--> Abstract: Rates of Burial and Disturbance for Experimentally Deployed Shell Accumulations from Shallow Carbonate Shelf to Deep Clastic Slope Environments, by K. M. Parsons-Hubbard, E. N. Powell, W. R. Callender, C. E. Brett, S. E. Walker, A. L. Raymond, and G. M. Staff; #90937 (1998).

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Abstract: Rates of Burial and Disturbance for Experimentally Deployed Shell Accumulations from Shallow Carbonate Shelf to Deep Clastic Slope Environments

PARSONS-HUBBARD, KARLA M., ERIC N. POWELL, Haskin Shellfish Research Laboratory, Rutgers University; W.RUSSELL CALLENDER, Virginia Graduate Marine Science Consortium, University of Virginia; CARLTON E. BRETT, Univ. of Rochester; SALLY E. WALKER, Univ. of Georgia; ANNE L. RAYMOND, Texas A&M Univ.; and GEORGE M. STAFF, Austin Comm. College

In order to document taphonomic rates on the deeper continental shelf and slope over time, an experimental approach is required to accurately document burial rates, transport, and taphonomic alteration. The SSETI (Shelf and Slope Experimental Taphonomy Initiative) research group has established a number of long-term experiments in a wide variety of depositional environments in the Gulf of Mexico (GOM) and on a steep carbonate slope in the Bahamas. One hundred shells were scattered over a 1m2 area in 50 locations and video-taped. After 2 years the sites were re-visited and video-taped again. Comparative analysis of video frames from year to year allow qualitative estimates of shell burial, disturbance, and alteration.

On the outer continental shelf and slope of the GOM (70-570m), burial rates were between 0.5 and 3.0cm over 2 years. These rates were consistent for open muddy shelf and slope sites as well as hydrocarbon and brine seeps and a collapsed carbonate bank. At all soft-bottom sites, shells showed little taphonomic alteration or transport. Mussels remained articulated and there was little loss of original color. At hardground sites in both the Bahamas and GOM, shells were quickly biont-encrusted and transported short distances.

Gastropods were more often missing from the deployments than bivalves. Hermit crab activity may account for their disappearance.

On the Bahamas carbonate shelf at 15m burial was complete within one year. At 30m, burial was complete in 2 years. On the steep forereef slope (70-260m), burial was variable. Input of carbonate sediment from the active shelf-edge reef above caused rapid burial at many sites, but the steepness of the slope caused intermittent exhumation and downslope transport of shells. Transport at one locality was in excess of 10 m downslope.

Burial should be complete in 5 to 10 years at soft-bottom sites on the outer continental shelf and slope (GOM) and on the Bahamas carbonate bank. Because preservability increases once shells are below the sediment/water interface, organism remains deposited in these environments have a high potential for being preserved. On the other hand, shells on hardgrounds are either transported away or are encrusted with epi- and endobionts, which rapidly degrades them and removes the shells from the potentially preservable assemblage.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah