At Terlago lake (near Trento, 415 m a.s.l.) lake sediments were drilled to a depth of 22,2 m where the bedrock was reached. Sedimentological, malacological and stable isotope analyses of freshwater shells were carried out on the recovered core. These analyses, in conjunction with 14C dating, allow the reconstruction of environmental change at Lake Terlago from the Younger Dryas to Holocene. The oldest age, 11,890±90 yr B.P. coincides with the first appearance of Pisidium sp. at 1410 cm and testifies to the complete deglaciation of the area by that time, linked to the rapid glacial retreat in the southern Alps almost completely accomplished at beginning of the Late Glacial. The mollusc assemblages of the lower part of the core indicate the water depth. During this interval a progressive rise in δ18O from 1268 to 1090 cm has been tentatively correlated with Younger Dryas/Pre Boreal climatic transition according to 14C ages and the δ18O variation. The interval between 1090-930 cm, with enriched δ18O values, may represent the Pre Boreal climatically favourable phase. In the following core section a progressive lowering of the water level and infilling of the lake is suggested from malacological analyses. Another shift in the oxygen stable isotope composition occurred just before (930-683 cm) at 9,310±80 14C yr B.P. in concomitance with lithological and molluscan assemblage changes. δ18O values progressively shift toward mean values found at the top of the core representative of a lake with isotopic composition similar to present-day precipitation. The change in lake level and temperature of calcification of the shell, hydrological factors and the effect of meteoric precipitation probably all contribute to this isotopic drift.
Younger Dryas to Early Holocene palaeoenvironmental evolution of the Lake Terlago (Southern Alps, Italy)
BARONI, CARLO;ZANCHETTA, GIOVANNI
2001-01-01
Abstract
At Terlago lake (near Trento, 415 m a.s.l.) lake sediments were drilled to a depth of 22,2 m where the bedrock was reached. Sedimentological, malacological and stable isotope analyses of freshwater shells were carried out on the recovered core. These analyses, in conjunction with 14C dating, allow the reconstruction of environmental change at Lake Terlago from the Younger Dryas to Holocene. The oldest age, 11,890±90 yr B.P. coincides with the first appearance of Pisidium sp. at 1410 cm and testifies to the complete deglaciation of the area by that time, linked to the rapid glacial retreat in the southern Alps almost completely accomplished at beginning of the Late Glacial. The mollusc assemblages of the lower part of the core indicate the water depth. During this interval a progressive rise in δ18O from 1268 to 1090 cm has been tentatively correlated with Younger Dryas/Pre Boreal climatic transition according to 14C ages and the δ18O variation. The interval between 1090-930 cm, with enriched δ18O values, may represent the Pre Boreal climatically favourable phase. In the following core section a progressive lowering of the water level and infilling of the lake is suggested from malacological analyses. Another shift in the oxygen stable isotope composition occurred just before (930-683 cm) at 9,310±80 14C yr B.P. in concomitance with lithological and molluscan assemblage changes. δ18O values progressively shift toward mean values found at the top of the core representative of a lake with isotopic composition similar to present-day precipitation. The change in lake level and temperature of calcification of the shell, hydrological factors and the effect of meteoric precipitation probably all contribute to this isotopic drift.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
