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Numerical simulations of fluid flow and heat transport in the South Eugene Island minibasin, offshore Louisiana, show that expulsion of geopressured fluids along faults can produce temperature and pressure anomalies similar to those observed in the area. In the simulations, abnormally pressured fluid moves along the fault through a fracture network. A thermal anomaly forms adjacent to the fault, while a larger fluid pressure anomaly extends into sediments on either side. Results from constant fault permeability simulations indicate that (1) geopressured sediments must be relatively permeable (5 × 10−17 m2) for expulsion to occur, (2) the size of thermal anomalies depend on the depth to which the fault is hydraulically open, and (3) fluid is vertically transported into shallow sediments when fault permeability is high, while lateral transport along deeper sands dominates when fault permeability is low. Excess fluid pressure in abnormally pressured sediments drops to half its original value throughout much of the minibasin after 10,000 years of expulsion; the associated thermal anomaly is also larger than observations, suggesting expulsion is not continuous. Variable fault permeability simulations, in which compaction of fault zone sediments closes the fracture network, indicate that fault permeability decreases by 1–2 orders of magnitude 1–200 years after expulsion begins. Thermal and baric anomalies from variable permeability simulations are smaller than from constant permeability simulations and are more consistent with available data. Faults must remain permeable for 20–30 years to produce thermal and baric anomalies similar to those observed in the area.

The trace element compositions of 13 samples from exposed granulite facies terrains and 17 granulitic lower crustal xenoliths were determined using an inductively coupled plasma‐mass spectrometer to constrain the composition and evolution of the Mexican lower crust. Most xenoliths found are pyroxeneplagioclase orthogneisses, although quartzo‐feldspathic paragneisses form up to 50% of the xenolith population in some areas. Lithologies in the exposed terrains consist of pelitic and carbonate‐rich paragneisses, charnockites, and less abundant basic, intermediate, and felsic orthogneisses. Both xenoliths and exposed granulites generally have low abundances of incompatible elements such as K, Rb, Th, and U. The xenoliths, however, often have lower abundances of these elements than the exposed granulites. High K/Rb ratios, coupled with an inverse correlation between K2O and K/Rb, indicate that most samples from the Mexican lower crust are depleted in both K and Rb. Furthermore, Th/U ratios similar to upper crustal materials and high La/Th ratios suggest depletion in both Th and U relative to average crustal material. Removal of a melt phase, either after the crystallization of cumulates or following a partial melting event, can explain many of the chemical features observed and may be responsible for the elemental depletions. Some samples, however, appear to have been unaffected during their residence in the lower crust and chemically resemble their presumed protoliths. Available geobarometric data suggest that xenoliths equilibrated near the crust/mantle boundary (∼10 kbar) and represent the lowermost crust, while the exposed granulites equilibrated at shallower crustal levels (∼7 kbar). Thus the differences observed between the xenoliths and exposed granulites indicate that there may be chemical and lithologic zonation in the Mexican lower crust. The lowermost crust in Mexico consists of crystallized basaltic liquids, cumulates, and/or residue after the removal of a partial melt as well as garnet‐rich metasediments.

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This is a study of the scientific component of an effort to restore an urban river by removing a low-head dam. The Secor Dam is owned by a local government entity near Toledo, Ohio. The proposed removal of the last structure impeding flow on the Ottawa River has broad appeal, but the owner is concerned about liability issues, particularly potential changes to the flood regime, the presence of contaminated sediments behind the dam, and possible downstream transport of reservoir sediments. Assessing sediment contamination involved sediment sampling and analysis of trace metals and organic contaminants. Forecasting sediment transport involved field methods to determine the volume and textural properties of reservoir and upstream sediment and calculations to determine the fate of reservoir sediments. Forecasting changes in the flood regime involved HEC-RAS hydrological models to determine before and after dam removal flood scenarios using LiDAR data imported into an ArcGIS database. The resulting assessment found potential sediment contamination to be minor, and modeling showed that the removal of the dam would have minimal impacts on sediment transport and flood hazards. Based on the assessment, the removal of the dam has been approved by its owners.