File:Oolitic limestone (Salem Limestone, Middle Mississippian; southern Indiana, USA) 1.jpg
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Summary
DescriptionOolitic limestone (Salem Limestone, Middle Mississippian; southern Indiana, USA) 1.jpg |
English: Oolitic limestone from the Mississippian of Indiana, USA.
(Click on the photo to zoom in & look around.) Sedimentary rocks form by the solidification of loose sediments. Loose sediments become hard rocks by the processes of deposition, burial, compaction, dewatering, and cementation. There are three categories of sedimentary rocks: 1) Siliciclastic sedimentary rocks form by the solidification of sediments produced by weathering & erosion of any previously existing rocks. 2) Biogenic sedimentary rocks form by the solidification of sediments that were once-living organisms (plants, animals, micro-organisms). 3) Chemical sedimentary rocks form by the solidification of sediments formed by inorganic chemical reactions. Most sedimentary rocks have a clastic texture, but some are crystalline. Limestone is a common sedimentary rock composed of the mineral calcite (CaCO3), which bubbles in acid. Many geologically young limestones are composed of aragonite (also CaCO3). Numerous varieties of limestone exist (e.g., fine-grained limestone/micritic limestone/lime mudstone, coquina, chalk, wackestone, packstone, grainstone, rudstone, rubblestone, coralstone, calcarenite, calcisiltite, calcilutite, calcirudite, floatstone, boundstone, framestone, oolitic limestone, oncolitic limestone, etc.). Most limestones represent deposition in ancient warm, shallow ocean environments. Oolitic limestones are whitish to cream-colored limestones composed of sand-sized (1/16 to 2 mm in size), well rounded, concentrically-layered calcite or aragonite grains called oolites (also known as ooliths or ooids). Oolites form by rolling back and forth on a shallow seafloor, or sometimes on a shallow lake bed, by wave action. Oolites are forming today on the Bahamas Platform and in Great Salt Lake, Utah, USA. The technical geologic term for most oolitic limestones is “oolitic grainstone”. Uncertainty exists about the specifics of the origin of oolites. Some researchers conclude that oolites form by completely inorganic chemical precipitation of CaCO3 from water around some nucleus (a tiny shell or skeletal fragment or sediment grain). Other researchers conclude that the presence of bacterial films on oolite grain surfaces play a significant role in the precipitation of CaCO3 layers. However, the undoubted presence of bacteria does not necessarily indicate a biogenic origin for oolites - bacteria are everywhere. Stratigraphy: Salem Limestone, Middle Mississippian Locality: unrecorded/undisclosed site in southern Indiana, USA |
Date | |
Source | Own work |
Author | James St. John |
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2 December 2018
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Date/Time | Thumbnail | Dimensions | User | Comment | |
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current | 04:24, 26 December 2018 | 3,682 × 2,566 (6.94 MB) | Jsj1771 | User created page with UploadWizard |
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F-number | f/3.2 |
ISO speed rating | 80 |
Date and time of data generation | 15:10, 2 December 2018 |
Lens focal length | 7.23 mm |
Width | 4,000 px |
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Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 180 dpi |
Vertical resolution | 180 dpi |
Software used | Adobe Photoshop Elements 13.0 (Macintosh) |
File change date and time | 20:51, 2 December 2018 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 15:10, 2 December 2018 |
Meaning of each component |
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File source | Digital still camera |
Custom image processing | Normal process |
Exposure mode | Manual exposure |
White balance | Auto white balance |
Digital zoom ratio | 1 |
Scene capture type | Portrait |
Lens used | 6.2-18.6 mm |
Date metadata was last modified | 15:51, 2 December 2018 |
Unique ID of original document | 5D359423C400665E3BD7E551970EE901 |