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Testing models that link climate and solid Earth tectonics in mountain belts requires independent erosional, structural and climatic histories. Two well‐preserved stratigraphic sections of the Himalayan foreland basin are exposed in NW India. The Jawalamukhi (13–5 Ma) and Joginder Nagar sections (21–13 Ma) are dated by magnetostratigraphy and span a period of significant climate change and tectonic evolution. We combine sediment geochemistry, detrital zircon U–Pb dating and apatite fission track analyses to reconstruct changes in the patterns of erosion and exhumation in this area from the Early Miocene to Pliocene. The provenance of the foreland sediments reflects a mixture of Tethyan and Greater Himalayan sources from 21 to 11 Ma, with influx from the Inner Lesser Himalaya starting after 11 Ma, and a strong increase in Crystalline Inner Lesser Himalayan erosion after 8 Ma. This distinct shift in provenance most likely reflects exhumation of the Kullu‐Rampur Window, as well as the northward motion of the Jawalamukhi section towards the Himalayas, drainage reorganization in the foreland, and/or tectonically driven drainage capture in the mountains. Prior to 10.5 Ma sediment came from a large river whose sources were Greater Himalaya and Haimanta dominated, likely a palaeo‐Sutlej, while after 8 Ma the source river was dominated by a more local drainage. Our work is consistent with Nd isotope and mica Ar‐Ar constraints from the same sections that demonstrate initial Inner Lesser Himalayan unroofing in this region from 11 Ma, earlier than the 2 Ma implied from the marine record and during a period of summer monsoon weakening when fission track data indicate very rapid cooling and erosion of the Lesser Himalaya sources from no later than 10 Ma. Tectonically driven rock uplift coupled with southerly migration of the maximum rainfall belt during a time of drying, may have focused erosion over the Lesser Himalayan Duplex and created the Kullu‐Rampur Window. [ABSTRACT FROM AUTHOR]

We report the results of a comparative study to explore the usefulness of 3D measurements of confined fission track lengths (TINTs) relative to horizontal confined track length measurements (dips ≤10°), and evaluate their suitability for thermal history modeling. Confined fission track lengths were measured in 10 annealed Fish Canyon Tuff apatites containing synthetic mixtures of different length components, and two Durango apatites containing spontaneous fission tracks. Measurements were primarily carried out using a digital image-based microscope system, and they were compared to those from a regular optical drawing tube-digitizing tablet setup, and a confocal laser scanning microscope. The results indicate that 3D measurements of confined track lengths are closely comparable to conventional horizontal track measurements, and the mean track lengths of inclined (dips >10°) and horizontal (dips ≤10°) confined tracks from the one sample are equivalent within the measurement uncertainty. A strong dip-bias was observed, so that almost all the confined tracks measured were dipping at <30°, and the great majority (~70%) were dipping at ≤10°, thereby qualifying as “horizontal” confined tracks. Our results suggest that a useful increase of more than 40% in sample size can be achieved from including dip-and refraction-corrected 3D track length measurements. Some evidence was seen for a small bias in favor of shorter tracks at higher dip angles but this has very little influence on the mean lengths or length distributions up to the practical limit of dips (~30°) observed in these measurements. Results obtained using the same measurement system by a single analyst over time and between six different observers in the one laboratory show good reproducibility. These results also agree well with conventional horizontal confined track length measurements in the same samples in the second laboratory involved. We conclude that 3D measurements of confined track lengths, including both horizontal and inclined tracks, are suitable for use in current fission track annealing models derived from experiments using horizontal confined tracks. [ABSTRACT FROM AUTHOR]

Apatite fission-track length and etch figure data are powerful tools for obtaining thermal history information, but both require human analysts making manual measurements and reproducibility is not assured. We report the results of an inter-laboratory study designed to clarify areas of congruence and divergence for these measurements and provide a basis for evaluating best practices to enhance intercompatibility of data sets. Four samples of megacrystic apatite from Durango, Mexico, with induced tracks, one unnannealed and three thermally annealed by varying amounts, were distributed internationally. In all, 55 analysts in 30 laboratory groups participated in the experiment. Relative mean track lengths among the samples were consistent across all analysts, but measurements for each sample showed scatter among labs and analysts considerably in excess of statistical expectation. Normalizing measurements of annealed samples using the unannealed sample improved consistency, as did normalizing for track angle using c-axis projection. Etch figure data also showed variability beyond statistical expectation, and consistency was improved by normalizing. Based on these data we recommend rigorous analyst training for length and etch figure measurement that includes measurement of standards, and that each analyst's data on unknowns be normalized by that analyst's own measurements on standards when using thermal history inverse modeling as part of the interpretation process. [ABSTRACT FROM AUTHOR]

This study provides 39 new thermochronometric analyses from the western part of the Greater Caucasus, a region in which existing data are extremely limited and of questionable quality. The new results are consistent with field studies that identify Triassic to Middle Jurassic (Cimmerian) and Oligo-Miocene (Alpine) orogenic erosional events. An inverse relationship between the fission track and depositional ages of Oligo-Miocene sedimentary samples also implies some degree of Eocene erosion of the Greater Caucasus and intermediate sediment storage. Cooling ages and field relationships within the core of the range, west of Mt Elbrus, require ∼ 5 km of Permo-Triassic exhumation and restrict the overall amount of Cenozoic exhumation to ∼ 2.5 km. Current exhumation rates are typically low, and do not support a Plio-Pleistocene increase in climate-driven denudation. High (∼ 1 kmMa-1) rates of exhumation are restricted to the southern flank of the range in northwest Georgia. Despite a general lack of significant seismicity within the study region, this exhumation peak is close to the largest instrumentally recorded earthquake in the Caucasus (Ms = 7.0). This may suggest that exhumation is associated with the decoupling of the sedimentary succession from its crystalline basement in the southern part of the range and the inversion of the largely Jurassic fill of the Greater Caucasus basin. Rates of exhumation are compatible with this being driven by active shortening. Further sampling and analysis are required to provide a higher-resolution, low-temperature thermochronology of Alpine exhumation, to isolate the drivers for Palaeogene Dziruli Massif cooling and uplift, and to constrain better the extent of the current, localized phase of rapid exhumation. [ABSTRACT FROM AUTHOR]

Two abiding issues impact the reliability of apatite fission-track analysis and thermal history inversion in particular: reproducibility of track-length measurements and variability of annealing kinetics. In the companion to this paper, we addressed the first by demonstrating that using c-axis projection to normalize track lengths for crystallographic angle improves reproducibility among measurements acquired by Barbarand et al. (2003a, 2003b). We continue here by looking at the effect of c-axis projection on extrapolation of laboratory measurements to geological time scales. We find that c-axis projection improves agreement between predictions of empirical annealing models fit to measurements by Barbarand et al. (2003b) analysts 1 and 3, further corroborating its effectiveness in ameliorating observer bias. Furthermore, these annealing models closely match predictions from the Carlson et al. (1999) annealing data set, which was obtained by a different analyst using a different etching protocol. Normalizing for angle thus allows us to create a single annealing model that encompasses both data sets and etching techniques. By combining the different compositional varieties of apatite in the two data sets, the resulting model provides an improved basis for estimating apatite kinetic properties in unknowns using proxies such as composition, etch-figure dimension, and unit-cell parameters. Predictions from a fanning curvilinear model form accord with conventional expectations of annealing at high and low temperatures, and its use for thermal history inversion will not introduce spurious late cooling events. [ABSTRACT FROM AUTHOR]

Recent work on asthenosphere–lithosphere coupling reinforces past observations that active and passive rifting models do not adequately describe real rifts. There remains insufficient knowledge of fundamental controls on rift architecture. In the actively extending Red Sea margin of eastern Eritrea, which lies at the Red Sea/Danakil–Gulf of Aden and the East African rift triple junction zone, the geometry and kinematics of extension are complex and poorly defined due to large data gaps. Extension and sea-floor spreading in both the Red Sea and Gulf of Aden have influenced the Neogene tectonic development of Eritrea but many of the structures have Pan-African origins and do not follow normal plate opening geometries. To constrain the rifting history in eastern Eritrea, apatite fission-track thermochronologic data were measured for 22 Pan-African rock samples. Results identify late Oligocene–early Miocene cooling coincident with extension and erosion along the conjugate margin in Yemen. A younger age group, confined to Mt Ghedem, relates to an episode of fault reactivation and dyke injection that began ∼10 Ma coincident with rotation of the nearby Danakil block. Initially this was driven by onset of sea-floor spreading in the Gulf of Aden and later, in the Pliocene, aided by northward rifting in the Afar depression concomitant with spreading in the Red Sea. These different processes highlight the complex linkage between different extensional events and rift architecture. [Copyright &y& Elsevier]

We present here bulk sediment major element chemistry, Nd and Sr isotope ratios, and detrital apatite fission-track (AFT) and U-Pb zircon ages to characterize the provenance of the southwestern Taklimakan Desert (northwest China) and the three major rivers draining this region. We establish the spatial and temporal controls on erosion and sediment transport in the modern Tibetan rain shadow. The Hotan River drains the North Kunlun block and is characterized by zircon populations at 160-230 Ma and 370-520 Ma. The Yarkand River shares these grains with the Hotan, but also has a very prominent zircon population at 40--160 Ma, which is common in Karakoram basement, indicating heavy sediment flux from these ranges to that drainage. This implies a strong control on erosion by topographic steepness and precipitation mediated through glaciation. Our zircon data confirm earlier studies that indicated that the Taklimakan sand is derived from both the Kunlun and Pamir Mountains. AFT ages are younger in the Hotan River than in the Kashgar River, which drains the Pamir, and in both are younger than in the Transhimalaya and parts of the western edge of the Tibetan Plateau. Exhumation is estimated at ~1000 m/m.y. in the North Kunlun and ~500 m/m.y. in the eastern Pamir, which have been exhuming more slowly than the western ranges in the recent past. Holocene aggradation terracing was dated using quartz optically stimulated luminescence methods and is mostly associated with times of fluctuating climate after 4 ka, with phases of valley filling dated at 2.6, 1.4, and 0.4 ka. The heights and volumes of the terraces show that sediment storage in the mountains is not a significant buffer to sediment transport, in contrast to the more monsoonal Indus system directly to the south. South of the Mazatag Ridge a significant eolian deposit accumulated ~500 yr ago, but this has been deflated in more recent times. Comparison of the modern river data with those previously measured from Cenozoic foreland sedimentary rocks shows that no sediment similar to that of the modern Yarkand River is seen in the geologic record, which is inferred to be younger than 11 Ma, and probably much less. Uplift of the North Kunlun had started by ca. 17 Ma, somewhat after that of the Pamir and Songpan Garze of northwestern Tibet, dated to before 24 Ma. Sediment from the Kunlun reached the foreland basin between 14 and 11 Ma. North Kunlun exhuma tion accelerated before 3.7 Ma, likely linked to faster rock uplift. [ABSTRACT FROM AUTHOR]

Terra Nova, 23, 116-126, 2011 Abstract New apatite fission track (AFT) and (U-Th)/He ages from the Argentera-Mercantour External Crystalline Massif of the SW Alps document an exhumation history along transcurrent dextral faults. Significant AFT age differences across the strikes of the main faults have been obtained from the NE (12.9 Ma) to the SW (5.2 Ma) and are linked to vertical uplifts along these right-lateral transpressional structures. Such segmentation is not observed in AHe ages. AHe ages have preserved younger ages (4-5 Ma) on the eastern hangingwall side of the High Durance extensional system. Such an exhumation history is interpreted to result from a transition of transpressional to transtensional regimes at 8-5 Ma during continuing Adria-Europe convergence. These data show that recent extensional deformation in the SW Alps can be related to the development of a transtensional domain in the Ubaye-Embrunais depression linked to ongoing strike-slip deformation along the Argentera-Mercantour. [ABSTRACT FROM AUTHOR]

Abstract: New fission track and Ar/Ar geochronological data provide time constraints on the exhumation history of the Himalayan nappes in the Mandi (Beas valley) – Tso Morari transect of the NW Indian Himalaya. Results from this and previous studies suggest that the SW-directed North Himalayan nappes were emplaced by detachment from the underthrusted upper Indian crust by 55Ma and metamorphosed by ca. 48–40Ma. The nappe stack was subsequently exhumed to shallow upper crustal depths (<10km) by 40–30Ma in the Tso Morari dome (northern section of the transect) and by 30–20Ma close to frontal thrusts in the Baralacha La region. From the Oligocene to the present, exhumation continued slowly. Metamorphism started in the High Himalayan nappe prior to the Late Oligocene. High temperatures and anatexis of the subducting upper Indian crust engendered the buoyancy-driven ductile detachment and extrusion of the High Himalayan nappe in the zone of continental collision. Late extrusion of the High Himalayan nappe started about 26Ma ago, accompanied by ductile extensional shearing in the Zanskar shear zone in its roof between 22 and 19Ma concomitant with thrusting along the basal Main Central Thrust to the south. The northern part of the nappe was then rapidly exhumed to shallow depth (<10km) between 20 and 6Ma, while its southern front reached this depth at 10–5Ma. [ABSTRACT FROM AUTHOR]

The south-west African margin is regarded as an example of a passive continental margin formed by continental rifting following a phase of lithospheric extension and thinning. Recent attention focused on this margin has included theoretical modelling studies of rift processes, plate kinematic studies of the opening geometry and timing, and empirical studies focused on documenting the crustal structure and offshore sedimentary record. Here, we examine the onshore geomorphic and tectonic response to rifting and breakup, with a specific focus on the SW Cape of South Africa. We present 75 new apatite and 8 new zircon fission track analyses from outcrop samples and onshore borehole profiles along the western margin of South Africa. The data are used to derive robust thermal histories that record two discrete phases of accelerated erosional cooling during the Early Cretaceous (150–130 Ma) and Late Cretaceous (100–80 Ma), respectively. Both periods of enhanced erosion are regional in extent, involved km-scale erosion, and extend well inland of the current escarpment zone, albeit with spatially variable intensity and style. The Late Cretaceous episode is also expressed more locally by tectonic reactivation and inversion of major faults causing km-scale differential displacement and erosion. The new AFT data do not exclude the possibility of modest surface uplift occurring during the Cenozoic, but they restrict the depth of regional Cenozoic erosion on the western margin to less than c. 1 km. The inferred pattern and chronology of erosion onshore is consistent with the key features and sediment accumulation patterns within the offshore Orange and Bredasdorp basins. It is suggested that the Late Cretaceous event was triggered by a combination of regional dynamic uplift augmented along the western margin and in the SW Cape by local tectonic forces arising from dextral displacement of the Falkland Plateau along the Falkland–Agulhas Fracture Zone. [ABSTRACT FROM AUTHOR]

Abstract: The mineralization ages reported in the past in the Altai Mountains, northern Xinjiang, China, not only are different, but also fall into the Hercynian epoch. This study has achieved 17 zircon fission track analysis results from different ore deposits. The zircon fission track ages range from 134±9Ma to 339±49Ma. We consider that the zircon fission track age could reveal the mineralization age based on an annealing zone temperature of 140–300°C and a retention temperature of ∼250°C for zircon fission tracks, and a metallogenetic temperature of 150–260°C in various ore districts. The mineralization age agrees with the regional tectonics. A total of four mineralization epochs have been identified, i.e., 339–312Ma, 255–234Ma, 218–174Ma and 158–126Ma, and these indicate occurrence of the mineralizations in the Indosinian and Yanshan epochs as well as the Hercynian epoch. [Copyright &y& Elsevier]

Namibia''s passive continental margin records a long history of tectonic activity since the Proterozoic. The orogenic belt produced during the collision of the Congo and Kalahari Cratons in the Early Proterozoic led to a zone of crustal weakness, which became the preferred location for tectonism during the Phanerozoic. The Pan-African Damara mobile belt forms this intraplate boundary in Namibia and its tectonostratigraphic zones are defined by ductile shear zones, where the most prominent is described as the Omaruru Lineament–Waterberg Thrust (OML–WT). The prominance of the continental margin escarpment is diminished in the area of the Central and Northern Zone of the Damara belt where the shear zones are located. This area has been targeted with a set of 66 outcrop samples over a 550-km-long, 60-km-broad coast-parallel transect from the top of the escarpment in the south across the Damara sector to the Kamanjab Inlier in the north. Apatite fission track age and length data from all samples reveal a regionally consistent cooling event. Thermal histories derived by forward modelling bracket this phase of accelerated cooling in the Late Cretaceous. Maximum palaeotemperatures immediately prior to the onset of cooling range from ca. 120 to ca. 60 °C with the maximum occurring directly south of the Omaruru Lineament. Because different palaeotemperatures indicate different burial depth at a given time, the amount of denudation can be estimated and used to constrain vertical displacements of the continental crust. We interpret this cooling pattern as the geomorphic response to reactivation of basement structures caused by a change in spreading geometry in the South Atlantic and South West Indian Oceans. [Copyright &y& Elsevier]