Late Quaternary deglacial history of the Mérida Andes, Venezuela.

Abstract

[EN] Radiocarbon-dated sediment cores from seven lakes and two bogs spanning the Cordillera de Me´rida in the Venezuelan Andes were used to identify and date the regional history of late Pleistocene and Holocene glacial activity. Coring sites were selected at different elevations across a pronounced rain shadow from southeast (wet) to northwest (dry). Sediment lithostratigraphy and magnetic susceptibility, in conjunction with AMS radiocarbon dates on macrofossils and charcoal, were used to constrain deglaciation. The local expression of the Last Glacial Maximum occurred between 22 750 and 19 960 cal. yr BP. On the wetter southeastern side of the Cordillera de Me´rida, glaciers had significantly retreated by 15 700 cal. yr BP, followed by several minor glacial advances and retreats between 14 850 and 13 830 cal. yr BP. At least one major glacial readvance occurred between 13 830 and 10 000 cal. yr BP in the wetter southeastern sector of the region. The drier northwest side of the Cordillera de Me´rida records initial glacial retreat by 14 240 cal. yr BP. Multiple sites on both sides of the Me´rida Andes record a further phase of extensive deglaciation approximately 10 000 cal. yr BP. However, the north-northwest facing Mucubajı´ catchment remained partially glaciated until ca. 6000 cal. yr BP. Deglacial ages from the Venezuelan Andes are consistently younger than those reported from the Southern Hemisphere Andes, suggesting an inter-hemispheric deglacial lag in the northern tropics of the order of two thousand years.