Early Cretaceous Research Articles

Genesis and Tectonic Implications of Early Cretaceous Granites in the Haobugao Area, Southern Great Xing’an Range: Insights from Zircon U–Pb Geochronology, Hf Isotopic Composition, and Petrochemistry

In the Huanggangliang–Ganzhuermiao metallogenic belt in the southern Great Xing’an Range, the Haobugao Pb‒Zn deposit is the most widespread skarn-type polymetallic deposit. The observed mineralization processes in this area are closely associated with both magmatic and tectonic activity. The zircon U‒Pb ages of two granitoid phases are 134.0 ± 0.6 Ma and 133.4 ± 0.9 Ma (Early Cretaceous). High SiO2 content (average mass fractions of 77.98 wt.% and 73.25 wt.%), high alkalinity (average mass fractions of 6.19 wt.% and 8.78 wt.%), and low CaO levels (average mass fractions of 0.16 wt.% and 0.12 wt.%) are characteristic of these rocks. They are also enriched in high-field-strength elements (HFSEs) (Th, U, Ta, Zr, Hf, etc.) and depleted in large ion lithophile elements (LILEs) (Ba, Sr, etc.). Furthermore, the Nb/Ta ratios (7.80~8.82, 10.00~10.83) point to a crustal origin of the magma. The zircon Hf isotopic compositions suggest that the melting of young crust derived from Meso-Neoproterozoic and Neoproterozoic depleted mantle gave rise to the magma in these granite porphyries. These rocks formed in an extensional environment driven by the subduction and retreat of the Paleo-Pacific plate during the Early Cretaceous.

Quantifying the temporal pattern of shape change in trigoniids through the Middle Jurassic–Early Cretaceous of Kutch: A geometric morphometric approach

Quantifying the temporal pattern of shape change in trigoniids through the Middle Jurassic–Early Cretaceous of Kutch: A geometric morphometric approach

Hydrologically sensitive carbonates: Tectonic and groundwater controls on synrift sedimentation in the Late Jurassic–Early Cretaceous of the western Cameros Basin, Northern Spain

AbstractBasin hydrology and subcrop are key controls on carbonate sedimentation in continental basins. Hydrologically sensitive carbonates can record groundwater fluctuations within an aquifer in deep time. Late Jurassic extension, footwall uplift, erosion and karstification of marine Jurassic carbonates in the western Cameros Basin (Spain) saw deposition of ?Upper Kimmeridgian‐Tithonian syntectonic alluvial fan deposits (Señora de Brezales Formation). Biogenic laminar calcretes and phreatophytic rhizocretions record roots exploiting capillary fringe groundwater. Progressive infill of rift topography and footwall erosion lowered sedimentary gradients and clastic supply during deposition of the ?Tithonian–Berriasian Rupelo Formation. Distal alluvial marls (Las Viñas Member) contain charophytes, with 2 m thick carbonate lenses at the top reflecting intermittent rise of groundwater in ponds on the basin floor. Stacked palustrine limestones with rare charophytes and laminar calcretes (Ladera Member) record overstep of seasonal carbonate wetlands onto basin margins and footwall highs with intense pedogenetic modification during lengthy seasonal exposure. Overlying Berriasian charophyte‐ostracod wackestones, displaying microkarst cavities and interbedded intraclastic conglomerates, with vivianite sauropod bones, footprints and polygonal desiccation cracks at the top (Mambrillas de Lara Member) record open lacustrine conditions with limited subaerial exposure and high water tables. Desiccation‐cracked limestones and marls with correlatable evaporite horizons (Rio Cabrera Member) contain marginal marine foraminifera and dasycladaceae at the top. Lagoonal conditions reflected transgression to seaward and intermittent marine connection via the Basco‐Cantabrian Basin. The distribution and thicknesses of hydrologically sensitive carbonates reflected onlap onto a faulted and karstified marine Jurassic carbonate pediment and the subtle influence on hydroperiod of fault (and potentially localised Triassic salt) controlled differential subsidence and transgressive groundwater rise. Hydrological facies evolution reflects progressive basin infilling and eustasy beyond. Transitions in this continental succession from clastic to carbonate facies and from closed to open hydrology record hydrological change over time rather than contemporaneous deposition under Walther's Law.

New evidence for the presence of carcharodontosaurid theropod dinosaurs in the Late Cretaceous of Uzbekistan

ABSTRACT An incomplete posterior dorsal vertebra ZIN PH 2646/16 from the Upper Cretaceous (Turonian) Bissekty Formation of Uzbekistan has a highly pneumatized centrum and neural arch. The centrum has a lateral pneumatic foramen that is divided by a septum. The neural arch is invaded through a lateral pneumatic foramen above the neurocentral suture and has deeply excavated prezygapophyseal-centrodiapophyseal and centrodiapophyseal fossae. The interior of the preserved portion of the neural spine is pneumatic. In the structure of the fossae on the neural arch and the presence of a double pneumatic foramen on the centrum, ZIN PH 2646/16 closely resembles the carcharodontosaurid Acrocanthosaurus from the Early Cretaceous of North America. Thus, we identify ZIN PH 2646/16 as Carcharodontosauridae indet. Carcharodontosauridae were previously known from the Bissekty Formation from Ulughbegsaurus uzbekistanensis, which is based on an incomplete maxilla.

Extremely rapid, yet noncatastrophic, preservation of the flattened-feathered and 3D dinosaurs of the Early Cretaceous of China

Northeast China's Early Cretaceous Yixian Formation preserves spectacular fossils that have proved extraordinarily important in testing evolutionary hypotheses involving the origin of birds and the distribution of feathers among nonavian dinosaurs. These fossils occur either flattened with soft tissue preservation (including feathers and color) in laminated lacustrine strata or as three-dimensional (3D) skeletons in "life-like" postures in more massive deposits. The relationships of these deposits to each other, their absolute ages, and the origin of the extraordinary fossil preservation have been vigorously debated for nearly a half century, with the prevailing view being that preservation was linked to violent volcanic eruptions or lahars, similar to processes that preserved human remains at Pompeii. We present high-precision zircon U-Pb geochronology from cores and outcrops, demonstrating that Yixian Formation accumulation rates are more than an order of magnitude higher than usually estimated. Additionally, we provide zircon provenance and sedimentological data from 3D dinosaur fossils, which imply that their death and burial occurred in collapsed burrows, rather than via a catastrophic volcanogenic mechanism. In the studied area, the three principal fossil-rich intervals of the Yixian occur as a cyclic sequence that correspond to periods of high precipitation. Using Bayesian-Markov Chain Monte Carlo approaches, we constrain the total duration of the sequence to less than ~93,000 y and suggest that climatic precession paced the expression of these cyclic sediments. Rather than representing multiple, Pompeii-like catastrophes, the Yixian Formation is instead a brief snapshot of normal life and death in an Early Cretaceous continental community.

The Scriniodinium crystallinum dinoflagellate cyst zone in the Middle–Upper Oxfordian, Upper Jurassic, Ilimananngip Nunaa (Milne Land), East Greenland

The biostratigraphy of the Jurassic in East Greenland is historically based on macroscopic fossils. Stratigraphy based on palynomorphs (spores, pollen and dinoflagellate cysts) has progressed more slowly and sporadically. The Scriniodinium crystallinum dinoflagellate cyst Zone is identified in middle – upper Oxfordian strata of Ilimananngip Nunaa (Milne Land), central East Greenland. The lower boundary is defined by the last occurrence of Trichodinium scarburghense in the Cardioceras tenuiserratum ammonite Zone. The upper boundary is defined by the last occurrence of S. crystallinum in the uppermost Amoeboceras rosenkrantzi ammonite Zone. However, the subzonal division of the S. crystallinum Zone recorded in North-West Europe is not identified in Greenland. Eighteen characteristic dinoflagellate cyst events are considered stratigraphically significant and useful in East Greenland. Fifteen of these events provide an informal, detailed stratigraphical subdivision of the S. crystallinum Zone into 10 subunits. Identification of the zone is an addition to the previously defined upper Bathonian – middle Oxfordian zonation, where the uppermost palynostratigraphical event was recorded to be the last occurrence of T. scarburghense. With this study, the correlation of dinoflagellate cyst and ammonite stratigraphy in the lower and middle Oxfordian is slightly modified. The S. crystallinum Zone documented here, in combination with the zonation used for the stratigraphy of the Blokelv-1, Rødryggen-1 and Brorson Halvø-1 cores of the Upper Jurassic to Lower Cretaceous, completes the dinoflagellate cyst stratigraphy of the marine Jurassic in East Greenland. Together with previous studies of spores and pollen in less marine units, the first complete palynological Jurassic stratigraphy is thus established for the Jurassic succession in East Greenland.

Influence of tectonic evolution processes on burial, thermal maturation and gas generation histories of the Wufeng-Longmaxi shale in the Sichuan Basin and adjacent areas

The Wufeng-Longmaxi (WL) shale is widely distributed in the Sichuan Basin and adjacent areas in southwest China. The basin experienced multiple-stage complex tectonic movements, whose influences on burial, thermal maturation and gas generation histories in different areas are poorly understood. Based on a detailed study of the denudation stages, strata thickness, and thermal history of the basin, burial and thermal maturation histories of seven wells in different areas were modelled using PetroMod software. Due to the high maturity of the WL shale, a low-maturity Silurian Polish Llandovery shale was used for gold tube closed-system pyrolysis experiments to obtain kinetic parameters for evaluating methane generation history. The Polish shale was selected due to its depositional age, sedimentary environment and organic type, which are similar to the WL shale. The burial history of the WL shale can be divided into five stages: I. Early to Middle Silurian rapid burial; II. Caledonian uplift and denudation; III. Permian to Triassic sustained burial and denudation; IV. sustained burial since the Late Triassic; and V. Late Cretaceous to present sustained uplift and denudation. The thermal maturity of the WL shale in all wells increased with burial depth during stage IV. In addition, high calculated reflectance increments in wells JY1 and N201 during stage III occurred due to the relatively high basal heat flow and deep burial depth, resulting in higher current thermal maturities than in the other wells. The late Permian–Early Triassic and the Middle Jurassic–Early (or Late) Cretaceous were the key methane generation periods for wells JY1 and N201. In contrast, the other five wells had a single methane generation stage, mainly determined by burial and thermal maturation processes. The time of uplift and the amount of denudation during stage V, the current burial depth, the development of faults and fractures, high proportion of retention and the seal capacity of the overlying caprock are key factors for shale gas preservation. Hence, this study will help guide future shale gas development in the Sichuan Basin.

First deciphering of large pterosaur footprints and their trackmaker in the Junggar Basin, China

Pterosaur footprints are important trace fossil for understanding the ecological habits of pterosaurs, and they are extremely rare worldwide. Within the Lower Cretaceous of the Junggar Basin of Xinjiang, hundreds of large pterosaur footprints have been unearthed. These imprints underwent a meticulous examination encompassing their dimensions, length-to-width ratio, proportions of digital and metatarsal parts, and divarication between digits of the manus imprints. A new ichnospecies, Pteraichnus junggarensis isp. nov., has been proposed based on these detailed analyses. By comparing these footprints with the anatomical characteristics of local larger pterosaur pedal bone fossils, it is suggested that the large-sized P. junggarensis footprints were produced by Dsungaripterus weii. The successful correlation between pterosaur fossils and their footprints within the Wuerho Pterosaur Fauna marks a momentous stride in deducing trackmakers based on their footprints. Moreover, estimates of pterosaur pes length and hip height were, for the first time, derived from a comprehensive scrutiny of 54 non-pterodactyloid and pterodactyloid specimens. A salient discovery was the markedly reduced ratio of hip height to pes length in non-pterodactyloid pterosaurs in comparison to their pterodactyloid counterparts. By employing fitted linear equations grounded on footprint dimensions, it is posited that the hip height for Noripterus complicidens ranges from 0.10 to 0.20 m, while for D. weii, it ranges from 0.28 to 0.46 m. Additionally, based on the ratio of stride length to hip height in the trackways, it is inferred that the trackmakers exhibited a typical walking gait, with speeds of 0.33 and 0.25 m/s, respectively.

Ichnotaxonomic and Morphological Differentiation in Pterosaur Tracks Using Geometric Morphometric Analysis: A Case Study on Pteraichnus Manus Tracks from Cretaceous East Asia

Pteraichnus is the most reported pterosaur ichnotaxa and the taxon with the largest number of reported ichnospecies. However, most ichnospecies of Pteraichnus are restricted to the type locality and type specimens and have not been expanded. This study employs two-dimensional landmark-based Geometric Morphometric analyses (GMA) to investigate the manus tracks of four ichnotaxa of Pteraichnus (P. koreanensis, P. nipponensis, P. wuerhoensis, and P. gracilis) from the Early Cretaceous of East Asia. These analyses are the first attempt to perform GMA on pterosaur ichnofossil and reveal that the morphological characteristics of these ichnotaxa are significantly distinguishable. In addition to traditional descriptive criteria, features such as the width of the digits and the metacarpal-phalangeal joint area were identified as valid criteria for numerical comparison. The results suggest that GMA can enhance the ichnotaxonomic classification of invalid or questionable ichnotaxa and provide taxonomic estimation for manus-only tracks. This approach highlights the potential for spatiotemporal comparisons between disparate pterosaur footprints. The distinct morphological features observed in tracks from relatively close localities suggest the presence of diverse pterosaur faunas across East Asia. Further research with an expanded dataset of pterosaurian ichnotaxa is recommended to refine ichnotaxonomic classifications and enhance our knowledge of pterosaur paleogeography.

The Jurassic through Early Cretaceous Magmatic Belt of the Southern Margin of the Chukotka Terrane, Northeast Russia: New Results of U–Pb Dating of Zircon

The Jurassic through Early Cretaceous Magmatic Belt of the Southern Margin of the Chukotka Terrane, Northeast Russia: New Results of U–Pb Dating of Zircon

Analysis of Pore Types in Lower Cretaceous Qingshankou Shale Influenced by Electric Heating

Analysis of Pore Types in Lower Cretaceous Qingshankou Shale Influenced by Electric Heating

Eolian-fluvial succession in the Early Cretaceous from the Ordos Basin

Cretaceous eolian deposits are widely developed in North China, among which the Lower Cretaceous eolian (erg) sedimentary strata in the Ordos Basin are the most representative. Many studies have been conducted on eolian deposits in the Ordos Basin, especially the Luohe Formation; however, there is a lack of systematic sedimentology research and the corresponding research on the evolution of sedimentary facies. Therefore, to explore the Mesozoic drought events and the systematic evolution of the sub-tropical erg zone, this study reports the fluvial–eolian sedimentary sequences of the Early Cretaceous Luohe and Yijinhuoluo Formations in the Ordos Basin. Spatially, through detailed sedimentary lithofacies and structural analysis of different outcrops, the combination law of sedimentary facies can be determined. Based on this, a three-dimensional sedimentary model of erg is reconstructed. The erg environment is divided into three sub-environments: erg margin, erg margin–centre transition and erg centre. According to the evolution of the sedimentary facies, the sedimentary evolution from the Latef Jurassic to the Early Cretaceous in the Ordos Basin is divided into five stages. The Ordos Basin has experienced the delta, erg formation, erg deposition, erg shrinkage and evaporating salt-lake stages. The vertical sedimentary evolution indicates climatic oscillation in North China from the Late Jurassic to the Early Cretaceous. Under the control of the sub-tropical high belt, the Ordos Basin experienced a hot and arid climate during the Cretaceous, forming a widely distributed erg belt in the region. During this period, a small-scale climate shock occurred under the hot and arid background, changing the sedimentary environment.

Geochemistry and Zircon U–Pb Chronology of Jinchanshan Gold-Hosted Granitoids, Inner Mongolia: Implications for Petrogenesis and Geodynamic Evolution

Jinchanshan is a medium-sized, granitoid-hosted gold deposit located in the Kalaqin area of Inner Mongolia. Mineralization predominantly occurs in the contact zone between biotite granites and quartz porphyry rocks, associated with the Jinchanshan minor intrusion, suggesting a genetic link to the granitoid-hosted gold deposit. In this study, the petrography, geochemistry, and LA-ICP-MS zircon U–Pb chronology of these two granitoid samples were studied. The results indicate that the zircon U–Pb age of the biotite granites is 127.9 ± 3.0 Ma, while that of the quartz porphyry is 121.4 ± 1.5 Ma, both dating back to the Early Cretaceous. The average SiO2 content of the granites is 66.64%, and the rocks have high total alkali (K2O + Na2O) content, averaging 9.13%. The average K2O content is 4.39%, with a K2O/Na2O ratio of 0.93. The quartz porphyry rocks are enriched in SiO2 (74.41%–76.85%) and have high Na2O + K2O content (8.67%–9.59%), but are low in MgO (0.03%–0.09%), CaO (0.44%–1.02 %), and TiO2 (0.08%–0.12%). Most samples of the biotite granite and the quartz porphyry rocks exhibit high-K peraluminous and medium-K calc-alkaline characteristics, respectively. Both rock types are enriched in Rb, Th, U, K, Zr, Hf, and Gd and relatively depleted in Ba, Sr, P, Ti, Nb, Ta, and Eu, with a pronounced negative Eu anomaly. The biotite granites show high ∑LREE/∑HREE ratios (6.1–6.9), while the quartz porphyry rocks exhibit lower ratios (2.0–4.2). Both granitoid types have elevated FeOT content and FeOT/(FeOT + MgO) ratios, indicating that the Jinchanshan granitoids are A-type granites. The zircon U–Pb ages, combined with the regional tectonic settings, suggest that these granitoids formed during large-scale metallogenic events in the Early Cretaceous, within the Yanshanian post-orogenic extensional tectonic regime. This is consistent with the lithospheric thinning and extensional processes in Eastern China during this period.

First occurrence of an acipenseriform (Chondrostei: Acipenseriformes) from the Upper Jurassic Kimmeridge Clay Formation of England

ABSTRACT Several fragmentary remains of an enigmatic acipenseriform, the order of fishes that includes living sturgeons and paddlefishes, are described from the Upper Jurassic Kimmeridge Clay Formation of southern England. These remains are significant because they represent the first definitive evidence of an acipenseriform from the Upper Jurassic described outside of Asia. In total, five associated dorsal caudal fulcra from the caudal fin and a paired pelvic fin from at least two separate individuals are identified as acipenseriform, although it is uncertain to which family they belong. Three families of Mesozoic acipenseriform are considered: the †Chondrostei (Lower Jurassic, Europe), the †Peipiaosteidae (Upper Jurassic to Lower Cretaceous, Asia), and the extant Acipenseroidei (Lower Cretaceous–recent, Laurasia). The new Kimmeridgian Clay acipenseriform fossils would significantly extend the temporal and spatial distribution of whichever family they are ascribed, but their affinities remain unclear. Regardless, the stratigraphic and paleobiogeographic occurrence of the new specimens holds novel implications for the poorly known evolutionary history of this primitive clade of extant non-Neopterygian fishes.

Evolutionary origins, macroevolutionary dynamics, and climatic niche space of the succulent plant syndrome in the Caryophyllales.

The succulent plant syndrome is defined by the coordination of traits that enhance internal water storage within plant tissues. Although distributed globally in different habitats, succulent plants are thought to have evolved to avoid drought in arid regions, due to trait modifications that decrease tissue water deficits. We evaluated the evolution and the ecological significance of the succulent strategy at a global scale by comparing the climatic niche of species displaying succulence within the Core Caryophyllales with their non-succulent relatives. We assembled and curated a worldwide dataset of 201K georeferenced records belonging to 5447 species within 28 families, and analyzed the climatic niche of species along with their origin and evolutionary trajectories using ecological niche modeling, phylogenetic regression, divergence dates and ancestral state estimation. Results indicate the Core Caryophyllales have inhabited drylands since their origin in the Early Cretaceous. However, the succulent syndrome appeared and diversified during later geologic periods. The climatic niche space of succulents is narrower than non-succulent relatives, but no climate niche separation was detected between groups. Our results support alternative interpretations on the environmental and ecological forces that spurred the origin and diversification of the succulent plant syndrome and the radiation of rich succulent lineages.

The First Report of Late Valanginian–Early Aptian (Early Cretaceous) Ammonites and Chemostratigraphy of Eastern Anatolian, Olur‐Erzurum, Türkiye

ABSTRACTThis study is based on stable isotope analysis of a rich ammonite assemblage from the Sogukcam Formation, which is widely exposed in Yesilbaglar (Olur‐Erzurum, NE Türkiye). The presence of ammonid, planktic, and benthic foraminifers in the marine sediments suggests that they are from the early Cretaceous period. The late Valanginian‐early Aptian‐rich ammonite assemblage includes the following genera and species: Acrioceras sp., Barremites difficilis, Barremites sp., Crioceratites duvalii, Crioceratites sp., Deshayesites aff. dechyi, Deshayesites sp.1, Deshayesites sp.2, Deshayesites sp.3, Deshayesites sp., Dufrenoyia cf. dufrenoyi, Dufrenoyia cf. furcata, Dufrenoyia sp., Hemihoplites sp., Heteroceras sp., Neocomites sp., Phyllopachyceras infundibulum, Protetragonites cf. quadrisulcatus, Protetragonites sp., Ptychoceras sp., Turkmeniceras cf. geokerense, and Turkmeniceras sp. This assemblage suggests that the Sogukcam Formation's deeper facies formed in the late Valanginian to early Aptian period. Fossils and δ18O data show normal paleosalinity levels. During the late Valanginian‐early Aptian period, δ18O values ranged from −3.67‰ to −2.24‰, with paleotemperatures ranging from 21.3°C to 27.9°C. δ13C positive values range from +0.65‰ to +2.86‰. δ13C isotope data show the oxygen minimum zone (OMZ) and changes in sea level and productivity. The presence of planktonic foraminifera and the ammonite assemblage indicates that the formation was deposited in warm subtropical waters ranging from the outer shelf to the open sea.

Ophiuroids (Echinodermata) from the Lower Cretaceous of Štramberk, Moravia (Czech Republic)

Ophiuroids (Echinodermata) from the Lower Cretaceous of Štramberk, Moravia (Czech Republic)

Comparative Mitogenomics Analysis Revealed Evolutionary Divergence among Purpureocillium Species and Gene Arrangement and Intron Dynamics of Ophiocordycipitaceae.

The species of Purpureocillium are cosmopolitan and multitrophic fungi that can infect a wide range of invertebrate hosts. This study reports the mitogenome of P. atypicola, a specialized spider pathogenic fungus. The 112,465 bp mitogenome encoded genes typically found in fungal mitogenomes, and a total of 52 introns inserted into seven genes. A comparison with three other Purpureocillium species revealed significant differences in length and intron number, primarily due to intron variation; however, there was no dynamic variation in the introns of the cox1 gene within the same species of the Purpureocillium genus. Different mitochondrial protein-coding genes showed variable degrees of genetic differentiation among these species, but they were all under purifying selection. Additionally, frequent intron loss or gain events were detected to have occurred during the evolution of the Ophiocordycipitaceae mitogenomes, yet the gene arrangement remains conserved. A phylogenetic analysis of the combined mitochondrial gene set gave identical and well-supported tree topologies. The estimated age of the crown of Ophiocordycipitaceae and Purpureocillium were around the Early Cretaceous period (127 Mya) and Late Cretaceous period (83 Mya), respectively. The results of this study advance our understanding of the genomics, evolution, and taxonomy of this important fungal group.

Light δD apatites reveal deep origin water in North China Craton intracontinental granites and basalts

Water is essential to the formation of intracontinental granites, but its origin remains elusive. Here we address this scientific problem by analyzing D/H isotopes of apatites, hydrous minerals in Jurassic and Early Cretaceous granites and basalts from eastern North China Craton, where water was previously interpreted as derived from subducting slab. Results reveal extremely low δD values in pristine Early Cretaceous granitic (−203‰ to −127‰) and basaltic (−197‰ to −107‰) apatites, contrasting with relatively high δD values (−137‰ to −47‰) in Jurassic granites. Given the depth-dependent D/H isotopic fractionation during slab dehydration and high-water contents in coeval primitive mafic magmas, the Early Cretaceous magma water is attributed to the stagnant slab within the mantle transition zone. Secular change in the depth of water aligns with steepening of subducting Paleo-Pacific plate from Jurassic to Early Cretaceous, demonstrating the potential of apatite H isotopes in tracing water origin in granites and basalts.

Vertebrate paleoburrow as a seasonality indicator in early Cretaceous Três Barras formation (Brazil)

Vertebrate burrows serve as windows into the past, revealing the activities of various organisms and providing clues about their paleoenvironmental conditions. This study focuses on a vertebrate paleoburrow from the Três Barras Formation, Minas Gerais state, southeastern Brazil, aiming to detail and reconstruct aspects of the paleoclimatic conditions that acted in this area during the early Cretaceous within a predominantly eolian paleoenvironment. Through detailed analysis of the sedimentary facies and morphological examination of the burrow, this study suggests that the structure was likely produced by lungfish or lizards. It is located within proximal crevasse splay deposits interbedded with fine floodplain sediments, indicating periods of flooding in a meandering fluvial setting that developed in the marginal areas of the eolian system of the Três Barras Formation. Comparison with other paleoburrows from neighboring basins further enhances our understanding of the paleoenvironmental conditions during the early Cretaceous Period. These findings reinforce evidence of seasonality and suggest a period of intense humidity during the deposition of the Três Barras Formation, which had previously been interpreted as exclusively aeolian.