Late pleistocene-holocene debris avalanche deposits from volcán de Colima, Mexico

Abstract

Volcán de Colima has experienced numerous partial edifice collapses with associated debris avalanche deposits, widely distributed toward the SW, S and SE sectors. According to new 40Ar/39Ar dates, activity began more than 97,000 years ago on the southern flank of Nevado de Colima with the formation of the so-called Paleofuego edifice. Several collapses occurred prior to a catastrophic edifice collapse event 7000 years ago, creating a horseshoe-shaped avalanche crater, 5 km wide, opened towards the south. After this last lateral collapse of Paleofuego, the currently active cone began to grow in the central part of the crater, which, during the Late Holocene, has experienced two lateral collapse events that generated debris avalanches. Based on new fieldwork and stratigraphic correlation of deposits supported by 14C dates, we present a description and approximate distribution of eight debris avalanche deposits generated by Volcán de Colima during the last 30,000 years. These debris avalanche deposits are exposed at 40 km to the S and 25 km in the SW and SE sectors of the volcano, and cover an area of 1200 km2 with an approximated volume of 86 km3. Field evidence indicates that at least some sector collapses were accompanied by magmatic activity. The regional tectonic setting that consists of the active N-S regional extension of the Colima graben, as well as E-W, and NE-SW structures, such as the Tamazula Fault, also played an important role in volcano instability. The contribution of a volcanic spreading component was also recently recognized. The emplacement of the most voluminous debris avalanches have obstructed the Armería and Tuxpan-Naranjo rivers producing temporary lakes, where thick lacustrine sediments were accumulated. The recurrence times of these sector collapses vary between 3000 and 6500 years during the Late Pleistocene and 1100–3400 years during the Holocene, with the youngest one having occurred ~2.5 ka BP. A future sector collapse of Volcán de Colima on the scale of past events could be catastrophic for up to about 350,000 inhabitants (including the city of Colima) that currently are located on top of ancient debris avalanche deposits.