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Catoctin Metabasalt at Point of Rocks Maryland by Chris Johnson

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About This Gigapan

Taken by
Chris Johnson Chris Johnson
Explore score
0.32 Gigapixels
Date added
Feb 01, 2013
Date taken
Jan 29, 2013

This is an exposure of the Catoctin formation at Point of Rocks in Maryland, on the north bank of the Potomac River. Point of Rocks is a prominent water gap cut by the Potomac River. The Catoctin formation is Neoproterozoic in age and was erupted as a series of flood basalts during the breakup of the Mesoproterozoic supercontinent Rodinia, and the opening of the Neoproterozoic and Paleozoic aged Iapetus Ocean basin. It overlies the basement complex at the core of the Blue Ridge Anticlinorium. In many places, clastic sedimentary rock occurs between the basement and the Catoctin. A simplified stratigraphic section may be seen here: web.wm.edu/geology/virginia/provinces/Blueridge/blue_ridge_strat.html Will open in a new tab or window The Catoctin was metamorphosed during Alleghanian mountain-building in the late Paleozoic (during the closure of the Iapetus and the assembly of the supercontinent Pangaea). This metamorphism imparted the characteristic green color as a result of the growth of the minerals chlorite and epidote. The image was taken from the public boat ramp on the Virginia side of the Potomac looking north into Maryland along the strike of the eastern limb of the anticlinorium. This area exhibits numerous veins of milky quartz. The western boundary of the Mesozoic Culpeper Basin lies just to the east of this site, an ancient rift valley that formed as Pangaea broke apart and the Atlantic Ocean basin began opening.
The United States Geologic Survey maintains a stream gauge just downstream of the bridge, where data are collected on the Potomac’s discharge: waterdata.usgs.gov/usa/nwis/uv?01638500 Will open in a new tab or window
Thanks go to Callan Bentley for help with such a great description!

Thanks Callan!

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Stitcher Notes


GigaPan Stitch version 2.0.0501 (Windows)
Panorama size: 321 megapixels (20784 x 15460 pixels)
Input images: 100 (10 columns by 10 rows)
Field of view: 32.4 degrees wide by 24.1 degrees high (top=29.7, bottom=5.6)
Vignette correction on: c1=-0.0653 c2=-0.0162
All default settings
Original image properties:
Camera make: Canon
Camera model: Canon PowerShot SX120 IS
Image size: 3648x2736 (10.0 megapixels)
Capture time: 2013-01-29 14:18:59 - 2013-01-29 14:29:50
Aperture: f/4.3
Exposure time: 0.00125
ISO: 80
Focal length (35mm equiv.): 361.4 mm
Digital zoom: off
White balance: Fixed
Exposure mode: Manual
Horizontal overlap: 48.0 to 55.7 percent
Vertical overlap: 47.1 to 49.9 percent
Computer stats: 8183.89 MB RAM, 4 CPUs
Total time 12:26 (7.5 seconds per picture)
Alignment: 4:35, Projection: 2:18, Blending: 5:33
(Preview finished in 8:02)

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