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<br />(( <br /> <br />(( <br /> <br />lC <br /> <br />.-:::t' <br />L!";l <br />l' <br /> <br />8 <br /> <br />(~ <br /> <br />c,;:) <br />0, <br /> <br />The sands and gravels within this deposit consist <br />principally of sandstone, chert, and shale derived from <br />the Book Cliffs. A large abandoned gravel pit is located <br />in the southeasternmost corner of the site. An <br />inspection of the pit revealed the material is relatively <br />well graded with local cemented zones. The cemented <br />zones are prominent at the bluffs and at the bottom of <br />the deposit as revealed by borings C-3, C-9, and C-21 <br />where the cemented pediments formed a conglomerate. This <br />conglomerate forms a relatively continuous capping on top <br />of the two major bluffs on the eastern side of the site <br />and is observed along the two major drainages on the west <br />side of the site. Outcrops of conglomerate are noted on <br />PIa te 1. <br /> <br />o <br /> <br />Quaternary Alluvium (Qal), Alluvium-Colluvium Mixed <br />(Qac), and Residuum (Qr)--these soils are generally quite <br />shallow with the alluvium and alluvium-colluvium mixed <br />ranging in thickness from 1 to 10 feet and the residuum <br />ranging from 0 to 4 feet. The alluvial soils consist of <br />brown silts, clays and sands derived from erosion of the <br />pediment, and bedrock deposits. The mixed alluvial- <br />colluvium soils represent material found in between the <br />pediments and the alluvium and the residuum and the <br />alluvium, in areas where contacts between these deposits <br />are ill-defined. The nature of these soils most closely <br />represents that of the material (pediment or residuum) it <br />was derived from. <br /> <br />The residuum consists of soils derived from the in-place <br />weathering of Mancos shale. These soils are located <br />primarily in the center of the site, along the bluffs and <br />within the more deeply incised drainages. <br /> <br />4.2 Bedrock Geology <br /> <br />The only exposed bedrock on the site is Mancos shale. The <br />exposures are limited in both areal extent and the quality of the <br />outcrop. Mapped outcrops of Mancos shale are shown on Plate 1. <br /> <br />The outcrops are generally grey to olive black and show good <br />bedding features as well as being highly fissile. The outcrops <br />are generally visible near or below overlying outcrops of <br />conglomerate. In a few instances, the shale is in direct contact <br />with the conglomerate. The shale generally increases in <br />thickness from the south towards the north as a result of <br />structural tilting and subsequent erosion. It is as thin as 500 <br />feet or less in the south and as thick as 1,400 feet in the <br />northern part of the site (Cashion, 1973). <br />