测井曲线Milankovitch周期分析与应用

利用沿井剖面滑动时窗内的ＦＦＴ和最大熵谱估计算法，选择合适的滤波器、窗长和步长，从测井曲线中分析出了Ｍｉｌａｎｋｏｖｉｔｃｈ周期．研究了波长比，谱峰等特征与周期的关系，确定出沉积速率的渐变与突变，求出了沉积速率，经分析，与岩性结果相符合．     

Investigating the sensitivity of the Atmospheric General Circulation Model ECHAM 3 to paleoclimatic boundary conditions

We present atmospheric simulations of three different time slices of the late Quaternary using the ECHAM 3 general circulation model in T42 resolution. In this work we describe the results of model runs for the time slices 6000 years BP (last climate optimum), 21 000 BP (last glacial maximum) and 115 000 years BP (glacial inception). Although the solar insolation is known for all time slices, a complete data set of the other boundary conditions which are necessary for running the atmospheric model exists only for the last glacial maximum in the form of the CLIMAP reconstruction. For the other two time slices, which are interglacial states like the modern climate, sea surface temperatures, land albedo and ice sheet topography are kept at modern values and only the solar insolation is changed appropriately. The response of the model to solar insolation changes is quite reasonable. The modelled anomalies are small and roughly opposite in sign for 6000 BP and 115 000 BP, respectively. In the case of last glacial maximum, the glacial ice sheet topography and ice albedo produce a much larger climate anomaly in the model. However, to enable a real test of model performance under glacial boundary conditions, the CLIMAP sea surface temperatures, which are now known to be partly inaccurate, should be replaced by an updated “state-of-the-art” reconstruction.     

“旋回地层学研究系统”(Version 1.0)简介

近年来随着石油勘探与开发,越来越多的人认识到天文地层学研究在油田生储盖地质年龄和剥蚀量的计算中是对油气资源评价的一个不可缺少的工作环节。中石化胜利油田地质科学研究院在三年的研究基础上借助于Matlab平台,开发出了“旋回地层学研究系统”(Version1.0),该系统在中石化     

Climate Changes and Cyclic Sedimentation in the Mid-Late Permian: Kennedy Group, Carnarvon Basin, Western Australia

Climate has an important direct and indirect influence of sedimentation, and especially on the development of cyclic sedimentation. Climate influences both accommodation and supply, the major controls on the architecture of sedimentary sequences. The Permian paleoclimate is the subject of increasing controversy, giving rise to numerous differing models developed and an expanding database of fossil evidence for climatic conditions.Western Australian basins, in particular the Carnarvon Basin, are unique among nearby Gondwanan basins in that they do not have extensive coal measures within their Permian successions. The Kennedy Group, the uppermost unit in the onshore Carnarvon Basin Permian succession, has a detrital composition indicative of arid weathering conditions. Within the Kennedy Group, even lagoonal and very nearshore sediments are devoid of plant debris or indications of the nearby presence of extensive flora. Presumed surfaces of subaerial exposure do not show paleosol development or root-traces. There has been little development of clay and chemical grain degradation is almost entirely related to diagenetic cementation and dissolution phases, rather than transport and source weathering. Nearby basins, at similar latitudes, in India and East Australia contain coal measures, consistent with the humid climates that are predicted for this latitude. It is suggested therefore that the inferred aridity in the climate of the Carnarvon Basin and other Western Australian Basins is due to local climatic effects, probably related to an interruption in atmospheric circulation caused by tectonic rifting and uplift to the west.Cyclicity in the Kennedy Group indicates regular Late Permian, Milankovitch scale eustatic sea-level change, and may signify the presence of some ice at the poles. The development of cycles may have been enhanced by shifting climate belts controlled by Milankovitch cyclicity.     

Origin of cyclicity in Triassic-Jurassic radiolarian bedded cherts of the Mino accretionary complex from Japan

Abstract The abundance of magnetic microspherules in a Triassic-Jurassic continuous sequence of alternating chert and shale beds in the Mino accretionary complex, central Japan, was measured systematically. Depending on time, the magnetic microspherules extracted from shale beds change in abundance considerably from the minimum 0.9ppm/cm³ at latest Triassic ( ca 208Ma) and the maximum 75ppm/cm³ at late Early Jurassic ( ca 187Ma); however, the abundance is always higher approximately 10–100 (average 70) times than those from adjacent chert bed at any stratigraphic horizon. Such systematic difference reveals the origin of radiolarian bedded chert as cyclic-rapid accumulation of biogenic SiO₂ under extremely slow accumulative environments of shale with probable aeolian dust in origin. The accumulation data for individual shale and chert beds were obtained based on the microspherule abundance and radiolarian biostratigraphy, i.e., ca 0.018g/cm²Ka for lower Jurassic shale beds and ca 1.9g/cm²Ka for adjacent chert beds.
Duration time to make a chert-shale couplet corresponds to a dominantly 15–20Ka interval (average 23 Ka) in Upper Triassic bedded cherts with a low paleolatitude, whereas a 40–45 Ka interval (average 42 Ka) in Lower Jurassic ones which may been formed in higher latitude than Triassics before the final accretion to the Asian continental margin. Depending on paleolatitude, the cyclicity of 23 and 42 Ka may correspond to Milankovitch cycles which have been well documented in deep-sea sediments.     

华北中元古代下马岭组旋回地层与前寒武纪轨道天文周期律

轨道驱动的气候变化在显生宙已被广泛证实。对于更早的前寒武纪,米兰科维奇周期性是否存在未有定论。本文选择华北中元古代下马岭组赵家山剖面,结合同位素年代学数据,对其三段中、上部开展旋回地层学研究。在对研究层段十分发育的岩性旋回进行高分辨率测量与分析的基础上,提出基于岩相认识的编码规则,建立时间序列,并对其展开定量分析。频谱分析结果与天文学理论计算吻合较好,这意味着前寒武纪也应该存在米兰科维奇天文周期律。此项研究为认识更早地质时期地球的轨道参数及天文状态提供了思路,对旋回地层学研究在前寒武纪的拓展有一定启示意义。     

过去200 ka北半球δ18O海温谱及其数值模拟

冰期和间冰期交替循环是第四纪古气候变化的基本特征,大洋底部沉积物中的有孔虫δ＾１８Ｏ记录表明了这种循环具有约１００ｋａ,４１ｋａ和２３ｋａ等几个主主要周期成分,它们均位于Ｍｉｌａｎｋｏｖｉｔｈｃ频率带上,用δ＾１８Ｏ记录恢复的海温谱不仅随纬度变化,而且冷季与暖之间存在着明显的差别,用一个由海、冰、气耦合的二维气候模式出了δ＾１８Ｏ海温谱的主要特征,在一定程度上检验了Ｍｉｌａｎｋｏｖｉｔｃｈ的天文古     

大庆长垣姚家组高频层序地层与米兰科维奇旋回对应性

选取典型取心井对大庆长垣姚家组进行高频层序划分,共识别出98个超短期旋回,33个短期旋回,9个中期旋回和3个长期旋回。同时大庆长垣姚家组自然伽马曲线频谱分析结果表明,该地层中很好地保存了米兰科维奇旋回。其中,偏心率短周期引起的沉积旋回厚度为2.679～3.972 m,地轴倾角周期引起的沉积旋回厚度为1.379～2.131 m,岁差周期引起的沉积旋回厚度为0.601～0.901 m。高频层序与米兰科维奇旋回之间存在着较好的一致性,高频层序中期旋回、短期旋回和超短期旋回大致分别与米兰科维奇旋回的偏心率长周期、偏心率短周期以及岁差周期对应。地球轨道变化所引起的湖平面变化是高频层序形成的主控因素。     

四川广元上寺剖面晚二叠世-早三叠世旋回地层:基于小波分析的P-T界线地质事件探讨

利用小波分析技术,对采集自四川广元上寺剖面上二叠统-下三叠统格里斯巴赫亚阶以碳酸盐岩为主的沉积序列的自然伽马(GR)能谱序列进行深入分析研究,结果表明,该沉积序列很大程度上受到410∶102.5∶42.6∶21.5的米兰科维奇旋回控制.晚二叠世上寺剖面位于古特提斯洋的深水环境,沉积速率较低,平均为5 cm/ka;二叠纪...