Passage of Eocene slab windows beneath the Pacific Northwest is documented by plate motion reconstructions as well as the on-land geologic record. The earliest known record of this process is the 55-44 Ma Basalt of Summit Creek (BSC), a steeply dipping 1600 m section of subaerial lavas exposed southeast of Mount Rainier. These tholeiitic basalts erupted in an arc setting (as evidenced by underlying tuffs) but display a mix of MORB and OIB traits and have isotopic signatures of a depleted mantle source. In chemical and isotopic composition BSC lavas overlap with the voluminous Crescent Formation basalts on the Olympic Peninsula, which are of similar age but located ~100 km farther west. A few BSC samples display arc traits (e.g., HFSE depletions); we suggest these may record interaction between ascending asthenospheric mantle / melts and a mantle wedge previously modified by subduction processes. Compositional diversity among BSC lavas appears to reflect both fractional crystallization and source heterogeneity. Modeling with MELTS (Ghiroso and Sack, 1995) indicates that differentiation dominated by removal of clinopyroxene and plagioclase took place at mid crustal depths (P = 5 kbar) and that the parent magma had <0.2 wt. % water. However, this process cannot account for all incompatible element data, which appear to require multiple parent magmas. The Eocene was a critical juncture in Pacific Northwest tectonics. Subduction, slab window magmatisim, terrane accretion and mantle plume activity were all ongoing at this time. Increased understanding of the petrology BSC will contribute to our overall knowledge of the evolution of the western margin of North America.

Wildlife suffer from many ecological and biological consequences after an oil spill. The use of chemical surfactants to convert oil spills to small droplets has been the source of ongoing debate since little is known about the impacts they have on plants and animals in the ocean. Surfactants are a natural byproduct of many bacteria that are uniquely adapted to the marine environment. Our research assessed surfactant activity of cell free supernatants (CFS) from several cold-adapted bacteria using crude oil. We cultured various bacterial isolates under optimal growth conditions to ensure surfactant production was not missed. Exudates, the chemically benign “leftovers” containing the extracellular surfactants from the bacteria, were extracted from the cultures by gentle centrifugation before filtration of the supernatant through a membrane filter. The oil-spread assay was then used to determine surfactant activity from the exudates of several organisms. CFS was pipetted to the center of a small oil slick and surfactant strength was indicated by the amount of oil displaced. Some organisms with high surfactant ability were identified for further examination as candidates for environmentally viable alternatives to chemical dispersants.