DEVELOPMENT OF HIGH-RESOLUTION ELEMENTAL ANALYSIS APPROACH FOR COASTAL SETTINGS: COLOR LINE SCANNING, SCANNING X-RAY FLUORESCENCE AND SCANNING LASER-ABLATION INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY

Sediment cores from salt ponds in St. John, USVI were utilized as a pilot study to develop a high-resolution non-destructive elemental analysis approach for coastal settings. Recent advances in technology have provided the ability to perform high-resolution, non-destructive scanning analysis of sediment cores, but this approach has been mainly utilized on deep-sea sediment cores. Elemental data from coastal settings will likely have different signatures and elements will not necessarily behave the same as in the deep-sea. Cores for this study contained mm to cm-scale laminations that represent variability in depositional processes from terrigenous sediment runoff from the land associated with intense rainfall events, growth of organic mats, atmospheric input of volcanic and African dust, to marine overwash of carbonate material associated with tropical cyclones and/or tsunamis.

This variability in sediment deposition provides very distinctive sediment sources with distinctive elemental signatures. Cores were analyzed using a color line scanner (sub-mm resolution), as well as scanning XRF (X-ray Fluorescence) with mm-scale resolution and sections of the cores were analyzed by scanning LA-ICP-MS (Laser Ablation Inductively Couple Mass Spectrometry) with micon-scale resolution. This provided a high-resolution elemental record that could discriminate individual laminations/sedimentation events. Each data set was processed to determine the most indicative elements and elemental ratios for each sediment source. Development of an approach to elemental analysis specific for coastal settings is necessary for accurate interpretation of elemental records from sediment cores in coastal settings. This will aid in measuring variability in depositional process (runoff/rainfall, overwash/tropical cyclones and/or tsunamis) on annual to decadal-scale resolution.