New data for the Valanginian strata of the Byers Peninsula (Livingston Island, Antarctica): palynological evidence and palaeoenvironmental assessment

Abstract

This study reevaluates the chronostratigraphic extent and depositional conditions of the President Beaches Formation at the Byers Peninsula, Livingston Island, South Shetland Islands (Antarctica). Our aim is to constrain its age and improve its regional correlation using new palynological evidence. Dinoflagellate cyst assemblages enabled the recognition of the mid–late Valanginian Senoniasphaera tabulata Interval Zone, identified by the presence of its index-species and the coeval occurrence of characteristic dinocyst taxa such as Canningia reticulata, Cerbia tabulata, Kaiwaradinium scrutillinum, Spiniferites sp., Oligosphaeridium complex, Circulodinium vermiculatum, and Heslertonia heslertoniensis. These data extend the scope of the President Beaches Formation, shifting its upper boundary compared to earlier findings. Examination of dinocysts indicates low-energy neritic conditions for the investigated succession, characterized by normal marine availability and relatively oligotrophic water masses. An elevated C/M ratio (predominance of saccate pollen grains among sporomorphs) further suggests an offshore setting with significant terrestrial input. Palynofacies data support a mid-to-distal shelf depositional environment, consistent with previous lithofacies evidence. The diversity of sporomorphs indicates the hinterland flora primarily comprised pteridophyte-spore generating plants and coniferous woodlands, with nearly equal amounts of Araucariacites and Podocarpidites. A warm temperate climate with high humidity is also proposed for the mid- to late Valanginian time in this area.