IANIGLA   20881
INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Dating Neoglacial evente in Monte San Lorenzo, Argentina, using lichenometric methods
Autor/es:
GARIBOTTI, I.A.; VILLALBA, R.
Lugar:
Uspallata
Reunión:
Workshop; Science Meeting IAI CRN 2047B, Documenting, understanding and projecting changes in the hydrological cycle in the America Cordillera; 2013
Institución organizadora:
IANIGLA
Resumen:
Monte San Lorenzo
(47°35′S, 72°18′W) is the highest mountain (3706 m) in the Argentinean
southern Patagonian Andes. Two major glaciers, Glaciar San Lorenzo Sur and San
Lorenzo Este, named according to Mercer (1968), are the largest ice bodies in
the Argentinean sector of Monte San Lorenzo. These glaciers present large and
conspicuous arcuate Neoglacial moraines.
At each glacier, we mapped the sequence of
moraines and dated the glacier deposits using lichenometric techniques. Historical
terrestrial and aerial photographs are available for the area, as well as a
radiocarbon date of organic material (Mercer, 1968) in an outer moraine of Glaciar
San Lorenzo Este. Combination of this information with lichenometric dating has
allowed a multi-proxy approach for dating glacier fluctuations.
Lichenometric measurements provide similar
dates for the set of glacier deposits at both glaciers, indicating four major
Neoglacial advances with minimum dates estimated at 4900 years BP, 2600 years
BP, 1800 years BP and 200-50 years BP. Concordance between lichenometric dates,
historical aerial and terrestrial photographs, and the radiocarbon dating of the
most external deposit, suggests that the established chronology for Neoglacial
fluctuations of Monte San Lorenzo glaciers is consistent. In addition, our
results show that lichenometric methods are reliable for dating landforms related
to Neoglacial events.
The
estimated scenario of glacier fluctuations at Monte San Lorenzo is in agreement
with both chronologies proposed for glacier fluctuation in the Patagonian Andes
during the last 5 millennia (Mercer 1968, Aniya 1996). Dates estimated for the earlier
event coincide with the Neoglacial Advance I proposed by Mercer. It is followed
by two minor events that corresponded to the Neoglacial Advances II and III
according to Aniya. Finally, both glaciers experienced 2 to 3 re-advances
during the Little Ice Age period (Neoglacial Advance IV).