A seismic study of salt dissolution in the Stettler area south-central Alberta, Canada
In Famennian (Late Devonian) time, bedded Wabamun Group rock salt with a net thickness of about 40m was deposited throughout the Stettler area (T25–40, R11-21W4M), south-central Alberta. However, as a result of extensive leaching, the Wabamun rock salt in the study area is now confined to a single, more-or-less laterally contiguous main body and numerous smaller isolated remanaants. The isolated remnants are located between the updip active margin (main dissolution front) of the large contiguous body of rock salt and the updip (northeastern) edge of the Wabamun subcrop.
In this paper, four example seismic lines, supporting well log data, and a contour map showing the present-day distribution (net thickness) of the Wabamun rock salt are presented in support of the thesis that the Wabamun salt in the Stettler study area has been leached extensively in places and that such dissolution is partially a result of several large scale processes. These processes include: 1) regional uplift and erosion, and the near-surface exposure of the rock salt during the pre-Cretaceous hiatus; 2) regional faulting during the mid-Late Cretaceous; and 3) glacial loading and unloading during the Quaternary.
The first example seismic profile crosses an isolated remnant of rock salt situated 20–25 km updip of the main dissolution front and immediately downdip of the Wabamun subcrop. The second seismic profile images the updip edge of the main dissolution front. The interpretation of these seismic data supports the thesis that the main dissolution front developed along the Wabamun outcrop during the pre-Cretaceous hiatus and that it has receded basinward (downdip) since that time. These data support the interpretation that the isolated bodies are those remnants of the original rock salt that survived the basinward recession of the main dissolution front. The third seismic profile images a linear dissolution feature that developed within the main body of rock salt (downdip of the main salt dissolution front), and is presented as evidence that regional faulting during the mid-Late Cretaceous initiated salt dissolution in places in the Stettler area. The fourth seismic line is also located downdip of the main dissolution front, but in an area where the rock salt is relatively undisturbed Together with the first three seismic data examples, it is presented in support of the present-day Wabamun net salt distribution map.
KeywordsCretaceous Devonian Shear Zone Seismic Data Seismic Profile
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