Características de los depósitos estrombolianos basales del volcán Cabeza Parda (Campo Volcánico de Calatrava)

Resumen

In a quarry open in the South hillside of Cabeza Parda volcano (Calatrava Volcanic Field, Ciudad Real, Spain; UTM: X = 413550, Y = 4303850), just overlying the lower Pliocene limestones that conform the volcanic basement, crops out a sec- tion near 10 m thick of pyroclastic deposits. Most of if is constituted by abundant bombs (≤ 3 m in diameter / length) and bomb-fragments (coarse lapilli to block in size, angular or partially rounded clasts) characteristic of Strombolian-type depo- sits (e.g., Valentine and Greeg, 2008). Additionally, interbedded into this tephra appear lenticular or irregular-shaped dis- continuous beds (length < 7 m, thickness < 2 m) constituted by angular to fluidal-shaped scoriaceous lapilli. This latter type of tephra (shape and size of clasts, vesicularity, unwelded) is characteristic of violent Strombolian eruptions (e.g., Valentine and Greeg, 2008). The basal deposits of the Cabeza Parda volcano indicate therefore that Strombolian activity, characterized by low intensity bursts and temporally discrete episodes, with emission of relatively small lava volumes, could alternate with discrete but more intense bursts, that is, violent Strombolian, with emission also of relatively small lava volumes.