ALBERT

Description: The archaeological Tell Ateret (North Israel), constructed on the active Dead Sea Fault, was intermittently settled for over six millennia. Structures on the Tell that have been offset by earthquake ruptures, provide a remarkable record of alternating construction and slip. We excavated the site in order to resolve the geometry and to time the earthquake rupture history back to the earliest settlement. The measurements of faulted archaeological walls are complemented with data from historical documents, numismatic analysis, and geological observations. We report three newly discovered offsets that add to two previously resolved slip events (the 20 May 1202 and 30 October 1759 earthquakes), completing a three-millennia archaeoseismic record. The oldest offset measuring at least ~2 m bisected Iron Age IIA fortifications. The second offset, the largest of all five, reaching ~2.5 m, is dated to circa 142 BCE; the third, whose post-Hellenistic date is not determined, is of ~1.5 m, possibly resulting from multiple earthquakes. We constrain the time of the largest offset by a hoard of 45 coins, the latest of which had been minted 143/142 BCE. Indicative pottery and historic texts support the year 143/142 as terminus post-quem of the rupture at this site. These observations, together with a new kinematic approach, show uneven slip distribution in time and variable amounts of slip along the Jordan Gorge segment of the DSF. We suggest, based on previous palaeomagnetic measurements, that distributed deformation west of Tell Ateret can explain the apparent missing slip of 4.5±3.5 m since the Hellenistic times.

Description: Previous analysis of triangulation data of the Survey of India concluded that the great 1897, Assam, earthquake occurred on a south-dipping fault near the northern edge of the Shillong Plateau, which was named the Oldham Fault. This attribution has been questioned on geological and geodetic grounds. We refine the triangulation data, adding recently discovered observations, and demonstrate that they require average slip of 25±5 m on a fault that dips south at ~40° beneath the Plateau. The best-fitting solution to the geodetic observations gives a rupture length of 79 km. However, the Chedrang Fault, immediately to the west of the Oldham Fault, appears to have slipped as a sub-vertical tear fault during or shortly after the 1897 earthquake, with over 10 m of down-to-the-west normal-sense slip. This observation suggests that the western end of the main rupture approached within a few kilometers of the Chedrang Fault, giving a length of 95 km for the rupture. This range of parameters gives a magnitude 8.15〈M w 〈8.35 for the earthquake. The triangulation data cannot be satisfied by slip on the north-dipping faults that border the southern edge of the Shillong Plateau, nor by slip on a south-dipping fault that has been postulated in the Brahmaputra Valley. GPS velocities show that up to 5 mm/yr of shortening is taken up across the Plateau and its borders; this suggests, via moment-frequency relations, that the interval between great earthquakes in the region is several thousand years, but that earthquakes of magnitude 7 or greater should occur roughly once per century.

Description: The Apuseni – Banat – Timok – Srednogorie (ABTS) Late Cretaceous magmatic arc in the Carpathian –Balkan orogen formed on the European margin during closure of the Neotethys Ocean. It was subsequently deformed into a complex orocline by continental collisions. The Cu-Au mineralised arc consists of geologically distinct segments: the Apuseni, Banat, Timok, Panagyurishte and Eastern Srednogorie segments. New U-Pb zircon ages and geochemical whole rock data for the Banat and Apuseni segments are combined with previously published data to reconstruct the original arc geometry and better constrain its tectonic evolution. Trace element and isotopic signatures of the arc magmas indicate a subduction-enriched source in all segments and variable contamination by continental crust. The magmatic arc was active for 25 m.y. (~92-67 Ma). Across-arc age trends of progressively younger ages towards the inferred paleo-trench indicate gradual steepening of the subducting slab away from the upper plate European margin. This leads to asthenospheric corner flow in the overriding plate, which is recorded by decreasing 87 Sr/ 86 Sr (0.70577 to 0.70373) and increasing 143 Nd/ 144 Nd (0.51234 to 0.51264) ratios over time in some segments. The close spatial relationship between arc magmatism, large-scale shear zones and related strike-slip sedimentary basins in the Timok and Pangyurishte segments indicates mild transtension in these central segments of the restored arc. In contrast, the Eastern Srednogorie segment underwent strong orthogonal intra-arc extension. Segmental distribution of tectonic stress may account for the concentration of rich porphyry Cu deposits in the transtensional segments, where lower-crustal magma storage and fractionation favoured the evolution of volatile-rich magmas.

Description: No abstract is available for this article.

Description: A precise age for the collision of the Kohistan-Ladakh block with Eurasia along the Shyok suture zone (SSZ) is one key to understanding the accretionary history of Tibet and the tectonics of Eurasia during the India-Eurasia collision. Knowing the age of the SSZ also allows the suture to be used as a piercing line for calculating total offset along the Karakoram fault, which effectively represents the SE border of the Tibetan Plateau and has played a major role in plateau evolution. We present a combined structural, geochemical, and geochronologic study of the SSZ as it is exposed in the Nubra region of India to test two competing hypotheses: that the SSZ is of Late Cretaceous or, alternatively, of Eocene age. Coarse-continental strata of the Saltoro Molasse, mapped in this area, contain detrital zircon populations suggestive of derivation from Eurasia despite the fact that the molasse itself is deposited unconformably onto Kohistan-Ladakh rocks, indicating that the molasse is post-collisional. The youngest population of detrital zircons in these rocks (ca. 92 Ma) and a U/Pb zircon date for a dike that cuts basal molasse outcrops (ca. 85 Ma) imply that deposition of the succession began in the Late Cretaceous. This establishes a minimum age for the SSZ and rules out the possibility of an Eocene collision between Kohistan-Ladakh and Eurasia. Our results support correlation of the SSZ with the Bangong suture zone in Tibet, which implies a total offset across the Karakoram fault of ca. 130–190 km.

Description: No abstract is available for this article.

Description: A reconstruction of the Tintina fault is applied to regional geophysical and topographic data, facilitating the definition of west-trending lineaments within the lower crust and/or mantle lithosphere, oblique to the NW-trending structure of the Cordilleran terranes. The lineaments, which exhibit a range of geophysical and geological signatures, are interpreted to be related to the Liard transfer zone, continuous to the Denali fault, that divided lower and upper plates during late Proterozoic-Cambrian rifting of the Laurentian margin. 3D gravity models show a density increase in the lower crust and mantle lithosphere to the north. The transfer zone also divides bimodal mantle xenolith suites to the south from unimodal suites to the north. These conclusions suggest that extended North American basement, related to Laurentian margin rifting that would have brought mantle lithosphere rocks to a shallow depth, continuously underlies a thin carapace of accreted terranes in western Yukon and eastern Alaska. The interpreted continuity of North American basement reaffirms that if oroclinal bending of the Intermontane terranes occurred, then it was prior to its emplacement upon the rifted basement. Examination of the spatial relationships between mineral occurrences and post-accretionary, Cretaceous lithospheric lineaments, from their manifestation in geophysical, geological, and topographic data, suggests that the late Proterozoic lineaments influenced Mesozoic mineralization through influence on the development of the shallow crustal structure, intrusion, and exhumation and erosion.

Description: In this paper, the long-term crustal flow of the Iranian Plateau is computed using a kinematic finite element model (NeoKinema software). Based on the iterated weighted least square method, the models are fitted to the newest data set of Iran including updated fault traces, geologic fault offset rates, geodetic benchmark velocities, principal stress directions, and velocity boundary conditions. We are successful to find the best kinematic model, in which geological slip rates, geodetic velocities, and interpolated stress directions are fitted at levels of 0.35, 1.0, and 1.0 datum standard deviation, respectively. The best fitted model, for the first time, provides long-term fault slip rates, velocity and anelastic strain rate field in the Iranian Plateau from all available kinematic data. In order to verify the model, the estimates of fault slip rates are compared to slip rates from merely analyzing geodetic benchmark velocities or paleoseismological studies or published geological rates which have not been used in the model. Our estimated rates are all in the range of geodetic rates and are even more consistent with geological rates than previous GPS-based estimates. Using the selected model, long-term-average seismicity maps and long-term moment rates are produced on the basis of the SHIFT hypothesis and previous global calibrations. Our kinematic model also provides a new constraint on ratio of seismic deformation to total deformation for different seismic zones of Iran. The resulting slip rates and the proposed seismic fraction of deformation provide the necessary input data for future time-dependent hazard studies in Iran. Moreover, spatial distribution and total number of strong (M〉6) and major (M〉7) earthquakes, which dominate the seismic hazard, are all compatible with the regional seismic catalog.

Description: The Cenozoic East African Rift System (EARS) extends from the Red Sea to Mozambique. Here we use seismic reflection and bathymetric data to investigate the tectonic evolution of the offshore branch of the EARS. The data indicate multiple and time-transgressive neotectonic deformations along ~800 km of the continental margin of northern Mozambique. We observe a transition from a mature rift basin in the north to a juvenile fault zone in the south. The respective timing of deformation is derived from detailed seismic stratigraphy. In the north, a ~30 km wide and more than 150 km long, N-S striking symmetric graben initiated as half-graben in the Late Miocene. Extension accelerated in the Pliocene, causing a continuous conjugate border fault and symmetric rift graben. Coevally the rift started to propagate southward, which resulted in a present-day ~30 km-wide half-graben, approximately 200 km further south. Since the Pleistocene, the rift has continued to propagate another ~300 km, where the incipient rift is reflected by sub-recent small-scale normal faulting. Estimates of the overall brittle extension of the matured rift range between 5 and 12 km, with an along-strike southward decrease of the extension rate. The offshore portion of the EARS evolves magma-poor, similar to the onshore western branch. The structural evolution of the offshore EARS is suggested to be related to and controlled by differing inherited lithospheric fabrics. Pre-existing fabrics may not only guide and focus extension but also control rift architecture.

Description: Key Points List of questionable points in Clerc and Lagabrielle (2014) paper Arguments against a Cretaceous age of the migmatites and granulites Data necessary for a new model of the Mesozoic evolution of the Pyrenees