Role of Precambrian compositions and fabrics in the development of foreland structures, southern Front Range, Colorado

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6875939

Chase, R B

The Front Range terminates to the south as three basement-cored uplifts located north and west of the Canon City embayment. Precambrian units consist of foliated and non-foliated granitic rocks, augen gneiss, interlayered schist and gneiss, amphibolite, quartzite, and pegmatite. Precambrian deformations include at least three phases of folding, two phases of crenulation cleavage development, and local mylonitization. Metamorphic conditions reached those of cordierite-sillimanite grade. Paleozoic and Mesozoic sediments surround and overlap the exposed uplifts to form south-plunging arches. Excellent three-dimensional exposure of structural relationships between Precambrian rocks and overlying Phanerozoic sediments is present. Deformation styles in the sedimentary cover are strongly influenced by underlying Precambrian lithologies and structural orientations. Where the crystalline units are granitic, with steeply-dipping foliation or no directional fabric, uplifts are bounded by high angle faults. Some such faults show evidence of repeated movements and reversals dating back to Precambrian time. The boundary between mechanical basement and suprastructure is clearly not defined as the base of the sedimentary section. Balanced cross-sections constructed through the southern Front Range must include contemporaneous flexural folds and thrusts in Precambrian schistose and gneissic rocks as well as in Phanerozoic sedimentary layers.

• Research Organization: Western Michigan Univ., Kalamazoo (USA)
• OSTI ID: 6875939
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100 -- Geology & Hydrology-- (-1989)
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
AMPHIBOLITES
BASEMENT ROCK
COLORADO
FEDERAL REGION VIII
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GEOLOGY
GNEISSES
GRANITES
IGNEOUS ROCKS
METAMORPHIC ROCKS
METAMORPHISM
MOUNTAINS
NORTH AMERICA
PETROLOGY
PLUTONIC ROCKS
PRECAMBRIAN ERA
ROCKS
ROCKY MOUNTAINS
SCHISTS
TECTONICS
USA