Abstract

The Shelf and Slope Experimental Taphonomy Initiative (SSETI) Program was established to measure taphonomic rates in a range of continental shelf and slope environments. Experiments were deployed on the forereef slope off Lee Stocking Island, Bahamas, for one and two years along two transects (AA and BA) in seven distinctive environments of deposition (EODs) along each transect: in sand channels on the platform top (15 m) and the platform edge (30 m), on ledges down the wall (70–88 m), on the upper (183 m—transect BA only) and lower (210–226 m) talus slope below the wall, and on the crest (256–264 m) and in the trough (259–267 m) of large sand dunes.

Discoloration was by far the dominant taphonomic process over the two-year deployment period, with dissolution or maceration of shell carbonate a close second. Periostracum breakdown was not significant, nor was loss of shell weight. Chipped edges and breakage (assayed by the edge alteration variable) were much less common, but were important in some species. The degrees of edge alteration and dissolution were correlated with discoloration more frequently than expected by chance, emphasizing that the process of discoloration progressed in a coordinated fashion with the other two over time. The degree of burial or the interaction between degree of burial and water depth explained most of the trends observed in discoloration.

The deep water sites, below the photic zone, including the talus slope and dune EODs, had very similar taphonomic signatures. Shells were characterized by a low degree of discoloration, little edge alteration, and varying degrees of dissolution. Photic zone sites, including the platform top and wall locations, followed the opposite trends, with the shallowest site, on the platform top, typically attaining the most extreme degree of alteration. The wall location was most similar to the platform top despite the greater depth and less rigorous physical and sedimentological regime. The platform edge occupied an intermediate position, likely due to the greater degree of burial that resulted in shells at this site being at least as frequently under aphotic conditions as under photic conditions. The data indicate that similar taphonomic signatures can be attained in distinctly different ways over a two-year exposure period, complicating the interpretation of taphofacies and the taphonomic process.

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