Hell Creek Formation

Brown, Barnum, 1907, The Hell Creek beds of the Upper Cretaceous of Montana; their relation to contiguous deposits with faunal and floral lists, and a discussion of their correlation: American Museum of Natural History Bulletin, v. 23, art. 33, p. 823-845. Pg. 829-835. Hell Creek beds. Fossil-bearing, fresh-water deposits of alternating sandstones and clays 560 feet thick in western half of Dawson County, Montana. Most constant member of series is massive sandstone at base, 0 to 160 feet thick. Probably continuous with the dinosaur-bearing beds of Little Missouri and Grand and Moreau Rivers, judging from fauna. These beds, with the underlying and overlying deposits, are typically exposed on Hell Creek [Garfield County] and nearby tributaries of Missouri River. Assigned to Upper Cretaceous. Separated from overlying Fort Union formation by 100 feet of lignite beds, here called Fort Union(?). Rests unconformably on Fox Hills formation. Lithologically similar in almost every respect to Ceratops beds of Converse County, Wyoming. Pg. 484-499. Hell Creek member of Lance formation as here defined is typically exposed on Hell Creek, Garfield County, Montana, and is = "HeII Creek beds" plus "lignite beds" of Brown (1907), occupying the interval between Fox Hills sandstone below and the yellow Tullock member of the Lance above. In southwestern North Dakota it is overlain by either Ludlow lignitic member of the Lance or the contemporaneous Cannonball marine member of the Lance, and it rests on Fox Hills sandstone. It consists of somber, badland clays, probably accumulated in topset swamps of a great delta, and fluviatile sandstones, the latter being more numerous and conspicuous toward southwest. Remains of a few small mammals have been found in the sandstones. Dinosaurs (including TRICERATOPS) are numerous below the "A" lignite, which marks base of Brown's "lignite beds," but probably have not been found above that horizon. [Mention other fossils.] Tbe Hell Creek and overlying strata are markedly calcareous in contrast with the brown member of the Fox Hills and older rocks, which are relatively free from lime. In Cedar Creek anticline, Montana, the Hell Creek member overlies Colgate sandstone member of Fox Hills sandstone; at mouth of Cannonball River, North Dakota, it rests on Fox Hills andstone. [Diagram on p. 484 shows no unconformity above or below Hell Creek member.] These rocks are now [ca. 1936] called Hell Creek formation by the USGS, and are classified as Upper Cretaceous, as explained under Lance formation, last entry [= GNC remark, ca. 1936, US geologic names lexicon, USGS Bull. 896, p. 1142]. Recognized in eastern, northern, and central southern MT, southwestern ND, and northwestern and northern SD. Pg. 5 (fig.), 6 (table), 8-9, geol. map. Hell Creek member of Lance formation. Gray gumbo sands and clay with coal. Often called "somber sands." Thickness estimated between 85 and 312 feet. In Harding County, South Dakota, includes Bull Creek sand (new) below Heikkila coal. Underlies Ludlow member of Lance formation; overlies Fox Hills Formation. Fossils (vertebrates). Beds interpreted to represent swamp and coastal plain deposits. Age is Cretaceous. Simpson, G.G., 1937, The Fort Union of the Crazy Mountain field, Montana, and its mammalian faunas: U.S. National Museum Bulletin, no. 169, 287 p. Pg. 15 (table), 16-20. Hell Creek formation. For purposes of present report [Fort Union of Crazy Mountain field, Montana], it is assumed that beds up to and including the true dinosaur-bearing Lance and Hell Creek and their equivalents belong to the Cretaceous and that overlying beds without dinosaurs (except by redeposition) and with mammals of Tertiary type (including carnivores, condylarths, and others) from the Puerco and its equivalents upward, are to be placed in the Tertiary. It is also assumed that Paleocene is accepted as separate epoch. Hell Creek formation underlies Bear formation (new). Pg. 10-11, pls. 1, 3. Hell Creek me