Use of X-Ray Fluorescence (XRF) in Atlantic Basin Paleotempestology

Part of a multi-proxy approach framework is presented to reconstruct the paleotempestology of Chezzetcook Inlet, Nova Scotia, on the eastern Canadian seaboard.

This study aims at identifying periods of elevated frequency of past tropical storms by using XRF core scanning to identify sediments which are allochthonous to fresh water basins. Previous research in the Pacific Basin has shown Sr to be a useful indicator of sediment overwash, and part of this study will test whether that element is also an indicator in coastal Nova Scotia. Sediment cores extracted from coastal lakes and marshes were chosen based on several criteria, such as elevation, distance from the Atlantic Ocean and the material composition of barriers. The XRF analysis was corroborated by several other laboratory analyses such as magnetic susceptibility, loss-on-ignition and sediment grain-size.

The focus of this study is on cores taken in Robinson Pond in the Chezzetcook inlet. One core (core RL01) is 110 cm long and was dated with four AMS dates which show that the pond began at least 1000 years ago. An age-depth model of the dates indicates that there is a mean sediment accumulation rate of 10 yr/cm, showing promising signs of variable energy fluxes in the lithology. Visible variations along the core in color and grain-size show obvious changes in sedimentation, including the presence of a coarse-grained layer at 25 cm below the surface (tentatively dated to 1848 AD) which might represent storm overwash. XRF results show peaks of various elements such as strontium (Sr) and titanium (Ti). One peak in Sr is at ~AD 1831, which corresponds to a major storm that hit Nova Scotia. Dips in Sr and Ti correspond with the 1950s and1970s which are two periods of relatively low storm activity. Another peak in Sr corresponds with a layer of obvious shells in the core at ~1200 AD.