Sequence Stratigraphy and Depositional Environment of the Zubair Formation in Rumaila Oilfields, Southern Iraq: Microfacies and Geochemistry

In the Rumaila oilfields in southern Iraq, the Zubair Formation was deposited in a shallow environment as three main facies, delta plain, backshore, and delta front depositional conditions indicating a transition from delta front and delta plain to a highstand level due to the finning upward mode. The facies of the Zubair clasts show well-sorted quartz arenite sandstone, poorly sorted quartz arenite sandstone, clayey sandstone that has not been properly sorted, sandy shale, and shale lithofacies. The minor lithofacies were identified using well-logging methods (gamma ray, spontaneous potential and sonic logs) and petrography. The Zubair clasts are of transition environment that appears to be transported from freshwater and deposited in a marine environment forming many fourth-order cycles reflect sea level rise fluctuations and still-stand under tectonics developed the sequence stratigraphy. A misalignment between relative sea-level and sediment supply caused asymmetry sedimentary cycles. A shallower environment of shale-dominated rocks rich in organic matter and pyrite were exposed. The basinal shale of Ratawi at the Zubair bottom and the shallow carbonate of Shuaiba emplace on the Zubair represent the beginning of the delta build up (delta front and delta plain) to a highstand stage.

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Clastic facies models, a personal perspective

Bulletin of the Geological Society of Denmark ◽

10.37570/bgsd-2001-48-05 ◽

2001 ◽

Vol 48 ◽

pp. 101-115

Author(s):

Harold G. Reading

Keyword(s):

Sea Level ◽

Sequence Stratigraphy ◽

Sedimentary Rocks ◽

Sediment Supply ◽

Personal Perspective ◽

Sea Level Changes ◽

Ancient Rock ◽

Tectonic Movements ◽

Over Time ◽

Facies Models

Facies models evolved from classifications that were mainly descriptive, based on observable, measureable features such as the composition and texture of sedimentary rocks. As our understanding of sedimentary processes expanded, genetic facies models were developed based on the inferred process of formation. Since individual facies cannot be interpreted in isolation, they must be studied with reference to their neighbours, emphasizing the association of facies and sequences, in particular those that coarsen and fine upward. Environmental facies models are based on the interaction of studies on modern environments and ancient rock facies. Earlier facies models tended to invoke intrinsic, autocyclic controls. The advent of sequence stratigraphy led to greater emphasis on the surfaces that separate sequences and to external allocyclic controls. These were, initially, sea-level changes; later, changes in climate, tectonic movements and sediment supply were invoked. Over time, simple, all embracing models have given way to increasingly complex ones as our knowledge of the variability of nature has increased. Complex though these models are, they are only simplifications of reality. In nature there are no models and the majority of past environments differed in some respect from any modern environment. Each environment and rock sequence is unique.

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Sedimentary system and coal seam distribution in the coal-bearing sequence stratigraphic framework in the Paleogene Meihe Formation (Meihe Basin, NE China)

10.21203/rs.3.rs-22238/v1 ◽

2020 ◽

Author(s):

Yueyue Bai ◽

Qingtian Lv ◽

Zhaojun Liu ◽

Pingchang Sun ◽

Rong Liu ◽

...

Keyword(s):

Coal Seam ◽

Accumulation Rate ◽

Mapping Method ◽

Sediment Supply ◽

Coal Seams ◽

Delta Front ◽

Contour Maps ◽

Delta Plain ◽

Fan Delta ◽

Wide Range

Abstract The Meihe Basin is one of the important Paleogene coal-bearing fault basins of northeastern China in the Dunhua-Mishan Fault Zone. The Lower Coal-bearing Member and the Upper Coal-bearing Member are the primary layers studied. Through field observation, core description and observation under microscope, fan delta facies and lake facies are observed as the main sedimentary facies of the coal-bearing layers, and subfacies of fan delta plain, fan delta front, shallow lake and swamp have also been recognized. Coal seams primarily accumulated in the subfacies of swamp and fan delta plain. The study on sequence stratigraphy is based on outcrop section, well-log analysis, core observation and geochemical analysis. From the Lower Coal-bearing Member to the Upper Coal-bearing Member, three third-order sequences have been recognized; the Lower Coal-bearing Member developed in Sequence I and the Upper Coal-bearing Member developed in Sequence III, both sequences have developed the lowstand systems tract (LST), the transgressive systems tract (TST) and the highstand systems tract (HST). Single-factor analysis and the multifactor comprehensive mapping method have been used to rebuild the lithofacies palaeogeography of each system tract in Sequence I and Sequence III. Through analysis of contour maps of total stratum thickness, sandstone thickness and sand content, as well as contour maps of thicknesses and numbers of layers of coal seams, the results indicate that the sedimentary environments and coal seam distributions are variable in different system tracts. Coal types accumulating in the swamp facies are primarily developed in the transgressive systems tract (TST) and the highstand systems tract (HST) of Sequence I with a wide range of continuous and large thicknesses and may be mined commercially. Both the balanced accommodation growth rate with peat accumulation rate and little or no influence from sediment supply and channel migration promote to form the stable coal accumulating environments.

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INTEGRATED SEDIMENTOLOGICAL ANALYSIS: THE EOCENE OF THE BASS BASIN

The APPEA Journal ◽

10.1071/aj88027 ◽

1989 ◽

Vol 29 (1) ◽

pp. 312

Author(s):

Peter W. Baillie ◽

Carol A. Bacon

Keyword(s):

Sea Level ◽

Sequence Stratigraphy ◽

Complex Mixture ◽

Sediment Supply ◽

Log Analysis ◽

Core Analysis ◽

Anaerobic Conditions ◽

Complex Interplay ◽

Maximum Thickness ◽

Sand Bars

The Eocene section in the Bass Basin comprises the upper part of the siliciclastic coal- bearing Eastern View Group and the thin but regionally extensive Demons Bluff Formation.An integrated sedimentological study utilising core analysis, log analysis, palynology, coal maceral studies and geochemistry, together with sequence stratigraphy, has been used to determine Eocene sedimentation styles in the basin.The most likely environment during deposition of the Upper Eastern View Group was a tide- dominated delta consisting of a complex mixture of distributary channels, strandline sand bars, peat swamps and shallow lagoons, the sedimentary successions resulting from a complex interplay between sea- level, tectonics and sediment supply. A major coal- forming episode occurring in the interval 48- 51.5 m.y. is related to oscillations of sea- level following a major highstand.A locally developed progradational unit, Konkon Sandstone, comprising two sandy parasequences separated by a very thin shaly interval is recognised at the top of the Eastern View Group in the northwestern sector of the basin and reaches a maximum thickness of 140 m.The Demons Bluff Formation is a diachronous unit consisting dominantly of siltstone probably deposited in a barred basin with anaerobic conditions.

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Outcrop analysis and facies model of an Upper Permian tidally influenced fluvio-deltaic system: Northern Sydney Basin, SE Australia

Geological Magazine ◽

10.1017/s0016756818000973 ◽

2019 ◽

Vol 156 (10) ◽

pp. 1715-1741 ◽

Cited By ~ 2

Author(s):

Jake Breckenridge ◽

Angelos G. Maravelis ◽

Octavian Catuneanu ◽

Kevin Ruming ◽

Erin Holmes ◽

...

Keyword(s):

Source Region ◽

Depositional Environments ◽

Sediment Supply ◽

Upper Permian ◽

Delta Front ◽

Sediment Grain Size ◽

Sequence Stratigraphic ◽

Delta Plain ◽

Facies Associations ◽

The Impact

AbstractAn integrated study of sedimentological, sequence-stratigraphic and palaeodispersal analysis was applied to the Upper-Permian clastic sedimentary succession in the Northern Sydney Basin, Australia. The succession is subdivided into fifteen facies and three facies associations. The facies associations are further subdivided into eight sub-facies associations. The sedimentary evolution involves progradation from delta-front to delta-plain to fluvial depositional environments, with a significant increase in sediment grain size across the unconformable contact that separates the deltaic from the overlying fluvial system. In contrast to the delta front that is wave/storm- and/or river-influenced, the delta plain is significantly affected by tides, with the impact of tidal currents decreasing up-sequence in the delta plain. The general lack of wave-influenced sedimentary structures suggests low wave energy in the delta plain. The abrupt termination of the tidal impact in the fluvial realm relates to the steep topographic gradients and high sediment supply, which accompanied the uplift of the New England Orogen. The sequence-stratigraphic framework includes highstand (deltaic forest and topset) and lowstand (fluvial topset) systems tracts, separated by a subaerial unconformity. In contrast to most of the mud-rich modern counterparts, this is an example of a sand-rich tidally influenced deltaic system, developed adjacent to the source region. This investigation presents a depositional model for tidal successions in regions of tectonic uplift and confinement.

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Small-amplitude lake-level fluctuations recorded in aggrading deltaic deposits of the Upper Pleistocene Thimi and Gokarna formations, Kathmandu Valley, Nepal

Journal of Nepal Geological Society ◽

10.3126/jngs.v25i0.32049 ◽

2001 ◽

Vol 25 ◽

Author(s):

Tetsuya Sakai ◽

Ananta Prasad Gajurel ◽

Hideo Tabata ◽

Bishal Nath Upreti

Keyword(s):

Small Amplitude ◽

Lake Level ◽

Fine Sediment ◽

Sediment Supply ◽

Kathmandu Valley ◽

Delta Front ◽

Lake Level Fluctuations ◽

Delta Plain ◽

Wet And Dry Cycles ◽

Sand Beds

Small-amplitude lake-level fluctuations have been recognized from the aggrading delta-plain deposits in the lower parts of the Thimi and Gokarna formations, Kathmandu Valley, Nepal. The delta-plain deposits consist or gravelly sand beds of fluvial channel origin (coarse-sediment interval) and alternation of' fine to very line sand and sandy silt beds (line-sediment interval). Wave generated structures occur in the sand beds or the fine sediment intervals. The vertical and lateral facies changes suggest that the deposition or a set of coarse- and fine-sediment intervals associated with prograding delta front deposits was controlled by a lake-level rise and fall sequence superimposed on a long-term lake level rise trend. The aggradation of fluvial sediments occurred during a lake-level rise period with sufficient sediment supply to fill a newly created accommodation space on the delta plain. The observation or wave-generated structures in an overlying fine-sediment interval suggests that the delta plain was subsequently inundated due to further lake-level rise, exceeding the sedimentation rate. Subsequent delta progradation occurred during a lake-level stabilized phase after a lake level fall. The small-amplitude lake-level changes are thought to be attribute able to seasonal wet and dry cycles, as inferred based on the presence of peculiar aggrading delta successions, implying that lake-level fluctuations may have occurred over short time scales, and on the results of a previous palaeopalynological study in which a moist palacoclimate was inferred in the lower part of the Gokarna Formation in particular.

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DEPOSITIONAL MODELLING OF THE GIPPSLAND BASIN AND THE BARROW-EXMOUTH SUB-BASINS

The APPEA Journal ◽

10.1071/aj93032 ◽

1994 ◽

Vol 34 (1) ◽

pp. 350 ◽

Cited By ~ 2

Author(s):

Keyu Liu ◽

Lincoln Paterson ◽

Feng Xu Jian

Keyword(s):

Sea Level ◽

Sequence Stratigraphy ◽

Seismic Data ◽

High Frequency ◽

Sedimentary Facies ◽

Sediment Supply ◽

Well Logs ◽

Tectonic Movement ◽

Depositional Processes ◽

Gippsland Basin

SEDPAK is a forward modelling computer program for depositional processes developed by the University of South Carolina's StratMod Group. It simulates the geometry of generalised lithofacies in a sedimentary sequence or a basin by considering principally four major geological variables: eustatic sea level, tectonic movement, sediment accumulation, and initial and evolving basin surfaces.Based on seismic data, well logs and other information from drill holes, the geometries of sedimentary sequences of the Gippsland Basin and the Barrow-Exmouth Sub-basins have been successfully reproduced on both basin and reservoir scales using SEDPAK 3.12. The simulation results indicate that eustacy, tectonics, sediment input and basin physiography can be equally important in controlling the geometry of strata and basin architecture. However, some differences exist: (1) tectonic movement normally contributes to long-term variations of the first order (megasequence) basin architecture and configuration; (2) the second order (sequence) basin architecture and stratal geometry can be controlled by either sediment supply, eustacy, tectonism or a combination; and (3) high frequency facies variations and stratal geometry within individual sequences are primarily controlled by eustatic sea level variations and basin physiography.This study has demonstrated that SEDPAK is a useful tool for reconstruction of basin evolution histories and for reservoir characterisation. It can also be used to predict sedimentary facies in undrilled exploration frontier areas. In addition, it can be used to address some critical assumptions and problems in the sequence stratigraphy concept. SEDPAK is particularly useful in the study of high frequency sequence stratigraphy and cyclicity, where various sequence or parasequence bounding surfaces and internal geometry can not be easily recognised from seismic data, well logs and outcrops.

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Evolution and stratigraphy of the Nakdong River valley deposits in response to late Quaternary sea-level change

10.5194/egusphere-egu2020-13340 ◽

2020 ◽

Author(s):

Dong-Geun Yoo ◽

Seok-Hwi Hong ◽

Gwang-Soo Lee ◽

Jin-Cheul Kim ◽

Gil-Young Kim ◽

...

Keyword(s):

Sea Level ◽

River Mouth ◽

River Valley ◽

Coarse Grained ◽

Nakdong River ◽

Delta Front ◽

Delta Plain ◽

Depositional System ◽

Depositional Systems ◽

The Nakdong River

<p>Sequence analysis using borehole samples and high-resolution seismic data in the Nakdong River valley reveals that the Nakdong River valley deposits, approximately 60 - 70 m thick, consist of a set of lowstand, transgressive, and highstand systems tracts that corresponds to a fifth-order (20 ka) sea-level cycle. Four main depositional systems, including ten sedimentary facies, constitute these systems tracts: fluvial, estuary, coastal/shoreface, and delta. The lowstand systems tract (LST), consisting of gravelly sand, forms a fluvial depositional system (Unit I) which fills the thalweg of river valley mainly developed approximately before 12 ka. The transgressive systems tract (TST) can be divided into two depositional systems (Unit II and III). The river-derived sediments were trapped within the paleo-estuary, forming an estuarine depositional system (Unit II) developed between 12 and 6 ka. As the transgression continued, the coarse sediments were deposited and redistributed by coastal processes, resulting in coastal/shoreface depositional system (Unit III). It is characterized by an isolated sand body and thin sand veneer. The HST is composed of deltaic depositional system including delta plain, delta front, and prodelta (Unit IV). During the delta progradation, most coarse-grained sands derived from the river were deposited in the lower delta plain and delta front, forming sand bars and shoals less than 15 m deep. The remaining fine-grained sediments were transported further offshore in a suspension mode and deposited in the inner shelf off the present river mouth, forming a subaqueous prodelta. Radiocarbon and optica<strong>lly stimulated luminescence (OSL</strong>) dating suggest that the recent deltaic system was initiated by aggradational and progradational stacking patterns at approximately 8 ka during the last stage of decelerated sea-level rise, and was then followed by a prograding clinoform after the highest sea level at approximately 6 ka.</p>

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Stratigraphic architecture and depositional environment of the Paleocene-Lower Eocene aquifers system (Douala onshore basin, SW Cameroon)

Journal of Petroleum Exploration and Production Technology ◽

10.1007/s13202-020-01057-2 ◽

2021 ◽

Vol 11 (2) ◽

pp. 549-560

Author(s):

Serge Parfait Koah Na Lebogo ◽

Dieudonnée Bisso ◽

Jeannette Ngo Elogan Ntem ◽

Joseph Mvondo Ondoa

Keyword(s):

Sequence Stratigraphy ◽

Depositional Environment ◽

Gamma Ray ◽

Clay Content ◽

Depositional Environments ◽

Well Log ◽

Delta Front ◽

Lower Eocene ◽

System Tracts ◽

System Tract

AbstractThe Paleocene-Lower Eocene N'kapa Formation has long been considered as an important groundwater and hydrocarbon resource in the eastern edge of the Douala Basin. The present study’s aim is to establish a possible link between the geological nature of this formation and the quality of potential aquifers using Gamma Ray well log, cuttings and outcrops through sedimentology and sequence stratigraphy studies. The results obtained from this study show that: lithofacies are dominated by clays, silts and sands/sandstones; gamma ray electrofacies are funnel-shaped to cylindrical-shaped with some bell-shaped; depositional environments are continental to shallow marine dominated by fluvial and sometimes tidal processes; fluvial channel-fill, tidal channel-fill and delta front bars sands are potential aquifers; sequence stratigraphy analysis reveals two transgressive–regressive cycles of second order (Danian to Selandian and Thanetian to Ypresian), two Highstand System Tracts, one Transgressive System Tract and one Lowstand System Tract; the high-resolution geometry of these sandy/sandstone sedimentary bodies shows that their distribution is linked to the hydrodynamic factors and the topography of the depositional environment. A total of two types of lithological facies of the reservoir levels were defined according to the volume of clay: clean sandstone (0–15%) and low clayey sandstone (15–30%). The gamma ray well log correlation shows that the thickness of the reservoir levels is variable and that the clay content (Vsh%) increases from the NE to the SW. As a result, the best potential aquifers appear to correspond to the fluvial channel-fill sands deposited during the base-level fall of Upper Paleocene age (Lower Thanetian).

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Postrift depositional evolution and sequence stratigraphy from offshore subsurface data of the Kribi-Campo subbasin (Cameroon, West African margin)

Interpretation ◽

10.1190/int-2015-0073.1 ◽

2016 ◽

Vol 4 (1) ◽

pp. T79-T101

Author(s):

Joseph Bertrand Iboum Kissaaka ◽

Joseph Marie Ntamak-Nida ◽

François Mvondo ◽

Paul Gustave Fowe Kwetche ◽

Adrien Lamire Djomeni Nitcheu ◽

...

Keyword(s):

Sea Level ◽

Sequence Stratigraphy ◽

West African ◽

Sediment Supply ◽

Sea Level Changes ◽

Third Order ◽

Normal Regression ◽

Basin Floor ◽

Depositional Evolution ◽

Forced Regression

Using 2D seismic data and well logs from the Kribi-Campo subbasin in the south Cameroon margin, we have analyzed the postrift succession with the aim of deriving a chronostratigraphic chart and identifying stratigraphic traps. The Kribi-Campo subbasin related to the rifting between Africa and South America could be divided into a structurally complex eastern depocenter and a relatively less disturbed western depocenter in which a break-up unconformity approximately 107.5 Ma underlined the beginning of postrift history. We have used the modern concepts of sequence stratigraphy to identify and characterize seven second-order (SS1, SS2, SS3, SS4, SS5, SS6, and SS7) sequences and one third-order (SS8) sequences grouped into three megasequences (A, B, and C) from Albian to Recent. Sequence 1 (Albian-Cenomanian) was characterized by a retrogradation overlying a lowstand progradational pattern. The SS2 (Campanian-Maastrichtian) and SS3 (Maastrichtian) sequences were deposited during a highstand normal regression. From Paleocene to Eocene, the deposition of sequences SS4–SS5 was controlled by the development of submarine fan turbiditic system related to a forced regression of coastline. From the Middle Miocene to Recent age, the SS6, SS7, and SS8 sequences have been characterized by the development of sigmoidal-oblique clinoforms of a deltaic system well observed in the northern part of the study area. We have studied a new undocumented phase of forced regression of Mio-Pliocene in age within the postrift sequence SS7. The forced regression phases are associated with the Paleogene and Neogene uplift. Relative sea-level curves were constructed and compared with the existing published curves. The processes involved in the formation of these sequences were interpreted as a combination of tectonics, sediment supply, and sea-level changes. Potential reservoirs embedded within the sequences include channel fill, shingled turbidites, slope fan, and basin-floor fan complex.

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