ABSTRACT

An obvious use of paleopedology for sequence stratigraphic analysis lies in the demarcation of erosional discontinuities or major pauses in sedimentation that allow us to recognize and map stratigraphically important surfaces, both in outcrop and subsurface. Many interfluve surfaces may be apparent on the basis of sedimentology and regional stratigraphy alone; however, their appearance can change markedly across a study area, making correlation difficult. A pedosedimentary approach has been utilized to reconstruct the sequence of pedogenic and sedimentary events recorded by the development of stratigraphically significant interfluve surfaces. This was based upon sets of closely-spaced thin sections taken from interfluve sequence-bounding paleosols exposed at Beatton River canyon, British Columbia, Canada. Micromorphology, field morphologies, and major physicochemical characteristics of three interfluve paleosols reveals a complex sequence of soil development related both to normal floodplain sedimentation and to periods of prolonged stasis resulting from valley incision. Two main pedosedimentary stages, related to regional changes in rates of generation of accommodation, are recorded at each interfluve, although the resolution, processes, and resultant features vary in a manner reflecting local differences in hydrology, topography, initial parent material composition, and time. These processes have operated through various pedogenic development pathways to produce polygenetic paleosol profiles on these Cretaceous interfluves. The pedosedimentary approach followed in this case study provides a means of deciphering the development of interfluve paleosols based upon detailed microstratigraphic associations and depth functions of their pedogenic features, in conjunction with ancilliary geochemical, mineralogical, sedimentological, and stratigraphic evidence. Consequently, potential sequence boundaries, identified on the basis of regional stratigraphic patterns, can be determined with a high degree of confidence on the basis of intrinsic evidence derived from the record of ancient landscape processes preserved within the interfluve paleosols.