Publications

The island of Sumba occupies a key position along the Sunda Arc.West of Sumba, a subduction zone lies along thousands of kilometres where the Oceanic crust and lithosphere of the Indian Ocean sink below the Sunda Shelf (Asian Craton).The succession of main morphological features seems to be very clear: trench, outer arc accretion prism, outer arc basin, and volcanic arc.East of Sumba, towards Saw, Timor, Tanimbar and as far as Seram, at first glance, things are different and the Eastern Indonesian Arc has provided matter for many hypotheses and theories.As for Timor, vaIious interpretations have been proposed considering Sumba series as derived either from the Australian Shelf or from Sundaland. The recent tectonic map of Indonesia (Hamilton 1978, USGS) considers Sumba as an isolated piece of Sundaland, south of the Eastern Indonesian Arc.The island of Sumba, some 220 kilometres long and about 60 kilometres wide was not mapped in detail geologically until recently and only few geological details were published. So, CFP (GEA department) and IFPs Marine Geology project group organised a common field trip with the technical help of TOTAL INDONESIA. The main purpose was to gain a better understanding of the geodynamic position of Sumba and to gather more information to prepare a program for the 1980-1981 CEPM offshore seismic campaign.The field party was composed of P.F. BUROLLET (CFP-GEA), C1. SALLE (IFP), A. JOHNSON and R. PHOA (TOTAL INDONESIA) and it operated from June 26 to July 3,1979.Two trips were organized along the main roads and trails of the island, after thorough study of the literature available. The first one was between Waingapu (Airport and accommodations). and Waikabubak (Western Sumba), and then to the Southern Coast (Rua).The second trip took place along the Eastern coast from Waingapu to Melolo and from there to Kananggar, a small village in the central mountains of the Southeast part of Sumba. Lack of time and many problems with the rough trails prevented the party from reaching the Southern Coast, South of Kananggar. The end of June was only just the beginning of the dry season and it was still very difficult to drive along the mountain paths.An additional section (100 m thick) was studied and sampled near the Kambaniru river, a few kilometres South of Waingapu.90 samples were collected: most of them are from 2 sections in the Upper Miocene (East Kananggar and Lainggatar), the others from various locations investigated during the travels.