Eocene volcanism in the Fuegian Andes: Evidence from petrography and detrital zircons in marine volcaniclastic sandstones

OLIVERO, EDUARDO B.; TORRES CARBONELL, PABLO J.; SVOJTKA, MARTIN; FANNING, MARK; HERVÉ, FRANCISCO; NÝVLT, DANIEL

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2020

0895-9811

The sedimentology, petrography, and U?Pb dating of two Eocene volcaniclastic horizons of the Punta Torcidaand Leticia formations, Austral basin, Tierra del Fuego, Argentina are interpreted and documented. The volcaniclasticdeposits, pumicite breccia and tuffaceous sandstones, are formed by glass shards, plagioclase crystals,and pumiceous and lithic andesitic fragments. Originally deposited as tephra fallout, they have been subsequentlyreworked and redeposited in marine settings. The final deposits, however, are interpreted essentially assyn-eruptive. U?Pb dating of detrital zircons gave a 46.3 ± 0.4 Ma (early Lutetian) age for the top of the PuntaTorcida Formation and 41.9 ± 0.71 (late Lutetian) to 39.6 ± 0.82 (Bartonian) ages for the Leticia Formation.Paleogene volcanic rocks are unknown in the Southern Patagonian-Fuegian Andes; hence the studied volcanicdeposits with minimal reworking are important to evaluate the time lag between eruption and true depositionalages in detrital zircons. The resulting dates allow evaluating the timing of the important, basin-wide, intra-Eocene unconformity known from Tierra del Fuego to Lago Argentino, Santa Cruz, Argentina. The documentederuptive phases are related to Andean magmatism, probably located in the outcrop area of the Seno A?no Nuevosuite in the Chilean Archipelago.