Volcanic debris avalanche deposits and their significance in the architecture and evolution of the Miocene-Quaternary Călimani-Gurghiu-Harghita volcanic range (Eastern Transylvania, Romania)

The Călimani-Gurghiu-Harghita volcanic range (CGH) represents the surface manifestation of the post-collisional magmatism that followed the docking of its basement, the Dacia Mega Unit, onto the East European margin. Between ca. 11 and 0.3 Ma, detachment of subducted slab, magma generation, and volcanic activity in CGH propagated south-southeastward, sub-parallel with the collisional Eastern Carpathian Orogen, resulting in the construction of a series of mostly composite volcanoes dominated by calc-alkaline lavas and pyroclastic products. The generally well-preserved axial row of the CGH volcanic edifices is accompanied by voluminous volcaniclastic deposits of which sources and emplacement history persist as a matter of debate. In the standard view reflected in regional scale geologic maps, these deposits represent products of complete erosion of hypothetical earlier volcanoes. Other interpretation, however, suggest that they are at least partially constituted by voluminous volcanic debris avalanche deposits (VDADs).