Primary and secondary Bouguer gravity trend analyses and structural implications for Early Proterozoic Kiernan Sills, Iron County, Michigan
The Kiernan Sills outcrop at the eastern edge of the Early Proterozoic Penokean orogenic belt. The sills strike north-northwest by south-southeast and extend approximately 20 km. They have been described as differentiated mafic bodies with MORB-like affinities and comagmatic to superposed pillow basalts. The igneous rocks are overlain by deep marine sediments. Petrogenesis of the sills suggests duplication of a single intrusive as opposed to two discrete sills. Penokean deformation is dominated by east-west trending structures from a south over north compressive regime. In the Kiernan Sills area, however, major and minor structural features are oriented north northwest-south southeast. Field evidence shows that this Penokean-oblique trend is primary rather than a reoriented Penokean-related fabric. Therefore, this deformation predated the major Penokean event and occurred during south-southwest over north-northeast compression. The Bouguer data show a 20 mGal difference between points southwest of the sills and points northeast of the sills. Profiles of simple Bouguer gravity data support northeastward emplacement of the sills on thrusts. First derivative contour maps are suggestive of one or more wrench faults oriented east-west along the sills, which were probably coeval with thrust emplacement.
- OSTI ID:
- 5011480
- Report Number(s):
- CONF-9303210-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:3; Conference: 27. annual Geological Society of America (GSA) North-Central Section meeting, Rolla, MO (United States), 29-30 Mar 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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