Basement-cover interaction in post-Mississippian folds in the San Juan Mountains, southwestern Colorado
- Univ. of Kentucky, Lexington, KY (United States). Dept. of Geological Sciences
In the San Juan Mountains of southwestern Colorado, a Cambrian-Mississippian cratonic succession (generally <100 m thick) of clastic and carbonate rocks unconformably overlies a variety of Precambrian basement rocks and structures. Basement and cover strata are broken by steep faults that were reactivated episodically during Cambrian, Devonian-Mississippian and later. On the block between the Coal Bank Pass and Snowdon faults, folded Paleozoic strata overlies a vertically dipping Precambrian succession of alternate units of quartzite and metapelite (each [approximately]150 to 250 m thick); average angular discordance is [approximately]90[degree] at the sub-Cambrian unconformity. Gently plunging anticlines and synclines in Paleozoic strata are distributed systematically with respect to five successive lithologic contacts in the quartzite-metapelite succession; wavelength of the folds in Paleozoic rocks correspond to thickness of the quartzite and metapelite units. The systematic location of anticlines over metapelites and synclines over quartzites suggests that the structural relief of the anticlines was filled by vertical upward extension of metapelite parallel with foliation. A possible mechanism includes subhorizontal compression at a high angle to strike of the quartzite-metapelite, layer-perpendicular shortening and layer-parallel upward ductile extension of the metapelite, and folding of the Paleozoic strata. Folding of the Paleozoic strata probably reflects passive draping over the upward-extending metapelite, but a component of buckle folding with axes perpendicular to compression is also possible.
- OSTI ID:
- 5022306
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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