zvi garfunkel - Academia.edu (original) (raw)

Papers by zvi garfunkel

Journal of the Geological Society, Sep 1, 1986

Oceanic transforms generally have a complex morphology and structure and they do not conform to t... more Oceanic transforms generally have a complex morphology and structure and they do not conform to the ideal concept of simple fractures that exactly follow small circles centered on Euler poles of relative plate motions. It is proposed that the special properties of transforms arise because they are inherently leaky, i.e. new plate area forms along them. As transforms have finite widths the adjacent ridge tips are at different distances from the Euler poles, and the plate boundaries along transforms are slightly oblique to the direction of plate motions, such that new plate area forms along them. However, along transforms the normal process of seafloor spreading is interrupted and new plate area forms by a different process. Transforms are underlain by crust consisting of variable proportions of (a) material emplaced in the transform domains and (b) stretched ridge-generated crust. The transform structure is further modified by shearing, deformation related to irregularities of lateral faults and because of propagation of adjacent ridges. Transform leakiness is not considered to result merely from changes of plate motions (though such changes will influence transform structure), but it reflects the segmented structure of mid-oceanic ridges. The persistence of transforms and their migration in the absolute reference frame, with a component perpendicular to their strikes, shows that the ridge structure is decoupled from flow in deeper levels. Thermal anomalies along transforms, especially enhanced heat losses, stabilize the segmented ridge structure.

AGUFM, Dec 1, 2004

ABSTRACT

Geological Society of America Bulletin, 1972

Transform faults do not differ in any fundamental manner from ordinary transcurrent faults. They ... more Transform faults do not differ in any fundamental manner from ordinary transcurrent faults. They all must terminate on structures in which surface area is increased or decreased. This is a direct consequence of the occurrence of strike-slips on these faults. The apparent differences between oceanic ridge-ridge faults and transcurrent faults on continents are the result of the former being embedded in oceanic crust which is younger than the faulting process. The two terms are, therefore, synonymous, and also equivalent to the broader term “strike-slip fault.” Within this broad class of faults, distinctions may be made according to the magnitude of displacement, length of fault, size of blocks delimited by the faults, relations to other structures, and age relations between the faulting process and the rocks in which the fault, or fault segment, is embedded.

Geophysical Research Letters, Jul 1, 2003

High-resolutionseismictomography and magnetotelluric (MT) soundings of the shallow crust show str... more High-resolutionseismictomography and magnetotelluric (MT) soundings of the shallow crust show strong changes in material properties across the Dead Sea Transform Fault (DST) in the Arava valley in Jordan. 2D inversion results of the MT data indicate that the DST is associated with a strong lateral conductivity contrast of a highly conductive layer at a depth of approximately 1.5 km cutoff at a position coinciding with the surface trace of the DST. At the same location, we observe a sharp increase of P wave velocities from <4 km/s west of the fault to >5 km/s to the east. The high velocities in the east probably reflect Precambrian rocks while the high electrical conductivity west of the DST is attributed to saline fluids within the sedimentary filling. In this sense, the DST appears to act as an impermeable barrier between two different rock formations. Such a localized fluid barrier is consistent with models of fault zone evolution but has so far not been imaged by geophysical methods. The situation at the DST is remarkably different from active segments of the San Andreas Fault which typically show a conductive fault core acting as a fluid conduit.

Geological Society, London, Special Publications, 1984

Page 1. Permian-early Mesozoic tectonism and continental margin formation in Israel and its impli... more Page 1. Permian-early Mesozoic tectonism and continental margin formation in Israel and its implications for the history of the Eastern Mediterranean ... It has been proposed that the EasternMediterranean basin also originated from Early Mesozoic rifting (Monod et al. ...

Nature, Oct 1, 1968

THE fact that quantitative results from unrelated earth sciences confirm and complement each othe... more THE fact that quantitative results from unrelated earth sciences confirm and complement each other is a significant success of the continental drift hypothesis. The results of geophysical and oceanographical research on the age and rate of opening of the Red Sea are compared ...

Journal of Geophysical Research, Aug 11, 2007

Tomographic inversion techniques were applied to first‐arrival traveltimes of refracted P waves t... more Tomographic inversion techniques were applied to first‐arrival traveltimes of refracted P waves to study the shallowest part of the crust in the vicinity of the Arava Fault (AF), the Dead Sea Transform (DST) segment between the Dead Sea and the Red Sea; tomographic inversion techniques were applied to first‐arrival traveltimes of refracted P waves. A 100‐km‐long seismic line was centered on and oriented approximately perpendicular to the AF. A large number of P wave traveltimes from vibroseis and explosive shots (>280,000) were picked manually and used to invert for shallow P wave velocity structure. The regularized inversion approach (Zelt and Barton, 1998) was used for the tomographic inversion of the traveltimes. Extensive testing of model and inversion parameters was carried out to derive a reliable P wave velocity model. Complementary checker‐board tests indicate that depending on the size of velocity homogeneities, the velocity structure is well resolved down to a depth of several kilometers. This model represents the first shallow P wave velocity across the whole width of the DST system, showing features that correlate well with surface geology and also some buried structures. The model further suggests that the AF extends vertically downward to at least 3 km. The observed variation in upper‐crustal velocity implies the existence of a simple deformation compatible with a large lateral fault offset. From this model, a structural and dynamic interpretation of the DST system is then presented. The depth extension and geometry of several additional major faults and DST‐associated shallow sedimentary basins were successfully imaged through the integration of the well‐known surface geology and nearby boreholes. This work again confirms the DST as a typical transform fault system with a dominant strike‐slip motion confined to a narrow zone.

Gondwana Research, Dec 1, 2015

This work examines the relations between the Cadomian-type peri-Gondwana blocks and West and Nort... more This work examines the relations between the Cadomian-type peri-Gondwana blocks and West and North Africa and Arabia (WNA) and the sediments derived therefrom during the Neoproterozoic. This provides insights regarding the formation, development, and paleogeography of the Cadomian domain, and when interpreted in the framework of plate tectonic processes allows proposing an internally consistent, though tentative, picture of the Neoproterozoic history of the domain before the Cadomian orogeny. Since WNA is built of terranes that were originally dispersed over a ≥2000 km wide area (E-W), it was only when their assembly was well advanced (≤ca. 680-650 Ma ago) that they formed a continuous continental area with a well-defined margin next to which a continuous peripheral Cadomian domain could be shaped. Most likely it formed by accretion of various elements to the newly formed WNA margin, which is supported by several lines of evidence. The exposed basement rocks of the Cadomian domain are usually ≤600-580 Ma old (Late Ediacaran and Early Paleozoic). Before the Cadomian orogeny much of the domain comprised marine basins, several hundred kilometers wide, filled mainly by thick siliciclastics associated with variable amounts of igneous rocks. A large fraction of the sediments was produced by extensive erosion of WNA, but the West African Craton probably had a secondary role as a sediment source. Subduction-related igneous rocks occur in basinal areas close to the northern active margin of the Cadomian domain, and these areas were affected by the Cadomian orogeny. There arc-derived, rather than WNA-derived detritus appears to be present, proving the existence of adjacent magmatic arcs, although the arcs are little exposed. As sediment transport was necessarily down-slope, the distribution of WNA-and arcderived detritus and its termporal changes provide insights regarding the slopes of basin-floors and thus the paleogeography, while changes in their distribution most likely record tectonic activity. However, these issues still require further study. The Late Ediacaran paleogeographic setting recorded by the exposures is interpreted as comprising backarc basins and magmatic arcs, with igneous activity and deformation being more pronounced in the outboard parts of the domain (including basinal areas), similar to the situation in the Western Pacific. It is hypothesized that, as in the latter area, the entire system was controlled by retreat (roll back) of the bordering subduction zone, and that this setting was produced ca. 600 Ma ago or somewhat earlier by modification of a preexisting active margin that was initially shaped by the accretion of the Cadomian domain to WNA. However, the absence of direct evidence about the early history of the domain does not allow interpretation beyond this general picture.

Philosophical transactions of the Royal Society of London, Sep 18, 1970

Recent surface and subsurface geological investigations in Israel and Jordan provide new data for... more Recent surface and subsurface geological investigations in Israel and Jordan provide new data for the re-examination of Dubertret's (1932) hypothesis of the left-hand shear along the Dead Sea rift. It is found that while none of the pre-Tertiary sedimentary or igneous rock units extend right across the rift, all of them resume a reasonable palaeographical configuration once the east side of the rift is placed 105 km south of its present position. It is therefore concluded that the 105 km post-Cretaceous, left-hand shear along the Dead Sea rift is well established. The 40 to 45 km offset of Miocene rocks and smaller offsets of younger features indicate an average shear movement rate of 0.4 to 0.6 cm a-1 during the last 7 to 10 Ma. Unfortunately, the 60 km pre-Miocene movement cannot be dated yet. Along the Arava and Gulf of Aqaba and in Lebanon the shear is divided over a wide fault zone within and outside the rift. H istorical r e v ie w The verse '.. . and the Mount of Olives shall cleave in the midst thereof towards the east and towards the west,.. . and half of the mountain shall remove towards the north, and half of it towards the south' (Zechariah, xiv. 4), can probably be regarded as a description of left-hand shear by an ingenious observer who lacked the professional terms. One century ago Lartet (1869) noticed that Arabia and Africa might have drifted apart in an oblique left-hand direction to open up the Red Sea. About 60 years later Dubertret (1932), following Lartet's idea, advocated also by Bogolepov (1930) and von Seidlitz (1931), suggested that a 160 km left-hand shear along the Dead Sea rift, associated with a 6° rotation between Arabia and Africa, might explain several structural relations in the Levant. Wellings (in Willis 1938) realized that this hypothesis corresponds to the offset of the marine Cambrian and Jurassic beds across the rift south of the Dead Sea. Willis, however, rejected this hypothesis, and during the following 20 years it was completely neglected in papers about the geology of the Levant (e.g. Picard 1943; Dubertret 1947). It was not mentioned even in papers which discussed other strike slip faults in this region (Bentor & Vroman 1954; Renouard 1955; Vroman 1957). Quennell (1958, 1959) revived Dubertret's hypothesis, though to his opinion the shear amounts to 107 km as indicated by the offsets across the rift of a Precambrian porphyry body, of Cambrian limestone, copper and manganese sandstone, of marine Triassic and Jurassic beds, of the southern extent of the marine Albian and the Upper Cretaceous transgressions, of Senonian bituminous chalk, and of three pairs of transverse faults. Quennell suggested that a Pleistocene movement of 45 km explains several geomorphic features, the most prominent of which is the shape of the deep depression of the Dead Sea. The remaining 62 km shear was in his opinion of Miocene age.

AAPG Bulletin, 1988

... Bookmark and Share (Link will open in a new window). ... Title, Phanerozoic tectonic history ... more ... Bookmark and Share (Link will open in a new window). ... Title, Phanerozoic tectonic history of the lands bordering the southeastern Mediterranean basin. Creator/Author, Garfunkel, Z.; Derin, B. (Hebrew Univ., Jerusalem (Israel)). Publication Date, 1988 Aug 01. ...

Journal of the Geological Society

Analysis and re-evaluation of recently obtained data from seismic reflection surveys and deep off... more Analysis and re-evaluation of recently obtained data from seismic reflection surveys and deep offshore and onland boreholes from the continental margin of Israel and the adjacent Levant basin, combined with pre-existing data, provide significant new insight into their early, Triassic to Middle Jurassic, development. Thick Middle Jurassic and older sediments in the Levant basin next to Israel cover a substantial relief of a pre-existing thin crust that was shaped in the Middle Triassic or earlier times. In the Levant margin near the present-day coastal area and further onshore the early development of the basin was accompanied by two major deformation phases, in the Triassic and in the Middle Jurassic, separated by a period (much of the Late Triassic and Early Jurassic) in which deformation and subsidence slowed down considerably or ceased. In contrast, in the Mt Carmel area conspicuous faulting and magmatism took place in the Late Triassic (older history unknown); that is, during th...

European Journal of Mineralogy, 1992

Résumé/Abstract Alpine high-pressure metamorphic rocks exposed in the Cyclades were overpinted du... more Résumé/Abstract Alpine high-pressure metamorphic rocks exposed in the Cyclades were overpinted during their exhumation. We studied the metamorphic evolution of a pervasively overprinted rock sequence, the greenschist unit, exposed in the island of Sifnos. We show ...

Reviews of Geophysics, 2009

Fault zones are the locations where motion of tectonic plates, often associated with earthquakes,... more Fault zones are the locations where motion of tectonic plates, often associated with earthquakes, is accommodated. Despite a rapid increase in the understanding of faults in the last decades, our knowledge of their geometry, petrophysical properties, and controlling processes remains incomplete. The central questions addressed here in our study of the Dead Sea Transform (DST) in the Middle East are as follows: (1) What are the structure and kinematics of a large fault zone? (2) What controls its structure and kinematics? (3) How does the DST compare to other plate boundary fault zones? The DST has accommodated a total of 105 km of left-lateral transform motion between the African and Arabian plates since early Miocene ($20 Ma). The DST segment between the Dead Sea and the Red Sea, called the Arava/Araba Fault (AF), is studied here using a multidisciplinary and multiscale approach from the mm to the plate tectonic scale. We observe that under the DST a 35 narrow, subvertical zone cuts through crust and lithosphere. 36 First, from west to east the crustal thickness increases 37 smoothly from 26 to 39 km, and a subhorizontal lower 38 crustal reflector is detected east of the AF. Second, several 39 faults exist in the upper crust in a 40 km wide zone centered 40 on the AF, but none have kilometer-size zones of decreased 41 seismic velocities or zones of high electrical conductivities 42 in the upper crust expected for large damage zones. Third, 43 the AF is the main branch of the DST system, even though it 44 has accommodated only a part (up to 60 km) of the overall 45 105 km of sinistral plate motion. Fourth, the AF acts as a 46 barrier to fluids to a depth of 4 km, and the lithology 47 changes abruptly across it. Fifth, in the top few hundred 48 meters of the AF a locally transpressional regime is 49 observed in a 100-300 m wide zone of deformed and 50 displaced material, bordered by subparallel faults forming a 51 positive flower structure. Other segments of the AF have a

Reviews of Geophysics, 2010