The role of dilute organic acids on calcite dissolution is important given the abundance of calcite and its importance in controlling surface and ground water geochemistry. The dissolution of calcite in the presence of three organic ligands, citrate, oxalate, and phthalate, has been investigated at 22° C and 10^5 Pa total pressure in a stirred, flow-through reactor. The input fluids were low salinity (I ranged from 0.001 to 0.02), Na-Ca-HCO3-CI solutions having an initial pH of 7.8. The dissolution rate of calcite in a ligand-free solution is essentially linear with respect to log undersaturation. In a purely inorganic solution, the dissolution rate equals 5.95 x 10·13 mol cm^-2 sec^-1 at log (IAP/K) of -1.25 and a surface area of 1890 cm^2/g. Concentrations of the ligands range from 10 to 5000 µm/1. Citrate at a concentration of 50 µm/1 appears to have no effect on calcite dissolution rates. Oxalate, at concentrations of 50 and 100 µm/l, decreases the rate of calcite dissolution. The dissolution rate of calcite in a solution containing 50 µM oxalate at log (IAP/K) -1.25 is approximately 2.60 x 10^-13 mol cm^-2 sec^-1. Phthalate decreases calcite dissolution at low concentrations, i.e., up to 50 µm/l. In some cases, the calcite dissolution rates were decreased to less than 10% of the rates found in the purely inorganic solution. For example, at a concentration of 50 µM phthalate, the calcite dissolution rate was approximately 0.49 x 10^-13 mol cm^-2 sec^-1. The decrease in calcite dissolution at low concentrations is believed due to the ligand complexing with surface dissolution sites. Higher concentrations of phthalate, 100 to 5000 µm/1, actually increase the rate of dissolution relative to changes due to simple IAP/K parameters. At a concentration of 100 µm/l phthalate, the calcite dissolution rate is 3.92 mol cm^-2 sec^-1 x 10^-13 at log (IAP/K) of -1.25. This increase in calcite dissolution is thought to be caused by the destabilization of surface sites. Calcite surfaces were examined by SEM at magnifications up to 4000x. Different organic ligands produce different etch and dissolution features. / Earth and Environmental Science

The magnetic conglomerate test was applied to samples from eight Cretaceous diatremes located in and around the Oka Carbonatite Complex near Montreal, Canada. Fifty-four subsamples from the eight diatremes were tested in an attempt to place constraints on their temperatures of emplacement. These eight outcrops were chosen because they appear to petrographically represent different facies of diatreme emplacement. The opaque minerals samples were petrographically analyzed using reflected light and chemically analyzed using an electron microprobe for evidence of major alterat1on. Several discrete subsamples from each sample were cleaned magnetically using A.F. and thermal demagnetizers. The subsamples of each sample were found to have similar high temperature primary thermoremanent magnetization. The alpha-95 numbers, a measure of the precision of the calculated mean plot, ranged from 10 ° to 25 ° . These small cone angles equate with a high degree of non-randomness. This concordancy of thermoremanent magnetizations (TRM's) suggests that the magnetic minerals of the diatremes were locked in place as constituents of a solidified magma before the temperature of the minerals dropped below the 555°C average blocking temperature (calculated using Vegardian assumptions) of the magnetic minerals in the diatremes. The temperature of 555°C determined by this project, allows heat budget modelling taking into account the Joule-Thomson effect, addition of relatively cold xenoliths, the heat of crystallization of magma, and the original heat of the magma. A maximum of 2.4 x 1019 calories (including 10km^3 of1200°C magma and an endothermic Joule-Thomson effect) and minimum of 4.2 x 1015 calories (including 0.1 km^3 of 720° C magma and an exothermic Joule-­Thomson effect) could be calculated as the heat given off from an entire diatreme. The endothermic Joule-Thomson effect could not have been important in the Oka diatreme outcrops because CO2 is not endothermic until a depth of 2.5 km. , and the erosion level at Oka is at least 2.4 km deep. Relative to the magnetic blocking temperature of 555° C from this study, if Oka diatremes were CO2-rich then the J-T cooling effect would only have been involved after the magnetic imprinting. The exothermic Joule-Thomson effect was relatively insignificant in magnitude, and had little effect on the overall heat budget of the diatremes. / Earth and Environmental Science

The Upper Silurian Williamsport Sandstone Member of the Bloomsburg Formation, upper Ludlovian to lower Pridolian in age, is the initial deposit of the Salina Group second order supersequence. The Salina Group supersequence includes the Wills Creek and Tonoloway Formations which together may encompass as much as 10 million years. The Williamsport Sandstone interval contains a unique combination of facies, including thick quartz sandstones, hematitic ironstones and fossiliferous limestones, not found together in the rest of the overlying Salina supersequence. The stratigraphy of the Williamsport Sandstone displays a hierarchic cyclic structure consistent with the Milankovitch model of orbital forcing. This distinctive carbonate and quartz sandstone unit is divisible into three 5th order (100 k.y.) short eccentricity cycles representing most of a 4th order (400 k.y.) long eccentricity cycle. Fifth order sequences contain two to five 6th order (20 k. y.) precessional cycles or PACs. Each 5th order sequence is highly asymmetric, with cycles containing deeper facies in the lower part of the sequence and cycles containing shallower facies toward the top. These 5th order sequences and most of their internal cyclic elements can be traced over 100 kilometers from Keyser, West Virginia to Mount Union, Pennsylvania. Their facies are largely marine to the south in West Virginia and Maryland and are predominantly non-marine to the north at Mt. Union, Pennsylvania. At Mt. Union there is a loss of PACs (6th order cycles) in the upper part of each 5th order sequence due to hiatus or vacuity in the onshore direction. Correlation of precessional and eccentricity cycles over significant distances constitutes evidence of a process-determined hierarchy of allocycles based upon the Milankovitch orbital forcing model. / Earth and Environmental Science

The Huntingdon Valley shear zone is a zone of high-strain ductile deformation which strikes N70E between the Schuylkill River and the Delaware River. In the study area, there are seven lithologic units within the shear zone: Wissahickon Formation (oligoclase-mica schist), Chickies Formation ( quartzite), felsic gneiss (pyroxene-bearing rock), mafic gneiss (hornblende-bearing rock), and three carbonate units. Strain is heterogeneous across these units. High soil-radon (222Rn) concentration correlates both with lithology and the magnitude of strain of the bedrock. High concentrations of radon gas {222Rn) were found in soils derived from highly deformed rocks of the Huntingdon Valley shear zone and two other zones to the south. For this study, the Huntingdon Valley shear zone (HVSZ) was verified as being a structure associated with high radon emissions regardless of lithology. Within one lithology, Wissahickon Formation, radon levels outside the zones of shear range from 170 to 2,639 pCi/L, whereas inside the zone, soil radon was recorded as high as 6,380 pCi/L. The Chickies Formation averages 1,931 pCi/L inside the shear zone and 634 pCi/L outside the shear zone. The felsic gneiss has low radon emissions throughout, while the Conestoga shows differences. These differences could be the result of unexposed shear zones. / Earth and Environmental Science

This study investigates major and trace element geochemistry of ground and surface water in the New Jersey Pine Barrens (around Wharton State Forest). The chemical composition of dissolved species of Cohansey Formation groundwater differs from that of the underlying Kirkwood Formation. The difference implies that groundwater from the two formations has different sources, geochemical processes and flow patterns and that cross-formational flow between them is minor. The source of iron in bog iron deposits in the New Jersey coastal plain is thus not from cross-formational flow from a deeper formation, but from within the Cohansey Formation. Chemistry of Cohansey groundwater is mainly controlled by precipitation (rain and snow) with limited water:rock reactions. Solutes in Kirkwood groundwater are mostly derived from water:rock reactions because Kirkwood groundwater is controlled by regional flows that have long residence time. The presence of clay and other confining layers contributes to the heterogeneity of groundwater composition, even over short distances. Most well waters did not show seasonal variations in composition because groundwater has residence time longer than a year. Stream water is similar to Cohansey groundwater in major element composition, which shows that stream and shallow groundwater are both dominated by precipitation composition and that there is extensive recharge interchange between them. The low pH values of surface water (average 4.5) and Cohansey groundwater (average pH = 5.3) appear to be affected by acid rain in this region. High pH of Kirkwood groundwater (average 8.3) is caused by water:rock reactions in the Kirkwood Formation. Na+/Cl- in the Cohansey groundwater has a ratio (0.577) close to that in seawater (0.55), indicating Na+ and Cl- are from marine aerosols. When pH is greater than 4.8, aluminum concentration is consistent with controls by gibbsite or/and kaolinite solubility. However, when pH is less than 4.8, Al is undersaturated with these minerals. At low pH, Al activity is controlled by saturation with organic aluminum phases having low Al/COOH ratios. / Earth and Environmental Science

Hydrogeological characteristics, including the elevation of the potentiometric surfaces of the major aquifers and their fluctuations over a 5-year period (1990-1994) in the coastal plain of New Castle County, Delaware, are discussed in detail in this study. Fluctuations in water levels and well production rates from data collected over a 15-year period (1980 to 1994) from more than 30 production - and 20 monitoring wells in the study area reveal that pumping in the tens of thousands of cubic meters (millions of gallons per day) has lowered potentiometric surfaces near major industrial wellfields by 20 meters or more. Since around the mid-l 970s equilibrium has been established between recharge to the aquifer system via annual rainfall and discharge from the aquifers through seepage into surface water bodies and industrial water usage. However, industrial, municipal, and agricultural users continue to place great demand on the aquifer system, and the centers of several cones-of-depression near industrial-use wellfields are now well below sea level. A steady-state simulation of regional flow aids in conceptualization of the interaction between the stresses which affect the regional aquifer system. The lowering of water levels by withdrawal of large amounts of water for industrial use opens the possibility of subsidence near the larger wellfields. Additionally, large cones-of-depression cause reversal of flow gradients, thereby complicating remediation efforts (such as those proposed for CERCLA sites, e.g. the Delaware City Industrial Zone) and potentially creating a water quality problem of salt-water intrusion from the nearby Delaware River estuary. / Earth and Environmental Science

The Huntingdon Valley-Cream Valley shear zone system (HV-CV) is a major structure in the Pennsylvania Piedmont that separates rocks with contrasting metamorphic and deformational histories. A steep gradient in Bouguer gravity anomalies, up to 3 mgal/km, coincides with the shear zone system. The gradient, a regional anomaly on both the Bouguer gravity anomaly map and the isostatic residual anomaly map, goes through the entire study area from southwest to northeast. The calculation of Bouguer horizontal derivative anomalies narrows the anomalous source of the gradient to the HV-CV shear zone, which is several kilometers south of the traditional Martic Line. The lack of linear anomalies along the HV-CV shear zone system on the Bouguer vertical second derivative anomaly map suggests that the major density contrast, which produces the gradient, is in the lower crust or upper mantle. Further modeling of Bouguer gravity profiles across the HV-CV shear zone shows that the best model is one with a density of 0.35 glee, and a steplike offset of about 8 km with a steep dip angle at depth of 25 km to 33 km, which could be an offset in the Moho surface. Therefore, the HV-CV shear zone system is interpreted to be a lower crustal structure producing a large offset in the Moho surface. The gravity modeling supports the interpretation that the HV-CV shear zone system is a steeply-dipping Paleozoic terrane boundary in the southeastern Pennsylvania Piedmont. / Earth and Environmental Science

The phosphate industry in the state of Florida is the largest producer of phosphate in the country, producing about one-third of the world's phosphate. By-product gypsum slurry from this industry is allowed to precipitate in large ponds where a topographical "stack" of waste material is created. Environmental concern for this practice is two-fold, involving the hydraulic impact of the topographic mound on the surficial aquifer, and the contaminants (radionuclides and hydrofluoric acid) contained within the highly acidic (pH = 1.0-3.0) process water (most stacks are unlined). This study has characterized hydrologic parameters (i.e. transmissivity and storativity) of this gypsum stack, and has mathematically modeled volumetric fluxes of water in the system. Results can be used to determine the chemical impact of contaminants through further geochemical speciation and transport modeling, although none has been attempted here. Although the water budget analysis of the stack indicates a large flux of process water from its base (1591 m^3/day), only a small portion (~1%) of this total is modeled as having an impact on regional flow. Most of the process water drains into ditches from which it evaporates. When other potential water losses are considered (i.e. drain dewatering from the stack interior and flank evaporation) the actual impact of stack waters may be even less. Sensitivity of the modeled environment shows that leakage rates from the gypsum stack are the most critical values determined in this research. Assumption of steady state water volumes in stack ponds provides a direct calculation of the leakage rate (3.0 x 10^-4 day^-1) from evaporative losses; essentially, output rates equal input rates. Findings in this research are in support of the topographical mounding theory, and provide a model upon which volumetric water flux from above-ground tailings piles can be determined. This groundwater model has been tailored to fit the site-specific characteristics of the situation considered, but can be applied to virtually any medium of groundwater flow in the same configuration / Earth and Environmental Science / Accompanied by one .pdf file: 1) Shinkawa-Supplemental-1997.pdf

Chertification in the 4th-order (400 ky) sequence of the Lower Devonian New Creek and Corriganville Formations is primarily controlled by high-frequency sea-level fluctuations. The New Creek Formation (one or two 5th-order sequences) is divisible into six small-scale allocycles, in which chert occurs at cycle boundaries. The Corriganville Formation (two 5th-order sequences) is composed of nine laterally correlative small-scale cycles, in which chert occurs at cycle boundaries as well as at sea-level-fall surfaces and in high-stand portions of the cycles. The position of chert in the allocyclic framework is primarily controlled by stratigraphic processes, while inhomogeneities in sediments and supply of diagenetic ingredients are secondary controls. For example, chert morphology, which varies from bedded to nodular, seems to be controlled by inhomogeneities in the sediments. Stratigraphic processes act through control of sedimentation rates; in these shallow, below-wave-base environments, seclimentation of carbonate and terrigeneous matter ceased at cycle boundaries in the New Creek and Corriganville Formations and at sea-level-fall surfaces in the Corriganville Formation, and was intermittent during the high-stand portions of cycles in the Corriganville Formation. Silica accumulated undiluted during cycle boundary times; the silica from these primary locations of accumulation migrated later to a nearby host. In addition to controlling concentrated accumulation of siliceous sediments, stratigraphic processes enhanced chert formation by promoting diagenetic reactions in the sulphate reduction zone. In this manner the occurrence of chert in the New Creek and Corriganville Formations corresponds to the allostratigraphic framework and was controlled by stratigraphic processes. / Earth and Environmental Science / Accompanied by one .pdf file: 1) WolfEskel-Supplemental-1997.pdf

The Cream Valley Shear Zone, in southeastern Pennsylvania, contains a proposed terrane boundary between Laurentia (north of the shear zone) and a displaced terrane (south of the shear zone). The Cream Valley shear zone is part of a Paleozoic dextral strike-slip shear zone system which extends from New Jersey through southeastern Pennsylvania and into Maryland. Within the field area, in southeastern Pennsylvania, the Cream Valley Shear Zone varies in width from 3 to 5 km and is characterized by a strong, penetrative, steeply dipping foliation with an overall strike of N70°E. The proposed terrane boundary lies between retrograde greenschist-facies phyllonite and prograde greenschist-facies phyllite near the southern edge of the shear zone. The terrane boundary divides Laurentian shelf sequence lithologies, including Cambrian Chickies quartzite and Cambro-Ordovician carbonates, from high-grade metamorphic rocks of the southern terrane. Rocks of the Laurentian cover sequence have experienced peak metamorphism of greenschist facies and a simple deformation history; at some localities primary structures are preserved. The southern terrane consists of schists and gneisses with some ultra-mafic pods. South of the boundary, Laurentian shelf-sequence rocks do not occur. Southern lithologies have experienced amphibolite to granulite facies metamorphism. Structures in these rocks indicate a complex deformation history not observed in the Laurentian rocks to the north. To the east the Cream Valley shear zone Is continuous with the Huntingdon Valley Shear Zone, which also separates distinct lithologies and metamorphic grades. A gravity anomaly, which is interpreted to result from major crustal offset coincides with the Cream Valley shear zone. Dissimilarities in lithology, metamorphic grade and deformation history north and south of this structure indicate that these rocks are not correlative. Paleozoic orogen-parallel displacement on a terrane boundary may explain the juxtaposition of these distinctly different metamorphic suites. / Earth and Environmental Science / Accompanied by one .pdf file: 1) Broh-Supplemental-1998.pdf