Abstract Despite the intriguing correlation between continental flood basalt provinces and environmental crises, little is known about how the local/regional sedimentary systems and environment respond to flood basalt volcanism. Active sedimentary systems, and their interaction with volcanism, provide an important rock record to understand palaeoenvironments in volcanic settings. The Paraná–Etendeka Igneous Province is a well-known example of a continental flood basalt emplaced on a dry desert environment, but evidence has also shown the existence of humid conditions during the volcanic episode. This work describes and interprets non-volcanic sedimentary and volcaniclastic rocks interbedded with Paraná–Etendeka Igneous Province lavas in southernmost Brazil to better understand the palaeoenvironmental process and changes during the onset of volcanism. Non-volcanic sedimentary rocks record the existence of ephemeral sheet-like flows and ponds/lakes while volcaniclastic rocks document hydromagmatic activity, supporting a change to more humid conditions. Stratigraphic constraints indicate that this change started with the onset of volcanism and affected the whole province. We suggest that SO 2 degassing from the Paraná–Etendeka province may have caused a net global surface cooling, resulting in precipitation redistribution and a local increase in rainfall. This hypothesis may help explain the cooling and increased humidity observed elsewhere to be closely related to the Paraná–Etendeka emplacement.

Las Cañadas caldera complex, on Tenerife, Canary Islands, truncated the construction of Las Cañadas edifice, a central composite volcanic complex formed after a main period of basaltic shield construction. The origin of the present Las Cañadas caldera complex is still a matter of considerable debate between two contrasting hypotheses, vertical (caldera forming) or lateral (landslide) collapse. However, there is increasing evidence that a long history of explosive phonolitic volcanism, including several caldera episodes, characterized the construction of Las Cañadas edifice. Los Roques de García forms a large spur that divides the Las Cañadas caldera complex into two morphological depressions. The sequence of rocks exposed along the spur consists of several formations that from base to top include: Los Roques de García Formation, Los Azulejos Formation, and the lower part of the Ucanca Formation. Los Roques de García Formation occupies the main part of Los Roques de García spur and includes proximal facies of pyroclastic (Lower Member) and sedimentary (epiclastic) (Upper Member) deposits, predominantly breccias, all of which are intruded by a dense network of phonolitic dikes and necks. Pyroclastic deposits mostly correspond to coignimbrite lag breccias, lithic-rich ignimbrites, and minor surge and ash-fall beds. Epiclastic rocks mainly include poorly to well-stratified, proximal debrisflows breccias deposited in an alluvial-fan environment, with some interbedded pyroclastic and epiclastic sandstone and conglomerate units. The central sector of Los Roques de García spur is highly fractured due to the movement of several normal faults, thus conferring a chaotic aspect to that zone. Strong hydrothermal alteration also has affected some sectors of Los Roques de García spur, enhancing this chaotic appearance. New detailed mapping and stratigraphic logging have been crucial to interpreting the nature and stratigraphy of Los Roques de García rocks, which represent two fundamental aspects for the interpretation of the origin and evolution of Las Cañadas caldera. Los Roques de García spur exhibits a stratigraphy that is concordant with the rest of Las Cañadas caldera wall and corresponds to the lower part (Lower Group) of Las Cañadas edifice, without having any relation to latter explosive episodes responsible for the deposition of its upper part (Upper Group). Lithological, sedimentological, and volcanological characteristics of Los Roques de García rocks allow them to be interpreted either as a former Las Cañadas intracaldera sequence or as the apron of an older stratovolcano, in contrast with previous interpretations, which have suggested that they correspond to the products of a major debris avalanche event that contributed to the formation of the present caldera.