Salt Contact Maps

Salt Contact Maps

Correlation of the intersection between the base salt surface (or its corresponding weld) and strata deposited in front of an advancing allochthonous salt body, provides a means of tracking the movement of salt through time, through the production of salt contact maps. In this study, preliminary salt contact maps were generated to better understand the relative timing and trajectory of salt expelled from the Huron and southwest Laurentian subbasins. Through time, the seaward boundary of the Banquereau salt nappe (described in a later section) and the corresponding salt-sediment contact, shift generally (but not exclusively) in the seaward direction. The ramp-to-flat geometry of the basal salt marker reflects a balance between the rate of horizontal salt advance and the rate of vertical sediment accumulation (Fletcher et al., 1995). During periods of rapid salt advance and/or slow sediment accumulation, the base salt surface will show only a very gradual low-angle climb up stratigraphic layers (producing a “flat”) as it moves seaward. In such instances, there are larger error bars on the position of the salt contact because of increased uncertainty about where the seismic horizon terminates along the nearly parallel base salt surface.  In contrast, during periods of slow horizontal salt advance and/or rapid sediment accumulation in front of the salt, the base salt surface will climb more abruptly through stratigraphic layers (producing a “ramp”). In such instances, the salt contacts are more confidently placed. In some instances, correlation of base salt ramps aided the generation of salt contact maps, and provided additional constraints on the movement of allochthonous salt on the eastern Scotian Slope.