EPISODIC GROWTH OF SALT DIAPIRS DRIVEN BY HORIZONTAL SHORTENING
Published:December 01, 1993
We use natural examples and mechanical and geometric reasoning to demonstrate that lateral contraction can trigger episodic rise of previously extinct salt diapirs, even after their source layer has been depleted. Contraction preferentially shortens diapirs, forcing salt upward, rather than deforms the stronger, adjacent sediment overburden. Contraction may be induced by regional compression, tectonic inversion, or by downslope gravity gliding along basin margins during basement subsidence. Contraction often remains cryptic; emergent diapirs rejuvenated by contraction rise with the apparent geometry of passive diapirs, whereas rejuvenated buried diapirs rise with the apparent geometry of active diapirs. Structural clues that interpreters can use to elucidate whether diapir rise was driven by contraction include thick, deformed diapir roofs; pinched-off diapir stems; salt pedestals; diapir rise through flatlying sediment strata; and folds, thrusts, or wrench blocks along the strike or dip of the diapirs.