Search USGS⌕ Search

Geology topics

Robert H. Tschudy

Publications and source records attributed to Robert H. Tschudy.

12 recordsLinked to original sources
USGS1975

Palynological evidence for late Cretaceous, Paleocene, and early and middle Eocene ages for strata in the kaolin belt, central Georgia

Falynomorphs of Late Cretaceous (Maestrichtian), Paleocene, Paleocene or early Eocene (Wilcox), and middle Eocene (Claiborne) ages have been found in lignitic and carbonaceous clays and silts in the Tuscaloosa Formation, as used in central and east-central Georgia. The occurrence of palynomorphs of Maestrichtian (Navarro) age above thick kaolin deposits at one locality and a suite of Claiborne age fossils below a thick deposit at another locality establish that kaolins of both Late Cretaceous and middle Eocene or younger ages are present. However, the recognition of the Paleocene and middle Eocene beds in the Tuscaloosa Formation of several authors indicates that part of it is much younger than previously thought. The palynomorphs and other characteristics of the carbonaceous materials of Cretaceous and middle Eocene ages indicate freshwater accumulation. The beds of Paleocene age contain both terrestrial and marine forms indicating deposition in marine swamps or estuaries. These findings and the range in ages support the conclusion that the deptositional history of the Late Cretaceous and early Tertiary formations in Georgia is complex.

Georgia↗
USGS1975

The megaspore genus Henrisporites from the Cretaceous of Massachusetts

A new megaspore species belonging to the genus Henrisporites was found in Cretaceous (probably Cenomanian) rocks from Massachusetts. Megaspores of Paxillitriletcs dakotaensis (Hall) Hall and Nicolson were found in the same rocks. This paper discusses the occurrence of these two megaspores in North America and describes Henrisporites angustus n. sp. from Massachusetts.

Massachusetts↗
USGS1970

Palynology of the Cretaceous-Tertiary boundary in the northern Rocky Mountain and Mississippi Embayment regions

In both the Rocky Mountain and the Mississippi Embayment regions it is often difficult to distinguish Upper Cretaceous from lower Tertiary rocks on the basis of physical characteristics; the transition can be recognized with relative ease, however, on the basis of abrupt qualitative changes in plant microfossils. Many Cretaceous species vanish and new species appear in the Paleocene. In both regions the Paleocene yields fewer species than does the underlying Cretaceous. A pronounced difference exists between the Late Cretaceous pollen and spore floras of the two regions. The spore-pollen assemblage from the Rocky Mountains is partially characterized by the presence of Aquilapollenites, Proteacidites, Wodehouseia, and an unnamed species of Tricolpites. These taxa are not found in the Late Cretaceous of the Mississippi Embayment region. The embayment region yields Rugubivesiculites, an unnamed species of Araucariacites, and several genera belonging to the Normapolles group that are not found in the Rocky Mountain region. The Mississippi Embayment Cretaceous and Paleocene pollen floras show greater similarities to pollen floras from Europe than to those from the northern Rocky Mountains. The Rocky Mountain pollen floras exhibit closer similarities to the Alaskan and Siberian floras. It is suggested that the floral dissimilarity between the Mississippi Embayment and the northern Rocky Mountain regions may be accounted for by the separation of the Rocky Mountain province from the Mississippi Embayment province during Late Cretaceous time by the great north-trending Cretaceous epeiric sea. It is further suggested that the floral changes across the Cretaceous-Tertiary transition may have been caused by slight climatic changes brought about by uplift or by withdrawal of the tempering influence of the epeiric sea.

Kentucky, Mississippi, Missouri, Montana, Tennesse↗
USGS1966

Plant microfossils from the Fort Union Formation

As a part of continuing studies to provide palynological data from critical sequences for comparative biostratigraphic studies, the microfossils found in two Paleocene samples have been examined and photographed.

Open-File Report↗