Late glacial ice decay

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As late glacial Eiszerfall in is Alps a glaziologisches development stage referred to, which is immediately to the maximum prior würmzeitlichen followed icing. It shows the rapid melting of the ice stream network in the period 19,250 to 17,550 BC. Chr .

Naming and conceptual history

In his work from 2007 Jürgen Reitner advocates initially described by Albrecht Penck and Eduard Brückner introduced in 1909, classic Buhl stage and the Steinach stage by the term Late Glacial Eiszerfall ( Engl. Lateglacial ice decay ) to replace, as in the type region of the lower Inntals, no terminal moraine of its own can be assigned to the Bühl stage .

stratigraphy

Temporal classification of the late glacial ice decay during the last 47,500 years

The late glacial ice decay immediately follows the last glacial maximum ( Last Glacial Maximum or LGM ). This is followed by the Gschnitz stage .

The late glacial ice decay correlates with the marine isotope stage 2 or the Greenland stage 2c ( GS-2c ).

Dating

Different radiocarbon ages show that the last glacial maximum in the Alps was up to around 19500 BC. Lasted. Surface dating of boulders from the terminal moraine of the Rhone glacier indicate the beginning of the remelting with around 19100 years BC. Chr. Firmly. Investigations on peat deposits of the Lanser See near Innsbruck showed that the Inn valley was at the latest from 15379 ± 282 years BC. Must have been totally free of ice. The Rödschitz peat shifts the age of complete de-icing even further back (to 16668 ± 503 years BC in the area of ​​the Traungletscher ). Results from the Längsee and Jerserzer See near Klagenfurt confirm plant recolonization in the area of ​​the Draugletscher around 16847 ± 254 years BC. Chr.

Overall, therefore, around 2200 years (period 19100 to around 16,900 BC) remain for the late glacial ice breakup.

Effects

The main effect of the late glacial ice decay was ultimately noticeable, somewhat delayed, in the signal of the sea ​​level , which for the northern hemisphere from 16000 BC. Recorded a steady rise from its lowest point by 120 meters below sea level. The enormous fresh water input from the meltwater pulse 1A immediately later led to a significantly increased circulation of the water masses in the Atlantic .

Classical structure in stages

The classic structure should be briefly illustrated using the Inn glacier (from young to old): In the interior of the Alps as an ice stream network:

In the foothills of the Alps as broad praise:

During the Kirchsseon stage with its multi-tiered terminal moraine walls, the Inn glacier had reached its northernmost position in the foothills of the Alps near Haag towards the end of the last Ice Age maximum . With the onset of the ice breakup, the first branch basins of the Ebersberg stadium, filled with frontal lobes, formed. The subsequent oil furnace stage with several relays saw a further increase in partial flap formation. The Stephanskirchen Stadium was already 25 kilometers further south around Rosenheim and was characterized by drum linings and existing or already silted lakes. At this point in time, the Rosenheimer See was created , which was gradually thinned out by warventone , sand and ceiling clay and finally ran out at the beginning of the Bölling Interstadial , fell dry and muddy .

Critical consideration

After their maximum expansion towards the end of the last Ice Age maximum in the Alpine foothills, the ice masses had retreated again into the interior of the mountains. According to the classical theory, which was further elaborated by Mayr and Heuberger in 1968, the tongue of the Inn glacier, for example in the Kitzbühel - Hopfgarten area, had its first stabilizing retreat with terminal moraine formation - the so-called Bühl stage. However, new investigations south of the Wilder Kaiser find no evidence of this. Rather, the situation is as follows:

Before the onset of the ice breakup, the Inn glacier was in the south of the Wilder Kaiser at an altitude of around 1800 meters above sea level. As a result of the collapse of the ice, the glacier lost around 500 meters in height in the initial phase and from then on formed a stagnant ice body that was cut off from its nutrient area. The decay had evidently been fairly continuous and without major incisions. Due to the removal of the ice masses blocking them, smaller, local Kar glaciers on the southern roof of the Wilder Kaiser were able to advance mechanically. They reached their maximum extent calving when the Inn glacier was only 1,000 to 1,100 meters high and at that time was bordered by an ice reservoir. The rest of the ice disintegration up to a height of around 600 meters evidently took place very quickly under high solar radiation; this final phase may not last more than 100 to 500 years. The short duration of this phase, which is very rich in melt water, is underlined by the extensive chimney terraces ; With their sedimentary structures, they document a rapid filling of the ice-free sedimentation area. During this final phase, in which the Inn glacier was reduced from 800 to 600 meters in height, there was a climatically-related ice advance in the area of ​​the Windau glacier, whereby a kameter terrace was crossed by 3 kilometers. The trigger for this wave of ice masses is likely to have been a brief climatic oscillation (temperature decrease or increase in precipitation).

Individual evidence

  1. ↑ Penck, A. and Brückner, E .: The Alps in the Ice Age . tape I-III . Leipzig 1909.
  2. ^ Reitner, Jürgen M .: Glacial dynamics at the beginning of Termination I in the Eastern Alps and their stratigraphic implications . In: Quaternary International . tape 164-165 , 2007, pp. 64-84 .
  3. ↑ Björck, S. et al.: An event stratigraphy fort the last Termination in the Nord Atlantic region based on the Greenland Ice-core record: a proposal by the INTIMATE group . In: J. Quaternary Sci. tape 13 , 1998, pp. 283-292 .
  4. ^ Preusser, F .: Towards a chronology of the Late Pleistocene in the northern Alpine Foreland . In: Boreas . tape 33 , 2004, pp. 195-210 .
  5. ^ Ivy-Ochs, S., Schäfer, J., Kubik, PW, Synal, H.-A. and Schlüchter, C .: Timing of deglaciation on the northern alpine foreland (Switzerland) . In: Eclogae Geologicae Helvetiae . tape 97 , 2004, p. 47-55 .
  6. ^ Sigmar Bortenschlager : Contributions to the vegetation history of Tyrol I. Inner Ötztal and lower Inntal . In: Reports of the Scientific Medical Association, Innsbruck . tape 71 , 1984, pp. 19-56 .
  7. ^ Van Husen, D .: On the facies and stratigraphy of the Young Pleistocene deposits in the Traun Valley . In: Yearbook of the Federal Geological Institute . tape 120 , 1977, pp. 1-130 .
  8. ^ Schmidt, R., van der Bogaard, C., Merkt, J. and Müller, J .: A new Lateglacial chronostratigraphic tephra marker for the southeastern Alps: The Neapolitan Yellow Tuff (NYT) in Längsee (Austria) in the context of a regional biostratigraphy and paleoclimate . In: Quaternary International . tape 88 , 2002, p. 45-56 .
  9. ↑ Ekkehard Schultze: New findings on the late and early post-glacial vegetation and climate history in the Klagenfurt Basin . In: Carinthia II . tape 174/94 . Klagenfurt 1984, p. 261–266 ( PDF on ZOBODAT ).
  10. ↑ Carl Troll: The diluvial Inn-Chiemsee-Glacier: The geographical picture of a typical Alpine foothills glacier . Research on German regional and national studies; Volume 23, Issue 1; 1924
  11. ↑ Hantke, R .: Ice Age. Western Eastern Alps with their Bavarian foothills to the Inn breakthrough and Southern Alps between the Dolomites and Mont Blanc . tape 3 . Ott Verlag, Thun 1983.
  12. ↑ Mayr, F. and Heuberger, H .: Type Areas of Late Glacial and Postglacial Deposits in Tyrol, Eastern Alps . In: Univ. Colorado Studies, Ser. in Earth Sci., No. 7 (Ed.): Proc. VII INQUA Congr. tape 14 , 1968, p. 143-165 .
  13. ^ Reitner, Jürgen M .: Different conditions and modes of glacial advances: Examples from the beginning of Termination I in the Eastern Alps . In: Geophysical Research Abstracts . tape 8, 04820 , 2006.