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Preliminary report on the geology and geophysics of drill hole UE25a-1, Yucca Mountain, Nevada Test Site

Open-File Report 79-1244
By: , , and 
https://doi.org/10.3133/ofr791244

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Abstract

A subsurface geologic study in connection with the Nevada Nuclear Waste Storage Investigations has furnished detailed stratigraphic and structural information about tuffs underlying northeastern Yucca Mountain on the Nevada Test Site. Drill hole UE25a-1 penetrated thick sequences of nonwelded to densely welded ash-flow and bedded tuffs of Tertiary age. Stratigraphic units that were identified from the drill-hole data include the Tiva Canyon and Topopah Spring Members of the Paintbrush Tuff, tuffaceous beds of Calico Hills, and the Prow Pass and Bullfrog Members of the Crater Flat Tuff. Structural analysis of the core indicated densely welded zones to be highly fractured. Many fractures show near-vertical inclinations and are commonly coated with secondary silica, manganese and iron oxides, and calcite. Five fault zones were recognized, most of which occurred in the Topopah Spring Member. Shear fractures commonly show oblique-slip movement and some suggest a sizable component of lateral compression. Graphic logs are included that show the correlation of lithology, structural properties, and geophysical logs. Many rock units have characteristic log responses but highly fractured zones, occurring principally in the Tiva Canyon and Topopah Spring Members, restricted log coverage to the lower half of the drill hole.
Publication type Report
Publication Subtype USGS Numbered Series
Title Preliminary report on the geology and geophysics of drill hole UE25a-1, Yucca Mountain, Nevada Test Site
Series title Open-File Report
Series number 79-1244
DOI 10.3133/ofr791244
Edition -
Year Published 1979
Language ENGLISH
Publisher U.S. Geological Survey,
Description iii, 46 p., 1 over-size sheet ;27 cm.
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