Search USGS⌕ Search

Geology topics

W. A. Cobban

Publications and source records attributed to W. A. Cobban.

35 records · Page 2Linked to original sources
USGS1983

Biostratigraphic correlation chart of some Upper Cretaceous rocks from the Lost Soldier area, Wyoming to west of Craig, Colorado

This chart depicts the time-stratigraphic relations of some Upper Cretaceous rocks along the eastern and southeastern margins of the Greater Green River Basin, south-central Wyoming and northwestern Colorado. The purpose of this report is to release a preferred set of correlations based upon marine mollusk biostratigraphy. The senior author, with the help of B. E. Law, has acquired, synthesized, compiled, and interpreted data from various sources. These include selected published documents (see "References Cited") and unpublished reports of fossil identifications by W. A. Cobban who examined collections made by the late J. R. Gill. Numerous measured sections of Gill's were also utilized. It must be emphasized that all interpretations on this chart are based on information obtained from these sources and the senior author has yet to substantiate these correlations in the field. Not all data from the area of this study is included herein because it is either repetitive in nature or its reliability is uncertain. This uncertainty is due to the ambiguity inherent in both fossil identification and stratigraphic interpretation. Questionable unpublished material has been omitted while published data which is inconsistent with the senior author's correlations may be found in the footnotes portion of this report. The rock units are assigned to a range of ammonites that have been related to an absolute time scale. The ammonite zonation and age boundaries are adapted from Obradovich and Cobban (1975). "D" numbers are provided for each geographic locality where fossils were collected and described by personnel of the U.S. Geological Survey. These fossils may be accessed at the offices of the Survey in Lakewood, Colorado.

Colorado, Wyoming↗
USGS1977

A new curved baculite from the Upper Cretaceous of Wyoming

Baculites reduncus , n. sp., is a moderately large ammonite that has a curved shell, a large angle of taper, and a stout ovate cross section. Conspicuous broad, arcuate ribs cross the upper two-thirds of the flank. The suture, which is fairly complex, has a distinctive lateral lobe. All the types are from the lower part of the Rock River Formation near Rock River, Wyo. The species is of late Campanian age and marks a zone between the Zones of Baculites gregoryensis Cobban and B. scotti Cobban

Wyoming, Colorado↗
USGS1973

The Late Cretaceous ammonite Baculites undatus Stephenson in Colorado and New Mexico

Baculites undatus Stephenson, originally described from the Nacatoch Sand of northeastern Texas, has been found in the Pierre Shale at 25 localities in Colorado and two in New Mexico. An early form of the species occurs in the zone of Didymoceras cheyennense (Meek and Hayden), and the typical form occurs in the overlying zones of Baculites compressus Say, B. cuneatus Cobban, and B. reesidei Elias. The species is characterized by its stout cross section, broad venter, conspicuous lateral and ventral ribs, and suture of about average complexity for the genus.

Colorado, Wyoming, New Mexico↗
USGS1973

The Late Cretaceous ammonite Trachyscaphites pulcherrimus (Roemer) in New Jersey and Texas

Trachyscaphites pulcherrimus , described originally by Ferdinand Roemer in 1841 from fragments of nodose ammonites from Germany, is characterized by having five rows of tubercles on each flank of the phragmocone and three to five rows on each side of the body chamber. Weak midventral tubercles are present on some specimens. Ribbing is dense and usually irregular. The species has been recorded from upper Campanian rocks in Germany, Austria, France, Poland, and Russia. Recently a few specimens have been found at the top of the Wenonah Formation of New Jersey and in the Taylor Marl of Texas.

Journal of Research of the U.S. Geological Survey↗