Late Miocene Research Articles

Miocene evolution of vegetation, climate, and elevation in the Wulan Basin of northeast Tibetan Plateau based on a CRACLE analysis of palynological assemblages

The uplift of the Tibetan Plateau (TP) during the Cenozoic has played a pivotal role in shaping global climate and vegetation evolution, however, understanding the uplift history of its various tectonic blocks remains complex. In this paper, we analyze palynological samples from the Miocene Xiayoushashan and Shangyoushashan formations in the Wulan Basin to explore the relationship between climate change and TP uplift. The analysis identified four distinct pollen zones: Zone I (18–15.3 Ma) characterized by Artemisia-Lycopodium-Aster-Polygonaceae; Zone II (15.3–12.7 Ma) dominated by Pinus-Picea-Aster-Artemisia; Zone III (12.7–11.7 Ma) featuring Lycopodium-Picea-Pinus-Polygonaceae; Zone IV (11.7–8.7 Ma) characterized by Picea-Chenopodiaceae-Lycopodium-Artemisia. Results indicate that the whole study interval was dominated by shrubs and grasses, interspersed with conifers and broad-leaved trees, exhibiting an altitudinally zonal pattern. Using the Coexistence Likelihood Estimation (CRACLE) method, we estimate a mean annual temperature (MAT) ranging from 6.0 to 14.7 °C and a mean annual precipitation (MAP) between 919.1 and 1612.4 mm during Miocene times. While minor climatic fluctuations occurred, the region experienced a cool-temperate and sub-humid climate significantly warmer and more humid conditions compared to the present. Based on MAT differences, the paleoelevation of the Wulan Basin during the Miocene was estimated to be c. 1655–2025 m, suggesting an uplift of c. 1275–1645 m since that time. These findings corroborate previous suggestions that the northeastern TP had not reached its current elevation prior to the Late Miocene.

Formation of vertical columnar seismic structures and seafloor depressions by groundwater discharge in drowned Miami Terrace platform and overlying deep-water carbonates, southeastern Florida

The presence of vertical cross-formational fluid migration passageways within sedimentary basins can profoundly impact aquifer and reservoir fluid-flow and their identification is fundamental to informing management of subsurface fluid resources (groundwater, oil, gas). In an onshore and offshore southeastern part of Florida, 2D/3D seismic-reflection and bathymetry data document ~153 vertical columnar structures composed of reflection disruptions up to 760 m in the height and averaging 360 m in diameter, and ~ 219 subcircular to circular seafloor depressions up to 1010 m wide. Our study focuses on these features found within the offshore shallow-marine carbonate Miami Terrace platform, which drowned approximately at the end of the middle Miocene, and within overlying Plio-Quaternary deep-water carbonate slope and drift deposits. Most columnar structures are rooted in stratiform aquifers of the Miami Terrace platform and associated with faults or fault intersections produced by Eocene and circa late Miocene tectonics. The columns commonly terminate within the platform or as subcircular depressions along an amalgamated karstic and drowning unconformity at the platform top. The columns typically stretch upwards from a zone of deep karst cavity collapse through the Miami Terrace platform with upward decreasing sag on internal reflections. Following drowning and Plio-Quaternary partial burial of the Miami Terrace platform by deep-water deposits, the subcircular depressions and faults along the platform top were points of origin for a second phase of column growth upward into the deep-water deposits. The continuation of deep platform cavity collapse and column evolution produced pockmarks along paleo-seafloors within the deep-water deposits and at the present-day sea floor. The Plio-Quaternary pockmarks formed at water depths too deep to suggest an origin related to meteoric karst above or near sea level, but rather their formation is suggested to be related to cyclic sea level falls that drove increased groundwater head and density gradients, and seafloor discharge of offshore freshened groundwater sourced from the underlying platform. Mixing of freshened groundwater and seawater at the seafloor discharge sites plausibly drove dissolution of the host deep-water deposits that contributed to the formation of the pockmarks and erosion by groundwater venting and current scouring.Seaward of the Plio-Quaternary seafloor pockmarks, at the late-middle Miocene upper slope of the Miami Terrace platform and along the regional karst/drowning unconformity is a slope-parallel band of ~188 densely distributed subcircular seafloor depressions with diameters up to 1010 m at water depths up to 663 m. It is plausible that along the upper slope, faults and fractures produced by gravity-driven slope instability and possibly tectonics formed a dense network of fluid passageways that promoted upward artesian freshened groundwater flow to sites of discharge where mixing with seawater generated limestone dissolution and the depressions. But tectonic uplift may have forced emersion and initial meteoric sinkhole formation circa late Miocene with later enhancement by freshened groundwater discharge and bottom current erosion.

The tibiotarsus of a giant darter from the upper Miocene of Amazonia and weight estimates for fossil darters

Fossil darters are known from every continent since the Oligocene. However, it was in the Miocene of South America that this group reached its maximum diversity. Macranhinga ranzii is the largest darter from the Solimões Formation, described based on the left and right femora as well as the distal end of a tarsometarsus and four vertebrae. Here, we describe for the first time the left tibiotarsus of this species by comparing it with the tibiotarsus of the extant Anhinga anhinga and other fossil anhingids. We also calculated and compared the body mass of Ma. ranzii to that of all known tibiotarsi fossil anhingids using two calculation methods. The tibiotarsus described here is morphologically similar to that of other anhingids, however, in addition to its large size and robustness, it presents diagnostic characters (e.g., torus linearis) that allow us to attribute it to the genus Macranhinga and differentiate it from other fossil species of this genus whose tibiotarsi are known. The estimated body mass of Ma. ranzii ranges from 14.39 to 19.1 kg, ranking it the highest estimated body mass among the darters where the tibiotarsi were found.

Paleogeographic implication of a titanosaur eggshell from the Neogene of the Entre Ríos Province, Argentina

The Lower Member of the Ituzaingó Formation (LMIF), fluvial in origin and assigned to the Upper Miocene, contains a conglomerate level known as “Mesopotamiense” or “Conglomerado osífero” that has yielded a rich fauna of vertebrates. The aim of this contribution is to describe a titanosaurian dinosaur eggshell fragment recovered from the LMIF at the locality of Toma Vieja (western Entre Ríos Province), discussing its paleogeographic history and implications. Fragments of eggshells referred to Titanosauria are frequent from litostratigraphic units of the Upper Cretaceous of western Uruguay (e.g., Guichón, Mercedes, and Queguay Formations). Besides, a fragment of eggshell recovered from the Puerto Yeruá Formation (Upper Cretaceous) at eastern Entre Ríos Province was described. Geophysical data from the Entre Ríos Province allow to propose the presence of a Lower Cretaceous field of extensional tectonic stresses that generated structural lineaments with a E-W and ENE-WSW trend. This ancient penetrative Cretaceous tectonic framework would have exerted control on the shape of the basin and sediment flow patterns and subsequent sedimentation, by promoting the generation of accommodation space over the late Paleogene and the Neogene. The phenomenon would have conditioned the deposition of the Fray Bentos Formation, the subsequent marine Paraná Formation, and the sedimentation of the LMIF, with source materials coming from the east. Thus, it is hypothesized that the fragment of eggshell of Titanosauria would come from the eastern area of the basin (western Uruguay) as a consequence of the existence of a paleohydric system with predominantly E-W and ENE-WSW directions. This late Neogene system would have been controlled by inherited Cretaceous structural lineaments with orientations similar to those that also govern the current fluvial systems of western Uruguay, developed on the Mesozoic substrate.

Mineralogy and Geochemistry of Upper Miocene Igneous Rocks, Kos Island, Greece: Extension during Strike-Slip Faulting and Subduction Rollback

Upper Miocene volcanic and plutonic rocks on Kos island preserve a record of magmatic and tectonic events in the transition zone between the Aegean and Anatolian microplates. Their field setting, syn-intrusion deformation, mineralogy, and geochemistry were investigated. Volcanic rocks, including trachyandesite flows and trachyandesite to rhyolite domes, were extruded on a central E–W horst and directly overlie Alpine basement. Thick successions of trachytic flow tuffs are interbedded with fluvial and lacustrine basinal sediments to the south of this horst. Volcanism was synchronous with the emplacement of the Dikeos monzonite pluton, which is geochemically similar to some lithic clasts in the thick flow tuffs and is cut by mafic dykes including lamprophyres. Two main types of mafic magma were present: a K-rich lamprophyric magma that evolved to trachyandesite and more calc-alkaline magma similar to mafic enclaves in the monzonite. Syn-intrusion structures in the monzonite indicate emplacement during E–W sinistral strike-slip faulting that created local transtensional deformation, providing accommodation for a Dikeos magma reservoir. A change in the style of deformation in the Late Miocene led to NW-striking extension in the footwall, occupied by mafic dykes and mineralized veins, and extensional detachment of the hanging wall, resulting in unroofing of the monzonite.

Modelo cinemático del control estructural 4D y metalogénesis del distrito auroargentífero Vetas-California (Santander, Colombia)

). The gold and silver deposits of the Vetas-California mining district are hosted in Paleozoic gneisses and Mesozoic granites of the Santander massif in the Eastern Cordillera of Colombia, far from the northern Andean volcanic arc. In the California area, there is ambiguity in defining the epithermal-type metallogenic model with high to intermediate sulfidation due to the presence of Late Triassic-Early Jurassic and Miocene magmatism. The best-known hydrothermal episodes comprise two early porphyritic-style phases: a) characterized by a propylitic alteration with molybdenite of the ~10.1 Ma-old La Mascota breccia, related to granodiorite porphyries and smaller-volume rhyodacitic dykes; and b) attributed to a magmatic-hydrothermal system due to phyllic alteration associated with quartz-pyrite veins with hydrothermal sericite dated at ~3.4 Ma. These two hydrothermal episodes were followed by four epithermal phases related to the development of multiphase hydrothermal breccias and quartz-alunite alteration, defined by bornite, covellite, and chalcopyrite, alongside wolframite, enargite, and sphalerite, with gold and silver mineralization between ~2.6 and ~ 1.6 Ma. To understand the relationship of the emplacement of the porphyries and the subsequent auro-argentiferous enrichments to the deformation front observed in the Pamplona buttress, to the east of the Santander Massif, a 4D structural model of the mineralization is formulated here. This model is based on the spatial analysis of the stresses responsible for the La Baja-Angostura dextral fault in terms of the regional kinematics of the Bucaramanga sinistral fault. It is considered that the SW sector of the deposit area corresponds to a well-defined, tabular, sub-vertical body of the La Mascota breccia. On the other hand, the NE sector in the La Baja-Angostura fault is expressed as a topographically elevated right horsetail splay, which controls the more disseminated distribution of the mineralization by means of veinlet swarms arranged in an ~E-W direction. The disseminated mineralization of Vetas-California was probably favored by late thermal expansion-contraction events in the gneissic sockets, which allowed the accumulation and precipitation of boiling solutions rich in volatiles and elements of economic interest.

Upper Miocene volcanic ash layers from central Italy: tracking down the volcanic source

Upper Miocene volcanic ash layers from central Italy: tracking down the volcanic source

Mio-pliocene evolution of deep-water channels on the northeastern Bengal fan: Records of signals of Himalaya uplift and South Asian Monsoon from source areas

Submarine channels, acting as major conduits for delivering terrestrial sediments into the deep sea, are sensitive to source-region uplift and climate variations. Using new 3D seismic data, previously published paleoenvironmental data, and IODP/ODP data, we characterize stratigraphic time changes in deep-water channels on the northeastern Bengal Fan and suggest that their long-term evolution relates to contemporaneous changes of Himalaya uplift and South Asian Monsoon. Our results show that around the boundary between the Miocene and Pliocene Epochs, the sedimentary characteristics of deep-water channels were changing at about the same time as decreased rates of Himalaya uplift and changes in the monsoonal climate. It is strongly suggested that environmental signals could successfully propagate from the Himalaya to the deep sea and play a dominant control on the long-term evolution of deep-water channels. During the late Miocene, orogen-wide and substantial Himalaya uplift and humid monsoonal climates (dominance of summer monsoon) generated a sediment supply with high fluxes, which allowed coarser-grained sediments to reach further into the basin and thus caused the formation of larger-scale, non-leveed erosional channels that have avulsion and confluence phenomena. After the Miocene, local and limited Himalaya uplift and arid monsoonal climates (dominance of winter monsoon) led to a sediment supply with low fluxes, during which only finer-grained sediments reached deep water and gave rise to smaller-scale, leveed aggradational channels that mainly have splay deposits. Between the late-Miocene and post-Miocene periods, detrital zircon U-Pb ages of Bengal Fan samples from IODP cores reflect a sediment provenance change from the mixing of Brahmaputra and Ganges Rivers to the end-member of Brahmaputra River, broadly coeval with the variations of Himalaya uplift and South Asian Monsoon. Moreover, Bengal Fan cores record a Mio-Pliocene decrease in sedimentation rates and maximum grain sizes and an increase in mudstone contents, consistent with the variations of sediment yield in the source catchments. Observations and interpretations from the current study, therefore, contribute to a better understanding of how the long-term evolution of submarine channels respond to tectonic and climatic perturbations in source areas and may help recognizing similar process-response relationships in other areas.

Phylogeny, historical biogeography and climate niche differentiation in extant species of Ceratophryidae (Anura, Hyloidea) frogs in South America

Ceratophryidae is a family of frogs containing twelve extant species distributed in South America. Several studies have been carried out concerning the systematics, morphology, karyotypes, and behaviour within this monophyletic family. However, little is known about the historical biogeography and the divergence in time of this group. Here, we present an updated phylogeny, along with a calibrated chronogram, to analyse the historical biogeographical pattern and climate niche differentiation among extant species of Ceratophryidae (Anura: Hyloidea) frogs in South America. A phylogeny based on morphological and genetic data was obtained from 256 morphological characters, six mitochondrial and eight nuclear genes for up to a total of 8428 characters in the homological matrix. Our results indicate that the genus Ceratophrys is sister to the clade Chacophrys + Lepidobatrachus. The divergence of the crown group of Ceratophryidae is estimated to have occurred 19.2 Ma at the beginning of the Miocene, with recent cladogenetic events related to the late Miocene (10.18–13.70 Ma) and the Pliocene (~5.3–2.6 Ma). Moreover, the Cerrado region is estimated to be the ancestral area of the family, as well for the genera Chacophrys and Lepidobatrachus. In addition, temperature seasonality and annual precipitation play a major role in the niche differentiation of extant species within Ceratophryidae. In conclusion, our data suggest multiple dispersal and vicariance events originating from the Cerrado region in the early Miocene, and recognize the role of the environment in the differentiation of the ecological niches among extant species of this family in South America. Ceratophryidae is hypothesized to have originated in the semi-arid Cerrado region in the early Miocene (~19.2 million years ago), from where species have diversified by independent dispersal and vicariance events across other South American regions. Ceratophrys frogs are phylogenetically recovered as the sister taxon to the clade comprising Chacophrys and Lepidobatrachus. Three lineages of Lepidobatrachus and four lineages from Ceratophrys diverged in the Pliocene, around 5.3 to 2.6 million years ago. Niche differentiation among extant species of Ceratophryidae appears to reflect roles for temperature seasonality and annual precipitation.

Neogene–Quaternary paleoenvironments and kerogen assessment of the NDO B-1 well, offshore Nile Delta, Egypt, Eastern Mediterranean: palynological evidence

Palynofacies and palynological investigations conducted on the Neogene–Quaternary succession from the NDO B-1 well, located in the offshore Nile Delta, Egypt, in the Eastern Mediterranean, suggest generally shallow marine (neritic) conditions. These environments are manifested by the overall palynofacies composition and the occurrence of dinoflagellate cysts (e.g., Spiniferites spp., Lingulodinium spp., Hystrichokolpoma spp., Homotryblium spp. and Selenopemphix spp.). Neritic environments are suggested for the lower and middle Miocene Sidi Salim, and the Pliocene to Pleistocene upper Kafr El Sheikh, El Wastani and Mit Ghamr formations, while shallower, coastal to inner neritic settings were interpreted for the late Miocene (Qawasim and Rosetta formations) and early Pliocene (Abu Madi and lower Kafr El Sheikh formations). Anoxic conditions existed during the deposition of the studied well succession, which can be seen from the occurrence of imprints of pyrite crystals and some types of oxygen-sensitive dinoflagellate cysts. The palynofacies fluctuated repeatedly between Amorphous Organic Matter (AOM)-dominated and phytoclast-dominated intervals, of kerogen types II and III, respectively. The spore coloration index (SCI) of indigenous thin-walled palynomorphs confirms thermally mature sediments, generative of dry gas and wet gas/condensates. Reworking during the deposition of the upper Sidi Salim, Qawasim and Rosetta formations is inferred from the occurrence of Cretaceous dinoflagellate cysts and pollen.

Comparison of organelle genomes between endangered mangrove plant Dolichandrone spathacea to terrestrial relative provides insights into its origin and adaptative evolution.

Dolichandrone spathacea is a mangrove associate with high medicinal and ecological values. However, due to the dual-pressure of climate change and human activities, D. spathacea has become endangered in China. Moreover, misidentification between D. spathacea and its terrestrial relative D. cauda-felina poses further challenges to field protection and proper medicinal usage of D. spathacea. Thus, to address these problems, we sequenced and assembled mitochondrial (mt) and chloroplast (cp) genomes for both D. spathacea and D. cauda-felina. Comparative analysis revealed apparently different size and scaffold number between the two mt genomes, but a high similarity between the cp genomes. Eight regions with high sequence divergence were identified between the two cp genomes, which might be used for developing candidate DNA markers for distinguishing the two species. The splitting between D. spathacea and D. cauda-felina was inferred to occur at ~6.8 - 7.7 million years ago (Mya), which may be driven by the environment fluctuations in late Miocene. In the cp genome, 12 genes related to the expression of photosynthesis-associated proteins were detected with signatures of positive selection, which may contribute to the origin and evolutionary adaptation of Dolichandrone mangrove species. These new findings do not only enrich organelle genomic resources of Dolichandrone species, but also provide important genetic clues for improving the conservation and proper usage of endangered mangrove associate D. spathacea.

Harnessing geothermal energy in Hungary

This paper provides a summary of the current status of geothermal energy utilisation in Hungary, with a brief reference to geothermal potential. Approximately 1,000 thermal wells are in operation, producing from two principal aquifers: carbonate aquifers (predominantly Mesozoic) and Upper Miocene siliciclastic aquifers. The utilisation of geothermal energy in Hungary commenced with balneological exploitation, with documented evidence dating back to the Roman era. Of particular note is the city of Budapest, which has the distinction of being home to 16 thermal spas, a fact that has led to its designation as the spa capital of Europe. In the Hungarian portion of the Pannonian Superbasin, 26 municipalities have implemented geothermal district heating systems. Furthermore, geothermal energy plays a significant role in the agricultural sector, with approximately 300 thermal wells currently in operation. Nevertheless, the generation of geothermal electricity is still in its infancy, with only one operational geothermal power plant. However, based on the exploration permits submitted, there are significant prospects for further development. The same is true for ground source heat pumps, where there is considerable potential for growth, particularly in comparison to our neighbouring country's utilisation. Recent research directions are promising, ranging from the use of geothermal energy from abandoned hydrocarbon wells as deep borehole heat exchangers, to the potential for extracting critical materials from thermal water, to exploring the possibility of underground heat storage. The favourable geothermal conditions in Hungary offer the potential to achieve up to 15-20 times the current production of 6.5 PJ, assuming the application of existing technologies. This presents a significant opportunity for the transition to a more sustainable energy source, particularly in the context of heating.

Ichnological indicators of physico-chemical stresses in wave- to tide-dominated Miocene shallow marine environments (Argentine Patagonia)

An integrated analysis of ichnological and sedimentological features in ancient successions provides a robust dataset of high-resolution interpretations of environmental parameters, encompassing both depositional and ecological aspects. By characterising discrete and recurring bioturbation patterns in the Puerto Madryn Formation (Late Miocene, Argentine Patagonia), we arrive at key knowledge about predominant environmental stresses within transgressive phase shallow marine and estuarine systems, shedding light on their palaeoenvironmental implications. Given the inherent complexities of coastal settings, including the challenges posed by omission/erosion surfaces, it becomes imperative to consider the intricate interplay of multiple depositional processes and environmental factors.Through a detailed integration of sedimentological and ichnological approaches, we discern the establishment of a wave-dominated system overlain by a tide-dominated estuarine system.The wave-dominated marine system involves tabular bodies extending laterally over tens of kilometres, with upward fining and coarsening successions from the mid- to lower-shoreface to offshore-shelf environments. The influence of waves and tides on these systems is discussed in the absence of physical sedimentary structures and the need to find elements that bring us closer to elucidating whether waves or tidal processes influence shoreface to offshore systems. The ichnological assemblages allow for the characterisation of Cruziana ichnofacies with proximal (Taenidium and Thalassinoides), archetypal (Asterosoma, Chondrites, Cylindrichnus, Ophiomorpha, ?Rhizocorallium, Rosselia, Scolicia, Sinusichnus, Siphonichnus, Teichichnus, and Thalassinoides), and distal expressions (Chondrites, Helicodromites, Phycodes, Thalassinoides, and ?Zoophycos) in the lower shoreface to lower offshore and transitional settings with the shelf. However, the transition from these deposits to Chondrites-dominated beds associated with lower offshore to shelf environments—determined by changes in oxygenation, nutrients, and energy conditions—impedes assignment of all the successions to a particular ichnofacies.The tide-dominated estuarine system features wide, channel-shaped bodies filled with sandy to heterolithic facies, interpreted as intertidal and subtidal deposits. To differentiate between estuary mouths and other settings, the analysis involved characterisation of transgressive and regressive surfaces, ichnological assemblages, and facies distribution, determining net sediment movement—whether landwards or seawards—and its influence on system classification. The ichnological assemblages could be assigned to the Skolithos (Arenicolites, Gyrolithes, Maiakarichnus, Ophiomorpha, Schaubcylindrichnus, Skolithos, and Thalassinoides) and Cruziana ichnofacies (Ophiomorpha, Rosselia, Scolicia, and Siphonichnus). Variations in diversity and abundance often help to determine certain stressful conditions, although the transition to more open areas is discussed, addressing how it could modify the typical models linked with a direct relationship between abundance/diversity and physico-chemical stress.

A new epifoliar melioloid fungus from the Siwalik (Miocene) of Himachal sub-Himalaya and its palaeoecological implications

A new fossil epifoliar ascomycete (Ascomycota), Meliolinites miocenicus nov. sp. (fossil Meliolaceae), occurs in situ on a compressed monocot leaf from middle Siwalik (Late Miocene, ca. 12–8 Ma) sediments of Himachal Pradesh, Western Himalaya. The fossil consists of a well-preserved mycelium of superficial, brown to dark brown, septate, thick-walled, branched hyphodiate hyphae; a sub-globose, dark brown putative ascoma, and an oblong to broadly cylindrical, five-celled, four-septate, mature germinating ascospore. The new fossil differs from earlier reported melioloid fossils primarily in the morphology of appressoria. Meliolinites miocenicus nov. sp. on its host is evidence of the existence of a biotrophic relationship at the time of deposition. Qualitative climate data using plant megafossils recovered from the same fossil locality indicate that M. miocenicus nov. sp. and its host thrived in a warm and humid tropical environment.

Continental rift evolution and drainage reorganization along the Dead Sea rift since the Miocene

The Dead Sea fault is a section of the Arabian-African plate boundary. Widespread field relations indicate that three major drainage systems (stages) occupied the landscape west of the Dead Sea fault since its initiation at ca. 20 Ma. Specifically, (1) an early to middle Miocene drainage system, only minorly reconfigured by the fault (all sediments of this system belong to the Hazeva Formation); (2) a late Miocene to early Pleistocene fault-parallel drainage system named Paran-Neqarot (all sediments of this system belong to the Arava and Zehiha Formations; and (3) the early Pleistocene to present drainage configuration. The temporal and spatial frameworks of drainage stage 1 are generally constrained by radiometric dating of interfingering volcanic units, and the onset and temporal and spatial frameworks of drainage stage 3 are well constrained by cosmogenic 10Be surface exposure ages. The timing and longevity of the rift-parallel drainage (stage 2) have until now been evasive to direct dating. The overall time gap between stages 1 and 3 is ∼12−13 million years. Thus, an early age (within this time gap) of stage 2 would imply an immediate response of drainage reorganization to rift tectonics, while a later age of this drainage system would imply a delayed response. We present 11 10Be-26Al cosmogenic burial ages of alluvial and colluvial units related to the fault-parallel drainage system (stage 2), which collectively constrain the time of deposition of the Arava Formation sediments in the central Negev to ca. 8 Ma. The general lack of stratigraphic order, together with the large dispersion of ages both across and within the sampling sites, attests to significant recycling of sediments from drainage stage 1 into the Arava Formation deposits. The termination of Arava and Zehiha Formation sediment deposition at ca. 1.8 Ma was determined previously using cosmogenic exposure ages of desert pavements that cover the formations. Combining the previously published data with our new data, we established the longevity and character of the Paran-Neqarot drainage system. This framework highlights the temporal aspect of drainage system build-up and collapse as it responded to transform and extensional plate boundary tectonics during the Neogene.

Tsuga leaves from the Neogene Baoshan Basin in southwest China and their palaeoecological implications

Tsuga (Endl.) Carrière (Pinaceae) has a rich fossil record represented by pollen, leaves, wood and seed cones. Although fossil leaves of the genus have been widely documented, most of them have not been examined microscopically, which may limit their taxonomic resolution. In this study, three-dimensionally preserved leaves and leaf fragments of Tsuga from the Neogene (latest Miocene to Pliocene) Baoshan Basin in western Yunnan, southwest China, were examined both morphologically and micromorphologically. The fossil leaves are characterized by flattened and bifacial shape, round to obtuse apex and petiolate base, adaxially sunken and abaxially elevated midvein, adaxial surface without stomata and with elongated, smooth-margined epidermal cells, and abaxial surface with two stomatal bands along the midvein, each stomatal band consisting of 6–8 longitudinal stomatal lines. Based on comparisons with extant species of the genus, we found that the fossil leaves show the closest affinity to Tsuga dumosa (D. Don) Eichler, an extant species growing in the modern western Yunnan. As modern species of Tsuga prefer humid conditions, our fossil find suggests a humid climate in the Baoshan Basin at the time of fossil deposition, probably due to the influence of the Indian summer monsoon from the southwest. This is consistent with previous results of quantitative palaeoclimate reconstructions using spore/pollen fossil assemblages. Our study provides new fossil evidence for the origin of modern conifer diversity in southwest China. It highlights the importance of microscopic studies in the taxonomic resolution of fossil leaves of Pinaceae.

Middle to late Miocene cooling and drying in the northern Tibetan Plateau based on evidence from plant-insect interactions

The Qaidam Basin in the northern Tibetan Plateau is currently arid, but may have had a semi-humid to semi-arid climate in Miocene times, as suggested by pollen and isotopic data; however, the lack of macroscopic fossils hinders more precise paleoclimatic calibration. In this paper, we report fossil leaves with insect damage from a late Miocene layer (HT-5) in the Huaitoutala section dated ∼11.4 Ma, and compare them with records from a middle Miocene layer (HT-1) dated ∼12.7 Ma. Results show that damage diversity dropped from 36 types in HT-1 to 24 types in HT-5, suggesting a fall in mean annual temperature. Damage frequency decreased from 70 % in HT-1 to 32 % in HT-5, pointing to a drop in the coldest month temperature. Moreover, a slight fall in the diversity of mining damage, from 5 types in HT-1 to 4 types in HT-5, suggests a shift towards a slightly more arid climate from the middle to late Miocene. The flora from HT-5 is composed mainly of Betulaceae, Populus, Ulmus, and shrubs. Based on the distribution of these taxa in modern vegetation, the climate was probably semi-humid, not entirely arid during the late Miocene. These results are corroborated by fossil mammal data from the same section. Therefore, despite a cooling and drying trend from the middle to late Miocene, the climate of the Qaidam Basin was not as extremely arid as today.

Multiphase Tectonic Processes in the Mesozoic and Formation of Early Regional Geomorphic Pattern in the Qilian Orogenic Belt, Northeastern Tibetan Plateau

Abstract Conventional orogenic settings are largely confined to plate boundaries and their immediate vicinity. However, there is growing recognition that deformation of the continental lithosphere may extend for considerable distances away from active plate boundaries. The Mesozoic Qilian orogenic belt occupies a key position in East Asia and thus is important to consider when interpreting intracontinental deformation there. To determine when and how the North Qilian orogenic belt developed, multiple sets of samples collected from the Dahuang Mountain of the North Qilian orogenic belt were analyzed for apatite (U-Th)/He and zircon (U-Th)/He thermochronology. The results show that the study area experienced multiphase tectonic exhumation events that took place in the Early-Middle Triassic (250–235 Ma), Middle-Late Jurassic (170–150 Ma), and Early Cretaceous (130–110 Ma). This study reveals that the generation deformation and stress distribution in the Dahuang Mountain fold-fault system have the characteristics of temporal–spatial migration from N to S. Results indicate widespread, continuous exhumation and deposition in the Qilian Mountain due to multiplate interaction since the Mesozoic, persisting till at least late Miocene. Multiphase intracontinental deformation is driven by stresses at plate boundaries, with lithosphere serving as stress pathway.

The postcranial skeleton of Amphimoschus Bourgeois, 1873 (Cetartiodactyla, Ruminantia, Pecora) sheds light on its phylogeny and the evolution of the clade Cervoidea

Here we present the first description of the postcranial skeleton of Amphimoschus, an enigmatic hornless ruminant known from the late Early to the late Middle Miocene of Eurasia (c. 17.5–13.8 Ma). This new fossil material that includes several elements of the appendicular skeleton comes from the French sites of Pontlevoy (MN5), Aérotrain (MN4), and Artenay (MN4). The postcranial skeleton of Amphimoschus is relevant to determine its phylogenetic affinities within the Pecora and to better understand the evolution of cervoids, the pecoran ruminants more closely related to deer. Our total-evidence tip-dating phylogenetic analysis recovers three well-supported main lineages of crown pecorans (Giraffomorpha, Bovidomorpha and Cervidomorpha) and places Amphimoschus as a basal member of a monophyletic Cervoidea. Thus, we reject the recent assignment of Amphimoschus to the Bovoidea, and confirm the presence of hornless forms at the base of the cervoid clade. We define the Cervoidea as the least inclusive clade of crown pecorans including Amphimoschus and the Cervidae. We also define the Cervidomorpha as the least inclusive clade of crown pecorans containing Namibiomeryx and the Cervidae. Cervidomorphs were relatively successful in the Miocene, spreading through Africa, Eurasia and North America during the Early–Middle Miocene. Amphimoschus xishuiensis Y.-K. Li et al., 2021 is recovered here as the closest sister group to the Bovidae and hence cannot be considered to belong to the genus Amphimoschus. We erect for it the new genus Dimidiomeryx. Our topology adds complexity to the recently revamped hypothesis based on molecular data regarding the single origin of the cranial appendages in pecoran ruminants. Amphimoschus probably had a sitatunga-like lifestyle, sporting sprawling-out fingers with very long third phalanges, long limbs and a general configuration of the appendicular skeleton that probably allowed it to live in swampy/semiaquatic environments.

The Xerias Window near Argos (Peloponnesus) - an example of a regional geological structure of interregional importance

The Argolic-Arcadian border range is built up by rocks of the Tripolitza and the Pindos Zones. Its tectonic architecture is deeply exposed in the area of the Xerias Window. Key structures are worked out in this article. The nappe-shaped superposition of the Tripolitza Zone by the Pindos Zone is obvious in the frame of the Xerias Window. The vergence of the key structures of the latter varies everywhere between W and SW, which proves a relative transport of the Pindos Zone as a whole in that direction. After finishing the nappe transport both Pindos and Tripolitza Zone experienced further, collective deformations, which are brought in a probable chronological order. Round about since Upper Miocene, the compressive stress of the Hellenides was followed by young extensional tectonics, which continues until today. Its influence on the development of the window and on the forming of its frame is described. The most important faults that can be related to the spreading tectonics are called within this investigation as Xerias Faults. Finally, the impacts of the strong regressive erosion, of the numerous landslides, and of the widespread slope waste both on exposing and on covering the tectonic elements are regarded.