Neogene paleoenvironment off NW Africa based on sediments from DSDP Leg 14

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doi: 10.1306/212F759A-2B24-11D7-8648000102C1865D
Author(s): Diester-Haass, L.; Chamley, H.
Volume Title: Journal of Sedimentary Petrology
Source: Journal of Sedimentary Petrology, 48(3), p.879-896. Publisher: Society of Economic Paleontologists and Mineralogists, Tulsa, OK, United States. ISSN: 0022-4472 CODEN: JSEPAK
Note: In English. 64 refs.; illus. incl. tables, sketch map
Summary: An analysis of the coarse (>40 µm) and clay fractions of Neogene sediments from Sites 135, 139, 140, 141 (DSDP Leg 14) has been carried out. The Early Miocene sediments of Sites 139 and 140 are eolian sand turbidites consisting of coarse quartz sand and shallow water particles. They have been formed during a period with arid climate and lowered sea-level. Upwelling on the upper slope produced a rather high opal content of the allochthonous sediments. Smectite (70-85%) and kaolinite (15-30%) are the dominant clay minerals. The clay assemblage of the Late Miocene of Site 141 indicates a climate with contrasting seasons on the African continent, the arid season being most important. The Early Pliocene (Sites 135, 141) and part of the Late Pliocene (141) reveal a mainly arid climate on the continent, with only small scale changes. Variations in detrital clay mineral contents, especially chlorite, mixed-layers and smectite, suggest some more humid periods on the continent, which cannot be detected from coarse terrigenous components, because the general trend in climate is more arid than humid and because transport agents were too weak to transport major amounts of terrigenous particles >40 µm. There is a good correlation between coarse and clay sized terrigenous components in the Late Pliocene and the Pleistocene of Site 141. Terrigenous components >40 µm reveal a constantly arid climate and changing trade wind velocities in the latitude of 20°N. Clay minerals, transported by the Canary current from African regions northeast of Site 141, suggest changes in humidity and in soil formation and soil destruction. Strong trade wind velocities in 20°N correlate with a humid climate north of 20°N ("glacial type"), small trade wind velocities with arid climate ("interglacial type"). The correspondence of results is due to rather strong transport energies, which supply clay and >40 µm sized terrigenous material. Calcium carbonate dissolution is strongest (100% fragmentation of planktonic foraminifers) in the Late Miocene of Site 141, decreasing in the Pliocene and showing cycles in the Late Pliocene/Pleistocene which might be correlated to periods of advancing cold arctic/antarctic bottom water. Sorting effects in the Late Pliocene/Pleistocene of Site 141 in those sections with strong CaCO3 dissolution and strong trade winds ("glacial type of climate") are tentatively interpreted by increased velocities of bottom currents, perhaps of arctic or antarctic origin.
Year of Publication: 1978
Research Program: DSDP Deep Sea Drilling Project
Key Words: 06 Petrology, Sedimentary; Algae; Atlantic Ocean; Benthic taxa; Calcite; Carbonates; Cenozoic; Clastic sediments; Clay minerals; DSDP Site 135; DSDP Site 139; DSDP Site 140; DSDP Site 141; Deep Sea Drilling Project; Diatoms; Dissolution; Foraminifera; Horseshoe Abyssal Plain; Invertebrata; Leg 14; Microfossils; Miocene; Neogene; Occurrence; Paleoclimatology; Petrography; Planktonic taxa; Plantae; Pleistocene; Pliocene; Protista; Provenance; Quaternary; Radiolaria; Sand; Sedimentary petrology; Sediments; Sheet silicates; Silicates; Tertiary; Thallophytes
Coordinates: N133000 N360000 W0100000 W0230000
Record ID: 1979003434
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.