The Mount Simon Sandstone is an Upper Cambrian sandstone and is found in many states in the Midwest such as Wisconsin, Minnesota, Iowa, Illinois, and Missouri.
| Mount Simon Sandstone | |
|---|---|
| Stratigraphic range: | |
| Type | Geological formation |
| Unit of | Potsdam Sandstone |
| Underlies | Eau Claire Formation and Rome Formation |
| Overlies | Hinckley Sandstone and Middle Run Formation |
| Thickness | up to 2,000 feet (610 m) |
| Lithology | |
| Primary | Coarse sandstones |
| Other | Occasional fine dark grey or maroon shales |
| Location | |
| Extent | Illinois, Indiana, Kentucky, Michigan, Minnesota, Ohio, and Wisconsin, |
| Type section | |
| Named for | Mount Simon escarpment in Eau Claire County, Wisconsin[1] |
| Named by | E. O. Ulrich |
| Thickness at type section | 235 feet |
The Mount Simon formation is the equivalent of the La Motte Sandstone formation in the St. Francois Mountains of Missouri.[1] It was deposited in a nearshore environment, unconformably overlying Precambrian basement, and underlying the Eau Claire Formation in Wisconsin.[2]
The Mount Simon sandstone is named after an escarpment of sandstone in Eau Claire, Wisconsin, called Mount Simon by E.O. Ulrich.[1]
Geology
editThe Mount Simon sandstone is composed of three main lithofacies. First, the lower Mount Simon is composed of a medium to coarse gained sandstone, which is interpreted to have a diagenesis of a high-energy river system.[3]
The middle Mount Simon is a fine to medium grained sandstone with shale beds in it, which is interpreted to be in a high-energy delta.[4]
Finally, the upper Mount Simon is a sandstone that is interpreted to be deposited in a sand shoal or a tidal flat deposits. The upper Mount Simon also has fossil content such as brachiopod shells that are broken up.[4]
There are also different lithofacies within the Mount Simon, which include siltstones, mudstones, and conglomerates. The mudstone and siltstone range from 8 cm to 1 m and is gray to green-gray; however, it is predominantly red. There are also some interbedded layers of small sand grains. The mudstone and siltstone layer is interpreted to be deposited in a distal braid plain (braided river).[5]
The conglomerate layer consists of quartz pebble (1-2 cm with a maximum of 3-4 cm) conglomerates that are well to poorly sorted. The conglomerate layer is at the basal scour of the bed and is 2.5-13 cm thick. This layer is interpreted to be deposited in a medial braid plain and the conglomerate is a result of fluctuations in the energy of the river.[5]
Accessory Minerals
editMinerals other than quartz grains are included in the Mount Simon. Zircon is the most abundant non-opaque mineral in the sandstone, ranging in length, with the average being .1-.2 mm. The color of the zircons was colorless to pink, and some were oxidized, leaving a reddish-orange to yellow color. The next most abundant mineral is tourmaline, which ranges between .15 to .3 mm. The vast majority of the grains are green to yellow-brown, and the minority are blue, pink, green, and violet colors. Rutile is the next most abundant mineral, ranging between .1-.2 mm in size, and is a yellow-brown or red color. Garnet is the next most abundant and is colorless to pinkish-brown, and ranges in size between .1-.3 mm. Apatite, amphibole, pyroxene, epidote, diaspore, staurolite, and anatase are all minerals that occur in the sandstone; however, they are not abundant and only take up a small percent of the grains in the rock. [6]
References
edit- ^ a b c "Mount Simon Sandstone". Indiana Geological & Water Survey. Retrieved 2024-04-08.
- ^ Hamblin, A. P. (2011). Detailed outcrop and core measured sections of Upper Cambrian and Middle Ordovician sandstones (and associated facies), southwestern Ontario (Report). Geological Survey of Canada. doi:10.4095/288671. Open File 6856.
- ^ A, Uribe; Dario, Ruben (1994). "Petrography and Diagenesis of the Upper Cambrian Mt. Simon Sandstone, Southeastern Minnesota". Southeastern Minnesota.
- ^ a b A, Uribe; Dario, Ruben (1994). "Petrography and Diagenesis of the Upper Cambrian Mt. Simon Sandstone, Southeastern Minnesota". Southeastern Minnesota.
- ^ a b Lovell, Thomas R.; Bowen, Brenda B. (2013). "Fluctuations in Sedimentary Provenance of the Upper Cambrian Mount Simon Sandstone, Illinois Basin, United States". The Journal of Geology. 121 (2): 129–154. doi:10.1086/669230. ISSN 0022-1376.
- ^ A, Uribe; Dario, Ruben (1994). "Petrography and Diagenesis of the Upper Cambrian Mt. Simon Sandstone, Southeastern Minnesota". Southeastern Minnesota.
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