Sedimentary record of 1960 major subduction earthquake (Mw 9.5) in Northern Patagonia (Chile, Argentina)

EMMANUEL CHAPRON; SANDOR MULSOW; DANIEL ARIZTEGUI; ETIENNE JUVIGNIE; GUSTAVO VILLAROSA; MARIO PINO; VALERIA OUTES

Paris, France

Otro; COLLOQUE International Q5 Le Quaternaire, Limites & Spécificités; 2006

Comité national Français de l’INQUA Association française pour l’étude du Quaternaire

The recent sedimentation processes in four contrasting lacustrine and marine basins of Northern Patagonia are documented by high-resolution seismic reflection profiling and short cores at selected sites in deep lacustrine basins. The regional correlation of the cores is provided by the combination of 137Cs dating in lakes Puyehue (Chile) and Frías (Argentina), and by the identification of Cordón Caulle 1921-22 and 1960 tephras in lakes Puyehue and Nahuel Huapi (Argentina) and in their catchment áreas. In lake Puyehue, cores retrieved in a proximal and in a more distal position with respect to the main tributary, are further correlated based on the identification of the tephra related to the nearby Riñinahue maar eruption in 1907. This event stratigraphy allows correlating the formation of striking sedimentary events in these basins with the consequences of May-June 1960 earthquakes and the induced Cordón Caulle eruption along the Liquiñe-Ofqui Fault Zone (LOFZ) in the Andes. While this catastrophe induced a major hyperpycnal flood deposit of ca. 3.106 m3 in the proximal basin of lago Puyehue, it only triggered an unusual organic rich layer in the proximal basin of Lago Frías, but destructive waves and a large sub-aqueous slide in the distal basin of Lago Nahuel Huapi. A very recent megaturbidite in the two distal basins of Reloncavi fiord located cióse to the LOFZ is suggesting that 1960 co-seismic movements in this área may have triggered the remobilization of ca. 187.106 m3 of marine sediments. This case study highlights the wide range of earthquake-induced sedimentary events in a subduction margin largely influenced by the melting of the Patagonian Ice Cap and the concomitant development of an intense volcanic activity since the Late Glacial.