File:Middle Run Formation (Proterozoic; Warren County core, Ohio, USA) 4.jpg
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Summary
| Description |
English: Sandstone from the Precambrian of Ohio, USA.
This is part of a continuously-cored section of Precambrian-aged, siliciclastic sedimentary rocks from southwestern Ohio's deep subsurface. The Ohio Geological Survey drilled this core from 1987 to 1989 in northeastern Warren County, Ohio. It was intended to be a stratigraphic reference section from the Upper Ordovician to Precambrian basement rocks. Instead of encountering igneous or metamorphic rocks below the Cambrian sedimentary cover, the core unexpectedly penetrated a thick, late Precambrian-aged sedimentary succession, which has been interpreted as a rift-basin fill. The rift fill sedimentary rocks were a new stratigraphic formation now called the Middle Run Formation. The cores shown here are part of that unit. The Middle Run Formation in the Warren County core consists principally of sandstone, with very minor siltstone and conglomerate. The colors in these rocks are from iron oxides. Available age information comes from zircon fission-track dating (580 Ma, 684 Ma, and 707 Ma), SHRIMP uranium-lead dating (1.012 Ga), and biostratigraphy (organic-walled microfossils similar to Neoproterozoic-aged fossils reported from elsewhere). The fission-track dates may be reset from the rocks experiencing >200 degrees Celsius temperatures for over 1 million years (see Richardson, 2015). Stratigraphy: Middle Run Formation, Proterozoic (probably Neoproterozoic). Locality: 4830 feet to 4840 feet interval (= feet below the surface well site), Ohio Division of Geological Survey core 2627, American Aggregates Corporation limestone quarry (now flooded), just northeast of the town of Lytle, northwestern Wayne Township, northeastern Warren County, southwestern Ohio, USA Core-specific info. from: Shrake (1991) - The Middle Run Formation: a subsurface stratigraphic unit in southwestern Ohio. Ohio Journal of Science 91: 49-55. Richardson (2015) - Organic microfossils of the Middle Run Formation (Neoproterozoic?) of Ohio, U.S.A. Northeastern Geoscience 33: 34-40. |
| Date | |
| Source | Own work |
| Author | James St. John |
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 03:54, 26 December 2018 | | 4,000 × 2,729 (6.33 MB) | Jsj1771 | User created page with UploadWizard |
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