Implications of reworking processes on tephra distribution during volcanic eruptions: The case of Parícutin (1943–1952, western Mexico)

Abstract

AbstractParícutin in western Mexico is considered one of the most studied monogenetic volcanoes worldwide. The volcano began its formation in the middle of a cornfield in February 1943 and lasted until March 1952. Descriptions of the eruption documented the remobilization of unconsolidated primary ashfall by rainfall and wind in minor proportions. Despite these descriptions, the resulting reworked deposits have not yet been described in stratigraphic sequence. We present the first stratigraphic study of interfingered primary pyroclastic and reworked deposits of Parícutin's succession. We identify 13 units, of which seven correspond to reworked deposits dispersed around the volcano. These deposits display sedimentary structures produced by tephra remobilization due to lahars and stream flows. In addition, some layers display dunes and ripples generated by dust storms. By using GIS tools, we integrated the existing data with our new composite stratigraphic column, the distribution map of the syn‐eruptive reworked deposits and a new isopach map. This new evaluation reveals that more than 70% of the total thicknesses around the volcano correspond to syn‐eruptive reworked deposits (R1–R4 units). Therefore, previous studies had overestimated the distribution of primary tephra from the Parícutin explosive phases. The lowest and flattest areas with wide rill networks, which are located 4–6 km north of the volcano, are composed of up to 90% reworked deposits. In contrast, proximal locations with gentler slopes located at medium altitudes better preserve pyroclastic deposits. This study brings new light to understanding the sedimentary processes that occur during volcanic eruptions and highlights the importance of recognizing pyroclastic and reworked deposits during monogenetic eruptions.