Geochemistry of sediments on the Rio Grande Rise and the redox evolution of the South Atlantic Ocean

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doi: 10.1016/0016-7037(88)90068-3
Author(s): Hu, X.; Wang, Y. L.; Schmitt, R. A.
Author Affiliation(s): Primary:
Oreg. State Univ., Dep. Chem. and Geol., Corvallis, OR, United States
Chengdu Coll. Geol., China
Volume Title: Geochimica et Cosmochimica Acta
Source: Geochimica et Cosmochimica Acta, 52(1), p.201-207. Publisher: Pergamon, Oxford, International. ISSN: 0016-7037 CODEN: GCACAK
Note: In English. 29 refs.; illus. incl. 2 tables, sketch map
Summary: Chalk and limestone core samples with contiguous dark mudstones from DSDP Holes 516 and 516F, Leg 72, Rio Grande Rise, were analysed for 32 major, minor and trace elements by NAA. The non-carbonate fractions include clay and tephra, and Al2O3 analyses of tephra and noncarbonate fractions are given; these indicate that volcanism was greatest from lower middle Eocene to late Oligocene. The trace elements, particularly the REE in marine carbonates, indicate an increase in volcanism at the Rio Grande Rise from approx 50 m.y. to a peak at approx 48 m.y. (middle Eocene), then diminishing from late Eocene (approx 38 m.y.) to late Oligocene (approx 26 m.y.). Ce anomaly values indicate that South Atlantic water was appreciably anoxic over the Rio Grande Rise from approx 88 m.y. to approx 70 m.y. With improved circulation, an increase in oxidation occurred from approx 70 m.y. to approx 55 m.y. Subsidence factors governing this increase in water circulation are discussed, as well as the redox environments.
Year of Publication: 1988
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 02 Geochemistry; 07 Marine Geology and Oceanography; Alkali metals; Atlantic Ocean; Carbonate sediments; Cesium; Cores; DSDP Site 516; DSDP Site 516F; DSDP Site 525; DSDP Site 530; Deep Sea Drilling Project; Eh; Geochemistry; IPOD; Leg 72; Leg 74; Leg 75; Marine sediments; Metals; Neutron activation analysis data; Oceanography; PH; Rare earths; Rio Grande Rise; Romanche fracture zone; Sediments; South Atlantic; Trace elements; Walvis Ridge
Record ID: 1988026391
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom

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