Be’eri-Shlevin, Y., Avigad, D., and Matthews, A. 2009. Granitoid intrusion and high temperature metamorphism in the Asteroussia Unit, Anafi Island (Greece): Petrology and geochronology. Isr. J. Earth Sci. 58: 13–27. A series of amphibolite facies metamorphic rocks and granitoid intrusions is exposed on Anafi Island, Cyclades (Aegean Sea). The rock association represents a klippe of the Asteroussia Unit, a high-temperature low-pressure (HT–LP) unit of Late Cretaceous age (ca. 70 Ma), which is a prominent constituent of the allochtonous Upper Unit (UU) of the Attic-Cycladic Crystalline Belt. Garnet–biotite and hornblende–plagioclase geothermometry of metapelitic and metabasic rocks and spinel chemistry of a meta-ophiolite indicate an upper amphibolite metamorphic overprint. Multigrain zircon ID-TIMS U–Pb dating of a granitic intrusion yielded an age of 85.3 ± 2.7 Ma, indicating that felsic magmatism slightly predated or was contemporary with HT–LP metamorphism. Rb–Sr dating of biotite–plagioclase pairs from two granite samples yielded ages of 63.4 ± 0.4 Ma and 48.2 ± 0.3 Ma. The older age may relate to penetrative deformation recorded in the granites, but the younger age probably represents partial resetting of the Rb–Sr system at a later stage. Comparison between the Asteroussia Unit and other occurrences of Late Cretaceous UU on Tinos, Syros, and Andros shows that the latter followed a slightly different P–T–t path. Nevertheless, all these occurrences are considered to represent the remnants of a once-continuous and extensive nappe, in agreement with previous estimates. Age resemblance of the Asteroussia Unit with Late Cretaceous magmatic arcs in NW Turkey may indicate correlation between these two terranes, although previously-suggested formation of the Late Cretaceous UU (including the Asteroussia Unit) in association with rifting of the Apulian continent cannot be ruled out. 14 Israel Journal of Earth Sciences Vol. 58, 2009
Katz, O., Amit, R., Yagoda-Biran, G., Hatzor, Y.H., Porat, N., Medvedev, B. 2009/2010. Quaternary earthquakes and landslides in the Sea of Galilee area, the Dead Sea Transform: Paleoseismic analysis and implication to the current hazard. Isr. J. Earth Sci. 58: 275–294. A few destructive large (Mw >6) earthquakes occurred close to the Sea of Galilee (SOG) in the last millennia and, along with recorded current seismicity, underscore the seismic hazard to populated areas in the region. In this study we investigate the Late-Pleistocene–Holocene seismic history of the southeastern SOG area, around the northern extension of the Jordan Valley Fault. We integrate results from paleoseismic trenching of recent fault segments rupturing the surface with slope stability analysis of a large landslide that spatially coincides with the faults, to develop a better understanding of the seismic hazard. We have dated fault rupture as well as sliding events with optically stimulated luminescence (OSL). In a series of paleoseismic trenches we found evidence for at least five Mw >6 earthquakes that were dated to ca. 45, 40, 35, 10, and 5 ka. A younger event of 6 and Mw >6.5, respectively. Such large earthquakes are expected to result in high ground acceleration of up to 0.5 g and earthquake-induced landslides around the SOG.
Lichter, M., Zviely, D., and Klein, M. 2009. Morphological changes in the last 200 years in the mouth of the Na’aman River, northern coastal plain, Israel. Isr. J. Earth sci. 58: 63–80. The Na’aman River mouth is located in Haifa Bay, at the northern end of the Nile littoral cell of Israel’s Mediterranean coast. This study documents the morphological changes to this river’s mouth over the last 200 years based on three historical maps from 1799 to 1930 as well as a series of 54 aerial photographs taken between 1945 and 2005. Mapping of morphological features and vegetation cover in the vicinity of the changing mouth was performed with a Geographic Information System (GIS); quantitative and qualitative parameters were derived from this mapping. The temporal and spatial patterns of the mouth migration were characterized and factors influencing its morphology such as vegetation cover, stream discharge, wave regime, and anthropogenic changes were analyzed. The Na’aman River mouth intermittently flows in a permanent channel along the back of the north–south beach berm. The channel remains stable for several years until a major flood diverts it. The mouth migrated 1.5 km, both north and south, along the coast during the last 200 years, about equally in either direction. An increase in vegetation cover over the years restricted the migration of the channel. River floods may cause the “resetting” of the mouth morphology and its location, but if the channel is robust, even large floods are unable to divert it. Wave direction does not seem to af fect the deflection of the channel. Anthropogenic intervention in the natural course of the mouth took place in two ways: artificial opening of the mouth to prevent flooding hazard and control the mosquito habitat, and channel diversion intended to prevent the pollution of nearby bathing beaches.
Shaked, Y., Lazar, B., Marco, S., Stein, M., and Agnon, A. 2009/2010. Late Holocene events that shaped the shoreline at the northern Gulf of Aqaba recorded by a buried fossil reef. Isr. J. Earth Sci. 58: 355‐368. Examination of fossil reefs in 3-D reveals a series of tectonic, climatic, and biological processes in the northwestern corner of the Gulf of Elat-Aqaba (GEA). We excavated a reef buried beneath clastic beach sediments, examined its morphology, and collected coral samples in situ. The reef is preserved in pristine condition due to the sedimentary cover and its position below the sea level. Coastal geomorphology and sediments are combined with evidence from the buried reef to describe the late Holocene evolution of this stretch of the coast that is shaped by activity of the Dead Sea Transform system. Radiocarbon and uranium series ages of coral samples from the reef set the temporal framework for events. At least two down-faulting events are inferred from the buried reef, at ~4.7 ka and ~2.4 ka. Following the second event the reef was completely buried and fossilized, and the shoreline propagated 100 m eastwards into the sea. Hence the present shoreline was shaped by recurrent tectonic displacements followed by redistribution of sediments along the coast.
Amotz Agnon,a Rivka Amit,b Susan Hough,c and Alessandro Maria Michettid aInstitute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel bGeological Survey of Israel, 30 Malkhe Israel Street, Jerusalem 95501, Israel cUnited States Geological Survey, 525 S. Wilson Avenue, Pasadena, California 91106, USA dDipartimento di Scienze Chimiche e Ambientali, Universita dell’Insubria, Via Valleggio 11, 22100 Como, Italy
Weinberger, R., Schattner, U., Medvedev, B., Frieslander, U., Sneh, A., Harlavan, Y., and Gross, M.R. 2009/2010. Convergent strike–slip across the Dead Sea Fault in northern Israel, imaged by high-resolution seismic reflection data. Isr. J. Earth Sci. 58: 203–216. We combine geological and geophysical observations made along the margin between the Arabian plate and Sinai sub-plate to investigate the style and sequence of deformation associated with motion along the Dead Sea Fault (DSF). Our analysis focuses on one of the youngest rock units—the Pleistocene Hazbani Basalt. Integration of field mapping, K-Ar dating, and interpretation of high-resolution seismic reflection profiles yields a map of the top surface of the Hazbani Basalt, which highlights the architecture of faulting and folding. Results attest to a dominance of both contractional structures and strike–slip faulting along the northwestern rim of the Hula basin. Our new find ings show how a series of faults extend from within the boundaries of an extensional basin and beyond its margins, and are associated with the formation of positive flower structures. The structural analysis provides evidence for a transition from an early (pre-Pleistocene) phase of almost pure strike–slip to a late (Pleistocene) phase of convergent strike–slip faulting. Many of the faults investigated in this study displace the Pleistocene Hazbani Basalt and the overlying sediments and should thus be considered as potential active faults for seismic hazard assessments.
