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Volume n° 2 - from B16 to B33 B16 B16 - Leaders: R. Bourrouilh, L. Moen-Maurel, J. Muñoz, A. Teixell Figure 2.1d - Schematic reconstruction of the Dano-Paleocene Aquitaine margin at Le Tucq, from R.Bourrouilh et al. 1993, unpub. data. The second one or the Guillampeau section is measured along the side of the road (fi g. 2.1ca and 2.1cb) Conclusions: fi gure 2.1d : the margins of the N- Pyrenean basin appear to be instable during the late Late Cretaceous to the Early Paleocene even though thicknesses across the North-Pyrenean domain do not vary as much as below in the Campanian and above in the Ypresian. This relative instability is due to a high amount of carbonates deposited on the edge of the shelf and to the progressive closure of the N-Pyrenean basin-Bay of Biscay, due to the progressive westward migration of the interplate compression. For further information: Stevaux and Zolnaï, 1975, G. Montagné, 1986, Seyve, 1984. Stop 2.2: the Ossau Valley: uplifting, glaciers and neotectonics: Sévignacq (fi gure 2.2) The small village of Sevignacq is built on the morainic frontal vallum of the glacier, which went down from the High Range and the Pic du Midi d’Ossau, fl owing northward through the Ossau Valley (in Béarnais, which is the local language: Aüssaü = high valley). Access: leaving the main road D 934 from Pau to Laruns, at Sevignacq, on the right take the small road Figure 2.2 - Panoramic view of the Mailh Arrouy and Ossau Valley (Total).
WESTERN PYRENEES FOLD-AND-THRUST-BELT: GEODYNAMICS, SEDIMENTATION AND PLATE BOUNDARY RECONSTRUCTION FROM RIFTING TO INVERSION B16 D 232, from Sevignacq to Bescat. The Stop is located after leaving Sevignacq and a few hundred metres down, after the cemetery, in the plain. Structural landscape: the panorama shows, from left to right: the Mesozoic high mountain of Mont du Rey, the glacial U-shaped valley of Ossau, with the high chain and the faulted caldera of Pic du Midi d’Ossau in the background, and on the right, the Mesozoic Lazerque (1,368m) and Mailh Arrouy (1,251m) mountain range. Interpretation: the Ossau glacier was one of the most important Würmian Pyrenean glaciers, which fl owed south to north, from the High Chain to Sevignacq. At its front, it produced a large moraine, which surrounds us as a morainic vallum. Deglaciation began some 11,000 years ago and the glacier was about 1,000 m thick here. Melting of the ice provoked a reduction of the ice weight on the crustal lithosphere, which began an upward isostatic buoyancy and slowly rose up. The mountain range is still being uplifted under relaxation at present. Rising of the mountain all around provoked in turn the Ossau river to change its course from north to west, cutting the moraine and the Urgonian limestone to the West. The Ossau river now fl ows towards the west after cutting the frontal moraine and the cretaceous bedrock in a narrow deep neo-tectonic canyon, located in the western outskirts of Arudy village. But an underground northward paleocirculation of the Ossau waters still exists and fl ows to the north, under the frontal moraine and producing a resurgent spring in the karstifi ed limestone north of Rébénacq. There, the river is called “Luy du Néez”. Stop 2.3: Arudy: opening of the rift as recorded by mud mound markers (fi g. 2.3a and 2.3b) Introduction: at the village of Arudy, several Aptian- Albian mud-mounds are or were worked for marble. Geological studies (Bouroullec et al., 1979), generally Figure 2.3a - Stratigraphy and geodynamic evolution of the Arudy basin, from R. Bourrouilh, 2000. 23 - B16 Volume n° 2 - from B16 to B33
Page 1 and 2: Field Trip Guide Book - B16 Volume
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Page 5 and 6: WESTERN PYRENEES FOLD-AND-THRUST-BE
Page 23: WESTERN PYRENEES FOLD-AND-THRUST-BE
Page 37 and 38: the North- WESTERN PYRENEES FOLD-AN
Page 67 and 68: Back Cover: Itinerary of the fi eld

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