White River Group Research Articles

Source Determination of White River Group Silicates from Two Archaeological Sites in the Great Plains

High-quality cryptocrystalline silicates from the Oligocene-age White River Group of the central Great Plains (referred to here as White River Group Silicates [WRGS]) were widely used prehistorically for chipped-stone tools. There are three known source areas for WRGS: Flattop Butte in northeastern Colorado, Table Mountain in east central Wyoming, and the White River Badlands of South Dakota. Specimens from these sources are often visually indistinguishable, making it difficult to specify the source of WRGS from nonquarry archaeological sites. Using a quantitative method—neutron-activation analysis—these sources were differentiated. The sources of WRGS in two Central Plains archaeological sites also were determined using this technique. The results show that the technique has important implications for studies of prehistoric mobility and for the refinement of cultural-historical affiliation.

Paleodrainage-Unconformity Model as Guide to Uranium Deposits: ABSTRACT

This paper considers a uranium occurrence model that shows how early Eocene and Oligocene depositional patterns and paleogeography can be used to identify favorable host rocks and to suggest where uraniferous ground water passed through these rocks. The uranium in the ground water was derived mostly from volcanic ash of the Oligocene White River Group. This model accounts for most known uranium deposits and occurrences in eastern Wyoming, western South Dakota, and western Nebraska. All major deposits in Eocene sandstones are in rocks of the fan-channel facies that were identified by sand grain size and shape studies, and most deposits are basinward of present-day major mountain valleys. Deposits occur only where rocks of this facies are less than 300 m (980 ft) below the reconstructed basal Oligocene surface--a distance calculated from roll-front migration and erosion rates. Uranium deposits in other than Eocene rocks also are related to the configuration of the pre-Oligocene surface. White River channel sandstones have deposits and occurrences along a 200-km (125-mi) section of a major Oligocene river in eastern Wyoming and Nebraska. Oligocene trans-mountain drainages localized uranium occurrences in Precambrian granitic rocks in the Laramie Mountains. Deposits in Cretaceous rocks in northern Colorado and along the flanks of the Black Hills lie beneath the axes of Oligocene channels. The channels were the major conduits that localized the movement of the uranium-bearing solutions. Rocks underlying the divides between the channels are unfavorable for uranium deposits where the channels are parallel to the regional dip, because the divides have a thick imp rvious lateritic soil cover. End_of_Article - Last_Page 526------------

Magnetostratigraphy of the White River Group and its implications for oligocene geochronology

Magnetostratigraphic studies of the Oligocene White River Group in Wyoming, Colorodo, Nebraska, and the Dakotas have yielded a radiometrically-dated polarity stratigraphy. They provided a mid-Tertiary calibration point for the marine magnetic polarity timescale. An unusually long interval of reversed polarity in the Flagstaff Rim section, Natrona Co., Wyoming, is bracketed by K/Ar dates (biotite) of 32.4 Ma slightly above its top and 34.6 Ma at its base (corrected for new decay-constants). It probably corresponds to the long reversed interval between marine magnetic anomalies 12 and 13. Also, the magnetostratigraphies of 17 other fossiliferous sections of Chadronian-Whitneyan (Oligocene) rocks have been correlated with anomalies 9–12. On this basis, the “boundaries” of the Oligocene North American land mammal “ages” are: Chadronian-Orellan — mid-anomaly 11–12 reversal (about 32.4 Ma); Orellan-Whitneyan — mid-anomaly 10–111 reversal (about 30.7 Ma); Whitneyan-Arikareenan — base anomaly 9 (about 29.0 Ma). These dates are in good agreement with recent estimates based on mammalian biochronology and with a corrected radiometric date of 28.7 ± 0.7 Ma at the base of the Arikareean.

Oligocene calibration of the magnetic polarity time scale

Magnetostratigraphic studies of the Oligocene White River Group in Wyoming, Colorado, Nebraska, and the Dakotas yield a radiometrically dated polarity stratigraphy that provides mid-Tertiary calibration points for the magnetic polarity time scale. Anomaly 12–13 reversal is bracketed by dates of 32.4 and 34.6 m.y., in best agreement with the time scale of LaBrecque and colleagues. The magnetostratigraphy also helps calibrate the Oligocene North American land mammal “ages” and allows correlation with the European marine microfossil zonation. This correlation suggests that the age of the Eocene-Oligocene boundary is 37.0 m.y., contrary to younger dates obtained from glauconites and microtektites.

A new species of Caracolus (Pulmonata: Camaenidae) from the Oligocene of Nebraska and the biotic history of the American camaenid land snails

A fossil land snail from the Oligocene White River Group of Nebraska is described as Caracolus aquilonaris sp nov. Living members of the genus Caracolus occur in tropical forest on the islands of the Greater Antilles. It is likely that C. aquilonaris occupied a similar habitat and that the present restricted occurrence of the genus Caracolus is a fragment of a previously wider range. The American carnaenid genera Pleurodonte, Polydontes and Zachrysia form a well defined monophyletic group, but there is an unresolved trichotomy involving this group, Labyrinthus and Caracolus. Well characterized fossil camaenids assigned to Pleurodonte (Jamaica, Carriacou) and the related Pleurodontites (Florida) occur in the Miocene. Antecedents to Labyrinthus were isolated in South America and to Caracolus and Pleurodonte in North America, possibly in the late Cretaceous. The latter genera reached the Antilles where Caracolus has persisted relatively unchanged. Ancestral Pleurodonte has diversified producing the distinctive subgenera Eurycratera and Thelidomus on Jamaica and the genus Polydontes on the other Greater Antilles. Drier conditions on Cuba have resulted in the divergence of Zachysia from Polydontes.

New Miocene Formation in South Dakota: GEOLOGICAL NOTE

A distinctive new stratigraphic unit, herein named the Sharps formation, occurs conformably between the underlying Brule formation of the Oligocene White River group and the overlying Monroe Creek formation of the Miocene Arikaree group. The formation is named for exposures near Sharps Corner in Shannon County, southwestern South Dakota, and consists of 390 ft. of massive tan silt and volcanic ash. The basal volcanic ash bed is called the Rockyford ash, as much as 38 ft. thick. Amid the silt beds are scattered small calcareous potato-ball concretions, impure gastropod-bearing limestones, clastic and chalcedony dikes, channel sands and gravels, and algal limestones. The formation has been traced eastward 50 mi. or more, and southwestward for 75 mi. to near Harrison, Nebraska. The stratigraphic position of the Sharps formation is similar to that of the basal, channel-fill Gering formation of the Arikaree group in that both underlie the Monroe Creek formation directly, but the lithologic characteristics are dissimilar. The age of the Sharps formation appears to be very early Miocene, based on a vertebrate fauna that includes 17 genera and 25 species.

Radioactivity and Uranium Content of Some Cretaceous Shales, Central Great Plains

The Sharon Springs member of the Pierre shale of Late Cretaceous age, a hard black organic-rich shale, similar in many characteristics to the Chattanooga shale, is radioactive throughout central and western South Dakota, most of Nebraska, northern Kansas, and northeastern Colorado. In the Missouri River valley, thin beds of the shale contain as much as 0.01 per cent uranium. Beds correlated with the Sharon Springs are as much as 20 feet thick or more and have a radioactivity of about 0.01 per cent equivalent uranium in southwestern Nebraska according to interpretation of gamma-ray well logs. The radioactivity and uranium content are highest in the Missouri River valley in South Dakota and in southwestern Nebraska where the shale rests disconformably on the underlying Niob ara formation, also of Cretaceous age. Near the Black Hills, and in the area on the north, the shale of the Sharon Springs member rests on a wedge of the Gammon ferruginous member of the Pierre, which is represented by a disconformity on the east and south, and the radioactivity of the shale is low although greater than that of overlying strata. The shale also contains a suite of trace elements in which arsenic, boron, chromium, copper, molybdenum, nickel, selenium, and vanadium are conspicuous. Molybdenum and tin are less abundant in the Sharon Springs than in similar shales of Paleozoic age, and silver and selenium are more abundant. In the Great Plains region, the upper 30-50 feet of Cretaceous shales overlain unconformably by the White River group of Oligocene age have been altered to bright-colored material. This altered zone is chiefly the result of pre-Oligocene weathering although post-Oligocene ground-water conditions also have affected the zone. The greatest radioactivity occurs in masses of unaltered shale measuring about 1 × 4 feet in cross section included in the lower part of the altered zone. Where the zone is made up of shale and marl of the Niobrara formation, parts of the included unaltered shale contain as much as 0.1 per cent equivalent uranium and 0.03 per cent uranium. The disequilibrium between equivalent uranium (radioactivity) and the uranium content of the shales is believed to be a su face feature caused by relatively recent leaching of uranium from the present outcrops. The co-extensive distribution of the altered Cretaceous zone and of the overlying White River group suggests that most of the uranium in the small masses of unaltered marl in the altered zone has been derived from the White River group.

Structure plan of clastic dikes

Conclusions drawn from field observations are that vertical sandstone dikes of the White River Badlands, South Dakota, originated as open fractures that were filled with debris supplied by erosion of overlying formations. One existing explanation is that the dikes formed in deep desiccation cracks which developed at the surface as the silts and clays of the Oligocene White River group became consolidated. Evidence from a recent study of a small area of clastic dikes is incompatible with the desiccation‐crack theory of origin. The pattern of intersecting dikes, when mapped, resembles a fracture system rather than having a hexagonal arrangement normally associated with desiccation cracks. Shear fractures appear on the map intersecting at angles of 54° to 71°, the acute bisectrix varying in strike from N 45°W to N 54°W. One dike occupies a major tension fracture, strikes N 50°W, and extends vertically through two beds of strikingly different lithology, a condition unlikely to occur with desiccation cracks. South of the area, normal faults of small vertical displacement, trending northwest, suggest minor regional tension, which may well have caused the development of a fracture pattern as displayed by the dikes. If these fractures were open at the surface, subsequent filling from above would follow, resulting in numerous intersecting clastic dikes.

Occurrence of Lower Oligocene Mammal-Bearing Beds Near Death Valley, California

It is a curious fact that while the White River deposits with their wealth of vertebrate fossils are widely distributed in the western Great Plains and occur also in certain of the intermontane basins of the Cordilleran province, no horizon, recognized on the basis of land mammals as equivalent in time to the lower Oligocene or Titanotherium Zone, has been found beyond these areas on the North American continent.(1) All the more unusual does this fact seem when it is realized that since the definition of the White River Group by Hayden in 1862 and the early researches on the White River fossil vertebrates by Leidy, Cope and Marsh, field investigations in the Tertiary have progressed broadly and intensively over the Far West.

Sand crystals and their relation to certain concretionary forms

Location and Geological Relations Concretions of various kinds are abundant in several formations in the Great Plains region, and their prominence is so marked that facts which throw light on their origin are greatly to be desired. Recently there has been discovered in one of the Tertiary formations an exposure which exhibits in a most instructive manner the development of concretions by evident crystallization, which it is the purpose of this paper to describe. The Tertiary of the Great Plains region comprises the White River group of the Bad lands, mainly of Oligocene age, and a great series of deposits which originally were included under the term Loup Fork. The greater portion of this series, extending through Nebraska into South Dakota, has been separated by Darton under the designation of Arikaree formation. It is believed to be of Miocene age. This formation consists mainly of sand which locally is consolidated . . .