Santos Florisbal L.,ITT Fossil UNISINOS |
Kochhann K.G.D.,ITT Fossil UNISINOS |
Baecker-Fauth S.,ITT Fossil UNISINOS |
Fauth G.,ITT Fossil UNISINOS |
And 3 more authors.
Revista Brasileira de Paleontologia | Year: 2013
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 identified. 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 identified 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 first 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. © 2013 by the Sociedade Brasileira de Paleontologia.