Abstract: Significant petrographic characteristics of dolomites from Dolostone lithofacies at the Plavno succession (locality near Knin) have been investigated. Dolostone lithofacies represents the oldest Early Triassic sedimentary rocks, deposited immediately after Permian-Triassic mass extinction. According to the presence of conodont species Hindeodus-Isarcicella this interval has been determined as Griesbachian. Sedimentary characteristics of Plavno sections were interpreted as deposited on a broad epeiric ramp. Dolostone lithofacies represents deposits of the most proximal and the shallowest part of the ramp. Fossil remains found in this lithofacies point to the oxygenated environment. Therefore it is difficult to interpret presence of pyrite in this lithofacies. It is especially true for the small pyrite framboids (< 20 μm). Pyrite occurs in the dolomite in following forms: a)pyrite within ostracod shells , b) large framboids >20 μm and c) small framboids (< 20μm). Pyrite that occurred within ostracod shells points to locally present anoxic conditions produced by decay of organic matter after dying of organisms. Therefore, the origin of pyrite is local and diagenetic. Large framboids (>20 μm) occur within the sediment, near the sediment-water interface. Genesis of large framboids can be related to locally present anoxic conditions that occur at the sediment-water interface due to decay of organic matter when all oxygen is used in decay processes. Shallow in the sediment there is no oxygen present and therefore bacteria start to reduce sulfates. In this reaction H2S is produced. A few centimeters below the surface of the sediment, in the anoxic conditions a large framboids usually occur.The most intriguing is the presence of small pyrite framboids (< 20 μm). This small sized framboids nucleate in the anoxic conditions in the water column. Genesis of small framboids is interpreted according to the model proposed by KERSHAW (2015). There is a possibility that in the distal part of epeiric ramp, bellow fair-weather wave base, anoxic conditions were occasionally present in the water column. As the storms strongly influenced sedimentation in the Early Triassic Plavno section, it is possible to assume that small framboid pyrite particles from distal ramp were caught by storm currents and transported to the shallowest part of the environment and are preserved in the Dolostone lithofacies.