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At least 145 records · Page 8Linked to original sources
USGS2022

Can’t see the flowers for the trees: Factors driving floral abundance within early-successional forests in the central Appalachian Mountains

Silviculture can be a powerful tool for restoring and enhancing habitat for forest-dependent wildlife. In eastern North America, regenerating timber harvests support abundant wildflowers that provide essential forage for native pollinators. Factors driving floral resource availability within regenerating forests remain almost entirely unstudied. Recent efforts to increase the area of regenerating forests (<10 years old) through overstory removal harvest in the central Appalachian Mountains provide an opportunity to investigate the development of forest wildflower communities following canopy removal. We conducted 1208 surveys of blooming plants across 143 harvests, recording 1 525 245 flowers representing 220 taxa spanning 47 families. The number of flowers within recently harvested stands was negatively associated with fern and sapling cover but positively associated with grass and bramble ( Rubus spp.) cover. Early in the growing season, more flowers bloomed in older regenerating stands (e.g., >5 years old), but this pattern reversed by the end of the growing season. Ultimately, our study demonstrates that the abundance of flowers available to pollinators within regenerating hardwood stands varies with factors associated with advancing succession. Recognizing the potential trade-off between woody regeneration (i.e., saplings) and pollinator forage availability may benefit forest managers who intend to provide floral resources to flower-dependent wildlife like pollinators via silviculture.

Pennsylvania↗
USGS2006

Feasibility of an implantable capsule for limiting lifespan of grass carp

The grass carp (Ctenopharyngodon idella) is an herbivorous cyprinid stocked to control undesirable aquatic vegetation. However, stocking grass carp presents several problems including complete eradication of submersed aquatic vegetation, dispersal out of the target area, adverse effects on fish communities, and damage to waterfowl habitat and native vegetation. The purpose of this research was to consider the feasibility of an implantable capsule for limiting the lifespan of grass carp. Stainless steel dowel pins were inserted into 49 fish to identify the most appropriate site to implant the capsule. The throat region along the body's longitudinal axis was identified as the most suitable location because it resulted in minimal loss over an 8-month holding period. Rotenone solutions were injected into the ventral surface between the pelvic fins to determine the lethal dosage to 95% of the population (LD 95). The LD95 for grass carp increased curvilin-early with fish weight. Four polymers that merit further evaluation in constructing the capsule are poly[bis(p-carboxyphenoxy) propane anhydride], poly[bis(p- carboxyphenoxy) hexane anhydride], poly-1-lactide, and poly(??-caprolactone) . Implants are commonly used to deliver pharmaceutical products in medical and veterinarian applications, and have been used in fish. Developing a bioerodible capsule could increase the safety and flexibility of stocking grass carp for control of aquatic plants, and may also be applicable for management of other exotic species.

Journal of Aquatic Plant Management↗
USGS2011

Soil warming alters seed-bank responses across the geographic range of freshwater Taxodium distichum (Cupressaceae) swamps

Premise of the Study: Climate warming is predicted to have far‐reaching effects on the distribution of species, but those effects may depend on the flexibility of regenerating species in responding to climate gradients. We conducted a study to determine whether the variation in the response of seed banks to temperature varied across the latitudinal range of Taxodium distichum swamps in North America. • Methods: The soil was collected in a long‐term research network and heated experimentally to three current‐day spring normal soil temperatures (average maximum daily spring normal soil temperatures during May in Illinois, Arkansas, and Louisiana, USA, respectively: 22°, 25°, and 29°C). A “normal” is the mean temperature calculated over a 30‐yr interval (1971–2000). Seed‐bank density and biomass responses were examined in relation to latitude and difference in the soil temperature of the experiment and the spring normal. • Key Results: Using first‐ and second‐order regression analysis, we determined that the variation in total germination density was lowest mid‐range and in experimental soil temperatures similar to the spring normal. For some dominant species, the variance in germination density was higher in the northern ( Cephalanthus occidentalis ) or the southern part of the network ( Saururus cernuus and Polygonum pensylvanicum ). Overall, the variance of total biomass (root, shoot, whole plant) was higher if the experimental soil temperature was warmer than the spring normal. • Conclusions: Our results suggest that the regeneration of some populations of swamp species may have more flexibility to respond to climate warming than others.

Alabama, Arkansas, Florida, Georgia, Illinois, Ken↗
USGS1993

Fluvial response to late Quaternary climatic fluctuations, central Kobuk Valley, northwestern Alaska

Much of northwestern Alaska remained unglaciated during the Pleistocene and thus offers a favorable setting for examining long-term records of high-latitude geological and biological change. Epiguruk, a large cut bank 3.5 km long and up to 36 m high on the Kobuk River south of the Brooks Range in eastern Beringia, exposes complex sedimentary successions representing cycles of upper Quaternary alluviation and eolian sedimentation, downcutting, and soil formation. A rich record of plants and mammals is also preserved in the section. Deposits of fluvial channels and flood plains, eolian dunes, sand sheets, loess, and ponds, as well as organic soils (Histosols) are represented. Parallel-bedded fine sand and coarse silt couplets that commonly contain root structures, ripple cross-lamination, and silt drapes are flood-plain sediments apparently deposited at the interface of fluvial and eolian environments. Multiple fluvial-to-eolian depositional sequences were caused by influx of eolian sediment to the river from intermittently active dune fields south of the Kobuk River. Alluviation in the Kobuk Valley was coeval with glaciation in the Brooks Range, whereas downcutting occurred during interstadials when dune stabilization limited sediment supply. The depositional model developed at Epiguruk may be useful in interpreting some of the widespread subhorizontally stratified late-glacial deposits of Europe and North America.

Alaska↗
USGS2008

Trends in abundance of collared lemmings near Cape Churchill, Manitoba, Canada

Regular, multiannual cycles observed in the population abundance of small mammals in many arctic and subarctic ecosystems have stimulated substantial research, particularly among population ecologists. Hypotheses of mechanisms generating regular cycles include predator-prey interactions, limitation of food resources, and migration or dispersal, as well as abiotic factors such as cyclic climatic variation and environmental stochasticity. In 2004 and 2005, we used indirect methods to estimate trends in population size of Richardson's collared lemmings (Dicrostonyx richardsoni) retrospectively, and evaluated the extent of synchrony between lemming populations at 2 coastal tundra study areas separated by approximately 60 km near Cape Churchill, Manitoba, Canada. We collected scars on willow plants (Salix) resulting from lemming feeding. Ages of scars ranged from 0 to 13 years at both study areas. Scar-age frequency appeared cyclic and we used nonlinear Poisson regression to model the observed scar-age frequency. Lemming populations cycled with 2.8-year periodicity and the phase of the cycle was synchronous between the 2 study areas. We suggest that our approach could be applied in multiple settings and may provide the most efficient way to gather data on small mammals across both space and time in a diversity of landscapes. ?? 2008 American Society of Mammalogists.

Journal of Mammalogy↗
USGS2003

Environmental fate and effects of the lampricide bayluscide: a review

Bayluscide is an additive to TFM that increases the effectiveness of TFM as a lampricide. A review of the literature was undertaken to determine the environmental fate and effects of Bayluscide. Niclosamide (2', 5-dichloro-4'-nitrosalicylanilide), the active ingredient of Bayluscide, degrades rapidly in natural water and sediment systems, however, the rate of degradation is very slow in autoclaved samples. This difference suggests that degradation under laboratory conditions is dependent on microbial activity and hydrolysis plays a minor role in degradation of niclosamide. The major degradation product of niclosamide has been reported to be aminoniclosamide (2',5-dichloro-4'-aminosalicylanilide), which represented more than 50% of the residues extractable from sediments. Significantly more of the chemical is adsorbed to sediments with higher organic content and at lower pH's. The mobility of niclosamide in soil can be characterized as slight to medium; the estimated leaching distance would range from 0 to > 25 cm depending on the soil type and pH. The active ingredient of Bayluscide (niclosamide) is decomposed by ultra-violet light depending on the intensity and duration of the exposure. The uptake of residues by most invertebrates exposed to super(14)C-niclosamide is fairly rapid and equilibrium is reached within 24 h. About 90% of the accumulated residues were lost within 48 h after the organisms were transferred to clean flowing water. As with invertebrates, fish rapidly accumulate and eliminate residues of niclosamide. Three distinct residues were isolated from the extracts of edible fillet tissue; parent niclosamide, the glucuronide conjugate of niclosamide, and the sulfate ester of niclosamide. Aquatic plants and agricultural crops do not appear to be adversely affected at concentrations of Bayluscide used for lamprey or snail control. Mayflies (Hexagenia sp.). tend to be susceptible to TFM, but are relatively resistant to the effects of exposure to Bayluscide. Bayluscide was originally developed as a molluscicide to eliminate snails. Therefore, it is not surprising that mollusks are extremely sensitive to Bayluscide. Oral, dermal, and ocular administration of Bayluscide to mammals resulted in no clinical signs of systemic toxicity. Tests of the chronic effects of Bayluscide indicated that it is not mutagenic or carcinogenic. Bayluscide is not persistent in the environment; it breaks down in natural water and sediment systems through hydrolysis, photolysis, and microbial degradation. Given the limited use and tight control maintained by the U.S. Fish and Wildlife Service during applications of lampricides, Bayluscide presents minimal risk to human health and safety of the environment.

Journal of Great Lakes Research↗
USGS2021

Dominant Sonoran Desert plant species have divergent phenological responses to climate change

The southwestern U.S. is a global hotspot of climate change. Models project that temperatures will continue to rise through the end of the 21st century, accompanied by significant changes to the hydrological cycle. Within the Sonoran Desert, a limited number of studies have documented climate change impacts on the phenology of native plant species. Much of this phenological work to understand climate change impacts to phenology builds on research conducted nearly three decades ago to define flowering triggers and developmental requirements for native keystone Sonoran Desert woody species. Here we expand on the drivers and explore recent phenological trends for six species using a unique 36-year observational data set. We use statistical models to determine which aspects of climate influence the probability of flowering, and how flowering time may respond to climate change. We move beyond traditional models of phenology by incorporating different metrics of moisture availability in addition to temperature, weather, and climate at several time scales, including daily, weekly, seasonal, and antecedent conditions. Our results provide evidence of a trend towards earlier flowering (on the order of 1–4 days per decade) for five of the six species analyzed, and no trend for one species. The species we evaluated had contrasting phenological responses to different aspects of climate, suggesting individualistic changes in phenology and the potential of divergent plant community flowering patterns under future climate change. Understanding recent changes in flowering phenology and their climatic triggers is important to anticipating whether plant species can attract pollinators, reproduce, and persist within the community under continued climate change.

Arizona↗
USGS2009

Using packrat middens to assess grazing effects on vegetation change

Research on grazing effects usually compares the same sites through time or grazed and ungrazed sites over the same time period. Both approaches are complicated in arid environments where grazing can have a long undocumented history and landscapes can be spatially heterogenous. This work employs both approaches simultaneously by comparing grazed and ungrazed samples through both time and space using fossil plant macrofossils and pollen from packrat middens. A series of 27 middens, spanning from 995 yr BP to the present, were collected from Glen Canyon in southeastern Utah, USA. These middens detail vegetation change just prior to, and following, the historical introduction of domesticated grazers and also compares assemblages from nearby ungrazable mesas. Pre-grazing middens, and modern middens from ungrazed areas, record more native grasses, native herbs, and native shrubs such as Rhus trilobata, Amelanchier utahensis, and Shepherdia rotundifolia than modern middens from grazed areas. Ordinations demonstrate that site-to-site variability is more important than any temporal changes, making selection of comparable grazed versus ungrazed study treatments difficult. But within similar sites, the changes through time show that grazing lowered the number of taxa recorded, and lessened the pre-existing site differences, homogenizing the resultant plant associations in this desert grassland.

Journal of Arid Environments↗
USGS2002

FTIR and py-GC-MS spectra of true-fern and seed-fern sphenopterids (Sydney Coalfield, Nova Scotia, Canada, Pennsylvanian)

Sphenopterid specimens from the Late Pennsylvanian of Sydney Coalfield, Canada, are investigated by FTIR and py-GC-MS techniques as part of an on-going research project into the biochemistry and chemotaxonomy of Pennsylvanian-age pteridophylls. Included in the investigation are samples of the true-fern species Oligocarpia brongniartii and Zeilleria delicatula that are preserved as naturally macerated cuticles (NMC), and the seed-fern Eusphenopteris neuropteroides that is also preserved as a compression/impression. FTIR spectra of NMC seed-fern E. neuropteroides, and fern sphenopterid O. brongniartii are very similar, except that the latter does not have aromatic bands in the 700-900 cm-1 out-of-plane region, py-GC-MS show more aromatic compounds for the seed fern than for the two true-fern sphenopterids. Another difference between seed-fern and true-fern sphenopterids is a lower ratio of CH2 to CH3 in chemically treated specimens (CTC) for the seed fern. These observations suggest slightly higher aromaticity for the seed ferns, perhaps related to some chemotaxonomic differences. Comparison of FTIR and py-GC-MS characteristics of sphenopterids and other plant groups shows that these two techniques have potential to identifying chemotaxonomic signals from Carboniferous pteridophylls in general, although more data are needed to confirm this. ?? 2002 Elsevier Science B.V. All rights reserved.

International Journal of Coal Geology↗
USGS2022

Effects of 17α-ethinylestradiol and density on juvenile fathead minnow survival and body size

Anthropogenic changes have led to the increased use of wastewater treatment plants in stream systems near urbanized areas. Synthetic oral contraceptives, observed in wastewater treatment effluents, can cause negative effects on fish life history metrics. Previous exposures of 17α-ethinylestradiol (EE2) have been shown to affect survival and reproduction of fathead minnows ( Pimephales promelas ). However, density effects were not considered, and additional research is needed to examine the role of density among fish exposed to EE2. Multiple hypotheses indicate the interaction of density with contaminant exposure may ameliorate or exacerbate mortality. We examined how nominal EE2 concentrations of 0 ng/L, 5 ng/L, and 10 ng/L affect body size and mortality at various densities. Fish body size was influenced by density but not EE2 exposure. When density was high, we did not detect an effect of EE2 exposure on mortality. However, when density was low, EE2 exposures increased mortality. Thus, toxic effects of EE2 exposures were observable at low density but at high density, density-dependence in body size and mortality overwhelmed the effect of EE2. The results from our study provide insight into the relationship between density and EE2 exposures on fish survival and can be used to adjust population dynamic parameters for more accurate population dynamic estimates.

Journal of Aquatic Pollution and Toxicology↗
USGS2008

Relating groundwater to seasonal wetlands in southeastern Wisconsin, USA

Historically, drier types of wetlands have been difficult to characterize and are not well researched. Nonetheless, they are considered to reflect the precipitation history with little, if any, regard for possible relation to groundwater. Two seasonal coastal wetland types (wet prairie, sedge meadow) were investigated during three growing seasons at three sites in the Lake Michigan Basin, Wisconsin, USA. The six seasonal wetlands were characterized using standard soil and vegetation techniques and groundwater measurements from the shallow and deep systems. They all met wetland hydrology criteria (e.g., water within 30 cm of land surface for 5% of the growing season) during the early portion of the growing season despite the lack of appreciable regional groundwater discharge into the wetland root zones. Although root-zone duration analyses did not fit a lognormal distribution previously noted in groundwater-dominated wetlands, they were able to discriminate between the plant communities and showed that wet prairie communities had shorter durations of continuous soil saturation than sedge meadow communities. These results demonstrate that the relative rates of groundwater outflows can be important for wetland hydrology and resulting wetland type. Thus, regional stresses to the shallow groundwater system such as pumping or low Great Lake levels can be expected to affect even drier wetland types. ?? Springer-Verlag 2008.

Hydrogeology Journal↗
USGS2010

Occurrence of herbicides and pharmaceutical and personal care products in surface water and groundwater around Liberty Bay, Puget Sound, Washington

Organic contaminants, such as pharmaceuticals and personal care products (PPCPs), pose a risk to water quality and the health of ecosystems. This study was designed to determine if a coastal community lacking point sources, such as waste water treatment plant effluent, could release PPCPs, herbicides, and plasticizers at detectable levels to their surface water and groundwater. Research was conducted in Liberty Bay, an embayment within Puget Sound, where 70% of the population (∼10,000) uses septic systems. Sampling included collection of groundwater and surface water with grab samples and the use of polar organic chemical integrative samplers (POCIS). We analyzed for a broad spectrum of 25 commonly used compounds, including PPCPs, herbicides, and a flame retardant. Twelve contaminants were detected at least once; only N,N-diethyl-meta-toluamide, caffeine, and mecoprop, a herbicide not attributed to septic systems, were detected in more than one grab sample. The use of POCIS was essential because contaminants were present at very low levels (nanograms), which is common for PPCPs in general, but particularly so in such a small community. The use of POCIS allowed the detection of five compounds that were not present in grab samples. Data suggest that the community is contaminating local water with PPCPs; this effect is likely to increase as the population and product usage increase. The results presented here are a first step toward assessing the transport of herbicides and PPCPs into this coastal system.

Washington↗
USGS2012

Invasive species management restores a plant-pollinator mutualism in Hawaii

1.The management and removal of invasive species may give rise to unanticipated changes in plant–pollinator mutualisms because they can alter the composition and functioning of plant–pollinator interactions in a variety of ways. To utilize a functional approach for invasive species management, we examined the restoration of plant–pollinator mutualisms following the large-scale removal of an invasive nectar thief and arthropod predator, Vespula pensylvanica. 2.We reduced V. pensylvanica populations in large plots managed over multiple years to examine the response of plant–pollinator mutualisms and the fruit production of a functionally important endemic Hawaiian tree species, Metrosideros polymorpha. To integrate knowledge of the invader's behaviour and the plant's mating system, we determined the efficacy of V. pensylvanica as a pollinator of M. polymorpha and quantified the dependence of M. polymorpha on animal pollination (e.g. level of self-compatibility and pollen limitation). 3.The reduction of V. pensylvanica in managed sites, when compared to unmanaged sites, resulted in a significant increase in the visitation rates of effective bee pollinators (e.g. introduced Apis mellifera and native Hylaeus spp.) and in the fruit production of M. polymorpha. 4.Apis mellifera, following the management of V. pensylvanica, appears to be acting as a substitute pollinator for M. polymorpha, replacing extinct or threatened bird and bee species in our study system. 5.Synthesis and applications. Fruit production of the native M. polymorpha was increased after management of the invasive pollinator predator V. pensylvanica; however, the main pollinators were no longer native but introduced. This research thus demonstrates the diverse impacts of introduced species on ecological function and the ambiguous role they play in restoration. We recommend incorporating ecological function and context into invasive species management as this approach may enable conservation managers to simultaneously minimize the negative and maximize the positive impacts (e.g. taxon substitution) of introduced species. Such novel restoration approaches are needed, especially in highly degraded ecosystems.

Hawai'i↗
USGS2026

Multi-year cut-to-drown management limits Phragmites australis growth, belowground resources, and rhizome viability in Great Lakes wetlands

The distribution and abundance of Phragmites in the Great Lakes coastal zone has expanded in part due to its unique ventilation physiology and its ability to take advantage of changes in lake levels over the past several decades. During an extended period of low lake levels in the early 2000s, Phragmites expanded into vast shallow water areas as lake bottoms were exposed. Many of those populations were able to persist when lake levels rose several years later. Here, we investigate a management strategy, known as cut-to-drown, that takes advantage of elevated water levels to effectively control Phragmites by cutting stems underwater, thereby drowning the plant and depleting its stored resources. We tested the impacts of cut timing and frequency on the effectiveness of the cut-to-drown strategy through a multi-year manipulative field study. After two seasons of treatments, we found a 92–99 % reduction in stem density, depending on cut timing. Carbohydrate reserves in rhizomes declined 75–92 %, such that rhizome viability was reduced by 73–100 %, depending on cut timing. We found that cutting continuously (every 2–3 weeks) throughout two growing seasons was the most effective way to implement cut-to-drown but provide evidence that less frequent cutting could produce similar results. Our study provides important evidence to inform best management practices for cut-to-drown. Particularly as lake level fluctuations become more frequent and extreme in the future, cut-to-drown could serve as a useful tool for limiting Phragmites’ ability to persist in high water environments.

Michigan, Ohio↗
USGS2025

Detroit River becoming a crucible for boundary organization experimentation

The Detroit River has a long history of human use and abuse, resulting in public outcry over water pollution and resource degradation. This public outcry helped catalyze the enactment of many laws and the Canada-U.S. Great Lakes Water Quality Agreement which led to enhanced research, monitoring, and water pollution control. As pollution from industries and municipal wastewater treatment plants came under control and progress was made in management of single species, the focus shifted to a more comprehensive ecosystem approach that accounted for all the sources of pollution and targeted restoring ecosystem health with resilience. Over time, the Detroit River became a “proving ground” or crucible for experimenting with boundary organizations to overcome geographical, political, institutional, and disciplinary boundaries and strengthen science-policy-management linkages for ecosystem-based management. This study identified 15 boundary organizations functioning in the Detroit River watershed and evaluated two case studies – St. Clair-Detroit River System Initiative and State of the Strait Conferences. Key lessons learned from this study include: 1) establishing boundary organizations, promoting cooperative learning, and building capacity for boundary-spanning are essential for use of an ecosystem approach; 2) boundary spanning requires specific skills, experience, and improved linkages between research and practice; 3) the 15 boundary organizations provide a unique opportunity to collaborate in a community of practice to share knowledge, foster cooperative learning, enhance problem-solving, build trust, and demonstrate leadership; and 4) continued actionable science, investment in capacity building, and cooperative learning are essential to meet long-term goals of sustainability.

Detroit River↗
USGS2023

Variation in leaf reflectance spectra across the California flora partitioned by evolutionary history, geographic origin, and deep time

Evolutionary relatedness underlies patterns of functional diversity in the natural world. Hyperspectral remote sensing has the potential to detect these patterns in plants through inherited patterns of leaf reflectance spectra. We collected leaf reflectance data from across the California flora from plants grown in a common garden. Regions of the reflectance spectra vary in the depth and strength of phylogenetic signal. We also show that these differences are much greater than variation due to the geographic origin of the plant. At the phylogenetic extent of the California flora, spectral variation explained by the combination of ecotypic variation (divergent evolution) and convergent evolution of disparate lineages was minimal (3 to 7 %) but statistically significant. Interestingly, at the extent of a single genus ( Arctostaphylos ) no unique variation could be attributed to geographic origin. However, up to 18% of the spectral variation among Arctostaphylos individuals was shared between phylogeny and intraspecific variation stemming from ecotypic differences (i.e., geographic origin). Future studies could conduct more structured experiments (e.g., transplants or observations along environmental gradients) to disentangle these sources of variation and include other intraspecific variation (e.g., plasticity). We constrain broad scale spectral variability due to ecotypic sources, providing further support for the idea that phylogenetic clusters of species might be detectable through remote sensing. Phylogenetic clusters could represent a valuable dimension of biodiversity monitoring and detection.

California↗
USGS1978

Recognition of oxidized sulfide minerals as an exploration guide for uranium

The difference in color between tan to red oxidized sandstone and gray reduced sandstone on either side of the reduction-oxidation (redox) interface, which is- the locus of uranium concentration in roll-type deposits, has been noted and used locally as an exploration guide within known uranium districts. Reduced sandstone is characterized in many deposits by the presence of iron sulflde minerals (particularly marcasite and pyrite) that occur as replacements of and overgrowths on iron-titanium oxide minerals and plant debris and as cement of detrital grains. Oxidation of the sulfldes by oxygenated ground water forms yellow to red ferric oxide and ferric hydroxide phases ("limonite") that replace the FeS 2 minerals. Processes other than the oxidation of sulfldes, however, can cause reddening of clastic sediments without the creation of a redox boundary, and so color alone is not a sufficient condition by which to judge the potential for uranium ore in frontier areas. Ferric oxides that form by the oxidation of iron sulflde minerals can be distinguished from other forms of ferric oxide by reflection microscopic examination of polished grain mounts- and polished thin sections'. Diagnostic features of oxidized sulfldes are limonite pseudomorphs of sulfldes and limonite containing internal textures that mimic characteristic textures of previously sulfldized detrital phases. Recognition of oxidized sulfides by reflection microscopy, then, can distinguish oxidized sandstones, which might have a redox boundary downdip and which would therefore be favorable hosts for uranium concentration, from those without such potential.

Journal of Research of the U.S. Geological Survey↗
USGS1973

Permian paleogeography of the Arctic

Three large land areas were dominant in the Arctic during the Permian: Fennoscandia, central and southern Siberia (Angara), and Canada. Smaller landmasses were in China, the Seward-Chukotskiy region, northern and eastern Siberia, and near Alaska. Coal deposits and strata bearing land plants covered a large area in central Siberia; saline basins containing red beds formed in the Zechstein, Perm, and West Texas basins as the seas withdrew, generally in the later Permian. Eugeosynclinal troughs, apparently limited to the Pacific border regions, were marked by volcanism and deposition of predominantly clastic sediments in many areas. Platform and miogeosynclinal deposits, dominated by carbonate rocks, preceded saline deposition in the basins and persisted on shallow shelves adjacent to the geosynclines. The Arctic Permian marine fauna evolved in middle Permian time because of partial isolation of the Arctic areas from the southern ocean. Endemism, latitudinal temperature controls, and the effect of ocean currents explain in large part the faunal patterns in Permian seas. Post-Permian tectonic movements account for anomalies in the present positions of some rock sequences and fossils. Northeasterly drift and counterclockwise rotation of the northern landmasses are suggested. Right-lateral shear along the southern edge of Asia is supported, followed by northward movement of peninsular India.

Journal of Research of the U.S. Geological Survey↗