Benedetta Andreucci

Interplay between the thermal evolution of an orogenic wedge and its retro-wedge basin: An example from the Ukrainian Carpathians

The Carpathian-Pannonian region is made up of the wide extensional Pannonian Basin surrounded by the Carpathian mountain belt. The Pannonian Basin formed in the Miocene by extension in a retro-wedge position while thrusting was still active at the Carpathian front. The Ukrainian region is an ideal area to reconstruct the relationship between the Pannonian Basin and the Carpathians, due to the relatively simple structural setting and to the progressive but neat transition between the two domains. This study uses low-temperature thermochronometry and vitrinite reflectance analysis to investigate the effect of the opening of the Pannonian Basin on the thermal and burial-exhumation histories of the Ukrainian Carpathians. The results show heating and burial maxima in the central units of the wedge (up to ~170 °C and 6 km, respectively), tapering out toward both the innermost and the outermost thrust sheets. Cooling and exhumation occurred by means of a first rapid stage between ca. 12 and 5 Ma (exhumation rates of up to ~1 mm/yr), followed by a slower stage from ca. 5 Ma to the present (exhumation rates within 0.5 mm/yr). Timing and spatial pattern of exhumation are compatible with post-thrusting erosion enhanced by isostatic uplift. The extent of exhumation progressively decreases toward the Pannonian Basin, characterized by a thinned crust. No further significant influence of the Pannonian Basin opening on the thermal and burial history of the Ukrainian Carpathians may be inferred based on our results, whereas the comparison of the tectonothermal evolution of the two domains suggests that they are both controlled by the same lithospheric processes.

Coupling sequential restoration of balanced cross sections and low-temperature thermochronometry: The case study of the Western Carpathians

In this paper, a new approach is applied to test a proposed scenario for the tectonic evolution of the Western Carpathian fold-and-thrust belt–foreland system. A N-S balanced section was constructed across the fold-and-thrust belt, from the Polish foreland to the Slovakia hinterland domain. Its sequential restoration allows us to delineate the tectonic evolution and to predict the cooling history along the section. In addition, the response of low-temperature thermochronometers (apatite fission-track and apatite [U-Th]/He) to the changes in the fold-and-thrust belt geometry produced by fault activity and topography evolution are tested. The effective integration of structural and thermochronometric methods provides, for the first time, a high-resolution thermo-kinematic model of the Western Carpathians from the Early Cretaceous onset of shortening to the present day. The interplay between thick- and thin-skinned thrusting exerts a discernible effect on the distribution of cooling ages along the profile. Our analysis unravels cooling of the Outer Carpathians since ca. 22 Ma. The combination of thrust-related hanging-wall uplift and erosion is interpreted as the dominant exhumation mechanism for the outer portion of the orogen. Younger cooling ages (13–4 Ma) obtained for the Inner Carpathian domain are mainly associated with a later, localized uplift, partly controlled by extensional faulting. These results, which help unravel the response of low-temperature thermochronometers to the sequence of tectonic events and topographic changes, allow us to constrain the tectonic scenario that best honors all available data.

Building and exhumation of the Western Carpathians: new constraints from sequentially restored, balanced cross‐sections integrated with low‐temperature thermochronometry

Western Carpathian orogeny has been the subject of intense scientific debate due to the occurrence of enigmatic features, leading several authors to provide contrasting geological models. In this paper, a new interpretation for the tectonic evolution of the Western Carpathians is provided based on: (i) an analysis of the stratigraphy of the Mesozoic-Tertiary successions across the thrust belt domains; (ii) a reappraisal of the stratigraphy and sedimentology of the tectonic melange (i.e. the so-called Pieniny Klippen Belt) marking the suture between the Inner and Outer Carpathians; and (iii) the construction of a series of balanced and restored cross-sections, validated by 2D forward modeling. Our analysis provides a robust correlation of the stratigraphy from the Outer to the Inner Carpathians, independently of the occurrence of oceanic lithosphere in the area, and allows for the reinterpretation of the tectonic relationships among the Inner Carpathians, the Outer Carpathians and the Pieniny Klippen Belt and the exhumation mechanisms affecting this orogenic belt. In order to constrain the evolution during the last 20 Ma, our model also integrates previously published and new apatite fission track and apatite (U-Th-Sm)/He data. These latter indicate a Middle-Late Miocene exhumation of the Pieniny Klippen Belt. In this study, the recent regional uplift of the Pieniny Klippen Belt is described for the first time using a 2D kinematic model for the tectonic evolution of the Western Carpathians.

Multianalytical provenance analysis of eastern Ross Sea LGM till sediments (Antarctica): Petrography, geochronology, and thermochronology detrital data

In order to reveal provenance of detrital sediments supplied by West Antarctic Ice Sheet (WAIS), 19 glaciomarine cores of Last Glacial Maximum age were analyzed from Eastern Ross Sea and Sulzberger Bay. Analytical techniques included petrographic analysis of gravel-sized clasts, geochronology (zircon U-Pb: Zrn-UPb) and thermochronology (apatite fission track: AFT) of sand-sized fractions. Petrographic analysis revealed a similarity with the lithologies presently exposed in western Marie Byrd Land (MBL), with major roles played by low grade metamorphic rocks and granitoids. Furthermore Zrn-UPb and AFT data allowed to identify the ages of formation and cooling of sedimentary source area, consisting of Cambrian-Precambrian basement (i.e. Swanson Formation in western MBL) which underwent at least two episodes of magma intrusion, migmatization and cooling during Devonian-Carboniferous and Cretaceous-Paleocene times. Scarcity of volcanic clasts in the region of Ross Sea along the front of West Antarctica Ice Streams in association with the occurrence of AFT Oligocene-Pliocene dates suggests a localized tectonic exhumation of portions of MBL, as already documented for the opposite side of West Antarctic Rift System in the Transantarctic Mountains. Furthermore, a Zrn-UPb and AFT population of Late Triassic-Jurassic age indicates the presence of unexposed rocks that formed or metamorphosed at that time in the sedimentary source area, which could be identified in McAyeal Ice Stream and Bindschadler Ice Stream catchment areas.