Paleoenvironmental History of the Walvis Ridge at the Cretaceous-Tertiary Transition, from Mineralogical and Geochemical Investigations

Chamley, Hervé; Maillot, H.; Duee, G.; Robert, Christian

doi:10.2973/dsdp.proc.74.120.1984

Cited by 15 publications

(18 citation statements)

References 8 publications

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“…Similar thick laths, sometimes associated with packs of laths, were observed near the Daito Ridge in the Philippine Sea (Chamley, 1980), and on the Walvis Ridge in the South Atlantic (Chamley et al, 1984). In both of these regions, smectites were chiefly formed during subaerial alteration processes in volcanic products.…”

Section: Volcanic Influencesupporting

confidence: 52%

Cenozoic Evolution and Significance of Clay Associations in the New Zealand Region of the Southwest Pacific, Deep Sea Drilling Project, Leg 90

Robert¹,

Stein²,

Acquaviva³

1986

Initial Reports of the Deep Sea Drilling Project

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Clay minerals, flux rates, and the size distribution of terrigenous matter in DSDP Sites 592, 593, and 594 have been used to reconstruct continental and marine paleoenvironments in the New Zealand sector of the southwest Pacific. Five stages are recognized from late Eocene to Pleistocene times.1. At the Eocene-Oligocene boundary, illite and mixed-layer clays marked a period of tectonic extension related to graben formation and volcanic activity.2. During the Oligocene, smectites formed abundantly in plains and perimarine lagoons which developed during subsidence-induced peneplanation of the relief.3. During the early Miocene, greater abundances of chlorite, illite, and irregular mixed-layer clays, and the appearance of kaolinite were due to an increase in the relief of New Zealand that followed the inception of a compressive regime; in the Tasman Sea, part of the detrital supply (smectites) was derived from the north and was deposited by southward-flowing currents.4. From middle Miocene to early late Miocene time, abundant chlorite, illite, mixed-layer clays, and kaolinite, and the appearance of stilpnomelane marked an important tectonic event in New Zealand which increased the detrital supply to the whole South Tasman Sea; on the Chatham Rise, abundant smectites from the north diluted the detrital supply influenced by the tectonic activity in New Zealand.5. From early late Miocene to Pleistocene time, abundant chlorite, illite, mixed-layer clays, kaolinite, and stilpnomelane were eroded from New Zealand, where the Kaikoura orogeny increased the relief, and deposited in the South Tasman Sea; during the late Pliocene, both grain size and amounts of clay particles eroded from New Zealand increased, related to reinforced bottom-current activity on the Lord Howe Rise; on the Chatham Rise, increased detrital components from the Southern Alps (chlorite, illite, mixed-layer clays, stilpnomelane) were supplied by northwardflowing currents.

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Section: Volcanic Influencesupporting

confidence: 52%

Cenozoic Evolution and Significance of Clay Associations in the New Zealand Region of the Southwest Pacific, Deep Sea Drilling Project, Leg 90

Robert¹,

Stein²,

Acquaviva³

1986

Initial Reports of the Deep Sea Drilling Project

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“…It thus seems that smectite forms by hydrolysis under climatic conditions between those necessary for the formation of kaolinite and those for chlorite and illite, i.e. between warm-humid and cold-dry conditions (Chamley, 1979(Chamley, ,1989Chamley et al, 1984). Often, however, smectite is assumed to be derived as a result of submarine weathering (halmyrolysis) of volcanic material (e.g.…”

Section: Origin Of Minerals In the Clay Fractionmentioning

confidence: 99%

Significance of clay mineral assemblages in the Antarctic Ocean

et al. 1992

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Ehrmann, W.U., Melles, M., Kuhn, G. and Grobe, H., 1992. Significance of clay mineral assemblages in the Antarctic Ocean.Mar. Geol., 107: 249-273. 249Typical examples from different morphological and geological settings in the Antarctic Ocean are reviewed in order to discuss the value of clay mineral assemblages for reconstructing the glacial history of Antarctica, the paleoceanographic history of the Antarctic Ocean and the sedimentary processes at the Antarctic continental margin. The significance of clay minerals for paleoenvironmental reconstructions strongly varies with both the position of the sites under investigation and the age of the sediments.In late Mesozoic to Paleogene sediments clay mineral assemblages are sensitive tools for reconstructing climatic conditions. For example, the shift from smectite-dominated assemblages to illite-and chlorite-dominated assemblages in the earliest Oligocene clearly documents the transition from chemical weathering conditions under a warm and humid climate to physical weathering under cooler conditions. Submarine elevations such as Maud Rise and Kerguelen Plateau give the best record for direct paleoclimatic and paleoceanographic studies. At the proximal sites of the continental slope and shelf, as well as in the deep sea, the paleoclimatic information normally is masked by a variety of processes resulting in sediment redistribution. At those sites, in contrast, the clay mineral assemblages bear a wealth of information on different sedimentary processes.After the establishment of a continental East Antarctic ice sheet, physical weathering prevailed. Variations in the clay mineral records predominantly reflect the influence of different sediment sources resulting from different glacial, hydrographic or gravitational transport processes. Because these sedimentation processes are generally linked to climatic variations, the clay mineral assemblages in most of the Neogene and Quaternary sediments provide indirect paleoclimatic information. The processes are best documented in the clay mineral composition in those areas where changes in source regions with distinct petrographic differences are expected and where distances from the source region are low.

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“…However, there is also input of smectite from the continents. Cretaceous and older smectites, especially, are often thought to have originated from subaerial weathering of basic rocks, such as basalts, under humid to arid climatic regimes (Chamley, 1979;Chamley et al, 1984).…”

Section: Clay Mineral Assemblages As Climatic Indicatorsmentioning

confidence: 99%

Implications of Sediment Composition on the Southern Kerguelen Plateau for Paleoclimate and Depositional Environment

Ehrmann¹

1991

Proceedings of the Ocean Drilling Program

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Cretaceous to Quaternary sediments recovered at Leg 119 Sites 738 and 744 on the southern tip of the Kerguelen Plateau were studied in order to determine the depositional environment and the paleoceanography of the southern Indian Ocean and especially the long-term glacial history of East Antarctica. Emphasis is given to bulk-sediment composition, grain-size data, and clay mineralogy.The sediment sequence at the two sites is generally of a highly pelagic character, with nannofossil oozes, chalks, and limestones dominant from the Turanian to upper Miocene and diatom oozes dominant within the uppermost Miocene to Holocene interval.The first indication of glaciation at sea level is the occurrence of isolated gravel and terrigenous sand grains, which indicate ice rafting in the middle Eocene interval of 45.0-42.3 Ma. A major intensification of glaciation, probably the onset of continental East Antarctic glaciation, is recorded in sediments of early Oligocene age (36.0 Ma). All major sediment parameters document this event. The clay mineralogy changes from smectite-dominated assemblages, typical of moderately warm and humid climatic conditions in which chemical weathering processes are prevalent, to illite-and chlorite-dominated assemblages, indicative of cooler climates and physical weathering. Ice-rafted debris of both gravel and sand size occurs in large quantities in that interval and coincides with a change in the mode of carbonate deposition. Carbonate contents are relatively high and uniform (90%-95%) in strata younger than early Oligocene; in Oligocene to upper Miocene strata they fluctuate between 65% and 95%.Oligocene and Neogene hiatuses reflect an intensification of oceanic circulation and the increased erosional force of Circumpolar Deep Water. The long-term Cenozoic cooling trend was interrupted by a phase of early Miocene warming indicated by maximum Neogene smectite concentrations. Although ice-rafted debris is present only in minor amounts and mainly in the silt fraction of early Oligocene to late Miocene age, it shows that glaciers advanced to the East Antarctic shoreline throughout that time. Ice-rafting activity drastically increased in latest Miocene time, when carbonate deposition decreased and diatom ooze sedimentation started. This suggests a pronounced intensification of Antarctic glaciation combined with a northward migration of the Polar Front.

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Paleoenvironmental History of the Walvis Ridge at the Cretaceous-Tertiary Transition, from Mineralogical and Geochemical Investigations

Cited by 15 publications

References 8 publications

Cenozoic Evolution and Significance of Clay Associations in the New Zealand Region of the Southwest Pacific, Deep Sea Drilling Project, Leg 90

Cenozoic Evolution and Significance of Clay Associations in the New Zealand Region of the Southwest Pacific, Deep Sea Drilling Project, Leg 90

Significance of clay mineral assemblages in the Antarctic Ocean

Implications of Sediment Composition on the Southern Kerguelen Plateau for Paleoclimate and Depositional Environment

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