Search Results (12)

The modern diversity of sharks, skates, and rays (Neoselachii) is the result of various diversification and extinction events during the Mesozoic (252–66 Ma). However, the key drivers of their diversity patterns remain poorly understood despite all the progress that has been accomplished in recent years. Here, we show that the interplay of climatic- and tectonic-linked trajectories, resulting in a high shallow marine habitat availability and lower atmospheric CO₂ concentration, were significant drivers and sustainers of Mesozoic neoselachian diversity. We show, for the first time, that higher atmospheric CO₂ content negatively affected neoselachian diversity in the past. The recognized gradual faunal changes throughout the Mesozoic and the two major diversification events during the Jurassic and Cretaceous, respectively, ultimately cumulated in an all-time diversity high in the Palaeogene despite the events during the end-Cretaceous extinction event, highlighting their remarkable resilience and adaptability despite severe environmental challenges. We thus provide novel perspectives on the processes underlying neoselachian diversification since the Mesozoic that contribute importantly to a better understanding of the selective forces that have shaped the long-term evolution and diversification of neoselachians. Given their vital role in modern ecosystems, our results provide information about possible future trends in the face of the current climate crisis. Full article

Based on the special geological background of the east and north slopes of the Baiyun Depression, the development conditions of Paleogene structure–lithology traps, the development conditions of high-quality reservoirs and the difficulty in characterizing the distribution characteristics are studied in this paper. It is concluded that the eastern Baiyun is located on the Baiyun–Liwan continental–oceanic large-scale intershell separation system, with a complex tectonic background and a tectono-sedimentary pattern of “fault and uplift interlocking and uplift and depression interphase”. The palaeo source sink system of the low bulge in the east of Yundong is restored, the favorable position of reservoir collective development and the favorable characteristics of reservoir–cap assemblage are clarified, and the paleo-geomorphology and sedimentary filling evolution law are clarified. Guided by the drive of oil and gas accumulation, three types of large and medium-sized structure–stratigraphic traps have been implemented in the eastern Baiyun system, including the convex inclined end, the restricted fault gully and the magmatic floor intrusion, and the corresponding oil and gas accumulation models have been perfected. By studying the structure, source and sink system and trap characterization of the eastern Baiyun basin, the development conditions and exploration direction of the large and medium-sized Palaeogene traps are systematically summarized. Full article

The integration of different sources of geological and hydrogeological information and the application of interdisciplinary methods have informed the origin of the thermal springs of Alhama de Aragón and Jaraba, as well as other associated semi thermal springs (1200 L/s of combined flow, 711 L/s at over 30 °C), which is the main objective of this article. These springs come mainly from the autogenous recharge that occurs in the Cretaceous calcareous outcrops that border the Almazán Basin to the north, both in the Ebro Basin (Jalón Valley) and in the Duero Basin. The aquifer, shaped by upper Cretaceous limestones under the Palaeogene and Neogene rocks of the Almazán Basin, has extensive depths of more than 4000 m in the NE sector. This hydrostratigraphic unit has been affected by a generalized pre-Paleogene karstification that provides the main porosity to the aquifer. The underground flow moves in a NW–SE direction, crossing the Duero–Ebro divide, favoured by the topographic difference in elevation between the two basins. The regional flow is coherent with the progressive increase in temperature, infiltrating recharge water age (about 20–25 years in the semi-thermal springs, and more than 60 years in the Alhama and Jaraba springs), mineralization, and flow of the springs through which the system discharges. This issue is key to being able to design any sustainable conservation strategy in terms of quantity and quality of resources within the recharge area of the most important thermal springs in Spain. The Jaraba and Alhama de Aragón hot springs share the same or similar temperature, chemical composition, and geological contact of the spring. Their tritium isotopic composition and its evolution over time are practically the same. Their isotopic composition in D and ¹⁸O is also very similar. Both springs share the same recharge zone of similar altitude and constitute the end of flow tubes of similar length and flow rate. Full article

The Aiza research area covers over 650 km² of the northern Adriatic offshore, a common Adriatic foreland of the older Dinarides on the NE, and the younger Apennines on the SW. High-quality 3D reflection seismic data were used to investigate the area’s Mesozoic to Cenozoic tectono-stratigraphic evolution. Four main seismo-stratigraphical horizons were recognized: Base of Carbonate Platform (BCP), Top of Carbonate Platform (TCP), Messinian Erosional Surface (MES), and a Plio-Quaternary horizon (PlQh), as well as the dominant faults. The results depict the geological setting and tectonic evolution of the area. A long-lasting (Jurassic to Cretaceous) stable NW-SE striking platform margin evolved probably along the inherited Triassic normal fault. The marginal belt of the platform was affected during the Late Cretaceous to Palaeogene by extension and opening of the intra-platform basin, probably on the southern limb of the then developing Dinaric forebulge. The transverse fault system (Kvarner fault) was probably reactivated as a strike-slip zone during the late Miocene tectonic reorganization. The area was tilted to the SW during the Pliocene, in the distal foreland of the progressively northward propagating Northern Apennines. Sub-horizontal late Quaternary cover of Dinaric and Apenninic structures could imply active subsidence of the foreland in between nowadays sub-vertically exhuming neighboring orogenic belts. Full article

The Pearl River Mouth Basin (PRMB) is located in the northern part of the South China Sea. The Palaeogene Wenchang Formation (Fm) was formed at the rift stage and contains the main source rocks. The migration of Wenchang subsidence centres in the western Zhu I Depression and northern Yangjiang-Yitong Fault Zone are controlled by tectonic transformation and partially influenced by magmatic activity. From the Eocene Wenchang (E₂WC) to the Eocene and Oligocene Enping (E₂₊₃EP) stages, the regional extension direction rotated clockwise from NW–SE to S–N, and the strike of the regional strike-slip fault was NW–SE. The subsidence centres of the Wenchang Fm in the western subsags of the Zhu I Depression migrated to the Beiweitan Fault in a convergent way. Magmatic activity at the E₂WC stage developed mostly along the central edge of the subsags. Local subsidence migrated to the side of the basin-controlling faults. The migration characteristics of the subsidence centre of the Wenchang Fm in each subsag are complex in the northern Yangjiang-Yitong Fault Zone. There was no magmatic activity at the E₂WC to E₂₊₃EP stage of the Enping 27 subsag, and the subsidence centre migrated eastwards, which is basically consistent with the migration pattern of the Enping sag. In the eastern Yangjiang sag, the strike of the subsags was ENE. The angle between the extensional direction and subsag strike at the E₂WC to E₂₊₃EP stage first increased and then decreased. Magmatic activity at the E₂WC stage mostly developed in the subsags. Tectonic transformation and magmatic activity at the E₂WC stage led to subsidence centre migration from the Enping 21 subsag to the Enping 20 subsag northwest. From the end of the E₂WC stage to the E₂₊₃EP stage, magmatic activity developed at the subsag margins, which resulted in severe denudation. Research on the entire area indicates that tectonic transformation controls subsidence centre migration. Magmatic activity influences the migration of subsidence centres locally or controls this process through tectonic transformation. Full article

In this study, the periodic evolution and characteristics of the Palaeogene tectonic activity in the deep-water area of the Qiongdongnan Basin were revealed through the identification and analysis of the regional angular unconformity and the characteristics of the periodic fault activity. In addition to a comprehensive analysis of the controls on sedimentary paleogeomorphologic background, sedimentary characteristics and evolution by periodic rifting are systematically discussed. The studies have shown that the tectonic activity of the Paleogene Qiongdongnan Basin underwent three separate rifting phases: Phase-I (T100–T80), Phase-II (T80–T70), and Phase-III (T70–T60). The early phase of rifting was dominated by strong differential block-fault settlement, while the later phase was gradually replaced by homogeneous settlement controlled by regional depressions and a small amount of fault activity, characterized by a weak-strong-weak evolution. From Phase-I to Phase-III, the paleo-geomorphology margin changed from a large gradient to a gentle gradient, the subsidence center moved from the initial basin margin to the later basin center, and the basin-marginal fans extended finitely before developing on a large lateral scale in the later Phase-III. Analyzing the characteristics of periodic tectonic evolution and sedimentation response is important for petroleum exploration in marine basins, such as locating economic reservoirs. Full article

The characteristics of laminae are critical to lacustrine shale strata. They are the keys to the quality of source rocks and reservoirs, as well as engineering operations in shale plays. This study uses organic geochemistry, thin section identification, X-ray diffraction, field emission scanning electron microscopy, and other analytical methods, to reveal the detailed lamination texture and vertical distribution of laminae in the second Member of the Kongdian Formation in Cangdong Sag. The principal results are as follows: (1) A classification of laminae is proposed to characterize reservoir and geochemical properties. The five types of laminae are as follows: feldspar-quartz laminae (FQL), clay laminae (CLL), carbonate laminae (CAL), organic matter laminae (OML), and bioclastic laminae (BCL). There are also four significant lamina combinations (with the increasing TOC values): FQL-CLL combination, FQL-CLL-BCL combination, FQL-CLL-OML combination, and FQL-CAL-CLL-OML combination; (2) differences between laminae occur because of the variability in pore types and structures. There appears to be a greater abundance of intercrystalline pores of clay minerals in the FQL, CAL, BCL, and OML, and well-developed organic pores in the CAL and CLL, and the counterparts of intragranular pores of bioclastic material in the BCL. This detailed characterization provides the following comparative quantification of the thin section porosity of laminae in the second Member of the Kongdian Formation can be differentiated: CAL > FQL > OML > BCL > CLL; (3) differentiation between vertical distributions of laminae is carried out in a single well. The FQL and CLL are widely distributed in all the samples, while the BCL is concentrated in the upper part of the second Member of the Kongdian Formation, and CAL is concentrated in the lower part. This detailed classification method, using geochemical analysis and vertical distribution descriptions, offers a detailed understanding of lamination texture and its effects on reservoir and geochemical properties, which will provide a scientific guidance and technical support to better estimate reservoir quality and to identify new sweet spots in the second Member of the Kongdian Formation in the Cangdong Sag. Full article

The present work focuses on palaeogeographic reconstruction of shallow-water carbonate deposition in the Outer Western Carpathian Tethys. Platform deposits are preserved only as a component of turbidites and olistostromes, and reconstructions of these platforms are based on clastic material redistributed into slopes and deep basins and occurring among the Outer Carpathian nappes. Similar platforms were also present on the Tethys margins. These reconstructions were performed using the global models of plate tectonics. Several ridges covered by carbonate platforms developed in that area during the latest Jurassic–Palaeogene times. Three main shallow-water facies associations—Štramberk, Urgonian, and Lithothamnion–bryozoan—could be distinguished. The Tithonian–lowermost Cretaceous Štramberk facies is related to early, synrift–postrift stage of the development of the Silesian Domain. Facies that are diversified, narrow, shallow-water platforms, rich in corals, sponges, green algae, echinoderms, foraminifera, microencrusters, and microbes are typical of this stage. The Urgonian facies developed mainly on the south margin of the Outer Carpathian basins and is characterised by organodetritic limestones built of bivalves (including rudists), larger benthic foraminifera, crinoids, echinoids, and corals. Since the Paleocene, in all the Western Outer Carpathian sedimentary areas, Lithothamnion–bryozoan facies developed and adapted to unstable conditions. Algae–bryozoan covers originating on the siliciclastic substrate are typical of these facies. This type of deposition was preserved practically until the final stage in the evolution of the Outer Carpathian basins. Full article

The genus Aldrovanda is a Palaeogene element containing a single extant species, Aldrovanda vesiculosa L. This aquatic carnivorous herb has a very wide range of distribution, natively covering four continents; however, it is a critically endangered aquatic plant species worldwide. Previous studies revealed that A. vesiculosa had an extremely low genetic variation. The main aim of the present paper is to explore, using chemometric tools, the diversity of 16 A. vesiculosa populations from various sites from four continents (Eurasia, Africa, Australia). Using chemometric data as markers for genetic diversity, we show the relationships of 16 A. vesiculosa populations from various sites, including four continents. Phytochemical markers allowed the identification of five well-supported (bootstrap > 90%) groups among the 16 populations sampled. The principal component analysis data support the idea that the strongly related African (Botswana) and Australian (Kimberley, NT, NW Australia) populations are the most distant ones, separated from the European and Asian ones. However, considering the five Australian populations sampled, three are nested within the Eurasian group. The chemometric data are correlated positively with the geographical distances between the samples, which suggests a tendency toward isolation for the most distant populations. Full article

Coal and oil shale are both organic matter-rich sedimentary rocks. However, their sources of organic matter and their depositional environments are different. The present study focuses on the Palaeogene Lijiaya Formation sequence in the Huangxian Basin, Shandong Province, East China, which has oil shales showing marine geochemical indicators overlain by coals indicating marine regression. We investigated the C1 coal seam and underlying OS2 oil shale layers, compared their geochemical and mineralogical characteristics, clarified the details of their constituents, in order to elucidate the features of their sources, their depositional environments, and the post depositional processes in the context of the geological evolution of the basin. The Al₂O₃/TiO₂ (18.1–64.9) and TiO₂/Zr ratios (28.2–66.5) in the C1 coals and OS2 oil shales, respectively, suggest a felsic to intermediate source, and the Mesozoic granite on the South of Huangxian Fault may be one of the provenances of these sediments. The low sulphur content (0.53–0.59%) and low Sr/Ba ratios (0.32–0.67) suggest a freshwater depositional environment for the C1 coals. In contrast, the higher total sulphur contents (0.60–1.44%), the higher Sr/Ba ratios (0.31–1.11%), and the occurrence of calcareous shells, indicate seawater intrusions during deposition of the oil shales. The V/Ni, V/(V + Ni), and V/Cr ratios of the OS2 oil shale suggest oxic to suboxic conditions with a distinct change in palaeo-redox between the lower and upper parts of OS2 seam. The high boron contents in C1 coals (average, 504 ppm) is related to the high content of analcime (with the correlation coefficient of 0.96), and the high concentration of boron was attributed to a secondary enrichment by epigenetic hydrothermal solutions. The occurrence of idiomorphic-authigenic albite in association with analcime and quartz in veins in the coals suggests that albite is a product of a reaction between analcime and silica, both of volcanic origin. The reaction takes place at about 190 °C, indicating that the area was affected by hydrothermal fluids. Full article

All 142 known species of Curculionoidea in Eocene amber are documented, including one species of Nemonychidae, 16 species of Anthribidae, six species of Belidae, 10 species of Rhynchitidae, 13 species of Brentidae, 70 species of Curcuionidae, two species of Platypodidae, and 24 species of Scolytidae. Oise amber has eight species, Baltic amber has 118 species, and Rovno amber has 16 species. Nine new genera and 18 new species are described from Baltic amber. Four new synonyms are noted: Palaeometrioxena Legalov, 2012, syn. nov. is synonymous with Archimetrioxena Voss, 1953; Paleopissodes weigangae Ulke, 1947, syn. nov. is synonymous with Electrotribus theryi Hustache, 1942; Electrotribus erectosquamata Rheinheimer, 2007, syn. nov. is synonymous with Succinostyphlus mroczkowskii Kuska, 1996; Protonaupactus Zherikhin, 1971, syn. nov. is synonymous with Paonaupactus Voss, 1953. Keys for Eocene amber Curculionoidea are given. There are the first records of Aedemonini and Camarotini, and genera Limalophus and Cenocephalus in Baltic amber. Full article

The provenance of the Proč and Strihovce sandstones is crucial for understanding the relationship between the Pieniny Klippen (PKB) and Flysch (FB) belts in the easternmost part of the Western Carpathian realm. Detrital Cr-spinels in these tectonic units were assertively interpreted as sourced from the southern sources representing the Meliata mélange. In this study, we use the geochemistry of detrital chromian spinels to identify the mafic and ultramafic source of the sediments and to compare them each other. Simultaneously, we compare their chemical compositions with those from the different Western Carpathian geological units, which could feed the Proč and Krynica basins during the Paleogene, where the Proč and Strihovce formations (fms), respectively, were deposited. Chromian spinels from the Proč and Strihovce fms exhibit similar geochemical characteristics (Cr# = 0.44–0.88 and 0.29–0.89, Mg# = 0.17–0.68 and 0.2–0.72, TiO₂ = 0.0–3.67 and 0.01–2.08 wt.%, respectively). The spinels show both supra-subduction zone (SSZ) peridotite signatures and volcanic origin. Whereas volcanic spinels from the Proč Formation (Fm.) were formed under an ocean island basalt (OIB) and back-arc basin basalt (BABB) geodynamic setting, those from the Strihovce Fm. suggest a predominantly mid-ocean ridge basalt (MORB) origin. To avoid mistakes in the provenance interpretations, the data from garnet geochemistry of both formations is supplied. The analysed Cr-spinels do not absolutely overlap with spinels reported from the Meliata Unit, and their composition indicates at least two independent sources. Full article