Palynological assemblages from Ekelöf Point (Upper Cretaceous) of southeast James Ross Island, Antarctic Peninsula.

AMENÁBAR, C.R., ; DA SILVA DO SANTOS, A.; FAUTH, G.

Río de Janeiro

Simposio; XIV Simpósio Brasileiro de Paleobotânica e Palinologia; 2013

Museo Nacional de la Universidad Federal de Rio de Janeiro (UFRJ)

A palynological analysis of a sedimentary succession from the Santa Marta Formation (Upper Cretaceous) at Ekelöf Point, southeast of James Ross Island, Antarctic Peninsula, is presented here. The study comprises one stratigraphic profile (ca. 300 meters of thickness) divided in three sections, lower, middle and upper. The palynological analysis of forty samples provided abundant dinoflagellate cysts, spores and pollen in variable percentage. The presence of Odontochitina porifera, Isabelidinium cretaceum, I. korojonense, Xenikoon australis, Chatangiella tripartita and C. victoriensis supported a Campanian age for the studied section. Terrestrial palynomorphs have long-ranging ranges and spores dominate over pollen in all levels. Osmundaceae, Lycopodiaceae, Selaginellaceae and Cyatheaceae are the most representative spore families and pollen is represented by gymnosperms (Araucariaceae, Podocarpaceae) and angiosperms (Proteaceae, Nothofagaceae). The palaeoenvironment and the proximity of samples to the shoreline were evaluated based on the relationship between marine and continental palynomorphs and the relative abundances of peridiniales and gonyaulacales cysts. Strong fluctuations of the marine vs. continental curve indicate a continuous terrestrial influx to the depocenter. On the other hand, well-characterized cysts assemblages can be recognized along the whole section: peridiniacean cyts including Isabelidinium cretaceum, Isabelidinium spp. and Isabelidinium/Manumiella complex dominate the lower section. Dinoflagellate diversity increases in the middle section and some species such as Isabelidinium pellucidum, Odontochitina porifera, Exochosphaeridium bifidum, Oligosphaeridium perforatum are frequently recorded. Odontochitina sp. cf. O. spinosa, Chatangiella tripartita, Isabelidinium korojonense, Phelodinium exilicornutum, Trichodinium castanea and Operculodinium centrocarpum are rare. The upper section is characterized by the presence of many of the genera that occurred in the middle section although in some levels, peridiniacean cysts become dominant again. The dominance of peridiniacean cyst registered in the lower section indicates a proximal marine environment. However, the increase of the dinoflagellate cysts diversity together with the occurrence of some gonyaulacoid cysts as Exochosphaeridium, Oligosphaeridium and Spiniferites in the middle section could represent more distal marine environment or at least deeper conditions. The dominance of peridiniacean cysts in some levels of the upper section suggests that the environment becomes more proximal upward.