FROM SHORT TO LONG-TERM VOLCANICLASTIC IMPACT ON SEDIMENTARY BASIN INFILLS

LÓPEZ, MANUEL; D'ELIA, LEANDRO; KAROLY NÉMETH

Paraná

Congreso; XVII Reunión Argentina de Sedimentología y VII Congreso Latinoamericano de Sedimentología; 2021

Asociación Argentina de Sedimentología

In volcanically active regions, the process, volume and the timescale of the production, transport, and accumulation of sediments are not exclusively determined by climatic and tectonic processes. Volcaniclastic sediments can be produced and incorporated into background sedimentary systems through volcano-sedimentary processes with greatly variable temporal and spatial span. In these scenarios, the volcanic impact depends on the volcanic style, magnitude, frequency and explosivity, and on environmental features such as the physiography, hydrology, and accommodation space. The interaction between these variables implies challenges in basin analysis, which are difficult to assess purely from the perspective of classical sedimentologic technics and conventional stratigraphic analysis, leaving behind conceptual gaps in our knowledge about how volcanism acts as a short- and long-term control on basin sediment infills.As a first approach to this major controversy, we present sedimentary and magnetostratigraphic data that allow unravelling the development of a Miocene syn-eruptive volcaniclastic sequence (e.i. The Collón Cura Formation) deposited within an intermontane basin located in the north Patagonian foreland (e.i. The Collón Cura Basin). The Collón Cura Formation is limited on its base and top by net discontinuity surfaces, implying erosional or non-depositional time-lapses which are in the order of 106 years. Internally, the Collón Cura Formation is characterized by a 150 m thick succession of extra-basinal pyroclastic density currents (PDC?s) and re-sedimented volcaniclastic materials. The absence of important discontinuity surfaces and paleosoil development suggest that the PDC?s were deposit in an extremely rapid time-lapse. After this extremely rapid filling episode, surrounding volcaniclastic materials were deposited in alluvial to aeolian environments in a time-lapse which is in the order of 105 years. The succession evidences that a short-term but high volume volcaniclastic supply partially filled the available accommodation space of the basin and triggered a longer syn-eruptive re-sedimentation process controlled by climate conditions. Moreover, the erosional surface towards the top of the sequence evidences an abrupt decrease in accommodation space, which was associated with the capture of the basin by an external drainage network. The onlapping fluvial sequence (e.i. Limay Chico Member) evidences a renewed alternation between inter-eruptive/syn-eruptive depositional periods, showing that volcanism is still being a predominant control for the basin infill but acting under different volcanic and environmental variables.Understanding the impact of volcanic and volcaniclastic products in sedimentary basin infills constitute a multidisciplinary discipline that depends on our temporal and spatial capabilities to unravel the dynamics of the volcanic and environmental variables. We propose that this integrated point of view of volcanism in basin analysis could be applied in contrasting geological contexts such as contractional or extensional depocenters, constituting an important tool for natural resources exploration and human hazards prevention.