Elevated marine deposits in Bermuda record a late Quaternary megatsunami

McMurtry, G. M., Tappin, D. R., Sedwick, P. N., Wilkinson, I., Fietzke, Jan and Sellwood, B. (2007) Elevated marine deposits in Bermuda record a late Quaternary megatsunami Sedimentary Geology, 200 (3-4). pp. 155-165. DOI 10.1016/j.sedgeo.2006.10.009.

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Abstract

Deposits of coral-bearing, marine shell conglomerate exposed at elevations higher than 20 m above present-day mean sea level (MSL) in Bermuda and the Bahamas have previously been interpreted as relict intertidal deposits formed during marine isotope stage (MIS) 11, ca. 360–420 ka before present. On the strength of this evidence, a sea level highstand more than 20 m higher than present-day MSL was inferred for the MIS 11 interglacial, despite a lack of clear supporting evidence in the oxygen-isotope records of deep-sea sediment cores. We have critically re-examined the elevated marine deposits in Bermuda, and find their geological setting, sedimentary relations, and microfaunal assemblages to be inconsistent with intertidal deposition over an extended period. Rather, these deposits, which comprise a poorly sorted mixture of reef, lagoon and shoreline sediments, appear to have been carried tens of meters inside karst caves, presumably by large waves, at some time earlier than ca. 310–360 ka before present (MIS 9–11). We hypothesize that these deposits are the result of a large tsunami during the mid-Pleistocene, in which Bermuda was impacted by a wave set that carried sediments from the surrounding reef platform and nearshore waters over the eolianite atoll. Likely causes for such a megatsunami are the flank collapse of an Atlantic island volcano, such as the roughly synchronous Julan or Orotava submarine landslides in the Canary Islands, or a giant submarine landslide on the Atlantic continental margin.

Document Type: Article
Keywords: Bermuda, Tsunami deposit, Interglacial, Submarine landslide
Research affiliation: OceanRep > GEOMAR > FB2 Marine Biogeochemistry > FB2-MG Marine Geosystems
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
DOI etc.: 10.1016/j.sedgeo.2006.10.009
ISSN: 0037-0738
Projects: Future Ocean
Date Deposited: 03 Dec 2008 16:51
Last Modified: 06 Sep 2016 13:06
URI: http://eprints.uni-kiel.de/id/eprint/5923

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