Heterolithic sequence, or tidal flat, is a very complex and heterogeneous sedimentary sequence. In Lambir formation, Sarawak, Malaysia, heterolithic sequence is quite common to be found. This study is an attempt to carefully define, characterize and describe the heterogeneity of a heterolithic sequence of Lambir formation to a meso-facies level of detail, using statistical tools and meso-facies development and evolution description at hign resolution. It was carried out by studying an outcrop of the Lambir formation. Four main facies were discovered in the outcrop, three of them being heterolithic sequence of different characteristics. Detailed analyses were done on one of the heterolithic sequence, which is the Grey Sand Dominant Heterolithic facies. The outcome of that heterolithic sequence possesses turbidity current element. Meanwhile, the meso-facies development and evolution study reveals a very close and alternating laminar and turbid/semi turbid flow elements. In summary, this study concluded that the complexity of heterolithic sequence in Lambir formation is very exclusive and non-homogeneous, even in a very single bed or lamina.