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October 2000 -24- 003-2141 <br />• The formation is about 600 feet thick and consists of hard yellowish-gray medium- <br />grained massive sandstone, soft light-gray sandstone, olive-gray siltstone and <br />claystone, soft lignitic coal layers, and moderate-brown hazd sandy ironstone layers <br />that contain fossil leaves. Thin conglomerate layers neaz the middle of the formation <br />contain chertified or agatized pebbles. Because the formation is mostly of terrestrial <br />origin, the sandstone and conglomerate beds aze concentrically banded and some aze <br />as lazge as 4 feet in maximum dimension. The upper contact is between olive-gray <br />siltstone of the Laramie and amoderate-brown pebble conglomerate at the base of the <br />Dawson azkose. <br />Dawson Arkose and Denver Formation as a Tongue <br />The Dawson arkose, which consists of conglomerate, sandstone, and claystone, and <br />. contains a tongue of the Denver formation, is of Late Cretaceous and Paleocene age. <br />Its thickness is greater than 1,000 feet; the lower beds, about 500 feet thick, aze of <br />Late Cretaceous age and the upper beds aze of Paleocene age. <br />The formation contains azkosic beds and a middle tongue of andestitic material. <br />Ridge-forming azkosic sandstone and conglomerate beds at the base aze equivalent to <br />the Arapahoe formation of the Golden quadrangle, the Arapahoe of common usage, <br />but aze here called Dawson azkose. The azkosic beds in the middle region also aze <br />typical of the Dawson azkose. <br />In the Littleton quadrangle to the north, the lower part of the Dawson azkose is mostly <br />a yellowish-gray cross-bedded sandstone. It is much finer grained here that it is either <br />north or south of the quadrangle. A few 1-inch pebbles and many 1 1/2-inch pebbles <br />were observed; most of these aze quartz but chalcedony, agate, and petrified wood aze <br />also common. This sandstone is well cemented and resists erosion effectively. Other <br />~J <br />VOM.191/31915aJYiWamiil000doc Sedalia Recycling Center and Depository <br />