The Shurijeh Formation (Early Cretaceous) consists of siliciclastic, evaporate, and carbonate facies with associated calcareous paleosols in the Kopet-Dagh basin. These calcareous paleosols (pedogenic carbonate nodules) include specific macromorphological and micromorphological features. Based on macroscopic and microscopic properties, the Shurijeh Calcareous paleosols are divided into pedogenic and non-pedogenic (ground water) types that are each formed under specific conditions. Estimated δ 13 C values of plant-CO 2 for Shurijeh vegetation range from −20.75‰ to −22.14‰ (with an average=−21.31‰). These values are consistent with plant type C3. The contribution of atmospheric CO 2 in δ 13 C values of plant-CO 2 of studied calcareous paleosols was 25 to 30%. The Neocomian (Berriasian–Barremian) paleoatmospheric PCO 2 gap was reconstructed by interpretation from measured carbon isotopic compositions of the Shurijeh Formation pedogenic carbonates. The paleoatmospheric CO 2 levels of the Shurijeh Formation are estimated to be 1226–2196ppmv. The general trend of Early Cretaceous estimates matches the modeled value trends for these times.