Paleogeographic Reconstructions Research Articles

Subduction‐Related Volcanic Activity as a Proxy for Global Subduction Flux Over the Past Billion Years, and Its Correlation With Geomagnetic Superchrons

AbstractWe investigate the frequency of subduction‐related volcanic events over the past billion years. Our analysis reveals distinct peaks and troughs interpreted as significant fluctuations in global subduction flux. This approach has the advantage of being independent of paleogeographic reconstructions. However, it does not provide information on the spatial distribution of thermal heterogeneities at the core‐mantle boundary. This likely explains why the long‐term evolution of global subduction flux does not correlate in any simple way with the frequency of geomagnetic polarity reversals throughout the Phanerozoic. As an additional parameter, we suggest focusing on how variations in the Earth's inertia, due to changing subduction configurations over time, influence the thermal conditions at the core‐mantle boundary and, consequently, the magnetic reversal frequency.

Significance of ∼1Ga granites from the South Delhi Fold Belt, NW India: Implications for paleogeographic reconstructions of Rodinia

Significance of ∼1Ga granites from the South Delhi Fold Belt, NW India: Implications for paleogeographic reconstructions of Rodinia

Paleomagnetic study of the curvature of the Segre oblique zone (Southern Pyrenees)

The origin of the obliquity of the structures at the eastern end of the central South-Pyrenean salient is investigated by means of Paleomagnetism. Earlier paleomagnetic data in the area are poorly distributed and insufficient to describe in detail the amount and age of vertical axis-rotations affecting the region. This work aims to address this issue by focusing on the Palaeocene rocks, whose magnetization if primary would record the entire rotation during the emplacement of the thrust sheet units, improving our understanding of the history of deformation and the paleogeographic implications during the Eocene. In addition to Palaeocene Garumnian facies, late Cretaceous and early Eocene marine facies were also sampled. The characteristic components of the magnetization were obtained after progressive demagnetization of the NRM of a minimum of 10 samples per site. The mean site direction, and the mean direction of groups of sites from the same structural unit were calculated. The fold test applied to a set of sites located on the Montsec thrust sheet gave positive results, indicating an age of the magnetization prior to deformation. However, evidence of postfolding magnetizations were found in other sites. The results of this study indicate significant counterclockwise rotations of the Cadí, Port del Comte, and the eastern termination of the Montsec thrust sheets, developed during the Mid Eocene to Oligocene times. These results are intended to contribute to the restitution of the initial geometry of the structures and to contribute to the paleogeographic reconstruction of the sedimentary systems of the eastern and central Pyrenees.

Study on Development Characteristics and Reservoir Formation Model of Lower Ordovician Reservoirs in Central Sichuan

Sichuan Basin is a large superimposed petroliferous basin, which has experienced multi-stage extension-convergence cycle and has great potential of oil and gas resources. In recent years, the lower combination oil and gas exploration in the middle Sichuan area has made great breakthroughs in the Sinian Dengying Formation and the Lower Cambrian Longwangmiao Formation, but has not achieved good results in the Ordovician. At present, a number of Wells in the middle Sichuan area show varying degrees of oil and gas in the Lower Ordovician strata, suggesting that the Ordovician strata in this area have the basic conditions for the formation of large-scale oil and gas reservoirs. However, no consensus has been reached on the paleogeographic pattern of Ordovician lithofacies and the distribution of favorable facies zones in this area, and the understanding of reservoir types and reservoir properties is quite different. Therefore, the weak basic research on the geological conditions of reservoir formation has severely restricted the hydrocarbon exploration of the Ordovician in this area. In this paper, the Lower Ordovician lithofacies paleogeography reconstruction and reservoir characteristics analysis are carried out by systematically combing the drilling and field profile data in the central Sichuan area, combined with core observation, thin section identification and reservoir analysis, and finally the Ordovician oil and gas accumulation model is established. The results show that the lithofacies paleogeography distribution of the Lower Ordovician Tongzi-Honghuayuanstage in the central Sichuan area is from the paleo-uplift to the east in the order of platform tidal flat to platform shoal to limited platform. The Lower Ordovician reservoir types in the middle Sichuan area include karst reservoir and dolomite reservoir, among which the karst reservoir is heavily filled and the reservoir performance is limited. The Ordovician reservoir-forming model in the middle Sichuan area reveals a new exploration model of dolomite superimposed bedding under karst in the epicontinental platform, which provides important geological basis for the new breakthrough of Ordovician oil and gas exploration.

УСЛОВИЯ НЕФТЕГАЗОНОСНОСТИ ВЕРХНЕЮРЯХСКОГО ГОРИЗОНТА НА СЕВЕРО-ВОСТОКЕ НЕПСКО-БОТУОБИНСКОЙ АНТЕКЛИЗЫ

The Yuryakha productive horizon is one of the most promising objects for a significant increment in the hydrocarbon resource base in the Republic of Sakha (Yakutia). Its low reservoir properties and compound distribution of the improved reservoir zones are noted. The analytical review of scientific notations about the relationship between petroleum potential of deposits and basement highs is carried out. The absence of lithological varieties in deposits and their thicknesses is shown on the basis of facies analysis of the Yuryakha Formation sections above basement highs and beyond. The influence of basement highs on the productivity of the Yuryakha Horizon is assumed to be limited by creating conditions for the development of secondary processes that potentially increase the void space. It is concluded that the search for zones of improved reservoirs in the Yuryakha formation based on paleogeographic reconstructions is a more promising direction than the justification of point sites with secondary changes.

Diachronous Cretaceous Closure of the Bangong‐Nujiang‐Shyok Ocean (Westernmost Central Tibet)

AbstractPrecisely reconstructing the diachroneity of continental collision along various Paleo‐, Meso‐, and Neo‐Tethyan branches has proved to be challenging, which limited our understanding of the dynamics of terrane suturing and associated topographic inheritance in the Tibetan Plateau. In this study, we present stratigraphic and sedimentological evidence to support, for the first time, the presence of a late Early Cretaceous remnant deep‐water basin active at least until 110 Ma in the westernmost Bangong‐Nujiang suture in central Tibet. This basin was confined by shallow‐marine deposition in the north, east, and southeast, as indicated by obitolinid biostratigraphy and maximum depositional ages for six lithostratigraphic units, while the corresponding ocean had already closed in the east by Aptian‐Albian time. Detrital zircon U‐Pb age data (n = 965), forward numerical mixture modeling, and in situ εHf(t) values point at syn‐collisional magmatic rocks along strike in the east as the main sediment source, with additional variable input from uplifted Jurassic‐lowermost Cretaceous turbidites. Our paleogeographic reconstruction indicates that the closure of the Bangong‐Nujiang Ocean progressed markedly diachronously from east to west, culminating in the final closure of the Shyok oceanic branch during the Late Cretaceous (probably by 95 and no later than 85 Ma). This westward‐younging ocean closure corresponds to a shorter duration of continental convergence in the west, resulting in less crustal shortening and tectonic uplift than in the east. This may have played a pivotal role in shaping Cenozoic topography, characterized by higher elevations in the east compared to the west along the Bangong‐Nujiang‐suture valley.

New paleomagnetic and geochronologic results from the eastern Tethyan Himalaya refine the size of Greater India in the Early Cretaceous

Knowledge of the original size of Greater India in the Early Cretaceous is critical for Late Mesozoic East Gondwana reconstructions. However, estimates of Greater India extent have significant discrepancies in the Early Cretaceous. Here we report geochronologic and paleomagnetic studies on rocks of the Jiabula Formation in the northern subzone of the Tethyan Himalaya. The studied limestones are characterized by two-component magnetizations carried by detrital magnetite, which retains a primary remanence. Correspondingly, the high temperature magnetization components (350−525 °C) are isolated from 204 specimens using high-resolution thermal demagnetization. The new paleomagnetic data provide, after inclination shallowing estimation, an Early Cretaceous paleopole of 11.2°N/300.5°E, A95 = 2.6°, which places the eastern part of the Tethyan Himalaya at a paleolatitude of 40.9° ± 2.6°S at ca. 126 Ma. Comparison of the new observed paleolatitude with the expected paleolatitude (49.7° ± 2.8°S) of India implies that Greater India had an extension of 968±418 km (8.8° ± 3.8°) at ca. 126 Ma. Integrating the new results with our previous Campanian results (ca. 75 Ma), we conclude that Greater India had a comparable extension of ∼900 km during ca. 126−75 Ma. The improved estimate of the dimensions of Greater India leads to an updated reconstruction of paleogeography in the Early Cretaceous.

Contact Metamorphism of Pelitic Rocks Constrains the Depth of Emplacement of the Re di Castello Intrusion (Adamello Batholith, Italy)

ABSTRACTRe di Castello is the southernmost unit of the composite Adamello batholith (central Alps, Italy). It was emplaced between 43 and 40 Ma, yet its depth of emplacement is not well constrained. We have studied the contact metamorphism of pelitic country rocks in two localities: the upper Caffaro Valley and the Borzago Valley in the southern and the northern sub‐units of the Re di Castello, respectively. In the Caffaro Valley, the country rocks comprise the Triassic sedimentary Lozio Shale, a carbon‐rich slate–siltstone, which was intruded by quartz‐dioritic magma. Near the contact, the hornfelses display the mineralogical assemblage Kfs‐Crd‐Bt‐Ms‐Pl‐Qz‐Gr, with rare fibrolitic sillimanite in a single sample. Andalusite was never observed throughout the aureole at this locality. In the Borzago Valley, contact metamorphism developed on schists of the pre‐Permian basement with a Variscan, regional metamorphic overprint. The sequence of contact metamorphic mineral assemblages progresses from And‐Bt‐bearing parageneses to the Sil‐Crd‐Bt‐Kfs‐Ms‐Pl‐Qz that characterizes peak conditions, at which incipient melting is also observed. K‐feldspar forms slightly upgrade the first appearance of sillimanite. For samples at both localities, thermodynamic modelling in the NCKFMASHT system failed at predicting a stability field for the sequences of mineral assemblages developed during contact metamorphism. Also the Ti‐in biotite thermometer did not constrain temperatures adequately. The P–T conditions at the thermal peak were thus evaluated by an alternative bathograd‐like approach, considering phase relationships in the simplified NKASH‐C system. To form sillimanite only as product of the incomplete Ms‐Qz breakdown—divariant for the presence of Na in Ms and Kfs and shifted to lower temperature due to the presence of graphite (in the Lozio Shale)—an isobaric path typical of contact metamophism must have crossed above the Msss‐Qz‐Kfsss‐Sil‐And‐fluid invariant point. This constrains an emplacement pressure >3.3 kbar in the Caffaro Valley, and >3.2 kbar in the Borzago Valley. Concerning temperature, the same univariant point also constrains the minimum temperature in the Caffaro Valley as >615°C–620°C, consistent with results of RSCM thermometry on graphite from the Lozio Shale. The evidence of incipient melting in some samples from the Borzago Valley indicates higher temperatures, probably approaching 670°C, near the contact to the intrusion. Assuming an average crust density of 2.7 g cm−3, the estimated pressures correspond to a minimum paleo‐depth of emplacement of about 12 km. These depths are somewhat greater than normally considered and should be regarded as revised constraints on models of the emplacement dynamics of the Adamello batholith and on paleogeographic reconstructions of this part of the Southalpine domain.

Using PySpark to accelerate batch data point rotation for paleogeographic reconstruction

ABSTRACT Batch paleogeographic point rotation (BPPR) is a PySpark-based extensible batch data point rotation method that accelerates rotation during paleogeographic reconstruction. Data point rotation is an important part of paleogeographic reconstruction and a significant tool for exploring the co-evolution of Earth and life. However, current point rotation techniques have challenges with processing speeds when handling extensive paleogeographic data. Therefore, this study introduced a parallel-computing framework to construct a BPPR. This method combines PySpark and PyGPlates, which can partition points and compute them simultaneously in multiple threads. The rotation of 232,277 fossil occurrences from the Cretaceous Period in the Paleobiology Database (PBDB) was completed within 26 s. By contrast, an alternative GPlates method completed the same task within 96 s. The proposed method supports CSV, EXCEL, SHP, and other data formats, thereby avoiding possible software switching requirements when using methods associated with GPlates. Using synthetic and real paleontological data as experimental datasets, BPPR proved to be nine times more efficient than GPlates when rotating 900,000 points. This efficiency improvement significantly enhanced data-driven paleogeographic analysis. The parallel strategy employed can be broadly applied to massive data analysis in geoscience.

Recognizing primary paleotopography utilizing Ichnofossils and 3-D models: Mill Canyon Dinosaur track site, Utah

Preservation and recognition of primary paleotopography along a bedding surface is often a neglected component in paleogeographic reconstruction. The Mill Canyon Dinosaur track site (MCDT) is a spectacular bedding plane exposure with a diverse assemblage of vertebrate ichnnofauna. Small-scale 3D-photogrammetric and ichnofossil analyses of two areas on the periphery of the MCDT surface demonstrate the presence of preserved primary paleotopography. The first area consists of a paleotopographic bench that drops off to a minimum of ∼0.5–0.6 meters. On this bench is at least one resting trace analogous to modern traces of crocodiles documented from topographic highs along rivers and lakes. At the second locality, systematic variations in track morphology indicate that the trackmaker gait was influenced by changes in surface elevation with movement across the ridge, thus affirming that paleorelief is preserved. The ichnofossils on this Cretaceous bedding surface likely represent months- to years-worth of biological activity.

Mesoproterozoic (∼1.4 Ga) magmatism in northern Alxa, China: Implications for tectonic affinity of microcontinents in the southern Central Asian Orogenic Belt

The origin and paleogeographic reconstruction of Precambrian microcontinents in the Central Asian Orogenic Belt (CAOB) are crucial for understanding continental crustal evolution, mechanisms of accretionary orogeny, and assemblage and breakup of the supercontinent during the Earth’s early history. The existence and basement nature of the South Gobi microcontinent within the central segment of the southern CAOB remain controversial. This study represents the first work to unveil the presence of Mesoproterozoic (∼1.4 Ga) intrusive rocks in the Zhusileng-Hangwula tectonic zone that is the central segment of the southern CAOB, and is distributed along the border areas between China and Mongolia. It offers pivotal evidence for the existence of the South Gobi microcontinent.Three alkali feldspar granites samples collected from the Zhusileng-Hangwula tectonic zone yielded crystallization ages ranging from 1371 ± 17 Ma to 1420 ± 29 Ma, while detrital zircons from a two-mica quartz schist xenolith yielded similar 206Pb/238U ages clustered around ∼1.4 Ga. The ∼1.4 Ga zircons display depleted Hf isotopic signatures (εHf(t) = 3.2–6.0) and relatively young two-stage Hf model ages (1.9–1.7 Ga), suggesting rapid reworking of juvenile mantle-derived materials. These findings indicate that the Zhusileng-Hangwula tectonic zone constitutes a microcontinental fragment with Mesoproterozoic basement, rather than a Paleozoic accretionary complex as previously postulated. Combining the contemporaneous magmatism data from the microcontinents in the southern CAOB, the 1.48–1.32 Ga arc-related magmatism exhibits a coherent trend of geochemical evolution, potentially indicating a geodynamic transition from a convergent to an extensional environment. Moreover, the temporal, tectonic evolution, and petrological similarities imply a tectonic affinity between these microcontinents and Fennoscandia, and they may have originated from an accretionary belt along the edge of Nuna during the Mesoproterozoic.

Conformably Variable Geocentric Axial Dipole at ca. 2.1 Ga: Paleomagnetic Dispersion of the Indin Dyke Swarm, Slave Craton

AbstractPrecambrian paleomagnetic studies are critical for testing paleogeographic reconstructions in deep time but rely on the fidelity of the assumption of the geocentric axial dipole (GAD) hypothesis. With high‐reliability data from mafic dykes and volcanic rocks, the scatter of individual virtual geomagnetic poles (VGPs) can be used to test simple GAD models. In order to conduct such a test, the VGPs must be adequate in number and in spatial coverage of the sampling sites. In this study, we targeted the 2.1 Ga Indin dyke swarm of the Slave craton. Building on previous sampling of the Indin dyke swarm in the western and central parts of southern Slave craton, we report results from 9 additional sites in the central and eastern parts of the craton, sites that significantly expand the width of the dyke swarm across the entire craton. The VGPs obtained from 7 of 9 newly identified Indin dykes are broadly similar to previously reported directions, expanding the total of VGPs for individual Indin dykes to n = 28, which is sufficient for a test of the GAD‐based statistical models using VGP scatter. The high VGP scatter of the Indin swarm can be attributed to the relatively high paleolatitude of 56° ± 6° for the Slave craton at the time of dyke emplacement. The Indin data have VGP scatter that is consistent with field models associated with the GAD hypothesis for the indicated paleolatitude, thus confirming the fidelity of the GAD field at ca. 2.1 Ga.

Integrated detrital rutile and detrital zircon ages: a new perspective on the tectonic evolution of South China.

Paleogeographic reconstructions are of key importance for understanding the history of continental breakups and amalgamations during Earth's history. A special case is the history of the Asian continent, which, compared to other continents, consists of several large cratons and numerous smaller continental blocks. The history of the assembly of South China remains controversial in terms of the timing, Late Neoproterozoic or Early Paleozoic, and the participating continental blocks, e.g. Yangtze, Cathaysia, India and Australia. Detrital rutile U-Pb dating has significant potential with regard to deciphering tectonic settings as rutile frequently crystallizes during orogenic events associated with the processes of collision and subduction. Detrital zircon U-Pb dating is a perfect instrument for identifying the provenance characteristics and age characteristics of sedimentary sources. An integration of these two methods of dating offers better opportunities for reconstructing tectonic settings. This paper presents a first attempt to reconstruct the Neoproterozoic to Early Paleozoic tectonic history and paleogeography of the whole South China based on U-Pb geochronology of rutile and zircon and Hf-in-zircon isotopes from Lower Jurassic Baitianba Formation sedimentary rocks of the western margin of the Yangtze Block, a major part of South China. Our obtained integrated U-Pb rutile and zircon age data show three main age populations of 960-940 Ma, 630-610 Ma and 530-520 Ma. The new U-Pb detrital rutile and zircon ages, compared with former data from Gondwana and Australia, suggest that Yangtze amalgamated with Cathaysia to form South China during the Sibao orogeny at 960-940 Ma. The detrital rutile and zircons of the new 630-610 Ma age group could have been delivered from western Australia during the Late Neoproterozoic to Cambrian Paterson-Petermann orogeny. The abundant 530-520 Ma detrital rutile and zircon ages fit well with the coeval zircon age populations recorded in Gondwana-derived terranes, like India and Indochina.

New data on the age and evolution of the late pleistocene cryogenesis in the southern caspian Lowland

The article presents new data on cryogenic structures of different periods found in sections in the south of the Lower Volga Region. Based on a comprehensive cryolithological analysis, cryogenic origin of these structures was confirmed. Absolute dating by the method of optically stimulated luminescence was used to determine the age of enclosing, overlying deposits and filler of the structures. Four stages of cryogenesis were established in in firth-marine deposits of the Lower Volga region: I stage ~115—105 ka (КОС-4 and КОС-3 horizons), II stage ~90—83 ka (КОС-2), III stage ~47—45 ka (CY-1), IV stage ~23—22 (КОС-1). In the south of the Caspian Lowland, with generally arid conditions existed throughout the Late Pleistocene, the humidity of sediments (determined by the geomorphological position of the sections) played a decisive role in the development of cryogenesis of cold stages. This study makes it possible to move the boundary of the maximum distribution of the Late Pleistocene permafrost area for this territory by 250 km to the south than previously assumed. The new data significantly refine our understanding of the stages and scales of the development of cryogenesis in the southeast of the East European Plain, and allow us to improve paleogeographic reconstructions for the Late Pleistocene of the Caspian Lowland.

Aeromagnetic data reveals buried Quaternary drainage patterns in the Gulf of St Lawrence (Canada)

Short-wavelength, low-amplitude magnetic anomalies form dendritic patterns on the shallow water (<100 m depth) Magdalen Plateau in the Gulf of St Lawrence, Canada. High-resolution seismic data indicate that these magnetic anomalies are associated with 0.6–2 km wide incised Quaternary valleys with relatively flat bottoms lying 30–70 m below the seafloor. The magnetic signature of the valleys is due to high magnetic susceptibility volcanic detritus derived from the erosion of the volcanic rocks that overlie most of the salt bodies in this area. This study shows that magnetic data may be a useful tool for mapping surficial sediments. These magnetic data provide the first offshore evidence for the direction of major water discharge. It remains unclear whether the valleys were formed by river incision during one or several regional lowstand(s) or from one or several sub-glacial discharge episode(s) across the Magdalen Plateau. The valley evidence should be incorporated into any future palaeogeographical reconstructions.

Paleogeographic reconstruction and sedimentary evolution of tidal-dominated estuarine depositional systems: Insights from the campanian M1 sandstone formation, Oriente Basin, Ecuador

The Oriente Basin is a back-arc basin located east of the Ecuadorian Andes in South America. Evidence suggests that during the Cretaceous period, the basin's margins received a terrigenous shallow marine sedimentation. Due to regional variations in accommodation and depositional controlling factors near a shoreline, the sedimentary environments in the fluvial-marine transitional zones exhibit considerable variability. In this study, we analyzed the sedimentological characteristics of the M1 Sandstone Formation unit (∼83 Ma-72 Ma), which comprises a set of ancient estuarine deposits preserved in the northern part of the basin. We quantified the impact of mixed hydrodynamic processes on the distribution of tidal-dominated estuarine facies and discussed the development conditions and evolutionary processes of an estuarine formation under the background of persistent transgression. Core, well log, and seismic data provide evidence for reconstructing the tidal-dominated estuarine environment. In the core section, we identified 14 lithofacies and 7 major facies association types. The frequent occurrence of sedimentary structures associated with tidal currents indicates that tidal processes extensively reworked the deposits. The spatial distribution trends of facies associations reveal the evolution of mixed hydrodynamic conditions dominated by tidal processes in the estuary and allow us to divide the M1 Sandstone Formation into four depositional periods: the initial development, rapid development, decline, and the post-infilling open coast tidal flat development periods. Furthermore, through a systematic analysis of hydrodynamic conditions and sediment distributions, we identified multiple depositional centers in the tidal-dominated estuary influenced by different hydrodynamic processes. These correspond to the upstream fluvial-dominated tidal point bar depositional region, the middle mixed-energy depositional interaction zone, and the downstream tidal-dominated tidal sand bar depositional region. In these regions, the substantial accumulation of sandy deposits, represented by tidal sand bars, reflects the high accommodation space characteristic of tidal-dominated estuaries. Our findings indicate that the slow subsidence of a broad and gently sloping coastal topography, stable material transport, and sea level change dominated by marine transgression ensured the necessary accommodation for the development of the estuary in the M1 Sandstone Formation. The sedimentological study of the M1 Sandstone Formation provides a case for understanding the sedimentary evolution in fluvial-marine transitional zones.

Cryophilic polychaetes at the subtropical Laurentian margin of the Iapetus Ocean: Evidence for cold-water ocean circulation and upwelling

Abstract Through the Phanerozoic eon, the trace fossil Macaronichnus—made by sediment-burrowing polychaetes—appears to be restricted to intermediate- and high-latitude shallow-marine habitats with cold to temperate waters or coastal areas closer to the equator with cold-water upwelling. We present records of such trace fossils in Ordovician (Darriwilian–Sandbian?) shallow- and deep-water marine deposits in the Central Norwegian Caledonides, pointing toward previously undocumented deep-ocean circulation and upwelling of cold water along the subtropical eastern Laurentian margin and adjacent volcanic arcs and microcontinents in the early Paleozoic Iapetus Ocean. Possible implications for Middle Ordovician ocean circulation patterns are discussed in relation to paleogeographic reconstructions and paleoclimatic models.

Spatiotemporal evolution of the early Permian multi-source-to-sink system in the northwestern margin of the North China Block: Implications for the paleogeographic reconstruction along the southern margin of the Paleo-Asian Ocean

The northwestern margin of the North China Block, situated at the intersection of multiple tectonic units, presents a complex geological setting that challenges paleogeographic reconstructions. The subduction and closure of the Paleo-Asian Ocean have further complicated the understanding of sediment provenance during the Early Permian. In this study, we integrated sedimentological, geochemical, and UPb dating methods to delineate the Early Permian source-to-sink systems along the northwestern margin of the North China Block. The identification of four key source-to-sink systems—the Alxa, Langshan, Serteng–Wula, and Jining–Daqing—reveals a pronounced east–west provenance differentiation, indicative of the regional tectonic and sedimentary responses to subduction of the Paleo-Asian Ocean.During the Shanxi Formation deposition, the western regions were dominated by the Inner Mongolian continental island arc as a principal sediment source, fostering distal meandering river deltas. Conversely, the eastern regions were predominantly influenced by the North China Block basement, leading to the deposition of proximal, shallow meandering river deltas. As the Shihezi Formation deposition ensued, the western source-to-sink systems continued to receive sediments from the uplifted Inner Mongolian Arc, transitioning to distal braided river deltas amidst an orogenic setting. Meanwhile, the eastern systems, particularly Jining–Daqing, showed increased contributions from the North China Block basement, forming mixed-source, shallow braided river deltas.This research provides a refined understanding of the spatiotemporal evolution of source-to-sink systems and their responses to the tectonic setting, offering valuable insights into the paleogeographic evolution along the southern margin of the Paleo-Asian Ocean.

Reconstructing the South American Miocene puzzle: An integrated analysis of the Paraná Formation (Argentina)

In recent decades, Miocene marine transgressions in South America have sparked ongoing debates concerning their boundaries, number of events, regional connectivity, and the existence of an epicontinental sea formed during the Andean orogeny. The bed-by-bed analysis of the Late Miocene Paraná Formation deposits in Entre Ríos Province (Argentina) allow defining six facies associations: (i) beach ridge, (ii) tidal inlet channel and washover fan, (iii) outer estuarine bioherms, (iv) central estuary, (v) tidal bar and sandflat, and (vi) tidal mudflat and creek deposits. Architectural and stacking pattern analyses reveal transgressive-regressive sequences typical of the coastal strip, encompassing shallow marine to estuarine sub-environments. The analysis identified diverse ecological guilds, including bivalve and gastropod assemblages in bioherms, and crustacean traces in tidal flats. Regressive units are characterized by wave-dominated shoreface deposits, while transgressive units comprise fine-grained estuarine deposits interbedded with bioclastic sandstones and storm deposits. The paleoenvironmental and paleoecological data indicate normal salinity marine environments with macroinvertebrates and estuarine components and suggesting tropical brackish conditions. Plant remains point to a range of vegetative communities, including mangroves, palm forests, grasslands, humid riparian forests, and dry upland forests, reflecting tropical to subtropical and humid to semiarid environments. This study concludes that the Paraná Formation correspond to a third-order transgressive system tract influenced by the Miocene Paranaense Sea. The basin-scale implications suggest that the distal Chaco-Paraná basin was affected by eustatic changes due to its low accommodation and topographic relief. The Chaco-Paraná foreland basin's evolution was driven by interactions between tectonic, climatic, and eustatic processes. The comprehensive analysis of sedimentary and fossil records provides a detailed paleogeographic reconstruction of the Miocene marine transgression in southern South America.

Phylogenetic Biogeography Inference Using Dynamic Paleogeography Models and Explicit Geographic Ranges.

To model distribution ranges, the most popular methods of phylogenetic biogeography divide Earth into a handful of predefined areas. Other methods use explicit geographic ranges, but unfortunately, these methods assume a static Earth, ignoring the effects of plate tectonics and the changes in the landscape. To address this limitation, I propose a method that uses explicit geographic ranges and incorporates a plate motion model and a paleolandscape model directly derived from the models used by geologists in their tectonic and paleogeographic reconstructions. The underlying geographic model is a high-resolution pixelation of a spherical Earth. Biogeographic inference is based on diffusion, approximates the effects of the landscape, uses a time-stratified model to take into account the geographic changes, and directly integrates over all probable histories. By using a simplified stochastic mapping algorithm, it is possible to infer the ancestral locations as well as the distance traveled by the ancestral lineages. For illustration, I applied the method to an empirical phylogeny of the Sapindaceae plants. This example shows that methods based on explicit geographic data, coupled with high-resolution paleogeographic models, can provide detailed reconstructions of the ancestral areas but also include inferences about the probable dispersal paths and diffusion speed across the taxon history. The method is implemented in the program PhyGeo.