SALT POND SEDIMENTS AS A PROXY FOR SEVERE PALEO-CLIMATIC EVENTS: ST. JOHN, USVI

Abstract:

Newfound Bay salt pond, located along the northeastern coast of St. John, USVI, contains finely laminated (mm- to cm-scale) sediments that provide a detailed record of depositional events.  Five sediment cores were collected throughout the pond and analyzed for texture, composition, and geochronology.  Laminations consist of three different sediments types: 1) white to light tan, fine sand-sized marine carbonates, 2) olive gray terrigenous sands and muds, 3) organic rich muds.  The carbonate laminae are interpreted as overwash deposits from high-energy events such as tropical cyclones.  The terrigenous sand/mud laminae are interpreted to represent the massive influx of sediments from the island watershed likely during large rain events.  The organic mud laminae originate from the in situ development of bacterial or algal mats.  A high-resolution age model produced from ¹⁴C, ²¹⁰Pb, ¹³⁷Cs, and ⁷Be data, was constructed to determine precise timing of deposition.  A prominent carbonate laminae found throughout the five cores has been correlated to a major hurricane that impacted the island around 1780 known as The Great Hurricane of 1780 or San Calixto II, which devastated the Lesser Antilles and surrounding areas.  Other laminae have been correlated to historical storm events, but were not observed in all cores.  Ongoing work is being conducted in order to build a more detailed record pertaining to frequency, intensity, and possibly direction (land-derived vs. overwash sediments) of paleo-storm events.  A long-term record could help create a greater understanding of severe paleo-climatic events.