Radiometric dates of uplifted marine fauna in Greece: Implications for the interpretation of recent earthquake and tectonic histories using lithophagid dates

Shaw, B. and Jackson, J. A. and Higham, T. F. G. and England, P. C. and Thomas, A. L. (2010) Radiometric dates of uplifted marine fauna in Greece: Implications for the interpretation of recent earthquake and tectonic histories using lithophagid dates. Earth and Planetary Science Letters, 297. pp. 395-404. ISSN 0012821X DOI 10.1016/j.epsl.2010.06.041

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n AD 365 a great (Mw N 8) earthquake lifted up western Crete, exposing a shoreline encrusted by marine organisms, and up to 10 m of marine substrate beneath it. Radiocarbon ages determined for corals and bryozoans exposed between the paleo-shoreline and present sea level are consistent, within measurement error, with each other and with the date of the earthquake. But radiocarbon ages determined for the boring bivalve Lithophaga lithophaga found on the same substrate are at least 350 years, and up to 2000 years, older than the date of the earthquake that lifted them above sea level. These observations reveal two important effects that limit the use of radiocarbon lithophagid ages in tectonic and paleoseismological studies. The first is that the exceptional preservation potential of lithophagids allows them to remain intact and in situ long after natural death, while the substrate continues to be colonised until eventual uplift. The second, which we confirm with radiocarbon analysis of museum specimens of known age, is the incorporation of old (14C-free) carbon into lithophagid shells from the limestone host rock into which the lithophagids bored. The two effects are both significant in Crete and central Greece, and can cause the radiocarbon lithophagid ages to be up to 2000 years older than the uplift event which exposed them. Understanding these effects is important because lithophagids are far more abundantly preserved, and used to date uplift, than most other marine organisms. This study shows that they can rarely be used to distinguish uplift events, or date them to better than 1000 years, or even to distinguish whether observed uplift occurred in a single or in multiple events. After taking account of these uncertainties, the ages of the lithophagids are, however, consistent with the hypothesis that the highest prominent marine notches and exposed lithophagid holes within a few metres of sea level in Greece formed when sea level became relatively stable ~ 6000 years ago, following rapid rise after the last glacial maximum.

Item Type: Article
Uncontrolled Keywords: 2010AREP; IA61;
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title: Earth and Planetary Science Letters
Volume: 297
Page Range: pp. 395-404
Identification Number: 10.1016/j.epsl.2010.06.041
Depositing User: Sarah Humbert
Date Deposited: 25 Aug 2010 10:53
Last Modified: 23 Jul 2013 10:00

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