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William C. Johnson
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In a nutshell, my research interests focus on Quaternary stratigraphy, soils, and paleoenvironments within the Central Great Plains. While I have done field research elsewhere in North America and in Central America, I have become entranced by the expansive vistas and fascinating landscapes of the Great Plains. Quaternary landscapes and the underlying stratigraphy have a vast number of stories to tell. Thank you for visiting my webpage. Bill Johnson
RESEARCH THEMES and A SAMPLING OF RESEARCH PROJECTS
Theme 1: Quaternary stratigraphy
Litho-, chrono-, pedo-, bio-, chemo- and magnetostratigraphy of eolian deposits (loess and sand) in the central Great Plains, and environmental (flora, fauna, climate) reconstruction. The Central Great Plains is mantled to a large extent by loess deposited during Pre-Illinoian, Illinoian and Wisconsinan times, resulting in a quasi-layer cake sequence of loess units and intercalated soils.
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The 34m-high face at the Eustis ash pit in southwestern Nebraska. On the left, the face exposes ~20m of Pre-Illinoian and Illinoian (Loveland) loess with its capping Sangamon Soil (Last Interglacial), Middle Wisconsin (Gilman Canyon Formation) loess and soil (dark soils zone mid-section) and uppermost Late Wisconsin (Peoria) loess.
The pit has healed, except for the face, located within the shadow below the bright upland area in the image above. |
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Buzzard’s Roost is the type locality for the Middle Wisconsin Gilman Canyon Formation loess and soil. Part of it is exposed along this ranch roadcut. Johnson, Willey, Mason, and May, in-press (2007), Quaternary Research. |
Data from a 22m-long core taken from the road bed depicted above. δ13C values (left) indicate that soil-forming periods were dominated by the warm-season C4 grasses. |
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Holocene (Bignell) loess deposits are thickest in Nebraska south and southeast of the Sand Hills. The Bignell Table (erosional remnant) on the south side of the Platte River exhibits several meters of Bignell Loess (upper left). A gully cutting into the table has exposed the Bignell and underlying Peoria loesses (lower left). The gully face (right) exposes the 6m of Bignell Loess, the underlying Brady Soil which caps the massive Peoria Loess. Two students are visible sampling the uppermost Peoria Loess.
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Stable C and %C data (left) and rock magnetic data (right) characterize the uppermost Peoria Loess, Brady Soil and Bignell Loess at the Sargent site gully.
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A view of and data from the Wauneta site in southwestern Nebraska. Note the in-phase relationships among organic C, spectrophotometer, OSL, 14C, and δ13C data for the Brady Soil and Bignell Loess from the Wauneta site. In particular, spectrophotometer data correspond well with organic C content. Miao, Mason, Johnson, and Wang, in press (2007) Palaeogeography, Palaeoclimatology and Palaeoecology. |
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Theme 2: Stable-isotope and rock magnetic signatures of modern upland prairie soils. Modern surface soils are being sampled along N-S and E-W transects here in the Central Great Plains in order to develop regional and large-scale depictions of profile patterns. Soils are being sampled in formal preserves of unplowed prairie and informal undisturbed areas such as pioneer cemeteries.
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Soils of the Konza Tallgrass Prairie Long-Term Ecological Research (LTER) site are among those being investigated. Here 137Cs studies are being conducted as well, in order to determine erosion rates. |
Theme 3: Geoarchaeology
Paleoenvironmental conditions and landscape evolution in the Central Great Plains, as related to prehistoric peoples; modeling the distribution of surface and buried cultural materials.
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High-resolution imagery, scores of backhoe trenches and soil cores, and hundreds radiocarbon ages were used to define the distribution and age of various alluvial surfaces and underlying stratigraphy on the Fort Riley Military Reservation in northeastern Kansas. The above images illustrate some of the alluvial surface mapping and pedochronologic data from a given locality.
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Rock magnetic expression (susceptibility) of the floor from a Woodland culture pit-house floor. The structure (right), located on the low terrace adjacent to Stranger Creek in northeastern Kansas, produced a living-surface magnetic signal (left) that clearly demarcates the fire pit (red spike) and the “cooler” food preparation and trash areas (dark blue).
Theme 4: Alluvial geomorphology
Stream system and playa wetland response to Late Quaternary (middle-late Pleistocene and Holocene) climatic variation, and development of alluvial chronostratigraphies.
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Late Holocene magnetic susceptibility and chronostratigraphy within terrace fill along the Solomon River at the upper end of Kirwin Reservoir in the Kirwin National Wildlife Refuge, northwestern Kansas.
| This animation presents a fly-by of the Kirwin Reservoir and National Wildlife Refuge that depicts extremes of water levels for the last few decades (highest is 1993). The intent is to illustrate the vulnerability of archaeological sites in this setting to damage or destruction by wave erosion. Created by J. Campbell (Ph.D. student). |
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Preliminary mapping of playa basins on the High Plains of western Kansas. EPA-funded high resolution mapping of the playas is underway.
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Dry lake, a large playa basin in Scott County, Kansas. |
Theme 5: Mapping Quaternary and Neogene geology in Kansas
While mapping may not seem like research, it is my vehicle for identifying and documenting key stratigraphic sections. Further, most of the previous geologic mapping (at the county level) was done at a reconnaissance-level many years ago, some dating to the 1910s. Mapping in Kansas has been funded by the USGS COGEOMAP and STATEMAP programs since the 1980s. In recent years, this activity has been enhanced by USGS EDMAP funding for undergraduate and graduate student involvement in the mapping. Information on the activities of this program may be found at http://www.kgs.ku.edu/General/Geology/index.html
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Surficial geology of Jewell County, north-central Kansas (KGS Map Series) was funded through the USGS EDMAP program and created with the assistance of T. Woodburn, Ph.D. student.
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This inset map shows detail from the northeast corner of the map above. |
