Konservat-Lagerstätten from the Upper Jurassic lithographic limestone of the Causse Méjean (Lozère, southern France): palaeontological and palaeoenvironmental synthesis

Since the 1980s, the Upper Jurassic lithographic limestone of the Causse Méjean (southern France) has been known by local naturalists to yield fossils. However, until the beginning of the 21st century, this plattenkalk remained largely undersampled and scientifically underestimated. Here, we present the results of two decades of prospection and sampling in the Drigas and the Nivoliers quarries. We provide the first palaeontological inventory of the fossil flora, the fauna and the ichnofauna for these localities. The fossil assemblages show the co-occurrence of marine and terrestrial organisms. Marine organisms include algae, bivalves, brachiopods, cephalopods (ammonites, belemnites and coleoids such as Trachyteuthis), echinoderms, decapod crustaceans (ghost shrimps, penaeoid shrimps and glypheoid lobsters) and fishes (including several actinopterygians and a coelacanth). Terrestrial organisms consist of plant remains (conifers, bennettitaleans, pteridosperms) and a single rhynchocephalian (Kallimodon cerinensis). Ichnofossils comprise traces of marine invertebrates (e.g. limulid trackways, ammonite touch mark) as well as coprolites and regurgitalites. Given the exquisite preservation of these fossils, the two quarries can be considered as Konservat-Lagerstätten. Both lithological features and fossil content suggest a calm, protected and shallow-marine environment such as a lagoon partially or occasionally open to the sea. Most fossils are allochthonous to parautochthonous and document diverse ecological habitats. Similarly to other famous Upper Jurassic plattenkalks of western Europe such as Solnhofen, Cerin or Canjuers, the Causse Méjean is a key landmark for our understanding of coastal/lagoonal palaeoecosystems during the Kimmeridgian–Tithonian interval.

Shakrook Anticline, a Very Complicated Structural Form, North Iraq, Kurdistan Region

The Shakrook anticline has very a complicated structural form, this is attributed to three thrust faults, and the presence of four anticlinal axes with the main anticlinal body. The most northwest existing anticline is called in the current study the Sisawa anticline, the main two anticlines are called the Shakrook East and Shakrook West, whereas the fourth one is called the Biluk anticline it is developed along the southwestern limb of the Shakrook East anticline. The exposed rocks in the Shakrook anticline range from Upper Jurassic to the Paleogene age. The bulk of the main Shakrook anticline is formed by the Bekhme Formation (Upper Cretaceous age), whereas the bulk of the Sisawa anticline is formed of the Shiranish Formation (Upper Cretaceous age) with Paleogene and Neogene aged rocks. Geological maps and high-quality satellite images were used to elucidate the complex structural form of the Shakrook anticline. The updated geological map is quite different from those existing geological maps. A field investigation was carried out to check the interpreted data and to implement photography to the interested structural and geomorphological forms. Different geomorphological forms also were interpreted; they all refer to the lateral growth of the Shakrook anticline.

Structural traps and seals for expanding CO2 storage in the northern Horda Platform, North Sea

The maturation of geological CCS along the Norwegian Continental Shelf is ongoing in the Norwegian North Sea, however, more storage sites are needed to reach climate mitigation goals by 2050. In order to augment the Aurora site and expand CO2 storage in the northern Horda Platform, regional traps and seals must be assessed to better understand the area’s potential. Here, we leverage wellbore and seismic data to map storage aquifers, identify structural traps, and assess possible top and fault seals associated with Lower and Upper Jurassic storage complexes in four major fault blocks. With respect to trap and seal, our results maintain that both prospective intervals represent viable CO2 storage options in various locations of each fault block. Mapping, modeling, and formation pressure analyses indicate that top seals are present across the entire study area, and are sufficiently thick over the majority of structural traps. Across-fault juxtaposition seals are abundant, but dominate the Upper Jurassic storage complexes. Lower Jurassic aquifers, however, are often upthrown against Upper Jurassic aquifers, but apparent across fault pressure differentials and moderate to high shale gouge ratio values correlate, suggesting fault rock membrane seal presence. Zones of aquifer self-juxtaposition, however, are likely areas of poor seal along faults. Overall, our results provide added support that the northern Horda Platform represents a promising location for expanding CO2 storage in the North Sea, carrying the potential to become a future injection hub for CCS in northern Europe.

Changing depositional environments in the semi-restricted Late Jurassic Lemeš Basin (Outer Dinarides; Croatia)

The up to 450 m-thick Upper Jurassic Lemeš Formation includes organic-rich deep-water (max. ~ 300 m) sedimentary rocks deposited in the Lemeš Basin within the Adriatic Carbonate Platform (AdCP). The Lemeš Formation was investigated regarding (1) bio- and chemostratigraphy, (2) depositional environment, and (3) source rock potential. A multi-proxy approach—microfacies, Rock–Eval pyrolysis, maceral analysis, biomarkers, and stable isotope ratios—was used. Based on the results, the Lemeš Formation is subdivided from base to top into Lemeš Units 1–3. Deposition of deep-water sediments was related to a late Oxfordian deepening event causing open-marine conditions and accumulation of radiolarian-rich wackestones (Unit 1). Unit 2, which is about 50 m thick and Lower early Kimmeridgian (E. bimammatum to S. platynota, ammonite zones) in age, was deposited in a restricted, strongly oxygen-depleted basin. It consists of radiolarian pack- and grainstones with high amounts of kerogen type II-S organic matter (avg. TOC 3.57 wt.%). Although the biomass is predominantly marine algal and bacterial in origin, minor terrestrial organic matter that was transported from nearby land areas is also present. The overlying Unit 3 records a shallowing of the basin and a return to oxygenated conditions. The evolution of the Lemeš Basin is explained by buckling of the AdCP due to ophiolite obduction and compressional tectonics in the Inner Dinarides. Lemeš Unit 2 contains prolific oil-prone source rocks. Though thermally immature at the study location, these rocks could generate about 1.3 t of hydrocarbon per m2 surface area when mature.

Theory-Guided Data Science, A Petrophysical Case Study from the Diyab Formation

A practical example of a theory-guided data science case study is presented to evaluate the potential of the Diyab formation, an Upper Jurassic interval, source rock of some of the largest reservoirs in the Arabian Peninsula. A workflow base on a three-step approach combining the physics of logging tool response and a probabilistic machine-learning algorithm was undertaken to evaluate four wells of the prospect. At first, a core-calibrated multi-mineral model was established on a concept well for which an extensive suite of logs and core measurements had been acquired. To transfer the knowledge gained from the latter physics-driven interpretation onto the other data-scarce wells, the relationship between the output rock and fluid volumes and their input log responses was then learned by means of a Gaussian Process Regression (GPR). Finally, once trained on the key well, the latter probabilistic algorithm was deployed on the three remaining wells to predict reservoir properties, quantify resource potential and estimate volumetric-related uncertainties. The physics-informed machine-learning approach introduced in this work was found to provide results which matches with the majority of the available core data, while discrepancies could generally be explained by the occurrence of laminations which thickness are under the resolution of nuclear logs. Overall, the GPR approach seems to enable an efficient transfer of knowledge from data-rich key wells to other data-scarce wells. As opposed to a more conventional formation evaluation process which is carried out more independently from the key well, the present approach ensures that the final petrophysical interpretation reflects and benefits from the insights and the physics-driven coherency achieved at key well location.

Jurodidae (Coleoptera: Archostemata) from Transbaikalia: new findings and redescription of type material

Two species of Jurodidae: Jurodes ignoramus and Jurodes minor are redescribed, new characters presented, and characters from original descriptions are phylogenetically reevaluated, justifying a placement of the family within the suborder Archostemata. The new species Jurodes shef sp. nov. from the Lower Cretaceous locality Khasurty (Berriasian-Barremian, Zakamenskiy district, Buryatia Republic, Russia) is described and 2 new specimens of J. ignoramus Ponomarenko, 1985 and 5 additional specimens of J. minor Ponomarenko, 1990 are recorded. Jurodids from Khasurty are morphologically closer to those from Daohugou locality (Middle–Upper Jurassic, Inner Mongolia, China).

Organic Petrology and Thermal Maturity of Dispersed Organic Matter from the Ramalhal-1 Well (Lusitanian Basin, Portugal)

Organic petrology is an important tool used to characterize dispersed organic matter (DOM) in sediments and sedimentary rocks, and to assess its thermal maturity. This study was carried out on 33 cutting samples (Middle-Upper Jurassic) from the Ramalhal-1 well to characterize the particulate organic matter and to evaluate its thermal maturity. The samples were submitted to optical petrography analysis (reflected white and blue incident lights) and the mean random reflectance was measured. Microscopic observations revealed a low DOM content, characterized by the predominance of macerals of the inertinite group (including charcoal), followed by solid bitumen. Huminite/vitrinite is usually small in size and quantity. Liptinite macerals were also present, represented by sporinite, cutinite, liptodetrinite and rare bituminite. A type III-IV kerogen was defined for the Ramalhal-1 sequence. Huminite/vitrinite mean random reflectance varied between 0.38% and 0.75%, pointing to an immature-to-mature stage of the organic matter. Multi-populations of solid bitumen occurred in almost all the samples, filling voids and fractures in the inorganic materials (mainly carbonates). The bitumen populations were quite heterogeneous, concerning both the optical characteristics and distribution, displaying different thermal maturities. No relationship between vitrinite and bitumen reflectance was established, indicating that these bitumens were not generated in situ.