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Expedition 319 Scientists2


This chapter documents the methods used for shipboard measurements and analyses during Integrated Ocean Drilling Program (IODP) Expedition 319. Riser drilling was conducted in IODP Hole C0009A, and cuttings, mud gas, and cores were recovered and analyzed. In addition, a suite of downhole measurements was performed, including measurement while drilling (MWD) and wireline logging (including vertical seismic profile [VSP] and Modular Formation Dynamics Tester [MDT] experiments). In IODP Hole C0010A, logging while drilling (LWD) and observatory activities were carried out, including a sensor dummy run and a temporary bridge plug sensor installation. In IODP Hole C0011A, LWD drilling was carried out as a contingency operation.

Reference depths

Depths of each measurement or sample are reported relative to both the drilling vessel rig floor (rotary table) and the seafloor (see Table T1 in the "Expedition 319 summary" chapter). These depths are determined by drill pipe and wireline length and are correlated to each other by use of distinct reference points. Drilling engineers refer to pipe length when reporting depth and report it as drilling depth below rig floor (DRF) in meters. Core depths are based on drilling depth below rig floor and converted to core depth below seafloor (CSF). IODP conventions are applied for cores with greater than or less than 100% recovery (IODP Depth Scales, Cuttings ("mud") depths are reported as mud depth below rig floor (MRF), based on drillers depth (DRF) and the calculated lag depth of the cuttings (see below for further details).

In referring to wireline logging results, depths are initially reported as wireline depth below rig floor (WRF). Wireline logging depths are corrected relative to drillers depth (DRF) using a known reference datum (e.g., seafloor ["mudline"] or base of casing ["casing shoe"] and relative to each logging data set down the borehole [including tool speed corrections where appropriate]). These corrected depths are then reported as wireline log matched depth below seafloor (WMSF) (see "Logging" for further details). LWD and MWD use the same depth scale (LWD depth below rig floor [LRF]); depths are described by adding the lengths of all drill string components deployed beneath the rig floor and accounting for the constant offset for each sensor based on its position within the tool assembly (IODP Depth Scales, In summary, the depths reported in depths below rig floor (DRF, MRF, WRF, and LRF) are converted to depths below seafloor (drilling depth below seafloor [DSF] or CSF, mud depth below seafloor [MSF], WMSF, and LWD depth below seafloor [LSF], respectively) by subtracting water depth and the height of the rig floor from the sea surface, with corrections relative to drillers depth where appropriate. These depths below seafloor (DSF, CSF, MSF, WMSF, and LSF) are therefore all equivalent. Seismic depths are reported in either time (s) or depth (m). For time sections, a two-way traveltime (s) scale is used, below sea level. For depth sections, seismic depth below seafloor (SSF) or seismic depth below sea level (SSL) are used. Where figures incorporate multiple data sets, including seismic data, meters below sea level (mbsl) or meters below seafloor (mbsf) are ordinarily used.

Cuttings depths

During riser drilling, drilling mud circulates within the riser pipe between the drillship and the bottom of the hole. As the drill bit cuts through the formation, the fragments (cuttings) are suspended in the drilling mud and carried with the formation pore water and gas back to the rig. A cuttings sample is assumed to be an averaged mixture of rock fragments and sediments from an ~5 m drilling interval. The time between when the formation is cut by the drill bit and when these cuttings arrive at the ship is known as the "lag time," which is a function of drilling mud pumping rate and annular mud volume, and is used to calculate the "lag depth." At a constant pump rate, lag time and lag depth increase as the hole is deepened and the volume of circulating mud increases. All of the depths recorded for cuttings at Site C0009 have been corrected for this lag. Twice during Site C0009 drilling, a calcium carbide lag test was conducted to check the calculated lag time. The carbide generates acetylene on contact with water; the acetylene acts as a tracer, and its lag time can be measured precisely by mud gas analysis.

Depth precision estimates of cuttings

Cuttings were retrieved from 5 m depth intervals, and lag depth was calculated and calibrated as discussed above. By comparison with wireline logging data measured relative to the drilling vessel rig floor at distinct marker horizons, we can assess the precision of cuttings depths relative to other data sets. At Site C0009, several parameters in log and cuttings data sets change sharply at ~1300 m MSF. For example, we find changes in values of magnetic susceptibility and MnO from cuttings are within 10 m of abrupt changes in P-wave velocity and spontaneous potential (SP) in the log data at this depth. This estimate of cuttings depth precision (~10 m) generally fits data set comparisons at other depths.

Sampling and classification of material transported by drilling mud

Three sets of cuttings were collected during drilling of Site C0009 (see Table T1 in the "Site C0009" chapter):

  1. 703.9–1509.7 m MSF during riser drilling (drilling Phase 2);

  2. 1509.7–1593.9 m MSF during the coring operation (drilling Phase 3); and

  3. 1509.7–1604 m MSF during opening of the borehole after coring (drilling Phase 4).

Cuttings were taken at every 5 m depth interval (DRF) from the shale shakers. Drilling mud and mud gases were also sampled during drilling (see "Geochemistry"). Mud gas, fluids, and cuttings samples were classified by drill site and hole using a sequential material number followed by an abbreviation describing the type of material. The material type identifiers are

  • SMW = solid taken from drilling mud (cuttings),

  • LMW = liquid taken from drilling mud, and

  • GMW = gas taken from drilling mud.

For example, "319-C0009A-123-SMW" represents the 123rd cuttings sample recovered from Hole C0009A during Expedition 319.

Influence of drilling mud composition on cuttings

Cuttings are mixed with drilling mud and various contaminants. The "Site C0009" chapter discusses the possible effects of contamination on different types of measurements. Three different batches of cuttings (drilling Phases 2, 3, and 4) were collected during drilling at Site C0009 (see "Cuttings handling" for details). Cuttings were not retrieved during the 17 inch hole opening (drilling Phase 8), principally because of an expected increase in contamination from cavings. Cuttings from Phase 4 were contaminated by CaCO3, which was added as a lost circulation material to reduce mud loss. These cuttings were deemed strongly affected physically and chemically and could only be used for lithologic and structural description. Changes in mud weight may also impact physical and chemical measurements made on cuttings. Mud weight was 1.08 specific gravity (SG) during Phase 2 and was increased to 1.09 SG and then 1.1 SG during Phase 3. Mud weight was 1.1 SG during Phase 4. The impact of the difference in mud weight between Phases 2 and 3 is discussed in various sections of the "Site C0009" chapter. The length of time between creating the cuttings material and retrieving them from the shale shakers (i.e., time spent within the drilling mud) may also affect the degree of alteration—cuttings collected during Phase 3 (coring) were suspended in the drilling mud significantly longer than cuttings from Phases 2 and 4.

Cuttings handling

Every 5 m, we recovered 400 cm3 of cuttings material for long-term archiving and postexpedition sample requests (including postmoratorium requests) and ~2000 cm3 for shipboard analyses and personal sampling (Fig. F1). Two different types of cuttings were recognized: "soft" and "semihard."

For both soft and semihard cuttings, unwashed cuttings samples were taken for the following measurements:

  • 70 cm3 was removed for photography and then micropaleontology.

  • 30 cm3 was removed for lithologic and grain-composition description.

  • 300 cm3 (10 cm of filled IODP core liner) was removed for natural gamma ray (NGR) measurement and then returned to the sample bottle for future analysis.

Cuttings from 703.9 to 1037.7 m MSF were classified as soft and were not washed because no usable chips could be retrieved without disaggregation. In this case, only photography, lithologic description, paleontological analysis, and NGR measurement could be conducted, as described above (Fig. F1).

Cuttings between 1037.7 and 1604 m MSF were classified as semihard. In this case, 650 cm3 of the cuttings sample was washed and separated into different size fractions (Fig. F1). These samples were processed as follows:

  • Cuttings and mud were gently washed with seawater using a sieve (opening 250 µm) at the core-cutting area.

  • Samples were sieved into different size fractions (>4 mm, 1–4 mm, or 0.25–1 mm) with seawater. During sieving, a hand magnet was used to remove iron contaminants originating from drilling tools and casing. Samples for moisture and density (MAD) analysis were removed (see below) and prepared separately (see "Physical properties"). All size fractions of Samples 319-C0009A-135-SMW through 173-SMW were lightly washed with freshwater and deionized water and then soaked for 11–37 h in deionized water. All size fractions of Samples 319-C0009A-75-SMW through 134-SMW and 176-SMW through 220-SMW were lightly washed with deionized water but not soaked.

  • MAD analyses were carried out on 35 cm3 of washed and sieved samples, using samples from both the 1–4 mm fraction and some from the >4 mm fraction for comparison.

  • The 1–4 mm fraction used for nondestructive MAD measurements was reused for magnetic susceptibility.

  • All sample fractions were then freeze-dried. Small samples (~10 cm3 each) were extracted from the 1–4 mm fraction and ground into powder for the following analyses: X-ray diffraction (XRD) and X-ray fluorescence (XRF), inorganic carbon content using a carbonate analyzer, and total carbon (TC) and total nitrogen (TN) content using a carbon-hydrogen-nitrogen-sulfur/oxygen (CHNS/O) elemental analyzer.

Core handling

The cores and plastic liners were cut into ≤1.5 m long sections in the core-cutting area. A small (5 cm3) sample was taken for micropaleontology from the core catcher section and a 40 cm long section, usually from a middle section of the core, was taken for pore water chemistry (interstitial water) (Fig. F2). This short section was immediately removed from the core-cutting area and scanned with the X-ray computed tomography (CT) scanner to examine the core's internal structure and to avoid destroying unique tectonic or sedimentary features. A 5 cm thick (primary) whole-round cluster was also selected and sampled next to, or close to, the whole-round interstitial water sampling interval (Araki et al., 2009). Both the interstitial water and cluster whole-round samples were taken from a homogeneous unfractured interval (preferred material for both sample types) based on X-ray CT scan images. In some cores, a homogeneous unfractured section (15 cm) was also removed for anelastic strain recovery measurement.

In the laboratory, X-ray CT images were taken of all remaining core sections. The cluster sample was divided into subsamples for discrete P-wave velocity measurement, MAD, anisotropy of magnetic susceptibility (AMS), paleomagnetism, inorganic carbon contents, TC and TN content, bulk XRD, and XRF analyses. A part of the cluster sample was used for time-sensitive personal samples for postexpedition studies.

After the core sections equilibrated to ambient room temperature (~3 h), they were run through the whole-round multisensor core logger (MSCL-W). After finishing these measurements, personal whole-round samples as well as community geotechnical archives from each core were removed before splitting the cores into working and archive halves (Araki et al., 2009). Additional whole-round cluster samples were taken adjacent to all whole-round samples for shipboard measurements. Digital images of archive-half sections were taken with the photo image logger (MSCL-I) before visual core description (VCD). Discrete samples were taken for P-wave velocity, MAD, paleomagnetism, and AMS measurement in each working-half section, excluding the primary whole-round cluster section (previously sampled for analysis). Thermal conductivity measurements were performed on a sample from each core using the half-space method. Additional samples were taken for inorganic carbon, TC and TN, XRD, and XRF analyses from every other section, again excluding the section from which the primary whole-round cluster was taken (samples already taken). Finally, core sections were wrapped in heat shrink plastic and transferred to cold storage. After the expedition, cores were transported for archiving at the Kochi Core Center in Kochi, Japan.

Personal sampling

IODP expeditions usually have a single science party. However, the Expedition 319 Science Party was divided into two groups (Araki et al., 2009). The following sampling procedure was used so that the second group would have equal sampling opportunities. During the first part of the expedition, scientists flagged their preferred personal sample locations, but these samples were not removed from the cores with the exception of (1) whole-round samples (see above), (2) time-sensitive samples, and (3) raw cuttings samples. During the second part of the expedition, scientists flagged their samples and all personal samples were then taken from the cores after resolving conflicts.

Authorship of site chapters

The separate sections of the site chapters and methods chapter were written by the following shipboard scientists (authors are listed in alphabetical order; no seniority is implied):

  • Principal results: Shipboard Science Party

  • X-ray computed tomography: Hayman

  • Logging: Moe

  • Lithology: Buchs, Buret, Efimenko, Flemings, Kawabata, Schleicher

  • Structural geology: Hayman, Huftile, Lin, Moore

  • Biostratigraphy: Jiang, Kameo

  • Geochemistry: Horiguchi, Wiersberg

  • Physical properties: Boutt, Conin, Cukur, Doan, Flemings, Ito, Kano, Kitada, Kopf, Lin

  • Downhole measurements: Boutt, Doan, Flemings, Hino, Ito, Kano, Lin, von Huene

  • Cuttings-Core-Log-Seismic integration: Conin, Cukur, Flemings, Kano, Kopf

  • Observatory: Kano, Kitada, Kopf

  • Paleomagnetism: Oda, Zhao


For reference, a list of commonly used acronyms in Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) science is included in the "Appendix: NanTroSEIZE acronyms" chapter.

1Expedition 319 Scientists, 2010. Methods. In Saffer, D., McNeill, L., Byrne, T., Araki, E., Toczko, S., Eguchi, N., Takahashi, K., and the Expedition 319 Scientists, Proc. IODP, 319: Tokyo (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/iodp.proc.319.102.2010

2Expedition 319 Scientists' addresses.

Publication: 31 August 2010
MS 319-102