Disentangling Late Quaternary climatic and seismo-tectonic controls on Lake Mucubají sedimentation (Mérida Andes, Venezuela)
Résumé
Lake Mucubají is a moraine-dammed lake, crossed by the Boconó Fault, in the Mérida Andes, Venezuela. Four long piston-cores (up to 8 m long) and 24 short gravity cores (0.6 to 0.8 m long) were collected to study the sedimentary fill of the lake. Lithostratigraphy, magnetic susceptibility, organic and inorganic contents, and 14C ages, permit lateral correlations between the cores, and with an emerged part of the former larger lacustrine basin fill. The cored succession spans the last 16,000 years. Several abrupt changes in sediment texture and composition are ascribed to depth and surface modifications. Together with soft-sediment disturbances, they are related to the seismo-tectonic activity of the Boconό Fault: shock-induced phenomena (slumps, seiche effects, liquefaction) and co-seismic scarps. Four major earthquakes indicate a mean minimum recurrence interval of 1200 years, which is consistent with trench data obtained from a neighbouring active trace of the Boconó Fault system. Despite the seismo-tectonic imprint, a general post-LGM climatic trend can be traced and correlated with northern-hemisphere global evolution, in particular for the last 13,000 years.