نتایج جستجو برای: upper precambrian
تعداد نتایج: 206308 فیلتر نتایج به سال:
The AOC Granite 7-32-89-10 hole, drilled to search for oil in the Precambrian basement below the Alberta bituminous (tar) sands near Fort McMurray, Canada, penetrates layered biotite-hypersthene quartz diorite-gabbro sills that occur between 543 and 2363.3 meters depth. Three episodes of fracturing and cataclasis affected these sills. The first allowed Kand Si-metasomatism to change many parts ...
A late Eocene erosion sudace of low relief, which extended throughout south-central Colorado, provides a post-Laramide, pre-Oligocene, regional structural datum. The age and geomorphic character of the sudace are documented for an area of more than 10,400 km2 in the southern Front Range, Rampart Range, South Park, Thirtynine Mile volcanic field, southern Mosquito Range, upper Arkansas River val...
The late Precambrian Shadli Metavolcanics of SE Egypt constitute a slightly metamorphosed bimodal sequence that has been previously interpreted as manifesting volcanic activity at an island arc. We report the first Rb-Sr geochronologic, trace element (including REE), and Nd isotopic data for these rocks. Two types of basalt are recognized, the stratigraphically lower suite having compositions l...
Protein engineering studies often suggest the emergence of completely new enzyme functionalities to be highly improbable. However, enzymes likely catalysed many different reactions already in the last universal common ancestor. Mechanisms for the emergence of completely new active sites must therefore either plausibly exist or at least have existed at the primordial protein stage. Here, we use ...
The distribution and abundance of Ixodes scapularis were studied in Wisconsin, northern Illinois, and portions of the Upper Peninsula of Michigan by inspecting small mammals for ticks and by collecting questing ticks at 138 locations in state parks and natural areas. Environmental data were gathered at a local level (i.e., micro and meso levels), and a geographic information system (GIS) was us...
Meta-ultramafi c rocks occur as small (2 to 100 m long), podiform bodies in all three major Precambrian rock suites of the Tobacco Root Mountains of southwest Montana. Most samples consist of a randomly oriented, coarse-grained assemblage of orthopyroxene, olivine, and magnesiohornblende ± spinel, partially replaced by a fi ne-grained assemblage that may include anthophyllite, talc, cummingtoni...
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