Early Cretaceous palynostratigraphy, palynofacies and palaeoenvironments of well sections in northeastern Tierra del Fuego, Argentina

Abstract

Palynostratigraphic and palynofacies analyses of the Springhill and Pampa Rincón formations in Argentina and the Estratos con Favrella in Chile, studied in 30 core samples from nine wells in northeast Tierra del Fuego, yielded an Upper Valanginian–Cenomanian(?) palynoflora. The occurrence of 71 terrestrial species (spores and pollen grains) and 39 species of organic-walled phytoplankton are considered in this paper. A correlation was made with the Upper Valanginian–Lower Aptian Cyclusphaera psilata- Classopollis Zone (Neuquén Basin) and the Interulobites-Foraminisporis Assemblage Zone in the Austral Basin (Upper Valanginian–Upper Hauterivian) owing to the presence of bryophytic species such as Interulobites spp. and Polycingulatisporites spp. and the incoming of Cyclusphaera psilata. Celyphus rallus and Balmeiopsis limbatus are also common in this zone. The Barremian tectifera-corrugatus Interval Zone (Austral Basin) was not recognized in the samples studied. The Antulsporites-Clavatipollenites Assemblage Zone of the Austral Basin (Aptian), which is characterized by the occurrence of early angiosperm pollen grains ( Clavatipollenites hughesii, Asteropollis asteroides) and Cyclusphaera crassa, among others, was recorded. Near the Aptian/Albian boundary, the succession of angiosperms is characterized by the appearance of rare tricolpates. Heterosphaeridium heteracanthun and Isabelidinium sp. were identified in the Heterosphaeridium Superzone (Australia), indicating an age not older than Cenomanian. This corresponds to the nearshore–shallow marine facies of the Nueva Argentina Formation. Six types of palynofacies (1–6) were distinguished and, together with the composition of the palynomorph assemblages, were linked to depositional conditions, deltaic, shallow marine, nearshore and offshore environments being recognised.