Iowa\u27s Sand Prairie State Preserves: Anomalous Grain-Size Distributions and Optically Stimulated Luminescence (OSL) Dates

Grain-size distributions and optically stimulated luminescence (OSL) dates were obtained for the sand from Iowa\u27s five sand prairie state preserves, which are Behren\u27s Ponds and Woodland, Cedar Hills Sand Prairie, Kish-Ke-Kosh Prairie, Marietta Sand Prairie and Rock Island. OSL dates ranged from the late Pleistocene (15,560 years B.P.) to the very late Holocene (as recent as 590 years B.P.), indicating that the late Pleistocene and Holocene Epochs in Iowa have seen multiple episodes of aridity, which is consistent with results from the Nebraska Sand Hills and eolian sand stringers in southeastern Minnesota. The grain-size distributions were anomalous in that, compared with typical eolian deposits, the transition grain sizes between the traction I saltation populations and saltation I suspension populations were shifted toward coarser grains, and the percentage of sand in the suspension population was high. The anomalous grain-size distributions could not be explained by post-depositional weathering or poor sorting in the source region, but were consistent with the eolian transport of sand through grass prior to deposition. It is suggested that the anomalous grain-size distribution could be one of a set of criteria for distinguishing paleo-sand prairies from other buried bodies of eolian sand or sandstone

Salt Tolerance of Sunflower and Lettuce in Cultivated and Uncultivated Grass Soil

We tested two hypotheses: 1) whether a vegetable crop will show greater growth under a given salinity treatment in an uncultivated grass soil than a cultivated soil and 2), if so, whether the greater growth is due to the occasional presence of relatively fresh water in macropores or the interaction between salinity and hypoxia in a soil without significant macropores. A previous study suggested uptake from. macropores was significant only for crops with high root water potential (Emerman and Dawson 1997). Hence, in this study, 21 miniature crops were grown in a greenhouse, and the ratio of root dry weight to transpiration rate was measured as a means of ranking crops in terms of root water potential. Based upon the ranking, \u27Elf’ sunflower (Helianthus annuus L.) was chosen as a crop with relatively high root water potential (ratio = (39 ± 7) mg/(g/day)) and \u27Tom Thumb\u27 lettuce (Lactuca sativa L.) as a crop with relatively low root water potential (rat10 = (0.8 ± 0.3) mg/(g/day)). The miniature cultivars of sunflower and lettuce were grown in a greenhouse in undisturbed cores of salinized, cultivated soil and salinized, uncultivated grass soil, and they were given tap water daily at the plant transpiration rate. There was no significant difference between growth in cultivated and uncultivated grass soil. With the addition of tap water, however, lettuce showed no reduction in growth from the no-salt control at NaCl concentration of 4 g/L. At the same NaCl concentration, mortality was 100% without the addition of cap water. It is suggested that daily irrigation with relatively fresh water in salinized soil may be more successful for crops with low root water potential

Pre-Settlement Vegetation at Casey\u27s Paha State Preserve, Iowa

Paha are loess-capped ridges standing 10-30 m above the surrounding plain of the Iowan Surface. Although Iowa was almost entirely covered with prairie and wetlands just prior to Euro-American settlement, the paha are believed to have been forested based on soil types and on early vegetation maps. The objective of this study was to find evidence that paha were forested by measuring the δ13C value of humin, the fraction of soil organic matter that is insoluble in acid and base. Previous work has shown that humin retains the δ13C signature of vegetation on a 1000-year time scale, as opposed to the more mobile and soluble humic and fulvic acids that reflect the δ13C signature of more recent vegetation. Soil samples were obtained from Casey\u27s Paha State Preserve in Tama County from four locations at depths ranging from 5-85 cm. Carbonates were removed with 1.0 M HCl and humic and fulvic acids were removed by repeated application of 0.5 M NaOH. The δ13C values of the humin fraction (-22.031% to -24.358%) were within or slightly above the upper range of δ13C values for woody vegetation (-23% to -34%) and well below the range for prairie grasses (-9% to -17%). Although it has been suggested that prairie fires bypassed the paha or that perched water tables maintained the forest, we suggest that the paha forests resulted from activity by Native Americans

Evidence from Detrital Zircon Ages for Middle Pennsylvanian Uplift and Drainage in the Source Area of the Chariton Conglomerate and Marmaton Group Sandstones, Southern Iowa and Northern Missouri

The Chariton Conglomerate is a quartz/limestone conglomerate of Middle Pennsylvanian age sparsely exposed in southern Iowa and northern Missouri. In Iowa it is characterized by quartz granules and rounded crinoid columnals. The objective of this study was to use detrital zircon ages to determine the provenance of the Chariton Conglomerate and possibly associated Marmaton Group sandstone beds. Detrital zircon ages were obtained for five conglomerate and two sandstone beds of the Chariton Conglomerate in Iowa, three conglomerate beds of the Chariton Conglomerate in Missouri, and two sandstone beds of the Marmaton Group in Iowa. According to the Kolmogorov-Smirnoff Test, the 12 detrital zircon age spectra were statistically indistinguishable, consistent with a common provenance for all beds. The combined age spectrum (879 zircons) showed both a young cluster (1.1 % of zircons) in the range 320-364 Ma (Late Devonian Period - Late Mississippian Subperiod) and a much older cluster (0.3% of zircons) in the range 3198-3269 Ma (Paleoarchean - Mesoarchean Eras). The Devonian Period - Mississippian Subperiod (318--416 Ma) and the Paleoarchean-Mesoarchean Eras (2800-3600 Ma) accounted for 2.8% and 3.6% of zircon ages, respectively. A model consistent with the above ages and the paleocurrent directions in the Chariton Conglomerate is an Early - Middle Pennsylvanian river originating in the Devonian - Mississippian crystalline rocks of New England and entering Minnesota - Wisconsin from the northeast to collect sediments from crystalline rocks of Paleoarchean - Mesoarchean age. However, a Middle Pennsylvanian uplift in the Minnesota - Wisconsin region is also required to produce the headwaters necessary for the production of quartz granules, which is consistent with the model of hotspot epeirogen

Artists\u27 Depictions of Catsteps in the Loess Hills of Iowa: Evidence for Mid-Nineteenth Century Climate Change

Catsteps are the staircase-like features common on hillslopes of the Loess Hills of western Iowa. The record of artistic depictions of the Loess Hills was examined to determine when catsteps appeared. George Catlin, Karl Bodmer, and John James Audubon traveled up the Missouri River m 1832, 1833 and 1843, respectively, and between them, produced 31 works of art depicting either the Loess Hills or the loess bluffs on the Nebraska side of the river. Only three works by Bodmer of Blackbird Hill on the Nebraska side possibly show catsteps. The Assistant State Geologist, Orestes St. John, produced six sketches of the Loess Hills in 1868, half of which show well-defined catsteps. In illustrated atlases of the Loess Hills, published in 1875 and 1885, 45-55% of drawings show well-defined catsteps. The appearance of catsteps during the late 1860s may be related to the appearance of gullies during the period 1860-1900. Census data show that peak grazing of the Loess Hills was not attained until about 1900 so that climate change following the end of the Little Ice Age in the mid-nineteenth century is a more likely explanation for the appearance of catsteps and gullies. The most probable climate change is a decrease in the periodicity of precipitation cycles, which will increase the slumping tendency of loess. Such a climate change is consistent with tree rings and ostracode shell chemistry from northeastern South Dakota, tree rings from eastern Montana, and fire scars from northwestern Minnesota, but not tree rings from central and eastern Iowa

Laboratory Abrasion of Crinoid Columnals and the Provenance of the Chariton Conglomerate, South-Central Iowa

The Chariton Conglomerate is a quartz limestone conglomerate of Pennsylvanian age found in six exposures in southern Iowa and three exposures in northern Missouri. Distinctive features of the exposures in Iowa include quartz granules and rounded crinoid columnals. The objective of this study was to determine whether the quartz clasts could have originated in the crystalline rocks of Minnesota or Wisconsin. The average paleocurrent direction measured in interbedded sandstones was 178° (S.D. = 35 °). The average roundness of 75 crinoid columnals extracted from four exposures in Iowa was 30% (S.D. = 14%), defined as roundness(%) = (D-d)/D x 100, where D is the maximum columnal diameter and d is the diameter of the flat circle at the end of the columnal. Previously unabtaded crinoid columnals were abraded in rotary tumblers, which were filled 90% with water and 10% with a mixture representative of the Chariton Conglomerate. The roundness values of the experimentally abraded columnals were consistent with the roundness values of the columnals collected in the field (within one standard deviation of the mean for the field data) for tumbling times in the range 0-33 days. Assuming the travel distance corresponding ro one revolution is the circumference of the barrel, the experimental roundness values were consistent with the field roundness values for travel distances in the range 0-700 km, which is sufficiently far to include the crystalline rocks of Minnesota and Wisconsin

Copy Number Variation of KIR Genes Influences HIV-1 Control

The authors that the number of activating and inhibitory KIR genes varies between individuals and plays a role in the regulation of immune mechanisms that determine HIV-1 control

AGU hydrology days 2012

2012 annual AGU hydrology days was held at Colorado State University on March 21 - March 23, 2012.Includes bibliographical references.The objective of this study was to investigate the possibility of a generic rating curve with a small number of adjustable parameters for the restricted class of bedrock step-pool rivers. The motivation for this study arose from Utah Valley University’s long-term program of groundwater development in the Trans-Mexican Volcanic Belt, which requires hydrographs for bedrock step-pool rivers near remote mountain villages. Based upon personal communications from USGS state hydrologists and Google Earth satellite images and aerial photos, 71 USGS active or historic gaging sites were identified as bedrock step-pool rivers, involving 403 rating numbers and 13,409 gage height vs. discharge measurements. For comparison, 71 gaging sites were chosen randomly, involving 268 rating numbers and 7617 gage height vs. discharge measurements. As the distributions of gage heights and discharges were a good fit to a lognormal distribution, the data were normalized by computing the Z-scores of the logarithms of discharge and gage height, in which the average and standard deviation were computed separately for each rating number. The linear relationships between Z-scores of gage height (y-axis) and discharge (x-axis) were surprisingly similar for bedrock step-pool and random rivers. For bedrock step-pool rivers, the slope was 0.8829 with R² = 0.78, while for random rivers, the slope was 0.8467 with R² = 0.72. Numerical experiments on generating rating curves based on two random measurements for each rating number showed that 50% of all observed discharges deviated from predicted discharges by less than 31.0% for bedrock step-pool rivers and 27.3% for random rivers

AGU hydrology days 2006

2006 annual AGU hydrology days was held at Colorado State University on March 20 - March 22, 2006.Includes bibliographical references.Catsteps (also known as terracettes) are the staircase-like features common on hillslopes of the Loess Hills of western Iowa. The record of artistic depictions of the Loess Hills was examined to determine when catsteps appeared. Landscape artists George Catlin and Karl Bodmer traveled up the Missouri River in 1832 and 1833, respectively, and between them, produced 30 works of art depicting either the Loess Hills or the loess bluffs on the Nebraska side of the river. Only one painting by Bodmer of Blackbird Hill on the Nebraska side possibly shows catsteps. Moreover, an engraving based on the painting and another painting of the same site by Bodmer do not show catsteps. The Assistant State Geologist, Orestes St. John, produced five sketches of the Loess Hills in 1868, three of which show well-defined catsteps. The appearance of catsteps during the period 1833-1868 may be related to the appearance of gullies during the period 1860-1900. An examination of census data shows that intensive grazing of the Loess Hills did not begin until about 1900 so that climate change is a more likely explanation for the appearance of both catsteps and gullies. Since catsteps are more common on the south- and west-facing slopes, which will dry most quickly, the most probable climate change is a decrease in the periodicity of precipitation cycles. Such a climate change is consistent with tree ring data from eastern South Dakota and eastern Montana, but not central and eastern Iowa