Distribution and biostratigraphical significance of Heterosphaeridium bellii sp. nov. and other Late Cretaceous dinoflagellate cysts from the southwestern Barents Sea

Abstract

A palynological study of the Upper Cretaceous Kveite Formation and Lower Palaeogene Torsk Formation in two exploration wells from the southwestern Barents Sea is presented. The investigation has revealed an interval characterised by the acme of a new dinoflagellate cyst species Heterosphaeridium bellii sp. nov. Its calibration to a comparable Heterosphaeridium event in ammonite-dated strata from the Western Interior Basin of North America supports the Late Campanian age. An emendation of Heterosphaeridium heteracanthum is provided in order to emphasize the differences between both Heterosphaeridium species. The Turonian to Coniacian age is based on the last common occurrence (LCO) of Heterosphaeridium difficile and the last occurrence (LO) of Stephodinium coronatum. The Early Campanian is established based on the last occurrence of Callaiosphaeridium asymmetricum, Chatangiella bondarenkoi and Palaeoglenodinium cretaceum. The Late Campanian to Early Maastrichtian age is suggested by the last common occurrence of the new species H. bellii, the last occurrence of Odontochitina operculata and common occurrence of Spongodinium delitiense. The last occurrence of Raetiaedinium truncigerum occurs within this interval coinciding with the last super abundant occurrence (LSAO) of H. bellii sp. nov. The palynological events are put alongside geophysical logs to check the validity of the correlation. The study documents several hiatuses, indicating that Upper Cenomanian, Santonian, Middle Campanian, Upper Maastrichtian and lowermost Palaeocene strata are missing in well 7120/7-3, whereas strata of Upper Cenomanian to Santonian and Upper Maastrichtian to lowermost Palaeocene age seem to be missing in well 7119/9-1. The interval represented by the acme of the new gonyaulacacean species H. bellii is considered here to be a useful Late Campanian biostratigraphic marker horizon.