Geomorphology Commons^™

Publications And Other Works By R. F. Diffendal, Jr., Robert F. Diffendal Jr.

School of Natural Resources: Faculty Publications

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Updated March 2024

The Role Of Eolian-Fluvial Interactions And Dune Dams In Landscape Change, Late Pleistocene-Holocene, Mojave Desert, Usa, Mark R. Sweeney, Eric V. Mcdonald, Lucas P. Chabela, Paul R. Hanson

School of Natural Resources: Faculty Publications

The formation of the Kelso Dunes in the eastern Mojave Desert, California, was a landscape-changing event triggered by an increase in sediment supply that followed the incision of Afton Canyon by the Mojave River ca. 25 ka. Eastward migration of sand dunes occurred along a well-defined eolian trans­port corridor. Dunes temporarily blocked washes resulting in substantial aggradation of eolian and fluvial sediments. Stratigraphic exposures reveal numerous fining-up sequences with interbedded eolian sands that provide evidence of dune dams and subsequent aggradation. Luminescence ages reveal that dune blocking and aggradation correspond to a regional pulse of alluvial fan sedimentation that occurred …

Resolving Time-Space Histories Of Late Cenozoic Bedrock Incision Along The Upper Colorado River, Usa, Andres Aslan, Karl E. Karlstrom, Eric Kirby, Matthew T. Heizler, Darryl E. Granger, James K. Feathers, Paul R. Hanson, Shannon A. Mahan

School of Natural Resources: Faculty Publications

The upper Colorado River basin drains the western slope of the Rocky Mountains province of North America and hosts a rich record of fluvial terraces and volcanic deposits that provide an archive of bedrock river incision since the Late Miocene. Here we present new geochronology from fluvial deposits and associated volcanic units using multiple methods (luminescence, cosmogenic-burial, 40Ar/39Ar basalt and detrital sanidine, and U/Pb detrital zircon) to reconstruct a detailed record of bedrock incision in the upper Colorado River over timescales ranging from Miocene to Late Pleistocene. Late Miocene (ca. 11–8 Ma) basalt flows perched 800–1700 m above the Colorado …

Chronology Of Dune Development In The White River Badlands, Northern Great Plains, Usa, P. E. Baldauf, P. A. Burkhart, Paul R. Hanson, M. Miles, Ashley Larsen

School of Natural Resources: Faculty Publications

Aeolian dune field chronologies provide important information on drought history on the Great Plains. The White River Badlands (WRB) dunes are located approximately 60 km north of the Nebraska Sand Hills (NSH), in the western section of the northern Great Plains. Clifftop dunes, sand sheets, and stabilized northwest-southeast trending parabolic dunes are found on upland mesas and buttes, locally called tables. The result of this study is a dune stabilization history determined from samples collected from stratigraphic exposures and dune crests. Thirty-seven OSL ages, from this and previous investigations, show three periods of dune activity: 1) ~21,000 years ago to …

Field Guide To The Geology Of The Harlan County Lake Area, Harlan County, Nebraska, With A History Of Events Leading To Construction Of Harlan County Dam, Robert F. Diffendal Jr., Duane R. Mohlman, R. George Corner, F. Edwin Harvey, K. J. Warren, Scott Summerside, Roger K. Pabian, Duane A. Eversoll

School of Natural Resources: Faculty Publications

The year 2002 will mark the fiftieth anniversary of completion of the Harlan County Dam and Multi-Purpose Reservoir. This seems a good time to write about the history of and reasons for building the dam, the effects of the dam and reservoir on the Republican River valley, and the geologic features seen along the shores of the lake and areas nearby. As many junior authors helped produced this educational circular, they are listed in the table of contents. All other sections were written by the senior author.

Includes July 2016 update: Addendum of photographs showing fault traces on drought-exposed lake …

Structural And Geomorphological Evolution Of Huangshan (Yellow Mountain), Anhui Province, China, Pei-Hua Huang, Robert F. Diffendal Jr., Ming-Qing Yang

School of Natural Resources: Faculty Publications

Huangshan (Yellow Mountain) is an 1864-m granite massif situated at 30° 10′ N and 118° 11′ E, south of the lower reaches of the Yangtze River. The granite formed during the Early Cretaceous and was subsequently uplifted several times along faults. After the initial uplift, about 54 Ma, erosion proceeded to wear away the mountain for the next 30 Ma. By 24 Ma the Bright Summit Peneplain had formed. Renewed uplift in the Miocene along the same fault systems produced a mountain in the same place as the original one. This mountain was eroded to produce a second mature denudational …

Sem Analysis Of Quartz Sand Grain Surface Textures Indicates Alluvial/Colluvial Origin Of The Quaternary "Glacial" Boulder Clays At Huangshan (Yellow Mountain), East-Central China, P. E. Helland, Pei-Hua Huang, Robert F. Diffendal Jr.

School of Natural Resources: Faculty Publications

Geomorphic features and Pleistocene deposits on Huangshan have been attributed to glaciation. Recent reassessment questions this interpretation. As part of the reassessment, quartz sand grains from deposits identified as glacial boulder clays (till composed of boulders in a clay or silt matrix) were analyzed by scanning electron microscope for evidence of their sedimentary history. Surface textures found on the boulder-clay grains were compared with those on grains with known sedimentary histories including glacial, grus, colluvial, and alluvial grains. The analysis shows that the grains lack typical glacial textures. The surface textures present indicate a complex history. Non-uniformly weathered grain surfaces …

Scanning Electron Microscopic Study Of Quartz Sand Surface Features, Ash Hollow Formation, Ogallala Group, Western Nebraska, Patricia E. Helland, Robert F. Diffendal Jr.

School of Natural Resources: Faculty Publications

In field studies of the late Tertiary Ash Hollow Formation of the Ogallala Group in western Nebraska the alluvial deposits are composed of large volumes of sand and gravel up to large cobbles. Because the current understanding of the climate of the region at the time of deposition does not provide for a source for deposits of this character, a scanning electron microscopic study of the surface features on the quartz sand grains from these sediments was undertaken. Nine samples, collected from locations in Banner, Morrill and Keith Counties, were examined to see if they had one or more of …

Plate Tectonics, Space, Geologic Time, And The Great Plains: A Primer For Non-Geologists, Robert F. Diffendal Jr.

School of Natural Resources: Faculty Publications

For most Americans, "The Great Plains" evokes images of grasslands, dust storms, prairie fires, Native Americans on horseback, cowboys and wheat lands, and perhaps flat valleys crossed by braided rivers carrying a heavy load of sand and gravel, extremes of weather, and a climate typified by an alternation of droughts and wetter periods. Geologists picture such general images, too, but they also see radical changes in the landscape over periods expressed in millions rather than hundreds of years. Geologically speaking, human activities on the Great Plains are too recent to have much of a place in the broad geologic history …

Late Paleozoic Cyclic Sedimentation In Southeastern Nebraska: A Field Guide, Roger K. Pabian, Robert F. Diffendal Jr.

School of Natural Resources: Faculty Publications

People studying and collecting sedimentary rocks, minerals, and fossils in eastern Nebraska often find that locating rock exposures can be difficult. Most of the rolling hills in the eastern sixth of the state are underlain by thick, interlayered, glacial deposits, loess (windblown silt), and alluvium (stream-deposited sediments) of very young geologic age. These sediments cover the bedrock in most of that area. Natural exposures and human excavations of bedrock are mostly confined to the sides and floors of stream valleys. However, in the southeasternmost counties of the state, the younger sediment cover is commonly thin or absent. Pawnee and Richardson …

New Evidence Supporting The Blancan Age Of The Sand And Gravel Sequence Capping The Ash Hollow Formation, Garden, Keith, And Lincoln Counties, Nebraska, Robert F. Diffendal Jr., James W. Goeke, Michael R. Voorhies

School of Natural Resources: Faculty Publications

Sandwiched between the overlying eolian Quaternary loesses and sands and the underlying beds of the Ash Hollow Formation, Ogallala Group, buried beneath the sliver of Cheyenne Tableland in Keith County and adjacent areas of western Nebraska, is a mass of fluvially deposited sand, gravelly sand, and sandy gravel of previously uncertain age. Some authors assigned these sediments to the Ogallala Group, while others have called them either the Broadwater Formation (Blancan), or a combination of the two rock units.

The Inapplicability Of The Concept Of The "Sidney Gravel" To The Ogallala Group (Late Tertiary) In Part Of Southern Banner County, Nebraska, Robert F. Diffendal Jr.

School of Natural Resources: Faculty Publications

A series of geologic maps of counties in western Nebraska was prepared for the Nebraska Geological Survey during the mid-1 930s. These maps showed the distribution of rock units of Tertiary age including a formation designated as the “Sidney.” The Sidney Gravel was described as a widespread sheetlike complex of channel deposits, but with small areas where it is not developed. In southern Banner County, Nebraska, there are several channels filled with sand and gravel that were mapped as Sidney in this series. Recently one of these channel fills has been observed to cut across the other. The fills are …

Further Comments On The Nature And Developmental History Of Quaternary Pumpkin Creek, Banner, And Morrill Counties, Nebraska, Robert F. Diffendal Jr.

School of Natural Resources: Faculty Publications

The occurrence of Quaternary anorthosite-rich sand and gravel deposits in south-central Morrill County, Nebraska, supports the idea that Pumpkin Creek formerly flowed farther east than it does today. This eastern extension of the creek was abandoned when another headward cutting tributary of the North Platte River cut through the divide between Pumpkin Creek and the North Platte just east of Jail and Courthouse rocks and captured Pumpkin Creek.

Unusual clast types found in Quaternary deposits along Pumpkin Creek in Banner County may be used to determine some characteristics of the streams that carried them. For example, armored mud balls and …

Geometries And General Features Of Some Cenozoic Valleys And Valley Fills, Western Nebraska, Robert F. Diffendal Jr.

School of Natural Resources: Faculty Publications

Portions of Tertiary and Quaternary valleys and valley fills have been exhumed by recent stream erosion at many sites in western Nebraska. Paleovalleys vary from narrow, steep-sided, high gradient tributary gullies less than 0.1 km wide to broad, flat-floored valleys produced by lateral erosion. Segments of valley floors may be nearly smooth in the case of a Quaternary example, or may be very irregular with potholes and other deep scour features. Paleovalley sides, when exposed, are often steeply sloping, and approaching or possibly going beyond the vertical where the valleys have been eroded into the Brule Formation. Paleovalleys range in …

A Gering Formation (Miocene) Pumice Conglomerate And Associated Beds From Broadwater, Nebraska, Robert F. Diffendal Jr.

School of Natural Resources: Faculty Publications

The Mitchell Pass Member of the Gering Formation was defined by Vondra, Schultz, and Stout in 1969 on the basis of exposures in the Wildcat Ridge area of western Nebraska. The basal part of the member in many areas of Wildcat Ridge is a pumice-pebble conglomerate bed. A newly discovered pumice-pebble conglomerate locality occurs north of Broadwater, Nebraska, some twenty miles east of the easternmost previously reported exposure of the pumice conglomerate at Redington Gap on Wildcat Ridge. Pumice samples from Redington Gap and Broadwater have the same index of refraction and similar inclusions. Beds above the conglomerate and below …

The Rush Creek Structure, Garden County, Nebraska, Robert F. Diffendal Jr.

School of Natural Resources: Faculty Publications

Detailed field mapping of surface outcrops in southern Garden County, Nebraska, has revealed a drop of 200 feet in three miles in the elevation of the contact between the Ogallala and pre-Ogallala (probably Brule) Formations exposed on the east side of Rush Creek. Beds of silt, sand, siltstone, and volcanic ash in the are a locally dip to the northwest at angles of up to 8½°. The contact between the two formations cannot be seen on the west side of Rush Creek but beds in the Ogallala Formation there dip to the north and northeast. The unusually long valley of …