REPLY TO DISCUSSION of J. Wendte and A. Embry: Toward a sequence stratigraphic framework for the Frasnian of the Western Canada Basin

Abstract

We appreciate the discussion of our recent paper (Potma et al., 2001) by J. Wendte and A. Embry. However, we strongly disagree with their assessment of our work. Our reply will begin with some general comments, address their arguments point by point, and conclude with a summary. Wendte and Embry (2002, this issue) recognize four of the ten sequence boundaries we consider significant and regionally correlatable. We interpret two of these, the base of the Gilwood Member and the “base Graminia silt”, as second-order sequence boundaries, occurring at the base and top, respectively, of our proposed second-order Givetian–Frasnian depositional sequence. We interpret two others, the base Calmar Formation and base Beaverhill Lake (BHL) Sequence 3, as third-order sequence boundaries. Wendte and Embry then describe our proposed stratigraphic framework as being “highly suspect”, “entirely untenable”, “fatally flawed”, etc. They state that many of our interpreted subaerial unconformities “have not been recognized by previous workers”. This is incorrect. We believe our work, presented at the AAPG conference (Gilhooly et al., 1992; Potma et al., 1992; Weissenberger et al., 1992; Wong et al.,1992) and subsequently (Gilhooly et al., 1995), was the first to interpret these surfaces as regionally correlatable sequence boundaries. These interpretations were presented again as part of a field seminar sponsored by the CSPG continuing education committee (Gilhooly et al., 1995). Numerous other authors ascribed stratigraphic significance to many of these surfaces. They have illustrated or described unconformities within these stratigraphic intervals. The pertinent literature is summarized in Table 1⇓. View this table: Table 1. Sequence boundaries defined by Potma et al. (2001) and previous literature that interprets comparable relationships, or otherwise corroborates these boundaries. Wendte and Embry (2002, this issue) then present two main criticisms of our work: 1) that we present insufficient evidence for the “identification of …