ABSTRACT An understanding of regional orogenic, climatic, and eustatic processes is critical to interbasinal correlation of Paleozoic strata in eastern North America. Tectonic activity associated with the culmination of Appalachian orogenic events has been shown to have regional influence on paleostructure and sediment dispersal in the Appalachian foreland basin and adjacent intracratonic Illinois and Michigan Basins. The culmination of the Acadian orogeny at the end of the Devonian represents the beginning of a period of general tectonic quiescence extending throughout the early and middle Mississippian in eastern North America. Early Mississippian strata in the Michigan Basin are distinctive and mark the transition from marine shale and carbonate-dominated sedimentation during much of the Late Ordovician through Late Devonian to siliciclastic-dominated deposition throughout much of the Carboniferous. The Osagean Stage Marshall Formation constitutes an important coarse-grained siliciclastic formation in the Michigan Basin. Despite numerous outcrop studies and early subsurface investigations, the Marshall Formation remains poorly understood in terms of depositional controls and stratigraphic relationships to related Mississippian strata in Michigan and correlative strata in adjacent basins. This work documents sedimentological and sequence stratigraphic relationships in early–middle Mississippian, generally clastic-dominated strata of the Marshall and lower Michigan Formations (as described in previous literature). Utilizing 535 well logs and core-to-log calibration in conjunction with detailed descriptions of seven cored intervals spanning the Michigan Basin, new stratigraphic relationships are presented suggesting the Marshall Formation and informal stray sandstone units are genetically related and reflect tectonic, eustatic, and climatic processes that occurred in the Michigan Basin during the early Carboniferous.

Abstract This field trip provides an overview of geological features in southwestern Missouri that are related to the American Civil War and to human culture. This includes the geology and history of the Wilson’s Creek National Battlefield (where the second important battle of the American Civil War was fought on 10 August 1861), Zágonyi’s Charge (25 October 1861), the Battle of Springfield (8 January 1863), and the gravestones and monuments of the National Cemetery in Springfield in which many of those who fought at Wilson’s Creek and other Civil War conflicts are buried. Other stops include the Springfield Underground and the quarries and facilities at what was once the town of Phenix (which, along with Carthage, Missouri, was the home of some of the largest dimension-stone quarries west of the Mississippi River); and a reconstructed mill site in Point Lookout, just south of Branson. Most of the field trip involves outcrops, quarries, and bedrock composed of the Mississippian Burlington-Keokuk limestones (undivided), providing numerous chances to examine outcrops and products made of limestone and chert.

Evidence for eustasy at the Kinderhookian-Osagean boundary is presented here in a new synthesis based on detailed analysis of the boundary in the central Appalachian Basin and regional mapping of the Kinderhookian-Osagean boundary unconformity in the conterminous United States. Detailed stratigraphic analysis within the central Appalachian Basin shows that coarse-grained, fluvial sandstones (Black Hand, Burgoon, Big Injun, Purslane) are associated with valley incision up to 60 m and a widespread sequence boundary (SB2) that is inferred to have resulted from a forced regression during the Kinderhookian-Osagean boundary interval. The extent of unconformity at the boundary was evaluated by mapping the inferred positions of shorelines during the Kinderhookian, Kinderhookian-Osagean boundary interval, and early Osagean based on stratigraphic data from Correlation of Stratigraphic Units of North America (COSUNA) charts. This analysis shows areas of extensive unconformity at the Kinderhookian-Osagean boundary across the United States inferred to be the result of sea-level fall and recovery during a period of ~2 m.y. or less, based on missing conodont zones. The Kinderhookian-Osagean boundary is equivalent in age to the global Tn2-Tn3 boundary, and supporting evidence for global regression and eustasy at this boundary is also reviewed. The combination of this evidence for eustasy with recently reported middle to early late Tournaisian (Tn2a-Tn3b) diamictites in South America permits the inference of continental glaciation at this time. Previous studies of oxygen and carbon isotope data from marine carbonates and fossils have shown strong positive anomalies suggestive of global cooling at the Kinderhookian-Osagean and Tn2-Tn3 boundary, providing further support for the hypothesis of continental glaciation in the late Tournaisian.