Charentese amber

Charentese amber (rare "Charentes amber") is a collective term often used in literature for amber from Cretaceous deposits from various sites in south-west France ( Les Charentes ).

Find area and geology

The fossil resins were found in various temporary outcrops (quarries, road construction) and in the coastal region of southwest France. The first finds can be dated to the first half of the 19th century. Of the around 100 kg that were obtained in the course of systematic scientific exploration, the vast majority comes from an outcrop at Archingeay , which in the summer of 1999 offered particularly favorable conditions for the amber harvest.

Almost all sediments in which amber was found can be assigned to the Cenomanium (90–100 million years), in one case a slightly older age ( albium ) cannot be ruled out. The fossil content of the sediments and the organic inclusions of the amber point to a coastal mixed forest in a warm temperate to subtropical climate in which araucarias predominated.

Properties of amber

The color spectrum of the Charentes amber ranges from a transparent yellow to orange and red to an opaque brown. The hard and usually very brittle amber splinters easily and is therefore unsuitable for jewelry processing. The fossil resin does not contain succinic acid and is therefore placed among the retinites .

Botanical origin

IR spectra indicate that the amber resins go back to representatives of the Araucariaceae and the Cheirolepidiaceae .

Organic inclusions

A significant part of the amber is opaque, making it impossible to examine inclusions using traditional methods. These pieces were examined using phase contrast X-ray microradiography. In addition, microtomographic data were obtained for a 3D reconstruction of particularly valuable inclusions. Using these techniques, around 1500 arthropods in a remarkable taxonomic range were discovered, especially in opaque pieces. These include various specimens of the extinct wasp families Falsiformicidae and Maimetshidae, from which only very few documents from the Cretaceous were previously available. Marine microorganisms identified in amber are likely to have entered the Harz forests near the coast through wind and spray.

literature

Vincent Perrichot, Didier Néraudeau & Paul Tafforeau: Charentes Amber. In: Biodiversity of fossils in amber from the major world deposits. Pp. 192-207. Manchester (UK) 2010. ISBN 9780955863646 .