Volcanic Rocks of Naturaliste Plateau, Eastern Indian Ocean, Site 264, DSDP Leg 28

Abstract

The upper part of a pile of andesitic volcanogenic sediments underlying Upper Cretaceous chalk was sampled on the Naturaliste Plateau at DSDP Site 264. Material recovered from the pile is entirely volcanic and is composed mainly of rock fragments that probably represent coarse clasts in the sequence. Minor conglomerate in which pebbles of volcanic rock are embedded in a highly altered tuffaceous matrix was recovered at two levels. In general, high alteration makes interpretation of original compositions uncertain. The volcanic clasts range widely in composition from rhyolite to probable andesite or basaltic andesite of an apparent calcalkaline andesitic suite unlike any volcanic suite now exposed on nearby parts of southwest Australia. Rhyolitic rocks show apparent ignimbritic textures, suggesting that volcanism in the unknown source volcanic complex was at least in part subaerial. The source terrain must have been nearby, possibly even the plateau which has been only superficially sampled itself. Petrologic and chemical characteristics of the rocks suggest a volcanic island-arc source or perhaps a continental margin volcanic and orogenic belt, now submerged, related to an early stage of development of the eastern Indian Ocean.

The origin of the Naturaliste Plateau, SE Indian Ocean: Implications from dredged basalts

“…Although our samples are altered, they are not nearly as altered as the set of igneous rocks from DSDP Site 264, to the south (Fig. 1), examined and analysed in part by Ford (1975a). As well, analyses of igneous rocks from oceanic plateaus such as the Naturaliste are relatively rare, and so those presented here may have intrinsic value.…”

“…' Jongsma & Petkovic (1977) paraphrased this opinion, as did other authors who had dealt with the plateau and adjacent regions, e.g. Markl (1974Markl ( , 1978, and Ford (1975a). Our objective was to report on the dredged continental material, but our examination soon showed that no undoubted continental rocks were present; the rock component was made up of basaltic lava cobbles.…”

“…Core 14 Core Catcher cobbles compare closely to the pinkish red-brown lava and to our tawny-yellow specimen, 12-3, respectively. These particular DSDP 264 samples were not analysed by Ford (1975a) for they are very altered. Our Eltanin samples are less altered than the DSDP ones, and the primary mineral phases are better preserved.…”

“…This conglomerate is probably a lateral correlative of the basaltic detrital sandstone of Site 258, and its source also most likely lies on the plateau itself. Ford (1975a) considered the cobble components of this conglomerate to be of andesitic origin, but the rocks are considerably altered; we discuss this later.…”

Improving the interpretability of air-gun seismic reflection data using deterministic filters: A case history from offshore Cape Leeuwin, southwest Australia

“…Due to the sparse data available, the origins of the Naturaliste Plateau are not fully understood. Geophysical seismic and potential field studies (Petkovic, 1975;Jongsma and Petkovic, 1977;Borissova, 2002;Direen et al, 2007) and chemical analysis of dredged material (Halpin et al, 2008) and borehole cores (Ford, 1975) suggest Figure 1. Study area offshore Cape Leeuwin, Australia.…”