An oxygen isotope excursion in planktonic foraminifera from the Red Sea as an indicator of coseismic hydrothermal activity

HR: 1340h
AN: T43A-1082 [Abstracts]
TI: An oxygen isotope excursion in planktonic foraminifera from the Red Sea as an indicator of coseismic hydrothermal activity
AU: Vita-Finzi, C
EM: cvitafinzi@aol.com
AF: Natural History Museum, Cromwell Rd, London, SW7 5BD, United Kingdom
AU: * Spiro, B
EM: b.spiro@nhm.ac.uk
AF: Natural History Museum, Cromwell Rd, London, SW7 5BD, United Kingdom
AB: Analysis of the active tectonics of the Dead Sea Transform is hampered by a lack of paleoseismic data from the Red Sea. Recent field observations in Saudi Arabia accord with the palaeoshore record of other parts of the central and southern Red Sea to the effect that the coasts have undergone negligible uplift during the last 120 ka, a finding which is consistent with strike-slip as the dominant style of axial deformation. As this is a marginal sea with limited exchange with the open ocean, tectonic episodes may be recorded by the products of enhanced hydrothermal inflow. Accordingly, geochemical analysis was undertaken of biogenic-planktonic carbonates from cores taken from the sea floor. Tests of Globigerinoides ruber from Core CH10003-3 PC taken at a water depth of 1374 m in the central rift of the Red Sea revealed a major positive (>2.5‰) δ ¹⁸O excursion older than 40,000 yr. The δ ¹⁸O excursion is not associated with hardgrounds, fluctuations in δ ¹³C or any other indicator of a climatic or hydrological phase, and is therefore provisionally ascribed to a major coseismic event during which there was an intense exchange of sea water and fresh basaltic rocks, or the sudden release of fluids that had interacted with basaltic rocks for a long time, or both. The lack of any corresponding signal in ⁸⁷Sr/⁸⁶Sr ratios could result from the relatively low concentration of Sr in the hydrothermal fluid.
DE: 1034 Hydrothermal systems (0450, 3017, 3616, 4832, 8135, 8424)
DE: 4243 Marginal and semi-enclosed seas
DE: 4860 Radioactivity and radioisotopes
DE: 4870 Stable isotopes (0454, 1041)
DE: 7221 Paleoseismology (8036)
SC: Tectonophysics [T]
MN: 2007 Fall Meeting