Fifteen years ago, scientists discovered traces of an ancient rainforest north of Paris. While several scientific articles have been written about it in recent years, one of the authors of the new scientific article published at the end of the year is an Estonian scientist - Eliise Kara, PhD candidate in geology at Tallinn University of Technology.
In the year 2009 layers of lignite, dating back 57 to 56 million years, were exposed during gravel and sand mining in the locality of Rivecourt, located about 80 km north of Paris. The layers exposed fossils that indicated a very different environment from the one around Paris today. The fossils are dated to the Late Palaeocene – a period that preceded a global warming phase, characterized by ice-free polar regions, Antarctic forests, and Earth's temperature being 15°C warmer than today.
The former Petit‐Pâtis quarry, where the layers were discovered, yielded thousands of animal and plant fossils over the following years, contributing to several scientific articles. At the end of last year, an article was published as a collaborative effort between a PhD student Eliise Kara from the Geology Department of Tallinn University of Technology and researchers from the National Museum of Natural History in Paris, that adds to the knowledge of the palaeoflora of this important fossil site.
The focus of their findings is on the fossil fruits of Europe's oldest moonseeds (Latin: Menispermaceae) and the article is devoted to the taxonomy, biogeography and ecological significance of these extinct plants. Moonseeds, known for their unique fruit shape, are mostly lianas that are primarily found today in subtropical and tropical forests. Moonseeds are of particular interest in the pharmacological industry today, as they are rich in alkaloids and have historical uses in traditional South American arrow poisons (curare).
Analyses of the site's stratigraphy and palaeontology confirm that northern France in the Late Palaeocene was a mosaic lowland, featuring rivers and floodplains. The riverbanks were home to a variety of subtropical, tropical and some temperate plant species. In addition to the moonseeds, the riverbank vegetation included plants from the cashew, pepper, and grape families. The fossil site also holds significance for studying the evolution of early mammals, such as rodents and the ancestors of primates.
As the Palaeocene-Eocene Thermal Maximum unfolded around 56 million years ago, the rainforest in northern France experienced increased warmth and humidity. This event, resulting in a global temperature rise of 5 to 8 degrees Celsius, had profound effects on marine life due to rising ocean temperatures and acidification. However, for tropical plant species like moonseeds around Paris, this warming was advantageous, leading to increased diversity and northward dispersion. The subsequent Eocene Epoch, spanning from 56 to 33.9 million years ago, marks both the peak of the global distribution of many tropical plants as well as the gradual retreat of the tropical flora from the northern hemisphere as a result of global cooling.
Although the remarkable climate warming 56 million years ago took place against a very different backdrop than today, it is still considered to be the closest analogue in Earth's history that can provide insights into the possible consequences of future climate warming.