Pennsylvanian

About: Pennsylvanian is a research topic. Over the lifetime, 3850 publications have been published within this topic receiving 62956 citations.

A chronology of Paleozoic sea-level changes.

Abstract: Sea levels have been determined for most of the Paleozoic Era (542 to 251 million years ago), but an integrated history of sea levels has remained unrealized. We reconstructed a history of sea-level fluctuations for the entire Paleozoic by using stratigraphic sections from pericratonic and cratonic basins. Evaluation of the timing and amplitude of individual sea-level events reveals that the magnitude of change is the most problematic to estimate accurately. The long-term sea level shows a gradual rise through the Cambrian, reaching a zenith in the Late Ordovician, then a short-lived but prominent withdrawal in response to Hirnantian glaciation. Subsequent but decreasingly substantial eustatic highs occurred in the mid-Silurian, near the Middle/Late Devonian boundary, and in the latest Carboniferous. Eustatic lows are recorded in the early Devonian, near the Mississippian/Pennsylvanian boundary, and in the Late Permian. One hundred and seventy-two eustatic events are documented for the Paleozoic, varying in magnitude from a few tens of meters to ∼125 meters.

Sea-level curve for Pennsylvanian eustatic marine transgressive-regressive depositional cycles along midcontinent outcrop belt, North America

Abstract: At least 55 cycles of marine inundation and withdrawal are recognized in the mid-Desmoinesian to mid-Virgilian Midcontinent outcrop sequence in North America. They range from widespread major cycles (classic cyclothems) with deep-water facies extending across the northern shelf, through intermediate cycles persisting as marine horizons across the shelf, to minor cycles developed on the lower shelf or as parts of major cycles. Biostratigraphic differentiation of the cycles should establish interbasinal correlation on a scale fine enough to allow evaluation of differential tectonics and sedimentation. Sequential groupings of cycles are more irregular than proposed megacyclothems or mesothems, but they may be obscured by the distinctness of the major cyclothems. Estimates of cycle periods range from about 40 to 120 x 10/sup 3/ yr for the minor cycles up to about 235 to 400 x 10/sup 3/ yr for the major cyclothems. The range for all cycles corresponds well to the range of periods of Earth's orbital parameters that constitute the Milankovitch insolation theory for the Pleistocene ice ages, and it further supports Gondwanan glacial control for the Pennsylvanian cycles. Even though the dominant period of the major Pennsylvanian cyclothems is up to four times longer than the dominant 100,000-yr period inmore » the Pleistocene, the shapes of both curves display rapid marine transgression (rapid melting of ice caps) and slow interrupted regression (slow buildup of ice caps), which suggest similar linkages between the climatic effects of the orbital parameters and ice-cap formation and melting, at the two different scales, widely separated in time. 28 references, 3 figures.« less

Plate tectonics of the Ancestral Rocky Mountains

Abstract: The Ancestral Rocky Mountains were intracratonic block uplifts that formed in Colorado and the surrounding region during Pennsylvanian time. Their development related to the collision of North America with South America–Africa, which produced the Ouachita-Marathon orogeny. In Early Pennsylvanian time, suturing was taking place only in the Ouachita region, and foreland deformation took place only in the mid-continent. By Middle Pennsylvanian time, the length of the suture zone had increased, and it was active from the Ouachita to the Marathon region. The extent of cratonic deformation also increased in intensity and in areal extent, culminating in the Ancestral Rocky Mountains. In Late Pennsylvanian time, suturing was taking place only in the Marathon region, and cratonic deformation decreased in extent and spread southward into New Mexico and West Texas. We suggest that the Ancestral Rocky Mountains, and related features over a broad area of the western United States, were formed while an irregularly bounded peninsula of the craton (including the transcontinental arch) was pushed northwestward by the progressive collision-suturing of North America and South America–Africa. This intraplate deformation is, in some respects, like the deformation of Asia in response to the Cenozoic collision with India.

The magnitude of late paleozoic glacioeustatic fluctuations: A synthesis

Abstract: A comprehensive literature review shows that the magnitude of eustatic fluctuations varied throughout the Carboniferous and Permian and that at least eight distinct phases can be recognized. Facies juxtapositions in carbonate successions and erosional relief in clastic successions indicate that glacioeustatic fluctuations of 20–25 m, and occasionally as much as 60 m, took place throughout the early Mississippian (Tournaisian)—a widely recognized glacial period. Middle Mississippian (mid-Chadian through Holkerian) shallow marine carbonate and clastic successions indicate that eustatic fluctuations were 10–25 m, a decrease that matches well with the paucity of coeval glacial deposits. Late Visean (Asbian through mid-Brigantian) glacioeustatic fluctuations of 10–50 m record the initial phases of ice accumulation in advance of the widespread mid-Carboniferous glacial event. The latest Mississippian–earliest Pennsylvanian (mid-Brigantian through Langsettian) was a time of widespread glaciation, and strata of this age commonly exhibit evidence of glacioeustatic fluctuations of as much as 40–100 m. Although middle Pennsylvanian (Duckmantian through Asturian) glacial deposits are present in eastern Australia, paleovalley depths suggest that coeval glacioeustatic fluctuations were less than 40 m. Glacioeustatic fluctuations of as much as 100–120 m have been widely reported from late Pennsylvanian–earliest Permian (Stephanian through mid-Sakmarian) successions in North America, an increase that corresponds to the growth of large ice sheets across much of Gondwana and the accumulation of ice in the northern hemisphere. Incision and facies juxtaposition in Early–middle Permian (mid-Sakmarian through Kungurian) successions in eastern Australia indicate that glacioeustatic fluctuations of 30–70 m occurred during the waning stages of major glaciation. Erosional relief in paleoequatorial carbonates and the presence of coeval glacial deposits in Australia suggests that eustatic fluctuations of 10–60 m occurred during the final stages of glaciation in the middle to Late Permian (Roadian through Capitanian), but the modest size of most of these fluctuations makes it difficult to isolate the glacioeustatic signature. This review demonstrates that far-field cyclic successions record changing glacial conditions in Gondwana, that the magnitude of glacioeustatic fluctuations was directly related to the volume of glacial ice, that Carboniferous–Permian glacioeustasy was more variable than previously recognized, and that generalizations from short temporal intervals are probably not representative of the late Paleozoic ice age as a whole. Although any attempt to quantify the magnitude of ancient eustatic changes is based on caveats and assumptions, this review incorporates the results of over 100 published papers on the topic in an attempt to minimize the errors inherent in any one study.