A SIMPLIFIED APPROACH TO COASTAL MICROPALEONTOLOGICAL INTERPRETATION FOR UNDERGRADUATE STUDENTS: CHARLESTON, SOUTH CAROLINA

Microfossils, and especially foraminifera, are valuable tools for paleoenvironmental interpretation in coastal regions. Nevertheless, their use as a teaching tool in undergraduate courses is limited by the difficulty of identification of some taxa. Students in UNC-Charlotte’s “Coastal Processes and Environments” course were required to differentiate downcore paleoenvironments from back-barrier marshes near Charleston, S.C. Although lithology was useful for interpreting subenvironments, sediments, combined with a simplified approach to microfossil identification, proved most useful for determining paleoenvironments.

Students had difficulty distinguishing coiled agglutinated species (Jadammina macrescens, Arenoparrella mexicana, and Trochammina inflata) because of their similar test morphology. Despite this, five facies were established: 1) Washover fans, containing medium-sand and shell fragments, were dominated by offshore-indicative Globigerina spp. and calcareous Oligo-Miocene foraminifera (dredged from offshore during storms); 2) Flood-tidal delta deposits varied between fine sand and mud and contained Elphidium sp., Ammonia sp., and Globigerina spp., but lacked the Oligo-Miocene foraminifera present in the washovers; 3) Beach deposits contained well sorted fine and medium sand and abraded Elphidium sp. and Ammonia sp.; 4) Low-marsh deposits were almost entirely mud and contained a higher percentage of Miliammina fusca and 5) High-marsh deposits contained up to 25% fine sand and a higher percentage of T. inflata, A. mexicana, and J. macrescens.

The Charleston region is ideal for undergraduate foraminiferal research for two reasons: 1) Offshore outcropping Oligo-Miocene foraminifera act as a natural tracer for washover sediments and differentiate washovers from flood-tidal deltas and 2) Morphologically distinct agglutinated foraminifera such as M. fusca simplify the identification of low and high marsh deposits. Based on foraminiferal identification, students used gauge-auger cores, GPS, and Civil War maps to find a 19th Century tidal inlet on Folly Island, SC. Paleoenvironments graded upwards from washover fans into flood tidal deposits and finally high and low marsh. These interpretations would not have been possible if they had been based on lithology and macrofossils alone.