TY - JOUR
T1 - Possible resetting of quartz OSL signals during earthquakes-Evidence from late Pleistocene injection dikes, Dead Sea basin, Israel
AU - Porat, N.
AU - Levi, T.
AU - Weinberger, R.
N1 - Funding Information:
This study was supported by grants from the Israeli Ministries of National Infrastructures and Science and the Arc en ciel—Keshet program. We would also like to thank R. Madmon and S. Zeffren for field assistance and sample preparation, Dr. M. Stein for the PZ section samples, and Dr. G.A.T. Duller from the University of Wales, Aberystwyth, for the use of the single grain reader and laboratory facilities.
PY - 2007/8/24
Y1 - 2007/8/24
N2 - Clastic dikes are formed either by passive deposition of clastic material into pre-existing fissures (depositional dikes), or by fracturing and injection of clastics during earthquakes (injection dikes). We proposed to use optically stimulated luminescence (OSL) dating to distinguish between the two modes of formation and hypothesized that (1) depositional dikes filled from above show OSL ages younger than the host rock; and (2) injection dikes filled from below show the same OSL ages as that of the host rock. We studied the mechanisms of clastic-dike formation and their ages within the seismically active Dead Sea basin, where hundreds of dikes crosscut the late Pleistocene (∼70-15 ka) lacustrine sediments of the Lisan Formation. Field observations and analysis of magnetic tensors show unequivocally that most of these dikes were emplaced by injection, inferred to be due to seismically triggered fluidization-liquefaction during earthquakes. Twenty-eight samples were collected from the Lisan source material and dikes that, based on field observations, are unmistakably either depositional dikes or injection dikes. Quartz single aliquot OSL ages of the source Lisan layers are between 43 and 34 ka, and are typical for the Lisan Formation. The ages of both depositional and injection dikes are between 15 and 17 ka, younger than the Lisan host rock. Depositional dikes show a highly scattered distribution of single grain ages, suggesting several episodes of infill. Single grain ages of injection dikes are of latest Pleistocene to Holocene, and do not contain recently bleached grains that infiltrated from above. These results imply that the OSL signals were reset at the time of fluidization-liquefaction and buildup of fluid pressure within the injection dikes. If this resetting mechanism has a physical ground, then OSL dating is an important tool for constraining the ages of earthquake-induced injection dikes and recovering paleoseismic data from them.
AB - Clastic dikes are formed either by passive deposition of clastic material into pre-existing fissures (depositional dikes), or by fracturing and injection of clastics during earthquakes (injection dikes). We proposed to use optically stimulated luminescence (OSL) dating to distinguish between the two modes of formation and hypothesized that (1) depositional dikes filled from above show OSL ages younger than the host rock; and (2) injection dikes filled from below show the same OSL ages as that of the host rock. We studied the mechanisms of clastic-dike formation and their ages within the seismically active Dead Sea basin, where hundreds of dikes crosscut the late Pleistocene (∼70-15 ka) lacustrine sediments of the Lisan Formation. Field observations and analysis of magnetic tensors show unequivocally that most of these dikes were emplaced by injection, inferred to be due to seismically triggered fluidization-liquefaction during earthquakes. Twenty-eight samples were collected from the Lisan source material and dikes that, based on field observations, are unmistakably either depositional dikes or injection dikes. Quartz single aliquot OSL ages of the source Lisan layers are between 43 and 34 ka, and are typical for the Lisan Formation. The ages of both depositional and injection dikes are between 15 and 17 ka, younger than the Lisan host rock. Depositional dikes show a highly scattered distribution of single grain ages, suggesting several episodes of infill. Single grain ages of injection dikes are of latest Pleistocene to Holocene, and do not contain recently bleached grains that infiltrated from above. These results imply that the OSL signals were reset at the time of fluidization-liquefaction and buildup of fluid pressure within the injection dikes. If this resetting mechanism has a physical ground, then OSL dating is an important tool for constraining the ages of earthquake-induced injection dikes and recovering paleoseismic data from them.
KW - Clastic dikes
KW - Dead Sea Transform
KW - Injection structures
KW - Luminescence dating
UR - http://www.scopus.com/inward/record.url?scp=34548024364&partnerID=8YFLogxK
U2 - 10.1016/j.quageo.2006.05.021
DO - 10.1016/j.quageo.2006.05.021
M3 - Article
AN - SCOPUS:34548024364
SN - 1871-1014
VL - 2
SP - 272
EP - 277
JO - Quaternary Geochronology
JF - Quaternary Geochronology
IS - 1-4
ER -