Abstract: Initiation and Early Growth of Salt Structures in the Paradox basin, Utah and Colorado: Insights from Dynamically Scaled Physical Experiments

Hongxing Ge, M. P. A. Jackson, B. C. Vendeville, M. R. Hudec

Seismic interpretation suggests that southwestward progradation of a sedimentary wedge of Cutler Formation initiated the major salt walls in the Paradox basin during late Paleozoic time. We carried out physical models to investigate these salt structures. Dry quartz sand experimentally simulated brittle sediments, and a viscous silicone simulated salt. Synkinematic sand wedges with a 5-degree surface slope prograded onto a starved or semi-starved basin containing salt covered with a thin, flat, prekinematic overburden. Initially, the base of the salt was either flat or stepped.

Over a flat base, salt was expelled basinward from beneath the prograding wedge, eventually creating a primary salt weld. In front of the wedge, the salt layer uniformly thickened, rising the overburden and creating a landward-facing monocline between the uplifted region and the wedge. As the monocline rolled ahead of the wedge, older strata subsided behind it, but no diapirs formed.

Over a stepped fault scarp base, lateral flow of salt was restricted, forming a gentle swell. Aggradation within the basin concurrent with progradation from the basin edge accentuated the salt swell. Non-deposition and erosion above the swell triggered diapirism there. The diapir wall widened by lifting the overburden and rose by downbuilding, as observed on the seismic profiles. This deformational cycle recurred as the prograding wedge reached each basement scarp, creating a series of basinward-younging salt structures. These models kinematically and dynamically reproduced the major salt structures and stratigraphic variations in the Paradox basin.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994