The formation of the present-day morphostructural ensemble of the Arctic basin was to a large extent controlled by sedimentological pattern that was, in turn, strongly affected by the influence of the Atlantic and Pacific oceans. Recently obtained new seismic data suggest several major structural rearrangements in the region, the largest events occurring during the Oligocene and the Late Miocene. Paleozoogeographic and hydrological evidence of the connections between deep-sea basins and surrounding shelves are of crucial importance for paleotectonic and paleoenvironmental reconstructions.
Paleogene diatom assemblages from the Fram Strait constrain the evidence of continental shelf environments in water depths not exceeding 300-400 m. Freshwater diatoms are also common, indicating environments of coastal marshes. The analysis of ODP materials from the Fram Strait shows that in the Oligocene this basin was isolated from both the North Atlantic and the Arctic basins. During the Miocene, this basin became deeper and was characterized by higher sedimentation rates, thus providing favorable environments for the preservation of benthic agglutinating foraminifera assemblages.
Apparently, this basin was at that time isolated from the Norwegian-Greenland Basin, as indicated by the absence here of the typical North Atlantic carbonate fauna. On the Alpha Ridge, Cretaceous-Eocene siliceous-rich sediments are overlain by late Miocene-Pliocene deposits containing secretional fauna. This may indicate a fundamental environmental change that began in the Oligocene and reached its maximum during the Miocene. Further restructuring of the Arctic Basin was signified by the appearance in the shelf and mainland sedimentary records of both the Atlantic and North Pacific fauna and flora assemblages and the onset of ice-house conditions imprinted in replacement of the Miocene thermophilic diatoms by cool-water species.