SPATIO-LATERAL CONTINUITY OF HURRICANE OVERWASH DEPOSITS IN BACK-BARRIER MARSHES

Sedimentological and micropaleontological analysis of fifteen 3-m gouge-auger cores revealed a lack of spatio-lateral continuity for paleohurricane deposits from the back-barrier marshes of Folly Island, South Carolina. The offshore-indicative calcareous microfossil assemblages of some storm deposits were taphonomically altered or destroyed and in many cases cores taken 10-m apart provided significantly different storm records. In several cores recovered from the low marsh, where bioturbation is more intense, storm deposits were unrecognizable using foraminiferal or sedimentological analyses. In nearly all cores the sedimentary record of storm deposits was more extensive than the record produced using foraminifers and, as a result, the sedimentological proxy recorded shorter hurricane return periods. Foraminifers, while providing a natural tracer for the source of the storm sands, are prone to taphonomic degradation and, as a result, produce a less complete storm record. The more robust sand layers, at least in terms of resistance to chemical alteration and destruction, allowed for the differentiation of 14 additional storm layers compared to the microfossil methodology, although the source of the sand and the method of deposition was no longer as conclusive.