Holocene tephras in the New Guinea highlands: Explosive volcanism in the Bismarck arc produces chronostratigraphic markers for interdisciplinary study

Abstract

In the highlands of Papua New Guinea (PNG), tephras are key chronostratigraphic markers for archaeological and palaeoenvironmental studies. Here, mid-Late-Holocene tephras are geochemically fingerprinted and correlated across seventeen sites in PNG. This enables the first regional scale assessment of the distribution of these tephras, with implications for both assessing eruption magnitude and interpreting site stratigraphy. In the past, stratigraphic relationships have been key to much of the tephra identification done in PNG. Fingerprinting presented here shows that tephras may be either locally or regionally absent, as a result of poor preservation or regional distribution patterns, reinforcing the need for geochemical identification. Fingerprinting has also allowed tephras to be correlated with their source volcano. In a number of cases (e.g. Kuning and Mun tephras), this has enabled significant refinement of tephra ages, as source eruptions have been accurately dated using charcoal in proximal pyroclastic sequences. This has significant implications for regional archaeological and palaeoenvironmental studies. Of the six regionally widespread tephras emplaced over the last 4–5 ka in PNG, four are sourced from either Long Island or Karkar volcanoes in the western Bismarck Arc, while two are the result of eruptions from Dakataua and Witori volcanoes in New Britain. Discovery on the PNG mainland of tephras sourced from New Britain significantly increases the known distribution of products from these eruptions, suggesting current evaluations of eruption magnitude may be underestimates.