No abstract

The finding of a prehistoric mummified corpse at the upper edge of the accumulation area of an alpine glacier, together with its unique set of artifacts, provided new information on glacier dimensions during the little-known phases of major glacier shrinkage that characterized the warmest parts of the Holocene. The sudden burial of the corpse in a permanent snow cover occurred 5300–5050 cal yr B.P., indicating a significant climatic change that induced glacier expansion at the beginning of Neoglaciation. New geomorphologic data and two AMS 14C ages from buried soils suggest that the present glacier size, following over 100 yr of shrinkage, is comparable to that immediately preceding Neoglaciation. Therefore, we can deduce that the current global climatic warming may have interrupted the environmental conditions prevailing in the Alps during Neoglacial time, restoring characteristics similar to those prevailing during the climatic optimum that were never achieved during the second half of the Holocene.

Holocene glacier variations pre‐dating the Little Ice Age are poorly known in the western Alps. Studied for two centuries, the Miage morainic amphitheatre (MMA) is composed of three subconcentric sets of c. 25 moraines. Because of its location and of a dominant mode of morainic accretion, the MMA is a well‐preserved marker of the glacier dynamics during the Neoglacial. Radiocarbon dates were obtained by digging and coring in inter‐ morainic depressions of the MMA and through a deep core drilling in a dammed‐lake infill (Combal); complementary data for the inner MMA were obtained by lichenometry and dendrochronology. Radiocarbon chronology shows that (i) the MMA not only pre‐dates the Little Ice Age (LIA), but was built at least since 5029–4648 cal. yr BP (beginning of the Neoglacial); (ii) outer sets of moraines pre‐date 2748–2362 cal. yr BP; (iii) the MMA dammed the Lake Combal from 4.8 to 1.5 cal. kyr BP, while lakes/ponds formed inside the moraines (e.g. from 2147–1928 to 1506–1295 cal. yr BP). The ‘Neoglacial model’ proposed here considers that the MMA formed during the whole Neoglacial by a succession of glacier advances at 4.8–4.6 cal. ky BP (early Neoglacial), around 2.5 cal. ky BP (end of Göschener I), at AD 600–900 (end of Göschener II) and during the LIA, separated by raising phases of the right‐lateral moraine by active dumping because of the Miage debris cover.

More than 40 14C dates for raised beaches at Terra Nova Bay ranging from the present to 7505 ± 230 yr B.P. supply minimum or maximum limiting ages that bracket a relative sea-level curve for this part of Victoria Land. Most samples consist of guano and penguin remains collected from abandoned nesting sites on beach deposits. Up to four 14C dates in stratigraphic sequence have been obtained in two soil profiles. Other samples consist of marine shells collected both within and on the surface of raised beaches. All 14C ages for organisms that lived or fed in circumantarctic waters were corrected for a large reservoir effect. The calibrated ages delimit a first relative sea-level curve for Victoria Land. Rates of uplift ranged from about 10 mm/yr following deglaciation to about 2 mm/yr in the last 3 millennia. Widespread presence of Adélie penguin nesting sites suggests that Terra Nova Bay was deglaciated before 7065 ± 250 yr B.P. (7059/6439 cal yr B.P.), when environmental conditions in the coastal area were similar to the present ones.