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Castle Rock Conglomerate
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The Castle Rock Conglomerate
is a very coarse, often boulder-filled unit that occurs as the "cap
rock" over wide areas of the central Denver Basin. This unit is quite
resistant to erosion and holds up the high, relatively flat surfaces in
eastern Douglas and Elbert Counties. About 36 million years old, Castle
Rock Conglomerate is younger than the Castle Rock Rhyolite; its age is determined
by the presence of entrained, angular fragments. Titanothere fossils are
found in this 30- to 60-foot rock unit. Bedding characteristics suggest
that the conglomerate was deposited by extremely energetic river systems,
perhaps during times of high flood, and that the rivers flowed from the
area of Waterton Canyon toward the southeast in the direction of Calhan. |