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The Peterson Quadrangle is located southeast of Ogden, Utah (plate 2). The major geographic features in and near the map area are Morgan Valley, the northern Wasatch Range to the west, Durst Mountain to the east, the Weber River in Morgan Valley, and lower Weber Canyon cut into the Wasatch Range by the river.The most complete map of the Peterson quadrangle prior to this study was by Bryant (1984, 1988) and he focused on the Precambrian Farmington Canyon Complex, as did an earlier dissertation by Bell (1951). King is largely responsible for the bedrock mapping in the quadrangle and after limited field checks chose to modify the Precambrian contacts from Bryant (1984, 1988). Because these rocks were not closely examined in the field, few attitudes are shown in Precambrian rocks on the map. Where strikes can be seen on aerial photographs and orthophotographs, corresponding planar attitudes shown by Bryant (1984, 1988) are included on our map. However, the type of attitudes depicted on our map are not always those shown by Bryant (1984, 1988). Because his attitudes differ from those shown by Yonkee and Lowe (2004) where their mapping overlaps in the Ogden 7.5' quadrangle, his lineations and most of his planar features (mostly foliations) are not included on our map, and we are uncertain that those included are all correct. King and McDonald worked on the surficial deposits in Morgan Valley, and King is responsible for the surficial geology in the Wasatch Range. Despite his focus on the Precambrian, Bryant (1984, 1988) was the first to map the glacial deposits in the Wasatch Range north of Salt Lake City and south of Mount Ogden. Bryant’s (1984, 1988) glacial mapping made our more detailed mapping easier; but, much work is still needed to define the glacial deposits and history. Ages (years) of surficial deposits in the text and tables are from various methods, as reported in the references. Ages have not been converted to calendar years for several reasons, in part because the results from some methods cannot be converted. Also, calendar year conversions of carbon-14 ages can only go back 24,000 to 50,000 years (depending on the method of conversion), several conversion methods and updates exist, and all conversions introduce non-analytical errors that decrease the age accuracy (see for example Stuiver, 1993; Stuiver and Reimer, 1993; Stuiver and others, 1998; Hughen and others, 2000; Reimer and others, 2004; Fairbanks and others, 2005; Reimer and others, 2006; Bronk Ramsey, 2009; Reimer and others, 2013). |