Post-Last Glacial Maximum evolution of a “fjord-type” lake based on high-resolution seismic data: the Lago Roca/Acigami (southern Tierra del Fuego, Argentina/Chile)

LOZANO, JORGE GABRIEL; CIVILE, DARIO; BRAN, DONALDO MAURICIO; CERREDO, MARÍA E.; TASSONE, ALEJANDRO; LODOLO, EMANUELE; GROSSI, MAURIZIO; VILAS, JUAN; BARADELLO, LUCA

JOURNAL OF QUATERNARY SCIENCE

JOHN WILEY & SONS LTD

Lugar: LOndres; Año: 2020 vol. 35 p. 396 - 409

0267-8179

Lago Roca/Acigami is a ?fjord‐type? lake located in the southernmost part of South America, in theproximity of the Beagle Channel. A high‐resolution seismic survey was carried out to analyse the seismic stratigraphyof the lake and to shed some light on the post‐Last Glacial Maximum history of the area. Six seismic units wererecognised, and their nature and depositional context were interpreted using seismic stratigraphy and acoustic faciesanalysis. A buried large ridge was identified within the glacial unit (SU1), interpreted as a frontal moraine thatindicates a stabilisation phase. After retreat of the glacier from the basin, the trough was flooded by meltwater and alake developed (SU2). The seismic facies, from bottom to top, depict a transition from ice‐contact (SU2; SU3) to icedistalproglacial conditions (SU4). A thick draping unit (SU5) marks a marine transgressive event and the instaurationof a fjord environment in the basin. The marine transgression was a rapid event preceded by a fall in the lake levelthat caused an erosional unconformity. During the fjord phase the sedimentation remained controlled by meltwaterdischarge. Sea level fall, and subsequent disconnection from the Beagle Channel was accompanied by aprogradation of the glaciofluvial deltaic sediments and the occurrence of several mass‐wasting deposits (SU6).