In 1977 RMAG published Subsurface Cross Sections of Colorado, a compilation of stratigraphic cross sections from all Colorado basins. This publication has been a valuable resource for geologists wanting to establish a basis for stratigraphic correlations. Well logs were presented on all cross sections, which was very helpful in understanding the log response for the different stratigraphic picks. During the 41 years since this publication, numerous wells have been drilled and digital logs now allow cross sections to be easily enhanced with color. In this update of the 1977 publication, we have expanded this volume to the southern Rocky Mountain basins. Some of the cross sections in this volume are timely in that there are emerging plays associated with the basin and stratigraphic interval represented in the cross sections. In the Uinta Basin, prolific horizontal wells are currently being drilled in the Wasatch-Green River formations. David Schmude’s cross section provides a great stratigraphic context for this play. Similarly, Nathan Rogers’ Mancos-Niobrara cross sections in the Piceance Basin establish a stratigraphic framework for the emerging prolific horizontal Niobrara play and Barbara Luneau and Mark Longman’s Niobrara cross sections provide a regional framework for a shale play that has good potential all through the Rocky Mountain basins. Anderson et al. and Cumella present a regional look at Triassic through Cretaceous strata from the southern Uinta Basin to the Piceance Basin. Steve Cumella’s Piceance cross sections focus on detailed correlations of the Mesaverde Group, host to the largest basin-centered gas accumulation in Colorado. Steve Cumella’s Piceance cross sections highlight the turbidite sands which are an ongoing unconventional play in the GGRB. Ed Coalson’s cross sections in the same region tie in to present the Cretaceous section that predates the Lewis transgression. Robin Swank weaves a biostratigraphic framework into the source rock-rich Mowry to Niobrara interval in a regional cross section stretching from the thrust belt of eastern Wyoming to the DJ Basin of Colorado. Don and Larry Rasmussen provide detailed stratigraphic correlations of the cyclic Pennsylvanian through Permian strata in the Paradox Basin, including the complex salt-bearing region of the Deep Fold and Fault Belt. Donna Anderson brings new insight to the lower Paleozoic onlap onto the Transcontinental Arch in southern Wyoming. Larry and Don Rasmussen provides an updated look at the same lower Paleozoic section to the south in Utah and Colorado. Ed Coalson’s cross sections of Colorado’s North Park and South Park basins bring a much needed comprehensive look at the stratigraphy from the surface to the Paleozoic basement. Connie Knight and Bruce Bartleson present the Paleozoic strata of the often-overlooked Eagle Basin of NW Colorado.
This publication would not have been possible without the generous donation of digital log data from IHS Markit. Special thanks go to John Roberts, Executive Director of Global Subsurface Operations, and Alex Pomadchin, Manager of U.S. Log Operations. We would like to thank the authors of the cross sections for their contributions and reviewers Donna Anderson, Marieke Dechesne, Ned Sterne, and John Ladd for their valuable suggestions. We also thank Terri Olson, the current RMAG president, and RMAG publication chairmen Mel Klinger (2016), John Roesink (2017), Steve Sturm (2018) and David Katz (2018) for their support.
—The Editors, November, 2018