Lateral fluctuations of shoreline positions along shallow basinal margins often result in spatially and temporally overprinted (palimpsested) firmground or hardground surfaces (Frey and Basan, 1981). Recent palimpsested surfaces can teach us a great deal about the fossil record, particularly when we view them taphonomically. For the last few years we have been studying such surfaces along the seaward coast of St. Catherines Island, Georgia. In this paper we will first briefly discuss the modern salt marsh at St. Catherines Island, and its invertebrate inhabitants. This will form a basis for recognition and description of relict marsh surfaces. We will next describe the relict salt marsh surface that is currently being exhumed by coastal erosion and palimpsested by other invertebrate communities. Such palimpsested events also represent heterochronous community replacement–the disjunct temporal and (usually) spatial overprinting of an older community (or biogenic surface) by one (or more) younger communities. This interprets “replacement” as a passive, generally species non-interactive, phenomenon (contra Miller, 1986). Lastly, we will make some rather broad comparisons between the St. Catherines Island setting and what we interpret as analogous situations recorded in the Carboniferous strata of the Appalachian Basin.

Although taphonomic processes alter or destroy much of the preservable portion of the original community, many of these processes also imprint valuable paleoecological information about the fauna and the environment of deposition which might be employed in paleoenvironmental reconstruction (Brett and Baird, 1986; Speyer and Brett, 1986, 1988). Accordingly, taphonomic analysis of modern and ancient death assemblages has received much attention recently (Powell et al., in press; Parsons et al., 1988; Kidwell and Behrensmeyer, 1988) and a new concept, that of the taphofacies, has been developed (e.g., Speyer, 1988). Taphofacies are based on distinct suites of taphonomic characteristics, taphonomic signatures, imprinted on the shell material and on its relationship to the sedimentary fabric by mixtures of physical, biological and chemical processes, which potentially are unique for a given environment. Ideally, if unique taphonomic signatures can be identified and the formative processes understood in a wide range of modern environments, this baseline can be employed to make more accurate reconstructions of equivalent paleoenvironments.

Empty molluscan shells retain paleoecological and taphonomic information that may be temporally complex (e.g., successive layers of encrusting organisms) to less complex (e.g., drill holes produced by predatory gastropods at one point in time). Yet, at all levels of complexity, unraveling the ancient “transcripts” requires not only a hopeful paleontologist but also knowledge of the various temporal roles molluscan shells play in community structure.