THE FORAMINIFERAL SIGNATURE OF HURRICANES RITA, KATRINA, AND IVAN IN CORES FROM SOUTHWEST PASS TO THE MISSISSIPPI CANYON, GULF OF MEXICO, USA

Deposits from Hurricanes Rita (2005), Katrina (2005), and Ivan (2004) have been detected in cores from the offshore Mississippi Delta using radionuclide analysis (⁷Be, ²³⁴Th, and ²¹⁰Pb) coupled with X-radiography. However, as ⁷Be, ²³⁴Th, ²¹⁰Pb have half lives of 53.3 days, 24.1 days, and 22.26 yr, respectively, their utility for the identification of hurricane events decreases with progressively older deposits. Foraminifera, on the other hand, can be preserved for geologically significant amounts of time. Here we 1) investigate whether recent hurricane and non-hurricane deposits can be discriminated using foraminiferal assemblages and 2) whether insights concerning mode of sediment transport and sediment provenance can be gained from foraminiferal data.

Samples were collected from cores taken in a series of cruises off the Mississippi Delta in 2004, 2005, and 2007 which reoccupied three of the same stations two to three times in a transect trending southwest from Southwest Pass (~30m water depth) to the upper boundary of the Mississippi Canyon (~90m water depth). Eight cores were selected, one from each station in 2004 and 2005, and one from each of two stations in 2007, as well as five ponar surface samples along the transect in 2007. From these, two 20 mL foraminiferal samples were taken from each hurricane deposit from each core as well as two from the pre- and post-storm deposits, where available.

Foraminifera contained in these deposits have been identified to the species level. ANOVAs performed on transformed abundances of some common taxa reveals that while the abundance of some species, such as Epistominella vitrea, are significantly different in storm versus non-storm deposits, others, such as Buliminella morgani, show little to no response. The specific taxa that are significantly different between storm versus non-storm deposits also seem to vary between stations, which is likely a function of depth. Further analyses will make inferences about the provenance of individual storm beds based on foraminiferal distribution data.