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  • 1
    Language: English
    In: Basin research, 2020-08, Vol.32 (4), p.636-651
    Description: The Dead Sea is an extensional basin developing along a transform fault plate boundary. It is also a terminal salt basin. Without knowledge of precise stratigraphy, it is difficult to differentiate between the role of plate and salt tectonics on sedimentary accumulation and deformation patterns. While the environmental conditions responsible for sediment supply are reasonably constrained by previous studies on the lake margins, the current study focuses on deciphering the detailed stratigraphy across the entire northern Dead Sea basin as well as syn and post‐depositional processes. The sedimentary architecture of the late Quaternary lacustrine succession was examined by integrating 851 km of seismic reflection data from three surveys with gamma ray and velocity logs and the stratigraphic division from an ICDP borehole cored in 2010. This allowed seismic interpretation to be anchored in time across the entire basin. Key surfaces were mapped based on borehole lithology and a newly constructed synthetic seismogram. Average interval velocities were used to calculate isopach maps and spatial and temporal sedimentation rates. Results show that the Amora Formation was deposited in a pre‐existing graben bounded by two N‐S trending longitudinal faults. Both faults remained active during deposition of the late Pleistocene Samra and Lisan Formations—the eastern fault continued to bound the basin while the western fault remained blind. On‐going plate motion introduced a third longitudinal fault, increasing accommodation space westwards from the onset of deposition of the Samra Formation. During accumulation of these two formations, sedimentation rates were uniform over the lake and similar. High lake levels caused an increase in hydrostatic pressure. This led to salt withdrawal, which flowed to the south and southwest causing increased uplift of the Lisan and En Gedi diapirs and the formation of localized salt rim synclines. This induced local seismicity and slumping, resulting in an increased thickness of the Lisan succession within the lake relative to its margins. Sedimentation rates of the Holocene Ze'elim Fm were 4–5 times higher than before. The analysis presented here resolves central questions of spatial extent and timing of lithology, deposition rates and their variability across the basin, timing of faulting at and below the lake floor, and timing and extent of salt and plate tectonic phases and their effect on syn and post‐depositional processes. Plate tectonics dictated the structure of the basin, while salt tectonics and sediment accumulation were primarily responsible for its fill architecture during the timeframe examined here.
    Subject(s): Dead Sea basin ; diapirism ; ICDP ; lake sediments ; late Quaternary ; salt tectonics ; subsidence rate ; well logs
    ISSN: 0950-091X
    E-ISSN: 1365-2117
    Source: Hellenic Academic Libraries Link
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  • 2
    Language: English
    In: Geophysical research letters, 2015-09-16, Vol.42 (17), p.6989-6996
    Description: The Dead Sea Fault (DSF) is a 1000 km long continental transform. It forms a narrow and elongated valley with uplifted shoulders showing an east‐west asymmetry, which is not common in other continental transforms. This topography may have strongly affected the course of human history. Several papers addressed the geomorphology of the DSF, but there is still no consensus with respect to the dominant mechanism of its formation. Our thermomechanical modeling demonstrates that existence of a transform prior to the rifting predefined high strain softening on the faults in the strong upper crust and created a precursor weak zone localizing deformations in the subsequent transtensional period. Together with a slow rate of extension over the Arabian plate, they controlled a narrow asymmetric morphology of the fault. This rift pattern was enhanced by a fast deposition of evaporites from the Sedom Lagoon, which occupied the rift depression for a short time period. Key Points Existence of a transform and a slow rate of extension control a narrow asymmetric morphology of DSF A transform created a precursor weak zone localizing deformations in the later transtensional period This narrow rift pattern was enhanced by a fast deposition of evaporites from Sedom Lagoon
    Subject(s): Asymmetry ; Dead Sea Fault ; Deposition ; Faults ; Formations ; geodynamic modeling ; Lagoons ; Morphology ; Precursors ; rift ; sediments ; Transforms
    ISSN: 0094-8276
    E-ISSN: 1944-8007
    Source: Wiley Online Library All Backfiles
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
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  • 3
    Language: English
    In: Sedimentology, 2022-04, Vol.69 (3), p.1231-1251
    Description: Transport of continental shelf sediments to the deep ocean can be studied from displaced symbiont‐bearing larger benthic foraminifera found in turbidity current deposits. The larger benthic foraminifera habitat depth, physical characteristics and preservation serve as indicators for understanding sediment transport dynamics near the seabed and in the water column. Here, an experiment was designed to explore sediment transport in a closed flume system using simulated high current velocities. Shelf sediments from the Gulf of Eilat/Aqaba, dominated by Amphistegina papillosa and Operculina ammonoides, were subjected to 60 cm s−1 and 80 cm s−1 current velocities while collected in a 10 cm vertical sediment trap. Larger benthic foraminifera abundance, shell physical properties and preservation were analyzed and compared with the original bulk sediments. The experiment results showed that at 80 cm s−1 velocity, larger benthic foraminifera shells of all sizes and preservations are efficiently resuspended and transported in large quantities throughout the water column, as opposed to their transport as bedload by the lower velocity current. Larger benthic foraminifera shape also has a role in the transport distances and accumulation depths. Operculina ammonoides shells were found to be more portable, compared to Amphistegina papillosa, due to their flatter discoid shape. The results suggest that a threshold velocity of ca 80 cm s−1 was needed to generate the thick coarse deposits found in the Gulf of Eilat/Aqaba slope sedimentary record, which were previously suggested to be triggered by large magnitude seismic events. Lower velocities probably winnowed minor amounts of larger benthic foraminifera shells (with little or no coarser sediments) that were deposited as a thin sand layer may point to lower magnitude seismic triggers. In conclusion, larger benthic foraminifera shells are transported and deposited in accordance with their hydrodynamic properties, resulting in assemblage differentiation along the transport pathway. This study shows that the fossil biogenic composition in slope sediments includes valuable information on current velocities, transport dynamics and possible triggers in the geological record.
    Subject(s): Analysis ; Benthos ; Current velocity ; flume experiment ; Ocean bottom ; Sediment transport ; symbiont‐bearing larger benthic foraminifera ; taphonomy ; turbidites
    ISSN: 0037-0746
    E-ISSN: 1365-3091
    Source: Hellenic Academic Libraries Link
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  • 4
    Language: English
    In: Journal of geophysical research. Solid earth, 2013-03, Vol.118 (3), p.1195-1202
    Description: Oceanic transform faults respond to changes in the direction of relative plate motion. Studies have shown that short‐offset transforms generally adjust with slight bends near the ridge axis, while long‐offset ones have a remarkably different behavior. The western Pacific‐Antarctic plate boundary highlights these differences. A set of previously unpublished seismic profiles, in combination with magnetic anomaly identifications, shows how across a former, ~1250 km long transform (the Emerald Fracture Zone), plate motion changes have produced a complex geometric readjustment. Three distinct sections are recognized along this plate boundary: an eastern section, characterized by parallel, multiple fault strand lineaments; a central section, shallower than the rest of the ridge system, overprinted by a mantle plume track; and a western section, organized in a cascade of short spreading axes/transform lineaments. This configuration was produced by changes that occurred since 30 Ma in the Australia‐Pacific relative plate motion, combined with a gradual clockwise change in Pacific‐Antarctic plate motion. These events caused extension along the former Emerald Fracture Zone, originally linking the Pacific‐Antarctic spreading ridge system with the Southeast Indian ridge. Then an intra‐transform propagating ridge started to develop in response to a ~6 Ma change in the Pacific‐Antarctic spreading direction. The close proximity of the Euler poles of rotation amplified the effects of the geometric readjustments that occurred along the transform system. This analysis shows that when a long‐offset transform older than 20 Ma is pulled apart by changes in spreading velocity vectors, it responds with the development of multiple discrete, parallel fault strands, whereas in younger lithosphere, locally modified by thermal anisotropies, tensional stresses generate an array of spreading axes offset by closely spaced transforms. Key Points Long‐offset transforms respond to plate motion changes with multiple strands In young lithosphere, plate motion changes produce intratransform ridges Main tectonic causes can be invoked for plate boundary reorganizations
    Subject(s): Boundaries ; Fracture mechanics ; Geological faults ; Lithosphere ; Pacific-Antarctic ridge ; Ridges ; Spreading ; Strands ; Transforms
    ISSN: 2169-9313
    E-ISSN: 2169-9356
    Source: Alma/SFX Local Collection
    Source: Wiley-Blackwell Full Collection 2014
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  • 5
    Language: English
    In: Journal of Geophysical Research, 2006-08-11, Vol.111 (B8), p.B08402-n/a
    Description: The southward propagation of the East Africa rift presents an opportunity to study plate boundary formation. We tabulate orientation data which confirm the province of NW‐SE directed most compressive horizontal principal stress (“Wegener stress anomaly”) earlier tentatively attributed to ridge push. We also collect information on stress “regime,” described by the associated Andersonian fault type(s). We use thin shell finite element models with realistic rheology to test three causes of stress: (1) lateral variations in density moment, (2) resistance of unbroken lithosphere to relative plate rotation, and (3) stress concentration ahead of a crack tip. Models with stress due primarily to variations in density moment are unsuccessful in their predictions (59–73% incorrect regimes; 32–40° azimuth errors). Models in which Africa‐Somalia spreading is regulated at realistic rates by remote boundary conditions are more accurate (18–41% incorrect regimes; 25–35° azimuth errors). Treating the East Africa rift as a frictionless crack degrades the fit in either case. Apparently, the Wegener stress anomaly is caused primarily by resistance to the relative rotation between the Somalia and Africa plates. The East Africa rift north of 21°S may be weakened by strain but has residual friction ≥0.1. Greater strength of oceanic lithosphere is likely to cause stress increases, reorientations, and regime changes offshore. The predicted strain rate map has high rates along the rift, curving at 12°S into a western arc through Angola‐Namibia‐South Africa. Seismic hazard in Namibia may be greater than the instrumental catalog suggests. However, a number of unfit data indicate that these models represent only a first step.
    Subject(s): Computational Geophysics ; Continental tectonics ; crust and lithosphere ; Earth sciences ; Earth, ocean, space ; Exact sciences and technology ; extension ; extensional ; lithosphere ; Marine Geology and Geophysics ; Modeling ; Seismicity and tectonics ; Seismology ; stress ; Stresses ; Submarine tectonics and volcanism ; Tectonophysics
    ISSN: 0148-0227
    E-ISSN: 2156-2202
    Source: Wiley Online Library All Backfiles
    Source: Alma/SFX Local Collection
    Source: Wiley-Blackwell Full Collection 2014
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  • 6
    Language: English
    In: PloS one, 2014, Vol.9 (3), p.e91456-e91456
    Description: During the 2010-2011 E/V Nautilus exploration of the Levantine basin's sediments at the depth of 300-1300 m, densely patched orange-yellow flocculent mats were observed at various locations along the continental margin of Israel. Cores from the mat and the control locations were collected by remotely operated vehicle system (ROV) operated by the E/V Nautilus team. Microscopic observation and phylogenetic analysis of microbial 16S and 23S rRNA gene sequences indicated the presence of zetaproteobacterial stalk forming Mariprofundus spp.-like prokaryotes in the mats. Bacterial tag-encoded FLX amplicon pyrosequencing determined that zetaproteobacterial populations were a dominant fraction of microbial community in the biofilm. We show for the first time that zetaproteobacterial may thrive at the continental margins, regardless of crustal iron supply, indicating significant fluxes of ferrous iron to the sediment-water interface. In light of this discovery, we discuss the potential bioavailability of sediment-water interface iron for organisms in the overlying water column.
    Subject(s): Bacteria ; Basins (Geology) ; Bioavailability ; Biofilms ; Biology ; Cladistic analysis ; Continental margins ; Cores ; Earth Sciences ; Fluxes ; Gene sequencing ; Geographical variations ; Geography ; Geologic Sediments - microbiology ; Iron ; Iron - metabolism ; Iron compounds ; Israel ; Mats ; Metabolism ; Metabolites ; Microorganisms ; Molecular Sequence Data ; Mud-water interfaces ; Oxidation ; Oxidation-Reduction ; Patched protein ; Phylogeny ; Prokaryotes ; Proteobacteria - metabolism ; Remote Sensing Technology ; Remotely operated vehicles ; RNA ; RNA, Ribosomal, 16S - genetics ; rRNA 16S ; rRNA 23S ; Sediment-water interface ; Sediment-water interfaces ; Sediments ; Sediments (Geology) ; Sequence Analysis, DNA ; Water ; Water column
    ISSN: 1932-6203
    E-ISSN: 1932-6203
    Source: Academic Search Ultimate
    Source: PubMed Central
    Source: DOAJ Directory of Open Access Journals - Not for CDI Discovery
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  • 7
    Language: English
    In: Sedimentology, 2015-02, Vol.62 (2), p.516-540
    Description: Quaternary reef development and demise have been shown to correspond to worldwide sea‐level fluctuations and related environmental changes, yet the mechanisms and rates affecting this relationship are not well resolved. A set of high‐resolution seismic reflection and multibeam bathymetric data were interpreted. Six distinct systems of relict fringing reefs embedded within the sedimentary cover of the northern shelf of the Gulf of Elat/Aqaba were identified. The two uppermost relict fringing reefs are also exposed on the sea floor in water depths of ca 20 m and ca 60 m, along the north‐western corner of the northern Gulf of Elat/Aqaba and sub‐parallel to the current northern coast, respectively. Two other relict fringing reefs are laterally correlated to each of the last two transgressive cycles, and are inferred to have formed during decelerations in sea‐level rise during the last two deglaciations. These reefs and the units to which they are laterally correlated portray a repeating stratigraphic pattern of reef development during deposition of seismically homogeneous sediment and an ensuing demise during deposition of heterogeneous sediment. Correlation of the reef stratigraphy with rates of Late Quaternary sea‐level rise and a sediment accumulation rate from one shelf core provide age estimations for the seismic stratigraphy. Two phases of fringing reef generation occurred during the last deglaciation (since ca 18 ka); the older reef probably developed between 12·8 ka and 11·5 ka at ca 60 m below present sea‐level and the younger reef after 8·4 to 8·0 ka at ca 20 m below present sea‐level. These last two phases of reef generation are separated by a lobate seismic unit that is interpreted as fluvial‐deltaic deposits that backstepped across the shelf during the Early Holocene transgression. Results suggest that fringing reefs evolved along the northern shelf of the Gulf of Elat/Aqaba only during relative decelerations in sea‐level rise, contemporaneous with low input of terrigenous sediment and probably during a period of aridity. At present, no fringing reef grows along the northern coast of the Gulf of Elat/Aqaba, suggesting that these relatively arid periods may have been drier than Recent. The pattern of slowdown in sea‐level rise contemporaneous with conditions of increased aridity seems to have repeated during the last two sea‐level rises, approximately at the same sea‐levels, suggesting a common mechanism of short (millennium‐scale) phases of eustatic and climatic alteration during deglaciations.
    Subject(s): Climate change ; Climatic changes ; fringing reef ; high-resolution ; Quaternary ; Reefs ; sea-level ; Sediments (Geology) ; seismic reflection ; seismic stratigraphy ; sequence stratigraphy
    ISSN: 0037-0746
    E-ISSN: 1365-3091
    Source: Hellenic Academic Libraries Link
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  • 8
    Language: English
    In: The Journal of geology, 2010-05, Vol.118 (3), p.261-276
    Description: The Jericho fault is considered to be the main active fault in the northern Dead Sea–lower Jordan Valley. In previous studies it has been identified by a prominent linear topographic escarpment that is thought to be the surface expression of this fault on land north of the Dead Sea. In this study, the paleoseismic natures of the escarpment and the fault were examined. Seismic activity was investigated in a series of three trenches excavated south of the fault trace on the surface. These trenches show evidence for Late Holocene faulting. A fourth trench excavated 300 m farther to the south exposed continuous, finely laminated marl from the ∼80‐ka Samra Formation at a depth of 2–0.6 m below the surface, with no evidence of faulting. This could suggest that the fault on land is segmented and that the nature of its activity changes from north to south toward the lake. Indeed, the continuation of this fault under the waters of the Dead Sea reveals active faulting along a sharp, segmented, linear bathymetric break, where the steep margin slope on the west meets the flat lake bottom. Evidence of drastic climatic changes and erosion are present in all trenches that were excavated, indicating that the prominent escarpment may in part be an erosional feature, perhaps formed by incision of an ancient Jordan River or along a Holocene lakeshore. A channel fill of a lacustrine nature that followed a period of erosion is interpreted as a high stand of the Dead Sea, which is contemporaneous with the Younger Dryas cooling period.
    Subject(s): Cliffs ; Earthquakes ; Escarpments ; Fault lines ; Faults (Geology) ; Geomorphology ; Lakes ; Paleoseismology ; Perceptual localization ; Research ; Sediments ; Shales ; Tectonics ; Tectonics (Geology) ; Trenches
    ISSN: 0022-1376
    E-ISSN: 1537-5269
    Source: Academic Search Ultimate
    Source: Get It Now
    Source: JSTOR Arts & Sciences VI
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  • 9
    Language: English
    In: Tectonics (Washington, D.C.), 2003-12-16, Vol.22 (6), p.1076-n/a
    Description: Multichannel seismic reflection profiles, gravity measurements, and bathymetric soundings, in conjunction with field geological reconnaissance and remote sensing images, reveal with unprecedented detail the morphostructure of a major segment of the South America–Scotia plate boundary in the Tierra del Fuego region. This segment, known as the Magallanes‐Fagnano fault system, is a continental transform margin arranged in an en echelon geometry, along which prominent asymmetric basins were developed. Data acquired off the Atlantic coast of Isla Grande (the main island of Tierra del Fuego), in its central and eastern part, and in the central and western Magallanes Strait image the surface and subsurface structure of the transform fault and its associated basins. The Magallanes‐Fagnano fault system is composed of distinct tectonic lineaments that are segments of the transform system and are represented by mostly near‐vertical faults. In the Atlantic sector, the fault system trends broadly N70°E and seems to be composed by a single master fault, along which a highly asymmetric basin has formed. At around 63°W, the fault terminates by splaying into secondary normal faults that dissipate the horizontal displacement along the system. In the central eastern part of Isla Grande, the fault segments have been principally identified from analyses of remote sensing images on the basis of their morphological expression. These segments are located within river valleys and are generally associated with localized gravity minima. Lago Fagnano, a 105‐km‐long, E‐W trending depression, is a large, mostly asymmetric pull‐apart basin developed within the principal displacement zone of the Magallanes‐Fagnano fault system. Restraining bends and overlapping step‐over geometry characterize the central part of the Magallanes Strait. Along the western part of the fault system, in the vicinity of the Pacific entrance of the Magallanes Strait, asymmetric sedimentary basins have also developed. The sedimentary architecture of the basins formed within the principal displacement zone of the fault, in which the thick end of the depositional wedge abuts the transform segment, suggest simultaneous strike‐slip motion and transform‐normal extension, a common feature found in other continental transtensional environments. Strike‐slip faulting in the Tierra del Fuego region is also documented along other prominent lineaments which parallel the Magallanes‐Fagnano fault system. Along at least two of these lineaments, characterized by a remarkable morphological expression, widespread Quaternary activity occurs. The present‐day motion between the South America and Scotia plates is slow (〈5 mm/yr). Also the modern seismicity monitored in the Tierra del Fuego region is low (individual events 〈3.5 in magnitude). The low seismicity may be explained by the slow relative motion between plates and may be further affected by slip partitioning along the different segments which make up the Magallanes‐Fagnano fault array, and along the subsidiary wrench lineaments that traverse the region.
    Subject(s): geophysical data ; Local crustal structure ; Magallanes-Fagnano fault system ; Plate boundary—general ; Plate motions—present and recent ; Remote sensing ; remote sensing images ; strike-slip tectonics ; Structural Geology ; Tectonophysics ; Tierra del Fuego region
    ISSN: 0278-7407
    E-ISSN: 1944-9194
    Source: Wiley Online Library All Backfiles
    Source: Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals
    Source: Wiley-Blackwell Full Collection 2014
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  • 10
    Language: English
    In: Annual review of earth and planetary sciences, 2008-05-01, Vol.36 (1), p.357-387
    Description: The Dead Sea Fault is an active transform fault linking opening in the Red Sea with collision in the Taurus/Zagros Mountains. Motion is left-lateral and estimated at approximately 5–7 mm year−1. The fault is seismically active, and can be divided into two distinct structural segments. This study focuses on the southern segment based mainly on the wealth of geophysical data. Owing to transtention caused by oblique-slip and the overlapping of en-echelon fault strands, a series of pull-apart basins were formed along the fault's length. These basins are long and deep-reaching in places more than 10 km deep. They are characterized by extensional, compressional, and asymmetrical structures varying in size from large-scale (defining the general structure of the Dead Sea fault valley) to small-scale (defining the internal structure). This study examines the internal structure of these basins from south to north and summarizes the state of knowledge to date.
    Subject(s): Geology ; Research
    ISSN: 0084-6597
    E-ISSN: 1545-4495
    Source: Get It Now
    Source: Electronic Back Volume Collection (EBVC)
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