Cenozoic deep-water agglutinated foraminifera in the North Atlantic

Abstract

Cenozoic (predominantly Paleogene) "flysch-type" agglutinated foraminiferal assemblages and their modern analogs in the North Atlantic and adjacent areas have been studied to provide an overview of their spatial and temporal distribution and utility for paleoenvironmental analysis. Over 200 species of agglutinated foraminifera have been recognized in Paleogene sediments from North Atlantic and Tethyan basins. This unified taxonomic data base enables the first general synthesis of biostratigraphic, paleobiogeographic and paleobathymetric patterns in flysch-type agglutinated assemblages from upper Cretaceous to Neogene sediments in the North Atlantic. The majority of taxa are cosmopolitan, but latitudinal, temporal and depth-related trends in diversity and species composition are observed among flysch-type assemblages.Modern deep-sea agglutinated foraminiferal faunas provide an analog to fossil flysch-type assemblages and serve as models for paleoecologic studies. Core-top samples from the Panama Basin, Gulf of Mexico and Nova Scotian continental rise were examined in order to determine the habitats of modern species of agglutinated foraminifera. The ecology of modern taxa provides constraints on the paleoenvironmental significance of fossil agglutinated assemblages in the North Atlantic, and their utility for paleoceanography.Towards this end, spade core samples from a 3912 m deep station in the Panama Basin were studied to determine abundance and microhabitat partitioning among living agglutinated foraminiferal populations and the preservation of dead assemblages. The genera Dendrophrya, Cribrostomoides and Ammodiscus have epifaunal habitats and the genus Reophax is predominantly infaunal. Species of Reophax are probably responsible for fine reticulate burrows observed in xradiographs. An experiment using recolonization trays in the Panama Basin was designed to identify opportunistic species of benthic foraminifera, and to assess the rate at which a population can colonize an abiotic substrate. The most successful colonizer at this site is Reophax, while Dendrophrya displays the lowest capability for dispersal. After nine months the abundance of living individuals in sediment trays was one-tenth to one-third that of background abundance, but the faunal diversity did not differ greatly from control samples. Recolonization by benthic foraminifera is more rapid than among macrofaunal invertebrates.Modern agglutinated assemblages from the Louisiana continental slope were examined to determine changes in species composition associated with hydrocarbon seeps. Organic-rich substrates are characterized by a decrease in astror--iihizids and an increase in trochamminids and textulariids. Highly organicenriched substrates with chemosynthetic macrofauna are dominated by Trochammina glabra and Glomospira charoides.The biostratigraphy of fossil agglutinated foraminifera in the North Atlantic is based on detailed analysis of 670 samples from 14 wells and one outcrop section, and examination of additional picked faunal...

Upper Cretaceous, K/T boundary, and Paleocene agglutinated foraminifers from Hole 959D (Côte d'Ivoire-Ghana Transform Margin)

“…7. The DWAF assemblage in Core 159-959D-48R is characterized by a distinct acme of Spiroplectammina spectabilis, a cosmopolitan Paleogene form (Kaminski, 1988). A single occurrence of Conotrochammina whangaia, a Paleocene marker in the North Atlantic and its marginal basins (Kuhnt and Kaminski, 1990), is observed in Sample 159-959D-48R-5, 28−31 cm.…”

“…Initial DWAF zonations for the Atlantic Ocean were developed by Moullade et al (1988) for the Cretaceous and by Kaminski (1988) for the Paleogene. More recent biostratigraphic work on DWAF includes material from the Cretaceous to Paleogene of various localities within the North Atlantic Kuhnt and Collins, 1996), the Western Tethys Bubik, 1995;Kaminski et al, 1996), the marginal basins of the South Atlantic (Volat et al, 1996), and the Western Pacific Ocean (Wightman and Kuhnt, 1992).…”

Paleoceanography and Biostratigraphy of Paleogene Radiolarians from the Norwegian-Greenland Sea

“…As currently defined (at -34.0 Ma), the Eocene/Oligocene boundary itself was a fairly quiet period geologically and climatically; this was followed by a 1-to 2-m.y. period of faunal and floral changes (Miller et al, 1982;Boersma et al, 1987;Kaminski, 1988;Thomas, 1992;Aubry, 1992;Baldauf 1992). Oxygen and carbon isotope studies of the late Eocene to early Oligocene boundary period support climatic cooling (e.g., Miller et al, 1987;Zachos et al, 1993) and/or changes in oceanic circulation as the causes of these faunal and floral extinctions, and they indicate the possibility for bipolar formation of deep waters in the earliest Oligocene.…”

“…The similarities between hiatuses in the Norwegian-Greenland Sea and the global record (Keller et al, 1987) provide support for the latter, but nonetheless there is little evidence against an Arctic incursion, inasmuch as little is known about the Paleogene Arctic. Kaminski (1988) stated that similarities between agglutinated foraminifers in the North Sea and on the V0ring Plateau during the early Eocene make a bathyal connection between these areas a strong possibility as well.…”

“…1). Potential paleoceanographic influences on the Eocene and Oligocene floras and faunas have been discussed by several workers (e.g., Berggren and Schnitker, 1983;Kaminski, 1988;Thiede et al, 1989) and include water exchange with the North Atlantic across shallow interruptions in the Greenland-Scotland Ridge, across epicontinental seaways, with the North Sea through deeper water connections, and with the Arctic Ocean.…”