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TABLE 2.7-1. <br />STRATIGRAPHY OF <br />THE MINE PLAN <br />AND ADJACENT AREAS <br />Estimated <br />System Formation <br />Member <br />Thickness <br />Lith ology <br />Quaternary <br />Alluvium <br />- <br />Variable <br />Sands and gravels <br />with some silts <br />and clays <br />Cretaceous <br />Lewis <br />-L <br />1500- <br />Mainly dark gray <br />Shale <br />1900 ft. <br />marine shales and <br />sandy shales with <br />minor sandstones <br />Cretaceous <br />Williams Fork <br />Upper Williams <br />680+ ft. <br />Interbedded shales, <br />' <br />(Mesa Verde <br />Fork <br />sandy shales and <br />Group) <br />coal seams; con- <br />tains several white <br />sandstones; <br />variably thin to <br />thick bedded <br />Twenty Mile <br />100+ ft. <br />Massive cliff <br />Sandstone <br />forming <br />quartzose <br />sandstone <br />Lower Williams <br />920+ ft. <br />Interbedded <br />Fork <br />soft sandstones <br />sandy shales <br />carbonaceous <br />shales and <br />coal seams; <br />and clinker zones <br />Cretaceous <br />Iles Formation <br />Trout Creek <br />100+ ft. <br />Massive white <br />(Mesa Verde <br />Sandstone <br />sandstone, <br />Group) <br />cliff former <br />_t. <br />Main Body <br />1300+ ft. Mainly sandstone <br />with interbedded <br />subordinate <br />shales <br />Cretaceous Mancos Shale 4000+ ft. Gray homogeneous <br />marine shales <br />2-350 <br />