Organic Matter Assessment And Paleoenvironmental Changes Of The Middle Jurassic Main Source Rocks (Khatatba Formation) In The North Western Desert, Egypt: Palynofacies And Palynomorph Perspectives

The Middle Jurassic in the north Western Desert, Egypt, was a time of complex tectonics and increased environmental perturbations attributed to the predominant sedimentation of organic carbon-rich fine siliciclastic and carbonate deposits of the Khatatba Formation. Although some studies have addressed the hydrocarbon potential and source rock characteristics of the Khatatba Formation, a regional-scale investigation of the prevalent paleoenvironmental conditions and organic matter characteristics is still necessary. In this study, the Khatatba Formation is investigated for detailed palynofacies analysis and palynomorph composition to assess organic matter kerogen types and reconstruct the depositional paleoenvironmental patterns on a regional scale. For this purpose, 116 drill cuttings were collected from five wells in the Matruh, Shushan, and Dahab-Mireir Basins. Moderately diverse assemblages of spores, pollen, and dinoflagellate cysts are reported. Age-diagnostic dinoflagellate cysts, including Adnatosphaeridium caulleryi, Dichadogonyaulax sellwoodii, Korystocysta gochtii, Wanaea acollaris, and Pareodinia ceratophora, along with occasional records of Systematophora areolate and Systematophora penicillate, defined a Bajocian–Callovian age. Based on particulate organic matter (POM) composition, four palynofacies assemblages (PFAs) are identified. PFA-1 is the most common within the Khatatba Formation in the five studied wells. It contains high proportions of phytoclast fragments versus low contents of amorphous organic matter (AOM) and palynomorphs and is defined by a gas-prone kerogen Type III. PFA-2 is comprised of moderate abundances of AOM and phytoclast characteristics of oil-prone kerogen Type II. PFA-3 is dominated by phytoclasts and moderate to low proportions of AOM and palynomorphs of kerogen Type III, whereas PFA-4 consists of AOM and palynomorphs defining kerogen Type II. PFA-1 indicates predominant deposition in proximal active fluvio-deltaic sources to marginal marine conditions with enhanced contributions of terrestrial/riverine influx. PFA-2 and PFA-3 reveal deposition under an enhanced dysoxic to anoxic proximal inner neritic shelf due to the abundant occurrences of spores and coastal to shallow marine dinoflagellate cysts. PFA-4 suggests deposition under enhanced suboxic to anoxic distal inner neritic conditions because of enhanced AOM and abundant proximate and some chorate dinoflagellate cysts. Thus, the Middle Jurassic experienced a predominantly marginal to shallow water column in this part of the southern margin of the Tethyan Ocean where the Matruh, Shushan, and Dahab-Mireir Basins were located

A Cretaceous dinoflagellate cyst palynozonation of northern Egypt

<p>The multiplicity of dinoflagellate cyst biozones in Cretaceous rocks limits their correlation applications, and the variations in the scientific bases of such zonations complicates age determinations and limits the validity of reliable inter-basinal correlations. The present work provides a useful summary of the dinoflagellate cyst occurrence data in Egypt and a proposed working Egyptian biozonation scheme for the area. The most diagnostic dinoflagellate cyst bioevents, in a definite time interval which occurs widely in most of the studied Egyptian, North African and Tethyan sections, are selected to be marker taxa for the erected zones. The eastern Canadian and northern European data consistently show much higher range tops for the dinoflagellate cysts at those high latitudes. The comparison and correlation of the contemporaneous dinoflagellate cyst range tops from Egypt and geographically neighbouring North African areas are vital for selecting widely distributed marker taxa and testing their validity and applicability to intercontinental correlations in the Tethyan Realm. Based on 29 wells located across Northern Egypt, this work provides a potentially useful scheme that unifies the different previously established dinoflagellate cyst palynozonation frameworks for Cretaceous rocks. The index palyno-events represented by the last occurrence datums (LODs) of the marker dinoflagellate cyst taxa are carefully picked from palynostratigraphies established earlier and methodically, consistently used to create a new regional palynostratigraphical scheme for all of the northern Egyptian territory. Ten dinoflagellate cyst interval zones were identified and described; these are, in descending stratigraphic order from youngest to oldest, <i>Dinogymnium acuminatum</i> (Maastrichtian–Campanian), <i>Odontochitina operculata</i> (Santonian–Coniacian), <i>Cyclonephelium vannophorum</i> (Turonian), <i>Dinopterygium cladoides</i> (late–middle Cenomanian), <i>Coronifera oceanica</i> (middle–early Cenomanian), <i>Oligosphaeridium complex</i> (late–middle Albian), <i>Subtilisphaera perlucida</i> (early Albian), <i>Cribroperidinium orthoceras</i> or <i>C. edwardsii</i> (Aptian–late Barremian), <i>Muderongia simplex</i> or <i>Pesudoceratium anaphrissum</i> (Barremian–late Hauterivian) and <i>Systematophora silybum</i> (Hauterivian–Berriasian).</p

Stratigraphic

The stratigraphic distribution of the palynomorphs and particulate organic matter was studied in the subsurface Lower/Middle Cretaceous sections in Ii-26-1 and Ig-30-1 wells, located in north Western Desert of Egypt. Some important palynofacies parameters were employed as indicators of proximal–distal trends. The spatial and stratigraphical variations of six palynofacies categories had been illustrated. Optically, the type and nature of the recovered particulate organic matter together with their quantity were combined to reveal the prevailing paleoenvironmental conditions during deposition of the concerning sections. Thirty-seven samples were selected from the two wells to carry the total organic carbon (TOC) and Rock–Eval Pyrolysis analyses in order to geochemically evaluate the source rock. TOC and Rock–Eval Pyrolysis analyses illustrate extremely low TOC and HI values, demonstrating that the Alam El Bueib, Alamein, Dahab, Kharita and Bahariya formations are comprised principally of type IV kerogen and a few type III kerogen components. Therefore, they are inert to slightly gas prone, signifying a strong deficiency of hydrogen-enriched organic matter. Palynofacies analysis implies that all the studied formations have highly oxidized terrestrial organic matter (brown phytoclasts and black woods)

A Cretaceous sporomorph palynozonation and the palaeobiogeography of northern Egypt

<p>The multiple biozonal nomenclatures given for the same time segment at different locations in northern Egypt are problematic, as such multiplicity is highly confusing and considerably limits the correlative value of these nomenclatures within the Egyptian territory, in the Elaterates phytogeoprovince and in the Tethyan Realm. Thirty-one wells are selected and used in this work to establish a standard and unified, semi-formal, generalised Egyptian sporomorph palynozonation scheme for northern Egypt. Marker taxa are carefully picked and tracked from the different previously established palynostratigraphies, and they are methodically re-used in the present unified framework on a regular basis, where their first down-hole appearance [last appearance datum (LAD)] palynoevents are utilised to erect a regional palynostratigraphical scheme. Ten sporomorph interval zones (IZ) and two subzones are reconstructed, established and palynologically specified from all of the studied wells. The authors surveyed the palynofloral assemblages characterising different areas of the world in order to derive meaningful palaeobiogeographical implications. Connecting these databases furnishes a comprehensive palynostratigraphical framework for inter-continental correlations with the Egyptian assemblages. In addition, such correlations confirm the dating acquired from the recovered palynological markers and assemblages presented in the current review. Comparisons of coeval assemblages confirm that the extensions and boundary limits of the palaeoprovinces of the recorded sporomorphs exhibited a gradual change and that their areal extent evolved with time. Due to the wide geographical occurrences of the recorded marker taxa during the pre-Albian stages of North and West Africa, western Atlantic and east South America, the proposed sporomorph zones can be confidently applied in these areas. During the Albian–Cenomanian such correlations can be applied only between North and West Africa and east South America.</p

Recurring Patterns of Sea Level Changes within a Palynological-Based Sequence Stratigraphy Framework of the Middle Jurassic Organic Matter-Rich Khatatba Formation, Egypt

The Middle Jurassic was a time of marginal to shallow shelf settings dominated by organic matter-rich deposition in northern Egypt, southern Tethys. Paleoenvironmental and sequence stratigraphic reconstructions are of paramount significance for a better understanding of basin history and related reservoirs and source rock units. For this purpose, a detailed palynomorph and palynofacies analysis of the Middle Jurassic Khatatba Formation in the Dahab-Mireir Basin, north Western Desert, was conducted. A moderately to well-preserved, moderately diverse palynomorph assemblage of spores, pollen, and dinoflagellate cysts is identified. Marker dinoflagellate cysts, including Dichadogonyaulax sellwoodii, Escharisphaeridia pocokii, Gonyaulacysta adecta, Korystocysta gochtii, Pareodinia ceratophora, and Wanaea acollaris, defined a Bajocian to Callovian age. Palynofacies analysis of the Khatatba Formation revealed two assemblages, whereby PFA-1 is the most abundant in the study well and is comprised mainly of terrestrial phytoclasts deposited nearby fluvio-deltaic sources. The infrequently reported PFA-2 consists of moderate abundances of phytoclasts and AOM, deposited in an inner shelf environment. A more reliable paleoenvironmental interpretation was indicated based on three palynomorph assemblages. The spore-dominated assemblage indicated deposition in a deltaic environment, while the mixed palynomorph assemblage revealed fluvio-deltaic to marginal shallow marine conditions. The microplankton-dominated assemblage is represented by minor samples and reflects an offshore inner shelf condition. Furthermore, the Middle Jurassic relative sea level was reconstructed based on the quantitative variations in the terrestrial/marine (T:M) ratios and abundances of spores, pollen, and dinoflagellate cysts. This led to the subdivide of the Khatatba Formation into thirteen third-order transgressive-regressive sequences, which can be correlated with the global Jurassic short-term sea level changes. Active tectonics and accelerated drifting of the Eurasian Plate during the Middle Jurassic are suggested to control basin uplift/subsidence and, therefore, recurring patterns of relative sea level change

Source rock evaluation of Kharita and Bahariya formations in some wells, North Western Desert, Egypt: Visual palynofacies and organic geochemical approaches

Palynofacies analyses were applied on ninety-one samples from the subsurface Albian – Cenomanian succession represented by Kharita and Bahariya formations, encountered in El-Noor, and South Sallum wells, located in the North Western Desert, Egypt, to visually characterize the content of dispersed organic matter, as well as, organic geochemical characterization to reveal the depositional paleoenvironments and source rock potentiality. The result recognized of five palynofacies associations in the studied interval. The deposition of Kharita Formation took place mainly in a steady and a relatively stable deltaic to marginal environment continued as well in the lower part of Bahariya Formation with minor changes. The marine influence became more common in the upper part of Bahariya Formation showing the exceptional high hydrocarbon potential recorded in the studied interval. This indicates marine transgression by the end of the early Cenomanian (Upper Bahariya) age. Samples from the Kharita Formation contain abundant brown phytoclasts which suggest gas-prone kerogen type III and IV. While Bahariya Formation includes translucent, brown cuticles and woody tracheid phytoclasts pointing to more promising gas-prone kerogen type III. The organic geochemical analysis shows poor to fair gas-prone source rock potential within the study section., Thermally, the color of the spore grains in Kharita and Bahariya formations show that dark yellow to orange, indicates immature besides their general little poor hydrocarbon generation potentiality. Keywords: Palynofacies, Rock eval pyrolysis, Bahariya formation, Kharita formation, North Western Desert, Egyp

Late Cretaceous Palynology and Paleoenvironment of the Razzak-3 Well, North Western Desert, Egypt

Palynological analysis of the Bahariya and Abu Roash Formations from the Razzak-3 (RZ-3) well, North Western Desert, Egypt, has yielded rich and very-well-diversified spores, pollen and dinoflagellate cysts which allow subdividing the studied rock units into four pollen/spore (PS) zones and three dinoflagellate cyst (D) zones. Miospores are abundant in the Cenomanian, while dinoflagellates predominate the Turonian-Santonian. A barren interzone delineates the oceanic anoxic event 2 and embraces member “F” of the Abu Roash Formation. The marine/nonmarine palynomorph ratio in the studied samples indicate that the Bahariya Formation was deposited in a nearshore paleoenvironment affected by continental sources with an arid to semiarid hinterland having local or seasonal humid conditions. Deposition of the Abu Roash Formation took place in the transitional zone between the inner and outer shelf. Dinoflagellate cysts in this study are of the Tethyan Realm