Origin of Supra-salt Synclines in the "Post-diapiric" Jurassic Morrison Formation, Big Gypsum Valley, Colorado

Abstract

The Jurassic Morrison Formation, composed of two members – the Salt Wash and Brushy Basin– can be found surrounding and overlapping the Gypsum Valley salt diapir in the Paradox Basin of southwestern Colorado. The salt began passively rising during the Late Pennsylvanian/Early Permian and continued rising differentially along the length of the salt wall until the late Jurassic, when the Morrison Formation was first deposited. Folds within the Morrison are preserved along the diapir margins where it overlies the salt. These are best exposed at the southeastern part of Big Gypsum Valley as a series of tight folds that get progressively more open to the northwest. This research study will focus on the Morrison Formation and its depositional interaction with the Gypsum Valley salt wall. An understanding of the stresses that existed during folding may allow a determination as to whether dissolution or movement of the underlying salt was important. Detailed measured sections around the margins of the salt diapir and 3D outcrop models of at least three of the folds will be generated with the goal of constraining the mechanisms that formed them. Samples will be gathered and diapir derived clasts will be point counted in thin section to determine the relationship between the Morrison beds and the underlying salt. Understanding the folds and their relationship to the underlying salt will expand our knowledge on how diapirs behave by updating our models to fit the observations that have been made throughout Gypsum Valley, when salt is the main driver of sedimentation patterns. Additionally, defining the mechanisms that formed these structures will help improve our knowledge on how salt diapirs impact the surrounding strata, which could ultimately serve as traps for resources such as oil and gas.

AAPG Datapages/Search and Discovery Article #90351 © 2019 AAPG Foundation 2019 Grants-in-Aid Projects