Publications

Several caves in the Shenandoah Valley in Virginia show evidence for early hypogenic conduit development with later-enhanced solution under partly confined phreatic conditions guided by geologic structures. Many (but not all) of these caves have been subsequently invaded by surface waters as a result of erosion and exhumation. Those not so affected are relict phreatic caves, bearing no relation to

Orogenic processes operate at scales ranging from the lithosphere to grain-scale, and are inexorably linked. For example, in many orogens, fault and shear zone architecture controls distribution of heat advection along faults and also acts as the primary mechanism for redistribution of heat-producing material. This sets up the thermal structure of the orogen, which in turn controls lithospheric rh

Ion microprobe U-Pb zircon rim ages from 39 samples from across the accreted terranes of the central Blue Ridge, eastward across the Inner Piedmont, delimit the timing and spatial extent of superposed metamorphism in the southern Appalachian orogen. Metamorphic zircon rims are 10–40 µm wide, mostly unzoned, and dark gray to black or bright white in cathodoluminescence, and truncate and/or embay in

Ratios of Na/Br, Br/Cl, and I/Cl were determined on leachates of fluid inclusions from the Broken Hill Pb-ZnAg deposit in Australia. Paragenetic relations suggest that whereas all analyzed inclusions formed during or after regional metamorphism, ion ratios are not greatly changed from those of the pre-metamorphic ore-forming fluids. Based on relatively high Br/Cl and I/Cl ratios, and low Na/Br rat

To address a paucity of Common Era data in the Gulf of Mexico, we reconstructed ~ 1.1 m of relative sea-level (RSL) rise over the past ~ 2000 years at Little Manatee River (Gulf Coast of Florida, USA). We applied a regional-scale foraminiferal transfer function to fossil assemblages preserved in a core of salt-marsh peat and organic silt that was dated using radiocarbon and recognition of pollutio

Meteorological and hydrologic conditions associated with shallow landslide initiation in the coastal bluffs of the Atlantic Highlands, New Jersey remain undocumented despite a history of damaging slope movement extending back to at least 1903. This study applies an empirical approach to quantify the rainfall conditions leading to shallow landsliding based on analysis of overlapping historical prec

The Bering Strait connects the Arctic and Pacific oceans and separates the North American and Asian landmasses. The presently shallow ( ∼  53 m) strait was exposed during the sea level lowstand of the last glacial period, which permitted human migration across a land bridge today referred to as the Bering Land Bridge. Proxy studies (stable isotope composition of foraminifera, whale migration into

The Paleocene-Eocene Thermal Maximum (PETM) was an interval of extreme warmth that caused disruption of marine and terrestrial ecosystems on a global scale. Here we examine the sediments, flora, and fauna from an expanded section at Mattawoman Creek-Billingsley Road (MCBR) in Maryland and explore the impact of warming at a nearshore shallow marine (30–100 m water depth) site in the Salisbury Embay

This study evaluates the use of a small unmanned aerial system (UAS) to collect imagery over artisanal mining sites in West Africa. The purpose of this study is to consider how very high-resolution imagery and digital surface models (DSMs) derived from structure-from-motion (SfM) photogrammetric techniques from a small UAS can fill the gap in geospatial data collection between satellite imagery an

Resource managers around the world are challenged to develop feasible plans for sustainable conservation and/or restoration of the lands, waters, and wildlife they administer—a challenge made greater by anticipated climate change and associated effects over the next century. Increasingly, paleoecologic and geologic archives are being used to extend the period of record of observed data and provide

The 1959 summit eruption of Kīlauea Volcano exhibited high lava fountains of gas-rich, primitive magma, containing olivine + chromian spinel in highly vesicular brown glass. Microprobe analysis of these samples shows that euhedral rims on olivine phenocrysts, in direct contact with glass, vary significantly in forsterite (Fo) content, at constant major-element melt composition, as do unzoned groun

Soils develop at the earth's surface via multiple processes that act through time. Precluding burial or disturbance, soil genetic horizons form progressively and reflect the balance among formation processes, surface age, and original substrate composition. Soil morphology provides a key link between process and time (soil age), enabling soils to serve as both relative and numerical dating tools f