Abstract
A detailed palynological analysis was conducted on 29 samples obtained from the Cretaceous interval of the well Campos- 01, drilled in the Northern portion of the offshore Campos Basin. The main objectives of this study were to precise the age the rocks and to perform an analysis and interpretation of the depositional environment of the interval. The material consists of mainly shales, marls, calcareous mudstones and sandstones deposited in a deep marine environment. The palynological analysis consisted on identification and counting of all palynomorphs. The paleoenvironmental and paleoecological investigations were supported by cluster analysis, ecological indices (e.g. diversity, dominance) and ratios (e.g. continental:marine) were used. A total of 97 taxa was identified, which included 46 genera of dinoflagellates cysts, 25 genera of spores, 21 genera of pollen grains, 2 genera of freshwater algae and microforaminiferal linings. The recorded assemblage (e.g. Trichodinium castanea, Dinogymnium acuminatum, Zlivisporis blanensis) was assigned to a late Campanian—late Maastrichtian age for the studied section. The interval is clearly dominated by the dinoflagellate cysts that reach 90.7% of total of palynomorphs. On the basis of cluster analysis (r-mode) three dinoflagellate associations were recognized: Systematophora, Areoligera and Spiniferites. The stratigraphic distribution of dinoflagellates associations indicates three intervals (I1-I3). The intervals I1 and I2, dominated by Systematophora and Spiniferites respectively, are interpreted as open marine environment. In the interval I3, the dominance of Areoligera Association indicates a nearshore environment, also supported by the large amount of continental elements, including the genus Callialasporites, which is attributed to high altitude flora, suggesting the presence of highland feeding areas.
Highlights
The growing knowledge on dinolagellates reported by Arai (2007) has shown the quite importance of these palynomorphs for paleoenvironmental and biostratigraphic studies in the Brazilian marginal basins
The present study aims to infer paleoenvironment changes for the Cretaceous interval of the Ubatuba Formation of Campos Basin
The last occurrence of some key species of palynomorphs was recorded in the well, viz. Dinogymnium acuminatum, Alisogymnium euclaense, Chatangiella spp., Gabonisporis vigourouxii, Triporoletes blanensis and Trichodinium castanea, Isabelidinium spp. (Figure 2)
Summary
The growing knowledge on dinolagellates reported by Arai (2007) has shown the quite importance of these palynomorphs for paleoenvironmental and biostratigraphic studies in the Brazilian marginal basins. Only few studies (e.g., Arai, 2007; Arai & Viviers, 2013; Carvalho et al, 2016) have correlated dinocyst distribution and ecological characteristics to the environmental changes. Palynological studies of Cretaceous sediments in Campos Basin have shown variations in palynomorphs, especially dinolagellates, and have been correlated with environmental parameters such as distance from shoreline, diversity, productivity, terrigenous inputs. The present study aims to infer paleoenvironment changes for the Cretaceous interval of the Ubatuba Formation of Campos Basin. The Campos Basin is located in the Southeastern part of the Brazilian margin and encompasses mainly the ofshore areas of Rio de Janeiro and Espírito Santo states, with an area of approximately 100.000 square kilometers. The basin is limited to the north by the Vitória High and south by the Cabo Frio High (Winter et al, 2007) (Figure 1)
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