Basin-and-range geothermal resources are typically fault-controlled, deep-circulation systems. They commonly occur beneath thick sequences of Tertiary and Quaternary basin-fill sediments which hinder understanding of fault geometries and faulting patterns. Recent experience at Dixie Valley and survey of the literature for other systems suggest a low-cost and rapid exploration strategy for estab...

Amazonian The youngest of the geologic epochs on Mars identified through geoiogic mapping of superposition relations, and the area! density of impact craters. caldera An irregular collapse feature formed over the evacuated magma chamber within a volcano. central volcano Emplacement of volcanic materials from a centralized source vent rather than along a distributed line of vents, composite volc...

Zinc is an essential micronutrient and its concentration and isotopic composition in marine sediments represent promising tracers of the ocean carbon cycle. However, gaps remain in our understanding of the modern marine cycle of Zn, including an explanation of the heavy Zn isotopic composition of seawater relative to the known inputs, and the identity of a required missing sink for light Zn iso...

Drilling mud and associated drill cuttings are the largest volume wastes associated with drilling of oil and gas wells and often are discharged to the ocean from offshore drilling platforms. Barite (BaSO4) often is added as a weighting agent to drilling muds to counteract pressure in the geologic formations being drilled, preventing a blowout. Some commercial drilling mud barites contain elevat...

Here we describe a new reaction-transport model that quantitatively examines δ13C profiles of porewater methane and dissolved inorganic carbon (DIC) (δCCH4 and δCDIC) in the anoxic sediments of the Santa Barbara Basin (California Borderland region). Best-fit solutions of the model to these data suggest that CO2 reduction is the predominant form of methanogenesis in these sediments. These soluti...

Iodine is an important element in studies of human nutrition to combat I deficiency disorders, and in protection of the environment and human health from anthropogenic release of radioactive I. Biogeochemical cycling of I in the subsurface environment is complex, because it occurs in multiple oxidation states and as inorganic and organic species that may be volatile, hydrophilic and biophilic. ...

The Mars Exploration Rover Spirit and its Athena science payload have been used to investigate a landing site in Gusev crater. Gusev is hypothesized to be the site of a former lake, but no clear evidence for lacustrine sedimentation has been found to date. Instead, the dominant lithology is basalt, and the dominant geologic processes are impact events and eolian transport. Many rocks exhibit co...

Sulfate reduction is the predominant anaerobic microbial process of organic matter mineralization in marine sediments, with recent studies revealing that sulfate reduction not only occurs in sulfate-rich sediments, but even extends to deeper, methanogenic sediments at very low background concentrations of sulfate. Using samples retrieved off the Shimokita Peninsula, Japan, during the Integrated...

In this study, 166 surface sediments and 3 sediment cores from the Bohai Sea (BS), Yellow Sea (YS) and East China Sea (ECS) in China were collected to investigate the spatial and temporal distributions and the transport of PFASs. PFASs concentrations in the surface sediments ranged from below detection limit (<LOD) to 2.78 ng g(-1) with an average value of 0.55 ng g(-1) on a dry weight basis (d...

Disturbance strongly impacts patterns of community diversity, yet the shape of the diversity-disturbance relationship remains a matter of debate. The topic has been of interest in theoretical ecology for decades as it has practical implications for the understanding of ecosystem services in nature. One of these processes is the remineralization of organic matter by microorganisms in coastal mar...