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Spatial analysis of terrestrial patterned ground in mid- and high latitudes

Spatial analysis of terrestrial patterned ground in mid- and high latitudes. Thierry FEUILLET. Laboratoire Géolittomer – UMR 6554 – LETG GDR CNRS 3062 « Mutations polaires ». Introduction Method Results Conclusions. Brief definition of patterned ground.

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Spatial analysis of terrestrial patterned ground in mid- and high latitudes

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  1. Spatial analysis of terrestrial patterned ground in mid- and high latitudes Thierry FEUILLET Laboratoire Géolittomer – UMR 6554 – LETG GDR CNRS 3062 « Mutations polaires »

  2. IntroductionMethod Results Conclusions Brief definition of patterned ground  Patterned ground is geometric features […] which develops in polar, subpolar and high alpine environments by repeated thawing and freezing cycles (Washburn, 1979) Thufur (nonsorted nets) Sorted stripes

  3. IntroductionMethod Results Conclusions Sorted polygons Sorted circles Stone-banked solifluction lobes

  4. IntroductionMethod Results Conclusions Patterned ground is mostly studied at a feature scale  Issues dealing with mechanisms of genesis and processes dynamics Patterned ground model simulations (Kessler and Werner, 2003)

  5. IntroductionMethod Results Conclusions Second kind of studies focusing on the spatial distribution of patterned ground •  Questioning about those issues: • In what kind of terrain settings patterned ground preferentially develops? • Is patterned ground occurrence always associated with the same environmental parameters? • Can we distinguish different types of patterned ground as a function of their environments?

  6. IntroductionMethod Results Conclusions Two regions were investigated 1. The Pyrenees

  7. IntroductionMethod Results Conclusions Northern slope Southern slope

  8. IntroductionMethod Results Conclusions

  9. IntroductionMethod Results Conclusions Patterned ground (> 2300 m) mostly miniature Climatic conditions Altitudes MAAT Freezing cycles (/yr) 2300 +2.7°C 116 2750 0°C 101 3300 - 3.2°C 61

  10. IntroductionMethod Results Conclusions 2. Northern Iceland Skagafjordur

  11. IntroductionMethod Results Conclusions MAAT: 3°C at 0 m; -4°C at 1000 m

  12. IntroductionMethod Results Conclusions Method 1. Mapping patterned ground > Photo-interpretation > Fieldwork 2. Determination of variables (database) > Environmental variables (GIS and DEM) > Intrinsic variables (grain-size analyses, morphometry) 3. Statistical analyses > Presence/absence approach > Classification techniques (factor analyses)

  13. IntroductionMethodResults Conclusions In the Pyrenees At the massif scale Taillon Glacier Black squares: absence White squares: presence

  14. IntroductionMethodResults Conclusions At the site scale (Taillon glacier) ~ 1900 2009

  15. IntroductionMethodResults Conclusions In Iceland 75 sites investigated from 20 to 960 m a.s.l., on three main geomorphological settings

  16. IntroductionMethodResults Conclusions 1. Clustering of patterned ground sites (typology) Factor analysis of mixed data led to 3 clusters

  17. IntroductionMethodResults Conclusions • First group: ‘protected’ areas (low insolation and altitude = valley bottom) 2. Second group: slope-connected areas (kame terraces) 3. Third group: ‘open’ areas (high altitude = plateaus)

  18. IntroductionMethodResults Conclusions 2. Relation between feature diameter and other variables

  19. IntroductionMethodResultsConclusions Several conclusions… • In the Pyrenees, the presence of glaciers is favourable for patterned ground development (> wetness, heterometric material), high surronding relief as well (domination effect) • Patterned ground develops rapidly after deglaciation • In Iceland, we highlighted 3 kind of environmental settings where patterned ground occurs • It was also noted that patterned ground diameter is highly correlated with clast lenght (and fine content)

  20. Thank you for your attention

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