Deep fluids migration and submarine emersion of the Kalang Anyar mud volcano (Java, Indonesia): A multidisciplinary study

North-east Java is part of a large sedimentary basin containing hydrocarbon provinces that feature diffuse hydrothermal systems, mud volcanoes, and degassing sites. Seismic profiles acquired to explore the reveal broad distribution palaeo- modern piercement structures. The Watukosek fault system links volcanic arc, south, with Sidoarjo province, north. Several structures, including Kalang Anyar volcano, are hosted along this left-lateral strike-slip favors migration crustal fluids in basin. Here, we present multidisciplinary geological, geophysical geochemical study conducted at where dozens seepage sites active crater area intermittently emit bursts oil, gas, mud, water. emitted gasses methane-dominated smaller amounts heavier hydrocarbons CO 2 . Unlike most mixed-thermogenic origin methane coupled geothermal anomalies, as indicated by helium isotopic values (? 13 C CO2 high ?4‰) suggest input mantle-derived gas. Our gas flux measurements emits about 1.62 5.75 t yr ?1 CH 4 , respectively. intense bubbling gives rise typical drumbeat seismic signal characterized dominant frequencies around 3–4 Hz (and up 15 Hz). We interpret rising resonating through shallow plumbing Anyar. Erupted clasts different lithologies shells scattered across volcano area, while edges zone include cubic meter-sized carbonate-cemented blocks ridges contain siliciclastic sediments abundant chemosymbiotic bivalves. Carbon isotope analyses carbonate cement low ?48.8‰) identify latter methanogenic chemoherms. Radiocarbon ( 14 C) dating bivalves cemented indicates an age 1890-1488 BP. These results indicate activity MV dates from when was below sea level microbially-mediated precipitation carbonates ongoing during subaqueous site. To best our knowledge, first example progressed subaerial conditions marine regression, displaying evidence former (i.e. carbonates) current numerous Potentially eruptive phases represent clear geohazard for settlements constructed inside volcano. In light this, it may be prudent apply stricter rules development activities, such housing construction permits consider possibility potentially catastrophic events, steps mitigate these hazards. • has emergent signal. Dating previous Holocene offshore vigorous degassing. Activity postglacial regression. Geochemistry seeping deep-sourced component. Tectonic discontinuities promote piercements formation.