Upheaval Dome

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Coordinates: 38 ° 26 '13 "  N , 109 ° 55' 45"  W.

Map: Utah
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Upheaval Dome​
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Utah
View from the ISS (May 2007) of the Upheaval Dome

The Upheaval Dome ( dt. "Uplift hill") is a crater-like geological structure in Canyonlands National Park near Moab in the US state of Utah .

The central crater depression measures approximately 1.4 kilometers in diameter and is over 400 meters deep. The maximum age of the crater is estimated at 170 million years ( Jurassic ). On the surface it can be clearly recognized by its light brown and black colored concentric rings.

Stratigraphic sequence

The oldest rock unit in the center of the Upheaval Dome is the White Rim Sandstone member of the Permian Cutler Formation . In the national park, this unit is normally covered by a sedimentary load of more than 1,600 meters. This is followed with a discordance by the Triassic Moenkopi Formation , which in turn is discordantly overlaid by the Chinle Formation . The frame is made up of the steep wall-forming Wingate Sandstone , the Kayenta Formation and the obliquely layered Navajo sandstone .

Structural structure

Structurally , the Upheaval Dome is a very unusual phenomenon. Incidentally, Canyonlands National Park, the rock strata are mostly horizontal or fall only slightly. When Upheaval Dome, but they form a dome-like state bulging ( Engl. "Central Uplift"), in the center, some layers are often almost vertical. Even in the U-shaped plateau ring, angles of incidence of 70 degrees were still measured in the Kayenta formation. A ring-shaped syncline 3.5 kilometers in diameter girdles the center. It can mainly be seen in the Navajo sandstone. A little further north, a concentric monocline with a diameter of around 5 kilometers has also been mapped.

What is striking about the structure is its deviation from a circular shape, it is rather slightly stretched in a north to north-northeast direction. The structures in the central mountain ( fold axes / radial anticlines, faults / thrusts ) also deviate from an ideal radial symmetry to be expected , rather they show bilateral symmetry in SE-NW direction. In addition, there are predominantly flat faults dipping towards the northwest (mainly in the central mountain, but also on the crater rim). This indicates a general transport of material to the southeast - possibly due to a meteorite impact from the northwest.

Attempts to explain

There are two popular, well-known theories that explain bulge:

  • Salt dome . Due to the load on the hanging wall, the salt from the Paradox formation was plastically deformed and made its way to the surface as a diapir . In the case of the Upheaval Dome, it is assumed that the former diapir including its covering has already been completely removed and the current surface only represents the torn stem of the diapir. If this proves to be true, then the Upheaval Dome would be the most deeply eroded salt structure on earth.
  • Eroded meteorite crater . Similar to the Barringer Crater near Winslow in Arizona, the impact of a meteorite is blamed for the structure, but the Upheaval Dome is said to have a significantly lower floor.

There is also a theory of a cryptovolcanic explosion.

In the nineties, geologists and seismologists from NASA and the University of Nevada in Reno examined the Upheaval Dome in great detail, it was mapped and seismically surveyed. The results of this study spoke in favor of the meteorite theory. A seismic reflection study from 1999 was able to confirm the salt layer of the Paradox formation at a depth of 1160 meters underground, but it is flat and shows only slight relief. Center-oriented Listrian faults also suggest a shock wave from above. In 2008, the discovery of shock quartz was announced, an indication of the impact of a meteorite. This find has so far been limited to a single location with only a few shocked grains. Further indications that suggest a meteorite impact are cones of rays , synsedimentary deformation structures such as compact deformation bands, dike injections, close-meshed fault networks in the centimeter range, internal brecciation, cataclastic flow and rock liquefaction .

Even if almost everything now speaks for a meteorite impact, the debate about the origin of the Upheaval Dome is still not entirely over.

Photo gallery

Panoramic shot of the Upheaval Dome. Photographed from the second vantage point on the high circular route

  • Upheaval Dome from the crater rim

  • Syncline in the Navajo Sandstone , northwest side.

  • Steep layers in the center of the crater

  • Panorama photo from three individual photos (2005-05-26)

See also

Individual evidence

  1. ↑ a b Geologic Map of Canyonlands National Park and Vicinity, Utah, 1982 Edition, by PW Huntoon et al. Scale: 1: 62500 (map)
  2. ↑ Jackson, MPA, Shultz-Ela, DD, Hudec, MR, Watson, IA and Porter, ML Structure and evolution of Upheaval Dome: A pinched-off salt diapir, Geological Society of America Bulletin: vol. 110, no. 12, pp. 1547-1573. 1998.
  3. ↑ Bucher, WH (1936). Cryptovolcanic structures in the United States: 16th International Geological Congress, Report Session 2, p. 1055-1084
  4. ↑ Herkenhoff, KE, Giegengack, R., Kriens, BJ, Louie, JN, Omar, GI, Plescia, JB, Shoemaker, EM Geological and Geophysical Studies of the Upheaval Dome Impact Structure, Utah, LPSC XXX, Lunar and Planetary Institute, Houston, TX, Abstr. 1932 (CD-ROM). 1999.
  5. ↑ Kanbur, Z., Louie, JN, Chavez-Perez, S., Plank, G. and Morey, D. Seismic reflection study of Upheaval Dome, Canyonlands National Park, Utah. Journal of Geophysical Research - Planets, 1999.
  6. ↑ Buchner, E., Kenkmann, T. Upheaval Dome, Utah, USA: Impact Origin Confirmed. Geology, v 36, no 3, p 227-230. 2008
  7. Jump up ↑ Alvarez, W., E. Staley, and MA Chan, Synsedimentary deformation in the Jurassic of southeastern Utah: A case of impact shaking, Geology, 26, 579-582, 1998
  8. ↑ Okubo, CH, Schultz, RA Compactional deformation bands in Wingate Sandstone; additional evience of an impact origin for Upheaval Dome, Utah. Earth and Planetary Science Letters, 256, pp. 169-181. 2007.
  9. ↑ Kenkmann, T., Dike formation, cataclastic flow, and rock fluidization during impact cratering: an example from the Upheaval Dome structure, Utah, Earth and Planetary Science Letters 214, pp. 43-58. 2003.

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