UPHEAVAL DOME NONIMPACT

UPHEAVAL DOME IMPACT CRATER, Utah

by: Charles O’Dale


I have received feedback on my comments regarding my personal observations of the Upheaval Dome. Professional geologists have stated to me that the Planar Deformation Features discovered by Buchner (paper quote below) is firm evidence that the Upheaval Dome is in fact impact related. That being said, these observations and conclusions must be considered as an amateur opinion (by me) derived from my personal observations.


UPHEAVAL DOME IMPACT EVIDENCE                      

Geology of the Upheaval Dome impact structure, southeast Utah

Bryan J. Kriens,  Eugene M. Shoemaker, Ken E. Herkenhoff
Abstract. “Two vastly different phenomena, impact and salt diapirism, have been proposed for the origin of Upheaval Dome, a spectacular scenic feature in southeast Utah. Detailed geologic mapping and seismic refraction data indicate that the dome originated by collapse of a transient cavity formed by impact. Evidence is as follows: (1) sedimentary strata in the center of the structure are pervasively imbricated by top-toward-the-center thrust faulting and are complexly folded as well; (2) top-toward-the-center nomal faults are found at the perimeter of the structure; (3 ) clastic dikes are widespread; (4 ) the top of the underlying salt horizon is at least 500 m below the surface at the center of the dome, and there are no exposures of salt or associated rocks of the Paradox Formation in the dome to support he possibility that a salt diapir has ascended through it; and (5) planar microstructures in quartz grains, fantailed fracture surfaces (shatter surfaces), and rare shatter cones are present near the center of the structure. We show that the dome formed mainly by centerward motion of rock units along listric faults. Outcrop-scale folding and upturning of beds, especially common in the center, are largely a consequence of this motion. We have also detected some centerward motion of fault-bounded wedges resulting from displacement on subhorizontal faults that conjoin and die out within horizontal bedding near the perimeter of the structure. The observed deformation corresponds to the central uplift and the encircling ring structural depression seen in complex impact craters.” (Kriens et al 1999)

A decorated PDF has fluid inclusions along the plane.” (D. Herd) 


In the spring of 2019 I explored the Upheaval Dome structure. I made several observations and now as a result I had my doubts that it is an impact structure . It was my amateur determination that the Upheaval Dome is a saltdome, an anticlinal structure which occurs when a salt diapir (a mobile ductily deformable material) is forced into brittle overlying rocks.

  • Type: Salt Diapira ?
  • Age (ma): <170 (geologically determined)bJURASSIC
  • Diameter: 2.57 km
  • Location: Utah, U.S.A. N 38° 26′ W 109° 54′

a A diapir (salt dome) is a type of structural dome formed when a thick bed of evaporite minerals (salt) found at depth intrudes vertically into surrounding rock strata.

b The precise age of Upheaval crater has not been determined. The problem is that the crater is deeply eroded. One certainty is that the crater is younger than the Jurassic Navajo Sandstonec which was deformed by the diapir and is the youngest unit exposed in the vicinity.

c Navajo Sandstone: Stratigraphic range: Early Jurassic (Toarcian and Pliensbachian): 191–174  Ma

UPHEAVAL DOME OBSERVATIONS (2019):

I compare the following characteristics of the Barringer Impact Crater  with those of the similarly sized Upheaval Dome to reach my hypothesis.

CRATER RIM: The rim of the Barringer Crater is uplifted 50 metres above the surrounding plain by the energy of the impact. The diminutive rim of the Upheaval Dome rim could have been “uplifted” by the salt diapir.

The rim of the Barringer Impact Crater uplifted by the impact energy. The rim rises nearly 50 metres above the surrounding plain.
The rim of the Upheaval Dome, possibly uplifted by the diapir (salt central peak), does not resemble an impact crater rim. The rim is penetrated by a salt-cored anticline.

CRATER RIM EJECTA: The rim of the Barringer Crater is covered by ejecta boulders of all sizes. Ejecta is absent on the rim of the Uphaval Dome.

The rim of the Barringer Impact Crater uplifted by the energy of the impact is covered with large ejecta boulders.
Ejecta boulders are completely absent around the Upheaval Dome.

CRATER INSIDE WALL: The rim of the Barringer Crater is totally shattered whereas the rim of the Uplift Dome has non-shattered sheer walls.

The country rock rim wall within the Barringer Impact Crater is totally shattered.  [COUNTRY-ROCK]
Upheaval Dome non-shattered inside rim with sheer walls. Note the anhydrite (evaporate material) within the crater.

OVERTURNED RIM: Overturn is documented at Barringer but is absent from the “rim” of the Upheaval Dome.

The Barringer Crater high energy [HIGH-ENERGY]  impact explosion ejected large amounts of material out of the crater, in some cases preserving stratigraphic relationships. Notice that the normal undisturbed sequence has the Coconino (oldest) at the bottom, followed by the Toroweap, Kaibab and Moenkopi (youngest) as you move upwards. In the overturned rocks near the crater, this sequence is repeated above the Moenkopi, but in a reverse (overturned) order. The ejected and overturned material extends 1 to 2 km from the crater.
CENTRAL PEAK: The size of the Barringer Impact Simple Crater (1.19 km dia) is comparable with the Upheaval Dome (2.57 km dia). A central peak is absent from simple craters (Barringer). The “central peak” of the Upheaval Dome is not impact related but is composed of diapir uplifted anhydrite (evaporate material).

The Barringer Crater is an excellent example of a simple crater (without a central peak).
Upheaval Dome, comparable in size to the Barringer simple crater, contains a central peak formed by uplifted diapir anhydrite (evaporate material). The central uplift is inferred to be “the toe of the convergent gravity spreading system” (Jackson et al. 1998). Note the crater rim penetration by a salt-cored anticline.

UPHEAVAL DOME DIAPIR HYPOTHESIS

Structure and evolution of Upheaval Dome: A pinched-off salt diapir

M. P. A. Jackson, D. D. Schultz-Ela, M. R. Hudec,I. A. Watson, M. L. Porter GSA Bulletin (1998)
Abstract:
“Upheaval Dome (Canyonlands National Park, Utah) is an enigmatic structure previously attributed to underlying salt doming, cryptovolcanic explosion, fluid escape, or meteoritic impact. We propose that an overhanging diapir of partly extrusive salt was pinched off from its stem and subsequently eroded. Many features support this inference, especially synsedimentary structures that indicate Jurassic growth of the dome over at least 20 m.y. Conversely, evidence favoring other hypotheses seems sparse and equivocal.

“In the rim syncline, strata were thinned by circumferentially striking, low-angle extensional faults verging both inward (toward the center of the dome) and outward. Near the dome’s core, radial shortening produced constrictional bulk strain, forming an inward-verging thrust duplex and tight to isoclinal, circumferentially trending folds. Farther inward, circumferential shortening predominated: Radially trending growth folds and imbricate thrusts pass inward into steep clastic dikes in the dome’s core. We infer that abortive salt glaciers spread from a passive salt stock during Late Triassic and Early Jurassic time. During Middle Jurassic time, the allochthonous salt spread into a pancake-shaped glacier inferred to be 3 km in diameter. Diapiric pinch-off may have involved inward gravitational collapse of the country rocks, which intensely constricted the center of the dome. Sediments in the axial shear zone beneath the glacier steepened to near vertical. The central uplift is inferred to be the toe of the convergent gravity spreading system.” (Jackson et al 1998)

THE COLORADO PLATEAU GEOLOGICAL PROVINCE

The Upheaval Dome is in the Canyonlands National Park, a place of relative geologic order. The layers of sedimentary deposits, with some exceptions, have not been altered, tilted or folded significantly in the millions of years since they were laid down by ancient seas, rivers or winds.

Within the park is the Paradox basin, an inland sea deposited during Middle Pennsylvanian. This sea dried up intermittently leaving behind a thick accumulation (1.525 km) of layered marine salt (a mobile ductily deformable material). Subsequently during the Permian, Jurassic, Triassic and Cretaceous the basin was covered by layers of sedimentary rock.

The Paradox Basin is an evaporite basin containing sediments from alternating cycles of deep marine and very shallow water. As a result of the thick salt sequences and the fact that salt is ductile at relatively low temperatures and pressures, salt tectonics play a major role in the post-Pennsylvanian structural deformation within the basin.

Salt has been moving in the Paradox basin since the Permian, influencing depositional patterns and creating significant thickness variations and causing angular unconformities. A rising plug of relatively low-density salt may cause overlying rock layers to dome up in a circular pattern underneath a blanket of sedimentary rock. The overlying rock layers are uplifted and then eroded, leaving the bull’s-eye surface pattern. The technical name for this is a salt Diapir.

Onion Creek diapir. Caprock with anhydrite (evaporate material) layers is light greenish while country rock is red. This structure looks like an Upheaval Dome cut in half! .

Diapir (sub-surface salt dome) :

The rim of Upheaval Dome is 2.57 km across and over 305 metres above the core floor. The central peak in the core is 915 metres in diameter and rises 230 metres from the floor.

A salt diapir is less dense than the surrounding rock and begins to flow upward causing the surface rocks to bend. The diapir pinches off as it continues its ascent. The uplift of the overlying rocks expose them to heightened rates of erosion. The pinched-off salt diapir along with the overlying strata, are eroded away leaving behind the circular Upheaval Dome.

REFERENCE:

What is a Salt Dome? – Geology.com

Bryan J. Kriens,  Eugene M. Shoemaker, Ken E. Herkenhoff Geology of the Upheaval Dome impact structure, southeast Utah JOURNAL OF GEOPHYSICAL RESEARCH AUGUST 25, 1999

Buchner, E. and Kenkmann, T, UPHEAVAL DOME, UTAH, USA: IMPACT ORIGIN CONFIRMED. Large Meteorite Impacts and Planetary Evolution IV (2008)

Chris H. Okubo ,Richard A. Schultz, Compactional deformation bands in Wingate Sandstone; additional evidence of an impact origin for Upheaval Dome, Utah. Lunar and Planetary Laboratory, University of Arizona, 2007

Structure and evolution of Upheaval Dome: A pinched-off salt diapir

M. P. A. Jackson, D. D. Schultz-Ela, M. R. Hudec,I. A. Watson, M. L. Porter GSA Bulletin (1998)