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Oncolites, Laminated Algal Deposits and Conglomerates in the Canyon Mountains --an Overlooked, but Important Stratigraphic Indicator

James Stolle

When you have eliminated all which is impossible, then whatever remains, however improbable, must be the truth. Sherlock Holmes Quote-The Blanched Soldier. Central Utah and the complex stratigraphic relationships is certainly a test of this statement. Ideas to possibly eliminate: 1) The Canyon Mountains, at least the Cretaceous-Tertiary conglomeratic section, are all non-marine, probably just a variety of fluvial and/or alluvial fans.(It sure looks like it) 2) Plus, the red beds and conglomeratic section is an unlikely place for pollen and spore preservation. Surprisingly, we have recovered an initial collection of trilete, spores of various ages, and more curious, some marine dinocysts. In the same samples also recovered were freshwater algal evidence, including multicellular algal bodies, i.e.a coenobia of Pediastrum. Strike also the assumption about not being able to recover any pollen or spores. Phase two of palynology efforts is already underway, and the third and fourth phases will occur this summer for additional confirmation and results to report. A decision point must be evaluated, either the trilete spores, dinocysts, and algal remains are in-place. If so, we may be developing evidence of a Campanian-Maestrichtian stratigraphic age with lithologic evidence for extensive lake or ponding environments. However, the alternative explanation that it represents a re-working of Cretaceous and older units, and redepositing into a Paleocene-Eocene lake environment must be considered.. More intriguing, is part of the section is a conglomerate section being dumped into a lacustrine environment. The transition from conglomerates to all varieties of algal limestones can occur within inches vertically and appears to be repeated many times. This generated the need for a 3-dimensional review of the outcrops, and expansion to other areas, and the type of environment really existed. Keep in mind this is within a few miles of the Pre-Cambrian section overriding the synorogenic section, probably just a bit younger and stratigraphically higher. Different areas and sections are reviewed. The algal laminated sections and oncolitic limestones in the Canyon Mountains may be a real indicator if indeed we show the palynology is indeed reflecting a re-worked section about the environment then present. The presence in the Canyon Mountains and also the Pavant Range pushes the western edge of Paleocene-Eocene deposition.

AAPG Search and Discovery Article #90169©2013 AAPG Rocky Mountain Section 62nd Annual Meeting, Salt Lake City, Utah, September 22-24, 2013