Association among active seafloor deformation, mound formation, and gas hydrate growth and accumulation within the seafloor of the Santa Monica Basin, offshore California

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doi: 10.1016/j.margeo.2008.01.011
Author(s): Paull, Charles K.; Normark, William R.; Ussler, William, III; Caress, David W.; Keaten, Rendy
Author Affiliation(s): Primary:
Monterey Bay Aquarium Research Institute, Moss Landing, CA, United States
Other:
U. S. Geological Survey, United States
Volume Title: Marine Geology
Source: Marine Geology, 250(3-4), p.258-275. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0025-3227 CODEN: MAGEA6
Note: In English. 63 refs.; illus., incl. sects., 6 tables, sketch map
Summary: Seafloor blister-like mounds, methane migration and gas hydrate formation were investigated through detailed seafloor surveys in Santa Monica Basin, offshore of Los Angeles, California. Two distinct deep-water (≥800 m water depth) topographic mounds were surveyed using an autonomous underwater vehicle (carrying a multibeam sonar and a chirp sub-bottom profiler) and one of these was explored with the remotely operated vehicle Tiburon. The mounds are >10 m high and >100 m wide dome-shaped bathymetric features. These mounds protrude from crests of broad anticlines (≈20 m high and 1 to 3 km long) formed within latest Quaternary-aged seafloor sediment associated with compression between lateral offsets in regional faults. No allochthonous sediments were observed on the mounds, except slumped material off the steep slopes of the mounds. Continuous streams of methane gas bubbles emanate from the crest of the northeastern mound, and extensive methane-derived authigenic carbonate pavements and chemosynthetic communities mantle the mound surface. The large local vertical displacements needed to produce these mounds suggests a corresponding net mass accumulation has occurred within the immediate subsurface. Formation and accumulation of pure gas hydrate lenses in the subsurface is proposed as a mechanism to blister the seafloor and form these mounds. Abstract Copyright (2008) Elsevier, B.V.
Year of Publication: 2008
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 07 Marine Geology and Oceanography; 20 Geophysics, Applied; Absolute age; Acoustical methods; Aliphatic hydrocarbons; Alkanes; Bathymetry; Biogenic structures; Bioherms; Bottom features; C-13/C-12; C-14; California; Carbon; Cenozoic; Chemosynthesis; Cores; Dates; Deformation; Diagenesis; East Pacific; Gas hydrates; Gas seeps; Geochemistry; Geophysical methods; Geophysical profiles; Geophysical surveys; Holocene; Hydrocarbons; Hydrochemistry; Isotope ratios; Isotopes; Leg 167; Los Angeles County California; Mapping; Marine sediments; Methane; Mud mounds; North Pacific; Northeast Pacific; ODP Site 1015; Ocean Drilling Program; Ocean floors; Organic compounds; Pacific Ocean; Pore water; Quaternary; Radioactive isotopes; Santa Monica Basin; Sedimentary structures; Sediments; Seismic methods; Seismic profiles; Sonar methods; Southern California; Stable isotopes; Surveys; Temperature; United States; Upper Holocene
Coordinates: N334700 N334900 W1183800 W1184030
Record ID: 2008094262
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands