Miracle-dz/UniFAR-FTUs huggingface dataset:
Nonlithostatic pressure during sediment subduction and the development and exhumation of high pressure metamorphic rocks

A subduction shear zone can be modeled as a long narrow channel, with the flow of subducted metasedimentary rocks in the channel driven by two sets of forces: the downward shearing force exerted by the subducting slab and the gradient in the hydraulic potential, which combines the effect of both pressure and buoyancy. If the channel walls are effectively rigid, very slight narrowing or broadening of the channel (convergence angles 2 GPa in the channel at only 40 km depth. The model is consistent with a horizontal balance of forces across the plates and with a reasonable value for the thickness of subducted sediment (∼650 m). The practical limit for overpressures attainable in subduction zones is determined by the strength and permeability of the channel walls. At 40 km depth the channel is effectively confined on both sides by cold lithospheric mantle, which should be strong enough to support a significant tectonic overpressure. Episodic failure of the upper plate to produce great earthquakes at 30–40 km focal depth could vent overpressured fluid from the channel, allowing a cyclical buildup and release of both rock and fluid pressure. Topography on the subducting plate (e.g., seamounts and thinned continental crust) may lead to an anvil-like jamming of the channel and local high overpressures. Tectonic erosion by topography on the lower plate of slivers from overlying continental crust and the compression of these slivers between the topography and the narrowing channel walls could produce high overpressures in continental rocks. A decrease in the convergence rate or cessation of subduction, with a consequent general warming within the channel and associated viscosity decrease, promotes exhumation by buoyant reverse flow. The most rapid reverse flow occurs in the region of previously greatest overpressure. Since the exhumation distance is shorter than for a simple lithostatic pressure distribution and any increase in temperature is coupled with a strong increase in the rate of exhumation, preservation of high-pressure assemblages at the surface in fossil subduction zones is promoted for such a model.
Application of a normalized difference impervious index (NDII) to extract urban impervious surface features based on Landsat TM images

The ecological conditions of urban areas have been deteriorating in some aspects due to population growth and increasing expansion, with significant effects on human health. Impervious surface areas are an important indicator of urban ecological environmental change, therefore quickly and accurately estimating impervious surface areas is essential to monitoring the urban dynamics of change and human activities and their effects on urban environmental quality. Currently, few methods that are applied in estimating urban impervious surfaces are capable of providing results quickly and accurately. Accordingly, this study proposes a new index, named the normalized difference impervious index (NDII), based on Landsat TM images, which uses the visible (red, green, and blue) and thermal bands. The index was used to extract the impervious surface areas of Nanjing city, Jiangsu Province, China, and we assume that the average value of five times strict supervised classification is the true value of impervious surfaces. A combination of red and thermal bands extracted the impervious surfaces with a producer’s accuracy of 86.9%, a user’s accuracy of 84.6%, an overall accuracy of 91.4%, and a kappa coefficient of 0.8. The accuracy is 87.7% validated by high-resolution images. This method can rapidly extract urban impervious surface areas with promising accuracy.
Near‐surface macropore flow and saturated hydraulic conductivity in drained and restored blanket peatlands

The impacts of blanket peatland management on water tables, near‐surface macropore flow and saturated hydraulic conductivity were investigated using automated dipwells and mini‐disc tension infiltrometers. Three neighbouring hillslopes which were undisturbed, drained and restored by drain blocking were studied. Mean water table depths at the undisturbed sites were slightly shallower than at the restored site and water tables at both sites were significantly shallower relative to the drained treatment. Through time, however, the water table at the restored treatment behaved in a markedly different way to that at the undisturbed site. Water tables reached the peat surface for only 2% of the time for the drained and restored treatments compared to 18% for the undisturbed treatment. The proportion of runoff flowing through macropores in the near‐surface layers of the peat was found to be large (≥60%) across all three treatments, yet functional macroporosity was found to be significantly greater in the undisturbed peat relative to the two other treatments. Meanwhile, saturated hydraulic conductivity was found to be significantly higher at the restored treatment relative to the two other treatments, with mean conductivities ca. 1.5 times greater, suggesting a form of heightened soil–water interaction. Combined, the results indicate that although restoration by ditch blocking may result in a relatively successful water table recovery, there may not be the full reinstatement of peatland hydrological processes.
Changes in matrix thermal conductivity of clays and claystones as a function of compaction

Vertical matrix thermal conductivities of clays and claystones in onshore Denmark decrease with decreasing porosity, probably because of increasing orientation of highly anisotropic clay platelets during compaction. The relationship between vertical matrix conductivity λvm and porosity for this dataset can be expressed as either λvm=2.544exp(0.943φ) or λvm=2.749exp (0.637φ), depending upon the statistical methods used to analyse the data. Using the first equation the vertical matrix conductivity of the Danish clays and claystones is found to be about 4.9 W m−1 K−1 in highly porous sediments, decreasing to 2.54 W m−1 K−1 when porosity reaches zero. Using the second equation the vertical matrix conductivity of the Danish clays and claystones is about 4.3 W m−1 K−1 in highly porous sediments, decreasing to about 2.75 W m−1 K−1 at zero porosity. Anisotropy varies from an assumed value of 1.02 in highly porous clays to 2.44 at zero porosity using the first equation, and 1.87 at zero porosity using the second equation. These values agree well with measured data. This phenomenon is probably common or universal in fine-grained clay-rich sediments, and this method of data analysis could probably be applied to most or all claystone datasets. However, the equations derived in this study will be most appropriate for shales and claystones with comparatively high quartz contents similar to those of the samples analysed. Other specific relationships will probably exist for clay-rich shales and more-pure claystones.
Tides and long-term modulations in the Caribbean Sea

The tidal signal and its long-term variation in the Caribbean Sea is analyzed on the basis of hourly records from thirteen tide gauges five of which span more than 20 years. The seven larger tidal constituents are studied, namely the fortnightly term Mf, diurnal K1, O1, and P1, and semidiurnal M2, S2 and N2. The 18.61 year nodal modulation is clearly identifiable in almost all the examined constituents of lunar origin. However, its signal in M2 is less clear while it is almost imperceptible in N2, where the 8.85 year cycle caused by the eccentricity of the Moon's orbit and the orientation of its major axis variation dominates the long-term variability. The effect of the nodal variation in the amplitude and phase lag of the various tidal constituents is in agreement (within the 95% error limits) with the theoretical gravitational estimate, with the exception of the 8.85 year cycle in N2, where larger values are found. Overall, in the Caribbean the net effect of the low frequency cycles can change the maximum tidal range from 16.5% to 23.5% in a nodal cycle. Although the Caribbean is a micro-tidal environment this still results in changes of the range of up to 8.4 cm. Significant, spatially coherent trends are found for the amplitude of S2 (2.3 to 8.8 mm/cy.
Stakeholder Willingness to Pay for Watershed Restoration in Rural Bolivia 1

Abstract: Two CVM surveys were administered to 211 urban households and 188 rural farmer‐irrigators in the Comarapa watershed in Bolivia, South America, to estimate stakeholder willingness to pay (WTP) for a proposed upper watershed restoration program. Mean monthly household WTP to improve drinking water was $1.95 (65% of current charges), while mean annual WTP among farmer‐irrigators to improve irrigation water was $17 per hectare (34% of current costs). Aggregated to the entire population of households and farmer‐irrigators total WTP is $77,400 per year, which is 77% of the minimum cost to implement a watershed restoration program.
Contribution of mechanical dispersion of vapor to soil evaporation

Conventional methods for numerical simulation of the soil evaporation process do not take into account the mechanical dispersion of vapor in the porous matrix. This omission is due to the uncertainties about the flow process that generates mechanical dispersion and about the numerical value of dispersivity. In this study we assess three processes that can generate mechanical dispersion: (a) temperature variation, (b) barometric pressure variation, and (c) Stefan flow. Order of magnitude estimates show that under natural conditions, only Stefan flow can contribute significantly to the generation of mechanical dispersion. However, a simple sensitivity analysis of the effects of dispersivity on the contribution of different mechanisms to the evaporation process shows that diffusion and mechanical dispersion act in a complementary way. In simulations of a natural system, the evaporation flux increases by only 12% when dispersivity is increased from 0 m (no mechanical dispersion) to 0.078 m, although at the latter value the mechanical dispersion flux contributes up to 40% of the total evaporation flux.
Torsional response of structures for SH waves: The case of hemispherical foundations

A study is made of the harmonic torsional response of an elastic structure placed on a rigid hemispherical foundation which is supported on an elastic medium and is subjected to the action of obliquely incident plane SH waves. As a basic step in the solution of the torsion interaction problem, a closed-form solution is obtained for the torsional response of a rigid hemispherical foundation excited externally by a harmonic torque and through the soil by an obliquely incident plane SH wave. Comparisons between the results for a hemispherical foundation with those for a circular plate allow the estimation of the effects that the embedment of the foundation has on the torsional response of the superstructure.
Strain and vorticity analysis of transpressional high-strain zones from the Virginia Piedmont, USA

Abstract Strain and vorticity analysis of two Late Palaeozoic high-strain zones from the southern Appalachian Piedmont indicates that these zones experienced general shear transpression with a monoclinic to triclinic symmetry. Granitic rocks in the Brookneal high-strain zone from the southwestern Virginia Piedmont were transformed into mylonites under greenschist facies conditions. Sectional strains, estimated from quartz grain shapes, in mylonites range from three to ten and three-dimensional fabrics record flattening strains. The mean vorticity number (Wm) estimated with the Rs/θ method ranges from 0.3 to 0.95. In the central Virginia Piedmont, lower amphibolite facies deformation in the Spotsylvania high-strain zone affected biotite gneisses, amphibolites, and granitic pegmatites. Minimum sectional strains, estimated from folded and boudinaged pegmatite dykes, of 8–20 are common and three-dimensional strains are dominantly constrictional. Porphyroclast hyperbolic distribution analysis of ultramylonites yields Wn values from 0.4 to 0.8. The kinematic significance of these transpressional high-strain zones is threefold: they record tens to hundreds of kilometres of strike-slip offset; 40 to 70% contraction normal to the zone; and significant orogen-parallel material elongation.
Cities in a World Economy

Chapter 1. Place and Production in the Global Economy Chapter 2. The Urban Impact of Economic Globalization Chapter 3. National and Transnational Urban Systems Chapter 4. The New Urban Economy: The Intersection of Global Processes and Place Chapter 5. Issues and Case Studies in the New Urban Economy Chapter 6. The New Inequalities Within Cities Chapter 7. Global Cities and Global Survival Circuits Chapter 8. The Urbanizing of Global Governance Challenges Chapter 9. A New Geography of Centers and Margins
Zircon U-Pb ages, geochemistry, and Sr-Nd-Pb-Hf isotopic compositions of the Pinghe pluton, Southwest China: implications for the evolution of the early Palaeozoic Proto-Tethys in Southeast Asia

The geological record of the Neoproterozoic to early Palaeozoic Proto-Tethyan Ocean in Southeast Asia is not clear. To better constrain the evolution of the Proto-Tethys, we present new geochronology, geochemistry, and petrology of the late Cambrian to Ordovician Pinghe pluton monzogranite from the Baoshan block, western Yunnan, southwest China. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of four zircon samples yield ages of 482–494 and 439–445 Ma for the pluton, interpreted as two episodes within one magmatic event accompanying the whole process of subduction–collision–orogeny between buoyant blocks and oceanic crust of the Proto-Tethys. The monzogranite belongs to the strong peraluminous, high-K, calc-alkaline series and shows characteristics of both I-type and S-type granitic rocks. It is characterized by extremely high Rb/Sr and Rb/Ba but low TiO2, MgO, FeOt, and CaO/Na2O ratios. The monzogranite is also moderately enriched in light rare earth elements (LREEs), depleted in heavy rare earth elements (HREEs), lacks HREE fractionation, and has strongly negative Eu (Eu/Eu* = 0.06–0.49), Ba, Nb, Ta, Sr, and Ti anomalies. Whole-rock εNd(t) and εHf(t) values range from −8.7 to −11.6 and −5.55 to −9.58, respectively. Nd and Hf two-stage model ages range from 1.66 to 2.06 Ga and 2.14 to 3.00 Ga, respectively, with variable radiogenic 206Pb/204Pb(t) (16.547–18.705), 207Pb/204Pb(t) (15.645–15.765), and 208Pb/204Pb(t) (38.273–38.830). These signatures suggest that the monzogranite magma was derived from partial melting of heterogeneous metapelite, which was generated from Neoarchean to Palaeoproterozoic materials mixed with basaltic magma. The monzogranite magma underwent crystallization differentiation of plagioclase, K-feldspar, and ilmenite. Magmatism to form the Pinghe pluton occurred in a post-collisional setting. Based on the comparison of coeval granites throughout adjacent regions (e.g. Himalayan orogen, Lhasa Terrane, and parts of Gondwana supercontinent), we propose that the Baoshan block was derived from the northern Australian Proto-Tethyan Andean-type active continental margin of Gondwana and experienced subduction of the Proto-Tethyan oceanic crust and accretion of an outboard micro-continent. The Pinghe pluton could have formed when a subducting oceanic slab broke off during collision.
Vertebrate extinctions and reorganizations during the Late Silurian Lau Event

During the Silurian Period, as shown here by data from Gotland, Sweden, and other regions of the Baltoscandian paleocontinent, fish faunas were struck hard by extinctions caused by the late Ludlow Lau Event, also known for being associated with the largest positive stable carbon isotope excursion of the Phanerozoic. This event had a profound impact on the early evolutionary history of vertebrates, wiping out two-thirds of the fish taxa and causing significant ecological reorganizations over an estimated time span of similar to 200 ka. Our data show that immediately prior to the event, jawed acanthodians dominated the fish faunas, whereas the event led to a diverse fauna and a brief but marked dominance of the jawless thelodonts. The stepwise changes observed mimic those of conodonts, suggesting a similar mode of life and response to atmospheric oceanic perturbations for these clades. (Less)
Modeling Long‐Term Plutonium Transport in the Savannah River Site Vadose Zone

Improved understanding of flow and radionuclide transport in vadose zone sediments is fundamental to future planning involving radioactive materials. To that end, long‐term experiments were conducted at the Savannah River Site (SRS), where a series of lysimeters containing sources of different Pu oxidation states were placed in the shallow subsurface and exposed to the environment for 2 to 11 yr. After the experiments, Pu activity concentrations were measured along vertical cores from the lysimeters. Plutonium distributions were anomalous in nature—transport from oxidized Pu sources was less than expected, and a small fraction of Pu from reduced sources moved more. Studies conducted with these lysimeter sediments indicated that surface‐mediated, oxidation–reduction (redox) reactions may be responsible for the anomalies. This hypothesis is tested by performing transient Pu transport simulations that include retardation and first‐order redox reactions on mineral surfaces within a steady‐state flow field. These simulations affirm the consistency of the surface‐mediated, redox hypothesis with observed Pu activity profiles below the source. Such profiles are captured well by a steady‐state, net downward flow model. The redox model explains how Pu(V/VI) sources release activity that moves downward more slowly than expected, and how Pu(III/IV) sources result in a small fraction of activity that moves downward farther than expected. The calibrated parameter values were robust and well defined throughout all simulations. Approximate retardation factors for Pu(V/VI) were 15, and for Pu(III/IV) were 10,000. For these values, ko averaged 2.4 × 10−7 h−1; kr averaged 7.1 × 10−4 h−1 (standard deviations are 1.6 × 10−7 h−1 and 1.6 × 10−4 h−1 respectively).
Modeling the evolution of climate‐sensitive Arctic subsea permafrost in regions of extensive gas expulsion at the West Yamal shelf

Thawing subsea permafrost controls methane release from the Russian Arctic shelf having a considerable impact on the climate‐sensitive Arctic environment. Expulsions of methane from shallow Russian Arctic shelf areas may continue to rise in response to intense degradation of relict subsea permafrost. Here we show modeling of the permafrost evolution from the Late Pleistocene to present time at the West Yamal shelf. Modeling results suggest a highly dynamic permafrost system that directly responds to even minor variations of lower and upper boundary conditions, e.g., geothermal heat flux from below and/or bottom water temperature changes from above permafrost. Scenarios of permafrost evolution show a potentially nearest landward modern extent of the permafrost at the West Yamal shelf limited by ~17 m isobaths, whereas its farthest seaward extent coincides with ~100 m isobaths. The model also predicts seaward tapering of relict permafrost with a maximal thickness of 275–390 m near the shoreline. Previous field observations detected extensive emissions of free gas into the water column at the transition zone between today's shallow water permafrost (<20 m) and deeper water nonpermafrost areas (>20 m). The model adapts well to corresponding heat flux and ocean temperature data, providing crucial information about the modern permafrost conditions. It shows current locations of upper and lower permafrost boundaries and evidences for possible release of methane from the seabed to the hydrosphere in a warming Arctic.
Migration persistence across twentieth century India

This paper shows the remarkable persistence of remittance-based migrations in India across the twentieth century. Drawing on recent national survey data and unique census data at the district level, we show that for regions covering 20% of the population of India, poor and rich, mobility has been persistently high in magnitude and has been male-dominated, remittance-based and circular in nature for well over a 100 years. This paper highlights the importance of social networks and deep rooted migration cultures influenced by source region conditions, in explaining migration persistence, and argues that remittance economies constitute a unique model of development that needs to be judged separately from other development models.
Isotopic dates and strontium isotopic ratios for plutonic and volcanic rocks in the Quesnel Trough and Nicola Belt, south–central British Columbia

Four distinct igneous events of the southern Intermontane Belt are represented in new K–Ar and Rb–Sr dates. The first and regionally most important event is sharply defined by new K–Ar dates between 200 and 209 Ma for the Thuya, Wildhorse, Iron Mask, and Allison batholiths and a 205 ± 10 Ma Rb–Sr isochron for the Guichon Creek batholith. All these plutons were emplaced approximately at the change from Triassic to Jurassic time. The related and slightly older Nicola volcanic rocks are altered by addition of more radiogenic sedimentary Sr (Carnian Nicola limestones having 87Sr/86Sr = 0.7075 ± 1) and do not give an isochron date. The Coldwater stock is anomalously old (K–Ar dates range from 215–267 Ma). The Mid- to Late Jurassic igneous event is indicated by a 141 Ma K–Ar date for the Mount Martley batholith. Mid-Cretaceous volcanic rocks of the Kingsvale Group give a Rb–Sr isochron date of 112 ± 10 Ma and are postdated by the crosscutting and slightly younger Summers Creek stock (100 Ma by K–Ar). The final ev.
Stratigraphy and depositional environments of the Mamfe Formation and its implication on the tectonosedimentary evolution of the Ikom-Mamfe Embayment, West Africa

A 42 m thick outcropping portion of the Mamfe Formation is subdivided into Manyu (31 m thick) and Kesham (11m thick) Members on the basis of textural, mineralogical and structural differences. The Manyu Member (Albian) consists of folded and indurated, medium to coarse grained arkosic sandstones and thickly laminated organic-rich shales deposited in a lacustrine environment. The Kesham Member (Cenomanian) consists of subarkoses intercalated with massive green shale and mudstone deposited in a fluvial environment. The change in depositional environment was tectonically controlled. The mid Cretaceous paleogeography of the embayment was governed by the NE-SW trending “Ikom ridge” which prevented marine incursion from adjacent the Benue Sea. Evaporites found within the basin were precipitated from ocean water that was periodically spilled by strong tides and storms across the ridge into the embayment. The filling-up of the embayment to base level in the Cenomanian resulted in a shift in the depositional center downstream to adjoining lower Benue Trough. Similarity in heavy mineral composition and maturity of the Cenomanian sandstones with recent clastics in the embayment indicates their derivation from the same source terrain and relatively stable tectonic and climatic conditions at the source area since the Cenomanian time.
Talc-kyanite-quartz schists and other high-pressure assemblages from Zambia

Summary Talc-kyanite-quartz schists, Mg-chlorite-kyanite-quartz schists, kyanite gedritites, and kyanite-bronzite gedritites occur in the Central Province of Zambia. Experimental work in the system MgO-Al2O3-SiO2-H2O suggests that these assemblages formed at pressures in excess of 10 kb.