Benthic foraminifera, ostracods and radiolarians from the Lachman Crags Member (Santa Marta Formation), upper Santonian-lower Campanian (Upper Cretaceous) of James Ross Island, Antarctica

Abstract

-This study presents the taxonomy of benthic foraminifera, ostracods, and radiolarians of a sedimentary succession within the Lachman Crags Member, Santa Marta Formation (upper Santonian-lower Campanian), northwestern James Ross Island. Twenty-seven benthic foraminiferal species, six ostracod species, and six radiolarian species were identifi ed. Calcareous microfossils occurrences are restricted to few stratigraphic levels described as tuffaceous sandstones cemented by calcium carbonate, while siliceous microfossils and agglutinated foraminifera also occur in different lithofacies. This suggests a preservational bias in the occurrences of microfossils within the studied section, possibly related to the presence/absence of calcium carbonate cement. The benthic foraminiferal fauna presents a low degree of endemism with the dominance of cosmopolitan taxa (e.g. Gyroidinoides globosus (Hagenow), Gavelinella sandidgei (Brotzen). Consistent occurrences of G. globosus suggest the dominance of deep-neritic to upper-bathyal paleodepths. The ostracod genera identifi ed herein have already been reported for the Cretaceous of the Gondwana region and suggest deposition on a shelf with warm water temperature and normal salinity. The studied radiolarian fauna, the fi rst one described for the James Ross Island region, can be considered Late Cretaceous in age, also presenting the dominance of robust (dissolution resistant) cosmopolitan taxa.

Calcareous nannofossils from the Santa Marta Formation (Upper Cretaceous), northern James Ross Island, Antarctic Peninsula

“…Barren intervals in the lower and upper parts of the section correspond to a similar pattern exhibited by foraminifera (Florisbal et al, 2013). This could reflect unsuitable facies, as part of a regressive sequence (Scasso et al, 1991;Olivero, 2012), or a dissolution effect (Florisbal et al, 2013).…”

“…tuffites cemented by carbonate sensu Scasso et al, 1991). Macrofossil content varied throughout the section, with frequent bivalves, belemnites, dispersed vegetation (stems, trunks, leaves), and rare microfossils, including Cretaceous benthic foraminifera, ostracods and radiolarians, which occur between Samples LC28 and LC95 (Florisbal et al, 2013). In general, macrofossils, where frequent at certain horizons, were contained in carbonate concretions (Fig.…”

“…They include studies on palynology by Dettman and Thomson (1987), Askin (1988), Harwood (1988), Pirrie and Reading (1988), Pirrie et al (1991), Keating (1992), Barreda and Olivero (1993) and Carvalho et al (2013), among others. However, micropalaeontological studies in the James Ross Basin are still scarce and are generally restricted to Mesozoic and Cenozoic foraminifera, ostracods, diatoms and radiolarians (MacFayden, 1966;Huber, 1988;G azdzicki and Webb, 1996;Concheyro et al, 1997Concheyro et al, , 2007Concheyro et al, , 2010Concheyro et al, , 2014Bertels-Psotka et al, 2001;Fauth et al, 2003;Caram es and Concheyro, 2013;Florisbal et al, 2013).…”

“…The study presented herein covers the upper part of the Alpha Member of the Santa Marta Formation in the Lachman Crags section, where 99 micropalaeontological samples were collected for the study of foraminifera, ostracods and radiolarians (Florisbal et al, 2013). In 17 of those samples, calcareous nannofossils have been recorded.…”

Nannofossils, foraminifera and microforaminiferal linings in the Cenozoic diamictites of Cape Lamb, Vega Island, Antarctica

“…Diverse foraminiferal assemblages from the Antarctic Peninsula have been documented from the Upper Cretaceous (MacFadyen 1966;Huber 1988;Gennari 1995;Concheyro et al 1997;Hradecká et al 2011;Florisbal et al 2013), Paleocene (Huber 1988) and Eocene outcrops (Gaździcki andMajewski 2009, 2012). Less diverse foraminiferal assemblages have been recorded from Oligo− cene (Gaździcki 1989), Miocene (Birkenmajer and Łuczkowska 1987;Bertels− −Psotka et al 2001;Jonkers et al 2002;Lirio et al 2003;Concheyro et al 2007;Majewski et al 2012;Nývlt et al 2011), Miocene-Pliocene (Adamonis et al 2010 and Pliocene to early Pleistocene exposures (Holland 1910;Gaździcki and Webb 1996;Jonkers et al 2002;Lirio et al 2003;Caramés and Concheyro 2013).…”