Lithological Stratigraphic column for Badlands National Park By ...

TertiaryMioceneOligoceneArikareeWhite RiverSharps FormationBrule FormationRockyfordPOLESLIDESCENICTsTbSharps Formation of Harksen (1960) -Massive poorly consolidated pinkish-tansilt containing calcareous concretions,local lenses of freshwater limestone,clastic dikes, and chalcedony veinlets.The basal unit is the Rockyford Member ofNicknish and McDonald (1962), is aconspicuous white locally silty zeolithicvolcanic ash as much as 15 m thick. Inmany places generally between Cedar Passand the Pinnacles, the basal unit is astream-channel fill consisting of pebbleconglomerate made up largely offragments of calcareous nodules derivedfrom ash layers and quarts sand in theupper part of the Brule. Rocks of theSharps Formation are found capping onlythe highest levels of the badlands; theygenerally form a flat barren highlandstudded with very sharp spires and nearvertical walls formed by clastic dikes. Thelithology of the Sharps Formation issimilar to that of the underlying BruleFormation, but the color of the SharpsFormation above the Rockyford Memberhas a somewhat more brownish tone thenthat of the underlying Brule Formation.About 100 m thickBrule Formation – Interbedded – pinkish –greenish – gray clay, silt, sand, andvolcanic ash containing channelsandstones, clastic dikes, and chalcedonyveinlets. Contains a conspicuous oreodonand turtle fauna. Rocks of this unitcompose most of the “wall of theBadlands” and many of the strikingbanded buttes. Due to its high content offine volcanic ash and calcareous cement,The Brule Formation characteristicallyweathers to very steep slopes and knife –edge ridges. This characteristic aloneprovides reasonably clear delineation ofthe Brule-Chadron contact in the badlands.As much as 150 m thick.