Onocerane testifies to dry climatic events during the Quaternary in the Tropics.

Jérémy Jacob (1) , Jean-Robert Disnar (1) , Mohammed Boussafir (1) , Marie-Pierre Ledru (2) , Ana Luiza Spadano Albuquerque (3) , Abdel Sifeddine (4) , Bruno Turcq (5)

1 ISTO - Institut des Sciences de la Terre d'Orléans
2 IRD/CNPQ - Universidade de Sao Paulo, Departamento Geologia Sedimentar e Ambiental
3 DEPARTAMENTO DE GEOQUIMICA - Departamento de Geoquimica
4 IRD/CNPQ - Departamento de Geoquimica, Universidade Federal Fluminense
5 PALEOTROPIQUE - Paléo-environnements tropicaux et variabilité climatique

An unusual molecular fossil (onocerane I) has been detected for the first time in Quaternary lacustrine sediments (Lagoa do Caçó, NE Brazil). This molecule was initially thought to attest to the former presence of ferns or club mosses. According to possible plant precursors of onocerane-related molecules recorded in the literature and by comparison with palynological results and palaeoclimatic data, we here provide evidence that club mosses and ferns cannot account as sources of onocerane I in this setting. Onocerane I is abundant in the lipid extracts of sediments deposited during the two driest periods recorded in Northern Brazil (Last Glacial Maximum and Younger Dryas). This molecule is therefore suspected to be diagnostic of the development of plants adapted to dry or semi-arid conditions in this region.

Domains: Geochemistry

Jérémy Jacob, Jean-Robert Disnar, Mohammed Boussafir, Marie-Pierre Ledru, Ana Luiza Spadano Albuquerque, et al.. Onocerane testifies to dry climatic events during the Quaternary in the Tropics.. Organic Geochemistry, 2004, 35, pp.289-297. ⟨10.1016/j.orggeochem.2003.11.005⟩. ⟨hal-00022457⟩