Title of article :
Stratotype for the Mérida Glaciation at Pueblo Llano in the northern Venezuelan Andes
Author/Authors :
Mahaney، نويسنده , , W.C and Milner، نويسنده , , M.W and Voros، نويسنده , , J and Kalm، نويسنده , , V and Hütt، نويسنده , , G and Bezada، نويسنده , , M and Hancock، نويسنده , , R.G.V and Aufreiter، نويسنده , , S، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2000
Abstract :
The Mérida Glaciation (cf. Wisconsinan, Weichselian) as proposed by Schubert (1974b) culminated at about 18 ka during the last glacial maximum (LGM) and ended at about 13 ka as indicated by 14C dating and correlation with the Cordillera Oriental of Colombia. Moraines of an early stade of Mérida Glaciation reached to 2800 m a.s.l. and were largely overrun or eradicated by the maximum Wisconsinan advance (LGM); where they outcrop, the older moraines are characterized by eroded, weathered glacial diamictons and outwash fans.
blo Llano in the central Mérida Andes (Cordillera de Trujillo), older to younger beds of contorted glacitectonized diamict, overlying beds of bouldery till and indurated outwash, all belong to the early Mérida stade. Overlying the early Mérida stade, deposits of rhythmically bedded glaciolacustrine sediments are in turn overlain with contorted sand and silt beds capped with outwash. Above the outwash terrace a loop moraine of LGM age completely encircles the margins of the basin. A stream cut exposed by catastrophic (tectonic or surge?) release of meltwater displays a lithostratigraphic succession that is bereft of organic material for radiocarbon dating. Five optically-stimulated luminescence (OSL) dates place the maximum age of the lowest till at 81 ka.
le size distributions allow clear distinctions between major lithic units. Heavy mineral analysis of the middle and lower coarse units in the section provide information on sediment sourcing and on major lithostratigraphic divisions. Trace element concentrations provide information on the relative homogeneity of the deposits. The HREE (heavy rare earth element) concentrations allow discrimination of the lower till from the rest of the section; the LREE (light rare earth element) concentrations highlight differences between the lower till, LGM till, and the rest of the section.
Keywords :
Mérida Glaciation , Last Glacial Maximum , Till inclusion , Mineral microtextures , REE geochemistry , OSL dates , heavy minerals
Journal title :
Journal of South American Earth Sciences
Journal title :
Journal of South American Earth Sciences