File:Silicified stromatolite boundstone with oolites & sinuous stromatolites (Biwabik Iron-Formation, Paleoproterozoic, ~1.878 Ga; near Mary Ellen Mine, near Biwabik, Minnesota, USA) 4 (47479738932).jpg
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editDescriptionSilicified stromatolite boundstone with oolites & sinuous stromatolites (Biwabik Iron-Formation, Paleoproterozoic, ~1.878 Ga; near Mary Ellen Mine, near Biwabik, Minnesota, USA) 4 (47479738932).jpg |
Silicified stromatolite boundstone with oolites from the Precambrian of Minnesota, USA. (field of view ~11.0 centimeters from top to bottom) Northern Minnesota’s Mesabi Iron Range has numerous iron mines that exploit the Biwabik Iron-Formation (upper Paleoproterozoic, ~1.878 billion years). The Biwabik contains numerous iron-rich lithologies. The most visually intriguing lithology is stromatolitic ferruginous chert (stromatolitic jasper) (a.k.a. “Mary Ellen Jasper”). Stromatolites also occur in other specific lithologies - this specimen is a silicified stromatolite boundstone. Oolites are common in the sediment infilling between the stromatolites. The light-colored, convex-upward, layered, columnal structures in the rock are the stromatolites, which are built up by mats of cyanobacteria living in (typically) very shallow marine settings. The layering of stromatolites is principally the result of tidally rhythmic deposition of sediments atop the cyanobacterial mats. These stromatolites have been assigned to Collenia undosa. What’s especially intriguing about “Mary Ellen Jasper” and other stromatolite rocks in the Biwabik Iron-Formation is the sinuosity of the stromatolite columns. This has been considered to represent tracking of the sun over many seasons. Cyanobacteria are photosynthetic and, like sunflowers, they “want to face the Sun”, wherever it is. Summer-winter seasonal changes in the sun's position in the sky will be expected to result in stromatolite sinuosity. Precambrian sinuous stromatolites from elsewhere have been used to show that the number of days per year has changed through time. Earth used to be rotating much more quickly than at present. The duration of the year hasn’t changed through time, but the rotation rate has. The early Earth had more than 1000 days per year! Stratigraphy: Biwabik Iron-Formation, Paleoproterozoic, ~1.878 Ga Locality: near the Mary Ellen Mine, near Biwabik, central St. Louis County, northeastern Minnesota, USA See info. at: <a href="https://en.wikipedia.org/wiki/Stromatolite" rel="noreferrer nofollow">en.wikipedia.org/wiki/Stromatolite</a> |
Date | |
Source | Silicified stromatolite boundstone with oolites & sinuous stromatolites (Biwabik Iron-Formation, Paleoproterozoic, ~1.878 Ga; near Mary Ellen Mine, near Biwabik, Minnesota, USA) 4 |
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@N05/47479738932 (archive). It was reviewed on 10 October 2019 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
10 October 2019
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current | 00:38, 10 October 2019 | 2,726 × 3,699 (7.12 MB) | Ser Amantio di Nicolao (talk | contribs) | Transferred from Flickr via #flickr2commons |
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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/11 |
ISO speed rating | 80 |
Date and time of data generation | 17:34, 3 April 2019 |
Lens focal length | 11.614 mm |
Image title | |
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 13.0 (Macintosh) |
File change date and time | 20:50, 3 April 2019 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 17:34, 3 April 2019 |
Meaning of each component |
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Image compression mode | 3 |
APEX shutter speed | 5.90625 |
APEX aperture | 6.90625 |
APEX exposure bias | −0.66666666666667 |
Maximum land aperture | 4 APEX (f/4) |
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 | 16:50, 3 April 2019 |
Unique ID of original document | 63AA47AFDCD7448182CDB7394C28F50F |
IIM version | 32,767 |