نتایج جستجو برای: late neoproterozoic
تعداد نتایج: 196368 فیلتر نتایج به سال:
Abstract Carbonate U-Pb dating of samples from rift-bounding faults intracontinental basins in the Borborema province, northeastern Brazil, indicate recurrent tectonic activity during Pangea breakup lasting for >150 m.y. Late Triassic to Paleocene, reactivating inherited strike-slip Neoproterozoic–Cambrian shear zones. ages that brittle deformation started some 80 before previously known...
Abstract The SHRIMP U–Pb dating of zircons from felsic subvolcanic rocks in the Carboniferous formations Intra-Sudetic Basin SW Poland verifies previous views on timing Late Palaeozoic magmatic activity this area and constrains links between regional tectonics intra-basinal volcanism mid-European Variscides. Two main stages magmatism are identified: late orogenic stage, Early Permian post-oroge...
In 1989, the International Commission on Stratigraphy established a Working Group on the Terminal Proterozoic Period. Nine years of intensive, multidisciplinary research by scientists from some two dozen countries have markedly improved the framework for the correlation and calibration of latest Proterozoic events. Three principal phenomena--the Marinoan ice age, Ediacaran animal diversificatio...
Meso– to Neoproterozoic geological and paleomagnetic data support a direct connection between Baltica Laurentia in both Nuna Rodinia supercontinents, however different relative configurations. Previous limit the time of break-up core configuration ca. 90° rotation 1.27 Ga 0.99 Ga. Despite well documented motion continents, tectonic mode during has been questioned operation single lid tectonics ...
[1] Recent modeling results have raised doubts about the ability to deglaciate from a global glaciation at atmospheric carbon dioxide levels that are realistic for a Neoproterozoic Snowball Earth. Here we argue that over the lifetime of a Snowball event, ice dynamics should lead to the development of a layer of continental and volcanic dust at the ice surface in the tropics that would significa...
Calcified rock-forming marine filamented benthic microand macrophytes of Dzhelindia Kolosov, 1970 (Figure 1(а)) and Chaptchaica Kolosov, 1975 (Figure 1(b)) genera, thrived in Neoproterozoic (1000 541 million years ago) Siberia together with cyanobacteria. Their belonging to Rhodophyta is well-grounded. These and other Neoproterozoic rodofits, as well as Epiphyton Bornemann 1886 (Figure 1(c)) an...
Sedimentary hydrocarbon remnants of eukaryotic C26-C30 sterols can be used to reconstruct early algal evolution. Enhanced C29 sterol abundances provide algal cell membranes a density advantage in large temperature fluctuations. Here, we combined a literature review with new analyses to generate a comprehensive inventory of unambiguously syngenetic steranes in Neoproterozoic rocks. Our results s...
[1] A large (11–15%) negative shift in dC is observed in shallow water carbonates directly beneath Neoproterozoic glacial deposits (or correlative disconformity) in northwest Namibia ascribed to a snowball Earth. Reproducibility and stratigraphic concordance of this anomaly in 16 sections across the ancient continental shelf support a primary origin, and field relations show it predates the fal...
Neoproterozoic (1,000-542 Myr ago) Earth experienced profound environmental change, including 'snowball' glaciations, oxygenation and the appearance of animals. However, an integrated understanding of these events remains elusive, partly because proxies that track subtle oceanic or atmospheric redox trends are lacking. Here we utilize selenium (Se) isotopes as a tracer of Earth redox conditions...
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