Bonebed amber deposits: A review of taphonomy and palaeontological significance

Abstract

Bonebeds and amber deposits provide a wealth of palaeontological information allowing palaeobiologists to reconstruct ancient ecosystems in great detail. It is a common view that these two sources of data rarely intersect in the fossil record, owing to distinct taphonomic pathways. Nonetheless, the past decades have seen an increasing number of bonebed amber deposits reported and investigated, suggesting that some depositional environments might provide the appropriate conditions for preserving plant material and bones. By reviewing the current knowledge of the taphonomy of amber deposits and that of bonebeds, and through examination of a series of Cretaceous deposits in North America and Europe, we identify a taphonomic window that permits the long-term preservation of both materials. This synthesis allows us to provide some keys for bonebed amber prospecting, which will hopefully lead to additional finds in the field. We also review the main findings of the first comprehensive studies of bonebed amber deposits which focus on the amber assemblage, the chemistry of the fossil resin, and its stable isotopic composition, to demonstrate the utility of combined studies. This approach enables palaeobiologists to reconstruct past forest habitats by (i) exploring the faunal communities (especially, arthropod communities) of the forests, (ii) identifying the dominant source tree, (iii) identifying the ecological conditions, and (iv) characterizing the palaeogeography of the region. These findings show that amber represents a source of complementary data within bonebeds and can help achieving a better knowledge of past terrestrial habitats.