The dolomitic barriers and baffles with different degrees of dolomitization are developed in marine clastic reservoirs，which will influence the water/oil/gas system identification and also seriously affect the further enhancement of oil recovery. The identification，formation mechanism analysis and distribution characterization of dolomitic barriers and baffles are important for the efficient development of the marine clastic reservoirs and can shed light on the mechanism of dolomitization. Typical clastic reservoir Upper Kirkuk（UK）Formation in the Middle East is taken as an example. Logging，core analysis，and dynamic production data are adopted to systematically study the classification，identification，formation mechanism，and distribution characteristics of the dolomitic barriers and baffles in the marine clastic reservoirs.The research results are as follows. ①Except for the pure sand and mudstones in the marine clastic reservoirs，the lithology of dolomitic barriers and baffles is dolomite bearing sandstones，dolomitic sandstones，sandy dolomites，and sand bearing dolomites. The dolomitic sandstones and sand bearing dolomites are the main lithology. ②The qualitative and quantitative criteria were made to identify different degrees of dolomitization. With the increase in the degree of dolomitization，the core appears to gradually brighten under normal light. The gamma，density，and resistivity values increase with the degree of dolomitization. ③The original underground magnesium-rich brine and mudstone compaction waters are the main ion sources. Pure sands with good physical properties and unconformities are main fluid migration channels.The difference in the physical properties of the reservoir leads to that in the contact time between the pore fluid and the particles（water-rock contact reaction），which ultimately results in different degrees of dolomitization. ④The distribution of dolomitic barriers and baffles is characterized in different levels. At the macro-level，the dolomitic barriers and baffles tend to occur in the middle period of sea level rising or descending semi-cycle. While at the meso-level，the dolomitic barriers and baffles are more likely to occur in the top and edge of channel and the bottom of the mouth bar with poor physical properties. When it comes to the micro-level，the dolomitic barriers and baffles tend to occur in areas where pore throats are poorly connected.