Distribution of cenozoic foraminifera from the northwestern atlantic margin analyzed by correspondence analysis

Abstract

Foraminiferal data from 36 offshore wells on the Labrador Shelf, Grand Banks, and Scotian Shelf have been analyzed statistically for biostratigraphic correlation and for systematic trends in distribution related to paleobiogeography. Ranking and Scaling (RASC) of the data allows the recognition of reliable assemblage zones, grouped for this analysis into six well-defined time slices. Correspondence analysis shows clearly geographic trends in faunal distribution, differing according to latitude. About one-half of the taxa are planktonic; many of these are restricted to southern and more offshore wells that were influenced by the presence of a proto-Gulf Stream. The remaining taxa are predominantly benthonic, and may be allocated broadly to two groups, one with widespread species occurring throughout the region, and a smaller group that is restricted to northern wells on the Labrador Shelf, possibly favored by the influence of terrigenous sediment supply. This threefold effect of southern planktonics, ubiquitous benthonics, and minor northern benthonics is recognized throughout the Cenozoic, with minor fluctuations. During Middle—Late Eocene, a large percentage of taxa are restricted northerly benthonics, reflecting the fossilferous, thick terrigenous mudstone sequence in northern wells. During Early—Middle Miocene, the southerly restricted planktonics predominate, reflecting Gulf Stream influence during climatic warming. In the late Neogene, a small group of benthonics are relatively ubiquitous due to the onset of the shelfbound Labrador current. The combined use of RASC and correspondence analysis provides a good tool for unscrambling the influence of both time and paleoenvironment on this dataset.