Organic Facies Variations in the Mesozoic South Atlantic

Gilbert, D.

doi:10.2973/dsdp.proc.75.135.1984

Cited by 12 publications

(4 citation statements)

References 9 publications

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“…Everywhere else in the North Atlantic, terrestrial organic matter with admixtures of highly degraded, residual, marine organic matter dominates the Lower Cretaceous OC-rich strata (Tissot andothers, 1979, 1980;Summerhayes, 1981). The Cretaceous OCrich strata in the southeastern North Atlantic, therefore, appear to have more in common with similar strata in the South Atlantic, where most of the organic matter is derived from marine sources, than with equivalent strata in the rest of the North Atlantic (Tissot andothers, 1979, 1980;Summerhayes, 1981;Gilbert, 1984).…”

Section: Descriptions Of Cyclesmentioning

confidence: 97%

“…They average about 4-5 percent (values as high as 24 percent have been reported for the lower Albian) at site 364 in the eastern Angola basin. Organic carbon concentrations average about 4 percent in the Hauterivian-lower Aptian strata at site 511 in the Argentine basin, and are less than one percent in the AptianAlbian (Dick and others, 1983;Gilbert, 1984). Black shale beds of Albian to Coniacian-Santonian age at site 530 contain as much as 19 percent OC and contain overall an average of 5.4 percent OC, as compared with less than 0.5 percent OC in intercalated beds of red and green claystone (Deroo and others, 1984;Meyers and others, 1984).…”

Section: Descriptions Of Cyclesmentioning

confidence: 99%

“…Black shale beds of Albian to Coniacian-Santonian age at site 530 contain as much as 19 percent OC and contain overall an average of 5.4 percent OC, as compared with less than 0.5 percent OC in intercalated beds of red and green claystone (Deroo and others, 1984;Meyers and others, 1984). Most of the organic matter in black shales at site 530 is of marine origin (Deroo and others, 1984;Gilbert, 1984). Much of the organic matter at site 361 in the Cape basin apparently is redeposited terrestrial organic matter, whereas the organic matter in black shales at sites 364 and 511 is mostly autochthonous marine organic matter (Gilbert, 1984).…”

Section: Descriptions Of Cyclesmentioning

confidence: 99%

“…Most of the organic matter in black shales at site 530 is of marine origin (Deroo and others, 1984;Gilbert, 1984). Much of the organic matter at site 361 in the Cape basin apparently is redeposited terrestrial organic matter, whereas the organic matter in black shales at sites 364 and 511 is mostly autochthonous marine organic matter (Gilbert, 1984). In spite of these differences in sources of organic matter, the OC-rich strata in all Atlantic basins are interbedded with bioturbated, OC-poor strata.…”

Section: Descriptions Of Cyclesmentioning

confidence: 99%

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Studies in diagenesis

Mumpton¹

1986

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U.S. GEOLOGICAL SURVEY BULLETIN 1578Cover shows scanning electron micrograph of late-stage smectite (lower left) coating earlier chabazite crystals formed on early-stage smectite, in altered Pliocene vitric tuff, Durkee, Oregon. See article by A.j . Gude 3rd, and R. A. Sheppard, (this volume, PREFACEThe collection of research papers in this volume evolved from a workshop on diagenesis in sedimentary rocks sponsored by the U.S. Geological Survey. The workshop was held March 16--18, 1982, in Golden, Colorado, and was attended by 248 participants from the Survey's Geologic and Water Resources Divisions.The idea for the workshop came to four of us-Walt Dean, Phoebe Hauff, Harry Tourtelot, and me-during a series of informal discussions in late 1980. The complexity and interdisciplinary nature of the broad range of diagenetic processes were clearly recognized, as was their importance in the genesis, transport, emplacement, and mode of occurrence of a wide variety of organic fuels and mineral resources. The advantages of bringing together scientists who were actively engaged in diagenesis studies from several branches in two divisions of the Survey were readily apparent, and so a proposal for such a multidisciplinary and interdivisional workshop was formulated. The proposal was accepted and approved by the Survey in early 1981 .The workshop comprised two days of technical sessions consisting of oral papers and concurrent poster displays. A third day was set aside so that participants could schedule one-on-one conferences with any of the invited guest speakers or arrange small group discussions on topics of mutual interest. Each of the four half-day technical sessions represented a different aspect of diagenesis---<=hemical, carbonate, fine clastic, and coarse clastic-and began with an invited review paper on the theme of that session. The program opened with an overview "keynote" paper by Robert M. Garrels on the role of diagenesis in the geochemical cycle. In the first session, Robert A. Berner reviewed advances in several aspects of sediment-fluid interaction accompanying early diagenesis, and Lynton Land surveyed diagenesis in carbonate rocks to lead off the second session. In the third session John Hower reviewed the advancements in clay mineral diagensis, and in the final session Raymond Siever discussed thermal and burial relationships during the history of sedimentary basins.During these sessions 50 Survey authors presented 22 talks and 9 poster displays on topics ranging from diagenesis in limestones to uranium deposits to zeolitic tuffs. The authors reported findings of field, laboratory, and theoretical investigations dealing with such disparate approaches as organic geochemistry of hydrocarbon maturation, stable isotope fractionation, petrographic analysis, mineral equilibria and dissolution kinetics, mapping and field relations, and trace element geochemistry. The concurrent poster sessions presented results of more intensely focused studies.The workshop's flavor and organization have been retained in this...

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Section: Descriptions Of Cyclesmentioning

confidence: 97%

Section: Descriptions Of Cyclesmentioning

confidence: 99%

Section: Descriptions Of Cyclesmentioning

confidence: 99%

Section: Descriptions Of Cyclesmentioning

confidence: 99%

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Studies in diagenesis

Mumpton¹

1986

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Models for the deposition of Mesozoic-Cenozoic fine-grained organic-carbon-rich sediment in the deep sea

Arthur

Dean

Stow

1984

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Summary The widespread occurrence of organic-carbon-rich strata (‘black shales’) in certain portions of Jurassic, Cretaceous and Cenozoic sequences has been well-documented from Deep Sea Drilling Project sites in the Atlantic and Pacific Oceans and from sequences, now exposed on land, originally deposited in the Tethyan ocean. These ancient black shales usually have been explained by analogy with examples of modern deep-sea sediments in which organic matter locally is preserved by (1) increasing the supply of organic matter, (2) increasing the rate of sedimentation, and/or (3) decreasing the oxygen content of the bottom water. However, detailed examination of many black shales reveals characteristics that cannot be explained by simple local models, including: their approximate coincidence in time globally; their occurrence in a variety of different environments, including open oxygenated oceans, restricted basins, deep and shallow water; their interbedding with organic-carbonpoor strata which often dominate a so-called black shale sequence; their deposition by pelagic, hemipelagic, turbiditic and other processes; and the variations in type and amount of organic matter that occur even within the same sequence. A more complex model for the origin of black shales therefore appears most appropriate, in which the cyclic preservation of organic matter depends on the interplay of the three main variables, namely supply of organic matter, sedimentation rate, and deep-water oxygenation, each of which varies independently to some extent. The variation and relative importance of these parameters in individual basins and widespread black shale deposition in general are linked globally and temporally by changes in global sea-level, climate and related changes in oceanic circulation. An important and often overlooked factor for the supply of organic matter to deep-basin sediments is the frequency and magnitude of redepositional processes. The interplay of these variables is discussed in relation to the middle Cretaceous and Cenozoic organic-carbon-rich strata, in particular, which show marked differences in the relative importance of the different variables.

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(Table 1) Lithology, total organic carbon, and kerogen distribution at DSDP Hole 36-330

Gilbert

1984

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Organic Facies Variations in the Mesozoic South Atlantic

Cited by 12 publications

References 9 publications

Studies in diagenesis

Studies in diagenesis

Models for the deposition of Mesozoic-Cenozoic fine-grained organic-carbon-rich sediment in the deep sea

(Table 1) Lithology, total organic carbon, and kerogen distribution at DSDP Hole 36-330

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