A structural analysis of the Midcontinent Rift in Michigan, based on a fault array analysis utilizing slickenside
- Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Geology and Geophysics
The Midcontinent Rift is a 1.1 billion year old crustal structure which has been defined primarily on the basis of geophysical studies. It displays evidence of both rifting and subsequent closure. Many studies have examined the rift from a petrologic view but few have examined it in any detail from a structural geological viewpoint. This paper examines the structural aspects of the rift, elucidates the direction of closing, and constrains the timing of the system by utilizing paleostress stratigraphy. Establishment of the relative age and sense of movement on faults was accomplished by analyzing slickensides and crystallization on the fault plane. Detailed work on the Keweenaw Peninsula of Michigan suggests a southerly direction for the closing of the rift system, while similar work on Isle Royale suggests an east-southeasterly closing direction. Faults in both areas with opposite sense of movement (dextral vs. sinistral, normal vs. reverse) have similar attitudes indicating a reversal of maximum and minimum stress directions. Stress tensors from both limbs of the Lake Superior syncline were isolated using identical methods, suggesting the geometry or lithology of the system interfered with the manifestation of the far-field stresses. The results suggest then the direction of opening and closing of the rift was constrained by the geometry of the major and minor fault systems and anisotropies in the lava flows.
- OSTI ID:
- 5578962
- Report Number(s):
- CONF-921058-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 24:7; Conference: 1992 annual meeting of the Geological Society of America (GSA), Cincinnati, OH (United States), 26-29 Oct 1992; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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