scholarly journals Basin margin sediment wedge build out of the Eastern Niger Delta: application of shelf-edge trajectory pattern studies

2021 ◽  
Vol 11 (3) ◽  
pp. 1093-1100
Author(s):  
Okwudiri A. Anyiam ◽  
Nicholas Hoggmascall ◽  
Daniel K. Amogu
Keyword(s):  
Niger Delta ◽  
Sudden Change ◽  
Sediment Flux ◽  
Outer Shelf ◽  
Shelf Edge ◽  
Structural Style ◽  
Shelf Slope ◽  
Trajectory Pattern ◽  
Shelf Margin ◽  
Basin Margin

AbstractThe understanding of how basin margin sediment wedge builds out causes shelf-edge migration with time is approached based on shelf-edge trajectory pattern analysis using a high-resolution mega-merge seismic data from the eastern Niger Delta, Nigeria. The study focuses on a seismic dip transect traversing the Greater Ughelli, Central Swamp, Coastal Swamp and the Shallow Offshore Depobelts of the Niger Delta. On the regional dip transects, shelf-edge sediments occur as clinoform-bearing wedges at and immediately updip of the shelf-slope break. The shelf edge is deeply buried (> 2–4 s, twt), around the Greater Ughelli and Central Swamps. But with changing structural style, sudden change of ascending shelf edge around the Central Swamp was observed. The huge listric growth fault in the Coastal Swamp; around Bonny area, once again cut the shelf edge into half, rotated it along the listric fault and buried it distally. Several depositional packages show low to moderate ascending shelf-edge trajectory with progradational to aggradational clinoform growth that is characterized by thin sand sheets across most of the shelf and upper slope, though few are also characterized by progradational clinoform growth with thick sand on the shelf, upper-tolower slope and basin floor. The deposition is usually on the Outer Shelf Terrace (OST) which is regressive in a flat and rising trajectory style. This study has demonstrated that accommodation and sediment flux are the dominant controls on how the study basin’s sediment wedge built out, whereby limited accommodation promotes sediments with significant shelf-edge advance and descending trajectories, while increasing accommodation promotes ascending trajectories and increased deposition on the outer shelf. The greater sediments on the Outer Shelf Terrace and the shelf margin than on the slope gives more hydrocarbon prospectivity search around the outer shelf and shelf margin.

Clinoform growth and sediment flux of Late Cenozoic Yinggehai and Qiongdongnan shelf margins, Northern South China Sea

2021 ◽  
Author(s):  
Si Chen ◽  
Hua Wang ◽  
Jianghao Ma ◽  
Tianhao Gong ◽  
Zhenghong Yu
Keyword(s):  
South China Sea ◽  
South China ◽  
Northern South China Sea ◽  
Sediment Flux ◽  
Shelf Edge ◽  
Late Cenozoic ◽  
China Sea ◽  
Shelf Margin ◽  
Shelf Margins ◽  
Basin Margin

<p>This study discusses the sedimentary flux, and sedimentary system source tracking on the shelf margins of Yinggehai (YGH) and Qiongdongnan (QDN) Basins, Northern South China Sea. The shelf margin clinoforms of YGH and QDN Basins, have grown since the Late Cenozoic (10.5 Ma), which generated more than 4 km-thick shelf prism above the T40 surface. By using the core, well drilling data, 2D and 3D seismic surveys, this study aims to: ① demonstrate the geometry morphology and architecture of the clinoforms, while the shelf margin trajectory (including the shelf-edge trajectory and toe of slope trajectory) showing down-flatting and rising patterns where the progradation and aggradation happened through the vertical evolution; ② estimate sediment supply values, load volumes, and their changes since the Late Cenozoic, predict ratio of the sediment flux across shelf-edge during their dynamic processes; ③ investigate the contradiction and correlation among the phenomena that sediments show distinctly increasing in flux, decreasing in grain size, and response delay of flux rate peak since 2-4 Ma. The preliminary results show that the vertical sediment accumulation rate increased significantly across the entire YGH and QDN Basin margin system after 2.4 Ma, with a marked increase in mud content that likely caused by long‐distance, alongshore currents with high content of mud during the Pleistocene. Furthermore, laterally, the estimated total sediment flux onto the margin shows a dramatic decline from west to east while moving away from the Red River depocenter, as well as a decrease in the percentage of total discharge crossing the shelf break in this same direction. The overall margin geometry shows a remarkable change from sigmoidal, strongly progradational and aggradational in the west to weakly progradational in the east of QDN Basin margin. The Late Cenozoic shelf margin growth, with its overall increased sediment flux, responded to global, high‐frequency transgressive‐regressive climate cycles during a falling global sea level and gradual cooling temperature in this icehouse period.</p>

Sedimentation and tectonism in the Middle Ordovician of the Girvan district, SW Scotland

1984 ◽  
Vol 75 (2) ◽  
pp. 225-237 ◽  
Author(s):  
David Ince
Keyword(s):  
Source Area ◽  
Outer Shelf ◽  
Shelf Area ◽  
Shallow Marine ◽  
Northern Margin ◽  
Middle Ordovician ◽  
Fan Delta ◽  
Shelf Slope ◽  
Marine Carbonates ◽  
Basin Margin

ABSTRACTThe Kirkland Conglomerate and the Benan Conglomerate and associated sediments of the Barr Group (Ordovician—Llanvirn-Llandeilo) of the Girvan district, SW Scotland record the development of two fan-delta systems situated on the northern margin of Iapetus. The intervening Stinchar Limestone represents a shallow marine fan-delta abandonment facies. Subaerial fan-delta deposits are seen at the lowest exposed horizons within the Kirkland Conglomerate. Transgression and eventual abandonment of the fan-delta system is recorded by (1) matrix-rich gravels forming the topmost horizons of the unit. (2) subaqueous distributary channel sands of the overlying transitional sandstone and associated shallow-marine carbonates of the Auchensoul Limestone and (3) shallow-marine sandstones of the Confinis Flags. Following a period of shallow-water sedimentation (Stinchar Limestone), a phase of rapid subsidence occurred during the upper Llandeilo, broadly synchronous with the Nemagraptus gracilis Zone transgression. Lowermost horizons of the succeeding Benan Conglomerate comprise re-sedimented gravels and laterally equivalent ‘outer shelf’ deposits (Superstes Mudstone). Renewal of coarse clastic sedimentation resulted from source area uplift related to granite plutonism, responsible also for the rapid subsidence of basinal areas. Fan-delta progradation is recorded by the occurrence of braided-fluvial deposits and shallow-marine carbonates at higher stratigraphical levels within the unit. Progradation of the fan-delta complex resulted from a gradual reduction in subsidence rates along basin-margin faults.Fan-deltas of the Barr Group prograded southwards, from a SW—NE-trending faultdelineated basin margin, across a narrow shelf area. To the S of the shelf area defined by Barr Group outcrop, sediments of the Tappins complex accumulated in outer shelf, ?slope and base of slope settings.The thickness of individual conglomerate units (>150 m—Kirkland Conglomerate, and up to 700 m—Benan Conglomerate), the associated high sedimentation rates, narrowness of the shelf area, and distribution and style of basin-margin faults indicate that oblique-slip motion along the northern margin of Iapetus may have provided a major control over Middle Ordovician sedimentation in the Girvan district.

scholarly journals Lateral variability of shelf-edge and basin-floor deposits, Santos Basin, offshore Brazil

2020 ◽  
Vol 90 (9) ◽  
pp. 1198-1221
Author(s):  
Michael J. Steventon ◽  
Christopher A-L. Jackson ◽  
David M. Hodgson ◽  
Howard D. Johnson
Keyword(s):  
Mass Movement ◽  
Three Dimensional ◽  
Outer Shelf ◽  
Continental Margins ◽  
Shelf Edge ◽  
Sequence Stratigraphic ◽  
Se Brazil ◽  
Basin Floor ◽  
Shelf Margin ◽  
Upper Slope

ABSTRACT Construction of continental margins is driven by sediment transported across the shelf to the shelf edge, where it is reworked by wave, tide, and fluvial processes in deltas and flanking clastic shorelines. Stalling of continental-margin progradation often results in degradation of the outer shelf to upper slope, with resedimentation to the lower slope and basin floor via a range of sediment gravity flows and mass-movement processes. Typically, our understanding of how these processes contribute to the long-term development of continental margins has been limited to observations from broadly two-dimensional, subsurface and outcrop datasets. Consequently, the three-dimensional variability in process regime and margin evolution is poorly constrained and often underappreciated. We use a large (90 km by 30 km, parallel to depositional strike and dip, respectively) post-stack time-migrated 3D seismic-reflection dataset to investigate along-strike variations in shelf-margin progradation and outer-shelf to upper-slope collapse in the Santos Basin, offshore SE Brazil. Early Paleogene to Eocene progradation of the shelf margin is recorded by spectacularly imaged, SE-dipping clinoforms. Periodic failure of the outer shelf and upper slope formed ca. 30-km-wide (parallel to shelf-margin strike) slump scars, which resulted in a strongly scalloped upper-slope. Margin collapse caused: 1) the emplacement of slope-attached mass-transport complexes (MTCs) (up to ca. 375 m thick, 12+ km long, 20 km wide) on the proximal basin floor, and 2) accommodation creation on the outer shelf to upper slope. This newly formed accommodation was infilled by shelf-edge-delta clinoforms (up to 685 m thick), that nucleated and prograded basinward from the margin-collapse headwall scarp, downlapping onto the underlying slump scar and/or MTCs. Trajectory analysis of the shelf-edge deltas suggests that slope degradation-created accommodation was generated throughout the sea-level cycle, rather than during base-level fall as would be predicted by conventional sequence-stratigraphic models. Our results highlight the significant along-strike variability in depositional style, geometry, and evolution that can occur on this and other continental margins. Coeval strata, separated by only a few kilometers, display strikingly different stratigraphic architectures; this variability, which could be missed in 2D datasets, is not currently captured in conventional 2D sequence stratigraphic models.

Controls on the sedimentary characteristics of shelf-edge deltas in a source-to-sink context

2021 ◽  
Author(s):  
Laura Bührig ◽  
Luca Colombera ◽  
Nigel P. Mountney ◽  
William D. McCaffrey
Keyword(s):  
Late Quaternary ◽  
Depositional Environments ◽  
Late Triassic ◽  
Hydrodynamic Process ◽  
Shelf Edge ◽  
Sea Level Changes ◽  
Sedimentary Characteristics ◽  
Shelf Slope ◽  
Source To Sink ◽  
Shelf Margin

<p>Shelf-edge deltas constitute important components of source-to-sink (S2S) systems. They distribute sediment to continental slopes and basin floors from rivers that have prograded across shelves, and due to their scale they form significant sediment accumulations at shelf margins. Because of their intimate relationship with regressive conditions, several geological controls govern their evolution, including relative sea-level changes, sediment budgets, river hydrology, and hydrodynamic processes; these factors are themselves influenced by characteristics of terrestrial catchments and continental shelves, and by climate. Despite their important role in sediment dispersal to shallow- and deep-marine environments, shelf-edge deltas are commonly overlooked in models that describe S2S systems, perhaps because of their relative paucity during the present-day highstand conditions. In subsurface and outcrop, their recognition can be difficult in cases where information with which to constrain the physiographic environment is limited, such that the spatial position of a delta relative to the shelf margin cannot be determined unequivocally.</p><p>This study aims to improve our understanding of controls on the sedimentary characteristics of shelf-edge deltas. For this purpose, >40 shelf-edge deltas of Late Triassic to late Quaternary age from >30 globally-distributed shelf-margin successions have been investigated, utilising literature-derived seafloor-, subsurface- and outcrop data. Following a database approach, sedimentary records have been quantitatively analysed in terms of geometry (e.g. dimensions, thickness, gradients) and facies characteristics (e.g. lithology, sedimentary structures) of depositional environments (e.g. delta top, delta front) and architectural elements (e.g. delta lobes, distributary mouth bars). Specific consideration has been given to assessment of palaeoenvironmental setting (e.g. hydrodynamic process regime, margin type, bathymetric setting, palaeolatitude). Moreover, scaling relationships between these properties and attributes of the S2S system (e.g. fluvial-system and catchment attributes, shelf configuration, shelf-slope transition) have been evaluated. Accordingly, the relative importance of controls on the sedimentary characteristics of shelf-edge deltas has been assessed.</p><p>This analysis demonstrates that environmental factors influence the sedimentary record of shelf-edge deltas via a complex interplay of dynamic processes and physiography of the S2S segments catchment, shelf and slope. Based on these findings, new facies models for shelf-edge delta types are developed, which are placed in the context of S2S linkages. Outcomes of this study aid the identification and classification of shelf-edge deltas and their preserved deposits, as well as the reconstruction of associated environmental conditions from stratigraphic records.</p>

scholarly journals A forced regressive shelf-margin wedge formed by transition-slope progradation: lowermost Cretaceous Rauk Plateau Member, Jameson Land, East Greenland

2005 ◽  
Vol 52 ◽  
pp. 227-243 ◽  
Author(s):  
F. Surlyk
Keyword(s):  
Sea Level ◽  
Large Scale ◽  
Coarse Grained ◽  
Shelf Edge ◽  
High Angle ◽  
Seismic Profiles ◽  
East Greenland ◽  
Shelf Slope ◽  
Forced Regression ◽  
Shelf Margin

The Middle Jurassic – lowermost Cretaceous succession of Jameson Land, East Greenland records a marine, overall regressive–transgressive–regressive cycle with regressive maxima in the Late Bajocian and Late Volgian separated by a transgressive maximum in the Kimmeridgian. Smaller-scale regressive interludes took place in the Late Callovian and Mid Oxfordian. A shelf-slope-basin physiography started to develop in the Late Callovian due to increasing rifting and a relief of several hundred metres was attained during maximum end-Jurassic regression and deposition of the Volgian Raukelv Formation. The formation consists of a forestepping stack of laterally extensive shelf-edge wedges, each several tens of metres thick, composed of coarse-grained sandstone, showing highangle clinoform bedding and containing marine body and trace fossils. These clinoform beds are superimposed on the large-scale clinoforms of the shelf–slope–basin. The wedges onlap older shelf deposits in a landward direction and are overlain by thin transgressive sandstones or mudstones, or directly by the next coarse-grained wedge. The top wedge, comprising the Rauk Plateau Member, is of Late Volgian (i.e. earliest Cretaceous) age and is characterized by steep clinoforms truncated by internal erosional downlap surfaces. The clinoforms are simple avalanche beds, a few tens of centimetres thick, or they may be several metres thick and contain large-scale cross-bedded intrasets of probable tidal origin. The erosional events were associated with downshift of the succeeding clinoforms, recording minor sea-level fall and forced regression. The top surface of the Rauk Plateau wedge is incised by a system of minor channels leading to a large canyon-like valley. The wedge was deposited by transition-slope progradation below wave base during a period of sea-level stillstand punctuated by minor, stepwise falls. It provides an excellently exposed example of a laterally derived, coarse-grained shelf-margin wedge, showing high-angle clinoform bedding and representing an ancient counterpart to Holocene and Late Pleistocene prograding infralittoral wedges seen on seismic profiles across Mediterranean shelf edges.

Seismic chronostratigraphy and basin development at a Mid-Cretaceous intrashelf basin margin

2015 ◽  
Vol 3 (2) ◽  
pp. SN1-SN20 ◽  
Author(s):  
Stanley Rich Wharton
Keyword(s):  
Source Rocks ◽  
Main Step ◽  
3D Seismic ◽  
Sea Level Changes ◽  
Seismic Reflection Data ◽  
Seismic Sequences ◽  
Shelf Slope ◽  
Intrashelf Basin ◽  
Shelf Margin ◽  
Basin Margin

The Mid-Cretaceous Wasia Formation represents one of the most productive hydrocarbon carbonate sequences in the Middle East. In Saudi Arabia, limited integrated studies have assessed the complexity and spatial distribution of its reservoir depositional systems near to an intrashelf basin margin. This study was focused on an assessment of its 3D seismic chronostratigraphy by integrating key well and seismic data to evaluate the gross depositional history of the mixed carbonate-clastic system. A seismic chronostratigraphy approach was introduced to assess the geometric relationships of depositional cycles and lithologic associations in response to relative sea-level changes. The main step entailed the correlation of well log chronostratigraphy from core and biostratigraphy interpretations with closely spaced, semiautomatically generated seismic horizons from seismic reflection data. A 3D seismic chronostratigraphy cube was built to interactively assess the basin history through the Mid-Cretaceous stages. Seismic sequences were selected to assess isopachs and gross depositional trends for demarcation of shelf, shelf margin, and slope from horizon attributes including root-mean-square amplitude and frequency decomposition. The results found the oldest Albian Safaniya member to be a generalized low-angle ramp shelf slope with thinning of sequences toward an intrashelf basin. Later, in the Albian, Cenomanian, and Turonian, carbonate factories developed distinct seismic sequences with steepened prograding systems in the Mauddud, Ahmadi/Rumaila, and Mishrif members at the intrashelf basin margin. Generally, areas immediately landward of the shelf margin possessed the most favorable reservoir lithologies of rudist-bearing platform carbonates, with source-rock distribution confined to basinal equivalents of sequences. The seismic chronostratigraphy approach proved to be fundamental to understanding the Wasia carbonate depositional system because it provided a technique to assess the varied stratal architectures of the main productive sequences. The integrated technique represents a unique methodology for exploration targeting of conventional reservoirs and unconventional source rocks.

The arrival of the paleo–Orinoco Delta at Trinidad: The Cruse Formation delta lobes and delivery to deepwater Atlantic

2020 ◽  
Vol 90 (8) ◽  
pp. 938-968
Author(s):  
Ariana Osman ◽  
Ronald J. Steel ◽  
Ryan Ramsook ◽  
Cornel Olariu ◽  
Si Chen
Keyword(s):  
Sea Level ◽  
Late Miocene ◽  
Sediment Supply ◽  
Average Height ◽  
Shelf Edge ◽  
Sea Level Changes ◽  
Orinoco Delta ◽  
Basin Floor ◽  
Shelf Margin ◽  
High Sediment

ABSTRACT Icehouse continental-shelf-margin accretion is typically driven by high-sediment-supply deltas and repeated glacio-eustatic, climate-driven sea-level changes on a ca. 100 ky time scale. The paleo–Orinoco margin is no exception to this, as the paleo–Orinoco River Delta with its high sediment load prograded across Venezuela, then into the Southern and Columbus basins of Trinidad since the late Miocene, depositing a continental-margin sedimentary prism that is > 12 km thick, 200 km wide, and 500 km along dip. The Cruse Formation (> 800 m thick; 3 My duration) records the first arrival of the paleo–Orinoco Delta into the Trinidad area. It then accreted eastwards, outwards onto the Atlantic margin, by shallow to deepwater clinoform increments since the late Miocene and is capped by a major, thick flooding interval (the Lower Forest Clay). Previous research has provided an understanding of the paleo–Orinoco Delta depositional system at seismic and outcrop scales, but a clinoform framework detailing proximal to distal reaches through the main fairway of the Southern Basin has never been built. We integrate data from 58 wells and outcrop observations to present a 3-D illustration of 15 mapped Cruse clinoforms, in order to understand the changing character of the first Orinoco clastic wedge on Trinidad. The clinoforms have an undecompacted average height of 550 m, estimated continental slope of 2.5° tapering to 1°, and a distance from shelf edge to near-base of slope of > 10 km. The clinoform framework shows trajectory changes from strong shelf-margin progradation (C10–C13) to aggradation (C14–C20) and to renewed progradation (C21–24). Cruse margin progradational phases illustrate oblique clinothem geometries that lack well-developed topsets but contain up to 70 m (200 ft) thick, deepwater slope channels. This suggests a high supply of sediment during periods of repeated icehouse rise and fall of eustatic sea level, with fall outpacing subsidence rates at times, and delivery of sand to the deepwater region of the embryonic Columbus channel region. Also, evidence of wholesale shelf-edge collapse and canyon features seen in outcrop strongly suggest that deepwater conduits for sediment dispersal and bypass surfaces for Cruse basin-floor fans do exist. The change to a topset aggradational pattern with a rising shelf trajectory may be linked to increased subsidence associated with eastward migration of the Caribbean plate. The Cruse-margin topsets were dominated by mixed fluvial–wave delta lobes that were effective in delivery of sands to the basin floor. The preservation of a fluvial regime of the delta may have been impacted by basin geometry which partly sheltered the area from the open Atlantic wave energy at the shelf edge. Ultimately, understanding shelf-edge migration style as well as process-regime changes during cross-shelf transits of the delta will help to predict the location of bypassed sands and their delivery to deepwater areas.

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