نتایج جستجو برای: cimmerian orogeny
تعداد نتایج: 807 فیلتر نتایج به سال:
There has been controversy over the number and timing of orogenies in the Precambrian Moine block in the Scottish Caledonides since the earliest radiometric dating in the 1960s. This work challenges a recent hypothesis, that this sector of the Laurentian margin was subjected to continuous crustal extension between .900 and 470 Ma. U–Pb dating (thermal ionization mass spectrometry) of titanite f...
The Andes are known to have influenced speciation patterns in many taxa, yet whether species diversification occurred simultaneously with their uplift or only after uplift was complete remains unknown. We examined both the phylogenetic pattern and dates of branching in Adelomyia hummingbirds in relation to Andean uplift to determine whether diversification coincides with the chronological phase...
the metamorphic complexes of south iran (namely sirdjan, hadji-abad and dolat-abad) are conspicuously related to two different cycles of orogeny and metamorphism . these two cycles are distinctly separate and have been mapped as such throughout the hadji - abad area . the older phase is definitely pre-cambrin, whereas the younger is considered to be early - kimmerian .
the kasian volcanic body is located in the eastern margin of the zagros thrust belt, close to the sanandaj-sirjan metamorphic zone. these volcanic rocks are mainly composed of andesite and andesite-basalt rocks with porphyritic, hypocrystalline porphyritic, hyalo-porphyritic and hyalo-microlitic porphyritic textures. analyses of the distributions of major, rare earth and trace elements reveal a...
In recent years, a rapidly expanding database, especially in sensitive high-resolution ion microprobe (SHRIMP) geochronology, has led to signifi cant advances in understanding of the Precambrian tectonic evolution of the Grenville Province, including its Adirondack outlier, and the Mesoproterozoic inliers of the Appalachians. Based upon this information, we review the geochronology and tectonic...
A common hypothesis for the rich biodiversity found in mountains is uplift-driven diversification-that orogeny creates conditions favoring rapid in situ speciation of resident lineages. We tested this hypothesis in the context of the Qinghai-Tibetan Plateau (QTP) and adjoining mountain ranges, using the phylogenetic and geographic histories of multiple groups of plants to infer the tempo (rate)...
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