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Stratigraphy Commons

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Geomorphology

1993

Robert F. Diffendal, Jr., Publications

Articles 1 - 4 of 4

Full-Text Articles in Stratigraphy

Probable Glacial Climatic Conditions In Source Areas During Deposition Of Parts Of The Ash Hollow Formation, Ogallala Group (Late Tertiary), Of Western Nebraska, Patricia E. Helland, Robert F. Diffendal Jr. Oct 1993

Probable Glacial Climatic Conditions In Source Areas During Deposition Of Parts Of The Ash Hollow Formation, Ogallala Group (Late Tertiary), Of Western Nebraska, Patricia E. Helland, Robert F. Diffendal Jr.

Robert F. Diffendal, Jr., Publications

Evidence of the climatic conditions in the mountain sediment source areas for the late Tertiary Ash Hollow Formation of the Ogallala Group in western Nebraska has been sought in an SEM (scanning electron microscope) study of surface features on detrital quartz grains from these deposits. The following lines of indirect evidence raised the possibility of glacial conditions: uplift of up to 3500 m in the source areas, paleohydrologic parameters indicative of a transport system analogous to the modern North Saskatchewan River, and possible cold climate surface features on cobbles from the deposits. SEM analysis shows that five of the nine …


Understanding Groundwater Starts With The Rocks: Geologic Fralnework, Groundwater Occurrence And Irrigation Development In Nebraska, Robert F. Diffendal Jr. Mar 1993

Understanding Groundwater Starts With The Rocks: Geologic Fralnework, Groundwater Occurrence And Irrigation Development In Nebraska, Robert F. Diffendal Jr.

Robert F. Diffendal, Jr., Publications

Nebraska is blessed with abundant groundwater. This groundwater is found beneath much of the state, principally in the sediments and sedimentary rocks that blanket the ancient and largely crystalline rocks geologists call Precambrian (see block diagram of Nebraska's geology, p. 50). These younger deposits contain pieces of evidence such as fossils and sedimentary features that reveal the tremendous changes in the environment that have gone on over the last 570 million years, during which these deposits accumulated. Change is the name of the game in geologic history, just as it is in human history. Fundamental changes in geologic history across …


Profiles: Nelson Horatio Darton: His Surveys Laid The Foundation, Robert F. Diffendal Jr. Mar 1993

Profiles: Nelson Horatio Darton: His Surveys Laid The Foundation, Robert F. Diffendal Jr.

Robert F. Diffendal, Jr., Publications

No serious researcher studying the development of water resources in Nebraska, or for that matter in the central Great Plains, can overlook the works of Nelson Horatio Darton, the first geologist to study and publish about those resources in any detail. Darton originally published the names and characteristics of many hydrogeologic units beneath much of Nebraska, now used by groups as diverse as scientists, well drillers and the general public. These works are listed below. As an indication of the value of these early efforts, I have used these works for my research and can testify to their accuracy and …


Application Of Sealevel Stratigraphy To Neogene Great Plains Stratigraphy, Robert F. Diffendal Jr., A. Lowrie Jan 1993

Application Of Sealevel Stratigraphy To Neogene Great Plains Stratigraphy, Robert F. Diffendal Jr., A. Lowrie

Robert F. Diffendal, Jr., Publications

Absolute-dated high frequency (Milankovitch cycles) marine climate/sealevel oscillatory stratigraphy can be correlated generally with continental stratigraphies. Improvements in absolute dating of Neogene formations across the North American Great Plains make this a candidate area in which to correlate marine and continental stratigraphies. Mid-latitude continental areas respond directly to climate variations. During glaciated/ cold climates, sealevel lowering results in steepened river gradients, increased erosion all along the river channel, and larger stress-bed loads. This, combined with glacial catastrophic flooding, produces greater cut-and-fill sequences along river systems than crevasse splays along the emergent coastal plain, deltas along the shelf, and submarine fans …