--> ABSTRACT: The Composite Salt Glacier: Extension of the Salt Glacier Model to Post-Burial Conditions, by M. R. Hudec, R. C. Fletcher, I. A. Watson; #91020 (1995).

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The Composite Salt Glacier: Extension of the Salt Glacier Model to Post-Burial Conditions

M. R. Hudec, R. C. Fletcher, I. A. Watson

Fluid dynamics modeling suggests that during emplacement, salt glaciers maintain a relief of hundreds of meters, and are thus unlikely to be buried. Most salt sheets are not buried until salt supply up the feeder stock slows or is cut off entirely, leading to relaxation of the dynamically supported topography of the sheet and progradation of sediments across its updip end.

The onset of sedimentation on top of a salt sheet does little to alter the mechanics controlling salt deformation. There is still relief on the sediment-water contact, driving downdip flow of the salt and sedimentary carapace. The salt itself may no longer be extrusive, but the system as a whole, which we term a composite salt-sediment glacier, is still governed by the mechanics of gravity spreading. Instead of being fed entirely by salt supply from below, a composite glacier is fed by sedimentation, especially in extensional minibasins near its updip end (Figure 1). The extension in the updip minibasins is compensated at the toe of the glacier either by extrusion of salt (if the toe remains uncovered) or by contractional folds and thrust faults (if the toe is buried, Figure 2). A com osite glacier will remain active as long as the relief on its upper surface is sufficient to overcome the forces resisting its lateral motion. Many composite glaciers stop moving shortly after the toe is buried. Once density inversion is achieved in the minibasins, buoyancy forces begin to compete with lateral spreading as a control on the style of salt tectonism, and a point will eventually be reached where it is no longer useful to consider the system as a glacier.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995