Bioclastic Turbidites in Trenton Limestone: Significance and Criteria for Recognition: ABSTRACT

Abstract

Bioclastic turbidites are identified and described from the Denley Limestone (Trenton Group) in the Mohawk Valley, New York. These turbidites are recognized by the repetitive Bouma sequences within limestone beds separated by shale interbeds interpreted as interturbidite deposits. The general characteristics of bioclastic turbidites includes internal structures identifiable as Bouma sequences Ta through Te. Bioclastic turbidites differ from the clastic turbidites described by A. Bouma in that they include an additional subdivision termed Td^prime. This unit, composed of unfossiliferous, bioturbated, but otherwise structureless carbonate mud, is similar to the ungraded, unlaminated mud described by others as representing the finest grained sediment emplaced by turbidity cu rents. The Trenton bioclastic turbidites are associated with slump-fold zones and syndepositional block faults and have been used by other workers to redefine the Trenton limestones as foreland basin or trench slope deposits. The Trenton Group sediments have been interpreted previously as deposits formed in situ on a subsiding shelf, rather than storm-generated shelf sediments from turbidites. It is suggested that the internal structures of the limestone beds are similar to those that would be produced by storm-surge ebb-flow currents, but differ in that they are associated with other indicators of the slope setting, are consistently associated with vertical burrows descending into the sediment rather than escape burrows, consistently exhibit Bouma sequences, and show a statistical relat onship between grain size and bed thickness. End_of_Article - Last_Page 1924------------