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Increased interest in paleoenvironmental studies is a result of climatic changes occurring at present and predicted for the future. Such studies could be done using the stable isotope compositions (delta H-2 and delta O-18) of kaolins, which provide knowledge on the paleoenvironmental conditions prevailing during the time of kaolinisation. In this study, the stable isotopic compositions of clay-size fraction of kaolins occurring in Cretaceous and Tertiary Formations of the Douala Sub-Basin in Cameroon are presented, with the aim of reconstructing the paleoenvironmental conditions of the Sub-Basin. To achieve this, the clay-size fraction (< 2 mu m fraction) of 8 kaolinite-rich samples were analysed for their delta H-2 and delta O-18 compositions, and results were reported as part per mil (parts per thousand) relative to the SMOW standard. The delta O-18 values of kaolins found in the Cretaceous-Tertiary Formations of the Douala Sub-Basin varied between +18.2 and +21.0 parts per thousand, whereas the delta H-2 values varied between -69 and -53 parts per thousand. Nine of the eleven samples plotted on the right of the supergene-hypogene line. Five of these nine samples plotted very close to the kaolinite line, which represents the composition of kaolinite in equilibrium with meteoric water at 20 degrees C; suggesting a supergene weathering origin of these kaolins. The determination of the temperature of kaolinisation yielded mean formation temperatures of 22 +/- 2 degrees C and 27 +/- 6 degrees C for Cretaceous and Tertiary kaolins, respectively. Excluding the two samples falling in the hypogene field, averages of kaolinisation temperatures were 20 and 25 degrees C during the Cretaceous and Tertiary periods, respectively. These temperatures are slightly below the present mean annual temperature in Douala (27 degrees C), thereby suggesting that the climate was becoming warmer from the Cretaceous to the Present. Therefore, Douala had a cooler and rainy climate during the Cretaceous, and the climate is gradually becoming hotter and more humid, favouring the refinement of existing kaolins and the kaolinisation of kaolin-forming minerals in the Sub-Basin. (C) 2019 Academie des sciences. Published by Elsevier Masson SAS.