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1.
The trace fossil assemblages of the ice-marginal shallow marine sediments of the Talchir Formation (Permo-Carboniferous), Raniganj Basin, India, record the adverse effect of extreme climatic conditions on biota. The glaciomarine Talchir succession starts with glacial sediments near the base and gradually passes to storm-laid shallow marine sediments up-section. The fine-grained storm sediments host abundant trace fossils. Although the studied ichnites characteristically show marginal marine affinity, the ichnodiversity and bioturbation intensity suggest a lower than normal shallow marine trace fossil population. Further, endobenthic annelids, worms and crustaceans are identified as dominant trace-makers.

Sediment reworking near the ice-grounding line, extremely cold climate, high-energy storm sedimentation and anomalous water chemistry hindered organic colonization during the early phases of Talchir sedimentation. Later, climatic amelioration ushered in a favourable ambience for the benthic community to colonize within or beyond the storm weather wave-base in the outer shoreface–shelf environment. Fluctuating storm energy dominantly controlled the availability and influence of other environmental stimuli in the environment, and thus, governed the distribution, abundance and association of the studied ichnites. However, impoverished ichnodiversity, sporadic distribution of the traces, overall smaller burrow dimensions, absence of body fossils, dominance of worms and annelids as trace-makers all indicate a stressed environmental condition, induced by cold climate and lowered marine salinity due to influx of glacier melt-out freshwater during climatic amelioration, in the Permo-Carboniferous ice-marginal sea.  相似文献   


2.
Cyclic characters of Karharbari, Barakar and Barren Measures Formations of the Talchir Gondwana basin have been studied in the subsurface logs statistically using first order Markov chain and entropy analyses. Results strongly suggest that the sediments of these formations were deposited by Markovian mechanism and all the three formations represent cyclic sedimentation. The complete cycles of all the three formations are identical and exhibit fining-upward character. Each complete cycle starts with a thin conglomerate or pebbly to coarse-grained sandstone at the base and successively followed by medium- and fine-grained sandstones, interbedded sandstone-shale, shale and terminates with a coal seam at the top. There are, however, minor variations of facies transition in different formations. Entropy analysis also corroborates these findings. The upward sequence of facies states, which is stationary at individual localities, is non-stationary over the entire area. Broad regional variations in the depositional environment, that are not significant at the local scale, may be the plausible explanation. The Karharbari, Barakar and Barren Measures sediments of the Talchir Gondwana basin fit suitably into the concept of fluvial cycles.  相似文献   

3.
The carbonate concretions occurring at the bottom of Talchir fissile shale facies preserved signatures of various trace fossils along with a cast of doubtful organisms and cyanobacterial mat structures. The host shale deposited under glacial melt water fed lacustrine condition. The concretions, formed in poorly oxygenated conditions, are either of syndepositional origin and/or deposited a little below the sediment water interface and were later exhumed to the depositional surface due to erosion of soft mud overlying them. The trace fossils are both megascopic and microscopic in nature. The megascopic trace fossils are identified on the basis of their morphology as Monocraterion and Rhizocorallium. Some of the megascopic structures described remain problematic at present. The microscopic trace fossils are formed due to the activity of marine meiofauna (possibly by nematodes), which, although produced morphologically show similar traces of known larger ichnogeneras but much smaller than them. The discovery of these trace fossils apparently indicate the influx of saline water into a lacustrine domain during the Talchir sedimentation at Giridih basin. Moreover, presence of the above two megascopic trace fossils in the marine lacustrine carbonate concretions may lead researchers to consider their much wider environmental significance than hitherto believed.  相似文献   

4.
The lowest unit of the Talchir Formation of Talchir Basin, Orissa, was described by pioneer workers as the ‘basal boulder bed’. In an attempt to explain the co-existence of gravel and clay, materials of contrasting hydraulic properties, a probable situation resembling the effects of the action of ground-ice enabled boulders to be carried down by sluggish currents resulting in an intermixture of large boulders and fine mud was conceived. Misinterpretation of this conclusion led to a general tendency to describe the ‘basal boulder bed’ as ‘glacial tillite’. However, the unit described as ‘basal boulder bed’ is actually represented by a matrix rich conglomerate with pockets of normally graded silty clay. The present study reveals that the depositional imprints preserved in this part of the sedimentary succession indicate emplacement of successive debris flows generated through remobilization of pre-existing unconsolidated sediments. Small pockets of fine-grained turbidites presumably deposited from the entrained turbidity currents associated with the debris flows suggest the composite character of the debris flow deposit.  相似文献   

5.
In peninsular India, Gondwana strata are disposed linearly as strings of isolated basins conforming to the trend of the present day Koel–Damodar, Son–Mahanadi and Prahnita–Godavari river valleys. There are seven exposed and one concealed Gondwana basins/outliers in Orissa belonging to the Son–Mahanadi valley system. The present study is concerned with the consanguinity of the Talchir and Ong-river basins of Orissa. Similarity and dissimilarity of palaeocurrent population in these two basins were taken into consideration to test the consanguinity of the basins under consideration. Statistical analysis suggests that the sampled palaeocurrent data of the same formation belong to the same population when considered for both basins. In geologic terms, the basin parameters were identical when considered for either the Talchir or the Karharbari Formation that proves the consanguinity of both the basins and the possible existence of a master basin that encompassed other sister Gondwana basins in Orissa.  相似文献   

6.
苏红图-银根盆地下白垩统层序地层学研究   总被引:2,自引:0,他引:2  
李文厚 《沉积学报》1997,15(3):18-22
本文根据沉积、古生物及地震资料对苏红图-银根盆地下白垩统的层序地层学特征进行了研究。把下白垩统划分为1个三级层序和低水位体系域、湖侵体系域、高水位体系域。根据准层序的叠置方式,准层序组有进积型、退积型和加积型,本区下白垩统可以划分9个准层序组,以退积型准层序组最为发育。苏红图-银根盆地早白垩世早期沉积格局曾发生过显著变化,从早到晚先后发育冲积扇、扇三角洲、浅湖和深湖相沉积,并在深湖相暗色页岩中夹有浊流和泥石流沉积,为退积型湖进层序。早白垩世晚期则由滨浅湖相演化为滨湖沼泽和河流相沉积,为进积型湖退层序。本区的湖侵体系域浅湖-深湖相暗色泥、页岩厚度大,有机质丰度高,类型好,是重要的烃源岩。低水位体系域的扇三角洲层序以加积型为特征,即下部为扇三角洲平原,中部为扇三角洲前缘,上部为前扇三角洲。反映了该区处于活动盆地边缘,湖水由浅变深,扇三角洲相应后退,沉降速率大于沉积速率。其中扇三角洲前缘砂体的储集作用不可低估。高水位体系域的滨浅湖滩砂也是重要的油气储集体。而湖侵体系域的深湖相泥、页岩和高水位体系域的滨湖沼泽相泥岩均可作为区域盖层。它们在垂向上构成了有利的生储盖组合。  相似文献   

7.
The Talchir Basin, one of India's oldest basins, has been a subject of interest because of its rich coal deposits. The maximum thickness of the basin is about 1500 m. Beyond the basin is the hard metamorphic rocks of Precambrian age. The ambient noise survey data have been analyzed for the Talchir Basin using Nakamura's technique of horizontal–vertical-spectral-ratio (HVSR) to ascertain the basin structure in terms of the predominant frequency. The predominant frequency varies from 0.25 Hz to 7.8 Hz but a major portion of the basin comes under the range of 0.3 Hz–2.4 Hz while on the metamorphic rocks it is as high as 7.8 Hz. The variation in predominant frequency shows a good correlation with the sediment thickness of the basin. The results have been compared with the previous studies by other researchers and it shows consistency with the northerly dip of the basin. The present study has also been compared with the results of the synthetic seismogram that was performed for the Talchir Basin. The predominant frequency obtained from HVSR technique complements well with the frequency at which the peak response spectra ratio is observed. The present study of the predominant frequency identifies quite well the characteristics of Talchir Basin and is in good agreement with the synthetic ground motion modeling of the region.  相似文献   

8.
The Denizli Basin (southwestern Anatolia, Turkey) contains a record of environmental changes dating since the Early Miocene. Detailed facies analysis of the Neogene formations in this half-graben enables us to document successive depositional regimes and palaeogeographic settings. Sedimentation commenced in the Early Miocene with the deposition of alluvial-fan and fluvial facies (K?z?lburun Formation). At this stage, alluvial fans sourced from elevated areas to the south prograded towards the basin centre. The Middle Miocene time saw the establishment of marginal lacustrine and wetland environments followed by the development of a shallow lake (Sazak Formation). The uppermost part of this unit consists of evaporitic saline lake and saline mudflat facies that grade upward into brackish lacustrine deposits of Late Miocene-Pliocene age (Kolankaya Formation). The lake became shallower at the end of the Pliocene time, as is indicated by expansion shoreface/foreshore facies. In the Early Quaternary, the Denizli Basin was transformed into a graben by the activation of ESE-trending normal faults. Alluvial fans were active at the basin margins, whereas a meandering river system occupied the basin central part.Oxygen isotope data from carbonates in the successive formations show an alternation of wetter climatic periods, when fresh water settings predominated, and very arid periods, when the basin hosted brackish to hypersaline lakes. The Neogene sedimentation was controlled by an active, ESE-trending major normal fault along the basin's southern margin and by climatically induced lake-level changes. The deposition was more or less continuous from the Early Miocene to Late Pliocene time, with local unconformities developed only in the uppermost part of the basin-fill succession. The unconformable base of the overlying Quaternary deposits reflects the basin's transformation from a half-graben into a graben system.  相似文献   

9.
A group of alluvial fans formed in the early Paleogene represent marginal sedimentary facies at the foot of the South Tianshan Mountain,Kuqa Depression,Tarim Basin,Xinjiang province. Two types of fans occurred in the middle-late Paleogene Kumugeliemu and Suweiyi formations:one alluvial,and the other fan delta deposited in a lacustrine setting.Within the early Neogene Jidike Formation,coastal subaqueous fans developed,probably in a deeper water lacustrine setting.The three types of fans are stacked vertic...  相似文献   

10.
塔里木盆地西南部沿昆仑山前分布一套逾千米厚的下白垩统碎屑岩,岩相以浅红色中、细砂岩,褐红色砂砾岩、砾岩为主,夹浅红色泥岩和薄层浅灰色细砂岩。按生物组合及岩性特征,自下而上可划分5个岩性段。第1段为灰绿色泥岩段,沉积环境以湖相和前扇三角洲沉积为主;第2段为砂砾岩段,沉积环境以扇三角洲前缘和平原沉积为主;第3段为含砾粗砂岩段,沉积环境以辫状河-辫状河三角洲平原沉积为主;第4段为细砂岩夹泥岩段,沉积环境以辫状河三角洲前缘水下分流河道沉积为主;第5段为泥岩夹砂岩段,沉积环境为辫状河三角洲前缘、前辫状河三角洲和滨浅湖相沉积。沉积环境由快速堆积的扇三角洲-冲积扇向辫状河-辫状河三角洲演化,沉积厚度达1000余米。构造背景为强烈拉张的构造环境,是断陷盆地发育的重要时期。中细砂岩达70%以上,砂岩孔隙类型为原生粒间孔,孔隙度10%~20%,渗透率1~1000×10-3μm2,是塔里木盆地中生代油气勘探的重要目的层系。  相似文献   

11.
Basal part of the Gondwana Supergroup represented by Talchir and Karharbari Formations (Permo-Carboniferous) records an abrupt change-over from glacio-marine to terrestrial fluviolacustrine depositional environment. The contact between the two is an unconformity. Facies analysis of the glacio-marine Talchir Formation reveals that basal glaciogenic and reworked glaciogenic sediments are buried under storm influenced inner and outer shelf sediments. Facies associations of the Karharbari Formation suggest deposition as fluvio-lacustrine deposits in fault-controlled troughs. An attempt has been made in this paper to explain the sedimentation pattern in Talchir and Karharbari basins, and the abrupt change-over from glacio-marine to terrestrial fluviolacustrine depositional environment in terms of glacio-isostacy.  相似文献   

12.
The Middle Devonian Gauja Formation in the Devonian Baltic Basin preserves tide‐influenced delta plain and delta front deposits associated with a large southward prograding delta complex. The outcrops extend over 250 km from southern Estonia to southern Lithuania. The succession can be divided into 10 facies associations recording distributary channel belts that became progressively more tide influenced when traced southwards towards the palaeo‐shoreline, separated by muddy intra‐channel areas where deposition was characterized by crevasse splays, delta plain lakes, abandoned channel deposits and tidal gullies. Tidal currents influenced deposition over the entire delta plain, extending up to 250 km from the contemporary shoreline. Tidal facies on the upper delta plain differ from those on the lower delta plain and delta front. In the former case, deposition from river currents was only occasionally interrupted by tidal currents, e.g. during spring tides, resulting in mica and mudstone drapes, and distinctive graded cross‐stratification. The lower delta plain was dominated by tidal facies and tidal currents regularly influenced deposition. There was a change from progradation to aggradation from the lower to the upper part of the Gauja Formation coupled with a vertical decrease in tidal influence and a decrease in coarse‐grained sediment input. The Gauja Formation contrasts with established models for tide‐influenced deltas as the active delta plain was not restricted by topography. The shape of the delta plain, the predominant southward (basinward)‐directed palaeocurrents, and the thick sandstone succession, show that although tidal currents strongly influenced deposition at bed scale, rivers still controlled the overall morphology of the delta and the larger‐scale bedforms. In addition, there are no signs of wave influence, indicating very low wave energy in the basin. The widespread tidal influence in the Devonian Baltic Basin is explained by changes in the wider basin geometry and by local bathymetrical differences in the basin during progradation and aggradation of the delta plain, with changes in tidal efficiency accompanying the change in basin geometry produced by shoreline progradation.  相似文献   

13.
针对陆相断陷盆地构造沉降与湖平面变化的响应关系问题, 笔者通过二维回剥分析, 并引入沉降通量和沉降速率通量两个参数以评价盆地沉降的整体特征。黄骅坳陷中区东营组二级层序内三角洲体系发育, 可细分为4个三级层序, 构造沉降上呈减弱到增强的变化, 并具有断陷作用逐渐减弱、坳陷作用加强的特点。拟合构造沉降、沉积演化、层序结构的关系表明, 湖平面下降、三角洲的繁盛与快速构造沉降耦合一致, 湖平面下降是不均衡的强烈构造沉降导致湖水体积向控凹断层或坳陷中心重新分配、且四周水系的补充滞后于构造沉降产生的新增可容纳空间的结果。相反, 湖平面上升和深湖相发育与慢速构造沉降耦合一致。此外, 湖平面变化与构造沉降总量的大小无关。  相似文献   

14.
The Athgarh Formation is the northernmost extension of the east coast Upper Gondwana sediments of Peninsular India. The formation of the present area is a clastic succession of 700 m thick and was built against an upland scarp along the north and northwestern boundary of the basin marked by an E-W-ENE-WSW boundary fault. A regular variation in the dominant facies types and association of lithofacies from the basin margin to the basin centre reveals deposition of the succession in an alluvial fan environment with the development of proximal, mid and distal fan subenvironments with the distal part of the fan merging into a lake. Several fans coalesced along the basin margin, forming a southeasterly sloping, broad and extensive alluvial plain terminating to a lake in the centre of the basin. Aggradation of fans along the subsiding margin of the basin resulted in the Athgarh succession showing remarkable lateral facies change in the down-dip direction. The proximal fan conglomerates pass into the sandstone-dominated mid-fan deposits, which, in turn, grade into the cyclic sequences of sandstone-mudstone of the distal fan origin. Further downslope, thick sequence of lacustrine shales occur. The faulted boundary condition of the basin and a thick pile of lacustrine sediments at the centre of the basin suggest that tectonism both in the source area and depositional site has played an important role throughout the deposition of the Athgarh succession of the present area. The vertical succession fines upward with the coarse proximal deposits at the base and fine distal deposits at the top, suggesting deposition of the succession during progressive reduction of the source area relief after a single rapid uplift related to a boundary fault movement.The NW-SE trending fault defining the Son-Mahanadi basin of Lower Gondwana sediments are shear zones of great antiquity and these were rejuvenated under neo-tensional stress during Lower Gondwana sedimentation. The E-W-ENE-WSW trending fault of the Athgarh basin, on the other hand, define tensional rupture of much younger date. In the Early Cretaceous period, there was a reversal of palaeoslope in the Athgarh basin (southward slope) with respect to the Son-Mahanadi basin (northward slope). During the phase drifting of the Indian continent and with the evolution of Indian Ocean in the Early Cretaceous period, the tectonic events in the plate interior was manifested by formation of new grabens like the Athgarh graben.  相似文献   

15.
珠江口盆地白云凹陷古近系沉积相类型   总被引:7,自引:1,他引:6  
以珠江口盆地白云凹陷的钻井和地震资料为基础,根据测井相、地震相综合分析白云凹陷文昌组与恩平组主要层序的沉积相发育演化特征.通过有限的单井资料在白云凹陷共识别出了三角洲相、扇三角洲相及湖泊相三种沉积相;三角洲沉积相在测井曲线上表现为从下至上由细变粗的反旋回,局部出现次一级的正旋回;扇三角洲沉积相测井曲线整体表现为从下至上由细变粗的反旋回及次一级的反旋回;湖泊沉积相表现为以泥岩沉积为主,局部夹有砂坝或碳酸盐滩坝.研究区发育9种地震相类型,地震相证据充足,为研究沉积相发育规律提供了可靠的依据.研究表明盆地的持续沉降造就了白云凹陷深湖相发育时间长,形成厚层烃源岩;受番禺低隆起影响,白云凹陷北坡缓坡带发育三角洲相,在西南至南部陡坡带发育扇三角洲相,部分三角洲的发育具有继承性.  相似文献   

16.
The cyclic arrangement of lithofacies of the Karharbari Formation of the Damuda Group from a part of the Talchir Gondwana basin has been examined by statistical techniques. The lithologies have been condensed into five facies states viz. coarse-, medium-, fine-grained sandstones, shale and coal for the convenience of statistical analyses. Markov chain analysis indicates the arrangement of Karharbari lithofacies in form of fining upward cycles. A complete cycle consists of conglomerate or coarse-grained sandstone at the base sequentially succeeded by medium-and fine-grained sandstones, shale and coal at the top. The entropy analysis categorizes the Karharbari cycles into the C-type cyclicity, which is essentially a random sequence of lithologic states. Regression analysis undertaken in the present study indicates the existence of sympathetic relationship between total thickness of strata (net subsidence) and number and average thickness of sedimentary cycle and antipathic relationship between number and average thickness of sedimentary cycle. These observations suggest that cyclic sedimentation of the Karharbari Formation was controlled by autocyclic process by means of lateral migration of streams activated by intrabasinal differential subsidence, which operated within the depositional basin and the channels carrying coarse grade clastic sediments, which make the cycles thicker, tend to be more common in the areas of maximum subsidence. Clastic sediments issued from the laterally migrating rivers interrupted the cyclic sedimentation of the Karharbari Formation in many instances.  相似文献   

17.
通过详细研究百岗组沉积相发育特征,将三角洲进行不同类型划分,认为百色盆地东部坳陷的南北两侧分别发育两套不同的沉积体系。沉积响应完整地记录了构造活动情况,在百岗早中期,盆地南部构造抬升强烈,北部构造相对稳定,三角.洲强烈向北西方向进积:百岗晚期,南部构造活动相对稳定,北部构造发生了强烈抬升。南部三角洲在百岗期表现为“发育-发展-稳定-萎缩”的一个完整的演化旋回特点,而北部扇三角洲则体现为“稳定-进积”的过程。整个盆地构造活动在百岗期表现出了两侧构造运动明显的不同步性。  相似文献   

18.
Major deepwater sand accumulations are known to be connected to sea-level lowstands in marine basins, due to the relative lack of accommodation space on the shelf. This model was tested for the Late Miocene Lake Pannon, a large endorheic lake depositing a sedimentary succession up to 3–4 km thick. The progradation of the shelf between 9.7 and 6 Ma was tracked along a 2D seismic network. The shelf-edge trajectory indicates continuous, moderate lake-level rise between 9.7 and 9 Ma. This is followed by alternating intervals of quasi-steady and rapidly rising relative lake level with a period of ca. 250 ky. However, due to the lack of significant lake-level drops, no third-order sequence boundary was identified in the studied time span (9.7–6 Ma). The sand ratio of the deepwater deposits does not show strong correlation with these lake-level changes; moreover, the units deposited under rising lake-level conditions generally contain slightly larger proportion of sand. These features can be explained by the climatic origin of water-level rises: increasing precipitation enhances not only water inflow, but also sediment influx, which can overwhelm the well-known effect of accommodation space on the sand transport toward the deep water. The results suggest that shelf-margin trajectory might not be an efficient tool for predicting deepwater accumulations of sand in endorheic lacustrine basins.  相似文献   

19.
松辽盆地盆西斜坡白垩系姚家组下切谷充填结构   总被引:3,自引:0,他引:3  
白垩纪青山口组沉积末期至姚家组沉积初期,松辽盆地发生了湖平面大幅度下降,湖区大规模萎缩,形成了SSQq-qn和SSQy-n之间的二级层序界面.这一时期,西部斜坡普遍暴露,缺失了三级层序SQqn4和SQy1地层,并在齐齐哈尔古水系的作用下在西部斜坡的北部形成了下切谷.下切谷长约70km,宽约20km,呈NW-SE延伸.在SQy23层序水进域,下切谷逐渐被充填.下切谷发育区SQy23水进域的地层厚度明显高于相邻区域,在沉积走向上的高地层厚度梯度带反映了下切谷的边界.下切谷充填序列具有多期旋回性特征,一个完整的短期充填旋回的底界为侵蚀面,侵蚀面之上依次发育泥砾岩、具交错层理含陆源砾石和泥砾中-细粒砂岩、具波纹层理粉砂质泥岩和泥岩.充填下切谷的不同短期旋回的砂体在空间上具有叠瓦状结构.在倾向剖面上,砂体沿下切谷底界面逐层叠置超覆,向盆地方向分叉并尖灭在泥岩中,反映了河-湖共同作用.在横剖面上,砂体呈透镜状错叠.早期的砂体主要发育于相对深谷部位,相对高部位以泥质充填为主,后期的砂体不受原始深谷限制.在SQy23最大湖泛期,下切谷内以泥质充填为主.   相似文献   

20.
The Sivas Basin, located on the Central Anatolian Plateau in Turkey, is an elongate Oligo‐Miocene basin that contains numerous salt‐walled mini‐basins. Through field analysis, including stratigraphic section logging, facies analysis and geological mapping, a detailed tectono‐stratigraphic study of the Emirhan mini‐basin and its 2·6 km thick sediment fill has been undertaken. Three main palaeoenvironments are recognized – playa‐lake, braided stream and lacustrine – each corresponds to a relatively long‐lived depositional episode within a system that was dominated overall by the development of a distributive fluvial system. At local scale, this affects the geometry of the succession and influences facies distributions within preserved sequences. Sequences affected by wedge geometries are characterized by localized channelized sandstone bodies in the area of maximum subsidence and these pass laterally to floodplain mudstone towards the diaper; several internal unconformities are recognized. By contrast, sequences affected by hook geometries display narrow and steep drape‐fold geometries with no evidence of lateral facies change and apparent conformity in the preserved succession. The sediment fill of the Emirhan mini‐basin records the remobilization of diapir‐derived detritus and the presence of evaporitic bodies interbedded within the mini‐basin, implying the growth of salt walls expressed at the surface as palaeo‐topographic highs. The mini‐basin also records the signature of a regional change in stratigraphic assemblage, passing from playa‐lake facies to large‐scale highly amalgamated fluvial facies that represent progradation of the fluvial system. The initiation and evolution of this mini‐basin involves a variety of local and regional controls. Local factors include: (i) salt withdrawal, which influenced the rate and style of subsidence and consequently temporal and spatial variation in the stratigraphic assemblage and the stratal response related to halokinesis; and (ii) salt inflation, which influenced the topographic expression of the diapirs and consequently the occurrence of diapir‐derived detritus intercalated within the otherwise clastic‐dominated succession.  相似文献   

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