【作者】 田世峰；

【导师】 查明； 陈中强；

【作者基本信息】 中国石油大学（华东） ， 地质资源与地质工程， 2012， 博士

【摘要】 旋回地层学是近年来国际上兴起的一个地层学分支学科，用于识别、描述、对比以及解释地层中周期性或准周期性的旋回变化，尤其可应用于地质年代学中，用来提高时间地层格架的精确性和分辨率。自从Hays于1976年在《Science》上发表文章报道他们在第四纪深海钻探岩芯中发现了米兰科维奇旋回以来，国际地学界对旋回地层学的研究如火如荼。在中国，虽然一些学者自上世纪九十年代以来对该学科进行了有益的尝试性研究，但却一直没有得到发展，甚至没有中文资料系统的介绍旋回地层学。因此，本论文首先详细归纳、总结旋回地层学的相关概念、发展历程、研究方法和研究现状，然后，对珠江口盆地惠州凹陷古近系和浙江煤山剖面早三叠世地层这两个实例进行详细解剖和系统研究，最后，尝试性地将旋回地层学与石油地质学结合，力争将级次结构及持续时间已知的米兰科维奇旋回引入油气地质勘探，满足其对研究精度日趋提高的要求。珠江口盆地古近系地层序列普遍发育三角洲相硅质碎屑岩及浅海相碳酸盐岩的韵律性互层，且显示出较强的周期性变化规律。为了提高地层分辨率以满足油气勘探需求，本研究选取珠江口盆地若干钻穿中新世的钻井，利用其自然伽马测井曲线进行频谱分析，找出旋回的主要周期从而判断其驱动机制。因为高频旋回地层学的应用需要其它地质定年手段提供的独立的年龄格架，本论文利用浮游有孔虫、钙质超微化石、颗石藻类、孢粉四个化石门类进行微体古生物地层格架的建立，根据标志种与《地质年代表2004》的对比获得旋回地层学所需的绝对年龄控制点。然后，从最新的天文周期解决方案中选择斜率和日照量作为目标曲线，将自然伽马测井曲线进行天文调谐，得到高分辨率天文调谐地质年代表或浮动天文年代表，并利用该地质年代表对发现的地质及古生物事件进行定年。针对研究层段完整性、沉积物类型及沉积持续时间等的不同，分别利用频谱分析法、滑动窗口频谱分析法、高密度滑动窗口法及相位对比法求取研究层段的精细沉积速率变化。最后还从替代指标的选择、频谱分析以及天文调谐过程，详细深入分析可能产生误差，并最终影响天文调谐地质年代表结果的可能因素。作为二叠-三叠系全球界限层型及“金钉子”剖面，浙江煤山剖面在生物地层、生态地层等方面得到了极大关注和发展，但层序地层、旋回地层学方面，却鲜有研究者涉及。前人依靠生境型等证据建立的层序地层格架及依靠定性分析得出的旋回地层学结果大大提高了我们对层型剖面地层学的认识，但难以满足在该剖面上对二叠纪末大绝灭之后生物复苏机制及古气候的研究对地层精确度的要求。二叠纪末生物大灭绝造成海洋生物的萧条，但同时也意味着较低的生物扰动，使得早三叠纪可以较好地保存精细的韵律性旋回。论文对浙江煤山剖面下三叠统可进行区域对比的高频泥岩、碳酸盐岩薄互层进行级次划分，利用相对碳酸盐岩含量作为替代指标进行频谱分析找出主要频率，定量分析其旋回驱动机制并分析天文轨道参数对沉积影响的可能途径。结合天文轨道理论，分析频谱分析结果中丢失的信号及仍然存在的噪音的主控因素，并尝试性地提出一种解决深度域-时间域转换过程中不同岩性沉积速率不同导致的时间序列不可信的算法。最后利用改进的Fischer图解重建煤山地区早三叠世相对海平面变化曲线，并与全球同时期海平面变化进行对比，分析其异同点及可能的影响因素。国际上对旋回地层学领域的研究，主要集中在天文轨道周期理论及其对气候的影响，古季风、冰川、古生物、海平面变化等的演化机制研究等方面，天文调谐建立的地质年代标尺这一高分辨率定年工具，始终没有在石油地质勘探中得到充分的应用。论文最后探讨了高频米兰科维奇旋回在经典层序地层学三级层序的起因和持续时间、高频层序划分、层序边界及沉积间断的识别、有利砂体预测、地层剥蚀厚度恢复及盆地沉积速率演化和动力过程等问题中的应用。更多还原

【Abstract】 Cyclostratigraphy is the subdiscipline of stratigraphy that deals with the identification,characterization, correlation, and interpretation of cyclic variations in the stratigraphic recordand, in particular, with their application in geochronology by improving the accuracy andresolution of time-stratigraphic frameworks. Since the recognition of ‘Milankovitch’ orbitalforcing as the ‘pacemaker of the ice ages’, cyclostratigraphy has attracted more and moreattentions from geoscientists and stratigraphers because it can considerably enhance bothrelative and absolute age controls at a resolution of10-100Ka, better understanding of thesedimentology, quantification of rates and duration of sedimentary, climatic, andpaleontological processes, as well as possibilities for correlation within and beyond the basin.During the past two decades, there have been many efforts to construct an accurate geologicaltimescale based on astronomical tuning of climatic response records to astronomical solutions.This provides a better accuracy than the conventional timescales which are often based onlinear interpolation between biozones and/or geomagnetic reversals and/or radiometricallydated calibration points. But in China, only few people focus on this discipline, with even nosystematic introduction of cyclostratigraphy in Chinese. In this dissertation, we introduce thefundamental conceptions, development history, research methods, and research status ofcyclostratigraphy in detail, and then undertake cyclostratigraphic research on several differentgeological times in the Huizhou Depression and the Meishan Section.Several formations of Tertiary in the Pearl River Mouth Basin of South China Seaconsist of deltaic siliciclastic and neritic shelf carbonate rhythmic alternations. To improve thestratigraphic resolutions for hydrocarbon prospecting and exploration in the basin, this study undertakes spectral analysis of high-resolution natural gamma-ray well-logging record todetermine the dominant frequency components and test whether Milankovitch orbital signalsare registered in the rhythmic successions. Because the high-frequency cyclostratigraphyrelies on the conventional timescales based on biostratigraphy, magnetostratigraphy, and/orradio dating, we use planktonic foraminifera, calcareous nannofossil, dinoflagellates, andspore-pollen to construct micropaleontology stratigraphic framework to providebiochronological constraints. Within biochronological constraint, a high-resolutionastronomical timescale was constructed through astronomical tuning of the naturalgamma-ray well-logging record to the most recent astronomically calculated variation ofearth’s orbit. The astronomically tuned timescale can be used to calculate astronomical agesfor geological events and bioevents recognized throughout the period. The differentsedimentary completeness, sedimentary duration, and types of sediment of the researchinterval determine that the sedimentary rate can not be obtained by the same method.Therefore, spectral analysis, sliding windows spectral analysis, high-density sliding windowsspectral analysis and phase relationship correlation methods were advanced to obtain thesedimentary rate in different research intervals.As the Global Stratotype Section and Point for the Permian-Triassic boundary (PTB), thebiostratigraphy, chronostratigraphy, event stratigraphy and ecostratigraphy of the intervalfrom the Upper Permian Changhsingian through the PTB to the lower Triassic YinkengFormation at Meishan section have been extensively studied. However, the sequencestratigraphy and cyclostratigraphy of the lower Triassic of this section have received far lessattention even though exposure of the Lower Triassic succession is also spectacular. Thesequence stratigraphic framework has been constructed by the regional sea-level changesinferred from the hatitat type which represents certain ecological geographic environments.As we know, the Permian-Triassic transition resulted in the most devastating biotic crisis inPhanerozoic history and drastically altered the balance of the biosphere and its subsequentevolution. As consequence of the most devastated biotic crisis, the Early Triassic marinefauna fossils appeared very rare worldwide. So, sequence stratigraphic framework constructedon the basis of ecostratigraphic analyses is questionable. Milankovitch signals have beendetected quanlitatively at Chaohu section which is near the Meishan section by previous works. While quantitative tests of Milankovitch climatic signals in Early Triassic marinerecords at Meishan section are lacking. Whether Milankovitch orbital forcing was a majorclimatic driver during this time is essential to understanding the controlling factors anddepositional mechanisms, and the prolonged biotic recovery after the end-permian massextinction. The depauperate nature of marine faunas suggests a rather low bioturbation level,which enables the excellent preservation of very fine rhythmic cyclicity in the Early Triassicsediments. The well-preserved rhythmic sediments are characteristics of the Lower Triassicsuccessions worldwide. Here, we present a case study of the lower Triassic YinkengFormation exposed at Meishan section, with objectives to distinguish different orders ofembedded cycles and employ modified version of Fischer plots to define the third-andhigher-order sea-level changes. Aiming at the lost signals and the existing noise in the resultof spectral analysis, we proposed an algorithm which deals with the depth-time domaintransformation in the last of this part, with advantages that it can take the differentsedimentation rates between different rock types into account during the transformationperiod.According to the recent published papers, most cyclostratigraphic researchs are focus onhow the variations of earth’s orbit affect the climatic system, and the evolution mechanisms ofthe monsoon, glaciations, bioevents, sea-level changes and etc. While the high-resolutionastronomically tuned Time Scale has still not been applied in hydrocarbon exploration. As thealready known cycles hierarchy and duration, in this dissertation, we attempt to probe intohow the high-frequency Milankovitch cycles can be used in the hydrocarbon explorationdomain like the orgin and duration of the third-order sequence in the classic sequencestratigraphy, high-frequency sequence division, the dection of sequence boundary andsedimentary discontinuity, the prediction of favorable sandbodies, and the estimation oferosion thickness.更多还原