Projet ANR-07-BLAN-0144 – AMBRACE : Evolution faunique, floristique et paléoclimatique des AMBRes crétaCEs de France
Programme : Blanc (BLANC) 2007
Année de financement : 2007
Coordinateur du projet : CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE - DELEGATION REGIONALE BRETAGNE ET PAYS- DE-LA-LOIRE (CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE - DELEGATION REGIONALE BRETAGNE ET PAYS- DE-LA-LOIRE)
Partenaires : Centre national de la recherche scientifique; EUROPEAN SYNCHROTRON RADIATION FACILITY
Montant : 240000.0 euros
Date de début : 2007
Durée : 36 mois
Résumé : At the worldwide scale, France is one of the 7 richest countries in Cretaceous fossiliferous ambers with Spain, Lebanon, Myanmar, USA, Russia and Canada. The numerous amber deposits found in France during the last 10 years by the palaeontologists of Rennes and Paris give access to ambers, an consequently to entomofaunas, microfaunas and microfloras, from the end of the Early Cretaceous (Albian from Charentes) to the end of the Cretaceous (Santono-Campanian from southern France). Thus, the AMBRACE project has two categories of objectives. A first category, in palaeoentomology, dedicated to fossil insects, arachnids and crustaceans; a second category with palaeoalgological, palaeomycological and palaeomicrobiological approaches and concerning fossil micro-algae, mycelium and protozoans. -  The expected results of the project are, from the most specialized to the most synthetical: (1)identification and integration, for the first time in the study of Cretaceous arthropods biodiversity, of the species preserved in milky and opaque ambers thanks to microradiography and Phase contrast X-ray synchrotron microtomography; milky and opaque ambers constitute more than 80% of some Cretaceous ambers from France and their entomofauna is at that day unknown because undetectable by classical optical methods; the methodological developments of microtomography and microradiography applicated to animal and plant inclusions of opaque ambers will allow to make 3D reconstruction and systematical descriptions of fossil arthropods, and sometimes will give access, for the first time, to the internal organs of these animals; finally, the knowledge of the biodiversity and the phylogeny of Cretaceous terrestrial arthropods will be considerably improved by the association of the results achieved on clear and opaque ambers respectively. (2)identification and integration, for the first time in the study of Cretaceous ambers, of an exhaustive study of micro-organisms preserved in amber thanks to methods destroying the Recent polluting micro-organisms; only a few studies have at that day detected and identified micro-organisms in amber and the few ones that did were realized without real precaution concerning the Recent pollution; the methods proposed at Rennes by V. Girard in 2006 allow now to eliminate the polluting micro-organisms and open new ways of research in the identification, without doubt, of various microflora and microfauna in Cretaceous ambers. (3) understanding of the origins of various lineages of insects, arachnids and crustaceans: the French Cretaceous ambers contain the oldest specimens of several arthropod groups, such as ants or Zodariid arachnids; these two examples are linked and thus especially interesting: on the one hand, the oldest ants are already differenciated in castes such as workers or winged females, and their origins are probably older and not documented by the fossil record; on the other hand, the Recent Zodariids are specialized in the predation of ants and the co-occurrence Zodariids/ants in a single Albian amber deposit from France suggests a very old co-evolution between the two groups. (4)interactions between insects and plants: several Cretaceous amber deposits from France provide rich fossil angiosperm accumulations; this opportunity will allow to study both the development of leave-eating and pollen transport by insects parallel to the diversification of angiosperms. A work on angiosperm leave diversity is in progress for the Late Albian and the Cenomanian and will be usefulll in these approaches. (5) comparison between the biodiversity variations of terrestrial arthropods and micro-organisms blooms with the climatical variations during the Cretaceous: the dozen of Cretaceous amber deposits discovered by the project members during the last seven years allow to access to arthropod and micro-organism biodiversity at three key-times of the Cretaceous: (a) the Albian (-100 Ma) which corresponds to a warming trend, record