Traces of Submarine Volcanism and Tectonic Uplift: Evidence of Geological Interaction at Watudodol Beach

¹ Department of Geography, Faculty of Social Sciences, State University of Malang, 65145 East Java, Indonesia
³ Ijen Geopark Geological Information Centre, 68465 East Java, Indonesia

^* Corresponding author: melatijuliarahma.fis@um.ac.id

Abstract

Watudodol Beach in Banyuwangi is an important location for understanding the interaction between undersea volcanism and tectonic uplift at the eastern tip of Java. The presence of pillow-structured basalt lava, fossilised limestone, and volcanic breccia records complex geological dynamics. This research was conducted through field observations, outcrop descriptions, sampling, petrographic analysis, and integration with regional geological literature studies. The results of the study show three main stratigraphic units: pillow-structured basalt lava and autobreccia with a thickness of >3 m, volcanic breccia ±1 m thick with basalt fragments and calcite veins, and clastic limestone associated with marine fossils (molluscs, corals, foraminifera) with a thickness of 20–50 cm. These outcrops are exposed at elevations ranging from 0 to 544 metres above sea level, indicating significant post-depositional uplift. Mineralogical analysis shows a dominance of plagioclase (36%), K-feldspar (11%), pyroxene (8%), and volcanic glass (24%), reflecting basaltic magma with a hypocrystalline texture. These findings confirm that the Watudodol area was formed through a sequence of submarine volcanism followed by tectonic uplift since the Early Pliocene. Regionally, these results reinforce our understanding of the geodynamic evolution of Banyuwangi and support the potential for developing geotourism based on geological heritage.