Richard G. Reider

Evidence for a shallow early or middle Wisconsin-age lake in the Bonneville Basin, Utah

Abstract Relatively complete stratigraphic records of the Bonneville cycle and of at least one and probably two earlier lacustrine are exposed along the Bear River below Cutler Dam in northern Utah between altitudes of 1290 and 1365 m. In most exposures the unconformity between the Bonneville Alloformation and the underlying unit, herein named the Cutler Dam Alloformation, is marked by slight erosional relief and by a weakly to moderately developed buried soil, herein named the Fielding Geosol. In truncated profiles, the Fielding Geosol reaches a maximum of stage II carbonate morphology. Wood from near the base of the Cutler Dam Alloformation yielded a 14 C date of >36,000 yr B.P. (Beta-9845). Alloisoleucine/isoleucine (aIle/Ile) ratios of Sphaerium shells from the Cutler Dam beds average 0.15 ± 0.01 in the total hydrolysate, which is significantly greater than the average for Sphaerium shells of Bonneville age elsewhere in the basin. Therefore, the Cutler Dam Alloformation is older than 36,000 yr B.P., but much younger than deposits of the Little Valley lake cycle (140,000 yr B.P.?) which bear shells having significantly higher aIle/Ile ratios. The Cutler Dam Alloformation along the Bear River may be broadly correlative with marine oxygen-isotope stages 4 or 3. Fine-grained, fossiliferous, marginal-lacustrine facies of the Cutler Dam Alloformation are exposed at altitudes near 1340 m, and are probably the highest exposures of sediments deposited in the early or middle Wisconsin lake in the Bonneville basin.

Soils of Cinnabar Park, Medicine Bow Mountains, Wyoming, U.S.A.: Indicators of Park Origin and Persistence

From phytolith and soil data, earlier researchers concluded that Cinnabar Park, a dry grassland surrounded by coniferous forest on a high interfluve (2928 m) in the Medicine Bow Mountains, Wyoming, has migrated downwind (east) by snowdrift action. However, recent soil mapping and studies of soil morphologies and stratigraphy, aided by radiocarbon dating and soil laboratory data, indicate precise alignment of moder soil-vegetation boundaries along the park edge and thus stability of the boundaries. An alternative explanation is that soil formation at the boundaries may be sufficiently rapid so that surface horizons readily reflect slow encroachment of forest onto parkland. In either case, soil characteristics do not support the interpretation that Cinnabar Park is migratory. In the park, ribbon forest, and snowglade (and some forested areas to the west), soil-sediment units give evidence of wind erosion of the interfluve modified by colluviation, resulting in a quartzite-rich, wind-polished stone line (or lines?) about 3 to 10 cm thick that acted as a lag gravel when erosion removed fine particles. The stone line, dated as old as about 2000 yr, is overlain by a surface eolian unit (or locally colluvium) about 5 to 20 cm thick. Soils in the park are developed into the eolian unit, the stone line (or colluvium), and underlying bedrock. We found no evidence that Cinnabar Park was ever forested since the time the stone line formed. Rather, the park is interpreted as a dry park, resulting from soil moisture deficits that prohibit tree expansion. In addition to snow deflation common across the park, moisture deficits are probably caused by poor water penetration from the eolian unit across the stone line into the coarse-textured subsoil. Only where snowdrifts adequately recharge the soil along park margins, or where the eolian unit is thin, can some tree invasion occur, providing that snowdrifting does not fatally damage young seedlings.

Late pleistocene and holocene soils of the Carter/Kerr-McGee archeological site, powder river basin, Wyoming

Summary Soil character and stratigraphy at the Carter/Kerr-McGee site indicate poorly drained conditions along the bottom of the paleo-arroyo in late Pleistocene time. This occurred under a relatively cool and humid climate during Clovis (ca. 11, 400 B.P.) and Folsom (ca. 10,700 B.P.) occupation and subsequently during occupation by Agate Basin (ca. 10,400 B.P.), Hell Gap (ca. 10,000 B.P.), and Cody (ca. 8700 B.P.) cultural groups. Under these conditions, Wiesenboden or Low Humic Gley or Humic Gley soils (BALDWIN et al. 1938, THORP & SMITH 1949), i.e., probably Typic Argiaquolls and Haplaquolls (SOIL SURVEY STAFF 1975, 276, 279–280), formed near the arroyo bottom under grasses and sedges in association with azonal (BALDWIN et al. 1938; THORP & SMITH 1949) and composite soils along its flanks. Wiesenboden or Low Humic Gley or Humic Gley soils do not now form in the area. Climatic change at the Pleistocene-Holocene boundary is marked by superposition of a calcareous soil, i.e., probably a Brown soil (BALDWIN et al. 1938; THORP & SMITH 1949) or Calciustoll or Haplustoll (SOIL SURVEY STAFF 1975, 301–302), into the late Pleistocene paleosols — a process indicative of ensuing dry and warmer climatic conditions and improved soil drainage thought to have occurred during Altithermal time. Following this, probably toward the end of the Altithermal, renewed arroyo cutting and slope instability partially or totally truncated this soil sequence. In turn, post-Altithermal events were marked by weak azonal soil formation (Ustifluvents and Ustipsamments; SOIL SURVEY STAFF 1975, 191, 207) in alluvium and colluvium along the paleo-channel as well as renewed arroyo incision and filling. The arroyo is presently incising itself and is cutting mainly along the alluviumbedrock contact.

Soil Evidence for Postglacial Forest-Grassland Fluctuation in the Absaroka Mountains of Northwestern Wyoming, U.S.A.

Soils on the west side of Dead Indian Pass (2414 m) in the Absaroka Mountains of northwestern Wyoming give indication of climatic and vegetational shift. This change is marked by a buried, truncated calcareous soil with abundant grass phytoliths (perhaps a Calcic Cryoboroll) which is unconformably overlain by a forest soil without abundant grass phytoliths (Typic Cryochrept). Using archaeological, geological, and soil data at the Dead Indian Creek archaeological site (48PA551), this shift appears to have happened sometime between about 5400 and 4400 BP, that is, near the Altithermal-Neoglacial boundary when climates shifted from dry to more humid, respectively. During the Altithermal, the west side of Dead Indian Pass, and much of the general area to elevations at least as high as 2400 m, were probably covered by grassland, including many north-facing slopes. In the Neoglacial, however, greater moisture probably encouraged forestation of north-facing slopes and others, as well as some stream terraces and ...

A groundwater vortex hypothesis for mima-like mounds, Laramie Basin, Wyoming

Abstract Mima-like mounds in the Laramie Basin occur where: (1) impervious bedrock (shale) is at a shallow depth (∼ 2–5 m); (2) bedrock is overlain by a thin veneer (∼ 1–4 m) of alluvial gravels; and (3) a strong argillic/calcic or petrocalcic soil caps the landform, typically a terrace. Active and inactive mounds contain churned materials, including pebbles derived from adjacent/subjacent units. The mounds are circular in plan view and lens- or funnel-shaped in cross-section. The strong intermound (premound) soil collapses beneath the mound, is entirely or partly destroyed at its base, or is truncated at the mound edge. Stratigraphic relationships on the youngest terrace of the Laramie River indicate that the inactive mounds are Holocene in age. Sodium concentrations (used as a tracer) in mound material and adjacent/subjacent units suggest that the mounds rotate counterclockwise. This movement may be driven by free spiral vortices (low hydraulic head) in confined (artesian) groundwater flow in alluvium between shallow bedrock and strong surface soil. The vortices (similar to water draining from a bathtub or a whirlpool in a river) may result from enlargements, constrictions, or changes in permeability of the aquifer — or meandering of groundwater flow. Groundwater, dissolved ions, and materials in suspension, or through friction and turbidity, then would move from adjacent high-hydraulic head areas into and down the vortex. In effect, the high head (intermound) areas would act as a pump whereas the vortex (which would form a mound) would act as a turbine — responding, therefore, to energy transformations between groundwater velocity and pressure according to the Bernoulli principle and Newtons Second Law of Motion. Soil or sediment, incapable of being fully moved into and down the vortex, would amass at the land surface as a circular mound that in cross-section would have a lens or funnel (turbine) shape. Computer modelling shows that mounds tend to form over deep bedrock and thick alluvium. The groundwater vortex hypothesis can account for the building of the mound higher at its center, the circular plan view and lens (or funnel) shape in cross-section, the inward spiral of sodium, the churned character of mound material, and the collapse (or truncation) of soils and other units beneath and along mound edges. The hypothesis, however, must not be applied to all other Mima or mima-like mounds, unless vortex motion can be determined and if stratigraphic similarities can be demonstrated.

Geomorphic implications of Pre-Wisconsin soils on the White River Plateau erosion surface of northwestern Colorado

Abstract The White River Plateau erosion surface (Miocene-Pliocene) at an elevation of approximately 2850 m (9500 ft) is dominated by weakly developed Holocene soils which commonly possess simple A-C horizonation. However, Pre-Wisconsin soils occur on the surface in isolated areas at both high and low topographic sites, most notably in Triangle Park. These Pre-Wisconsin soils consist of composite, polygenetic profiles having truncated, clayey subsoils which are overlain by stone or pebble lines, colluvium, soil creep, and probable local eolian deposits Truncation of the paleosols preceded development of the Holocene soils, which have formed on bedrock surfaces and have been superposed on the truncated, buried paleosols Soil distribution and character, in relation to structure of bedrock on the erosion surface, indicate that the surface as it now exists is structurally controlled and has a topography generated in late Tertiary to Pre-Wisconsin time.

STRATIGRAPHY, SOILS, AND AGE RELATIONSHIPS OF MIMA-LIKE MOUNDS, LARAMIE BASIN, WYOMING

Mima-like mounds in the Laramie Basin, Wyoming, are circular in plan view, lens or funnel-shaped in cross-section, and frequently have relief of 15 to 65 cm. They consist of churned materials derived from adjacent/subjacent soils and sediments. Strong intermound (premound) soils, or parts of them, usually collapse beneath the mounds or are sometimes truncated at mound edges. Both active and inactive mounds occur in areas of shallow, impermeable bedrock, thin alluvium overlying the bedrock, and strong premound soil development on terraces and benches. Radiocarbon dating, along with stratigraphic and soil relationships at various sites, indicates that the mounds are late Holocene (Neoglacial) in age. The premound soils and sediments beneath the mounds, in addition to those in intermound areas, appear to be affected chemically by salty groundwater related to mound formation or salt leached from overlying mound material into these units after the mounds formed. Accordingly, in response to the Hilgard reaction...