CONTRIBUTION OF sigma18 AND sigma13C FROM SIDERITE TO THE HISTORY OF LAKE KAMALETE (CENTRAL GABON)

Located in the center of Gabon, in the South East of the Lope National Park, Lake Kamalete has so far been the subject of several studies through the KAM1 core. We present here the study of the isotopic analyzes of 18O and 13C of the siderite crystals found in this core. This study provides new informations on the history of Lake Kamalete. Thus, the results indicate the existence of two dissolved inorganic carbon sources at the origin of the siderites present in the KAM1 core. This is atmospheric CO2 for beige mud sediments (1410 to 520 years B.P) whose values of 13C are between -0.81 and +3.69 , and CO2 from methanogenesis for gray to gray green mud (from 520 years B.P to the present day) characterized by positive values of 13C between +3 and +9. These analyzes also indicate that Lake Kamalete has not known only a level of hydrological stability between 1255 and 520 years B.P but also an increase in evaporation during all its sedimentation marked by values of 18O ranging from -14. to -2.8.