Volcanic rocks along the Panama Canal present a world-class opportunity to examine the relationship between arc magmatism, tectonic forcing, wet and dry magmas, and volcanic structures. Major and trace element geochemistry of Canal volcanic rocks indicate a significant petrologic transition at 21-25 Ma. Oligocene Bas Obispo Fm. rocks have large negative Nb-Ta anomalies, low HREE, fluid mobile e...

The permafrost on the North Slope of Alaska is densely populated by shallow lakes that result from thermokarst erosion. These lakes release methane (CH4 ) derived from a combination of ancient thermogenic pools and contemporary biogenic production. Despite the potential importance of CH4 as a greenhouse gas, the contribution of biogenic CH4 production in arctic thermokarst lakes in Alaska is no...

Large variations in the boron isotopic composition of sedimentary environments make boron an attractive monitor of fluidrrock interactions during diagenesis. Studies of B in marine sediments have shown that preferential adsorption of B on clay minerals leaves pore waters enriched in B. During diagenesis, clay minerals recrystallize and incorporate B into Ž the mineral structure Spivack, A.J., P...

Lake-level history for Birch Lake, Alaska, was reconstructed using seismic profiles and multiproxy sedimentary analyses including sedimentology, geochemistry, magnetic susceptibility, and palynology. Twenty-two seismic profiles (18 km total) and eight sediment cores taken from the lake margin to its depocenter at 13.5 m provide evidence for low lake stands during the late Pleistocene and Holoce...

We present major and trace element concentrations in conjunction with Sr–Nd isotope ratios to investigate the geochemical characteristics of mélange formation along the subduction zone slab–mantle interface. Mélange matrix of the Catalina Schist formed within an active subduction zone of the southern California borderland in Cretaceous time. Mélange formed through the synergistic effects of def...

Elemental geochemistry, Nd isotopes, clay minerals, and U-Pb zircon ages integrated by petrographic heavy-mineral data offer a multiproxy panorama of mud sand composition across the Zambezi sediment-routing system. Detrital geochronology highlights four major episodes crustal growth in southern Africa: Irumide predominate over Pan-African, Eburnean, Neoarchean ages. Smectite, dominant generated...