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The AAPG/Datapages Combined Publications Database

AAPG Special Volumes

Abstract


Pub. Id: A145 (1974)

First Page: 430

Last Page: 455

Book Title: M 20: The Black Sea--Geology, Chemistry, and Biology

Article/Chapter: Geochemistry of Sediments from Eleven Black Sea Cores: Geochemistry

Subject Group: Sedimentology

Spec. Pub. Type: Memoir

Pub. Year: 1974

Author(s): D. M. Hirst (2)

Abstract:

The interrelations among 25 chemical variables in 172 samples of Black Sea sediments were assessed by means of Previous HitfactorNext Hit analysis. This analysis indicates that the main variance of the data is controlled by the relative amounts of silicate phases, carbonate, organic carbon, and sulfur in the sediments, and is related to the Eh and pH of the depositional environment. Part of the variance is ascribed to variation in the clay mineralogy and is related to a southern and southwestern provenance for chlorite and/or
montmorillonite. Trend-surface analyses of Previous HitfactorNext Hit scores indicate both areal and stratigraphic variation in the chemistry, which are notable on the bipolar carbonate-silicate Previous HitfactorNext Hit and the Previous HitfactorTop containing loadings for carbon and related elements. Both carbonate and organic carbon are relatively concentrated in sediments from the central Black Sea, particularly in the uppermost 100-200 cm of the cores. Detailed investigation of chemical variation within individual cores confirms a threefold stratigraphy comprising a thin recent carbonate sequence overlying sapropelic muds, which in turn overlie more normal lutite. This stratigraphy is recognized most easily in cores from the central Black Sea. Near the southern margin, it is obscured by a high rate of accumulation of detrital silicates in the eastern Black Sea, deposition of turbidites produces nonstandard sequences.

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