نتایج جستجو برای: late neoproterozoic

تعداد نتایج: 196368  

Journal: :International Geology Review 2021

Neoproterozoic and Palaeozoic rocks of the Mérida Massif (SW Iberia) have been grouped into tectonostratigraphic units. Each unit is separated from rest ones by either crustal-scale thrusts and/or extensional detachments. The lowermost (Magdalena Gneisses; lower plate) has continental crust affinity, below a mafic-ultramafic ensemble, referred to as Ophiolite (suture zone). Serie Negra Group co...

Journal: :Science 2009
Huiming Bao Ian J Fairchild Peter M Wynn Christoph Spötl

The oxygen isotope composition of terrestrial sulfate is affected measurably by many Earth-surface processes. During the Neoproterozoic, severe "snowball" glaciations would have had an extreme impact on the biosphere and the atmosphere. Here, we report that sulfate extracted from carbonate lenses within a Neoproterozoic glacial diamictite suite from Svalbard, with an age of approximately 635 mi...

Journal: :Science 2005
Bernd Bodiselitsch Christian Koeberl Sharad Master Wolf U Reimold

The Neoproterozoic glaciations supposedly ended in a supergreenhouse environment, which led to rapid melting of the ice cover and precipitation of the so-called cap carbonates. If Earth was covered with ice, then extraterrestrial material would have accumulated on and within the ice and precipitated during rapid melting at the end of the glaciation. We found iridium (Ir) anomalies at the base o...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 1994
A H Knoll

In rocks of late Paleoproterozoic and Mesoproterozoic age (ca. 1700-1000 million years ago), probable eukaryotic microfossils are widespread and well preserved, but assemblage and global diversities are low and turnover is slow. Near the Mesoproterozoic-Neoproterozoic boundary (1000 million years ago), red, green, and chromophytic algae diversified; molecular phylogenies suggest that this was p...

2003
ANINDA MAZUMDAR KAZUYA TANAKA TAKAFUMI TAKAHASHI IWAO KAWABE

We have studied the REE distribution in shallow marine continental platform carbonates belonging to two late Neoproterozoic basins of India. Their REE abundance patterns normalized by chondrite display well defined W-type tetrad effect. Based on chondrite-normalized Gd/Ho, La/Nd ratios, the REE abundance patterns have been classified into three groups. (Y/Ho) and (Y/Dy) concentration ratios ref...

Journal: :Science 2006
Martin Kennedy Mary Droser Lawrence M Mayer David Pevear David Mrofka

An enigmatic stepwise increase in oxygen in the late Precambrian is widely considered a prerequisite for the expansion of animal life. Accumulation of oxygen requires organic matter burial in sediments, which is largely controlled by the sheltering or preservational effects of detrital clay minerals in modern marine continental margin depocenters. Here, we show mineralogical and geochemical evi...

Journal: :Global and Planetary Change 2021

The Congo basin (CB) occupies a large part of the craton, which derived from amalgamation different cratonic pieces. As intracratonic basin, it initiated, possibly as failed rift, in late Mesoproterozoic and evolved during Neoproterozoic Phanerozoic an intraplate setting. For this reason, CB can be considered natural laboratory for investigating processes that govern long–term evolution contine...

Ghasemi, habiballah, Lambrini, Papa, Rezaei, Mojgan, Sadeghian, mahmood,

Do-Chah metamorphic-igneous complex is one of the Iranian crystalline basement complexess which is located in the SE Shahrood in northern edge of Central Iran structural zone. This complex includes a wide compositional range of metamorphic rocks such as metabasite, metapelite, metacarbonate and metapsammite, and meanwhile is host of leucogranite and biotite granite intrusions. Protolith of meta...

Journal: :Proceedings of the National Academy of Sciences of the United States of America 1998
F J Ayala A Rzhetsky F J Ayala

The time of origin of the animal phyla is controversial. Abundant fossils from the major animal phyla are found in the Cambrian, starting 544 million years ago. Many paleontologists hold that these phyla originated in the late Neoproterozoic, during the 160 million years preceding the Cambrian fossil explosion. We have analyzed 18 protein-coding gene loci and estimated that protostomes (arthrop...

Journal: :Science 1996
Sonett Kvale Zakharian Chan Demko

The tidal rhythmites in the Proterozoic Big Cottonwood Formation (Utah, United States), the Neoproterozoic Elatina Formation of the Flinders Range (southern Australia), and the Lower Pennsylvanian Pottsville Formation (Alabama, United States) and Mansfield Formation (Indiana, United States) indicate that the rate of retreat of the lunar orbit is dxi/dt approximately k2 sin(2delta) (where xi is ...

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