Dredged Rocks from the Armorican and Celtic Margins

Auffret, Gérard-André; Pastouret, Léo; Cassat, G.; Charpal, O. De; Cravatte, J.; Guennoc, Pol

doi:10.2973/dsdp.proc.48.152.1979

Cited by 11 publications

(10 citation statements)

References 13 publications

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“…The basement of the Canadian margin appears to have been lit tle affected by the Acadian Orogeny and was not involved in the Hercynian; therefore, this type of basement cannot be linked di rectly to the western Iberian margin, where there are abundant Hercynian granitic and metamorphic rocks. By the same line of reasoning, Devonian and Carboniferous sediments from the Goban Spur (Auffret et al, 1979; are too poorly deformed and metamorphosed to be long to the internal zones of the Hercynian fold belt. Thus, it is not possible to extend the northwestern Iberian margin basement either to the north or to the west, as proposed in previous models.…”

Section: Samples Locationmentioning

confidence: 98%

Pre-Mesozoic Basement of the Western Iberian Continental Margin and Its Place in the Variscan Belt

Capdevila¹,

Mougenot²

1988

Proceedings of the Ocean Drilling Program

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Section: Samples Locationmentioning

confidence: 98%

Pre-Mesozoic Basement of the Western Iberian Continental Margin and Its Place in the Variscan Belt

Capdevila¹,

Mougenot²

1988

Proceedings of the Ocean Drilling Program

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“…Calcareous bioclastic fragments dredged at the boundary between the continental shelf and slope (Auffret et al, 1979) Figure 2 of this article and Figures 3 and 8 in Rat et al (this volume) clearly indicate that a single homogeneous formation and fauna constitute the entire Albian section drilled. As in the third assemblage of the Barremian, the sporadic presence (and the "stepped" nature of the first occurrences of species) could result from actual fossil rarity, but could also result from insufficient sampling and pure chance in collecting the samples and picking the specimens.…”

Section: Comparisonsmentioning

confidence: 63%

Barremian and Albian Foraminifera, Site 549, Leg 80

Magniez¹,

Sigal²

1985

Initial Reports of the Deep Sea Drilling Project

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The Early Cretaceous series of Site 549 have been analyzed from both an ecological and a chronostratigraphical viewpoint. Lithology and microfaunal assemblages allow the division of these deposits into two parts. The lower part extends from the lower Barremian to the basal upper Barremian and possibly down into the upper Hauterivian. Three foraminiferal associations suggest an orderly evolution from a low-energy, littoral environment, in which continental influences dominated, to progressively more open marine conditions. A dolosparite bed (which has not yet been dated) separates these synrift deposits from lower to basal middle Albian postrift sediments that developed in a pelagic bathyal environment on the middle to nearby lower continental slope.

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“…Ice-rafted pebbles such as those described here were previously described by Auffret et al (1979), but his samples were all from dredge samples collected around DSDP Hole 440. detrital pebbles occur in Lower Cretaceous sediments cored in Hole 549, associated with terrigenous sediments; both have a sedimentary origin.…”

Section: Discussionmentioning

confidence: 99%

X-Ray Mineralogy and Mineral Geochemistry of Cenozoic Strata (Leg 80) and Petrographic Study of Associated Pebbles

Chennaux¹,

Esquevin²,

Jourdan³

et al. 1985

Initial Reports of the Deep Sea Drilling Project

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Cenozoic sediments recovered from Sites 548, 549, and 550 were the objects of mineralogical (bulk sample and <2-µm fraction) and geochemical (HCl extract) studies. Thin sections of rock pebbles embedded in sediments (upper levels at Site 548, particularly) were examined on a polarizing microscope.This study outlines the vertical and lateral variation and evolution of the sedimentation. In the Paleocene and lower Eocene, the clay fraction is abundant and smectite is practically the sole existing clay mineral. High Mn, Al, Fe, Mg, and K contents were measured in HCl extracts. Through the middle Eocene, carbonates become more abundant-highly dominant at Site 548. Metal contents in HCl extracts are very low. The clay fraction, although dominated at all sites by smectites, becomes richer in illite and poorly crystallized chlorite. At the middle/upper Miocene boundary, a significant decrease in the smectite/(illite + chlorite) ratio occurs at all sites, and this decrease continues into the middle Pliocene. This decrease is marked by an abrupt increase of quartz at Site 548. At the two other sites, carbonates remain highly predominant; HCl extracts reflect the relative abundance of the clay and carbonate fractions. After a brief recurrence of smectite in a high-metal-content interval, illite and chlorite become the dominant clay minerals in the upper Pliocene and the Pleistocene, where numerous variations in mineralogical composition occur in the clay fraction (Sites 548 and 549) or in non-clay components (Site 548). Several pebbles of various nature and origin, encountered in different levels of this interval at Site 548, appear to have an ice-rafting origin.This study points out three main breaks in the general evolution of the sedimentation: the first, corresponding to the lower/middle Eocene boundary, is marked by the increase of carbonates and associated elements; the second, corresponding to the middle/upper Miocene boundary, is marked by a major decrease of the smectite/(illite + chlorite) ratio at all sites and by a massive appearance of quartz at Site 548; and the third, which occurred toward the late Pliocene, is marked by the dominance of primary clay minerals and the arrival of ice-rafted pebbles.Our interpretation of results considers paleohydrological and paleoclimatic phenomena. It is suggested that the major middle/late Miocene break was associated with an increase of the deep bottom-water circulation between the Norwegian Sea and the North Atlantic Ocean, and/or a climatic evolution: humidification and cooling of climate. The changes toward the late Pliocene appear to have been the first effects of the glaciations at the end of Cenozoic.

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Dredged Rocks from the Armorican and Celtic Margins

Cited by 11 publications

References 13 publications

Pre-Mesozoic Basement of the Western Iberian Continental Margin and Its Place in the Variscan Belt

Pre-Mesozoic Basement of the Western Iberian Continental Margin and Its Place in the Variscan Belt

Barremian and Albian Foraminifera, Site 549, Leg 80

X-Ray Mineralogy and Mineral Geochemistry of Cenozoic Strata (Leg 80) and Petrographic Study of Associated Pebbles

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