Martin Fisk and Nicola McLoughlin provide a comprehensive photographic atlas of the intricate alteration features found in glass in igneous rocks from the ocean basins. These textures have previously been termed "bioalteration textures" or "etch pits." Fisk and McLoughlin use transmitted-light color photomicrographs to illustrate the range of granular and tubular textures as well as their relationship to fractures, minerals, vesicles, and multiple episodes of alteration in the same sample. They describe the tubular forms using seven morphological characteristics: (1) length and width; (2) density; (3) curvature; (4) roughness; (5) variations in width; (6) branching; and (7) tunnel contents. The photomicrographs are a starting point for understanding the factors that control the formation of the alteration textures, for evaluating the biogenicity of the various forms, for inferring subsurface conditions during alteration, and for making comparisons to similar textures in ancient ophiolites, some of which have been attributed to the earliest life on Earth.
Late Quaternary slip rates of the thrust faults in western Hexi Corridor (Northern Qilian Shan, China) and their implications for northeastward growth of the Tibetan Plateau
Zheng Wen-Jun et al., State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China. Posted online 5 Feb. 2013; http://dx.doi.org/10.1130/GES00775.1.
Based on 10Be exposure dating and topographic profiling, Zheng Wen-Jun and colleagues determined vertical components of slip rates for the Jiayuguan Fault and the Jintanan Shan Fault in the NE Tibetan Plateau. They found that the rates are consistent with previous geological and GPS constraints, and conclude that the Tibetan Pla
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Geological Society of America