Abstract

GARDUNO-MONROY, Victor Hugo et al. Evidence of tsunami events in the Paleolimnological record of Lake Pátzcuaro, Michoacán, Mexico. Geofís. Intl [online]. 2011, vol.50, n.2, pp.147-161. ISSN 2954-436X.

Modern Lake Pátzcuaro has a surface elevation of 2035 m a.s.l. Historically, it reached an elevation of 2041 m a.s.l., which isolated a portion of the island near the town of Jarácuaro in the southeastern part of the lake. Two trenches in the former island reveal similar tripartite stratigraphic sequences. In a 3.1 m deep trench, the sequence from bottom to top comprises Unit A constituted by folded and faulted diatom-rich clay and silt with beds of volcanic sand. These deposits are dated between 24 and 10 ky BP; Unit B constituted by a 10 of cm chaotic mixture of volcanic sand and lapilli with abundant remains of fish, bivalves, gastropods and ostracodes that is rests on above an erosional unconformity. The ostracodes include articulated valves with a mixture of deep-water pelagic species and attached littoral species. Highly fractured diatom shows a mixture of planktonic and benthic habitats. Fragments of ceramic artifacts dated to the Post-Classic Period (900 to 1520 AD) are abundant; Unit Cconstituted by a 20 cm thick unit of organic-rich argillaceous silt with remains of gastropods, seeds, angular lithoclasts and fragments of Post-Classic ceramic artifacts. Unit B suggests a catastrophic resedi mentation of lake floor deposits attributed to a tsunami. Unit C is consistent with sublacustrine conditions that are historically documented from 1858 to 1947. A tsunami in Lake Pátzcuaro in 1858 has been historically recorded. The tsunami was created either by fault movement or collapse of the SW flank of the island of Janitzio. The tsunami wave may have contributed to the rapid rise of Lake Pátzcuaro following the 1858 seismic event.

Keywords : Tsunamis lakes; historical seismicity; ostracodes; lake Pátzcuaro.

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