ABOUT GRAVEL DEPOSITS OF THE SOUTH PLATTE RIVER NORTH OF DENVER, COLORADO U. S. Geological Survey Open-File Report 98-148. This report consists of three parts: Part A, "Stratigraphy and sedimentary structures," by David A. Lindsey, William H. Langer, Linda Scott Cummings, and John F. Shary Part A describes the stratigraphy and sedimentary structures of gravel deposits in the South Platte River valley, with emphasis on producing gravels beneath the floodplain and low terraces. Stratigraphy and history of gravel deposition is interpreted with the aid of new information on the age of the gravel deposits. Part B, "Quality of gravel deposits for aggregate," by David A. Lindsey, William H. Langer, and John F. Shary Part B describes the quality of gravel deposits in terms of particle size, lithology, shape and roundness. Stratigraphic and regional variation is statistically analyzed, and lithologic control of some characteristics is evaluated. Laboratory tests were conducted on gravel and individual lithologies within gravel to measure resistance to abrasion. Part C, "Description, composition, and origin of clay lenses in gravel," by David A. Lindsey, Joseph E. Taggart, Jr., and Gregory P. Meeker Part C describes the physical character and composition of clay lenses in gravel. Possible explanations for the origin of clay lenses are proposed, and implications for prediction of their extent in the subsurface are summarized. The accompanying files 98-148.pdf, 98-148-a.pdf, 98-148-b.pdf, and 98-148-c.pdf are in Portable Document Format (PDF) and require Adobe Acrobat ReaderTM (v. 3.0 or later) for viewing and printing. The first-named file is the title page; the other files are parts A, B, and C. Acrobat Reader can be downloaded free from .