Abstract: Thin Section Analysis of Coastal-Marsh Sediments and Its Use in Paleoenvironmental Reconstruction

Elizabeth A. Allen, Arthur D. Cohen

Thin sections of Holocene salt- and brackish-marsh sediments from the western shoreline of Delaware Bay were analyzed using the paraffin embedding technique to relate the organic-rich sediments to their original depositional settings. The proportions and types of plant fragments, fecal pellets, forams, diatoms, charcoal, pyrite, and other microscopic components were used to characterize each sediment type.

The salt-marsh environments which could be distinguished were "high marsh" (Spartina patens, Distichlis spicata), "low marsh" (Spartina alterniflora), "transitional marsh" (Baccharis, Iva), "creek bank," "salt pans," and "pools." The brackish-marsh environments which could be distinguished were the Phragmites communis marsh, the Spartina cynosuroides marsh, the Scirpus marsh, and the Hibiscus-Kosteletzkya-Panicum marsh. Surface conditions, such as frequency and duration of tidal inundation, salinity, and animal activity were important in determining sediment type.

Identification of these different sediment types in cores and outcrops is critical in reconstructing the history and evolution of coastal wetlands and in developing models of organic sedimentation in shoreline environments.

AAPG Search and Discovery Article #90968©1977 AAPG-SEPM Annual Convention and Exhibition, Washington, DC