REPLY TO DISCUSSION of H.G. Machel, E.W. Mountjoy, G.D. Jones and B.J. Rostron: Toward a sequence stratigraphic framework for the Frasnian of the Western Canada Basin

Abstract

We are gratified by the interest that our publication has generated and thank Machel et al. (2002, this issue) for their discussion. However, we do not agree with their assessment of the part of our paper dealing with a mechanism for the formation of replacement dolomite in the Frasnian second-order sequence. We assert that, considering all the data, the most logical explanation for the mechanism of formation for these dolomites is by seepage refluxion with fluids originating at or near the top of the Frasnian sequence. One of the hallmarks of a good dolomitization model is its ability to explain and predict dolomite distribution in space and time. This makes it useful to researchers and to geologists exploring for dolomite reservoirs. The proposed mechanism accomplishes this. We have taken a substantially different approach to understand the mechanism of dolomite formation than that taken by H.G. Machel and his colleagues. Our conclusions about dolomite timing and dolomitizing fluid are based primarily on regional stratigraphic analysis; their conclusions have relied somewhat more heavily on isotopic analyses. We do not apologize for taking a more straightforward, observational approach. Rather, we regard our work as an important contribution to the understanding of these rocks, because it presents a model based on knowledge of the regional stratigraphic distribution of the replacement dolomite. Many dolomitization studies in the Western Canada Sedimentary Basin (WCSB) have been investigations of relatively small areas, have not incorporated all of the relevant stratigraphy, or have lacked the scope to tackle the regional issues. The intent of our paper was to present a regional stratigraphic framework and not to criticize previous work. Rather, we wished to propose an alternative mechanism tied closely to a stratigraphic model. Amthor et al. (1994) also recognize the importance of a predictive model in their assertion …