HOLOCENE LANDSCAPE EVOLUTION AND BIOCLIMATIC CHANGE IN THE REPUBLICAN RIVER VALLEY, SOUTH-CENTRAL NEBRASKA: IMPLICATIONS FOR GEOARCHAEOLOGY IN THE CENTRAL GREAT PLAINS

2018 ◽  
Author(s):  
Anthony L. Layzell ◽  
◽  
Rolfe D. Mandel
Keyword(s):  
Great Plains ◽  
Landscape Evolution ◽  
River Valley ◽  
South Central ◽  
Republican River

Late Quaternary landscape evolution and bioclimatic change in the central Great Plains, USA

2020 ◽  
Vol 132 (11-12) ◽  
pp. 2553-2571
Author(s):  
Anthony L. Layzell ◽  
Rolfe D. Mandel
Keyword(s):  
Great Plains ◽  
Landscape Evolution ◽  
Late Quaternary ◽  
Stable Carbon Isotope ◽  
Soil Formation ◽  
River Valley ◽  
Sediment Supply ◽  
Alluvial Fans ◽  
Buried Soils ◽  
South Central

Abstract A systematic study of floodplains, terraces, and alluvial fans in the Republican River valley of south-central Nebraska provided a well-dated, detailed reconstruction of late Quaternary landscape evolution and resolved outstanding issues related to previously proposed Holocene terrace sequences. Stable carbon isotope (δ13C) values determined on soil organic matter from buried soils in alluvial landforms were used to reconstruct the structure of vegetation communities and provided a means to investigate the relationships between bioclimatic change and fluvial activity for the period of record. Our study serves as a model for geomorphological and geoarcheological investigations in stream valleys throughout the central Great Plains and wherever loess-derived late Quaternary alluvial fans occur, in particular. Holocene alluvial landforms in the river valley include a broad floodplain complex (T-0a, T-0b, and T-0c), a single alluvial terrace (T-1), and alluvial fans that mostly grade to the T-1 (AF-1) and T-0c (AF-0c) surfaces. Remnants of a late Pleistocene terrace (T-2), mantled by Holocene (Bignell) loess, are also preserved, and some Holocene alluvial fans (AF-2) grade to T-2 surfaces. Radiocarbon ages suggest that the T-1 fill and AF-1 fans aggraded between ca. 9000–1000 yr B.P. Hence, nearly all of the Holocene alluvium in the river valley is stored in these landforms. Sedimentation, however, was interrupted by several periods of landscape stability and soil formation. Radiocarbon ages from the upper A horizons of buried soils in the T-1 and AF-1 fills, indicating approximate burial ages, cluster at ca. 6500, 4500, 3500, and 1000 yr B.P. Also, based on the radiocarbon ages, the T-0c fill and AF-0c fans were aggrading between ca. 2000–900 yr B.P. Given that the T-0c fill and upper parts of the T-1 fill were both aggrading after ca. 2000 yr B.P., we suggest that the T-1 surface was abandoned between ca. 4500–3500 yr B.P., but subsequent aggradation of both the T-1 and T-0c fills occurred due to large-magnitude flood events during the late Holocene. The δ13C data indicate a shift from ∼40% C4 biomass at ca. 6000 to ∼85% at ca. 4500 yr B.P. We propose a scenario where (1) a reduction in C3 vegetation after 6000 yr B.P. destabilized the uplands, resulting in an increase in sediment supply and aggradation of the T-1 fill and AF-1 fans, and (2) the establishment of C4 vegetation by ca. 4500 yr B.P. stabilized the uplands, resulting in a reduction in sediment supply and subsequent incision and abandonment of the T-1 and most AF-1 surfaces. The proposed timing and nature of landscape and bioclimatic change are consistent with regional records from the central Great Plains.

Radiocarbon Ages of Soils and Charcoal in Late Wisconsinan Loess, South-Central Nebraska

1993 ◽  
Vol 39 (1) ◽  
pp. 55-58 ◽  
Author(s):  
David W. May ◽  
Steven R. Holen
Keyword(s):  
Organic Matter ◽  
Great Plains ◽  
Bulk Sample ◽  
River Valley ◽  
South Central ◽  
Republican River ◽  
Late Wisconsinan ◽  
The U.S ◽  
Bt Horizon

AbstractThe Farmdale Soil occurs below late Wisconsinan loess throughout the U.S. Midwest. At the La Sena site in the central Great Plains, humates in the Farmdale Interstadial Soil have a corrected age of 21,000 yr B.P. Humates in a buried Bt horizon and a bulk sample of overlying loess 2.5 m above the Farmdale Interstadial Soil have ages of 17,000 and 19,000 yr B.P., respectively. In the Republican River Valley Picea (spruce) charcoal is common in the lower meter of Peoria loess. Near Bloomington, Nebraska, humates from burned organic matter only 60 cm above the base of Peoria loess have a corrected age of ca. 19,000 yr B.P.

scholarly journals Seasonal energy and water balance of a Phragmites australis-dominated wetland in the Republican River basin of south-central Nebraska (USA)

2011 ◽  
Vol 408 (1-2) ◽  
pp. 19-34 ◽  
Author(s):  
J.D. Lenters ◽  
G.J. Cutrell ◽  
E. Istanbulluoglu ◽  
D.T. Scott ◽  
K.S. Herrman ◽  
...  
Keyword(s):  
Water Balance ◽  
River Basin ◽  
Phragmites Australis ◽  
South Central ◽  
Republican River ◽  
Republican River Basin

scholarly journals Assimilation of Satellite-Derived Soil Moisture for Improved Forecasts of the Great Plains Low-Level Jet

2020 ◽  
Vol 148 (11) ◽  
pp. 4607-4627
Author(s):  
Craig R. Ferguson ◽  
Shubhi Agrawal ◽  
Mark C. Beauharnois ◽  
Geng Xia ◽  
D. Alex Burrows ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Wind Speed ◽  
Data Assimilation ◽  
Great Plains ◽  
Wrf Model ◽  
Added Value ◽  
Low Level ◽  
Convective Systems ◽  
South Central ◽  
Mesoscale Convective

AbstractIn the context of forecasting societally impactful Great Plains low-level jets (GPLLJs), the potential added value of satellite soil moisture (SM) data assimilation (DA) is high. GPLLJs are both sensitive to regional soil moisture gradients and frequent drivers of severe weather, including mesoscale convective systems. An untested hypothesis is that SM DA is more effective in forecasts of weakly synoptically forced, or uncoupled GPLLJs, than in forecasts of cyclone-induced coupled GPLLJs. Using the NASA Unified Weather Research and Forecasting (NU-WRF) Model, 75 GPLLJs are simulated at 9-km resolution both with and without NASA Soil Moisture Active Passive SM DA. Differences in modeled SM, surface sensible (SH) and latent heat (LH) fluxes, 2-m temperature (T2), 2-m humidity (Q2), PBL height (PBLH), and 850-hPa wind speed (W850) are quantified for individual jets and jet-type event subsets over the south-central Great Plains, as well as separately for each GPLLJ sector (entrance, core, and exit). At the GPLLJ core, DA-related changes of up to 5.4 kg m−2 in SM can result in T2, Q2, LH, SH, PBLH, and W850 differences of 0.68°C, 0.71 g kg−2, 59.9 W m−2, 52.4 W m−2, 240 m, and 4 m s−1, respectively. W850 differences focus along the jet axis and tend to increase from south to north. Jet-type differences are most evident at the GPLLJ exit where DA increases and decreases W850 in uncoupled and coupled GPLLJs, respectively. Data assimilation marginally reduces negative wind speed bias for all jets, but the correction is greater for uncoupled GPLLJs, as hypothesized.

Patchy bedrock explained: Tectonic fracture control on landscape evolution patterns in south-Central Chile 

2021 ◽  
Author(s):  
Emma Lodes ◽  
Dirk Scherler ◽  
Hella Wittmann ◽  
Renee Van Dongen
Keyword(s):  
Chemical Weathering ◽  
Landscape Evolution ◽  
Tectonic Deformation ◽  
Fracture Density ◽  
Rock Fracturing ◽  
Central Chile ◽  
Erosion Rates ◽  
Denudation Rates ◽  
South Central

<p>Rock fracturing induced by tectonic deformation is thought to promote faster denudation in more highly fractured areas by lowering grain size and directing the flow of water. That the density and pattern of fractures in a landscape play a role in controlling erosion and landscape evolution has been known for over a century, but not until recently do we have tools, like cosmogenic nuclides, to quantify erosion rates in places with varying fracture densities. In the Nahuelbuta Range in south-central Chile, we observed that >30-m thick regolith exists next to patches of unweathered bedrock. We hypothesize that the density of fractures dictates the pace and patterns of chemical weathering, regolith conversion, and erosion in the Nahuelbuta Range. To test this, we used in situ cosmogenic <sup>10</sup>Be to obtain denudation rates from amalgamated samples of bedrock, corestones and soils, and measured fracture density and orientation, as well as hillslope boulder size in several sites in the Nahuelbuta Range. We found that more highly fractured areas indeed have higher denudation rates than less fractured areas, and that bedrock denudation rates are ~10 m/Myr while soil denudation rates are ~30 m/Myr, suggesting that soil-covered areas may be sites of higher fracture density at depth. Fractures have orientations that match mapped faults across the Nahuelbuta range, and thus are considered to be tectonically-induced. In addition, both fracture and fault orientations match the orientation of streams incising the range, suggesting that fractures control stream channel orientation by weakening bedrock and thus directing flow.</p>

Identifying areas of wetland and wind turbine overlap in the south-central Great Plains of North America

2020 ◽  
Vol 35 (9) ◽  
pp. 1995-2011
Author(s):  
L. J. Heintzman ◽  
E. S. Auerbach ◽  
D. H. Kilborn ◽  
S. M. Starr ◽  
K. R. Mulligan ◽  
...  
Keyword(s):  
North America ◽  
Wind Turbine ◽  
Great Plains ◽  
The South ◽  
South Central

Silver Maple Seed Sources for Increased Biomass Production

1988 ◽  
Vol 5 (3) ◽  
pp. 180-184 ◽  
Author(s):  
Richard F. Kopp ◽  
Wayne A. Geyer ◽  
William R. Lovett
Keyword(s):  
Biomass Production ◽  
Great Plains ◽  
Height Growth ◽  
Seed Source ◽  
Stem Number ◽  
Seed Sources ◽  
Short Rotation ◽  
Silver Maple ◽  
South Central ◽  
Maple Seed

Abstract Silver maple shows promise for use in short-rotation intensive culture energy plantings. A seed source study composed of trees from 26 midwest locations was established in south-central Nebraska in 1979 to determine where silver maple seed should be collected for use in the central Great Plains. Trees were evaluated for survival, height growth, and number of dominant stems per tree during their seventh growing season. Sources from eastern Nebraska, western Iowa, eastern Kansas, and northwest Missouri generally exhibited the greatest survival, height growth, and number of dominant stems. Height growth appears to be under stronger genetic control than stem number, suggesting that selection for height should take priority when selecting trees for biomass production. Geographic trends related to survival and height growth, but not stem number, were observed. Environmental or geographic factors that are strong predictors of seed source performance could not be identified. Planting the most locally produced seed is advisable for the central Plains. North. J. Appl. For. 5:180-184, Sept. 1988.

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