Ratschbacher, Lothar; Wetzel, Andreas; Brokmeier, Heinz-Günter (1994): Physical properties and neutron texture measuerments of deep-sea carbonates of DSDP Holes 62-463 and 62-465A [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.763683, Supplement to: Ratschbacher, L et al. (1994): A neutron goniometer study of the preferred orientation of calcite in fine-grained deep-sea carbonate. Sedimentary Geology, 89(3-4), 315-324, https://doi.org/10.1016/0037-0738(94)90100-7
Always quote citation above when using data! You can download the citation in several formats below.
Abstract:
In weakly indurated, nannofossil-rich, deep-sea carbonates compressional wave velocity is up to twice as fast parallel to bedding than normal to it. It has been suggested that this anisotropy is due to alignment of calcite c-axes perpendicular to the shields of coccoliths and shield deposition parallel to bedding. This hypothesis was tested by measuring the preferred orientation (fabric) of calcite c-axes in acoustic anisotropic, calcareous DSDP sediment samples by X-ray goniometry, and it was found that the maximum c-axis concentrations are by far too low to explain the anisotropies.
The X-ray method is subject to a number of uncertainties due to preparatory and technical shortcomings in weakly indurated rocks. The most serious weaknesses are: sample preparation, volume of measured sample (fraction of a mm3), beam defocusing and background intensity corrections, combination of incomplete pole figures, and necessity of recalculation of the c-axis orientations from other crystallographic directions.
Goniometry using thermal neutrons overcomes most of these difficulties, but it is time consuming. We test the interferences made about velocity anisotropy by X-ray studies about the concentration of c-axes in deep-sea carbonates by employing neutron texture goniometry to eight DSDP samples comprising mostly nannofossil material. Fabric and sonic velocity were determined directly on the core specimens, thus from the same rock volume and requiring no preparation. The c-axis orientation is obtained directly from the [0006] calcite diffraction peak without corrections.
The fabrics are clearly defined, but weak (1.1 to 1.86 times uniform) with the maximum about normal to bedding. They have crudely orthorhombic symmetry, but are not axisymmetric around the bedding normal. The observed c-axis intensities, although higher than determined by the X-ray method on other samples, are by far too low to explain the observed acoustic anisotropies.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Median Latitude: 27.585350 * Median Longitude: 176.793400 * South-bound Latitude: 21.350200 * West-bound Longitude: 174.667800 * North-bound Latitude: 33.820500 * East-bound Longitude: 178.919000
Date/Time Start: 1978-08-02T00:00:00 * Date/Time End: 1978-08-23T00:00:00
Event(s):
62-463 * Latitude: 21.350200 * Longitude: 174.667800 * Date/Time: 1978-08-02T00:00:00 * Elevation: -2525.0 m * Penetration: 822.5 m * Recovery: 305.5 m * Location: North Pacific/SEAMOUNT * Campaign: Leg62 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 92 cores; 820.5 m cored; 0 m drilled; 37.2 % recovery
62-465A * Latitude: 33.820500 * Longitude: 178.919000 * Date/Time: 1978-08-23T00:00:00 * Elevation: -2161.0 m * Penetration: 476 m * Recovery: 98.9 m * Location: North Pacific/CONT RISE * Campaign: Leg62 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 43 cores; 408.5 m cored; 9.5 m drilled; 24.2 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
2 datasets
Download Data
Datasets listed in this publication series
- Ratschbacher, L; Wetzel, A; Brokmeier, H-G (1994): (Table 2) Neutron texture measurement characteristics of deep-sea carbonates from DSDP Holes 62-463 and 62-465A. https://doi.org/10.1594/PANGAEA.763682
- Ratschbacher, L; Wetzel, A; Brokmeier, H-G (1994): (Table 1) Physical parameters of deep-sea carbonates from DSDP cores of DSDP Holes 62-463 and 62-465A. https://doi.org/10.1594/PANGAEA.763681