December 2017

Quaternary Stratigraphy and Stratigraphic Nomenclature Revisions in Kansas, Anthony L. Layzell, Robert S. Sawin, Rolfe D. Mandel, Greg A. Ludvigson, Evan K. Franseen, Ronald R. West, and W. Lynn Watney


This paper outlines Quaternary nomenclature changes to Zeller (1968) that have been adopted by the Kansas Geological Survey (KGS). The KGS formally recognizes two series/epochs for the Quaternary: the Holocene and Pleistocene. Pleistocene stage/age names Kansan, Aftonian, Nebraskan, and Yarmouthian are abandoned and replaced with the broader term "pre-Illinoian." Formation names Bignell, Peoria, Gilman Canyon, and Loveland are maintained for loess units. Formation names for the following alluvial lithostratigraphic units are abandoned: Crete, Sappa, Grand Island, Fullerton, and Holdrege. The Severance Formation is adopted as a new lithostratigraphic unit for thick packages of late Pleistocene alluvium and colluvium in Kansas. The DeForest Formation is accepted as a valid lithostratigraphic unit for deposits of fine-grained Holocene alluvium in Kansas. Formation names Iowa Point, Nickerson, and Cedar Bluffs for glacial tills and Atchison and David City for glaciofluvial deposits are abandoned. The Afton and Yarmouth Soils are abandoned as pedostratigraphic units, whereas the Sangamon Geosol and Brady Geosol are maintained.


August 2016

Classification of Red Beds at Point of Rocks, Morton County, Kansas: A Historical Review, Robert S. Sawin


The age of red beds exposed below the bluff-capping Ogallala Formation at Point of Rocks in Morton County, Kansas, has been disputed since they were first recognized in the late 1800s. Over the years, nearly 25 maps and reports have variously classified the strata as Cretaceous, Jurassic, Triassic, or Permian, creating an interesting history of speculation and stratigraphic nomenclature. Many of the interpretations relied on the indirect method of comparing lithologies to similar exposures in surrounding states, but none were in-depth studies. Until recently, the Kansas Geological Survey has considered the rocks to be Jurassic based on Zeller (1968), the currently recognized stratigraphic guide and chart for Kansas. A comprehensive study by Smith et al. (2015)--using outcrop descriptions, subsurface information, and detrital zircon data--constrained the age of the red beds at Point of Rocks, assigning them to the Guadalupian Big Basin Formation, the uppermost Permian unit in Kansas.


November 2015

Enigmatic Red Beds Exposed at Point of Rocks, Cimarron National Grassland, Morton County, Kansas: Chronostratigraphic Constraints from Uranium-Lead Dating of Detrital Zircons, Jon J. Smith, Brian F. Platt, Greg A. Ludvigson, Robert S. Sawin, Craig P. Marshall, and Alison Olcott-Marshall


Point of Rocks, a high-relief bluff overlooking the Cimarron River valley in Morton County, Kansas, is capped by distinct white beds of Neogene Ogallala Formation calcrete that overlie red beds of shale, siltstone, and sandstone. These unfossiliferous red beds are currently assigned to the Jurassic System; however, their age has long been debated due to a lack of marker beds, index fossils, and nearby correlative outcrops. As a result, geologists over the years have assigned the rocks to systems ranging from the Permian to the Cretaceous. In this study, four stratigraphic sections were measured in the red beds and three bulk samples were collected to determine the uranium-lead age distributions of detrital zircon (DZ) populations. Red-bed strata composed of fissile shale and sandstone are interpreted as alluvial overbank deposits, while dominantly trough cross-bedded and planar-laminated sandstones are interpreted as tidally influenced fluvial deposits. Detrital zircon age peaks can be grouped into at least seven subpopulations with a youngest single zircon age of 263.8 ± 12.1 Ma, a more conservative age of 293.0 ± 6.95 Ma based on the youngest grouping of three grain ages overlapping at 2σ, and a complete absence of Mesozoic age zircons. In addition, copper oxides along partings and fractures suggest that the red beds once hosted copper sulfides, a common constituent of regional Permian-Triassic red beds. The DZ data--in conjunction with the identification of the Permian Day Creek Dolomite marker bed in logs of nearby drilling tests--strongly suggest that the enigmatic red beds cropping out at the base of Point of Rocks should be assigned to the Guadalupian Big Basin Formation, the uppermost Permian unit in Kansas.


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Current Research in Earth Sciences is a peer-reviewed publication of the Kansas Geological Survey. More ...