Geologic map of the Round Hill quadrangle, Clarke and Loudoun Counties, Virginia, and Jefferson County, West Virginia
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Geologic Quadrangle↗
Geology topics
Daniel J. Milton
Publications and source records attributed to Daniel J. Milton.
Reconnaissance geologic map of part of the Milan quadrangle, New Hampshire-Maine, and the Percy quadrangle, New Hampshire
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Open-File Report↗
Fused rock from Köfels, Tyrol
The vesicular glass from Köfels, Tyrol, contains grains of quartz that have been partially melted but not dissolved in the matrix glass. This phenomenon has been observed in similar glasses formed by friction along a thrust fault and by meteorite impact, but not in volcanic glasses. The explosion of a small nuclear device buried behind a steep slope produced a geologic structure that is a good small-scale model of that at Köfels. Impact of a large meteorite would have an effect analogous to that of a subsurface nuclear explosion and is the probable cause of the Köfels feature.
Tschermaks Mineralogische und Petrographische Mitt↗
Maskelynite: Formation by explosive shock
When high pressure (250 to 300 kilobars) was applied suddenly (shock-loading) to gabbro, the plagioclase was transformed to a noncrystalline phase (maskelynite) by a solid-state reaction at a low temperature, while the proxene remained crystalline. The shock-loaded gabbro resembles meteorites of the shergottite class; this suggests that the latter formed as a result of shock. The shock-loading of gabbro at 600 to 800 kilobars raised the temperature above the melting range of the plagioclase.
Science↗
Geology of the Old Speck Mountain quadrangle, Maine
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Open-File Report↗