Northern Black Hills CASTLE ROCK Oligocene WR cap on >200 feet of lower Hell Creek. Draw on NW side of butte has best section - down to Fox Hills or what I would call Fox Hills: a tabular X-1zm sand some clay patches possibly outlining Ophio but indec. Grades down to banded bed lithology which has 2 few beds sand up to 2' thick that weather yellowish. Top "FH" sand is light gray yellowish cast, much yellow - ?zvosite-like crud in upper part. At top rootlets in sand. Capped by liq shale + lignite along irregular contact (photo). Above this Hell Creek succession with alternating shale-lignite units and channel sands - about 60' up benonitic clays come in. The Hell Cr. - W.R. contact obscure on butte side Does not look like any place for finding lower FH anywhere S or E or W of Castle Rock in vicinity. Suspect best place at HaysButte Butte. This section of Hell Creek should be measured. It may tie in with the Bullhead lithofacies. One horizon 36