Hell Creek Formation includes an isolated section that was designated a monument on which date?
Hell Creek Formation The Hell Creek Formation is an intensively-studied division of mostly Upper Cretaceous and some lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana. The formation includes portions of Montana, North Dakota, South Dakota, and Wyoming. In Montana, the Hell Creek Formation overlies the Fox Hills Formation. "Pompey's Pillar" at the Pompeys Pillar National Monument is a small isolated section of the Hell Creek Formation.
Independence Rock (Wyoming) Independence Rock is a large granite rock, approximately 130 ft high, 1900 ft long and 850 ft wide, in southwestern Natrona County, Wyoming, along Wyoming Highway 220. During the middle of the 19th century, the rock was a prominent and well-known landmark on the Oregon, Mormon, and California emigrant trails. Many of these emigrants carved their names on the rock, and it was described by early missionary and explorer Father Pierre-Jean De Smet in 1840 as the "Register of the Desert". The site was designated a National Historic Landmark on January 20, 1961. It is now part of Independence Rock State Historic Site, owned and operated by the state of Wyoming.