ABSTRACT Mississippian (Tournaisian–Viséan) carbonate mounds in the Compton and Pierson limestones, Ozark region, North America, have been called Waulsortian. However, European Waulsortian mounds contain features such as geopetals with multigenerations of carbonate mud (polymuds) and stromatactis cavity systems that are rare to absent in Ozark mounds. To determine similarities and differences, examine their origins, and clarify nomenclature, mounds in the Compton and Pierson limestones are compared with Waulsortian mounds in the Feltrim Limestone, Ireland. Features considered included mound size, geometry, style of aggradation, composition, depositional setting, and diagenetic history. Mounds in the Compton and Pierson limestones are <10 m (33 ft) thick and form singular knoll-form or aggregates with a strong lateral growth component. In contrast, individual Waulsortian mounds in the Feltrim Limestone range from 5 to > 30 m ( 16 – 100 ft ) thick, but coalesce and vertically aggrade to form complexes that exceed 500 m ( 1600 ft ) . Pierson mounds are crinoidal and grain-rich, whereas Compton and Feltrim mounds are bryozoan-rich and mud-dominated. All mounds have similar cement stratigraphy and diagenetic histories. Mud-rich Compton mounds and Feltrim mounds are interpreted as deeper water than skeletal-rich Pierson mounds. Limited accommodation constrained Compton and Pierson mound size and forced lateral aggradation. Subsidence-driven accommodation in the Dublin Basin allowed Feltrim mounds to grow larger, coalesce, and aggrade vertically. Three types of mounds are recognized: true Waulsortian in the Feltrim Limestone, mud-cored Waulsortian-type Compton and Pierson mounds, and Pierson transported bioaccumulation mounds. Small dimensions of Waulsortian-type Pierson and Compton mounds limit their potential as oil and gas reservoirs, whereas Pierson crinoidal sediment piles are known to form reservoir-size accumulations.

Abstract The bromide “ nothing is constant but change ” could have been coined to describe the geological history of the Permo-Carboniferous—the Mississippian, Pennsylvanian, and Permian Periods. Global tectonics, fluctuations in atmospheric and oceanic chemistry, changes in global climate, and evolutionary changes in survivors of mass extinctions created the backdrop for the shifting panorama of this remarkable time in earth history. Catastrophic extinctions during the Frasnian-Famennian crisis decimated global plant and animal populations, leaving survivors to initially struggle through the Devonian-Carboniferous transition. The ensuing evolutionary diversification into less-populated niches was brought to an abrupt end at the close of the Permian Period by the largest of all mass extinctions. Upheavals in plate motion changed the configuration of continents and oceans during this time, resulting in the docking of Gondwana and Euramerica to create the supercontinent Pangea and the “world ocean”, Panthalassa . Within the evolving Permo-Carboniferous “landscape,” a wide diversity of carbonate platforms and reefs flourished. They ranged in size from small mounds a few square meters in size to mega-platforms occupying hundreds of square kilometers, some of which are important mineral and petroleum reservoirs. It is the diversity (carbonate sequence stratigraphy, platform architecture, diagenesis, reservoir characterization, and the composition of reefs and mounds) which Permo-Carboniferous rocks offer that has led to their intensive study by researchers from industry and academia around the globe. This book stems mostly from presentations given at the SEPM-and IAS-sponsored research conference Permo-Carboniferous Carbonate Platforms and Reefs , held May 12-19, 2000, in El Paso, Texas. To an extent, the

Abstract This paper evaluates the limits of using well-cuttings data and wireline logs in conjunction with limited core and outcrop data to generate a regional, high-resolution sequence stratigraphy for upper Mississippian (Chesterian) Greenbrier carbonates, West Virginia, U.S.A. These data are then used to document the stratigraphic response of the distal to proximal foreland basin to tectonics and Carboniferous glacio-eustasy during the transition into ice-house times. The major mappable sequences are fourth-order sequences, a few meters to over a hundred meters thick. They consist of updip red beds and eolianites, lagoonal muddy carbonates, ooid grainstone and skeletal grainstone-packstone shoal complexes, open-ramp skeletal wackestone, and slope-basinal laminated argillaceous carbonates. The sequences are bounded downdip by lowstand sandstones and calcareous siltstones, and locally on the ramp by basal transgressive shales; only a few sequence boundaries are calichified, compared with updip sections in Kentucky, where caliche and breccias are common. Transgressive systems tracts range from thin units to others that constitute the lower half of the sequence. The highstand systems tracts contain significant grainstone units. Maximum flooding surfaces on the ramp slope occur at the base of slope or basinal facies that rest on lowstand to transgressive complexes, whereas on the ramp they occur beneath widespread grainstones that overlie nearshore shale or lime mudstone. In the Greenbrier succession, fourth-order sequences are arranged into weak third-order composite sequences bounded updip by red beds, and by lowstand sands and oolite along the ramp slope. The composite sequences contain three to four fourth-order sequences. Correlation of the foreland basin units with third-order global sea-level curves, and with high-frequency sequences within the intracratonic Illinois Basin, shows that in spite of differential subsidence rates ranging from 2 to 30 cm/ky across the foreland, global third-and fourth-order sea-level changes whose amplitude increased with time were a strong influence on sequence development. Thrust-load-induced differential subsidence of fault blocks of the foreland basement controlled the rapid basinward thickening of the depositional wedge, and modified the eustatic effects on the accumulating succession. Moderate-amplitude eustatic sea-level change and semiarid climate were the dominant causes of the widespread reservoirs of ooid grainstone and lowstand sands. The overall stratigraphy suggests upward increase in amplitudes of sea-level change, and cooling, which likely records the initiation of Gondwana ice-sheet growth.

Abstract High-resolution sequence stratigraphic cross sections (based on outcrops and shallow cores) of Mississippian (Meramecian to Chesterian) strata in the Appalachian Basin, Kentucky, U.S.A, are the marine stratigraphic record of the interaction of tectonics on a slowly subsiding distal foreland, with the Carboniferous glacio-eustatic transition into icehouse conditions. Late Mississippian paleoslopes were to the southeast into the foreland basin, probably because of thrust loading and accompanying block faulting of the distal foreland. The succession is dominated by fourth-order sequences that are only a few meters to 15 meters thick, which is an order of magnitude thinner than those of the proximal foreland. Regional disconformities marked by paleosols, caliche, micro-karsting, brecciation, tepee formation, or sharp contacts between limestone and the overlying transgressive marine shale bound fourth-order sequences. The sequences are stacked into several siliciclastic-bounded third-order or composite sequences that make up the broadly transgressive Mississippian supersequence. Facies are dominated by oolitic grainstones passing downslope into skeletal grainstone-packstone and updip into lagoonal muddy carbonates, green shale, eolianites, and rare red beds. Marine shales occur at bases of the younger sequences. The fourth-order sequences can be correlated from the Appalachian distal foreland, into the proximal foreland, as well as into the intracratonic Illinois Basin, suggesting a eustatic origin. However, local and regional tectonics strongly influenced thickness and distribution of sequences as well as the distribution and timing of unconformities locally. The facies stacking in the lower sequences indicates that they formed under the influence of moderate sea-level changes that effectively flooded the ramp to depths of 10 m or less. This resulted in grainstones within sequences being partitioned by caliches and muddy carbonates near or at sequence boundaries. Facies stacking in the upper sequences suggests that the magnitude of fourth-order sea-level changes increased in the later Chesterian, causing flooding of the ramp to depths of tens of meters, probably synchronous with buildup of ice sheets on Gondwana. This was accompanied by a change to more humid climates, which decreased oolite deposition on the ramp and favored deposition of open marine skeletal limestones bounded by marine siliciclastic units. Such moderate-amplitude global eustasy may account for the widespread, highly partitioned grainy reservoirs typical of the Mississippian worldwide.