BEYOND SIMILARITY: EXAMINING LIVE-DEAD AGREEMENT BY MODELING DEATH ASSEMBLAGE FORMATION USING LIVE-COLLECTED SPECIMENS

Because death assemblages are accumulations of shell productivity whereas a census of living individuals measures standing crop, death assemblages and living assemblages are only expected to match under a very specific set of conditions. If preservation potential is taxon-independent then organisms with higher birth and death rates should be over represented in the death assemblage relative to organisms with lower birth and death rates. Measured shell half-lives show significant differences between taxa, so live abundance is expected to the same as dead abundance only if a taxon's preservation potential is inversely proportional to its productivity, i.e., shorter lived organisms have lower probabilities of preservation whereas longer-lived organisms have higher probabilities of preservation. While this assertion is intuitively appealing, it has not been widely tested. Molluscan samples from the central Great Barrier Reef (Australia), are used to determine taxon-specific preservation potential and productivity. Extending on previous work, shell size, density, shape and thickness are used to predict taphonomic durability. These predicted durabilities are then compared to the observed relative durability based on acid dissolution experiments. The agreement between predicted durability and observed durability is quite high, at least amongst aragonitic taxa. For taxa sufficiently numerous to estimate recruitment and mortality rates, the relation between durability and productivity is examined.