decalcil'icii~ionand are represented by moulds. some ct ill.. 1988: Biickcridgc. 2000) ;ind the S~ibantarctic of which retain a veneer of chalky carbonate. Shell (Carriol ci (it., 1992: (iirct et al.. 1994). The CRP-3 breakage ;ind fragmentation is common in the CRP-3 material consists of a very small fi~agiiientof the core but we are unsure whether it is mostly linked to ~iiar~inof a sti.oiigly ribbed shell at 168.39 mbsf. skeletal dissolution (as we suspect) or to rev,!orkiiig. (presumably a friigment of a barnacle plate. recorded CaCO:; concretioning has been observed around in the Initial Report as "small crenulate shell bivalves and gastropods at 141.20 and 359.07 mbsf fragment"), and one sm;ill. incomplete but well- and in the sediment matrix infilling serpulid prescrvei-1 balanoicl barnacle plate. plus several polycliiicte tubes (e.g., at 38.53 mbsf). Pyritized fragments of other plates. at 308.68 mbsf (recorded in moulds of bivalves occur in LSU 1.3 at 64.42 mbsl'. the Initial Report as "many small fragments of unidentified bivalves").
TAXONOMY
Eight phyla of marine Invertebrata have been identified positively in the CRP-3 drill core. They are, BIVALVIA in order of relative abundance, Mollusca, Annelida, Cnidaria. Brachiopoda. Crustacea, Bryozoa, WUCULIDAE Echinodennata and Porifera (Fis. 1). Re-examination ?N~/culasp. of the inferred Vertebrata (fish remains) recorded in - 122.22-122.24 mbsf: One very small. articulated, the Initial Report at 406.36 and 406.38 mbsf (Cape chalky bivalve. hinge not visible. Roberts Science Team, 2000) reveals that such Remarks: Small Nuculidae occur in the Cretaceous- macrofossils are very likely plant fragments. Palaeogene of Antarctica. including the Ross Sea Macroplant remains were also identified in CRP-3, as region (Beu & Dell, 1989; Stilwell, 2000: Taviani leaves (Nothofagus sp.) and stems (Cape Roberts et al., 2000). Science Team, 2000, fig. 5.9d, 111) and are discussed in detail by Cantrill (this volume). The organic nature SAREPTIDAE of putative macrofossils from LSU 12.3 (465.77, ?Yolcliella sp. 509.16 and 533.47 mbsf: Cape Roberts Science Team, - 120.34-120.37 mbsf: Incomplete left valve of small, 2000) could not be confirmed. elongate, smooth protobranch bivalve, taxodont Macrofossils from CRP-3 have been treated in hinge visible, aff. Yoldiella. some detail in the Initial Report (Cape Roberts - 122.22-122.24 n~bsf: One small left valve of a smooth pi-otobranch(?) bivalve, shaped as in Science Team. 2000) and the best preserved Ti~iclc~ria,Jupiferia, etc., hinge not visible; outline specimens are figured there. The present article offers most nearly resembles those of Yoldiella antarctica an updated perspective of the macrofossil assemblages (Thiele) and Y. prof~indora(Melvill & Standen) with special reference to Mollusca, and their (Dell, 1990, figs. 17, 21). ecological and biogeographical significance. Annelida - 124.93-124.96 mbsf: Several small bivalves, at least are also discussed here. 3 valves, smooth, chalky, no hinges visible, but Mollusca are by far the dominant group and presumably the same taxon as above; another include, conservatively, at least 15 species of Bivalvia, smaller, moderately elongate, weakly rostrate, rather 6 of Gastropoda and 1 of Scaphopoda. Cnidaria thick-shelled protobranch bivalve, also a ?Yolcliella (scleractinian corals) are discussed by Stolarski & sp., ventral margin strongly abraded before Taviani (this volume). fossilisation. indeterminable. Brachiopoda, Echinodermata, and Bryozoa are - 124.96-125.01 mbsf: 6-7 small bivalves, rather poor under consideration for a detailed systematic study in and chalky, no hinges visible but apparently all the near future and only limited information is given smooth, rostrate protobranchs, the same two species here. Brachiopoda are represented by a smooth as above (a smaller and a larger ?Yoldiella species). punctate species, presumably a terebratulid, reaching - 125.18-125.20 mbsf: 5-6 more small fragments of at least 20 mm in height (e.g. 62.61, 121.19 mbsf). apparently the same, larger ?Yoldiella sp. as in the Echinodei-mata are represented by echinoid debris above three samples. (including a crushed shell) at 44.12, 114.23 and - 126.40-126.42 mbsf: Two bivalve fragments; (a) 121.4 1 mbsf. An undetermined encrusting bryozoan from the shape, one is probably ?Yoldiella sp., as partially envelops a lonestone at 88.19 mbsf. above; (b) the other is very small, indeterminable. Crustacea (a group not recorded in the Initial Report) - 127.34-127.36 mbsf: One poor, chalky valve of is added to the list of taxa on the basis of barnacle ?Yoldiella sp., as above, plus two small, plates previously recorded from LSU 5.1 and LSU unidentifiable bivalve fra_oments. Remarks: Members of this family inhiihit cold. deep ?Modiolux sp. 2 (('iipc Roberts Science Tea111,2000, waters world-wide. including modern Antarctica fig. 5.911) (Dell, 1990): Yoldiella has been recorded recently - 78 1.34-78 1.36 m17sf: One articulated, highly from Eocene erratics at Mt Discovery. McMurdo decalcified shell. Sound, by Stilwell (2000). Remarks: The single specimen (Fig. 2a) rcprt.-senis the lowermost occurrence of marine macrol'ossils in 7LIMOPSIDAE CRP-3. The poorly preserved shell belongs 10:i ?l^inwpsis sp. species of Mytilidac tentatively ascribed to - 200.12-200.14 mbsf: Two fragments of one valve of Mocliolus s.1. Because of advanced decalcil'icatioii, a relatively thick-shelled, symmetrical, s~ibcirc~~lar no important shell characters are visible. Some bivalve with weak cornmarginal sculpture; small growth lines are evident near the edge of the right area of symmetrical, serrated hinge visible in valve. The shell consists of articulated valves lying profile; probably Limopsis sp. parallel to bedding (in a polymictic, coiirse Remarks: The small species Limopsi,~ sandstone) but it is difficult to ascertain whether the a~ifarcfomin~/tahas been described from Eocene shell is in life position or has suffered some minor erratics in the McMurdo Sound (Stilwell. 2000): the displacement. Comparison with other mussels in extant, large circum-Antarctic taxon L. ~~iurionensis Antartica suggests that ?Modiol~i.ssp. 2 is dilTcrent occurs in the Pleistocene deposits of Cape Barne, from any other Mytilidae described so far from {lie Ross Island (personal observations). Cenozoic rocks of Antarctica (Zinsmeistcr. 1084; Stilwell & Zinsmeister. 1992; Stilwell, 2000). MYTILIDAE ?Modiolus sp. 1 (Cape Roberts Science Team, 2000, PECTINIDAE fig. 5.9a) ?AcIamussi~i17in. sp. - 6.80-6.88 mbsf: One decalcified shell. - 29.94-29.96 mbsf: Fresh broken valve (Cape - 10.80-10.85 mbsf: One articulated mould. Roberts Science Team, 2000: fig. 5.913) with - 10.88-10.89 mbsf: Two articulated, decalcified auricles. shells. - 38.8 1-38.82 mbsf: Broken fragment, fresh. Remarks: This species is the same as that recovered - 41.61-41.63 mbsf: Two fresh, broken valves. in the Early Oligocene sediments of the CRP-212A - 47.55-47.57 mbsf: One fragment. drill core (Taviani et al., 2000, fig. 6). The muddy - 83.95-83.97 mbsf: Fragments of a smooth pectinid lithologies of LSU 1.1 of core CRP-3 contain (?); no unibo or auricles; apparently ?Adam~/.s.sii//~i some articulated mussels, mostly decalcified. n. sp. as in CRP-I and CRP-212A.
Fig. 2 - Macrofossils from CRP-3 drill core: (a) Modiolid mussel (?Modiolns sp. 2) from 781.34 mbsf; note that the highly decalcified specimen is an articulated shell, slightly gaping (age uncertain: Early Oligogene-?Late Eocene): (b) bivalve-scleractinian assemblage at 140.69 mbsf: CY = articulated carditid bivalve (Cyclocardia sp.), SC = solitary scleractinian coral (FIubelliim rariseptatiim). both probably in life position (Age: Early Oligocene): (c) well preserved serpulid polychaete tube aggregates (?Sup10 sp.) from 38.53 rnbsf: this taxon shows distinct growth wrinkles and rings (arrow). - 1 14.10- 1 14.22 mbsf Fragments. I ,D("lNll)AIi - 190.20 100.3 1 inbsl Fragments. 1 ,t~cini(iiicspp. - 308.20 308.25 mbsf: One articulated shell and - 190.90 197.02 nibsf.: One small piece ol' an fragments (Cape Roberts Science Team, 2000: fig. incomplete valve (umbonal area lost during core 5.9i). prepai'ation) of a fairly thick-shelled. weakly - 309.20-309.33 mbsf: Two broken. well preserved inf'hilcd l~ivalvewith an almost circular shell and valves (Cape Roberts Science Team, 2000: fig. prominent, narrow. widely spaced cornmarginal 5.91). amcl lac; possibly the lucinid Liicinoma. - 320.40-320.43 mbsf: Fragment, probably - 127.84- 127.87 mbsf: One very poor, chalky, 7Acl11111iixxium11. sp. weakly inflated. s~iperficiallysmooth, s~~bcirculai-, Remarks: This taxon evidently is the same irticulated bivalve, Lucinidae?, not determinable. ?Adcuinissium n. sp. as in CRP-l and CRP-2/2A Remarks: Lucinids (Sa.voliicinu, Miltha) previously and discussed in detail by Jonkers & Taviani (1998) have been recorded from Eocene rocks of the and Taviani et al. (2000). The stratigraphic Antarctic Peninsula and McMurdo Sound significance of pectinids in the Cenozoic of (Zinsmeiste~-,1984; Stilwell & Zinsmeister, 1992; Antarctica has been discussed by Jonkers (1998). Stilwell, 2000).
Pectinidae sp. CARDITlDAE - 38.8 1-38.83 mbsf: A small fragment (severely Cyclocardia spp. damaged during core preparation, less than a - 6.48-6.51 inbsf: One chalky fragment from a quarter of the disc; but 20 mm in longest radially ribbed, subtriangular bivalve, probably dimension) of an external mould of the exterior of Cyclocardia sp. the disc of a strongly radially costate pectinid, shell - 120.34-120.37 inbsf: C\clocardia sp., with narrow, material chalky; many very fine radial costellae on well defined radial costae, as in CRP-2/2A (Taviani surface of radial costae. A latex cast confirms that et al., 2000), one small valve. this is from a pectinid with wide, convex-crested - 120.43-120.47 mbsf: One fragment of a fairly thick costae and narrow costal interspaces. shell with prominent radial sculpture and weaker Remarks: This pectinid has not been reported from commarginal sculpture; presumably Cyclocardia sp. Antarctica before (Dell & Fleming, 1975; Dell, - 120.58-120.60 mbsf: Two fragments (part and 1990; Stilwell & Zinsmeister, 1992; Jonkers, 1998; counterpart of one fragment?) of Cyclocardia sp., Jonkei-s & Taviani, 1998; Stilwell, 2000) and as above. probably is unnamed, but the material is too poor - 120.60-120.62 mbsf: One slightly incomplete valve for further coniment. The auricle was abraded off of Cyclocardia sp., as at 120.34-120.37 m, and before fossilisation, an indication that the fossil probably the same as at 120.58-120.60 inbsf. - 121.19-121.22 mbsf: One small fragment of a underwent transport or reworking. coarsely radially sculptured bivalve, probably C\clocardia. PLIMIDAE - 121.23-121.27 mbsf: Cyclocardia sp., as above, and ?Lima sp. as at 120.34. 120.58 and 120.60 inbsf, one fairly - 163.65-163.68 mbsf: Part of an incomplete, complete (but very chalky) valve, one incomplete articulated specimen of a bivalve, perhaps ?Lima articulated pair (chalky), and a few fra-"merits. sp.; superficially similar to the narrowly ribbed - 121.29 mbsf: Cyclocarclia sp., as above, one Cyclocardia sp. that is common above this level, articulated but opened pair (part and counterpart on but differs in being (a) apparently originally broken faces of core) and one good fragment with calcitic, rather than aragonitic; (b) larger; and (c) relatively undisturbed sculpture. with costae that diverge at a much lower angle, i.e., - 121.49-121.51 inbsf: Cyclocardia sp. (as above), one this specimen originally was significantly taller and articulated pair, sawn through in preparing core; narrower than Cyclocardia. shell chalky. Remarks: If confirmed, this is the first record of - 126.48-126.51 mbsf: Fragments of one valve of a Limidae in the Oligocene of Antarctica, although narrowly ribbed Cyclocardia sp., as above. this family is known from Late Cretaceous - 126.66-126.69 nibsf: Fragments of two valves of a (Zinsmeister & Macellari, 1988) and Eocene beds narrowly ribbed Cyclocardia sp., as above. of Seymour Island (Zinsmeister & Stilwell, 1992; - 127.84-127.87 inbsf: One fairly good but very Stilwell & Gazdicki, 1998), as well as from chalky, articulated specimen of Cyclocc~i~dic~sp., as Pleistocene deposits of McMurdo Sound (Cape above. Barne: Speden, 1962; and personal observations) - 128.58-128.60 mbsf: One small fragment of a and the Ross Sea (Taviani et al., 1998). Limidae narrowly ribbed Cyclocmlia. are also among the most conspicuous elements of - 136.35-136.38 mbsf: One very chalky, poor, the Recent Antarctic shelf fauna (e.g., Bullivant, incomplete, articulated specimen of a narrowly 1967; Dell, 1990). ribbed C\clocardia sp. - 1 37.33-1 37.35 mbsf One small, chalky fragment of Stilwell, 2000). An undescribed species ;ilso Ims a narrowly ribbed C\cli)c.tirclici sp., as above. been repoi'tcd f'rom Laic Oligocenc sediments in ~lir 140.02-140.04 mbsf: Fragments of the umbonal area ('RP-212A drill core (Taviani et al.. 2000). of a chalky, articulated specimen of a narrowly ribbed Cyclocc~rcliusp.. as above. ?PliRIPI .OMATIDAE - 140.11-140.14 mbsf: One poor, chalky fragment of iff. P~~i~i/)loiiidsp. a narrowly ribbed Cyclo(~~rclic~sp.. as above. - 62.61-62.69 nibsf: Fragments of moulds (with sonic - 140.69-140.74 mbsf: Fragments and shells chalky shell material remaining) of ca. 20 nun (including articulated ones) of 7-8 specimens of the long. very thin-shelled, weakly biconvex hiviilvr narrowly ribbed Cyclociirdia sp. (Fig. 2b). as with two valves articulated, and with weak, roundc(t above. commargiinal folds, aff. Periploma or similar'.' hut - 140.79-140.8 1 nibsf: One chalky, poor valve (and no umbonal area or outline visible. indeterminable. fragments from the same specimen) of the narrowly - 120.34-120.37 mbsf: Fragment of a small. thin- ribbed Cyclocardia sp.. as above. shelled bivalve with one valve almost flat, the other - 141.92-141.95 nibsf: Part of one very poorly more convex. cf. Periploma?~but smaller and morc preserved. chalky valve of the narrowly ribbed inflated than usual for Periploma. Cjclocardia sp., as above. Remarks: Taviani et al. (2000) discussed pre~''1011s - 165.66- 165.68 nibsf: Narrowly ribbed Cyclocardia records of Pei~iplonuifrom the Cenozoic rocks of sp., as above: one incomplete. chalky, articulated Antarctica, to which must be added the rcccnl specimen. cut in preparing core, report from McMurdo Sound erratics by Stilwcll - 319.97-319.99 mbsf: Poor, chalky fragments of an (2000). articulated specimen of a narrowly ribbed bivalve, presumably the same Cxclocardici sp. as is so 7LATERNULIDAE common above. aft. Later~iiilasp. Remarks: Two different species seems to be present - 140.69-140.74 mbsf: One large fragment (c(/. 24 of the cosmopolitan genus Cyclocardia Conrad, mm long) of a very thin-shelled, fragile (now 867, which is well represented in the Cenozoic severely distorted) bivalve with weak commarginal and Recent of the palaeoaustral region, including growth ridges (aff. LciternuW). Antarctica (Hendy et al., 1969; Beu & Maxwell, Remarks: The extant species Laterniila elliptic(/ 1990; Dell, 1990; Stilwell & Zinsmeister. 1992; (King & Broderip, 1831) is one the most common Taviani et al., 1998: Stilwell, 2000; Taviani et al., shallow-water circum-Antarctic bivalves. It also is 2000). One species, characterized by a subcircular recorded from a number of Pleistocene outcrops outline. seems conspecific with Cycloca~dicisp. (Berkmann et al., 1998), but the pre-Pleistocenc identified in the Late Oligocene of CRP-212A history of this family is obscure. (Taviani et al., 2000; fg. 2c); the second species has a more elongate shell (Fig. 2; and Cape Roberts 7THRACIIDAE Science Team. 2000, fig. 5.9f). ?T/~mcic/sp. - 75.54 mbsf: Partial. chalky, crushed, elongate, VENEROIDEA articulated bivalve with weak comniarginal - 127.94-127.97 mbsf: One very poor, incomplete, sculpture, damaged in core preparation, no hinge chalky bivalve, severely compressed diagentically, visible. Indeterminable but possibly Thracia sp.? apparent posterior-un~bonalridge probably produced - 76.03-76.04 mbsf: At least three articulated (but all entirely by compression; weak commarginal slightly to severely incomplete and chalky) sculpture; shape resembles a venerid, but identity specimens of a small (m. 10-12 mm long). not determinable. elongate, moderately inflated (but right valve less - 139.46-1 39.47 n~bsf:One indeterminate, chalky strongly inflated than left), weakly con~n~arginally bivalve fragment; shape resembles a venerid, but no sculptured bivalve, with rounded anterior end and useful characters visible. weakly rostrate, truncated posterior end, possibly - 197.85-197.86 mbsf: Small fragment of the posterior Thracia sp.? area of a small bivalve; presence of a weak radial Remarks: The Cenozoic record of Thraciidae in posterior-umbonal angulation and of low Antarctica previously has been limited to commarginal sculpture suggests that this is a Pleistocene records of the extant taxon T. veneroidean, but family not identifiable; appears to meridionalis Smith, 1885 (e.g., Speden, 1962, be the same taxon as above. listing earlier records; Berckmann et al., 1998). Remarks: Absent from the Antarctic Recent fauna. veneroid bivalves were in contrast. common in the Indeterminate bivalves: warmer Palaeogene waters around this continent Indeterminable fragments (mostly chalky moulds) (Zinsmeister, 1984: Stilwell & Zinsmeister. 1992; of bivalves were recognised at the following depths: I'alaropcnc Macrol'ossils froin CRP-3 Drillliolc 429
10.88-10.99 mbsf (cf. Macornu, hlernula); 50.46- position. Troclioiilea are among the most 50.48 nihsf: 5 1.20-51.23 nibsf; 64.42-64.43 nibsf'; conspicuous elements ol' the Recent Antarctic 89.02-89.03 mbsf; 96.27-96.29 mbsf: 94.37- macrofauna (Smith. 1902: Dell. 1990; Hain, 1990) 94.38 inhsf; 98.31-98.33 mbsf ('.' aff. l/nnopxis. but and have a continuous record in Antarctica since at shell thin): 99.59-99.61 mbsf (?Veiicriclac): 1 15.43- least Eocene time (Stilwell & Zinsmeister, 1992; l 15.45 mhsf (?Pectinidae); 1 19.08-1 19. 10 nibsf (;ifS. Stilwell. 2000). Thrcicin" or Yolclia?); 119.45- 1 19.47 nibsf (aff. Tl~racici'?or Yoldia?); 120.75-120.79 mbsf (cu. 8 small TURRITELLIDAE (8-10 mm) bivalves, Yohiielld): 12 1.29 mbsf': Tiirrifellci (sensii Icito) sp. (Cape Roberts Science 122.22 inbsf: 126.32-126.35 inbsf; 126.45- Team. 2000. fig. 5.911) 126.47 mbsf; 127.34-127.36 inbsf: 127.84- - 3 1 1.25-3 1 1.27 mbsl Fragment, at least 20 mm high. ca. 127.87 nibsf; 128.58-128.60 mbsf (Lucinidae or and formerly >35 mm high and 8-10 mm in diameter, of the interior of a calcitic replacement of Veneridac?): 128.64-128.66 mbsf; 157.7 1- a very high-spired, almost flat-sided t~irritellid(?) 157.75 nibsf; 274.27-274.3 1 mbsf (?Pcctinidae. but gastropocl. The large number (6-7) of primary spiral with widely spaced commarginal grooves); 308.68- ridges and several orders of secondary and tertiary 308.71 mbsf; 315.66-315.69 mbsf (taxondont); ridgelets suggest that it might be a previously 320.40-320.43 mbsf. unknown genus of Turritellidae. Remarks: Members of Family T~~~ritellidaeoccur SCAPHOPODA quite commonly in Cenozoic outcrops of Antarctica and Subantarctica. Colposigma euthenici Stilwell & DENTAL1IDAE Zins~neister1992. is common in the Late Eocene aff. Dentalium sp. macrofauna of La Meseta Formation, Seymour - 38.44-38.45 mbsf : Chalky fragments of a straight, Island (Stilwell & Zinsmeister 1992). Karczewski approximately cylindrical calcareous tube, now (1987) mentioned three species from the Miocene conlpressed. One fragment of exterior shows both Cape Melville Formation of King George Island irregular commarginal rings (growth ridges?) and (South Shetlands), including the European Neogene longitudinal costae; evidently a scaphopod Arc11i111edielIc~cf .s~~bangiilafci(Brocchi, 18 14), a Remarks: Scaphopods identified in the Oligocene inisintepretation. A turritellid is also recorded from successions at Cape Roberts (CRP-212A: Taviani et the Miocene of Kerguelen (Giret et al.. 1994). al., 2000; CRP-3: this paper) are all poorly More recently, two species of Turritellidae have preserved but belong to at least two different taxa, been identified by Stilwell (2000) in McMurdo one with a smooth shell (CRP-2/2A), the other Sound en'atics: C. euthenia (erratics from Mt. costate, like the specimen collected at 157.83 mbsf Discovery, Middle to Late Eocene; see Harwood & (see below). Scaphopods, including Dentaliz~m,have Levy, 2000) and Zeacolpiis? sp. (erratics from Mt. been recorded previously from Cenozoic beds of Discovery, age not specified; see Harwood & Levy, Antarctica and Subantai-ctica (Pugaczewska, 1984; 2000) but both appear to be different from the Stilwell & Zinsmeister, 1992; Stilwell, 2000). CRP-3 taxon.
Scaphopod. not determinable 7CALYPTRAEIDAE - 157.83-157.86 mbsf: Short length of a gently ?Sigapafellci sp. tapering, cylindrical tube, cut during core - 66.64-166.66 inbsf: Good internal mould of a preparation; not compressed: very chalky. not calyptraeid gastropod, similar to Sigapatella. determinable, but certainly a scaphopod. Remarks: The single CRP-3 specimen has a taller spire than any Sigcipafellci species we know of, with the possible exception of S. colossa recently GASTROPODA described by Stilwell (2000) from PEocene (age not reported) erratics in McMurdo Sound. TROCHOIDEA Trochoidea, family not determinable: NATICIDAE - 198.88-198.89 inbsf: Small fragment of the outer Naticidae, indeterminable lip and base of a nacreous indeterminable gastropod - 198.50-198.53 mbsf: Poor, chalky specimen of a (PTrochidae) with sculpture of numerous low, naticid gastropod (Cape Roberts Science Team, narrow, close spiral ridges. 2000; fig. 5.9g); not identifiable, but the moderately Remarks: The poorly preserved moulds and thick shell and moderately exert spire suggest aff. fragnients of trochoidean shells recorded so far in Polinices or Amai/ropsis (etc.) rather than Bulbiis the Cenozoic successions at Cape Roberts (CRP- (cf. Dell, 1990). 2/2A: Taviani et al., 2000; CRP-3: this paper) are - 3 17.88-317.92 inbsf: Indeterminable naticid difficult to classify even at family level, although gastropod; comments as for specimen above, but the nacreous internal layer confirms the superfamily this one is even more poorly preserved. of the few fossils recorded in this part of (lie ('RI' 3 core. It is important to note that the s[x-cinn.'ii resembles a turritcllid or similar tall-spirctl inariiu' 8-o~ipof gastropods. It therefore probably i nd iriik~ a marine depositional setting for LSU 9.1.
Mollusca incertue sails 166.64-166.66 mbsf: Part of one valve of ;\ strange bivalve(?) with a calcitic outer layer (particularly shown on the counterpart) and ;I chalky (presumably aragonitic) inner layer, and with sculpture of low coinrnarginal folds, surface otherwise smooth; the alternative hypothesis of belonging to :I thecoson~ato~~spteropod (such as Cavolinia or Diacria?) should be also taken into account. 319.09-319.10 mbsf: Another fragment with the same shell structure as above; apparently the same taxon.
Fig. 3 - Undetermined gastropod from LSU 9.1 at 359.07 mbsf: the original ~nacrofossilis a highly decalcified shell sliced by core splitting and embedded in a coarse sandy matrix: camera liiciela ANNELIDA hand drawing (M.T.) elaborated by Alessandro Remia. Polychaeta Calcareous polychaete tubes are scattered within the upper part of the CRP-3 drill core. Reasonably - 326.72-326.78 mbsf: Incomplete internal and well preserved tubes occur in LSU 1.2 and 3.1. external mould of a large, indeterminable naticid(?) associated with predominantly sandy and muddy gastropod, ca. >40 mm in diameter, cut through by lithologies respectively. Possible polycliacke the drill. bioturbation is also indicated by burrow-fillings of en. Remarks: Members of family Naticidae have been 3-5 111111 diameter (e.g., 50.46 and 62.62 mbsf). recorded frequently from the Cenozoic of Antarctica and Subantarctica (Dell & Fleming, 1975; ?SerpuIa sp. Gazdzicki & Pugaczewska, 1984; Giret et al., 1994; - 38.44-38.45 mbsf: Fragments. Stilwell & Zinsmeiester, 1992; Stilwell, 2000; - 38.53-38.66 mbsf: Various tubes, well preserved, Taviani et al., 2000). aggregated (Cape Roberts Science Team, 2000. fig. 5.14 g and Fig. 2c). 7PYRAMIDELLIDAE - 50.42-50.43 mbsf: One short length of a relatively ?Pyramidellidae sp. large, almost smooth, now severely compressed, - 157-76-157.83 mbsf Internal mould of a gastropod thin-shelled, cylindrical calcareous tube; with very protoconch, apparently heterostrophic. possibly fine commarginal growth ridges, but the thinness ?Pyramidellidae, genus indeterminable. and finely fibrous shell structure suggest it is a Remarks: Our determination is uncertain; this polychaete tube rather than a scaphopod. family of ectoparasitic opisthobranch gastropods has Preservation better than at 38.53-38.66 mbsf, shell an extremely poor fossil record in Antarctica material pale brown; sulfides in matrix perhaps (Pleistocene of Cape Barne, Ross Island: Hedley, suggest a different diagenetic history at this level 1916) and very few modern representatives (Dell, from that above and below. 1990). - 94.37-94.38 mbsf: Two fragments from a mould of a small tube, ca. 2 mm diameter, presumably Indeterminable gastropods: formerly calcareous (polychaete?). - 197.29-197.32 mbsf: Internal view of the spire of a 120.60-120.62 mbsf: One moderately large (ca. low-spired gastropod, poor, very chalky; 7 mm diameter) calcareous tube, smooth apart from indeterminable. growth ridges, relatively thin, slightly compressed; 359.07-359.1 1 mbsf: Internal view of high-spired evidently a polychaete tube. gastropod, very poorly preserved, longitudinally 121.06-121.07 mbsf: One badly crushed, sliced by core splitting (Fig. 3). cylindrical, smooth calcareous tube, presumably a Remarks: Not much can be said about this polychaete. gastropod (from 359.07-359.11 mbsf) because of its Remarks: The best preserved material consists of an extremely poor preservation. This finding is, aggregation of various specimens (>3) at however, of some relevance since it represents one 38.53 mbsf (Fig. 2c). Based on tube features, Palaeogene Macrofossils from Cl including raised collars and growth rings, similar to asscinhliigcs of low diversity. consistingof epifaunal those of the extant Antarctic species Sprpiilci ('?Alidini~,v.si~iiiin.sp.. terebratulid brachiopods, nan'oi~(~iisisBaird, 1865 (~em'i.-Iron) Coi;11;1;(11ity".It is true that today such peculiar sedinients of established Oligocene age in ~licKoss iniissel-supporting environments occur in a wide Sea re"o11 possibly indicates an older age, k-aviny spectrum of water depths, from brackish-lagoonal to open (lie possibility that it is Eocene. However, this abyssal. However. in the case of shallow ptirticiilar mussel is not recorded from any l+n~i.~iitt communities, mussels arc but one of many outcrops in Antarctica, neither on the Antiirc~ir components of such assemblages. while in the CRP-3 Peninsula (Stilwell & Zinsmeister, 1992) nor in ilu5 core (as in many deep-sea mussel communities) there McMurdo Sound erratics (Stilwcll, 2000). If' our is no sign of accompanying macrofossils. environmental interpretion is correct, however. ils Furthermore, nearshore environments are normally absence from other Eocene rocks could rel'lcd tinx marked by a substantial signature of adjacent lack of comparable depositional settings; other terrestrial biota (such as phytoliths), but this is not the Antarctic Palaeogene rocks apparently all vvci'r situation in the CRP-3 drill core. This seems to deposited in shallow water. CRP-3 may represeiit tli' indicate that deposition took place at a significant distance from reservoirs of terrestrial biota. first record of "deep-sea" Eocene sediments extiiiiiii~~d Historical record: Our knowledge of the so far in Antarctica. A possible Eocene age for ('RP3 biodiversity of macsoinvertebrates inhabiting shallow at ca. 780 mbsf is not in conflict with the oilier Antarctic waters during the Palaeogene is now available palaeontological evidence. relatively advanced. None of the mussel taxa so far An interesting aspect of the CRP-3 n~acrof';uina lor described appears to be conspecific (or even the history of the Antarctic fauna is its preservation in congeneric) with the CRP-3 mussel, a possible diamicton-doininated rocks. Relatively wasni-water indication of CRP-3 environmental settings decidely taxa (such as turritellid gastropods, modiolid mussels different from the shallow-water ones reported and veneroidean bivalves), not now living arountl elsewhere in Antarctica. Antarctica, apparently still lived there after the onsct Our interpretation of the lithostratigraphic unit of Antarctic glaciation. A still more diverse iiiolliisc;iii containing this mussel as possibly deposited in a fauna inhabited Antarctica during Eocene time deep-sea dysoxiclanoxic environment has some (Stilwell & Zinsnieistes, 1992; Stilwell, 2000). important implications for determining the age of this incl~~dingdiverse mussels, mactrid bivalves, diverse critical part of the CRP-3 core. Veneridae, shallow-water Trochidae, and large, shallow-water tuKid and volutid gastropods. It seems that, rather than undergoing an abrupt extinction with BIOGEOGRAPHICAL AND CHRONOLOGICAL the onset of major Antarctic glaciation, these taxa that IMPLICATIONS are not present around Antarctica today progressively were lost from the Southern Ocean as sea The lithostratigraphic unit of the core top temperatures continued gradually to decrease. Rather (LSU 1.1) contains almost monospecific modiolid than being expelled suddenly with the onset of assemblages, correlatable with mussel beds recovered Uslaciation (a "mass extinction"), the Antarctic biota in the bottom part of the CRP-212A core (Taviani et may have waned gradually to its present impoverished al., 2000), consistent with this part of the core being diversity. the same age (Early Oligocene) as that postulated for CRP-212A. Units LSU 1.2 and 2.1 contain the pectinid CONCLUSIONS ?A~CLITIL/,YS~L/~IIn.sp., whose known stratigraphic range extends from the Oligocene to the Miocene of Identified marine macrofossils in core CRP-3 Antarctica (Taviani et al., 2000). Unit LSU 3.1 belong to eight phyla of marine In~e~tebratawhich contains the solitary coral Flabellum rariseptatum and are, in order of relative abundance. Mollusca. ?Ac/a1-11iissiiimn.sp., with a known stratigraphic range Annelida, Bryozoa, Cnidaria, Crustacea. Brachiopoda, extending from the Oligocene to the Early Miocene Echinodermata and Porifera. Mollusca are by far the of Antarctica. LSU 8.1 represents the lowerniost dominant group and include, conservatively, 15 occurrence of ?Ac/c~~;~i(ssi~~i~~n.sp., establishing an species of Bivalvia, 6 of Gastropods and 1 of Oligocene age for the CRP-3 core down to 320.43 Scaphopoda. Unfortunately, the poor preservation of mbsf. the available material means that most taxa must Macrofossils reappear in LSU 13.2 with the single remain unidentified at the generic and specific level. mussel, a species different from the modiolid Mussel-dominated beds from the core top unit observed in the top of the CRP-3 drill core and from (LSU 1.1) are correlatable with mussel assemblages other mussels recorded from the Palaeogene of from CRP-212A bottom units, suggesting similar Antarctica (Zinsmeister, 1984; Stilwell & Zinsmeister, environmental conditions (deep sea muddy shelflslope. warmer-than-present sea water conditions and peculiar H$-enriclicd sediments) and age (Early Oligocene). licrckmann P.A.. Andrews .l.'!'.. Biocrck S.. Collioun E.A.. Emslie Macrol'ossiliferous horizons arc common in CRP-3 S.D.. Goodwill ID.. Hall HI,,. II;iri C.P.. Hirakawa K.. down to c(/. 325 mbsf (LSU 1.2 to 8.1 ) ancl contain Igarashi A.. Ingocl t'sson 0.. I .opc~-M:ii-tine/.l.. Berry Lyons fossils whose stratigraphic range does not extend W., Mahin M.C.G.. Quilty P.C;.. Taviani M. & Yoshida Y.. earlier than Early Oligocene (the pectinid 098. Circuin-Antcirctic co;isi;il ciiviroiiinci~al shifts during the Laic Quaternary rcl'lccictl by cmcr~cclmarine deposits. ?Aclcimii,ssIiim n.sp. and the scleractinian coral ¥\iil(ii'r/iScience. 10. 345-362. Flc~belliinirari,~eptajzim). These assemblages arc Bcu A.G. & Ddl R.K.. 1989. Molluscc~.In: l3;irreIt P.J. (eel.). interpreted as deposited in shelf settings. most Antarctic Ccno~oichistory from the CIROS-l drillhole. typically muddy, organic-rich middle-outer shclf iVIcMui-clo Sound. /\Icir Zc,tiliiiiil Dcptii.lineiil of Scientific and Industrial Rcwircli Hidlclin. 245. 135- 14 1 . environments. as testified by the dominance of Ben A.G. & Maxwell P.A.. 1990. Ceno/.oic Mollusca of New infauna1 deposit- and suspension-feeding bivalvcs Zealand. Drawings by R. C. Bra~icr./\/cn. Z'/.cl(iad Geological (largely, carditids and protobranchs). 5'11n'c'y Pcilc~~oiilolo~ccilBulletin. 58. 5 18 p. Below 325 mbsf the macrofossil content is limited Biickcriclge J. St. J. S.. 2000. A new species of Aii.\troba!ann.\ to single occurrences of marine molluscs: an (Cirripedia. Thoracica) Sroni Eocene erraties, Mount Discovery. McMurdo Sound. East ant arc tic;^. In: Palacobioloey and undetermined gastropod at 359.07 mbsf (LSU 9.1) Palaeoenvimnments of Eocenc Rocks. McMnrdo Soiind. East and an articulated modiolid mussel at 78 1.34 mbsf Antarctica. Antarctic Research Series. 76. 329-333. (LSU 13.2). The latter is significant, as it is one of Bullivant J.S.. 1967. Ecology of the Ross Sea benthos. The Fauna New the few fossils found within a ca. 350 m-thick of the Ross Sea, Zealand Oceiino,yrop/iic Institute Memoir. 32. 49-77. sedimentary succession at the base of the core, almost Cantrill D.J.. 2001. Early Oligocenc /\~o/hof~sfrom CRP-3. barren of fossils, of uncertain age and problematic Antarctica: Implications for the Vegetation History. This depositional setting (LSU 9.1 to 13.2). It is possible volume. that this mussel lived on a relatively deep slope Cape Roberts Science Team. 2000. Studies from the Cape Roberts Project, Ross Sea. Antarctica. Initial Report on CRP-3. Term influenced by gravity flows, and it is compatible with Antiirticci, 7. 1-209. a (?Late) Eocene age. c.'unol . ' R.-P,. Leyrit H. & Giret A.. 1992. Balanoidea (Crustacea. Taxa of relatively warm-water affinities that do not Cin'ipedia) du Miocene des Kerguelen. Geol~ios,25. 383-388. now live around Antarctica are present in the Cosel. R. v011 & Oki, K.. 1998. Gigantism in Mytilidae. A new Bathymodioliis from cold seeps on the Barbados accretionary diamicton-dominated rocks of CRP-3, and evidently prism. Compte Renclii de I'Acadhie des Sciences, Paris, continued to live around Antarctica after the onset of Sciences de lei Vie, 321. 655-663. major glaciation. The Antarctic biota apparently did Dell R.K.. 1990. Antarctic Mollusca. with special reference to the not undergo a "mass extinction" with the onset of fauna of the Ross Sea. The Royal Society of New Zealand Buiilletin. 27. 3 11 p. glaciation, but progressively waned to its present Dell R.K. & Fleniing C.A., 1975. Oligocene-Miocene bivalve impoverished diversity as sea temperatures gradually Mollusca and other macrofossils from Sites 270 and 272 (Ross continued to fall. Sea). DSDP. leg 28. Initial Reports of the Deep Sea Drilling Project. 28. 693-703. Gazdzicki A. & Pugaczewska H.. 1984. Biota of the "Pecten conglon~erate" (Polonez Cove Formation. Pliocene) of King George Island (South Shetland Islands. Antarctica). Studio ACKNOWLEDGEMENTS - All on-ice colleagues of the Geologica Polonica. 79. 59-120. Cape Roberts Project during the 1999-2000 drilling season Giret A.. Leyrit H.. Lauriat-Rage A.. Carriol R.-P. & Lozouet P.. are warmly thanked for their stimulating conversations 1994. Mioccne des Kcrguelcn: la fauna marine du Mont Rond about environmental and chronological issues and. in et ses implications geologiques et palaeoclimatologiques. Coniptes Rendns de I'Academie des Scieiice de Paris. serie 11. particular, David Harwood. Michele Claps, Chris Fielding. 319. 719-726. Fabio Florindo, Peter-Noel Webb. Peter Barrett, Ross Hain S.. 1990. Die beschalten bentliischen Mollusken (Gastropoda Powell. Rosemary Askin, John Simes. Massimo Sarti and und Bivalvia) des Weddellmeeres. Antarktis. The benthic Malcom Laird. Mark Lavelle is gratefully acknowledged for seashells (Gastropoda and Bivalvia) of the Weddell Sea. his painstaking activity spotting macrofossil horizons in the Antarctica. Alfred Wegener Institute for Polar and Marine CRP-3 drill core at the Cape Roberts Campsite laboratory. Research. Germany, Bericlzte ;U; Polorforschiing (Reports on Tom Janacek and Matt Curren assisted with sampling and Polar Research). 70. 181 p. handling of the macrofossil samples. We are indebted to Harwood D. M. & Levy R. H.. 2000. The McMurdo Erratics: introduction and overview. In: Stilwell J.D. & Feldmann R.M. Alessandro Remia. Barbara Gualandi. Paolino Ferrieri. (eds.). Palaeobiology and pnieieoeiivironment.~ of Eocene rocks, Stefano Parisini. Vanessa Thorn. and Bruno Sabelli who McMnrdo Sound, East Antcirctica. Antarctic Research Series. helped at various stages of the manuscript with photography 76. 1-18. and figure preparation. We are also grateful to John Simes. Hartman 0.. 1966. Polychaeta Myzostomidae and Sedentaria of Adam Harris and Luciano Perrozzi for technical support. Antarctica. Antarctic Research Series. 7. 158 p. We are grateful to the referees. Ian Raine, Ewan Fordyce, Hedley C.. 1916. Report on Mollusca from elevated marine beds Hamish Campbell and an anonymous referee, for helpful ("Raised Beaches) of McMurdo Sound. Reports of the improvements to the manuscript. This study was partially Scientific Investigcitions, British Antarctic Expedition, 1907-9, supported by the Italian Programma Nazionale di Ricerche Geology, 2. 85-88. Hendy C.H.. Neall V.E. & Wilson A.T.. 1969. Recent marine in Antarticle and the New Zealand Foundation for Research. deposits from Cape Barne. McMurdo Sound. Antarctica. New Science and Technology. This is IGM scientific contribution Zealand Joi(ri7cil of Geolosy and Geophysics. 12. 707-712. n. 1255. and Institute of Geological and Nuclear Sciences Jonkers H.A.. 1998. Stratigraphy of Antarctic late Cenozoic contribution no. 21 32. pectinid-bearing deposits. Antarctic Science. 10. 161-170. p. 1,oenvironmcnii , of Eoccne Rocks. McMurdo Soui~l.hsi A>~~arciicit.Anmrmc /<~~,s~wrd~.Swi<>,~, 76, 372 l>. Siilwcll J.11. & Xi1,s8,,cislcr, 1992. M~~ll~~sc~~~~sysim:tlics l~i~~slr:~iigr~s~~l~y.1,nwcs 'Tcrii;~ry 1.2, h4csci8 1:~~rnx~iim.Scyal~>$tv lsl~~~~~l,AnIasc1ic llc~,insulz~.An,tric'z%~, (jcopt~ysic:~l1Jnins1, Wns1iingi~)iiD.C.. Ani ...,>,L,,<,,,,<. , l'ugttc~enska H.. 1984. 'Tertiary Bi\mIvia ztncl Scq~l~~~xxlafron, i M,, 13e,, ,,,G. 1 ,,t)r< c;., ]998. l,lcisi<>cc,,e gIz3cinn1>winc ~I~~~~~sils:M ;MagIa N~tnalak. Ki11g Gewge lsl>!~,O~Im, 11ze ~~~~ll~~~~i~~~~.~o/n~,~t~r~,l/ri,s~,~ry CI