Handbook for Shipboard Paleomagnetists1, 2

Carl Richter,3 Gary Acton,4 Charles Endris,5 and Mads Radsted6

ABOUT THIS TECHNICAL NOTE

The shipboard paleomagnetic laboratory, the Ocean Drilling Program (ODP) database structure, and the hardware and software environment on the JOIDES Resolution have changed almost entirely since the first publication of Technical Note 18 in 1993 (Stokking et al., 1993). Although in constant flux, the shipboard paleomagnetic laboratory environment, equipped in the past few years with new magnetometers, a new demagnetizer, a new database structure (a relational Oracle database), and new software, has come to a point where it is stable enough to redefine the paleomagnetic data acquisition and archiving procedures and requirements. In contrast, the role of the shipboard paleomagnetist has changed little since 1993, so part of this technical note builds upon the information that was provided in Stokking et al. (1993). In addition, we have benefitted from the input of many paleomagnetists and shipboard paleomagnetism technicians who have sailed on the JOIDES Resolution over the past decade.

Draft versions of this technical note were available during the last 2 years of ODP. The completed version of this technical note will become a legacy document for ODP and a starting point for the Integrated Ocean Drilling Program (IODP).

The objectives of this note are to

  1. Introduce the novice laboratory user to procedures and equipment,
  2. Provide expert users with a reference of measurement principles and data specifications,
  3. Document the laboratory practices that were typical of the final 6 years of ODP, and
  4. Create a foundation for effective management and further development of the shipboard paleomagnetism laboratory for the current program and for future programs focused on ocean drilling.

This handbook is divided into eight sections and four appendixes. "Introduction" discusses research objectives of paleomagnetic measurements and gives an overview of the shipboard laboratory, paleomagnetic sampling strategies commonly used, and the new ODP database. "Remanent Magnetization" and "Magnetic Susceptibility" are dedicated to magnetic remanence and magnetic susceptibility measurements that are routinely obtained on the ship. These sections give a brief introduction to paleomagnetism principles, shipboard environmental factors that influence data quality, and some common uses of the paleomagnetic data. They also describe the equipment, the physical property being measured, measurement principles and procedures, and equipment calibration and performance. Each section covering a measurement system also presents the exact data model implemented in the new ODP database, the Web-based data queries available to the user for data retrieval, and algorithms used in the queries.

Each section covering a measurement system presents calibration and measurement procedures in only a generic way, focusing on issues essential for maintaining the best data quality possible. Step-by-step tutorials for operating the data acquisition programs and instruments are not included here. The programs controlling the instrumentation evolve rapidly as new computer hardware and software become available, and user interfaces are improved almost continuously. In most cases, these upgrades do not affect the principles and data models presented here, but do slightly modify the hands-on procedures. ODP typically staffs a shipboard technician who has experience running equipment in the paleomagnetism laboratory and is available to assist with details of instrument use. In addition, the "Explanatory Notes" chapters from previous cruises, the technical reports written at the end of each cruise by the paleomagnetism-laboratory technician, and other laboratory manuals or "cook books," which are available for most of the instruments and software, provide valuable resources for the shipboard paleomagnetists.

"Alternating Field and Thermal Demagnetization" and "Laboratory-Induced Magnetization" introduce the equipment available for the demagnetization (thermal and AF) and magnetization (isothermal and anhysteretic) of discrete samples. The magnetic orientation of hydraulic piston cores is discussed in "Core Orientation."  "Measurement Guidelines and Strategies" provides a practical guide to what can be measured during a cruise. The drilling magnetic overprint and other common problems in ODP cores are examined in "Problems with Magnetic Measurements in the Shipboard Environment." This section also summarizes problems encountered on past cruises, the identification of coring-induced overprints and deformation, and experiments that have been done to narrow down the sources of the drilling overprint.

The appendixes contain a list of magnetic units ("Appendix A") example data files with information on file formats ("Appendix B") operation and calibration procedures for the Kappabridge ("Appendix C,") and a table to convert voltage to magnetic fields for the IM-10 impulse magnetizer ("Appendix D.") The first version of Technical Note 18 by Stokking et al. (1993) is available online (www-odp.tamu.edu/publications/tnotes/tn18/f_pal.htm).

1Richter, C., Acton, G., Endris, C., and Radsted, M., 2007. Handbook for shipboard paleomagnetists. ODP Tech. Note, 34 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/tnotes/tn34/INDEX.HTM>. [Cited YYYY-MM-DD]

2See Disclaimer.

3Department of Geology, University of Louisiana at Lafayette, PO Box 44530, Lafayette LA 70504-0002, USA.

4Department of Geology, University of California, One Shields Avenue, Davis CA 95616, USA. acton@geology.ucdavis.edu

51275 Country Club Drive, Ben Lomond CA 95005, USA.

6Lasbygade 67-69, 6000 Kolding, Denmark.

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