Carbon cycle perturbations and environmental change of the middle permian and Late Triassic Paleo-Antarctic circle.

During the middle Permian through the Triassic, Tasmania moved from paleo-latitudes of 78° to 69°S, wedged between Antarctica and Australia, within the paleo-South polar circle. During this time, significant global carbon cycle disturbances triggered major environmental and climatic changes and mass extinction events globally. The Bicheno-5 core from Eastern Tasmania, Australia, provides the opportunity to examine middle Permian and Upper Triassic sediments from the paleo-Antarctic, using high-resolution organic carbon isotope (δ13CTOC) chemostratigraphy, pXRF, and sedimentology, combined with new palynological data integrated with the existing radiometric age model. While there is a significant unconformity in the Upper Permian to the middle Triassic associated with eustatic sea-level fall as a result of regional uplift in eastern Australia, three distinct carbon isotope excursions (CIEs), characterized by negative shifts of up to - 6 ‰ were identified; the middle Permian Guadalupian Carbon Isotope Excursions (G-CIE), the Carnian Pluvial Episode (CPE), and the mid-Norian Event (MNE). These three events highlight a significant climate shift through glacial and interglacial cycles to warmer non-glacial intervals in the Late Triassic, with evidence of the polar record of the Carnian Pluvial Episode and the mid-Norian Event, which are poorly studied in the Southern Hemisphere, specifically within the Paleo-Antarctic circle.

The influence of Cenozoic Eurasia-Arabia convergence on the Southeast Arabian Foreland Basin: new geochronological and geochemical constraints from syn-kinematic carbonate mineralization.

The Cenozoic succession of the Jabal Hafeet anticline yields the most complete surface expression of the deformation that affected the Southeast Arabian Foreland Basin (SEAFB). The carbonate rocks of the Eocene Rus Formation comprise the core of the Jabal Hafeet anticline and host a network of fractures and carbonate veins associated with dynamic fracture opening and sealing events. These fracture networks developed during the propagation of compressional stresses from the Makran and Zagros fold-and-thrust belts into their foreland basin system (the SEAFB) and are associated with Arabia-Eurasia convergence. Syn-kinematic calcite veins associated with the Cenozoic folding events in the SEAFB were dated by U-Pb LA-ICP-MS carbonate geochronology and characterized further by Raman fluid-inclusion geochemistry. The U-Pb data show that Cenozoic compression linked to the propagation of the Makran fold-and-thrust belt into the SEAFB took place from c. 20 Ma (early Miocene) to c. 2 Ma (mid Pleistocene). Raman fluid-inclusion data reveal the presence of complex hydrocarbons within the parent carbonate-bearing fluids, reflecting a fluid transport pathway between the upper Cenozoic rocks and deeper hydrocarbon-bearing Mesozoic sequences. Combined isotopic and geochemical datasets show that the deformational history of the SEAFB is likely related to the reactivation of inherited deep-seated structures in the upper Cenozoic stratigraphic sequence due to the far-field stress propagation from the Makran belt into the Arabian peninsula, rather than the propagation of a thin-skinned deformation architecture.

Solar forcing of early Holocene droughts on the Yucatán peninsula.

A speleothem record from the north-eastern Yucatán peninsula (Mexico) provides new insights into the tropical hydro-climate of the Americas between 11,040 and 9520 a BP on up to sub-decadal scale. Despite the complex atmospheric reorganization during the end of the last deglaciation, the dominant internal leading modes of precipitation variability during the late Holocene were also active during the time of record. While multi-decadal variations were not persistent, Mesoamerican precipitation was dominated by changes on the decadal- and centennial scale, which may be attributed to ENSO activity driven by solar forcing. Freshwater fluxes from the remnant Laurentide ice sheet into the Gulf of Mexico and the North Atlantic have additionally modulated the regional evaporation/precipitation balance. In particular, this study underlines the importance of solar activity on tropical and subtropical climate variability through forcing of the tropical Pacific, providing a plausible scenario for observed recurrent droughts on the decadal scale throughout the Holocene.