ABSTRACT

Microfabric evidence from mudstones combined with taphonomic information provides important clues to sedimentary processes. The microfabric of the Lewiston Member, Rochester Shale (Silurian, Wenlockian) of New York has yielded evidence of episodic sedimentation from storm-generated sediment plumes or tempestites. A cardhouse arrangement of clay flakes in the mudstones indicates rapid deposition of flocculated clay. In addition, taphonomic observations such as the presence of articulated crinoids buried in life position also indicate rapid burial by the flocculated clay sediment. Four intervals of Lewiston mudstones show evidence of periods of "background sedimentation" during which skeletal debris slowly accumulated. These conditions were punctuated by brief events of deposition from storm-generated, silty clay sediment plume that rapidly (hours to days) covered the depositional site. This study provides an example of the utility of an integrated microfabric and taphonomic analysis in determining the nature of mudstone depositional processes.