File:Intergranular calcite in autobrecciated amygdaloidal tholeiite basalt aa lava flow top (flow B, Two Harbors Basalts, North Shore Volcanic Series, Mesoproterozoic, 1097-1098 Ma; Burlington Bay, Two Harbors, Minnesota, USA) 1.jpg
Original file (2,903 × 2,635 pixels, file size: 3.28 MB, MIME type: image/jpeg)
Captions
Summary
[edit]DescriptionIntergranular calcite in autobrecciated amygdaloidal tholeiite basalt aa lava flow top (flow B, Two Harbors Basalts, North Shore Volcanic Series, Mesoproterozoic, 1097-1098 Ma; Burlington Bay, Two Harbors, Minnesota, USA) 1.jpg |
English: Intergranular calcite in autobrecciated amygdaloidal quartz tholeiite basalt aa lava flow in the Precambrian of Minnesota, USA.
Along the northern shore of western Lake Superior are numerous exposures of a lava flow-dominated succession called the North Shore Volcanic Series. This is equivalent to & the same age as the Portage Lake Volcanic Series of northern Michigan's Keweenaw Peninsula (www.flickr.com/photos/jsjgeology/albums/72157632266738191). The North Shore and Portage Lake successions are ~1.1 billion years old and represent basalt lava flows, plus minor sedimentary rocks, that filled up an ancient rift valley. This old rift is the Lake Superior segment of the Mid-Continent Rift System, a tear in the ancient North American paleocontinent of Laurentia (see: minerals.usgs.gov/science/midcontinent-rift-minerals/imag...). Tectonic rifting started along this tear, exactly like the modern-day East African Rift Valley. Laurentia's Mid-Continent Rift System started and then stopped and was subsequently filled and buried. This ancient failed rift is now exposed on either side of Lake Superior in North America's Great Lakes. The outcrop shown above is along the shoreline of Burlington Bay at the town of Two Harbors, Minnesota. The rocks are quartz tholeiite basalts - they are part of the Two Harbors Basalts succession. Three lava flows are exposed at this site, designated flow A, flow B, and flow C in the geologic literature. The above photo is a close-up of the upper part of flow B. The basalt has been broken into angular clasts, forming an autobreccia (= dark brown areas). The basalt itself has numerous gas vesicles that have since been filled with minerals, resulting in amygdaloidal basalt. The top of this lava flow is rough, angular, and blocky. The originally-Hawaiian word "aa" is used to refer to lava flows with such surfaces. So, the full term for the rock unit at this outcrop is: autobrecciated amygdaloidal quartz tholeiite basalt aa lava flow. The spaces between the angular clasts of the basalt autobreccia are filled principally with the salmon-colored mineral laumontite. Laumontite is one of the zeolite minerals. Zeolites are often found filling or partially filling cavities in volcanic rocks. Laumonite is a hydrous calcium aluminosilicate mineral, CaAl2Si4O12·4H2O. The intergranular spaces also have some coarsely-crystalline calcite (CaCO3 - calcium carbonate), which is the blocky material at the center of the above photo. Stratigraphy: flow B, Two Harbors Basalts, Upper Southwest Sequence, North Shore Volcanic Series, Keweenawan Supergroup, upper Mesoproterozoic, ~1097-1098 Ma Locality: shoreline exposure on the western side of Burlington Bay, eastern side of the town of Two Harbors, northeastern Minnesota, USA |
Date | |
Source | https://www.flickr.com/photos/47445767@N05/21857722313/ |
Author | James St. John |
Licensing
[edit]- You are free:
- to share – to copy, distribute and transmit the work
- to remix – to adapt the work
- Under the following conditions:
- attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
This image was originally posted to Flickr by James St. John at https://flickr.com/photos/47445767@N05/21857722313. It was reviewed on 8 October 2020 by FlickreviewR 2 and was confirmed to be licensed under the terms of the cc-by-2.0. |
8 October 2020
File history
Click on a date/time to view the file as it appeared at that time.
Date/Time | Thumbnail | Dimensions | User | Comment | |
---|---|---|---|---|---|
current | 15:08, 8 October 2020 | 2,903 × 2,635 (3.28 MB) | Ser Amantio di Nicolao (talk | contribs) | Uploaded a work by James St. John from https://www.flickr.com/photos/47445767@N05/21857722313/ with UploadWizard |
You cannot overwrite this file.
File usage on Commons
There are no pages that use this file.
Metadata
This file contains additional information such as Exif metadata which may have been added by the digital camera, scanner, or software program used to create or digitize it. If the file has been modified from its original state, some details such as the timestamp may not fully reflect those of the original file. The timestamp is only as accurate as the clock in the camera, and it may be completely wrong.
Camera manufacturer | Canon |
---|---|
Camera model | Canon PowerShot D10 |
Exposure time | 1/400 sec (0.0025) |
F-number | f/2.8 |
ISO speed rating | 80 |
Date and time of data generation | 11:53, 8 June 2015 |
Lens focal length | 6.2 mm |
Image title | |
Width | 4,000 px |
Height | 3,000 px |
Bits per component |
|
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 | 21:54, 25 October 2015 |
Y and C positioning | Co-sited |
Exif version | 2.21 |
Date and time of digitizing | 11:53, 8 June 2015 |
Meaning of each component |
|
Image compression mode | 3 |
APEX shutter speed | 8.65625 |
APEX aperture | 2.96875 |
APEX exposure bias | −0.33333333333333 |
Maximum land aperture | 2.96875 APEX (f/2.8) |
Metering mode | Pattern |
Flash | Flash did not fire, auto 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 | 15:54, 25 October 2015 |
Unique ID of original document | 03F04BE3141BB4FBEF51C982C9D9C49B |