38. LATEST CRETACEOUS AND EOCENE PALEOENVIRONMENTS IN THE BLAKE-BAHAMA
At Site 534 in the Blake-Bahama Basin, western North Atlantic, an interval of 68 m of Maestrichtian (Upper Creta-ceous) and upper middle to upper Eocene sediments consists of terrigenous siltstones, mudstones, and varicolored zeo-litic claystones; minor recovery of micritic limestones, porcellanites...
| Main Authors: | , |
|---|---|
| Other Authors: | |
| Format: | Text |
| Language: | English |
| Subjects: | |
| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.565.2537 http://www.deepseadrilling.org/76/volume/dsdp76_38.pdf |
| Summary: | At Site 534 in the Blake-Bahama Basin, western North Atlantic, an interval of 68 m of Maestrichtian (Upper Creta-ceous) and upper middle to upper Eocene sediments consists of terrigenous siltstones, mudstones, and varicolored zeo-litic claystones; minor recovery of micritic limestones, porcellanites, and quartzitic chert was made at this site as well. Comparisons with other Deep Sea Drilling Project (DSDP) sites in the western North Atlantic suggest that the following formations are present in this interval: Hatteras (Maestrichtian), Plantagenet (Maestrichtian and upper Eocene), Ber-muda Rise (upper middle to upper Eocene), and the basal Blake Ridge Formation (upper middle to upper Eocene). Rec-ognition of a Tertiary interval of the Plantagenet allows that formation to be divided into lower and upper informal units. Condensation makes this formal lithostratigraphic subdivision difficult. Together the formations record marked net condensed sedimentation (average rate ca. 2.5 m/m.y.) in strongly oxi-dizing bottom waters. From sedimentary structures and petrography, it is inferred that the terrigenous siltstones and micritic limestones were redeposited from the continental margin by turbidity currents. Chemical data plus petrography confirm relatively high plankton productivity during the upper Eocene. Much of the nonrecovered Eocene interval may represent chert and porcellanite. Fragments recovered were formed by replacement of relatively porous calciturbidites by opal-CT and quartz. Radiolarians in interbedded claystones rich in clinoptilolite show extensive dissolution. Relative |
|---|