Outcrop sedimentology of the Natih Formation, northern Oman: A field guide to selected outcrops in the Adam Foothills and Al Jabal al Akhdar areas

ABSTRACT This field guide describes eleven outcrops of the Natih Formation in the Al Jabal al Akhdar-Jabal Shams and Adam Foothills areas, not far from Nizwa, at the foot of the Oman Mountains. The outcrops have been chosen for their accessibility, as well as for the fairly complete picture of the Natih Formation, which they piece together. To visit all eleven outcrops requires several days and the use of 4-wheel-drive vehicles, but the locations offer no serious physical difficulty, nor long hiking, to gain access. The outcrop descriptions follow in stratigraphic order from the lower to the upper Natih members, roving back-and-forth across the outcrop area. Much of the detailed account of the sedimentology and stratigraphy of the Natih that has been used as the basis of this field guide, has been given previously by van Buchem et al. (1996, 2002), Grélaud (2005), Schwab et al. (2005) and Grélaud et al. (2006). The observations and interpretations given here come in part from those studies, but this paper is also largely the product of a subsequent project that was carried out for the Fahud Studies Team of Petroleum Development Oman (PDO), to provide detailed sedimentology and high-resolution sequence stratigraphy of the Natih Formation for further development of the Fahud field (Homewood et al. 2006). In this respect, this field guide is not so much intended to be an original contribution in terms of the science concerning the Natih Formation. The intent is to provide the ways-and-means for all to gain a first-hand personal understanding of the rocks we have enjoyed working on. Following the outcrop descriptions, a general section provides a discussion on facies and facies associations in terms of the constraints of sequence stratigraphy, sea-level change and clay influx on the carbonate factory. With the incorporation of limited subsurface seismic and well data, geobodies and depositional assemblages, the three-dimensional objects that form the stratigraphic packages at outcrop and seismic scales, respectively, are also discussed. Facies are thus interpreted not only in terms of depositional environments, but are also placed within both geometrical (geobody, depositional assemblage) and sequence-stratigraphic frameworks. In the conclusion, it is argued that a deeper understanding of the Natih Formation has been gained by comparison of outcrop data with subsurface data, and by contrast with modern analogs. The detail required to apply what was learned from outcrop to the nearby subsurface, in a practical manner (but also properly to reconstruct the successive Natih scenarios), requires building several facies models. This is in contrast to giving a single composite picture of Natih facies distribution in space and time, under one single facies model.

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High-resolution anatomy of a grainstone package in Khuff Sequence KS4, Oman Mountains, Sultanate of Oman

GeoArabia ◽

10.2113/geoarabia180417 ◽

2013 ◽

Vol 18 (4) ◽

pp. 17-44 ◽

Cited By ~ 3

Author(s):

Marlene Maria-Louise Haase ◽

Thomas Aigner

Keyword(s):

High Resolution ◽

Large Scale ◽

Lower Triassic ◽

Depositional Environments ◽

Sultanate Of Oman ◽

Heterogeneous Architecture ◽

Sequence Stratigraphic ◽

Oman Mountains ◽

Facies Associations ◽

Outcrop Analog

ABSTRACT This study is part of a large-scale outcrop analog study on Middle Permian to Lower Triassic Khuff-equivalent strata in the Oman Mountains, Al Jabal al-Akhdar, Sultanate of Oman. The Khuff outcrop equivalent can be divided into six sequences (Khuff sequences KS6 to KS1, from base to top). The main focus of this study is the description of the internal anatomy of the shoal grainstone bodies in the lower part of Sequence KS4 (“lower KS4”). High-resolution sedimentological logging of three outcrop sections in wadis Sahtan, Bani Awf and Mistal yielded eight lithofacies types that were grouped into five facies associations. Lower KS4 strata were mainly deposited within a “shoal complex” of an epeiric carbonate ramp, resulting in a thick pile of up to 70 m of grainstones that, on first sight, appear relatively homogeneous. However, detailed facies and microfacies analysis revealed their heterogeneous architecture on various scales: (1) Minor changes in depositional environments directly affected the type of carbonate grains (ooids versus peloids/cortoids versus bioclasts), leading potentially to highly variable pore systems (moldic versus interparticle versus intraparticle). (2) Vertically, detailed sequence-stratigraphic analysis revealed a higher-order of cyclicity (“mini-cycles”) on a decimeter- to meter-scale. Four mini-cycle types were recognized. (3) Laterally, facies changes, the amalgamation of grainstone beds and mini-cycle pinch-outs were observed in 2-D correlations on a scale of a few kilometers. These different types of heterogeneities may contribute to varying production rates commonly observed in the subsurface KS4 reservoir.

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Facies and stratigraphic framework of a Khuff outcrop equivalent: Saiq and Mahil formations, Al Jabal al-Akhdar, Sultanate of Oman

GeoArabia ◽

10.2113/geoarabia150291 ◽

2010 ◽

Vol 15 (2) ◽

pp. 91-156 ◽

Cited By ~ 15

Author(s):

Bastian Koehrer ◽

Michael Zeller ◽

Thomas Aigner ◽

Michael Poeppelreiter ◽

Paul Milroy ◽

...

Keyword(s):

Middle East ◽

Lower Triassic ◽

Distal Portion ◽

Marine Fauna ◽

Sequence Stratigraphic ◽

Stratigraphic Analysis ◽

Oman Mountains ◽

Stratigraphic Framework ◽

Al Jabal Al Akhdar ◽

Fifth Order

ABSTRACT The Middle Permian to Lower Triassic Khuff Formation is one of the most important reservoir intervals in the Middle East. This study presents a sequence stratigraphic analysis of the Khuff Formation of a well-exposed outcrop in the Oman Mountains, which may provide a reference section for correlations across the entire Middle East. On the Saiq Plateau of the Al Jabal al-Akhdar, the Permian Upper Saiq Formation is time-equivalent to the Lower and Middle Khuff Formation (K5–K3 reservoir units in Oman). The Permian section is dominated by graded skeletal and peloidal packstones and cross-bedded grainstones with a diverse marine fauna. The Lower Mahil Member (Induan Stage), time-equivalent to the Upper Khuff Formation (K2–K1 reservoir units in Oman), is dominated by grainstones composed of microbially-coated intra-clasts and ooids. In general, the studied outcrop is characterized by a very high percentage of grain-dominated textures representing storm-dominated shoal to foreshoal deposits of a paleogeographically more distal portion of the Khuff carbonate ramp. A sequence-stratigraphic analysis was carried out by integrating lithostratigraphic marker beds, facies cycles, bio- and chemostratigraphy. The investigated outcrop section was subdivided into six third-order sequences, named KS 6 to KS 1. KS 6–KS 5 are interpreted to correspond to the Murgabian to Midian (ca. Wordian to Capitanian) stages. KS 4-Lower KS 2 correspond to the Dzhulfian (Wuchiapingian) to Dorashamian (Changhsingian) stages. Upper KS 2–KS 1 represent the Triassic Induan stage. Each of the six sequences was further subdivided into fourth-order cycle sets and fifth-order cycles. The documentation of this outcrop may contribute to a better regional understanding of the Khuff Formation on the Arabian Platform.

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Facies, sequence stratigraphy, reservoir and seal potential of the Mafraq Formation, Sultanate of Oman: An integrated outcrop analogue study

GeoArabia ◽

10.2113/geoarabia200317 ◽

2015 ◽

Vol 20 (3) ◽

pp. 17-94

Author(s):

Daniel Bendias ◽

Thomas Aigner

Keyword(s):

Sequence Stratigraphy ◽

Northwestern Part ◽

Southeastern Part ◽

Terrestrial Environment ◽

Oman Mountains ◽

Facies Associations ◽

Potential Reservoir ◽

Lateral Extent ◽

Member Sequence ◽

Mixed Carbonate

ABSTRACT The mixed carbonate-siliciclastic Lower to Middle Jurassic Mafraq Formation unconformably overlies the Triassic Mahil Formation in outcrops of the Oman Mountains (pre-Mafraq Unconformity, known as pre-Marrat unconformity in other regions of Arabia). Together with the overlying Dhruma Formation, it is part of the Sahtan Group. This study provides: (1) a detailed facies analysis based on sedimentological logging of 12 outcrops. Twenty-four facies types were established and grouped into five facies associations, which can also be recognized in subsurface core intervals; (2) a detailed sequence-stratigraphic framework of the Mafraq Formation. Facies stacking and log patterns reveal cycle hierarchies on four scales from m-scale cycles, to several m-thick cycle sets, to tens of m-thick, high-frequency sequences, to 100 m-thick composite sequences; and (3) a documentation of potential reservoir and seal units. The study follows an approach from 1-D (outcrop sections) to 2-D (correlations and potential reservoir dimensions). The Mafraq outcrop type section, located in Wadi Sahtan is documented in an integrated way (facies, litho-, bio-, chemo- and sequence stratigraphy), together with additional outcrops of the Mafraq Formation throughout North Oman. 2-D correlation of the Mafraq Formation throughout North Oman is essentially based on cycle sets and provides key information about the lateral paleogeographic development of the formation. A general proximal-distal trend, from south to north, has been proposed by Ziegler (2001); outcrop data from the Oman Mountains confirms this trend and adds an EW-deepening component. The mixed carbonate-clastic Lower Mafraq Member (Sequence) with a coastal/estuarine to shallow-marine environment forms onlaps onto the pre-Mafraq Unconformity below, and thins out completely after some 10s of kilometers towards the southeast. The Upper Mafraq Member (Sequence) seems to be continuous over 10s of kilometers with less thickness decrease. Instead, a transition from a more distal carbonate shoal - backshoal environment in the northwest to a proximal clastic coastal/estuarine/terrestrial environment in the southeast can be observed. On a 100s km-scale significant thinning and a change towards terrestrial clastic facies can be observed southeast of the Oman Mountains area. Combined results from lateral/vertical logging, paleoenvironmental interpretations and correlation provided 3-D information about the dimensions of potential reservoir and seal units. Several potential reservoir/seal intervals and their dimensions in dip direction could be identified: (1) Lower Mafraq Sequence: various types of sandbodies, most of them with a lateral extent ca. 5 km, sealed by shales. (2) Upper Mafraq Sequence, northwestern part: oolitic grainstones, laterally correlative over 10–20 km, sealed by shales. (3) Upper Mafraq Sequence, southeastern part: channelized sandstones units, lateral extent up to km, sealed by shales.

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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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Facies Analysis and Depositional Environments of the Late Palaeozoic Coal-Bearing Madzaringwe Formation in the Tshipise-Pafuri Basin, South Africa

ISRN Geology ◽

10.1155/2013/120380 ◽

2013 ◽

Vol 2013 ◽

pp. 1-11 ◽

Cited By ~ 5

Author(s):

Ntokozo Malaza ◽

Kuiwu Liu ◽

Baojin Zhao

Keyword(s):

South Africa ◽

Flood Plain ◽

Depositional Environments ◽

Limpopo Province ◽

Sequence Stratigraphic ◽

Fine Grained ◽

Lower Member ◽

Late Palaeozoic ◽

Facies Associations ◽

Middle Member

The late Palaeozoic coal-bearing Madzaringwe Formation of the Karoo Supergroup in the Tshipise-Pafuri Basin in the Limpopo Province, South Africa, records part of the infill of a passive continental margin terrain. Lithofacies analysis was performed with a view to deduce the nature of depositional environments of the Formation. Sedimentological and sequence stratigraphic evidence indicates that this unit represents a complex siliciclastic facies that reflects a fluvial paleodepositional environment. Eleven facies, which were grouped into five facies associations, were recognised. The base of the Madzaringwe Formation (Lower Member) represents a sequence deposited by braided channels. The coal deposits represent flood plain and swamp deposits, which is characterised by shale, thick coal seams, siltstone, and sandstone. The Middle Member is characterised by both clast and matrix supported conglomerates, major tubular and lenticular sandstones, and finely calcareous, micaceous siltstone. The deposition represents a sequence being formed from fluvial and particularly braided channels. The crudely stratified, coarse to pebbly sandstone indicates channel lag deposits within a heavy loaded fluvial system. The fine-grained sandstone represents deposition by shift channel and side bar deposits during lower flow conditions. The Upper Member is characterised by facies associations similar to the Lower Member, representing a new depositional cyclothem.

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Browse Basin sequence stratigraphic study

The APPEA Journal ◽

10.1071/aj11117 ◽

2012 ◽

Vol 52 (2) ◽

pp. 703

Author(s):

Jim Raggatt ◽

Tim Gibbons ◽

James Stockley ◽

Ian Deighton

Keyword(s):

Depositional Environments ◽

Geological Model ◽

Depositional History ◽

Sequence Stratigraphic ◽

Facies Associations ◽

Recoverable Reserve ◽

Background Database ◽

The Many ◽

Gas Fields ◽

Order Sequence

In addition to the large gas fields already discovered in the Browse Basin, there is considerable scope for further exploration success because this basin holds an estimated recoverable reserve of 30 tcf gas. TGS has completed the Browse Basin Sequence stratigraphic study to specifically understand the many depositional environments of this basin by a comprehensive analysis of 75 key wells all tied to extensive 2D seismic interpretation. With a standardized lithostratigraphic and chronostratigraphic interpretation, each well has a full 3rd order sequence boundary record across all logged sections, and was subsequently assigned detailed gross depositional environments (GDE). Tied to the GDE’s are specific and highly detailed facies associations, displayed in 26 facies maps, thereby building a robust multi-sequence geological model constrained by sequences. These basin-wide facies maps delineate known source, reservoir and seal and propose where—within the robust geological model—potentially similar facies have been deposited and preserved. This extended abstract is delivered by the Facies Map Browser (FMB), a unique product, containing all data and interpreted maps. The Browse Basin FMB allows users to quickly understand the basin-wide depositional history and interpreted facies. With the multi-well and multi-source background database, the FMB product has proven to shorten the exploration cycle by its sheer level of detail and wide ranging interpretation.

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Sedimentology and Stratigraphy of an Upper Permian Sedimentary Succession: Northern Sydney Basin, Southeastern Australia

Geosciences ◽

10.3390/geosciences11070273 ◽

2021 ◽

Vol 11 (7) ◽

pp. 273

Author(s):

Sean Melehan ◽

Chrysanthos Botziolis ◽

Angelos G. Maravelis ◽

Octavian Catuneanu ◽

Kevin Ruming ◽

...

Keyword(s):

New England ◽

Depositional Environments ◽

Upper Permian ◽

Delta Front ◽

Sequence Stratigraphic ◽

Delta Plain ◽

Southeastern Australia ◽

Normal Regression ◽

Facies Associations ◽

The Impact

This study integrates sedimentological and stratigraphic insights into the Upper Permian sedimentary rocks of the Wittingham, Tomago and Newcastle Coal Measures in the Northern Sydney Basin, Australia. Facies analysis documented fifteen facies that belong to seven facies associations. These facies associations correspond to different depositional environments and sub-environments including prodelta, delta-front, upper, lower delta-plain and fluvial. The stratigraphic development points to a shallowing upward trend and is reflected with fluvial deposits sitting on top of the deltaic deposits. The fluvio-deltaic contact is represented by an unconformity and displays an upward increase in sediment caliber. The delta front is mainly controlled by wave, storms- and/or river currents, even though the contribution of tides also occurs in the form of sedimentary structures that suggest tidal influence. In contrast, prodelta and delta-plain are significantly modulated by tidal currents. The impact of tides in the delta plain is fading away upward and therefore, the upper delta plain is much less impacted compared to the lower delta plain. The low abundance of wave ripples suggests that the wave action was not very important in the delta plain. Steep topographic gradients and increased sediment input are suggested, based on the limited or absent evidence of tides in the fluvial realm, related to the growing New England Orogen. In sequence stratigraphic terms, the deltaic system accumulated during highstand normal regression, while the deposition of the overlying fluvial system occurred during lowstand normal regression. The two systems are separated by a subaerial unconformity developed during an intervening forced regression. Short periods of transgression are inferred from the presence of higher frequency cycles in the delta-front.

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Biological patterns in sequence stratigraphy; Cretaceous of the Western Interior Basin, North America

The Paleontological Society Special Publications ◽

10.1017/s2475262200007188 ◽

1992 ◽

Vol 6 ◽

pp. 158-158 ◽

Cited By ~ 1

Author(s):

Erle G. Kauffman ◽

Bradley B Sageman

Keyword(s):

North America ◽

Sequence Stratigraphy ◽

Benthic Communities ◽

Three Dimensional ◽

Character Displacement ◽

Community Diversity ◽

Sequence Stratigraphic ◽

Stratigraphic Analysis ◽

Western Interior Basin ◽

Sequence Boundaries

High-resolution stratigraphic analysis of Cretaceous strata in the Western Interior Basin (WIB) of North America has allowed definition of numerous disconformity-bounded, eustatically and/or tectonically driven sequences and their systems tracts at 2nd- through 4th-order scale, as well as 5th- to 7th-order climate-induced cycles. Integrated event chronostratigraphy and biostratigraphy allow detailed regional tracing and facies analysis of these sequences, leading to three-dimensional modeling of facies evolution. Whether driven by relative sealevel changes or smaller scale climate cycles, Cretaceous sequences and their bounding disconformities reflect dynamic changes in many factors which moderate biological systems (e.g. sealevel and paleobathymetric changes, changes in current velocity and in erosion/sedimentation rates and patterns, watermass temperature and chemistry, etc). Predictable biological responses (patterns) to varying environmental conditions and different systems tracts are expected in sequence stratigraphy. Once defined within well-studied systems, these patterns can then be used as an independent tool for sequence stratigraphic analysis. To date, our research has focused on the development of paleobiological criteria which aid in the recognition of sequence stratigraphic frameworks, especially in basinal facies where sequence boundaries and systems tracts may be subtly defined in the physical stratigraphy. Such criteria may include the identification of sequence boundaries and other omission surfaces by punctuated character displacement in evolutionary series, by condensation or omission of biostratigraphic zones, by mixed or time-averaged community elements and biozones, and by selective colonization by firm substrate-dependent benthic communities. Gradients within and between systems are characterized by different community composition, biofacies, taxonomic and community diversity patterns, adaptive bauplans among resident taxa, taphonomic signatures, and bioevents that allow predictive biological characterization in sequence stratigraphy. Once established and correlated, sequence stratigraphic systems among different basins provide a chronostratigaphic and environmental framework within which the regional dynamics of ancient populations and communities can be evaluated, leading to the analysis and modeling of relationships between sealevel changes and biogeographic migration patterns, and the rates and patterns of evolution and extinction.

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Mid-Turonian–early Campanian sequence stratigraphy of northeast Iraq

GeoArabia ◽

10.2113/geoarabia1202135 ◽

2007 ◽

Vol 12 (2) ◽

pp. 135-176 ◽

Cited By ~ 1

Author(s):

Sabah Noori Saleem Haddad ◽

Momtaz Ahmed Amin

Keyword(s):

Sequence Stratigraphy ◽

Middle Part ◽

Normal Faults ◽

Reservoir Properties ◽

Third Order ◽

Sequence Stratigraphic ◽

Tectonic Model ◽

Facies Associations ◽

North Iraq ◽

Depositional Architecture

ABSTRACT A sequence stratigraphic and tectonic model for the mid-Turonian-early Campanian carbonate sequence in North Iraq was constructed based on subsurface lithologic, thin-section and well-log analyses of ten boreholes. The studied sequence is represented by the Gulneri, Kometan and Mushorah formations in the eastern sector (seven wells) and their correlative Khasib, Tanuma, Sa’adi and lower part of the Hartha formations in the western sector of the study area (three wells). Three second-order sequences (from oldest to youngest A, B and C) were identified. Sequence A consists of two third-order sequences (A1 and A2) and is represented by the mid-Turonian Gulneri Formation. Sequence B consists of three third-order sequences: B1 corresponds to the late Turonian-early Coniacian Khasib Formation and correlative lower part of Kometan Formation. Sequences B2 and B3 are exclusive to the late Coniacian-early Santonian Tanuma Formation and correlative middle part of the Kometan Formation. Sequence C is comprised of three third-order sequences of which C1 and C2 encompass the late Santonian Sa’adi Formation and correlative upper part of the Kometan Formation, while C3 corresponds to the early Campanian Mushorah Formation and correlative lower part of the Hartha Formation. Each of the third-order sequences is comprised of transgressive and highstand systems tracts, while the lowstand systems tract is restricted to sequences B2, B3, C1 and C2. These systems tracts are, in turn, comprised of vertically stacked parasequences of shallowing upward packages. The tectono-depositional model that was deduced from the sequence analysis is characterised by two flat-topped ramps that formed as a consequence of extensional tectonism. Three NW-trending normal faults are interpreted to separate the ramps whose inclined apex was continuously being eroded. The eroded detritus from the apex consists of shallow-marine carbonates that were deposited in basinal sites. Within this structural framework, the ten boreholes are placed within their appropriate depositional sites within the ramp system. Facies analysis demonstrated an array of facies associations, which generally accumulate in basins that are fed by an influx of eroded shallow-water derivatives. The depositional architecture developed in an open-marine, low-energy, middle- to outer-ramp setting in the case of Gulneri and Kometan formations. A middle–inner ramp setting is attributed to the Khasib, Tanuma and the lower part of the Hartha formations. A transition to a slope setting is suggested during the deposition of the Mushorah Formation; whereas slope-apron facies are common to all formations in the well Quwair-2. Diagenetic modification overprinted the carbonates and its effect on reservoir properties is considered. Recognition of third-order cycles demonstrates the utility of using genetic units and sequence stratigraphy to discern the depositional architecture of these formations. Local tectonic influences, which control sedimentation patterns, eustasy and sedimentation rates are additional determinants for the final stratigraphic framework.

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Facies Analysis and Sequence Stratigraphy of Missole Outcrops: N’Kapa Formation of the South-Eastern Edge of Douala Sub-Basin (Cameroon)

Earth Science Research ◽

10.5539/esr.v7n1p35 ◽

2017 ◽

Vol 7 (1) ◽

pp. 35

Author(s):

Paul Gustave Fowe Kwetche ◽

Marie Joseph Ntamak-Nida ◽

Adrien Lamire Djomeni Nitcheu ◽

Jacques Etame ◽

François Mvondo Owono ◽

...

Keyword(s):

Sequence Stratigraphy ◽

Early Stage ◽

Depositional Environments ◽

Facies Association ◽

Base Level ◽

Facies Associations ◽

Climate Evolution ◽

Floodplain Deposits ◽

Channel Deposits ◽

Eastern Edge

Missole facies description and sequence stratigraphy analysis allow a new proposal of depositional environments of the Douala sub-basin eastern part. The sediments of Missole outcrops (N’kapa Formation) correspond to fluvial/tidal channel to shallow shelf deposits with in some place embayment deposits within a warm and semi-arid climate. Integrated sedimentologic, palynologic and mineralogical data document a comprehensive sequence stratigraphy of this part of the Douala sub-basin. Five facies associations occur: (1) facies association I is characterized by Floodplain deposits; (2) facies association II is Fluvial to mouth bar deposits; (3) facies association III characterise Shallow Shelf deposits; (4) facies association IV represents Distal bay or Lacustrine déposits; and (5) Facies association V is made of Fluvial channel deposits. Six depositional sequences were identified. These sequences are composed of four progradational sequences and two retrogradational sequences containing a fluvial channel portion represented by lag deposits at the base of retrogradational sequences. These deposits represent the outset of the relative sea level rise period. In the study area, the N’kapa Formation is composed of non-marine/coastal aggradational deposits representing the early stage of the regressive period. The occurrence of the estuarine/bay deposits with paleosols development is interpreted as evidence of climate change with significant relative base level fluctuation. The study of key minerals associated to sequence stratigraphy as well as palynology demonstrated that sequence architecture has been controlled mostly by climate evolution and outcrops are dated Paleocene – early Eocene.

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