Local variability of taphonomic attributes in a parautochthonous assemblage: can taphonomic signature distinguish a heterogeneous environment?

Abstract

Taphofacies have been based on the likelihood that considerable variability exists in taphonomic processes between different environments and that this variability produces predictable variations in taphonomic signature between assemblages. Three stations above storm wave base that differed little in sediment texture and depth were sampled on the inner continental shelf of central Texas. Taphonomic analysis revealed subtle gradients in sediment grain size and water depth that would not be revealed by most other analyses. These gradients may exist over very small spatial scales, equivalent to those within a single extensive outcrop. Not all taphonomic attributes are equally likely to be preserved in the fossil record. Those varying with depth in our study area, such as fragmentation and articulation, are more likely to be preserved than those documenting changes in sediment texture, such as variation in the frequency of dissolution features on the shells. Nevertheless, siting and sampling protocols are important when characterizing a taphofacies because within-habitat variation is potentially as large as between-habitat variation. Description of the average taphofacies for an environment must include documentation of the variation in taphonomic attributes within the sampled area because few conservative taphonomic attributes exist. Fragments, even those that are unidentifiable, retain significant taphonomic information and should not be ignored. Careful sampling should permit the simultaneous description of general taphofacies as well as the detection of important but unsuspected gradients in the environment.