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Contribution of non-pollen palynomorphs to the paleolimnological study of a high-altitude Andean lake (Laguna Verde Alta, Venezuela)
13 p.[EN]This paper evaluates the potential usefulness
of non-pollen palynomorphs or NPPs (microfossils
other than pollen and spores present in palynological
preparations) contained in lake sediments in the paleolimnological
reconstruction of high altitude environ
ments ([4,000 m) from the Venezuelan Andes. A
synthetic, quantitative approach is employed, instead of
the classical analytical and mostly qualitative approach
commonly used so far for NPPs. The main sources of
variation are the Pediastrum–Botryococcus alternation
and the relationship between these two algae and animal
remains such asAcari legs, postabdomina of Cladocera,
mandibles of other invertebrates, and an unknown type
called LVA-1. Other significant microfossils are
remains of Rivularia-type and turbellarian oocytes,
including Gyratrix. The sequence initiates around
15,000 calibrated years before present (cal BP) with
the deglaciation of the lake catchment, high water levels
and still cold climates. A phase of lower lake levels was
recorded between about 12,000 and 6,000 cal BP.
Temperatures increased by around 9,000 and 7,000 cal
BP, and then decreased until 6,000 cal BP. Since that
time, both lake levels and temperature increased again
and stabilized at about 4,000 cal BP, when they reach
modern-like values. These results show a good agreement
with previous studies based on pollen, diatom and
oxygen isotope analyses, and provide additional paleoecological
information, as for example the possibility
of a previously unrecorded Younger Dryas signal. The
inclusion of quantitative NPP analysis in routine
paleolimnological studies using synthetic methods is
thus recommended. Possible future improvements are
suggested, mainly those related with the development
and use of NPP modern analogs.Peer reviewe