Climate change in the Lake Valencia Basin, Venezuela, ~12,600 yr BP to Present

Curtis, J.H., M. Brenner, and D.A. Hodell
The Holocene (1999), v. 9, p. 609-619.

Abstract

We present a paleoclimate record for northern South America, extending from the latest Pleistocene (~12,600 14C yr BP) to present. Climate reconstruction for the Valencia Basin, Venezuela, was based on sediment geochemistry and delta 18O records from ostracod and gastropod shells in a 568-cm sediment core. Sediment chronology was established by AMS 14C dating of terrestrial wood fragments. From ~12,600 to ~10,000 14C yr BP the Valencia basin was drier than present and the coring site, now under 9.4 m of water, was only intermittently wet. After ~10,000 14C yr BP, moisture availability increased and lake level rose, permanently covering the core site. From ~10,000 to ~8,200 14C yr BP, Lake Valencia was hydrologically closed and the isotope records reflect pronounced variability in the ratio of evaporation to precipitation. During the wetter early to middle Holocene (~8,200 to ~3,000 14C yr BP), lake level was high and water was lost to outflow. Greater moisture availability at this time may have been caused by increased intensity of the annual cycle (with wetter wet seasons and drier dry seasons), a result of large, orbitally-driven differences in seasonal insolation. Two brief periods of lower lake level, at ~7,000 and ~3,300 14C yr BP, are indicated in the oxygen isotope and calcium carbonate records. Since ~3,000 14C yr BP, water level in Lake Valencia has been dropping.

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