@conference {2821,
	title = {Evaluating Playas as Point Sources for Recharge of the High Plains Aquifer, Western Kansas},
	booktitle = {Joint 53rd Annual South-Central/53rd North-Central/71st Rocky Mtn GSA Section Meeting - 2019},
	year = {2019},
	publisher = {Geological Society of America},
	organization = {Geological Society of America},
	doi = {10.1130/abs/2019SC-327385},
	url = {https://www.researchgate.net/publication/333623353_EVALUATING_PLAYAS_AS_SOURCES_OF_RECHARGE_TO_THE_HIGH_PLAINS_AQUIFER_IN_WESTERN_KANSAS},
	author = {Stotler, Randy L. and Salley, Kaitlin A. and Johnson, William C. and Ryuh, Yon-Gyung}
}
@article {2822,
	title = {Sediment accumulation and sedimentation rates in playas on the High Plains of western Kansas, USA},
	journal = {Geomorphology},
	volume = {342},
	year = {2019},
	month = {Jan-10-2019},
	pages = {117 - 126},
	abstract = {Grassland ecosystems are some of the most modified ecosystems in the world, largely due to conversion to cropland, and the High Plains of the central United States is no exception. Playa wetlands are ubiquitous features of the High Plains and have experienced increased sediment accumulation, which is the primary cause of reduced playa ecosystem function. Seven playas on the High Plains of western Kansas, five with cropland-dominated watersheds and two with grassland-dominated watersheds, were examined to quantify the amount of recent (past ~100{\textendash}175 yr) sediment accumulated within playas and to establish chronologies of playa filling. Thicknesses of recent sediment were determined in the field, and soil cores were extracted from study playas. Four playa cores were analyzed for 210Pb to establish the chronology of recent sediment accumulation and sedimentation rates. Chronologies of pre-agricultural sediments and sedimentation rates were calculated by 14C dating of buried soils preserved within playa cores. Radiocarbon ages indicate playa stratigraphic records span the Holocene and that these playas have persisted on the landscape since at least the Late Pleistocene. Long-term, natural sedimentation rates were highest during the Pleistocene-Holocene transition and early Holocene, at ~2{\textendash}4 cm/century. During the middle and late Holocene, sedimentation rates averaged ~1 cm/century. Cropland playas accumulated ~10{\textendash}15 cm of recent sediment at average rates of ~6.5{\textendash}10 cm/century, while grassland playas accumulated only ~2 cm of recent sediment. Conversion of watersheds to cropland has greatly accelerated sediment accumulation within playas, which is generally resulting in a decline in critical playa ecosystem functions.},
	keywords = {210Pb, Agricultural, chronology, Holocene, Radiocarbon dating, sedimentation},
	issn = {0169555X},
	doi = {10.1016/j.geomorph.2019.06.014},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0169555X19302612},
	author = {Bowen, Mark W. and Johnson, William C.}
}
@article {219,
	title = {Late Quaternary environmental change inferred from phytoliths and other soil-related proxies: Case studies from the central and southern Great Plains, USA},
	journal = {Catena},
	volume = {85},
	year = {2011},
	note = {id: 1992; PT: J; SI: SI; UT: WOS:000288642200002},
	pages = {87-108},
	abstract = {This study investigates stable carbon isotopes (delta(13)C), opal phytolith assemblages, burnt phytoliths, microscopic charcoal and Sporormiella spores from modern soils and paleosols in Kansas and Oklahoma. Grass and dicot phytoliths in combination with delta(13)C are used as proxies for reconstructing the structure of grasslands and woodlands. Burnt grass phytoliths and microscopic charcoal are evaluated as proxies for reconstructing paleofire incidence. Concentrations of the fungal spore Sporormiella are used as a proxy for assessing large herbivore activity. These proxies were tested on various modern grassland communities of the central and southern Great Plains, including areas with bison, cattle, and small herbivores, and areas under different fire frequencies. Opal phytolith assemblages and delta(13)C values show that before cal 11 ka, C(3) grasses and woody plants predominated in areas that today are dominated by C(4) grasses. The origin of the shortgrass prairie dates back to about cal 10 ka. The origin of the tallgrass prairie, however, is not clear as phytolith data show variable assemblages throughout the Holocene (mixed-grass, tallgrass, and tallgrass-woodland mosaic). Different proxies (burnt phytoliths vs. charcoal) reveal different fire frequencies, but it is apparent that microfossil evidence for fire incidence is closely related to the abundance of woody plants in the landscape. Before cal 12 ka, soils show somewhat elevated concentration of Spororrniella, but lower concentrations than the modern high-density bison and cattle grazing areas. Throughout the Holocene. Sporormiella frequencies are low, which suggests lower large ungulate densities and perhaps high mobility. (C) 2010 Elsevier B.V. All rights reserved.},
	issn = {0341-8162},
	doi = {10.1016/j.catena.2010.08.015},
	author = {Cordova, Carlos E. and Johnson, William C. and Mandel, Rolfe D. and Palmer, Michael W.}
}
@article {437,
	title = {Loess record of the Pleistocene-Holocene transition on the northern and central Great Plains, USA},
	journal = {Quaternary Science Reviews},
	volume = {27},
	year = {2008},
	note = {id: 1993; PT: J; UT: WOS:000260545800008},
	pages = {1772-1783},
	abstract = {Various lines of evidence support conflicting interpretations of the timing, abruptness. and nature of climate change in the Great Plains during the Pleistocene-Holocene transition. Loess deposits and paleosols on both the central and northern Great Plains provide a valuable record that can help address these issues. A synthesis of new and previously reported optical and radiocarbon ages indicates that the Brady Soil, which marks the boundary between late Pleistocene Peoria Loess and Holocene Bignell Loess, began forming after a reduction in the rate of Peoria Loess accumulation that most likely occurred between 13.5 and 15 cal ka. Brady Soil formation spanned all or part of the Bolling-Allerod episode (approximately 14.7-12.9 cal ka) and all of the Younger Dryas episode (12.9-11.5 cal ka) and extended at least 1000 years beyond the end of the Younger Dryas. The Brady Soil was buried by Bignell Loess sedimentation beginning around 10.5-9 cal ka, and continuing episodically through the Holocene. Evidence for a brief increase in loess influx during the Younger Dryas is noteworthy but very limited. Most late Quaternary loess accumulation in the central Great Plains was nonglacigenic and was under relatively direct climatic control. Thus, Brady Soil formation records climatic conditions that minimized eolian activity and allowed effective pedogenesis, probably through relatively high effective moisture. Optical dating of loess in North Dakota supports correlation of the Leonard Paleosol on the northern Great Plains with the Brady Soil. Thick loess in North Dakota was primarily derived from the Missouri River floodplain; thus, its stratigraphy may in part reflect glacial influence on the Missouri River. Nonetheless, the persistence of minimal loess accumulation and soil formation until 10 cal ka at our North Dakota study site is best explained by a prolonged interval of high effective moisture correlative with the conditions that favored Brady Soil formation. Burial of both the Brady Soil and the Leonard Paleosol by renewed loess influx probably represents eolian system response that occurred when gradual change toward a drier climate eventually crossed the threshold for eolian activity. Overall, the loess-paleosol sequences of the central and northern Great Plains record a broad peak of high effective moisture across the late Pleistocene to Holocene boundary, rather than well-defined climatic episodes corresponding to the Bolling-Allerod and Younger Dryas episodes in the North Atlantic region. (C) 2008 Elsevier Ltd. All rights reserved.},
	issn = {0277-3791},
	doi = {10.1016/j.quascirev.2008.07.004},
	author = {Mason, Joseph A. and Miao, Xiaodong and Hanson, Paul R. and Johnson, William C. and Jacobs, Peter M. and Goble, Ronald J.}
}
@article {454,
	title = {High-resolution proxy record of Holocene climate from a loess section in Southwestern Nebraska, USA},
	journal = {Palaeogeography Palaeoclimatology Palaeoecology},
	volume = {245},
	year = {2007},
	note = {id: 1994; PT: J; UT: WOS:000245026900004},
	pages = {368-381},
	abstract = {Multi-proxy analysis was used to produce a high-resolution paleoclimatic record from an exceptionally thick section of the Holocene Bignell Loess near Wauneta, Southwestern Nebraska, in the central Great Plains. The Wauneta section has excellent age control, based on optically stimulated luminescence (OSL) and radiocarbon dating, and records multiple episodes of rapid loess deposition alternating with slower deposition and soil formation. The lowermost and uppermost OSL ages obtained from the Bignell Loess are 10,250 +/- 610 years (5.9 in depth) and 100 +/- 10 years (0.1 in depth), respectively. As a result, the Holocene has been temporally confined. Stratigraphically, the Bignell Loess overlies the Late Pleistocene Peoria Loess (deposited similar to 21-14 ka), and the two units are separated by the Brady Soil which is distinguished by its color and other pedogenic features. L*a*b* color parameters and organic carbon content of Bignell Loess are sensitive proxies to differentiate drought-induced aeolian sediment layers from the intercalated soil horizons. Soil organic carbon-derived delta(13)C data suggest that the C(3)-dominated floral environment during Peoria Loess deposition shifted dramatically to a C(4)-dominated environment during Brady Soil formation in response to a warming trend. Even greater C(4) abundance characterized the late Holocene. High-resolution delta(13)C data support the contention that C(3) vs. C(4) vegetation change in the Holocene reflects ecosystem response to frequent vegetation disturbance under and conditions. Time series analysis reveals that delta(13)C and color parameters display high frequency variation with periodicities of 103-118 years and 103 years, respectively. Similar periodicities were also reported in studies of North Dakota takes, though the physical mechanism responsible is uncertain. Comparison of Bignell Loess color and tropical Pacific sea surface temperatures (SSTs) allows evaluation of a proposed teleconnection between drought in the Great Plains and La Nina-like conditions in the tropical Pacific. The loess color index and eastern tropical Pacific SST display broad similarities through the late Pleistocene and Holocene that are consistent with this teleconnection. On the other hand, drought centered at 3800 years ago is not consistent with the teleconnection, and the end of early Holocene aridity at the Wauneta section, around 6500 years ago, is much earlier than the corresponding rise in SST and increase in El Nino frequency in the eastern tropical Pacific. (c) 2006 Elsevier B.V. All rights reserved.},
	issn = {0031-0182},
	doi = {10.1016/j.palaeo.2006.09.004},
	author = {Miao, Xiaodong and Mason, Joseph A. and Johnson, William C. and Wang, Hong}
}
@article {1922,
	title = {National register evaluation and geoarchaeological analysis of the sites and shovel testing at Fort Riley, Kansas},
	journal = {Center for Environmental Management of Military Lands, Colorado State Univ.},
	volume = {TPS 06-13},
	year = {2006},
	note = {id: 696},
	month = {2006},
	author = {Sherman, Stephen A. and Johnson, William C.}
}
