Search Results (259)

The studied areas (the Ionian Islands: Paxoi, Lefkas, Kefalonia, and Zakynthos), are situated at the western ends of the Ionian Basin in contact with the Apulian Platform and named as Apulian Platform Margins. The proposed model is based on fieldwork, previously published data, and balanced geologic cross-sections. Late Jurassic to Early Eocene NNW–SSE extension, followed by Middle Eocene to Middle Miocene (NNW–SSE compression, characterizes the Ionian basin). The space availability, the distance of the Ionian Thrust from the Kefalonia transform fault and the altitude between the Apulian Platform and the Ionian Basin that was produced during the extensional regime were the main factors for the produced structures due to inversion tectonics. In Zakynthos Island, the space availability (far from the Kefalonia Transform Fault), and the reactivation of normal bounding faults formed an open geometry anticline (Vrachionas anticline) and a foreland basin (Kalamaki thrust foreland basin). In Kefalonia Island, the space from the Kefalonia Transform Fault was limited, and the tectonic inversion formed anticline geometries (Aenos Mountain), nappes (within the Aenos Mountain) and small foreland basins (Argostoli gulf), all within the margins. In Lefkas Island, the lack of space, very close to the Kefalonia Transform Fault, led to the movement of the Ionian Basin over the margins, attempting to overthrust the Apulian Platform. Because the obstacle between the basin and the platform was very large, the moving part of the Ionian Basin strongly deformed producing nappes and anticlines in the external part of the Ionian Basin, and a very narrow foreland basin (Ionian Thrust foreland basin). Full article

Combined heavy mineral analysis and detrital zircon geochronology have enabled us to track detritus supplied by the ancestral river systems draining the North American continent into the deep subsurface of the Gulf of Mexico, in both the coastal plain and the offshore deep water areas. During deposition of the Paleocene–Eocene Wilcox Group, sandstones in the western part of the area are interpreted as the products of the Rosita system derived via paleo-Rio Grande material, with a large component of sediment shed from the Western Cordillera. By contrast, samples from wells further east have high proportions of zircons derived from the Yavapai-Mazatzal Province and are attributed to the Rockdale system with sediment fed predominantly by the paleo-Colorado or paleo-Colorado-Brazos. There is evidence that sediment from the Rosita system occasionally extended into the central Gulf of Mexico, and, likewise, data indicate that the Rockdale system sporadically supplied sediment to the western part of the basin. During the Late Eocene of the central Gulf of Mexico (Yegua Formation) there was a distinct shift in provenance. The earlier Yegua sandstones have a large Grenville zircon component and are most likely to have had a paleo-Mississippi origin, whereas the later Yegua sandstones are dominated by zircons of Western Cordilleran origin, similar to Wilcox sandstones fed by the Rosita system via the paleo-Rio Grande. The switch from paleo-Mississippi to paleo-Rio Grande sourcing implies there was a major reorganisation of drainage patterns during the Late Eocene. Miocene sandstones in the deepwater Gulf of Mexico were principally sourced from the paleo-Mississippi, although the paleo-Red River is inferred to have contributed to the more westerly-located wells. Full article

Tetrastigma (Vitaceae) is known for its ornamental, medicinal, and ecological significance. However, the structural and variational characteristics of the Tetrastigma chloroplast genome and their impact on phylogenetic relationships remain underexplored. This study utilized bioinformatics methods to assemble and annotate the chloroplast genomes of 10 Tetrastigma species and compare them with five previously sequenced species. This study analyzed gene composition, simple sequence repeats, and codon usage patterns, revealing a high A/T content, uniquely identified pentanucleotide repeats in five species and several preferred codons. In addition, comparative analyses were conducted of the chloroplast genomes of 15 Tetrastigma species, examining their structural differences and identifying polymorphic hotspots (rps16, rps16-trnQ, trnS, trnD, psbC-trnS-psbZ, accD-psaI, psbE-petL-petG, etc.) suitable for DNA marker development. Furthermore, phylogenetic and selective pressure analyses were performed based on the chloroplast genomes of these 15 Tetrastigma species, validating and elucidating intra-genus relationships within Tetrastigma. Futhermore, several genes under positive selection, such as atpF and accD, were identified, shedding light on the adaptive evolution of Tetrastigma. Utilizing 40 Vitaceae species, the divergence time of Tetrastigma was estimated, clarifying the evolutionary relationships within Tetrastigma relative to other genera. The analysis revealed diverse divergences of Tetrastigma in the Miocene and Pliocene, with possible ancient divergence events before the Eocene. Furthermore, family-level selective pressure analysis identified key features distinguishing Tetrastigma from other genera, showing a higher degree of purifying selection. This research enriches the chloroplast genome data for Tetrastigma and offers new insights into species identification, phylogenetic analysis, and adaptive evolution, enhancing our understanding of the genetic diversity and evolutionary history of these species. Full article

This study investigates the Batha endorheic basin in Chad, situated east of the Lake Chad basin in the arid to semi-arid Sahelian zone. This region has not yet undergone comprehensive geological and hydrogeological studies. More broadly, the transition zone between semi-arid and arid climates has been minimally explored. This research aims to evaluate the resources and dynamics of this multi-layered system using a combined geology-hydrogeology-hydrochemistry-isotopes approach. The multilayer system includes sedimentary layers (Quaternary, Pliocene, and Eocene) over a crystalline basement. A piezometric investigation of the system shows a general SE–NW groundwater, indicating an interconnection between all layers. Hydrochemical analyses identifies four main facies (calcium-bicarbonate, sodium-bicarbonate, sulphate-sodium, and mixed), primarily controlled by water–rock interaction with secondary influences from base-exchange and evaporation. Saturation indices indicate that these waters are close to equilibrium with the calcite-Mg phases, gaylussite and gypsum. Stable isotopes (oxygen-18 and deuterium) categorize groundwater into three groups: ancient water, recent and older meteoric water mixtures affected by evaporation, and mixtures more heavily impacted by evaporation. Tritium contents reveal three groups: current rainwater, modern water, and sub-modern water. These results indicate that ionic and isotopic differentiations cannot be strictly linked to specific layers, confirming the interconnected nature of the Batha system. The observed heterogeneity is mainly influenced by lithological and climatic variations. This study, though still limited, enhances significantly the understanding of the basin’s functioning and supports the rational exploitation of its vital resources for the Batha area’s development. Future investigations to complete the present study are highlighted. Full article

This paper focuses on the structural and finite strain analysis of the Pelagonian nappe, the HP/LT Ampelakia unit, and the Olympos-Ossa unit in the Olympos-Ossa mountainous area in order to better understand the exhumation history of the Ampelakia unit and the underlain Olympos-Ossa unit. Two main stages of Tertiary deformation were revealed, related to nappe stacking and exhumation processes. During the Paleocene–Eocene crustal subduction, HP/LT metamorphism, compression, and nappe stacking were developed progressively. This D₁ stage was terminated with the final SW-ward emplacement of the Ampelakia and Pelagonian nappe on the Olympos-Ossa unit during the Eocene–Early Oligocene. The next stage of deformation, D₂, was developed during the Oligocene–Miocene following the orogenic nappes stacking. D₂ was considered an extensional event, related to metamorphic isothermal decompression, nappes tectonic denudation, crustal uplift, and final exhumation of the Ampelakia unit and the Olympos-Ossa unit as a tectonic window. The calculated finite strain ellipsoids indicate a main flattening type strain geometry and middle strain intensity, increasing along the nappe contacts. The quartz C-axes diagrams also reveal a flattening type of deformation and non-coaxial flow towards the southwest and northeast at the western and eastern flanks of Olympos-Ossa Mountain, respectively. The calculated W_k vorticity number ranges from 0.23 to 0.93. Full article

SE Anatolia is witnessing the final stage of the Wilson Cycle, where a continental collision between the Tauride–Anatolide block and Arabian platform occurred, and a 1.5 km Eastern Tauride mountain chain formed. We present new low-temperature thermochronology (LTT) ages, including eight apatite fission track (AFT) and seven apatite and zircon U-Th-Sm/He (AHe, ZHe) ages, for the metamorphic rocks from the Nappe Zone of the Southeast Anatolian Orogenic Belt. The ZHe ages vary from 51.2 ± 0.7 Ma to 30.4 ± 0.6 Ma, the AFT ages range from 33.1 ± 1.6 Ma to 18.1 ± 0.9 Ma, and the AHe ages range from 23.6 ± 2.5 Ma to 6 ± 1.9 Ma. The LTT data show a continuous slow uplift of the region. However, the thermal modeling results suggest an Eocene and middle–late Miocene fast uplift of the region. Similar to our results, the LTT studies along the SAOB show that the vertical movements initiated during the Eocene period have continued in a steady-state regime to recent times. The Eocene epoch is identified by arc–back-arc setting in the region, whereas the Miocene epoch is marked by the continental collision. Within this tectonic framework, vertical movements on the overriding plate are controlled by both extensional and compressional tectonics. The LTT data obtained along the SAOB show fingerprints of thrust propagation from north to south. Full article

In the SE Alps, two Cretaceous–Eocene flysch basins, Julian and Brkini, filled with turbidite sediments, are present. This study novelly reports heavy mineral assemblage counts and detrital tourmaline characterization for 11 samples. It is possible to define three different groups, characterized by the presence of (1) a clinopyroxene–epidote–low-ZTR (zircon+tourmaline+rutile; 5%) sample association, (2) a high-ZTR (>48%)–garnet–apatite association and (3) a low-ZTR (<40%)–Cr-spinel–garnet association. Detrital tourmalines from both the Julian and Brkini flysch basins are rather similar in composition, associated with metapelites and metapsammites coexisting or not coexisting with an Al-saturating phase, ferric-iron-rich quartz–tourmaline rocks and calc–silicate rocks; however, their number is drastically different. In fact, even if the percentage of heavy minerals is very low and similar in both basins (0.17–1.34% in weight), in the Julian basin, the number of tourmaline crystals is much lower than that in Brkini (1–14 vs. 30–100), suggesting an important change in the provenance area. Interestingly, the presence of a high amount of tourmaline derived from ferric-iron-rich quartz–tourmaline rocks and calc–silicate rocks makes these two basins different from all the Cretaceous flysch basins of Bosnia and the Northern Dinaric zone, where these supplies are missing or very limited. Full article

This study focuses on the critical issue of access to clean water in water-stressed regions like the Middle East and North Africa (MENA). To address the challenges of water stress, the study proposes an integrated approach involving geographical, statistical, and geophysical analysis. The objectives are to assess the distribution of pollutants such as heavy metals, salts, and water turbidity near industrial facilities; identify their sources and pathways; evaluate water quality and its impact on human health; and improve environmental classification using geophysical and geochemical methods. The study area, located southeast of Qena city, is characterized by an arid climate with minimal rainfall and is primarily covered by Upper Cretaceous and Lower Eocene rocks. The third layer in the study area is considered a shallow aquifer of Quaternary alluvial deposits; it deepens from 20 m to 93 m, displaying resistivity from 18 Ω∙m to 120 Ω∙m, with thickness increasing downstream to approximately 90 m. Understanding groundwater flow from northeast to southeast is crucial for understanding pollutant distribution in the region. The research reveals variations in groundwater quality, including high total dissolved solids (TDS) ranging from 240 to 531 mg/L and electrical conductivity (EC) values ranging from 376–802 μS/cm, as well as the presence of heavy metals. Some water samples exceeded the recommended limits for certain parameters set by the World Health Organization (WHO). Spatial distribution analysis showed higher mineralization toward the northeast of the study area. Overall, the integrated approach proposed in this study can contribute to effective water-management strategies to ensure sustainable water resources and protect public health in water-stressed regions like Egypt. Full article

The Zhu III Depression, situated in the northern Pearl River Mouth Basin, features a complex fault system composed of NE–SW-, nearly E–W-, and NW–SE-oriented faults. However, there is limited research on NW-trending faults, especially regarding their formation mechanisms. Through structural analysis of 3D seismic profiles, we have revealed the geometric and kinematic characteristics of NW-trending faults and categorized them into three types based on their formation mechanisms: extensional fault, dextral transtensional fault, and sinistral strike–slip fault. The extensional faults predominantly developed as boundary faults during the rifting I period, caused by tectonic inversion of the NW–NWW-trending basement faults since early Eocene. The transtensional fault resulted from the dextral strike–slip motion of the NE-trending basin-controlling faults since late Eocene, under the regional dextral extension stress setting. The sinistral strike–slip faults have been dominant during the post-rifting period since early Oligocene. This is due to the sinistral shearing action related to the southeastward lateral extrusion of the Indochina Block and slab pull southward by subduction of the proto-SCS. The NW-trending faults controlled the development of local tectonics and structures, the depocenter migration during the rifting period, and the trapping, migration, and preservation of oil and gas. Full article

Previous studies on microtaphonomy have identified multiple types of organic microstructures in fossil vertebrates from a variety of time periods and past environmental settings. This study investigates potential taphonomic, paleoenvironmental, and paleoclimatic controls on soft tissue and cellular preservation in fossil bone. To this end, fifteen vertebrate fossils were studied: eight fossils collected from the Oligocene Sharps Formation of the Arikaree Group in Badlands National Park, South Dakota, and seven fossils from formations in the underlying White River Group, including the Oligocene Brule Formation of Badlands National Park, and the Eocene Chadron Formation of Flagstaff Rim, Wyoming; Toadstool Geologic Park, Nebraska; and Badlands National Park, South Dakota. A portion of each fossil was demineralized to identify any organic microstructures preserved within the fossils. We investigated several factors which may have influenced cellular/soft tissue decay and/or preservation pathways, including taxonomic identity, paleoclimatic conditions, depositional environment, and general diagenetic history (as interpreted through thin section analysis). Soft tissue microstructures were preserved in all fossil samples, and cellular structures morphologically consistent with osteocytes were recovered from 11 of the 15 fossil specimens. Preservation of these microstructures was found to be independent of taxonomy, paleoclimate regime, apatite crystallinity, depositional environment, and general diagenetic history, indicating that biogeochemical reactions operating within microenvironments within skeletal tissues, such as within individual osteocyte lacunae or Haversian canals, may exert stronger controls on soft tissue and biomolecular decay or stabilization than external environmental (or climatic) conditions. Full article

The Epyrinae are the second largest subfamily of Bethylidae and the most diverse in the fossil record. However, although six of the nine bethylid subfamilies are known during the Cretaceous (either as compression or amber fossils), the Epyrinae were hitherto unknown before the lower Eocene. In this contribution, we report the discovery of the oldest member of this group, based on a female specimen from the early Cenomanian amber of Kachin, Myanmar. We describe and illustrate a new genus and species, Hukawngepyris setosus gen. et sp. nov. The new genus is compared with the other epyrine genera and characterized by a unique combination of characters not known in the subfamily. Hukawngepyris setosus gen. et sp. nov. is especially unique in the configuration of the forewing venation, with a complete 2r-rs&Rs vein, curved towards the anterior wing margin, and the presence of three proximal and three distal hamuli. The key to the genera of Epyrinae is accommodated to include the newly erected genus. Full article

The Paleogene system of the Zhuyi Depression exhibits a pronounced mechanical compaction background. Despite this compaction, remarkable secondary porosity is observed in deep clastic rocks due to dissolution processes, with well-developed hydrocarbon reservoirs persisting in deeper strata. We conducted a comprehensive study utilising various analytical techniques to gain insights into the dissolution and transformation mechanisms of deep clastic rock reservoirs in the steep slope zone of the Lufeng Sag. The study encompassed the collection and analysis of the rock thin sections, XRD whole-rock mineralogy, and petrophysical properties from seven wells drilled into the Eocene. Our findings reveal that the nature of the parent rock, tuffaceous content, dominant sedimentary facies, and the thickness of individual sand bodies are crucial factors that influence the development of high-quality reservoirs under intense compaction conditions. Moreover, the sustained modification and efficient expulsion of organic–inorganic acidic fluids play a main role in forming secondary dissolution porosity zones within the En-4 Member of the LF X transition zone. Notably, it has been established that the front edge of the fan delta, the front of the thin layer, and the near margin of the thick layer of the braided river delta represent favorable zones for developing deep sweet-spot reservoirs. Furthermore, we have identified the LF X and LF Y areas as favourable exploration zones and established an Eocene petroleum-accumulation model. These insights will significantly aid in predicting high-quality dissolution reservoirs and facilitate deep oil and gas exploration efforts in the steep slope zone of the Zhuyi Depression. Full article

The Mahour base metal deposit is located northeast of Badroud in the middle of the Urumieh–Dokhtar magmatic arc in the Isfahan province of Iran. The main host rocks to the ores are Eocene volcanic and volcaniclastic rocks. Hypogene ore minerals constituting the main ore body are galena, sphalerite, pyrite, and chalcopyrite. In addition to gangue quartz, a variety of supergene minerals comprising gypsum, goethite, hematite, “limonite”, malachite, azurite, covellite, and chalcocite are also present; gangue minerals are quartz, barite, calcite, sericite, and chlorite. Silicification, intermediate argillic, and propylitic are the main wall-rock alteration types. The presence of fluid inclusions with different vapor/liquid ratios in quartz and sphalerite could indicate a boiling process. The primary liquid-rich fluid inclusions suggest that the homogenization temperature was between 107 and 298 °C from fluids with salinities from 1.5 to 13.7 wt.% NaCl equiv. These data suggest that the ore-forming fluids were magmatic with a contribution from meteoric waters. The δ³⁴S values of sulfides range from 1.9 to 3.4‰, those of barite range from 12.1 to 13.2‰, and those of gypsum range from 4.3 to 5.6‰. These data suggest that sulfur was mostly of magmatic origin with a minor contribution from sedimentary rocks. Our data suggest that the boiling of fluids formed an intermediate-sulfidation style of epithermal mineralization for the Mahour deposit. Full article

Diptera are one of the four megadiverse groups of holometabolan insects. Flies perform numerous ecological functions, especially in their larval stages. We can assume that this was already the case in the past; however, fly larvae remain rare in most deposits. Here we report new dipteran larvae preserved in Cretaceous (about 99 Ma) Kachin amber from Myanmar and, even older, Jurassic (about 165 Ma) compression fossils from China. Through light microscopy and micro-CT scanning we explore their peculiar morphology and discuss their possible phylogenetic affinities. Several larvae seem to represent the lineage of Stratiomyomorpha. A few others present characters unique to Xylophagidae (awl-flies), as well as to Athericidae (water sniper-flies), resulting in a chimeric morphology. Understanding the exact relationships of most of these specimens with a particular lineage remains challenging, since they differ considerably from any other known dipteran larvae and present some unique traits. Additionally, we report new specimens of Qiyia jurassica Chen et al., 2014, supposedly parasitic larvae, most likely representatives of Athericidae. These new findings offer valuable insights into the evolution of the early diversification of the brachyceran flies and underscore the importance of immature stages in understanding the evolutionary history and ecology of flies. Full article

Pycnodont fishes were a successful clade of neopterygian fishes that are predominantly found in shallow marine deposits. However, throughout their long 180 million year reign (Late Triassic–end Eocene), they made multiple incursions into both brackish and freshwater environments. This fossil record mostly consists of fragmentary dental material, but articulated specimens are known from Early Cretaceous lacustrine localities in Spain. This review article aims to document all non-marine occurrences of Pycnodontiformes throughout most of the Mesozoic and early Paleogene. This review highlights two interesting trends in the history of non-marine habitat colonization by pycnodonts: (1) a huge spike in non-marine occurrences during the Cretaceous; and (2) that most occurrences in non-marine localities occurred at the latest Cretaceous period, the Maastrichtian. The high number of colonization events within the Cretaceous lines up with extreme climatic events, such as high temperatures resulting in high sea levels which regularly flooded continental masses, allowing pycnodonts easier access to non-marine habitats. The increased presence of pycnodonts in brackish and freshwater habitats during the Maastrichtian might have played a role in their survival through the K/Pg extinction event. Freshwater habitats are not as vulnerable as marine ecosystems to environmental disturbance as the base of their food chain relies on detritus. Pycnodonts might have used such environments as a refuge and began to occupy marine waters after the K/Pg extinction event. Full article