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1.
The composition and genesis of the cyclic sequence of Upper Cretaceous sediments near the town of Volsk (Saratov Region) were first investigated using a series of analytical methods. The results were statistically processed using methods of manual counting, as well as spectral and wavelet analyses. Elementary formation cyclites and cyclic variations in several parameters are correlated with astronomo-climatic Milankovitch cycles.  相似文献   

2.
For paleogeographic reconstruction of the West Siberian basin during the Cretaceous we used a set of paleogeographic maps, which were compiled for the main epochs of the Cretaceous period. The paleogeographic maps presented in this study suggest progradational filling of the deep basin with avalanche-type sedimentation during Volgian-Barremian regression. The paleorelief and provenance of terrigenous sediments were reconstructed.  相似文献   

3.
苏新  郭宪璞  丁孝忠 《现代地质》2003,17(4):370-377
库车前陆盆地是中国大型油气基地之一,盆地中的白垩系及古近系为盆地油气的主要储层。对本区白垩系的时代划分和沉积环境的精确确定直接关系到对油气田的规模、储量和分布范围的正确评价。本研究在前人划分为陆相下白垩统巴什基奇克组的顶部首次发现了由10属15种组成的晚白垩世海相钙质超微化石组合Arkangelskiellacymbiformis—Quadrumgartneri。此外,在由前人定为古新统—始新统的塔拉克组下段也发现了晚白垩世Arkangel skiellacymbiformis—Quadrumgartneri组合,在该组上段发现了古新世化石Biantholithussparsus。该成果既为准确确定这两个岩组的地质时代提供了可靠的古生物证据,又为本区存在晚白垩世地层和海相沉积提供了佐证,表明巴什基奇克组顶部存在晚白垩世的海相沉积,塔拉克组下段属于上白垩统,上段属于古新统。  相似文献   

4.
In the present study, over 3000?m of Upper Cretaceous sediments (Tarbur Formation) in seven stratigraphic, columnar sections were studied. The area is located in the Zagros mountain ranges of southwestern Iran, attributed to the converging continental Arabian Shield, and is interpreted as the result of subduction and collision. Based on foraminiferal studies of the Tarbur Formation in the sections, we have established many new biozones in the stratigraphic sections. However, investigations of the biozones indicate that there is no lithostratigraphic variation between the Upper Cretaceous and Lower Paleocene sediments in some of the studied sections. The concept of widespread formations and lithologic correlations is not applicable in this area, probably as a result of the tectonic unrest at that time. The biostratigraphic boundary between the Cretaceous and the Lower Paleocene is nevertheless well defined by the intraformational boundary in the sections.  相似文献   

5.
The development of the Yugoslavian, Albanian, and Italian segments of the Mediterranean geosyncline is compared, using the province of Montenegro as the standard for correlation of the paleogeographic analysis during the Alpine tectonic cycle. The tectonic zones, characteristic of the Montenegro area are four in number and given as the Maritime zone with rocks ranging from Upper Carboniferous to Oligocene; the old Montenegro zone consisting of Triassic, Jurassic, Cretaceous and upper Oligocene sediments; the Ku?a zone deposits ranging from Upper Permian through Mesozoic; and the Durmitor zone with Devonian, Carboniferous, Permian, Triassic, and Jurassic sedimentary and volcanic-sedimentary bodies and Upper Cretaceous flysch.—IGR Staff.  相似文献   

6.
Spectrogram analysis of seven natural gamma-ray logging of Member 1 of the Qingshankou Formation (K2qn1) and Member 1 and 2 of the Nenjiang Formation (K2n1-2) of Late Cretaceous age in the Songliao Basin reveals sedimentary cyclicities controlled by Milankovitch climate periodicities. The recognition of Milankovitch cycles allows estimation of an average accumulation rate of ~7.55–8.62 cm/ka for the K2qn1 sections, and ~6.69–10.16 cm/ka for the K2n1-2 sections. Two marine transgression events occurred during the deposition of K2qn1 and K2n1-2 and their ages are at ~0.74–1.10 Ma and ~2.38–4.84 Ma, respectively. Identification of Milankovitch cycles from fine-grained deep lake sedimentary rocks in the Songliao Basin may provide great potential for high-resolution stratigraphic subdivisions and correlations.  相似文献   

7.
A dense grid of multichannel high-resolution seismic sections from the Bay of Kiel in the western Baltic Sea has been interpreted in order to reveal the Mesozoic and Cenozoic geological evolution of the northern part of the North German Basin. The overall geological evolution of the study area can be separated into four distinct periods. During the Triassic and the Early Jurassic, E–W extension and the deposition of clastic sediments initiated the movement of the underlying Zechstein evaporites. The deposition ceased during the Middle Jurassic, when the entire area was uplifted as a result of the Mid North Sea Doming. The uplift resulted in a pronounced erosion of Upper Triassic and Lower Jurassic strata. This event is marked by a clear angular unconformity on all the seismic sections. The region remained an area of non-deposition until the end of the Early Cretaceous, when the sedimentation resumed in the area. Throughout the Late Cretaceous the sedimentation took place under tectonic quiescence. Reactivated salt movement is observed at the Cretaceous Cenozoic transition as a result of the change from an extensional to compressional regional stress field. The vertical salt movement influenced the Cenozoic sedimentation and resulted in thin-skinned faulting.  相似文献   

8.
陆相红层因为其含古生物化石稀少给高精度生物、年代地层的对比带来了较大的困难。旋回地层学可以将地层与地时结合起来,解决地层沉积的时限问题。基于前人在对胶莱盆地K/Pg界线识别的基础上,主要利用了一维连续小波变换尺度分析法与频谱分析法对胶莱盆地胶州组K/Pg界线之下、晚白垩世红土崖组玄武岩夹层之上的陆相红层进行旋回地层分析,认为胶莱盆地晚白垩世的陆相红层中保存有米兰科维奇旋回,岁差、斜率和偏心率各个周期在不同的层段响应程度略有不同。根据旋回识别结果及K/Pg界线建立了“浮动天文年代标尺”,推测在66~67.77 Ma期间,胶莱盆地陆相红层的平均沉积速率约为5.15 cm/kyr,胶州地区［（67.77~73）±0.3］ Ma期间为玄武岩岩浆冷凝固结形成玄武岩进而遭受风化剥蚀及构造沉降的时期,红土崖组与胶州组的时间界线约为67.28 Ma,红土崖组玄武岩夹层的年龄应早于67.77 Ma。  相似文献   

9.
Geologic and paleogeographic settings of the Upper Jurassic, Cretaceous, and Paleogene phosphorite-bearing rocks in the Kaliningrad and southeastern Baltic regions are considered. The paper discusses structures of the phosphorite-bearing sections, outlines phosphorite types, and compares them with the adjacent regions and phosphorite-bearing basins of the East European Platform. It is noted that the age of Meso-Cenozoic phosphorite-bearing horizons in the Kaliningrad and southeastern Baltic regions are similar or akin to the age of phosphorite-bearing horizons in other regions of the East European Platform. The age also matches that of ancient weathering crusts in provenances. Data on the composition of rare and rare earth elements in phosphorites from the northwestern basins of the East European Platform are used to estimate the role of igneous rocks, in particular, alkaline mafic-ultramafic rocks of Karelia that delivered phosphorus to sedimentation basins.  相似文献   

10.
米兰柯维奇韵律层及其年代地层意义   总被引：22，自引：4，他引：22  
吴智勇 《地层学杂志》1995,19(2):156-160
本文简要介绍了米兰柯维奇轨道三要素（岁差、黄赤交角及偏心率）及其变化周期，并对因轨道要素的变化引起的韵律沉积层的研究现状进行了综述，由于气候变化的全球性以及轨道参数的相对稳定性，本文认为，米兰柯维奇韵律层可以作为盆际，盆内地层对比的重要辅助手段，并可用来测定地层单元的延续时间，实际应用结果表明，其精度要高于现行的生物地层学对比及同位素测龄法。  相似文献   

11.
Problems of geochronological correlation are considered for the formations established in the study region with due account for data on the Mezino-Lapshinovka, Lokh and Teplovka sections studied earlier on the northwest of the Saratov region. New paleontological data are used to define more precisely stratigraphic ranges of some stratigraphic subdivisions, to consider correlation between standard and local zones established for different groups of fossils, and to suggest how the Upper Cretaceous regional scale of the East European platform can be improved. Considered in addition are paleogeographic environments in the study region during the Late Cretaceous epoch and principal stages of the regional geological evolution.  相似文献   

12.
The early Jurassic-Early Cretaceous tectonic environments were reconstructed for the first time on the basis of the study of sandstones from the Soloni-Urgal interfluve (Bureya sedimentary basin, Far East). The mineralogical-petrographic and lithochemical studies revealed that the sandstones are mostly quartz-feldspathic and feldspathic graywackes of acid composition with less common litites, graywacke arkoses, and arkoses. It was shown that the Lower-Middle Jurassic sediments were formed in active continental margin and continental volcanic arc settings, while the Upper Jurassic-Lower Cretaceous sediments were accumulated in a passive continental margin setting. Orogenic events in the Toarcian-Aalenian, Late Bajocian, and Late Oxfordian-Kimmeridgian led to sedimentation gaps.  相似文献   

13.
The Upper Cretaceous-Eocene Purilactis Group of the north Chilean Precordillera consists of over 4100 meters of continental strata deposited in a retro-arc extensional basin. Deposited in an arid/semi-arid climate with no marine influence, the group comprises alluvial fan (51%), playa (35%), aeolian (8%), and lacustrine (6%) facies associations locally interbedded with volcaniclastic material. The basin-fill has an overall coarsening-upward profile and shows an increase in proximal fan facies up section, indicating basinward (eastward) fan progradation. Within the coarsening-upward profile, fan and playa facies are organized into: 1) large-scale (50–700 m thick) coarsening- (CU) and fining- (FU) upward cycles extending tens of kilometers, in which CU cycles represent tectonically induced (allocyclic) fan progradation during periods of decreased accomodation space (FU cycles reflect vertical aggradation and fan retreat during periods of increased accomodation space); 2) medium-scale cycles (15–50 m thick) extending up to 9 km, also representing tectonically induced fan progradation and retreat but superimposed on the larger scale cycles; and 3) small-scale, predominantly FU cycles (up to 15 m thick) extending only a few hundred meters and reflecting minor, autocyclically induced changes in sedimentation. Purilactis Group sediments were derived from a westerly (footwall) source of: 1) Upper Triassic to Lower Cretaceous sediments and volcanics (back-arc basin-fill), and 2) an andesite-dominated Upper Cretaceous volcanic arc sequence, unroofing of which is indicated by a systematic provenance change in the upper 500 meters of the group from dominantly andesitic to granodioritic detritus. Localized development of volcaniclastics in the uppermost part of the group — together with evidence of arc unroofing — indicates that arc activity, although synchronous, did not contribute significantly to the overall Purilactis basin-fill. Basin subsidence may have been influenced by thermal contraction related to cooling of the Late Cretaceous arc and/or isostatic uplift following arc unroofing, processes likely to result in relatively localized extension. A larger scale cause of extension may have resulted from the relatively slow convergence rates along the Andean margin during Late Cretaceous to Eocene times (< 55 mm/yr), which would have promoted subduction roll-back and, together with the slab pull force active at the subduction zone, resulted in the development of an extensional tectonic regime across the Andean margin.  相似文献   

14.
周期性潮积岩及其研究意义   总被引：2，自引：0，他引：2  
回顾了最近十余年来国外对周期性潮汐沉积物，特别是潮汐韵律层的研究进展，系统介绍了几种从古代沉积物中识别出来的潮汐周期，包括基本潮汐（半日潮，全日潮和混合潮），大一小潮周期以及一些长周期波动等。最后，对潮汐韵律层在推测地史时期地－月系的演化历史及计算短期沉积速率中的意义作了评述。  相似文献   

15.
This paper deals with the tectonic and paleogeographic relations of two main internal zones of the Western Alps: The Briançonnais zone (“geanticline”, with thin sedimentation during Jurassic and Cretaceous times), and the still more internal Piemont zone (“eugeosyncline”, with Mesozoic-Post-Triassic-“Schistes lustrés” and Ophiolites). From structural, and especially stratigraphic and paleontological proofs, it can be concluded that, the Schistes-lustrés-complex (with or without his fossiliferous triassic-liassic basis) is thrusted over the Briançonnais zone; intermediate tectonic units are known; they belong to the intermediate paleogeographic Acclegio zone having undergone intensive Post-Triassic erosion; thus Upper Jurassic and Cretaceous limestones and breccias are transgressive upon the Lower Triassic and Paleozoic basement rocks. This Acceglio zone can be linked with the upper portion of a “Prepiemontese Flexure” parting the Briançonnais geanticline and the Piemont geosyncline. At the lower part of this flexure, no erosion occured, but breccias and microbreccias are interbedded in Post-Triassic “Prepiemontese” sediments (“Schistes lustrés” facies but no ophiolites) belonging to the “Gondran zone” (an external portion of the Piemont zone with triassic dolomites followed by fossiliferous rhaetic an liassic beds). The ophiolite-bearing Schistes lustrés often lie conformably upon the sediments of this Gondran zone, but the contact is not definitely a stratigraphic one: More field research is necessary to decide if these ophiolites and Schistes lustrés really are the stratigraphc continuation (upper jurassic and lower cretaceous?) of the triassic-liassic (and meso-Jurassic?) sequence of the Gondran zone, or if they belong to an independant tectonic unit, coming from some internal zone.  相似文献   

16.
Upper Cretaceous and Cenozoic formations of the western Transbaikal and southeastern Baikal regions are considered. Molasses and molassoids (molasse-type sediments) were included into these formations in previous works. In our opinion, the following formations are developed in these regions: plain fan formation divided into the terrigenous (Upper Cretaceous) and coaliferous (Upper Oligocene-Lower Pliocene) subformations; plain fine-clastic formation (Paleogene, except the Upper Oligocene); and orogenic molasse formation (Upper Pliocene-Holocene) divided into the lower red-colored and upper gray-colored subformations. Main textural features of these formations are considered. Paleogeographic and paleotectonic settings of their accumulation are reconstructed. It is shown that coarse-clastic sediments of fan formations accumulated in grabens among ancient denudation plains due to the destruction of rocks in near-wall benches. These plains probably hosted in some areas remnants of the mountainous relief. Origination and development of the Baikal rift zone was the main geological event in the Baikal region during the Late Cretaceous and Cenozoic. Based on study of the southeastern Baikal region with the thickest and most representative Cenozoic sections, the prerifting and rifting stages of this zone and correlative events in the adjacent (relatively stable) areas of the western Transbaikal region are characterized.  相似文献   

17.
上二叠统记录了地质历史时期最大规模的生物灭绝事件和最深刻的环境变化。对上二叠统的层序地层格架进行精细 描绘，建立高分辨率的地层序列，是深入了解此次事件及其演化的基础和关键。基于钻测井、岩心观测及地球化学分析测 试结果等资料综合分析，并运用小波分析技术，对黔西盘县上二叠统煤系进行了米氏旋回的识别和划分，结果表明，研究 区上二叠统煤系记录了稳定的米兰科维奇旋回，天文轨道周期对其沉积过程具有明显影响，由长、短偏心率、地轴斜率和 岁差周期引起的地层旋回厚度分别为16.06~17.24 m、5.39~5.70 m、2.11~2.15 m、1.12~1.21 m，长偏心率周期对地层中沉积 旋回的控制和影响最强。对长、短偏心率周期进行滤波分析后，建立了上二叠统煤系“浮动”天文年代标尺，为约束同沉 积火山事件层（Tonstein） 的形成及其持续时限提供了年代学依据。以区域等时对比效果明显的长偏心率旋回为标尺，并结 合旋回沉积序列、旋回界面特征等，将上二叠统煤系划分为4个三级层序，并进一步划分为16个四级层序（对应于中期旋 回），建立了研究区高频层序地层格架。  相似文献   

18.
The analysis of Upper Jurassic and Lower Cretaceous marine sections developed in surrounding structures of the Laptev Sea revealed that all of them are composed of terrigenous rocks, which enclose abundant concretions cemented by calcareous material. The Upper Jurassic portion of the section is the most variable in thickness and stratigraphic range of sediments usually including hiatuses. Its Lower Cretaceous part represented by the Boreal Berriasian (=Ryazanian) and lower Valanginian stages is most complete. The Upper Jurassic and Lower Cretaceous sections are usually composed of fine-grained rocks (clays and mudstones) in the west and coarser cemented varieties (siltstones and sandstones) with rare mudstone intercalations in the east. Practically all the investigated Upper Jurassic and Lower Cretaceous sections include readily recognizable age and facies analogs of the Bazhenovo Formation and Achimov sandstones, which are petroliferous in West Siberia. There are grounds to assume the occurrence of these formations also on the Laptev Sea shelf, which is confirmed by seismic records. Conditions favorable for the formation of potential hydrocarbon reservoirs could exist in the western part of the paleobasin along the Nordvik Peninsula coast and northeastern Tamyr Peninsula margin. Paleotectonic reconstructions presented in this work are well consistent with stratigraphic conclusions.  相似文献   

19.
《China Geology》2021,4(2):274-287
As cyclical orbital movements of Earth, Milankovitch cycles can be recorded in sedimentary strata. The time they reflect can be used to accurately divide and compare strata. Milankovitch cycles recorded in strata enrich the stratigraphic theory, especially the theories of cycle stratigraphy, and thus they are widely used in geological survey engineering nowadays. This study explored the characteristics of the Milankovitch cycles recorded in the eastern depression of the North Yellow Sea Basin, highlighting their control over high-frequency stratigraphic sequences. The Eocene Milankovitch cycles in the depression were calculated based on the method proposed by J. Laskar, and their parameters primarily include eccentricity cycles of 125 ka and 99 ka, obliquity cycles of 51 ka and 39 ka, and precession cycles of 23 ka and 19 ka. Spectral analysis of gamma-ray (GR) and spontaneous potential (SP) log curves of the Eocene strata was carried out to divide and compare stratigraphic sequences, revealing that the spectral peaks correspond well to astronomical cycles. This indicates that the strata in the depression fully record Milankovitch cycles. Furthermore, there are long-, medium-, and short-term stratigraphic cycles in the eastern depression, with a thickness of 13.03–15.89 m, 3.70–5.21 m, and 2.17–2.94 m, respectively. The sedimentation rates of the Eocene strata were calculated to be 121.2–127.12 m/Ma accordingly. From the uplift to the center of the lacustrine basin along the slope in the eastern depression, both the sedimentation duration and the sediment thickness increase, while the sedimentation rate remains relatively stable. The Eocene strata can be divided into six stages of high-frequency sequences by continuous wavelet transformation, namely E6–E1 from bottom to top. The sedimentation duration and sedimentation rates of the sequences were calculated using spectral analysis with each of the sequences as a separate window. Moreover, the impacts of climate change on the sedimentary environment in the eastern depression were analyzed. It can be concluded that E6 was a lowstand system tract, E5 and E4 were lacustrine expansion system tracts, E3 was a highstand system tract, and E2 and E1 were lacustrine contraction system tracts. All these verify that Milankovitch cycles serve as an effective approach for the analysis of sedimentary cycles.  相似文献   

20.
上二叠统记录了地质历史时期最大规模的生物灭绝事件和最深刻的环境变化。对上二叠统的层序地层格架进行精细 描绘,建立高分辨率的地层序列,是深入了解此次事件及其演化的基础和关键。基于钻测井、岩心观测及地球化学分析测 试结果等资料综合分析,并运用小波分析技术,对黔西盘县上二叠统煤系进行了米氏旋回的识别和划分,结果表明,研究 区上二叠统煤系记录了稳定的米兰科维奇旋回,天文轨道周期对其沉积过程具有明显影响,由长、短偏心率、地轴斜率和 岁差周期引起的地层旋回厚度分别为16.06~17.24 m、5.39~5.70 m、2.11~2.15 m、1.12~1.21 m,长偏心率周期对地层中沉积 旋回的控制和影响最强。对长、短偏心率周期进行滤波分析后,建立了上二叠统煤系“浮动”天文年代标尺,为约束同沉 积火山事件层（Tonstein） 的形成及其持续时限提供了年代学依据。以区域等时对比效果明显的长偏心率旋回为标尺,并结 合旋回沉积序列、旋回界面特征等,将上二叠统煤系划分为4个三级层序,并进一步划分为16个四级层序（对应于中期旋 回）,建立了研究区高频层序地层格架。  相似文献   

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