Fig. S5: 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?
journal contributionposted on 09.07.2021, 15:51 by V.G.P. Cruz, E.F. Lima, L.M.M. Rossetti, N.G. Pasqualon
Usina Velha volcaniclastic rocks. (a), (b) Dyke-like protrusions (dashed white in a, behind the tree trunk, and dashed red in b) intruding into the host chaotic volcaniclastic breccia. (c) Transition between the massive, non-fractured core of the lower dacite into the rim zone characterized by dense vertical fracturing (dashed red). (d) Hand sample from the in-situ fragmented lower dacite showing a network of millimetric cooling joints (closed framework). Notice the transition from fresh black glass to altered pale brown glass and that some joints are filled by non-volcanic grains/secondary minerals (red arrow). (e) Detail of a portion of the chaotic volcaniclastic breccia composed of altered pale-brown pumiceous dacite blocks (red arrows) set in light red matrix of non-volcanic grains with faint lamination locally preserved (black arrow). (f) Well-preserved heterolithic lamination in the chaotic volcaniclastic breccia matrix, parallel nichols.