Fig. 3

Petrographic characteristics of the described facies. A Field photograph of the autoclastic basalt facies outcrop. Some basalt clasts are outlined in dark. Notice also the hand sized limestone clasts (Lms). The rocks are very chaotic and poorly sorted. B Fossils of Plexoramea cerebriformis MELLO and Olangocoelia otti BECHSTÄDT and BRANDNER from limestone clast found in the autoclastic basalt facies, sample VU II–2A. C A stitched microphotograph exhibiting flow texture matrix between the basalt lithoclasts. The matrix area is outlined with dark lines. In the lower middle part of the photograph the matrix is rounding the plagioclase crystalloclast – sample VU I–4a. D Between the clasts in the autoclastic basalt facies chlorite cement is seen with small needle like crystals of plagioclase – sample VU III–1. E Clasts of vitroclastic tuffs seen in the resedimented autoclastic facies. The clasts are outlined in the field photograph. F Photomicrograph of the lapilli-sized basalt breccia with epiclasts from the resedimented autoclastic facies (sample VU V–10). Notice that the matrix is composed of finely fragmented volcanic particles. Clasts are very irregular. The amount of the crystaloclastic particles is more abundant in this facies. G The same lithotype of the same facies but with different material in the pore spaces between the clasts (sample VU V–6a). Here the unsorted and irregular clasts mostly of different types of basalts are cemented by calcite cement. H A scanned polished sample VU IV–6 of the resedimented autoclastic facies exhibiting grading texture indicated by the arrow. Grading texture results in the transition from lapilli-sized basalt breccia to the coarse-sized ash lithoclastic tuff that is composed mostly of basalt clasts. I Photomicrograph of the coarse ash crystalloclastic tuff of the secondary pyroclastic facies composed mostly of plagioclase crystalloclast, and vitric particles. Notice the vesical rich particles of dark pumice fragments. The whole sample exhibits a strong imbrication pattern of particles indicated by the grey arrows – sample VU III–4 J Fine ash crystalloclastic tuff of the secondary pyroclastic facies composed mostly of crystalloclasts (VU III–6c). Notice the abundance of quartz crystalloclast in this facies indicating the acidic origin of the pyroclastic material. Also seen from the geochemical analysis. K Fine ash vitroclastic tuff with horizontal lamination from the secondary pyroclastic facies composed of very fine glass shards barely visible with the polarizing microscope (sample VU III–6)