High resolution seismic reflection to characterize small scale mechanisms of large scale natural dissolution in the Hutchinson Salt Member

Abstract

High resolution seismic reflection imaging of the local scale processes along the eastern natural dissolution front of the Hutchinson Salt Member were correlated with its regional scale progression to define a more complete dissolution model that accounts for all observations along the front. 2-D high resolution seismic reflection imaging suggests dissolution along the eastern margin has resulted in a complex system of dissolution channels that have intruded westward into the salt body. Anomalous thinning of the rock salt and resulting sinkholes imaged between 8-20 km from the dissolution front provide evidence to support protruding dissolution has extended west into the salt body in a very irregular fashion. Subsidence features along the eastern margin appear to increase in width (700 m) due to episodic re-activation of subsidence after long periods of dormancy. Time varying access to unsaturated water continues to expand these dissolution corridors and is forming expansive solution networks that grossly make up the dissolution front. It is suggested that dissolution is predominantly progressed horizontally through the salt interval driven by both hydrologic and geologic influences. Geometric distortion of reflections from the salt interval indicate recent activity (e.g. Brandy Lake) and dormant paleo-dissolution networks that discontinuously span a zone approximately 6 km wide along the eastern margin of the Hutchinson salt. High resolution seismic imaging of subsidence related to Brandy Lake is indicative of the complex dissolution history along the front. This dynamic dissolution zone has resulted in the formation of four seismically identified and interpreted subsidence episodes that directly correspond to recent road subsidence along the western flank of Brandy Lake. This unique growth structure represents the continued westward encroachment of horizontally driven dissolution channels into the salt.