Quantifying the slip rates, spatial distribution and evolution of active normal faults from geomorphic analysis: Field examples from an oblique-extensional graben, southern Turkey

Quantifying the extent to which geomorphic features can be used to extract tectonic signals is a key challenge in the Earth Sciences. Here we analyse the drainage patterns, geomorphic impact, and long profiles of bedrock rivers that drain across and around normal faults in a regionally significant oblique-extensional graben (Hatay Graben) in southern Turkey that has been mapped geologically, but for which there are poor constraints on the activity, slip rates and Plio-Pleistocene evolution of basin-bounding faults. We show that drainage in the Hatay Graben is strongly asymmetric, and by mapping the distribution of wind gaps, we are able to evaluate how the drainage network has evolved through time. By comparing the presence, size, and distribution of long profile convexities, we demonstrate that the northern margin of the graben is tectonically quiescent, whereas the southern margin is bounded by active faults. Our analysis suggests that rivers crossing these latter faults are undergoing a transient response to ongoing tectonic uplift, and this interpretation is supported by classic signals of transience such as gorge formation and hill slope rejuvenation within the convex reach. Additionally, we show that the height of long profile convexities varies systematically along the strike of the southern margin faults, and we argue that this effect is best explained if fault linkage has led to an increase in slip rate on the faults through time from ∼ 0.1 to 0.45 mm/yr. By measuring the average length of the original fault segments, we estimate the slip rate enhancement along the faults, and thus calculate the range of times for which fault acceleration could have occurred, given geological estimates of fault throw. These values are compared with the times and slip rates required to grow the documented long-profile convexities enabling us to quantify both the present-day slip rate on the fault (0.45 ± 0.05 mm/yr) and the timing of fault acceleration (1.4 ± 0.2 Ma). Our results have substantial implications for predicting earthquake hazard in this densely populated area (calculated potential Mw = 6.0-6.6), enable us to constrain the tectonic evolution of the graben through time, and more widely, demonstrate that geomorphic analysis can be used as an effective tool for estimating fault slip rates over time periods > 106 years, even in the absence of direct geodetic constraints. © 2008 Elsevier B.V. All rights reserved

Record of Cenozoic sedimentation from the Amanos Mountains, Southern Turkey: Implications for the inception and evolution of the Arabia-Eurasia continental collision

The sedimentary succession of the southern Amanos Mountains, bordering the eastern margin of the Karasu Rift in south central Turkey, provides a record of environmental change from the Eocene (Lutetian) to the Upper Miocene (Tortonian) that charts the final evolution of the northern margin of the Arabian plate prior to and during continental collision. Eocene shallow-marine carbonates (Haci{dotless}daǧi{dotless} Formation) are interpreted as the youngest unit of the Arabian passive margin succession deposited on a northwards facing carbonate ramp. Subsequent deformation and uplift took place during the Oligocene represented by folding of the Eocene and older strata. This is interpreted to be the result of initial continental collision between Arabia and Eurasia. Unconformably overlying the Eocene limestone are Lower Miocene conglomerates, sandstones and palaeosols up to 150 m thick (Ki{dotless}ci{dotless} Formation). These were deposited in a range of marginal marine settings consisting of alluvial fan/fan delta facies, flood plain as well as basinal facies. Subsequently, during the Middle Miocene, local patch reefs developed in restricted areas (Kepez Formation) followed by Upper Miocene sediments (Gökdere Formation) composed of relatively deep water hemipelagic marl, with clastic interbeds, which represent a transgression during this period. The Upper Miocene becomes sandier upwards, this records the regression from the relatively deep water facies to coastal sediments. Water depth gradually became shallower until during Pliocene time the area became continental in nature. By the Quaternary rifting had resulted in the development of the Karasu Rift with active alluvial fans along the margins and braided rivers depositing coarse conglomerates in the axial zone. These conglomerates are interbedded with basaltic lava flows that resulted from the region extension across the area. This research shows that initial continental collision occurred in this area after the Lutetian (40.4 Ma) and before the Aquitanian (23.03 Ma) supporting the hypothesis that the southern Neotethys Ocean closed during the Late Eocene to Oligocene. This was a time of climatic change including the onset of southern hemisphere glaciation, in which the closure of the southern Neotethys may have had played an important role. © 2009 Elsevier B.V. All rights reserved

Block and boulder accumulations on the southern coast of Crete (Greece): evidence for the 365 CE tsunami in the Eastern Mediterranean

The Eastern Mediterranean is one of the most seismically active regions in Europe. Crete, located in the centre of the Eastern Mediterranean, should experience tsunamis resulting from large magnitude earthquakes or volcanic eruptions. At three locations boulders were observed that may relate to tsunami or storm events. At Lakki, the size of the boulders slightly favours a tsunami origin for deposition. By contrast, at Kommos boulder size and geomorphology is consistent with storm parameters in the Mediterranean. The most compelling evidence for tsunami transport is found at Diplomo Petris, where a lithologically varied grouping of large boulders (≤ 690 t) is exposed at sea level. The calculated storm wave heights (15 m) required to transport the observed boulders significantly exceeds winter averages; therefore, these accumulations are interpreted as tsunami deposits. Radiocarbon dating of encrusting biological material was undertaken to constrain periods of boulder motion. Encrustations from Diplomo Petris and Lakki pre-date the 365 CE earthquake suggesting that this event transported the largest boulders; the first time boulder deposits have been identified on Crete from this tsunami. Therefore, these data are important for developing local and regional hazard assessments but also to inform numerical models of tsunami propagation in the Mediterranean

Spotlight on the Replisome: Aetiology of DNA Replication-Associated Genetic Diseases.

Human development and tissue homeostasis depend on the regulated control of cellular proliferation and differentiation. DNA replication is essential to couple genome duplication and cell division with the establishment and maintenance of cellular differentiation programs. In eukaryotes, DNA replication is performed by a large machine known as the 'replisome,' which is strictly regulated in a cell cycle-dependent manner. Inherited mutations of replisome components have been identified in a range of genetic conditions characterised by developmental abnormalities and reduced organismal growth in addition to an involvement of the immune and endocrine systems and/or heightened tumour predisposition. Here, we review the current knowledge of the molecular genetics of replisome dysfunction disorders and discuss recent mechanistic insights into their pathogenesis, with a focus on the specific steps of DNA replication affected in these human diseases

Geomorphic and geological constraints on the active normal faulting of the Gediz (Alaşehir) Graben, Western Turkey.

The Gediz (Alaşehir) Graben is located in the highly tectonically active region of Western Turkey. Extension due to regional geodynamic controls has resulted in a broadly two-phase evolution of the graben; firstly, low-angle normal faulting relating to the exhumation of the Menderes Massif metamorphic core complex took place between 16 - 2.6 Ma. Secondly, high-angle normal faulting initiated ~ 2 Ma forming the Gediz and other E-W trending grabens in the region. Here we quantify the throw rate along the fault array over the last 2.6, 2 and 0.7 Ma using structural and geological constraints, along with analysis of topographic relief as a proxy for footwall uplift. We derive, for the first time, time averaged rates of fault motion from 0.4 mm/yr to 1.3 mm/yr along the strike of the Gediz Graben, with variation in throw-rate associated with the geometry of individual fault strands. Patterns in throw-rate along strike of the graben bounding fault array also suggest that the fault segments have become linked during the last 2.6 - 2 Ma, possibly at 0.8 – 0.7 Ma. Furthermore, these data suggest that an earthquake occurring along the graben bounding fault could have a maximum predicted Mw of 6.3 - 7.6