To constrain the fluxes of methane (CH4) in the water column above the accretionary
wedge along the Cascadia continental margin, we measured methane and its stable carbon
isotope signature (δ¹³C-CH₄). The studies focused on Hydrate Ridge (HR), where
venting occurs in the presence of gas-hydrate-bearing sediments. The vent CH₄ has...
Methane derived authigenic carbonate (MDAC) precipitation occurs within marine sediments as a byproduct of the microbial anaerobic oxidation of methane (AOM). While these carbonates form in chemical and isotopic equilibrium with the fluids from which they precipitate, burial diagenesis and recrystallization can overprint these signals. Plane polarized light (PPL) and...
During Ocean Drilling Program Leg 204, 80 in situ measurements of
subseafloor temperature were made; 68 of these showed good frictional
pulses on insertion and extraction from the seafloor and were used to
constrain the subsurface temperature. Considering uncertainties from
various sources, uncertainties in the in situ temperatures are estimated...
Three successful vertical seismic profiles (VSPs) were acquired during
Ocean Drilling Program (ODP) Leg 204 at South Hydrate Ridge. The
data confirm earlier results from ocean bottom seismometer data and
analysis of moveout from common midpoint reflection data that the
average velocity between the seafloor and the bottom-simulating reflector
(BSR)...
Quantifying the mass transport through marine sediments, and the geochemical response to such flow with numerical models has become a common and powerful approach for geochemical data interpretation. In this dissertation, I developed and applied transport-reaction models to unravel complex and interdependent reactions involving carbon, sulfur and silica transformations in...
Authigenic carbonates and chemosymbiotic biota are archives of seepage 1 history and record paleo-environmental conditions at seep sites. Based on mineral and stable isotope compositions and U/Th-isotope systematics of seep carbonates and Calyptogena sp shell fragments from three seep sites located at 22°02' ~22°09'N, 118°43'~118°52'E (water depths: 473 m to...
Subduction zone earthquake and tsunami hazards affect tens of millions worldwide and the recurrence of these disasters can be evaluated with paleoseismic techniques, because earthquake cycles (and their supercycles) typically span many millennia. In these three chapters, I discuss a suite of analyses I use to evaluate the sedimentary record...
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, I es mate that slopes become unstable when a seismic
load of <0.2 g is imparted. Using infi nite
A 3D seismic volume was acquired summer 2000 over the southern end of Hydrate Ridge (FIR), an anomalously shallow ridge 100 km offshore Newport, Oregon. The survey followed a succession of scientific expeditions aimed at studying the gas hydrates present in the shallow subsurface that gave the name to the...
Carbonate communities:The activity of anaerobic methane oxidizing microbes facilitates
precipitation of vast quantities of authigenic carbonate at methane seeps. Here we demonstrate
the significant role of carbonate rocks in promoting diversity by providing unique habitat
and food resources for macrofaunal assemblages at seeps on the Costa Rica margin
(400–1850 m)....
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Carbonate at Costa Rica Methane Seeps
Levin, L. A., Mendoza, G. F., Grupe, B. M., Gonzalez, J. P., Jellison
Log and core data document gas saturations as high as
90% in a coarse-grained turbidite sequence beneath the gas
hydrate stability zone (GHSZ) at south Hydrate Ridge, in the
Cascadia accretionary complex. The geometry of this gas-saturated
bed is defined by a strong, negative-polarity
reflection in 3D seismic data. Because...