Abstract Volcán de Colima, one of the most active volcanoes in Mexico, experienced at least nine flank failures during the last 30 000 years, with catastrophic effects on the environment that implies the formation of temporary dams where lacustrine sediments accumulated for hundreds of years. These lacustrine sequences preserve an exceptional record from which to reconstruct the effect of subsequent volcanic eruptions and, eventually, contemporary environmental and climatic conditions. Here we analyse an Early Holocene lacustrine sequence, named ‘Gypsum King’, which accumulated in a short-lived temporary lake, likely formed by emplacement of the 10 755–11 230 cal years BP Mesa-Yerbabuena debris avalanche. Through detailed analysis of the 1.8 m thick lacustrine sequence ( 14 C ages, sulfur content, grain size), it was possible to identify the 8.2 kyr global climate event and better constrain the Early Holocene main sub-plinian to plinian eruptions of Volcán de Colima. The results presented here highlight the potential to explore sulfur content and abrupt change in grain size in lacustrine sediments as additional proxies to better constrain eruptive phases in volcanic environments. Finally, the Gypsum King sequence provides the first evidence of the 8.2 kyr global climate event along the Eastern tropical Pacific Coast.

ABSTRACT Two main tectonic scenarios have been proposed for the area corresponding to the Guerrero terrane in western Mexico. The first model suggests that the Guerrero terrane was an allochthonous volcanic arc developed over oceanic substrate, which was accreted to nuclear Mexico. The second tectonic model proposes that the Guerrero terrane was a para-autochthonous volcanic arc developed over continental crust, which was rifted during the extensional phase of the Arperos back-arc basin and then tectonically attached to nuclear Mexico. Based on U-Pb geochronology and Hf isotope analyses of detrital zircon grains extracted from Mesozoic sedimentary successions of the Guerrero terrane and western nuclear Mexico, this study provides new evidence to support the interpretation that the Late Jurassic–Early Cretaceous Guerrero terrane was built above a pre–Late Jurassic continentally sourced basement. Hf isotopic signatures of detrital zircon from Late Jurassic–Early Cretaceous sedimentary rocks of the Guerrero terrane range from –14 to +13 and display depleted mantle model ages (T DMc , using a mean crustal value of 176 Lu/ 177 Hf = 0.015) between ca. 2.0 and 0.3 Ga, indicating provenance from both pre–Late Jurassic basement and juvenile crustal components. The most juvenile magmas were formed during the earliest Cretaceous extensional phase, which resulted in the formation of the Arperos basin. Additionally, the negative ε Hf ( t ) values are consistent with recycling of Proterozoic and Paleozoic continental materials in Mesozoic magmas.

Abstract Determining the timescales of magma degassing is essential for understanding the mechanisms controlling the eruption style and the dynamics of magmatic systems. Towards this end, we measured 210 Pb– 226 Ra disequilibria in andesite lavas erupted from Volcán de Colima between 1998 and 2010. ( 210 Pb/ 226 Ra) 0 activity ratios range from 0.86 to 1.09, and are best explained in terms of 222 Rn degassing and accumulation. The range in 210 Pb deficits indicates that the timescales of 222 Rn degassing did not exceed 11 years. 210 Pb excesses are rare and small (<10%), which signifies that 222 Rn degassing is more effective than 210 Pb accumulation in this intermediate system despite the relatively low gas output at the surface. The absence of significant 210 Pb excesses strongly suggests that the volcanic activity results from episodic ascent of small magma batches through the vapour-saturated section of the magmatic system. Overall, the degassing models based on 210 Pb– 226 Ra disequilibrium suggest an open and complex subvolcanic magmatic system comprising several conduits in which multiple magma batches reside for up to 10 years. Shifts from effusive to explosive Vulcanian eruptive phases are not related to changes in degassing mode on timescales resolvable using 210 Pb– 226 Ra disequilibria.