Glaciolacustrine record chronology (Poster IAG 2013)


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The La Massana and Ordino Palaeolake (SE Pyrenees), Valentí Turu (FMC) & Jaume Bordonau (UB).

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  • Glaciolacustrine record chronology (Poster IAG 2013)

    1. 1. Glaciolacustrine record chronology Para ver esta película, debe disponer de QuickTime™ y de un descompresor TIFF (LZW). The La Massana and Ordino Palaeolake (SE Pyrenees) Valentí Turu (FMC) & Jaume Bordonau (UB) Palaeogeography of the glacial dammed lake Three glacial tongues converged on the La Massana site during the local glacial maximum prior to the LGM. A post maximum glacial retreat occured followed by a glacial advance and stabilisation (post maximum stabilisation). At that moment the glacial tongues converged several times at La Massana damming intermittently the lake. A final disjunction phase gave way to an ice-free lake until its final drainage. Geochemistry: A key tool to study palaeoclimate changes Geochemistry studies give all its potential if a good chronostratigraphic model has been previously stablished. Data about weathering, chemical conditions in paleolake waters and its relationship with paleoclimate are available with this kind of studies. The relation between immobile (Ti) and mobile (Al) elements is shown. Basement weathering by climatic favourable conditions promote Al leaching. Idealized palaeoreconstruction of the dammed lake by Marta Vilaplana (1981) Sketch map of the palaeolake at the post-maximum phase Outcrop at the Hortals proglacial delta Sequence Stratigraphy: A key tool to study palaeolake sediments Sequence stratigraphy is a toolkit that allows us to study more efficiently the geometry of the glaciolacustrine sediments. Isotope analysis: A key tool to reconstruct palaeoenvironments In proglacial palaeoenvironments, pollen can be distroyed by the energy of the glacial meltwaters. In such cases it is possible to reconstruct the palaeovegetation from the δ13C ratio. In continental environments less depletion in δ13C values are correlated with an increasing presence of aquatic plants (C4), on the other hand high depleted values are related to terrestrial plants (C3 plants), frequently a mixture of them is recorded in such environments. During the LGM, δ13C shows a very low depletion value. At the same time the weathering Al/Ti ratio is low. How should we interpret this evidences?, cooling?, high amount of metwaters?, increasing of aridity?... Relationships between Al/Ti and isotope ratio -13C/12C ‰ (AMS) GIS-3 Erts delta sequence stratigraphy (Arinsal valley). Relative position of the glaciolacustrine samples for geochemical analysis and AMS available data (from all valleys). More than 150 outcrops were described in the Arinsal valley Al/Ti GIS-1ad GS-2a GS-2b GS-2c GIS-2 GS 3 GIS-4 GS-5 GS-4 28 GS-1 26 24 22 20 18 16 He2 He1 14 12000 13000 14000 15000 16000 17000 18000 19000 20000 21000 22000 23000 24000 25000 26000 27000 28000 29000 30000 31000 32000 NGRIP (2bk) Age (Cal BP) Al/Ti d13C Decoding the sedimentological record of the palaeolake Glacial extent curve obtained from the volume of the stored sediments in the lake. More than 250 outcrops were used in order to obtain this curve RESEARCH POSTER PRESENTATION DESIGN © 2012 A similar glacial evolution was previously proposed (Bordonau, 1992) from sedimentological studies of glacial paleolakes from Southern Pyrenees. However a more complete chronological reconstruction can be stablished here.