sign in sign up
<<
Home , Ablation Point, Aconeceras, Acrioceras, Alexander Island, Berriasella, Beudanticeras

J. geol. Soc. London, Vol. 139, 1982, pp. 763-770, 1 fig, 1 table. Printed in Northern Ireland

A comparison of the ammonite faunas of the and Magallanes Basin

M. R. A. Thomson

SUMMARY: Ammonite-bearingJurassic and sedimentary successions are well developed in the Antarctic Peninsula and the Magallanes Basin of Patagonia. Faunas of middle - age are present in but those of Patagonia range no earlier than . Although the late Jurassic perisphinctid-dominated faunas of the Antarctic Peninsulashow wide-ranging Gondwana affinities, it is not yet possible to effect a close comparison with faunas of similar age in Patagonia because of the latter's poor preservation and our scant knowledge of them. In both regions the Neocomian is not well represented in the ammonite record, although uninterrupted sedimentary successions appear to be present. Lack of correspondence between the and faunas of Alexander I. and Patagonia may be due to major differences in palaeogeographical setting. -Coniacian ammonite faunas are known only from Patagonia, although bivalve faunas indicate that rocks of this age are present in Antarctica. Kossmaticeratid faunas mark the late Cretaceous in both regions. In Antarcticathese have been classified as , whereas in Patagonia it is generally accepted, perhaps incorrectly, that these also range into the Maestrichtian.

Fossiliferous Jurassic and Cretaceous marine rocks are rize first those of the Antarctic Peninsula and then to well developedin theAntarctic Peninsula, Scotia compare them with those of Patagonia. Comparisons Ridge andPatagonia (Fig. 1A).In Antarcticathese between Antarctic ammonite faunas and other Gond- rocks are distributed along the western and eastern wana areas wereoutlined by Thomson (1981a), and margins of theAntarctic Peninsula, formerly the the faunas of the marginal basin were discussed in magmatic arc from which the sediments were derived. Thomson et al. (1982). Upper Jurassic-Lower Cretaceous fore-arc rocks are represented by the Bluff Formation of Alexan- der I. (Taylor et al. 1979), whereas Middle and Upper Antarctic Peninsula region Jurassic back-arc deposits occur in south-eastern Pal- mer Land and Orville Coast (Latady Formation; Row- Middle Jurassic ley & Williams 1982), and the Cretaceous sequence of theJames Ross I. area hasbeen directly compared Middle Jurassic faunasare known only from the with that of the Magallanes Basin of Patagonia (Bibby southern Behrendt Mountains (Fig. 1A). pre- 1966). Local intra-arc marine sequences occur in the sent include Normannites cf. vulgaricostatus Wester- South Shetland Is (Smellie et al. 1980) and Adelaide I. mann, Skirroceras cf. bigoti (Munier-Chalmas), (Thomson 1972), and the Nordenskjold Formation of Teloceras cf. lotharingicum Maubeuge, Mega- NE Graham Land (Farquharson 1982) may represent sphaeroceras cf. rotundum Imlay, and Nothocephalites a sedimentary phase that pre-dated the main period of (?) sp. (Quilty 1970). Unfortunately these interesting arc building. and Callovian species are not well preserved By contrast, in Patagonia (Fig. 1B) stratigraphically and they occur in isolatednunataks whose strati- equivalentsedimentary rocks are largely confined to graphical relationships with the rest of the sequence the Magallanes or Austral Basin (Natland et al. 1974) are obscure. that developed in a back-arc setting. Although much of this region is covered with Cenozoic rocks, Jurassic Late Jurassic and Cretaceous units are exposedalong the western margin of the basin and have been proved at depth to Late Jurassic ammonites are far more abundant and the E in wildcat and hydrocarbon-producing wells. In occur in the South Shetland Is, north-eastern Graham late Jurassic times a marginal basin opened within the Land, Adelaide I., Carse Point, Alexander I., Lassiter magmatic arc of theeastern Andes, but this was and Orville Coasts and Behrendt Mountains. Howev- short-lived and closed in the mid-Cretaceous. The er, with few exceptions they are poorly preserved and rocks of South (54"20'S,36'40'W) represent confident identifications are normally possible only an isolated fragment of this basin (SuBrez & Pettigrew when several specimens are available. Everywhere the 1976). faunas aredominated by perisphinctids,a difficult Ammonites are varied and locally abundant in all group tounderstand even when dealing with good these areas, and it is the aim of this paper to summa- material. 0016-7649/8211100-0763$02.00 01982 The Geological Society

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/139/6/763/4887516/gsjgs.139.6.0763.pdf by guest on 28 September 2021 764 M. R. A. Thomson

0 300 I 1 km 75' 70'W 65"

FIG. 1. Sketchmaps of theAntarctic Peninsula (A)and southern South America (B) to show the localities mentioned in the text. AV = , CP = Carse Point, C2 = Cape Zumberge, FB = , L1 = Low Island, SHI = Snow Hill Island. Thick lines in Fig. 1B indicate the western and eastern limits of the Magallanes Basin.

Oxfordian ammonites arepoorly known but isolated Shetland Is. Although this is an species it specimens suggest that this stage may be represented occurs with a bivalve fragment having coarse concen- locally. A possible fragment of thelate Oxfordian- tric ornament similar tothat of the early Kimmeridgian Orthosphinctestransatlanticus Retroceramushaasti (Hochstetter) type. Poorly pre- (Steinmann) from James Ross I. was said to be loose servedperisphinctids from theBehrendt Mountains (Spath 1953), but Bibby (1966, p. 22) indicated that have beencompared to Oxfordian Discosphinctes perisphinctids occur in the rocks nearby. Other exam- (Quilty 1970). ples from Alexander I., compared to the same species Kimmeridgian ammonite faunas are also difficult to (Howarth 1958), are doubtfully conspecific. A juvenile identify,although bivalve studies (Crame 1982) indi- mayitid,resembling Epimayites trunsiens (Waagen), cate that sedimentary rocks of this age are widespread has been identified by the author from Low I., South in the region. Collections from the Orville Coast area

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/139/6/763/4887516/gsjgs.139.6.0763.pdf by guest on 28 September 2021 Ammonitefaunas of the Antarctic PeninsulaandMagallanes Basin 765

(Fig. 1A) include many fragmentary and sometimes Ablation Valley, Alexander I., wherea Haplophyl- tectonically distortedperisphinctids reminiscent of 1ocerasIBochianites fauna is present (Thomson 1979). mainly Kimmeridgiangenera such as Subdichoto- Although similar faunas inIndonesia have been in- rnoceras, Torquatisphinctes and possibly Pachysphinc- cluded in the (Westermann et al. 1978), in tes (Thomson 1980). Although it is difficult to rule out Alexander I. they occur much higher in the succession similarities with some Tithonian species, local occur- than thelate Tithonian fauna and in rences of Katroliceras and Subplanites (?) confirm the association with Spiticeras aff. spitiensis (Blanford), presence of Kimmeridgian strata.The presence of Rairnondiceras, earlyCretaceous belemnites (Thom- Aspidoceras at one locality could indicate an age be- son 1979) and bivalves (Crame 1982). Thus, tween Kimmeridgian and Middle Tithonian. an early Berriasian age is considered most probable. A Kimmeridgian age for a possible Pachysphinctes Higher levels of the Berriasian are represented at from some of the oldest strata exposed at Ablation Callisto andTombaugh cliffs whereisolated occur- Point, Alexander I. (Thomson 1979) is supported by rences of Bochianitesgracilis Thomson, Substreblites its association with the bivalves Retrocerarnus haasti (?) sp., Hirnalayites (?) sp., Neocosmoceras aff. sayni and R. subhaasti (Wandel) (Crame 1982). Ammonites (Simionescu) and Sarasinella aff. hondana Haasare from the Nordenskjold Formation (Farquharson 1982) known (Thomson 1974). have been severely compressed but include haplocera- Although there is an apparent stratigraphicalcon- tids, Tararnelliceras and avariety of perisphinctids formity within the Fossil Bluff Formation up to beds resembling Torquatisphinctes and a finely ribbed with Aptian and Albian faunas (below), the interven- Lithacoceras, for which Kimmeridgiana or early ing strata are almost devoid of ammonites,and the Tithonian age seems most likely. bulk of the Neocomian is apparently unrepresented in TheTithonian faunas are less problematicalthan the ammonite record (Taylor et al. 1979). This absence those of the (?) Oxfordianand Kimmeridgian. has yet to be explained satisfactorily but the possibility Although they are no better preserved than the latter, of there being an undetectedstratigraphical break those ofAlexander I. in particular are distinctive must be kept in mind. It is also possible that some enough to allow comparison with the faunas of many aconeceratid faunas from the Fossil Bluff area might other regions (Thomson 1979). Perisphinctids domin- be better regarded as in age (below), rather ate with avariety of Virgatosphinctes and Aulaco- than early Aptian (Thomson 1974). No species which sphinctoides that can be matched with both central might indicate Valanginian and levels has South American and Himalayanhladagascan species. yet been identified in Alexander I., but Covacevich Phylloceratids,lytoceratids (including the distinctive (1976) documented the Valanginian in the South Shet- Pterolytocerasexoticurn (Oppel)), haploceratidsand land Is on the basis of a NeocorniteslBochianites fauna oppeliids are also present. There is a clear distinction with SouthAfrican affinities. Apoorly preserved betweenthese asyet undifferentiated perisphinctid fauna of berriasellid and olcostephanid species from faunas of the early-late Tithonian and an assemblage Matthews I.,South Orkney Is (60°45’S, 45’09’W) of Blanfordiceras and ‘’subprivasensis (Thomson 1981c) seems to have mid-Neocomian Krantz, which seems to mark the latest Tithonian. A affinities. Therecent discovery of neocomitid frag- similar fauna is also present in the Latady Formation ments at Pedersen Nunatak, NE Graham Land, is an at Cape Zumberge, Orville Coast (Thomson 1980). In important one. Their ornament of strongly projected the SouthShetland Is an association of Bochianites, spaced ribs closely resembles that of the Patagonian Hirnalayites and Blanfordiceras may represent a level Favrella arnericana (Favre 1908), an ammonite whose very close to the Jurassic-Cretaceous boundary (Smel- stratigraphical age has been the subject of much dis- lie et al. 1980). cussion but is probably Hauterivian-Barremian (Ric- Kossmatia faunas occur both at Carse Point (Thom- cardi 1970). son 1975) and in the Latady Formation of Lassiter and A recurring problem with the stratigraphical inter- OrvilleCoasts (Rowley & Williams 1982; Thomson pretation of Antarctic ammonitefaunas is the frequent 1980), but not in Alexander I. Presumably they belong lack of at least one readily identifiable species to which to astratigraphical level either notpreserved or yet a confident age may be assigned. This is particularly located in the Fossil Bluff Formation. Although Ver- true of the ‘Aptian-Albian’ faunas of Alexander I. (cf. ma & Westermann (1973) concluded that Kossmatia Thomson 1974, 1981b), where the ages suggested by was an entirely late Tithonian genus, its age in New ammonites fromthe same stratigraphical unit are Zealand is still unresolved (Stevens & Speden 1978, p. often contradictory. After a fauna1 break of approx- 267). imately 800 mabove the Berriasian, the ammonites Acrioceras (?) aff. voyanurn (Anderson), Eulytoceras aff. polare (Ravn) and small Aconeceras and The- ganeceras are commonly associated.Although these The oldest known Cretaceous ammonites in Antarc- faunas were assigned to the Lower Aptian (Thomson tica occur in the Fossil Bluff Formation at the head of 1974), it is possible that greater weighting should be

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/139/6/763/4887516/gsjgs.139.6.0763.pdf by guest on 28 September 2021 766 M. R. A. Thornson given tothe lateNeocomian affinities of Acrioceras (Crame 1980). Thus, there are good possibilities that (?), and the fact that Eulytoceras and Aconeceras also pre-Campanian ammonite faunas will eventually be haveBarremian representatives,and to assign the recovered from the James Ross I. sequence. An inde- assemblage a late Neocomian (? Barremian) age. This terminate desmoceratid from easternJames Ross I. is supported by the recent discovery of a - and Tetragonites cf. epigonus from Cape Longing are like species associated with the same fauna. probably the first known representatives of these (cf. The age significance of Sanmartinoceraspatagoni- Thomson 1981b, p. 283). cum Bonarelli in the succeeding fauna was reviewed The Campanian faunas are superbly preserved and by Thomson (1974), when it was concluded that the are characterized by a wide variety of kossmaticeratids genus couldonly beregarded as an indicator of a belonging to thegenera Maorites,Jacobites, Neo- general Aptianage, rather than late Aptian as had grahamites,Grossouvrites and Gunnarites that show been widely supposed.However, species associated wide-ranging Southern Hemisphere affinities (Thom- with S. patagonicum in Alexander I. indude the hetero-son 1981a). In addition there are phylloceratids, tetra- morph Emericiceras (?) sp., which would be taken as gonitids,hamitids, baculitid,a desmoceratids. and a Barremian species if found in Europe. The recently pachydiscids. An early suggestion that assemblages reported occurrence of Sanmartinoceras in the Upper from Snow Hill I.ranged from theUpper Albian- Barremian of (Kennedy & Klinger 1979) Cenomanian (Kilian & Reboul 1909)was shown by places the Aptian age of Sanmartinoceras in Alexander Spath (1953) to be based on misidentifications of some I. in further doubt. of the species present. The stratigraphy of the ammo- Late Aptian-early Albian faunas are represented by nite faunas from the Snow Hill I. 'Series' was summa- and Aconeceras aff. nisoides Sarasin, rized by Howarth (1966), who identified assemblages succeeded by an enigmatic assemblage of silesitids of the Lower, Middle and Upper Campanian only. with Phyllopachyceras aureliae (Feruglio), Ptychoceras sp., and a crioceratitid-coiled species, Antarcticoceras Magallanes Basin antarcticum Thomson(Thomson 1974). Even higher In view of the close geological comparisons which have occur small (?) heteromorphs resembling Pseudothur- often beendrawn between southern South America mannia,Macroscaphites and Hemihoplites (Thomson and the Antarctic Peninsula, the correspondence be- 1981b, fig. 7). Although the Eotetragonites and silesi- tween the ammonite faunas of the two regions, other tid faunas are separated by a slump zone up to 100 m than for those of the late Cretaceous, is often dis- thick and there are undeniable morphological similar- appointing. Although this may be due in part to our ities between elements in the latter fauna and Euro- imperfect knowledge of the faunas concerned, many peanlate Neocomian forms,there is no reason to of the differences may bereal, in which case itis suppose that there is any structural repetition or rever- possible that palaeogeography may have played an sal of strata. Furthermore, the silesitid faunas are not important role. Throughout much of Jurassic and Cre- interposedbetween the Berriasian faunas and the taceous time it appears that the Andes and Antarctic aconeceratid assemblage of the (?) BarremianiAptian Peninsula were part of a geologically continuous arc elsewhere, as might be expected if the latter were true. terrane (cf. Suarez 1976; Dott et al. 1982). Thus, the Therefore, with the possible exception of Hamites aff. contrastinglate Jurassic-early Cretaceousfaunas of tenuis Sowerby in isolated nunataks (Thomson 1981b) the Magallanes Basin and Alexander I. were separated the silesitid faunas must be taken as the youngest by 15-20' of latitudeand abarrier of islands and (? Albian) so far described from Alexander I. shallow seas that probably comprised the magmatic arc. Conversely, closely similar late Cretaceous faunas Late Cretaceous in southern Patagonia and the JamesRoss I. area both lived in back-arcsituations that were geographically The known lateCretaceous ammonite record in closer together. Antarctica is almost entirely confined to the Campa- Much has been done in recent years to simplify the nian (Spath 1953; Howarth 1958, 1966) and to the NE confused state of stratigraphicalnomenclature in coast of GrahamLand. The describedfaunas come South America and an excellent summary of the strat- from the upper part (Snow Hill I. 'Series') of a thick igraphy of the PatagonianCordillera was presented sedimentary sequence, exposed on James Ross I. and by Riccardi & Rolleri (1980). Only a few of the better othernearby islands and headlands (Bibby 1966). known formation names are needed to put the ammo- Collections suggest that the lower part of the sequence nite faunas in their stratigraphical context (cf. Riccardi is apparently almost devoid of ammonites but inocer- & Rolleri 1980, table 11). amid bivalves (Crame 1981) from these beds indicate that rocks at least as old as Cenomanian are present. Correlated rocks at Pedersen Nunatak contain prob- Late Jurassic able Neocomianammonites (above),and Albian No middle Jurassic ammonites have been described bivalves are present in moraine debris on Dundee I. from the Magallanes Basin and all known late Jurassic

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/139/6/763/4887516/gsjgs.139.6.0763.pdf by guest on 28 September 2021 Ammonitefaunas of theAntarctic Peninsula and Magallanes Basin 767

species are poorly preserved. Marine mudstones inter- la in the lower Formacion Rio Mayer. Its strati- bedded in the upper part and immediately overlying graphical age has been the subject of much discussion the mainly volcanic Complejo e1 Quemado locally (summarized by Riccardi 1970) but itis probably contain ammonite faunas of Kimmeridgian-Tithonian Hauterivian-Barremian. Little is known of associated age. The most varied are those of the Lago Argentino species, although in the Lago Belgrano area it occurs region (Feruglio 1936). According to a revision by with Protaconeceras patagoniensis (Favre 1908). Frag- Leanza (1968) these include Torquatisphinctes (?) sp., mentary remains, which may belong to Favrella, have Aulacosphinctoides (?) sp., Virgatosphinctes aff. now been found in Antarctica (p. 765). andesensis Douville, Corongoceras cf. mendozanum The Hatchericeras fauna (Stanton 1901; Favre 1908; (Behrendsen)and Berriasella sp., but the identifica- Leanza 1970) iswell known from the Lago Pueyrre- tions of some of these are still doubtful and a meaning- don, Belgrano and Posados areas but, with the excep- ful comparison with the faunas of the Antarctic Penin- tion of a single example from Australia (Woods 1962), sula will have to await the collection of better mate- it is an essentially Patagonian genus andits strati- rial.Alenticular development of the Formacion graphical age is poorly known. It has been discovered Springhill above the Complejo El Quemado at Lago recently in eastern Santa Cruz Province in beds about Argentino has yielded Aspidoceras cf. haupti Krantz, 20 m below strata with Sanmartinoceras patagonicum Aulacosphinctoides and Virgatosphinctes (Blasco et al. and Colchidites (Blasco et al. 1980), and in the Lago 1979). This early-middle Tithonian assemblage may Belgrano areait occurs above beds with Favrella relate to some of those from the Orville Coast. (Favre 1908). Thus it appearsto belong to a level The FormacionSpringhill, first recognized in the between Favrella and Sanmartinoceras faunas (Riccar- subsurface of Manantiales,, appearsto be di- di & Rolleri 1980). Hatchericeras has not been found achronous at least in the western part of the Magal- in Antarctica. lanesBasin. It is usually confined to topographical The discovery of Sanmartinoceraspatagonicum depressions in the upper surface of the Quemado, and (Howarth 1958) and bivalves of the Aucellina andinal its age has been assessed as Tithonian-early Neoco- radiatostriata group (Cox 1953) in Alexander I. mian in Manantiales, early Neocomian near Lago San offered prospects of effecting a close correlation be- Martin, and early-middle Tithonian at Lago Argentino tween the Formacion Rio Mayer of Lago San Martin (Blasco et al. 1979). However, reports of Oxfordian- andthe Fossil Bluff Formation.However, further Kimmeridgian foraminifera and late Neocomian Fav- collecting in Patagoniaand Antarctica has failed to rella in the same formation are difficult to reconcile strengthen this correlation(Taylor etal. 1979). The (Riccardi 1976) and itis possible that misidentifica- Favrella fauna at Lago San Martin is followed by a tions of some species, in addition to diachronism, have Barremian-Aptian heteromorph assemblage of ‘Heli- contributed to this confused picture. cancylus’ patagonicum (Stolley), Peltocrioceras sarasi- Although the presence of the bivalve ‘Gryphaea ni (Favre) and Acrioceras spp. with Aconeceras sp. balli’ (Stefanini) in the Formacion Coyhaique of Chile and Feruglioceras piatnitzky Leanza. There is no fauna suggests that the latter may be Oxfordian-Kimmerid- to match this in Alexander I., although the Aconecer- gian in age (Cecioni & Charrier 1974) the fossil’s aslTheganeceras fauna with Acrioceras (?) maybe of identification is open to question, since it also closely roughly comparableage. Fragments, whichmay be resembles Aetostreon from the Berriasian of Lago San related to ‘H’.patagonicum, occur higher in the Fossil Martin (Riccardi 1977). Bluff Formation, in andabove the Sanmartinoceras beds. At LagoSan Martin, Sanmartinoceras occurs with Early Cretaceous Aiolocerasargentinum (Bonarelli)and Silesitesdes- Exposures of the Formacion Springhill in the Lago moceratoides (Stolley) and was assigned an Aptian SanMartin area have yielded aBerriasian fauna, age. A similar age was proposed forthe Sanmarti- which includes the ammonitesJabronella aff. michaelis noceras fauna of Alexander I. (Thomson 1974), (Uhlig), Neocosmoceras sp. and Delphinella sp. (Ric- although it is now appreciated that it could be older cardi 1977). Again there is little comparison with (p. 765). Because of its occurrence with Colchidites and Antarctic faunas. Only Neocosmoceras occurs also in Emericiceras near EstanciaTucu-Tucu, Blasco etal. Alexander I. but that species is a more finely ribbed (1980) suggested that it was late Barremian in age at form, similar to N sayni Simionescu from . that locality. Aioloceras has not been found in Antarc- AlthoughRiccardi (1970) suggested thatthere is tica and Silesites desmoceratoides does not occur with no regional stratigraphical break between the Berria- Sanmartinoceras in Alexander I., although possible sian and Aptian in southern Patagonia, thepresence of examples are present in the Silesites fauna of supposed Valanginian ammonites has yet to be demonstrated. In Albian age. Antarctica this stage has only been recognized in the The stratigraphy of probable Albian faunas in Pata- South Shetland Is (Covacevich 1976). gonia needs careful investigation. New species of The next youngest ammonite fauna is that of Favrel- Hypophylloceras,Paraleptoceras, Sciponoceras, Calli-

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/139/6/763/4887516/gsjgs.139.6.0763.pdf by guest on 28 September 2021 768 M. R. A. Thomson scaphites,Mariella, Desmoceras, Beudanticeras, Calycoceras sp. (lower Formaci6n las Hayas of Lago Anadesmoceras, Puzosia and Parasilesites from several Argentino = Formaci6n Cerro Toro), ‘Mantelliceras’ localities in the Lago San Martin-Lago Viedma area yrigoyeni Leanza and Acanthocerashoggi Leanza (Leanza) were all grouped by Riccardi & Rolleri (Formacion Punta Barrosa, SenoUltima Esperanza) (1980) ina general Albian fauna.None has been all of Cenomanian-(?)early Turonian age, andthe recognized in Antarctica. Coniacian Peronicerassantacrucense Leanza (Forma- ci6n Mata Amarilla of Lago Viedma) (see Riccardi & Rolleri 1980). None of these hasbeen found in Late Cretaceous Antarctica, althoughinoceramid bivalves (Crame Early lateCretaceous ammonites are still poorly 1981) indicate that rocks of this age are present in the known in the Magallanes Basin and our knowledge of James Ross I. area. them is limited to isolated occurrences. These include Uppermost Cretaceous rocks with diverse ammonite

TABLE1: SimplGedammonite biostratigraphy of theAntarctic Peninsula and Magallanes Basin

Antarctic Peninsula MagallanesBasin

Hoplitoplacenticeras, Pseudokossmaticeras, Neograhamites, Maorites,Gunnarites Campanian Gaudryceras,Diplomoceras, Gunnarites, Maorites, Gaudryceras,Diplomoceras, baculitids, Grossouvrites, NeoRrahamites,Jacobites, Grossouvrites, Pachydiscus Placenticeras,Anapachydiscus Santonian Coniacian Peroniceras Turonian- Cenomanian Calycoceras,‘Mantelliceras’, Acanthoceras, Turrilites Puzosia

~~~~ Albian Phyliopachyceras, Ptychoceras, Silesites, Eotetragonites, Sciponoceras,Calliscaphites, Paraleptoceras, variousdes- Aconeceras moceratids incl. Parasilesites

Aptian Eulytoceras,Emericiceras (?), Toxoceratoides,San- Aioioceras,Silesites, Pseudosaynella, Sanmartinoceras martinoceras (?), Crioceratites,Aconeceras ‘Heiicancylus’,Acrioceras, Peltocrioceras, Aconeceras, Eulytoceras, Acrioceras Feruglioceras,Coichidites, Sanmartinoceras Barremian Hatchericeras Favreila (7) Favrella,Protaconeceras Hauterivian Valanginian NeocomitesUhligites,Bochianites, I Berriasian Bochianites,Substrebiites, Himalayites, Spiticeras Jabronella,Neocosmoceras, Delphinella neocomitids Haplophylloceras,Bochianites, Spiticeras Tithonian Blanfordiceras,‘Berriasella’, Corongoceras, Kossmatia Berriasella,Corongoceras Pterolytoceras, haploceratids, Uhligites,Virgatosphinc- Virgatosphinctes, Aulacosphinctoides, Aspidoceras tes,Aulacosphinctoides

Tithonian-Kim- Subdichotomoceras (?), Torquatisphinctes (?), Katro- Torquatisphinctes (?) meridgian liceras,Pachysphinctes (?), Lithacoceras (?), Aspi- doceras,Taramelliceras

Oxfordian Orthosphinctes (71, Dircosphinctes (?), Epimayites

Middle Jurassic Normannites,Skirroceras, Teloceras, Mega- sphaeroceras, Nofhocephalites I

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/139/6/763/4887516/gsjgs.139.6.0763.pdf by guest on 28 September 2021 A :c, S"*.."-" -S +L" A-+"-,.*:,. firrwnurtuc JUUUUJ UJ fircurt,~~LPeninsula Magallanesand Basin 769

faunas are well represented along the SW margin of zone is normally taken as the lower of the two zones of the MagallanesBasin (cf. Riccardi & Rolleri 1980). the Upper Campanian, and kossmaticeratids appear to Kossmaticeratids are an important constituent of the range well above the genus in Patagonia. faunas, with many species of Grossouvrites,Gunna- rites, Maorites and Neograhamites in common with the Antarctic faunas. However, there are some important Conclusions differences. Jacobites hasnot been reported from Patagonia, whereas pachydiscids and baculitids are The principal components of the ammonite faunas more diverse there, and the placenticeratids (Paulcke of Antarctica and the Magallanes Basin are summa- 1906; Leanza 1967) appear to be absent in Antarctica. rized in Table 1, which also presents an approximate In Patagonia it is generallyaccepted thatthe kos- biostratigraphical correlation between the two regions. smaticeratids range up intothe Maestrichtian. Thus Scant knowledge of southern Patagonian late Jurassic Maorites seymourianus, M. densicostatus Kilian & Re- faunas prevents a close correlation with corresponding boul and Hoplitoplacenticeras in the lower part of the Antarctic faunas, but thelatter have wide-ranging Formaci6n Dorotea(Katz 1963) wereregarded as affinities and this may be possible intime. In both Maestrichtian, and Lahsen & Charrier (1972) assigned regions the Neocomian is poorlyrepresented in the several dominantly kossmaticeratid assemblages of the ammonite record, and there are real differences be- Seno Skyring area to the Maestrichtian on the basis of tween the Aptian-Albian faunas of the two regions, associated foraminifera and ages assigned to similar which may be due to palaeogeographical separation. species elsewhere. The early late Cretaceous is so far unrepresented in However,more work is requiredto establish the theammonite record of the AntarcticPeninsula, exactstratigraphical ranges of kossmaticeratids in although representatives may be found eventually in Patagonia. Faunas with species in common also occur the lower part of the sequence off NE Graham Land. in South Africa (Kennedy & Klinger 1975), Madagas- Campanian faunas of Antarctica have much in com- car (Collignon 1970) and New Zealand(Henderson mon with late Cretaceous ones in the SW Magallanes 1970) where they are considered to be essentially Basin but, in the latter region, species are considered Campanian in age.In Patagonia the position of Hoplito- to have longer ranges. Claims that some persisted into placenticeras appearsto be critical since the H. vari the Maestrichtian need further investigation.

References BIBBY, J. S. 1966. The stratigraphy of part of north-east - 1982. Late Mesozoic bivalve biostratigraphy of the GrahamLand and the James RossIsland group. Sci. Antarctic Peninsula J. geol. Soc. London, 139, 771-8. Rep. Br. Antarct. Surv. 53, 37 pp. Don, R.H., JR., WINN,R. D., JR.& SMITH,C. H. L. 1982. BLASCO,G., NULLO,F. & PROSERPIO,C. 1979. Aspidoceras Relationship of late Mesozoic and earlyCenozoic enCuenca Austral, Lago Argentino,prov. de Santa sedimentation to the tectonic evolution of the southern- Cruz. Rev. Asoc. geol. , 34, 282-93. most Andesand Scotia arc. In: CRADDOCK,C. (ed.). --& PLOSZKIEWICZ,J. V. 1980. El gCnero Antarctic Geoscience. Univ. Wisconsin Press, Madison, Colchidifes DjanClidzC, 1926 y la posicibn estratig- 195202. rifica del gtnero Hatchericeras Stanton, 1901 en la FARQUHARSON,G. W. 1982. Late Mesozoic sedimentation in estancia Tucu-Tucu provincia deSanta Cruz. Rev. the northern Antarctic Peninsula and its relationship to Asoc. geol. Argentina, 35, 41-58. the southern Andes. J. geol. Soc. London, 139, 721-7. CECIONI,G. & CHARRIER,R. 1974. Relaciones entre la FAVRE,F. 1908. Die Ammoniten der unteren Kreide Patago- Cuenca Patagdnica, laCuenca Andina y e1 Canalde niens. Beilage Band, Neues Jahrb. Mineral. Geol. Mozambique. Ameghiniana, 11, 1-38. Palaeontol. 25, 601-47. COLLIGNON,M. 1970. Atlas des fossiles caracteristiques de FERUGLIO,E. 1936. Palaeontographiapatagonica. Pt. 1. (Ammonites). XVI, Campanien moyen et Mem. 1st. geol. mineral. Vniv. Padova, 11, 1-192. superieur. Service GCologique, Tananarive, 82 pp. HENDERSON,R. A. 1970. from the Mata Series COVACEVICH,V. C. 1976. Fauna valanginiana de Peninsula (Santonian-) of New Zealand. Spec. Pap. Byers, Isla Livingston, Antarctica. Rev.geol. Chile, 3, Palaeontology, 6, 81 pp. 25-46. HOWARTH,M. K. 1958. Upper Jurassic andCretaceous Cox,L. R. 1953. Lower CretaceousGastropoda, Lamelli- ammonitefaunas of AlexanderIsland andGraham branchia and Anellida from Alexander I Land (Falkland Land. Sci. Rep. Falkld Isl. Depend. Surv. 21, 16 pp. Islands Dependencies). Sci. Rep. Falkld Is[. Depend. - 1966. Ammonites from theUpper Cretaceous of the Surv. 4,14 pp. JamesRoss Island group. Bull.Br. Antarct. Surv. 10, CRAME,J. A. 1980. The occurrence of the bivalve Inocer- 55-69. amus concentricus onDundee Island, Joinville Island KATZ, H. R. 1963. Revision of Cretaceousstratigraphy in group. Bull. Br. Antarct. Surv. 49, 283-86. Patagonian Cordillera of Ultima Esperanza, Magallanes - 1981. UpperCretaceous inoceramids (Bivalvia) from Province,Chile. Bull. Am.Assoc. Petrol.Geol. 47, theJames RossIsland groupand theirstratigraphical 506-24. significance. Bull. Br. Antarct. Surv. 53, 29-56. KENNEDY,W. J. & KLINGER,H. C. 1975. Cretaceous faunas

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/139/6/763/4887516/gsjgs.139.6.0763.pdf by guest on 28 September 2021 770 M. R. A. Thomson

fromZululand and Natal, South Africa:introduction, of Graham Land Sci.Rep. Falkld Is. Depend.Surv. 3, stratigraphy. Bull.Br. MW. (Nat.Hist.), Geology, 25, 60 PP. 263-315. STANTON,T. W. 1901. The marine Cretaceous invertebrates. - & - 1979. Cretaceousfaunas fromZululand and In: SCOTT, W. B. (ed.). Reportsof the Princeton Uni- Natal, South Africa. The ammonite superfamily Haplo- versityExpeditions to Patagonia, 1896-1899, IV. The cerataceaeZittel, 1884. Ann. S. Afr.Mus. 77, University, Princeton, N.J., 1-43. 85-121. STEVENS,G. R. & SPEDEN,I. G. 1978. New Zealand. In: KILIAN,W. & REBOUL, P.1909. Les cCphalopodes ntocrtta- MOULLADE,M. & NAIRN, A. E.M. (eds). The Phanero- cCs des isles Seymour et Snow Hill. WissErgebn. zoic Geology of the World, 11: The Mesozoic, A. Else- schwed. Siidpolarexped. 3 (6), 75 pp. vier Scientific Publishing Co., Amsterdam, 251-328. LAHSEN,A. & CHARRIER, R.1972. Late Cretaceous ammo- SUAREZ,M. 1976. Plate-tectonic model for southern Antarc- nites from Seno Skyring-Strait of Magellan area, Magal- tic Peninsula and its relation to southern Andes. Geolo- lanes Province, Chile. J. Paleontol. 46, 520-32. gy, 4, 211-14. LEANZA,A.F. 1967. Descripcion de la fauna de -& PETTIGREW,T. H. 1976. An Upper Mesozoic island- Placenticeras del Cretftcico superior de Patagonia Aus- arc-back-arc system in the southernAndes and South tral con consideraciones acerca de su posicion estratigra- Georgia. Geol. Mag. 113, 305-28. fica. Bol. Acad. Nac. Cienc. Cordoba, 46, 5-28. TAYLOR, B. J.,THOMSON, M. R. A. & WILLEY,L. E. 1979. - 1968. Anotaciones sobre 10s fosiles jurtisico-cretacicos The geology of the -Keystone Cliffs area, dePatagonia Austral (colleci6n Feruglio)conservados . Sci. Rep. Br. Antarct. Surv. 82,65 pp. en la Universidad de Bologna. Actageol. lilloana, 9, THOMSON,M. R. A. 1972. New discoveries of in the 121-79. Upper Jurassic Volcanic Group of . Bull. - 1970. Ammonites nuevos o pocos conocidosdel Br. Antarct. Surv. 30, 95-101. Aptiano,Albiano y Cenomanianode 10s AndesAu- __ 1974. Ammonite faunas of the Lower Cretaceous of strales con notas acerca su posicion estratigrkfica. Rev. south-eastern Alexander Island. Sci.Rep. Br. Antarct. Asoc. geol. Argentina, 25, 197-261. Surv. 80, 44 pp.

NATLAND, M. L., GONZALEZ, E.P,, CANON,A. & ERNST, ~ 1975. Upper Jurassic from Carse Point, Pal- M. 1974. A system of stages for the correlation of mer Land. Bull. Br. Antarct. Surv. 41 & 42, 31-42. Magallanes Basin sediments. Mem. geol. Soc. Am. 139, __ 1979. Upper Jurassic and Lower Cretaceous ammonite 126 pp. faunas of theAblation Point area, Alexander Island. Sci. PAULCKE,W. 1906. DieCephalopoden der oberen Kreide Rep. Br. Antarct. Surv. 97, 37 pp. Siidpatagoniens. Ber.naturforsch. Ges. Freiburg, 15, - 1980. Late Jurassic ammonite faunas from the Latady 167-244. Formation, Orville Coast. Antarct. J. U.S. 15, 28-30. QUILTY,P. G. 1970. Jurassicammonites from Ellsworth -1981a. Mesozoic ammonite faunas of Antarctica and the Land, Antarctica. J. Paleontol. 44, 110-16. break-up of Gondwana. In: CRESSWELL, M.M. & VEL- RICCARDI, A. C.1970. Favrella R. DouvillC, 1909 (Ammoni- LA, P. (eds). Gondwanafive. A. A. Balkema, Rotter- tina, CretAcico inferior): edad y distribucih. Ameghi- dam, 269-75. niana, 7, 119-38. - 1981b. Antarctica. In: REYMENT,R. E. & BENGTSON, -1976. Paleontologia y edad de la Formacih Springhill. P. (eds). Aspects of mid-Cretaceous Regional Geology. In: CHARRIER,R. (ed.). ActasPrimer Congreso Geo- Academic Press. London, 269-96. logic0Chileno, I. Universidad de Chile,Santiago, - 1981c. Late Mesozoic stratigraphyand invertebrate C41-56. palaeontology of theSouth Orkney Islands. Bull.Br. - 1977. Berriasian invertebrate fauna from the Springhill Antarct. Surv. 54, 65-83. Formation of southern Patagonia. NeuesJahrb. Geol. __ , TANNER,P. W. G. & REX,D. C. 1982. Fossil and Palaeontol. Abhandlungen, 155, 216-52. radiometricevidence for ages of deposition and meta- -& ROLLERI,E. A. 1980. Cordillera Patagonica austral. morphism of sedimentary sequences on South Georgia. In: Segundo simposio de geologia regional Argentina, 11. In: CRADDOCK,C. (ed.). AntarcticGeoscience. Univ. AcademiaNacional de Ciencias, Cordoba,Argentina, Wisconsin Press, Madison, 177-184. 1173-1306. VERMA.H. M. & WESTERMANN,G. E. G. 1973. The Titho- ROWLEY,P. D. & WILLIAMS,P. L. 1982. Geology of the nian (Jurassic) ammonite fauna and stratigraphy of Sierra northern Lassiter Coastand southern Black Coast, Catorcie, SanLuis Potosi, . Bull. Am. Paleon- Antarctic Peninsula. In: CRADDOCK, C. (ed.).Antarctic tol. 63, 103-320. Geoscience. Univ. Wisconsin Press, Madison, 339-48. WESTERMANN,G. E. G., SATO,T. & SKWARKO,S. K. 1978. SMELLIE,J. L., DAVIES, R. E. S. & THOMSON,M. R. A. Brief report on the Jurassic biostratigraphy of the Sula 1980. Geology of a Mesozoic intra-arc sequence on Islands, Indonesia. Newsl. Stratigr. 7, 96-101. ByersPeninsula, Livingston Island. Bull.Br. Antarct. WOODS, J. T. 1962. A new species of Hatchericeras (Ammo- Surv. 50, 55-76. noidea) from northQueensland. J. geol.Soc. Aust. 8, SPATH,L. F. 1953. The Upper Cretaceous fauna 239-44.

Received 21 October 1981; revised typescript received 16 June 1982. M. R. A. THOMSON,,Natural Environment Research Council, Madingley Road, Cambridge CB3 OET.

Downloaded from http://pubs.geoscienceworld.org/jgs/article-pdf/139/6/763/4887516/gsjgs.139.6.0763.pdf by guest on 28 September 2021