The absolute abundance calibration project: the <i>Lycopodium</i> marker-grain method put to the test

Traditionally, dinoflagellate cyst concentrations are calculated by adding an exotic marker or “spike” (such as Lycopodium clavatum) to each sample following the method of Stockmarr (1971). According to Maher (1981), the total error is controlled mainly by the error on the count of Lycopodium clavatum spores. In general, the more L. clavatum spores counted, the lower the error. A dinocyst / L. clavatum spore ratio of ~2 will give optimal results in terms of precision and time spent on a sample. It has also been proven that the use of the aliquot method yields comparable results to the marker-grain method (de Vernal et al., 1987). Critical evaluation of the effect of different laboratory procedures on the marker grain concentration in each sample has never been executed. Although, it has been reported that different processing methods (e.g. ultrasonication, oxidizing, etc.) are to a certain extent damaging to microfossils (e.g. Hodgkinson, 1991), it is not clear how this is translated into concentration calculations. It is wellknown from the literature that concentration calculations of dinoflagellate cysts from different laboratories are hard to resolve into a consistent picture. The aim of this study is to remove these inconsistencies and to make recommendations for the use of a standardized methodology. Sediment surface samples from four different localities (North Sea, Celtic Sea, NW Africa and Benguela) were macerated in different laboratories each using its own palynological maceration technique. A fixed amount of Lycopodium clavatum tablets was added to each sample. The uses of different preparation methodologies (sieving, ultrasonicating, oxidizing …) are compared using both concentrations – calculated from Lycopodium tablets - and relative abundances (more destructive methods will increase the amount of resistant taxa). Additionally, this study focuses on some important taxonomic issues, since obvious interlaboratorial differences in nomenclature are recorded

Cretaceous palynology (spores, pollen and dinoflagellate cysts) of the Siqeifa 1-X borehole, northern Egypt

Diverse and well preserved palynofloras were recognized in the Lower Cretaceous succession penetrated by well Siqeifa 1-X in northern Egypt. Dinoflagellate cysts such as Subtilisphaera senegalensis was regarded, with the spores Impardecispora apiverrucata and Aequitriradites spinulosus, as important Berriasian to Barremian species. Afropollis operculatus/zonatus pollen and spores such as Balmeisporites holodictyus, Trilobosporites laevigatus and Duplexisporites generalis are diagnostic of Aptian. The lowest occurrences of the pollen Afropollis jardinus, the spore Crybelosporites pannuceus and elaterates such as Elaterosporites klaszii, Elaterocolpites castelainii and Elateroplicites africaensis characterize the Albian/lower Cenomanian interval. The palynofloras enabled the recognition of five spore-pollen and four dinoflagellate zones, which are correlated with regional records, mainly from Egypt and Libya. The vertical distribution of terrestrial and marine palynomorphs, along with palynodebris, reflects two regressive marginal marine cycles during Berriasian-Barremian and Albian-lower Cenomanian times whereas the Aptian witnessed a transgressive open marine (inner shelf) environment. A warm humid palaeoclimate was inferred during deposition of the investigated succession of the borehole, in contrast to the known warm arid to semi-arid climate, suggested for the Northern Gondwana Realm during Early Cretaceous times. This is probably due to the palaeogeographic position of Egypt during Early Cretaceous times or, to a local reason. Palynofloras from Siqeifa 1-X borehole, with Afropollis pollen and elaterates, are of North African aspect and share the broad characteristics of the "Albian-Cenomanian Elaterates Province" of Herngreen et al. (1996). Abundance of spores and araucariacean pollen are transitional features between those in North Gondwana and Southern Laurasia but, unlikely, typical transitional assemblages lack bisaccates conifers and have Gleicheniaceae spores

Organic geochemical, palynofacies, and petrographic analyses examining the hydrocarbon potential of the Cretaceous (Albian) Kharita Formation in the Matruh Basin, northwestern Egypt

A recent study of selected samples from the Cretaceous (Albian) Kharita Formation of Egypt revealed very good to excellent source rock (SR) potential for six intraformational, organic-rich intervals. This work investigates the SR potential of the entire Kharita Formation across the Matruh Basin, using samples from two wells: the Abu Tunis 1X well from the central part of the basin, and the Siqeifa 1X well drilled on the eastern margin of the basin. More strongly reducing conditions were developed in the centre of the basin, and resulted in the deposition of more organic-rich shales by comparison to the less reducing conditions that prevailed on the eastern basin margin, where the shales contain less organic matter. Deltaic intraformational shales and carbonates in the Kharita Formation of Abu Tunis 1X constitute a significant 120 m net of the potential SR. The lower Kharita Formation contains 34 m net shale SR of good to very good/excellent organic richness, yielding values of 1.14–11.59 wt % total organic carbon (TOC). The organic matter has low Hydrogen Index (HI) values (184–389 mg HC/g TOC) and amorphous organic matter (AOM) and relatively high non-opaque phytoclast frequencies indicating mainly gas/oil-prone organofacies (kerogen types II/III). The upper Kharita is more important, containing 86 m net shale/carbonate SR that has fair to good organic richness (0.8–1.8 wt % TOC), and lower HI (126–250 mg HC/g TOC), a dominance of non-opaque phytoclasts, and subordinate AOM frequencies, which together indicate gas/oil-prone organofacies (kerogen Types III/II). In the Siqeifa 1X well, Kharita deltaic intraformational shales and shaley dolostones comprise 80 m net SR, which has mainly fair to good to less very good organic richness (0.8–2.1 wt % TOC), whilst low HI (93–220 mg HC/g TOC), dominance of non-opaque phytoclasts and subordinate AOM indicate gas-prone organofacies (kerogen Type III). A relative upward increase in deposition of lignite and coaly carbonaceous material supports a gas-prone organofacies. Whilst thermal maturity indices only point to immature to early mature (pre- to early oil-window) SRs in both the Abu Tunis 1X and Siqeifa 1X wells, hydrocarbon exploration focussing on this potential source rock may be justified in areas to the southeast of the Matruh Basin, where modelling indicates this unit may have reached the late mature oil- to main gas-generation window