Lucas Valore

Large Igneous Provinces, hydrovolcanism and paleoenvironments/paleohydrology: lessons from the Paraná Basin in South Brazil

In many continental flood basalt provinces (CFBPs), primary mafic volcaniclastic deposits have been shown to be significant counterparts of better-known effusive (lava flow) facies, a notion that challenged traditional views of CFB stratigraphy some decades ago. Many of such deposits have been linked to hydrovolcanic phenomena, which are basically all sorts of magma – water interaction that induce magma fragmentation and create specific types of volcaniclastic deposits. At the time, some studies linked this to how LIPs have been able to induce massive extinctions in the geological record. Until the early 2000s, one of the only exceptions to this was the Paraná Igneous Province in South America, where the enormous amounts of lavas from the so-called Serra Geral Group were emplaced above a seemingly completely arid paleoerg (Botucatu). However, this was later shown to not be entirely true, as during syn-volcanic times multiple types of humid environments have been recorded – many have been responsible for the repeated formation of peperites, a volcanic breccia with sedimentary matrix that in this case is formed as lava flows invade bodies of humid sediment. Further studies have shown that other hydrovolcanic deposits also exist in Paraná, although this has stirred a lot of controversy. These include pillow lavas, hydrothermal injectites and pyroclastic rocks – the latter, which were my main focus during my master’s, will be the main subject of the talk. Ultimately, detailed mapping of these facies show that they are far from being the exception, and that perhaps the volcanic activity is somehow linked to this change in paleoenvironmental conditions.