Fig. S3: Rapid changes from arid to humid conditions during the onset of the Paraná-Etendeka Igneous Provinces: can volcanic gas emissions from Continental Flood Basalts affect the precipitation regime?

(a) Complex network of sand dykes, including conjugate pairs (white arrows) cutting through altered basalt flows of the Vale do Sol Fm. in the RS-153 highway. In this case no obvious interbedded sandstone could be linked to the sand dykes. (b) Small sand dyke (white arrow) emanating from the lower peperitic contact between pāhoehoe flows and heterolithic sandstones. In this case the sand dykes can be linked to the parent heterolithic sandstone beds and fluidization was likely a response of hydromagmatic interactions. (c) Very thin sand dyke (white arrow) emanating from the contact between two pāhoehoe lobes (dashed white, note oxidized lower crust). Note how the sand dyke only cuts through the upper lobe. In this case sand was likely sourced from small sandstones that infilled depressions in between the lobes. (d) Sand-filled fracture in obsidian flows of the Palmas Fm. In this case the downward termination of the fracture and sedimentary lamination perpendicular to the fracture walls support an interpretation as sand-filled fractures.