干旱区生态环境知识资源中心

The Lower-Middle Triassic marine evaporatic-bearing sequences in the northeastern Sichuan Basin received much attention in the petroleum exploration. However, little research was focused on the evaporatic sequences and thus the distribution regularities about potash-bearing sequences are poorly constrained. Based on drilling core, outcrop, and logging data, sequence-based lithofacies-paleogeography, evaporite distribution and conditions for potash formation of the Lower-Middle Triassic in northeastern Sichuan Basin were performed. The results show that evaporite of Jianglingjiang Formation was affected by third order sea-level change obviously and developed mainly in the high system track, corresponding to T(2)j(2) of the SQ1’ s HST and T(2)j(4+5) of the SQ2’ s HST; The evaporites of the Leikoupo Formation was controlled by tectonic regime change of the Yangtze Block leading to basin uplift integrally and formation of palaeo-land or palaeo-uplift, then restricted environment was formed. Therefore, evaporite distribution bears no obvious difference in TST and HST. Under combined control of carbonate restricted platform of craton shallow marine environment, warm and arid climate in low latitude and falling of sea level, sea water concentrated and salinized centripetally. Xuanhan-Dazhou area is the salinization center, as well as the favorable exploration zone for potash salts.