Cretaceous Research Articles

A passage through India: The biotic ferry model supports the build‐up of Indo‐Australian biodiversity of an ancient soil arthropod clade

AbstractAimScutigeromorpha is a globally distributed, ancient group of centipedes with at least 400 million years of evolutionary history. We assess the biogeographic history of the order, with a particular focus on the Peninsular Indian Plate (PIP), a Gondwanan fragment. We hypothesize that continental vicariance explains the disjunct distribution of extant scutigeromorphs, that PIP scutigeromorphs are of ancient Gondwanan origins, and that East Gondwana vicariance explains the diversification of the subfamily Thereuoneminae into its Asian and Australian clades.LocationGlobal.TaxaCentipedes, Scutigeromorpha.MethodsWe use a novel molecular dataset sampled across the PIP and a global sequence database representing the geographic distribution of all families and subfamilies. We employ molecular phylogenetic analyses on two mitochondrial and three nuclear markers, molecular species delimitation and ancestral range estimation to reconstruct biogeographic history.ResultsAncestral scutigeromorphs were likely widely distributed across Gondwana and diverged prior to any continental vicariance. Their subsequent biogeography is shaped by continental vicariance, long‐distance dispersal and jump dispersal, indicating an ability to colonize areas far from their ancestral range. The PIP emerged as the ancestral range of Thereuoneminae, which started diversifying during the Cretaceous Period. Subsequent in‐situ diversification within the PIP and dispersals into Asia, Australia and the Pacific Islands best explained the extant distribution of Thereuoneminae, more so than East Gondwana vicariance.Main ConclusionsThe in‐situ diversification of PIP species and their ancient divergence suggest they represent Gondwanan relicts in a landmass whose biota is primarily dispersal‐driven. A single dispersal event from the PIP generated most of the extant diversity in Australia, another Gondwanan fragment. Furthermore, the discovery of 11 putative species from the PIP and the Andaman Islands, five times more than was known, highlights the Wallacean and Linnean shortfalls in tropical Asia.

The Campanian-Maastrichtian benthic foraminiferal assemblages at the Elles section (Tunisia): A perspective for paleoenvironmental, paleobathymetric and sea-level fluctuation reconstruction

The Late Cretaceous Period experienced prevailing hothouse conditions that were characterized by relatively elevated atmospheric pCO2 concentrations, high global mean sea level and mostly lacking ice sheets. These conditions were interrupted by an overall global decreasing trend in temperature during the Campanian-Maastrichtian interval (83.65 to 66.04 Ma). The Upper Cretaceous sedimentary successions in Tunisia (southwestern Tethyan Ocean) like at the Elles section are regarded as unique archives for investigating paleoenvironmental and paleoclimatic changes, as well as constrain oscillations of sea-level. Here, we perform high resolution quantitative analysis of the benthic foraminiferal assemblages in the Campanian-Maastrichtian interval at the Elles section in order to infer palaeoenvironmental and paleobathymetric changes in relative sea-level. The Campanian succession (Abiod Fm.) is inferred to be deposited at upper to middle bathyal (i.e., 540–675 m) and is characterized by prevailing well‑oxygenated conditions and low organic matter flux to the seafloor. The Campanian/Maastrichtian transition-coincides with the lowermost part of the El Haria Fm. deposited in outer neritic to upper bathyal settings under oligotrophic, well‑oxygenated and reduced productivity conditions. Shallower depositional setting (i.e., 436–515 m) is inferred for the Maastrichtian succession (El Haria Fm.) that is also characterized by a lowering in oxygen availability at the seafloor associated with an increase of organic matter. Eight main sea-level regressions (four in the Campanian, one at the Campanian-Maastrichtian transition and three in the Maastrichtian) have been identified and biostratigraphically constrained. These sea-level regression events are mostly accompanied by a negative excursion carbon isotope (δ13C) and their stratigraphical positions appear to be quite consistent with those previously recognized at the nearby El Kef section.

Evolution of a confined gravelly river to a braided-meandering river in the Late Cretaceous Khasi group, southern Shillong plateau, NE India

This paper intends to unravel the depositional condition of the Basal Conglomerate/Jadukata Formation and the Lower Mahadek Formation in southern Shillong Plateau, NE India deposited during the Late Cretaceous period. The studied succession is entirely siliciclastics in composition and was built up on the Precambrian basement rocks. State-of-art facies analysis and palaeocurrent evidence helped us to reconstruct the palaeogeography and palaeoenvironment. The facies tracts reveal that frequent hyperconcentrated mass flow deposits dominated the proximal part of the river channels. Gradually, the river evolved to a sandy braided and finally mud-dominated, meandering system. The river channel changed its pattern through onlapping and progressive elimination of the accommodation space created by the tectonic subsidence/upliftment. Major shifts in palaeocurrent direction at different stages of the river evolution confirm the role of tectonics on the river channel evolution. QFL detrital modes of the sandstones reflecting lithic wacke composition and the recycled orogeny corroborate the interpretation. Rapid lateral and vertical facies transition suggests a pull-apart type basin due to ongoing rifting. Geochemical analyses also show signatures of the overlapping tectonic conditions supporting the pull-apart basin model.

Organic richness and maturity modeling of cretaceous age Chichali shales for enhanced hydrocarbon exploration in Punjab platform, Pakistan

This study employs comprehensive source rock evaluation using seismic inversion, rock-eval pyrolysis, organic petrography and basin modeling techniques. The kerogen type is determined by using the Van Krevelen diagram, confirming Bahu-01, Nandpur-01 and Zakria-01 wells have kerogen type III, whereas Panjpir-01 well exhibits kerogen type II to III. The TOC was calculated using core data from (34) samples by employing organic geochemistry technique and post stack seismic inversion, applied on 2D seismic data. Bahu-01 well indicates poor source rock potential, with an average TOC value of 0.34%. In contrast, Panjpir-01 and Nandpur-01 wells represent moderate to good organic richness, with average TOC values of 1.25% and 1.36%, respectively. However, Zakria-01 well with a TOC of 0.72%, exhibits fair organic richness. The Maturity estimation from organic petrography and basin modeling reveals that the Bahu-01, Panjpir-01, and Nandpur-01 wells have average vitrinite reflectance (%Ro) values below 0.50, indicating immature source rock. In contrast, the average %Ro value for the Zakria-01 well is 0.63, confirming the source maturity in the early oil window, with peak generation occurring during Eocene age. Finally, the source rock evaluation proves the source is mature in the western part only and future hydrocarbon exploration should be focused in the western area. The integrated source rock evaluation approach is novel in Punjab Platform. The diverse methodologies enhanced our understanding about source rock characteristics for pursuing hydrocarbon resources. An integrated approach will also provide valuable insights for hydrocarbon exploration in numerous other basins worldwide.

Paleoseamounts in Yarlung Zangbo suture zone reveal dynamic processes of the Early Cretaceous Neo-Tethys lithosphere

Dynamic processes of the oceanic crust of seamounts trapped in continental sutures are poorly understood. The discovery and analysis of seamount sequences in the Yarlung Zangbo suture zone allowed us to detect vertical lithospheric movements of the eastern Neo-Tethys Ocean. In this study, we used petrological, geochemical, facies, paleontological, and stratigraphic methods to study composite blocks of mafic and sedimentary rocks in the Zhongba area of Xizang, China. Radiolarian fossils indicate an (early) Early Cretaceous age. Petrofacies and geochemistry show that most basalts occur as pillow lava and are enriched in light rare earth elements and high field strength elements, which suggests an oceanic-island basalt tectonic setting. Sedimentary lithofacies are grouped into breccias, shales, cherts, and limestones (ooid and cortoid grainstone microfacies). Three types of contact between basaltic basements and caps were identified as regular, talus, and erosive. These results demonstrate that two more superposed seamounts exist in the western Yarlung Zangbo suture zone than was known previously, and they comprise at least eight seamount sequences of basalts to sediments. Cap lithofacies and seamount textures illustrate that overall, the Zhongba paleo-seamounts record multiple cycles of abrupt deepening to shallowing, with water depth variations of ∼3000 m to ∼5 m due to multiple episodes of quick subsidence and uplift of seamounts (lithospheric “ups and downs”). The model of oceanic bypass recurrence and plume rejuvenation is hypothesized to explain the dynamic subsidence and uplift. While plume activities produced the mafic basement and considerable buoyancy-related lift, oceanic crust bypassed drift, created distance from the plumes, and led to cooling, loss of buoyancy, and rapid subsidence. This model provides a new approach to interpret the evolution of oceanic crusts that have disappeared.

Facies distribution, paleoenvironment and hydrocarbon potential of Kanawa Member of Pindiga Formation, Gongola Basin, Northern Benue Trough, Nigeria

The Gongola sub-basin is a frontier inland sedimentary basin consisting of Cretaceous to Tertiary sediments, believed to have been deposited in continental to coastal shallow marine complex. The Kanawa Member of Pindiga Formation is a sequence of limestone and shale. Sedimentology, facies analysis, biostratigraphy, thermal maturity assessment and kerogen typing were conducted on these strata to determine the facies, facies associations, facies successions, paleoenvironment, age, and hydrocarbon generation potential. The studied sequences are of Turonian–Santonian age, deposited due to a major transgression of the basal part of the Pindiga Formation. The shale-limestone series of the Kanawa Member is interpreted as lagoon-to-shallow marine deposits of a carbonate ramp depositional system. The sediments consist of mainly wackestone and packstone facies and shallow marine foraminiferal, suggesting that the Kanawa Member was deposited under low-energy condition. The presence of Ammobaculites subcretacea, Haplophragmoides bauchensis, Haplophragmoides pindigensis, Haplophragmoides excavata, Ammobaulites pindigensis, Ammobaculites bauchensis, Ammobaculites gombensis, Ammobaculites benuensis Ammoastuta nigeriana, Reophax guineana and Miliammina pindigensis foraminiferal assemblages, indicating Late Cretaceous age. Hydrocarbon potential is interpreted to be gas prone although, minor oil could be expected. These correspond to temperature range (TAI values) of 60 to 75 indicating thermally matured for both oil and gas generation.

The Volcanic Rocks and Hydrocarbon Accumulation in the Offshore Indus Basin, Pakistan

To analyze the impact of volcanic rocks in the Offshore Indus Basin on hydrocarbon reservoir formation, seismic data interpretation, seismic data inversion, and sea–land correlation analysis were carried out. The results show that, longitudinally, volcanic rocks are mainly distributed at the top of the Cretaceous system or at the bottom of the Paleocene, and carbonate rock platforms or reefs of the Paleocene–Eocene are usually developed on them. On the plane, volcanic rocks are mainly distributed on the Saurashtra High in the southeastern part of the basin. In terms of thickness, the volcanic rocks revealed by drilling in Karachi nearshore are about 70 m thick. We conducted sparse spike inversion for acoustic impedance in the volcanic rock area. The results show that the thickness of the Deccan volcanic rocks in the study area is between 250 and 750 m which is thinning from southeast to northwest. Based on sea–land comparison and comprehensive research, the distribution of volcanic rocks in the Indian Fan Offshore Basin played a constructive role in the Mesozoic oil and gas accumulation in the Indus offshore. Therefore, in the Indian Fan Offshore Basin, attention should be paid to finding Mesozoic self-generated and self-stored hydrocarbon reservoirs and Cenozoic lower-generated and upper-stored hydrocarbon reservoirs.

Lu-Hf and U-Pb dating of the Zayanderud eclogites: Implications for Jurassic subduction initiation along the Neotethys margin in Iran

The time at which the Neotethys Ocean started to subduct along the southern margin of Eurasia within Iran has been debated in recent years. This margin, referred to as the Sanandaj-Sirjan Zone (SaSZ), features a series of Jurassic calc-alkaline igneous formations which were emplaced at c. 170 Ma. However, an alternative model suggests that subduction initiation occurred during the Cretaceous period. To address this age controversy, we utilized the Lu-Hf isochron method and employed SIMS U-Pb zircon and rutile geochronology to determine the metamorphic history of the earliest known Neotethyan eclogite outcrop along the upper Zayanderud River section of the SaSZ. Two eclogites separated by ∼25 km yielded Lu-Hf garnet dates of 175.1 ± 1.0 Ma and 172.5 ± 0.6 Ma. Rare <20 μm eclogitic zircon crystals in one of the eclogites are strongly zoned and yielded U-Pb dates for which a 177 ± 10 Ma rim age was deconvolved. The relatively low Dy/Yb of these zircon rims suggests that they crystallized prior to garnet formation, or retrograde in disequilibrium with garnet. Homogeneous U-Pb rutile ages averaging 162 ± 7 Ma are only marginally younger than the Lu-Hf garnet ages, consistent with the petrographic observation that rutile is predominantly found in the matrix or within garnet rims, and open-system behavior of radiogenic Pb during cooling. The newly obtained ages are close to previously published 40Ar/39Ar phengite dates and indicate a narrow time window during the Middle Jurassic for deep burial within a subduction channel, followed by eclogitization and rapid exhumation. These new constraints on the metamorphic history support subduction initiation along the SaSZ margin in the Jurassic period.

Cretaceous turtle tracks from central and southern Mexico

Turtle tracks are relatively common in Laurasia during the Mesozoic. In Mexico, Cretaceous turtle tracks have been reported in Coahuila, Zacatecas, and Puebla. Here we describe 20 turtle tracks from the Early Cretaceous Jaltepetongo formation of Oaxaca and the Early Cretaceous San Juan Raya Formation of Puebla. The morphology of the tracks shows that the producers were engaged in different activities, such as swimming, bottom walking, or that were partially buoyant. The presence of turtle tracks indicates marginal environments in both geologic formations. The turtle tracks from San Juan Raya in Puebla add to the diverse ichno-assemblage of dinosaur, pterosaur, turtle, and invertebrate tracks that have been already recorded in the area. The turtle tracks from Oaxaca are the most southern in North America of Early Cretaceous age.

The Phylogenetic Relationships of Major Lizard Families Using Mitochondrial Genomes and Selection Pressure Analyses in Anguimorpha.

Anguimorpha, within the order Squamata, represents a group with distinct morphological and behavioral characteristics in different ecological niches among lizards. Within Anguimorpha, there is a group characterized by limb loss, occupying lower ecological niches, concentrated within the subfamily Anguinae. Lizards with limbs and those without exhibit distinct locomotor abilities when adapting to their habitats, which in turn necessitate varying degrees of energy expenditure. Mitochondria, known as the metabolic powerhouses of cells, play a crucial role in providing approximately 95% of an organism's energy. Functionally, mitogenomes (mitochondrial genomes) can serve as a valuable tool for investigating potential adaptive evolutionary selection behind limb loss in reptiles. Due to the variation of mitogenome structures among each species, as well as its simple genetic structure, maternal inheritance, and high evolutionary rate, the mitogenome is increasingly utilized to reconstruct phylogenetic relationships of squamate animals. In this study, we sequenced the mitogenomes of two species within Anguimorpha as well as the mitogenomes of two species in Gekkota and four species in Scincoidea. We compared these data with the mitogenome content and evolutionary history of related species. Within Anguimorpha, between the mitogenomes of limbless and limbed lizards, a branch-site model analysis supported the presence of 10 positively selected sites: Cytb protein (at sites 183 and 187), ND2 protein (at sites 90, 155, and 198), ND3 protein (at site 21), ND5 protein (at sites 12 and 267), and ND6 protein (at sites 72 and 119). These findings suggested that positive selection of mitogenome in limbless lizards may be associated with the energy requirements for their locomotion. Additionally, we acquired data from 205 mitogenomes from the NCBI database. Bayesian inference (BI) and Maximum Likelihood (ML) trees were constructed using the 13 mitochondrial protein-coding genes (PCGs) and two rRNAs (12S rRNA and 16S rRNA) from 213 mitogenomes. Our phylogenetic tree and the divergence time estimates for Squamata based on mitogenome data are consistent with results from previous studies. Gekkota was placed at the root of Squamata in both BI and ML trees. However, within the Toxicofera clade, due to long-branch attraction, Anguimorpha and (Pleurodonta + (Serpentes + Acrodonta)) were closely related groupings, which might indicate errors and also demonstrate that mitogenome-based phylogenetic trees may not effectively resolve long-branch attraction issues. Additionally, we reviewed the origin and diversification of Squamata throughout the Mesozoic era, suggesting that Squamata originated in the Late Triassic (206.05 Mya), with the diversification of various superfamilies occurring during the Cretaceous period. Future improvements in constructing squamate phylogenetic relationships using mitogenomes will rely on identifying snake and acrodont species with slower evolutionary rates, ensuring comprehensive taxonomic coverage of squamate diversity, and increasing the number of genes analyzed.

Solid bitumen Rhenium-Osmium (Re–Os) isotope geochronology and existing problems: Sampled of Sinian-Cambrian gas reservoir in Sichuan Basin, China

Understanding the key timings related to petroleum evolution is crucial for optimizing exploration targets and assessing oil/gas resources, attract petroleum geologists’ attention worldwide. Recently, hydrocarbon (oil and bitumen) Re–Os isotope dating has been innovatively applied to constrain the timing related to oil/gas generation, however, the resulting Re–Os isochron ages can be complex and challenging to interpret. This study utilizes various geochemical and geochronological data from Sinian to Cambrian natural gas reservoirs in the Sichuan Basin to reconstruct the hydrocarbon evolution process and discuss the significance of different bitumen Re–Os dating results. The gas accumulation in the Sinian-Cambrian reservoirs experienced four stages of evolution: (1) initial oil generation during the Ordovician to Silurian periods, (2) secondary oil generation during the Triassic period, (3) gas generation through thermal cracking of liquid oil from the Jurassic to Cretaceous periods, and (4) gas reservoir redistribution since the late Cretaceous. The Re–Os dates (ca. 485 Ma) of low maturity and biodegraded bitumen from the western Sichuan Basin record the oil generation during the Ordovician before the Caledonian tectonic event. The Re–Os dates (ca.184–128 Ma) of highly mature bitumen associated with MVT Pb–Zn deposits in northern Sichuan Basin provide insights into both liquid oil-cracking and thermochemical sulfate reduction (TSR) processes. The complex Re–Os dates (ca.414 Ma, ca.154 Ma) of highly mature bitumen from the central Sichuan Basin may represent different periods related to either oil or gas generation. Future studies should explore the genetic type, maturity, thermal cracking, or TSR degrees of bitumen to better understand the significance of Re–Os dates.

2D Seismic Structural Study of the Area Between Halfaya, Noor and Amara Oil Fields, Southeastern Iraq

The study area is located in the Missan government in southeastern Iraq, including oilfields (Halfaya, Noor, and Amara). The study area is about 966 Km2. Based on the 2D seismic reflection interpretation, well-logs data (sonic and estimated density logs), and synthetic seismogram of well Am-2, two horizons were identified and picked (Nahr Umr and Shuaiba) within the Lower Cretaceous age. For the picked reflectors, two-way time and depth maps were created to display the subsurface's structural makeup. The structural interpretation shows two structural axes in the study area. The first is the Halfaya-Amara axis, whose direction is WNW-ESE corresponding with the Amara structure. This axis deviates southeast due to the tectonic effect at the Halfaya structure. Another tectonic force affected the Halfaya structure in the northwest-southeast direction leading to the appearance of a branch of a convex extension towards the north from the middle of the Halfaya structure, completing this branch to a structural closure as nose towards the Noor structure in the northern part of the study area. The second axis of Halfaya-Noor oilfields trending northwest-southeast direction.

Early Cretaceous troodontine troodontid (Dinosauria: Theropoda) from the Ohyamashimo Formation of Japan reveals the early evolution of Troodontinae

A new troodontid dinosaur, Hypnovenator matsubaraetoheorum gen. et sp. nov., is described based on an articulated postcranial skeleton recovered from the fluvial deposits of the Albian Ohyamashimo Formation of the Sasayama Group in Tambasasayama City, Hyogo Prefecture, Japan. Hypnovenator is distinguished from other troodontids by four autapomorphies and a combination of additional features. Our phylogenetic analysis positions Hypnovenator as the oldest and one of the most basal troodontines, forming a clade with Gobivenator mongoliensis. The discovery of Hypnovenator suggests that small-bodied maniraptorans with a sleeping posture were common not only in environments with volcanic and eolian events or alluvial systems but also in fluvial systems. Geometric morphometric analysis of manual ungual phalanges shows that manual ungual phalanges I and III of Hypnovenator exhibit considerable morphological variation but are functionally similar, which differs from those of non-troodontine troodontids, reflecting the transition of manual motion within Troodontinae. Hypnovenator also has mosaic features in the pes related to cursoriality. This study reveals that asymmetrical arctometatarsus occurred by the Albian, and some morphological changes, such as shorter digit IV than digit III and non-ungual phalanges of digits III with roller joints and digit IV with weakly ginglymoid articulation, arose during the early Late Cretaceous.

Monchique alkaline magmatic intrusion (SW Iberia): Geophysical modeling and relationship with active seismicity and hydrothermalism

Monchique is a prominent 902 m topographic high in SW Iberia, which stands out in the general flat landscape of southern Portugal. It lies to the north of the Africa-Eurasia plate boundary, which locally accommodates a slow oblique convergence (∼5 mm/yr). Monchique comprises alkaline magmatic rocks of Late Cretaceous age, intruded in a post-rift context. It hosts the most active seismic cluster in mainland Portugal and important hydrothermal activity.This work investigates the relationship between the alkaline intrusion, local seismicity and hydrothermalism.We present magnetic and gravity modeling based on new drone-borne magnetic data and ground gravity data. New magnetic mapping of Monchique shows a ∼ 15 km long dipolar anomaly with 7–8 km wavelength and 2000 nT amplitude. 3D magnetic inversion models the main Monchique intrusion as a high-susceptibility body, 15 km long and 6 km wide, located below the Monchique mountain and extending 5–7 km depth. 2D forward modeling and geological interpretation further support the existence of ENE-WSW oriented dike-like gabbroic bodies that may extend deeper, around which syenite units have later emplaced.We relocate the seismicity using NonLinLoc and a 3D regional tomographic model, and find that earthquakes align along four main lineations that radiate outwards from the intrusion. We also find that most earthquakes cluster between 8 and 18 km depth, below the magmatic intrusion. The b-value at the core of the seismic cluster is higher than at the surrounding region, possibly related to the local hydrothermalism. We present five new focal mechanisms that are compatible with the regional stress field, supporting a regional tectonic control.The emplacement of the Monchique alkaline intrusion left fractures in the lithosphere that currently act as preferred pathways for fluids. In the context of the present-day stress field, the enhanced fracturing and fluid circulation facilitate the localization of small-magnitude earthquakes.

The origin and migration laws of hydrocarbons in uranium‐bearing Luohe Formation, Pengyang area, SW Ordos Basin

The hydrocarbon activity in Pengyang area, situated in the southwestern Ordos Basin, is notably prominent. Investigation on the migration laws of hydrocarbons is imperative for comprehending the involvement in uranium mineralization. Based on the analysis of spatial distribution of hydrocarbon containing fluid and hydrocarbon generation conditions of sandstone in the Luohe Formation, the organic geochemical characteristics including hydrocarbon components, carbon isotopes and biomarker compounds were analysed. The research results indicate that: (1) hydrocarbon fluid activities in the Luohe Formation are predominantly observed in layers exhibiting higher uranium mineralization. The mudstone of the Luohe Formation had low organic matter content and low thermal maturity, which was not conducive to hydrocarbon generation. (2) Hydrocarbon‐containing fluid in the sandstone of Luohe Formation not only contained reducing gases such as methane and hydrogen but also chloroform asphalt components. The carbon isotopes of hydrocarbon in sandstone inform Luohe Formation resemble oil and gas in the Mesozoic. The biomarker parameter inferred that the parent rock of hydrocarbons in the Luohe Formation was formed under reducing and freshwater conditions, and hydrocarbon generation occurred at the mature stage. As above mentioned, a comparison was carried out between the affinity of hydrocarbon‐containing fluid in the Luohe Formation and different layers of hydrocarbon source rocks. The migration behaviour of hydrocarbon‐containing fluid in the Pengyang area has been summarized, and the involvement of hydrocarbon‐containing fluid in uranium mineralization has been discussed. The main concepts are as follows: the sedimentary environment and thermal evolution conditions of hydrocarbons in the sandstone of Luohe Formation resemble those of the primary hydrocarbon source rocks in the Yanchang Formation. The main hydrocarbon charging events in the Luohe Formation occurred before the Late Cretaceous period, which is primarily related to two hydrocarbon generation events from 130 to 100 Ma in the Yanchang Formation and fault conduits connecting the Triassic to the Cretaceous Strata. The hydrocarbon‐containing fluid released from Yanchang Formation migrating to the Luohe Formation provides reducing conditions for the precipitation of uranium in oxygen‐bearing water bodies.

The Kerguelen mantle plume activity in Sylhet Trap mafic rocks of Southern Shillong Plateau,NEIndia: Implications for its role in magmatism of eastern India

Mantle plumes related to Large Igneous Provinces have been linked to continental break‐up and validated by the outpouring of mafic‐ultramafic magmas that range from continental flood basalt magmatism to submarine plateau volcanism. This study presents a new set of geochemical and mineralogical data on mafic magmatic rocks from the Sylhet Trap of the Shillong Plateau, northeast India. The investigated mafic rocks (basalt and dolerite) are predominantly sub‐alkaline‐tholeiitic, composed of bytownite+labradorite and diopside+augite, with ophitic to sub‐ophitic and glomeroporphyritic textures, the dark interstitial region of much finer grains consisting of opaque minerals and devitrified glass. The mafic rocks of Sylhet Trap show light rare earth elements enrichment with (La/Yb)Nratio (1.92–2.86) and (La/Sm)Nratio (1.11–1.40), an almost flat pattern of heavy rare earth elements along with mild europium anomalies (Eu/Eu*= 0.94–1.11). Trace element characteristics suggest their affinity towards enriched mid‐oceanic ridge basalt and generated from low degree of partial melting of spinel source with minor involvement of crustal contamination. The similarity in geochemical characteristics of the investigated mafic rocks with the magmatism of Rajmahal Traps, eastern Peninsular India, Abor Volcanics, eastern Himalaya, along with Bunbury Basalt of western Australia and Cona Mafic exposed in southeastern Tibet, suggests their genetic linkage with mantle plume activities. Thus, we argue that the magmatic event of the Sylhet Trap is related to the Kerguelen mantle plume activity that played a significant role in the fragmentation of eastern Gondwana during the Lower Cretaceous period, giving rise to Greater India, Antarctica and northwest Australia.

Geochronology, Geochemical Characterization and Tectonic Background of Volcanic Rocks of the Longjiang Formation in the Lengjimanda Plate Area, Middle Da Hinggan Mountains

The Lengjimanda plate is situated in the middle section of the Da Hinggan mountains, in the eastern section of the Tianshan Xingmeng orogenic belt. To determine the formation age of the volcanic rocks in the Longjiang formation in this area, to explore their origin and tectonic background, and to reconstruct the geodynamic evolution of the region, this study conducted petrological, zircon U–Pb geochronological, geochemical, and isotopic analyses of the volcanic rocks in the Longjiang formation. The Longjiang formation’s volcanic rocks are primarily composed of trachyandesite, trachyte trachydacite, and andesite, which are intermediate basic volcanic rocks. They are enriched in large-ion lithophile elements, are depleted in high-field-strength elements, are significantly fractionated between light and heavy rare earth elements, and exhibit a moderate negative Eu anomaly in most samples. The results of the LA–ICP–MS zircon U–Pb dating indicate that the volcanic rocks in this group were formed in the Early Cretaceous period at 129.1 ± 0.82 Ma. The zircon εHf(t) ranges from +1.13 to +43.77, the tDM2 ranges from +655 to +1427 Ma, the initial Sr ratio (87Sr/86Sr)i ranges from 0.7030 to 0.7036, and the εNd(t) ranges from +2.1 to +6.6. Based on the geochemical compositions and isotopic characteristics of the rocks, the initial magma of the volcanic rocks in the Longjiang formation originated from the partial melting of basaltic crustal materials, with a source material inferred to be depleted mantle-derived young crustal. These rocks were formed in a superimposed post-collisional and continental arc environment, possibly associated with the Mongol-Okhotsk Ocean closure and the oblique subduction of the Pacific plate. This study addresses a research gap regarding the volcanic rocks of the Longjiang formation in this area. Its findings can be applied to exploration and prospecting in the region.

Plastome evolution of Engelhardia facilitates phylogeny of Juglandaceae

BackgroundEngelhardia (Juglandaceae) is a genus of significant ecological and economic importance, prevalent in the tropics and subtropics of East Asia. Although previous efforts based on multiple molecular markers providing profound insights into species delimitation and phylogeography of Engelhardia, the maternal genome evolution and phylogeny of Engelhardia in Juglandaceae still need to be comprehensively evaluated. In this study, we sequenced plastomes from 14 samples of eight Engelhardia species and the outgroup Rhoiptelea chiliantha, and incorporated published data from 36 Juglandaceae and six outgroup species to test phylogenetic resolution. Moreover, comparative analyses of the plastomes were conducted to investigate the plastomes evolution of Engelhardia and the whole Juglandaceae family.ResultsThe 13 Engelhardia plastomes were highly similar in genome size, gene content, and order. They exhibited a typical quadripartite structure, with lengths from 161,069 bp to 162,336 bp. Three mutation hotspot regions (TrnK-rps16, ndhF-rpl32, and ycf1) could be used as effective molecular markers for further phylogenetic analyses and species identification. Insertion and deletion (InDels) may be an important driving factor for the evolution of plastomes in Juglandoideae and Engelhardioideae. A total of ten codons were identified as the optimal codons in Juglandaceae. The mutation pressure mostly contributed to shaping codon usage. Seventy-eight protein-coding genes in Juglandaceae experienced relaxed purifying selection, only rpl22 and psaI genes showed positive selection (Ka/Ks > 1). Phylogenetic results fully supported Engelhardia as a monophyletic group including two sects and the division of Juglandaceae into three subfamilies. The Engelhardia originated in the Late Cretaceous and diversified in the Late Eocene, and Juglandaceae originated in the Early Cretaceous and differentiated in Middle Cretaceous. The phylogeny and divergence times didn’t support rapid radiation occurred in the evolution history of Engelhardia.ConclusionOur study fully supported the taxonomic treatment of at the section for Engelhardia species and three subfamilies for Juglandaceae and confirmed the power of phylogenetic resolution using plastome sequences. Moreover, our results also laid the foundation for further studying the course, tempo and mode of plastome evolution of Engelhardia and the whole Juglandaceae family.

Phylogeny and diversification analyses of extant planthopper families (Hemiptera: Fulgoromorpha) based on a mitochondrial dataset reveal ancient lineages originating during the Jurassic and originally feeding on gymnosperms

Abstract Phylogenetic analyses of planthoppers were conducted using a mitogenome dataset to examine the evolutionary relationships of current families based on both maximum likelihood (ML) and Bayesian inference methods. Delphacoidea, including Cixiidae and Delphacidae, and Fulgoroidea, including all other families, were consistently identified as monophyletic groups. However, Nogodinidae displayed a polyphyletic pattern, with various lineages emerging sister to several issidoid families. Variations were observed across different analyses in the positioning of (Dictyopharidae + Fulgoridae) and the relationships of Ricaniidae sister either to Issidae or to (Flatidae + Acanaloniidae). Several statistical tests indicate that the ML topology has the highest level of statistical confidence. The (Dictyopharidae + Fulgoridae) clade is best positioned as sister to (Derbidae + (Achilidae + (Tropiduchidae + other “higher” planthoppers families))) and the Ricaniidae as sister to (Flatidae + Acanaloniidae). With 13 fossil calibration points, origin times for Delphacoidea and Fulgoroidea were dated back to the Late Permian, approximately 257.46 million years ago. Delphacidae and Cixiidae split during the Late Triassic, while Fulgoroidea diversified earlier during the Middle Triassic. Divergence and diversification times are also provided for all other extant planthopper families. These results suggest that Delphacoidea and Fulgoroidea likely diverged from the older planthopper fossil families prior to the emergence of angiosperms and may have initially fed on gymnosperms and ancient ferns. The diversification of extant planthopper families occurred during the Jurassic and Cretaceous periods, influenced by evolving climatic conditions, the decline in gymnosperms, and the increasing diversity of angiosperm plants.

Sauropod dinosaur tracks from the Purbeck Group (Early Cretaceous) of Spyway Quarry, Dorset, UK.

Dinosaur tracks have a long history of discovery and study in the UK, but track sites for sauropodomorph dinosaurs-the group that included the giant, graviportal herbivorous sauropods-are comparatively rare. Here, we provide a description of a sauropod dinosaur track site at Spyway Quarry in Dorset, southern England. The tracks at Spyway were discovered in the late 1990s and occur in the Stair Hole Member of the Durlston Formation in the Purbeck Limestone Group, of earliest Cretaceous age. More than 130 individual tracks of large sauropod dinosaurs are present at the site, but they are generally poorly preserved and do not form clear trackways, although it is likely that they represent multiple individuals. They provide further evidence for sauropods living in or passing through coastal lagoonal environments. Although poorly preserved, Spyway represents the largest in situ dinosaur track site currently accessible within the Purbeck Group, with considerable potential for further discoveries through ongoing quarrying in the surrounding area.