Tracking the burial and tectonic history of Devonian shale of the Appalachian Basin by analysis of joint intersection style
Gary G. Lash and Terry Engelder, Dept. of Geosciences, State University of New York-College at Fredonia, Fredonia, New York 14063, USA. Pages 265-277.
Lash and Engelder address the timing and chronology of fracturing of Middle and Upper Devonian black shale deposits, including the Marcellus Shale, exposed on the Appalachian Plateau of western New York State. Specifically, the case is made that these rocks were hydraulically fractured during the Alleghanian Orogeny as a consequence of the transformation of organic matter to hydrocarbons close to, or at peak burial depth. These results are especially important in that they suggest that the organic-rich shale, an emerging natural gas play in the Appalachian Basin, carries the fractures, which enhance the permeability of these otherwise tight hydrocarbon source rocks, at present depths of 6000-7000 feet.
An iron shuttle for deepwater silica in Late Archean and early Paleoproterozoic iron formation
Woodward W. Fischer et al., Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA. Pages 222-235.
It has been known for almost a century that banded iron formations (BIFs) are an enigmatic rock type unique to discrete intervals in the Precambrian, and are, in some fashion, related to the redox state of the oceans and atmosphere. Previous interest in BIFs largely concerned the source and oxidation of the iron. However these deposits contain equal or more silica, suggesting that the elemental cycles of iron and silica were coupled in a fashion unseen in younger d
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