Volcanic Facies Architecture of Sedringo Volcano, Dieng Volcanic Complex

The Dieng Volcanic Complex (DVC) in Central Java, Indonesia, is situated within an active magmatic arc formed by the oblique subduction of the Indo-Australian Plate beneath Eurasia, with an additional influence from the Pacific Plate. Despite its importance as a major geothermal field, the eruptive history of Sedringo Volcano—a key but poorly studied edifice within the DVC remains undocumented. This study presents the first systematic reconstruction of Sedringo’s volcanic evolution and introduces a novel, process-based volcanic facies model to link surface geology with subsurface reservoir architecture. We integrate field mapping, stratigraphic logging, and petrographic analysis of volcanic lithologies. Results reveal a bipartite facies architecture: (1) a central facies of coherent andesitic lava flows and caldera-related agglomerates, and (2) a proximal facies dominated by poorly sorted pyroclastic flow deposits. This pattern records a clear shift from effusive to explosive activity, culminating in caldera collapse and the formation of peripheral cones. The new facies model provides the first geologically constrained framework for interpreting geothermal reservoir geometry in the Sedringo sector. Moreover, the identification of hazardous pyroclastic units and caldera structures offers actionable guidance for geothermal well placement and volcanic hazard zonation. By directly connecting volcanic stratigraphy to energy exploration and risk mitigation, this work demonstrates how fundamental geological research enhances sustainable development in active volcanic systems.