scholarly journals Significant new biostratigraphic horizons in the Qusaiba Member of the Silurian Qalibah Formation of central Saudi Arabia, and their sedimentologic expression in a sequence stratigraphic context

GeoArabia ◽  
2005 ◽  
Vol 10 (1) ◽  
pp. 49-92 ◽  
Author(s):  
A. Miller Merrell ◽  
Melvin John
Keyword(s):  
Saudi Arabia ◽  
Sea Level ◽  
Arabian Plate ◽  
Important Species ◽  
Sequence Stratigraphic ◽  
Facies Associations ◽  
Global Sea Level ◽  
High Level ◽  
A Minor ◽  
Stratigraphic Evolution

ABSTRACT Detailed analysis of over 1,000 subsurface Silurian palynology samples from 34 wells has allowed the development of a robust biostratigraphy based on acritarchs, chitinozoans and cryptospores for the Qusaiba Member of the Qalibah Formation, central Saudi Arabia. The new index fossils described herein augment the Arabian Plate Silurian chitinozoan zonation. The high-resolution biostratigraphic zonation consists of nine First Downhole Occurrences (FDOs) from the lower Telychian through Aeronian. In particular, three regionally recognizable palynologic horizons were identified within the lower part of the informally designated Mid-Qusaiba Sandstone (Angochitina hemeri Interval Zone), and above the FDO of Sphaerochitina solutidina. This high level of biostratigraphic resolution provides a framework for the integration of the sedimentology and calibration with global sea level curves, leading to a detailed understanding of the sequence stratigraphic evolution of this part of the Silurian in Saudi Arabia. Sedimentological core studies identify three Depositional Facies Associations (DFAs) within the Mid-Qusaiba Sandstone interval, including: (1) shelfal deposits (DFA-I) characterized by interbedded hummocky cross-stratified sandstones, graded siltstones and bioturbated mudstones; (2) turbiditic deposits (DFA-II); and (3) an association of heavily contorted and re-sedimented sandstones, siltstones and mudstones (DFA-III) that is considered representative of oversteepened slopes upon the Qusaiba shelf. Integration of the newly recognized palynostratigraphic horizons and the sedimentological data facilitates an understanding of the sequence stratigraphic evolution of the Mid-Qusaiba Sandstone interval and its immediate precursors. Thus a Maximum Flooding Surface (MFS) is identified from significant palynostratigraphic, as well as sedimentological evidence, and concurs with the MFS identified regionally with the Monograptus convolutus Graptolite Zone. Several mud-prone cyclothems downlap onto the MFS. Each of these is identified by its own palynostratigraphic marker: these mud-prone cyclothems represent the distal parts of a Highstand Systems Tract (HST). The end of the HST is marked by evidence of a major, episodic drop in relative sea level. Thus, a relationship is identified wherein successive palynostratigraphic marker horizons, newly identified in this study, are partially eroded by the introduction of sandy turbidites (DFA-II). These turbidites arise from storm-induced erosion of gully complexes in the upper submarine slopes that are present as topography upon the Qusaiba shelf. Each of the successive drops in sea level is separated from the next by a minor, subsequent sea level rise, which precludes further submarine erosion and turbidite deposition, and is instead evident in the widespread occurrence of shallow marine (shelfal) muds and sandy tempestites (DFA-I). The lowstand per se is considered to be represented by the most widespread distribution of the DFA-II turbidite deposits, and is associated with the youngest Mid-Qusaiba Sandstone marker horizon identified in this study, namely Rugosphaera agglomerata n.sp. The youngest unit of DFA-II lowstand turbidites is limited in its occurrence to the more proximal parts of the study area, and thus is considered to represent the onset of the succeeding Transgressive Systems Tract (TST). Of the biostratigraphic indices used for correlation within the Qusaiba Member, Rugosphaera agglomerata and Eupoikilofusa curvata are formally described and two additional important species, Fractoricoronula n.sp. and ?Oppilatala n.sp., are retained in open nomenclature.

scholarly journals Phanerozoic cycles of sea-level change on the Arabian Platform

GeoArabia ◽  
2005 ◽  
Vol 10 (2) ◽  
pp. 127-160 ◽  
Author(s):  
Bilal U. Haq ◽  
Abdul Motaleb Al-Qahtani
Keyword(s):  
Sea Level ◽  
Time Scale ◽  
Sediment Accumulation ◽  
Arabian Plate ◽  
Sea Level Changes ◽  
Sequence Stratigraphic ◽  
Sea Level Fluctuations ◽  
Regional Sea Level ◽  
Global Sea Level ◽  
Arabian Platform

ABSTRACT The Arabian Plate has experienced a complex tectonic history while also being widely influenced by eustatic sea-level changes. These diastrophic events either affected changes in the rate and/or location of subsidence that in turn led to the creation of significant new sedimentary accommodation, or caused major erosional hiatuses. As a result, both eustasy and tectonics have played important roles in the development of sedimentary sequences and in determining the locus and characteristics of reservoir, source and seal facies on the Arabian Platform. Here, we present a synthesis (Cycle Chart) of the regional sea-level fluctuations affecting the Platform that is based on Phanerozoic epi- and peri-Platform sequence-stratigraphic data. Information used for the synthesis includes sections from Saudi Arabia, Kuwait, the Greater Gulf area, Oman and Yemen. The regional Cycle Chart incorporates interpreted sedimentary onlap patterns on the margins of the Arabian Platform, as well as models of regional sea-level fluctuations that controlled these patterns. These are compared to eustatic data that represents the ‘global-mean’ models of sea-level changes, largely at second-order cycle level for the Paleozoic and third-order cycle level for the Mesozoic and Cenozoic eras. The comparisons reveal that Phanerozoic sediment accumulation patterns on the Platform were broadly controlled by eustasy, with a strong overprint of tectonics for several long intervals. During periods of tectonic quiescence, however, correlations with the eustatic events improve significantly. Thus, for example, during the Cambrian through early Silurian and mid Jurassic through early Paleogene intervals eustasy may have been the significant controlling factor for sedimentary patterns when long-term trends in both regional and global sea-level curves show similarities. The use of the Cycle Chart could facilitate exploration efforts on the Arabian Platform, provide better chronostratigraphic estimates and global correlations, and prove a useful accompaniment for sequence-stratigraphic studies. This integrative effort was greatly facilitated by the recent publication of the sequence stratigraphic synthesis of the Arabian Plate. The ages of Maximum Flooding Surfaces, however, have been recalibrated to the new (GTS 2004) time scale. This synthesis also represents a new recalibration of the Mesozoic and Cenozoic eustatic curves of Haq et al. (1988) to an up-to-date numerical time scale (GTS 2004).

Crinoid columnal associations and sequence stratigraphy architecture: the Le Faou Formation, Lower Devonian of the Massif armoricain (France)

2006 ◽  
Vol 177 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Arnaud Botquelen ◽  
Jean Le Menn ◽  
Rémy Gourvennec ◽  
Alfredo Loi
Keyword(s):  
Cluster Analysis ◽  
Sea Level ◽  
Sequence Stratigraphy ◽  
Close Relationships ◽  
Lower Devonian ◽  
Suspension Feeders ◽  
Sequence Stratigraphic ◽  
Stratigraphic Architecture ◽  
Sea Level Variations ◽  
High Level

Abstract Crinoid columnals are major macrobenthic components of the Lower Devonian faunas of the Massif armoricain particularly in the Seillou section. Three crinoid columnal associations have been delineated based on R and Q-mode cluster analysis. Distribution of these associations is correlated to the sequence stratigraphic architecture, showing the close relationships between crinoid columnal association dynamics and relative sea-level variations. Comparing the distribution of benthic associations, we note a lesser diversity in crinoid columnal associations than in brachiopod ones. Crinoids (high-level suspension feeders) seem to occupy broader specialised niches than brachiopods (reclining and low-level suspension feeders) and are characterised by a different ecological space utilisation.

scholarly journals Sedimentary facies, depositional environments and conceptual outcrop analogue (Dam Formation, early Miocene) Eastern Arabian Platform, Saudi Arabia: a new high-resolution approach

2021 ◽  
Vol 11 (6) ◽  
pp. 2497-2518
Author(s):  
Syed Haroon Ali ◽  
Osman M. Abdullatif ◽  
Lamidi O. Babalola ◽  
Fawwaz M. Alkhaldi ◽  
Yasir Bashir ◽  
...  
Keyword(s):  
Saudi Arabia ◽  
High Resolution ◽  
Sea Level ◽  
Depositional Environments ◽  
Early Miocene ◽  
Arabian Plate ◽  
Relative Sea Level ◽  
Thin Sections ◽  
Mixed Carbonate ◽  
Arabian Platform

AbstractThis paper presents the facies and depositional environment of the early Miocene Dam Formation, Eastern Arabian platform, Saudi Arabia. Deposition of Dam Formation (Fm.) was considered as a restricted shallow marine deposition. Few studies suggest the role of sea-level change in its deposition but were without decisive substantiation. Here, we describe the facies and high-resolution model of Dam Fm. under varying depositional conditions. The depositional conditions were subjected to changing relative sea level and tectonics. High-resolution outcrop photographs, sedimentological logs, and thin sections present that the mixed carbonate–siliciclastic sequence was affected by a regional tectonics. The lower part of Dam Fm. presents the development of carbonate ramp conditions that are represented by limestones and marl. The depositional conditions fluctuated with the fall of sea level, and uplift in the region pushed the siliciclastic down-dip and covered the whole platform. The subsequent rise in sea level was not as pronounced and thus allowed the deposition of microbial laminites and stromatolitic facies. The southeast outcrops, down-dip, are more carbonate prone as compared to the northwest outcrop, which allowed the deposition of siliciclastic-prone sedimentation up-dip. All facies, architecture, heterogeneity, and deposition were controlled by tectonic events including uplift, subsidence, tilting, and syn-sedimentary faulting, consequently affecting relative sea level. The resulting conceptual outcrop model would help to improve our understanding of mixed carbonate–siliciclastic systems and serve as an analogue for other stratigraphic units in the Arabian plate and region. Our results show that Dam Fm. can be a good target for exploration in the Northern Arabian Gulf.

scholarly journals Stratigraphy of the Valanginian? to Early Paleocene succession in central Saudi Arabia outcrops: Implications for regional Arabian sequence stratigraphy

GeoArabia ◽  
2008 ◽  
Vol 13 (2) ◽  
pp. 51-86 ◽  
Author(s):  
Yves-Michel Le Nindre ◽  
Denis Vaslet ◽  
Sami S. Maddah ◽  
Moujahed I. Al-Husseini
Keyword(s):  
Saudi Arabia ◽  
Arabian Plate ◽  
Marine Fauna ◽  
Sequence Stratigraphic ◽  
Aruma Formation ◽  
Stratigraphic Position ◽  
Early Paleocene ◽  
Az Zabirah ◽  
Definition Of ◽  
Flooding Events

ABSTRACT On the basis of regional lithostratigraphic field mapping, and biostratigraphic and sequence stratigraphic interpretations, the definitions and ranks of the Late Valanginian? to Paleocene rock units that crop out in central Saudi Arabia were revised. The definition of the Late Valanginian? to Early Aptian Biyadh Sandstone is inconsistent with that of the same-named formation in subsurface Saudi Arabia. In outcrop, only the lower Dughum member of the Biyadh Sandstone corresponds to the subsurface Biyadh Sandstone. Accordingly, the Biyadh Sandstone at outcrop was redefined so as to correlate to the same-named subsurface formation; the term Dughum member is considered obsolete. Above the redefined Biyadh Sandstone, the Sallah Formation at outcrop (previously Sallah member of Biyadh Sandstone) yielded the Aptian and/or earliest Albian? ammonite Hypacanthoplites cf. milletianus d’Orbigny; it correlates (in part or completely) to the undifferentiated-Aptian Shu’aiba Formation in Abu Jifan field. The overlying Huraysan Formation (previously Huraysan member of Biyadh Sandstone) is assigned an Albian age based on its stratigraphic position above the Sallah Formation and below the Upper Albian and Cenomanian Majma Formation (previously Majma member of Wasia formation). The Huraysan Formation correlates by stratigraphic position and lithology to the Khafji and Safaniya members of the Wasia Formation in subsurface Saudi Arabia. The Majma Formation may correlate to the Mauddud, Wara and lower part of the Ahmadi members of the subsurface Wasia Formation in Saudi Arabia. The successively overlying Qibah and Malihah formations (previously Qibah and Malihah members of Wasia formation) complete the Cenomanian and Early Turonian succession below the pre-Aruma unconformity. These two formations may correlate to the upper part of the Ahmadi, Rumaila and Mishrif members of the subsurface Wasia Formation in Saudi Arabia. In central Saudi Arabia, the pre-Aruma unconformity is overlain by the Upper Campanian and Lower Maastrichtian Khanasir Member of the Aruma Formation. The Upper Maastrichtian Hajajah and Paleocene Lina members form the upper part of the Aruma Formation. In contrast, the subsurface Aruma Formation in Saudi Arabia may extend to the Coniacian Stage. The Biyadh Sandstone consists of coastal-plain clastics deposited during several transgressive-regressive sequences. It overlies the pre-Biyadh unconformity, which is represented by west-cutting regional erosion that reaches down to the Jurassic Dhruma and underlying Marrat formations. The overlying Sallah Formation represents a transgressive-regressive sequence deposited in lagoonal and tidal settings, and includes limestone beds with marine fauna. The overlying Huraysan Formation consists of fluvial, fining-upward clastics and is, together with older units, regionally eroded by the pre-Majma unconformity. The associated pre-Majma hiatus probably occurred in the Late Albian and is characterized by the Az Zabirah Bauxite, a deposit that reflects a pedogenic episode that occurred in tropical humid conditions. The fluvial and marginal marine clastics of the Majma Formation, and marine clastics and carbonates of the Qibah Formation, can together be characterized in terms of three flooding events. The Malihah Formation was deposited in mixed proximal settings (tidal to fluvio-deltaic) and exposed (paleosols with bauxite). It represents a regression associated with the eastward tilting of the Arabian Plate during Turonian tectonism along the Neo-Tethyan margin. Central Saudi Arabia remained exposed during the Late Turonian through Middle Campanian, during which times the pre-Aruma Bauxite formed. The Aruma Formation is characterized by four third-order sequences; one in the Khanasir Member, two in the Hajajah Member – all of Late Cretaceous age, and the Paleogene Lina sequence.

scholarly journals Early to mid-Cretaceous mixed carbonate-clastic shelfal systems: examples, issues and models from the Arabian Plate

GeoArabia ◽  
2002 ◽  
Vol 7 (3) ◽  
pp. 541-598 ◽  
Author(s):  
Roger B. Davies ◽  
David M. Casey ◽  
Andrew D. Horbury ◽  
Peter R. Sharland ◽  
Michael D. Simmons
Keyword(s):  
Saudi Arabia ◽  
Passive Margin ◽  
Arabian Plate ◽  
Carbonate Platforms ◽  
Carbonate Production ◽  
Sequence Stratigraphic ◽  
Stratigraphic Model ◽  
Depositional Systems ◽  
Migration Pathways ◽  
Mixed Carbonate

ABSTRACT Maximum Flooding Surfaces (MFS) in the Early to mid-Cretaceous mixed carbonate-clastic shelfal systems of the Arabian Plate have been incorporated into a new sequence stratigraphic model that links Kuwait, Iran, Saudi Arabia, Qatar, and the United Arab Emirates, to Oman and Yemen. It is based on regional sequence stratigraphic concepts supported by biostratigraphic, sedimentological and mineralogical data. The model has amended the positions of some existing MFS. The diachronous interplay between large-scale, proximal clastic systems and outboard (down-systems-tract) carbonate platforms was emphasized by concentrating on the depositional history of prodelta areas during delta advance and retreat. The prodelta area of relatively deep water separating the depositional systems has been termed the ‘Migratory Carbonate Suppressed Belt’ (MCSB). The model proposes that platform limestones expanded back over preceding prodelta areas during transgressions. The most extensive transgressions ultimately led to the demise of MCSBs. The maximum landward retreat of the shoreline coincided with the cessation of clastic input in the most up-systems-tract localities. Thus, the model has predicted that in many places MFS are located in the basal parts of clean carbonates even though these are not the deepest-water sediments. Examples are the Zubair-Shu’aiba (K70 MFS) and the upper Burgan-Maddud (K100) sections of the northern Gulf. Where carbonate platforms did not expand completely across the MCSBs, perhaps because of fault-control, the MCSBs survived and MFS are present within deeper-water, prodelta shales deposited below the most efficient window for carbonate production. Examples are the K40 to K60 MFS in intraformational shales of the Zubair, Biyadh, and Qishn formations of Kuwait, Saudi Arabia, and Yemen, and K100 in the Burgan-Wasia formations of Kuwait and Saudi Arabia. Even in these cases, the MFS are present within limestones deposited further down-systems-tract, notably in Iran (K60—Khalij Member, Gadvan Formation; K100—Dair Limestone Member, Burgan-Kazhdumi formations). Deeper-water dense limestones and shales with accompanying MFS were deposited along the northeastern passive margin of the Arabian Plate, or within intrashelf basins with some limited connection to the open ocean. From a regional perspective it can be seen that eustatic or tectonically forced MFS do not necessarily occur within the deepest-water facies. A regional understanding is needed for a more precise sequence stratigraphic interpretation of the Early to mid-Cretaceous succession of the Arabian Plate. The identification of the stratigraphic architecture is of major economic importance at the reservoir scale, for instance in recognizing vertical permeability and transmissibility barriers, as well as at the regional-play fairway scale in the distribution of seals and their potential influence on migration pathways. Our interpretations are also relevant to the prediction of source-rock distributions and, in the longer term, may help identify stratigraphic trap potential related to the interplay between clastic and carbonate depositional systems. Although the model proposed relates to the Arabian Plate, general conclusions may be applicable to other regions where mixed carbonate-clastic systems are well developed, for example in many basins of Tertiary age in South East Asia.

scholarly journals Palaeogeographic reconstruction of a fluvio-marine transitional system in Narmada rift basin, India — Implications on Late Cretaceous global sea-level rise

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Biplab Bhattacharya ◽  
Suparna Jha ◽  
Prantik Mondal
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
High Frequency ◽  
Depositional Environments ◽  
Systematic Change ◽  
Rift Basin ◽  
Facies Association ◽  
Facies Associations ◽  
Sandstone Formation ◽  
Global Sea Level

AbstractRising sea-levels in tectonically active epicontinental basins often lead to varied depositional settings and palaeogeography, mostly influenced by the net accommodation resulting from mutual interference of the extent and nature of landward encroachment by the sea and the net sedimentation. The Cenomanian Nimar Sandstone Formation, Bagh Group, Narmada rift basin, uniquely portrays the effect of sea-level rise within an intra-cratonic setting and attributes to the corresponding palaeogeographic changes in west-central India. An integrated sedimentological–sequence-stratigraphic study of the broadly fining-upward Nimar Sandstone Formation (thickness ~ 20–30 m) depicts the actual nature of changeover from a fluvial to a marine-dominated transitional depositional setting. Detailed sedimentological study reveals total seventeen facies, grouped in five facies associations, viz., the channel-fill facies association (FA-1), the overbank facies association (FA-2), the fluvial-dominated fluvio-tidal facies association (FA-3), the tide-dominated fluvio-tidal facies association (FA-4), and the shoreface facies association (FA-5). Overall facies architecture indicates a west-to-eastward marine encroachment, resulting in stacking of three distinct palaeo-depositional conditions: (i) an initial fluvial system with channel and overbank, changing into a tide-influenced fluvial bay-head delta in the inner estuary, followed by (ii) marine encroachment leading to a tide-dominated central estuary with inter- to sub-tidal settings, and finally, (iii) with further intense marine encroachments, a wave-reworked open shore condition in the outer estuary zone. The overall fining-up succession with a systematic change from fluvial to marine-dominated depositional systems points to a landward shift of the shoreline, signifying a major transgressive event correlated to the Cenomanian global sea-level rise. Characteristic stratal stacking patterns point to four coarsening- and fining-up hemicycles, embedded within the major transgressive succession. These high-frequency cycles attest to the varied interplay of sedimentation, tectonics and sea-level changes, and the resultant net accommodations. A palaeogeographic model is proposed based on the high-frequency transgressive–regressive hemicycles, which envisages the evolution of the depositional environments in relation to the Cenomanian eustatic rise in the intra-cratonic riftogenic fluvio-marine transitional basinal setup.

Depositional sequence stratigraphy of Turonian to Santonian sediments, Cape Fear arch, North Carolina Coastal Plain, USA

Stratigraphy ◽  
2020 ◽  
Vol 16 (1) ◽  
pp. 293-314
Author(s):  
Wilma B. Aleman Gonzalez ◽  
Jean M. Self-Trail ◽  
W. Burleigh Harris ◽  
Jessica Pierson Moore ◽  
Kathleen M. Farrell
Keyword(s):  
North Carolina ◽  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Plain ◽  
Atlantic Coastal Plain ◽  
Sequence Stratigraphic ◽  
Stratigraphic Framework ◽  
Cape Fear ◽  
Global Sea Level ◽  
Atlantic Coastal

ABSTRACT: A new sequence stratigraphic framework for Turonian to Santonian (94-84 Ma) sediments is established using data from the USGS Kure Beach and Elizabethtown cores collected from the Atlantic Coastal Plain of North Carolina (NC). These sediments represent some of the oldest marine units deposited on the southeastern Atlantic Coastal Plain and record the early development of a clastic wedge atop crystalline basement. Sediments were deposited as transitional marginal-marine to marine units in a complex interplay of fluvial, estuarine, and shelf environments. Repetitive lithologies and minimal biostratigraphic control requires an integrated analysis of grain-size data, geophysical logs, biostratigraphy, and 87Sr/86Sr isotopic data to identify systems tracts and establish a sequence stratigraphic framework. From this integrated approach, three Turonian to Santonian sequences in the Elizabethtown core and six in the Kure Beach core are identified. The new sequences from oldest to youngest are Clubhouse II, Fort Fisher I, Fort Fisher II, Collins Creek I, Collins Creek II, Pleasant Creek I, and Pleasant Creek II. Sequences from North Carolina document significant shifts of global and regional sea-level during greenhouse conditions in the early Late Cretaceous. Maximum sea-level rise occurred globally during the early Turonian and is documented from the marine sediments of the Clubhouse II sequence. This sequence is unconformably overlain by terrestrial sediments deposited during a major fall in sea level and maximum progradation of the shoreline, as evidenced by the Fort Fisher I sequence. Global sea-level rise in the Coniacian resulted in the deposition of the Fort Fisher II sequence, which is present only in the Kure Beach core. Local marine circulation and erosion on the shelf is suggested by the absence of the Collins Creek I sequence at Kure Beach; this sequence is present only in the up-dip Elizabethtown core. Activation of a possible buried fault structure along the Cape Fear arch resulted in the formation of a regional depocenter during the late Coniacian to early Santonian and is reflected in the unusual thickness of the Collins Creek II and Pleasant Creek I sequences. The return to a more global sea-level influence occurred in the late Santonian with the deposition of the Pleasant Creek II sequence. A comparison of temporal distribution of sequences in the Elizabethtown and Kure Beach cores to corresponding sequences in New Jersey indicates significant differences in erosional and tectonic processes in the Cape Fear region during the Turonian and Santonian.

scholarly journals Miocene Kareem Sequence, Gulf of Suez, Egypt

GeoArabia ◽  
2010 ◽  
Vol 15 (2) ◽  
pp. 175-204 ◽  
Author(s):  
Moujahed I. Al-Husseini ◽  
M. Dia Mahmoud ◽  
Robley K. Matthews
Keyword(s):  
Sea Level ◽  
Red Sea ◽  
Arabian Plate ◽  
Gulf Of Suez ◽  
Rift Basins ◽  
Third Order ◽  
Depositional Sequence ◽  
Marine Deposits ◽  
Red Sea Rift ◽  
Global Sea Level

ABSTRACT The Miocene Kareem Formation in the Egyptian Gulf of Suez, and its equivalent formations throughout the Red Sea (250–550 m thick), contain one of the most important petroleum reservoirs in these highly faulted rift basins. They present a difficult exploration target, particularly over the shelves of the sparsely explored Red Sea for several reasons: (1) water depth exceeds one kilometer, (2) they underlie thick evaporites (including salt exceeding one kilometer in thickness), (3) they are difficult to image by conventional seismic techniques, and (4) their lithology is laterally variable and difficult to predict (anhydrite, carbonate, sandstone, shale and marl). The target Red Sea formations are best controlled by boreholes in the Gulf of Suez, where the Kareem Formation and its members are characterized by various synonymous units. A review of representative data and interpretations shows that the formation and its members are better understood when considered as a third-order, transgressive-regressive (T-R) depositional sequence, named the Kareem Sequence in the Middle East Geologic Time Scale (ME GTS). The Sequence is bounded above by the Belayim Sequence Boundary (Sub-Belayim Unconformity) and below by the Kareem Sequence Boundary (Sub-Kareem Unconformity), both corresponding to major sea-level lowstands. It contains the Arabian Plate Langhian Maximum Flooding Surface Neogene 30 (MFS Ng30) at the top of the Kareem Maximum Flooding Interval (MFI). Its lower Rahmi Member forms the majority of the transgressive systems tract (TST). The Kareem MFI and regressive systems tract (RST or HST) occur within the upper Shagar Member. The paleontology of the Formation is characterized by Planktonic Foraminiferal Zone N9 and in recent papers also N8, and Calcareous Nannofossil Biozone NN5, but the Formation’s assignment to Miocene stages (Burdigalian, Langhian and Serravallian) is unresolved in the literature. In this paper, the Kareem Sequence is interpreted in terms of Kareem subsequences 1 to 6. At semi-regional scales (10s of km), the older three are each represented by an anhydrite bed (Rahmi Anhydrite 1 to 3, each c. 10 m thick) overlain by deep-marine deposits (shale, marl and carbonate, 10s of meters thick). Subsequences 4 to 6 are represented in El Morgan field (Kareem A to C units), and in representative boreholes, by three deep-marine shale/marl units, each of which is overlain by a regressive shallow-marine sandstone unit. The Kareem Sequence is correlated to third-order orbital sequence DS3 1.1 with a depositional period of ca. 2.43 million years between ca. 16.1 and 13.7 million years before present (Ma), or numerically the latest Burdigalian, Langhian and earliest Serravallian (Langhian: 15.97–13.65 Ma in GTS 2004; 15.97–13.82 Ma in GTS 2009). The six subsequences are correlated to the orbital 405,000 year eccentricity cycle (referred to as Stratons 40–35 or DS4 1.1.1 to 1.1.6). The older three subsequences form the transgressive systems tract; the fourth contains the maximum flooding interval MFI (ca. 14.9–14.7 Ma) in its lower part. The regressive systems tract starts in the upper part of the fourth subsequence and encompasses subsequences 5 and 6. The orbital architecture of the Sequence provides a simplified framework for predicting lithology and reservoir development. The six Kareem subsequences carry the orbital-forcing glacio-eustatic signal. During low eccentricity, Antarctic ice-making and global sea-level drops, the northernmost Gulf of Suez and Bab Al Mandeb Strait restricted marine circulation in the Gulf and Red Sea rift basins. The resulting evaporitic setting was associated with the deposition of the Rahmi Anhydrite 1 to 3 beds and exposure over paleohighs. The deeper-marine deposits above the three Rahmi Anhydrite beds, and those of subsequences 4 to 6 reflect high eccentricity, Antarctic ice-melting, global sea-level rises, pluvial conditions at low latitudes (10–30oN), and open-marine circulation in the Red Sea. During pluvial periods, fluvio-deltaic systems prevailed over the mountainous rift shoulders and coastal plains and carried massive clastics into the Gulf and Red Sea Basins.

Sign in / Sign up

Export Citation Format

Share Document