A landslide in Tertiary marine shale with superheated fumaroles, Coast Ranges, California
- Robert H. Mariner1,
- Scott A. Minor2,
- Allen P. King3,
- James R. Boles4,
- Karl S. Kellogg2,
- William C. Evans1,
- Gary A. Landis5,
- Andrew G. Hunt5 and
- Christy B. Till6
- 11U.S. Geological Survey, MS 434, 345 Middlefield Road, Menlo Park, California 94025, USA
- 22U.S. Geological Survey, MS 980, Federal Center, Denver, Colorado 80225, USA
- 33Los Padres National Forest, 6755 Hollister Avenue, Goleta, California 93117, USA
- 44Department of Earth Science, University of California, Santa Barbara, California 93106, USA
- 55U.S. Geological Survey, MS 963, Federal Center, Denver, Colorado 80225, USA
- 66Department of Earth, Atmosphere, and Planetary Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
Abstract
In August 2004, a National Forest fire crew extinguished a 1.2 ha fire in a wilderness area ~40 km northeast of Santa Barbara, California. Examination revealed that the fire originated on a landslide dotted with superheated fumaroles. A 4 m borehole punched near the hottest (262 °C) fumarole had a maximum temperature of 307 °C. Temperatures in this borehole have been decreasing by ~0.1 °C/d, although the cooling rate is higher when the slide is dry. Gas from the fumaroles and boreholes is mostly air with 3–8 vol% carbon dioxide and trace amounts of carbon monoxide, methane, ethane, and propane. The carbon dioxide is 14C-dead. The ratios of methane to ethane plus propane [C1/(C2 + C3)] range from 3.6 to 14. Carbon isotope values for the CO2 range from −14‰ to −23‰ δ13C. 3He/4He values range from 0.96 to 0.97 times that of air. The anomalous heat is interpreted to be due to rapid oxidation of iron sulfide augmented by combustion of carbonaceous matter within the formation.
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- Received 26 June 2008.
- Revision received 18 August 2008.
- Accepted 26 August 2008.
- © 2008 Geological Society of America
