Flysch-Type Agglutinated Benthic Foraminifera and Maestrichtian to Paleogene History of Labrador and North Seas: ABSTRACT

Abstract

Virtually identical agglutinated (arenaceous) benthonic foraminiferal assemblages (ca 30 genera, 45-50 taxa), characteristic of the Alpine-Carpathian flysch basins, occur in the Upper Cretaceous-Paleogene fine-grained clastic (?turbidite) sequences of the East Newfoundland basin, Labrador and North Seas. The assemblages terminate in both areas in the late Eocene or Oligocene although, in the central (deepest) part of the North Sea, elements of this flysch-type fauna have been observed extending into lower or middle Miocene levels. Independent geologic evidence indicates that these assemblages have an extensive (paleo)bathymetric distribution ( 4 km). Depth alone is not considered a significant factor in their occurrence. In marginal basins, we favor a model which involves relatively rapid deposition of organic rich, fine-grained clastics under somewhat restricted bottom-water circulation conditions, leading to lower pH and low positive or negative eH at the sea floor. The disappearance of the agglutinated assemblage in all but the deepest part of the North Sea may have been due to the shallowing of the basin by sediment infilling resulting in shallower, more oxygenated conditions. On the Canadian margin, decreases in clay and organic carbon content are associated with the exit of the agglutinated assemblages. In contrast, in the deep Labrador Sea (Site 112), lithology and percent organic carbon are relatively constant across this faunal change. This suggests that, at least in the deep sea, these properties may not be critical to the development of predominantly agglutinated assemblages. We suggest that the exit of agglutinated assemblages in the deep Labrador Sea was due to a change in hydrographic properties associated with the evolution of the psychrosphere. Sedimentologic evidence indicates initiation of northern sources of vigorous bottom water in the late Eocene-early Oligocene which may explain the exit of agglutinated foraminifera. This circulation chang resulted in the influx of higher oxygen bottom waters and a lowering of the CCD which may have favored the replacement of predominantly agglutinated assemblages by calcareous assemblages. End_of_Article - Last_Page 892------------