New paleontologic evidence requires a revision of previous interpretations of the stratigraphy of Mississippian sequences in the Cordilleran miogeosyncline of eastern Idaho and northeastern Utah. A postulated unconformity between rocks of early Osagean age and rocks of middle Meramecian age is no longer tenable in the light of new data. The new evidence supports continuous deposition from the Lodgepole Limestone (Kinderhookian and early Osagean age) into the Little Flat Formation (early Osagean to middle Meramecian age) and its equivalents, and the interpretation of a phosphatic siltstone and shale interval in the lower part of the Little Flat Formation as a starved-basin facies.

Idaho, Utah↗

USGS1975

Carboniferous biostratigraphy, northeastern Brooks Range, Arctic Alaska

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Professional Paper↗

USGS1974

New evidence on the age of the top of the Madison Limestone (Mississippian), Bighorn Mountains, Wyoming and Montana

The youngest strata recognized in the Madison Limestone arc dated by foraminifers and corals at two localities on the west flank of the Bighorn Mountains in Wyoming and Montana. Fossils collected in situ from the Madison at Shell Canyon represent Zone 12 of Mamet and Skipp of late Salem age (middle Visean), previously thought to be unrepresented by strata in the northern Cordilleran region of the United States. A block of residual chert found at Devils Canyon contains fossils with a possible age range of microfaunal Zones 12 15 (late Salem to Ste. Genevieve, middle to late Visean), providing further evidence of an extended age range for Madison strata prior to post-Madison, pre-Amsden erosion.

Montana, Wyoming↗

USGS1970

Foraminiferal zonation and carbonate facies of Carboniferous (Mississippian and Pennsylvanian) Lisburne group, central and eastern Brooks range, Arctic Alaska

The Lisburne Group carbonate rocks of the central and eastern Brooks Range contain foraminiferal assemblages assigned to zones of late Tournaisian (Osage) to early Moscovian (Atoka) age. Representatives of both Eurasiatic and American cratonic microfaunas permit correlation with the original Carboniferous type sections in western Europe as well as with the standard Mississippian and Pennsylvanian sequences in the Mid-Continent region of North America. Correlation anomalies in the lower part of the sequence are discussed.

Alaska↗

USGS1970

Biostratigraphy and dolomite porosity trends of the Lisburne Group

This preliminary study is based on measured and carefully collected sections of the Lisburne Group (fig. 1, sees. 1-29). The outcrops extend from Cape Lisburne (sec. 1) in the west to Egaksrak River (sec. 29) in northeastern Alaska and are used as the basic building blocks for the carbonate facies maps and the cross section. Lithologic and foraminifera samples were collected at 10-foot intervals and rugose corals were collected within each section where found. The rock material was cut into thin section, and petrographic and microfossil studies were made to determine environments of deposition, facies, diagenetic changes, and microfossil content. Coral collections were studied in thin section.

Alaska↗