| 中-晚二叠世上扬子地块(四川盆地区)裂解的沉积响应 |
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| 引用本文： | 邓莉,闫全人,宋博,高山林.中-晚二叠世上扬子地块(四川盆地区)裂解的沉积响应[J].岩石学报,2021,37(8):2465-2482. |
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| 作者姓名： | 邓莉 闫全人 宋博 高山林 |
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| 作者单位： | 中国科学院大学地球与行星科学学院, 北京 100049;中国科学院大学地球与行星科学学院, 北京 100049;中国地质调查局西安地质调查中心, 西安 710054;中国石油化工股份有限公司油田勘探开发事业部, 北京 100728 |
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| 基金项目： | 本文受中国石油化工股份有限公司勘探分公司项目（35450004-19-ZC0607-0002）和国家重点研发计划重点专项（2016YFC0600401）联合资助. |
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| 摘 要： | 中-晚二叠世,上扬子(四川盆地区)碳酸盐岩台地内发育三条北西-南东走向的裂谷,它们是重要的油气储集区带,如普光和元坝气田就产于开江-梁平裂谷两侧。但是对这些裂谷的开始时代和构造成因等关键地质问题,还缺乏详细的沉积学研究,且存在较大争议。本文通过大比例露头剖面和钻井岩芯测量以及详细的沉积相分析对比,对开江-梁平裂谷的构造沉积过程进行了深入细致的研究。调查发现,在开江-梁平裂谷北缘,中二叠统栖霞组上段至茅口组2段发育大规模斜坡相碳酸盐岩滑塌堆积,揭上扬子地块四川盆地区于中二叠世栖霞晚期开始发生伸展裂解。茅口组3段至上二叠统长兴组为超覆于滑塌堆积之上的硅质岩和碳-硅质泥岩等深水盆地相沉积,表明开江-梁平裂谷从中二叠世茅口晚期开始由伸展裂解转变为区域沉降,即开江-梁平裂谷经历了伸展裂解和区域沉降两个构造沉积阶段。伸展裂解阶段,开江-梁平裂谷是一个发育于碳酸盐岩台地内的不对称海相半地堑盆地,北侧为发育大规模碳酸盐岩滑塌堆积的下盘断斜坡带,南侧为发育缓斜坡生物碎屑滩和礁灰岩的上盘缓斜坡带;区域沉降阶段,开江-梁平裂谷表现为东翘西降的不均匀沉降,发育自东向西不断进积的潮坪-潟湖相和高能浅滩相沉积等。本文研究成结果对分析和圈定四川盆地区中-晚二叠世油气储集相带的时空分布具有重要科学意义,也为研究碳酸盐岩滑塌堆积提供了一个新范例。
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| 关 键 词： | 上扬子地块 开江-梁平裂谷 中-晚二叠世 碳酸盐岩滑塌堆积 伸展裂解 不均匀沉降 |
| 收稿时间： | 2021/2/3 0:00:00 |
| 修稿时间： | 2021/6/2 0:00:00 |
Sedimentary responses to rifting of the Upper Yangtze Block (Sichuan basin area) in the Middle-Late Permian |
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| DENG Li,YAN QuanRen,SONG Bo,GAO ShanLin.Sedimentary responses to rifting of the Upper Yangtze Block (Sichuan basin area) in the Middle-Late Permian[J].Acta Petrologica Sinica,2021,37(8):2465-2482. |
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| Authors: | DENG Li YAN QuanRen SONG Bo GAO ShanLin |
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| Institution: | College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China;College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China;Xi''an Center, China Geological Survey, Xi''an 710054, China; Exploration and Development Affairs Department, SINOPEC, Beijing 100728, China |
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| Abstract: | Three rift valleys in NW-SE strike have been outlined by the gas and oil explorations in the Upper Yangtze Block in the past 20 years. More importantly, these two rift valleys are the locations of proved gas fields in the present Sichuan Basin, such as the Puguang and Yuanba gas fields developed on both sides of the Kaijiang-Liangping (KL) rift valley. However, the initiating ages of these rift valleys and their tectono-sedimentary evolutionary processes are still unclear, mainly because of lacking the sedimentary constraints. Based on careful observations of field outcrops along three sections and a drill core, we analyzed the sequences of the KL rift valley in the Permian and reconstructed its tectonic and filling processes. The results presented in this paper show that carbonate olistostromes were highly developed in the upper section of the Qixia Formation to the second member of the Maokou Formation of the Middle Permian in the northern flank of the KL rift valley, floored by platform carbonates and overlapped by deep-water deposits, which indicates that the slope facies related to the rifting occurred in the Upper Yangtze carbonate platform in the Middle Permian. The lowest carbonate olistostromes suggest the rifting initiated at the Middle Qixia Stage (approximately the Early Wordian) and gradually developed from west to east. Overlapped deep basin deposits in the third member of the Maokou Formation to the Changhsing Formation of the Upper Permian demonstrate the change from the rifting to post-rift subsidence at the beginning of the Late Maokou Stage (approximately the Late Capitanian). In a word, the KL rift valley underwent the tectono-sedimentary processes of the rifting and then post-rift subsidence. During the rifting, the KL rift valley was a marine half-graben developed on the Upper Yangtze carbonate platform, and its northern flank was a fault-controlled slope and characterized by massive carbonate olistostromes. The drill core (Yuanba 8) shows that deeply buried southern flank of the half-graben was a gentle slope and deposited bioclastic and reef limestones. During the post-rift subsidence, the KL rift valley was characterized by cherts and cherty mudstones of the deep basin facies enriched the fossils such as Ammonites. The post-rift subsidence was highly uneven and therefore resulted in the lagoon-tidal flat facies and high-energy shoal facies progressively overlapping the deep basin sediments from east to west along the KL rift valley. |
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| Keywords: | Carbonate olistostrome Carbonate platform rifting Post-rift subsidence Kaijiang-Liangping rift valley Middle-Late Permian Upper Yangtze Block |
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