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1.
The Cretaceous Tres Pasos Formation of southern Chile records a slope system characterized by >800 m of paleo-bathymetric relief. Channel deposits are exposed in an outcrop 2.5 km long by 125 m thick and are located in proximity to the toe of a slope clinoform. Exquisite exposures of channel strata offer a unique opportunity for high-resolution analyses of channel stacking patterns and provide insight into the evolution of conduits that transport sediment from continents to the deep ocean.Eighteen slope channels, or channel elements, are present in the strata studied. They are 6–15 m thick and comprised of stacked turbiditic sedimentation units. Channel fills are characterized by a gradational transition from amalgamated sandstone-rich facies in the channel axes to thinly interbedded sandstone and siltstone at the channel margins over distances of 10–30 m. These elements are generally considered to be ∼300 m wide and were formed by punctuated periods of incision and sedimentary bypass, followed by in-filling by collapsing turbidity currents. Out-of-channel deposits consist primarily of fine-grained facies, which are typically covered by vegetation in the study area.The channel strata of the mapped portion of the Tres Pasos Formation can be grouped into three channel complexes 25–70 m thick. Complexes are differentiated based on the preservation of siltstone-dominated deposits (bypass drapes and channel margin), which persist across the entire outcrop belt and coincide with shifts in channel stacking pattern. The oldest four channel elements (channel complex 1) are characterized by the highest lateral offsets, relative to one another. These are interpreted to record the most unconfined channel-stacking pattern present. As the channel system evolved (channel complexes 2 and 3), channel elements began to stack on top of one another, due to the increased confinement imparted on the slope channel system. The amount of vertical offset between successive channel elements preserves the record of channel aggradation as well as erosional degradation. The greatest vertical offset observed is associated with the oldest channels; as the system matured, vertical offset decreased. This decrease in vertical offset is coincident with the decrease in lateral offset of channels. The lateral offset decrease is attributed to establishment of constructional confinement and is the consequence of increased focusing of successive channel-initiating gravity flows. As confinement establishes, channels are predisposed toward underfilled conditions upon abandonment. The capture of channel-initiating currents along channel abandonment relief fairways focused incision and resulted in increased erosion and decreased vertical offset. The consequence of these conditions is an upward increase in channel element amalgamation.The organized stacking of slope channels observed in the Tres Pasos Formation is comparable to that of seismically imaged channel-levee or entrenched slope valley systems. By analogy to these 3-dimentionally constrained systems, a portion of the poorly exposed out-of-channel facies in the Tres Pasos Formation is attributed to aggradational internal levee deposits. The facies insight derived from the studied outcrop provides insight into analogous hydrocarbon-bearing units from numerous continental margins. 相似文献
2.
A. Milia 《Geo-Marine Letters》1999,19(4):237-244
High-resolution seismic reflection data are used in the identification of the stratigraphic succession filling Naples Bay,
a tectonically active half-graben located in the extensional margin of the eastern Tyrrhenian Sea. The architecture of the
basin infill is characterized by fourth-order depositional sequences correlated to Quaternary eustatic oscillations. These
depositional sequences form aggrading and prograding stacking patterns bounded by tectonically enhanced unconformities. The
changes that the stacking patterns undergo record variations in accommodation space rates. These variations are a result of
the tectonic subsidence produced during the evolution of the half-graben.
Received: 7 July 1998 / Revision received: 29 March 1999 相似文献
3.
Differential compaction plays a key role in influencing the palaeogeographic organisation of many depositional systems. In the Jurassic Walloon Subgroup, Surat Basin, Eastern Australia, the process of compensational stacking contributes significantly to the complex coal layer architecture and is documented in mine exposure, borehole and seismic datasets. Despite this understanding, current best-practices do not formally consider the mechanics of compensational stacking when populating palaeogeography facies in coal seam gas (CSG) reservoir models. To address this limitation, a hybrid modelling workflow was developed in which numerical rules representing the process of differential compaction are used explicitly to condition an iterative workflow containing traditional geostatistical facies modelling algorithms. The workflow is facilitated by a newly developed open source plugin which allows grid decompaction in Schlumberger PETREL™ 2015. Application of the workflow was tested in a CSG production area containing closely spaced wellbores and a 3D seismic survey. In this area, facies models were constructed using both traditional geostatistical approaches and the newly developed hybrid methodology. Comparison of these models suggests that facies models constructed via unconstrained geostatistical approaches often result in unrepresentative realisations, inconsistent with coal seam architectures as observed in seismic and outcrop. The hybrid geostatistical-forward modelling approach developed during this study was better able to reproduce complex alluvial stacking patterns, particularly with respect to coal seam amalgamation, bifurcation and washout. 相似文献
4.
The South Caspian Basin contains major hydrocarbon reservoirs within the largely Early Pliocene Productive Series. This paper describes and contrasts outcrops of the uppermost ∼500 m of the series (the Surakhany Suite) deposited by two of the main fluvial systems that supplied the Azeri margin of the basin. Sedimentary facies and, for the first time from the Productive Series, palynological analyses document fluvial channel belt complexes, sheetflood overbank and flood plain to flood plain lake environments. The Productive Series on the Apsheron Peninsula, Azerbaijan, was supplied predominantly from the north by the palaeo-Volga river system. It displays an overall fining-upward trend, such that the Surakhany Suite at Lokbatan is dominated by mudstone. Siltstone and coarser-grained sediments make up 28% of the section. Channel bodies are on average 1.5 m thick and form 13% of the succession. In the sub-surface of the Apsheron Peninsula, ratty wireline log responses also indicate that siltstone and sandstone bodies are predominantly thin bedded, with SP-derived net-to-gross sand ratios of ∼0.35–0.40. The succession in the Kura Basin was sourced predominantly from the west by the palaeo-Kura river system. It displays a coarsening-upward trend, such that in the middle and upper Surakhany Suite at Babazanan siltstone and coarser sediments make up 52% of the section. It is characterised by numerous stacked and laterally continuous channel sandstone bodies that are on average 5.8 m thick and comprise 42% of the outcrop. In the sub-surface of the Kura Basin, wireline log responses of the Surakhany Suite have a blocky character and indicate SP-derived net-to-gross sand ratios of 0.26–0.38. These values are similar to calculated sandstone volumes at outcrop (44%). The palynological data, including multivariate analyses, show that the main controls on palynomorph distribution are the degree of fluvial or lacustrine influence, subaerial exposure and salinity. Despite their more lithic nature, Surakhany Suite sandstones derived from the palaeo-Kura river system along the Kurovdag-Babazanan-Neftchala trend have similar or better petrophysical properties than those derived from the palaeo-Volga river on the Apsheron Peninsula and its offshore continuation. This is probably due to their coarser-grain size. This, combined with their greater sandstone body thickness, would suggest that the axis of the Kura Basin forms the most promising part of the Azeri sector of the South Caspian Basin for exploration within the uppermost part of the Productive Series. 相似文献
5.
Deep water fold and thrust belts (DWFTBs) are sedimentary wedges that accommodate plate-scale deformation on both active and passive continental margins. Internally, these wedges consist of individual structures that strongly influence sediment dispersal, bathymetry and fluid migration. Most DWFTB studies investigate basin- and intra-wedge- scale processes using seismic reflection profiles, yet are inherently limited by seismic resolution. Of critical importance is strain distribution and its accommodation on discrete faults compared to distributed deformation. Recent studies have considered strain distribution by investigating regional reflection DWFTBs profiles within coupled systems, which contain down-dip compression and up-dip extension. There is broad agreement of a mis-balance in compression versus extension, with ∼5% excess in the latter associated with horizontal compaction, yet this remains unproven.Using two exceptionally well exposed outcrops in the Spanish Pyrenees we consider deformation of DWFTB at a scale comparable to, and beyond, seismic resolution for the first time. By coupling outcrop observations (decametre to hectometre scale) with a re-evaluation of seismic profiles from the Orange Basin, South Africa, which contains one of the best imaged DWFTBs globally, we provide a unique insight into the deformation from metre to margin scale. Our observations reveal hitherto unrecognised second order structures that account for the majority of the previously recognised missing strain. This re-evaluation implies that ∼5% missing strain should be accounted for in all DWFTBs, therefore existing studies using restorations of the sediment wedge will have underestimated crustal shortening in active margins, or sedimentary shortening in gravity driven systems by this amount. In contrast to previous studies, our observations imply that the majority of this strain is accommodated on discrete fault surfaces and this can explain the occurrence and location of a range of intra-wedge processes that are intimately linked to structures including sediment dispersal, fluid migration pathways and reservoir compartmentalisation. 相似文献
6.
Quaternary sediments at the southwest end of the Faeroe-Shetland Channel are preserved as a basin plain succession of variable fill geometry and lithology. In high-resolution seismic profiles the basin plain succession is characterised by laterally discontinuous and transparent, mounded lensoid bodies interbedded with acoustically well-layered sediments which display drape and onlapping reflection configurations. The lensoid bodies comprise an up to 50 m thick amalgamated package of mass-flow deposits consisting primarily of debris-flow diamictons. They represent resedimented glacigenic deposits derived from the West Shetland Shelf. Accumulation of these packages was episodic and related to specific rapid phases of downslope resedimentation, most probably concomitant with ice-marginal deposition on the West Shetland Slope. The acoustically well-layered sediments include glaciomarine hemipelagites and contourites. These indicate phases of reduced sediment supply from the adjacent shelf and slope areas, and probably represent the more pervasive “background” sedimentation in the basin. Although weak bottom-current activity may have prevailed throughout the glacial episodes, the onset of vigorous bottom-current circulation occurred at the changeover from a glacial to an interglacial regime. The debris flow packages form about 50% of the basin-plain sediments in this part of the Faeroe-Shetland Channel, thereby forming a significant component of the deep-water succession. 相似文献
7.
本文根据反射地震、折射地震、磁力等资料，结合周边地质，探讨冲绳海槽南段基底组成。在海槽周边的东海陆架盆地、台湾褶皱带和琉球岛弧褶皱带，均出露不同程度变质的晚古生代、中生代和早第三纪地层。多道反射地震表明，海槽南段沉积盖层由上第三系和第四系组成，声学基底由下第三系及更老地层构成。邻近海槽的折射地震揭示，除第四系-中新统速度层之外，还存在纵波速度分别为4．7～5．3km／s和6．3km／s的下第三系和中生界速度层。磁异常分析和正反演拟合计算结果表明，海槽磁性基底主要由变质岩系构成，次为燕山期中酸性岩浆岩和喜山期中基性岩浆岩，磁性基底大部分相当声学基底。综合分析表明，海槽南段基底主要由不同程度变质的下第三系、中生界和上古生界构成；在海槽某些构造部位，已有喜山期基性岩浆岩形成。 相似文献
8.
A Deep-sea Channel in the Northwestern Mediterranean Sea: Morphology and seismic structure of the Valencia Channel and its surroundings 总被引：2，自引：0，他引：2
Belen Alonso Miquel Canals Alberto Palanques Jean-Pierre Rehault 《Marine Geophysical Researches》1995,17(5):469-484
The 400 km long Valencia Channel occupies the axis of the Valencia Trough in the Northwestern Mediterranean. Four different types of seismic reflection profiles were used to analyze the morphology and structure of the Valencia Channel with regard to the role played by both margins, Balearic and Iberian, of the Valencia Trough. From a detailed morphoseismic analysis of the Valencia Channel, its upper, middle, and lower courses can be characterized as follows: (1) in the upper course, tributaries are short and only slightly incised, with recent mass-transport deposits occurring on the adjacent continental slopes; (2) in the middle course, the channel deepens, and tributary valleys merge into it; and (3) the lower course begins after a sudden change in the direction of the channel, has a meandering path, is flanked by levees, and is fed by some valleys.During the Pliocene and Quaternary, at least four erosional and filling phases are observed in seismic profiles of the lower course of the Valencia Channel. The varying intensity of mass-transport processes and associated retrogressive slumping, which are related with fluctuations in sediment supply and relative sea-level changes, have played a major role in the formation, maintenance and deepening of the Valencia Channel. In addition to these sedimentary processes, a basement tectonic control and some morphostructural features affect the direction of the Valencia Channel locally. 相似文献
9.
《Marine and Petroleum Geology》2003,20(6-8):649-676
High-resolution multichannel 2-D and 3-D seismic data, primarily from upper fan reaches of near-seafloor channel-levee systems on the Niger Delta slope and in the Arabian Sea, reveal a high level of detail and architectural complexity. Several architectural elements are common to each system examined in this study. They include inner levees, outer levees, erosional fairways, channel-axis deposits, rotational slumps blocks, and mass transport deposits. Although the scale of individual systems varies significantly, similarities in first-order architectural elements and their configurations suggest that common depositional processes are involved regardless of scale differences.Most of the channel-levee systems examined in this study are characterized by a basal erosional fairway that is bordered by outer levees of varying thickness. Together these elements define the base and margins of the channel-belt, where channel-axis deposits and inner levees are the dominant architectural elements. Vertical, sub-vertical, and lateral stacking patterns of sinuous and/or meandering channels create seismic facies that range from narrow to wide zones of high amplitude reflections (HARs) with chaotic to continuous and shingled to horizontal reflections. Some HARs appear as isolated or stacked asymmetric to symmetric u- and v-shaped reflections, referred to here as channel-forms. Channel-belts evolve within the confines of the scalloped erosional fairway walls (flanked by outer levee), and are similar in morphology to meander-belts in fluvial systems, but commonly have a greater component of vertical aggradation. Detailed study of one particular channel-levee system on the Niger Delta slope shows a period of incision followed by three distinct phases of channel development during its aggradational history. Each fill phase corresponds to a different channel stacking architecture, planform geometry, and nature of terrace development, with important implications for reservoir architecture. In some cases, multiple phases of inner levee growth are observed, each intimately linked to the channel migration and aggradation history. Channel sinuosity evolves dynamically, with some meander loops undergoing periods of accelerated meander growth at the same time that others show little lateral migration. 相似文献
10.
冲绳海槽西部陆坡地震相模式与沉积体系 总被引：8，自引：3，他引：5
对冲绳海槽西部陆坡上两个航次(95航次和99航次)共计2000多公里的单道地震资料进行分析和解译,对斜坡沉积环境下沉积体系发育、分布特征进行了研究。结果表明：a)冲绳海槽西部斜坡环境下,上新世以来的沉积层均不同程度的变形和错动;b)存在两种斜坡相地震反射模式——退覆模式和叠覆模式,这两种模式都反映了冲绳海槽西部陆坡得到充足的沉积物供给;c)斜坡环境下主要发育陆架边缘三角洲、重力流沉积和水道充填等沉积体系;d)沉积层发育特征表明,冲绳海槽西部陆坡具有北段坡度缓、沉积物供应丰富、构造相对不活跃,中段坡度陡、沉积物供应充足、构造活动强烈,南段坡度陡、沉积供应相对较少、构造和火山活动十分强烈3种主要沉积环境。西部陆坡的沉积特征也揭示了东海陆架向陆坡提供了大量碎屑沉积物质。 相似文献
11.
The interpretation of 2D and 3D seismic reflection data complemented with gravity data allows the crustal architecture of the deepwater west Niger Delta passive margin to be defined. The data show that the area is underlain by oceanic crust that is characterised by a thickness of 5–7 km and by internal reflectivity consisting of both dipping and sub-horizontal reflectors. Some of the dipping reflections can be traced up to the top of the basement where they offset it across a series of minor to major thrust faults. Other internal reflections are attributed to extensional shear zones and possibly due to intrusions in the lower crust. The Moho can be correlated as a discrete reflection over >70% of the study area. It is generally smooth, but localised relief of up to 1 km is observed. The southeastern part of the study area is dominated by a zone of SW–NE striking basement thrusts. 相似文献
12.
13.
《Marine and Petroleum Geology》2012,36(1):176-189
High-quality 3D seismic data are used in this paper to: a) investigate the geometry of Miocene–Holocene submarine channels in confluence regions, and b) to correlate the geometry of channel confluences with the styles of topographic confinement imposed by salt structures in the Espírito Santo Basin (SE Brazil). A new method is used to analyse geomorphic parameters of three channel intervals (Units 1–3) and a modern channel. 5348 Channel Points (CP) are recorded on a sinusoidal slope interrupted by salt structures. In the upper-slope region, diapir confinement directly controls the location of channel confluences. These are characterised by a sharp increase in channel width and height at their junctions. Scale relationships show an increase in channel width of the order of 1.19 < W < 1.22 in confluence regions. Ratios of channel height between confluence and pre-confluence regions are 1.09 < H < 1.40, with ratios of <1 observed in post-confluence regions. This work proves the existence of a direct relationship between topographic confinement, confluence location and relative channel distribution. The studied submarine confluences are located in regions with high confinement created by salt diapirs. The results of this work are significant, as they show clustered distribution patterns in channels, with higher channel densities being observed in pre-confluence regions. Thus, we propose a new classification for submarine confluences based on a combined analysis of channel geometry and seismic attribute data. Confluences may be symmetric or asymmetric based on the equality of the angles the tributaries bear to the post-confluence channel. Symmetric confluences can be left or right symmetric, based on whether the dominant flow path is in the left- or right-hand tributary. Asymmetric confluences are pure asymmetric or secondary asymmetric depending on whether the dominant flow takes place along the main tributary and the post-confluence channel alignement, or along the secondary tributary which is at an angle with the main alignement. 相似文献
14.
The southern Makran fold-thrust belt, Pakistan, displays unique outcrop examples of well-exposed, kilometre-scale, listric growth faults that displace Miocene-age deltaic growth strata by several hundreds of metres to kilometers. The largest growth faults are counter-regional (landward-dipping), bounding major clastic depocentres exposed over areas > 1000 km2. Stratal offset along these faults can exceed 1.5 km. Fault-zone thicknesses range between ca. 100 and 400 m, and average fault thickness-displacement ratios are around 1:10. High-resolution satellite data show in unprecedented detail the faults and the stratigraphic architecture of associated growth sequences, which comprise kilometre-scale progradational clinoforms, thick mudstone units and basinwards wedging sandstone-shale deposits. The true vertical thickness of the syn-kinematic record is, in places, up to 8 km, making the outcrop examples equivalent to major growth faulted successions known from seismic data of large deltas, and at least an order of magnitude larger than other outcrop examples. A comparison of the Makran outcrops with seismic-reflection examples offshore NW Borneo reveals distinct similarities in the gross depocentre geometries and internal architecture. The key control for growth faulting is interpreted to result from sedimentary loading, with rapid sedimentary progradation causing the development of rollover synclines by differential compaction and fluid expulsion, and counter-regional growth faults preferentially forming on the basinward side of these synclines. The data and interpretations presented can be used to assess the key parameters that contribute to the development of growth faults and growth successions above shale, reinforcing structural and stratigraphic observations from seismic interpretation and modelling studies in demonstrating their occurrence in exposure. 相似文献
15.
浙江三门湾猫头深潭风暴快速沉积研究 总被引：2，自引：2，他引：2
三门湾频受热带风暴的影响,风暴期出现剧烈的滩冲、槽淤的泥沙交换,而在风暴后的正常天气条件下,则产生滩淤、槽冲的泥沙交换过程.通过猫头深潭(槽)9417号台风前后剖面水深重复测量、沉积特征及沉积物放射性同位素(210Pb,137Cs)测年等资料,揭示猫头深潭风暴快速沉积(骤淤).正常天气条件下风暴沉积产生再悬浮随潮运移,深潭水深得以恢复.在连续强热带风暴的影响下,又遇强的风暴增水,风暴沉积难以完全被冲刷,部分残留在深潭内,在猫头深潭沉积层中储存着风暴沉积的信息 相似文献
16.
按河道形态,河流分为４类：（１）顺直河;（２）曲流河;（３）辫状河;（４）网状河。根据河道砂岩体主体的宽（ｗ）与（ｈ）高之比,河道砂岩体分为带状砂岩体（ｗ∶ｈ小于１５）和席状砂岩体（ｗ∶ｈ大于１５）。在参考前人资料的基础上,总结了在横切河道的地震剖面上河道砂岩体的反射形态、结构及振幅变化。重点介绍了曲流河内侧沙洲地震勘探,以及三维地震勘探技术在寻找河道砂岩体方面的应用。并强调指出,在河道砂岩体地震勘探中,应当加强地震资料与钻井资料、测井资料的结合。 相似文献
17.
Magnetic signature of the Sicily Channel volcanism 总被引：1，自引：0，他引：1
Widespread Late Miocene to Quaternary volcanic activity is know to have occurred in the Sicily Channel continuing up to historical
time. New magnetic anomaly data acquired in the Pantelleria Graben, one of the three main tectonic depressions forming the
WNW-trending Sicily Channel rift system, integrated with available profiles, are used to identify and map volcanic bodies
in this sector of the northern African margin. Some of these manifestations, both outcropping at the sea-floor or buried beneath
a variable thickness of Plio-Quaternary sedimentary cover, have been imaged by seismic reflection profiles. Three main positive
magnetic anomalies have been found: to the S–E of the Pantelleria Island, the largest emerged caldera of the Sicily Channel,
along the eastern margin of the Nameless Bank, and at the north–western termination of the Linosa Graben. Only the anomaly
located off the south–eastern coast of the Pantelleria Island, associated with a large outcropping body gradually buried beneath
a substantially undisturbed Upper Pliocene-Quaternary sediments, aligns with the trend of the tectonic depression. 2-D geophysical
models produced along seismic transects perpendicularly crossing the Pantelleria Graben have allowed to derive its deep crustal
structure, and detect the presence of buried magmatic bodies which generate the anomalies. Marginal faults seem to have played
a major role in focussing magma emplacement in this sector of the Sicily Channel. The other anomalies represent off-axis volcanic
episodes and generally do not show evident magmatic manifestations at the sea-floor. These magnetic maxima seem to follow
a NNE-SSW-trending belt extending from Linosa Island to the Nameless Bank, where pre-existing crustal anisotropies may have
conditioned magma emplacement both at deep and shallow crustal levels. In general, data analysis has shown that there is a
structural control on magma emplacement, with the major magmatic features located in specific locations like boundary faults
and transfer zones, in a manner similar to that found along several segments of the East African Rift system. 相似文献
18.
《Marine and Petroleum Geology》2012,37(1):83-99
Three-dimensional seismic data from the Sørvestsnaget Basin, SW Barents Sea supported by well data, are used to investigate a Middle Eocene deep-water depositional system. The system forms a NNW-oriented sediment accumulation, characterized by increased seismic amplitudes, and abrupt western termination. The data indicate that post-depositional sand remobilization and injection led to formation of sub-circular sediment blocks up to several km wide to the east of the main accumulation. The deep-water depositional system was deformed by wing-like sandstone intrusions, extending 200–400 m upwards from the margins of the parent sand bodies. The intrusions have polygonal or broadly circular plan view geometries. Deformation is inferred to have been associated with overpressure of the sand bodies as a result of rapid burial, fluid migration into the sealed sand bodies from deeper sources via synsedimentary faults, and fluid drainage from the surrounding mudrock during early compaction. The final triggering mechanism for sand remobilization and injection is inferred to have been fracture propagation due to differential compaction and/or fault-induced earthquakes. The injectite complexes are often associated with folding of overlying strata, which we relate to differential compaction. Intrusion of sand took place during the Middle Eocene. Post-depositional sand remobilization and injection have important implications for hydrocarbon exploration because they cause changes in the reservoir primary architecture, connectivity and structure. 相似文献
19.
Camerlenghi Angelo Domack Eugene Rebesco Michele Gilbert Robert Ishman Scott Leventer Amy Brachfeld Stefanie Drake Allison 《Marine Geophysical Researches》2001,22(5-6):417-443
We present the results of a marine geophysical investigation of the northern Prince Gustav Channel. By comparative analysis of multibeam bathymetric data, single channel seismic reflection profiles, underway chirp sonar data, ADCP current data and sediment coring, we define the main morphological elements of the area. In particular we define the glacial morphogenesis in relation to the excavation of inner shelf basins and troughs along structural discontinuities and lithologic boundaries. We identify streamlined surfaces that testify to the grounding of ice and past ice flow directions. These glacial forms are found only on glacial tills preserved in the deepest part of the basins, while net erosion to bedrock has occurred elsewhere. Since the Last Glacial Maximum (LGM), the relict glacial morphology has been draped by hemipelagic and diatomaceous mud, and bottom currents have played a major role in focusing sedimentation within small depocentres, that we define as contouritic drifts. Based on shallow sediment architecture and supported by direct measurements, we propose that the direction of bottom water flow is from the outer shelf into the Prince Gustav channel as a result of a combination of tidal currents and ice shelf-related thermohaline circulation. 相似文献
20.
The Barcelona continental shelf is part of a 6–20 km wide canyon-bounded shelf located off the city of Barcelona (NE Spain). This study integrates newly acquired high-resolution single channel seismic reflection profiles and available lithological information of the Barcelona shelf to describe its late Quaternary architecture and the role of global glacio-eustatic fluctuations and local factors in its development.
Four major sequence boundaries are identified throughout the seismic dataset. They are tentatively correlated with the four last 4th order (100–120 ka) high-amplitude late Quaternary glacio-eustatic lowstands. Most of the stratigraphic record is formed by falling stage systems tracts with forced-regressive deposits, which confers a general progradational vertical stacking pattern. Transgressive systems tracts are represented by continuous units confined directly off river sources and on previously eroded surfaces. Stillstand deposits are difficult to recognize in the available dataset. The uppermost seismic unit corresponds to the Holocene shore-parallel Besos and Llobregat joint prodelta affected by the prevailing south-westward circulation.
The general architecture of the late Quaternary Barcelona shelf deposits is determined by global glacio-eustatic cycles. However, the lateral variability of the seismic units depends largely on local factors such as (i) the position of sediment sources (essentially the Llobregat River); (ii) differential subsidence and, especially, sediment compaction; (iii) erosive processes such as canyon incision, mass wasting or wave base dynamics; and (iv) underlying geomorphic restrictions. 相似文献