Sedimentologic and diagenetic history of the Mission Canyon Formation (Mississippian) and stratigraphic equivalents, southwestern Montana and east-central Idaho and determination of rare earth element abundances in diagenetic carbonates

Abstract

The Mission Canyon Formation and its stratigraphic equivalents in Montana and Idaho were deposited during collision of the western continental margin of North America with an inferred volcanic arc (Antler orogeny). An integrated petrographic and geochemical study of the diagenetic history of the Mission Canyon Formation was carried out within the sedimentologic context established by field studies. Petrographic and geochemical data from individual diagenetic phases were used to interpret extent of diagenetic alteration, sources of ions incorporated into cements, and paleohydrology of diagenetic fluids. We have documented third- to fifth-order scale (10{sup 6} to 10{sup 4} yr) cyclic sedimentary sequences in shallow platform to deep basin environments. The third-order cycles have been correlated from the Antler foredeep, across the platform, and into the Willistron Basin to the east, an area approximately 1200 km wide (nonpalinspastic). From this analysis, were constructed a detailed sequence stratigraphic model for the Mission Canyon Formation and its stratigraphic equivalents from southwestern Montana to east-central Idaho.