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Syrian Miocene alkali basalts have been sampled in the area south of Damascus. Thirty two flows were collected from short vertical sections (one to six flows) at ten sites. The sequence of polarity observed at each site is compatible with a magmatic event taking place during a reversal. Change of polarity and the presence of transitional directions allows: (1) correlation of flows between sites, (2) the assessment of the short duration of this volcanism. Moreover, the mean direction of magnetization (D = 179, I = -34, K = 28, a95=6 degrees) shows clearly that since Miocene times no tectonic rotation occurred in this deformed area close to the east side of the Levant fault and south of the Palmyra chain. Paper not available from original source so put here to have online and a DOI assigned

International audience; The formation of mountain belts from the Tibetan plateau to the Alps associated with the closure of the Tethys is thought to be a major driver of Cenozoic climate and biotic evolutions. However, various competing geodynamic models imply very different mountain growth histories involving debated tectonic mechanisms. Furthermore, a growing dataset of environmental proxies is used to constrain surface uplift but the reliability of these proxies and the age of their sedimentary records are strongly debated. As a result, there is a crucial lack of reliable boundary conditions required to validate modeling of climate, landscape and biotic evolution. To fill this fundamental gap we review here diverging tectonic models and data to propose a set of global paleogeographies focusing on Eurasia. The construction of the paleogeographic maps was performed with Terra Antiqua a new dedicated QGIS plugin with user-friendly set of paleogeographic tools (http://paleoenvironment.eu/terra-antiqua/). It integrates into a revised plate tectonic circuit, paleoshorelines and paleo-elevation/bathymetry estimated from a global database of quantitative and qualitative surface proxies from an extensive literature reviews focused on key orogenic areas. The maps are available through an interactive website that enables to plot various proxy databases and plot user data rotated into past tectonic positions (https://map.paleoenvironment.eu/). We explore various landscape distributions with a focus on how the Tibetan Plateau, the neo-Tethys closure and the Paratethys epicontinental sea retreat may have contributed to Cenozoic atmospheric CO2 drawdown, the evolution of Asian monsoons and aridification or biotic interchange associated with the Grande Coupure.

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National audience; Recent paleomagnetic data from Myanmar demonstrate that the Burma Terrane (BT)underwent an impressive northward translation alongside India in the Cenozoic(Westerweel et al., 2019, 10.1038/s41561-019-0443-2).Thick sedimentary basins, filled during the Cenozoic, characterize the geology of the BTand were first considered as the receptacle for the erosion products of the India-Asiacollision (Métivier et al., 1999; 10.1046/j.1365-246X.1999.00802.x). More local sourceshave however been proposed for the infill of the Eocene Myanmar basins oftenpresented as forearc and backarc basins of an Andean-type magmatic arc along thewestern margin of Sibumasu with uplifted parts of Eastern Myanmar e.g. MogokMetamorphics and Shan Plateau as additional sediment sources (Licht et al., 2013,10.1144/jgs2012-126, Licht et al. 2016, 10.1111/bre.12108; Cai et al., 2019,10.1046/j.1365-246X.1999.00802.x; Najman et al., 2020,10.1016/j.epsl.2019.115948). However, the Late Eocene equatorial position of the BTimplies that the Myanmar sedimentary basins were far away from a potential source ineastern Myanmar and challenges all these previous interpretations. We review thenumerous studies on detrital zircons (>5000 zircons) from the Late Cretaceous -Paleogene sediments of the Myanmar central basins. While the age spectrum isdominated by a mid-Cretaceous peak compatible with the main magmatic event alongthe Myanmar magmatic arc or the Gangdese arc, more than 40% of the zircons fromsediments of the Central Basins have pre-Cretaceous ages. There is a clear correlationin the distribution of these ages with those from the Triassic turbidites of the PaneChaung Fm. of the Indo-Burman ranges (Yao et al. 2017, 10.1016/j.tecto.2017.09.016)and the Triassic sediments from the Tethyan Himalaya. This observation clearlysupports a paleogeography where the Burma terrane is on the India plate and linked toGreater India during the Paleogene.The large northward motion of the BT likely also impeded active subduction belowMyanmar during the Paleogene. Filling of the BT sedimentary basins is clearlycontrolled by Cenozoic tectonics north of the BT due to the collision of India first withthe trans-Tethyan arc and then with Asia.Paleoenvironments of Myanmar need to be reinterpreted using the new paleogeography.

International audience; Widespread carbonate rocks from the Tibetan plateau have been extensively used to constrainterrane paleolatitudes involved in the India-Asia collision. However, their reliability in preserving aprimary magnetization has been recently put into question.A transformation of pyrite tomagnetite has been recently proposed as a cause for late re-magnetizations in Paleocene TethyanHimalaya carbonates (1) and late Triassic carbonates from the Qiantang (2), thus discarding suchCharacteristic Remanent Magnetizations (ChRM) for tectonic purposes. We have re-examined thepaleomagnetic data obtained on late Triassic carbonate rocks from the Qiantang. Our SEMobservations indicate pristine pyrite in non-weathered carbonate rocks. Optical microscopeobservations in reflected light demonstrate that pyrite, when it is weathered, is transformed toiron hydroxides minerals but not to magnetite. This is at odds with previously proposed pyrite tomagnetite transformation hypothesis mainly based on interpretations of Scanning ElectronMicroscope data (SEM/EDS). We thus interpret the ChRM more likely related to an early diageneticmagnetization of Late Triassic age. Knowing that the arguments put forward for a remagnetizationof Triassic carbonates are the same as those proposed for the remagnetization of Paleocenecarbonates, the ChRM in some Paleocene carbonates could also be of early diagenetic origin.However, there is also a growing number of studies where remagnetization is obvious in theTethyan Himalaya and undetected remagnetizations (3) are likely the cause of the largedifferences in the estimation of the size of Greater India. These examples show the urgent need topublish the complete demagnetization dataset in an open database like MAGIC or the FAIR datainitiative from (4) in order to reassess previous interpretations if we want to solve problems likethe size of Greater India and hypothesis like the Greater India basin

The timing and mechanisms of the Cretaceous sea incursions into Central Asia are still poorly constrained. We provide a new chronostratigraphic framework based on biostratigraphy and magnetostratigraphy together with detailed paleoenvironmental analyses of Cretaceous records of the proto-Paratethys Sea fluctuations in the Tajik and Tarim basins. The Early Cretaceous marine incursion in the western Tajik Basin was followed by major marine incursions during the Cenomanian (ca. 100 Ma) and Santonian (ca. 86 Ma) that reached far into the eastern Tajik and Tarim basins. These marine incursions were separated by a Turonian-Coniacian (ca. 92-86 Ma) regression. Basin-wide tectonic subsidence analyses imply that the Early Cretaceous sea incursion into the Tajik Basin was related to increased Pamir tectonism. We find that thrusting along the northern edge of the Pamir at ca. 130-90 Ma resulted in increased subsidence in a retro-arc basin setting. This tectonic event and coeval eustatic highstand resulted in the maximum observed geographic extent of the sea during the Cenomanian (ca. 100 Ma). The following Turonian-Coniacian (ca. 92-86 Ma) major regression, driven by eustasy, coincides with a sharp slowdown in tectonic subsidence during the late orogenic unloading period with limited thrusting. The Santonian (ca. 86 Ma) major sea incursion was likely controlled by eustasy as evidenced by the coeval fluctuations in the west Siberian Basin. An early Maastrichtian cooling (ca. 71-70 Ma), potentially connected to global Late Cretaceous trends, is inferred from the replacement of mollusk-rich limestones by bryozoan- and echinoderm-rich limestones.

International audience; The paleogeographic evolution of the India-Asia collision and the resulting formation of the Himalayan orogen remain an intensely debated topic. A variety of disputed models propose different collision ages for the numerous terranes incorporated into the collision with variable paleolatitudes and tectonic rotations that can be constrained using paleomagnetism. Recent plate tectonic reconstructions have shown that the Burma Terrane (BT), a microplate at the eastern edge of the Himalayan orogen, is a key element to solve the India-Asia collision puzzle. Here we provide new paleomagnetic and geochronological data of Paleocene, Eocene, Oligocene and Miocene age, in addition to our previously published Late Cretaceous and late Eocene results. We present a robust plate tectonic reconstruction for the BT with GPlates software, and show that the BT moved towards southern hemisphere latitudes between the Late Cretaceous and Paleocene without significant rotation. Starting in the Paleocene, the BT and India coevally moved northwards and the BT started to undergo a major clockwise rotation of ~60 ̊. By the late Eocene, most of this rotation was completed and the BT was translated ~2000 km northward from near-equatorial latitudes without significant rotation. This northward translation culminated with the early Miocene indentation of the BT into the eastern Himalayan collision zone, leading to the setup of the modern Eastern Himalayan Syntaxis. These first order constraints are used to infer a Trans-Tethyan arc collision model including timing of rollback, extrusion and initiation of strike-slip systems. Our model has important implications for Asian biotic and climatic evolution.

International audience; The Pamir orogen in Central Asia has formed by the amalgamation of several Gondwana-derived terranes and their accretion to the southern Eurasian margin in the Mesozoic. Later on, the crust of the Pamir orogen was strongly deformed and uplifted as a result of the Cenozoic India-Asia collision. The deformation of the Pamir orogen, which resulted in shortening, crustal thickening and exhumation of deep crustal rocks within the gneiss domes of the Central and Southern Pamir makes the area an ideal site for studying the India-Asia collision and its paleogeographic and climatic effects. To account for today’s 70-km-thick crust of the Pamir orogen and more than 400 km of convergence accommodated in the Pamir, pre- and syn-collisional processes have been proposed including, continental subduction, delamination, extrusion and oroclinal bending of the Pamir arc. However, testing these models requires constraints on the pre-collisional state of the Pamir lithosphere and its tectono-magmatic evolution. During most of the Cretaceous, the southern Pamir terrane was a site of a widespread arc-related magmatism, which resulted in the formation of many plutons and a volcanic suite of intermediate to acidic composition, whereas the central Pamir terrane lacked any sign of magmatic activity. However, in the late Cretaceous to early Paleogene (78 – 61 Ma) a less widespread magmatic activity in the western part of the Central Pamir resulted in the formation of the Bartang mafic to intermediate volcanic and volcaniclastic rocks. We report here the geochemical and Sr-Nd isotopic features of the late Cretaceous – early Paleogene Bartang volcanics. This volcanic suite bears geochemical and radiogenic isotope features that differ from the arc-related southern Pamir igneous rocks. Mafic basalts that comprise the lowest portion of the section exhibit MORB-like pattern with slightly depleted light rare earth elements (LREE) and large ion lithophile elements (LILE). Further up in the section this pattern shifts towards an arc-related pattern with enriched LREE and LILE. The 87Sr/86Sri isotope ratios are lower (0.705335 – 0.706693) than those from the southern Pamir igneous rocks (0.706915 – 0.711105) and epsilon Nd values exhibit ratios close to mantle domain, ranging between -0.7 and -2.7, with the lower part of the section showing less negative values then the upper. In contrast to the Bartang volcanics, the southern Pamir igneous rocks exhibit more negative epsilon Nd values (from -4.7 to -13). The relatively low initial 87Sr/86Sr isotope ratios and slightly negative epsilon Nd values of the Bartang volcanic rocks together with the trace elements pattern that shifts from MORB-like to arc-related indicate mixing of two magmas derived from depleted and enriched mantle sources, with the latter inheriting the arc-related pattern from the subduction stage. Alternatively, the arc-related pattern could be derived through contamination of the primary magma by the crustal material. These features, compared to the southern Pamir arc-related igneous rocks, also indicate that the tectonic setting in the Pamir changed during the late Cretaceous from a continental arc to a within-plate extensional setting.

International audience; The Pamir Plateau forms a prominent salient into central Asia. Previous kinetic models suggest that the salient was formed since the late Eocene, by radial thrusting and dextral transfer faulting along its western and eastern boundaries, respectively. In this study, a new sedimentary section in the southeastern Tajik Basin that spans the Early Cretaceous to late Miocene was examined using sedimentological and paleomagnetic methods. Vertical-axis tectonic rotation data indicate counterclockwise rotation of 54.6±5.4º for Late Cretaceous–early Paleogene rocks, 55.5±5.2º for late Eocene–early Miocene rocks, and 67.3±5.0º for middle–late Miocene rocks. These new data, agreeing with previous studies, indicate that large counterclockwise rotation of the Tajik Basin did not happen until the middle–late Miocene; and thus challenge kinetic models that require earlier initiation of the Tajik Basin rotation, e.g., late Eocene or Oligocene, in response to growth of the Pamir salient. Field observations and AMS (anisotropy of magmatic susceptibility) data show contrast deformation styles between the middle–late Miocene and older strata, most likely indicating deformation of the Early Cretaceous–early Miocene rocks during deposition of the middle–late Miocene strata. This deformation style is consistent with recent low-temperature thermochronology data, which infer intensified middle–late Miocene exhumation in the surrounding north Pamir and southwest Tianshan. Results of this study call for reconsideration of previous kinetic models for evolution of the Pamir salient.

International audience; Magma flow record on plutonic rocks is usually interpreted from mineral and magnetic fabric patterns. The shear caused by a crystallizing viscous flow can align minerals and leave a magnetic signature through the anisotropy of magnetic susceptibility (AMS), which should not be higher than 8%. In order to infer the magma flow patterns, in this contribution we present AMS and field-observed petrographic fabric data on three plutons with similar characteristics of composition and age, but its mineralogy heterogeneity increase southward. Our case studies are three well exposed shallow plutons that belongs to a NNW belt of 10 to 13 Ma quartz-monzonites in Central Chile, including, from North to South, La Gloria Pluton, San Gabriel pluton and Alfalfalito pluton.In La Gloria Pluton the magnetic lineation is horizontal in NNW direction, following the main pluton elongation. The magnetic foliation changes regularly from vertical close to the walls, to horizontal at the center of the pluton. The petrographic fabric is generally weak and hard to recognize in the field, except in the central zones of the pluton, where it shows subvertical foliation and horizontal lineation. These data suggest whole scale convection and horizontal pluton propagation.In San Gabriel Pluton the magnetic fabric also follows the borders of the pluton. The irregular shape of San Gabriel pluton give place to an irregular magma flow and consequently, the magnetic fabric. At the wall of the pluton, samples (1, 5, 3, 13, 12, 14, 17) have subvertical foliation following the borders of the pluton and NNW magnetic lineations; except at the southern and northern ends (2, 18, 11), where lineation and foliations are NEE. At the pluton interior (8) and under the roof (4), foliations are horizontal. The big wall exposed at the northern part of the pluton (7, 15, 16, 6) has a subvertical foliation in a NEE direction, suggesting that a subvertical magma flow and internal contacts inside the pluton (19, 10?). In general, these patterns are consistent with the observed petrographic fabric, which is well developed close to the borders, with two major trends between NNW and NEE (variation range of 60°), in detriment of the central middle levels of the pluton, where the fabric is isotropic.The magnetic fabric of Alfalfalito Pluton also reflects the magma flow at walls and internal contacts. At the upper levels of the pluton (6, 3) magnetic lineation is subvertical, suggesting a vertical magma transport to upper levels. These three examples suggest that magma flow is conditioned by host rock at the limits of the magma reservoir, as well as, internal contacts, when magma with different mineral or enclave’s cargo coexists inside the reservoir.This research has been supported by the National Fund for Scientific and Technological Development (FONDECYT) Project #1180577 granted by National Commission for Scientific and Technological Research (CONICYT) and the Fund for Publication Developments project [PEP I-2019071] granted by Universidad Mayor - Vicerrectoría de Investigación. I. Payacán was supported by the CONICYT doctoral grant [PFCHA-CONICYT #21151102].

The northward indentation of the Pamir salient into the Tarim basin at the western syntaxis of the India-Asia collision zone is the focus of controversial models linking lithospheric to surface and atmospheric processes. Here we report on tectonic events recorded in the most complete and best-dated sedimentary sequences from the western Tarim basin flanking the eastern Pamir (the Aertashi section), based on sedimentologic, provenance, and magnetostratigraphic analyses. Increased tectonic subsidence and a shift from marine to continental fluvio-deltaic deposition at 41Ma indicate that far-field deformation from the south started to affect the Tarim region. A sediment accumulation hiatus from 24.3 to 21.6Ma followed by deposition of proximal conglomerates is linked to fault propagation into the Tarim basin. From 21.6 to 15.0Ma, increasing accumulation rates of fining upward clastics is interpreted as the expression of a major dextral transtensional system linking the Kunlun to the Tian Shan ahead of the northward Pamir indentation. At 15.0Ma, the appearance of North Pamir-sourced conglomerates followed at 11Ma by Central Pamir-sourced volcanics coincides with a shift to E-W compression, clockwise vertical-axis rotations and the onset of growth strata associated with the activation of the local east vergent Qimugen thrust wedge. Together, this enables us to interpret that Pamir indentation into Tarim had started by 24.3Ma, reached the study location by 15.0Ma and had passed it by 11Ma, providing kinematic constraints on proposed tectonic models involving intracontinental subduction and delamination.

International audience