SCIENTIFIC MEASUREMENTS STRATEGY
Because the central theme of Leg 184 was the Neogene coevolution of
tectonics and climate, the shipboard focus was on recovering continuous
sediment sections capable of recording millennial- to orbital-scale
variations. This concentration on orbital-scale and higher resolution
variability is reflected in the Leg 184 shipboard measurements program
as well as its sampling plan and shore-based analysis.
Shipboard measurement strategy was to acquire high-resolution (2-5 cm)
core-logging records from all holes, including MS, gamma-ray attenuation
(GRA) bulk density, NGR, and CR These data were used to construct the
meters composite depth (mcd) scale, which was used to evaluate the
completeness of the stratigraphic section and to splice an intact,
representative record for each site. Routine measurements, taken at
frequencies of one per section to one per core (intervals of ~1.5-10 m),
included biostratigraphy (calcareous nannofossils and foraminifers),
paleomagnetism, hydrocarbon gas analysis, interstitial water chemistry,
moisture and density, carbonate, and P-wave velocities.
The Leg 184 downhole logging plan was designed to provide (1) complete
stratigraphic coverage, especially in the incomplete XCB intervals; (2)
proxy data not available from core measurements, such as resistivity and
yields of K, U, and Th; and (3) in situ sonic velocity for the construction of
synthetic seismograms. Sites 1143, 1144, 1146, and 1148 were logged
using the following three downhole tool strings:
- The triple combo tool string, which includes the dual
induction tool to measure resistivity, the accelerator
porosity sonde to measure porosity, and the hostile
environment lithodensity sonde that measures bulk
density and general lithology. Also included on this tool
string were the hostile environment natural gamma-ray
sonde (HNGS) to measure total NGR and to calculate K, U,
and Th yields and the Lamont-Doherty Earth Observatory
temperature logging tool to measure borehole fluid
temperature.
- The FMS-sonic tool string, which includes the Formation
MicroScanner (FMS) with the general-purpose
inclinometry tool to measure microresistivity at
centimeter resolution and the dipole sonic imager to
measure compressional and shear-wave velocity.
- The geological high-resolution magnetic tool (GHMT),
which includes the nuclear magnetic remanence sonde to
measure the total magnetic field and the susceptibility
measurement sonde to measure the MS from induction.
Site Summaries - Site 1143
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