Volcanic stratigraphy of the Quaternary La Garrotxa Volcanic Field (north‐east Iberian Peninsula)

Abstract

The monogenetic Quaternary La Garrotxa Volcanic Field forms part of the Catalan Volcanic Zone (north‐east Iberian Peninsula), one of the alkaline volcanic provinces of the European rift system. It harbours more than 50 basaltic monogenetic cones that range in age from the Middle Pleistocene to the Early Holocene and include cinder and scoria cones, lava flows, tuff rings and maars. This study is the result of extensive fieldwork, including the study of ephemeral outcrops and the stratigraphic logging of new water wells and geotechnical drill holes, also taking into account existing information gathered by recent geophysical studies that have applied shallow geophysical methods to establish the substrate geology of this volcanic field. We have obtained a comprehensive volcanic stratigraphy of the area that identifies the products of each single eruption, their relative stratigraphy and their surface area. This volcanic stratigraphy constitutes an essential tool for understanding the evolution of this volcanic field and for establishing a correct volcanic hazard assessment for the area, but it also provides a precise reference for the Quaternary tephrochronology of the lake sediments in neighbouring areas.

Monogenetic volcanism: personal views and discussion

“…These eruptive styles are primarily controlled by the magma flux rates and the magma's physicochemical properties Parfitt 2004), and the bulk ratio of magma to external water/waterbearing sediments and the style of interaction between them (Lorenz 1985(Lorenz , 1986Valentine and White 2012;Valentine and Cortes 2013;van Otterloo et al 2013;Valentine and de Vries 2014;. Research focused on understanding the above-mentioned complexity has become common in many different volcanic fields, revealing the spatiotemporal variation of recorded eruption styles and volcano types that can form in a single volcanic field (Sohn 1996;Carn 2000;Godchaux and Bonnichsen 2002;Gutmann 2002;Houghton and Gonnermann 2008;Bolos et al 2014;Tadini et al 2014;Herrero-Hernandez et al 2015).…”

Hydrogeomorphic and sedimentary response to the Late Pleistocene violent Strombolian eruption of the Croscat volcano (Garrotxa Volcanic Field, Spain)

“…The overall structure of the area can be described as a system of E-W-oriented folds dissected by normal faults parallel to their axes (Gallart et al 1991;Giménez-Montsant et al 1999). According to Bolós et al (2014aBolós et al ( , 2015, normal faults are perpendicular to the E-W folds formed during the Alpine orogeny. The Quaternary sedimentary rocks consist of fluvial and lacustrine sediments and subordinate travertine deposits precedent and contemporaneous to the deposition of the volcanic products ( Fig.…”

Geotourism at the Natural Park of La Garrotxa Volcanic Zone (Catalonia, Spain): Impact, Viability, and Sustainability

“…Geologically, La Garrotxa Volcanic Zone is one of the best-preserved volcanic regions in the Iberian Peninsula from those pertaining to the Neogene-Quaternary basaltic volcanism of the European rifts system [17,18,20] (Figure 1), with intense human activity, which at times, impedes the conservation of the land. Volcanic activity began some 700,000 years ago in La Garrotxa [20], and continued until the early Holocene with the eruption of the Croscat volcano about 10,000 years ago [21].…”

“…In total, at least 50 eruptions have been identified [2,3], leading to volcanic cinder and spatter cones, maars and tuff rings, as well as several lava flows that filled the valleys in the area. The stratigraphic, structural, and hydrogeological characteristics of the substrate above which these volcanoes were emplaced favored phreatomagmatic activity, which combined with the magmatic Strombolian activity, caused a large variety of eruption sequences [17,18].…”