Characteristics and emplacement mechanisms of the Coranzulí ignimbrites (Central Andes)

Abstract

We present a detailed stratigraphy of the Coranzulí calderaforming deposits. This caldera, located in the Altiplano-Puna Volcanic Complex (Central Andes), generated four ignimbrite deposits with similar field characteristics and facies that differ from each other in, above all, the nature of the lithic fragments they contain. Three different lithofacies (fine-grained cross-stratified facies, massive lithic breccia facies and massive ignimbrite facies) are found in all the ignimbrite deposits, which occasionally also contain a lenticular lithic-rich facies and/or a pumice-rich facies. These field characteristics and, in particular, local deposit thicknesses were used to develop a theoretical model of the dynamics and emplacement mode of the Coranzulí pyroclastic flows. Our results show that these ignimbrites were emplaced by dense pyroclastic density currents subjected to high accumulation rates and velocities, thereby indicating rapid en masse emplacement that was also influenced by local paleotopography as deduced from facies analysis.

Granular mixture deflation and generation of pore fluid pressure at the impact zone of a pyroclastic fountain: Experimental insights

“…Sustained fountaining is also called "boiling over" in the literature and has been suggested to operate during single vent as well as ring fracture eruptions. In the latter case, sustained fountaining associated with caldera collapse is thought to generate voluminous pyroclastic flows that travel more than 50-100 km and form widespread ignimbrites (Cas et al, 2011;Guzmán et al, 2020;Pacheco-Hoyos et al, 2018;Roche et al, 2016). Several issues related to pyroclastic fountaining are yet poorly known.…”

Energy facies: A global view of pyroclastic currents from vent to deposit

“…The forced regime primarily depends on the source condition, with negligible topographic control (Table 2). This facies has been recognized for Cerro Galan, Cerro Blanco, Colli Albani RED, Latera ARL and Coranzulí (Giordano & Doronzo, 2017;Trolese et al, 2017;Palladino & Giordano, 2019;Guzman et al, 2020; see Table 1).…”

“…The distributions of the deposit thickness, lithic and juvenile clasts and temperature in pyroclastic successions are key, as they record the macroscopic eruptive conditions that occur in ancient explosive volcanic eruptions. They also give insights on the temporal evolution of pyroclastic currents at active volcanoes, where the source dynamics can be better constrained and the topographic interaction can be inferred Cas et al, 2011;Cashman & Giordano, 2014;Di Vito et al, 2009;Doronzo, 2012;Doronzo et al, 2017;Dufek & Bergantz, 2007;Esposti Ongaro et al, 2020;Giordano & Doronzo, 2017;Guzman et al, 2020;Palladino et al, 2014;Palladino & Giordano, 2019;Wright et al, 2016).…”

Lahar events in the last 2,000 years from Vesuvius eruptions. Part 1: Distribution and impact on densely-inhabited territory estimated from field data analysis

“…CC BY 4.0 License. by flow dynamic pressure is recognized as a it is quite common feature (e.g., Zanchetta et al, 2004a;Pittari et al, 2007;Duller et al, 2008;Toyos et al, 2008;Cas et al, 2011;Carling, 2013;Doronzo, 2013;Jenkins et al, 2015;Roche, 2015;Martí et al, 2019;Guzman et al, 2020). The capability of a flow to entrain a clast is a function of flow properties (velocity, density) and clast properties (dimension, density, shape), and dynamic pressure well syntheses and quantifies such capability also in terms of flow hazard (Toyos et al, 2008;Zuccaro and De Gregorio, 2013;Jenkins et al, 2015).…”