Contributions to Geology 21.2

Age and depth of burial, Cambrian Lodore Formation, northeastern Utah and northwestern Colorado

RANDY G. HERR Southland Royalty Company, Midland, Texas 79701
M. DANE PICARD and STANLEY H. EVANS, JR. Department of Geology and Geophysics, The University of Utah, Salt Lake City, Utah 84112

Pages
115-122

Keywords
Lodore, Cambrian, Utah, Colorado, ichnofossils

Abstract
The Lodore Formation is a transgressive sandstone which crops out along the Uinta Mountain uplift in northeastern Utah and northwestern Colorado. Although the formation has been studied for more than a 100 years, its precise age is uncertain because there are few fossils. Rare trilobites and brachiopods display a late Middle to early Late Cambrian aspect. Ichnofossils, characterized by ichnogenera of the Cruziana and Skolithos facies, are long-ranging, but they are common in Cambrian rocks throughout the world.

We have measured a 387 + 35 m.y. K-Ar age for the upper part of the formation and a 428 + 14 m.y. age for the lower part based on glauconite. Argon loss apparently has occurred in the glauconite, but the magnitude is uncertain. The maximum noted correction in cratonic sequences for argon loss is 25%. The maximum age of any of our samples, based on the glauconite ages, is 535 + 14 m.y. They may be younger than that, but probably not less than about 483 + 35 m.y.

Argon loss in glauconite is closely related to depth of burial. Burial of the Lodore Formation to more than 5 km would have led to substantial loss of argon which has not occurred, indicating that the stratigraphic sequence above the Lodore was thin.

Paleontology and paleoecology of the Lance Formation (Masstrichtian), east flank of Rock Springs Uplift, Sweetwater County, Wyoming

BRENT H. BREITHAUPT Department of Geology and Geophysics, The University of Wyoming, Laramie, Wyoming 82071-3006

Pages
123-152

Keywords
Lance, Rock Springs Uplift, Wyoming, vertebrates, Cretaceous, ankylosaurs

Abstract
Several fossiliferous sites occur in the upper part of the latest Cretaceous Lance Formation on the east flank of the Rock Springs Uplift. These sites have a high diversity of animals, especially lower vertebrates. Biotic and lithologic analyses of the most diverse of these sites, UW loc. V-79032, indicate deposition in a warm, subtropical, lowland floodplain environment on the west coast of the latest Cretaceous, eastward-regressing intracratonic seaway. This is the first study of latest Cretaceous vertebrate paleontology in the area since the work of Cope in 1872, and represents the only Late Cretaceous terrestrial faunal analysis from Wyoming west of Niobrara County.

Although most of the vertebrate fauna is typical for deposits of "Lancian" age, remains of nodosaurid ankylosaurs extend the known North American range of this family into the latest Cretaceous.

Paleontology and correlation of Eocene volcanic rocks in the Carter Mountain area, Park County, southeastern Absaroka Range, Wyoming

JEFFREY G. EATON Department of Geology and Geophysics, The University of Wyoming, Laramie, Wyoming 82071-3006

Pages
153-194

Keywords
Wapiti, Aycross, Pitchfork, Eocene, Absaroka, Wyoming, Carter, paleomagnetic, volcanic

Abstract
The Wapiti and Aycross formations are lateral and time equivalent units. Use of the name Pitchfork Formation is abandoned. Based on paleomagnetic studies, flows on Ptarmigan and Carter mountains are assigned to the Wapiti Formation (Jim Mountain Member?) and an unnamed sequence rather than to the Trout Peak Trachyandesite. The Blue Point marker overlies the Aycross and Wapiti formations (and the unnamed sequence), and underlies the Tepee Trail and Wiggins formations. The Tepee Trail Formation intertongues with the lower part of the Wiggins Formation in the Greybull Valley area, and is overlain by the Wiggins Formation to the south.

The fauna from the Wapiti Formation compares with those of the Bridger "B. " The faunas from the "turtle-lake beds" (unnamed sequence) and from the Blue Point marker appear to be transitional between those of the Bridger "B" and "C." Two new species, Pseudotomus sundelli and Hyopsodus tonksi, are described.

The Wapiti Formation was probably deposited during normal event 21 of the magnetic anomaly scale. The unnamed sequence and the Blue Point marker may have been deposited during a short reversed episode within normal event 21.

The soil of Clovis age at the Sheaman archaeological site, eastern Wyoming

RICHARD G. REIDER Department of Geography, The University of Wyoming, Laramie, Wyoming 82071-3006

Pages
195-200

Keywords
Clovis, Wyoming, Sheaman, gley, climate

Abstract
A Clovis-age soil (c. 11,400 B.P.) at the Sheaman site has qualities of a Haplaquoll (Wiesenboden, Low Humic Gley, or Humic Gley) grading to an Argiaquoll which suggests inhibited soil drainage and high water table along arroyo bottoms under a cool and humid climate. Vegetation was probably grasses and sedges and possibly some woodland.

Weakly developed modern soils on arroyo bottoms are Fluvents or Alluvial Soils formed generally under semiarid climate with good soil drainage. The Altithermal soil, and in some cases those developed under dry climates in postAltithermal time, are superposed into the Clovis-age soil, thus impregnating it with calcium carbonate and perhaps other salts.