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<br />~ <br /> <br />Front Range. Also, the paleohydrologic methods developed for this study may <br />be used for paleoflood reconstruction in subsequent studies. <br /> <br />PROGRESS/SIGNIFICANT FINDINGS: <br /> <br />[A] Cross-Section Surveyinq. Four sites in Arthurs Rock Gulch have been <br />selected to reconstruct paleoflood discharges. At each site, two to <br />four recent and paleoflood deposits have been identified. Cross- <br />section surveys have been completed at three sites. Field notes have <br />been checked, and cross sections and plan views have been plotted. The <br />fourth site will be surveyed in early November. <br /> <br />[B] Surficial Mappinq. Surficial deposits within Arthurs Rock Gulch <br />drainage basin have been mapped at a scale of approximately 1:5,000. A <br />map suitable for publication currently is being compiled. <br /> <br />[C] Relative-aqe Datinq. Data pertaining to the relative age of flood <br />deposits and debris flows have been collected from all sites designated <br />for cross-section surveying. Measurements of the degree of weathering <br />of surficial deposits, soil development, and the size, lithologic <br />composition, and shape of constituent boulders and clasts also has been <br />collected. <br /> <br />[0] Stratiqraphic Analyses and Sediment Samplinq. Several stratigraphic <br />profiles in Arthurs Rock Gulch and Mill Creek (the adjoining basin to <br />the south) have been examined and recorded. Material suitable for <br />radiocarbon dating has not yet been discovered in Arthurs Rock Gulch. <br />Efforts are still being made to locate these samples. Additional <br />efforts are being directed to other dating techniques and locating <br />datable material in adjacent basins. Several stratigraphic sections <br />along lower Mill Creek indicate multiple coarse-grained flood deposits <br />and associated woody material. These deposits may be related to <br />similar in-channel deposits in Arthurs Rock Gulch. <br />Sediment samples have been collected from almost all major surficial <br />deposits within the study area. Particle-size analyses of all samples <br />will be made. Samples from major soil horizons also will be analyzed <br />for particle-size distribution, clay mineralogy, and dithionite <br />extractable iron. <br /> <br />[E] Flood deposits in Adiacent Basins. Flood deposits consisting of <br />accumulations of bouldery detritus in stratigraphic sections and <br />boulder concentrations along channel margins have been discovered <br />within downstream reaches of several nearby drainage basins. The flood <br />evidence indicates that several large floods have occurred in the <br />foothills west of Fort Collins throughout the last 1,000 to 2,000 <br />years. These deposits are significant for regional flood-magnitude and <br />frequency estimates. <br /> <br />[F] Field trips. In addition to the numerous trips made by project <br />personnel to make measurements described above, the following specific <br />trips also have been made: (1) On September 19, a field trip was made <br />to provide U.S. Bureau of Reclamation personnel with an overview and <br />status of the project, and; (2) On October 10. a field trip was made to <br />provide U.S. Geological Survey researchers with an overview of the <br />project. These researchers believe that this project will provide <br />