Data release for Geologic Map of the Leadville North 7.5'
quadrangle, Eagle and Lake Counties, Colorado
Description
The Leadville North 7.5' quadrangle lies at the northern end
of the Upper Arkansas Valley, where the Continental Divide at
Tennessee Pass creates a low drainage divide between the
Colorado and Arkansas River watersheds. In the eastern half
of the quadrangle, the Paleozoic sedimentary section dips
generally 20–30 degrees east. At Tennessee Pass and Missouri
Hill, the core of the Sawatch anticlinorium is mapped as
displaying a tight hanging-wall syncline and foot-wall
anticline within the basement-cored structure. High-angle,
west-dipping, Neogene normal faults cut the eastern margin
of the broad, Sawatch anticlinorium. Minor displacements along
high-angle, east- and west-dipping Laramide reverse faults
occurred in the core of the north-plunging anticlinorium
along the western and eastern flanks of Missouri Hill. Within
the western half of the quadrangle, Meso- and Paleoproterozoic
metamorphic and igneous rocks are uplifted along the generally
east-dipping, high-angle Sawatch fault system and are overlain
by at least three generations of glacial deposits in the
western part of the quadrangle. 10Be and 26Al cosmogenic nuclide
ages of the youngest glacial deposits indicate a last glacial
maximum age of about 21–22 kilo-annum and complete deglaciation
by about 14 kilo-annum, supported by chronologic studies in
adjacent drainages. No late Pleistocene tectonic activity is
apparent within the quadrangle.