--> Abstract: An Empirical Paleosol-Landscape Model of a Dissected Coastal Plain, Cenomanian Dunvegan Formation, Western Canada Foreland Basin: Implications for Nonmarine Sequence Stratigraphy, by Paul J. McCarthy and A. Guy Plint; #90039 (2005)

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An Empirical Paleosol-Landscape Model of a Dissected Coastal Plain, Cenomanian Dunvegan Formation, Western Canada Foreland Basin: Implications for Nonmarine Sequence Stratigraphy

Paul J. McCarthy1 and A. Guy Plint2
1 University of Alaska, Fairbanks, AK
2 University of Western Ontario, Department of Earth Sciences, London, ON

A detailed sequence stratigraphic framework has been established for the alluvial/deltaic Dunvegan Formation. Paleopedological analyses along two dip-oriented transects permit interpretation of paleosol development with respect to paleogeographic position relative to adjacent valleys and marine shorelines. The coastal plains can be partitioned into three zones. Zone 1 occurs in down-dip locations near the maximum regressive shoreline and is characterized by hydromorphic, cumulative paleosols typical of poorly drained, progradational coastal plains, with elevated levels of Ca, Mg and Sr that suggest marine overprinting during transgression. Zone 2 occurs in intermediate locations and is characterized by well-developed Alfisol-like paleosols that record: (i) an aggradational phase; (ii) a subsequent static and/or degradational phase related to valley incision, non-deposition and soil thickening, and (iii) a final aggradational phase related to valley filling and renewed sedimentation across the coastal plain. Zone 3 occurs in more orogen-proximal settings and is characterized by less well-developed, compound and complex Inceptisol-like paleosol development. This analysis shows that the best-developed paleosols occur in intermediate locations along the interfluve transects (Zone 2), which were characterized by moderate to low subsidence rates and where valley incision resulted in interfluves being starved of sediment for the longest periods of time. Weaker paleosol development both up-dip and down-dip from this intermediate location suggests that valley incision began initially at the early Falling Stage shoreline, progressing up-dip by knick-point migration, while down-dip, paleosols continued to develop on the coastal plain that continued to prograde in response to sea level fall.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005