Palinomorfos continentales de Punta Ekelöf (Cretácico Superior), Isla James Ross, Antártida: inferencias bioestratigráficas y paleoecológicas

AMENABAR, CECILIA R.; DA SILVA DO SANTOS, A.; FAUTH, G.

Gramado

Congreso; XXIII Congresso Brasileiro de Paleontologia; 2013

SOCIEDADE BRASILEIRA DE PALEONTOLOGIA

A palynologicalanalysis 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 (c.a. 300 meters of thickness) divided inthree sections, lower, middle and upper. The palynological analysis of fortysamples provided abundant dinoflagellate cysts, spores and pollen in variablepercentage. 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 palynomorphshave long-ranging ranges and sporesdominate over pollen in all levels. Osmundaceae, Lycopodiaceae, Selaginellaceaeand Cyatheaceae are the most representative spore families and pollen is represented by gymnosperms (Araucariaceae, Podocarpaceae) and angiosperms (Proteaceae, Nothofagaceae). The palaeoenvironment and the proximityof samples to the shoreline were evaluated based on the relationship betweenmarine and continental palynomorphs and the relative abundances of peridinialesand gonyaulacales cysts. Strong fluctuations of the marine vs. continental curve indicate a continuous terrestrial influx to the depocenter. On the otherhand, well-characterized cysts assemblages can be recognized along the wholesection: 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 thepresence of many of the genera that occurred in the middle section although insome 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 marineenvironment or at least deeper conditions. The dominance of peridiniacean cysts in some levels ofthe upper section suggests that the environment becomes more proximally upward.