167 D33. Recent Advances in Volcanology

Tuesday, 12 October 2021
1:30 PM - 5:30 PM
D135

LOCATIONAL CONTROLS OF HOLOCENE MAAR VOLCANOES IN THE EASTERN MEXICAN VOLCANIC BELT

Paper number: 167-5
Program: Technical Sessions
Time: 2:20 PM – 2:35 PM

Authors

Abstract

The Serdán-Oriental basin (SOB), a broad closed basin located in the easternmost sector of the Trans-Mexican Volcanic Belt, records an intense and widespread Quaternary monogenetic volcanism of bimodal composition. This volcanism is expressed in the form of scoria and lava cones, large isolated rhyolitic domes and tuff rings, an active caldera complex (Los Humeros), and a maar-type volcanic field. The maar volcanoes are of special interest when studying the subsurface hydrology in volcanic fields as their stratigraphy and shapes record key information of the hydrological dynamics and their relationship with the magmatic and structural setting.

A detailed geological examination of the maar volcanoes reveals that these formed during alternating episodes of intense phreatomagmatic and magmatic activity in the SOB. Evidence of this is the variety of sizes and shapes of their craters, as well as the composition of their products. Some maars are ellipsoidal, and in some cases, are accompanied by E-W trending aligned scoria and spatter cones, such as Aljojuca or Tecuitlapa, which are located to the southern part of the SOB. This may suggest an apparent regional tectonic control on their formation for that sector only. Others show irregular, elongated shapes, such as Alchichica, Atexcac, Quechulac, and La Preciosa, inferred to be due to multiple vent locations indicating a spatio-temporal migration of the explosion locus. Furthermore, several maars also record eruptive-style transitions controlled by changes in the hydromagmatic dynamics, as is the case of the Alchichica maar (the largest in the SOB), which transitioned from strombolian to phreatomagmatic. Recent 14C dating reveals that the SOB maar volcanism is Holocene and its widespread and random distribution points to a complex basin-wide magmatic source with no systematic locational control. All the area appears to be volcanically active, which has important implications for hazard assessment.

Geological Society of America Abstracts with Programs. Vol. 53, No. 6

doi: 10.1130/abs/2021AM-370742

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