Filters: Tags: Gallatin Range (X)
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The geology of western and northern Gallatin National Forest was mapped in two parts as part of an evaluation of its mineral resource potential by the USGS. Previously, the western part was released as Map A and the northern part as Map B of USGS Geologic Investigations Series Map I-2584. These maps were compiled, digitized, and produced using the USGS software program GSMAP. All the original source maps were simplified on mylar overlays, digitized at their original map scales and projections, and then merged into the final maps. After editing, the digital maps were filtered to remove all points not necessary for improving resolution at a scale of 1:126,720 (2 mi per in., the scale used by the USDA Forest Service)....
The Ennis 1:100,000 quadrangle lies within both the Laramide (LateCretaceous to early Tertiary) foreland province of southwesternMontana and the northeastern margin of the middle to late TertiaryBasin and Range province.The oldest rocks in the quadrangle are Archean high-grade gneiss, andgranitic to ultramafic intrusive rocks that are as old as about 3.0Ga. The gneiss includes a supracrustal assemblage of quartz-feldspargneiss, amphibolite, quartzite, and biotite schist and gneiss. Thebasement rocks are overlain by a platform sequence of sedimentaryrocks as old as Cambrian Flathead Quartzite and as young as UpperCretaceous Livingston Group sandstones, shales, and volcanic rocks.The Archean crystalline rocks crop...
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