Gutâi Mts. had started to be built up in Middle Miocene, ca. 15.4 Ma ago. A series of explosive events developed starting with a major magmatic explosion and caldera collapse responsible for large volumes of ignimbrites. Successive explosions followed caldera collapse triggering a series of pyroclastic currents that underwent subsequent reworking. Mass flow has been the main transport mechanism recorded by the sedimentary structures of either ignimbrites or post-ignimbrites volcaniclastics. Multiple ignimbrite units resulted from subaerial mass flows, successively emplaced by progressive aggradation from the basal layer of a density-stratified pyroclastic current. The overlying sequence is composed of different volcaniclastics of pyroclastic origin interlayered with mudstones. They preserve the original composition of ignimbrites, but lack the evidence of hot-state deposition, recording the emplacement from more or less dilute mass flows. A syn-eruptive stage of resedimentation is suggested prior to emplacement in submarine conditions, determined by the transformation of gas-supported pyroclastic currents into water-supported mass flows after transition from subaerial to submarine conditions. The syn-eruptive resedimented volcaniclastics may be correlated with the ignimbrite-type subaerial pyroclastic flows, but they show different degrees of fluidization due to the impact of submarine environment.
Transport and emplacement of ignimbrites and resedimented volcaniclastics from Gutai Mts., Eastern Carpathians, Romania,
Studia UBB Geologia
Available at: http://scholarcommons.usf.edu/geologia/vol49/iss1/art6