--> Abstract: Early Diagenesis of Sapropel and Peat from Mud Lake, Florida: Carbon and Sulfur Isotope Geochemistry, by E. C. Spiker, A. L. Bates, V. C. Weintraub, P. G. Hatcher, and S. A. Stout; #90987 (1993).

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SPIKER, ELLIOTT C., A. L. BATES, and V. C. WEINTRAUB, U.S. Geological Survey, Reston, VA; P. G. HATCHER, Pennsylvania State Univ., University Park, PA; and S. A. STOUT, Unocal Science and Technology Division, Brea, CA

ABSTRACT: Early Diagenesis of Sapropel and Peat from Mud Lake, Florida: Carbon and Sulfur Isotope Geochemistry

Analysis of a 4-m core of organic-rich sediment from Mud Lake, Florida, revealed large variations in chemical and stable isotopic composition that reflect differences in depositional environment, source of organic matter, and degree of decomposition. The sediment grades downward from a lacustrine algal sapropel to a highly degraded aquatic Nymphaea peat and then to a better preserved fibrous Cladium peat at the base of the core. The ratio of lignin to aliphatic organic carbon increases with depth because of the greater lignin content of the peat compared to the sapropel. The stable carbon isotope isotope{13}C values decrease nearly 8 per mil as a result of the degradation and loss of {13}C-enriched carbohydrates and the change from algae to herbaceous plants. Total sulfur in the sedim nt ranges from about 2 to 6 percent. Sulfate sulfur ranges from about 0.05 to 1.2 wt. %, pyritic sulfur ranges from about 0.4 to 3 wt. %, and organic sulfur ranges from about 0.04 to 1.6 wt. %. Pyritic and organic sulfur increase with depth in the sapropel as a result of sulfate reduction and the loss of labile organic matter. The transition from the marsh peat to the overlying lacustrine sapropel is marked by a large negative shift in the sulfur isotope{34}S values, reflecting an increased supply of dissolved sulfate in the lake compared to the marsh.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.