Rea, B.R., Gaillot, P., Lyle, M., Wilson, P.A., Janecek, T.R., Backman, J., Busch, W.H., Coxall, H.K., Faul, K., Hovan, S.A., Knoop, P., Kruse, S., Lanci, L., Lear, C.H., Moore, T.C., Nigrini, C.A., Nishi, H., Nomura, R., Norris, R.D., Pälike, H., Parés, J.M., Quintin, L., Raffi, I., Rea, D.K., Steiger, T.H., Tripati, A.K., Vanden Berg, M.D. and Wade, B.S. (2002) ODP Leg 199 – Paleogene equatorial transect: preliminary logging results. In, 4th European ODP Forum Abstract Volume. 4th European ODP Forum (11/04/02 - 12/04/02) Tromsø, Norway. European Consortium for Ocean Research Drilling.
Abstract
During Leg 199 two of the drilled sites (1218 and 1219) were logged using the Triple Combo (geophysical toolstring), FMS-Sonic (borehole imaging and sonic velocity) and the high resolution Lamont-Doherty Earth Observatory (LDEO) Multi-Sensor Gamma Ray Tool (MGT). Site 1218 was drilled on 40Ma crust and will be used to investigate paleoceanographic processes in the equatorial Paleogene Pacific Ocean during the transition from the Early Palaeogene ‘greenhouse’ to the Late Paleogene ‘icehouse’. Site 1219 was the southernmost site and was drilled on 55 Ma crust. It contains all the seismic horizons identified for a Paleogene equatorial seismic stratigraphy, and will also be used to study equatorial ocean circulation from the late Paleocene to the Late Eocene. Logging operations at both sites went well with heave of <2.5m experienced at both sites. Conditions in Hole 1218A were excellent and tools made good contact along the length of the borehole. In Hole 1219A there were a number of areas where washouts had widened the borehole beyond the width of both the FMS and Triple Combo callipers. At both sites no bridges were encountered during any logging run and the bottom of the hole was reached on all passes. Wavelet transform analyses on tool acceleration and density data are used to evaluate the effects of ship heave, borehole diameter and rugosity on the log data. Obtaining velocity data from slow sediments such as those drilled on Leg 199 is notoriously difficult. At Site 1219 the potential use of First Motion Detection (FMD) measurement mode for obtaining sonic velocity data was investigated. The results obtained from FMD are compared to those obtained by the ‘normal’ P-wave data acquisition procedure. Log and lithological stratigraphy from site 1218 and 1219 are presented along with selected core and log data sets. The high core recovery at both sites provides excellent core data sets that correlate well with the log data. High-resolution FMS imagery showing sub-metre depth scale cyclicity is presented from both sites. Chert bands and nodules are generally poorly recovered in cores but readily show up on the FMS imagery. An example is presented where the FMS imagery is used to locate and map the chert layers. Core, log and seismic data may be linked using synthetic seismograms which provide a means for interpreting seismic data in terms of the measured formation properties, for example lithological or chronological boundaries may be picked out as specific reflectors. Synthetic seismograms, which have been obtained for both sites, are presented.
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