Petrology and provenance of a conglomerate facies of the Jacobsville sandstone: Ironwood to Bergland, Michigan
- Geological Survey, Reston, VA (United States)
West of Lake Gogebic, from Ironwood to Bergland, Michigan, the Middle Proterozoic Jacobsville Sandstone is dominated by conglomerate and coarse lithic arenite. In contrast, farther east, the Jacobsville is dominated by a finer grained quartzose, feldspathic, arenite and only minor shale, siltstone, and conglomerate. West of Lake Gogebic, the conglomerate clasts consist of iron formation and quartzite from Early Proterozoic units and vein quartz from Archean units. The only source area for these clasts is to the south. Coarse sand-size lithic clasts from two drill cores approximately 8 km west of Lake Gogebic consist of mafic and felsic volcanic grains and granitic grains. While the mafic and felsic volcanic grains derived from Keweenawan units decrease upsection, the granitic grains derived from Archean units increase upsection. Dips within the western portion of the Jacobsville Sandstone range from 34 N. in the lower part of the section to 9 N. in the upper part, except in area where the Jacobsville has been dragged up on the Keweenaw fault. In contrast, most of the Jacobsville east of Lake Gogebic is relatively flat lying. The northward fanning of the dips west of Lake Gogebic is consistent with deposition on a fault block that was rotating to the north during sedimentation. This rotation was caused by thrust faulting to the north along the Keweenaw fault and to the south along the Pelton Creek fault. Uplift and erosion of Keweenawan, Early Proterozoic and Archean units along the southern edge of this fault block provided the source of the conglomerates and coarse sandstone in the Jacobsville Sandstone west of Lake Gogebic.
- OSTI ID:
- 5505061
- Report Number(s):
- CONF-921058--
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Journal Name: Geological Society of America, Abstracts with Programs; (United States) Vol. 24:7; ISSN GAAPBC; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
Similar Records
Hydrogeochemical and Stream Sediment Reconnaissance basic data for Iron River NTMS Quadrangle, Michigan/Wisconsin
Petrology of the Middle Run Formation (Precambrian), East Continent Rift Basin, western Ohio and north-central Kentucky