Early Jurassic Research Articles

Mesozoic tectonic evolution of the northeastern margin of the North China Craton: Insight from the mountain-basin system

The Mesozoic era marks a pivotal transformation in the tectonic framework of the North China Craton, particularly involving the eastern margin, where multiple geodynamic domains converge. Despite its significance, the interplay and transitional processes among the Paleo-Asian, Paleo-Tethys, and Paleo-Pacific oceanic domains in this region remain inadequately resolved. This study focuses on the Qinglong region, a key tectonic transitional zone superimposed along the northeastern North China Craton margin, to reconstruct its Mesozoic tectonic and topographic evolution triggered by the interplay of multiple tectonic domains. We integrated provenance analysis, multimethod geochronology, low-temperature thermochronology, and thermal history modeling to unravel the multistage tectonic history of the region. The results from zircon and apatite U-Pb dating indicate a Neoarchean (ca. 2500 Ma) crystallization age and significant Paleoproterozoic (1900−1600 Ma) tectono-thermal overprinting. Apatite fission-track ages further show that the basement experienced a cooling event from the late Early Cretaceous to the Late Cretaceous (119−60 Ma), highlighting a prolonged, multistage tectonic evolution. The sedimentary provenance analysis demonstrates a notable shift in sedimentary sources due to geodynamic domain transition from the local Qinglong region and the western Trans−North China orogen in the Early Jurassic, to the local Qinglong region and the eastern Jiao−Liao−Ji Belt in the Early Cretaceous. Thermal history modeling further delineates a five-stage tectonic evolution from the Late Triassic to the Late Cretaceous, revealing alternating compressional and extensional regimes that are associated with the closure of the Paleo-Asian Ocean (to the north) and the Paleo-Tethys Ocean (to the south), followed by the subduction of the Paleo-Pacific plate (to the east). Of particular significance is the topographic inversion during the Early Cretaceous, which marks a critical transition from earlier collisional regimes dominated by the closure of the Paleo-Asian Ocean and Paleo-Tethys Ocean to the subduction regime of the Paleo-Pacific plate. These results provide new insights into the geodynamic mechanisms underlying the formation and evolution of the eastern North China Craton’s topography, broadening our understanding of Mesozoic tectonic processes in the northeastern North China Craton and their role in shaping the tectonic framework of East Asia.

Earliest Jurassic plant assemblages from Sweden reveal a low-diversity ginkgoalean and cheirolepid flora dominating the post-extinction landscape.

Rich Triassic-Jurassic plant assemblages from Skåne, southern Sweden, have been documented extensively over the past two centuries. However, no macrofloras from the lowermost part of the Helsingborg Member (Lower Jurassic) have been forthcoming and thus the age of the successions has not been well-constrained. Here we systematically describe and assess the palaeoecology and age of a newly discovered flora from the Boserup beds at Norra Albert Quarry, Skåne. Plant macrofossils were examined using macrophotography, fluorescence microscopy, and scanning electron microscopy (SEM). Palynological analysis of the strata hosting the macroflora contributed to the palaeoenvironmental interpretations and refined the age of the deposits. The low-diversity post-extinction recovery forests of the earliest Jurassic were dominated by ginkgoopsids, cheirolepid conifers, and ferns, growing under seasonal mesothermal conditions. Dispersed charcoal indicates wildfires were present in the landscape at this time. Despite the poor preservation of the fossils, the Boserup beds flora provides a window into vegetation recovery in the immediate aftermath of the end-Triassic extinction event. Initial recovery is characterised by the presence of needle- and scale-leafed seed plants (notably czekanowskialeans and Brachyphyllum producing Classopollis), along with a range of ground ferns.

On the Incompleteness of the Coelacanth Fossil Record

This study conducted a spatiotemporal review of the coelacanth fossil record and explored its distribution and diversity patterns. Coelacanth research can be divided into two distinct periods: the first period, which is based solely on the fossil record, and the second period following the discovery of extant taxa, significantly stimulating research interest. The distribution and research intensity of coelacanth fossils exhibit marked spatial heterogeneity, with Europe and North America being the most extensively studied regions. In contrast, Asia, South America, and Oceania offer substantial potential for future research. Temporally, the coelacanth fossil record also demonstrates significant variation across geological periods, revealing three diversity peaks in the Middle Devonian, Early Triassic, and Late Jurassic, with the Early Triassic peak exhibiting the highest diversity. With the exception of the Late Devonian, Carboniferous, and Late Cretaceous, most periods remain understudied, particularly the Permian, Early Jurassic, and Middle Jurassic, where the record is notably scarce. Integrating the fossil record with phylogenetic analyses enables more robust estimations of coelacanth diversity patterns through deep time. The diversity peak observed in the Middle Devonian is consistent with early burst models of diversification, whereas the Early and Middle Triassic peaks are considered robust, and the Late Jurassic peak may be influenced by taphonomic biases. The low population abundance and limited diversity of coelacanths reduce the number of specimens available for fossilization. The absence of a Cenozoic coelacanth fossil record may be linked to their moderately deep-sea habitat. Future research should prioritize addressing gaps in the fossil record, particularly in Africa, Asia, and Latin America; employing multiple metrics to mitigate sampling biases; and integrating a broader range of taxa into phylogenetic analyses. In contrast to the widespread distribution of the fossil record, extant coelacanths exhibit a restricted distribution, underscoring the urgent need to increase conservation efforts.

Provenance and tectonic settings of late Triassic–Jurassic deposits in the Southwestern Yangtze block: evidence from the geochemistry, SW China

During the Late Triassic to Jurassic, the western Yangtze Block transitioned from marine carbonate deposits to terrestrial detrital deposits. There are different views on the orogen evolution of the western margin of the Yangtze Block, such as whether the Longmenshan Thrust Belt was uplifted in the Late Triassic or Early Jurassic, and when the Yangtze Block began to receive the source from Yidun Terrane. In this paper, whole-rock elemental compositions and zircon U–Pb ages and Hf isotope data from the Upper Triassic to Jurassic successions are introduced. The whole-rock elemental compositions reveal that the clastic rocks were deposited in a collisional setting and were derived mainly from intermediate–felsic magmatic rocks and recycled sediments. The Upper Triassic zircon sample shows a single age peak at ~ 831 Ma. The three Jurassic samples show similar age patterns with four main age populations (e.g., 200–500 Ma, 788–834 Ma, 1863–1875 Ma, and 2462–2531 Ma). The results revealed that the Kangdian Palaeo-land was the main provenance area in the Late Triassic. In contrast, in the Early Jurassic (~ 198.7 Ma), the Longmenshan was massively uplifted, and the recycled sediments from the Longmenshan, Songpan–Ganzi Terrane and Yidun Terrane provided large amounts of detrital material to the southwestern Yangtze Block. Volcanic rocks from the Yidun Terrane also provided a partial source for the southwestern Yangtze Block. In the Middle Jurassic, owing to the weathering and erosion of the Longmenshan Thrust Belt in the Early Jurassic, the provenance supply in Longmenshan decreased, and the provenances from the Yidun Terrane and the Songpan–Ganzi Terrane increased. In the Late Triassic to the Early Jurassic, the tectonic setting of the southwestern Yangtze Block may have changed from a passive continental margin to a foreland basin.

Multicostate terebratulides (Brachiopoda, Early Jurassic) from the South and Eastern peri-Iberian paleomargins: paleobiogeographical and biostratigraphical perspectives in the westernmost Tethys Ocean

Abstract Lower Jurassic multicostate Terebratulida are substantiated in the Subbetic Domain and reported in the Iberian Range for the first time. Records of this clade are revised in the peri-Iberian platforms (Subbetic, Iberian Range, Gibraltar, North and NE Spain, Lusitanian basin) in order to evaluate their global pattern distribution across the Tethys Ocean. After a new tectonosedimentary analysis, marine swells are proposed as depositional scenarios for the assemblages containing Hesperithyris aff. sinuosa in the southernmost Subbetic paleomargin, sheding light to the intrincate paleogeography of this part from the Betic Range. In the Iberian Range, the same species and Merophricus? fimbrioides occurred in extensive flooding intervals arriving from the deepest marine populations. As results of taxonomic and paleobiogeographical analyses, two morphotypes, Merophricus- and Hesperithyris-type, are discriminated forming part of the westernmost Tethys migration route. It can be ascertained that their E-W Tethyan spreading was fulfilled for the Merophricus-type from the intra-Mediterranean basins to the westernmost arc of the Tethys Ocean, via the Betic–Gibraltar seaway, reaching the proto-Atlantic northwards (Lusitanian basin) and possibly the northern margin of the Iberian Massif and Western France. In contrast, Hesperithyris aff. sinuosa from the Iberian and Betic ranges correspond to the intra- and peri-Mediterranean Hesperithyris-type, with a different dispersal pattern. The only Lower Jurassic Hesperithyrys-type multicostate terebratulides reported in the boundaries of the NW-Boreal bioprovince derive from the Northeastern Iberian paleomargins, probably due to sporadic incursion events at transgressive episodes. The row of Subbetic epioceanic seamount stepping stones helped the Merophricus-type migration in the E-W Mediterranean route and their pivotal position facilitated the dispersal of both morphotypes via the epicontinental Iberian seaway. In the Subbetic, the Hesperithyris-bearing assemblages are recorded in the Pliensbachian Lavinianum Zone (Portisi and Cornacaldense subzones) equivalent to the basal part of the Margaritatus Zone (Stokesi Subzone) from the Iberian Range where the same species is now recorded, thus correlating the Southern epioceanic paleomargins with the Eastern epicontinental platforms. The origin and dispersal of the Merophricus-type around the Si–Pl boundary concurred with the Western Tethys early pre-rifting stage, and the pre-Domerian drowning of Tethyan platforms is synchronically consistent with the origin and spreading of the Hesperithyris-type.

An exceptional window into the Triassic-Jurassic boundary on the margins of the Ardenno-Rhenish Massif: stratigraphy and palaeontology of the Irrel section (Rhineland-Palatinate, Germany)

The Triassic-Jurassic (T/J) boundary witnessed one of the five major mass extinctions during the Phanerozoic, paving the way towards the evolution of modern ecosystems. However, the study of biotic change during this interval is hampered by the scarcity of outcrops exposing the T/J-boundary without major interruptions or abrupt facies change. Here, we present a previously undocumented succession of Rhaetian (Upper Triassic) to Hettangian (Lower Jurassic) strata, exposed on two sections along the banks of the river Prüm near the town of Irrel, Rhineland-Palatinate, Germany. The new succession holds an unusual palaeogeographic position squeezed between the Rhenish and London Brabant (including the Ardennes) massifs, thus filling a gap in the T/J-boundary record of the Central European Basin. It includes some unusual facies such as a thick and highly fossiliferous, conglomeratic bonebed close to the top of the middle Rhaetian and bituminous black claystones in the middle Hettangian. Finally, it stands out in yielding well preserved fossils of taxa that are rare or undocumented in the region. We provide a comprehensive account of the lithostratigraphy of the new succession and assess its biostratigraphic framework using ammonite, ostracod and palynomorph occurrences.

Jurassic Paleomagnetic Data From the Eastern Tethyan Himalaya Support a Smaller Greater India

Abstract Knowledge of the original dimension of Greater India in the Jurassic Period is critical for reconstructing the paleogeographic framework of Gondwana. However, two end‐member reconstructions for Greater India (≤1,000 or ≥2,000 km) exist in the Jurassic. Here, we conduct comprehensive petrographic, rock magnetic, and paleomagnetic studies on Lower to Middle Jurassic Lure Formation marlstones from the eastern Tethyan Himalaya. The new paleomagnetic data fulfill stringent quality criteria and provide a reliable Early Jurassic paleopole of 16.6°N/308.8°E, A95 = 1.2°, n = 396 (specimens), which constrains the Tethyan Himalaya to a paleolatitude of 31.8° ± 1.2°S at ca. 177.3 Ma. The overlap of this paleolatitude with the expected paleolatitude of India is consistent with a small Greater India (∼900 km) in the Jurassic. The improved estimate of the dimension of Greater India contributes to an updated reconstruction of the paleogeography of Gondwana during the Early Jurassic.

Geochemistry of the kaolinite-rich claystone in Western Iraq

It is important to spotlight the non-oil Iraqi wealth used in industry, including the kaolin clays in western Iraq, specifically in Anbar Governorate, where they are found in large quantities suitable for investment. This study focuses on the red kaolin clays found in the Hussainiyat Formation (Lower Jurassic) in the southeast of the Hussainiyat Valley. These clays are important in various industries, including ceramics, cement, and bricks. Geochemical analysis plays a an important role in determining the suitability of these clays for industrial use. Kaolinite was studied in the Northeastern Hussainiyat Area within the Hussainiyat Formation (Lower Jurassic). The presence of kaolinite and illite-smectite was noted, in addition to montmorillonite, quartz, hematite, and goethite. The concentrations of the main oxides in the study area reached Al2O3 23.35%, SiO2 51.33, Fe2O3 9.05%, MgO 1.9%, CaO 1.13%, K2O 1.34%, P2O5 0.04%, and LOI 10.2%. Aluminium in kaolin clay has a positive relationship with Cr2O3 and TiO2, a negative relationship with iron, potassium, magnesium, and sodium oxides, and a negative relationship with quartz, which increases with the decrease of these oxides. The deposits were chemically classified into shale and Fe-shale and formed in extensive weathering.

Revision of the Limoniidae Described from Issyk-Kul by Rohdendorf (Diptera; Lower Jurassic)

Revision of the Limoniidae Described from Issyk-Kul by Rohdendorf (Diptera; Lower Jurassic)

New occurrence of Ostracodes used as indications of paleoecology and age for Scots Bay Formation, Bay of Fundy, Canada

Fossils in the Jurassic Scots Bay Formation are rare but silicified, speciesinclude ostracodes, small gastropods, small clams, fragments of charophyte stems, andfreshwater stromatolites. The silicified ostracodes and algae are found in thin to thickbeds of mixed carbonate and siliciclastic units deposited in erosional paleotopographiclows on the top of the Early Jurassic North Mountain Basalt (NMB).Ostracodes are the most common type of fossil in the Scots Bay Formation, in thisstudy nearly 800 specimens have been extracted. These ostracodes are moderately towell preserved, thin-shelled, and occur as whole silicified carapaces, separated valves,and internal molds. Three ostracodes genera have been identified: Darwinula, Timiriasevia, and Metacypris. Determining the exact age for this Formation has been a matter of mild dispute. Therecorded new occurrence of these ostracodes assemblage will help to revise age andprovide enough knowledge about paleoecology of Scots Bay Formation.

Pore Evolution Characteristics and Accumulation Effect of Lower Jurassic Continental Shale Gas Reservoirs in Northeastern Sichuan Basin

The Sichuan Basin is a key area for shale gas energy exploration in China. However, the pore evolution mechanism and accumulation effect of the Lower Jurassic continental shale gas in the northeastern Sichuan Basin remain poorly understood. In this study, the pore structure characteristics of shale reservoirs and the dynamic accumulation and evolution of shale gas in the northern Fuling and Yuanba areas were systematically analyzed by adsorption experiments, high-pressure mercury injection joint measurement, and thermal simulation experiments. The results indicate the following: (1) The continental shale in the study area is predominantly composed of mesopores (10–50 nm), which account for approximately 55.21% of the total pore volume, followed by macropores (5–50 μm) contributing around 35.15%. Micropores exhibit the lowest proportion, typically less than 10%. Soluble minerals such as clay minerals and calcite significantly promote pore development, while soluble organic matter may block small pores during hydrocarbon generation, which facilitates the enrichment of free gas. (2) The thermal simulation experiment reveals that pore evolution can be divided into two distinct stages. Prior to 450 °C, hydrocarbon generation leads to a reduction in pore volume due to the compaction and transformation of organic matter. After 450 °C, organic matter undergoes cracking processes accompanied by the formation of shrinkage fractures, resulting in the development of new macropores and a significant increase in pore volume. This indicates that thermal energy input during the thermal evolution stage plays a key role in reservoir reconstruction. (3) The early Jurassic sedimentary environment controls the enrichment of organic matter, and the Cretaceous is the key period of hydrocarbon accumulation. Hydrocarbon generation and diagenesis synergistically promote the formation of gas reservoirs. The Cenozoic tectonic activity adjusted the distribution of gas reservoirs, and finally formed the enrichment model with the core of source–reservoir–preservation dynamic matching. For the first time, combined with dynamic thermal simulation experiments, this study clarifies the stage characteristics of pore evolution of continental shale and identifies the main controlling factors of shale gas accumulation in the Lower Jurassic in northeastern Sichuan, which provides a theoretical basis for continental shale gas exploration and energy resource development, offering important guidance for optimizing the selection of exploration target areas.

Folding of Oceanic Crust Along the Davie Fracture Zone, Offshore Tanzania

The Davie Fracture Zone (Davie FZ)—among the longest offshore transform systems in East Africa—mediated Madagascar’s southward displacement following Gondwana’s Early Jurassic breakup. This giant structure has a distinct topography and gravity field signals. However, it is buried by thick sediments in its northern segment offshore Tanzania, hindering understanding of the internal structures and their origin. In this study, we applied 2-D multichannel seismic to analyze the structural characteristics and evolution of the Davie FZ. The Davie FZ is located in the oceanic domain, which is bordered by the landwards-dipping overthrust fault at the continent–ocean boundary. Volcano sediments atop the basement with undulating Moho reflection below depict a typical oceanic domain. Distinct compressive deformation characterized by the crustal undulation of around 40 km wavelength forms folded oceanic crust, and Late Jurassic sediments onlap onto the crest of the folded basement. The Davie FZ is localized in a corridor with the thickened oceanic crust and is presented by positive flower structures with faulted uplifted basement and deepened Moho. The Davie FZ evolved from a proto-transform fault located in Gondwana before the spreading of the West Somali Basin. During the Late Jurassic, a kinematic change shifted the spreading direction from NW–SE to N–S, resulting in a strike-slip of the Davie FZ and contemporaneous transpressional deformation offshore Tanzania. The Davie FZ is an excellent case to understand the tectonic-magmatic process forming this transform margin.

First record of a latimeriid coelacanth (Actinistia: Latimeriidae) in the Lower Jurassic of Germany

First record of a latimeriid coelacanth (Actinistia: Latimeriidae) in the Lower Jurassic of Germany

New biostratigraphic data and U–Pb geochronology for the Middle Permian to Triassic succession of the South Qiangtang Block, Xizang

The general lack of Middle Permian to Lower Triassic deposits associated with the South Qiangtang Block (SQB) has restricted biostratigraphic correlation of the SQB with the Lhasa Block (LSB) and the North Qiangtang Block (NQB). In this study, we document for the first time a continuous Middle Permian to Lower Triassic succession and an Upper Triassic Norian–Rhaetian succession in the Samenxiong area of the west SQB using biostratigraphy and detrital zircon U–Pb geochronology. Identified fusuline zones include the Middle Permian Parafusulina–Neoschwagerina Assemblage Zone and the Late Permian Codonofusiella Zone. Conodont zones include the Middle Permian Mesogondolella Fauna, the Early Triassic Hadrodontina Zone and Eurygnathodus cf. costatus–Neospathodus pakistanensis Assemblage Zone and the Late Triassic Mockina bidentata Zone. U–Pb age data confirm the viability of the proposed Rhaetian to Lower Jurassic Samenxiong Formation. Our biostratigraphic and geochronological data permit re-evaluation of the originally described Longge, Jipuria and Riganpeico formations. The fact that the Middle Permian to Lower Triassic and the Norian–Rhaetian successions of the SQB can be correlated with deposits of the LSB and NQB demonstrates their close palaeogeographical relationship during Middle Permian to Late Triassic time.

A LARGE SILESAURID SPECIMEN FROM PETRIFIED FOREST NATIONAL PARK, U.S.A., WITH COMMENTS ON LARGE BODY SIZES IN LATEST TRIASSIC ORNITHODIRANS

Compared to other regions of Pangea, what is now western North America is not known for preserving larger-bodied dinosauriforms from the Triassic Period, partly because sauropodomorphs were apparently climatically excluded from the region until the Early Jurassic. However, the presence of the Liliensternus-sized coelophysoid Gojirasaurus quayi in the middle Norian of New Mexico suggests that increased sampling will recover larger-sized silesaurids and theropods in the Chinle Formation and Dockum Group. This contribution describes a relatively large silesaurid from the Petrified Forest Member of the Chinle Formation at Petrified Forest National Park, Arizona, U.S.A., second only in estimated size to a Middle Triassic form from Tanzania. This site also preserves a large-bodied coelophysoid comparable in size to other specimens from the same or correlated strata from Arizona and New Mexico. These specimens add more support to the decoupling of an increase in body size of theropod dinosaurs with the end-Triassic mass extinction and suggests that silesaurids may have undergone a similar increase in body size prior to that biotic event.

New insights into the stratigraphy, basin configuration and development of the Upper Triassic–Lower Jurassic evaporites and carbonates of southern Tunisia, Saharan platform: integrated surface and subsurface data analysis

New insights into the stratigraphy, basin configuration and development of the Upper Triassic–Lower Jurassic evaporites and carbonates of southern Tunisia, Saharan platform: integrated surface and subsurface data analysis

A new specimen of the early branching crocodyliform Platyognathus hsui extends the record of gobiosuchids back 67 million years

Abstract Crocodyliforms are poorly known from the Early Jurassic Lufeng Formation of China, and a new specimen of Platyognathus hsui is by far the most complete specimen yet known. It shares with the missing holotype and the neotype the very unusual features of a dentary caniniform that is polygonal in cross-section and the complete fusion of the dentary symphysis, and the new specimen provides four additional features diagnosing the species. Features such as a relatively broad rostrum and a posteroventrolateral process on the squamosal place it with taxa closer to extant crocodylians than are Orthosuchus and Protosuchus, as an early branching relative of the Gobiosuchidae. The oldest previous record of the gobiosuchid lineage was from the late Barremian stage of the Early Cretaceous, and this extends the fossil record of the lineage back by 67 Myr. We recognize a new superfamily, Gobiosuchoidea, to include Platyognathus hsui and gobiosuchids.

Foraminiferal assemblages from the Toarcian (Lower Jurassic) ‘Spotted limestone’ of the northern Adriatic Carbonate Platform

Foraminiferal assemblages from the Toarcian (Lower Jurassic) ‘Spotted limestone’ of the northern Adriatic Carbonate Platform

Revisiting the “Klondike Orogeny”: Permian to Jurassic Development of the Yukon‐Tanana Terrane, Northern Canadian Cordillera

Abstract The Permian evolution of the Yukon‐Tanana terrane and closure of the Slide Mountain Ocean in the northern Cordillera have been inferred to culminate in the collisional “Klondike orogeny,” a northern extension of the Sonoma orogeny of the western USA. The “Klondike orogeny” was thought to be associated with mid‐crustal deformation and metamorphism and development of a thick orogenic welt in the late Permian (ca. 260–252 Ma; Lopingian). A review of lithogeochemical data combined with new U‐Pb geochronology and Hf isotope data of igneous and detrital zircons from the western Yukon‐Tanana terrane supports development of a mid to late Permian (ca. 265–255 Ma; Guadalupian‐Lopingian) arc in a supra‐subduction zone setting. Arc development was preceded by hyper‐extension and emplacement of supra‐subduction zone ophiolites (ca. 268–264 Ma). Precise CA‐TIMS U‐Pb dating of zircon in plutons inferred to constrain the timing of the “Klondike orogeny” show that they are the same age (ca. 260.9 Ma) and that previous dates are too young due to unmitigated Pb loss. A critical review of evidence for regional metamorphism indicates that mid‐crustal deformation and metamorphism is related to accretion of the Intermontane terranes in the Early Jurassic. Mica cooling ages show that the western Yukon‐Tanana terrane was exhumed to upper crustal level in the Jurassic. Sinistral transpression facilitated development of the Yukon‐Tanana terrane and subsequent tectonic activity from mid‐Paleozoic to early Mesozoic and probably linked the Permian closure of the Slide Mountain Ocean with intermittent late Paleozoic deformation culminating in the Sonoma orogeny of the U.S. Cordillera.

Environmental and oceanographic evolution in the Southern Qiangtang Basin (eastern Tethys) during the latest Pliensbachian to early Toarcian (Early Jurassic)

Environmental and oceanographic evolution in the Southern Qiangtang Basin (eastern Tethys) during the latest Pliensbachian to early Toarcian (Early Jurassic)