TY - JOUR A1 - Ezpeleta, Miguel A1 - Parra, Mauricio A1 - Collo, Gilda A1 - Wunderlin, Cecilia A1 - Borrego, Angeles G. A1 - Sobel, Edward R. A1 - Glodny, Johannes T1 - Thermochronometry unveils ancient thermal regimes in the NW Pampean Ranges, Argentina BT - from Mesozoic rifting to Miocene flat-slab subduction JF - Basin research N2 - Reconstructing thermal histories in thrust belts is commonly used to infer the age and rates of thrusting and hence the driving mechanisms of orogenesis. In areas where ancient basins have been incorporated into the orogenic wedge, a quantitative reconstruction of the thermal history helps distinguish among potential mechanisms responsible for heating events. We present such a reconstruction for the Ischigualasto-Villa Union basin in the western Pampean Ranges of Argentina, where Triassic rifting and late Cretaceous-Cenozoic retroarc foreland basin development has been widely documented, including Miocene flat-slab subduction. We report results of organic and inorganic thermal indicators acquired along three stratigraphic sections, including vitrinite reflectance and X-ray diffractometry in claystones and new thermochronological [(apatite fission-track and apatite and zircon [U-Th]/He)] analyses. Despite up to 5 km-thick Cenozoic overburden and unlike previously thought, the thermal peak in the basin is not due to Cenozoic burial but occurred in the Triassic, associated with a high heat flow of up to 90 mWm(-2) and <2 km of burial, which heated the base of the Triassic strata to similar to 160 degrees C. Following exhumation, attested by the development of an unconformity between the Triassic and Late-Cretaceous-Cenozoic sequences, Cenozoic re-burial increased the temperature to similar to 110 degrees C at the base of the Triassic section and only similar to 50 degrees C 7 km upsection, suggesting a dramatic decrease in the thermal gradient. The onset of Cenozoic cooling occurred at similar to 10(-8) Ma, concomitant with sediment accumulation and thus preceding the latest Miocene onset of thrusting that has been independently documented by stratigraphic-cross-cutting relationships. We argue that the onset of cooling is associated with lithospheric refrigeration following establishment of flat-slab subduction, leading to the eastward displacement of the asthenospheric wedge beneath the South American plate. Our study places time and temperature constraints on flat-slab cooling that calls for a careful interpretation of exhumation signals in thrustbelts inferred from thermochronology only. KW - %Ro KW - Cenozoic flat-slab KW - Ischigualasto-Villa Union Basin KW - thermochronological modelling (AFT, AHe and ZHe) KW - Triassic rifting KW - XRD in the clay fraction KW - heat flow KW - burial Y1 - 2022 U6 - https://doi.org/10.1111/bre.12693 SN - 0950-091X SN - 1365-2117 VL - 34 IS - 6 SP - 1983 EP - 2012 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Ghani, Humaad A1 - Sobel, Edward A1 - Zeilinger, Gerold A1 - Glodny, Johannes A1 - Irum, Irum A1 - Sajid, Muhammad T1 - Spatio-temporal structural evolution of the Kohat fold and thrust belt of Pakistan JF - Journal of structural geology N2 - The Kohat fold and thrust belt in Pakistan shows a significantly different structural style due to the structural evolution on the double décollement compared to the rest of the Subhimalaya. In order to better understand the spatio-temporal structural evolution of the Kohat fold and thrust belt, we combine balanced cross sections with apatite (U?Th-Sm)/He (AHe) and apatite fission track (AFT) dating. The AHe and AFT ages appear to be totally reset, allowing us to date exhumation above structural ramps. The results suggest that deformation began on the frontal Surghar thrust at-15 Ma, predating or coeval with the development of the Main Boundary thrust at-12 Ma. Deformation propagated southward from the Main Boundary thrust on double de?collements between 10 Ma and 2 Ma, resulting in a disharmonic structural style inside the Kohat fold and thrust belt. Thermal modeling of the thermochronologic data suggest that samples inside Kohat fold and thrust belt experienced cooling due to formation of the duplexes; this deformation facilitated tectonic thickening of the wedge and erosion of the Miocene to Pliocene foreland strata. The spatial distribution of AHe and AFT ages in combination with the structural forward model suggest that, in the Kohat fold and thrust belt, the wedge deformed in-sequence as a supercritical wedge (-15-12 Ma), then readjusted by out-sequence deformation (-12-0 Ma) within the Kohat fold and thrust belt into a sub-critical wedge. KW - Balanced cross section KW - Fold and thrust belt KW - Duplex KW - Exhumation KW - Décollement Y1 - 2021 U6 - https://doi.org/10.1016/j.jsg.2021.104310 SN - 0191-8141 VL - 145 PB - Elsevier CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Ghani, Humaad A1 - Sobel, Edward A1 - Zeilinger, Gerold A1 - Glodny, Johannes A1 - Zapata, Sebastian A1 - Irum, Irum T1 - Palaeozoic and Pliocene tectonic evolution of the Salt Range constrained by low-temperature thermochronology JF - Terra nova N2 - The Salt Range in Pakistan exposes Precambrian to Pleistocene strata outcropping along the Salt Range Thrust (SRT). To better understand the in-situ Cambrian and Pliocene tectonic evolution of the Pakistan Subhimalaya, we have conducted low-temperature thermochronological analysis using apatite (U-Th-Sm)/He and fission track dating. We combine cooling ages from different samples located along the thrust front of the SRT into a thermal model that shows two major cooling events associated with rifting and regional erosion in the Late Palaeozoic and SRT activity since the Pliocene. Our results suggest that the SRT maintained a long-term average shortening rate of similar to 5-6 mm/yr and a high exhumation rate above the SRT ramp since similar to 4 Ma. KW - exhumation KW - fault bend fold KW - ramp KW - Salt Range Y1 - 2020 U6 - https://doi.org/10.1111/ter.12515 SN - 0954-4879 SN - 1365-3121 VL - 33 IS - 3 SP - 293 EP - 305 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Leon, Santiago A1 - Cardona, Agustin A1 - Parra, Mauricio A1 - Sobel, Edward A1 - Jaramillo, Juan S. A1 - Glodny, Johannes A1 - Valencia, Victor A. A1 - Chew, David A1 - Montes, Camilo A1 - Posada, Gustavo A1 - Monsalve, Gaspar A1 - Pardo-Trujillo, Andres T1 - Transition from collisional to subduction-related regimes BT - an example from neogene Panama-Nazca-South america interactions JF - Tectonics N2 - A geological transect across the suture separating northwestern South America from the Panama Arc helps document the provenance and thermal history of both crustal domains and the suture zone. During middle Miocene, strata were being accumulated over the suture zone between the Panama Arc and the continental margin. Integrated provenance analyses of those middle Miocene strata show the presence of mixed sources that includes material derived from the two major crustal domains: the old northwestern South American orogens and the younger Panama Arc. Coeval moderately rapid exhumation of Upper Cretaceous to Paleogene sediments forming the reference continental margin is suggested from our inverse thermal modeling. Strata within the suture zone are intruded by similar to 12 Ma magmatic arc-related plutons, marking the transition from a collisional orogen to a subduction-related one. Renewed late Miocene to Pliocene acceleration of the exhumation rates is the consequence of a second tectonic pulse, which is likely to be triggered by the onset of a flat-slab subduction of the Nazca plate underneath the northernmost Andes of Colombia, suggesting that late Miocene to Pliocene orogeny in the Northern Andes is controlled by at least two different tectonic mechanisms. Y1 - 2017 U6 - https://doi.org/10.1002/2017TC004785 SN - 0278-7407 SN - 1944-9194 VL - 37 IS - 1 SP - 119 EP - 139 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Zapata, Sebastian A1 - Sobel, Edward A1 - Del Papa, Cecilia A1 - Glodny, Johannes T1 - Upper Plate Controls on the Formation of Broken Foreland Basins in the Andean Retroarc Between 26°S and 28°S BT - From Cretaceous Rifting to Paleogene and Miocene Broken Foreland Basins JF - Geochemistry, Geophysics, Geosystems N2 - Marked along-strike changes in stratigraphy, mountain belt morphology, basement exhumation, and deformation styles characterize the Andean retroarc; these changes have previously been related to spatiotemporal variations in the subduction angle. We modeled new apatite fission track and apatite (U-Th-Sm)/He data from nine ranges located between 26 degrees S and 28 degrees S. Using new and previously published data, we constructed a Cretaceous to Pliocene paleogeographic model that delineates a four-stage tectonic evolution: extensional tectonics during the Cretaceous (120-75 Ma), the formation of a broken foreland basin between 55 and 30 Ma, reheating due to burial beneath sedimentary rocks (18-13 Ma), and deformation, exhumation, and surface uplift during the Late Miocene and the Pliocene (13-3 Ma). Our model highlights how preexisting upper plate structures control the deformation patterns of broken foreland basins. Because retroarc deformation predates flat-slab subduction, we propose that slab anchoring may have been the precursor of Eocene-Oligocene compression in the Andean retroarc. Our model challenges models which consider broken foreland basins and retroarc deformation in the NW Argentinian Andes to be directly related to Miocene flat subduction. KW - Northern Sierras Pampeanas KW - Fission-track thermochronology KW - Middle Eocene deformation KW - Santa-Barbara system KW - flat-slab subduction KW - tectonic inversion KW - Apatite (U-TH)/HE KW - Puna Plateau KW - radiation-damage KW - length measurements Y1 - 2019 VL - 21 IS - 7 PB - John Wiley & Sons, Inc. CY - New Jersey ER - TY - JOUR A1 - Halama, Ralf A1 - Glodny, Johannes A1 - Konrad-Schmolke, Matthias A1 - Sudo, Masafumi T1 - Rb-Sr and in situ Ar-40/Ar-39 dating of exhumation-related shearing and fluid-induced recrystallization in the Sesia zone (Western Alps, Italy) JF - Geosphere N2 - The Sesia zone in the Italian Western Alps is a piece of continental crust that has been subducted to eclogite-facies conditions and records a complex metamorphic history. The exact timing of events and the significance of geochronological information are debated due to the interplay of tectonic, metamorphic, and metasomatic processes. Here we present new geochronological data using Rb-Sr internal mineral isochrons and in situ Ar-40/Ar-39 laser ablation data to provide constraints on the relative importance of fluid-mediated mineral replacement reactions and diffusion for the interpretation of radiogenic isotope signatures, and on the use of these isotopic systems for dating metamorphic and variably deformed rocks. Our study focuses on the shear zone at the contact between two major lithological units of the Sesia zone, the eclogitic micaschists and the gneiss minuti. Metasedimentary rocks of the eclogitic micaschists unit contain phengite with step-like zoning in major element chemistry as evidence for petrologic disequilibrium. Distinct Ar-40/Ar-39 spot ages of relict phengite cores and over-printed rims demonstrate the preservation of individual age domains in the crystals. The eclogitic micaschists also show systematic Sr isotope disequilibria among different phengite populations, so that minimum ages of relict assemblage crystallization can be differentiated from the timing of late increments of deformation. The preservation of these disequilibrium features shows the lack of diffusive re-equilibration and underpins that fluid-assisted dissolution and recrystallization reactions are the main factors controlling the isotope record in these subduction-related metamorphic rocks. Blueschist-facies mylonites record deformation along the major shear zone that separates the eclogitic micaschists from the gneiss minuti. Two Rb-Sr isochrones that comprise several white mica fractions and glaucophane constrain the timing of this deformation and accompanying near-complete blueschist-facies re-equilibration of the Rb-Sr system to 60.1 +/- 0.9 Ma and 60.9 +/- 2.1 Ma, respectively. Overlapping ages in eclogitic micaschists of 60.1 +/- 1.1 (Rb-Sr isochron of sheared matrix assemblage), 58.6 +/- 0.8, and 60.9 +/- 0.4 Ma (white mica Ar-40/Ar-39 inverse isochron ages) support the significance of this age and show that fluid-rock interaction and partial re-equilibration occurred as much as several kilometers away from the shear zone. An earlier equilibration during high-pressure conditions in the eclogitic mica schists is recorded in minimum Rb-Sr ages for relict assemblages (77.2 +/- 0.8 and 72.4 +/- 1.1 Ma) and an Ar-40/Ar-39 inverse isochron age of 75.4 +/- 0.8 Ma for white mica cores, again demonstrating that the two isotope systems provide mutually supporting geochronological information. Local reactivation and recrystallization along the shear zone lasted >15 m.y., as late increments of deformation are recorded in a greenschist-facies mylonite by a Rb-Sr isochron age of 46.5 +/- 0.7 Ma. Y1 - 2018 U6 - https://doi.org/10.1130/GES01521.1 SN - 1553-040X VL - 14 IS - 4 SP - 1425 EP - 1450 PB - American Institute of Physics CY - Boulder ER - TY - JOUR A1 - Willner, Arne P. A1 - van Staal, Cees R. A1 - Zagorevski, A. A1 - Glodny, Johannes A1 - Romer, Rolf L. A1 - Sudo, Masafumi T1 - Tectonometamorphic evolution along the Iapetus suture zone in Newfoundland BT - Evidence for polyphase Salinic, Acadian and Neoacadian very low- to medium-grade metamorphism and deformation JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - The Red Indian Line (RIL) in central Newfoundland is the suture, where the main tract of the Iapetus Ocean was closed at similar to 452 Ma during accretion of the peri-Gondwanan Victoria arc with the composite active Laurentian margin. The protracted deformation history of this soft collision started at similar to 471 Ma with accretion of oceanic terranes to the active composite Laurentian margin. After Iapetus closure both colliding active margins were progressively deformed and metamorphosed during Silurian and Devonian (Salinic, Acadian and Neoacadian orogenic cycles). Peak conditions of the very low- to medium-grade, heterogeneously distributed metamorphism were determined by pseudosection techniques within the range of 2-7 kbar, 230-450 degrees C during increase of the metamorphic field gradient from similar to 12 degrees C/km to similar to 32 degrees C/km over time. Multiple metamorphic crystallisation stages were dated by white mica Ar-40/Ar-39 spot and plateau ages, additional Rb-Sr mineral isochrons involving white mica and one U/Pb age of titanite. All resulting ages between 439 +/- 4 Ma and 356 +/- 16 Ma postdate the closure of Iapetus. Results differ along two transects: The oldest ages of 443-421 Ma (Salinic orogenic cycle) were observed along the northern transect through the RIL zone with minimal younger overprint. Hence low temperature, intermediate to high pressure conditions (4.0-7.0 kbar, 230-340 degrees C) achieved during Taconic-Salinic underthrusting are well preserved. During Acadian dextral transpression the Taconic-Salinic structural wedge was tilted subvertically. In contrast, rocks along the southern transect through the RIL zone mainly show Acadian ages of 408-390 Ma with local preservation of older ages. Acadian deformation occurred under low temperature/low pressure conditions (similar to 250-450 degrees C, 2.5-4.6 kbar). Also Silurian terrestrial cover rocks were buried under these conditions. Acadian-Neoacadian deformation (393-340 Ma) becomes younger towards the northwest and progressively localized in transcurrent fault zones. This final foreland deformation at shallow crustal level established the Acadian/Neoacadian orogenic front in central Newfoundland slightly northwest of the RIL. KW - IAPETUS suture KW - PT pseudosection KW - White mica Ar-40/ Ar-39 spot ages KW - Rb-Sr mineral isochron KW - U/Pb dating of titanite KW - Salinic KW - Acadian KW - Neoacadian orogenic cycles Y1 - 2018 U6 - https://doi.org/10.1016/j.tecto.2018.05.023 SN - 0040-1951 SN - 1879-3266 VL - 742 SP - 137 EP - 167 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Willner, Arne P. A1 - Barr, Sandra M. A1 - Glodny, Johannes A1 - Massonne, Hans-Joachim A1 - Sudo, Masafumi A1 - Thomson, Stuart N. A1 - Van Staal, Cees R. A1 - White, Chris E. T1 - Effects of fluid flow, cooling and deformation as recorded by Ar-40/Ar-39, Rb-Sr and zircon fission track ages in very low- to low-grade metamorphic rocks in Avalonian SE Cape Breton Island (Nova Scotia, Canada) JF - Geological magazine N2 - Ar-40/Ar-39 in situ UV laser ablation of white mica, Rb-Sr mineral isochrons and zircon fission track dating were applied to determine ages of very low- to low-grade metamorphic processes at 3.5 +/- 0.4 kbar, 280 +/- 30 degrees C in the Avalonian Mira terrane of SE Cape Breton Island (Nova Scotia). The Mira terrane comprises Neoproterozoic volcanic-arc rocks overlain by Cambrian sedimentary rocks. Crystallization of metamorphic white mica was dated in six metavolcanic samples by Ar-40/Ar-39 spot age peaks between 396 +/- 3 and 363 +/- 14 Ma. Rb-Sr systematics of minerals and mineral aggregates yielded two isochrons at 389 +/- 7 Ma and 365 +/- 8 Ma, corroborating equilibrium conditions during very low- to low-grade metamorphism. The dated white mica is oriented parallel to foliations produced by sinistral strike-slip faulting and/or folding related to the Middle-Late Devonian transpressive assembly of Avalonian terranes during convergence and emplacement of the neighbouring Meguma terrane. Exhumation occurred earlier in the NW Mira terrane than in the SE. Transpression was related to the closure of the Rheic Ocean between Gondwana and Laurussia by NW-directed convergence. The Ar-40/Ar-39 spot age spectra also display relict age peaks at 477-465 Ma, 439 Ma and 420-428 Ma attributed to deformation and fluid access, possibly related to the collision of Avalonia with composite Laurentia or to earlier Ordovician-Silurian rifting. Fission track ages of zircon from Mira terrane samples range between 242 +/- 18 and 225 +/- 21 Ma and reflect late Palaeozoic reburial and reheating close to previous peak metamorphic temperatures under fluid-absent conditions during rifting prior to opening of the Central Atlantic Ocean. KW - Ar-40/Ar-39 spot ages KW - Rb-Sr mineral isochrons KW - zircon fission tracks KW - very low-low-grade metamorphism KW - Avalonia KW - Devonian transpression KW - Rheic Ocean Y1 - 2015 U6 - https://doi.org/10.1017/S0016756814000508 SN - 0016-7568 SN - 1469-5081 VL - 152 IS - 5 SP - 767 EP - 787 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Bachmann, Raik A1 - Oncken, Onno A1 - Glodny, Johannes A1 - Seifert, Wolfgang A1 - Georgieva, Viktoria A1 - Sudo, Masafumi T1 - Exposed plate interface in the European Alps reveals fabric styles and gradients related to an ancient seismogenic coupling zone N2 - We present observations from a continuous exposure of an ancient plate interface in the depth range of its former seismogenic zone in the central Alps of Europe related to Late Cretaceous-early Tertiary subduction and accretion of the South Penninic lower plate underneath the Adriatic upper plate. The material forming the exposed plate interface zone has experienced flow and fracturing over an extended period of time followed by syncollisional exhumation, thus reflecting a multistage evolution. Fabric formation and metamorphism, however, chiefly record the deformation conditions of the precollisional setting along the plate interface. We identify an unstable slip domain from pseudotachylytes occurring in the temperature range between 200 and 300 degrees C. This zone coincides with a domain of intense veining in the subduction melange with mineral growth into open cavities, indicating fast, possibly seismic, rupture. Evidence for transient near-lithostatic fluid pressure as well as brittle fractures competing with mylonitic shear zones continues into the region below the occurrence of pseudotachylytes, possibly reflecting a zone of conditionally stable slip. The zone above the unstable slip area is devoid of veins but displays ample evidence of fluid-assisted processes similar to the deeper zone: solution-precipitation creep and dehydration reactions in the melange matrix, hydration, and sealing of the base of the upper plate. Seismic rupture here is possibly expressed by ubiquitous localized deformation zones. We hypothesize that trenchward sealing of parts of the plate interface as well as reaction-enhanced destruction of upper plate permeability is an important component, localizing the unstable slip zone. This relation may result from the competition of the pervasive, presumably interseismic, pressure solution creep destroying permeability and building elevated fluid pressure until the strength threshold is reached with seismic failure. Y1 - 2009 UR - http://www.agu.org/journals/jb/ U6 - https://doi.org/10.1029/2008jb005927 SN - 0148-0227 ER - TY - JOUR A1 - Blisniuk, Peter Michael A1 - Hacker, Bradley R. A1 - Glodny, Johannes A1 - Ratschbacher, Lothar A1 - Bi, Siwen A1 - Wu, Zhenhan A1 - McWilliams, Michael O. A1 - Calvert, Andy T1 - Normal faulting in central Tibet since at least 13.5 Myr Y1 - 2001 ER -