Late Pennsylvanian-Early Permian Research Articles

The Late Paleozoic Ice Age in western equatorial Pangea: Context for complex interactions among aeolian, alluvial, and shoreface sedimentary environments during the Late Pennsylvanian – early Permian

The evolution of depositional environments in the Late Pennsylvanian-early Permian of the Paradox Basin in Utah, USA, is investigated through detailed sedimentological and high-resolution sequence stratigraphic analyses, in order to define a model of landscape evolution, to discuss the stratigraphic model, and to evaluate the significance of the cyclicity in the paleoclimatic context. Forty high-resolution cycles integrated in 15 minor and two major cycles are observed for the first time throughout the Late Pennsylvanian-early Permian units. A-three steps landscape evolution is recognized. First, the lower Cutler beds, mainly corresponded to a marine environment, with longshore bar, subtidal, tidal, mouth-bar, and with locally fluvial deposits. The upper part of the lower Cutler beds also contains an aeolian dune. Second, the Cedar Mesa Sandstone, corresponded to broad erg deposits which are present across the entire study area, whereas longshore bar, subtidal, mouth-bar, and some fluvial deposits are mainly preserved in the northern part of the studied area. Third, the Organ Rock Formation records decreasing aeolian dune field preservation. To the south, the aeolian environments are interbedded with shoreface deposits, whereas to the north, fluvial deposits with some mouth-bars are more developed. Semi-arid climatic conditions persisted, as indicated by the presence of calcretes. Everywhere in these three steps, root traces within sandstone bars indicate that a soil was once present above the sand dunes. This new model of landscape evolution documents complex interactions between aeolian, fluvial and marine environments within the entire Permian succession of the Paradox Basin. High-resolution stratigraphic analyses allow to discuss the significance of the cyclicity in a scenario that take into consideration sea-level variation in the Late Paleozoic Ice Age paleoclimatic context. This Late Pennsylvanian to early Permian succession reflects both relative sea-level fluctuations and the variability of sediment supply.

Identifying sources of non-unique detrital age distributions through integrated provenance analysis: An example from the Paleozoic Central Colorado Trough

AbstractTo address the longstanding issue of provenance interpretation of non-unique detrital zircon age populations, we integrated zircon U-Pb, rare earth element (REE), and εHf(t) data from upper Paleozoic strata in the northern Central Colorado Trough and Cambrian intrusions with petrography, paleocurrent data, and structural and stratigraphic observations. This data set indicates that Cambrian sediment was shed by multiple local sources instead of distant sources hundreds of kilometers away, and it reveals a detailed history of tectonic drainage reorganization in the northern Central Colorado Trough during Ancestral Rocky Mountain deformation. During the Early–Middle Pennsylvanian, Cambrian detrital zircons were a minor constituent of northern Central Colorado Trough sediment. However, during the Late Pennsylvanian–early Permian, westward advancement of the adjacent Apishapa Uplift deformation front precipitated drainage reorganization, which resulted in an episode of dominant Cambrian detrital zircon sourcing. Paleocurrent and petrographic data indicate that the source of Cambrian detritus was shed by an igneous rock body that was ≤15 km northeast of the depocenter, which has since been eroded away or mantled by Tertiary volcanic rocks. The addition of zircon petrochronology to the data set applied here was critical in confirming this hidden source of detritus and elucidating the compositional characteristics of that igneous rock. Zircon εHf(t) provided a regional provenance indicator of a western Laurentian affinity, and REE composition aided in discriminating possible local sources of Cambrian zircon. Furthermore, this work serves as a case study of a dominant Cambrian detrital zircon signature sourced from outside of the wellknown Amarillo-Wichita Uplift, and it has implications for the interpretation of such detrital spectra in the context of a direct-from-basement source or the recycling of Cambrian zircon-dominated rocks. In summary, we demonstrate the utility of this multi-provenance proxy approach in interpreting a complex structural history of a dynamic hinterland and concomitant drainage reorganization through an in-depth investigation into the basin record.

Factors controlling the development of Fomichevella coral bioconstructions in the Gzhelian-Asselian (Late Pennsylvanian-early Permian) of Houchang, southern Guizhou, South China

Bioconstructions (five biostromes, one patch reef, and one large reef) of the colonial coral Fomichevella are well exposed, if infrequent, in the Upper Pennsylvanian-lower Permian of the Houchang area (southern Guizhou, China). Though they are primarily built by the same species, different growth morphologies and internal constructions are evident, which indicate different factors controlling their formation and development. The coral biostromes alternate with shoal deposits, being attributed to level-bottom communities that were closest to the reef ecosystem. The patch reef consists of a simple coral framework and a low biodiversity community. In contrast, rigid skeletal frameworks of Fomichevella are common and the biodiversity of the community is relatively higher in the large coral reef. Comparing these coral biostromes, the patch reef, and the large coral reef, several factors controlling their formation and development are suggested: stable substrate, water turbulence, sea-level fluctuation, and community structure. Hard substrates can provide stable habitats for the coral larvae during the initial colonisation stage, while the frequently changing sedimentary conditions were not conducive to the healthy development of Fomichevella. The simple community (e.g. the biostromes, patch reef) lacking encrusters and binders was too fragile to tolerate a turbulent environment. In Houchang, though intrinsic and extrinsic factors influenced the development of the Fomichevella bioconstructions, the extrinsic factors seem more important, which may be the key aspects controlling the Carboniferous coral bioconstructions.

Yangquanoxylon miscellum gen. nov. et sp. nov., a gymnospermous wood from the Upper Pennsylvanian–lower Permian Taiyuan Formation of Yangquan City, Shanxi Province, with reference to the palaeoclimate in North China

A silicified gymnospermous wood, Yangquanoxylon miscellum gen. nov. et sp. nov., is described from the Upper Pennsylvanian-lower Permian Taiyuan Formation, Yangquan City, Shanxi Province, North China. The pycnoxylic wood is composed of thick-walled tracheids and thin-walled rays. It is characterized by mixed radial tracheid pits, uniseriate and homogeneous rays, occurrence of scalariform radial pitting, and various types of cross-field pitting. There are four types of cross-field pitting in Y. miscellum gen. nov. et sp. nov., including simple, taxodioid, phyllocladoid, and araucarioid. The absence of growth rings within fossil woods described here and reported previously from North China suggests a humid climate with minimal precipitation variations during the Late Pennsylvanian-early Permian.

A sulfate conundrum: Dissolved sulfates of deep-saline brines and carbonate-associated sulfates

Sulfates in deeply circulating brines and carbonate-associated sulfates (CAS) within sedimentary units of the Cambrian strata in the Illinois Basin record a complex history. Dissolved sulfate within the Mt. Simon Sandstone brines exhibits average δ34SSO4 values of 35.4‰ and δ18OSO4 values of 14.6‰ and appears to be related to Cambrian seawater sulfate, either original seawater or sourced from evaporite deposits such as those in the Michigan Basin. Theoretical and empirical relationships based on stable oxygen isotope fractionation suggest that sulfate within the lower depths of the Mt. Simon brines has experienced a long period of isolation, possibly several tens of millions of years. Comparison with brines from other stratigraphic units shows the Mt. Simon brines are geochemically unique. Dissolved sulfate from brines within the Ironton-Galesville Sandstone averages 22.7‰ for δ34SSO4 values and 13.0‰ for δ18OSO4 values. The Ironton-Galesville brine has mixed with younger groundwater, possibly of Ordovician to Devonian age and younger. The Eau Claire Formation lies between the Mt. Simon and Ironton-Galesville Sandstones. The carbonate units of the Eau Claire and stratigraphically equivalent Bonneterre Formation contain CAS that appears isotopically related to the Late Pennsylvanian-Early Permian Mississippi Valley-type ore pulses that deposited large sulfide minerals in the Viburnum Trend/Old Lead Belt ore districts. The δ34SCAS values range from 21.3‰ to 9.3‰, and δ18OCAS values range from +1.4‰ to −2.6‰ and show a strong covariance (R2=0.94). The largely wholesale replacement of Cambrian seawater sulfate signatures in these dolomites does not appear to have affected the sulfate signatures in the Mt. Simon brines even though these sulfide deposits are found in the stratigraphically equivalent Lamotte Sandstone to the southwest. On the basis of this and previous studies, greater fluid densities of the Mt. Simon brines may have prevented the less dense Mississippi Valley-type fluids from interacting with these deeply circulating brines. Progressive in situ quartz cementation that occurred in the Mt. Simon Sandstone contemporaneous to the ore pulses may also have precluded fluid migration. The Mt. Simon brines appear to be a mixture of evaporated connate Cambrian seawater, recirculating deep-seated crystalline basement brines, and meteoric water.

U–Pb geochronology of the Acatlán Complex and implications for the Paleozoic paleogeography and tectonic evolution of southern Mexico

Even though the Acatlán Complex in southern Mexico contains the largest exposure of Paleozoic rocks in Mexico, it is commonly ignored in reconstructions of Pangea because of poor geochronologic data. Presently, this complex is understood to be composed of metasedimentary units (Cosoltepec, Magdalena, Chazumba and Tecomate Formations), a major magmatic suite (Esperanza Granitoids), and a suite with eclogites and blueschists (Xayacatlán Fm). Sedimentary cover includes unmetamorphosed upper Paleozoic units. Here we provide single-crystal laser ablation U–Pb geochronology of the metasedimentary and magmatic suites of the Acatlán Complex and its upper Paleozoic sedimentary cover. The data reveal a complex geological evolution recording tectonic events from the assembly of Rodinia to the break-up of Pangea. Data for the Esperanza Granitoids record three major tectonothermal events: (1) a Grenvillian (1165 ± 30 to 1043 ± 50 Ma), (2) a Taconian (478 ± 5 to 471 ± 5 Ma), and (3) a Salinian (Acatecan; 461 ± 9 to 440 ± 14 Ma). Eclogitic rocks from the Xayacatlán Formation of Neoproterozoic–Early Ordovician age contain detrital zircons derived most probably from the southwestern North America Grenville province. Data for the blueschists are consistent with a Middle Ordovician depositional age and derivation from Laurentian sources. The Tecomate Formation is composed of two unrelated units of contrasting age and lithology: a Neoproterozoic–Early Ordovician, arc- and rift-related volcanosedimentary unit containing detrital zircons derived from the southwestern North America Grenville province; and an essentially sedimentary unit containing Early Permian fauna. The Cosoltepec Formation has a maximum Devonian depositional age and contains detrital zircons consistent with derivation from South American sources. The age of the Magdalena and Chazumba Formations is established to be Late Pennsylvanian–Early Permian. These units contain detrital zircons indicating ultimate derivation from both North and South America crustal sources. The Late Paleozoic sedimentary cover contains detrital zircons shed mainly from Grenvillian sources with a significant contribution of Pennsylvanian magmatic rocks. The new U–Pb geochronologic data indicate that the traditional stratigraphic scheme used for the Acatlán Complex needs complete revision. Data further indicate that the earliest stages of the tectonic evolution of the Acatlán Complex are tied to the evolution of Rodinia and that the actual configuration of the Acatlán Complex was ultimately achieved by amalgamation of the Magdalena–Chazumba suite during the final stages of Pangea assembly. The Early Jurassic tectonothermal event affecting only the Chazumba and Cosoltepec units to produce the Magdalena Migmatite is related to the break-up of Pangea and the opening of the Gulf of Mexico. The Acatlán Complex contains a section of the suture between Laurentia and Gondwana with some sediments arriving from Laurentia and others from Gondwana and mirrors the structure and evolution of the Appalachian–Caledonian chains of North America.

Depositional environment and biofacies characterization of the Upper Pennsylvanian–Lower Permian deposits of the San Salvador Patlanoaya section (Puebla, Mexico)

The San Salvador Patlanoaya section (Puebla State of Mexico) has been subdivided into seven informal members labeled A–F. Members C–F have been dated as Missourian to Leonardian (equivalent to Kasimovian to Kungurian, i.e. lower Upper Pennsylvanian to upper Lower Permian). Members C–E display a shallowing-upward trend as does member F. The biodiversity of these carbonate deposits outcropping in the San Salvador Patlanoaya section is relatively low, although multiple microfossils (algae, small foraminifera, fusulinids and fish remains) are represented. Member C consists of calcarenitic limestone interpreted as distal tempestites interbedded with shaly limestone facies. These storm beds are composed mainly of silt, sand-sized quartz grains and bioclasts. Member D corresponds to coarse bioclastic limestones represented by calcareous tempestites and channel beds with erosional bases. Member E is composed of green shales and cross-bedded sandstones and gravelly conglomerates. Member F corresponds to a condensed package of limestones and interbedded siliciclastics and is Cisuralian (Early Permian) in age. Member G consists of condensed black shales and limestone nodules. The results of the study have significant implications for recognition of climatic and/or sea-level fluctuations in bioclastic–siliciclastic facies during the Late Pennsylvanian–Early Permian. The skeletal limestones and channel sandstones, common throughout the Pennsylvanian–Permian section, provide a constraint on palaeobathymetry, with the water depth fluctuating frequently around a position below, but near, the storm wave base.

A NEW DIADECTID (DIADECTOMORPHA), OROBATES PABSTI, FROM THE EARLY PERMIAN OF CENTRAL GERMANY

A new genus and species of the herbivorous Diadectidae, Orobates pabsti, is described on the basis of several specimens, including two complete, articulated skeletons, a skull with partial postcranium, a partial skull, and a dentigerous jaw fragment. All were collected from the Lower Permian (Wolfcampian) Tambach Formation, lowermost formational unit of the Upper Rotliegend of the Bromacker quarry locality in the midregion of the Thuringian Forest near Gotha, central Germany. A combination of autapomorphic and plesiomorphic character states clearly distinguishes O. pabsti from all other well-known members of Diadectidae and identifies it as the sister taxon to all other diadectids.The description of Orobates pabsti expands further our understanding of the Late Pennsylvanian-Early Permian Diadectidae and records the earliest specialization of tetrapods to high-fiber herbivory.On the basis of paleobiological and paleoenvironmental data only one other Early Permian locality is comparable to the Bro-macker locality, the somewhat younger (Leonardian) fissure fill deposits at Richards Spur, southeastern Oklahoma. This further supports the previously proposed hypothesis, based on similar grounds, that the vertebrates of both localities may have been part of a widespread, terrestrial upland faunal assemblage during the Early Permian.

China’s nanoparticulate CaCO 3 industry attracts new entrants

A silicified gymnospermous wood, Yangquanoxylon miscellum gen. nov. et sp. nov., is described from the Upper Pennsylvanian-lower Permian Taiyuan Formation, Yangquan City, Shanxi Province, North China. The pycnoxylic wood is composed of thick-walled tracheids and thin-walled rays. It is characterized by mixed radial tracheid pits, uniseriate and homogeneous rays, occurrence of scalariform radial pitting, and various types of cross-field pitting. There are four types of cross-field pitting in Y. miscellum gen. nov. et sp. nov., including simple, taxodioid, phyllocladoid, and araucarioid. The absence of growth rings within fossil woods described here and reported previously from North China suggests a humid climate with minimal precipitation variations during the Late Pennsylvanian-early Permian.

Coalbed methane resource potential and current prospects in Pennsylvania

Coalbed methane gas content analyses from exploratory coal cores and existing data indicate that gas content generally increases with increasing depth and rank. The coal beds studied are from the Main Bituminous field of Pennsylvania (which currently contains 24 coalbed methane pools) and the Northern and Southern Anthracite coal fields. They range from the Middle Pennsylvanian Allegheny Group to the Late Pennsylvanian–Early Permian Dunkard Group. Previous US Bureau of Mines studies revealed gas contents from 0.4 to 13.8 cm 3/g at depths of 99 to 432 m for the bituminous coal beds of the Allegheny Group. More recent core data from the Allegheny Group yielded gas contents from 2.2 to 8.9 cm 3/g at depths from 167 to 387 m. In the Anthracite region of eastern Pennsylvania, the little data that are available show that gas content is anomalously high or low. Gas yields from test holes in eastern Pennsylvania are low with or without artificial stimulation mainly due to the lack of a good cleat system. Overall estimates of coalbed methane resources indicate there may be 1.7 Tm 3 (61 Tcf) of gas-in-place contained in the Northern Appalachian coal basin. The amount of technically recoverable coalbed methane resources is projected by the US Geological Survey National Oil and Gas Resource Assessment Team [US Geological Survey National Oil and Gas Resource Assessment Team, 1996. 1995 National assessment of United States oil and gas resources—results, methodology, and supporting data, US Geological Survey Digital Data Series DDS-30, CD-ROM, Denver, CO, 80 pp.] and Lyons [Lyons, P.C., 1997. Central-northern Appalachian coalbed methane flow grows. Oil and Gas Journal 95 (27) 76–79] at 0.3 Tm 3 (11.48 Tcf). This includes portions of Pennsylvania, Ohio, West Virginia, and a small part of Maryland. Consequently, a mapping investigation was conducted to evaluate the regional geology of the bituminous coal-bearing intervals in southwestern Pennsylvania and its influence on coalbed methane potential. Phase I of this study involved the entire Pennsylvanian coal-bearing interval of southwestern Pennsylvania. Phase II focused on a stratigraphic delineation and evaluation of Allegheny Group coal beds and associated sandstones. Several prospective coal beds and associated facies relationships with channel–fill sandstones were determined. Possible non-coal scenarios for coalbed methane include erosional contacts between coal beds and overlying channel–fill sandstones and areas of stacked channel–fill sandstones. Repetitive sequences of coal accumulation are stacked, commonly with shale interburden, and are also potential coalbed methane targets. Additional Pennsylvania Geological Survey drilling/coalbed methane sampling occurred in Armstrong, Beaver, Cambria, Greene, Lawrence, Somerset, and Washington Counties. Raw coalbed methane desorption data tables/graphical displays of gas contents versus depth, thickness, and time, and average composition and heating values from coal beds of the Allegheny Group to the Dunkard Group are available at the Pennsylvania Geological Survey. Further information on cross-sections, isopleth maps, isopach maps, raw drillhole data, and ownership issues can also be obtained from the same source.

Dating of the time of sedimentation using UPb ages for paleosol calcite

We have sampled paleosol horizons from a continuous core of a rapidly deposited Late Pennsylvanian-Early Permian marine shelf section in Texas, USA. The paleosols occur on the tops of shoaling upward cycles and, based on current time constraints, these cycles average 250 ka and cannot represent longer than 400 ka. As the unconformity which is represented by the paleosol can only be a fraction of the time allowed for deposition of the cycle, the age of minerals that form in the paleosol is effectively the time of sedimentation. The uncertainty on the 238U 206Pb age of brown paleosol calcite from one exposure surface is only 1 Ma. Reported uncertainties on Paleozoic boundaries are greater than 10 Ma. Our early results suggest that the marine sedimentary record may be dated to a precision of 1 Ma with UPb analyses of carefully selected paleosol calcite. These results have implications for vastly improving time resolution of the rock record.

Alleghanian development of the Goat Rock fault zone, southernmost Appalachians: Temporal compatibility with the master decollement

The Goat Rock and associated Bartletts Ferry fault zones, which mark the eastern margin of the Pine Mountain Grenville basement massif, are controversial due to the suggestion that they are rare exposed segments of the late Paleozoic southern Appalachian master decollement. The controversy in part stems from reported middle Paleozoic (Acadian) radiometric dates postulated as the time of movement along these fault zones. Ultramylonite samples from the type area at Goat Rock Dam yield a 287 [plus minus] 15 Ma Rb-Sr isochron interpreted as the time of Sr isotopic rehomgenization during mylonitization. This date is corroborated by Late Pennsylvanian-Early Permian [sup 40]Ar/[sup 39]Ar mineral ages on hornblende (297-288 Ma) and muscovite (285-278 Ma) from neomineralized and dynamically recrystallized rocks within and straddling the fault zone. These Late Pennsylvanian-Early Permian dates indicate the time of right-slip movement (Alleghenian) along the Goat Rock fault zone, which is compatible with the timing suggested by COCORP for thrusting along the southern Appalachian master decollement.

Reinterpretation of faulting in southeast Missouri

New observations are presented on the character of Late Proterozoic-Early Cambrian, rift-related faulting in southeast Missouri. The principal fault set, which influences southeast Missouri structures, is composed of northwest-striking transfer faults. Initial Late Cambrian reactivations extended the faults northwest across the mid-continent and formed several major lineaments. Transpressive wrench-fault reactivations of these faults during Late Pennsylvanian-Early Permian time uplifted the St. Francois igneous terrane into a positive flower structure. This deformation was of an ancestral Rocky Mountain type (compressive block fault), and it produced the present structural framework of southeast Missouri. During Cretaceous rifting, the faults acted as transfer faults again, and intersections with related extension faults localized associated intrusive activity. These structures appear to be controlling present intraplate seismicity. These series of events indicate that the northwest striking transfer faults have been active for more than 600 m.y. Proper dentification of this faulting, its spacial relations, and its reactivations offer new understanding of present intraplate seismicity along the northwest margin of the Mississippi Embayment.

Preliminary Basin Analysis of Late Pennsylvanian-Permian Wood River Basin, South-Central Idaho: ABSTRACT

Stratigraphic correlation of partly coeval tectonostratigraphic units in the Smoky and Boulder Mountains, west and north (respectively) of Ketchum, Idaho, allows for reconstruction of the Late Pennsylvanian-Early Permian Wood River basin. These tectonostratigraphic units contain calcareous sandstones, silty limestones, and carbonaceous siltites and shales of the Wood River Formation (units 6 and 7 - Virgilian-Wolfcampian), Grand Prize Formation (Wolfcampian(.)), and Dollarhide Formation (Wolfcampian). Interpretation of sedimentary facies, petrologic characteristics, and structural relations suggests contiguous deposition of these units in a westward deepening basin in shallow shelf, outer shelf to upper slope, and lower slope to basin environments, respectively. In the Wood River basin, vertical facies changes within each formation are similar to lateral facies changes progressively westward between formations, as suggested by palinspastic reconstructions. Upsection and to the west, thick sequences of calcareous sands give way to fine-grained carbonaceous sediments, suggesting a deepening of depositional environments through time. Regional sea level rise, basin subsidence, or both, during Virgilian to early Wolfcampian time, is suggested by deepening-upward facies transitions in rocks of both the Wood River basin of central Utah and Oquirrh basin of northern Utah. Both basins evolved from shallow to moderate depth shelf-and-slope environments to more restricted, deeper watermore » environments. Paleogeography and basin development are relatively well constrained in the Oquirrh basin, but is more tentative in the Wood River basin where a lack of biostratigraphic control and structural complexities permit only tentative paleogeographic reconstruction.« less

Absolute dating of dedolomitization by means of paleomagnetic techniques

Research Article| August 01, 1985 Absolute dating of dedolomitization by means of paleomagnetic techniques R. Douglas Elmore; R. Douglas Elmore 1School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019 Search for other works by this author on: GSW Google Scholar William Dunn; William Dunn 1School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019 Search for other works by this author on: GSW Google Scholar Craig Peck Craig Peck 1School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019 Search for other works by this author on: GSW Google Scholar Author and Article Information R. Douglas Elmore 1School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019 William Dunn 1School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019 Craig Peck 1School of Geology and Geophysics, University of Oklahoma, Norman, Oklahoma 73019 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1985) 13 (8): 558–561. https://doi.org/10.1130/0091-7613(1985)13<558:ADODBM>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation R. Douglas Elmore, William Dunn, Craig Peck; Absolute dating of dedolomitization by means of paleomagnetic techniques. Geology 1985;; 13 (8): 558–561. doi: https://doi.org/10.1130/0091-7613(1985)13<558:ADODBM>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Paleomagnetic analysis, in conjunction with petrographic studies, is an approach whereby absolute dates can be placed on diagenetic events. Hematite is associated with dedolomite in the Lower Ordovician Kindblade Formation in south-central Oklahoma and is interpreted as a by-product of the dedolomitization of ferroan dolomite. Paleomagnetic results date the time of dedolomitization as Late Pennsylvanian-Early Permian. Dedolomitization was probably caused by oxidizing fluids with high calcium contents that migrated through the Kindblade Formation following uplift of the Arbuckle Mountains. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Genetic Lithostratigraphy of Dunkard Group, Southwestern Pennsylvania and Northern West Virginia: ABSTRACT

The Dunkard Group (Late Pennsylvanian-Early Permian) consists of 400 m of clastic sedimentary rocks with thin limestones and coals that were deposited in deltaic and alluvial-plain environments during the final stages of late Paleozoic sedimentation in the Appalachian basin. Lithofacies indicative of deposition in prograding, tidally influenced, high-constructive deltas dominate the lower Dunkard; these lithofacies are superseded up-section by alluvial-plain lithofacies. The distribution of lithofacies and paleocurrent data indicates that the fluival-deltaic systems prograded northward during deposition of the Dunkard. Sandstones of the Dunkard Group are typically multistory belt sands which were deposited by meandering rivers and highly sinuous delta distributaries. Petrographic analysis indicates that Dunkard sandstones are immature to submature litharenites derived from a mixed sedimentary, metasedimentary, and volcanic terrane, suggesting a collision orogene provenance related to Alleghenian suturing. Composition of the sandstones is strongly grain-size controlled and depositional environments influenced composition by controlling grain size. Constant composition through the section suggests no major change in source lithology or tectonic regime of the source area during Dunkard deposition. End_of_Article - Last_Page 960------------

Carboniferous-Permian Boundary Sequence of Northern Oquirrh Basin, Idaho-Utah: ABSTRACT

The Carboniferous-Permian boundary occurs in the middle of the Oquirrh Group in the northern part of the Oquirrh basin, the largest basin formed east of the Antler tectonic belt during the middle Carboniferous. Good sequences of fusulinid faunas for the northern part of the basin are exposed in the Sublett and Deep Creek Ranges of southern Idaho, a position midway between the basin's bathymetric low and the basin edge. In the Sublett Range, Late Pennsylvanian-Early Permian fusulinids occur through 1,500 m of mixed quartose sands and limestones of the Trail Canyon Formation and basal part of the overlying Hudspeth Cutoff Formation. The Missourian interval is thin relative to the Virgilian interval. Near the base of the Trail Canyon Formation, possible Missourian fusulinid aunas appear containing Triticites and Eowaeringella, and extend through a 250-m section, which is overlain by a 400-m section with Virgilian fusulinids, including Triticites sp. aff. T. cullomenensis and T. sp. aff. T. subventricosus. The Carboniferous-Permian boundary occurs at about the top of the middle limy unit of the Trail Canyon Formation, and Wolfcampian fusulinids, including Schwagerina and Pseudoschwagerina, occur through 800 m of section. Pseudofusulinella is common through Virgilian and Wolfcampian interval on the western side of the Sublett Range, but has not been found in this interval on the eastern side. Leonardian fusulinids have yet to be found here, contrary to earlier published reports. End_of_Article - Last_Page 1010------------

Paleogeography and Structural Development of Late Pennsylvanian-Early Permian Oquirrh Basin, Northwest Utah: ABSTRACT

Deposition in the late Paleozoic Oquirrh basin of northwest Utah produced as much as 7.5 km of limestone and sandstone. Study of Upper Pennsylvanian and Lower Permian lithofacies, trace fossils, and body fossils relative to a time framework determined by fusulinid biostratigraphy reveals a spatial mosaic of depositional environments which shifted through time. The Oquirrh basin changed in form from a broad, topographically subdued, shelf area in the Middle Pennsylvanian to a northwest-trending topographic basin in the Late Pennsylvanian. Water depths may have reached 300 to 400 m. Coarse conglomerates, commonly composed of older Oquirrh Group clasts, are common in latest Pennsylvanian and early Wolfcampian deep-water deposits. They record rapid lithification, uplift, and erosion of the margins of the trough, and imply that the Oquirrh basin was bounded by active northwest-trending high angle faults. The faults, with offset rates of about 25 cm/1,000 years, were apparently initiated in the Late Pennsylvanian, and became inactive by the late Wolfcampian. The upper Oquirrh Group records the passive filling of the remnant graben-like trough.The histories of the Oquirrh basin and of basement uplifts and yoked basins throughout the region to the south and east are similar. The northwest trend, high angle fault margins, and rapid structural development in the latest Pennsylvanian and early Wolfcampian demonstrate the Oquirrh basin's tectonic association with the regional deformation responsible for the Ancestral Rocky Mountains. End_of_Article - Last_Page 730------------

Reservoir Analysis, Pennsylvanian Tensleep Formation, Little Buffalo Basin, Wyoming: ABSTRACT

The Little Buffalo Basin field, in northwestern Wyoming on the southwest side of the Big Horn basin, is a north-south asymmetric anticline 3½ mi long, 1½ mi wide, with about 1,000 ft of structural closure. Oil was discovered in 1943 in the Pennsylvanian Tensleep. Cumulative production has been over 30 million bbl of oil from the 1,500 acres. Reservoir energy is from an active water drive from the north-northwest. A core study of the Tensleep revealed that extensive crossbedding, permeability variation, and fracture orientation influence oil recovery from this reservoir. The Tensleep sandstone and dolomite gradationally overlie the Amsden Formation carbonates and shales, and average 275 ft in thickness. There is a general increase in average grain size of the Tensleep sandstone progressing upward in the section and also an increasing amount of crossbedding and poor sorting. Deposition occurred in relatively high-energy transporting currents in a shallow water, nearshore, and/or deltaic marine environment. Nonmarine channeling and sanddunes also occur in the upper part of the section. Pore-filling cements of carbonate, silica, anhydrite, and clay particles are generally due to 2 factors: (1) primary deposition of carbonate and clay with dissolution of these and other minerals during fluvial channeling and erosion in Late Pennsylvanian-Early Permian, an (2) redeposition of these minerals in open pore spaces and fractures by downward-percolating groundwater. As a direct result of this reservoir study, well spacing has been reduced from 40 to 20 acres by drilling 30 new wells in certain areas of the field that would not otherwise have been efficiently depleted. These additional wells have accelerated production from 3,000 b/d to a new peak rate of 9,400 b/d and have increased ultimate oil recovery. End_of_Article - Last_Page 352------------

Paleomagnetism of the Hopewell Group, New Brunswick

Samples from 15 sites in the Shepody (11) and Enrage (4) formations (Late Mississippian and Early Pennsylvanian red sediments) in New Brunswick, Canada, were subjected to thermal demagnetization. At all but two sites, the fossil magnetization appears to be composed of two nearly opposed magnetizations. The sites fall naturally into two groups: group 1 with scattered directions and group 2 with well-grouped directions. At the 8 sites of groups 1, the two magnetizations (owing to different but overlapping stability spectra) can be detected but not separated. It is shown that at 5 of the 7 sites of group 2 both magnetizations were acquired before folding. The folding was Early Pennsylvanian, indicating that the fossil magnetization was acquired in the early history of the rock and partly before and partly after a field reversal. It is suggested that the magnetization is wholly or partly diagenetic in origin. The group 2 results (mean 357°, −19°; k = 19; pole 34°N, 119°E) are in close agreement with previously published results from the Maringouin formation of the Hopewell group. Comparison of the Hopewell group mean direction (178°, +20°; k = 32; pole 34°N, 118°E) with that of Late Pennsylvanian formations indicates that an apparent polar wandering (10°–15°) took place between Early Pennsylvanian and Late Pennsylvanian-Early Permian times. Direction analysis of the two magnetizations reveals no evidence of an inclination error in these sediments.