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1.
松辽盆地上白垩统青山口组一段富有机质泥页岩岩发育,层系内部滞留烃富集,具有可观的页岩油资源潜力。沉积古环境控制了泥页岩的分布、有机质发育特征及滞留烃富集程度。因此,恢复青一段泥页岩沉积古环境,明确沉积特征,对揭示青一段泥页岩中页岩油富集规律具有重要意义。本文基于长岭凹陷乾安地区青一段取心井——吉页油1井的岩心观察及测井曲线组合特征,划分了青一段泥页岩沉积微相,应用自然伽马能谱测井、岩性扫描测井数据,选取环境评价参数,对青一段沉积古环境及其演化过程进行了恢复,分析了古环境参数与泥页岩中滞留烃含量的相关性。结果表明:松辽盆地长岭凹陷乾安地区青一段泥页岩是在三角洲外前缘-浅湖-半深湖-深湖沉积体系中形成的,主要发育半深湖-深湖泥、浅湖泥沉积微相。青一段泥页岩沉积古环境经历了水深由浅变深,气候由半潮湿到潮湿,水体由淡水-微咸水,还原性由弱到强,水动力条件由中等到弱的演化,在青一段地层中存在明显的沉积环境变化界面,上下层段沉积环境不同。青一段泥页岩中滞留烃含量主要受沉积古气候、古氧化还原条件控制,潮湿气候还原条件下形成的泥页岩有机质类型好,以腐泥质为主,生油能力强,滞留烃含量高。  相似文献   

2.
The Upper Cretaceous Qingshankou Formation (K2qn) and Nenjiang Formation (K2n) in the Songliao Basin (SLB), China, contain discrete ostracod-bearing deposits. The ostracod-bearing layers range in thickness from 5 to 380 cm. Based on integrated analysis of seismic, drilling, core and logging data, the sedimentary characteristics, distribution patterns and hydrocarbon implications of the ostracod-bearing beds have been studied. Compared with mudstone and sandstone in lacustrine settings, ostracod-bearing beds have distinctive characteristics in terms of seismic response and logging features. Three types of depositional pattern of ostracod-bearing beds are recognised in different facies: mixed siliciclastic–ostracod deposits in the delta front, sheeted ostracod deposits, and dotted ostracod deposits in shallow or semi-deep lacustrine settings. In plan view, ostracod-bearing beds mainly occur in the Daqing area, the Longhupao–Honggang terraces and the Heidimiao depression, and are relatively less developed in the east of the SLB. Shallow and semi-deep lacustrine settings were favourable environments for the survival of ostracods. In the stratigraphic succession, ostracod-bearing beds mainly occur in the upper K2qn1, K2qn2, lower K2qn3 and K2n1 units. High-frequency sequence cycles controlled ostracod reproduction and death, and mass mortalities of ostracods commonly occurred during periods in which the lake base-level fell, leading to water shallowing, increasing salinity and sand intrusion into the shore-shallow lakes. Ostracod mortality was not associated with expansion of the lake area, marine transgression or volcanic eruptions. The ostracod-bearing beds were widely formed in shallow and semi-deep lacustrine settings in the SLB. Tight oil/gas reservoirs can be developed in thick ostracod-bearing beds. In addition, areas containing ostracod can be regarded as sweet spots for mud or shale oil/gas exploration, because extensive ostracods can improve the content of brittle minerals in mudstone.  相似文献   

3.
Well‐exposed Mesozoic sections of the Bahama‐like Adriatic Platform along the Dalmatian coast (southern Croatia) reveal the detailed stacking patterns of cyclic facies within the rapidly subsiding Late Jurassic (Tithonian) shallow platform‐interior (over 750 m thick, ca 5–6 Myr duration). Facies within parasequences include dasyclad‐oncoid mudstone‐wackestone‐floatstone and skeletal‐peloid wackestone‐packstone (shallow lagoon), intraclast‐peloid packstone and grainstone (shoal), radial‐ooid grainstone (hypersaline shallow subtidal/intertidal shoals and ponds), lime mudstone (restricted lagoon), fenestral carbonates and microbial laminites (tidal flat). Parasequences in the overall transgressive Lower Tithonian sections are 1–4·5 m thick, and dominated by subtidal facies, some of which are capped by very shallow‐water grainstone‐packstone or restricted lime mudstone; laminated tidal caps become common only towards the interior of the platform. Parasequences in the regressive Upper Tithonian are dominated by peritidal facies with distinctive basal oolite units and well‐developed laminate caps. Maximum water depths of facies within parasequences (estimated from stratigraphic distance of the facies to the base of the tidal flat units capping parasequences) were generally <4 m, and facies show strongly overlapping depth ranges suggesting facies mosaics. Parasequences were formed by precessional (20 kyr) orbital forcing and form parasequence sets of 100 and 400 kyr eccentricity bundles. Parasequences are arranged in third‐order sequences that lack significant bounding disconformities, and are evident on accommodation (Fischer) plots of cumulative departure from average cycle thickness plotted against cycle number or stratigraphic position. Modelling suggests that precessional sea‐level changes were small (several metres) as were eccentricity sea‐level changes (or precessional sea‐level changes modulated by eccentricity), supporting a global, hot greenhouse climate for the Late Jurassic (Tithonian) within the overall ‘cool’ mode of the Middle Jurassic to Early Cretaceous.  相似文献   

4.
松辽盆地构造演化及成盆动力学探讨   总被引：99，自引：25，他引：74  
松辽盆地晚侏罗世以来的构造演化经历了10个阶段:缓慢裂陷和快速坳陷—加速裂陷和快速坳陷—减速裂陷和慢速坳陷—慢速裂陷和快速坳陷—加速裂陷和加速坳陷—减速裂陷和减速坳陷—裂陷、坳陷终止和缓慢反转—快速反转和快速差异坳陷—慢速反转和慢速差异坳陷—反转停止和坳陷终止。构造发育演化的结果形成了“下断中坳上隆顶平”的盆地结构。“中坳”部分沉积的可容纳空间,54%来源于盆地基底的长期伸展坳陷;“上隆”部分沉积的可容纳空间,31%来源于盆地基底的受压坳陷。构造作用的转换起因于东部区域应力场的转变。  相似文献   

5.
The chronology and glass composition of 43 andesitic tephra layers in palaeolake sediments in northern New Zealand provide the basis for a fine‐resolution tephrostratigraphy of the interval 10–70 cal. ka. Their ages are constrained by 14 interbedded, (mostly) well‐dated rhyolitic tephra layers. The andesitic tephra have the potential to subdivide time intervals (1–5 kyr) bracketed by well known rhyolitic layers, including periods of rapid climate change such as the last glacial–interglacial transition and the Younger Dryas. The source of the distal andesitic tephra is identified as Egmont volcano (some 270 km S‐SW) on the basis of glass shard composition. The tephra contain high‐K2O (3–6 wt%) andesitic‐dacitic (SiO2 = 60–73 wt%) glass, with commonly heterogeneous shard populations (2–10 wt% SiO2). Within stratigraphic intervals of < 10 kyr, individual tephra layers can be distinguished on the basis of their SiO2 and K2O contents, and variability in these contents can also be a distinguishing characteristic. The tephra record greatly extends the dated pyroclastic and geochemical record of Egmont volcano, and demonstrates that the volcano has frequently produced widely dispersed tephra over the last 70 kyr at a generally constant rate. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

6.
《Gondwana Research》2014,26(4):1348-1356
The Early Toarcian Oceanic Anoxic Event (OAE) in the Early Jurassic Period is associated with a major negative carbon isotope excursion (CIE), mass extinction, marine transgression and global warming. The Toarcian OAE is thought to have been caused by flood basalt magmatism, and may have been a trigger for mass extinction. However, these proposed causes of the Toarcian OAE and associated biotic crisis are not adequately resolved by a precise chronology. The duration of the Toarcian OAE has been estimated to be anywhere from ~ 0.12 to ~ 0.9 Myr, most recently 0.74 to 3.26 Myr from U–Pb dating. The CIE associated with the Toarcian OAE has a similar pattern at numerous localities, and there is evidence that the marine carbon isotope variations recorded astronomical forcing signals. Here we estimate a duration of ~ 620 kyr for the main negative CIE, ~ 860 kyr for the polymorphum zone and > 1.58 Myr for the levisoni zone based on 405-kyr astronomical eccentricity tuning of the marine section at Peniche (Portugal). This 405-kyr tuned series provides a ~ 2.5 Myr continuous high-resolution chronology through the Early Toarcian. There are 6, or possibly 7 short eccentricity cycles in the main CIE interval at Peniche. To confirm this astronomically based estimate, we analyzed three other sections at Yorkshire (UK), Dotternhausen (Germany), and Valdorbia (Italy) from marine carbon isotopic series. These four stratigraphic sections from Early Jurassic western Tethys record the Toarcian OAE with ~ 6 prominent carbon isotope cycles in the CIE that span a 600 ± 100 kyr duration. The Peniche 405-kyr tuned series indicates that the pre- and post-CIE intervals experienced strong precession–eccentricity-forced climate change, whereas the CIE interval is marked by dominant obliquity forcing. These dramatic and abrupt changes in astronomical response in the carbon isotopes point to fundamental shifting in the Early Toarcian paleoclimate system that was directly linked to the global carbon cycle.  相似文献   

7.
Cross-wavelet transform (XWT) is proposed as a data analysis technique for geological time-series. XWT permits the detection of cross-magnitude, phase differences (= lag time), nonstationarity, and coherency between signals from different paleoclimate records that may exhibit large stratigraphic uncertainties and noise levels. The approach presented herein utilizes a continuous XWT technique with Morlet wavelet as the mother function, allows for variable scaling factors for time and scale sampling, and the automatic extraction of the most significant periodic signals. XWT and cross-spectral analysis is applied on computer generated time-series as well as two independently sampled proxy records (CO2 content approximated from plant cuticles and paleotemperature derived from δ 18O from marine fossil carbonate) of the last 290 Ma. The influence of nonstationarities in the paleoclimate records that are introduced by stratigraphic uncertainties were a particular focus of this study. The XWT outputs of the computer-models indicate that a potential causal relationship can be distorted if different geological time-scale and/or large stratigraphic uncertainties have been used. XWT detect strong cross-amplitudes (∼200 ppm ‰) between the CO2 and δ 18O record in the 20–50 Myr waveband, however, fluctuating phase differences prevent a statistical conclusion on causal relationship at this waveband.  相似文献   

8.
The Upper Permian (Zechstein) slope carbonates in the Roker Formation (Zechstein 2nd‐cycle Carbonate) in North‐east England consist of turbidites interbedded with laminated lime‐mudstone. Studies of turbidite bed thickness and relative proportion of turbidites (percentage turbidites in 20 cm of section) reveal well‐developed cyclicities consisting of thinning‐upward and thickening‐upward packages of turbidite beds. These packages are on four scales, from less than a metre, up to 50 m in thickness. Assuming that the laminae of the hemipelagic background sediment are annual allows the durations of the cycles to be estimated. In addition, counting the number and thickness of turbidite beds in 20 cm of laminated lime‐mudstone, which is approximately equivalent to 1000 years (each lamina is 200 μm), gives the frequencies of the turbidite beds, the average thicknesses and the overall sedimentation rates through the succession for 1000 year time‐slots. Figures obtained are comparable with modern rates of deposition on carbonate slopes. The cyclicity present in the Roker Formation can be shown to include: Milankovitch‐band ca 100 kyr short‐eccentricity, ca 20 kyr precession and ca 10 kyr semi‐precession cycles and sub‐Milankovitch millennial‐scale cycles (0·7 to 4·3 kyr). Eccentricity and precession‐scale cycles are related to ‘highstand‐shedding’ and relative sea‐level change caused by Milankovitch‐band orbital forcing controlling carbonate productivity. The millennial‐scale cycles, which are quasi‐periodic, probably are produced by environmental changes controlled by solar forcing, i.e. variations in solar irradiance, or volcanic activity. Most probable here are fluctuations in carbonate productivity related to aridity–humidity and/or temperature changes. Precession and millennial‐scale cycles are defined most strongly in early transgressive and highstand parts of the larger‐scale short‐eccentricity cycles. The duration of the Roker Formation as a whole can be estimated from the thickness of the laminated lithotype as ca 0·3 Myr.  相似文献   

9.
High resolution(939 samples)total organic carbon content(TOC)analyses were conducted on the Shuanghe Section of^152.6 m in the Changning area,Sichuan Basin.The sampling section was divided into two units considering the distinct-different deposit environment and sediments accumulation rate.The lower part(Unit 1)and the peer part(Unit 2)with high resolution sample spacing(0.08–0.4 m)enables the identification of the precession cycle in two sedimentary sequences with distinct different sedimentary accumulation rate.MTM Power spectral analyses on untuned TOC series reveals significant peaks exceeding above the 95%confidence level and shows that both Unit 1 and Unit 2 have recorded Milankovitch cycles of 405 kyr long eccentricity,short eccentricity,obliquity and precession.The floating astronomical time scale(ATS)was constructed on the Shuanghe Section in the Early Silurian(~439.673–444.681 Ma),and which was calibrated by 405 kyr long eccentricity cycles.The total duration of the Wufeng and Longmaxi shales is 5.01 Myr.The floating ATS used for estimating the duration of the graptolite zones and each stage in the study interval.Finally,we postulated two models that could verify the linkage between orbital cycle and organic accumulation.To make sure whether productivity or preservation is the main factor that under long eccentricity control,the phase correlation between the obtained filtered signal and the theoretical orbital solution should be made clear in the further research.  相似文献   

10.
A group of methyltrimethyltridecyl chromans (MTTCs) was found in core samples of Member 1 (K2n1) and Member 2 (K2n2) of the Nenjiang Formation (Upper Cretaceous) from the SK-l southern borehole (Songliao Basin, China). They are assigned for the first time in sediments older than the Tertiary in China. Their composition and distribution are indicative mainly of the redox and salinity conditions in the depositional environment. The δ-MTTC isomer is in relatively higher abundance in samples from enhanced salinity and reducing conditions, but was not detected in samples from aerobic and low salinity environments, while α-MTTC appears to be present in samples from environments with a broad range of salinity and redox conditions. The α-MTTC/γ-MTTC (α/γ) ratio has a similar indication as that of the α/δ ratio and could be used as a corroborative ratio of paleosalinity. A combination of biomarker parameters suggests that the massive lacustrine petroleum-prone source rocks associated with the K2n1 interval were likely developed under a stratified water column with enhanced salinity and an anoxic bottom water layer, associated with a much less saline (fresh to brackish) upper water layer.  相似文献   

11.
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   

12.
《Sedimentology》2018,65(3):775-808
Fluvial systems in which peat formation occurs are typified by autogenic processes such as river meandering, crevasse splaying and channel avulsion. Nevertheless, autogenic processes cannot satisfactorily explain the repetitive nature and lateral continuity of many coal seams (compacted peats). The fluvial lower Palaeocene Tullock Member of the Fort Union Formation (Western Interior Williston Basin; Montana, USA ) contains lignite rank coal seams that are traceable over distances of several kilometres. This sequence is used to test the hypothesis that peat formation in the fluvial system was controlled by orbitally forced climate change interacting with autogenic processes. Major successions are documented with an average thickness of 6·8 m consisting of ca 6 m thick intervals of channel and overbank deposits overlain by ca 1 m thick coal seam units. These major coal seams locally split and merge. Time‐stratigraphic correlation, using a Cretaceous–Palaeogene boundary event horizon, several distinctive volcanic ash‐fall layers, and the C29r/C29n magnetic polarity reversal, shows consistent lateral recurrence of seven successive major successions along a 10 km wide fence panel perpendicular to east/south‐east palaeo‐flow. The stratigraphic pattern, complemented by stratigraphic age control and cyclostratigraphic tests, suggests that the major peat‐forming phases, resulting in major coal seams, were driven by 100 kyr eccentricity‐related climate cycles. Two distinct conceptual models were developed, both based on the hypothesis that the major peat‐forming phases ended when enhanced seasonal contrast, at times of minimum precession during increasing eccentricity, intensified mire degradation and flooding. In model 1, orbitally forced climate change controls the timing of peat compaction, leading to enhancement of autogenic channel avulsions. In model 2, orbitally forced climate change controls upstream sediment supply and clastic influx determining the persistence of peat‐forming conditions. At the scale of the major successions, model 2 is supported because interfingering channel sandstones do not interrupt lateral continuity of major coal seams.  相似文献   

13.
对松辽盆地东南隆起区嫩江组剖面进行厘米级刻画,分析其为一套深湖相与滨浅湖交互相沉积。在滨浅湖交互相沉积段,水体频繁波动,且波动幅度大。根据颜色、岩性将嫩江组一段地层划分为34个米级旋回,Fischer图解分析将米级旋回归并为11个五级旋回和2个四级旋回。剖面中发育的介形虫灰岩、白云岩结核和火山灰层在松科1井嫩江组一段连续取心中都有响应;剖面和井的Fischer图解对比发现,第15个旋回开始到第25个旋回结束,松辽盆地沉积中心向西北方向迁移,且可能伴随着盆地东缘的抬升运动。  相似文献   

14.
Oil shales were deposited in the Songliao Basin (NE China) during the Upper Cretaceous period, representing excellent hydrocarbon source rocks. High organic matter (OM) contents, a predominance of type-I kerogen, and a low maturity of OM in the oil shales are indicated by bulk geochemical parameters and biomarker data. A major contribution of aquatic organisms and minor inputs from terrigenous land plants to OM input are indicated by n-alkane distribution patterns, composition of steroids, and organic macerals. Strongly reducing bottom water conditions during the deposition of the oil shale sequences are indicated by low pristane/phytane ratios, high C14-aryl-isoprenoid contents, homohopane distribution patterns, and high V/Ni ratios. Enhanced salinity stratification with mesosaline and alkaline bottom waters during deposition of the oil shales are indicated by high gammacerane index values, low MTTC ratios, high β-carotene contents, low TOC/S ratios, and high Sr/Ba ratios. The stratified water column with anoxic conditions in the bottom water enhanced preservation of OM. Moderate input of detrital minerals during the deposition of the oil shale sequences is reflected by titanium concentrations. In this study, environmental conditions in the paleo-lake leading to OM accumulation in the sediments are related to sequence stratigraphy governed by climate and tectonics. The first Member of the Qingshankou Formation (K2qn1) in the Songliao Basin, containing the oil shale sequence, encompasses a third-order sequence that can be divided into three system tracts (transgressive system tract—TST, highstand system tract—HST, and regressive system tract—RST). Enrichment of OM changed from low values during TST-I to high-moderate values during TST-II/III and HST-I/II. Low OM enrichment occurs during RST-I and RST-II. Therefore, the highest enrichment of OM in the sediments is related to stages of mid-late TST and early HST.  相似文献   

15.
A detailed cyclostratigraphy is present in the rhythmically bedded Cenomanian hemipelagic chalks of the northern Anglo-Paris Basin, which can be correlated over 100,000 km2. Individual decimetre-scale couplets probably represent the precession cycle (modes at 18 or 23 kyr), and can be readily grouped in sets averaging five, indicative of the short cycle of eccentricity (100 kyr). A composite cyclostratigraphy for the basin is presented here, and is used as the basis for a Cenomanian time-scale (20 and 100 kyr units). The total duration of the Cenomanian thus obtained (4.4 Myr) compares well with recent radiometric dates of 4.0–4.5 Myr. The time-scale is used to estimate the length of ammonite, inoceramid, and planktonic foraminiferal zones, the rates of formation of authigenic minerals (glauconite), sedimentation rates and the duration of transgressions and anoxic events.  相似文献   

16.
Time series analysis of the Cenomanian through Aptian interval, in well logs from offshore Adriatic boreholes, facilitates a cycle-by-cycle correlation with measured sections of equivalent age in Umbria, central Italy. The cycle-by-cycle match can be demonstrated between filtered spontaneous potential logs and filtered bed thickness data, but is unequivocal only at wavelengths of greater than 10 metres, which are believed to represent a 2 Myr eccentricity signal; at shorter wavelengths tool resolution becomes a limiting factor. As a result of low sedimentation rates the 100, 41, and 21 kyr Milankovitch signals all appear to be aliased to longer wavelengths in the sonic and gamma ray log records and tend to blend with the 400 kyr signal; this is especially true in the Aptian-Albian interval. Attempts to filter and correlate on the bases of these shorter wavelengths were therefore unsuccessful.
Accepting a 2 Myr duration for each cycle permits an estimation of less than 7 Myr to be made for the duration of the Cenomanian Stage.  相似文献   

17.
为精确划分松辽盆地沙河子组层序地层,限定断陷期沙河子组与营城组地层时代,进而研究断陷期盆地的演化,笔者利用松辽盆地大陆科学钻探松科2井获取的下白垩统地层岩芯资料,从岩芯尺度对沙河子组与营城组界面进行揭示,结合过松科2井地震剖面解释、松科2井及邻井测井响应特征分析和岩芯精细描述,总结出沙河子组顶界面在不同尺度的具体特征:(1)在地震剖面尺度,其表现为明显上超的特征;(2)在测井曲线上,界面附近表现为由下到上自然伽马曲线变化幅度增大,双侧向电阻率曲线由低值变为中高值的特征;(3)岩芯尺度上,表现为细粒沉积的砂泥岩突变为砾岩或火山岩。  相似文献   

18.
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19.
Studies on long-chain n-alkan-2-ones from lake sediments remain sparse. In this study, we present an n-alkan-2-one record from Qionghai Lake, southwest China, to assess the paleoclimate significance of variations in their compositions. A homologous series of n-alkan-2-ones ranging from C21 to C35 were identified, with maximum concentrations of the C29 or C31 chain lengths and a strong odd-over-even predominance. This type of n-alkan-2-one is considered to derive mainly from microbial oxidation of the corresponding n-alkanes, and partial inputs from plants. The n-alkan-2-one-derived average chain length (ACL) and carbon preference index (CPI) values changed significantly over the past 28k cal a bp , consistent with the sediment grain size and n-alkane proxies from the same core. Generally, the high CPI27-33-ket and low ACL27-33-ket values indicated cold and dry climates such as for the Last Glacial Maximum (23.2–19.7k cal a bp ), Heinrich 1 event (17.6–15.6k cal a bp ) and Younger Dryas (12.8–11.6k cal a bp ), but low CPI27-33-ket and high ACL27-33-ket values denoted a warm and humid Holocene Climatic Optimum (7.0–4.3k cal a bp ). Therefore, n-alkan-2-ones have great paleoclimatic potential and can be applied together with other biomarkers to reconstruct a reliable paleoclimate record in lake sediments.  相似文献   

20.
Based on the study of magnetostratigraphy, magnetic susceptibility and grain size of Garzê A section on the southeastern margin of the Qinghai-Tibetan Plateau since the late early-Pleistocene, the basal age of Garzê loess is located at ~1.16?MaBP and a series of abrupt paleoclimatic changes is detected. The times of abrupt changes are of distinct series features, and the interval between each two adjacent abrupt changes is ~50 kyr or ~100?kyr. The most significant abrupt changes occur at around 1.06, 0.85, 0.6, 0.46, 0.39 and 0.14?MaBP. There is a chronological link between the abrupt changes of paleoclimate and the formation of river terraces and it is almost simultaneous with a strengthening trend of neotectonic activities. Therefore, maybe the climatic transition controll the timing of terrace formation, and the tectonic uplift originate potential energy and has a direct effect on channel incision, both the climatic transition and the tectonic uplift are important. Terraces are the products of the interaction of instable climatic variations and tectonic uplift. Like the loess-paleosol sequences, river terrace sequences are also controlled by the climate-tectonic coupling system and are ruled by climate-tectonic gyration with a ~100?kyr paracycle, which may be the short eccentricity period of the earth.  相似文献   

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