Radiolarian contourites record Eocene AABW circulation in the equatorial East Atlantic

Author(s): Sarnthein, M.; Faugères, Jean-Claude
Author Affiliation(s): Primary:
Universität Kiel, Geologisch-Paläontologisches Institut, Kiel, Federal Republic of Germany
URA Geologie et Oceanographie, France
Université de Bordeaux I, Bordeaux, France
Volume Title: Contourites and bottom currents
Volume Author(s): Stow, Dorrik A. V., editor; Faugères, Jean-Claude
Source: Contourites and bottom currents, edited by Dorrik A. V. Stow and Jean-Claude Faugères. Sedimentary Geology, 82(1-4), p.145-155. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0037-0738 CODEN: SEGEBX
Note: In English. 19 refs.; illus. incl. geol. sketch maps, 1 table, sects.
Summary: 50 m of Middle Eocene pure radiolarian ooze were drilled at ODP Site 660 in the equatorial East Atlantic, 80 km northeast of the Kane Gap. The oozes comprise a 10 m high and 2 km broad mound of seismic reverberations, covered by manganese-rich sediment, and contain trace amounts of sponge spicules and diatoms, negligible organic carbon (0.15%), clay, and variable amounts of pyrite. The yellow to pale brown silty sediments are relatively coarse-grained (30-45% coarser than 6 µm), little bioturbated, and commonly massive or laminated on a cm-scale. The unlithified radiolarian ooze may indicate an interval of high oceanic productivity, probably linked to a palaeoposition of Site 660 close to the equatorial upwelling belt during Middle Eocene time. The absence of organic matter, however, and both the laminated bedding and the mound-like structure of the deposit on the lower slope of a continental rise indicate deposition by relatively intense contour currents of oxygen-rich deep water, which passed through the Kane Gap, winnowed the fine clay fraction, and prevented the preservation of organic carbon. The ooze may be either a contourite-lag deposit, or a contourite accumulation of displaced radiolarians, originating south of the Kane Gap and being deposited in its northern lee, thus documenting the passage of a strong cross-equatorial bottom-water current formed near Antarctica. These Eocene contourites may be an analogue for ancient radiolarites in the Tethyan Ocean.
Year of Publication: 1993
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Antarctic Ocean; Antarctic bottom water; Atlantic Bottom Water; Atlantic Ocean; Cenozoic; Circulation; Clastic rocks; Clastic sediments; Contourite; Deep-water environment; Drift; East Atlantic; Eocene; Geophysical methods; Geophysical profiles; Invertebrata; Kane Gap; Leg 108; Microfossils; ODP Site 660; Ocean Drilling Program; Paleogene; Paleoproductivity; Protista; Radiolaria; Reflection methods; Sedimentary rocks; Sediments; Seismic profiles; Tertiary
Coordinates: N100000 N100000 W0190000 W0190000
Record ID: 1993012848
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands