Groundwater resources associated with sediments filling the Marion and Mahomet Valley Sections of the Lafayette Bedrock Valley System vary from miniscule to substantial, reflecting the wide range of glacigenic aquifer facies contained in the fill. These aquifer facies include braid-stream deposits that range from thin units within till sequences to immense, valley-filling masses. Also included is a variety of proximal to distal, subaerial to subaqueous, fan and fan-delta deposits; these range from thick masses of ice-proximal, cobbly rubble interspersed with thin diamicts and clays, to thin, discontinuous lentils of sand confined within lacustrine clays. Valley-fill aquifers are confined by capping till units, except where exhumed at the crossings of the Maumee-Wabash Trough (modern Wabash River Valley). A variety of aquifers typically are available within the valley-capping sediments; for this reason, much of the deep valley-fill has not been extensively explored or developed. Some valley-fill aquifers are so thin and/or deeply buried that their exploitation is unlikely, but others are so thick and areally extensive that exploitation easily can support sustainable yields of tens of millions of gallons per day.

The Lafayette Bedrock Valley System is a complex of bedrock valleys that converge on and diverge from Lafayette, Indiana. The primary trunk valley of the system, composed of the narrow Marion Valley Section on the east and the broad Mahomet Valley Section on the west, is the classic “Teays Valley” of the Midwest. If such a continuous Teays drainage truly existed, it represents only the early part of the history of the Lafayette Bedrock Valley System in Indiana. Origins of the valley parts and their form remain enigmatic. Although the Marion crosses major rock structure, the course and the contrasting forms of the parts reflect structural and lithologic control. Contrasting valley forms, valley deeps, and possible inset benches may reflect one event or multiple events in a single valley, or disparate events in other valleys; or the features may reflect external events, such as incision through forebulge or erosion beneath bursting ice dams. Although the origins of the valley system are conjectural, the fill sequences within give evidence of the nature and timing of the demise of the system. The Marion valley is filled with a plug of old lacustrine and glaciolacustrine sediments included in the Blackford Member of the Banner and Jessup Formations. These sediments were deposited in a lake dammed between ice at the valley bends at Logansport, Indiana, and St. Marys, Ohio. Deposited at the dams were subaqueous fan deposits of coarse-grained outwash and tills of both basal-meltout and sediment gravity-flow origin. The tills include the red claystone-bearing West Lebanon Till Member on the west, and the Wilshire Till Member on the east. An uppermost tongue of the West Lebanon till caps the Blackford lacustrine sediments, indicating southeastward progression of the West Lebanon ice into the lake and ultimately over the entire fill sequence. The relative age of plugging of this valley section is suggested by the West Lebanon, which overlies magnetically reversed (>0.7-m.y.-old; marine isotopic stage 22?) sediments in western Indiana. The plugging of the Marion valley by West Lebanon ice corresponds in time with the plugging of the valley in Ohio by Wilshire ice (and the deposition of the Minford Silts) and marks the end of classic Teays-stage regional drainage. The Mahomet valley subsequently was reexcavated as part of a Metea-Mahomet drainage system, heading in northeastern Indiana. This valley is filled with younger, interfingered outwash and till, which are included in the Mahomet Member and the Brookston Till Member of the Banner and Jessup Formations. These deposits represent aggrading braided stream and fan environments in front of southwestward-advancing Brookston ice. The relative age of plugging of this valley section is given by the Vandalia Till Member of the Glasford Formation, an Illinoian till that caps the valley fill, and by the West Lebanon till, which was apparently cut out prior to valley filling. The final plugging of the Mahomet marks the end of any deeply incised drainage in north-central Indiana. With the demise of the Mahomet drainage outlet, development of an upper Wabash drainage system began. The fill of bedrock valleys south of the Marion-Mahomet trunk valley contains evidence of multiple erosional surfaces. The gradients of these surfaces suggest a merging at Lafayette into early equivalents of the modern Wabash drainage, exiting into the Wabash bedrock valley via the Attica cutoff or across the rock sill above Independence.

Research in stratigraphy is increasingly multidisciplinary and conducted by diverse research teams whose members can be widely separated. This developing distributed-research process, facilitated by the availability of the Internet, promises tremendous future benefits to researchers. However, its full potential is hindered by the absence of a development strategy for the necessary infrastructure. At a National Science Foundation workshop convened in November 2001, thirty quantitative stratigraphers and database specialists from both academia and industry met to discuss how best to integrate their respective chronostratigraphic databases. The main goal was to develop a strategy that would allow efficient distribution and integration of existing data relevant to the study of geologic time. Discussions concentrated on three major themes: database standards and compatibility, strategies and tools for information retrieval and analysis of all types of global and regional stratigraphic data, and future directions for database integration and centralization of currently distributed depositories. The result was a recommendation to establish an integrated chronostratigraphic database, to be called Chronos, which would facilitate greater efficiency in stratigraphic studies ( http://www.chronos.org/ ). The Chronos system will both provide greater ease of data gathering and allow for multidisciplinary synergies, functions of fundamental importance in a variety of research, including time scale construction, paleoenvironmental analysis, paleoclimatology and paleoceanography. Beyond scientific research, Chronos will also provide educational and societal benefits by providing an accessible source of information of general interest (e.g., mass extinctions) and concern (e.g., climatic change). The National Science Foundation has currently funded a three-year program for implementing Chronos.

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.