On-the-Rocks – June 26, 2004

Title: On-the-Rocks – June 26, 2004: Lower Paleozoic History of the Front Range
Trip Leader: Dr. Paul Myrow, Professor of Geology, The Colorado College
Publication: The Outcrop, June 2004, p. 12

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Basal beds of the Sawatch Formation onlap onto projecting Precambrian core stones along a nonconformity; the Sawatch exposure is approximately 4m thick.

The trip will begin with an overview stop to look at the structure and stratigraphy of the Pikes Peak region. We will then examine the sedimentology and stratigraphy of the Cambrian section and nonconformity with the Pikes Peak Granite. This will include study of well-exposed, large-scale, cross-bedded, glauconitic sand wave deposits. We will look at evidence for a prominent Early Ordovician unconformity developed during the Rossodus manitouensis conodont zone. Recent biostratigraphic, chemo-stratigraphic, and physical stratigraphic data suggest that the loss of strata due to erosion associated with this mid-Rossodus uplift event led to inaccurate reconstructions of the Transcontinental Arch during the Cambrian. We will then look at two sites within the Ordovician Manitou Formation. The first contains enigmatic shallow-water, meter-scale carbonate cycles in the lower Manitou. At the second Manitou stop we will examine small stromatolitic mounds and spectacularly preserved sponge fossils. We will then look at Devonian limestone deposits and associated paleokarst. The trip will finish at an outcrop of marginal marine deposits of the Pennsylvanian Glen Eyrie Shale with associated plant fossils, including extraordinary Lepidodendrum specimens.

To make a reservation for the trip, e-mail the names of those that will be attending, and a phone number that can be used to contact you if there are any last minute developments to fredmark@wispertel.com or call 303-674-1682.