Middle Miocene Research Articles

Miocene Construction of the High Andes Recorded by Exhumation of the Frontal Cordillera, La Ramada Massif of Western Argentina (32°S)

AbstractThe Frontal Cordillera is a first‐order geologic feature of the southern central Andes, hosting the highest hinterland topography above the modern Pampean flat‐slab segment. The timing of Frontal Cordillera exhumation is important for testing models of Andean tectonics, yet large latitudinal gaps exist between structural and thermochronological constraints for the region. We conducted a thermochronometric study using a 4.4 km age‐elevation transect along the northeast ridge of Cerro Mercedario, the highest peak in the La Ramada massif at ∼32°S. Zircon (U‐Th)/He dates indicate partial resetting, supporting a limited magnitude of exhumation in even the most extreme Andean topography. Single grain apatite (U‐Th‐Sm)/He dates range from 8.5 ± 0.9 to 35.8 ± 3.6 Ma, with median dates of ∼10.5 to ∼15.7 Ma with increasing elevation. Integrated with geologic mapping and thermal history modeling, these data suggest Early to Middle Miocene exhumation along the Santa Cruz and Espinacito faults concomitant with uplift of the La Ramada massif. New apatite helium data from the Cordillera del Tigre segment of the Frontal Cordillera are partially reset and preferred modeling interpretations suggest exhumation ca. 11–9 Ma, coeval with shortening in the eastward adjacent Precordillera. These data add to accumulating regional evidence for out‐of‐sequence deformation during the Miocene, consistent with internal (hinterland) growth of a subcritical orogenic wedge contemporaneous with surface uplift and crustal thickening in the south‐central Andes.

Revised astrochronology for the lower to middle Miocene of IODP site U1337. Implications for the Cenozoic megasplice (CENOGRID)

Revised astrochronology for the lower to middle Miocene of IODP site U1337. Implications for the Cenozoic megasplice (CENOGRID)

A new Archipsocidae (Psocodea: Psocomorpha) from the middle Miocene Zhangpu amber, China

A new Archipsocidae (Psocodea: Psocomorpha) from the middle Miocene Zhangpu amber, China

A small catarrhine talus from the middle Miocene Nachola, northern Kenya

A small catarrhine talus from the middle Miocene Nachola, northern Kenya

The Middle Miocene Takano Formation (Ishizuchi Group) along the Namekawa Gorge, Toon, Ehime, SW Japan, and the early stage of the Ishizuchi igneous activity

The Middle Miocene Takano Formation (Ishizuchi Group) along the Namekawa Gorge, Toon, Ehime, SW Japan, and the early stage of the Ishizuchi igneous activity

Two new genera of killifish (Cyprinodontiformes) from the Middle Miocene of the Bugojno Basin, Bosnia and Herzegovina: insights into the lost diversity of Valenciidae

Present-day killifishes (Cyprinodontiformes, toothcarps), known for their diversity and ecological adaptability, are represented in Eurasia by two families that each have their own taxonomic diversity, namely the diverse Aphaniidae (eight genera, > 40 species) and the less diverse Valenciidae (one genus, three species). The fossil record of both families is quite extensive in the area of Western and Central Europe, but is poor elsewhere. Here we present new fossil killifish material (consisting of 179 individuals, in many cases with otoliths in situ) from the Middle Miocene of south-eastern Europe (that is, site Gračanica in the Bugojno Basin, Bosnia and Herzegovina) using both comparative morphology (including meristics, osteology and otoliths) and phylogenetic analysis. For the latter, we used a substantially expanded morphological matrix of a previous work and conducted implied-weight maximum parsimony analyses both without constraints and with a molecular scaffold as a backbone for the extant taxa (with fossils left as floaters). Our results show that the Bugojno killifish assemblage consists exclusively of members of two new genera of the Valenciidae, †Miovalencia gen. nov. and †Wilsonilebias gen. nov., each of which is represented by two species (three new and one genus reassignment). We also found that not only the saccular otolith (sagitta), which is well known for its taxonomic information, but also the utricular otolith (lapillus) provide important taxonomic information for generic diagnosis. The discovery of the new species from the Bugojno Basin expands the known geographical distribution of the fossil Valenciidae to the Dinaride Lake System of south-eastern Europe. Furthermore, by surveying previous works, we uncovered that the fossil Valenciidae were taxonomically diverse and widely distributed geographically, which is in stark contrast with their diversity and biogeography today. Our results highlight the importance of detailed taxonomic and phylogenetic investigations of fossil killifishes in gaining insight into the evolutionary history of this remarkable group among today’s freshwater fish faunas. http://zoobank.org/urn:urn:lsid:zoobank.org:pub:890009C0-2758-49AA-931F-0F63A4E46C8E

Niche Evolution and Conservation of a Chinese Endemic Genus Sinojackia (Styracaceae).

Climate change and human activities are expected to have a profound impact on the distribution of species, especially for narrowly distributed species. Sinojackia is endemically distributed in China, and all species are listed under Chinese protected wild species. Here, we reconstructed the phylogeny and estimated the divergence time of Sinojackia based on whole plastomes, conducted the niche evolution, and predicted the potential habitat area of Sinojackia from the LGM to the future. Our results strongly supported the monophyly of Sinojackia based on whole plastomes. This genus originated in the middle Miocene and diversified since the late Miocene. The aridity index was the highest significant factor for its niche evolution, and the niche evolution rate increased slowly since its divergence. The precipitation of the warmest quarter was a main environmental variable affecting the distribution of Sinojackia in the LGM, while the human footprint is the main variable in the near-current era and 2081-2100. Compared to the current distribution of Sinojackia, the highly suitable distribution area contracted in the LGM, but expanded during 2081-2100. This study provides potential areas for the in situ conservation of Sinojackia.

Филогеографическая характеристика скорпионов рода Mesobuthus Vachon, 1950

The study of zoogeographic characteristics in combination with the use of modern methods for assessing phylogenetic relationships allowed us to examine in detail the phylogeographic structure in scorpions of the genus Mesobuthus. In this work, to assess phylogenetic relationships, we used the decoded sequences of the COI gene fragment obtained by the team of authors in collaborative work and deposited in the Genbank database (NCBI). Previously published results of zoogeographic studies, due to the lack of data on the distribution of species of this genus, did not fully reflect the zoogeographic structure of the genus Mesobuthus. Therefore, the previously typified ranges of some species of the genus Mesobuthus were revised in this work. For this purpose, specimens from the collection of the Zoological Institute of the Russian Academy of Sciences were studied. To establish the zoogeographic position of the genus Mesobuthus, the biogeographic zoning of the Palaearctic, proposed by Emelyanov A. F. and Krivokhatsky V. A., was chosen. According to the results of the study, five species groups (phillipsii, kirmanensis, eupeus, afghanus, thersites) were identified in the genus Mesobuthus using phylogenetic analysis. The zoogeographic analysis identified two clusters consisting of eight elemental faunas. In addition, transition zones between the North Central Asian and Iranian-Mekranian elemental faunas, as well as between the Khorasan-Girkan and South Turkana-Afghan elemental faunas were identified. In this study, based on the dates obtained, it was found that in scorpions of the genus Mesobuthus, the hypothetical center of origin coincides with the modern chorological center, which is the Iranian-Mekranian elemental fauna. Phylogenetic relationships between five groups of species prove that the genus Mesobuthus spread from the Iranian-Mekranian elemental fauna to the north, forming the other elemental faunas. Also, it is established that the main processes of Mesobuthus genus faunagenesis fall on the period from the middle Miocene to the late Pliocene.

Review and updates of the lithosphere structure and geodynamics evolution of the Neogene Transcarpathian Basin and its substratum (Ukraine)

Geological and geophysical data about the structure of Mukachevo and Solotvyno sub-basins of Transcarpathian Basin (TB), located in hinterland of Outer Carpathians, are integrated and adapted to modern ideas about the Carpathian realm geodynamics. Analysis of published data and newly compiled geological map and cross-sections suggests: Mukachevo sub-basin substratum can be attributed to Alcapa terrane, and significant portion of Solotvyno sub-basin basement may belong to Pieniny Klippen Belt. Model of lithospheric structure, supported by deep seismic PANCAKE and P-17 profiles, and density modeling identifies crustal domain beneath Mukachevo sub-basin as rootless fragment of Alcapa terrane. Substratum of Solotvyno sub-basin is interpreted as thrust-sheets of Pieniny Klippen Belt, Czorsztyn continental block, Monastyrets nappe, and Tisza-Dacia terrane at their base. Paleostress reconstruction allowed to identify four evolutionary phases: (1) opening of TB as dextral shear pull-apart (earliest Middle Miocene), (2) rapid subsidence of TB (Badenian), (3) inversion of Solotvyno and slow subsidence in Mukachevo sub-basins (Sarmatian - Pliocene), (4) inversion of TB (Quaternary). Lithosphere of TB is significantly thermally reworked and is characterized by: 1) thinned crust with zones of reduced velocity and density, 2) astenospheric uplift, 3) absence of residual slab, 4) presence of reflector in upper mantle descending under the Carpathians.

A New Genus for the Sarmatian (Uppermost middle miocene) mackerels (Scombridae) from the North Caucasus

V.V. Bogachev (1933) described the scombrid fish Auxis caucasica based on the incomplete skeleton from the Sarmatian (Middle Miocene) of the North Caucasus (Stavropol Region). Subsequently, this species was assigned to the mackerel genus Scomber. New findings in the Sarmatian of the North Caucasus (Krasnodar Region, Pshekha River) revealed a serious reduction in the number of vertebrae in S. caucasicus (Bogatshov) (up to 28), which is extremely unusual for Scombridae with at least 31 vertebrae. A new genus Mioscomber is established to accommodate the Sarmatian species of scombrids. The scombrids from the Sarmatian of the former Yugoslavia, originally described as Auxis vrabcensis Kramberger, 1882, A. thynnoides Kramberger, 1882 and Scomber sujedanus Steindachner, 1860, are assigned to the same genus – these also have a reduction in the number of vertebrae. The generic character of Mioscomber gen. nov. assumes correction of the diagnosis of the family Scombridae, from “Vertebrae 31–66” to “Vertebrae 28–66”.

Sedimentary Model and Geological Control of the Ganquan Platform in the Xisha Sea Area, South China Sea

The Ganquan Platform, located in the South China Sea, exhibits distinctive topographic and geomorphological features shaped by complex geological processes. Utilizing high-resolution multibeam bathymetry and multi-channel seismic data, this study provides a comprehensive investigation into the sedimentary evolution and stratigraphic framework of the platform. Morphologically, the platform is identified as an elongated seamount, with water depths ranging from 530 m to 800 m and a maximum elevation of 538.115 m. Seismic facies analysis reveals seven distinct facies, reflecting a dynamic and intricate history of carbonate deposition. The stratigraphic framework delineates three primary evolutionary stages: the growth phase (Early Miocene), characterized by the initial accumulation of carbonate sediments; the flourishing phase (Middle Miocene), marked by extensive deposition and platform expansion; and the submergence phase (Late Miocene), defined by progressive submersion and erosion of carbonate features. This evolutionary trajectory was driven by key factors such as terrigenous clastic input, tectonic activity, sea-level fluctuations, and paleoenvironmental dynamics. The findings contribute to a deeper understanding of the Ganquan Platform’s geological history and its role in the broader context of submarine geology in the Xisha region.

First occurrence of Ischyrictis zibethoides (Carnivora, Mustelidae, Guloninae) from the Middle Miocene of Southwestern Europe

First occurrence of Ischyrictis zibethoides (Carnivora, Mustelidae, Guloninae) from the Middle Miocene of Southwestern Europe

Integrated geochronological and chemostratigraphic study of middle Miocene strata (Ogallala Group) at the eastern margin of the North American Great Plains

Global and regional shifts in climate and environmental conditions during the Miocene gradually gave rise to the grassland biomes that now dominate the modern North American Great Plains. Strata comprising the Ogallala Group provide critical information for understanding these transitions. Geologic mapping and scientific drilling at the eastern edge of the Ogallala Group in northeastern Nebraska, reveal a basal, pedogenically modified siltstone-dominated interval that was hitherto barely known and never firmly placed in a regional stratigraphic context. Herein, we distinguish this basal siltstone unit of the Ogallala Group in the eastern Niobrara River Valley from the overlying sand-dominated strata of the Valentine Formation on the basis of lithologic characteristics, trends in organic-carbon δ13C chemostratigraphic profiles, and U-Pb dating of detrital zircons. This siltstone unit bears some similarities to the middle Miocene Fort Randall Formation in its type area, which lies ∼75 km to the northwest in the Bijou Hills of South Dakota. Organic δ13C chemostratigraphic profiles generated from outcrops and cores of the basal siltstone in Nebraska indicate that the study area consistently had C3-dominated paleofloras while it was deposited, presumably in the middle Miocene. The youngest detrital zircons from the siltstone-dominated unit were probably deposited directly onto ancient landscapes by supervolcanic airfall events originating some 1,500 km to the west near the intersection of the boundaries of present Oregon, Nevada, and Idaho. These youngest zircons yield a maximum depositional age of ∼15 Ma. This age is in general agreement with the Barstovian (Ba2) mammal biostratigraphic age of the Fort Randall Formation in South Dakota. It is also significantly older than the ∼13 Ma youngest single grain zircon we recovered from sands of the overlying Valentine Formation. Thus, we propose that our integrated geochronologic and chemostratigraphic approach can date Late Cenozoic strata with constraints on the order of 1 m.y., portending broad applicability of our methods in reducing the uncertainties in dating terrigenous sediments in continental basins.

Petrophysical Evaluation and Hydrocarbon Potentials of the Belayim Formation of Middle Miocene Successions in Tawilla West Oilfield, Gulf of Suez, Egypt.

Petrophysical Evaluation and Hydrocarbon Potentials of the Belayim Formation of Middle Miocene Successions in Tawilla West Oilfield, Gulf of Suez, Egypt.

Catching the cooling after the Middle Miocene Climatic Transition at a back-arc basin of the West Pacific based on sublittoral ostracod assemblages

Catching the cooling after the Middle Miocene Climatic Transition at a back-arc basin of the West Pacific based on sublittoral ostracod assemblages

Seawater Lead Isotopes Record Early Miocene to Modern Circulation Dynamics in the Pacific Sector of the Southern Ocean

AbstractThe Antarctic Circumpolar Current (ACC) is Earth's largest current flowing around Antarctica at all depths and connecting major ocean basins, thus representing an important component of Earth's climate. However, the timing and key controls determining ACC flow path and its strength as a function of past climatic boundary conditions that ultimately resulted in its modern configuration remain unclear due to major uncertainties in paleoceanographic and tectonic reconstructions. Here we present a unique high‐resolution laser ablation‐derived late Cenozoic seawater lead isotope record obtained from a hydrogenetic ferromanganese crust from the Pacific sector of the Southern Ocean. Our Pb isotope data reveal that the ACC has experienced five stable circulation states since the early Miocene which were separated by four major transitions observed at 17.5‐14.6, 12, 10 and 5 Ma. We suggest that the relatively abrupt transitions between ACC circulation state were mainly induced by tectonic changes, whereas the impact of climatic changes was of secondary importance. According to our data the modern ACC configuration formed 5 million years ago, likely in response to the closure of the Panama Seaway. Since the Drake Passage (DP) has already been an open seaway since at least the late Miocene, our results demonstrate that DP opening was not the only factor affecting past ACC circulation. Our data also show that changes in the latitudinal position of the ACC were linked to the middle Miocene waxing and waning of the Antarctic ice sheets, which emphasizes the ACC's critical role as a key control of Antarctic glaciation.

Observations on palynology of the Tukau Formation in northwest Sarawak, Malaysia

This palynological study analysed 15 samples of the Tukau Formation, comprising intensely bioturbated sandy mudstone and organic-rich mudstones. Diverse vegetation types, including hinterland, mangroves, back mangroves, and montane regions, characterise the landscape of the region during the Tukau sediment deposition. Certain palynomorph types, such as Rhizophora type, Laevigatosporites sp., Elaeocarpus type, Euphorbiaceae, and Verrucatosporites usmensis (Stenochlaena), dominated the pollen assemblage, which represents the ancient landscape at that time. The influx of non-mangrove palynomorphs from the hinterland, likely transported by water, underscores the role of fluvial processes in controlling pollen distribution. Notably, the presence of age-specific marker pollen, such as Florschuetzia levipoli, Florschuetzia meridionalis, and Florschuetzia trilobata, confirms the age of the formation as Middle Miocene or younger. The presence of Acrostichum aureum pollen suggests a warm and humid tropical climate. Recognition of mangrove pollen from both front and back mangrove vegetation suggests deposition in the seaward region of the coast with significant tidal influences.

Palynology of Late Oligocene to Pliocene succession in Temana Field of Balingian Province, offshore Sarawak

Palynological records in Late Cenozoic succession from two Temana wells were reviewed and investigated for palynomorph assemblages, biostratigraphic correlation and age dating, as well as for paleoenvironment and paleoclimate interpretation. The data indicates abundant and diverse pollen and spores deposited in marginal marine with tidal influence setting. Three main palynomorph assemblages were identified from the Temana wells: (1) Zone-1 (dated as Late Oligocene), characterized by abundant Florschuetzia trilobata and dominant montane and seasonal elements such as Picea, Tsuga and Pinus, (2) Zone-2 (Early to Middle Miocene), dominated by Kerapah Casuarina-type pollen and characterized by increasing abundance of Rhizophoraceae mangrove pollen. Zone-2 can be further differentiated into Subzone-2a and Subzone-2b based on later appearance of Florschuetzia levipoli, and (3) Zone-3 (Late Miocene to Pliocene) occurring above a major angular unconformity is marked by a high percentage of the rainforest pollen Rubiaceae and a minor increase in seasonal elements. The interpreted paleoclimate inferred from temporal variations in hinterland-derived pollen shows cyclical pattern from seasonally dry climate in the Oligocene to warm and ever-wet climate, marked by the growth of Kerapah peat swamp during Early to Middle Miocene, and finally a prolong humid climate characterized by rainforest vegetation with minor intermittent seasonality since Late Miocene/Pliocene.

Hybrid turbidite-contourite system on the upper-slope continental margin of the offshore southern Tanzania

Cretaceous-Cenozoic hybrid turbidite-contourite (HTCs) systems on the upper-slope region of the northern Rovuma Basin, southern offshore Tanzania have been poorly studied. HTCs have been widely studied from several places due to their petroleum prospectivity, link to geohazards, and potential to help understand deep marine circulation processes and past climates. We have studied 3D seismic data into the northern Rovuma Basin to establish variation and orientation of seismic facies, architectural elements and geomorphologies (based on RMS amplitude maps) characterizing the Cretaceous-Cenozoic HTCs linked to channelized sediment transport and deposition. Two different migration patterns for channelized systems are recognized. They include Cretaceous-Middle Miocene and Middle Miocene-Holocene systems migrating toward SE and NW, respectively. Timing of change in migration trends coincides with change in traverse directions of major submarine channels that allowed sediment transportation by gravity flows. Trajectory of the submarine channels shifted from S-N to SW-NE and approximately W-E during the Middle Miocene, agreeing with the change in channel fills migration trends. The trajectory shift, for the revealed submarine channels was caused by tectonic activity linked to East African Rift System, so does the distribution and migration trends of the HTCs. The study area has hydrocarbon accumulations in the Oligo-Miocene sandstones containing HTCs characterized by a clearly defined depositional system with high RMS amplitudes. The Middle Miocene-Early Pliocene interval has a clear depositional configuration as well, but its low RMS amplitude indicates dominance of fine-grained HTCs with limited reservoir potential. The Late Pliocene-Holocene interval has very high RMS amplitude, but its chaotic configuration implies the presence of poorly sorted sedimentary fills having limited reservoir potential as well. This may be one of the reasons for hydrocarbon discoveries in the study area being limited within the Oligo-Miocene sandstones, and not the younger stratigraphic levels.

Combined geophysical approach as a tool to identify spatial groundwater aquifer distribution in structurally complex area. Case study of Kasserine aquifer system (central Tunisia)

Many countries are facing water resource scarcity. The Kasserine region in central Tunisia, is characterized with semi-arid climate and it is one of the most affected areas by drought in the country. Groundwater constitutes the main resource for drinking and irrigation water in Kasserine region. The groundwater aquifer levels are very structured, in this geologically complex zone, and their geometry needs to be well characterized. The present study aims to identify the geometry and the distribution of Campanian to Quaternary main aquifers in the Kasserine hydrogeological basin.In this study, we adopted a combined geophysical approach; we analyzed and interpreted gravity and seismic existent data in addition to acquiring conventional vertical electrical soundings. The gravity data analysis and mapping revealed that the study area is structured in numerous geological blocks. It highlighted the existence of two major negative gravity anomalies associated with the Megdoudech basin and the Kasserine graben. The gravity maps illustrated the role of the NW-SE Kasserine major Fault in the block structuring. The seismic reflection sections have emphasized the same structuring of the basins. They have exposed the fault network responsible for the compartmentalization of geological structures and which plays an important role in the hydrodynamics of the aquifer system in the region. The geoelectrical investigation highlighted the existence of three aquifer units: the sandy to sandy-clay levels of the Plio-Quaternary in the Kasserine graben, the sandstones of the middle Miocene with an average resistivity of 75 Ω m profiled at different depths, and the Campanian limestones with high resistivities in the Kasserine plateau.This combined approach is proven to be very useful to understand groundwater distribution in such geologically complex zones. The results will help the decision makers to ensure the safe management of groundwater resources especially in semi-arid and arid regions.