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1.
《Marine and Petroleum Geology》2012,34(1):69-79
Earth’s climate during the Proterozoic Eon was marked by major glacial events with evidence for large continental ice sheets on many cratons, and with sedimentological data indicating that glaciers had extended to sea-level. This paper emphasizes the sedimentological and sequence stratigraphic responses to glaciations and evaluates the major driving forces of glaciations during the Precambrian. First- and second-order sequences are recognized related to continental-scale fragmentation and formation of marine rift basins wherein sedimentary rocks indicate glacial influences and pronounced tectonic-climatic linkages. Coarse syn-rift deposits are typically characterized by mass flow diamictites and conglomerates. It is important to undertake sedimentological facies and sequence stratigraphic analysis of these syn-rift and capping passive margin sequences, as well as of slope turbidite deposits which formed if enhanced subsidence of the basins was occurring. More generally, latitude and syn-rift tectonic uplift can cause formation of glacial ice and enhance distinctive glacial influences on extensional basin sedimentation, thus supporting a causal relationship between thermal subsidence and the formation of glacier ice on inland areas. During the Precambrian, however, it is suggested that long-lived marine-terminated glaciers also situated at low paleolatitudes, were related to an extensional tectonic setting. In such settings, glacial deposits associated with sedimentary sequences of distinctively different origin, e.g. carbonate and chemically mature siliciclastic sequences, can well be used to detect the prominent sequence boundaries to verify depositional systems tracts. Internal sediment stacking patterns in sequences are indicative of dynamic processes along glaciated continental margins and without always having the need for global synchroneity. In glacially influenced rift basins and continental margins it is important to recognize the sequence boundaries of significant subaerial unconformities and their correlative conformities. A sequence boundary is a chronostratigraphically significant surface always produced as a consequence of a change in relative sea-level. These can then be well related to initiation and decay of glaciations, however on-land glacial deposits in a very few cases are prevented from later erosion. Attenuation of continental crust during rifting and breakup of the continent raises relative sea-level and also many of the shallow intra-cratonic basins subsided below sea-level, in favourable conditions being affected by major continental glaciations.Paleoproterozoic and Neoproterozoic glacial deposits are known in North and South America, South Africa, India, Western Australia and Fennoscandia. Against this background, continental-scale to global glaciations in the Precambrian appear to be possible, however views on the causes and timing of these glaciations, as well as on planetary extent of ice cover are still contradictory. There is a need to continue detailed sedimentological studies of pre-glacial and post-glacial deposits as well as to interpret syn-glacial lithofacies for their inferred transportation and depositional processes. Pre-glacial deposits, especially, should provide a new target to help us understand the processes that initiated these Precambrian glaciations. The sequence stratigraphic approach with understanding of the stacking pattern of depositional systems could prevent oversimplification and use of just single events to explain the complexity of evolution of glacially influenced Precambrian continental margin sediments. 相似文献
2.
渤海湾盆地渤中凹陷古近系沉积体系演化及物源分析 总被引：22，自引：0，他引：22
综合运用地质、测井、地震及分析化验等资料,对渤海湾盆地渤中凹陷古近系沉积体系进行了较深入的研究,研究表明渤中凹陷古近系的沉积体系主要受构造升降和湖平面变化的控制,经历了3期裂陷和湖侵,发育5套沉积体系,其中沙河街组沉积时期为裂陷期,以扇三角洲、湖底扇沉积为主,并发育特征的滩坝及浅水台地相沉积;东营组沉积时期为湖侵期,主要发育大型湖泊三角洲沉积,并逐渐向辫状河相过渡。构造及沉积体系分析认为,沙三段沉积时期物源丰富,主要来自石臼坨凸起、渤南和庙西凸起,沙一、二段沉积时期物源有限,东三沉积期物源主要来自石臼坨和沙东南凸起,东二沉积期大面积的湖侵使得本区处于浅湖-半深湖环境,凹陷周边大量古水系将石臼坨凸起、沙垒田凸起的物源带入凹陷中沉积,使得大型三角洲叠覆体广泛发育。 相似文献
3.
Distribution and origin of hybrid beds in sand-rich submarine fans of the Tanqua depocentre, Karoo Basin, South Africa 总被引：2，自引：1，他引：1
This study documents the stratigraphic and palaeogeographic distribution of hybrid event beds that comprise both debris-flow (cohesive) and turbidity current (non-cohesive) deposits. This is the first study of such beds in a submarine fan system to combine outcrop and research borehole control, and uses a dataset from the Skoorsteenberg Formation of the Tanqua depocentre in the Karoo Basin, South Africa. Three types of 0.1–1.0 m thick hybrid beds are observed, which have a basal weakly graded fine-grained sandstone turbidite division overlain by a division of variable composition that can comprise 1) poorly sorted carbonaceous-rich material supported by a mud-rich and micaceous sand-matrix; 2) poorly sorted mudstone clasts in a mud-rich sand-silt matrix; or 3) gravel-grade, rounded mudstone clasts in a well sorted (mud-poor) sandstone matrix. These upper divisions are interpreted respectively as: 1) the deposit of a debris-flow most likely derived from shelf-edge collapse; 2) the deposit of a debris flow, most likely developed through flow transformation from turbidity current that eroded a muddy substrate; and 3) from a turbidity current with mudstone clasts transported towards the rear of the flow. All three hybrid bed types are found concentrated at the fringes of lobes that were deposited during fan initiation and growth. The basinward stepping of successive lobes means that the hybrid beds are concentrated at the base of stratigraphic successions in medial and distal fan settings. Hybrid beds are absent in proximal fan positions, and rare and thin in landward-stepping lobes deposited during fan retreat. This distribution is interpreted to reflect the enhanced amounts of erosion and availability of mud along the transport route during early lowstands of sea level. Therefore, hybrid beds can be used to indicate a fan fringe setting, infer lobe stacking patterns, and have a sequence stratigraphic significance. 相似文献
4.
A chemostratigraphic study of Upper Jurassic sandstones in the northern Danish Central Graben has been undertaken within the framework of a well-defined stratigraphic/sedimentological model based particularly on cored well sections. Two reservoir sandstone units are recognised, the transgressive marginal marine to shoreface sandstone of the Gert Member and the regressive to transgressive shoreface sandstone of the Ravn Member. Both members belong to the Heno Formation, which is equivalent to the Fulmar Formation (UK) and the Ula Formation (Norway). 相似文献
5.
The estimated in-place hydrocarbon volume of the giant Johan Sverdrup field is 3.5 billion barrels of oil, the bulk of which is contained in the Upper Jurassic intra-Draupne Formation sandstone. The intra-Draupne Formation sandstone is composed of unusually coarse grained siliciclastic sediments, with an average net/gross of 97% and average porosity of 28%. The median core permeability ranges from 0.5 to 40 Darcies in individual wells, and may reach even higher values based on drill stem testing.The reservoir is interpreted to be a time-transgressive sheet sand, ranging from 2 to 38 m in thickness and covering an area of more than 200 km2. Vertical and lateral facies and grain size trends, combined with biostratigraphy and palaeocurrent indicators, are interpreted to demonstrate a westward onlapping, transgressive shoreface depositional system, with local fan delta input.Reservoir properties vary significantly across the field and relative to facies association. In terms of permeability, the upper and lower shoreface associations in the Avaldsnes High area in the east show the highest median values of 25–27 Darcies. The upper and lower shoreface associations in the Augvald Graben area to the west show median values of 15 and 21 Darcies, respectively. The lowest values are observed in the transgressive shoreline, fan delta and spiculitic shoreface associations, i.e. 8 Darcies, 2 Darcies and 0.1 Darcies, respectively. The latter two facies associations are restricted to local areas in the west and northwest.The coarse grain size, lack of fines, scarcity of cementation and extensive sheet-like distribution of siliciclastic sediments make the intra-Draupne Formation sandstone an ideal reservoir. The depositional model presented in this paper may be used as an analogue when exploring for similar, high quality, shallow marine reservoir sands. 相似文献
6.
《Marine and Petroleum Geology》2003,20(6-8):691-710
The Pab Formation consists of deltaic and turbiditic sediments which were deposited during the Late Maastrichtian on the Indo-Pakistani passive margin. The margin geometry has been restored in the Pab Range from a regional transect 120 km long. Two superposed turbiditic systems onlap the slope carbonates and completely pinch-out southward. The lowest turbiditic system (Lower Pab) is a sand-rich basin floor fan, which consists of sand-rich channel complexes distally passing to lobes northward. This basin floor fan is overlain by a mud-rich slope fan formed during the subsequent sea-level rise, which drowned the shelf. The upper turbiditic system (Upper Pab) is a sand-rich slope fan, formed during the progradation of a deltaic system in the shelf setting. It consists of prograding tabular lobes passing upward to conglomeratic channels, and thins out northwards. The Lower Pab turbiditic system consists of three channel complexes (LP1, 2, 3) organised in a backstepping succession. Each channel complex has a multi-storey internal architecture, resulting from the amalgamation of several individual turbiditic channels. Five major facies associations have been determined in the LP3 channel complex. FA-1 corresponds to polygenic and monogenic debris-flows, FA-2 to high-density gravelly or sandy turbidites, FA-3 to by-pass deposits, FA-4 to thin-bedded turbidites (spill-over lobes and levees) and FA-5 to hemipelagites. The downstream evolution of the LP3 channel complex can be studied from canyon to mid-fan settings. Where it is confined in the canyon, the channel complex is 50 m thick and 1 km large, and shows a high sand/shale ratio. The development of overflow deposits is limited and occurs only at the top of the channel complex. At the canyon mouth, the channel complex is still deeply incised but overflow deposits start to expand laterally as a result of the decreased confinement. By-pass facies here are well-developed, and are related to hydraulic jump processes. In the mid-fan setting, the channel complex widens and the sand/shale ratio decreases. Erosion at the channel base is less developed, whereas internal and external levees are well-developed. Spill-over lobes form the last stage of the channel complex infill. The internal geometry of the channel complexes is a result of a complex interaction between lateral confinement, by-pass and lateral migration processes. 相似文献
7.
The Mississippi Fan is a Quarternary accumulation composed of more than seven elongated fan lobes. Isopach and structure maps
show frequent shifting of these lobes. The Mississippi Canyon, formed by retrogressive slumping, connects to the youngest
fan lobe. The upper fan-lobe is characterized by a large, incised, partially infilled, leveed channel. The middle fan-lobe
is aggradational, convex in cross section, with a channel-levee complex on its apex. The lower fan-lobe contains a recently
active small channel and several abandoned ones. Depositional patterns can be explained by several processes: “fluvial,” debris
flows, and turbidity currents.
Margin setting represents fan and/or source area 相似文献
8.
The newly discovered Weddell Fan, Antarctica, covers 0.75 million km2. The adjacent continental shelf is characterized by deep, rugged topography; the inner shelf is covered by a grounded polar ice sheet. The upper fan has numerous deep, V-shaped canyons that intersect a slope-base, leveed fan valley. Piston cores from the valley contain disorganized gravel grading upward into graded gravel and sand. Levee cores contain interbedded hemipelagic sediments and fine-grained turbidites. The lower fan is sand-rich. Sediment supply to the fan apparently occurred before development of glacial shelf topography and during a more temperate glacial setting. 相似文献
9.
The Cengio sandstone member of the Tertiary Piedmont Basin in northwestern Italy has a conservatively estimated volume of
2.5 to 3 km3 (length: 6.4 km; width: 4.8 km; thickness: 170 m). It is interpreted as a sandstone-rich submarine fan deposit. The Cengio
member consists of eight tabular depositional sandstone lobes that are 5- to 25-m thick. These lobes filled a submarine structural
depression and onlap and/or pinch-out against bounding slope mudstones. The stacking of the lobe units was related to synsedimentary
tectonism.
Margin setting represents fan and/or source area 相似文献
10.
长江南京段末次盛冰期以来的古河谷沉积 总被引：3，自引：0，他引：3
末次冰期盛冰期海平面大幅度下降,长江发育古深槽。根据沉积物的颗粒状况,南京段古河谷的充填可以分为3期明显的由粗到细的沉积韵律:末次盛冰期深切古河谷,河床窄陡,沉积物颗粒粗,为卵砾石到中砂、粗砂;冰后期河床较宽,沉积物为砾石、粗砂到中砂、细砂;全新世,河流进一步展宽,沉积物为粗砂、中砂到细砂、粉砂,细砂沉积厚度很大。全新世中期河床有数次左右摆动,两侧形成了细砂—砂质黏土互层的沉积。根据不同时期沉积物的颗粒级配情况,推算出各时期河流的起动流速和平均流速,验证不同时期的沉积环境,认为剖面的深切河槽是局部深切的结果。各期河床形态和沉积物的特征,反映了末次盛冰期、冰后期、全新世的气候变化和环境演变。 相似文献
11.
Franco Ricci Lucchi Albina Colella Gianni Gabbianelli Sergio Rossi William R. Normark 《Geo-Marine Letters》1984,3(2-4):71-77
The Crati Fan is located in the tectonically active submerged extension of the Apennines chain and foretrough. The small fan
system is growing in a relatively shallow (200 to 450 m), elongate nearshore basin receiving abundant input from the Crati
River. The fan is characterized by a short, steep, channelized section (inner or upper fan) and a smooth, slightly bulging
distal section (outer or lower fan). The numerous subparallel channels head in the shelf or littoral zone and do not form
branching distributary patterns. Sand and mud depositional lobes of the outer fan stretch over more than 60% of fan length.
Margin setting represents fan and/or source area 相似文献
12.
《Marine and Petroleum Geology》2003,20(6-8):711-726
Detailed bed-by-bed correlations in sheetlike lobes and basin-plain elements of the Hecho Group were carried out through a hierarchical decomposition based on three orders of correlation. This procedure provides the most detailed correlation framework with chronostratigraphic significance. First-order decomposition is based on physical correlation by mapping of major megaturbidites. Second-order decomposition consists in matching a series of marker beds within first-order units, leading to the definition of units several metres thick. Finally, third-order decomposition relies on the matching of serial features within second-order packages (number, vertical arrangement and facies features of beds), and further testing the coherence of the downstream evolution of facies in single beds. Sheetlike lobes and basin plain are closely related and display a distinctive sheet-like geometry. Basin-plain beds are deposited by the same flows that build the sheetlike lobes, with the existence of a transitional facies change from the lobe to the basin-plain. Thickening of some beds towards the basin plain due to ponding of the fine-grained (silt and mud) divisions, a diagnostic feature of the basin plain, controls the sheet-like stacking pattern by balancing the wedging-out of thinner lobe beds upcurrent from, or within, the basin plain. As a consequence, the whole area can be geomorphically classified as a basin plain, which comprises both lobe and basin plain facies associations. 相似文献
13.
Nikolaos Kontopoulos Teresa Fokianou Abraham Zelilidis Christos Alexiadis Nikolaos Rigakis 《Marine and Petroleum Geology》1999,16(8):223
Two depocentres, >4200 m and >3200 m thick, have been recognized in the Mesohellenic piggy-back basin of middle Eocene to middle Miocene age, where submarine fans have accumulated unconformably over an ophiolite complex. The hydrocarbon potential is indicated by the presence of kerogen types II/III with minor amounts of type I; the evidence is mostly for wet gas and gas, with minor oil. Source rocks are the middle Eocene to lower Oligocene Krania and Eptachori formations, of up to 2000 m total thickness, reaching maturation during the early Miocene. The source rocks consist of outer fan and basin plain deposits. They are conformably overlain by the lower member (late Oligocene) of the up to 2600 m thick Pentalophos Formation, which consists mostly of thick submarine sandstone lobes. Possible stratigraphically trapped reservoirs include the lower member of the Pentalophos Formation, which overlies source rocks, as well as limestones tectonically intercalated within the ophiolite complex, underlying the source rocks. Traps may have formed also on the western side of an internal thrust (Theotokos Thrust), which influenced the evolution of the depocentres. 相似文献
14.
The Rhone Fan is a large Plio-Pleistocene turbidite deposit in the western Mediterranean Sea. The fan is fed from the broad
Rhone River delta, but only one canyon, the Petit-Rhone, has fed most of the major turbidite depositional sequences that have
been mapped. Slumping of sediment from intercanyon areas on the delta slope also has provided much sediment for the fan. The
lack of Recent turbidite deposition on the fan suggests that turbidite sedimentation dominates during glacial low stands of
sea level, building major leveed valley sequences, while surficial slumping of the valley levee deposits and pelagic sedimentation
seem to mark high stands of sea level during interglacial periods.
Margin setting represents fan and/or source area 相似文献
15.
16.
The 0.5- to 2-km thick Quaternary Laurentian Fan is built over Tertiary and Mesozoic sediments that rest on oceanic crust.
Two 400-km long fan valleys, with asymmetric levees up to 700-m high, lead to an equally long, sandy, lobate basin plain (northern
Sohm Abyssal Plain). The muddy distal Sohm Abyssal Plain is a further 400-km long. The sediment supplied to the fan is glacial
in origin, and in part results from seismically triggered slumping on the upper continental slope. Sandy turbidity currents,
such as the 1929 Grand Banks earthquake event, probably erode the fan-valley floors; but thick muddy turbidity currents build
up the high levees.
Margin setting represents fan and/or source area 相似文献
17.
上新世——早更新世青藏高原北缘隆升的磁性地层学证据 总被引：9，自引：0，他引：9
对新疆叶城剖面西域砾岩及下伏第三纪地层的磁性地层学研究表明 ,西域砾岩的沉积时代为晚上新世至早更新世 ,磁性地层年龄为 3.5至 <1.8Ma。阿图什组沉积于早上新世 ,古地磁年龄为 4 .6～ 3.5 Ma。阿图什组以砂岩和粉砂岩为主夹薄层砾岩 ,为河流相及冲积扇前缘相。西域砾岩以厚层砾岩为主夹风成粉砂岩 ,为典型洪积—冲积扇堆积。西域砾岩的沉积反映了青藏高原北缘晚上新世至早更新世强烈的隆起和剥蚀 相似文献
18.
Franco Ricci Lucchi Albina Colella Gianni Gabbianelli Sergio Rossi William R. Normark 《Geo-Marine Letters》1983,3(2-4):71-77
The Crati Fan is located in the tectonically active submerged extension of the Apennines chain and foretrough. The small fan system is growing in a relatively shallow (200 to 450 m), elongate nearshore basin receiving abundant input from the Crati River. The fan is characterized by a short, steep, channelized section (inner or upper fan) and a smooth, slightly bulging distal section (outer or lower fan). The numerous subparallel channels head in the shelf or littoral zone and do not form branching distributary patterns. Sand and mud depositional lobes of the outer fan stretch over more than 60% of fan length. 相似文献
19.
The Mississippi Fan is a Quarternary accumulation composed of more than seven elongated fan lobes. Isopach and structure maps show frequent shifting of these lobes. The Mississippi Canyon, formed by retrogressive slumping, connects to the youngest fan lobe. The upper fan-lobe is characterized by a large, incised, partially infilled, leveed channel. The middle fan-lobe is aggradational, convex in cross section, with a channel-levee complex on its apex. The lower fan-lobe contains a recently active small channel and several abandoned ones. Depositional patterns can be explained by several processes: “fluvial,” debris flows, and turbidity currents. 相似文献