13-14 September 2005, Bremen, Germany
Presented by the Libyan Biostratigraphy Group (LBG)
The Dynamic Stratigraphy of Cyrenaica:
Ahmed S. El Hawat
The North African coastal promontory of Cyrenaica , NE Libya, consists of two distinct tectonic provinces separated by a hinge line of the Cyrenaican fault system. These are the northern, and presently active inverted basin of Al Jabal al Akhdar; and the more stable Cyrenaica platform to the south. Cyrenaica represents a topographic, geological as well as a geophysical anomaly in the Mediterranean basin as consequence of the direct impact of compressive forces induced by the convergence between the European - Aegean and African plates.
The northern limit of Al Jabal al Akhdar inversion anticlinorium is down faulted to the coastal plain, which extends northward to the offshore to form a narrow, steep, faulted and folded continental margin. It is separated from the Mediterranean Accretion Ridge by an east west trending, narrow furrow at 2500 to 3000 meters of water depth. It represents a scare of a major fault system running in the offshore parallel to the Cyrenaican coast and is referred to as north Cyrenaica fault system. Significantly, the Cyrenaican continental slope is being differentially overthrusted by the Mediterranean Ridge in what is regarded as active incipient continental collision processes.
These ongoing tectonic activities were impacted on the stratigraphic record of northern Cyrenaica and were manifested in the recurring upward shallowing sequences and associated unconformities. Constrained temporal palaeogeographic maps and cross sections demonstrate dynamic stratigraphic changes of palaeotopography attributed to changing structural configurations through time. These were often associated with reworking and syndepositional mass movement of sediments, as well as development of post depositional structural deformation, which are observed in the Cyrenaican stratigraphic record since the Upper Cretaceous. Furthermore, younger tectonic signatures are recorded as up faulted Pleistocene coastal terraces, and in the destruction of Cyrenaican towns from antiquity to present. Finally, an integrated approach to the study of geology and biostratigraphy in Cyrenaica taking into account analysis of associated tectonic events and signatures is urgently required in order to reach a rational interpretation of stratigraphy.
The stratigraphic positions of Wadi Dukhan and Al Uwayliah Formations, north-east Libya – A review
By Ahmed Tmalla
Nationaal Natuurhistorisch Museum, Naturalis, P.O. Box 9517, 2300 RA Leiden - The Netherlands, E-mail address: email@example.com
Following the rules of nomenclature the type section of Al Uwayliah Formation should be considered a composite-stratotype. The section east of al Uwayliah village is the holostratotype (upper part of the formation) and the Jrdas al Jarrari section is the parastratotype (lower part of the formation). The combined thickness of the two component-stratotypes seems to be too thin to represent the whole Paleocene Series. Paleontologic evidence also suggests that parts of the Paleocene standard foraminiferal zones are not represented in either of the two component- stratotypes. Most probably a middle part of Al Uwayliah Formation, below the holostratotype and above the parastratotype, (late Danian to Selandian), has not yet been recognized. More paleontologic work is needed to clarify this point.
Biostratigraphic review of the Al Athrun and Apollonia formations, Cyrenaica, NE Libya, based on calcareous nannofossils
Ali Ahmed El-Mehaghag and Ali Daw El-Mehdawi
Arabian Gulf Oil Company, Geol. Lab., P.O. Box 263 , Benghazi , Libya E-mail: firstname.lastname@example.org
The Al Athrun and Apollonia Formations at two locations in Wadi Al Athrun area in Cyrenaica , NE Libya, have been reviewed biostratigraphically, based on their calcareous nannofossil content. i) Wadi al Athrun section, representing the upper part of Al Athrun Formation, is assigned to the Quadrum trifidium CC22 Zone of Campanian age,while, has been the lower part of the Apollonia Formation is assigned to Discoaster multiradiatus zone NP9 of Late Paleocene age. An undifferentiated Apollonia horizon belongs to Eocene Tribrachiatus contortus to Discoaster binodosus zones NP10-NP12. ii) The a slump section representing a part of the Al Athrun Formation also contains Quadrum trifidium CC22 zone, previously assigned to late Coniacian to late Maastrichtian age based on the study of their planktonic foraminiferal content (Barr and Hammuda, 1971). However, Barr and Berggren (1980) and Haq and Aubry (1980) interpreted the typical Palaeocene planktonic foraminifera and calcareous nannofossil assemblages present in both sections of the Apollonia Formation as being reworked. The present study proves that this conclusion is unreliable and the interpretations were based on inadequate results.
Biostratigraphic analysis of the upper part of Apollonia Formation in Northeastern Libya
Ali, A. El-Mehaghag 1 and Akmal M. Marzouk 2
1 Arabian Gulf Oil Company, Exploration Division, Geological Laboratory, P. O. Box 263 , Benghazi- , Libya . 2 University of Tanta , Department of Geology, Tanta , Egypt .
Thirty calcareous nannoplankton species, retrieved from the upper part of Apollonia Formation at the Wadi Bacur road-cut (Al Jabal al Akhdar), have been documented. The diagnostic nannofossil species: Cyclicargolithus floridanus, Reticulofenestra bisecta, Cribrocentrum reticulatum, Reticulofenestra umbilica, Dictycoccites scrippsae, Reticulofenestra pelycomorpha and Discoaster saipanensis confirms Late Eocene Sphenolithus pseudoradians (NP20) zone. The presence of very rare Tribrachiatus orthostylus and T. bramlettei points to Early Eocene, at this stratigraphic level is considered to be a result of reworking of older sedimentary deposits.
Palynological Analysis of the Upper Cretaceous Al Hilal Formation, Ras Al Hilal area, Al Jabal Al Akhdar, NE Libya
Ali Daw El-Mehdawi
Arabian Gulf Oil Company, Geological Lab, P.O. Box: 263, Benghazi , Libya , GSLAJ.
Twelve surface samples from the Al Hilal Formation, exposed in Ras Al Hilal area, Al Jabal Al Akhdar, NE Libya have been palynologically examined. Productive samples yielded a low recovery of organic matter dominated by herbaceous debris including low abundance and diversity of palynomorphs, dominated by pale dinoflagellate cysts, with rare terrestrial miospores. About thirty species of dinoflagellate cysts and miospores were recognised . The most characteristic species are peridinioid forms including Chatangiella biapertura , C. ditissima , C. serratula , C. cf. tripartita , Eucladinium cf. gambangense , E. madurense , Isabelidinium acuminatum , I . belfastense , I. Cooksoniae , and Other chorate, marginate, ceratioid, and gymnodinoid species such as Cannosphaeropsis cf. utinensis, Nematosphaeropsis sp., Tanyosphaeridium cf. regulare , Cyclonephelium vannophorum , Senoniasphaera sp. A, Xenascus sarjeantii, Dinogymnium acuminatum, D . cf. cooksoniae , and D . undulosum . Two important Upper Cretaceous terrestrial miospores Araedinaesporites sp., and Foveotriletes margaritae are also recognized.
Palynological Contribution to the Stratigraphy of the Al Faidiyah Formation, Al Jabal Al Akhdar, NE Libya
Ali Daw El-Mehdawi (1) and Salah Yousef El Beialy (2)
1 Arabian Gulf Oil Company, Geology Department, Geological Lab, P.O.Box: 263, Benghazi , Libya , GSLAJ. E-mail: email@example.com
2 Department of Geology, Faculty of Science, University of El Mansoura , El Mansoura , 35516 , Egypt . E-mail: firstname.lastname@example.org
Well preserved palynomorphs (dinoflagellate cysts, tasmanites, microforaminiferal test lingings and rare sporomorphs) of moderate abundance and diversity have been recognized from eight surface samples . These were nearly eight metres thick collected from the Al Faidiyah Formation exposed at the Cyrene-Apollonia road cut, Al Jabal Al Akhdar, NE Libya.
Biostratigraphic and sedimentological analyses of the Al Abraq Formation in Jabal Al Akhdar, NE Libya
Ali A. El-Mehaghag 2 , Ahmed M. Muftah 1 , Salem Bushiha 1 and Abuessoud A. Addaloush 2
1 University of Garyounis, Faculty of Science, Department of Earth Sciences, P. O. Box 9480, Benghazi-Libya.
Three road-cut sections of Al Abraq Formation at (Daryanah-Abyar, Shahhat-Susa and Dabousseyiah) and the Type Locality, has been examined on the basis of its calcareous nannoplankton and foraminiferal contents. The examined sections yield few calcareous nannofossils, with the exposure at Dabousseyiah being barren.
Biostratigraphic evaluation of Tukrah Formation in Cyrenaica, NE Libya
Ali A. El Mehaghag 1 , Ahmed M. Muftah 2 and Sami Daw 2
1 Arabian Gulf Oil Company, Exploration Division, P.O. Box 263 , Benghazi Libya . < email@example.com >
Tukrah Formation was assigned to the Late Cretaceous age by some authors, and to the Eocene by others, based mainly on its macrofossils, foraminiferal and calcareous nannofossil content. The present study is based on the nannofossil and foraminiferal content of this formation in two localities. Calcareous nannofossils in Tukrah samples from the Tukrah coastal plain indicate a range of Late Eocene to Early Oligocene age. The presence of moderate to poorly preserved and rare small benthic foraminifera such as Bulimina sp. and bolivinids confirms the nannoplankton dating. Tukrah argillaceous bioclastic packstones from an exposure at the ancient ruins of Greek City , yielded moderate to good preserved diagnostic calcareous nannoplanktons, including Cyclicargolithus floridanus, Dictyococcites bisectus and Cribrocentum coenurum. Accordingly, the age of this formation ranges from Late Eocene ( Sphenolithus pseudoradians NP20) to Oligocene ( Sphenolithus distentus NP24),based on Martini's (1971).zones. Tukrah samples, retrieved from areas between these two localities, yielded a Late Eocene-Oligocene age range, based on micropaleontological, analysis .
Biostratigraphic analysis of Al Faidiyah Formation in Northeastern Libya
Ahmed M. Muftah 1 and Ali. A. El-Mehaghag 2
1 University of Garyounis, Faculty of Science, Department of Earth Sciences, P. O. Box 9480, Benghazi-,Libya. <firstname.lastname@example.org>
Ten planktic and forty benthic foraminifera species, together with twenty-seven calcareous nannoplankton species, retrieved from Al Faidiyah Formation, at a Shahhat-Susa road cut (Al Jabal al Akhdar) and a shallow water borehole in the proximity of Al Qawarishah area, have been documented. The diagnostic planktic species Globigerina ciperoensis ciperoensis, G. ciperoensis angulisuturalis and Globorotalia opima nana assign the sampled stratigraphic horizon at the Shahhat-Susa road cut to the G. ciperoensis ciperoensis zone. By comparison, the diagnostic nannofossil species: Sphenolithus ciperoensis, S. predistantus, Cyclicargolithus abisectus, Reticulofenestra bisecta and Zygrhablithus bijugatus assign the same horizon to the S. distantus zone (NP24). The integration of these results confirms early Late Oligocene age for that part of Al Faidiyah Formation exposed at the Shahhat-Susa locality.
Palynological age dating and facies analysis of the Nubian Group,
By Sadeg M. Ghnia (1) , Nuri Fello (1), Sebastian Lüning (2)
The Nubian Group in the Hameimat Trough is subdivided into the three units Lower Nubian Sandstone, Varicoloured Shale and Upper Nubian Sandstone. Core slabs from 271 feet of cored intervals from the Lower Nubian Sandstone in well R9-82 and 424 feet of cored intervals from the Upper Nubian Sandstone in well A1-NC125 have been analysed. Nine lithofacies have been identified and classified according to their lithological characteristics and sedimentary and biogenic structures. These include (1) conglomeratic sandstone with mud rip-up clasts, (2) trough cross bedded sandstone, (3) planar cross-bedded sandstone, (4) poorly stratified sandstone with rare flaser bedding, (5) ripple cross laminated sandstone, (6) silty mudstone, (7) mudstone, (8) deformed fine sandstone and mudstones, and (9) interbedded fine sandstone and mudstone with marine trace fossils. Sandstones in the Lower Nubian are interbedded with muds, but display braid channel characteristics. They were deposited in a subsiding basin which created ample accommodation space for fines to accumulate. The overlying sandstones were most likely laid down in lagoonal/marginal flood plain environments. Trace fossils indicate harsh, restricted marine environments for the sand bodies and they are interpreted as shoreline or barrier shoals to lagoons and marshes. Escape structures indicate storm events. The topmost sand show a return to fluvial influence but interbedded shales and the succeeding Varicoloured Shale contain lagoonal palynofacies. The Upper Nubian Sandstone comprises of two sand bodies and an intervening thick shale. The sandstones are fluvial braided deposits; the shale is brackish/lagoonal. The overall environment for the group is interpreted as marginal marine to flood plain. Palynological age dating indicate an Early Cretaceous age, the Varicoloured Shale being most probably Aptian. The dinoflagellate Lagenorhytis sp and the presence of Odontoihina sp indicate an age range from Barremian to Campanian. The large number of Ephederites sp strongly point to Aptian.
An Early–Middle Miocene dinoflagellate cyst biozonation for the Gulf of Suez, Egypt
Soliman, A. (1, 2) ; Head, M.J. ( 3) ; El Beialy, S. (4) & Piller, W. (1)
1 Institut für Erdewissenschaften (Geologie und Paläontologie), Karl-Franzens Universität GRAZ, Heinrichstrasse 26, A- 8010 Graz (Austria), ali. email@example.com ; firstname.lastname@example.org .
2 Geology Deaprtment, Faculty of Science, Tanta University, Tanta 31527, Egypt.
3 Department of Geography, University of Cambridge, Downing Place, Cambridge, CB2 3EN (England), email@example.com .
4 Department of Geology, Faculty of Science, El Mansoura University, El Mansoura 35516 (Egypt), firstname.lastname@example.org
A new dinoflagellate cyst zonation for the Early-Middle Miocene of the Gulf of Suez is proposed. The zonation is constructed using biostratigraphic data obtained from five deep wells in the southern Gulf of Suez, Egypt, and is based on the highest occurrences of selected dinoflagellate cyst taxa. The zonation is tied to a chronostratigraphic framework by using correlation to calcareous nannoplankton datums. The presence of diverse dinoflagellate cyst taxa allows the establishment of four interval zones covering the late Aquitanian? to Serravallian. The oldest is the Cordosphaeridium cantharellus Zone of late Aquitanian?–early Burdigalian age (NN2). This is followed by the Apteodinium spiridoides Zone of Burdigalian age (NN2–NN4) and the Selenopemphix denticulatum n. sp. Zone of Langhian age (NN4). The youngest interval zone is the Cleistosphaeridium spp. Zone of late Langhian–Serravallian age (NN5). Comparisons with other Miocene zonations from the Mediterranean, North Atlantic, eastern USA and central Paratethys indicate that the highest occurrences of Cordosphaeridium cantharellus, Exochosphaeridium insigne, Distatodinium paradoxum and Apteodinium spiridoides , and the lowest occurrences of Hystrichosphaeropsis obscura , Sumatradinium soucouyantiae , Sumatradinium druggii , Labyrinthodinium truncatum are important horizons. This is the first study to demonstrate the applicability of Early and Middle Miocene dinoflagellate cyst markers for detailed stratigraphic correlation in the Gulf of Suez, Egypt.
Cenomanian-Turonian biostratigraphy in North Western Desert, Egypt
By Safaa A. Sharabi
The study area in the northern Western Desert lies at the eastern margin of the Abu Gharadig Basin and at the northern marhin of the El Gindi Basin. Three exploration wells were selected from the area to the north of Lake Qarun (wells 1-BRE 6-1, 1-BRE 3-1, and WD 19-2). The Cenomanian - Turonian successions were studied in detail (lithologic description, faunal content, biostratigraphic age dating), and the results were correlated with surface and subsurface sections in the Western Desert, Sinai, Palestine, Jordan and Kuwait. The Cenomanian is characterized by two rock units: the Bahariya Formation (Late Albian to Early Cenomanian) and the Abu Roash “ G” Member of Late Cenomanian age. The Early and Middle Turonian is represented by the Abu Roash “ D “, “ E “, “ F “ members. Palaeontologically the Rotalipora brotzeni Zone (international zone of Late Albian - Early Cenomanian age) is recorded within the Cenomanian sequence.
Subsurface Upper Cretaceous successions in the northern Western Desert, Egypt, in relation to global sea level changes and sedimentation
By Safaa A. Sharabi
Upper Cretaceous units from the subsurface were studied in three selected wells to the north of Lake Qarun in the eastern part of the North Western Desert, Egypt (1- BRE 3-1, 1- BRE 6-1 and WD 19-2 Wells). The lithology, log characteristics and faunal content was studied with special attention to sedimentary breaks. Nine breaks in sedimentation are recognized within the Upper Cretaceous sequences of the study area.
Some remarks on the Upper Cretaceous Microbiostratigraphy of Libya
By Prof. Joseph Salaj
Proved specimens of the genus Whiteinella Pessagno, 1967 from the Zone of Whiteinella gigantea Lehmann, 1964 (= syn.: Whiteinella archaeocretacea Pessagno, 1967) without Helvetoglobotruncana helvetica (Bolli) confirm that the Helvetoglobotruncana helvetica Zone in the area of Marsa al Hilal (Barr 1972) is not closely overlying the Rotalipora cushmani Zone. Otherwise in Cyrenaica we should accept the existence of a stratigraphical hiatus and specimens of the genus Whiteinella Pessagno, 1967 would belong to the Helvetoglobotruncana helvetica Zone, in which the species Helvetoglobotruncana helvetica (Bolli) occurs sporadically or as a consequence of unfavourable ecological conditions is not present.
Bank - basin model for the Paleogene of NE Libya
Hamed O. Elwerfalli* and Dorrik A. V. Stow**
* Geology Department, Arabian Gulf Oil Company, P.O. Box 263, Benghazi , Libya.
Detailed sedimentological studies of the Paleogene section from both the subsurface (14 boreholes) and surface outcrops (5 localities) have shown that the western margin of the Cyrenaica Platform was rimmed by a shallow-water carbonate bank. Characteristic features of bank facies include an abundant shallow marine fauna (nummulites, algae, mollusks, miliolids, echinoderms) and dominant packstone to grainstone textures, interbedded with minor bioclastic wackestones. These data together with evidence from red algae and micro-borings suggest deposition in the lower aphotic zone above storm wave base. The fore-bank region is characterized by chalk, shale and lithoclastic packstone facies that accumulated by both pelagic processes and downslope re-sedimentation, whereas the back-bank region comprises a restricted fauna (miliolids and mollusks) and interbedded dolostone/evaporite facies indicative of a moderately to hypersaline lagoonal environment. A double cycle of high to low stand system tracts characterize the Paleocene succession in NE Libya and are approximately coincident with eustatic changes of sea level. Expansion of the nummulites bank facies association occurred during relative high-stand deposition, whereas a greater extent of lagoonal dolostone and evaporates is evident during low stands. Local tectonic activity was a secondary control on facies distribution, thicknesses and rates of accumulation. Despite a complex diagenetic history, porosity-permeability data show that the nummulitic limestone and parts of the dolostone section have good reservoir potential. Both structural and stratigraphic trap types can be identified on seismic sections and known hydrocarbon shows suggest mid Miocene generation and migration.
Microfacies and palaeoenvironment analysis of the algal Limestone Member of the Al Bayda FormationI, Al Jabal Al Akhdar, NE Libya.
Ahmed M. Muftah and Hassan S. Hassan
Department of Earth Science, University of Garyounis , P.O. Box 9480 , Benghazi , Libya .
Two sections of the Algal Limestone Member of Al Bayda Formation have been examined along Daryanah–Al Abyar road-cut (17 samples) and Susa-Shahhat road-cut (31 samples) in Al Jabal al Akhdar region, northeast Libya . This study aims to review the depositional environment of this member based on lithofacies and micropaleontological content, with particular reference to coralline red algae. Extreme indurations have prevented desegregations and recovery of individual foraminiferal specimens, consequently this study is limited to thin sections of the rock samples. Some encrusting coralline red algal species have been documented and illustrated, belong to some genera such as Sporolithon, Lithoporella, Lithophyllum, Lithothamnion, Mesolphyllum , Neogoniolithon as well as Corallina . The associated benthic foraminifers are rare to spares with general aspects of marginal to shallow marine forms in which dominated by nummulitids, miliolids and gypsinids with few amphisteginids.
The Biostratigraphy of the Early Cretaceous Sarir Group of the Maragh Low and Western Cyrenaican Platform , Libya
P. H. Swire (1), I. A. Rabti (2) and M. Y. Baair (3)
(1) Veba, (2) Woodside
Palynological analysis of twenty-three Pre- Tertiary well sections from the Maragh Low and surrounding area, has allowed high resolution biostratigraphical correlations to be undertaken. Pre-Sirt Unconformity two superimposed rifting cycles have been identified. The oldest of Cambrian to Triassic age is represented by the Amal Group and the youngest of Early Cretaceous age belongs to the Sarir Group.
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