This volume, prepared for the 130th Annual Meeting of the Geological Society of America in Indianapolis, includes compelling science and field trips in Indiana, Illinois, Kentucky, Michigan, and Ohio. A wealth of geologic and human history collides in the Midwest, a confluence that led to the growth of America's industry over the past two centuries. Guides in this volume depict this development from the establishment of New Harmony, the birthplace of American geology, through the construction of Indianapolis's modern skyline. Underpinning this growth were the widespread natural resources-limestone, coal, and water-that built, powered, and connected a growing nation. Take a journey through the Heartland to sand dunes, outcrops, quarries, rivers, caves, and springs that connect Paleozoic stratigraphy with the assembly of Gondwana, continental glaciation with Quaternary geomorphology and hydrology, and landscape with the human environment.

ABSTRACT The Middle Devonian Sylvania Sandstone in the Michigan Basin, United States, is noteworthy for its mixed, cherty dolomitic carbonate, limestone, and sandstone composition and excellent reservoir quality and fluid-flow properties in many areas of the basin. Substantial commercial brine production was initiated in the middle twentieth century, and liquid waste disposal continues today in the Sylvania Sandstone, although little or no hydrocarbon production is known from this unit. The Sylvania Sandstone pinches out to the south and west in the basin and overlies either the Bass Islands Group at the regional base Kaskaskia unconformity to the south or the Bois Blanc Formation, with which it is proposed to be in facies relationship to the northeast. The Sylvania Sandstone is overlain by and apparently interfingers with the Meldrum Member of the Amherstburg Formation throughout the basin. The Sylvania unit predominantly consists of siliciclastic rocks in the southeastern Michigan Basin and in outcrop in Ohio, but it is transitional to predominantly cherty carbonate in the northwest along a depositional hinge striking from southeast to northwest through the central basin. This hinge zone is dominated by mixed carbonate and siliciclastic strata deposited in normal-salinity, tidally influenced paralic and shallow-marine environments. Excellent reservoir quality is present in quartz sandstones and, especially, mixed sandy dolomite lithofacies in the central basin. Cherty facies may also possess significant porosity, but typically with low permeability. Limestone lithofacies are commonly non-reservoir-quality facies. Multiple high-frequency, low-magnitude relative sea-level cycles within the Sylvania Sandstone are suggested from regional stratigraphic analysis. The Sylvania Sandstone in the Michigan Basin is interpreted as a mixed carbonate and siliciclastic, basin-margin facies assemblage deposited in an overall transgressive systems tract above the base Kaskaskia unconformity and in conformable relationship with more basinal facies of the Bois Blanc Formation.

Abstract: The most extensive Permian tetrapod (amphibian and reptile) fossil records from the western USA (New Mexico to Texas) and South Africa have been used to define 11 land vertebrate faunachrons (LVFs). These are, in ascending order, the Coyotean, Seymouran, Mitchellcreekian, Redtankian, Littlecrotonian, Kapteinskraalian, Gamkan, Hoedemakeran, Steilkransian, Platbergian and Lootsbergian. These faunachrons provide a biochronological framework with which to assign ages to, and correlate, Permian tetrapod fossil assemblages. Intercalated marine strata, radioisotopic ages and magnetostratigraphy were used to correlate the Permian LVFs to the standard global chronostratigraphic scale with varying degrees of precision. Such correlations identified the following significant events in Permian tetrapod evolution: a Coyotean chronofaunal event (end Coyotean); Redtankian events (Mitchellcreekian–Littlecrotonian); Olson’s gap (late Littlecrotonian); a therapsid event (Kapteinskraalian); a dinocephalian extinction event (end Gamkan); and a latest Permian extinction event (Platbergian–Lootsbergian boundary). Problems of incompleteness, endemism and taxonomy, and the relative lack of non-biochronological age control continue to hinder the refinement and correlation of a Permian timescale based on tetrapod biochronology. Nevertheless, the global Permian timescale based on tetrapod biochronology is a robust tool for both global and regional age assignment and correlation. Advances in Permian tetrapod biochronology will come from new fossil discoveries, more detailed biostratigraphy and additional alpha taxonomic studies based on sound evolutionary taxonomic principles.