Determining the origin of volcanic rocks in the mélange complex of Karangsambung based on the electrical resistivity imaging

An ENE-WSW-trending localized basalt-diabase outcrop along the SE margin of Luk Ulo Mélange Complex has been suggested as intrusive rocks cut through the Paleogene Totogan and Karangsambung formations. However, the absolute dating of the volcanics is older than the inferred relative age of the sedimentary formations, hence the in-situ intrusion theory is less likely. A subsurface imaging should delineate the possibility of the in-situ nature of volcanic rock by looking at the continuation of the rocks to the depth. In this study, we did a subsurface imaging by electrical resistivity method. The electrical resistivity surveys were conducted at 3 (three) lines across the ENE-WSW trend of the volcanic distribution. From those three measurements, we obtained three inversion models that present the distribution of the resistivity. We could differentiate between the high resistivity of volcanic rocks and the low resistivity of the clay-dominated sediments. Instead of the deep-rooted intrusions, the geometry of the volcanic rocks is concordant with the sedimentary strata. Since we do not observe any spatial continuity of the bodies, both laterally and vertically, the volcanic rocks might be part of broken intrusive rocks. Furthermore, the size and the sporadically distributed of the rocks also indicated that they are more likely as fragments during the olistostrome deposition, transported from its original location.     

Livelihoods, fire and policy in eastern Indonesia

Indonesian legislation calls for a zero-burning policy. This approach to fire management is largely in response to significant negative impacts on the economy and the environment, not only in Indonesia but also the neighbouring region, that result annually from peat fires in Kalimantan and Sumatra. In this context, the present paper investigates the local use and management of fire in Flores and Sumba islands in eastern Indonesia. Our appraisals show that people's livelihoods depend on fire to maintain grasslands and, therefore, that the national policy and legislation for zero-burning is inappropriate and needs to be revised. This follows from the fact that not all fires cause damage and are unwanted. Through a series of rapid rural appraisal interviews, we found that the fires in grasslands are often lit intentionally to maintain the grasslands that local people use to sustain a variety of livelihood activities such as cattle rearing, hunting and farming. Although fires can damage or destroy remnant dry forests in eastern Indonesia, in order to be effective, future policy formulations need to account for this human livelihood dimension and the geographic variation in fuels, climate and land use.