Contributions to Geology 13.1

Middle Eocene rodents (Mammalia) from southwestern Wyoming

MICHAEL E. NELSON Department of Earth Sciences and Sternberg Memorial Museum, Fort Hays Kansas State College, Hays, Kansas 67601

Pages
1-10

Keywords
fossil, Eocene, Mammalia, rodents, Wyoming, Thomas Canyon, Bridger

Abstract
A small collection of fossil vertebrates from the Fowkes Formation in Uinta County, Wyoming, includes the rodents: Thisbemys corrugatus, Leptotomus bridgerensis, Leptotomus sp., Paramys sp., 2 large Paramyids, Microparamys minutus, Tillomys? sp., a large Sciuravid, Pauromys sp., and Mysops parvus. This assemblage, the Thomas Canyon local fauna, is late middle Eocene in age and correlates with Twin Buttes Bridgerian faunas from the Bridger Basin, Wyoming.

Wyoming specimens of the trace fossil Bergaueria

DONALD W. BOYD Department of Geology, University of Wyoming, Laramie, Wyoming 82071

Pages
11-16

Keywords
Bergaueria, sea anemone, Wyoming, burrow

Abstract
A specimen of Gros Ventre Shale (Middle Cambrian) from north-central Wyoming contains several distinctive burrows referable to Bergaueria. This trace fossil, thought to represent the burrow of a sea anemone, is known from Cambrian and Ordovician strata in Europe and North America. The Wyoming specimens, the first reported from the Rocky Mountains of the United States, closely resemble material previously described from Lower Cambrian rocks in Alberta. Burrow casts from both places exhibit a basal depression but lack surrounding radial ridges. Mud containing artificially constructed "burrows" similar to Bergaueria was deformed experimentally, confirming the expectation that shape and dimensions of burrow casts are subject to change during compaction of sediment.

Infrared detection of kimberlitic diatremes in northern Colorado and southern Wyoming

M. E. MCCALLUM Department of Earth Resources, Colorado State University, Fort Collins, Colorado 80523

Pages
17-18

Keywords
Wyoming, Colorado, diatremes, kimberlite, aerial, infrared

Abstract
Kimberlitic diatremes in northern Colorado and southern Wyoming are poorly exposed and have little surface definition. Most are covered by a thin veneer of grus derived from the surrounding granitic rocks, and discoveries generally have been fortuitous. However, soils over kimberlite generally are well developed and have a higher moisture content than adjacent soils developed on granite. The moisture contrasts are seasonally accentuated and may be reflected by differences in relative lushness of vegetation. These differences are detectable on color infrared aerial photographs taken at low altitude over several known pipe localities. Preliminary evaluation suggests that this technique will be useful in exploration for local kimberlites.

Notes on some Early Eocene anaptomorphine primates

THOMAS M. BOWN Department of Geology, University of Wyoming, Laramie, Wyoming 82071

Pages
19-26

Keywords
Tetonius ambigaus, Eocene, primates, dental

Abstract
Restudy of the type specimen of Tetonius ambigaus and description of a new and better preserved mandible indicates populations of this species possessed radically different antemolar dentitions than did those of Tetonius homunculus. Tetonius ambiguas materials are therefore transferred to a new genus, Pseudotetonius (infra). Tetonius, as judged from known materials, is monotypic; only T. homunculus may be logically retained in this genus. In many dental characters Pseudotetonius is similar to Bridgerian Trogolemur myodes. A mandible from the Four Mile Wasatchian of Colorado which was previously referred to Trogolemur sp. is believed to actually represent Pseudotetonius ambigaus. The early Wasatchian anaptomorphine Anemorhysis shares many morphological characters with early Graybullian Tetonius and with the late Wasatchian omomyine Loveina. The earliest known omomyine and anaptomorphine primates are believed to have differentiated from a common ancestor which had a dentition most closely resembling that of early Graybullian Anemorhysis but with less specialised molar trigonids.

Soil development on Wisconsin moraines of the Libby Creek area, Medicine Bow Mountains, Wyoming

BENJAMIN R. SANSOM and RICHARD G. REIDER Department of Geography, University of Wyoming, Laramie, Wyoming 82071

Pages
27-40

Keywords
soil, Wisconsin, moraines, Libby Creek, Medicine Bow, Wyoming, tills, Pinedale, elevation

Abstract
Soils on Wisconsin moraines of the Libby Creek area do not show signs of pedological maturity commensurate with mapped ages of the tills. Instead, all soils indicate an equivalent degree of maturity and possess profiles reflecting vertical zonation of climate and vegetation as the dominant soil forming factors. However, soils on Pinedale II till display polygenetic characteristics which denote vertical shifting of climates and vegetation at elevations of approximately 9000 to 10,200 feet since late Wisconsin and early Holocene time. This shifting as recorded in the soils involved a change from grassland to coniferous forest at these intermediate elevations. No indication exists of a comparable change in vegetation at lower or higher elevations.

Karst of western Wyoming - an alpine karst in Tosi Creek Basin, Gros Ventre Mountains

EBERHARD WERNER Department of Geology and Geography, West Virginia University, Morgantown, WV 26506

Pages
41-46

Keywords
karst, Wyoming, alpine, Tosi Creek, Gros Ventre, fracture, Madison

Abstract
Extensive alpine-type surface karst development occurs in Tosi Creek Basin, northwestern Sublette County, Wyoming. Karren of various types ranging in dimension from a few inches in width and depth to 4 feet wide and 40 feet deep are found on the Mississippian Madison Limestones of high purity and low primary permeability. Alignment with joints or fractures increases as the karren forms increase in size; the smaller forms cross joint traces without noticeable effect. The basin is entirely occupied by dolines up to one-half mile in diameter. Only a few of the smaller of these are collapse sinks. The basin differs from other reported instances of alpine karst in that the very flat, nearly horizontal type of pavement does not occur here.