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Abstract. The Walanae Formation is the youngest sedimentary rock that formed a mountainous area along the Walanae river valley. It is very interesting and challenging to prove that Walanae depression developed from the Late Miocene to the Late Pliocene. This area gradually became a marine environment and how the climatic conditions at that time were particularly on the Salo Mario section. Soppeng Regency. Measuring section on Salo Mario obtained 32 layers, consists of interbedded claystone, sandstone and conglomerate on the upper part of the outcrop. Samples from the layers are then made into smear slides and dried using a UV lamp and the preparations were analyzed under a microscope at a magnification of 1000x. The result of laboratory observations, nannofossil is only found in 11 layers consisting of coccolith and Discoaster. The nannofossils were determined namely Discoaster asymmetricus Gartner, Discoaster berggrenii Bukry, Discoaster bollii Martini and Bramlette, Discoaster brouweri Tan Sin Hok, Discoaster calcaris Gartner, Discoaster deflandrei Bramlette and Riedel, Discoaster neohamatus Bukry and Bramlette, Discoaster pentaradiatus Tan Sin Hok, Discoaster pseudovariabilis Martini and Worsley, Discoaster surculus Martini and Bramlette, Discoaster tamalis Kamptner, Discoaster triradiatus Tan Sin Hok, and Discoaster variabilis Martini and Bramlette. The occurence of Discoster indicates the warming of the lower photic zone caused by the weakening of upwelling.