Bonneterre Formation
The Bonneterre Formation is an Upper Cambrian geologic formation which outcrops in the St. Francois Mountains of the Missouri Ozarks. The Bonneterre is a major host rock for the lead ores of the Missouri Lead Belt.
| Bonneterre Formation Stratigraphic range: Upper Cambrian | |
|---|---|
_2_(40704497164).jpg) Galena in Bonneterre Dolomite (Upper Cambrian; Missouri) | |
| Type | Formation |
| Underlies | Davis Formation |
| Overlies | Lamotte Sandstone[1] |
| Lithology | |
| Primary | Dolomite |
| Other | Shale, limestone, sandstone[2] |
| Location | |
| Coordinates | 37.636°N 90.578°W |
| Country | United States |
| Extent | Illinois, Minnesota, and Missouri |
The Bonneterre Formation lies conformably on the Lamotte Sandstone and in places lies directly on the Proterozoic igneous core of the mountains. The Bonneterre is conformably overlain by the Davis Formation. In the outcrop area the Bonneterre has an average thickness of 375 to 400 feet. It is present in the subsurface throughout Missouri and has a maximum recorded thickness of 1580 feet under Pemiscot County in the Missouri Bootheel.[2]
The formation is dominantly dolomite with areas or layers of pure limestone. A shaley or glauconitic zone occurs in the lower portion and the base contains sand and conglomerate or breccia where the formation overlaps the Lamotte and lies directly on the granite of the mountain core.[2]
Paleofauna
References
- Thompson, Thomas L., 2001, Lexicon of Stratigraphic Nomenclature in Missouri, Missouri Department of Natural Resources, Division of Geology and Land Survey, Report of Investigation Number 73, p 37
- Howe, W. B. and J. W. Koenig, The Stratigraphic Section in Missouri, Missouri Geological Survey, 1961, pp. 15-18
- Stinchcomb, Bruce; Angeli, Nicholas (2002). "New Cambrian and Lower Ordovician monoplacophorans form the Ozark Uplift, Missouri". Journal of Paleontology. 76 (6): 965–974.
- Various Contributors to the Paleobiology Database. "Fossilworks: Gateway to the Paleobiology Database". Archived from the original on 31 July 2014. Retrieved 8 July 2014.