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Analysis and Correlation of Growth Strata of the Lower Dawson Formation: Insight into the Tectono-stratigraphic Evolution of the Colorado Front Range

Korey Harvey and Jennifer Aschoff

Preliminary analysis and correlation of several growth strata outcrops along the eastern Colorado Front Range (CFR) help decipher the along strike component of basement-cored uplift during the Laramide orogeny. Although the CFR has been studied extensively, the 4-dimensional development of Laramide-style uplifts like the CFR is not well understood. Growth strata are stratigraphic successions that can be used to constrain uplift sequence, location and geometry of ancient structures and are critical to reconstructing the along-strike development and linkage of structures that constitute Laramide structures. This study presents preliminary data and interpretations from growth strata at two outcrop locales on the eastern CFR between Colorado Springs, CO and Sadalia, CO to constrain the along-strike development of the eastern CFR. Eight measured sections with eleven lithofacies were analyzed from three outcrops, ranging from braided fluvial to anastomosing fluvial depositional environments with paleocurrents from northeast to south. Ten syntectonic unconformities were identified at the Air Force Academy study site near Colorado Springs, CO. These syntectonic unconformities are interpreted to represent ten uplift/tilting events along frontal structures near Colorado Springs, Colorado. Forty miles north of the AFA study site, one syntectonic unconformity has been identified at Wildcat Mountain, and two syntectonic unconformities at the nearby Wildcat Tail in Sedalia, CO, suggesting one uplift/tilting event at the second study site. Preliminary interpretations of the correlation of the identified syntectonic unconformities show diachronous development of emerging structures that began in the south near Colorado Springs and expanded northward to Wildcat Mountain. Future work will include a third study site and along-strike correlations that will link the two aforementioned sites and elucidate the lateral linkning of these areas. In addition, future work will emphasize of the co-evolution of the CFR and adjacent depositional systems.


AAPG Search and Discovery Article #90156©2012 AAPG Rocky Mountain Section Meeting, Grand Junction, Colorado, 9-12 September 2012