(2) Spéléo Club de Villefranche de Conflent, Pyrénées-Orientales, France. (3) Université de ... to the terrace materiel and with the same alteration degree.
25th International Karstological School 2017
Spatio-temporal relations between karstification levels and alluvial terraces : the example of the stepped karst in Villefranche de Conflent in the Têt valley. Pyrénées-Orientales - France
Balcon cave
HEZ G. (1-2), JAILLET S. (1), CALVET M. (3), DELMAS M. (3) (1) Université de Savoie, UMR 5204 CNRS, Laboratoire EDYTEM, Le Bourget du Lac, France (2) Spéléo Club de Villefranche de Conflent, Pyrénées-Orientales, France (3) Université de Perpignan Via Domitia, UMR 7194 - Histoire naturelle de l’homme préhistorique
N-W
Scallops in Lachambre cave
S-E
Coronat massif
Ambulla massif lley Têt va
Serre massif
Badebany massif
Notre Dame de Vie cave
1. Nine Karstification levels on about 1000 m height (Calvet et al 2013,2015 ; Hez et al, 2015)
The Villefranche karst is dug in Devonian limestone. The epiphreatic subhorizontal paleodrains are the result of the Têt successive autocaptures and give the valley local base paleolevels (Palmer, 1987 ; Audra and Palmer, 2013). Alluvial allochton deposits can be found in the endokarst stepping. The hight cavities (K4 and K9) represent the neogen evolution of the valley. Five levels of the Têt alluvial terraces (T1 to T5, Calvet 1996) are in altimetric relation with K1, K2 and K3. Terrace T 2 Ancient cemented talus deposit
Dated terrace
Malou 2 cave Mas Py cave
70 m
Pourques cave
550 m
Faubourg network
540 m
Terrace T5
T2
T1 Têt river
T2 T1
T1 En Gorner upper entrance 460 m
M. Calvet
Alluvial sediment in faubourg cave
S. Jaillet
2 . Stepping of the karstic networks and upstream quaternary alluvial terraces in the gorges
Paragenetic galery in Puits des Racines cave
A notch, unbroken for more than one kilometer, is fossilized by the same alluvial sequence. The notch slope is 0.1 %. These deposits and the notch are contemporary to table T2. 4 . Conceptual model of valley scale karstic and fluvial developement in relation to river terrace records.
double notch in Lachambre cave
Three distinct karstic levels are related to 3 alluvial water tables maintained in the gorges. These karst/valley correlations are founded on geometrical arguments, by the altimetric concordance between these two objects. They are sedimentologic and alterologic, with facies alluvial materiel comparable to the terrace materiel and with the same alteration degree. The Faubourg cave is immediately located under table T5 dated at Villefranche Fort. The ESR ages (unpublished data) are approximately in keeping with the burial ages obtained in the Faubourg cave (Calvet et al, 2015). A potential T6 level corresponds to the Faubourg superior entrance. The Malou 2 cave marks out a possible terrace T3 level. Terrace 2 level is in relation with epiphreatic of Mas Py cave, Pourques cave and Sandglass galery, this last one being in Puits de Racines cave. These galeries are made up of deteriorated pebble filling which are similar to those in T2. The lowest galeries in Puits des Racines cave are associated with table T1 and contain sound pebble fillings. The withdrawings between two kartic levels produce a mixture of sound and deteriorated pebbles likely to disrupt datations by burial.
Model like the karstic Villefranche network ( Harmand et al, 2017)
3 . Genesis of the karstic system of Puits des Racines during the last 100 K. years climatic cycles Phase 1 - 3 : S. Jaillet
pre-Wurmian climatic cycle. Terrace T2 Phase 4 - 6 : Wurmian climatic cycle. Terrace T1
Another notch in Lachambre cave
Aggradation M. Thomas
The endokarstic dynamic ( paragenetic evolution and later incision) is in phase with the fluvial dynamic of incision-aggradation, which controls the terrace system formation.
Sandglass gallery
Conclusions : -
Exceptional model of stepped karst. The karstic recording is more efficient than the terrace recording : 3 river levels are kept, but 5 endokarstic levels. Narrow parallelism of endokarstic and river dynamics. Problem with the sedimentary mixture from one level to the other, Which can impact datation by burial.
REFERENCES : AUDRA P., PALMER A. N., 2013. The vertical dimension of karst : controls of vertical cave patterns. Geomorphology vol. 6, p. 186-206. CALVET M., 1996. Morphogenèse d’une montagne méditerranéenne, le Pyrénées-Orientales. Thèse de doctotat d’Etat, 3 tomes, pochette de carte hors texte, Univresité de Paris l, 1177p.CALVET M., GUNNEL Y., HEZ G., BRAUCHER R., GUILLOU V., BOURLES D., DELMAS M., SORRIAUX P., 2013. Capturing the timingand rates of valley incision through cave dating in the eastern Pyrenees : gedynamic implications. Poster for the 8 th IAG Paris 2013. CALVET M., GUNNEL Y., BRAUCHER R., HEZ G., BOURLES D.,GUILLOU V., DELMAS M., ASTER TEAM., 2015. Cave levels as proxies for measuring post-orogenic uplift : Evidence from cosmogenic dating of alluvium-filled caves in the French Pyrenees. Geomorphology 246, p. 617-633. DELMAS M et al, in preparation. Fluvial strath-terrace as a proxy of vertical uplift. Coupling in situ produced 10 Be deph pro and ESR apprroach. The case of the Têt river, Southern France. HARMAND D., ADamson K., RIXHON G., JAILLET S., LOSSON B., DEVOS A., HEZ G., CALVET M., AUDRA P., 2017. Relationships between fluvial evolution and karstification related climatic, tectonic and eustatic forcing in temperate regions. Quaternary science review, p. 1-18. HEZ G., JAILLET S., CALVET M., DELANNOY J.J., 2015. Un enregisteur exceptionnel de l’incision de la vallée de la Têt : le karst de Villefranche de Conflent, Pyrénées-Orientales. Karstologia 65, p.9-32. MANEL C., 2015. La datation des terrasses alluviales de la Têt par RPE sur quartz et par profil vertical de nucléides cosmogéniques (10 Be in situ). Mémoire de Master 2, Université de Perpignan Via Domitia. Programme RGF Pyrénées BRGM. PALMER A.N., 1987. Cave levels and their interpretation. The NSS Bulletin, December 1987, p. 50-66.
Incision
Puits des Racines gallery
M. Thomas
