Comparison of Otolith-based Paleoecology to other Fossil Groups: an Example from the Cane River Formation (Eocene) of Louisiana : ABSTRACT

Abstract

ABSTRACT Teleostean otoliths are utilized to determine the paleoecological parameters of the middle Glauconitic Clay Member of the Middle Eocene Cane River Formation near Natchitoches, Louisiana. The otolith-based paleoenvironment is compared to reconstructions based on other fossil groups commonly used for paleoecology. Analysis of approximately 300 teleost otoliths revealed an assemblage of 18 species of teleosts representing 12 families. The teleostean fauna is dominated by ophidiids (cusk eels), Myripristis, Pterothrissus, Ariosoma, and gobiids. Several unusual occurrences include the complete absence of sciaenids (drums) and the abundance of Myripristis and Pterothrissus, which are typically scarce in fish-bearing Tertiary deposits of the Gulf Coast. Evaluation of two microfossil groups from the site indicates a diverse fauna of 59 benthic and 12 planktonic species of foraminifera and 27 species of ostracodes. The planktonic foraminifera Morozovella aragonensis (Nuttall) constrains the age of this fauna to Zone P11 of the Lutetian Stage. A low diversity macrofauna (about 30 species) is dominated by several clams (Venericardia and Corbula) and two colonial corals (Madracis and Madrepora). Otolith-based ecology suggests paleobathymetry ranging from 40-100 m. By comparison, ostracodes suggest a range from 0-50 m, foraminifera suggest 20-40 m, and macroinvertebrates 0-50 m. Combining the paleoecological indicators from the various groups, a patch reef environment far offshore but in relatively shallow water (20-50 m) is proposed and explains the unusual teleost association with abundant squirrelfish (Myripristis). The otoliths are judged to be reliable indicators of paleoecological parameters when compared to other commonly utilized fossil groups.