Open University Uranium-Series Laboratory    
Earth and Environmental Sciences, The Open University, Milton Keynes, UK    

Quaternary Glaciation in the Pindus Mountains, Northwest Greece. (Dr P D Gibbard, Cambridge, PDRA Phil Hughes, IP/754/0302)

 
The aim of the project was to establish the extent, dynamics and age of glaciation in the high Pindus Mountains of Northwest Greece. Four glacial events are recorded in the sedimentological and geomorphological records. During the glacial maximum of the last glacial stage, mean annual temperatures were ca. 8-9°C lower than at present and mean annual precipitation greater than 2000 mm - similar to modern values. Maximum glacier extent in the Pindus Mountains has preceded the most severe arid phase of glacial cycles indicated in the pollen record because of the small size of the Pindus glaciers and their rapid response to climate change.
 
 
Detailed sedimentological analyses of diamicton (till) sequences in two areas of the Pindus Mountains, indicate multiple episodes of glacier advance and retreat during cold stages of the Middle-Pleistocene. These glacial sequences represent some of the most southerly in Europe and are important archives of regional and global climate change.
The Pindus glaciers were relatively small by world standards and would have been highly responsive to changes in air temperature and precipitation. Stacked diamictons separated by gravels, record multiple phases of glacier advance and retreat in the Pindus Mountains. There is evidence of at least three episodes of glacier advance and retreat during the Skamnellian Stage and of two phases of advance and retreat during the later Vlasian Stage. These records highlight the dynamic nature of glacier behaviour in the Mediterranean mountains during the Middle Pleistocene and provide new evidence for unstable cold stage climates. Morpho-stratigraphical position, supported by pedo-stratigraphical evidence, is the fundamental criterion for establishing the relative age of the glacial sedimentary units. In these isolated deposits, far-field correlations depend entirely on radiometric dating, in this case using uranium-series methodology.
 
Xeroloutsa moraine dam
Figure 1. Lake on Mount Tymphi. This seasonal lake occupies a shallow infilled basin dammed by moraines. Secondary calcites cementing the moraines have been dated to the last interglacial, Marine Isotope Stage 5e, c.120,000 kyr.

Vadose zone calcite cements often coat large clasts, fill interclast voids and are usually localised deposits with little detrital quartz contamination. Sometimes the calcites are up to 5 cm thick and consist of multiple layers and, in places, small dripstones or stalactites, have developed within sediment voids.

U-series dating to estimate the age of host glacial sediments (Fig 1) is based on the oldest ages obtained from secondary carbonates Fig 2) in a given glacial sedimentary unit. Phases of secondary carbonate formation can take place long after the deposition of the host sediments, and various calcites may form at a range of different times. Thus, multiple samples from any given stratigraphical unit should be dated in order to understand the history of secondary carbonates formation.
The records highlight the dynamic nature of glacier behaviour in the E Mediterranean mountains during the Middle Pleistocene and provide newevidence for unstable cold stage climates.U-series dating shows that the Skamnellian Stage is correlated with the Elsterian Stage of northern Europe and MIS 12 and the Vlasian Stage is correlated with the late Saalian Stage of northern Europe and MIS 6. The earliest glacial deposits formed before 350 ky. and that a later phase of glaciation took place before the last interglacial. This represented a marked shift from the common view for Greece that the glacial sequences formed during the last glacial stage (Weichselian/Würmian).
In the Pindus Mountains complex glacial sedimentological sequences provide evidence not only for glacial advances during multiple Middle Pleistocene cold stages, but also for climate instability within single cold stages. Evidence for the latter is important in understanding variations in former glacier mass balance and is essential for unravelling complex glacier–climate histories based on the glacial record.
 
 
Pindus moraine with secondary calcite
Figure 2. Moraine in the Pindus Mountains, Greece with vadose secondary calcite (mantle, curtains and stalagmite) partially cementing the moraine boulder deposit.
 
The geomorphological and geological investigations, combined with the soil evidence and U-series dating enabled the development of a chronostratigraphical and geochronological framework for the cold-stage deposits of Greece.
 
The glacial sequence in the Pindus Mountains represents the best-dated and longest recognised record of glaciation in the Mediterranean region and provides a stratigraphical framework for Quaternary cold-stage climates in Greece.
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© Peter van Calsteren
Last updated: date December 23, 2011 11:27
 
December 23, 2011 11:2723 December, 2011 11:27