Abstract

The Onion Creek Diapir is one of many salt domes proximal to the Uncompahgre thrust front of the ancestral rockies in the Paradox Basin. It is comprised of Paradox Formation evaporites and large blocks of Honaker Trail Formation carbonates that were deformed by loading of Permian Cutler Formation progradational alluvial to fluvial fans. The history of salt movement in the Onion Creek Diapir is recorded in the near-salt strata. Large salt bodies and their adjacent mini-basins evolve conforming to a complex relationship between salt withdrawal, creating localized accommodation, and sediment deposition. Migrating mini-basin depo-centers, thinned and folded strata, and spatial facies trends reveal the relative rates of diapirism and sedimentation. The study area outcrop, north of the diapir, is divided by significant stratigraphic horizons that help define depositional periods. Six measured sections in the study area reveal higher preservation rates of fine grained floodplain deposits, typically destroyed in alluvial environments, than at locations correlating to stratigraphic levels high in the outcrop suggesting a low accommodation environment evolving into higher accommodation where stacked channel complexes are preserved. Preserved slump folding at the base of the outcrop reveals that although some salt emergence occurred in the earliest depositional period it was not significant enough to preclude sediment deposition or to divert the Cutler fluvial network and destroy floodplain facies. A 3-D digital outcrop, modeled from photogrammetric data, illustrates the development of localized accommodation, attracting fluvial channel in a near-salt, tight axial syncline during the later depositional period. These evidences suggest a greater emergence of the diapir and likely diversion of the Cutler channel complexes.

Degree

College and Department

Physical and Mathematical Sciences; Geological Sciences

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