Upheaval Dome.

May 25, 2012 § 4 Comments

 

Canyonlands is a place of relative geologic order. Layers of sedimentary deposits systematically record chapters in the park’s past. With some exceptions, these layers have not been altered, tilted or folded significantly in the millions of years since they were laid down by ancient seas rivers or winds.

Upheaval Dome is quite a different story. In an area approximately three miles (5km) across, rock layers are dramatically deformed. In the center, the rocks are pushed up into a circular structure called a dome, or an anticline. Surrounding this dome is a downwarp in the rock layers called a syncline. What caused these folds at Upheaval Dome? Geologists do not know for sure, but there are two main theories which are hotly debated.

http://www.nps.gov/cany/naturescience/upheavaldome.htm

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Upheaval Dome in Canyonlands National Park

 

The creation of Upheaval Dome, in Canyonlands National Park, Utah, has long confounded geologists. This giant circular hole in the Utah desert is actually a structural dome with an eroded central region caused by weaker, older rocks (possible salt) at the center of the dome. It has long been debated whether the dome represents the long-term effects of salt diapirism in the Paradox Basin or a meteorite impact scar. Recent work seems to support the meteorite impact hypothesis. Our work suggests that Upheaval Dome represents the end-result of a long history of deformation that was triggered by a meteorite impact but subsequently evolved as salt diapirism continued below the original impact site. We have undertaken detailed field mapping of structural features as well as thin-section petrographic work to unravel the mechanics of disparate deformation styles present in the rock units around the dome.

http://www.webpages.uidaho.edu/~simkat/research.html

and

http://www.webpages.uidaho.edu/~simkat/abstracts/gsa10.html

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Upheaval Dome

Upheaval Dome is a striking geologic structure in the Canyonlands National Park of southern Utah. Viewed from directly above (and on geologic maps), the alternating rock layers make a nearly circular, 5.5-kilometer- (3.4-mile-) diameter “bull’s-eye.” The oldest rocks are in the center (Chinle and Moenkopi Formations, with limited exposures of even older rocks), and progressively younger rocks are exposed farther out: Wingate Sandstone, Kayenta Formation, and Navajo Sandstone (in order of decreasing age). This kind of rock formation—a fold in the Earth’s crust in which the rocks slope downward from either side of a central point—is called an anticline. If the exposed rock layers form a closed circle at the surface, the anticline is called a dome. It is typical of these formations for the central rocks to be the oldest.

This photograph of Upheaval Dome was taken by an astronaut onboard the International Space Station. The oblique viewing angle—in other words, not looking straight down—provides a sense of the topography within and around the structure. The dome appears more like an ellipse than a circle due to the oblique viewing perspective. Dark regions in the image are cloud and cliff shadows.

http://earthobservatory.nasa.gov/IOTD/view.php?id=7887

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Beyond Upheaval Dome is the Island in the Sky District

Looking east from our Cessna Skyhawk II at an elevation of about 1,000 feet (the surrounding plateau is barely 5,300 feet), the concentric rings of Upheaval Dome are clearly visible. Note a small stretch of theGreen River at the bottom left and Upheaval Canyon leading into the center of the dome (right of center).Beyond Upheaval Dome is the Island in the Sky District of Canyonlands and the La Sal Mountains at the horizon.

http://written-in-stone-seen-through-my-lens.blogspot.com/2011/05/enigma-of-upheaval-dome-diapiric-salt.html

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Upheaval Dome very odd geologic feature

http://cedarmesa.blogspot.com/2008_07_01_archive.html

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Chinle Formation western side of Upheaval Dome

http://www.stubotics.com/geoalbum/geoalbum2002.html

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Upheaval Dome Trail

http://www.tripfinding.com/listings/canyonlands_national_park/

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Four Corner States Geology Map

“Back in the Pennsylvanian Period of geologic time, some 310 million years ago, the area was flooded with seawater and formed what we today call the Paradox Basin.

Tectonic activity forming the ancestral Rockies pushed up highlands on the edge of the basin trapping the seawater.  North America was straddling the equator back then and the climate was hot and arid in the region we now call Utah.  Large amounts of seawater evaporated leaving behind thick layers of evaporite minerals like halite (salt – NaCl) and gypsum.

Northeast of the basin, the rising Uncompahgre Uplift was eroding and sediments washed down into the basin eventually filling in the sea and covering the salt with thick layers of clastic sedimentary rocks (clastic rocks are sedimentary rocks formed from sediments – e.g. sandstone).

The pressure from thousands of feet of overlying sediments causes the underlying salt to become plastic and flow.  Being less dense than the ovelying material, it tends to form a plug (diapir) which pushed upward, warping and deforming the overlying flat-lying strata.”

http://hudsonvalleygeologist.blogspot.com/2011/06/upheaval-dome-canyonlands-national-park.html

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