Taphonomy on the continental shelf and slope: two-year trends ^ Gulf of Mexico and Bahamas Eric N. Powell a; Ã , Karla M. Parsons-Hubbard b , W. Russell Callender c , George M. Sta¡ d , Gilbert T. Rowe e , Carlton E. Brett f , Sally E. Walker g , Anne Raymond h , Donna D. Carlson f , Suzanne White g , Elizabeth A. Heise h a Haskin Shell¢sh Research Laboratory, Institute of Marine and Coastal Sciences, Rutgers University, 6959 Miller Ave., Port Norris, NJ 08349, USA b Department of Geology, Oberlin College, Oberlin, OH 44074, USA c National Oceanic and Atmospheric Administration, Oceanic and Atmospheric Research (R/0SS), Room 11560, 1315 East West Highway, Silver Spring, MD 20910 USA d Geology Department, Austin Community College, NRG Campus, 11928 Stonehollow Drive, Austin, TX 78758, USA e Department of Oceanography, Texas ApM University, College Station, TX 77843, USA f Department of Geology, University of Cincinnati, Cincinnati, OH 45221, USA g Department of Geology, University of Georgia, Athens, GA 30602, USA h Department of Geology and Geophysics, Texas ApM University, College Station, TX 77843, USA Received 19 July 2000; accepted 2 November 2001 Abstract TheShelfandSlopeExperimentalTaphonomyInitiativewasestablishedtomeasuretaphonomicratesinarange of continental shelf and slope environments of deposition (EODs) over a multiyear period. We deployed experiments ontheforereefslopeoffLeeStockingIsland,Bahamas,andonthecontinentalshelfandslopeoftheGulfofMexico for2yrin18distinctiveEODsatdepthsfrom15to530m.Overall,mostshellsdeployedatmostsiteshadrelatively minor changes in shell condition. Most EODs generated relatively similar taphonomic signatures. A few sites did produce taphonomic signatures clearly distinguishable from the central group and these sites were characterized by one or more of the following: high rates of oxidation of reduced compounds, presence in the photic zone, and significant burial and exhumation events. Thus, unique taphonomic signatures are created by unique combinations of environmental conditions that include variables associated with regional gradients, such as depth and light, and variables associated with edaphic processes, such as the seepage of brine or petroleum or the resuspension and redeposition of sediment. Most sites, however, showed similar taphonomic signatures, despite the variety of EOD characteristics present, suggesting that insufficient time had elapsed over 2 yr to generate a more diverse array of taphonomic signatures. Discoloration and dissolution were by far the dominant processes over the 2-yr deployment period. Periostracum breakdown, loss of shell weight, and chipping and breakage was less noticeable. EODs were chosen based on the expectation that the process of burial and the influence of depth and sediment type should play the greatest roles in determining between-EOD differences in taphonomic signature. EOD-specific edaphic factors often overrode the influence of geographic-scale environmental gradients. Taphonomic alteration was greater on 0031-0182/02/$ ^ see front matter ß 2002 Elsevier Science B.V. All rights reserved. PII:S0031-0182(01)00457-6 * Corresponding author. Fax: +1-609-785-1544. E-mail address: eric@hsrl.rutgers.edu (E.N. Powell). Palaeogeography, Palaeoclimatology, Palaeoecology 184 (2002) 1^35 www.elsevier.com/locate/palaeo