TY - JOUR A1 - Garcin, Yannick A1 - Junginger, Annett A1 - Melnick, Daniel A1 - Olago, Daniel O. A1 - Strecker, Manfred A1 - Trauth, Martin H. T1 - Late Pleistocene-Holocene rise and collapse of the Lake Suguta, northern Kenya Rift Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/02773791 U6 - https://doi.org/10.1016/j.quascirev.2008.12.006 ER - TY - JOUR A1 - Garcin, Yannick A1 - Melnick, Daniel A1 - Strecker, Manfred A1 - Olago, Daniel A1 - Tiercelin, Jean-Jacques T1 - East African mid-Holocene wet-dry transition recorded in palaeo-shorelines of Lake Turkana, northern Kenya Rift JF - Earth & planetary science letters N2 - The 'wet' early to mid-Holocene of tropical Africa, with its enhanced monsoon, ended with an abrupt shift toward drier conditions and was ultimately replaced by a drier climate that has persisted until the present day. The forcing mechanisms, the timing, and the spatial extent of this major climatic transition are not well understood and remain the subject of ongoing research. We have used a detailed palaeo-shoreline record from Lake Turkana (Kenya) to decipher and characterise this marked climatic transition in East Africa. We present a high-precision survey of well-preserved palaeo-shorelines, new radiocarbon ages from shoreline deposits, and oxygen-isotope measurements on freshwater mollusk shells to elucidate the Holocene moisture history from former lake water-levels in this climatically sensitive region. In combination with previously published data our study shows that during the early Holocene the water-level in Lake Turkana was high and the lake overflowed temporarily into the White Nile drainage system. During the mid-Holocene (similar to 5270 +/- 300 cal. yr BP), however, the lake water-level fell by similar to 50 m, coeval with major episodes of aridity on the African continent. A comparison between palaeo-hydrological and archaeological data from the Turkana Basin suggests that the mid-Holocene climatic transition was associated with fundamental changes in prehistoric cultures, highlighting the significance of natural climate variability and associated periods of protracted drought as major environmental stress factors affecting human occupation in the East African Rift System. ( KW - East African Rift System KW - Lake Turkana KW - Palaeo-shorelines KW - African Humid Period KW - Holocene KW - Tectonic deformation Y1 - 2012 U6 - https://doi.org/10.1016/j.epsl.2012.03.016 SN - 0012-821X VL - 331 SP - 322 EP - 334 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ozsayin, Erman A1 - Ciner, T. Attila A1 - Rojay, F. Bora A1 - Dirik, R. Kadir A1 - Melnick, Daniel A1 - Fernandez-Blanco, David A1 - Bertotti, Giovanni A1 - Schildgen, Taylor F. A1 - Garcin, Yannick A1 - Strecker, Manfred A1 - Sudo, Masafumi T1 - Plio-Quaternary extensional tectonics of the Central Anatolian Plateau a case study from the Tuz Golu Basin, Turkey JF - Turkish journal of earth sciences = Türk yerbilimleri dergisi N2 - The Tuz Golu Basin is the largest sedimentary depression located at the center of the Central Anatolian Plateau, an extensive, low-relief region with elevations of ca. 1 km located between the Pontide and Tauride mountains. Presently, the basin morphology and sedimentation processes are mainly controlled by the extensional Tuz Golu Fault Zone in the east and the transtensional Inonu-Eskisehir Fault System in the west. The purpose of this study is to contribute to the understanding of the Plio-Quaternary deformation history and to refine the timing of the latest extensional phase of the Tuz Golu Basin. Field observations, kinematic analyses, interpretations of seismic reflection lines, and Ar-40/Ar-39 dating of a key ignimbrite layer suggest that a regional phase of NNW-SSE to NE-SW contraction ended by 6.81 +/- 0.24 Ma and was followed by N-S to NE-SW extension during the Pliocene-Quaternary periods. Based on sedimentological and chronostratigraphic markers, the average vertical displacement rates over the past 5 or 3 Ma with respect to the central part of Tuz Golu Lake are 0.03 to 0.05 mm/year for the fault system at the western flank of the basin and 0.08 to 0.13 mm/year at the eastern flank. Paleo-shorelines of the Tuz Golu Lake, vestiges of higher lake levels related to Quaternary climate change, are important strain markers and were formed during Last Glacial Maximum conditions as indicated by a radiocarbon age of 21.8 +/- 0.4 ka BP obtained from a stromatolitic crust. Geomorphic observations and deformed lacustrine shorelines suggest that the main strand of the Tuz Golu Fault Zone straddling the foothills of the Sereflikochisar-Aksaray range has not been active during the Holocene. Instead, deformation appears to have migrated towards the interior of the basin along an offshore fault that runs immediately west of Sereflikochisar Peninsula. This basinward migration of deformation is probably associated with various processes acting at the lithospheric scale, such as plateau uplift and/or microplate extrusion. KW - Central Anatolia KW - Tuz Golu Basin KW - orogenic plateau evolution KW - extensional tectonics KW - kinematic analysis KW - lake shoreline Y1 - 2013 U6 - https://doi.org/10.3906/yer-1210-5 SN - 1300-0985 VL - 22 IS - 5 SP - 691 EP - 714 PB - Tübitak CY - Ankara ER - TY - JOUR A1 - Ballato, Paolo A1 - Uba, Cornelius Eji A1 - Landgraf, Angela A1 - Strecker, Manfred A1 - Sudo, Masafumi A1 - Stockli, Daniel F. A1 - Friedrich, Anke M. A1 - Tabatabaei, Saeid H. T1 - Arabia-Eurasia continental collision insights from late Tertiary foreland-basin evolution in the Alborz Mountains, northern Iran JF - Geological Society of America bulletin N2 - A poorly understood lag time of 15-20 m.y. exists between the initial Arabia-Eurasia continental collision in late Eocene to early Oligocene time and the acceleration of tectonic and sedimentary processes across the collision zone in the early to late Miocene. The late Eocene to Miocene-Pliocene clastic and shallow-marine sedimentary rocks of the Kond, Eyvanekey, and Semnan Basins in the Alborz Mountains (northern Iran) offer the possibility to track the evolution of this orogen in the framework of collision processes. A transition from volcaniclastic submarine deposits to shallow-marine evaporites and terrestrial sediments occurred shortly after 36 Ma in association with reversals in sediment provenance, strata tilting, and erosional unroofing. These events followed the termination of subduction arc magmatism and marked a changeover from an extensional to a contractional regime in response to initiation of continental collision with the subduction of stretched Arabian lithosphere. This early stage of collision produced topographic relief associated with shallow foreland basins, suggesting that shortening and tectonic loading occurred at low rates. Starting from the early Miocene (17.5 Ma), flexural subsidence in response to foreland basin initiation occurred. Fast sediment accumulation rates and erosional unroofing trends point to acceleration of shortening by the early Miocene. We suggest that the lag time between the initiation of continental collision (36 Ma) and the acceleration of regional deformation (20-17.5 Ma) reflects a two-stage collision process, involving the "soft" collision of stretched lithosphere at first and "hard" collision following the arrival of unstretched Arabian continental litho sphere in the subduction zone. Y1 - 2011 U6 - https://doi.org/10.1130/B30091.1 SN - 0016-7606 VL - 123 IS - 1-2 SP - 106 EP - 131 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Thiede, Rasmus Christoph A1 - Sobel, Edward A1 - Chen, Jie A1 - Schoenbohm, Lindsay M. A1 - Stockli, Daniel F. A1 - Sudo, Masafumi A1 - Strecker, Manfred T1 - Late Cenozoic extension and crustal doming in the India-Eurasia collision zone new thermochronologic constraints from the NE Chinese Pamir JF - Tectonics N2 - The northward motion of the Pamir indenter with respect to Eurasia has resulted in coeval thrusting, strike-slip faulting, and normal faulting. The eastern Pamir is currently deformed by east-west oriented extension, accompanied by uplift and exhumation of the Kongur Shan (7719m) and Muztagh Ata (7546m) gneiss domes. Both domes are an integral part of the footwall of the Kongur Shan extensional fault system (KES), a 250 km long, north-south oriented graben. Why active normal faulting within the Pamir is primarily localized along the KES and not distributed more widely throughout the orogen has remained unclear. In addition, relatively little is known about how deformation has evolved throughout the Cenozoic, despite refined estimates on present-day crustal deformation rates and microseismicity, which indicate where crustal deformation is presently being accommodated. To better constrain the spatiotemporal evolution of faulting along the KES, we present 39 new apatite fission track, zircon U-Th-Sm/He, and Ar-40/Ar-39 cooling ages from a series of footwall transects along the KES graben shoulder. Combining these data with present-day topographic relief, 1-D thermokinematic and exhumational modeling documents successive stages, rather than synchronous deformation and gneiss dome exhumation. While the exhumation of the Kongur Shan commenced during the late Miocene, extensional processes in the Muztagh Ata massif began earlier and have slowed down since the late Miocene. We present a new model of synorogenic extension suggesting that thermal and density effects associated with a lithospheric tear fault along the eastern margin of the subducting Alai slab localize extensional upper plate deformation along the KES and decouple crustal motion between the central/western Pamir and eastern Pamir/Tarim basin. KW - Pamir KW - gneiss domes KW - collision KW - extension KW - thermochronology KW - exhumation Y1 - 2013 U6 - https://doi.org/10.1002/tect.20050 SN - 0278-7407 VL - 32 IS - 3 SP - 763 EP - 779 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Sobel, Edward A1 - Chen, Jie A1 - Schoenbohm, Lindsay M. A1 - Thiede, Rasmus Christoph A1 - Stockli, Daniel F. A1 - Sudo, Masafumi A1 - Strecker, Manfred T1 - Oceanic-style subduction controls late Cenozoic deformation of the Northern Pamir orogen JF - Earth & planetary science letters N2 - The northern part of the Pamir orogen is the preeminent example of an active intracontinental subduction zone in the early stages of continent-continent collision. Such zones are the least understood type of plate boundaries because modern examples are few and of limited access, and ancient analogs have been extensively overprinted by subsequent tectonic and erosion processes. In the Pamir, it has been assumed that most of the plate convergence was accommodated by overthrusting along the plate-bounding Main Pamir Thrust (MPT), which forms the principal northern mountain and deformation front of the Pamir. However, the synopsis of our new and previously published thermochronologic data from this region shows that the hanging wall of the MPT experienced relatively minor amounts of late Cenozoic exhumation. The Pamir orogen as a whole is an integral part of the overriding plate in a subduction system, while the remnant basin to the north constitutes the downgoing plate, with the bulk of the convergence accommodated by underthrusting. Herein, we demonstrate that the observed deformation of the upper and lower plates within the Pamir-Alai convergence zone resembles highly arcuate oceanic subduction systems characterized by slab rollback, subduction erosion, subduction accretion, and marginal slab-tear faults. We suggest that the curvature of the North Pamir is genetically linked to the short width and rollback of the south-dipping Alai slab; northward motion (indentation) of the Pamir is accommodated by crustal processes related to this rollback. The onset of south-dipping subduction is tentatively linked to intense Pamir contraction following break-off of the north-dipping Indian slab beneath the Karakoram. KW - subduction accretion KW - subduction erosion KW - exhumation KW - thermochronology KW - intracontinental deformation KW - Pamir Y1 - 2013 U6 - https://doi.org/10.1016/j.epsl.2012.12.009 SN - 0012-821X VL - 363 IS - 1 SP - 204 EP - 218 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Erbello Doelesso, Asfaw A1 - Melnick, Daniel A1 - Zeilinger, Gerold A1 - Bookhagen, Bodo A1 - Pingel, Heiko A1 - Strecker, Manfred T1 - Geomorphic expression of a tectonically active rift-transfer zone in southern Ethiopia JF - Geomorphology : an international journal on pure and applied geomorphology N2 - The Gofa Province and the Chew Bahir Basin of southern Ethiopia constitute tectonically active regions, where the Southern Main Ethiopian Rift converges with the Northern Kenya Rift through a wide zone of extensional deformation with several north to northeast-trending, left-stepping en-e & PRIME;chelon basins. This sector of the Southern Main Ethiopian Rift is characterized by a semi-arid climate and a largely uniform lithology, and thus provides ideal conditions for studying the different parameters that define the tectonic and geomorphic features of this complex kinematic transfer zone. In this study, the degree of tectonic activity, spatiotemporal variations in extension, and the nature of kinematic linkage between different fault systems of the transfer zone are constrained by detailed quantitative geomorphic analysis of river catchments and focused field work. We analyzed fluvial and landscape morphometric characteristics in combination with structural, seismicity, and climatic data to better evaluate the tectono-geomorphic history of this transfer zone. Our data reveal significant north-south variations in the degree of extension from the Sawula Basin in the north (mature) to the Chew Bahir Basin in the south (juvenile). First, normalized channel-steepness indices and the spatial arrangement of knickpoints in footwall-draining streams suggest a gradual, southward shift in extensional deformation and recent tectonic activity. Second, based on 1-k(m) radius local relief and mean-hillslope maximum values that are consistent with ksn anomalies, we confirm strain localization within zones of fault interaction. Third, morphometric indices such as hypsometry, basin asymmetry factor, and valley floor width to valley height ratio also indicate a north to south gradient in tectonic activity, highlighting the importance of such a wide transfer zone with diffuse extension linking different rift segments during the break-up of continental crust. KW - rift transfer zone KW - Ethiopia rift KW - renya Rift KW - morphometric indices KW - knickpoints Y1 - 2022 U6 - https://doi.org/10.1016/j.geomorph.2022.108162 SN - 0169-555X SN - 1872-695X VL - 403 PB - Elsevier Science CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Riedl, Simon A1 - Melnick, Daniel A1 - Njue, Lucy A1 - Sudo, Masafumi A1 - Strecker, Manfred T1 - Mid-Pleistocene to recent crustal extension in the inner graben of the Northern Kenya Rift JF - Geochemistry, geophysics, geosystems N2 - Magmatic continental rifts often constitute nascent plate boundaries, yet long-term extension rates and transient rate changes associated with these early stages of continental breakup remain difficult to determine. Here, we derive a time-averaged minimum extension rate for the inner graben of the Northern Kenya Rift (NKR) of the East African Rift System for the last 0.5 m.y. We use the TanDEM-X science digital elevation model to evaluate fault-scarp geometries and determine fault throws across the volcano-tectonic axis of the inner graben of the NKR. Along rift-perpendicular profiles, amounts of cumulative extension are determined, and by integrating four new Ar-40/Ar-39 radiometric dates for the Silali volcano into the existing geochronology of the faulted volcanic units, time-averaged extension rates are calculated. This study reveals that in the inner graben of the NKR, the long-term extension rate based on mid-Pleistocene to recent brittle deformation has minimum values of 1.0-1.6 mm yr(-1), locally with values up to 2.0 mm yr(-1). A comparison with the decadal, geodetically determined extension rate reveals that at least 65% of the extension must be accommodated within a narrow, 20-km-wide zone of the inner rift. In light of virtually inactive border faults of the NKR, we show that extension is focused in the region of the active volcano-tectonic axis in the inner graben, thus highlighting the maturing of continental rifting in the NKR. KW - extensional tectonics KW - Kenya Rift KW - TanDEM-X DEM KW - DEM analysis KW - geochronology KW - normal faults Y1 - 2022 U6 - https://doi.org/10.1029/2021GC010123 SN - 1525-2027 VL - 23 IS - 3 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Georgieva, Viktoria A1 - Melnick, Daniel A1 - Schildgen, Taylor F. A1 - Ehlers, Todd A1 - Lagabrielle, Yves A1 - Enkelmann, Eva A1 - Strecker, Manfred T1 - Tectonic control on rock uplift, exhumation, and topography above an oceanic ridge collision: Southern Patagonian Andes (47 degrees S), Chile JF - Tectonics N2 - The subduction of bathymetric anomalies at convergent margins can profoundly affect subduction dynamics, magmatism, and the structural and geomorphic evolution of the overriding plate. The Northern Patagonian Icefield (NPI) is located east of the Chile Triple Junction at similar to 47 degrees S, where the Chile Rise spreading center collides with South America. This region is characterized by an abrupt increase in summit elevations and relief that has been controversially debated in the context of geodynamic versus glacial erosion effects on topography. Here we present geomorphic, thermochronological, and structural data that document neotectonic activity along hitherto unrecognized faults along the flanks of the NPI. New apatite (U-Th)/He bedrock cooling ages suggest faulting since 2-3 Ma. We infer the northward translation of an similar to 140 km long fore-arc sliver-the NPI block-results from enhanced partitioning of oblique plate convergence due to the closely spaced collision of three successive segments of the Chile Rise. In this model, greater uplift occurs in the hanging wall of the Exploradores thrust at the northern leading edge of the NPI block, whereas the Cachet and Liquine-Ofqui dextral faults decouple the NPI block along its eastern and western flanks, respectively. Localized extension possibly occurs at its southern trailing edge along normal faults associated with margin-parallel extension, tectonic subsidence, and lower elevations along the Andean crest line. Our neotectonic model provides a novel explanation for the abrupt topographic variations inland of the Chile Triple Junction and emphasizes the fundamental effects of local tectonics on exhumation and topographic patterns in this glaciated landscape. Y1 - 2016 U6 - https://doi.org/10.1002/2016TC004120 SN - 0278-7407 SN - 1944-9194 VL - 35 SP - 1317 EP - 1341 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Bookhagen, Bodo A1 - Echtler, Helmut Peter A1 - Melnick, Daniel A1 - Strecker, Manfred A1 - Spencer, Joel Q. G. T1 - Using uplifted Holocene beach berms for paleoseismic analysis on the Santa Maria Island, south-central Chile N2 - Major earthquakes ( M > 8) have repeatedly ruptured the Nazca-South America plate interface of south-central Chile involving meter scale land-level changes. Earthquake recurrence intervals, however, extending beyond limited historical records are virtually unknown, but would provide crucial data on the tectonic behavior of forearcs. We analyzed the spatiotemporal pattern of Holocene earthquakes on Santa Maria Island (SMI; 37 degrees S), located 20 km off the Chilean coast and approximately 70 km east of the trench. SMI hosts a minimum of 21 uplifted beach berms, of which a subset were dated to calculate a mean uplift rate of 2.3 +/- 0.2 m/ky and a tilting rate of 0.022 +/- 0.002 degrees/ky. The inferred recurrence interval of strandline-forming earthquakes is similar to 180 years. Combining coseismic uplift and aseismic subsidence during an earthquake cycle, the net gain in strandline elevation in this environment is similar to 0.4 m per event Y1 - 2006 UR - http://www.agu.org/journals/gl/ U6 - https://doi.org/10.1029/2006gl026734 SN - 0094-8276 ER -