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doi:10.2204/iodp.proc.302.103.2006 Methods1Expedition 302 Scientists2IntroductionInformation assembled in this chapter will help the reader understand the basis for the preliminary conclusions of the Expedition 302 Scientists and will also enable the interested investigator to select samples for further analyses. This information concerns offshore and onshore operations and analyses described in the “Sites M0001–M0004” chapter. Methods used by various investigators for shore-based analyses of Expedition 302 samples will be described in the individual contributions published in the Expedition Research Results and in various professional journals. Authorship of site chapterThe separate sections of the site chapter were written by the following authors, listed in alphabetical order:
Offshore and onshore science activitiesArctic Coring Expedition (ACEX) Expedition 302, science activities were partially conducted offshore during the field expedition aboard the Oden and Vidar Viking and completed onshore at the Integrated Ocean Drilling Program (IODP) Bremen Core Repository (BCR) after the expedition. A subset of the expedition scientists participated in the offshore phase of Expedition 302, and all expedition scientists participated onshore. This chapter is organized by discipline, and each section describes the methods and standard procedures used in both the offshore and onshore phases. Cores were collected offshore in lengths of up to 5 m, cut into 1.5 m lengths, nondestructively tested using the multisensor core logger (MSCL), stored in a refrigerated container, and then transported to BCR after the offshore phase ended. Core catchers from each core were analyzed offshore for biostratigraphy, visual core description, moisture and density (MAD), and chemistry. A limited suite of whole-round samples was taken from cores collected for offshore analyses, pore water sampling, and microbiology. MAD samples were taken and analyzed offshore. Onshore, at BCR, cores underwent the complete IODP suite of analyses and sampling by the expedition scientists. Methods describe offshore and onshore activities, including biostratigraphy, lithostratigraphy, timescale and sedimentation rates, stratigraphic correlation, petrophysics, chemistry, and microbiology. Coring methodsDrilling and coring toolsA number of different coring tools were mobilized for Expedition 302, including a complete back-up system of wireline coring tools in case the requested tools did not perform as anticipated or losses were greater than the three complete sets of new equipment carried. In the event that only the new coring tools were used, the level of new system spares carried was sufficient for all of the work conducted. All drilling operations were contracted to Seacore Ltd. of Gweek (Cornwall, U.K.), who constructed, installed, and operated an R100 rig designed for cold-weather operations. The rig was installed on the Expedition 302 drillship (Vidar Viking), a modified icebreaker ICE-10 class ship with dynamic positioning. During drilling, officers on board positioned the vessel manually by joystick control. A 2 m diameter moonpool was installed with an underhull steel skirt that protected the drill string from damage or severing by ice. Drill stringA Deep Sea Drilling Project (DSDP)/Ocean Drilling Program (ODP) 5 inch drill string with 5½ inch full hole connections and a 4⅛ inch inner diameter (ID) was used. It was downgraded to grade 2 but was acceptable for Expedition 302 requirements. All pipes were prepared at Texas A&M University (TAMU) or Houston (Texas, USA) and shipped to the United Kingdom in pipe bins specially made in Houston for the British Geological Survey (BGS). These pipe bins were also used for pipe storage on the drillship during operations. BGS acquired 2.5, 3.5, and 5 m “pup” joints machined from solid bar to allow for “spacing out” and setting up the top drive. All of the new joints were of certified American Petroleum Institute (API) materials, manufacture, and threads. Drill collarsDrill collars were provided by the drilling contractor, Seacore Ltd. All were Certified API materials and threads (7 inch outer diameter (OD) [178 mm], 4 inch ID [101 mm], and 5 m long) and were new for the project. Coring toolsThe coring tools used belonged to the new BGS Marine Wireline Corebarrel System (BGS-MWCBS). This system uses a common outer core barrel assembly to house wireline-retrievable tools for piston coring, extended coring, push coring, and nonrotating hard rock coring. A separate inner tube configuration allows push sampling or probe (e.g., temperature) insertion at the base of the hole, and an insert full-face drill bit can be added to allow open-hole wash drilling in selected borehole intervals. A sliding hammer was also fabricated on board, and a modified version of the hammer will be added to the suite of tools carried on any future operations with the BGS-MWCBS. Outer core barrel assemblyThe outer core barrel assembly is a 7 inch (178 mm) OD steel tube 7 m long with a section at the bottom that accepts a drill bit, a honed ID central section to allow a sealed bore for piston coring, and a set of top sections to allow for inner barrel landing and latching. All materials, manufacture, and threads on the core barrel were to API standard with 5½ inch full hole threads to match the bottom-hole assembly (BHA) except for two subs, where the pin section had a modified length to allow for inner rings. The box thread on the head section of the outer core barrel is directly compatible with the drill collar threads used for the BHA. The drill bits used with the system were 9½ inch OD (242 mm) with a clear 98 mm ID through which tools or seat core bits were passed. Three types of bits were aboard the ship: natural diamond, polycrystalline diamond, and six-cone roller. Only the six-cone roller bit was used. Piston corerThe piston corer (PC) is a modified version of the ODP advanced piston corer (APC) system which, with the exception of orientation, was made to the same specification with the same materials. The main difference is that the PC is 5 m in length so that the tool could be used with smaller drill rigs. Various flapper, dog, and basket catchers were carried, and standard ODP core liner was used. Extended corerThe extended corer is similar to the ODP extended core barrel (XCB) in that it is designed to obtain core in “difficult formations.” It is a rotating core barrel that extends some 100 mm ahead of the main drill bit and collects core from there. However, if the material becomes too hard for core collection, then a spring assembly allows the small XCB bit to retract into the face of the main drill bit that then assists with the coring as well as the hole cutting. Replacing the cutting end enables the best core recovery, and a variety of bits, cutting shoes, and catchers are available for the extended corer. The BGS extended corer also uses standard ODP core liner. Latch-in indicator and nonreturn valve systemsIncorporated into the landing and latching assemblies of all but the piston corer inner assemblies are two features that allow indication of latch-in and nonreturn of fluids up the drill pipe should unexpected pressures be encountered in the formation. Wireline retrieval systemWireline retrieval is by means of a standard Boart Longyear PQ overshot. An overshot fishing tool and release sleeves compatible with the tool but modified by BGS for deepwater work were also available but were not used. All inner core barrels latch onto the overshot retrieval tool using a Boart Longyear Spear Point Assembly. Bridon Fibres Ltd. provided the special wireline wire, selected on the recommendation of Weatherford, who also supplied the termination. This wire allowed a packer to be deployed around it to seal the borehole for piston coring. Core handling and curationOnce the coring tool arrived on deck, the plastic-lined core was removed from the core barrel and each core was cut into 1.5 m sections and labeled. Consistent with IODP policy, all cores were named and labeled with the appropriate expedition number, site number, hole letter, core number, core type (Table T1), section number, and an indication of whether a split-core half was working or archive. Samples and data labels also included the sample interval. Cores taken from a hole were numbered serially from the top of the hole downward. When full recovery was obtained, core sections were numbered 1 through 3 or 4, beginning at the top of the core. The core catcher sample was extruded into a short piece of split plastic liner and treated as a separate section below the last core section. When sediment recovery was <100%, the recovered sediment was measured from the top of the cored interval and then each of the sections were numbered serially, starting with section 1 at the top. Sections were cut starting at the top of the recovered sediment so that the lowest section was in many cases shorter than the nominal 1.5 m section length. Core sections were labeled at each end, and the working (double line) and archive (single line) side of the liners were engraved with the standard IODP identifier, “Expedition-Site-Hole-Core-Core type-Section” (e.g., 302-M0001A-1H-1, W) along with an “up” arrow. This ensured that each section could be permanently and uniquely identified. Blue end-caps (top of section) were marked with the core, core type, and section number (Fig. F1). At section breaks, the liner was cut with a liner pipe-cutting tool and the sediment was separated with a wire saw or spatula, depending on the level of sediment induration. Core sections were then moved into the curation container and capped. Caps were temporarily fastened until whole cores were taken for geochemistry and microbiology. Blue end-caps were placed at the top of each section, with clear end-caps at the bottom. Whole-round samples were taken after MSCL core logging (see “Petrophysics”), provided that the logging was completed within 40 min of recovery. Whole-round samples were taken on a selected basis at an interval of approximately one every third core. Yellow end-caps were placed at the end of any section from which a whole-round sample was taken. Core sections were not split offshore, and onboard sampling was limited to whole-round and core catcher samples. Although most sampling was conducted during the onshore science party at BCR, shipboard scientists (microbiologist and geochemists) collected samples offshore because of the ephemeral nature of these properties. All full core sections, core catcher samples, and some pore water aliquots were stored in the temperature-controlled container aboard the drillship. Pore water subsamples that required freezing were sent and stored aboard the Oden at –20°C (see “Geochemistry”). Microbiology samples were further treated, subsampled, and stored for different types of analyses (see “Microbiology”). Data handling, database structure, and accessData management during offshore and onshore phases of Expedition 302 had two overlapping stages. The first stage was the capture of metadata and data during the expedition (offshore and onshore). Central to this was the ACEX-Offshore Drilling Information System (OffshoreDIS), which stored drilling information, core curation information, and primary measurement data. The second stage was the longer-term postexpedition archiving of Expedition 302 data sets, core material, and samples. This function was performed by the World Data Center for Marine Environmental Sciences (WDC-MARE) and BCR. OffshoreDIS is a flexible and scalable drilling information system, originally developed for the International Continental Drilling Program (ICDP). The underlying data model for OffshoreDIS is compatible with Janus, BCR, PANGAEA, and LacCore in Minneapolis (Minnesota, USA). For the specific expedition platform configuration and offshore and onshore workflow requirements of Expedition 302, the OffshoreDIS data model, data pumps, and user interfaces were adapted to form ACEX-OffshoreDIS. This was the first implementation of OffshoreDIS, so it was very much a test of the system. Consequently, improvements and enhancements to the underlying database tables and user interfaces were made as a result of experience gained both during the expedition and postexpedition, which will serve future IODP mission-specific platforms (MSPs) and ICDP expeditions. Offshore, the system captured basic information related to core and sample curation, core photographs, section and sample label printing, and daily drilling logs. In addition, the database also stored primary data measurements. These included
In practice, it was not possible to capture some data sets during the offshore phase because the data model was incompatible with the actual data captured (e.g., MSCL calibration data). Also, scientists produced a variety of spreadsheet files and text documents containing data, descriptions, and interpretations in many different formats. Therefore, in addition to ACEX-OffshoreDIS, all data files were stored in a structured file system on a shared hard drive. For the onshore phase, the system was expanded to manage additional data types, and deficiencies in the original implementation were corrected. In addition, a visual core description tool, a Web interface, and a file management system were developed. Expedition 302 data were then transferred to the information system of WDC-MARE during the second phase. WDC-MARE was founded in 2000 and is a member of the International Council of Scientific Unions World Data Center system. PANGAEA is the geoscience information system used by WDC-MARE. It has a flexible data model that reflects the information processing steps in Earth science fields and can handle any related analytical data (Diepenbroek et al., 1999, 2002). It is used for processing, long-term storage, and publication of georeferenced data related to Earth sciences. Essential services supplied by WDC-MARE/PANGAEA are project data management and distribution of visualization and analysis software. Data management functions include quality checking, data publication, and metadata dissemination following international standards. Data captured by the ACEX-OffshoreDIS were transferred to this long-term archive following initial validation procedures as soon as they became available; data transfer was completed by the time of publication of this IODP Proceedings volume. Until the end of the moratorium period, the data were not public and access was restricted to the expedition scientists. However, following the moratorium, the data were published on the Internet (http://www.wdc-mare.org) and WDC-MARE will continue to acquire, archive, and publish new results derived from ACEX samples and data sets. OffshoreDIS was not able to produce standard barrel sheets for this volume. Visual core descriptions (VCDs) were manually reentered into AppleCORE for this purpose at the University of Rhode Island (USA). Future MSP expedition managers should consider VCD presentation during project planning stages. Hardware installationOffshoreDIS was implemented in SQLServer2000 with Microsoft-based client PCs connected to the system through a Microsoft Access-like user interface. For the offshore phase of the expedition, OffshoreDIS was installed on servers on both the Vidar Viking and the Oden. The system was configured to provide merge replication with the primary server on the Vidar Viking. This allowed the parties on both ships to operate independently in case of breaks in intership communications. In practice, the communications worked very well and the second server on the Oden was used as a hotstandby and data backup system. Core, section, and sample curation using ACEX-OffshoreDISExpedition 302 followed IODP procedures and naming conventions in core, section, and sample handling (see “Core handling and curation”). OffshoreDIS handled the curation of data and printed the appropriate labels also to IODP standards. Curation data comprise the following:
Section and sample label formats follow standard ODP/IODP conventions. They include the barcodes of the section/sample code and the complete section/sample code (Expedition-Site-Hole-Core-Core type-Section-Half-Interval and sample request code). This standardization guarantees data exchange among the repositories and enables information flow between the implementing organizations. |
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