Palaeopalynology is the study of microfossils formed of organic matter, called palynomorphs; they are preserved in certain sedimentary rocks in all the geological periods. Most palynomorphs are of plant origin.
The palaeopalynology collection contains several thousands of microscopic preparations and many tubes of "residue" (organic matter diluted in glycerine). Each palynological slide generally contains hundreds of very diverse microfossils: dinoflagellate cysts, spores, pollen grains, etc.
Some slides are mounted using the "isolated grain" technique. This major component, named the "Boltenhagen collection", contains hundreds of type and figured specimens. It is a fundamental reference for world palynology, as it has played a key role in weaving the biostratigraphic framework of the Northern Gondwana province from the Cretaceous onwards, and enabled many morphographic concepts to be developed.
In addition, a particular aspect of palaeopalynology is represented by a number of amber slides (dinoflagellates and pollen grains). The group, located within the Muséum’s fossil plant collection, is managed by Sandra Daillie and Jean Dejax.
The Boltenhagen collection comes from sediments (clay, salt, etc.) extracted from several dozens of drilling projects during oil explorations in West Africa (Gabon, Congo, Cameroon) at the beginning of the second half of the 20th century.
The stratigraphic interval covered ranges from the Lower Cretaceous to the Tertiary era, depending on the drilling project. The depth of each slide is precisely identified along the stratigraphic column, according to the sediment sampling method used (core or cutting). The inventory, classification, restoration and computerisation of the Boltenhagen collection are nearing completion.
Another vast collection, currently at the inventory stage, comes from drilling carried out in the same period during the search for oil in the Sahara. This group is of considerable heritage and scientific value, especially since many such archives of the planet are no longer accessible.
The research areas related to the collection are biostratigraphy, palaeoenvironments, palaeogeography, systematics and vegetal evolution. Biostratigraphy is one of the research areas of the Muséum’s "Origines et évolution" Department, and palaeopalynology is one aspect of this.
The palynological analysis enables us to characterise the palaeoenvironment and precisely date the sediments, then draw correlations between sedimentary basins and precisely establish the palaeogeography. In the absence of any other fossil, the palynomorphs are very useful; in some cases, they even enable us to solve dating enigmas! The Boltenhagen collection is used in international collaboration, particularly with Brazil.
There is a database covering the entire collection (slides and tubes), listing and illustrating the type and figured specimens, as well as some other remarkable palynomorphs. A set of archives and a bibliography are associated with it (field information, slide analysis, documentation and publications). The Boltenhagen collection is consulted, generally with the aim of examining certain type specimens.
One innovative and surprising area of research is amber palaeopalynology: we have recently been able to highlight the cellular content of pollen grains preserved in the organic state and the "motile" stage of dinoflagellates in this fossilised resin, whereas they cannot be preserved in sediments.
Dario De Franceschi
dario.de-franceschi [@] mnhn.fr
Cédric Del Rio
cedric.del-rio [@] mnhn.fr