Earth-Science Reviews
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Abstract Pyrite is the most abundant ore mineral in gold-bearing quartz pebble conglomerates (QPCs) of the Witwatersrand Basin and similar Archaean sedimentary units. Much of the pyrite in Archaean conglomerates is detrital in origin, implying that it survived weathering, transport, and reworking under anoxic conditions. Detrital pyrite is generally found together with authigenic pyrite formed in situ as a result of syn- to post-depositional processes. As pyrite is frequently associated with gol...
Abstract The Dharwar Supergroup comprises the unconformity bound Bababudan and Chitradurga groups. The Bababudan Group, which is best preserved in the Western Dharwar Craton, records a divergent margin comprising a basalt-dominant intracontinental rift sequence, a shale-BIF drift sequence, and a sandstone-shale thermal-subsidence sequence. The rift stage evolved from ∼2765 Ma to ∼2720 Ma, whereas the succession was folded, uplifted and eroded during development of a convergent continental margin...
Abstract About six million years ago, the Mediterranean Sea underwent a period of isolation from the ocean and widespread salt deposition known as the Messinian Salinity Crisis (MSC), allegedly leading to a kilometer-scale level drawdown by evaporation. One of the competing scenarios proposed for the termination of this environmental crisis 5.3 million years ago consists of a megaflooding event refilling the Mediterranean Sea through the Strait of Gibraltar: the Zanclean flood. The main evidence...
Abstract Reactive nitrogen (N) input can profoundly alter soil N transformations and long-term productivity of forest ecosystems. However, critical knowledge gaps exist in our understanding of N deposition effects on internal soil N cycling in forest ecosystems. It is well established that N addition enhances soil N availability based on traditional net mineralization rate assays. Yet, experimental additions of inorganic N to soils broadly show a suppression of microbial activity and protein dep...
Abstract This article proposes a review of the researches dealing with the interaction between watersheds and coastal areas. Watersheds and coasts were traditionally regarded as two separate areas with a contact point in which the output of the watershed constitutes the input of the coastal area. However, the open literature of the last two decades recognized the importance of adopting a holistic perspective in the analysis of these two systems. Such a point of view is so consolidated that nowad...
Abstract Rose diagrams are powerful tools for visually representing two-dimensional orientation (and other cyclic) data. The conventional practice of scaling the wedge radius to frequency leads to exaggeration of modal orientations and should be replaced by using wedges whose area is proportional to frequency (the equal-area wedge diagram). We outline a workflow in which the type of data (vectorial or axial), sample size and the degree of preferred orientation are used to control the type of plo...
Abstract Despite the influence of other geological and geomorphological factors, chemical weathering at the Earth's surface is strongly controlled by climate. Thus, a measure of weathering intensity determined from soils or sediments should provide information about the climatic conditions associated with their formation. Available geochemical and mineralogical data on modern fluvial and marine muds from different regions of southern Africa and its Atlantic continental margin are used to review ...
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Abstract The Tonian to Ediacaran geology of Tasmania, Australia preserves an extensive record of continental rifting related to the Neoproterozoic opening of the Pacific Ocean. We integrate new and previously published structural, stratigraphic, sedimentary provenance, age, and geochemical data to establish four tectonostratigraphic stages in Tasmania that formed during three episodes of Neoproterozoic rifting. Rift Event 1 initiated with Tonian (780–750 Ma) intraplate magmatism and clastic sedi...
Abstract Emplacement of the Central Atlantic Magmatic Province (CAMP) during the Triassic-Jurassic (Tr-J) transition is believed to have indirectly increased wildfire frequency through climatic warming and drying. To date, evidence for wildfires has come mainly from within the CAMP region. Here, we present biomarker evidence for wildfires in the form of polycyclic aromatic hydrocarbons (PAHs) in two terrestrial Triassic-Jurassic boundary sections in the Sichuan Basin, southwestern China. Pyrolyt...
Abstract How large must an extraterrestrial impact be to cause a peak episode of increased extinctions of life? Impact energies ≥ 3 × 107 Mt TNT (associated with terrestrial impact craters with final diameters ≥ 100 km) seem to be required to generate significant widespread climatic effects from sub-micron dust and soot in the atmosphere, leading to a distinct extinction episode (≥ 15% extinction of marine genera). Impacts creating craters smaller than ∼100 km in final diameter (in the 106 to 10...
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