PALEOBIOGEOGRAPHICAL RECONSTRUCTIONS FOR THE END OF THE LATE CAMPANIANS BY PLANKTONIC FORAMINIFERA IN THE PACIFIC OCEAN

Abstract

The paper considers the results of the analysis of the taxonomic composition of planktonic foraminifera (PF) from the end of the Late Campanian in the Pacific Ocean. To identify the latitudinal-zonal faunas of the PF, an assessment was made of the species similarity and differences of the PF complexes of the same age from different wells. Based on the difference in species composition, the fauna of the PF is divided into non-arctic regional and oceanic latitudinal-zonal: subtropical western, tropical central and subtropical central oceanic faunas. To reconstruct the climatic fluctuations that occurred at the end of the Campanian century in the Pacific Ocean, the systematic composition of the shells of planktonic foraminifera was studied from the core samples of eleven deep-sea drilling wells.The identified PF thanatocenoses were assigned to two types (Tethyan, intermediate) and one subtype (thermal-boreal). Based on the spatial distribution of thanatocenoses, the position of climatic zones for two sections of the late Campanian was determined. Within the studied water area, two climatic zones were developed during the studied age interval: intermediate and Tethyan. In the middle of the Late Campanian, the boundary between them passed in the paleoequator region. At the end of the late Campanian, it became sharply colder. The intermediate and Tethyan zones narrowed. In the northern part of the studied water area, a warm-boreal subzone was revealed, in the southern part, the Tethyan subzone was replaced by an intermediate zone. The obtained reconstructions are confirmed by our own and published data of oxygen isotope analysis.