Upper crustal fluid flow in the outboard region of the Southern Alps,New Zealand

The currently active fluid regime within the outboard region of the Southern Alps, New Zealand was investigated using a combination of field observations, carbon‐ and oxygen‐stable isotopes from fault‐hosted calcites and interpretation of magnetotelluric (MT) data. Active faulting in the region is dominated by NE striking and N striking, oppositely dipping thrust fault pairs. Stable isotopic analyses of calcites hosted within these fault zones range from 10 to 25‰δ¹⁸O and from ?33 to 0‰δ¹³C. These values reflect mixing of three parent fluids: meteoric water, carbon‐exchanged groundwater and minor deeper rock‐exchanged fluids, at temperatures of 10–90°C in the upper 3–4 km of the crust. A broad, ‘U‐shaped’ zone of high electrical conductivity (maximum depth c. 28 km) underlies the central Southern Alps. In the ductile region of the crust, the high‐conductivity zone is subhorizontal. Near‐vertical zones of high conductivity extend upward to the surface on both sides of the conductive zone. On the outboard side of the orogen, the conductive zone reaches the surface coincident with the trace of the active Forest Creek Faults. Near‐surface flow is shown to dominate the outboard region. Topographically driven meteoric water interacts, on a kilometre scale, with either carbon‐exchanged groundwater or directly with organic material within Pliocene gravels, resulting in a distinctive low ¹³C signal within fault‐hosted calcites of the outboard region. The high‐strain zone in the lower crust focuses the migration of deeply sourced fluids upward to the base of the brittle–ductile transition. Interconnected fluid is imaged as a narrow vertical zone of high conductivity in the upper crust, implying continuous permeability and possibly buoyancy‐driven flow of deeply sourced fluids to higher levels of the crust where they are detected by the isotopic analysis of the fault‐hosted calcites.     

Permeability of the continental crust: dynamic variations inferred from seismicity and metamorphism

The variation of permeability with depth can be probed indirectly by various means, including hydrologic models that use geothermal data as constraints and the progress of metamorphic reactions driven by fluid flow. Geothermal and metamorphic data combine to indicate that mean permeability ( k ) of tectonically active continental crust decreases with depth ( z ) according to log  k  ≈ −14–3.2 log  z , where k is in m² and z in km. Other independently derived, crustal-scale k – z relations are generally similar to this power-law curve. Yet there is also substantial evidence for local-to-regional-scale, transient, permeability-generation events that entail permeabilities much higher than these mean k – z relations would suggest. Compilation of such data yields a fit to these elevated, transient values of log  k  ≈ −11.5–3.2 log  z , suggesting a functional form similar to that of tectonically active crust, but shifted to higher permeability at a given depth. In addition, it seems possible that, in the absence of active prograde metamorphism, permeability in the deeper crust will decay toward values below the mean k – z curves. Several lines of evidence suggest geologically rapid (years to 10³ years) decay of high-permeability transients toward background values. Crustal-scale k – z curves may reflect a dynamic competition between permeability creation by processes such as fluid sourcing and rock failure, and permeability destruction by processes such as compaction, hydrothermal alteration, and retrograde metamorphism.     

Heterogeneity effects on possible salinity-driven free convection in low-permeability strata

Although studies of free convection commonly focus on highly permeable strata, but numerical analyses indicate that density-driven free convection may also occur in heterogeneous low-permeability strata. Traditional Rayleigh number criteria are overly conservative in predicting thermohaline convection in these systems; so, numerical models are used to make inferences on the process. Simulations with stochastic realizations of permeability fields show that dense plumes can take preferential pathways to sink through generally low-permeability strata; patch analysis using percolation theory shows that the threshold permeability for the onset of free convection can be as low as 10⁻¹⁶ m² even with a mean permeability of 10⁻¹⁸ m². Threshold permeability for the percolation pathways decreases with increasing concentration gradient, vertical correlation length and the mean and variance of the permeability. The connectedness of relatively high-permeability zones is important in initiating and controlling plume fingers of free convection in both single-layer and sand-shale sequence models. Permeable units above and below are conducive to free convection through intervening low-permeability strata if buoyancy gradients exist. This heterogeneity is on scales that are difficult to sample by drilling and too localized to be simulated in regional models but may be significant in solute transport in these systems.     

Justice Sandra Day O'Connor: The Framers' "First Woman"

Sandra Day O'Connor's appointment to the Supreme Court was a historic stride in American women's slow but determined march towards full equality. At our nation's birth, Abigail Adams urged her husband and other members of the Continental Congress to "Remember the Ladies" in their new government. ¹ "We know better than to repeal our Masculine systems," John Adams replied only half jokingly. ² More than two centuries would pass before a woman donned Supreme Court robes to help interpret the United States Constitution.     

Modeling fluid flow in a heterogeneous, fault-controlled hydrothermal system

Previous studies have shown that most hydrothermal systems discharging at the land surface are associated with faulting, and that the location, temperature and rate of discharge of these systems are controlled by the geometry and style of the controlling fault(s). Unfortunately, the transport of heat and fluid in fault-controlled hydrothermal systems is difficult to model realistically; although heterogeneity and anisotropy are assumed to place important controls on flow in faults, few data or observations are available to constrain the distribution of hydraulic properties within active faults. Here, analytical and numerical models are combined with geostatistical models of spatially varying hydraulic properties to model the flow of heat and fluid in the Borax Lake fault of south-east Oregon, USA. A geometric mean permeability within the fault of 7 × 10⁻¹⁴ m² with 2× vertical/horizontal anisotropy in correlation length scale is shown to give the closest match to field observations. Furthermore, the simulations demonstrate that continuity of flow paths is an important factor in reproducing the observed behavior. In addition to providing some insight into possible spatial distributions of hydraulic properties at the Borax Lake site, the study highlights one potential avenue for integrating field observations with simulation results in order to gain greater understanding of fluid flow in faults and fault-controlled hydrothermal and petroleum reservoirs.     

The interplay of permeability and fluid properties as a first order control of heat transport, venting temperatures and venting salinities at mid-ocean ridge hydrothermal systems

While the fundamental influence of fluid properties on venting temperatures in mid-ocean ridge (MOR) hydrothermal systems is now well established, the potential interplay of fluid properties with permeability in controlling heat transfer, venting temperatures, and venting salinities has so far received little attention. A series of numerical simulations of fully transient fluid flow in a generic, across-axis model of a MOR with a heat input equivalent to magmatic supply at a spreading rate of 10 cm year⁻¹ shows a strong dependence of venting temperature and salinity on the system's permeability. At high permeability, venting temperatures are low because fluid fluxes are so high that the basal conductive heating cannot warm the large fluid masses rapidly enough. The highest venting temperature around 400°C as well as sub-seafloor fluid phase separation occur when the permeability is just high enough that the fluid flux can still accommodate all heat input for advection, or for lower permeabilities where advection is no longer capable to transfer all incoming magmatic heat. In the latter case, additional mechanisms such as eruptions of basaltic magma may become relevant in balancing heat flow in MOR settings. The results can quantitatively be explained by the 'fluxibility' hypothesis of Jupp & Schultz (Nature, 403 , 2000, 880), which is used to derive diagrams for the relations between basal heat input, permeability and venting temperatures. Its predictive capabilities are tested against additional simulations. Potential implications of this work are that permeability in high-temperature MOR hydrothermal systems may be lower than previously thought and that low-temperature systems at high permeability may be an efficient way of removing heat at MOR.     

Oral Advocacy and the Re-emergence of a Supreme Court Bar

Over the past generation, roughly the period since 1980, there has been a discernible professionalization among the advocates before the Supreme Court, to the extent that one can speak of the emergence of a real Supreme Court bar. Before defending that proposition, it is probably worth considering whether advocacy makes a difference—whether oral argument matters. My view after one year on the opposite side of the bench is the same as that expressed by no less a figure than Justice John Marshall Harlan—the second one—forty-nine years ago, after he completed his year on the Court of Appeals for the Second Circuit. ¹ Justice Harlan lamented what he saw as a growing tendency among the bar "to regard the oral argument as little more than a traditionally tolerated part of the appellate process," a chore "of little importance in the decision of appeals." ² This view, he said, was "greatly mistaken." ³ As Justice Harlan told the bar, "[Y]our oral argument on appeal is perhaps the most effective weapon you have got." ⁴     

Effects of episodic fluid flow on hydrocarbon migration in the Newport‐Inglewood Fault Zone,Southern California

Fault permeability may vary through time due to tectonic deformations, transients in pore pressure and effective stress, and mineralization associated with water‐rock reactions. Time‐varying permeability will affect subsurface fluid migration rates and patterns of petroleum accumulation in densely faulted sedimentary basins such as those associated with the borderland basins of Southern California. This study explores the petroleum fluid dynamics of this migration. As a multiphase flow and petroleum migration case study on the role of faults, computational models for both episodic and continuous hydrocarbon migration are constructed to investigate large‐scale fluid flow and petroleum accumulation along a northern section of the Newport‐Inglewood fault zone in the Los Angeles basin, Southern California. The numerical code solves the governing equations for oil, water, and heat transport in heterogeneous and anisotropic geologic cross sections but neglects flow in the third dimension for practical applications. Our numerical results suggest that fault permeability and fluid pressure fluctuations are crucial factors for distributing hydrocarbon accumulations associated with fault zones, and they also play important roles in controlling the geologic timing for reservoir filling. Episodic flow appears to enhance hydrocarbon accumulation more strongly by enabling stepwise build‐up in oil saturation in adjacent sedimentary formations due to temporally high pore pressure and high permeability caused by periodic fault rupture. Under assumptions that fault permeability fluctuate within the range of 1–1000 millidarcys (10^?15–10^?12 m²) and fault pressures fluctuate within 10–80% of overpressure ratio, the estimated oil volume in the Inglewood oil field (approximately 450 million barrels oil equivalent) can be accumulated in about 24 000 years, assuming a seismically induced fluid flow event occurs every 2000 years. This episodic petroleum migration model could be more geologically important than a continuous‐flow model, when considering the observed patterns of hydrocarbons and seismically active tectonic setting of the Los Angeles basin.     

Permeability of continental crust influenced by internal and external forcing

The permeability of continental crust is so highly variable that it is often considered to defy systematic characterization. However, despite this variability, some order has been gleaned from globally compiled data. What accounts for the apparent coherence of mean permeability in the continental crust (and permeability–depth relations) on a very large scale? Here we argue that large‐scale crustal permeability adjusts to accommodate rates of internal and external forcing. In the deeper crust, internal forcing – fluxes induced by metamorphism, magmatism, and mantle degassing – is dominant, whereas in the shallow crust, external forcing – the vigor of the hydrologic cycle – is a primary control. Crustal petrologists have long recognized the likelihood of a causal relation between fluid flux and permeability in the deep, ductile crust, where fluid pressures are typically near‐lithostatic. It is less obvious that such a relation should pertain in the relatively cool, brittle upper crust, where near‐hydrostatic fluid pressures are the norm. We use first‐order calculations and numerical modeling to explore the hypothesis that upper‐crustal permeability is influenced by the magnitude of external fluid sources, much as lower‐crustal permeability is influenced by the magnitude of internal fluid sources. We compare model‐generated permeability structures with various observations of crustal permeability.     

Joseph P. Bradley's Journey: The Meaning of Privileges and Immunities

Justice Joseph P. Bradley of New Jersey will forever be remembered as the judge who in 1883 cruelly scorned black rights in the Civil Rights Cases . ¹ Yet Bradley's position that year marked the end of a journey that had started in a quite different place. Thirteen years before, when he first joined the Court, Bradley had read Fourteenth Amendment protections of citizens' rights expansively, believing that "it is possible that those who framed the [Fourteenth Amendment] were not themselves aware of the far reaching character of its terms." In 1870 and 1871, Bradley wrote that the Fourteenth Amendment's Privileges and Immunities Clause reached "social evils … never before prohibited" and represented a commitment to " fundamental " or "sacred" rights of citizenship that stood outside the political process and "cannot be abridged by any state." ² By 1883, however, Bradley had turned away from such views. In the Civil Rights Cases , he wrote that nothing in the Thirteenth or Fourteenth Amendments countenanced a law against segregation. Blacks, he said, must take "the rank of mere citizen" and cease "to be the special favorite of the laws." ³     

Evolution of porosity, permeability and fluid pressure in dilatant faults post-failure: implications for fluid flow and mineralization

Mineralization of brittle fault zones is associated with sudden dilation, and the corresponding changes in porosity, permeability and fluid pressure, that occur during fault slip events. The resulting fluid pressure gradients cause fluid to flow into and along the fault until it is sealed. The volume of fluid that can pass through the deforming region depends on the degree of dilation, the porosity and permeability of the fault and wall rocks, and the rate of fault sealing. A numerical model representing a steep fault cutting through a horizontal seal is used to investigate patterns of fluid flow following a dilatant fault slip event. The model is initialized with porosity, permeability and fluid pressure representing the static mechanical state of the system immediately after such an event. Fault sealing is represented by a specified evolution of porosity, coupled to changes in permeability and fluid pressure, with the rate of porosity reduction being constrained by independent estimates of the rate of fault sealing by pressure solution. The general pattern of fluid flow predicted by the model is of initial flow into the fault from all directions, followed by upward flow driven by overpressure beneath the seal. The integrated fluid flux through the fault after a single failure event is insufficient to account for observed mineralization in faults; mineralization would require multiple fault slip events. Downward flow is predicted if the wall rocks below the seal are less permeable than those above. This phenomenon could at least partially explain the occurrence of uranium deposits in reactivated basement faults that cross an unconformity between relatively impermeable basement and overlying sedimentary rocks.     

Modelling the Lost City hydrothermal field: influence of topography and permeability structure

The Lost City hydrothermal field (LCHF) is hosted in serpentinite at the crest of the Atlantis Massif, an oceanic core complex close to the mid‐Atlantic Ridge. It is remarkable for its longevity and for venting low‐temperature (40–91°C) alkaline fluids rich in hydrogen and methane. IODP Hole U1309D, 5 km north of the LCHF, penetrated 1415 m of gabbroic rocks and contains a near‐conductive thermal gradient close to 100°C km^?1. This is remarkable so close to an active hydrothermal field. We present hydrothermal modelling using a topographic profile through the vent field and IODP site U1309. Long‐lived circulation with vent temperatures similar to the LCHF can be sustained at moderate permeabilities of 10^?14 to 10^?15 m² with a basal heatflow of 0.22 W m^?2. Seafloor topography is an important control, with vents tending to form and remain in higher topography. Models with a uniform permeability throughout the Massif cannot simultaneously maintain circulation at the LCHF and the near‐conductive gradient in the borehole, where permeabilities <10^?16 m² are required. A steeply dipping permeability discontinuity between the LCHF and the drill hole is required to stabilize venting at the summit of the massif by creating a lateral conductive boundary layer. The discontinuity needs to be close to the vent site, supporting previous inferences that high permeability is most likely produced by faulting related to the transform fault. Rapid increases in modelled fluid temperatures with depth beneath the vent agree with previous estimates of reaction temperature based on geochemical modelling.     

Supreme Court Activism in Economic Policy in the Waning Days of the New Deal: Interpreting the Fair Labor Standards Act, 1941–1946

Students of the Supreme Court universally agree that it made a dramatic shift in 1937. First, in West Coast Hotel Company v. Parrish, ¹ it retreated from the unbridled use of the Fourteenth Amendment's Due Process Clause to invalidate state economic regulatory legislation. Then, in National Labor Relations Board v. Jones and Laughlin Steel Corporation , ² the Justices widened the reach of congressional power under the Commerce Clause. This looser reading of the Commerce Clause was solidified in 1941 with United States v. Darby Lumber Company ³ and Wickard v. Filburn. ⁴ So decisive were these cases in dividing what went before from what came afterward that Bernard Schwartz has said, "The 1937 reversal marked the accession of what may be considered the second Hughes Court—so different was its jurisprudence from that of the Hughes Court that had preceded it." ⁵ Whereas the defining jurisprudence of the former had been close supervision of economic policy, the latter refused to second guess the economic wisdom of congressional (and state) regulatory initiatives. Alpheus T. Mason summarized Justice Harlan Fisk Stone's approach, which was indicative of the entire Court of this era, as one that would not say that "no economic legislation would ever violate constitutional restraints, [but that] … in this area the court's role would be strictly confined." ⁶ Confirming this approach, between 1937 and 1957 the Supreme Court struck down only four federal statutes as unconstitutional, none of which were economic in nature. ⁷     

An exhumed palaeo-hydrocarbon migration fairway in a faulted carrier system, Entrada Sandstone of SE Utah, USA

The Moab Anticline, east‐central Utah, is an exhumed hydrocarbon palaeo‐reservoir which was supplied by hydrocarbons that migrated from the Moab Fault up‐dip towards the crest of the structure beneath the regional seal of the Tidwell mudstone. Iron oxide reduction in porous, high permeability aeolian sandstones records the secondary migration of hydrocarbons, filling of traps against small sealing faults and spill pathways through the Middle Jurassic Entrada Sandstone. Hydrocarbons entered the Entrada Sandstone carrier system from bends and other leak points on the Moab Fault producing discrete zones of reduction that extend for up to 400 m from these leak points. They then migrated in focused stringers, 2–5 m in height, to produce accumulations on the crest of the anticline. Normal faults on the anticline were transient permeability barriers to hydrocarbon migration producing a series of small compartmentalized accumulations. Exsolution of CO₂ as local fault seals were breached resulted in calcite cementation on the up‐dip side of faults. Field observations on the distribution of iron oxide reduction and calcite cements within the anticline indicate that the advancing reduction fronts were affected neither by individual slip bands in damage zones around faults nor by small faults with sand: sand juxtapositions. Faults with larger throws produced either sand: mudstone juxtapositions or sand: sand contacts and fault zones with shale smears. Shale‐smeared fault zones provided seals to the reducing fluid which filled the structural traps to spill points.     

Writing the First Draft of History: Anthony Lewis as Supreme Court Correspondent

The legendary Washington Bureau Chief and columnist of The New York Times , James Reston, with a push from Felix Frankfurter, decided that the paper of record would have its own correspondent specializing in the Supreme Court. ¹ With his eye for excellent young talent, ² Reston chose Anthony Lewis, already a Pulitzer-Prize winner before his thirtieth birthday, ³ and sent him to Harvard for the 1956–57 academic year as a Nieman Fellow to study law.     

Pore pressure evolution and fluid flow during visco‐elastic single‐layer buckle folding

Pore pressure and fluid flow during the deformational history of geologic structures are directly influenced by tectonic deformation events. In this contribution, 2D plane strain finite element analysis is used to study the influence of different permeability distributions on the pore pressure field and associated flow regimes during the evolution of visco‐elastic single‐layer buckle folds. The buckling‐induced fluid flow regimes indicate that flow directions and, to a lesser degree, their magnitudes vary significantly throughout the deformation and as a function of the stratigraphic permeability distribution. The modelling results suggest that the volumetric strain and the permeability distribution significantly affect the resulting flow regime at different stages of fold development. For homogeneous permeability models (k > 10^?21 m²), low strain results in a mostly pervasive fluid flow regime and is in agreement with previous studies. For larger strain conditions, fluid focusing occurs in the buckling layer towards the top of the fold hinge. For low permeabilities (<10^?21 m²), local focused flow regimes inside the buckling layer emerge throughout the deformation history. For models featuring a low‐permeability layer embedded in a high‐permeability matrix or sandwiched between high‐permeability layers, focused flow regimes inside the folded layer result throughout the deformation history, but with significant differences in the flow vectors of the surrounding layers. Fluid flow vectors induced by the fold can result in different, even reversed, directions depending on the amount of strain. In summary, fluid flow regimes during single‐layer buckling can change from pervasive to focused and fluid flow vectors can be opposite at different strain levels, that is the flow vectors change significantly through time. Thus, a complete understanding of fluid flow regimes associated with single‐layer buckle folds requires consideration of the complete deformation history of the fold.     

Soil erosion and flooding on the eastern South Downs, southern England, 1976–2001

The South Downs in southern England have been farmed for 5000 years: the initial loess cover is now a thin, stony remnant as a result of erosion. During the 1980s, field monitoring of erosion events in an area of 36 km² showed that average rates of erosion are low (0.5–5.0 m³ ha⁻¹ yr⁻¹), but that occasional storms result in losses of over 200 m³ ha⁻¹ yr⁻¹ on individual fields. On soils that are only 15 cm thick, such rates pose a threat to future farming. Almost all recent erosion has been on fields of winter cereals, which are bare in the wet autumn period. Of greater significance in the short term are the effects of soil-laden runoff (or muddy floods) on urban areas. Flood damage to property has been a regular event since the conversion of this area to winter cereals in the 1970s. Soil conservation measures have been negligible and flood protection has consisted mainly of engineering works and limited land-use change at sites where property damage has occurred. Conversion to grass under the Set Aside, and an Environmentally Sensitive Area (ESA) scheme, could be an effective soil conservation and flood protection approach. In the longer term, increasing stoniness of soils, the economic incentives for arable farming in marginal areas, and the success of legal proceedings relating to flood damage, will determine the future of erosion on the South Downs. Current farming systems clearly are unsustainable and would become more so under future climates without substantial site-targeted land use change.     

The Development of the Supreme Court Practice of Calling for the Views of the Solicitor General

"When the Supreme Court invites you, that's the equivalent of a royal command. An invitation from the Supreme Court just can't be rejected." ¹ The guest most frequently invited to the Supreme Court is the Solicitor General. Even before the practice of the Supreme Court calling for the views of the Solicitor General process developed, the Court occasionally invited the Solicitor General to participate as amicus in important cases by submitting a brief and/or participating in oral arguments before the Court. ² As then–Solicitor General Simon E. Sobeloff remarked to then–Attorney General Herbert Brownell in a 1954 letter about the landmark school desegregation cases, "The Supreme Court has expressly extended an invitation to the United States to participate in the reargument. While this by no means compels participation, such an invitation is not to be lightly declined." ³     

The Canadian Council of Muslim Women: A Chapter in the History of Muslim Women in Canada

We want to identify and collect data on the special need concerns, interests, talents, successes and frustrations of Canadian Muslim women; we intend to sensitize Canadian Muslim men and women, young and old, so that they may understand each other better and relate to one another more meaningfully and effectively. We want to inform and educate fellow Canadians about our Islamic heritage. We also plan to reach out to, and build coalitions with, other women's groups who share and respect our ideals and concerns. Beyond Canada, we shall join hands with sister organizations in promoting human dignity and world peace. In these endeavors, we seek your cooperation and support. The Canadian Muslim Woman is your voice. Help us make it a voice of reason and moderation.¹     

Measurements of gas permeability and diffusivity of tight reservoir rocks: different approaches and their applications

Permeability and diffusivity are critical parameters of tight reservoir rocks that determine their viability for commercial development. Current methods for measuring permeability and/or diffusivity may lead to erroneous results when applied to very tight rocks including gas shales, coal, and tight gas sands, as well as rocks considered as seals for nuclear waste repositories and strata for geological sequestration of CO₂. The use of He as routinely applied to measure porosity, permeability, and diffusivity may result in non-systematic errors because of the molecular sieving effect of the fine pore structure to larger molecules such as reservoir gases. Utilizing gases with larger adsorption potentials than He, such as N₂, and including all reservoir gases to measure porosity or permeability of rocks with high surface area is a viable alternative, but requires correcting for adsorption in the analyses. This study expands several approaches to measure permeability and diffusivity with considerations for gas adsorption, which has not been explicitly considered in previous studies. We present new models that explicitly correct for adsorption during pulse-decay measurements of core under reservoir conditions, as well as on crushed samples used to approximate permeability or diffusivity. We also present a method to determine permeability or diffusivity from on-site drill-core desorption test data as carried out to determine gas in place in coals or gas shales. Our new approach utilizes late-time data from experimental pressure-decay tests, which we show to be more reliable and theoretically (and practically) accurate than the early-time approach commonly used to estimate gas-transport properties.