USGS Coastal and Marine Geology Program
Initial Report of the IMAGES VIII/PAGE 127 Gas Hydrate and Paleoclimate Cruise on the RV Marion Dufresne in the Gulf of Mexico, 2-18 July 2002
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READMEBackgroundThis report is divided into three main sections, the first two of which are the chapters in PDF format, described below. The third part is the appendixes, which link to the ancillary data produced at sea. Part 1The first part (Chapters 1 through 9) describes the interpretation of measurements integrated across all of our sample sites in the northern Gulf of Mexico. Chapter 1, Introduction: General introduction, scientific objectives and conclusions. Chapter 2, Geologic Setting: Results of prior USGS seismic-reflection cruises conducted in the northern Gulf of Mexico that provided the stratigraphic framework for the present coring program. Site characteristics of Tunica Mound, Bush Hill, the Mississippi Canyon region, and Pigmy and Orca Basins are discussed. Chapter 3, Coring and Gas Hydrate Operations: An illustrated record of the procedures used to acquire, subsample, and process sediment samples from the various sampling devices used during the cruise. Special emphasis is placed on safety-related aspects dealing with dissociating gas hydrates. Chapter 4, Physical Properties: Results of shear strength, electrical resistivity, texture, carbon content, and index property tests performed at sea and in a shore-based laboratory. Chapter 5, Sedimentology: Sedimentologic descriptions and discussion of longitudinally split cores obtained during the cruise. In addition, techniques used to obtain Multi-Sensor Core Logs (MSCL), core photographs, and spectrophotometric logs are presented. Chapter 6, Heat Flow: Results of instrumented gravity core penetrations of the sea floor. Geothermal gradients and heat-flow parameters at 17 locations distributed throughout the three main study areas. Chapter 7, Thermal Conductivity: Methods and results of thermal conductivity (TC) tests performed on whole-round sections from 23 cores. Chapter 8, Pore-Water Geochemistry: Interpretations of chloride, sulfate, and methane concentration in relation to subbottom depth of 483 water samples squeezed from sediment of Tunica Mound, Bush Hill, and the Mississippi Canyon region. Chapter 9, Sediment Gas Geochemistry: Results of hydrocarbon and carbon dioxide gas analyses of sediment samples taken from four distinct regions in order to constrain concentrations and sources of gas that may form gas hydrate. Gas from dissociated hydrate, gas dissolved in sediment pore water, and gas from voids in the core were analyzed. |
The second part of this report (Chapters 10 through 14) is related to analyses that were performed on just one or a limited number of cores.
Chapter 10, Microbiology: An analysis of the archaeal small-subunit ribosomal RNA gene diversity from core MD02-2571C2, located near a gas chimney at a site west of the Mississippi Canyon.
Chapter 11, Biostratigraphy: A preliminary age-depth model for core MD02-2570 (west flank of the Mississippi Canyon), based on datums defined by the regional biostratigraphic zonation of planktonic foraminifers.
Chapter 12, Scanning Electron Microscopy (SEM): SEM analyses of natural gas hydrate nodules from core MD02-2569, from a site west of the Mississippi Canyon. Similarities in grain and pore structure were compared with images of laboratory-synthesized gas hydrates.
Chapter 13, Pollution Transport: Results of textural analyses of samples from Pigmy Basin and from low-oxygen, hyper-saline Orca Basin. Trace metal compositions of basin sediments were determined using a variable-pressure scanning electron microscope (SEM) equipped with energy-dispersive spectroscopy (EDS).
Chapter 14, Carbonate Mineralogy and Isotopes: Analyses of carbonates sampled from various subbottom depths at Tunica Mound and the Mississippi Canyon.
The third part of this report consists of appendixes that typically, but not exclusively, present information and data produced at sea. Most of the at-sea data sets required the use of proprietary software that was not available for post-cruise editing and, thus, are in their original, unedited formats.
Appendix A, Cruise Logistics: A table of core information, core and sediment recovery statistics, photographs, and contact information for cruise participants.
Appendix B, Maps: Regional and local bathymetric maps showing core locations.
Appendix C, Combined Station Results: Compiled, measured properties, and information for individual core sites.
Appendix D, Seismic profiles/Track lines: Regional and local core-specific seismic profiles and track lines.
Appendix E, Core Summaries: Information about individual core recovery and sediment observations.
Appendix F, Lithologic Descriptions: Unedited lithologic descriptions produced at sea of longitudinally split cores.
Appendix G, Core Photographs: At-sea photographs of freshly exposed longitudinally split cores (combined from individual digital files representing 0.5-m long core sections).
Appendix H, Multi-Sensor Core Logger (MSCL) Results: Individual core at-sea records of unedited acoustic velocity and amplitude, density, magnetic susceptibility, and related properties.
Appendix I, Spectrophotometry Results: Unedited, at-sea spectrophotometry records of individual cores.
Appendix J, Photographs: Digital photographs of shipboard activities.
Appendix K, U.S. Geological Survey (USGS) Video Press Release: Produced for the USGS in Tampa Bay.
Appendix L, Gas Hydrate Stability Models: Gas hydrate stability models related to gas type and geothermal conditions.
Appendix M, Metadata: Cruise logistics and information.
Appendix N, Abbreviations and Symbols: Selected abbreviations and symbols used in this report.
There are two top-level files and fifteen top-level directories contained on this DVD.
The top-level files are:
The fifteen main directories include:
Directories AppendixA-L/
These directories contain subdirectories of supporting cruise data in various formats, including Microsoft Excel, Word, and Powerpoint, Adobe Reader and Illustrator, JPEG, PICT, and GIF files, RTF, and several short AVI movies. In addition to containing images from the cruise, Appendix J contains HTML files that display thumbnail images for each directory of images.
Directory htmldocs/
This directory contains the HTML pages used on this DVD and the subdirectory containing images.
Directory pdf_chapters/
This directory contains the 14 PDF chapters comprising the text part of the DVD.
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