Abstract The U.S. Geological Survey (USGS) operates the Core Research Center (CRC) in Denver, Colorado, USA, a public access repository of rock cores from over 9800 wells and drill cuttings from over 53 000 wells, primarily from states in or adjacent to the Rocky Mountain Region. Annually, approximately 1400 visitors use the collection for traditional and innovative research. The CRC has an online, searchable database which includes downloadable core photos, analytical data, and thin-section images. When visitors sample for analyses, the results must be returned to the CRC for public dissemination providing immediate, free access to users while sparing the finite, irreplaceable collection from redundant testing. A representative quantity of every core depth is preserved in perpetuity. Studies on CRC materials, paired with new extraction methods, have unlocked new productive deposits. Materials drilled and curated decades ago remain in high demand while materials receiving little attention today may be crucial for future research. The collection provides immediate, inexpensive access to subsurface materials at a fraction of the cost of new drilling, sparing money, time and environmental impacts.

Alluvial fans offer a means to unravel the intricacies of landscape, tectonic, and climatic dynamics. This book and accompanying geologic map highlight alluvial fans and their deposits exemplified by a suite of debris-flow alluvial fans emanating from the Holocene-active western range front of the Sangre de Cristo Mountains in south-central Colorado. The link between morphologies of fan surfaces and the sedimentary facies of their deposits permits a basis for evolutionary process interpretation of debris-flow alluvial fan geomorphology. A grasp of these processes will help earth scientists better discern complexities between buried paleo-surfaces (intraformational progressive unconformities), surficial deformation, and landform development as recorded in debris-flow fan deposits in the sedimentary record.