Abstract The frequent sinkholes along the temporary water streams in Saffré basin can be compared with those occurring in Upper Normandy which are commonly referred to as ‘bétoires’. These collapses are not directly linked to karst cavities. They result from a draw-off effect of fine particles contained in the Plio-Quaternary alluvium lying above the carbonate Oligocene series. The draw-off phenomenon appears through fine cracks (1 to a few millimetres) open in soft palustrine limestones broadly comparable with chalk. Based on the knowledge of backfilling work design undertaken at some ‘bétoires’ in Upper Normandy, a new project was undertaken at four sinkhole funnels, which appeared near the surface in the Saffré basin at the end of the winter in 2017. The works consisted of digging the decompressed surface and filling up the excavation pit with materials of decreasing granulometry from bottom to top in order to ease the surface water infiltration through the identified fractured zones to the bottom of the excavation. This design was also complemented by the implementation of a filtering trench in between the watercourse and the filtering bed, laid above the fractured zones, which were enlarged by the dissolution process, on the one hand, and by the construction of a pipe network on top of the filtering bed to allow for pressurized air exhaust towards the surface, on the other hand. The pressurized air comes up from the aquifer as it recharges as soon as the surface water streamflow resumes and takes part in the mechanism, leading to sinkhole collapse, which should be prevented by this backfilling design.

Abstract Recent ichnological analysis conducted in two sections (Rodiles and Lastres) of the Asturian Basin revealed the presence of Halimedides Lorenz von Liburnau 1902 , which occurs just above the black shales related to the end of the Toarcian Oceanic Anoxic Event (T-OAE). Halimedides is associated with recovery of the trace-maker community after the re-establishment of favourable, oxic, conditions. The appearance of Halimedides after the T-OAE event, previously not registered, supports the close relationship of the trace maker with oxygen conditions, as occurs in other anoxic events including the Cretaceous OAE-1a and OAE-2. Also, a relationship between morphometric and palaeoenvironmental parameters is observed: occurring larger and densely chambered specimens in darker, weakly oxygenated facies, while smaller and sparsely chambered forms are registered in lighter, better oxygenated sediments.