File:Sioux Quartzite (Paleoproterozoic, 1.65 to 1.70 Ga; Transcontinental Arch, USA) 1.jpg
![File:Sioux Quartzite (Paleoproterozoic, 1.65 to 1.70 Ga; Transcontinental Arch, USA) 1.jpg](https://upload.wikimedia.org/wikipedia/commons/thumb/d/d8/Sioux_Quartzite_%28Paleoproterozoic%2C_1.65_to_1.70_Ga%3B_Transcontinental_Arch%2C_USA%29_1.jpg/800px-Sioux_Quartzite_%28Paleoproterozoic%2C_1.65_to_1.70_Ga%3B_Transcontinental_Arch%2C_USA%29_1.jpg?20200904052138)
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[edit]DescriptionSioux Quartzite (Paleoproterozoic, 1.65 to 1.70 Ga; Transcontinental Arch, USA) 1.jpg |
English: Quartzite from the Precambrian of the Transcontinental Arch, USA. (7.6 centimeters across at its widest)
Metamorphic rocks result from intense alteration of any previously existing rocks by heat and/or pressure and/or chemical change. This can happen as a result of regional metamorphism (large-scale tectonic events, such as continental collision or subduction), burial metamorphism (super-deep burial), contact metamorphism (by the heat & chemicals from nearby magma or lava), hydrothermal metamorphism (by superheated groundwater), shear metamorphism (in or near a fault zone), or shock metamorphism (by an impact event). Other categories include thermal metamorphism, kinetic metamorphism, and nuclear metamorphism. Many metamorphic rocks have a foliated texture, but some are crystalline or glassy. Quartzite is a common, crystalline-textured, intermediate- to high-grade metamorphic rock. It forms by metamorphism of quartzose sandstones or siltstones. Quartzite can be entirely composed of interlocking quartz crystals, or the original sand grains may still be visible. This rock is hard (H = 7), will not bubble in acid (unlike marble), and can be almost any color. The term “quartzite” has been used in geology to refer to crystalline, quartzose metamorphic rocks and to hard, well-cemented quartzose sandstones that have not been subjected to metamorphism. It is difficult to not call hard, well-cemented sandstones “quartzite” - for example, the Clinch Quartzite in the Appalachian Mountains and the Eureka Quartzite of the Great Basin in western USA, but the Clinch and Eureka aren’t metamorphic rocks. The term "metaquartzite" has been used by some geologists to refer to crystalline-textured, quartzose rocks that have been metamorphosed. This implies that “quartzite” be restricted to well-cemented, non-metamorphosed sandstones. I don’t often see the term metaquartzite in the geologic literature. The quartzite sample seen here is from the Precambrian-aged Sioux Quartzite, which outcrops in southeastern South Dakota and southwestern Minnesota. Despite being regionally metamorphed, the unit’s original sedimentary features, such as horizontal stratification, cross-bedding, and ripple marks, are still apparent in some outcrops. The Sioux Quartzite is a erosion-resistant unit in a long-lived paleotopographic high called the Sioux tectonic core. This high has existed since Precambrian times and is part of a northeast-southwest trending series of paleotopographic highs & depressions known as the Transcontinental Arch, which extends from Arizona to Minnesota (see Carlson, 1999). Stratigraphy: Sioux Quartzite, upper Paleoproterozoic, 1.65 to 1.70 Ga Locality: undetermined quarry; collected from railroad ballast at Missouri Valley, Iowa, USA Reference cited: Carlson (1999) - Transcontinental Arch - a pattern formed by rejuvenation of local features across central North America. Tectonophysics 305: 225-233. |
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Source | https://www.flickr.com/photos/47445767@N05/50303264912/ |
Author | James St. John |
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This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/50303264912. It was reviewed on 4 September 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
4 September 2020
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current | 05:21, 4 September 2020 | ![]() | 2,995 × 1,697 (4.99 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/50303264912/ with UploadWizard |
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Camera manufacturer | Canon |
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Camera model | Canon PowerShot D10 |
Exposure time | 1/60 sec (0.016666666666667) |
F-number | f/10 |
ISO speed rating | 80 |
Date and time of data generation | 13:43, 1 September 2020 |
Lens focal length | 9.681 mm |
Width | 4,000 px |
Height | 3,000 px |
Bits per component |
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Pixel composition | RGB |
Orientation | Normal |
Number of components | 3 |
Horizontal resolution | 180 dpi |
Vertical resolution | 180 dpi |
Software used | Adobe Photoshop Elements 18.0 (Macintosh) |
File change date and time | 18:53, 3 September 2020 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 13:43, 1 September 2020 |
Meaning of each component |
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Image compression mode | 3 |
APEX shutter speed | 5.90625 |
APEX aperture | 6.65625 |
APEX exposure bias | −0.33333333333333 |
Maximum land aperture | 3.625 APEX (f/3.51) |
Metering mode | Pattern |
Flash | Flash fired, compulsory flash firing, red-eye reduction mode |
Supported Flashpix version | 1 |
Color space | sRGB |
Focal plane X resolution | 16,460.905349794 |
Focal plane Y resolution | 16,483.516483516 |
Focal plane resolution unit | inches |
Sensing method | One-chip color area sensor |
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 | 14:53, 3 September 2020 |
Unique ID of original document | F9D44C240A8FD0ED1DBFC19D9646CE4F |
IIM version | 53,248 |