The lower Ohio River valley is a terraced fluvial landscape that has been profoundly influenced by Quaternary climate change and glaciation. A modern Quaternary chronostratigraphic framework was developed for the lower Ohio River valley using optically stimulated luminescence (OSL) dating and allostratigraphic mapping to gain insights into the nature of fluvial responses to glacial-interglacial/stadial-interstadial transitions and Holocene climate change. River deposits, T0 (youngest) to T7 (oldest), were mapped along a 75km reach of the lower Ohio River and were dated using 46 OSL and 5 radiocarbon samples. The examination of cores combined with OSL and radiocarbon dating shows that fluvial sediments older than marine oxygen isotope stage (MIS) 2 are present only in the subsurface. Aggradation during MIS 6 (Illinoian glaciation) filled the valley to within ~7m of the modern floodplain, and by ~114ka (MIS 5e/Sangamon interglacial) the Ohio River had scoured the MIS 6 sediments to ~22m below the modern floodplain surface. There were no fluvial sediments in the valley with ages between MIS 5e and the middle of MIS 3. The MIS 3 ages (~39ka) and stratigraphic position of T5 deposits suggest the Ohio River aggraded 8-14m during MIS 4 or MIS 3. Near the end of MIS 3, the Ohio River incised the mid Last Glacial (mid-Wisconsinan) deposits ~10m and began aggrading again by ~30ka. Aggradation continued into MIS 2, with maximum MIS 2 aggradation occurring before ~21ka, which is coincident with the global Last Glacial Maximum (LGM). As the Ohio River adjusted to changing fluxes in sediment load and discharge following the LGM, it formed a sequence of fill-cut terraces in the MIS 2 outwash that get progressively younger with decreasing elevation, ranging in age from ~21ka to ~13ka. From ~14ka to ~13ka the Ohio River rapidly incised ~3m to form a new terrace, and by ~12ka at the onset of the Holocene, the Ohio River established a meandering channel pattern. The river formed a broad floodplain surface from ~12ka to ~6ka, and then incised ~1m and formed a fill-cut terrace from ~6ka to ~5ka. After ~5ka, likely in response to mid-Holocene drought in North America, the Ohio River incised ~5m, and by ~4ka the river began aggrading again. The Ohio River has aggraded ~4m since aggradation began at ~4ka. The chronostratigraphic framework and reconstructed history developed here suggest that the lower Ohio River is highly sensitive to glacial-interglacial transitions and abrupt Holocene climate change and responds rapidly to these allogenic forcings.
Bibliographical noteFunding Information:
This research was supported by multiple funding sources, including the U.S. Geological Survey 's National Cooperative Geologic Mapping Program (STATEMAP and FEDMAP awards 03HQPA003, 04HQPA003, 05HQAG0007, 06HQAG0003, 07HQAG0062, 08HQPA0003, 09HQPA0003, and 11HQPA003), the U.S. Geological Survey 's National Earthquakes Hazard Reduction Program (awards 06HQGR0192, 07HGGR0052, and G11AP20011), the Kentucky Geological Survey, and the University of Cincinnati. We thank Matt McCauley and Steve Neyhouse from the National Resource Conservation Service, Scott Waninger and Amy Bleithcroft from the Kentucky Geological Survey, and William Monaghan from the Indiana Geological Survey for help with coring and field mapping. We also thank Kristina Brady and Amy Myrbo from the Limnological Research Center, where some of the cores from this study were processed. We appreciate and acknowledge Kevin Kincare and an anonymous reviewer, whose comments and suggestions improved the quality of this manuscript. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Copyright 2015 Elsevier B.V., All rights reserved.
- Fluvial terraces
- Holocene climate
- Lower ohio river
- Optically-stimulated luminescence