Aretz et al_2011.pdf - ORBi - Université de Liège

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Kölner Forum Geol. Paläont., 19 (2011)
M. ARETZ, S. DELCULÉE, J. DENAYER & E. POTY (Eds.)
Abstracts, 11th Symposium on Fossil Cnidaria and Sponges, Liège, August 19-29, 2011
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Jean Gabriel LAFUSTE (1930-1990) and the « French » interpretation of
microstructures in Palaeozoic corals.
Francis TOURNEUR 1 & Yves PLUSQUELLEC 2
1 Pierres et Marbres de Wallonie ASBL, 11 rue des Pieds d’Alouettes, B-5100 Naninne, Belgium;
francis.tourneur@pierresetmarbres.be
2 Université de Bretagne Occidentale, CNRS-UMR 6535 « Domaines océaniques », Laboratoire de
Paléontologie, UFR Sciences, 6 av. Le Gorgeu, CS 93837, F-29 238 Brest, France;
yves.plusquellec@univ-brest.fr
The French palaeontologist Jean Gabriel LAFUSTE was born in La Rochelle (South West France) in 1930,
where he died prematurely at the age of sixty. After studies at the University of Poitiers, where he worked
on Jurassic reefs, he quickly joined Paris, first at the Sorbonne and finally at the Institut de Paléontologie of
the Muséum national d’Histoire naturelle, where he made most of his career. He was called by James
ALLOITEAU (1890-1969) to join the « coral team » as the specialist of tabulate corals. Talented with a great
manual skill, he prepared himself his specimens and thin sections and he invented different special
technical improvements, allowing the thickness of the sections to be strongly reduced, until a few
micrometers. This reduced thickness permits very subtle observations of microstructures, as the boundaries
of the very thin crystals appear sharply in polarized light. As he was very curious, he prepared these
« ultra-thin » sections or sections with polished sides (« lames à faces polies » or LFP) in a lot of different
objects (corals of course, but also shells, eggs, bones, etc.), making comparisons between the different kinds
of biomineralisation processes.
He studied most of the classical Tabulate corals faunas – Siluro-Ordovician of Scandinavia and of the
British Isles, Devono-Carboniferous of Western Europe, Permian of Timor, etc. – during visits to the most
important museums and collections in the world. But he also received many « fresh » collections from field
geologists, among others from the Devono-Carboniferous strata of Northern Africa (Algeria and Morocco)
– among others the very large collection of Henry HOLLARD. His approach was very carefull, beginning
with observation of morphological characters of the colonies, then of thin sections and finally of the
microstructure of the skeletons. Each step was connected with the other ones, to understand the growth
form and the precise morphology of all these species. He used for these studies all the possible tools – thin
and ultra-thin sections for optical microscopy but also SEM and other contemporary means.
As these studies were very carefully conducted, they were also rather slow and the main problem for
J.G. LAFUSTE was to conclude them and to write communications. So many results unfortunately remained
unpublished – as a comprehensive approach of the Alveolitids or an attempt to understand the complex
relationships between Favosites and Thecia! Most of these « dossiers » were transmitted after the death of
J.G. LAFUSTE to his co-workers, but it is difficult for them to conclude these researchs without the principal
author.
It could be avanced that J.G. LAFUSTE was not sufficiently aware of the diagenetic evolution of
carbonates and that its interpretations were too close to the rough observations. But the precision of these
observations is without doubt a very precious contribution to the knowledge of the Tabulate corals, of their
structure, microstructure and organization – with general trends, like the global evolution from
(micro)lamellar in Siluro-Ordovician forms to fibrous ones in the Permian. Unquestionably a great
« naturalist » in the best, noble meaning of the word!
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