Bohrmann, Gerhard and Ehrmann, Werner U. (1991) Analysis of Sedimentary Facies Using Bulk Mineralogic Characteristics in Cretaceous to Quaternary Sediments from the Kerguelen Plateau: Sites 737, 738, and 744. Proceedings of the Ocean Drilling Program: Scientific Results, 119 . pp. 211-223. DOI 10.2973/odp.proc.sr.119.122.1991.

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Abstract

Carbonate-free portions of Upper Cretaceous to Holocene sediment samples from the Kerguelen Plateau in the
southern Indian Ocean were investigated by X-ray diffraction. Downhole variations in the content of opal-A, opal-CT,
quartz, feldspar, barite, and clinoptilolite were studied at Site 737 on the northern Kerguelen Plateau and at Sites 744
and 738 on the southern Kerguelen Plateau. The variation of these components reflects temporal changes in the depositional
history of the Kerguelen Plateau as well as major differences in the sedimentary evolution between the northern
plateau and the southern plateau.
Carbonate is the dominant component in the pelagic sediments on the Kerguelen Plateau. In addition, biogenic opal
sedimentation plays an important role throughout most of the sequence. A major increase in opal accumulation is documented
at all sites in late Miocene time, which is in accordance with the well-known increase in silica productivity
probably caused by a major cooling step. Because of its position near the Polar Frontal Zone, sediments from Site 737
show a more extensive opal deposition than at Sites 744 and 738. An earlier productivity pulse is documented at Site 744
on the southern plateau within the early Oligocene, following the initial phase of intense East Antarctic glaciation. This
cooling event resulted in higher amounts of ice-rafted terrigenous quartz and, to a lesser extent, feldspar. With the exception
of the Site 744 sediments, opal deposition in Paleogene and older sediments can be reconstructed only from the
diagenetic transformation products of opal-CT and probably clinoptilolite. In contrast to the southern sequence, on the
northern Kerguelen Plateau higher amounts of clinoptilolite and no opal-CT were found. These major differences in the
diagenetic environments may be due to extensive volcanism in the northern area. The volcanic influence at Site 737 is
well recorded by the higher feldspar content and higher amounts of volcanic glass shards.

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