Morphostratigraphy, Chronostratigraphy, and Evolution of Alluvial Terraces Within the Kansas River Valley, Kansas, USA
Abstract
The Kansas River valley, located in the Central Great Plains, is an important locale for studying the relationships between climate and river evolution because, unlike other Great Plains rivers, i.e., the Missouri, Platte, and Arkansas, it and its tributaries lie entirely within the Great Plains. Four terraces are formally recognized within the Kansas River valley: the Menoken, Buck Creek, Newman, and Holliday; however, little is known of their stratigraphy and chronology of formation. To increase our understanding, these terraces were mapped and stratigraphic and chronologic evaluations were conducted, yielding new data on the evolution and history of the Kansas River. Oldest and highest of the terraces (T4) is the Menoken, with fill consisting of a thick, clay-rich diamicton hypothesized to have formed from fluvially reworked glacial sediments deposited during a Pre-Illinoian glacial stage. Independent, but limited, age control based on the presence of Lava Creek B ash found within the terrace provides a maximum limiting age of ~620 ka. Mantling the Menoken Terrace are isolated aeolian dunes constructed of sand winnowed from the Kansas River floodplain following Menoken deposition. Optical dating documents this deposition during MIS 3, between 36 and 31 ka. About 15 m below the Menoken is the Buck Creek (T3), a late-Pleistocene feature. This terrace is characterized by thick, fine-grain deposits, which were deposited prior to ~ 15 ka. Some data suggest that the Buck Creek may contain a sandy unit in the upper reaches of the river valley, and unpublished AMS 14C ages place this sand deposition after ~ 40 ka. Holocene river evolution has resulted in two terraces. The Newman (T2), older of the two, is the most extensive of all terraces in the river valley and is characterized by a thick basal soil formed at ~ 14-10 ka, and overlying Holocene alluvial sediments and soils. Most recent intrenchment produced the Holliday terrace (T1), which is the youngest of the alluvial terraces and is elevated only two meters above the modern floodplain (T0). The Holliday is predominantly comprised of sandy alluvial packages interspersed between weak floodplain (soil) deposits. In addition, the Holliday is morphologically distinct from the other terraces in that it is comprised primarily of meander scars. AMS 14C ages from the Holliday suggest alluviation occurred within the last 3.5 k years with limited entrenchment occurring ~ 1.2 ka.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFMEP43A0670H
- Keywords:
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- 1105 GEOCHRONOLOGY / Quaternary geochronology;
- 1130 GEOCHRONOLOGY / Geomorphological geochronology;
- 1165 GEOCHRONOLOGY / Sedimentary geochronology;
- 5470 PLANETARY SCIENCES: SOLID SURFACE PLANETS / Surface materials and properties