Abstract In spite of numerous revisions from 1966 to present, the Cantabrian Substage of the Stephanian Stage (Pennsylvanian) was never properly defined as a chronostratigraphic unit. Defined and redefined at least three times, the Cantabrian lacks boundary stratotypes that correspond to clear and correlateable biochronological signals. Thus, instead of using a biochronological datum of well-established validity and utility, Cantabrian advocates have relied on ill-defined macrofloral assemblage zones and on lithostratigraphic boundaries to define the substage. As a result, the Cantabrian is demonstrably diachronous, even within Europe; indeed, the Cantabrian has proven to be unusable for correlations outside its type area in northern Spain. To resolve these problems, we recommend that the Cantabrian Substage be abandoned, and the Westphalian–Stephanian boundary be redefined at the major floral turnover that has been documented in the USA, western and central Europe, and in the Donets Basin. We further recommend that the bases of the Kasimovian Series, Stephanian Series, Missourian Series, and Upper Pennsylvanian Series all be aligned with this same floral turnover.

Abstract A threshold-like vegetational change in tropical wetlands occurred in the early Kasimovian (the US Desmoinesian–Missourian boundary) – Event 3. Two earlier significant changes occurred, first in the mid-Moscovian (Atokan–Desmoinesian; ∼Bolsovian–Asturian) – Event 1, and the second in the late Moscovian (mid-Desmoinesian; mid-Asturian) – Event 2. These changes occurred during a time period of dynamic and complex physical change in Euramerican Pangaea driven by changes in polar ice volume and accompanying changes in sea level, atmospheric circulation, rainfall, and temperature. During the Event 3 change, hyperbolized as ‘the Carboniferous rainforest collapse’, lycopsid dominance of (mostly peat) swamps changed to marattialean tree-fern and medullosan pteridosperm dominance, and biodiversity decreased. Event 3 encompassed one glacial–interglacial cycle and included vegetational turnover in other wetland habitats. For several subsequent glacial–interglacial cycles peatland dominance varied, known from palynology, before stabilizing. These vegetational changes likely reflect climatic events driving unidirectional, non-reversible wetland vegetational changes, during cooler, wetter parts of glacial–interglacial cycles. Discussion is complicated by different placements of crucial stratigraphic boundaries, but under the same names, compromising both clear communication and understanding of the literature. Not the least is the floating base of the Cantabrian Substage, together with the position of the Westphalian–Stephanian Stage boundary.

Abstract We present the first analysis of vegetational change in far western equatorial Pangaea (New Mexico, USA) during the Middle–Late Pennsylvanian transition (determined by conodonts and fusulinids) of the Late Paleozoic Ice Age. The study is based on the largest database assembled from this region: 28 of 44 quantitatively analysed floras from 14 of 26 stratigraphic levels. Most sampled floras are ‘mixed’, both below and above the boundary, including both hygromorphic and mesomorphic/xeromorphic taxa. The taxonomic data were recalibrated morphometrically focusing on foliar traits of lamina width and venation. All data were examined using stratigraphic credible intervals, capture–mark–recapture analyses, and resampling analyses. Results indicate no substantive taxonomic turnover across the boundary. This stands in marked contrast to patterns in mid-Pangaean coal basins where there is a large wetland vegetational turnover. However, plant and physical geological data indicate that immediately following the boundary in New Mexico, and for approximately half of the Missourian Stage, floras previously dominated by hygromorphs become overwhelmingly dominated by mesomorphic/xeromorphic taxa. Although expressed differently, the western Pangaean physical and palaeobotanical patterns parallel those from mid-Pangaean coal basins and suggest a widespread environmental change.

Numerous faults in the Mississippi Embayment area of far southern Illinois have been active since Late Cretaceous time. They have been documented via geologic mapping, drilling and trenching studies, and high-resolution seismic-reflection surveys. The majority lie within the Fluorspar area fault complex, directly in line with the New Madrid seismic zone. Other active elements include the Commerce fault zone and southern end of the Ste. Genevieve fault zone. Most Cenozoic faults strike northeast; a few strike north to north-northwest. Dips are generally 60° to vertical. Narrow grabens, often deeper than they are wide, are typical. Some grabens contain sedimentary units that are elsewhere eroded, or restricted to the grabens. Faults have undergone multiple episodes of movement since the Late Cretaceous. Offsets of tens of meters are common in the late Miocene to early Pleistocene Mounds Gravel. At one site, the Mounds Gravel is downthrown by 150 m within a graben. Younger Pleistocene sediments overlie the Mounds Gravel and are confined to the graben. Illinoian and younger displacements are less common and amount to a few meters, at the most. Two sites show possible Holocene faulting. The overall fault pattern implies transtensional, right-lateral wrenching that produced pull-apart grabens. Such a pattern is consistent with the contemporary stress regime, both in southernmost Illinois and in the New Madrid seismic zone.

Abstract The purposes of this trip are to assist in interpreting the complexities of Pennsylvanian stratigraphy and sedimentation and to collect representative conodonts. The first stop is the West Franklin Limestone Member of the Shelburn Formation, which represents the Desmoinesian-Missourian boundary and the second is the Atokan Lead Creek Limestone Member of the Mansfield Formation. To help provide a general overview of the somewhat repetitive Pennsylvanian rock sequences in southwestern Indiana, we will visit two coal mines, each displaying several hundred feet of Desmoinesian rocks. We will be able to collect conodonts at all stops except Stop 3.

Abstract Minerals have been extracted from the Illinois-Kentucky Fluorite District for over 170 years. Theories concerning the inter-relationship between the fluorite mineralization, tectonism, and igneous activity will be discussed by several geologists during this field trip. The Columbia mine (vein deposit) will be visited in Kentucky, and the only mine currently producing fluorite in this district, the Hastie Limestone Quarry (strata-bound deposit), will be visited in Illinois. The mining history of this region will be explained at the American Fluorite Museum, where numerous mineral specimens can be examined. The Hicks Dome, a Permian crypto-volcanic feature (?) in Illinois, will also be discussed. The trip will conclude with a walking tour at the Garden of the Gods Recreational Area to view the Eagle Valley Syncline and Lower Pennsylvanian units.

Diverse wetland vegetation flourished at the margins of the Midland Basin in north-central Texas during the Pennsylvanian Period. Extensive coastal swamps and an ever-wet, tropical climate supported lush growth of pteridosperm, marattialean fern, lycopsid, and calamite trees, and a wide array of ground cover and vines. As the Pennsylvanian passed into the Permian, the climate of the area became drier and more seasonal, the great swamps disappeared regionally, and aridity spread. The climatic inferences are based on changes in sedimentary patterns and paleosols as well as the general paleobotanical trends. The lithological patterns include a change from a diverse array of paleosols, including Histosols (ever-wet waterlogged soils), in the late Pennsylvanian to greatly diminished paleosol diversity with poorly developed Vertisols by the Early–Middle Permian transition. In addition, coal seams were present with wide areal distribution in the late Pennsylvanian whereas beds of evaporates were common by the end of the Early Permian. During this climatic transition, wetland plants were confined to shrinking “wet spots” found along permanent streams where the vegetation they constituted remained distinct if increasingly depauperate in terms of species richness. By Leonardian (late Early Permian) time, most of the landscape was dominated by plants adapted to seasonal drought and a deep water table. Wetland elements were reduced to scattered pockets, dominated primarily by weedy forms and riparian specialists tolerant of flooding and burial. By the Middle Permian, even these small wetland pockets had disappeared from the region.