Composition, Provenance, and Diagenesis of Cretaceous Clastic Sediments Drilled on the Atlantic Continental Rise off Southern Africa, DSDP Site 361Implications for the Early Circulation of the South Atlantic

Natland, J.H.

doi:10.2973/dsdp.proc.40.130.1978

Cited by 26 publications

(25 citation statements)

References 26 publications

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“…During the early Albian, the final ventilation of the Weddell Basin was taking place and sufficiently strong flow was being established to cause upwelling and the accumulation of diatom ooze in a reasonably well oxy genated environment at Site 693. By middle Albian time, the Falkland Plateau was clearing the southern tip of Africa, and the progressive ventilation of the South Atlantic Basin would have proceeded as suggested by , , Natland (1978), and others. SYSTEMATIC PALEONTOLOGY Genus COROLLITHION Stradner, 1961 Corollithion covingtonii, n. sp.…”

Section: Termination Of "Black Shale" Deposition In the Weddell Basinmentioning

confidence: 82%

“…To explain the anoxic conditions, Farquharson (1983) suggested a productivity-driven, expanded oxygen mini mum zone for the Weddell Basin probably coupled with a barred basin model for the South Atlantic basins as suggested earlier by , , Natland (1978), and others. Zimmerman et al (1987) favored a silled basin "preser vational" model for preserving organic carbon in sediments of the incipient Weddell and South Atlantic basins.…”

Section: Termination Of "Black Shale" Deposition In the Weddell Basinmentioning

confidence: 91%

“…There is a suggestion from Figure 8 that the change is manifested first at the Indian Ocean Site 249 on the Mozambique Ridge and that it progresses sequentially west ward across the Weddell Sea and finally north into the South Atlantic Basin. Such a progression from the Falkland Plateau northward was postulated by , Natland (1978). Third, it appears from the record on the Falkland Plateau that once the change to oxic conditions occurred in the Southern Ocean during the Albian, there was no reversion back to suboxic or anoxic environments.…”

Section: Termination Of "Black Shale" Deposition In the Weddell Basinmentioning

confidence: 93%

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Lower Cretaceous Nannofossil Biostratigraphy of ODP Leg 113 Holes 692B and 693A|Continental Slope off East Antarctica|Weddell Sea

Mutterlose¹,

Wise²

1990

Proceedings of the Ocean Drilling Program

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Organic-rich, moderately to sparsely nannofossiliferous Lower Cretaceous claystones ("black shales") were cored at two Ocean Drilling Program Leg 113 sites on the continental slope of East Antarctica off Dronning Maud Land. A 39 m section at Site 692 yielded a Neocomian assemblage of limited diversity with rare Cyclagelosphaera deflandrei, Di adorhombus rectus, and Cruciellipsis cuvillieri, and is probably Valanginian in age. A 70-m section at Site 693 is as signed to the Rhagodiscus angustus Zone (late Aptian-early Albian in age). The latter zone is represented at DSDP sites on the Falkland Plateau, but equivalents to the Neocomian section are absent there, probably due to a disconformity. Watznaueria barnesae is the dominant species at both ODP sites, but it shares dominance with Repagulum parvidentatum at Site 693, where they total 70%-90% of the assemblage; their dominance is attributed to a paleogeographic set ting within a restricted basin rather than to postdepositional dissolution of other species. The evolutionary development of this restricted basin and its eventual ventilation in early Albian times is discussed in terms of the regional stratigraphy and the breakup and dispersal of southwestern Gondwanaland. One new species, Corollithion covingtonii, is described.

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Section: Termination Of "Black Shale" Deposition In the Weddell Basinmentioning

confidence: 82%

Section: Termination Of "Black Shale" Deposition In the Weddell Basinmentioning

confidence: 91%

Section: Termination Of "Black Shale" Deposition In the Weddell Basinmentioning

confidence: 93%

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Lower Cretaceous Nannofossil Biostratigraphy of ODP Leg 113 Holes 692B and 693A|Continental Slope off East Antarctica|Weddell Sea

Mutterlose¹,

Wise²

1990

Proceedings of the Ocean Drilling Program

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“…The change from reducing to oxic conditions on the Maurice Ewing Bank occurred at a time corresponding to the transitional zone near the Albian/Aptian boundary. At Site 361, this important change in environmental conditions is indicated by the lithologic change from Unit 7 to Unit 6 (Natland, 1978), which occurred either simultaneously with that of Site 511 or somewhat later in the lower Albian (the Aptian/Albian boundary is not definitively identified at Site 361; Bolli et al, 1978).…”

Section: Paleoenvironmental Comparison With the Black Shales Of The Cmentioning

confidence: 99%

Content, Type, and Thermal Evolution of Organic Matter in Sediments from the Eastern Falkland Plateau, Deep Sea Drilling Project, Leg 71

Dick¹,

Rullkötter²,

Welte³

1983

Initial Reports of the Deep Sea Drilling Project

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The quantity, type, and maturity of the organic matter in Recent through Upper Jurassic sediments from the Falkland Plateau, DSDP Site 511, have been determined. Sediments were investigated for their hydrocarbon potential by organic carbon and Rock-Eval pyrolysis. Kerogen concentrates were prepared and analyzed in reflected and transmitted light to determine vitrinite reflectance and maceral content. Total extractable organic compounds were analyzed for their elemental composition, and the fraction of the nonaromatic hydrocarbons was determined by capillary column gas chromatography and combined gas chromatography/mass spectrometry.Three main classes of organic matter can be determined at DSDP Site 511 by a qualitative and quantitative evaluation of microscopic and geochemical results. The Upper Jurassic to lower Albian black shales contain high amounts of organic matter of dominantly marine origin. The content of terrigenous organic matter increases at the base of the black shales, whereas the shallowest black shales near the Aptian/Albian boundary are transitional in composition, with increasing amounts of inert, partly oxidized organic matter which is the dominant component in all Albian through Tertiary sediments investigated.The organic matter in the black shales has a low level of maturity and has not yet reached the onset of thermal hydrocarbon generation. This is demonstrated by the low amounts of total extractable organic compounds, low percentages of hydrocarbons, and the pattern and composition of nonaromatic hydrocarbons. The observed reflectance of huminite and vitrinite particles (between 0.4% and 0.5% RQ at bottom-hole depth of 632 m) is consistent with this interpretation. Several geochemical parameters indicate, however, a rapid increase in the maturation of organic matter with depth of burial. This appears to result from the relatively high heat flow observed at Site 511. If we relate the level of maturation of the black shales at the bottom of Hole 511 to their present shallow depth of burial, they appear rather mature. On the basis of comparisons with other sedimentary basins of a known geothermal history, a somewhat higher paleotemperature gradient and/or additional overburden are required to give the observed maturity at shallow depth.A comparison with contemporaneous sediments of DSDP Site 361, Cape Basin, which was the basin adjacent and to the north of the Falkland Plateau during the early stages of the South Atlantic Ocean, demonstrates differences in sedimentological features and in the nature of sedimentary organic matter. We interpret these differences to be the result of the different geological settings for Sites 361 and 511.

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“…Organic-carbon concentrations average about 4% in the Hauterivian to lower Aptian strata at Site 511 in the Argentine Basin, and are less than 1% in the Aptian to Albian strata (von der Dick et al, 1983;Gilbert, this volume). Site 361 in the Cape Basin recovered Aptian dark gray shales with organic carbon contents that vary from 0.4% to 21.7% (Natland, 1978;Gilbert, this volume). Sites 356 and 357 on the Sào Paulo Plateau and Rio Grande Rise comprise interbedded marlstone, chalk, limestone, and black shale containing mostly less than 1 % organic carbon.…”

Section: Introductionmentioning

confidence: 95%

Geologic Evolution, Sedimentation, and Paleoenvironments of the Angola Basin and Adjacent Walvis Ridge: Synthesis of Results of Deep Sea Drilling Project Leg 75

Dean¹,

Hay²,

Sibuet³

1984

Initial Reports of the Deep Sea Drilling Project

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The section recovered at Site 530 (Holes 53OA and 530B) consists of eight sedimentary units and one basalt unit. The composition of the basalt recovered in Hole 53OA is distinct from typical mid-ocean ridge basalts (MORBs) but is similar to that of Hawaiian tholeiites and basalt from the central part of Walvis Ridge. Throughout most of its history, the southern Angola Basin received large volumes of redeposited material in the form of turbidites and, most recently, debris-flow deposits. Most of this material was derived from Walvis Ridge to the south, but thickness trends of acoustic units suggest that some of the sediment was derived from the African continental margin to the east.The basal sedimentary unit (Albian to Santonian) at Site 530 contains 262 beds of black shale that are interbedded with green and red claystone. Black shale makes up less than 10% of the total section, but in two cores of early Turonian age, black shale beds compose about 50% of the section. The black shales contain up to 19% organic carbon (average of about 5%) that is mainly of autochthonous marine origin but with significant contributions from terrigenous organic matter. The origin of these more-and less-reduced interbedded lithologies with varying amounts and types of organic matter, and variable amounts of pelagic, hemipelagic, and turbiditic sediment is complex and cannot be explained by any one simple process. Many factors affecting the concentration of dissolved oxygen in the bottom waters of the Angola Basin varied throughout the middle Cretaceous to produce bottom-water conditions that fluctuated between mildly oxic and oxygen-deficient, but most of the time bottom-waters and sediment-interstitial waters were sufficiently oxic to permit the accumulation of red oxidized sediment.A relatively complete sedimentary record of the Cretaceous/Tertiary boundary was recovered within a sequence of mudstone and marlstone turbidites in Hole 530A. There is a significant increase in the concentration of iridium above background levels at the boundary. High concentrations of many other elements also occur within the same stratigraphic interval as the iridium anomaly. Furthermore, there is a marked decrease in CaCO 3 in the Tertiary strata above the iridium anomaly which suggests that the production of shallow-water carbonate also may have been affected by whatever caused elevated concentrations of iridium and other elements. These observations are consistent with the asteroid-impact theory proposed to explain the worldwide occurrence of an iridium anomaly at the Cretaceous/Tertiary boundary.The Cenozoic history of the Angola Basin was controlled mainly by (1) restriction of bottom-water flow from the south by Walvis Ridge; (2) development of glaciation on Antarctica; (3) opening of circulation passages in the southern oceans; (4) rapid turnover of cold, nutrient-rich waters that resulted in high productivity of diatoms; (5) influx of terrigenous sediment mainly by turbidity currents; and (6) production and preservation of carbonate...

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Composition, Provenance, and Diagenesis of Cretaceous Clastic Sediments Drilled on the Atlantic Continental Rise off Southern Africa, DSDP Site 361Implications for the Early Circulation of the South Atlantic

Cited by 26 publications

References 26 publications

Lower Cretaceous Nannofossil Biostratigraphy of ODP Leg 113 Holes 692B and 693A|Continental Slope off East Antarctica|Weddell Sea

Lower Cretaceous Nannofossil Biostratigraphy of ODP Leg 113 Holes 692B and 693A|Continental Slope off East Antarctica|Weddell Sea

Content, Type, and Thermal Evolution of Organic Matter in Sediments from the Eastern Falkland Plateau, Deep Sea Drilling Project, Leg 71

Geologic Evolution, Sedimentation, and Paleoenvironments of the Angola Basin and Adjacent Walvis Ridge: Synthesis of Results of Deep Sea Drilling Project Leg 75

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Composition, Provenance, and Diagenesis of Cretaceous Clastic Sediments Drilled on the Atlantic Continental Rise off Southern Africa, DSDP Site 361Implications for the Early Circulation of the South Atlantic

Cited by 26 publications

References 26 publications

Lower Cretaceous Nannofossil Biostratigraphy of ODP Leg 113 Holes 692B and 693A|Continental Slope off East Antarctica|Weddell Sea

Lower Cretaceous Nannofossil Biostratigraphy of ODP Leg 113 Holes 692B and 693A|Continental Slope off East Antarctica|Weddell Sea

Content, Type, and Thermal Evolution of Organic Matter in Sediments from the Eastern Falkland Plateau, Deep Sea Drilling Project, Leg 71

Geologic Evolution, Sedimentation, and Paleoenvironments of the Angola Basin and Adjacent Walvis Ridge: Synthesis of Results of Deep Sea Drilling Project Leg 75

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Composition, Provenance, and Diagenesis of Cretaceous Clastic Sediments Drilled on the Atlantic Continental Rise off Southern Africa, DSDP Site 361Implications for the Early Circulation of the South Atlantic