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Tracking Storms through Time: Event Deposition and Biologic Response in Storr…#8482;s Lake, San Salvador Island, Bahamas
| Title: | Tracking Storms through Time: Event Deposition and Biologic Response in Storr…#8482;s Lake, San Salvador Island, Bahamas |
| Author: | Sipahioglu, Sara M. |
| Description: | Because of its position within the southwestern Atlantic Ocean, San Salvador Island, Bahamas has been the site of many hurricane strikes throughout its history. As such, it remains an effective setting in which to examine hurricane intensity in the Late Holocene. The lakes along the island…#8482;s margin provide a depositional archive recording the paleotempestites from these storm events. Storrs Lake is a shallow (66µS) lake located along the eastern side of the island and is separated from the ocean by Holocene dunes. It, like other lakes on San Salvador, is constantly recording climatic changes, vegetation shifts and the history of colonization. This study addresses the following questions: 1) What is the depositional history of Storrs Lake through the last 3,000 years and 2) Can we see large storm events in the sediment record and determine the biologic response to these events? Cores were recovered from Storrs Lake that varied in length from 5 to 200 cm, including transects across the Fortune Hill basin. The cores from Fortune Hill basin were analyzed for organic and carbonate content, dry bulk density, grain size, chemical composition, sediment fabric, trace elements, spectralphotometry, ostracode and mollusk faunal composition. Large storms can be identified through time by a distinct increase in grain size and a change in dry bulk density. The adjacent dunes have been mapped and sediment analyzed. The allochthonous sand found within the basin matches the sand found on the dune faces and identified as storm wash-over deposits. Biologic patterns suggest that species richness and abundance change after these large storm events, possibly due to the freshening that occurs from the storm and a change in the basin substrate. Cyanobacterial mats, or stromatolites, that are prevalent throughout many of the lakes on San Salvador also have a documented response to these freshening events by a community shift and increase in productivity. These cores record a major climatic shift occurring approximately 700 ybp and which is contemporaneous with colonization of the island. There is also evidence of multiple hurricane strikes, and a hurricane ‘hyperactivity period…#8482; from 1000 …ldquo; 3000 ybp that has been identified in other records along the Gulf Coast of North America. Caribbean hurricanes are directly related to the position and strength of the Bermuda High and North Atlantic Oscillation. The ability to identify paleohurricane strikes in the Bahamas may be useful in climatic reconstructions as well generating a recurrence interval and predicting the frequency of CAT 5 hurricanes through this area and the ecological response to these disturbances. |
| Permanent Link: |
http://rave.ohiolink.edu/etdc/view?acc_num=akron1227031927
http://hdl.handle.net/2374.OX/103798 |
| Date: | 2008 |
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