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Lateral movement of lithospheric fragments along strike-slip faults in response to collision (escape tectonics) has characterized convergent settings since the onset of plate tectonics and is a mechanism for the formation of new plates. The Anatolian plate was created by the sequential connection of strike-slip faults following ≥10 m.y. of distributed deformation that ultimately localized into plate-bounding faults. Thermochronology data and seismic images of lithosphere structure near the East Anatolian fault zone (EAFZ) provide insights into the development of the new plate and escape system. Low-temperature thermochronology ages of rocks in and near the EAFZ are significantly younger than in other fault zones in the region, e.g., apatite (U-Th)/He: 11–1 Ma versus 27–13 Ma. Young apatite (U-Th)/He ages and thermal history modeling record thermal resetting along the EAFZ over the past ~5 m.y. and are interpreted to indicate thermal activity triggered by strike-slip faulting in the EAFZ as it formed as a through-going, lithosphere-scale structure. The mechanism for EAFZ formation may be discerned from S-wave velocity images from the Continental Dynamics–Central Anatolian Tectonics (CD-CAT) seismic experiment. These images indicate that thin but strong Arabian lithospheric mantle extends ~50–150 km north beneath Anatolian crust and would have been located near the present surficial location of the Bitlis-Zagros suture zone (co-located with the EAFZ in our study area) at ca. 5 Ma. Underthrusting of strong Arabian lithosphere facilitated localization of the EAFZ and thus was a fundamental control on the formation of the Anatolian plate and escape system.

Marine sediments, obtained from cores and captures from deep sea and continental shelf sites of West Antarctica, contain rich records of latest Miocene to Present glacial and deglacial processes and conditions at the margin of the West Antarctic ice sheet (WAIS). The materials we are investigating were recovered from a) Resolution Drift on the Amundsen Sea continental rise (water depths >3900m), b)the continental shelf in the Amundsen Sea, Wrigley Gulf, and Sultzberger Bay (water depths

The effects of Arabia-Eurasia collision are recorded in faults, basins, and exhumed metamorphic massifs across eastern and central Anatolia. These faults and basins also preserve evidence of major changes in deformation and associated sedimentary processes along major suture zones including the Inner Tauride suture where it lies along the southern (Ecemiş) segment of the Central Anatolian fault zone. Stratigraphic and structural data from the Ecemiş fault zone, adjacent NE Ulukışla basin, and metamorphic dome (Niğde Massif) record two fundamentally different stages in the Cenozoic tectonic evolution of this part of central Anatolia. The Paleogene sedimentary and volcanic strata of the NE Ulukışla basin (Ecemiş corridor) were deposited in marginal marine to marine environments on the exhuming Niğde Massif and east of it. A late Eocene–Oligocene transpressional stage of deformation involved oblique northward thrusting of older Paleogene strata onto the eastern Niğde Massif and of the eastern massif onto the rest of the massif, reburying the entire massif to >10 km depth and accompanied by left-lateral motion on the Ecemiş fault zone. A profound change in the tectonic setting at the end of the Oligocene produced widespread transtensional deformation across the area west of the Ecemiş fault zone in the Miocene. In this stage, the Ecemiş fault zone had at least 25 km of left-lateral offset. Before and during this faulting episode, the central Tauride Mountains to the east became a source of sediments that were deposited in small Miocene transtensional basins formed on the Eocene–Oligocene thrust belt between the Ecemiş fault zone and the Niğde Massif. Normal faults compatible with SW-directed extension cut across the Niğde Massif and are associated with a second (Miocene) re-exhumation of the Massif. Geochronology and thermochronology indicate that the transtensional stage started at ca. 23–22 Ma, coeval with large and diverse geological and tectonic changes across Anatolia.

The stratigraphic record of Cenozoic uplift and denudation of the Himalayas is distributed across its peripheral foreland basins, as well as in the sediments of the Ganges–Brahmaputra Delta (GBD) and the Bengal–Nicobar Fan (BNF). Recent interrogation of Miocene–Quaternary sediments of the GBD and BNF advance our knowledge of Himalayan sediment dispersal and its relationship to regional tectonics and climate, but these studies are limited to IODP boreholes from the BNF (IODP 354 and 362, 2015-16) and Quaternary sediment cores from the GBD (NSF-PIRE: Life on a tectonically active delta, 2010-18). We examine a complementary yet understudied stratigraphic record of the Miocene–Pliocene ancestral Brahmaputra Delta in outcrops of the Indo-Burman Ranges fold–thrust belt (IBR) of eastern India. We present detailed lithofacies assemblages of Neogene delta plain (Tipam Group) and intertidal to upper-shelf (Surma Group) deposits of the IBR based on two ∼ 500 m stratigraphic sections. New detrital-apatite fission-track (dAFT) and (U-Th)/He (dAHe) dates from the Surma Group in the IBR help to constrain maximum depositional ages (MDA), thermal histories, and sediment accumulation rates. Three fluvial facies (F1–F3) and four shallow marine to intertidal facies (M1–M4) are delineated based on analog depositional environments of the Holocene–modern GBD. Unreset dAFT and dAHe ages constrain MDA to ∼ 9–11 Ma for the Surma Group, which is bracketed by intensification of turbidite deposition on the eastern BNF (∼ 13.5–6.8 Ma). Two dAHe samples yielded younger (∼ 3 Ma) reset ages that we interpret to record cooling from denudation following burial resetting due to a thicker (∼ 2.2–3.2 km) accumulation of sediments near the depocenter. Thermal modeling of the dAFT and dAHe results using QTQt and HeFTy suggest that late Miocene marginal marine sediment accumulation rates may have ranged from ∼ 0.9 to 1.1 mm/yr near the center of the paleodelta. Thermal modeling results imply postdepositional cooling beginning at ∼ 8–6.5 Ma, interpreted to record onset of exhumation associated with the advancing IBR fold belt. The timing of post-burial exhumation of the IBR strata is consistent with previously published constraints for the avulsion of the paleo-Brahmaputra to the west and a westward shift of turbidite deposition on the BNF that started at ∼ 6.8 Ma. Our results contextualize tectonic controls on basin history, creating a pathway for future investigations into autogenic and climatic drivers of behavior of fluvial systems that can be extracted from the stratigraphic record.

We present the first results of fission-track dating of apatite monofractions from two rock samples taken from the Southern carbonatite massif of the world’s largest alkaline ultrabasic Guli pluton (~250 Ma), located within the Maymecha-Kotuy region of the Siberain Traps. Based on the apatite fission-track data and computer modeling, we propose two alternative model of the Guli pluton's tectonothermal history. The models suggest (1) rapid post-magmatic cooling of the studied rocks in hypabyssal conditions at depth about 1.5 km, or (2) their burial under a 2-3 km thick volcano-sedimentary cover and reheating above 110°C, followed by uplift and exhumation ca. 218 Ma.

U.S. National Science Foundation (NSF) [Tectonics-EAR-1140068]; Conoco Fellowship scholarship (2016); Chevron Texaco Geology Fellowship (2016); University of Arizona Galileo Circle Scholarship (2017); U.S. National Science Foundation (NSF) [NSF EAR-1338583, EAR1649254]

The Harz Mountains represent one of the most prominent surface expressions of Late Cretaceous intraplate shortening in Central Europe. We present a comprehensive low-temperature thermochronological data set (zircon and apatite, fission track and [U–Th]/He) covering the exhumed Paleozoic basement of the Harz Mountains and the adjacent Kyffhauser block, as well as Lower Triassic sedimentary rocks of the western and southern rim of the Harz Mountains. Integration of results with sedimentological data from the syntectonic Late Cretaceous Subhercynian Basin allows for a detailed reconstruction of the timing of uplift and erosion of the Harz Mountains. The data reveal that (i) tectonic reorganization and initial exhumation started at around 90 Ma, (ii) uplift and emergence caused erosion of the Mesozoic sedimentary cover between 86–85 Ma and 83–82 Ma, and (iii) erosion of at least 3–4 km of underlying Paleozoic rocks followed and continued into the Paleogene. The thickness of removed overburden amounts to at least 6 km, and most erosion occurred in Santonian to Campanian time at minimum rates of ~ 0.5 km/Myr. The southwestern rim of the Harz has exhumed slower over a longer period of time, and may record a phase of Late Cretaceous, syntectonic sediment accumulation.

Russian Science Foundation [16-17-10260]; Russian Government [220, 14.Z50.31.0017]; grant of President of Russian Federation [MD1116.2018.5]; State scientific program of IPGG; IPE RAS; state assignment project of Sobolev Institute of Geology and Mineralogy, Siberian Branch of Russian Academy of Sciences [0330-2016-0013]

International audience; The Cenozoic history of crustal deformation, surface uplift, and erosion of the central Colorado Plateau (southwestern USA) is distinct from and relatively poorly understood compared with surrounding regions in the North American Cordillera, including the Grand Canyon region and the southwestern Plateau margin. Here, we present new apatite thermochronologic results from Paleozoic-Mesozoic sandstones sampled in the Canyonlands region-the interior of the Colorado Plateau in southeastern Utah. The apatite (U-Th-Sm)/He (He) ages are highly dispersed, with both positive-slope and negative-slope age-effective U (eU) trends. Samples with apatite He results suitable for thermal history modeling are from the Abajo and La Sal mountains intrusive complexes and the Permian, Triassic, and Jurassic rocks sampled near the Colorado River at Lees Ferry, Arizona, and Hite, Utah. Samples with the richest thermal history information have positive-slope apatite He age-[eU] trends, with ages ca. 10 to 5 Ma at [eU] < 10 ppm and ca. 25 to 20 Ma at [eU] > 60 ppm. Modeled thermal histories that best predict this pattern require two periods of rock cooling: one during the middle Cenozoic ca. 30 to 20 Ma and the other since the latest Miocene ca. 6 Ma. The most recent cooling documents the transition from a slowly eroding Miocene landscape to recent rapid erosion that likely postdates 6 Ma and the integration of the modern Colorado River. Middle Cenozoic rock cooling can be attributed to either ϳ1 km of erosion between ca. 25 and 15 Ma, as previous workers have suggested in other parts of the Colorado Plateau region, or relaxation of a geothermal gradient transiently doubled by magmatism associated with the vigorous magmatic flare-up that swept through the region ca. 34 to 20 Ma. The ambiguity of using middle Cenozoic rock cooling as a proxy for erosion in this region means that this event should be described using a nongenetic term: the Middle Cenozoic Cooling Event.

Cenozoic growth of the Andes has been strongly influenced by subduction dynamics, inherited crustal heterogeneities, and the superposed effects of climate. Subduction of the Carnegie Ridge in Ecuador has impacted late Cenozoic magmatism and tectonic activity, including the formation of a crustal sliver escaping northward. However, the relationship between ridge subduction and topographic growth has remained unclear. We present new thermochronological data from the Western Cordillera of Ecuador to (1) pinpoint the timing of ridge subduction, and (2) evaluate the role of ridge subduction in prompting growth of the Ecuadorian Andes. Time-temperature inverse modeling of our results shows two phases of cooling separated by tectonic quiescence. The first cooling phase immediately post-dates magmatism in the Western Cordillera, and hence we attribute it to magmatic cooling. The second cooling phase starts at ~6-5 Ma. This we associate with onset of enhanced exhumation at this time in the Western Cordillera, synchronous with the last cooling phase in the Eastern Cordillera. Based on our thermal modeling and thermochronological age patterns along geological cross-sections we propose that recent crustal shortening and rock uplift triggered exhumation of Western Ecuadorian Andes starting at ~6-5 Ma. We suggest that the onset of Carnegie Ridge subduction in the latest Miocene increased the coupling at the subduction interface and promoted shortening and regional rock uplift in the northern Andes. Overall, our new thermochronological results highlight the pivotal role of bathymetric anomalies in distinct upper-plate deformation processes at non-collisional convergent plate margins.

IODP Expedition 379 to the Amundsen Sea continental rise recovered latest Miocene-Holocene sediments from two sites on a drift in water depths >3900m. Sediments are dominated by clay and silty clay with coarser-grained intervals and ice-rafted detritus (IRD) (Gohl et al. 2021, doi:10.14379/iodp.proc.379.2021). Cobble-sized dropstones appear as fall-in, in cores recovered from sediments >5.3 Ma. We consider that abundant IRD and the sparse dropstones melted out of icebergs formed due to Antarctic ice-sheet calving events. We are using petrological and age characteristics of the clasts from the Exp379 sites to fingerprint their bedrock provenance. The results may aid in reconstruction of past changes in icesheet extent and extend knowledge of subglacial bedrock.Mapped onshore geology shows pronounced distinctions in bedrock age between tectonic provinces of West or East Antarctica (e.g. Cox et al. 2020, doi:10.21420/7SH7-6K05; Jordan et al. 2020, doi.org/10.1038/s43017-019-0013-6). This allows us to use geochronology and thermochronology of rock clasts and minerals for tracing their provenance, and ascertain whether IRD deposited at IODP379 drillsites originated from proximal or distal Antarctic sources. We here report zircon and apatite U-Pb dates from four sand samples and five dropstones taken from latest Miocene, early Pliocene, and Plio-Pleistocene-boundary sediments. Additional Hf isotope data, and apatite fission track and 40Ar/39Ar Kfeldspar ages for some of the same samples help to strengthen provenance interpretations.The study revealed three distinct zircon age populations at ca. 100, 175, and 250 Ma. Using Kolmogorov-Smirnov (K-S) statistical tests to compare our new igneous and detrital zircon (DZ) U-Pb results with previously published data, we found strong similarities to West Antarctic bedrock, but low correspondence to prospective sources in East Antarctica, implying a role for icebergs calved from the West Antarctic Ice Sheet (WAIS). The ~100 Ma age resembles plutonic ages from Marie Byrd Land and islands in Pine Island Bay. The ~250 and 175 Ma populations match published mineral dates from shelf sediments in the eastern Amundsen Sea Embayment as well as granite ages from the Antarctic Peninsula and the Ellsworth-Whitmore Mountains (EWM). The different derivation of coarse sediment sources requires changes in iceberg origin through the latest Miocene, early Pliocene, and Plio/Pleistocene, likely the result of changes in WAIS extent.One unique dropstone recovered from Exp379 Site U1533B is green quartz arenite, which yielded mostly 500-625 Ma detrital zircons. In visual appearance and dominant U-Pb age population, it resembles a sandstone dropstone recovered from Exp382 Site U1536 in the Scotia Sea (Hemming et al. 2020, https://gsa.confex.com/gsa/2020AM/meetingapp.cgi/Paper/357276). K-S tests yield high values (P ≥ 0.6), suggesting a common provenance for both dropstones recovered from late Miocene to Pliocene sediments, despite the 3270 km distance separating the sites. Comparisons to published data, in progress, narrow the group of potential on-land sources to exposures in the EWM or isolated ranges at far south latitudes in the Antarctic interior. If both dropstones originated from the same source area, they could signify dramatic shifts in the WAIS grounding line position, and the possibility of the periodic opening of a seaway connecting the Amundsen and Weddell Seas.

Phosphatic peloids and pebble-sized microbially-bound sediment clasts have been identified within dolomitic sediment that separates centimetric columnar stromatolites in a 20–150 cm thick horizon from the 2.4–2.2 Ga Turee Creek Group in Western Australia. Petrographic examination of the phosphatic clasts reveals complex internal textures that are defined by different mixtures of fine-grained apatite, medium-grained dolomite, irregular domains of partly euhedral micro-quartz, and carbonaceous matter. Phosphatic sand-sized peloids observed within microbially-bound sediment clasts are similar in size, texture, and composition to the individual peloids in the intercolumn sediment. Both occurrences have finely dispersed kerogen throughout and zoned cores that are packed with both microscopic apatite granules and larger, euhedral quartz crystals. The percentage of apatite vs quartz vs kerogen varies between studied peloids. Similar-sized, white peloids in the intercolumn sediment and in the microbially-bound sediment clasts contain illite and are lined internally by euhedral apatite crystals, 20–100 µm in size. Some peloids are kerogenous in one domain and illite-bearing in another. The phosphatic microbially-bound sediment clasts and peloids are interpreted to represent fragments of a peritidal phosphorite, redeposited in an offshore setting during high energy events. Peloids formed within the microbially-bound sediment and were subsequently eroded out and redeposited in the intercolumn sediment. White peloids are interpreted to represent peloids affected by surficial weathering during temporary exposure, when the fine-grained kerogenous interior was replaced by clays. These weathered peloids were then re-sedimented and captured both within microbially-bound sediment and in the intercolumn sediment. Euhedral apatite crystals that line the insides of illite-bearing white peloids were dated to 2104 ± 70 Ma and 2041 ± 33 Ma, using U-Pb and Th-Pb dating methods, respectively. This age is interpreted to represent the time of metamorphic fluid circulation during a period of known regional metamorphism, and provides a minimum age of the reef complex.

The thermal history of the Siberian platform has not been studied and only single thermochronological study is available now [Rosen et al., 2009]. According to high-precision U-Pb dating the main phase of magmatic activity of the Siberian Traps Large Igneous Province took place ~252.0-251.3 Ma [Kamo et al., 2003] and its duration didn’t exceed ~1 Myr. But according to Ar/Ar dating (~240 Ma) [Ivanov et al., 2013] the total duration of the Siberian Traps formation may be estimated as long as ~10 Myr. In addition, single apatite fission track (AFT) ages are approximately 222-185 Ma [Rosen et al., 2009].We present the first results of AFT dating from the Guli pluton and computer modeling of its post-magmatic cooling, as well as some new AFT ages from other magmatic bodies within the Siberian platform. Based on these data we present the first model of the tectonothermal evolution of the Siberian platform in Mesozoic and Cenozoic.The Guli massif is located within the Maymecha-Kotuy region of the Siberian Permian-Triassic Traps and is the world's largest alkaline-ultrabasic complex. Results of U-Pb dating of baddeleyite from the carbonatites – the latest intrusion phase – 250.2±0.3 Ma [Kamo et al., 2003] correspond to the time of massif’s crystallization.AFT dating was conducted by an external detector method at the University of Arizona (Tucson). The fission track ages of the Guli are in the range of ~250-231 Ma with the mean standard error (1σ) ±34 Myr. In addition, we obtain five new AFT ages as well as U-Pb age obtained from different intrusive bodies within the Siberian platform: Kontayskaya intrusion, Odikhincha massif and Padunsky sill. All obtained AFT ages are in the range of 195-173 ±13 (1σ) Ma, which corresponds to the Early-Middle Jurassic. At the same time, the U-Pb LA-ICPMS age of apatite from Padunsky sill is 242±7 Ma.Thermal history modeling using fission track age data and track lengths distribution was performed in HeFTy v.1.8.3. Based on the obtained results we consider the following model of tectonic-thermal evolution of the studied intrusive massifs: (1) the emplacement of intrusions ca. 250 Ma; (2) their burial under a thick sedimentary (volcanic?) cover; (3) regional exhumation and cooling below 110°C about 220-190 Ma.The research was carried out with the support of RFBR (grants 18-35-20058 and 18-05-00590) and Programs of development of Lomonosov Moscow State University.

The Tavakaiv Quartzite (informal) in Colorado, USA, is one of the world's largest basement-hosted clastic injectite systems and provides a glimpse into the tectonic and near-surface environment of ancient North America. The age, origin, and significance of Tavakaiv injectites has been debated for over a century, owing to inherent difficulties with assigning absolute age constraints to unfossiliferous sandstone intrusions. Here, we apply an innovative combination of single-crystal hematite (U–Th)/He thermochronometry and fluid inclusion microthermometry to hematite mineralization associated with the injectites to document the age and ambient fluid conditions of Tavakaiv injectite formation. Our approach confirms individual hematite crystals comprising commonly analyzed polycrystalline aggregates are the He diffusion domains and that hematite (U–Th)/He closure temperature increases with crystal size. We apply apatite and zircon fission-track thermochronometry to the Tavakaiv Quartzite and host rock to account for the consequences of Phanerozoic orogenic episodes on the hematite (U–Th)/He dates and explain the observed trends between hematite He date and crystal size. Our results indicate that hematite formed 676 ± 26 million years ago (arithmetic mean date ± 1 σ ), constraining the timing of the Tavakaiv injection event. Fluid inclusion studies reveal that this mineralizing fluid was at least 200 °C and saline (>20 wt% CaCl2 equiv.). Comparison of new and previously published detrital zircon U–Pb age populations from quartzite samples yield a sediment source common to Tavakaiv bodies across a broader region and illuminate the greater areal extent of the Cryogenian injection event. We interpret that formation of basement-penetrating fracture arrays was associated with crustal extension within Rodinia at this time. This was accompanied by sand remobilization that promoted widespread sand injection within horsts bounding Neoproterozoic rift basins. The resulting sand injectites served as permeable pathways for contemporaneous circulation of saline groundwater, driven by fluid gradients in extensional and/or transtensional basins.

The Žermanice locality represents the best-exposed example of the meta-basaltoid/meta-gabbroic rock type of the teschenite association. It forms a subhorizontal volcanic body (sill) 27–30 m thick. The subvolcanic rock is inhomogeneous and slightly differentiated. The predominant rock type is a basaltoid (diabase-dolerite), medium-grained, speckled, mesocratic rock exhibiting an evident subophitic texture. Miarolitic cavities are abundant in some places. The major rock constituents are albite, microcline, chlorite, and pyroxene, as well as analcime and plagioclase in places. The accessory magmatic phases are biotite, ilmenite, fluorapatite, sulphides, Ti-rich magnetite, Nb-rich baddeleyite, and chevkinite–(Ce) or perrierite–(Ce). A large extent of alteration is evident from the presence of chloritization, albitization of plagioclases, and zeolitization (analcimization). Geochemical analyses reveal an affinity for metaluminous igneous rocks. The best fit is with the within-plate basalts or the within-plate volcanic zones. The classification of this rock is problematic because of the mixed intrusive and extrusive features; the choice is between meta-alkali basalt and metadolerite (meta-microgabbro). 207Pb common lead-corrected U–Pb apatite dating yields a weighted mean age of 120.4 ± 9.6 Ma, which corresponds to the middle Aptian. The igneous body is at most ca. 10 Ma younger than the surrounding late Hauterivian sediments and might have been emplaced into unconsolidated or partly consolidated sediments. According to our research, it is evident that at least some teschenite association rocks are in fact low-grade metamorphic rocks.

Apatite (U-Th)/He thermochronology has the potential to reconstruct records of erosional exhumation that are critical to understanding interactions between climate, tectonics, and the cryosphere at high latitudes on million-year timescales. However this approach is often hindered by the problem of intrasample single-grain date dispersion. Here we present an extensive new apatite (U-Th)/He dataset (n = 361) from the central Transantarctic Mountains of East Antarctica between 160°E to 170°W and 84 to 86°S, and show that apparently uninterpretable data in most samples are a reflection of inadequate sampling of skewed date distributions. We outline a workflow for interpreting such dispersed data and demonstrate that geologically meaningful age interpretations are possible in the case of rapidly cooled samples, despite the wide array of potential causes for date dispersion. We show that for samples and compilations with a large number of single-grain analyses (n > ∼25), the youngest probability distribution peak represents the most likely time of fast cooling through the apatite (U-Th)/He closure temperature. When fewer grains are analyzed, the youngest peak is represented best by the minimum date or first quartile date, depending on sample size. Using this workflow, we show that since the latest Eocene, up to 8.8 km of exhumation occurred to incise the deepest point of the Beardmore Glacier trough. Rapid incision began at c. 37-34 Ma (at the latest by 34±3 Ma), coinciding with or slightly preceding the initiation of Antarctic glaciation at the Eocene-Oligocene transition, and contributed to at least 2.6 km of exhumation within the first 3-6 million years, at an apparent exhumation rate of no less than 0.4 mm/a.

Bolin Centre for Climate Research; Royal Swedish Academy of Sciences [GS2015-0002]; Stiftelsen Lars Hiertas Minne [FO2015-0130]; Swedish Foundation for International Cooperation in Research and Higher Education [IB2015-6002]; Stiftelsen Anna-Greta och Holger Crafoords fond; Stockholm University

We report apatite and zircon fission-track data across the contact zones between the Menderes nappes, the Cycladic blueschist unit, and the Oren nappe, in the Anatolide belt of southwest Turkey. These data resolve previous debate on the deformation history of these Cretaceous to Eocene nappe contacts, including whether they were reactivated during late Oligocene to Miocene crustal extension. Apatite fission-track ages range from 18 to 28 Ma in the Menderes nappes, and 31 to 42 Ma in the Oren nappe. Zircon fission-track ages are 29 to 31 Ma in the Menderes nappes, 30 to 33 Ma in the Cycladic blueschist unit, and between 93 Ma and 129 Ma in the Oren nappe. The data reveal that the tectonic contacts within the Menderes nappes, and with the overlying Cycladic blueschist unit have been sealed since ~ 35–30 Ma. In the Oren nappe, zircon fission-track ages are distinctly older (with mixed single grain ages between ~ 300 and 75 Ma) reflecting partial to full resetting during late Cretaceous high-pressure metamorphism. The contact between the Cycladic blueschist unit and the Oren nappe shows no significant tectonic movement in the brittle crust after ~ 70 Ma. These data reveal that the nappe boundaries in the southern Menderes Massif have undergone no significant differential offset relative to the Earth's surface since the Oligocene and therefore were not reactivated during late Oligocene to Miocene continental extension. We interpret the steeply dipping portion of the nappe pile in the southern Menderes Massif as a tilted crustal section, which we name the ‘South Menderes Monocline’. We speculate this monocline formed by differential uplift in the Miocene, either at the hinge zone of a plateau, or by unloading of the Simav detachment footwall.

We report fault-slip data across the boundary between the highly extended and largely submerged crust underlying the Aegean Sea from Samos in the north to eastern Crete in the south, and the much less extended and emergent crust of western Anatolia. We identify three brittle deformation increments, a late Miocene (mainly Pliocene) to Recent crustal stretching increment, an intermittent early to late Miocene shortening increment concurrent with extension and magmatism, and a Miocene extensional event. The youngest increment documents late Miocene to Recent NNE extension over large areas, but can locally also be oriented SE (Amorgos and Astipalea Islands), and ESE (eastern Crete) suggesting overall oblate strain geometry. The intermittent Miocene (~ 24–5 Ma) fault-slip records suggest overall prolate strain geometry, where NNE stretching is accompanied by E–W shortening. The older extension event is mainly NNE directed but on Samos Island extension is E–W, probably reflecting local extension in a sinistral wrench corridor in the early/mid Miocene. Overall it seems that since the early Miocene NNE-trending extension is the dominant regime in the eastern Aegean with an intermittent component of short-lived E–W shortening. The existence of a corridor of heterogeneous crustal deformation – which is spatially associated with uncharacteristically old fission track ages – and the apparent change in strain geometry in time challenge concepts that propose that the eastern Aegean Sea and western Anatolia have been deformed as a continuous tectonic domain since the Miocene. We propose that the regional variation in extensional strain geometry resulted from a sinistral wrench component that was superimposed on the regional ‘background’ NNE extension by translation across a diffuse plate boundary. We conclude that the eastern shoreline of the Aegean Sea is controlled by a Miocene to Recent sinistral wrench corridor that accommodated movement between different lithospheric domains.

Exhumation and landscape evolution along strike‐slip fault systems reflect tectonic processes that accommodate and partition deformation in orogenic settings. We present 17 new apatite (U‐Th)/He (He), zircon He, apatite fission‐track (FT), and zircon FT dates from the eastern Denali fault zone (EDFZ) that bounds the Kluane Ranges in Yukon, Canada. The dates elucidate patterns of deformation along the EDFZ. Mean apatite He, apatite FT, zircon He, and zircon FT sample dates range within ~26–4, ~110–12, ~94–28, and ~137–83 Ma, respectively. A new zircon U‐Pb date of 113.9 ± 1.7 Ma (2σ) complements existing geochronology and aids in interpretation of low‐temperature thermochronometry data patterns. Samples ≤2 km southwest of the EDFZ trace yield the youngest thermochronometry dates. Multimethod thermochronometry, zircon He date‐effective U patterns, and thermal history modeling reveal rapid cooling ~95–75 Ma, slow cooling ~75–30 Ma, and renewed rapid cooling ~30 Ma to present. The magnitude of net surface uplift constrained by published paleobotanical data, exhumation, and total surface uplift from ~30 Ma to present are ~1, ~2–6, and ~1–7 km, respectively. Exhumation is highest closest to the EDFZ trace but substantially lower than reported for the central Denali fault zone. We infer exhumation and elevation changes associated with ~95–75 Ma terrane accretion and EDFZ activity, relief degradation from ~75–30 Ma, and ~30 Ma to present exhumation and surface uplift as a response to flat‐slab subduction and transpressional deformation. Integrated results reveal new constraints on landscape evolution within the Kluane Ranges directly tied to the EDFZ during the last ~100 Myr.

National Science Foundation (NSF); ARCS (Achievement Rewards for College Scientists); P.E.O. (Philanthropic Educational Organization); NSF grant [EAR-1219653, EAR-1338583]

The Chinese Altai Mountains in western China are bound by Cenozoic transpressional strike-slip faults, many of which show Quaternary activity. To better understand how Mesozoic–Cenozoic deformation has affected the history of exhumation and uplift of the Chinese Altai Mountains, we collected Paleozoic granitoid samples for apatite fission track and apatite U-Th-Sm/He thermochronology. Central apatite fission track ages for N = 6 samples range from 68 to 104 Ma, whereas apatite U-Th-Sm/He ages range from 56 to 272 Ma for N = 23 samples (n = 80 individual analyses) across four transects in the western Chinese Altai. Our results indicate fast cooling during the late Early Cretaceous followed by slow cooling since. Thermal modeling results suggests

Following Appalachian orogenesis, metamorphic rocks in central Newfoundland were exhumed and reburied under Tournaisian strata. New zircon fission‐track (ZFT) ages of metamorphic rocks below the Tournaisian unconformity yield post‐depositionally reset ages of 212–235 Ma indicating regional fluid‐absent reheating to at least ≥220°C. Post‐Tournaisian sedimentary thicknesses in surrounding basins show that burial alone cannot explain such temperatures, thus requiring that palaeo‐geothermal gradients increased to ≥30–40°C/km before final late Triassic accelerated cooling. We attribute these elevated palaeo‐geothermal gradients to localized thermal blanketing by insulating sediments overlying radiogenic high‐heat‐producing granitoids. Late Triassic rifting and magmatism before break up of Pangaea likely also contributed to elevated heat flow, as well as uplift, triggering late Triassic accelerated cooling and exhumation. Thermochronological ages of 240–200 Ma are seen throughout Atlantic Canada, and record rifting and basaltic magmatism on the conjugate margins of the Central Atlantic Ocean preceding the onset of oceanic spreading at ~190 Ma.

40Ar/39Ar 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°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 40Ar/39Ar 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 40Ar/39Ar 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., Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe, 584

The paleogeographic reconstruction of the Variscan Mountains during late Carboniferous-Permian post-orogenic extension remains poorly understood, owing to the subsequent erosion and/or burial of most associated sedimentary basins during the Mesozoic. The Graissessac-Lodeve Basin (southern France) preserves a thick and exceptionally complete record of continental sedimentation spanning late Carboniferous through late Permian time. This section records the localized tectonic and paleogeographic evolution of southern France in the context of the low-latitude Variscan Belt of Western Europe. This study presents new detrital zircon and framework mineralogy data that address the provenance of siliciclastic strata exposed in the basin. The ages and compositions of units that constitute the Montagne Noire metamorphic core complex (west of the basin) dictate the detrital zircon age populations and sandstone compositions in Permian strata, recording rapid exhumation and unroofing of the Montagne Noire dome. Cambrian-Archean zircons and metamorphic lithic-rich compositions record derivation from recycled detritus of the earliest Paleozoic sedimentary cover and Neoproterozoic-early Cambrian metasedimentary Schistes X, which formerly covered the Montagne Noire dome. Ordovician zircons and subarkosic framework compositions indicate erosion of orthogneiss units that formed a large part of the dome. The youngest zircon population (320–285 Ma) reflects derivation from late Carboniferous-early Permian granite units in the axial zone of the Montagne Noire. This population appears first in the early Permian, persists throughout the Permian section and is accompanied by sandstone compositions dominated by feldspar, polycrystalline quartz and metamorphic lithic fragments. The most recent migmatization, magmatism and deformation occurred ca. 298 ± 2 Ma, at ca. 17 km depth (based on peak metamorphic conditions). Accordingly, these new provenance data, together with zircon fission-track thermochronology, demonstrate that exhumation of the Montagne Noire core complex was rapid (1–17 mm year−1) and early (300–285 Ma), reflecting deep-seated uplift in the southern Massif Central during post-orogenic extension.

The thermal history of the Kola Peninsula area of NE Fennoscandia remains almost fully unknown because of the absence of any thermochronological data such as apatite and/or zircon fission track or (U Th)/He ages. In order to fill this gap and to constrain the post-Devonian erosion and exhumation history of this region, we present the results of apatite fission track (AFT) dating of eleven samples selected from the cores taken from different depths of the northern part of the Khibina intrusive massif. The Rb Sr isochron age of this alkaline magmatic complex which is located at the center of Kola Peninsula is 368 + 6 Ma (Kramm and Kogarko, 1994). Samples were analyzed from depths between + 520 and − 950 m and yielded AFT ages between 290 and 268 Ma with an age uncertainty (1σ) of between ± 19 Ma (7%) and ± 42 Ma (15%). Mean track lengths (MTL) lie between 12.5 and 14.4 μm. Inverse time–temperature modeling was conducted on the age and track length data from seven samples of the Khibina massif. Thermal histories that best predict the measured data from three samples with the most reliable data show three stages: (1) 290–250 Ma—rapid cooling from > 110 °C to 70 °C/50 °C for lower/upper sample correspondingly; (2) 250–50 Ma—a stable temperature stage; (3) 50–0 Ma—slightly increased cooling rates down to modern temperatures. We propose that the first cooling stage is related to late-Hercynian orogenesis; the second cooling stage may be associated with tectonics accompanying with opening of Arctic oceanic basin. The obtained data show that geothermal gradient at the center of Kola Peninsula has remained close to the modern value of 20 °C/km for at least the last 250 Myr. AFT data show that the Khibina massif has been exhumed not more then 5–6 km in the last 290 Myr.

Synconvergent extension within orogenic systems is often interpreted as gravitational spreading of thickened crust or as a response to thrust belt dynamics. However, the processes that spatially localize extension during orogenesis are not fully understood. Here, a case study from the United States Cordillera demonstrates that localized upper-crustal thickening can exert a first-order control on the spatial location of synorogenic extension. The Eureka culmination, a 20-km-wide, north-trending anticline with 4.5 km of structural relief in the hinterland plateau of the Sevier orogenic belt (or “Nevadaplano”) in eastern Nevada was deformed by two sets of north-striking normal faults that pre-date late Eocene volcanism. (U-Th)/He and fission-track thermochronology data collected from Paleozoic quartzite in the footwalls of two normal faults demonstrate rapid (10 °C/m.y.), Late Cretaceous to Paleocene (75–60 Ma) cooling, which we interpret as tectonic exhumation during extension, and which was concurrent with late-stage shortening in the frontal Sevier thrust belt. This example illustrates that structural and topographic relief generated within zones of localized upper-crustal thickening can spatially focus extension during orogenesis, and adds to a growing body of evidence that Late Cretaceous–Paleocene extension in the Nevadaplano occurred at both mid- and upper-crustal levels.

Unaweep Canyon (Colorado, USA) is a large, Precambrian-cored gorge that bisects the Uncompahgre Plateau of the northeastern Colorado Plateau, but has no through-flowing axial stream; it is drained by two underfit creeks (East and West Creek) that head at a divide within the canyon. The history of the canyon and its role in drainage evolution of the Colorado River system remain controversial. New mapping of both bedrock and Quaternary units as well as analyses of Quaternary deposits in and near the canyon shed light on its late Cenozoic history, and call into question whether the canyon was incised by a Cenozoic river, or merely exhumed by one. Gravels near the western mouth of Unaweep Canyon (Gateway, Colorado) exhibit a distinctive intermediate volcanic provenance recording the presence of an ancestral Gunnison River; the youngest gravels are dated to 1.46 ± 0.33 Ma. Previously documented coring within the canyon reveals a thick (locally >330 m) fill that includes a lacustrine succession (∼140 m thick), dated to 1.4–1.3 Ma, overlain by stacked paleosols and a thick (∼160 m) conglomeratic unit emplaced between 1.3 Ma and the present, in addition to a basal unit of possible late Paleozoic age. Lake formation reflects catastrophic mass wasting in western Unaweep Canyon that blocked the ancestral Gunnison River, causing partial backfilling of the canyon, and forcing the river to seek a lower elevation exit eastward by breaching the Mesozoic rim at the northeast end of Cactus Park (Mesa County, Colorado). Ultimately, the ancestral Gunnison River joined the lower elevation Colorado River near Grand Junction by 1.3 Ma, incising the East Creek of Unaweep Canyon during the overspilling event. Thermochronological data from Precambrian basement within Unaweep Canyon and Permian strata at the western mouth of the canyon indicate onset of incision in latest Miocene time (ca. 6–5 Ma), at a time-averaged rate of ∼210–275 m/m.y. Onset of canyon occupation and rapid incision by the ancestral Gunnison River coincided with the timing of integration of the lower Colorado River system to the Gulf of California. The synchroneity of this incision across the Colorado Plateau supports the inference of an ultimate tectonic or epeirorogenic driver for this widespread incision and ultimate drainage integration. Several aspects of this data set support the previously published hypothesis that the ancestral Gunnison River exhumed a paleovalley. New mapping at the western mouth of the canyon documents a paleovalley filled with Permian strata that leads into the modern Precambrian-hosted gorge of Unaweep Canyon. In addition, the ancestral Gunnison River paralleled the Uncompahgre Plateau before making a 90° turn to bisect the structural axis in a manner that opposes both the northwestward plunge of the uplift and the northeastward dip of its northern flank. The rate of incision of Unaweep Canyon exceeds regional time-averaged incision rates, consistent with removal of sedimentary fill rather than incision of crystalline basement. This hypothesis implies that very ancient landforms can influence drainage evolution in even tectonically active landscapes.