Restoration of Cross Sections Above Intrusive Salt Domes

Abstract

The applicability of bed-length restoration to the sequence above a vertical intrusion of salt was tested on an experimental model that included deposition of units during uplift. Restoration of the model resulted in an apparently unbalanced cross section due to excess bed length in the pre-growth interval. The excess bed length was due to significant internal strain. For a correct restoration, it is thus important to distinguish between the growth and pre-growth sequences. The thinning index, which quantifies the thinning onto the uplift, aids in making this distinction. A thinning index vs. depth curve has a sharp inflection at the top of the pre-growth sequence. The pre-growth sequence is restored by area balancing. The growth sequence deforms mainly by formation of a restal graben, with little other strain. Sequential restoration of growth intervals shows the growth history of the dome. When applied to the Pool Creek salt dome from the Mississippi Interior Salt basin, the methods developed for the model served to separate the pre-growth from the growth sequence and to indicate a growth history of vertical intrusion changing through time to vertical intrusion plus regional extension.