--> Abstract: Magnetic Susceptibility, Biostratigraphy, and Sequence Stratigraphy: Insights into Timing of Devonian Carbonate Platform Development and Basin Infilling, Western Alberta, by Michael T. Whalen and Jed Day; #90039 (2005)

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Magnetic Susceptibility, Biostratigraphy, and Sequence Stratigraphy: Insights into Timing of Devonian Carbonate Platform Development and Basin Infilling, Western Alberta

Michael T. Whalen1 and Jed Day2
1 University of Alaska-Fairbanks, Fairbanks, AK
2 Illinois State University, Normal, IL

High-resolution magnetic susceptibility (MS) data from slope and basin deposits near Miette and Ancient Wall provide insight into patterns of carbonate platform development and infilling of the Devonian Alberta basin. These MS data, combined with conodont-brachiopod biostratigraphic data and sequence stratigraphy, provides additional control on the relative timing of five major and fifteen higher frequency MS excursions and nine depositional sequences, seven of which correlate to Johnson et al. Devonian Transgressive-Regressive cycles IIa-2 to IIe. Spikes in the MS record coincide to events associated with lowstand or initial transgression. The first positive MS excursion (Thornton Cr. Mb., Flume Fm., IIa-2) represents initial mid-Devonian (late Givetian)onlap at Ancient Wall. The remaining Flume consists of two carbonate ramp sequences with fluctuating MS corresponding to T-R cycle IIb-1 (norrisi Zone) and IIb-2. The second significant MS spike (Maligne Fm., Montagne Noir (MN) Zone 4) is associated with an early Frasnian flooding (IIb-3) that resulted in isolated prograding rimmed platforms (lower Cairn Fm.) and lower MS values. An MS spike near the base of the Perdrix Fm. coincides with the IIc transgression (MN 5) and upper Cairn backstepping. An MS increase in the upper Perdrix/lowermost Mount Hawk Fm. signals lowstand/initial transgression of an intra-T-R cycle IIc sea-level event (MN 7?-10), that resulted in platform aggradation (Peechee Mb., Southesk Fm.). The lower-middle Mount Hawk Fm. (MN 11-12) displays increasing MS values related to clastic influx that continued until swamped by increased highstand carbonate input (Arcs Mbr., Southesk, IId-1). The uppermost Mount Hawk and overlying Simla/Ronde Mbs. (Southesk) record fluctuating MS values (MN 13, IId-2). The early Famennian Sassenach Fm. records the initial triangularis Zone flooding (T-R IIe) with somewhat higher MS values than seen in latest Frasnian carbonate ramp deposits of sequence 8.

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