Pliocene Planktonic and Benthic Foraminifers from the Southeastern Atlantic Angola Margin: Leg 75, Site 532, Deep Sea Drilling Project

Boersma, Anne

doi:10.2973/dsdp.proc.75.113.1984

Cited by 2 publications

(5 citation statements)

References 6 publications

(11 reference statements)

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“…Increased epifaunal abundance occurs in well-oxygenated (hereafter called oxic) areas of low-carbon rain rates in the Norwegian Sea (Corliss and Chen, 1988). In the southwest (Corliss, 1983;Boersma, 1985a). The AAIW is well oxygenated, but less so than the NADW (Reid et al, 1977).…”

Section: Discussionmentioning

confidence: 99%

“…umbonifera. Either through dissolution, redeposition, or ecology, bottom-water faunas close to 3800 mbsl differ from their southern Atlantic analogs Clarke and Wright, 1984;Boersma, 1985a) in their scarcity of TV. umbonifera.…”

Section: Deep-water Sitesmentioning

confidence: 99%

“…Most typical of this water type are the uvigerinids, which occur in the higher latitude South Atlantic and the southeastern Indian Oceans, but not in the modern Mascarene Basin. Indexes for this water mass include C. carinata, P. bulloides, B. aculeata, and in the South Atlantic Astrononion (Corliss, 1983;Hodell et al, 1985;Clarke and Wright, 1984;Boersma, 1985b;Mead, 1985).…”

Section: Site 710mentioning

confidence: 99%

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Late Oligocene to Late Pliocene Benthic Foraminifers from Depth Traverses in the Central Indian Ocean

Boersma¹

1990

Proceedings of the Ocean Drilling Program

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Section: Discussionmentioning

confidence: 99%

Section: Deep-water Sitesmentioning

confidence: 99%

Section: Site 710mentioning

confidence: 99%

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Late Oligocene to Late Pliocene Benthic Foraminifers from Depth Traverses in the Central Indian Ocean

Boersma¹

1990

Proceedings of the Ocean Drilling Program

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“…An influx of miliolids and an abundance peak in the spinose uvigerinids (Core 115-709A-9H), accompanied by deteriorating preservation, is a signal for the late Miocene carbon excursion documented in all oceans (Lutze, 1977;Vincent et al, 1980;Boersma, 1984). Following this event, the poorly preserved levels with miliolids, hispidocostate uvigerinids, and an influx of bottom-water benthic foraminifers (Core 115-709A-7H) may indicate the latest Miocene episode of glacial accumulation in polar regions (Elmstrom and Kennett, 1986).…”

Section: Neogenementioning

confidence: 98%

“…Gyroidinids are also frequent. The stilostomellid is Stilo-stomella subspinosa, and the uvigerinid is Uvigerina auberiana, a form correlated with oxidizing conditions in the bottom environment (Boersma, 1984). The fact that a large number of these forms are dissolution resistant suggests that these small-sized faunas and individuals may be the result of corrosive conditions on the seafloor.…”

Section: Neogenementioning

confidence: 99%

Site 709

1988

Proceedings of the Ocean Drilling Program

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Principal results: Site 709 is located in the western equatorial Indian Ocean at 3°54.9'S and 60°33.1 'E, in water depths of 3038.2 m (Fig. 1). The site lies in a small basin perched near the summit of the Madingley Rise, a regional topographic high between the Carlsberg Ridge and the northern Mascarene Plateau. The irregular basement topography is draped with sediment, varying in thickness from less than 50 m to over 400 m. Site 709 was placed in one of the thicker sediment sequences because our primary objective was to study the Neogene history of carbonate preservation at this intermediate-depth site. Three holes were continuously cored at Site 709. Hole 709A terminated in nannofossil ooze of late Oligocene age at 203.1 mbsf. All 21 cores were taken with the advanced hydraulic piston corer (APC), and the recovery rate was 91%. Hole 709B yielded 27 cores and ended at 254.8 mbsf in lower Oligocene oozes, for a recovery rate of 92%. The 7 deepest cores were taken with the extended core barrel (XCB), and all shallower cores with the APC. Hole 709C was cored to 353.7 mbsf, yielding 20 APC and 17 XCB cores, for a total recovery of 93%. This last hole ended in nannofossil chalks of middle Eocene age .The recently modified XCB, with its newly developed cutting shoe with seal, was tested for the first time during Leg 115; it performed extraordinarily well. The XCB recovery rates in Holes 709B and 709C were 91% and 87%, respectively, implying that complete and virtually undisturbed sediment sections can be retrieved from sub-bottom depths beneath the APC-penetration capability.Cored sediments at Site 709 are fairly homogeneous in composition, comprising a single major lithostratigraphic unit consisting of alternate clay-bearing nannofossil ooze and nannofossil ooze layers. This major unit is tentatively subdivided into three subunits on the basis of distinctive correlatable changes in color. 460 SITE 709ter, until chalk occurs consistently toward the bottom of Hole 709C. The cored stratigraphic sequence is summarized in Figure 2. We observed many ash layers; two particularly prominent ones, observed at the same sub-bottom depth in all three holes, bracket the Miocene/Pliocene boundary. Sedimentation rates are on the order of 13 m/m.y. during late Miocene-Pleistocene times and are followed by a drastic downhole decrease close to the middle/late Miocene boundary. Large portions of both the middle and lower Miocene are stratigraphically disordered. Sediments from the lower part of the lower Miocene are intercalated into sediments of late early and early middle Miocene age. Thus, stratigraphic data are unreliable between approximately 14 and 17 Ma.All three holes cross the Oligocene/Miocene boundary, although Hole 709A cored just a few meters of Oligocene sediments before being terminated. Oligocene sedimentation rates are on the average around 7 m/m.y., and these comparatively low rates continue well into the middle Eocene.Measurements of magnetic susceptibility at 5-cm intervals provide the basis for numerous interhole...

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Pliocene Planktonic and Benthic Foraminifers from the Southeastern Atlantic Angola Margin: Leg 75, Site 532, Deep Sea Drilling Project

Cited by 2 publications

References 6 publications

Late Oligocene to Late Pliocene Benthic Foraminifers from Depth Traverses in the Central Indian Ocean

Late Oligocene to Late Pliocene Benthic Foraminifers from Depth Traverses in the Central Indian Ocean

Site 709

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