Late Pleistocene evolution of the lower Mississippi River valley, southern Missouri to Arkansas

Abstract

Research Article| February 01, 2000 Late Pleistocene evolution of the lower Mississippi River valley, southern Missouri to Arkansas M. D. Blum; M. D. Blum 1Department of Geosciences, 214 Bessey Hall, University of Nebraska, Lincoln, Nebraska 68588 Search for other works by this author on: GSW Google Scholar M. J. Guccione; M. J. Guccione 2Department of Geology, Ozark Hall 118, University of Arkansas, Fayetteville, Arkansas 72701 Search for other works by this author on: GSW Google Scholar D. A. Wysocki; D. A. Wysocki 3Natural Resources Conservation Service, U.S. Department of Agriculture, 110 Centennial Mall, Lincoln, Nebraska 68516 Search for other works by this author on: GSW Google Scholar P. C. Robnett; P. C. Robnett 4Department of Geology, Southern Illinois University, Carbondale, Illinois 62901 Search for other works by this author on: GSW Google Scholar E. M. Rutledge E. M. Rutledge 5Department of Agronomy, University of Arkansas, Fayetteville, Arkansas 72701 Search for other works by this author on: GSW Google Scholar Author and Article Information M. D. Blum 1Department of Geosciences, 214 Bessey Hall, University of Nebraska, Lincoln, Nebraska 68588 M. J. Guccione 2Department of Geology, Ozark Hall 118, University of Arkansas, Fayetteville, Arkansas 72701 D. A. Wysocki 3Natural Resources Conservation Service, U.S. Department of Agriculture, 110 Centennial Mall, Lincoln, Nebraska 68516 P. C. Robnett 4Department of Geology, Southern Illinois University, Carbondale, Illinois 62901 E. M. Rutledge 5Department of Agronomy, University of Arkansas, Fayetteville, Arkansas 72701 Publisher: Geological Society of America Received: 22 May 1998 Revision Received: 22 Feb 1999 Accepted: 28 Apr 1999 First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2000) 112 (2): 221–235. https://doi.org/10.1130/0016-7606(2000)112<221:LPEOTL>2.0.CO;2 Article history Received: 22 May 1998 Revision Received: 22 Feb 1999 Accepted: 28 Apr 1999 First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation M. D. Blum, M. J. Guccione, D. A. Wysocki, P. C. Robnett, E. M. Rutledge; Late Pleistocene evolution of the lower Mississippi River valley, southern Missouri to Arkansas. GSA Bulletin 2000;; 112 (2): 221–235. doi: https://doi.org/10.1130/0016-7606(2000)112<221:LPEOTL>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Mississippi River served as the principal conduit for meltwaters discharging from the southern margins of North American ice sheets. The northern half of the Mississippi River alluvial valley in Missouri and Arkansas can be subdivided into two distinct channel courses, the Western and Eastern Lowlands, which are separated by Crowleys Ridge. The Eastern Lowlands contain two entry points, the Bell City–Oran and Thebes Gaps; the latter is a narrow bedrock gorge that contains the modern river. This paper summarizes a model for evolution of channel courses in the Western and Eastern Lowlands during the Illinoian and Wisconsin glacial stages.For the Western Lowlands, stratigraphic relations between loess units and subjacent fluvial deposits show that major continuous terrace surfaces, or valley trains, are Illinoian or late Wisconsin in age. Investigations of tributary valley fills further show the Western Lowlands were deeply incised during the early to middle Wisconsin stage, then aggraded during the late Wisconsin stage to such an extent that tributary valleys were backfilled with slackwater deposits. Moreover, analysis of loess thinning and fining trends shows that early to middle Wisconsin Roxana Silt and the late Wisconsin Peoria Loess covers on Western Lowlands valley trains were derived from deflation of valley trains in the Eastern Lowlands. We conclude that the Western Lowlands were the primary Mississippi River course during Illinoian deglaciation but were abandoned shortly thereafter, then episodically reoccupied during the late Wisconsin stage.For the Eastern Lowlands course, valley trains of early to middle Wisconsin age are not preserved, with the exception of a small remnant where the Mississippi River broke through a gap in the southern margins of Crowleys Ridge and reentered the Western Lowlands. All valley trains in the Eastern Lowlands are late Wisconsin age. A series of discontinuous terrace surfaces in the Bell City–Oran Gap represent dissected remnants of the primary late Wisconsin full glacial and early late glacial course of the Mississippi River or combined Mississippi and Ohio Rivers, whereas younger continuous braided stream surfaces in the Bell City–Oran and Thebes Gap courses represent valley trains of latest Wisconsin and earliest Holocene age. Hence, the Bell City–Oran Gap was the primary course during the entire Wisconsin stage, and the Thebes Gap was permanently occupied in earliest Holocene time.As much as 5 m difference in elevation between successive late Wisconsin terrace surfaces of the Eastern Lowlands indicates that valley trains were rapidly constructed, incised, and abandoned in response to fluctuations in the delivery of meltwater and outwash from the former ice margin. Moreover, a variety of data indicates that deglacial meltwater floods were commonly of sufficient magnitude to overflow from the primary course in the Bell City–Oran Gap. Throughout the late Wisconsin substage, floodwaters overflowed into the Western Lowlands, constructed a series of secondary valley trains, and filled tributary valleys with slackwater deposits. During the latest Wisconsin stage, perhaps in association with the drainage of Glacial Lake Agassiz, floodwaters overflowed into the Western Lowlands and broke through the Thebes Gap. The Charleston fan represents the initial deposits of the Thebes Gap course. Following deposition of a large crevasse splay at the Western Lowlands entrance, that course was no longer active, but flow was routed through the Thebes Gap during periods of high-magnitude flooding until the Bell City–Oran Gap was abandoned and the Thebes Gap course was permanently occupied during earliest Holocene time. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.