Project period: 9 1 24-8 31 25PROJECT title: joint iowa-kansas-missouri-nebraska working group for the unification of pre-illinoian till stratigraphypre-illinois episode glacial deposits blanket the…

Project period: 9 1 24-8 31 25PROJECT title: joint iowa-kansas-missouri-nebraska working group for the unification of pre-illinoian till stratigraphypre-illinois episode glacial deposits blanket the midcontinent and date between 0.5-2.6 MA. Early researchers used the terms kansan and nebraskan to delineate these tills as no more than two had been identified at the same locality. Later work in the 1970S and 1980S revealed the complexity of the sequence, including the presence of multiple tills and paleosols beneath the so-called nebraskan till and the recognition that the pearlette ASH bed, which was used to mark the end of kansan time, actually consisted of multiple distinct ASH beds with significantly different ages. Hence, the two-part stratigraphy was abandoned in favor of labelling these glacial deposits as pre-illinoian. Despite the fact that at least seven pre-illinoian tills have been identified, dating these deposits and correlating them remains problematic. This problem stems in part because several reliable dating methods (e.g. radiocarbon and optically stimulated luminescence) cannot be applied to deposits that are this old, limiting chronostratigraphic approaches to dating volcanic ASH deposits when present, paleomagnetism of tills, and cosmogenic nuclide exposure dating of paleosols, each of which has limitations. In addition, few sites contain multiple till bodies, and studies conducted by geologic surveys and other researchers used varied methodologies and terminology, further limiting the ability for regional correlation. Inconsistent stratigraphic nomenclature and boundary delineation have historically hindered research and stratigraphic correlations on a regional, national, and even global scale. These inconsistencies have created confusion in the academic and research communities, including those in the respective states. Therefore, the geological surveys from iowa, kansas, nebraska, and missouri propose to create a working group to address lithostratigraphic and chronostratigraphic discrepancies within and across state boundaries. Great importance lies in creating a unified regional assessment of pre-illinoian nomenclature. This study will significantly benefit the individual states and the USGS, as they conduct new geologic mapping studies and work together to refine the nation s stratigraphic framework, which is applied to purposes ranging from local land-use and groundwater planning to compilation of regional and national-scale geoscience assessments.activities, deliverables, and expected outcomeseach respective state survey will create inventories of datasets and historic references. The working group will develop a plan to address the most pertinent issues. All proposed and adopted nomenclature changes, including supporting rationale, will be documented. Geolex will be updated with current terminology in collaboration with USGS staff and in accordance with the north american stratigraphic code (nacsn, 2005). Appropriate stratigraphic charts will be created for each state as well as an inter-state correlation chart to the extent possible based on project results. All adopted nomenclature changes will be provided to the USGS and will also be published as open file reports within the respective state surveys, in formal peer-reviewed outlets, and or in USGS stratigraphic notes. Publications will include documentation of historic terminology, intra- and inter-state correlation charts, and a summary of future correlation issues in need of further study.