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1.
A continuous terrestrial succession was recovered from the Songke-2(SK-2) borehole in the Songliao Basin, Northeastern China. This borehole provides a unique material for further research on the continental paleoclimate during Cretaceous greenhouse period, following a series of achievements of the Songke-1(SK-1) core. In this study, thorium(Th) logging data were chosen as a paleoclimate proxy to conduct a detailed cyclostratigraphic analysis. The Th series varies quasi-periodically; power spectra and evolutionary fast Fourier transformation(FFT) analysis reveal significant cycles in the Quantou(K2 q), Qingshankou(K2 qn), Yaojia(K2 y) and Nenjiang(K2 n) formations. The ratio of cycle wavelengths in these stratigraphic units is approximately 20:5:2:1, corresponding to long orbital eccentricity(405 kyr), short orbital eccentricity(100 kyr), obliquity(37 kyr), and precession cycles(22.5 kyr and 18.4 kyr). The durations of the K2 n, K2 y, K2 qn and K2 q are estimated as 6.97, 1.83, 5.30 and 4.52 Myr, respectively, based on the constructed ～18.62 Myr "floating" astronomical time scale(ATS). Comparison of the durations between the SK-1 s and SK-2 boreholes exhibits a slight difference of 0.06 Myr and 0.459 Myr for K2 qn and K2 y. Nevertheless, our ATS of K2 n supports the chronostratigraphic frame constructed by the CA-ID-TIMS data of the SK-1 s borehole. This new "floating" ATS provides precise numerical ages for stratigraphic boundaries, biozones and geological events in the Songliao Basin, and can serve as a basis for correlation of strata and events between marine and terrestrial systems.  相似文献   

2.
正Objective The Songliao Basin is located in northeastern China. The Upper Cretaceous Qingshankou Formation(Fm.)(K2 qn), Yaojia Fm.(K2 y), and Nenjiang Fm.(K2 n) were deposited in its depression. The sediments are mainly continental clastic rocks. The first member of the Qingshankou Fm.(K2 qn1) in the southern Songliao Basin mainly comprises semi-deep to deep lacustrine shale of large thickness, generally 30,100 m, with wide distribution; the thickness of the shale has an average thickness of 70 m.  相似文献   

3.
Sedimentary deposits of the Lower Cretaceous Xiagou Formation form the most significant potential hydrocarbon reservoirs in the Qingxi Sag, Jiuquan Basin(NW China). Zircon U-Pb ages of the dated basalts at the top of the Xiagou Formation give an isochron age of 115.6 Ma, and the sedimentation interval of the Xiagou Formation was speculated to range from about 125/124 Ma to 115 Ma based on paleontological research and stratigraphic correlation analysis. Here we use GR logging data as a palaeoenvironmental and palaeoclimatic proxy to conduct a detailed cyclostratigraphic study of five selected wells. Power spectra, evolutionary fast Fourier transformation and wavelet analysis all reveal significant sedimentary cycles in the Xiagou Formation. The ratios of cycle wavelengths in these stratigraphic units are 33.82 m : 7.91 m : 3.06 m : 1.79 m, which is similar to the ratio of orbital targets of 20 : 5 : 2 : 1. The ratio of 20 : 5 : 2 : 1 is interpreted as Milankovitch cycles of 405 kyr long eccentricity,100 kyr short eccentricity, 37 kyr obliquity, and 22 kyr precession cycles respectively. A high-resolution astronomical time scale is constructed by tuning the stratigraphy into target curves of orbital cycles respectively. Based on the astronomical time scale, the absolute ages of 55 samples were estimated,which are used for subsequent stable carbon and oxygen isotope stratigraphy analysis. The analysis results of the five studied wells in the Qingxi Sag indicate:(1) a negative trend of δ~(13)C values upwards in the Xiagou Formation, and(2) negative δ~(18)O values with a positive trend upwards. Both relatively heavy values and pronounced covariances of δ~(13)C values and δ~(18)O values indicate an arid-evaporationcontrolled climate during the sedimentary period of the Lower Cretaceous Xiagou Formation, Qingxi Sag, Jiuquan Basin. Moreover, positive covariances of SQK_1g_(2+3) indicate extremely high temperature, and negative covariances of SQK_1g_1 indicate a relatively low temperature.  相似文献   

4.
We clarified three stages of dolomitization and secondary changes by studying the petrology and geochemistry characteristics of dolomite from the Ma55–Ma510 sub-members of the Ordovician Majiagou Formation in the Jingxi area in the Ordos Basin: (1) Syngenetic microbial dolomitization is characterized by formation of dolomite with a mainly micrite structure and horse tooth-shape dolomite cements. (2) Seepage reflux dolomitization during the penecontemporaneous period superposed adjustment functions such as recrystallization and stabilization in the middle-deep burial stage, forming dolomites mainly consisting of micro crystal and powder crystal structure. (3) Powder dolomite, fine dolomite, and medium-coarse crystalline dolomite formed in pores and fractures in the middle-deep burial stage. The secondary concussive transgression-regression under a regressive background is an important condition for the occurrence of many stages of dolomitization in the study area. The basin was an occlusive epicontinental sea environment in the Ma5 member of the Ordovician Majiagou Formation sedimentary period. In the sediments, sulfate content was high, which is conducive to the preservation of microbial activity and microbial dolomitization. Micritic dolomite formed by microbial dolomitization provides good migration pathways for seepage reflux dolomitization. Affected by evaporation seawater with increased Mg/Ca ratio, seepage reflux dolomitization was widely developed and formed large-scale dolomite, and underwater uplifts and slopes are favorable areas for dolomite. In the middle-deep burial stage, dolomitizing fluid in the stratum recrystallized or stabilized the previous dolomite and formed a small amount of euhedral dolomite in the pores and fractures.  相似文献   

5.
The Quaternary sediments in the Yili Basin can serve as archives for studying the Cenozoic basin–mountain relationship. In this study, based on typical natural sections and boreholes, the surficial sediments of the Huocheng area were studied, and their sedimentary ages were obtained using the optically stimulated luminescence(OSL) and electron spin resonance(ESR) dating methods. These dates, combined with changes in the sedimentary facies, provided details of the neotectonic movement in the Yili Basin and adjacent areas. By dating sediments from five sections and three boreholes, we determined that the surficial sediments of the Huocheng area were mainly formed in the Late Pleistocene, with scattered instances of Holocene sediments. The surficial sediments mainly consisted of alluvial fan facies, fluvial facies, lacustrine facies, and desert facies. Based on the activity on the Hongshanzui fault and the northern margin fault of the Wusun Mountains, the Huocheng area was uplifted synchronously with the Tianshan Mountains during the last stage of the Late Pleistocene, causing the desert facies sediments to be superimposed on the former paleo–lake sediments.  相似文献   

6.
The sedimentary, paleogeomorphological and reservoir characteristics of the Jurassic Yan’an Formation in the southwestern Ordos Basin, northwestern China, were studied by means of casting thin sections, scanning electron microscopy, inclusion analysis and identification of low-amplitude structures. A model for reservoir formation is established, and the controlling effects of sedimentary facies, paleotopography, low-amplitude structures and formation water on oil reservoirs are revealed. There are significant differences in the sedimentary characteristics, structural morphology and paleowater characteristics between the reservoirs above the Yan 10 Member and those in the Yan 9 to Yan 7 Members. The Yan 10 Member contains fluvial sediments, whereas the Yan 9 to Yan 7 members contain delta-plain anastomosing-river deposits. The distribution of high-permeability reservoir is controlled by pre-Jurassic paleogeomorphology and sedimentary facies. Some of these facies exhibit high porosity and high permeability in a lowpermeability background. The main hydrocarbon accumulation period was the late Early Cretaceous, filling was continuous, and the charging strength altered from weak to strong and then from strong to weak. The Yan 10 reservoir is mainly controlled by the paleogeomorphology: hydrocarbons migrated upward at a high speed through the unconformity surface, and accumulated in the favorable traps formed by paleogeomorphic structural units, such as gentle slopes or channel island. Furthermore, groundwater alternation in these areas was relatively stagnant, providing good reservoir preservation conditions. The reservoirs in the Yan 9 and higher members are controlled by the sedimentary facies, lowamplitude structure and paleowater characteristics. Hydrocarbons migrated through the three-dimensional delivery system, influenced by favorable sedimentary facies and high-salinity groundwater, then accumulated in the favorable low-amplitude structural traps that formed during the hydrocarbon production period.  相似文献   

7.
The Ordos Basin, as the second largest petroliferous basin of China, contains abundant oil and gas resources, oil shale, and sandstone-type uranium mineral resources. Chang 7 shale is not only the major source rock of the Mesozoic petroliferous system of the Basin, but is also crucial in determining the space-time distribution relationship of the shale section for the effective exploration and development of the Basin's oil and gas resources. To obtain a highly precise age of the shale development section, we collected tuff samples from the top and bottom profile of the Chang 7 Member, Yishi Village, Yaoqu Town, Tongchuan District, on the southern margin of the Ordos Basin and performed high-precision chemical abrasion(CA)–isotope dilution(ID)–thermal ionization mass spectrometry(TIMS) zircon U-Pb dating on the basis of extensive laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS) zircon U-Pb dating data. Our results show the precise ages of the top and bottom zircon in the Chang 7 shale to be 241.06±0.12 Ma and 241.558±0.093 Ma, respectively. We first obtained Chang 7 age data with Grade 0.1-Ma precision and then determined the age of the shale development in the Chang 7 Member to be the early-Middle Triassic Ladinian. This result is supported by paleontological evidence. The deposition duration of the Chang 7 shale is 0.5 Ma with an average deposition rate of the shale section being 5.3 cm/ka. Our research results provide time scale and basic data for further investigation of the basin–mountain coupling relation of the shale section, the sedimentary environment and volcanic ash and organic-matter-rich shale development relation, and the organism break-out and organic-matter enrichment mechanism.  相似文献   

8.
The Neoproterozoic Jiangnan orogen plays an important role in the study of the Precambrian tectonic evolution of South China. The tectonic nature of the Neoproterozoic sedimentary basins is still controversial, due to poor understanding of the sedimentary sequences and the lack of geochronological data. Here, we present sedimentological, provenance and geochronological data from the Heshangzhen Group in the eastern Jiangnan orogen. Sedimentological analysis shows that the Luojiamen Formation was deposited in a submarine fan, and the overlying Hongchicun Formation was deposited in front of a fan delta. The youngest detrital zircons constrain the lower Luojiamen and Hongchicun formations with ages of 827.3 ± 8.4 Ma and 825 ± 12 Ma, respectively. The sandstones of the Luojiamen Formation are characterized by a large number of intermediate to felsic volcanic grains, suggesting a volcanic arc source. In contrast, quartz and sedimentary lithic grains increase in the Hongchicun Formation, showing a new input from a collisional orogenic source. Detrital zircon from six sandstone samples in the Luojiamen and Hongchicun formations yield similar age spectra of 930–820 Ma with a peak at ca. 845–860 Ma, with one main cluster at 930–820 Ma. Detrital zircons of 930–845 Ma show a positive value of εHf(t)(+2.4 to +11, mean +7.6), which is similar to the volcanic arc of the nearby Shuangxiwu Group. There are a minor group of zircons with U-Pb ages ranging from 820 Ma to 845 Ma from the middle part of the Luojiamen Formation and Hongchicun Formation, with εHf(t) values between-20 to +2.4, which are consistent with the characteristics of the Shuangqiaoshan Group. within light of the bidirectional paleocurrents in the Luojiamen Formation, it is speculated that the zircons of 820–845 Ma were recycled from the Shuangqiaoshan Group, which is derived from a continental arc to the northwest. Our data suggests that the Luojiamen Formation was formed in an inter-arc basin, while the Hongchicun Formation was formed in an accretionary wedge-top basin. When juxtaposed with the conglomeratic characteristics at the bottom of the Luojiamen Formation, it is believed that the unconformity represented by the ‘Shen Gong Movement' reflects the rapid erosion and accumulation process of island arc volcanic material. The disconformity between the Luojiamen and Hongchicun formations is the imprint of transition from inter-arc basin to accretionary wedge-top basin,which represents the collision between the Shuangxiwu arc and the Yangtze Plate.  相似文献   

9.
On the basis of reprocessing 34 new two-dimensional spliced long sections(20,191 km) in the Tarim Basin, the deep structure features of the Tarim Basin were analyzed through interpreting 30,451 km of two-dimensional seismic data and compiling basic maps. Seismic interpretation and geological analysis conclude that the Nanhua-Sinian strata are a set of rift-depression depositional systems according to their tectonic and depositional features. The rift valley formed in the Nanhua Period, and the transformation became weaker during the late Sinian Period, which eventually turned into depression. From bottom to top, the deposited strata include mafic igneous, tillite, mudstone, and dolomite. Three major depocenters developed inside this basin during the rift stage and are distributed in the eastern Tarim Basin, the Awati area, and the southwestern Tarim Basin. Among them, the rift in the eastern Tarim Basin strikes in the near east-west direction on the plane and coincides with the aeromagnetic anomaly belt. This represents a strong magnetic zone formed by upwelling basic volcanic rock along high, steep normal faults of the Nanhua Period. Controlled by the tectonic background, two types of sedimentary systems were developed in the rift stage and depression stage, showing two types of sequence features in the Sinian depositional stage. The Nanhua System appears as a wedge-shaped formation, with its bottom in unconformable contact with the base. The rifting event has a strong influence on the current tectonic units in the Tarim Basin, and affects the distribution of source rock in the Yuertus Formation and reservoir beds in the Xiaoerbulake Formation in Lower Cambrian, as well as the gypseous cap rock in Middle Cambrian. The distribution features of the rifts have important and realistic significance for determining the direction of oil and gas exploration in the deep strata of the Tarim Basin. Comprehensive analysis suggests that the Tazhong region is the most favorable zone, and the Kalpin-Bachu region is the optimal potential zone for exploring sub-salt oil and gas in deep Cambrian strata.  相似文献   

10.
Isotopic ages of synsedimentary clay minerals were directly determined with the ultrasonicscattering-settlement separation-K-Ar dilution technique. The apparent age of black mudstoneis 123 Ma for the Quantou Formation, 111.9-89.0 Ma for the Qingshankou Formation and77.6-76.8 Ma for the upper part of the Nenjiang Formation. The Rb-Sr isochrone age of themuddy limestone-mudstone sequence of the lower part of the Nenjiang Formation is 81 Ma andthat of the muddy evaporite of the middle part of the Quantou Formation is 122.2 Ma. On thebasis of the above isotopic ages, the authors propose a modified scheme of stratigraphic classifi-cation of the Cretaceous of the Songliao basin.  相似文献   

11.
松辽盆地上白垩统青山口组主要由深湖相黑色泥岩、页岩组成,是大庆油田最重要的烃源岩之一,但长期以来对其年代学框架存在很大争议。对松辽盆地"松科1井"南井(茂206井)自然伽马测井和密度测井数据进行小波分析和连续滑动窗口频谱分析,表明茂206井青山口组记录了稳定的Milankovitch旋回。由长、短偏心率、地轴斜率和岁差周期造成的地层旋回厚度分别为39、13.5~9、5~3.8和2.5~1.7m。茂206井青山口组沉积速率变化不大,平均沉积速率为9.63cm/ka,沉积时限为5.16Ma。通过对长、短偏心率周期进行高斯带通滤波,建立了茂206井青山口组的"浮动"天文年代标尺。青山口组共记录了12.7个长偏心率周期和47.7个短偏心率周期。确定出青山口组1段下部油页岩层段对应的古湖泊缺氧事件(LAE1)持续时间约为250ka,与白垩纪Cenomanian-Turonian时期第二次大洋缺氧事件(OAE2)的持续时间接近。青山口组天文年代标尺的确立为约束青山口组沉积期各种地质事件的持续时间提供了年代学依据。  相似文献   

12.
杨雪  柳波  张金川  霍志鹏 《沉积学报》2019,37(4):661-673
松辽盆地青山口组湖相深水细粒沉积岩厚度大,具有巨大的非常规油气勘探潜力。利用小波变化和频谱分析方法,对研究区取芯井青一段地层的大段深水细粒沉积岩进行米兰科维奇旋回划分,并通过地球化学、全岩矿物等参数分析古沉积环境,将古环境的沉积响应与所划分的旋回进行对应分析,建立受控于米兰科维奇旋回的地层响应特征。研究表明,青一段地层中共识别出四级米氏旋回,分别为68个米级旋回、25个Ⅴ级旋回、6个IV级旋回以及1个Ⅲ级旋回界面,地层沉积主要受控于128 ka短偏心率和48 ka斜率旋回。青一段沉积环境整体上具有气候由干到湿,水体加深、还原性增强、盐度降低的旋回变化特征,6种环境组合表明了厚层泥页岩岩相与沉积环境之间的对应关系,其中暖湿气候控制的层状灰质泥岩有利于油页岩层发育。因此利用米氏旋回细分深水细粒沉积层,有望对页岩油气勘探获得突破。  相似文献   

13.
显生宙沉积旋回会受到地球轨道参数偏心率、地轴斜率和岁差的周期性变化(米兰科维奇旋回)的控制,但目前对前寒武系的相关研究较为薄弱。天津蓟县剖面中元古界洪水庄组-铁岭组为一套潟湖-潮坪相沉积,主要呈砂岩-页岩互层的韵律性产出。为探索这种岩性韵律是否与轨道旋回有关,对其进行了高分辨率的岩性刻画,并以磁化率和伽马能谱数据作为古气候-古环境替代性指标,通过频谱分析等方法进行旋回地层学分析。结果表明各指标均记录了完整的米兰科维奇旋回。铁岭组一段下部由短偏心率、斜率和岁差控制的地层旋回厚度分别为1.2~1.5 m、0.4 m和0.17~0.19 m,其中0.1 m的半岁差周期也较明显;洪水庄组二段顶部由长偏心率、短偏心率、斜率和岁差控制的地层旋回厚度分别为1.1~1.8 m、0.34~0.54 m、0.14~0.16 m和0.08~0.09 m。以识别出的稳定长偏心率周期405 ka旋回对洪水庄组进行了天文年代校准,并估计出当时的短偏心率、斜率以及岁差周期分别为100 ka、22~24 ka和15 ka。在洪水庄组中记录的偏心率振幅变化周期为~2 Ma,比现今~2.4 Ma的周期略短。  相似文献   

14.
华南上奥陶统宝塔组天文年代格架及其地质意义   总被引：1，自引：0，他引：1  
对华南四川盆地及周缘地区的四川省南江县桥亭剖面、重庆市南川区三泉剖面和贵州省习水县良村剖面上奥陶统宝塔组高分辨率磁化率(MS)数据进行了旋回地层学分析,识别出405 ka长偏心率、100 ka短偏心率、30 ka斜率和20 ka岁差沉积旋回,其中偏心率和岁差旋回信号最强。利用405 ka长偏心率旋回进行天文调谐后得出三条剖面宝塔组的沉积时限分别为4.17 Ma、5.64 Ma和5.05 Ma,平均沉积速率分别为7.67 m·Ma-1、4.68 m·Ma-1 和6.37 m·Ma-1,呈现出从北往南沉积时限变长,沉积速率变小的趋势,指示了北部接受沉积时间要比南部更晚,海侵从南向北推进。良村剖面宝塔组中所产牙形石Hamarodus brevirameus带和Protopanderodus insculptus带的延续时限分别为3.62 Ma和1.43 Ma;桥亭剖面三叶虫Niuchangella angustilimbata间隔带、Dislobosaspis xixiangensis延限带和未建带的延续时限分别是2.83 Ma、0.41 Ma和0.81 Ma。  相似文献   

15.
松辽盆地科学钻探工程松科二井获取了白垩纪陆相沉积资料, 其中连续、多参数、高分辨率的地球物理测井资料为研究松辽盆地地层的沉积速率变化规律提供了机会。本文利用GR、Th、K、Th/K多种测井数据, 采用天文旋回的方法来计算松科二井登娄库组地层的沉积速率, 并探讨影响地层沉积的主控因素。多种测井数据的频谱分析结果表明了登娄库组地层记录着米兰科维奇旋回信息, 这说明登娄库组沉积过程受天文轨道驱动力影响。Th测井数据对天文旋回信息的敏感性强, 综合考虑多种测井数据的测试结果获得了连续、相对准确的地层沉积速率。登娄库组地层沉积速率从下往上整体呈现为由高到低的趋势。 登二段至登三段时期地层沉积主要受盆地断陷活动控制, 地层整体具有高沉积速率特征, 最高达到 16.2 cm/ka。随后至登四段时期由于断陷活动逐渐减弱, 盆地向区域坳陷的构造格局转化, 登四段整体具有沉积速率较低的特征, 最低为5.9 cm/ka。该研究建立了松科二井登娄库组地层连续的沉积速率剖面, 为揭示松辽盆地由断陷活动过渡到坳陷活动的地质规律提供了测井证据。  相似文献   

16.
松辽盆地东岭地区泉头组高频沉积旋回的叠加型式分析   总被引：1，自引：1，他引：0  
根据自然伽马测井曲线计算的旋回厚度,采用Fischer图解识别高频旋回的叠加型式,试图揭示湖相沉积中GR测井曲线反映的泥质含量波动与气候旋回的关系。选择松辽盆地东岭地区顶底清楚,地层连续的SN109井泉头组测井曲线中作为实验数据,根据极值点法共识别出1166个高频沉积旋回,旋回厚度变化于0.25~2.75 m之间,旋回平均厚度为0.62 m;根据Fischer图解,估算高频旋回的平均周期为17.2 ka,中频旋回周期在86.1~103.3 ka之间,低频旋回周期在305~416 ka之间,分别与米兰科维奇旋回岁差周期19~24 ka,轴斜率周期85~140 ka,偏心率周期350~400 ka存在着对应关系,说明SN109井泉头组湖相沉积旋回的形成受米兰科维奇气候旋回机制的控制。  相似文献   

17.
松辽盆地是我国东北地区一个大型的晚中生代含油气沉积盆地。在盆地发育早期阶段受强烈伸展作用影响形成了大规模的断陷和大量的火山活动。本文以松辽盆地北部徐家围子断陷区火山岩的年代学研究为切入点,通过对徐家围子断陷升深更2井和徐深9-2井营城组(K_1y)火山岩的岩芯样品进行SHRIMP U-Pb定年,获得了营城组火山岩年龄为114～112 Ma,并认为该年龄结果代表了松辽盆地区域晚中生代岩浆作用的上限时间。通过对松辽盆地及邻区的火山年代学的对比发现:中国东北地区晚中生代曾发生过多期的岩浆事件,时间分别为:166～150 Ma;140～130 Ma;130～120 Ma;114～109 Ma。松辽盆地内早白垩世营城组火山岩年龄与我国东北地区中生代最后一期岩浆作用时间一致,指示了东北地区中生代最后一期岩浆事件年龄。松辽盆地营城组火山岩年龄的厘定将为本区中生代岩石圈减薄的上限时间提供进一步可靠的年代学约束。  相似文献   

18.
选择黔西地区盘1井、威宁1井、纳雍1井和织金1井,对长兴组自然伽马测井数据进行频谱分析,识别出其中的米兰科维奇周期,并采用滤波手段提取出其中的稳定周期,进行连井对比。结果表明频谱峰值与米兰科维奇周期存在良好的对应关系,研究区长兴组地层中保存着123. 0 ka的偏心率周期、45. 0 ka和35. 6 ka的斜率周期、21. 2 ka和17. 7 ka的岁差周期,各级周期的旋回厚度分别为4. 59~5. 73 m、1. 37~2. 15 m和0. 66~0. 98 m;各井的短偏心率旋回曲线显示研究区长兴组地层记录了约18个短偏心率旋回,据此估计出长兴组沉积时限约为2. 21 Ma;通过短偏心率旋回层和所计算沉积速率的连井对比,发现地层中海相标志岩层段等时性对比效果明显,反映了区域快速海侵的过程,而沉积速率的变化可能受到了海平面变化和物源供应的共同影响。  相似文献   

19.
松辽盆地是我国东北地区一个大型的晚中生代含油气沉积盆地。在盆地发育早期阶段受强烈伸展作用影响形成了大规模的断陷和大量的火山活动。本文以松辽盆地北部徐家围子断陷区火山岩的年代学研究为切入点,通过对徐家围子断陷升深更2井和徐深9 2井营城组（K1y）火山岩的岩芯样品进行SHRIMP U Pb定年,获得了营城组火山岩年龄为114～112Ma,并认为该年龄结果代表了松辽盆地区域晚中生代岩浆作用的上限时间。通过对松辽盆地及邻区的火山年代学的对比发现：中国东北地区晚中生代曾发生过多期的岩浆事件,时间分别为： 166～150 Ma; 140～130 Ma; 130～120 Ma; 114～109 Ma。松辽盆地内早白垩世营城组火山岩年龄与我国东北地区中生代最后一期岩浆作用时间一致,指示了东北地区中生代最后一期岩浆事件年龄。松辽盆地营城组火山岩年龄的厘定将为本区中生代岩石圈减薄的上限时间提供进一步可靠的年代学约束。  相似文献   

20.
火山地层常具穿时和倒转现象,并且缺少化石资料,致使其地层序列划分和对比困难.营城组火山地层序列是松辽盆地火山岩油气勘探的基础和关键,火山岩中的厚层沉积夹层（营城组二段）在火山地层序列划分中可作为标志层,是营城组进一步分段的关键层位.从盆缘露头剖面入手,根据实测剖面、钻井、测井、地震、同位素年龄等资料,证实徐家围子断陷存在营二段地层,通过地层对比,总结其地层发育时限、岩性及序列特征、地层分布规律及其成因、地球物理识别标志,并将其作为标志层对火山地层进行准确划分和对比.结果显示:营二段形成于早白垩世Albian期（110~108 Ma）,沉积时限2~3 Ma;以富含凝灰质夹煤层为主要特征,其碎屑粒度自下至上呈现"粗-细-粗"的全韵律;断陷内营二段地层厚度变化大,平面上存在着两类沉积中心:（1）与营一段火山岩最大厚度中心重叠的火山期后热沉降中心;（2）继承性古地貌凹陷.不同成因地层其地球物理识别特征不同.以营二段为标志层可将徐家围子断陷营城组分为3段,其中一段和三段均以火山岩为主.而原分层中的营四段实属盆地不同充填期的两套地层:下部细粒砂泥岩段应为断陷期的营二段,上部粗粒砂砾岩段应为拗陷期的登娄库组一段.该方法可为其他地区火山地层划分与对比提供借鉴.   相似文献   

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