Alkaline-lacustrine deposition and paleoenvironmental evolution in Permian Fengcheng Formation at the Mahu sag, Junggar Basin,NW China

• 作者: CHEN Xingyu CHENG Dawei LIN Minjie TANG Yong WANG Mengshi YUAN Xuanjun ZHANG Zhijie ZHOU Chuanmin
• 来源期刊: 石油勘探与开发:英文版
• 学科: 地球科学
• 关键词: Junggar Basin PERMIAN Fengcheng FORMATION depositional characteristics paleoenvironment reconstruction alkaline-lacustrine DEPOSITION lithofacies Mahu SAG
• 年，卷（期）: 2018,（6）
• 页码范围: 1036-1049
• 页数: 14页
• 分类号: P618.13

摘要

Alkaline-lacustrine deposition and its evolution model in Permian Fengcheng Formation at the Mahu sag, Junggar Basin were investigated through core and thin-section observation, geochemical and elemental analysis, logging response and lithofacies identification. Six lithofacies are developed in the Fengcheng Formation. The Feng 2 Member(P1 f2) is dominated by lithofacies with alkaline minerals, while the upper part of the Feng 1 Member(P1 f1) and the lower part of the Feng 3 Member(P1 f3) are primarily organic-rich mudstones that are interbedded with dolomite and dolomitic rock. Paleoenvironment evolution of Fengcheng Formation can be divided into 5 stages, which was controlled by volcanic activity and paleoclimate. The first stage(the early phase of P1 f1) was characterized by intensive volcanic activity and arid climate, developing pyroclastics and sedimentary volcaniclastic rocks. The secondary stage(the later phase of P1 f1) had weak volcanic activity and humid climate that contributed to the development of organic-rich mudstone, forming primary source rock in the Fengcheng Formation. The increasing arid climate at the third stage(the early phase of P1 f2) resulted in shrinking of lake basin and increasing of salinity, giving rise to dolomite and dolomitic rocks. The continuous aird climate, low lake level and high salinity at the fourth stage(the later phase of P1 f2) generated special alkaline minerals, e.g., trona, indicating the formation of alkaline-lacustrine. The humid climate made lake level rise and desalted lake water, therefore, the fifth stage(P1 f3) dominated by the deposition of terrigenous clastic rocks and dolomitic rocks.