News Release, Kansas Geological Survey, March 12, 2018
LAWRENCE—Glaciers that dipped at least twice into northeast Kansas are a cornerstone of the Quaternary Period, which runs from 2.6 million years ago to the present. Based on decades of scientific evidence, the Kansas Geological Survey has published a new report to formally adopt internationally recognized name changes for glacial intervals and other stratigraphic units associated with the Quaternary.
Stratigraphic units are sequential bodies of rock or sediment grouped together based on their age, fossil content, mineral composition, radioactivity, and other characteristics. The Quaternary Period is divided into the glacier-packed Pleistocene Epoch, which is further subdivided into stages, and the ongoing Holocene Epoch.
In 2005, the KGS revitalized the Stratigraphic Nomenclature Committee to address stratigraphic issues and establish formally accepted stratigraphic names for Kansas.
"Stratigraphy is now contemplated on a global scale, which necessitates consideration beyond the borders of Kansas," said KGS geologist Tony Layzell. "Our nomenclature changes therefore conform to international standards."
The KGS last updated Quaternary nomenclature for Kansas 40 years ago when the glacial and interglacial intervals during the Pleistocene were thought to be fairly straight forward. The original four glacial intervals—from earliest to most recent—were the Nebraskan, Kansan, Illinoian, and Wisconsian stages. The new nomenclature drops the names Nebraskan and Kansan and combines them into the pre-Illinoian Stage.
"The changes are based on the recognized complexity of the glacial stratigraphy in the midcontinent, apparent and widespread miscorrelations of different deposits, and the past assignment of erroneous ages to various stratigraphic units," Layzell said.
The Pleistocene Epoch lasted from about 2.6 million to 11,700 years ago. Although climatic conditions during the early Pleistocene were cold enough to generate advances of continental glaciers into northeast Kansas, evidence suggests that late Pleistocene climates were more equable than today, with cooler summers and warmer winters.
Wooly mammoths and camels were among the animals able to thrive in Kansas when the equable climates prevailed. A climatic shift at the end of the Pleistocene resulted in dramatic changes in the plant and animal life across the state, including the demise of mammoths, camels, and other megafauna.
Archaeological evidence suggests that people began to populate the Great Plains during the late Pleistocene, which may have also contributed to the disappearance of the megafauna. The current Holocene interglacial period has been characterized by climatic variability, resulting in successive periods of erosion and deposition of sediment layers.
"The Kansas landscape that we see today is largely a product of the processes of erosion and deposition during the Quaternary," Layzell said. "The majority of the surface geology consists of sediments deposited by glaciers, wind, and water."
Glacial deposits, limited to the northeast corner, are an unsorted mix of boulders, gravel, sand, silt, and clay. Pink quartzite boulders, commonly called Sioux quartzite, were carried in from outcrops at the intersection of Iowa, Minnesota, and South Dakota. Fertile soils developed from loess, a windblown silt, cover most of the state.
Recent stratigraphic work conducted by the KGS is done mainly in conjunction with the KGS county mapping program. The work focuses on the geology at or near the surface and related issues, including water and mineral resources and earthquake hazards.
Quaternary stratigraphy is also an important component of archaeology. Knowledge of the relationships between layers of sediment and rock can be used to locate buried cultural materials and evaluate the integrity of archaeological data.
The KGS houses the ODYSSEY Archaeological Research Program, which was established to support the search for evidence of the earliest people in the Great Plains and Midwest and to gain a better understanding of their late Pleistocene and early Holocene environments.
Besides the Quaternary report, the KGS has published accepted nomenclature changes for the earlier Permian, Carboniferous, and Neogene periods and Precambrian time. All can be accessed at http://www.kgs.ku.edu/Current/index.html.