Miocene to Pleistocene Sporomorphs and Dinoflagellates from Plankton-Dated Sediments in the NDO B-1 Well, Offshore Nile Delta, Egypt

The Nile Delta area is well known for its geological and geophysical complexity due to:the presence of gas clouds, chimneys, channels and growth faults in the Pliocene/Late Pliocene series;the variability in terms of lithology, structure and thickness of the Messinian formations that cause a highly irregular and laterally varying velocity structure;the low SNR of seismic data in the pre-Messinian series caused by the above described irregularities combined with the contamination of seismic data due to the presence of multiples. All these characteristics make the seismic investigation of the area very challenging for both depth imaging and velocity model building, especially when the final goal is the exploration of pre-Messinian targets. Moreover the Nile Delta region is also well known for being affected by overpressures, especially in the pre-Messinian sequences. Recent deep exploration wells, targeting Mio/Oligocene reservoirs, have raised the importance of predicting the overpressure behaviour during the well design phase in order to assess all the exploration risks. Since pore pressure can be estimated from seismic velocities this requirement puts further importance on accurate estimation of seismic velocity. In this paper a case history from the offshore Nile Delta is presented, showing the application of an integrated procedure for solving these problems based on a rigorous depth imaging approach. In particular the focus will be put on the added value given by the continuous interaction between geological and geophysical contexts during the processing phase in all their aspects, such as well information, regional geological knowledge of the areas and interpretation on one side, and acquisition methodologies, imaging technologies and rock physics properties on the geophysical side. Introduction Areas characterized by complex geology, with strong lateral velocity variations and dipping structures are the natural domain of application of Depth Imaging. There the assumptions at the basis of Time Imaging break down, and Depth Imaging is mandatory in order to obtain reliable images of subsurface structures. In order to reach best results, the most sensitive ingredient is the velocity field. No matter which kind of migration is used (either Kirchhoff, Wave Equation, or RTM), if the velocity is not correct the imaging will be distorted. The velocity field must be estimated from seismic data by using tomography, but nonetheless seismic data alone do not provide enough information to determine the velocity unambiguously. Some a-priori information must be provided, and one of the available sources of such information is the geological knowledge of the area under study. On the other hand, as it will be shown here, velocity in its turn can be used to support the validation of geological hypotheses, so that the integration of geology in the process can be of benefit not only for velocity estimation but also for geology itself. Moreover, velocity plays a key role not only for imaging purposes but also for pore pressure prediction, providing a further motivation for getting accurate estimates of seismic velocity [1]. The standard approach to pore pressure prediction based on conventional velocity estimation methodologies deriving from standard time processing does not seem effective enough in the Nile Delta area. In particular, here overpressures and gas presence determine low velocity anomalies that are not properly resolved by the focusing velocities provided by time processing. Hence more sophisticated tools are needed, like those used for depth imaging, in order to improve the reliability of the velocity volume and accordingly to derive reliable pore pressure estimates.

Planktonic foraminifera and dinoflagellate cysts across the Cretaceous/Tertiary boundary in the Nile Delta area, Egypt

Rich and diverse assemblages of dinoflagellate cysts were recovered from the Gearle Siltstone in the Boologooro‐1 stratigraphic well, Southern Carnarvon Basin, Western Australia. The cored interval through the Winning Group is proposed as a reference interval for the Canninginopsis denticulata, Endoceratium ludbrookiae, Dioxya armata and Xenascus asperatus dinoflagellate cyst zones of the Australian dinoflagellate cyst zonal scheme. The ranges of sixty‐three dinoflagellate cyst species are documented in detail over this interval. Apart from the bioevents that define the widely‐used dinoflagellate cyst subzones, the highest occurrences of Endoceratium turneri, Craspedodinium indistinctum and Litosphaeridium arundum, and the lowest occurrences of Nematosphaeropsis densiradiata,Canninginopsis denticulata, Leberidocysta chlamydata, Aptea? sp. cf. Aptea polymorpha, Litosphaeridium siphoniphorum, Balcattia cirribarbata and Stephodinium australicum are recognized as potential biostratigraphic datums in the Southern Carnarvon Basin. Species diversity increased in the highest Canninginopsis denticulata Zone at approximately the horizon where Diconodinium spp. become dominant. Foraminiferal data indicate the interval from 361.15 m to 312.12 m is marginally inner neritic and corresponds with an interval of abundant Diconodinium spp., and fewer Spiniferites spp. Diversity increased in the Xenascus asperatus Zone with an increase in Spiniferites spp., and a shift to middle neritic paleobathymetry. The age of the top of the Xenascus asperatus Zone is constrained by calcareous nannofossils and dinoflagellate cyst correlations to the latest Albian, or possibly the early Cenomanian. The age of the base of the Canninginopsis denticulata Zone is constrained by dinoflagellate cyst and foraminiferal data to the early Albian, above the earliest Albian. One new species, Chlamydophorella haigii, is erected and aspects of several other dinoflagellate cyst taxa are reviewed.

Palynofacies and palynological investigations conducted on the Neogene–Quaternary succession from the NDO B-1 well, located in the offshore Nile Delta, Egypt, in the Eastern Mediterranean, suggest generally shallow marine (neritic) conditions. These environments are manifested by the overall palynofacies composition and the occurrence of dinoflagellate cysts (e.g., Spiniferites spp., Lingulodinium spp., Hystrichokolpoma spp., Homotryblium spp. and Selenopemphix spp.). Neritic environments are suggested for the lower and middle Miocene Sidi Salim, and the Pliocene to Pleistocene upper Kafr El Sheikh, El Wastani and Mit Ghamr formations, while shallower, coastal to inner neritic settings were interpreted for the late Miocene (Qawasim and Rosetta formations) and early Pliocene (Abu Madi and lower Kafr El Sheikh formations). Anoxic conditions existed during the deposition of the studied well succession, which can be seen from the occurrence of imprints of pyrite crystals and some types of oxygen-sensitive dinoflagellate cysts. The palynofacies fluctuated repeatedly between Amorphous Organic Matter (AOM)-dominated and phytoclast-dominated intervals, of kerogen types II and III, respectively. The spore coloration index (SCI) of indigenous thin-walled palynomorphs confirms thermally mature sediments, generative of dry gas and wet gas/condensates. Reworking during the deposition of the upper Sidi Salim, Qawasim and Rosetta formations is inferred from the occurrence of Cretaceous dinoflagellate cysts and pollen.

Seasonal dinoflagellate cyst production and terrestrial palynomorph deposition in the East Asian Monsoon influenced South China Sea: A sediment trap study from the Southwest Taiwan waters

The Cretaceous–Paleogene (K/Pg) boundary in the Dababiya Borehole, southern Egypt: An organic-walled dinoflagellate cyst approach

Origin of the Sinai–Negev erg, Egypt and Israel: mineralogical and geochemical evidence for the importance of the Nile and sea level history

The morphology and taxonomy of the two dinoflagellate cyst taxa viz., Fibrocysta variabilis and Fibrocysts sp., described by Mehrotra and Sarjeant (1987) from the subsurface conventional core samples collected at 2703-2706 m (cc10) and 3621-3624 m (cc13) depths of Narsapur Well-1. Krishna-Godavari Basin, are discussed and reassessed. The two species are found to be the junior synonyms of Apectodinium paniculatum (Costa & Downie) Lentin & Williams 1977 and Apectodinium quinquelatum (Williams & Downie) Lentin & Williams 1981, respectively. A few other specimens comparable to A. paniculatum and A. augustum have also been described. The stratigraphic significance of the reported Apectodinium species is discussed. It is suggested that the dinoflagellate cyst assemblage at sample depth 2703-2706 is the latest Paleocene- ?earliest Eocene in age. The occurrence of Apectodinium species in infra-trappean sample at 3621-3624 m depth, dated as Maastrichtian by Mehrotra and Sarjeant (1987), indicates that this level is not older than the Late Palaeocene in age. This creates an anomalous situation because the youngest infra-trappean sediments at 3336-3339 m depth (cc 12), on planktonic formainiferal data, are dated to be latest Maastrichtian. This discrepancy creates doubt over the slide/sample numbering which needs conformation. Palaeoenvironmental significance of Apectodinium is discussed. A restudy of dinoflagellate cyst biostratigraphy of Narsapur Well-1 is recommended.

Pyritization of dinoflagellate cysts: A case study from the Polish Middle Jurassic (Bathonian)

A detailed study was carried out on dinoflagellate cyst taxa in the interval between 4995 m and 4725 m in Andimadam Formation (Pre-Albian) of well Komarakshi # A of Ariyalur-Pondicherry sub-basin in the Cauvery Basin. The study recognises five dinoflagellate cyst biozones, ranging from Late Jurassic to Early Cretaceous (Early Oxfordian & older - Aptian) age. The stratigraphic order of these biozones are; Sentusidinium rioultii - Polystephanephorus calathus Interval zone, Polystephanephorus calathus - Wanaea clathrata Interval zone, Wanaea clathrata - Gochteodinia mutabilis Interval zone, Gochteodinia mutabilis - Egmontodinium torynum Interval zone and Odontochitina operculata - Pseudoceratium pelliferum Assemblage zone. The presence of dinoflagellate cysts throughout the study interval suggests that the marine influence was prevalent through Late Jurassic (Early Oxfordian) to Early Cretaceous (Aptian) period. The record of Late Jurassic dinoflagellate cysts in the well Komarakshi # A, amply suggests that the marine incursion had taken place during Early Oxfordian in the Cauvery Basin. This also leads to the hypothesis that the rifting of Gondwanaland and opening up of Indian Ocean might have begun during Late Jurassic (Early Oxfordian) period, which led to the first marine transgression into the basin.

The composition and diversity of dinosporin in species of the Apectodinium complex (Dinoflagellata)

Dinoflagellate cysts from the upper Campanian (Upper Cretaceous) of Hornby Island, British Columbia, Canada, with implications for Nanaimo Group biostratigraphy and paleoenvironmental reconstructions

The offshore Nile Delta remains a sparsely explored area of the Mediterranean, Nile Delta considered as a prospective area for hydrocarbon exploration. It is located at the western side offshore Nile Delta. The available geophysical, geologic and well logging data obtained from exploration and development wells were used to establish static and dynamic models of the area to calculate gas in place prior to production. High resolution 3D seismic data and recent exploration activities proved several plays with complex depositional settings. Tertiary channels systems can be recognized using 3-D seismic and attributes interpretations with tying channel characteristics to well control within a sequence stratigraphic framework to predict the reservoir facies within undrilled exploration areas. The interpretation and mapping of Oligocene, Miocene and Pliocene sequences together with the seismic attribute extractions indicate the presence of several upsides potential developed within the area of study. Oligocene channels complex running in a NW-SE direction. The sequence stratigraphic approach has shown very applicable for mapping the Pre-Messinian depositional systems, Nile Delta and present drilling of these features have confirmed the presence of Pre-Messinian channel complexes as indicated in seismic data, and introduces a new play in the study area. Well logging data proved the presence of reservoir, with good porosity and permeability, ranged from clean sandstone to interbedd nature. The depositional environment and tectonic evolutions of offshore Nile Delta Basin allow the presence of hydrocarbon source rocks with adequate maturity. The hydrocarbon migration path which goes laterally up dip toward the prism of Nile Delta basin The shallow gas discoveries in the Pliocene sands and condensate oil in the Oligocene – Miocene and Mesozoic reservoirs indicate the presence of multiple source rocks and a suitable conditions for hydrocarbon accumulations in both biogenic and thermoginic petroleum system. Leakage of natural gas from traps in the Tertiary rocks resulted in gas chimneys related to the deep seated faults in the Nile delta.

A palynological investigation of two shallow boreholes in Anna, Bingerville area, at 13 km Northwest Abidjan, Southern Cote d’Ivoire, yielded rich and relatively well-preserved dinoflagellate cyst’s assemblages that allowed recognition of Oligocene age. This recognition was based on global dinoflagellate cyst events, including mainly Lejeunecystaspecies represented by cf. Lejeunecysta communis, L. lata, L. pulchra, Lejeunecysta sp. cf.L. granosa, cf. L. globosa, L. beninensis and other Pheolodinium magnificum, P. africanum, Selenopemphix nephroides and Cordosphaeridium inodes. They are associated to terrestrial spores and pollen grains such as Magnastriatites howardii, Spirosyncolpites spiralis, Perfotricolpites digitatus, Retitricoporites irregularis, Retimonocolpites irregularis, Pachydermites diederixii, Psilatricolporites operculatus and Punctodiporites harrisii. The palynostratigraphic interpretations are based on a comparison with calibrated dinoflagellate cyst ranges from several reference sections, mainly in the peri-atlantic and incidentally peri-pacific basins. This study showed changes in the relative abundances of different species or groups of morphologically related species. These changes are palaeoenvironmentally controlled, indicating a deposition occurred between the continental nearshore and marginal marine areas under continental influence. The prevalence of peridinioid dinocysts assemblage suggests deposition in a subtropical province whereas terrestrial pollen grains and spores provided by plants of coastal vegetation dominated by pteridophyts and angiosperms evoke mangrove and swamp forests. These new palynological data, notably the presence of Oligocene especially in the Ivorian terrestrial basin north of the so called “faille des lagunes”, specifies and modifies the previous local stratigraphic scale. Key words: Palynostratigraphy, palaeoenvironment, Oligocene, sedimentary basin, Cote d’Ivoire

A combined biostratigraphic study of dinoflagellate cysts and foraminifera was carried out on Early Cretaceous subsurface well cutting sediments from well A (DNG) (2800–2746 m depth) from the Krishna-Godavari Basin, India. The last appearance datum of marker species of dinoflagellate cysts and planktonic foraminifera was considered for the construction of the biostratigraphic framework. The study shows dominance of Early Cretaceous marker dinoflagellate cysts Cassiculosphaeridia magna, Cribroperidinium perforans, Hystrichodinium voigtii, Kleithriasphaeridium eoinodes, and planktonic foraminifera Hedbergella aptiana, Hedbergella mitra, Hedbergella praelippa, Hedbergella tardita, Microhedbergella miniglobularis and Hedbergella mitra species. In addition to this, the dinoflagellate cyst data were compared with the dinoflagellate biozones of Austral and Tethyan provinces. Based on earlier micropalaeontological records from the Krishna-Godavari Basin and the present study, a latest Barremian-early Aptian age has been determined for the earliest marine transgression in the Krishna-Godavari Basin. The early marine incursion during late Barremian-earliest Aptian in the Krishna-Godavari Basin compared to Albian age in Cauvery Basin suggests the opening of east coast from north to south.