ABSTRACT Pleistocene glacial and interglacial episodes had a profound influence on erosion, sediment transport, and topographic expression in the Midwestern United States. Northern Kentucky hosts a variety of fluvial and glacial features that record these Quaternary advances and retreats of the Laurentide ice sheet. This field trip highlights the major glacial and interglacial episodes of the Pleistocene, including the Pliocene–Early Pleistocene Teays drainage system, the Early–Middle Pleistocene pre–Illinois glacial Episode, the Middle Pleistocene Yarmouth interglacial, the Illinois glacial Episode in the Middle Pleistocene, the Sangamon interglacial, and the Late Pleistocene Wisconsin Episode. The Old Kentucky River was tributary to the Teays, depositing sands at ca. 1.5 Ma, confirmed by multiple 10 Be- 26 Al cosmogenic radionuclide burial ages. Glacial till uncoformably overlies Old Kentucky River sands and demonstrates that pre-Illinois ice extended into Kentucky. The modern-day course of the Ohio River was incised after the pre−Illinois Episode, and then aggraded with transportation of Illinois Episode glacial outwash. Deposition of outwash at the mouths of tributaries caused impoundment and slackwater deposition in tributary valleys; the Claryville Clay has long been assumed to represent a pre-Illinois lacustrine deposit, but new optically stimulated luminescence feldspar geochronology yields a Middle Pleistocene age of ca. 320 ka. We have not observed Illinoian till in Kentucky. The final advance of the Laurentide ice sheet did not reach Kentucky, however, high sediment volumes were transported along the Ohio River and impounded tributaries, similar to the Illinois Episode.

Abstract This guidebook chapter outlines a walking tour that provides an introduction to the geological, archaeological, and historical setting of Pittsburgh, with an emphasis on the use of local and imported geologic materials and resources in the eighteenth and nineteenth centuries. The focus is on downtown Pittsburgh, the low-lying triangle of land where the Monongahela and Allegheny Rivers join to form the Ohio River, and Coal Hill (Mount Washington), the escarpment along the Monongahela River to its south. Topics include the importance of—and concomitant effect of—historic coal use; use of local and imported geologic materials, including dimension stone used for buildings and gravestones, and chert used for gunflints and millstones; the frontier forts built at the site; and the ubiquitous landslides along Coal Hill.

Approximately 8000 lignite exploration cores, each 91 m (300 ft) deep, were used to map the gravel facies of the Upland Complex (Lafayette gravel) preserved on drainage divides in western Kentucky and Tennessee and on Crowley's Ridge in southeastern Missouri and eastern Arkansas. The Upland Complex is interpreted to be the remnant of a high-level terrace of the ancestral Mississippi-Ohio River system. The longitudinal profile of the Upland Complex and its projection on sea-level curves suggest that this alluvial deposit is early Pliocene in age (5.5–4.5 Ma). Sea level during the early Pliocene was +100 m, and the Upland Complex is interpreted to have been an ∼100-m-thick floodplain when initially deposited. Sea-level decline to −20 m at 4 Ma resulted in incision through the Pliocene floodplain, which formed the high-level terrace. Incision through the floodplain occurred in the Western and Eastern Lowlands of eastern Arkansas and their tributary valleys. The upper silt and sand facies of the terrace (∼60 m) were eroded, leaving the basal gravel-rich Upland Complex preserved on drainage divides. The New Madrid seismic zone lies beneath the Eastern Lowlands. There has been up to 100 m of denudation above the seismic zone in the past 4 m.y., and the most recent denudation occurred in the Holocene due to the confluence of the Mississippi and Ohio Rivers stepping north to Thebes Gap, Missouri. The late Wisconsin and Holocene denudation may have perturbed the local stress field and reactivated the New Madrid seismic zone.

At some time during the Pleistocene Epoch, a part of the modern Ohio River drainage system in Ohio and West Virginia developed in response to impoundment of the ancestral Teays River drainage system. Rhythmites formed in the lacustrine slackwaters and remain today, extending as much as 150 to 200 km upstream from the Pleistocene ice front, in Teays Valley, West Virginia. A total of 303 oriented paleomagnetic specimens represent a composite stratigraphic section from the Minford Silt Member of the Teays Formation in Teays Valley. Of these, 224 specimens carry a stable reversed magnetization due to detrital magnetite and hematite. Two distinctive lithologic intervals with definitive magnetic intensities were found in the stratigraphic section; thick, light-colored rhythmites carry six times more remanent magnetization intensity than thin, dark-colored rhythmites, reflecting variations in the ratio of magnetite to hematite. From the Pleistocene paleomagnetic chronology, the glacial diversion of the Teays River in Ohio and West Virginia took place during the Matuyama reversed polarity chron, in the time interval between 0.79 and 1.60 Ma, the change attributed to an Early Pleistocene age, most probably the F or G glaciation. We propose that the Minford Silt was deposited between 0.79 and 0.88 Ma.