The relationship between silica diagenesis, methane, and seismic reflections on the South Orkney microcontinent

Online Access: Get full text
doi: 10.2973/
Author(s): Lonsdale, Malcolm J.
Author Affiliation(s): Primary:
Univ. Birmingham, Sch. Earth Sci., Birmingham, United Kingdom
Univ. R.I. at Narragansett, United States
Ocean Drilling Program, United States
Tex. A&M Univ., United States
Lamont-Doherty Geol. Obs., United States
Univ. Oslo, Norway
Alfred Wegener Inst. Polar and Ocean Res., Federal Republic of Germany
Univ. Southampton, United Kingdom
Univ. Tex. at Austin, United States
Woods Hole Oceanogr. Inst., United States
Fed. Inst. Tech., Switzerland
Univ. Tokyo, Japan
Mem. Univ. Newfoundland, Canada
CNRS-Luminy, France
R. Ont. Mus., Canada
Univ. Bremen, Federal Republic of Germany
Wesleyan Univ., United States
Fla. State Univ., United States
Volume Title: Proceedings of the Ocean Drilling Program, Weddell Sea, Antarctica, covering Leg 113 of the cruises of the Drilling Vessel JOIDES Resolution, Valparaiso, Chile, to East Cove, Falkland Islands, sites 689-697, 25 December 1986-11 March 1987
Volume Author(s): Barker, Peter F.; Kennett, James P.; O'Connell, Suzanne B.; Berkowitz, Stephen; Bryant, William R.; Burckle, Lloyd H.; Egeberg, Per Kristian; Fütterer, Dieter Karl; Gersonde, Rainer Erich; Golovchenko, Xenia; Hamilton, Norman; Lawver, Lawrence; Lazarus, David B.; Lonsdale, Malcolm J.; Mohr, Barbara A. R.; Nagao, Toshiyasu; Pereira, Christopher P. G.; Pudsey, Carol J.; Robert, Christian M.; Schandl, Eva S.; Spiess, Volkhard; Stott, Lowell D.; Thomas, Ellen; Thompson, Keith F. M.; Wise, Sherwood W., Jr.; Kennett, Diana M.; Masterson, Amanda; Stewart, Norman J.
Source: Proceedings of the Ocean Drilling Program, Weddell Sea, Antarctica, covering Leg 113 of the cruises of the Drilling Vessel JOIDES Resolution, Valparaiso, Chile, to East Cove, Falkland Islands, sites 689-697, 25 December 1986-11 March 1987, Peter F. Barker, James P. Kennett, Suzanne B. O'Connell, Stephen Berkowitz, William R. Bryant, Lloyd H. Burckle, Per Kristian Egeberg, Dieter Karl Fütterer, Rainer Erich Gersonde, Xenia Golovchenko, Norman Hamilton, Lawrence Lawver, David B. Lazarus, Malcolm J. Lonsdale, Barbara A. R. Mohr, Toshiyasu Nagao, Christopher P. G. Pereira, Carol J. Pudsey, Christian M. Robert, Eva S. Schandl, Volkhard Spiess, Lowell D. Stott, Ellen Thomas, Keith F. M. Thompson, Sherwood W. Wise, Jr., Diana M. Kennett, Amanda Masterson and Norman J. Stewart. Proceedings of the Ocean Drilling Program, Scientific Results, Vol.113, p.27-37. Publisher: Texas A & M University, Ocean Drilling Program, College Station, TX, United States. ISSN: 0884-5891
Note: In English. 21 refs.; illus. incl. 2 tables, 1 plate, sketch map, sects.
Summary: Seismic data acquired over the eastern shelf and margin of the South Orkney microcontinent have shown a high-amplitude reflection lying at a sub-bottom two-way travel time (TWT) of 0.5-0.8 s. There appear to be two causes for the reflection which apply in different parts of the shelf. The more widespread cause of the reflection is a break-up unconformity associated with the opening of Jane Basin to the east. This is clearly seen where reflections in the underlying sequence are discordant. In contrast, in Eotvos Basin and the southeastern part of Bouguer Basin, the high-amplitude reflection in places cuts across bedding and is interpreted to be caused by silica diagenesis. Analysis of core samples from the Eotvos Basin by X-ray diffraction and scanning electron microscopy revealed the presence of a silica diagenetic front at 520-530 mbsf. In Bouguer Basin the depth of the high-amplitude reflection was not reached by drilling; however, the reflection is probably also caused by silica diagenesis because of the biogenic silica-rich composition of the sediments cored. The estimated temperatures and ages of the sediments at the depths of the high-amplitude reflections at both sites compare favorably with similar data from other diagenetic fronts of the world. The high-amplitude reflection in Bouguer Basin is commonly of inverse polarity, possibly caused either by interference between reflections from several closely-spaced reflecting layers, such as chert horizons, or by free gas trapped near the diagenetic front. (Auth. mod.)
Year of Publication: 1990
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 07 Marine Geology and Oceanography; 20 Geophysics, Applied; Acoustical logging; Aliphatic hydrocarbons; Alkanes; Antarctic Ocean; Antarctica; Bouguer Basin; Chemical composition; Composition; Diagenesis; Eotvos Basin; Gas hydrates; Geophysical methods; Geophysical profiles; Geophysical surveys; Hydrocarbons; Interpretation; Inverse problem; James Basin; Leg 113; Marine geology; Methane; Methods; Minerals; ODP Site 695; ODP Site 696; Ocean Drilling Program; Oceanography; Organic compounds; Organic materials; Physical properties; Processes; Reflection; Scotia Sea Islands; Seismic methods; Seismic profiles; Silicification; South Orkney Islands; Southern Ocean; Surveys; Weddell Sea; Well-logging
Coordinates: S704954 S614837 E0030559 W0432706
Record ID: 1991051144
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from the Antarctic Bibliography, United States