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

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 inwardverging 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.

Morphotectonic and Morphodynamic investigations revealed by isobase surfaces analysis and derived differential mapping using GIS, Teboursouk area, northern Tunisia

“…These isobase interpretations which reveal the diminished of sedimentary thickness were confirmed by local geological observations (Perthuisot 1981;Perthuisot et al 1999), particularly in the peridiapiric areas of the Triassic extrusion of JEC. In fact, toward the tow flanks of this massif, thinning of the postTriassic layers (mainly Cretaceous and Paleogene) were observed, described (Dali 1979;Chikhaoui 2002) and recently confirmed from seismic reflection profile and complete Bouguer gravity analysis (Benassi 2011); suggesting therefore a model of deep-rooted diapiric structure (Jackson et al 1998;Vendeville 2002) which the morphostructural evolution was reflected by local sedimentological variations displayed around the diapiric structure.…”

Compactional deformation bands in Wingate Sandstone; additional evidence of an impact origin for Upheaval Dome, Utah

“…The oldest rocks consist of White Rim Sandstone, which consists of coastal eolian sediment and is present in Upheaval Dome only as cataclastic dikes intruded into the overlying strata Various origins for Upheaval Dome have been proposed. Two commonly cited origins are meteoritic impact [3][4][5][6][7][8][9] and salt diapirism from the subjacent Pennsylvanian-aged Paradox Formation [10][11][12][13]. Upheaval Dome has also been interpreted to be the result of igneous intrusion [10,11], explosive volcanism [14] or tectonically driven fluid overpressure [15], however these three latter mechanisms are not supported by recent literature.…”

“…This maximum value of lithostatic load is calculated from the maximum depth of burial for the Wingate Sandstone at Upheaval Dome. Regional exposures suggest a maximum depth of burial for the Wingate Sandstone of 2.2 km, during the Tertiary period [13]. Assuming an average overburden density of 2450 kg/m 3 (e.g., [42,47]), this depth of burial corresponds to a maximum of ca.…”

“…Furthermore, planar-deformed quartz grains occur within the cataclastic dikes of White Rim Sandstone [6,8]. TEM and SEM analyses of deformed quartz grains from these cataclastic dikes reveal microcracks, isolated [13], and the orthophotograph from the U.S. Geological Survey [2]. Illumination is from the bottom of the image.…”

A new aetosaur (Reptilia: Archosauria) from the Upper Triassic of Texas and the phylogeny of aetosaurs

“…Due to stratigraphic disruption caused by the salt diapir that forms Upheaval Dome (Jackson et al, 1998), the section dips 20 degrees to N60 degrees east. The Chinle Group at this section consists of the following named units The partial skeleton we describe here was found in a grayish-green, pisolitic calcrete ledge 11.5 m above the base of the Blue Mesa Member of the Petrified Forest Formation (Fig.…”