UNDERSTANDING THE ROLE OF TAPHONOMY AND POST-DEPOSITIONAL PROCESSES ON THE INTERTIDAL STRATIGRAPHIC RECORD

Abstract

Benthic foraminifera from muddy, intertidal sediments have received considerable attention in the past few decades for their use as sensitive indicators of Holocene sea-level change. Studies of their ecology and taphonomy, however, have suggested that the formation of foraminiferal assemblages may be complex in some settings, often involving processes that occur during and subsequent to burial. Buried foraminiferal assemblages to a greater or lesser extent, therefore, represent the product of both subtle environmental changes and postdepositional modifications. Our ability to recognize and delineate the effects of each is crucial if the effective environmental resolution of fossilized assemblages is to be accurately understood. The application of intertidal foraminifera to studies of relative sea-level (RSL) change arises from the observation that species in modern sediments occur in narrowly constrained zones at specific positions relative to the tide. In the three decades since this relationship was first recognized (Scott & Medioli, 1978), the zonation of intertidal foraminiferal species has been documented from dozens of low-energy coastal systems around the world. Both high- and low-latitude shorelines exhibit surface (upper 1 cm) assemblages organized according to their position between the high and low tidal benchmarks, with significant variations in species composition occurring over elevational distances of just a few decimeters or less within the prevailing tidal range (Horton et al., 1999; Edwards et al., 2004; Barbosa et al., 2005). An important, recent development is the application of sophisticated statistical methods for calculating the elevation at which …