Late Holocene tectonic land-level changes and tsunamis at Mitla lagoon, Guerrero, Mexico

Sedimentological, stratigraphic and geochemical data record abrupt land elevation change, coastal subsidence, and changes in the salinity of Mitla lagoon that may be associated with a tsunami around 3400-3500 yr BP. The observations are supported by microfossil data (pollen, diatoms and phytolith) from other studies on the Guerrero coast. Stratigraphic data indicate an average Late Holocene sedimentation rate of about 1 mm/yr. Short-term sea-level records from 1952 of tide gauge data are compared with expected coseismic coastal deformation, and long-term records of coastal deformation from the sediment record c. 3500 yr BP. Recent large earthquakes in the Central Mexico subduction zone ruptured an area of limited width of about ~60 km, but some prehistoric earthquakes may have ruptured the entire coupled plate interface almost up to the trench, thus generating significant coastal subsidence and possibly a large tsunami.