HOLOCENE EXPLOSIVE ERUPTIONS OF WITORI AND DAKATAUA CALDERA VOLCANOS IN WEST NEW-BRITAIN, PAPUA-NEW-GUINEA

Witori and Dakataua caldera volcanoes have been very active in the mid dle to late Holocene. Using tephrochronology, this paper establishes t he chronostratigraphy of these eruptions and their magnitude, and the frequency of explosive volcanism at Witori and Dakataua. After a long dormancy, Witori started explosive activity at ca. 5600 conventional r adiocarbon years BP, producing in the next 4500 years five major tephr a layers (W-K1 to W-K4, W-G) with VEIs of 5 to 6. After the W-G erupti on at around 1200 BP, the activity decreased in magnitude but increase d in frequency, with some eruptions forming central cones. The major e ruption of Dakataua began with alternating ejections of phreatomagmati c ashfalls and plinian deposits followed by the cataclysmic eruption r esulting in lithic-rich pyroclastic flows ca. 1100-1200 BP. The major tephra layers cover extensive areas in West New Britain due to their l arge volumes and the prevailing easterly winds, providing valuable tim e markers for establishing Holocene chronology. The largest eruption, the W-K2 event of ca. 3300 BP, shaped much of the present landscape, w ith an extensive area significantly devastated by tephra falls and pyr oclastic flows. Obsidian and other artefacts buried by the tephras ind icate that the area was repeatedly occupied. The major tephra events f ormed new coastal plains favourable for human occupation. Copyright (C ) 1996 INQUA/Elsevier Science Ltd