Midcontinental United States Research Articles

A geostatistical analysis of seismicity in Oklahoma using regression trees and neural networks

ABSTRACT Induced seismicity in the mid-continental United States remains an ongoing concern. In 2016, 4,672 small-magnitude earthquakes occurred in Oklahoma, which now ranks number one for earthquake frequency in the United States. It is thought that this rise in seismicity is related to wastewater disposal (WWD) into Oklahoma’s subsurface near previously inactive faults. Here we model these earthquake frequencies using Geographic Information Systems (GIS), spatial analysis, and machine learning statistical processes. Data representing WWD sites considered Area of Interest (AOI) by the Oklahoma Geological Survey (OGS) and Oklahoma Corporation Commission (OCC) were used, as well as the 2016 Oklahoma earthquake and fault data. Euclidean distance values from each earthquake to its nearest WWD site, nearest fault, and average fluid injection rate at each nearest AOI WWD site were used to develop two non-parametric regression models using Classification and Regression Trees (CART) and Neural Networks (NN). Results show (NN R2 = 0.745, RMSE = 0.47; CART R2 = 0.62, RMSE = 0.31) that proximity to AOI WWD sites, fluid injection rates, and adjacency to subsurface faults are sufficient to model seismicity in north-central Oklahoma. These results provide further support for the need for more restrictive guidelines related to WWD.

Explications des pressions de fluides transitoires à longue portée engendrées par le stockage d’eaux usées de champs pétrolifères à l’aide du principe de superposition hydrogéologique

Injection-induced earthquakes are now a regular occurrence across the midcontinent United States. This phenomenon is primarily caused by oilfield wastewater disposal into deep geologic formations, which induces fluid pressure transients that decrease effective stress and trigger earthquakes on critically stressed faults. It is now generally accepted that the cumulative effects of multiple injection wells may result in fluid pressure transients migrating 20–40 km from well clusters. However, one recent study found that oilfield wastewater volume and earthquake occurrence are spatially cross-correlated at length-scales exceeding 100 km across Oklahoma. Moreover, researchers recently reported observations of increasing fluid pressure in wells located ~90 km north of the regionally expansive oilfield wastewater disposal operations at the Oklahoma-Kansas border. Thus, injection-induced fluid pressure transients may travel much longer distances than previously considered possible. This study utilizes numerical simulation to demonstrate how the hydrogeologic principle of superposition reasonably explains the occurrence of long-range pressure transients during oilfield wastewater disposal. The principle of superposition states that the cumulative effects of multiple pumping wells are additive and results from this study show that just nine high-rate injection wells drives a 10-kPa pressure front to radial distances exceeding 70 km after 10 years, regardless of basement permeability. These results yield compelling evidence that superposition is a plausible mechanistic process to explain long-range pressure accumulation and earthquake-triggering in Oklahoma and Kansas.

Pre-Columbian lead pollution from Native American galena processing and land use in the midcontinental United States

Abstract The presence and sources of pre-Columbian (before 1492 CE) lead (Pb) pollution in the midcontinental United States were investigated using geochemical and Pb isotope analyses on sediment cores recovered from Avery Lake, a floodplain lake located directly adjacent to the Kincaid Mounds archaeological site on the lower Ohio River, Illinois. Geochemical results indicate the presence of Pb pollution during the Baumer (300 BCE to 300 CE) and Mississippian (1150–1450 CE) occupations, and since the 1800s. Pb isotope results link Mississippian Pb pollution to the processing and use of galena primarily from southeastern and/or central Missouri, and to a lesser extent the upper Mississippi River valley, with ∼1.5 t (metric tons) of galena-derived Pb deposited in Avery Lake during this time. Pb pollution during the Baumer phase, equating to ∼0.4 t of Pb, was not accompanied by a Pb isotope excursion and most likely originated from local biomass burning. These results provide new information about the environmental impacts associated with pre-Columbian Native Americans’ interaction with and utilization of their landscape and its resources.

Chronology of a Fortified Mississippian Village in the Central Illinois River Valley

ABSTRACTGeophysical survey and excavations from 2010–2016 at Lawrenz Gun Club (11CS4), a late pre-Columbian village located in the central Illinois River valley in Illinois, identified 10 mounds, a central plaza, and dozens of structures enclosed within a stout 10 hectare bastioned palisade. Nineteen radiocarbon (14C) measurements were taken from single entities of wood charcoal, short-lived plants, and animal bones. A site chronology has been constructed using a Bayesian approach that considers the stratigraphic contexts and feature formation processes. The village was host to hundreds of years of continuous human activity during the Mississippi Period. Mississippian activity at the site is estimated to have begun incal AD 990–1165 (95% probability), ended incal AD 1295–1450 (95% probability), and lasted150–420 yr (95% probability)in the primary Bayesian model with similar results obtained in two alternative models. The palisade is estimated to have been constructed incal AD 1150–1230 (95% probability)and was continuously repaired and rebuilt for15–125 yr (95% probability), probably for40–85 yr (68% probability). Comparison to other studies demonstrates that the bastioned palisade at Lawrenz was one of the earliest constructed in the midcontinental United States.

Mound building and summit architecture at the Carson site, a Mississippian mound center in the southeastern United States

Significant scholarly attention has been paid to monument construction, craft production, and leadership strategies in the Mississippian world (A.D. 1000 to A.D. 1540) of the Southeastern and Midcontinental United States. As new sites are discovered and new data brought into consideration, greater consideration can be made linking the building of large earthen mounds to social and political relationships. This article presents an archaeological and ethnohistoric consideration of mound building and mound summit use at Mound D at the Carson site, located in northwest Mississippi. Data from earthen mound excavation, mound summit architecture, material culture, and optically stimulated luminescence and radiocarbon (accelerator mass spectrometry) dating are used to discuss the formation of the monumental landscape beginning in the early 13th century. Several postulates are offered for the interpretation of mound construction and mound summit use.

Identification of a global sequence boundary within the upper Homerian (Silurian) Mulde Event: High-resolution chronostratigraphic correlation of the midcontinent United States with Sweden and the United Kingdom

Identification of a global sequence boundary within the upper Homerian (Silurian) Mulde Event: High-resolution chronostratigraphic correlation of the midcontinent United States with Sweden and the United Kingdom

Lead isotope trends and metal sources in the Mississippi Valley-type districts from the mid-continent United States

This study identifies metal-contributing source regions for Mississippi Valley-type (MVT) ore deposits in the Northern Arkansas district, the Tri-State district, and the Burkesville deposit in the Central Kentucky district. The Pb isotope ratios of sphalerite ores from the Tri-State district (208Pb/204Pb between 40.7443 and 41.2626; 207Pb/204Pb between 15.8633 and 15.9571; 206Pb/204Pb between 21.8373 and 22.1956) are congruent with the Pb isotope ratios defined by samples from the Central Missouri district, suggesting similar Pb sources. The ores from the Tri-State district plot in a narrow field and have higher 208Pb/204Pb values than samples from the Southeast Missouri district (Viburnum Trend and Old Lead Belt). The sphalerite samples from the Northern Arkansas district yield lower Pb isotope values (208Pb/204Pb between 39.4633 and 40.8863; 207Pb/204Pb between 15.8216 and 15.9176; 206Pb/204Pb between 20.2396 and 21.6438) than the Tri-State district ores and overlap the Southeast Missouri ores. The Northern Arkansas samples show a wide range of isotopic ratios with a linear trend, suggesting mixing of two end-member components. Age-corrected (250 Ma) Pb isotope ratios of Devonian-Mississippian Chattanooga shales from the Arkoma basin analyzed in this study plot close to the non-radiogenic end of the Northern Arkansas ores, implying that the shales may represent the non-radiogenic end-member that contributed Pb to the ores. The slope of the linear Pb isotope trend for the Northern Arkansas ores corresponds to an age of about 1.23 Ga, suggesting that the radiogenic Precambrian igneous basement may have supplied some of the ore Pb. Therefore, current data may indicate that the linear trend defined by Northern Arkansas ores may be the result of mixing of two end-members: the radiogenic basement rocks and the non-radiogenic shales.Pb isotope values of sphalerite from the Burkesville deposit are lower (208Pb/204Pb between 39.294 and 39.583; 207Pb/204Pb between 15.709 and 15.806; 206Pb/204Pb between 19.639 and 19.803) than those from the Northern Arkansas and Tri-State districts. The Pb isotope ratios of the Burkesville ores are similar to the Pb isotope values of the Central Tennessee (Elmwood deposit) and East Tennessee (Young deposit) ores and show evidence, the first of its kind for the region, of fluid mixing between the Illinois and Appalachian basins along the Cincinnati Arch that divides them.On the 208Pb/204Pb vs. 206Pb/204Pb diagram, the Pb isotope values of MVT ore samples from districts within the mid-continent US show two collinear, parallel trends, suggesting a different Th/U trend: (1) Tri-State and Central Missouri ore samples are collinear with Southeast Missouri and Northern Arkansas district samples; (2) Upper Mississippi Valley and Illinois-Kentucky ores are collinear with the Central Appalachian, Southern Appalachian (including East Tennessee), Central Tennessee, and Burkesville (Central Kentucky) ores.

Pitfalls in three-dimensional seismic interpretation: Footprints of an irregular source–receiver layout

ABSTRACT This paper shows how nonuniform source–receiver spacing in a three-dimensional (3-D) land acquisition creates footprints that could easily be mistaken for geology. In a 3-D time-migrated seismic volume from the midcontinent United States, amplitude extraction along the top of the Mississippian limestone formation shows a sinkhole-like feature, which is justified from a depositional perspective. However, an inspection of the acquisition layout shows that the sinkhole is a replica of the fold distribution. In land surveys where source and receivers seldom have a regular distribution and for unconventional plays that are not developed through patterned drilling, a thorough review of processing and acquisition parameters is necessary before interpreting amplitude maps.

Midcontinental Native American population dynamics and late Holocene hydroclimate extremes

Climate’s influence on late Pre-Columbian (pre-1492 CE), maize-dependent Native American populations in the midcontinental United States (US) is poorly understood as regional paleoclimate records are sparse and/or provide conflicting perspectives. Here, we reconstruct regional changes in precipitation source and seasonality and local changes in warm-season duration and rainstorm events related to the Pacific North American pattern (PNA) using a 2100-year-long multi-proxy lake-sediment record from the midcontinental US. Wet midcontinental climate reflecting negative PNA-like conditions occurred during the Medieval Climate Anomaly (950–1250 CE) as Native American populations adopted intensive maize agriculture, facilitating population aggregation and the development of urban centers between 1000–1200 CE. Intensifying midcontinental socio-political instability and warfare between 1250–1350 CE corresponded with drier positive PNA-like conditions, culminating in the staggered abandonment of many major Native American river valley settlements and large urban centers between 1350–1450 CE during an especially severe warm-season drought. We hypothesize that this sustained drought interval rendered it difficult to support dense populations and large urban centers in the midcontinental US by destabilizing regional agricultural systems, thereby contributing to the host of socio-political factors that led to population reorganization and migration in the midcontinent and neighboring regions shortly before European contact.

New productide brachiopods (Productoidea) from the Carboniferous of Ixtaltepec Formation, Oaxaca, Mexico

AbstractFrom the Santiago Ixtaltepec area, in Oaxaca State, southern Mexico, 11 species of productoid brachiopods, including a new genus and five new species, are described.Semicostellasp.,Antiquatoniasp.,Keokukia? sp.,Inflatia inflata,Reticulatiacf.R.huecoensis,Buxtonia websteri,Weberproductus donajiaen. gen. n. sp.,Dictyoclostus transversumn. sp.,Inflatia coodzavuiin. sp.,Buxtonia inexpletucostan. sp., andFlexaria magnan. sp. were collected from eight stratigraphic levels of the Ixtaltepec Formation. The presence ofSemicostellasp.,Keokukia? sp. andInflatia inflatain the basal strata, Units 1 to 3, of the formation indicate a Viséan-Serpukhovian (Late Mississippian) age.Reticulatiacf.R.huecoensisandBuxtonia websteri, found in Units 6 to 8, confirm the Pennsylvanian age for upper strata of the Ixtaltepec Formation.InflatiaandFlexariaare present in the uppermost beds of the formation so it is possible to extend their upper stratigraphic range to the Middle Pennsylvanian. All these taxa also occur in the United States Midcontinent, suggesting that during the Carboniferous the epicontinental sea extended at least to central Mexico.

Conuláridos misisípicos de Nochixtlán, Oaxaca, México: consideraciones sistemáticas, estratigráficas y paleobiogeográficas

MISSISSIPPIAN CONULARIIDS FROM NOCHIXTLAN, OAXACA, MEXICO: SYSTEMATICS, STRATIGRAPHIC AND PALEOBIOGEOGRAPHIC CONSIDERATIONS. This work represents the fi rst systematic study of conulariids of Mexico. Three species are described and illustrated: Conularia cf. C. subcarbonaria, Paraconularia chesterensis and P. cf. P. subulata, all of which come from four outcrops of the Santiago formation (informal unit), in the Santiago Ixtaltepec region, Nochixtlan municipality, Oaxaca. The stratigraphical distribution of these species corroborates the early Mississippian age (Osagean = late Tournaisian-early Visean) of the calcareous sandy lower member of the Santiago formation, and also supports the idea that at least part of the upper member belongs to the middle-late Mississippian (Meramecian-Chesterian = middle-late Visean). The studied conulariids reaffi rm the similarity between Carboniferous faunas of southwestern Mexico and those of the Mid-Continental United States, and hence the continuity of the epicontinental sea that covered both regions.

Palaeontological and sedimentological effects of micro-bioherms in the Middle Silurian Massie Formation of southeastern Indiana, USA

Small build-ups composed primarily of micrite and benthic skeletal remains, termed ‘micro-bioherms’, have been recognized within Silurian strata of eastern and midcontinental United States for well over 75 years; however, previous research has focused nearly entirely on such structures within the upper Wenlock (Homerian) Waldron Shale. An undolomitized section of the lower Wenlock (Sheinwoodian) Massie Formation in Ripley County, southeastern Indiana, was studied to assess the influence of micro-bioherms on palaeoecological, taphonomical and sedimentological patterns. Increased baffling of fine-grained material by organisms composing and/or encrusting build-ups is evidenced by muddy sediment containing pascichnial traces surrounding micro-bioherms. Pelmatozoan attachment structures densely encrust micro-bioherms, but are swollen by secondary stereomic overgrowths reflecting some form of antagonistic interaction or investment in strong affixation to elevated substrates. Clusters of bumastine trilobite material occur in ‘pockets’ related to cavities within build-ups, and otherwise rare spathacalymenid trilobites, often exceptionally preserved, are found in muds in the vicinity of partially buried micro-bioherms. Coeval sections nearby are nearly unfossiliferous as result of dolomitization, but contain recognizable skeletal material in greatest abundance in micro-bioherm flank beds. The occurrence of these bodies within the Massie Formation is genetically linked to a major transgressive episode, but also reflects a mid-Silurian climatic/palaeoceanographic change.

Evaluating a SAR TT-OSL protocol for dating fine-grained quartz within Late Pleistocene loess deposits in the Missouri and Mississippi river valleys, United States

The Mississippi and Missouri river valleys in the midcontinental United States contain extensive loess-paleosol sequences that are used to constrain the timing of expansion and retreat of the Laurentide Ice Sheet. Previous studies have been unsuccessful in producing finite ages for sediments older than ∼150 ka due to saturation of luminescence emissions. The thermally transferred optically stimulated luminescence (TT-OSL) dating technique is tested on the fine-grained (4–11 μm) quartz fraction of these loess deposits because the TT-OSL signal has been shown to grow with high (kGy) radiation doses. The TT-OSL signal continued to increase with radiation dose above 900 Gy. The optical and thermal stabilities of this TT-OSL signal are evaluated. Equivalent dose values are highly sensitive to preheat temperatures. Recycling ratios, zero-dose response values, and dose recovery tests all yield acceptable values for samples with burial doses >∼200 Gy. The apparent TT-OSL ages for the Roxana Silt (∼52–63 ka), Teneriffe Silt (∼66 ka), and Loveland Silt (∼133–192 ka) agree at 1σ level with previously published TL and IRSL ages derived from the same samples. For the oldest unit, the Crowley's Ridge Silt, TT-OSL ages (∼167–200 ka) are younger than IRSL or TL ages by ∼20%. This is interpreted as underestimation related to TT-OSL signal contamination, which can be avoided by isolating the fast component of the TT-OSL. Preliminary fast component TT-OSL ages for the Crowley's Ridge Silt (∼197–241 ka) favor deposition during marine oxygen-isotope stage (MIS) 7 or 8, contrary to a previous inference of a MIS 12 deposition.

Refining the identification of native American pipestone quarries in the midcontinental United States

Midcontinental pipestone quarries in Missouri, Minnesota, Wisconsin, Illinois, Ohio, and Kansas were utilized by a number of native cultures from 5000 YRBP through historic times. Except for Gunderson’s pioneering work on catlinite, the mineralogy of these sources was poorly understood until recently. For fifteen years, a University of Illinois team of archaeologists and geologists has used well-established mineralogical methods (X-ray diffraction [XRD] and reflectance near-infrared spectroscopy [NIS]) to identify and characterize nine pipestone quarries and match sources with archaeological artifacts from major Hopewell and Mississippian culture sites. NIS analyses of raw materials from nine major pipestone quarries show distinct mineralogical differences between sources but relatively uniform composition within each source. The major distinguishing minerals estimated from NIS spectra match very well with earlier results from XRD and inductively-coupled plasma (ICP) analyses. Results demonstrate that NIS is a reliable non-destructive technique for discriminating between midcontinental pipestones and for sourcing pipestone artifacts.

Hepatic Element Concentrations of Lesser Scaup (Aythya affinis) During Spring Migration in the Upper Midwest

High concentrations of some hepatic elements might be contributing to the decline of the continental lesser scaup (Aythya affinis) population. We evaluated hepatic element concentrations of male and female lesser scaup collected from the upper Midwest (Iowa, Minnesota, North Dakota, and South Dakota) during the 2003 and 2004 spring migrations. We measured concentrations of 24 elements in livers of 117 lesser scaup. We found that only selenium concentrations were at levels (>3.0 μg/g wet weight [ww)]) proposed to adversely affect reproduction. Approximately 49% of females (n = 61) had individual hepatic concentrations >3.0 μg/g ww selenium (Se). Our observed hepatic concentration of Se was similar to that reported in lesser scaup collected from the mid-continental United States but less than Se concentrations reported from the Great Lakes region. We found that the liver cadmium (Cd) concentration for males was significantly higher than that for females. Gender differences in hepatic Cd concentrations have not been previously reported for lesser scaup, but Cd is known to have negative impacts on male reproduction. Our results indicate that lesser scaup migrating through the upper Midwest in spring have elevated Se levels and that males carry a significantly greater Cd burden than females. Moreover, elemental concentrations might be high enough to affect reproduction in both male and female lesser scaup, but controlled laboratory studies are needed to adequately assess the effects of Se and Cd on lesser scaup reproduction.

Bromus tectorum (Poaceae) in midcontinental United States: Population genetic analysis of an ongoing invasion

Biological invasions can be substantially influenced by the genetic sampling associated with a species' introduction. As a result, we assessed the genetic and evolutionary consequences of the entry and spread of the invasive grass Bromus tectorum (cheatgrass) across the United States midcontinent through an analysis of 54 populations, using enzyme electrophoresis. On average, these populations display 1.04 alleles per locus (A), 4.1% percent polymorphic loci per population (%P) and an expected mean heterozygosity (H(exp)) value of 0.009. Heterozygotes, which have been rarely reported for B. tectorum in North America, occur in three populations in the midcontinent and are likely novel multilocus genotypes that arose postimmigration. The midcontinent distribution of multilocus genotypes suggests that plant immigrants came directly from either the native range or the eastern United States, or both. Continued dispersal of preadapted genotypes and the assembly of populations that are genetic admixtures may enhance this invasion by increasing both the genetic diversity within populations and the selection of novel genotypes arising from occasional outcrossing. The potential for postimmigration evolution in most species points to the largely unrecognized need to block the introduction of new, potentially aggressive genotypes of an alien species already in the United States.

New record ofChrysomya rufifacies(Diptera: Calliphoridae) in Canada: predicted range expansion and potential effects on native species

AbstractThis is the first report of the hairy maggot blow fly,Chrysomya rufifacies(Macquart), in Canada since its arrival in the continental United States of America in 1982. Specimens were collected from one swine (Sus scrofaL.) carcass in fall 2004 and again from six swine carcasses at three rural sites within the Windsor/Essex County region of southwestern Ontario in fall 2005. Based upon the biological characteristics of the species and the absence of specimens from spring and summer carrion-insect collections, it is suggested thatC. rufifaciesis present in southwestern Ontario during the fall season, after range expansion from the midcontinental United States of America during the spring and summer months. However, considering the projected increases in temperature due to global warming, establishment ofC. rufifaciesis predicted to extend well into southern Ontario and Quebec. Current and predicted distributions based upon the biological temperature requirements ofC. rufifaciesare depicted through geographic range maps. The potential economic and ecological impacts are discussed, with emphasis upon negative interactions betweenC. rufifaciesand several native blow fly species, particularlyCochliomyia macellaria(Fabr.).

Carbon–oxygen isotope signal of Mississippian slope carbonates, Appalachians, USA: A complex response to climate-driven fourth-order glacio-eustasy

Mississippian (Chesterian) ramp-slope muds in Virginia, deposited on the margin of a rapidly subsiding foreland basin, were not significantly reset isotopically by regional meteoric aquifer systems that affected units on the adjacent platform. Carbon and oxygen isotopic ratios of these muds tend to covary at the scale of the twelve 4th-order sequences that dominate the platform succession. The δ 13C values of the slope muds range from + 0.5 to + 4‰ PDB and lie in the range of least-altered contemporaneous brachiopods from North America, indicating little resetting of carbon isotopes by diagenesis. There is an approximately 1 to 2‰ decrease in δ 13C in the maximum flooding zone relative to the lowstand, followed by a positive shift upward in the highstand before becoming more negative toward 4th-order correlative conformities. Meteoric diagenesis might have reset some sediments just beneath a sequence boundary to lighter values; it cannot account for the observed shifts evident throughout the sequences. The 13C-enriched values in δ 13C profiles could be due to increased productivity during glacial stages. The increased productivity during glacial stages was probably due to increased ocean circulation, coupled with shallowing, which brought the ramp top into waters with more 13C-enriched dissolved inorganic carbon, with the opposite effects occurring during deglaciation. The δ 18O values of muds range from about − 2.2 to about − 4.6‰ PDB, falling within and beyond the lighter part of the range of contemporaneous North American brachiopods [Mii, H.S., Grossman, E.L., Yancey, T.E., 1999. Carboniferous isotope stratigraphies of North America; implications for Carboniferous paleoceanography and Mississippian glaciation. Geol. Soc. Am. Bull., 111, 960–973]. These values likely have been reset by burial diagenesis, and perhaps by some meteoric diagenesis just beneath correlative conformities. The sequences show negative excursions of 1 to 2‰ in δ 18O in the maximum flooding zone relative to the lowstand, and then become more positive upward in the highstand, then decrease toward the correlative conformities. Some of the preserved signal could reflect ice-volume changes, although this would account for only 0.5 to 1‰ change. The ice-volume effect during lowstands, plus cooling of ramp-top waters and small increases in salinity due to increased aridity in the Appalachian Basin, could account for the remaining 0.5 to 1.5‰ of oxygen isotope excursions, with the opposite effect occurring during high sea levels. The δ 18O and δ 13C of the Appalachian ramp-slope facies lack the strong 3rd-order trends of the mid-continental United States and Europe. The remnant 4th-order carbon and oxygen isotope signal is similar in structure to Cenozoic deep-sea isotope profiles that are due in large part to 4th-order glacio-eustasy. This would be compatible with onset of Late Paleozoic glaciation of Gondwana.

Tools for Carex revegetation in freshwater wetlands: understanding dormancy loss and germination temperature requirements

Carex is a globally distributed genus with more than 2000 species worldwide and Carex species are the characteristic vegetation of sedge meadow wetlands. In the mid-continental United States, Carex species are dominant in natural freshwater wetlands yet are slow to recolonize hydrologically restored wetlands. To aid in Carex revegetation efforts, we determined the dormancy breaking and temperature germination requirements of 12 Carex species. Seeds were cold stratified at 5/1°C for 0–6 months and then incubated in light at 5/1°C, 14/1°C, 22/8°C, 27/15°C, or 35/30°C. We found that all Carex species produced conditionally dormant seeds. The optimal temperature for germination for all but three species was 27/15°C. As is the case in other species with physiological dormancy, cold stratification increased germination percentages, broadened the temperature range suitable for germination, and increased germination rates for most species, but the magnitude of the effects varied among species. Many species germinated to 80% at 27/15°C without cold stratification and at 22/8°C with ≤1 month of stratification but required much longer stratification (up to 6 months depending on the species) to germinate to 80% at 14/1°C and 35/30°C. Our findings illustrate how a stratification pretreatment can greatly benefit Carex seed sowing efforts by triggering rapid germination to higher percentages. We recommend that cold stratification be targeted towards species with strong dormancy or used across a wider range of species when seed supplies for restoration are limiting. For Carex revegetation, establishing Carex canopies rapidly may help to prevent the invasion of undesirable species such as Phalaris arundinacea.

Cyclothem [“digital”] correlation and biostratigraphy across the global Moscovian-Kasimovian-Gzhelian stage boundary interval (Middle-Upper Pennsylvanian) in North America and eastern Europe

The long-standing difficulty of correlating Pennsylvanian strata among provincial faunal regions is resolved by effecting “digital” correlation of major glacial-eustatic cyclothems that represent high-stands when certain species achieved more global distribution than usual. In the late Moscovian–early Gzhelian (late Desmoinesian–early Virgilian) succession in the midcontinent United States, several major cyclothems are correlated, by both conodont species in common and cyclothem scale, with cyclothems in Russia (Moscow Basin) and Ukraine (Donets Basin), and the remaining cyclothems fit into the framework by position and scale. In this way the suggested event marker for the global Kasimovian-Gzhelian stage boundary (first appearance of Idiognathodus simulator ) is supported, while possible event markers for the Moscovian-Kasimovian boundary await further evaluation.