The document presents a 25,000-year palaeoenvironmental record related to glaciation in the eastern Pyrenees, specifically in the Valira valleys of Andorra. It discusses various geological analyses, including stratigraphy and geochemistry, while identifying climatic cycles and events responsible for shifts in the environment. The findings highlight five aridity cycles and three Heinrich events that occur at regular intervals, emphasizing their potential interactions and impact on past climates.

1. Glaciation in the Eastern Pyrenees between NGRIP/GRIP GS-9 and
GS-2a stadials: 25,000 years of palaeoenvironmental record in the
Valira Valleys (Principality of Andorra)
Valentí Turu and Guy Jalut
Marcel Chevalier Earth Science Foundation, Ed. sociocultural La Llacuna, AD500 Andorra la Vella, Principality of Andorra.
Corresponding author (E-mail: igeofundacio@andorra.ad

2. AMS 14C dating and δ13C
Total carbon (bulk) from
• Pure colluvial
• Colluvial-alluvial mixture
• Supraglacial-colluvial m.
• Subglacial till
• Gl-Fl over bedrock
δ13C from vegetation average
and can be used as a proxy
• No laminites has been
dated (aquatic plants), only
subaerial sediments except
subglacial tills (mixture)

3. Glaciolacustrine
geochemistry
• 232 stratigraphical descriptions
• Basin analysis using sequence
stratigraphy (Turu et al., 2016).
• Chronostratigraphic benchmark for
paleoenvironmental studies
• Online database
• Depicting the paleolake alkalinity
using 21 samples
• Major elements (Al, Si, Ca, Ti, ..)
• Proxys: Ca, Fe, Al, Ti
• Al/Ti ratio as detrital proxy

4. La Massana paleolake
TURU. V., CALVET, M., BORDONAU J., GUNNELL, Y., DELMAS M.,
VILAPLANA J.M. & JALUT, G. (2016) Did Pyrenean glaciers
dance to the beat of global climatic events? Evidence from the
Wurmian sequence stratigraphy of an ice-dammed palaeolake
depocentre in Andorra; HUGHES P.D. & WOODWARD J.C. (eds)
Quaternary Glaciation in the Mediterranean Mountains.
Geological Society, London, SP 433. DOI: 10.1144/SP433.6

5. Stratigraphy
Stratigraphy based on the study of proglacial deltas

6. Arinsal tributary stratigraphy
Sequence Stratigraphy classification by identifying unconformity surfaces

7. Chronostratigraphy
TILL --->
TILL --->
TILL --->
TILL --->
TILL --->
Glacier front unstability is recorded on the basin (subglacial till sedimentation)

8. δ13C data
Rythmic trend & decreassing δ13C values in each one

9. Fast Fourier Transform
Wave length of 6.1 and 4.0 Kyrs are depicted
!13C Valira Nord FFT
-8
-7
-6
-5
-4
-3
-2
-1
0
0 2 4 6 8 10 12 14
Ka
Magnituddel'armonic
-!13C

10. All data
Climate
Aride
Cold
&
Moist
Moister
Warmer

11. Aridity

12. Cold and moist

13. Moister

14. Warmer conditions

15. Conclusions
• Five aridity cycles, one each 4 Ka (FFT)
• Three Heinrich events, one each 6.1 Ka (FFT)
• These climatic events may be independent but
their interference produce abrupt climatic
shiftings between 17 and 36 Ka (19,000 yrs)
• For that reason He are barely recognizable

16. Thank you
Where is the key?