Author:
Publisher:
Published: 2005
Total Pages:
ISBN-13:
DOWNLOAD EBOOK →
Environmental and climatic changes during the last 20,000 years were investigated along an east-west transect across the southernmost Andes (53°S) within the interdisciplinary project "Late and Post Glacial Environmental Conditions in the Range of the Southern Hemispheric Westerlies". Twelve coring locations in the different geographical, geological and vegetational zones of the transect, were selected as drill sites on the basis of parametric echo sounding sediment profiles in the fjords of the Gran Campo Nevado area. The stratigraphy of the sediment cores is based on 14C-AMS ages and tephrachronology. Sedimentological and geochemical characteristics were investigated in order to determine sediment sources and their pathways as well as climate and environmental changes. The ice retreat after the Last Glacial Maximum (LGM) is marked in a sediment core from the eastern section of the proglacial lake Seno Skyring by an ice rafted debris layer (IRD), which was formed at around 18,700 to 17,800 cal. years B.P. This indicates a rapid response of the Seno Skyring glaciers to warming of the southeast Pacific soon after the LGM. However, between around 16,000 and 13,000 cal. years B.P. this core still shows relatively high amounts of Andean-derived glacial clay, characterized by high-MgO andesitic composition with low SiO2/Al2O3 ratios. This suggests a still extended glaciation of the Andes and a slowdown of the ice retreat. Further towards the Andes a core from an ancient glacial valley (Estero Vogel) contains an IRD layer formed at around 13,600 cal. years B.P, indicating a still extended glaciation at that time. Moreover, subaquatic ridges located in an echo sounding profile of Estero Vogel are interpreted as a moraine system, which can be related to a moraine system identified in the middle section of the Gajardo Channel. These moraines may be coeval with the moraine E system in the Strait of Magellan dated 15,043±607 to 12,275±201 cal. years B.P. by Clapperton et al.).