The use of mineral magnetic analyses as an aid in investigating the recent volcanic disturbance history of the Krakatau Islands, Indonesia

Abstract

The recent disturbance of vegetation on islands within the Krakatau group, Indonesia, by a succession of ash falls from Anak Krakatau, has complicated studies of tropical ecosystem recovery since the major eruption of 1883 provided a 'clean slate'. Mineral magnetic analyses are applied to a series of ash/soil profiles from Sertung, Panjang and Rakata Islands to determine whether the technique can provide a means of stratigraphic correlation of horizons both between sites and between islands (and in particular, correlation and separation of ash layers). The initial results suggest that the technique is sensitive enough to distinguish between particular horizon types (as identified in the field) such as contemporary top-soils, post-1927 ash layers and material of 1883 age. Good agreement is found between the mineral magnetic and traditional geochemical data. The former appear to hold further potential for the separation of (geologically) very close eruptive events from the same magma chamber. The results indicate considerable potential for the approach in the Krakatau context and warrant further investigation of these mineral magnetic properties. If successful, the technique could also find application in other localities where multiple volcanic disturbance events characterize Holocene sediments.