The Relationship Of Bionts And Taphonomic Processes In Molluscan Taphofacies Formation On The Continental Shelf And Slope: Eight-year Trends: Gulf Of Mexico And Bahamas

Eric N. Powell
Carlton E. Brett
Karla Parsons-Hubbard, Oberlin College
W. Russell Callender
George M. Staff
Sally E. Walker
Anne L. Raymond
Kathryn A. Ashton-Alcox


The Shelf and Slope Experimental Taphonomy Initiative (SSETI) deployed a suite of molluscan species in environments covering a range of depths and sediment types in the Bahamas and on the Gulf of Mexico continental shelf and upper slope for 8 years. Taphonomic state rarely correlated with the distribution of biont guilds among environments. The preservable and nonpreservable biont guilds were also routinely orthogonal. Several coincidences of taphonomic trait and biont guild occurred, including green discoloration that consistently co-occurred with boring algae and bacterial films associated with the development of chalkiness and a soft shell surface. Environments of preservation (EOPs) of disparate taphonomic signature and biont guild complement occur in similar sediment types and environments with similar rates of burial. A paucity of biont coverage is no more a reliable indicator of rapid burial than is a limited degree of shell degradation. The suggestion that preservable bionts might protect shells from taphonomic processes is not well supported. Certain EOP groups are delineated from others most readily by a combination of biont guild and taphonomic trait. Thus, biont guilds augment taphonomic analysis in differentiating EOPs. Shell preservational state, including taphonomic signature and biont coverage, is influenced in a complex way by environment. The analysis confirms an expectation that the diversity of EOPs should be greater in shallow water. Clustering of EOPs reveals that visually distinctive environments may be taphonomically and biotically similar. Visually similar environments may be quite disparate in taphonomic state and biont complement. EOPs grouped by similarity in taphonomic signature and biont coverage very likely define geographically widespread biological and taphonomic regimes, which, however, are everywhere restricted locally in areal dimension.