En 2011, l'association INECOBA avait coordonné et accompagné le chercheur Adrian Patrut lors d'une mission de 15 jours au Sénégal intitulé "Mission Darabao : comment dater des baobabs millénaires ?" afin de dater les plus vieux baobabs du Sénégal.

Les résultats scientifiques seront présentés à l'occasion de la 14th International Conference on Accelerator Mass  Spectrometry qui se tiendra du 14-18 août 2017 à l'Université d'Ottawa.

Un poster reprenant l'ensemble des résultats sera présenté sous le titre :

 

AMS radiocarbon dating of the largest and oldest African baobabs of Senegal

Adrian Patrut¹, Roxana Patrut², Stephan Woodborne³, Karl von Reden⁴, Oumar Ka⁵, Sébastien Garnaud⁶, Daniel Lowy⁷

¹ Babeş-Bolyai University, Faculty of Chemistry, Cluj-Napoca, Romania.

²Babeş-Bolyai University, Faculty of Biology and Geology, Cluj-Napoca, Romania.

³ iThemba LABS, Private Bag 11, WITS 2050, South Africa.

⁴NOSAMS Facility, Dept. of Geology & Geophysics, Woods Hole Oceanographic Institution,

Woods Hole, MA 02543, U.S.A.

⁵ Faculty of Sciences and Techniques, Cheikh Anta Diop University, Dakar, Senegal.

⁶INECOBA, Aulnay-sous-Bois, France.

⁷Nova University, Alexandria Campus, Alexandria, VA 22311-509, U.S.A.

The scientific name Adansonia digitata honours Michel Adanson, who documented and described the African baobab in its native habitat after his voyage to Senegal (1749-1754). Even if Senegal hosts more baobab specimens than all countries from southern Africa combined, the number of significant investigations and surveys of Senegalese baobabs was scarce over the past 50 years.

The aim of our investigations by AMS radiocarbon was to determine the architecture and age of the largest and potentially oldest Senegalese baobabs.

Senegal hosts 6 very large baobabs with girth values over 23 m, i.e., the baobab of Warang (28.69 m), of Lalam, called “Ngokole” (28.10 m), of Sinthiou-Keita (27.10 m), of Diyabougou/Samba Dia (26.31 m), of Nianing (24.76 m) and of Iwol (23.52 m). Our investigation has revealed that they are all multi-stemmed, with up to 14 (Ngokole) and even 16 stems (Warang). Some of them exhibit closed ring-shaped structures, with one ring and one false cavity (Diyabougou, Warang) and even 3 rings and 3 false cavities (Nianing). The large Senegalese baobabs have often false stems, which emerge from another adjacent stem, and act as anchor in sandy soils. The false stems have a peculiar aspect, have a triangular or trapezoidal horizontal section and may reach lengths up to 5 m. Their oldest age can be found toward the upper contact area with the larger adjacent stem. According to radiocarbon dates, the 6 large baobabs exhibit ages between 400-700 yr.

The oldest baobab of Senegal and of the Northern Hemisphere is the historic “Gouye Ndiouly” of Kahone, the old capital of the Saloum kingdom. The baobab toppled ca. 200 yr ago and only one old stem survived, from which 7 new stems emerged. The oldest dated sample had a radiocarbon date of 833±25 BP. This value suggests an age of 1000 yr in the missing pith.

The research was funded by the Romanian Ministry of National Education CNCS-UEFISCDI.

 

Topic: Applications of C-14