Apatite triple dating (fission track, U‐Pb and U‐Th/He techniques) has been applied to detrital grains from the sedimentary core drilled during the ANDRILL 2A project, which documents the Miocene history of the Victoria Land Basin (western Ross Sea). High‐temperature cooling ages show two main clusters (about 30 and 500 Ma) whereas most of low‐temperature data are late Oligocene‐Early Miocene in age. These latter data are related to the exhumation of the Transantarctic Mountains south of the Discovery Accommodation Zone. Comparison between low‐temperature ages suggests that the Transantarctic Mountains have been in a phase of post‐orogenic decay since at least 30 Ma. The Oligocene U‐Pb data demonstrate the presence of a volcanic event well before the McMurdo volcanic group, whose onset is commonly places at 19 Ma. The location of the volcanic centers is unknown, but they could be below the Ross Ice Shelf south of drilling site. As a whole, these data indicate a major flow of sediments from south to north with only minor contributions from nearby outlet glaciers of the East Antarctic Ice Sheet.
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.
In this paper, a new approach is applied to test a proposed scenario for the tectonic evolution of the Western Carpathian fold-and-thrust beltforeland 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.
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