Onset of foreland -- Basin subsidence in the Middle Jurassic Utah -- Idaho trough, E Nevada and W Utah
- Northern Arizona Univ., Flagstaff, AZ (United States). Dept. of Geology
Analysis of Middle Jurassic strata and regional unconformities of the central Colorado Plateau indicates that these sediments were deposited in the distal part of a retroarc foreland basin. Middle Jurassic strata are divided into two major unconformity-bounded sequences (of Riggs and Blakey, 1993) for modeling purposes. Numerical flexural modeling has produced deflection profiles that match published regional stratigraphic profiles of the two sequences. The best fits between the flexural models and stratigraphic data were obtained using an infinite plate with a flexural rigidity of 10[sup 24] Nm, a mountain-belt topography similar to the Cretaceous Sevier fold-thrust belt, and a tapered alluvial-fluvial system extending 400 km and 600 km, respectively, eastward from the margin of the inferred thrust load. The match between the model and the data is improved by including a dune-field topography on the edge of the forebulge. The models do not include post-depositional uplift, erosion, and development of regional unconformities in the area of the forebulge. However, the stratigraphic architecture and geometry of unconformities closely resemble facies patterns produced in recent numerical models of sedimentation and erosion in foreland basins controlled by episodic thrusting. The data and model results strongly suggest that the onset of regional flexural subsidence in the early Sevier foreland basin took place at the time of formation of the J-2 (or possibly J-1) unconformity. Initial erosion of the J-2 occurred approximately during early Bajocian time ([approximately]170 Ma), which is close to the time of earliest known regional contraction in SE California and Nevada.
- OSTI ID:
- 5343061
- 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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