PI will investigate the time span required for death assemblage formation and the extent to which the temporal events in its formation, and hence the temporal history of the community, are discretely preserved. To do so requires an inexpensive method for dating time-since-death of shells. The method under development is based on the observation that the proteinaceous matrix in the shells of bivalves gradually decomposes, freeing protein-bound amino acids which then accumulate, and the observation that these free amino acids gradually diffuse out of the shell. Accordingly, the degree of proteinaceous matrix remaining and the amount of free amino acid present (determined by the balance of production and diffusional loss) are both time dependent properties of the shell. For the technique to be useful, it is essential that it be usable on shelf assemblages. The shelf is typified by a preponderance of small species and a significant cross-shelf thermal gradient, each of which would tax the capabilities of the technique. Accordingly, the purpose of this proposal is to demonstrate the ability of the amino acid dating method to answer the following important questions about death assemblage formation: (1) What time span is required for death assemblage formation in clastic depositional regimes? (2) Which temporal events in the community are discretely preserved during death assemblage formation (not how stratigraphically compressed they are, but are they discreetly preserved in stratigraphic sequence)? (3) Can the rates of taphonomic alteration be determined or at least can the extent to which taphonomic alteration is correlation with shell age (time-since-death) be measured?
