Abstract: This study aims to reveal the mineralogical characteristics of the carbonate and pelitic rocks in the LowerTriassic Çığlı Group in the Uludere-Uzungeçit (Şırnak) region from Southeast Anatolian Autochthone(SEAA). Çığlı Group is represented by Yoncalı Formation (dolomite-siltstone-shale with limestoneintercalation), Uludere Formation (shale/shale with carbonate-clayey limestone intercalated withdolomite) and Uzungeçit Formation (limestone with chert nodule-dolomitic limestone-shale) from bottomto top. In order of abundances of minerals obtained by XRD investigations as follows; Yoncalı Formationcontains carbonate (calcite, dolomite), feldspar, phyllosilicate (illite, chlorite) and goethite minerals, andUludere Formation is made up of carbonate (calcite, dolomite), quartz, feldspar, phyllosilicate (illite,chlorite, mixed-layered chlorite-vermiculite/C-V, and very minor amount of kaolinite in only a sample)and hematite minerals. Uzungeçit Formation has carbonate (dolomite, calcite), silica (quartz, opalCT, moganite), phyllosilicate (chlorite, illite), and feldspar and hematite minerals. On the basis of illitKübler Index values; Yoncalı Formation reflects the degrees of anchizone; as for Uludere and Uzungeçitformations, they have the degrees of anchizone-high diagenesis, respectively. Similarly, Chlorite ArkaiIndex (AI, °2Ɵ) values indicate the grades of anchizone-diagenesis. Illites exhibit 2M1 ve 2M1 + 1M +1Md polytypes and the values of b unit-cell distances show a composition close to ideal muscovite and lowpressure conditions.The rocks of the Çığlı Group offer differences in terms of rare occurrence of kaolinite, appearanceof moganite and C-V and the dominance of dolomite and hematite in most levels, and diagenesis/metamorphism grades are also high, when compared with the equivalent units in the Diyarbakır-Hazroarea. Lower Triassic series regionally seem to have a deeper depositional environment, and have relativelyhigher maturation because of the volcanic feeding and tectonic burial in the Diyarbakır-Şırnak directionfrom west to east.