The occurrence of sapropels and sapropel-like sediments has been documented to the far western basins of the Mediterranean Sea in cores obtained by drilling during Leg 161. Multiple, dark-colored layers in which total organic-carbon (TOC) concentrations exceed 0.5% occur in the Pleistocene sedimentary sequences of the Tyrrhenian Basin, the Menorca Ridge, and the basins of the Alboran Sea. Higher Rock-Eval Hydrogen Index values and elemental C/N values in the sediments that have higher TOC concentrations indicate that variations in the production and preservation of marine organic matter are the principal factors involved in the formation of the sapropels and sapropel-like layers at these locations. TOC concentrations generally decrease from east to west as sedimentation rates increase, reflecting dilution of the organic matter. Precessional climate changes that increased delivery of land-derived nutrients and thereby enhanced paleoproductivity appear to be central to formation of the sapropels and sapropel-like layers.
1Examples
of how to reference the whole or part of this volume can be found under "Citations"
in the preliminary pages of the volume.
2Marine Geology and Geochemistry Program, Department of Geological Sciences, The University of Michigan, Ann Arbor, MI 48109-1063, U.S.A.
pameyers@umich.edu
3GEOMAR, Christian-Albrechts Universität zu Kiel, Wischhofstraße 1-3, 24148 Kiel, Federal Republic of Germany.
Date of
initial receipt: 6 May 1997
Date of acceptance: 16 December 1997
Reproduced
online: 27 January 2004
Ms 161SR-235