Unsuspected explosive activity of Montagne Pelée (Lesser Antilles) during the 25–10 ka period

Abstract

The recent eruptive history of Montagne Pelée volcano was dominated by a period of vigorous basaltic andesitic magma production (36−25 ka) followed by a long period of lower activity (i.e., with less frequent and less voluminous eruptions) and a renewal of felsic magma production in the last 10 ka. The temporal succession of volcanic events that occurred during the 25−10 ka period and the timing of felsic magma production are currently poorly constrained. This study focuses on the stratigraphy and eruptive dynamics of the pyroclastic deposits emplaced immediately after 25 ka. New on-land stratigraphic correlations and radiocarbon dating measurements allow us identifying six major explosive eruptions. We use field data on tephra dispersal, thickness and grain-size distribution together with physical models of explosive volcanic plumes to estimate the eruption source parameters. Our results show that these events are VEI 4 eruptions with intermediate magnitudes (from M = 4.2 to M = 5.1) and intensities (from I = 10.6 to I = 11.6). These eruptions share several characteristics with the most recent Plinian eruptions of Montagne Pelée volcano (i.e., mass eruption rate, maximum column height, runout of pyroclastic density currents, glass composition). The tephra succession documents two phases of magma production rates. The first phase from 25 to 14 ka corresponds to a period of low activity with a magma production rate of 0.04 km3 kyr−1. The second phase from 14 to 10 ka is characterized by a significant increase of the volcanic activity with a magma production rate of 0.4 km3 kyr−1, consistent with previous estimates.