ENVIRONMENTAL-INFLUENCES ON THE FORMATION OF SEDIMENTARY FABRIC IN A FINE-GRAINED CARBONATE-SHELF ENVIRONMENT - DRY TORTUGAS, FLORIDA KEYS

Sedimentological studies were undertaken in the Dry Tortugas to examin e environmental influences on the formation of sedimentary fabric. Th- 234, Pb-210, grain size, porosity, and fabric analyses reveal the pres ence of a soft, fine-grained, well mixed surface layer underlain by co mpact, shelly, intensely bioturbated carbonate muds. Vertical zonation of biogenic structures indicates that deep bioturbation is advective and results in transport of fine material to the seabed surface. The i mpact of physical oceanographic processes appears to be restricted to the surface layer; however, potential for preservation of this layer i n the sediment record is low due to intense mixing in deeper sediments . Thus, preserved sediments retain an incomplete record of the dominan t benthic processes at the study area.