... craters and acoustic anomalies deeper in the section might indicate gas saturation in sediment at some localities. Sediment physical properties other than grain size also show consistent change parallel to the northeasterly trend of the area: water content, plasticity index, and liquidity index increase...

... that has a carbon isotopic composition (? 13 C PDB ) of -80%. This isotopic value suggests that the methane originated from active biological processes operating on peat in the top 4 m of sediment. At the other site, characterized by a large subsurface acoustic anomaly, smaller near-surface acoustic...

... depression sea floor environmental assessment han alaska ice gouge sediment investigator nelson potential geologic hazard cacchione norton basin reservoir characterization us government crater gouging acoustic anomaly OTC 3400 ASUMMARY OF INTERACTING, SURFICIAL GEOLOGIC PROCESSES...

... in the vicinity of the seep. Also conspicuous on the seismic reflection records are two different types of acoustic anomalies: reflector pull-downs and abrupt reflector terminations. Both of these anomalous acoustic responses are indicative of gas-charged sediment. The seep is located directly over an anomaly...

... of the penetrometer, and more rapid penetration of the vibracorer in sediment at the station with near-surface acoustic anomalies and seafloor craters. Analyses of hydrocarbon gases in sediments from a 1.6-m vibracore taken at this station showed unusually high concentrations of hydrocarbon gases heavier than...