Oiselier

The carbonate encrustations observed in the “Conglomérats de Porrentruy” are scattered on the whole outcrops of “Oiselier” (POR-OIP and POR-OIC) and can be present in each described lithofacies (limestone, gravel, sand, calcarenite, marl).

Duringer & Gall (1993, 1994) observed similar encrusations in the southern part of the Rhine Graben, interpreted as microbial constructions or encrustations in an Oligocene fan-delta context.

These carbonate encrustations of “Oiselier” are also interpreted as microbial ecosystems. In reference to benthic deposits with a microbial origin and in accord with the definition of Dupraz (1999) they can be defined as microbialites. All these facies illustrate zonations of different types of constructions, from fluvio-deltaic to lacustrine environments.

Beuchille

The mammal community contains species with aquatic or palustral affinities (Anthracotherium, the hippo-like “coal beast”; Iberomeryx, a small rabbit-sized primitive hornless ruminant), as well as species living in dense forests (Iberomeryx and numerous Gliridae). The faunal spectrum also includes aquatic turtles (Tryonichidae), indicating a relatively high air paleotemperature. The most interesting aspect of the paleoflora is the abundance of tree remains, which indicate close and dense forests, and a bi-seasonal climate.

Most paleontological and sedimentological features suggest a humid and relatively hot subtropical climate, with little temperature variation and seasonal humidity contrast, but with a relatively high humidity rate all year long. 30 million years ago the area of “Beuchille” was a vast and relatively flat wooded zone with frequent floods depositing large quantities of sand and transporting numerous tree trunks and branches (Fig.3).

Fig.3:
Paleoecological reconstruction of “Beuchille”: 1 Iberomeryx minor, 2 Anthracotherium sp.,
3 Gliridae, 4 Trionychidae. ©OCC-SAP 2004 

Beuchille Est

The paleobathymetrical estimations based on ostracods, foraminifers and fish correspond to marginal to coastal paleoenviroments not exceeding 50 m of depth. Fossil associations can be very different showing a high degree of endemism, especially for ostracods.