Taphonomy of the Recent molluscs of Bahia la Choya (Gulf of California, Sonora, Mexico)

The “target genera” Prototbaca, Chione, Dosinia, Tagelus, Cerithium, Cerithidea and Encope have been used to study taphonomic differences between the subenvironments of a sandy tidal flat at Bahia la Choya near the head of the Gulf of California. The most important taphonomic agents (e. g. physical abrasion, bioerosion, encrustation) are identified and briefly discussed. The degree of taphonomic alteration of shells expressed by loss of ornament, loss of color, fragmentation, encrustation, boring, shell solution, and sorting was calculated semi-quantitativelv for each target genus and each subenvironment (outer, mid, inner flat, outer, mid, and salt marsh channel). Because taphonomic features vary between various subenvironments, taphofacies, corresponding to subenvironments can be distinguished. Applying the taphonomic approach to subrecent shell banks, shelly beachrock, and shelly Pleistocene rocks, we demonstrate that taphonomic features are a very useful tool for reconstructing ancient environments.