Beyond a simple wet-to-dry transition: Staged eruptive evolution during growth of the alkaline Bárcena volcano, Isla San Benedicto, México

In 1952–1953, the Bárcena volcano erupted on Isla San Benedicto, a pre-existing ocean-island edifice in the Archipiélago de Revillagigedo, Mexico. The eruption constructed a pyroclastic cone, then shifted to intra-crater dome extrusion, and culminated in a lateral lava breakout. The eastern flank succession provides a proximal record for evaluating the transition from water-influenced, explosive cone construction to effusion. We integrate stratigraphy, grain-size distributions, componentry, petrography, SEM observations of juvenile clasts, and whole-rock geochemistry to test whether cone growth followed a simple wet-to-dry progression or a staged evolution of eruptive and magmatic processes. The pyroclastic succession comprises discontinuous basal deposits followed by four stratigraphic packages. The basal deposits preserve an incomplete and heterogeneous opening record. Package 1 marks establishment of proximal pyroclastic cone-building stratigraphy and contains evidence of early petrographic disequilibrium, expressed by sieve-textured plagioclase. Package 2 preserves the strongest evidence for recurrent magma–water interaction, including fine–coarse alternation, structured ash-rich beds, ash aggregates, black-glassy juvenile enrichment, and the strongest particulate signal. Package 3 records the principal lithic- and altered-clast-rich unit interpreted as a short-lived excavation pulse. Package 4 remains mixed and laterally variable, with weaker or less consistent record of magma-water interaction than in P2. Whole-rock data place the pyroclastic products within an evolved alkaline suite, with most peralkaline samples falling in the comenditic field. The late lava is less siliceous, metaluminous, more crystalline, less vesicular, and geochemically distinct from the most evolved pyroclastic pumice domain, consistent with delayed eruption of a related but less evolved magma domain. Bárcena records a broad transition from water-influenced pyroclastic cone building to subsequent effusion through staged changes in eruptive conditions and magma supply rather than a monotonic wet-to-dry progression.