22. BIOLOGICAL MARKER SIGNIFICANCE OF ORGANIC MATTER ORIGIN AND TRANSFORMATION IN SAPROPELS FROM THE PISANO PLATEAU, SITE 964¹

J. Rullkötter^,2 J. Rinna,² I. Bouloubassi,³ B.M. Scholz-Böttcher,² P.A. Meyers,⁴ L. Johns,⁵ and S.J. Rowland⁵

ABSTRACT

The organic matter in a series of 39 sapropel samples from Hole 964D drilled during Ocean Drilling Program Leg 160 in the Ionian Basin of the Eastern Mediterranean Sea has been characterized. Organic carbon contents exceed 20% in many sapropels of Pliocene to early Pleistocene age, but are conspicuously lower in those of the late Pleistocene and Holocene. The organic matter is predominantly of marine origin, with varying admixtures of terrigenous organic matter. The most abundant molecular algal markers are long-chain alkenones, alkandiols, and alkanolones (ketools) as well as a significant proportion of sterols. Terrigenous markers include long-chain alkanes, n-alcohols, and fatty acids. Although strong alteration of the organic matter by sulfate-reducing bacteria is inferred from the high total sulfur contents of the sapropels, there was little direct molecular evidence of a bacterial biomass contribution. High C_org:N ratios, exceeding values of 20, particularly in the most organic-carbon-rich sapropels, have to be interpreted as the result of partial degradation of the sinking organic matter with selective remineralization of nitrogen-bearing compounds.

¹Robertson, A.H.F., Emeis, K.-C., Richter, C., and Camerlenghi, A. (Eds.), 1998. Proc. ODP, Sci. Results, 160: College Station, TX (Ocean Drilling Program).
²Institut für Chemie und Biologie des Meeres (ICBM), Carl von Ossietzky Universität Oldenburg, Postfach 2503, D-26111 Oldenburg, Germany.
J.Rullkoetter@ogc.icbm.uni-oldenburg.de
³Department of Geology and Oceanography, Université Bordeaux I, Avenue de Facultés, F-33405 Talence Cedex, France. (Current address: Laboratoire de Physique et Chimie Marines, Université P. et M. Curie, Case 134, Tour 25, 5ème étage, 4, place Jussieu, F-75252 Paris Cedex 05, France.)
⁴Department of Geological Sciences, The University of Michigan, C.C. Little Building, Ann Arbor, MI 48109-1063, U.S.A.
⁵Department of Environmental Sciences, University of Plymouth, Drake Circus, Plymouth, Devon PL4 8AA, United Kingdom.