Plate Tectonic Reconstructions Research Articles

Terrestrial impact craters track the voyage of lithospheric plates

The paradigm of plate tectonics has aided in the identification of the journey of continents on the globe, their assembly into supercontinents, disruption, and re‐assembly. Here, we use meteorite impact craters as proxies for tracking the voyage of lithospheric plates. Employing the provisions in GPlates, an interactive geographic information system‐based plate tectonic reconstruction model, we were able to identify the palaeo‐position, and velocity of the 174 terrestrial impact craters, formed after 1,100 Ma, across the globe. These parameters of craters were evaluated for independent tectonic plates and were correlated with global tectonic events. For example, the similarity in the velocity of Beaverhead (900 Ma) and Holleford (550 Ma) craters since 550 Ma is traced to the connection between the Eastern Basin and North America Craton commencing 1,100 Ma, and through the South Basin and Range. Likewise, the drastic reduction in the velocity of Spider Crater (700 Ma) in Australia after 600 Ma can be attributed to the subduction between east and west Gondwana. The accelerated motion of the Indian Plate at 63 Ma, when the lithosphere was hovering over the Réunion hotspot, is also explained. With the advent of more improved plate tectonic models and the discovery of more impact craters, improvised interpretations will be possible.

Comprehensive evaluation of Neoproterozoic source rocks formation

Based on comprehensive analysis of geological, geochemical, and paleotectonic settings, the conditions for the formation of Neoproterozoic oil and gas source rocks of the Earth are analyzed. A brief review of oil and gas fields in Eastern Siberia, China, the Middle East, Africa, and Australia is given, with Riphean and Vendian terrigenous and carbonate source rock. An overview of the oil and gas bearing basins of the world and a stratigraphic reference of the Neoproterozoic strata discovered within them, containing proven and suspected oil and gas source rocks, are given. The formation of Neoproterozoic oil and gas source rocks is analyzed in a complex way: simultaneously from the point of view of paleotectonics, paleogeographic and paleoclimatic conditions, paleobiological diversity and geochemical conditions. As part of paleotectonic analysis, the results of plate tectonic reconstructions for the Neoproterozoic stage are presented in accordance with one of the most currently relevant geodynamic models. Paleogeographic events and paleoclimatic conditions are described in the context of the specifics of the formation settings of carbonate-terrigenous oil and gas source rocks. In particular, the reasons for the accumulation of sediments enriched with organic carbon in the interglacial epochs of the Neoproterozoic and possible mechanisms for maintaining conditions favorable for their accumulation are considered. The conditions for the accumulation of oil and gas source rocks are also linked to global paleobiological pre-Phanerozoic events, and the analysis of the geochemical data of rocks makes it possible to characterize and correlate Neoproterozoic oil and gas source rocks on a global scale. On the basis of such a comprehensive assessment, a conclusion was made about fundamentally similar geological conditions for the formation of Neoproterozoic oil and gas source rocks in oil and gas bearing basins.

Proterozoic-Mesozoic development of the Quanji block from northern Tibet and the cratonic assembly of eastern Asia

Unraveling the timing, location, and mechanisms of cratonic aggregation in Earth9s continental jigsaw puzzle is a key factor for plate tectonic reconstructions. The Quanji Block (QB) is a sliver of anomalously old and well-preserved continental crust embedded within the Paleozoic-Mesozoic tectonic collage of the northeastern Tibetan Plateau and has played a critical role in Proto-/Paleotethys paleogeographic reconstructions. New geological mapping, stratigraphic logging, and geochronological analysis lead to a refined understanding of QB9s history from Paleoproterozoic to present. Deposited atop a largely Paleoproterozoic basement, the Quanji Group records rifting and epicratonic cover at 1.7 to 1.6 Ga. The Quanji Group is unconformably overlain by the Xiaogaolu Group, which preserves black shale, Ediacaran-type <i>Charnia</i>, ribbon-shaped fossils and a late Ediacaran glaciation. U-Pb detrital zircon ages from Cambrian Olongbuluke Group marine platform deposits are quite different from ages in underlying units, with a minor component of Neoproterozoic (880–815 Ma) ages. The apparent change in detrital zircon sources coincides with a regionally expressed Great Unconformity during the Precambrian–Cambrian transition. The new stratigraphy and U-Pb geochronology of QB suggest that the late Paleoproterozoic to Cambrian history of QB has a remarkable similarity to that of the southern margin of North China Block (NCB), indicating that the QB has been displaced dextrally from an initial location adjacent to NCB. The transform motion occurred in stages between <i>ca.</i> 350 and 200 Ma, which suggests that transform tectonism appears to be an essential element of any viable model for kinematic development of the Paleo-Tethyan oceanic domains and the ultimate cratonic assembly of eastern Asia.

Diachronous initiation of Arabia–Eurasia collision from eastern Anatolia to the southeastern Zagros Mountains since middle Eocene time

ABSTRACT The persistent debate over the timing of initial Arabia–Eurasia collision has eluded consensus for decades, with most estimates ranging widely from ~50 to 10 Ma along both the Anatolian and Zagros segments of the orogen. Here, we independently evaluate the timing and location of initial collision using a quantitative plate tectonic reconstruction that is the first to include the entire Arabian microcontinent and regions to the north in eastern Anatolia, northwestern Iran, and the Caucasus. The reconstruction combines new kinematic constraints from recent global plate models with a synthesis of available constraints on crustal shortening and continental and back-arc subduction to restore the pre-collisional geometries of the Arabian and Eurasian continental margins and to track their interaction through time. Our preferred model suggests that initial continental underthrusting, or soft collision, of the relatively thin Arabian passive margin with Eurasia occurred by ca. 42 Ma along the eastern Bitlis suture zone and began transmitting strain across central and eastern Anatolia, the Caucasus, and northwestern Iran. Collision inception then propagated westward into central Anatolia and southeastward into the northwestern Zagros Mountains by late Eocene time (ca. 40–35 Ma), the central Zagros by latest Eocene to early Oligocene time, (ca. 35–25 Ma), and finally the southeastern Zagros by latest Oligocene to middle Miocene time (ca. 25–15 Ma). The diachroneity of Arabia collision led to widespread upper-plate (Eurasian) contraction and a similarly time-transgressive magmatic lull that lagged behind the onset of collision by ~2–12 Myr. By incorporating the entire Arabian microcontinent and regions to the north, this new tectonic reconstruction highlights the diachronous nature of Arabia–Eurasia collision that occurred first along the Bitlis suture zone in eastern Anatolia during late middle Eocene time and became progressively younger to the southeast along strike of the Zagros suture zone.

Long-term Phanerozoic sea level change from solid Earth processes

The sedimentary rock record suggests that global sea levels may have fluctuated by hundreds of meters throughout Phanerozoic times. Long-term (10–80 Myr) sea level change can be inferred from paleogeographic reconstructions and stratigraphic methods can be used to estimate sea level change over 1–10 Myr in tectonically quiescent regions assumed to be stable. Plate tectonic reconstructions and mantle flow models make it possible to isolate, quantify and estimate the contribution of different solid Earth mechanisms to sea level change through time, including: the volume of water deeper than mid-oceanic ridges, mantle dynamic topography, marine sedimentation, oceanic large igneous province emplacement, deep-water cycle, volume above oceanic trenches and changes in continental area. Although these processes are intrinsically linked, their impact on sea level change is rarely studied in combination, and time-dependent models of long-term eustasy from tectonic and geodynamic processes are in their infancy. Here we couple plate tectonic reconstructions with time-dependent models of past mantle flow and develop a new holistic framework to model sea level change that accounts for the main solid Earth drivers of eustatic rise and fall. We present the first model of the effect of individual solid Earth mechanisms on eustatic change over the past 560 Myr, including time-dependent continental and oceanic dynamic topography, volume above oceanic trenches and changing continental slope. Our results are consistent with the Cretaceous highstand and Paleozoic and early Mesozoic lowstands deduced from stratigraphy, provided that the deep-water cycle contributed ∼240 m of sea level drop since 250 Myr. We find that changes in the volume of water below the depth of mid-ocean ridges are not balanced by changes in the volume of water above subduction zones or by global dynamic topography. Our results confirm that a young seafloor decreased the volume of water below the depth of ridges and contributed +280 m [+90/−0 m] to a sea level high at approximately 120 Ma, and show that changes in dynamic topography were the primary driver (−320 m [+80/−60 m]) of lowering sea level between ∼240–160 Ma when Pangea was assembled. Predicted sea level changes by up to −220/+470 m when Panthalassan mid-ocean ridge spreading rates are varied between 50 mm/yr and 200 mm/yr. We compute sea level estimates for two alternative global tectonic reconstructions and while the results differ (by ∼150 m) between 250-560 Ma, both suggest a sea level fall during Pangea assembly (between ∼380-320 Ma) that is consistent with published constraints.

Choosing between a dichotomy of methods in stratigraphy

An overview of stratigraphical methods here focusses on the tectonically active basins of Southeast Asia, where studies over the past three decades have tried to adopt global methods. Unfortunately, these attempts inevitably moved towards a hybrid method that is argued to be neither satisfactory or even scientific. It is proposed that, in order to understand a complex area controlled by tectonism, a paradigm shift to a fully inductive, or evidence‐based methodology is required. Initial attempts to do this are improving our understanding of the sedimentary geology, as well as enhancing plate tectonic reconstructions and mechanisms.

The continent-to-ocean transition in the Iberia Abyssal Plain

Abstract Conceptual models of magma-poor rifting are strongly based on studies of the nature of the basement in the continent-to-ocean transition of the Iberia Abyssal Plain, and suggest that exhumed mantle abuts extended continental crust. Yet, basement has only been sampled at a few sites, and its regional nature and the transition to seafloor spreading inferred from relatively low-resolution geophysical data are inadequately constrained. This uncertainty has led to a debate about the subcontinental or seafloor-spreading origin of exhumed mantle and the rift-related or oceanic nature of magmatic crust causing the magnetic J anomaly. Different interpretations change the locus of break-up by &amp;gt;100 km and lead to debate of the causative processes. We present the tomographic velocity structure along a 360-km-long seismic profile centered at the J anomaly in the Iberia Abyssal Plain. Rather than delineating an excessive outpouring of magma, the J anomaly occurs over subdued basement. Furthermore, its thin crust shows the characteristic layering of oceanic crust and is juxtaposed to exhumed mantle, marking the onset of magma-starved seafloor spreading, which yields the westward limit of an ~160-km-wide continent–ocean transition zone where continental mantle has been unroofed. This zone is profoundly asymmetric with respect to its conjugate margin, suggesting that the majority of mantle exhumation occurs off Iberia. Because the J anomaly is related to the final break-up and emplacement of oceanic crust, it neither represents synrift magmatism nor defines an isochron, and hence it poorly constrains plate tectonic reconstructions.

Subduction and carbonate platform interactions

AbstractPlate tectonics, as the unifying theory in Earth sciences, controls the functioning of important planetary processes on geological timescales. Here, we present an open‐source workflow that interrogates community digital plate tectonic reconstructions, primarily in the context of the planetary deep carbon cycle. We present an updated plate tectonic reconstruction covering the last 400 million years of Earth evolution and explore components of the plate–mantle system that is involved in the exchange and storage of carbon. First, the workflow enables us to estimate subduction zone lengths through time, which represent the “tap” of carbon that is released at convergent tectonic margins. Second, we explore the role of Andean‐style versus intra‐oceanic subduction regimes during Pangea assembly and breakup. Third, we provide an improved model for carbonate platform evolution since the Devonian and evaluate the interaction of subduction zones and buried carbonate platforms. Last, we present a new model for estimating oceanic age, carbon content in the upper oceanic crust, and estimated (carbon‐containing) sediment thicknesses through time and present methods to track the subduction of this material through time. These components of the deep carbon cycle are key mechanisms controlling, or at least modulating, atmospheric CO2 on geological timescales and hence strongly influencing long‐term climate. We find that the mid to Late Cretaceous greenhouse climates were likely driven by increased subduction fluxes of volatiles and increased subduction zone interactions with carbonate platforms in the Tethyan tectonic domain. Our work highlights the importance of community digital plate tectonic reconstructions as a framework for studying key systems, such as the deep carbon cycle, that influence the life‐support mechanisms on our planet.

Integrated thermodynamic and thermomechanical numerical modeling: A useful method for studying deep Earth water and carbon cycling

The plate tectonic evolution controls the mass and energy circulation between the Earth's surface and interior, during which the volatiles (e.g., water and carbon) could also accompany the tectonic up- and down-wellings. The deep Earth injection of volatiles (ingassing mainly via subduction) can modify the physical and chemical properties of rocks and thus strongly affect the processes and dynamics of Earth's interior. On the other hand, the emission of volatiles to the Earth's surface (outgassing mainly through volcanism and rifting) can influence the evolution of atmosphere, climate and habitability. Thus, the deep water and carbon cycling plays important roles in not only the solid Earth dynamics, but also the surficial environments. The time-dependent evolution of deep Earth condition and large-scale plate tectonic reconstruction have generally been used to infer the fluxes and pathways of water and carbon cycling, as well as the resulting ocean water and atmospheric carbon evolution in the Earth's surficial reservoirs. Besides multiple observations and experiments, the integrated thermodynamic and thermomechanical numerical modeling provides as a useful way for studying deep Earth water and carbon cycling in variable tectonic settings and with different conditions. In the review, I firstly introduce the numerical method integrating thermodynamic data into thermomechanical principles. Then, several typical numerical models are introduced, which highlight, respectively, the (de)hydration in shallow lithospheric subduction channel, the deep water cycling in the upper mantle and transition zone, as well as the subduction-induced carbon cycling. Finally, the general issues about water and carbon fluxes between the Earth's interior and surface are discussed, which are less constrained issues and require further studies with possible contributions from the integrated thermodynamic and thermomechanical numerical modeling.

U‐Pb Zircon Geochronology From the Northern Cordillera, Central Yukon, With Implications for Its Tectonic Assembly

AbstractThe tectonic assembly of the Northern Cordillera is currently disputed and directly impacts Paleozoic‐to‐recent paleogeographic and plate tectonic reconstructions of North America. In this study, we present new U‐Pb zircon geochronology from the allochthonous Yukon‐Tanana terrane and the parautochthonous Cassiar terrane of the Northern Cordillera from south‐central Yukon, Canada. Our data provide new constraints for the assembly of the Northern Cordillera in this region. Metasedimentary samples from the Ingenika Group (Cassiar terrane) and the Snowcap and Finlayson assemblages (Yukon‐Tanana terrane) yielded detrital zircon age spectra that are comparable to known northwest Laurentia age spectra. One of our samples from the Snowcap assemblage yields a detrital zircon age spectrum that is anomalous for northwest Laurentia, but comparable to Early Paleozoic strata deposited in the Nevada‐Idaho‐Utah region. Zircon rim growth and Pb‐loss recorded by detrital zircon in the Snowcap assemblage and Ingenika Group samples record metamorphism at 370 ± 4 Ma and between 171 ± 5 and 135 ± 3 Ma. Late Devonian metamorphism and magmatism possibly corresponds to rifting of the Snowcap assemblage from the Laurentian margin. Middle Jurassic‐Early Cretaceous metamorphic zircon rim ages from the Cassiar terrane record metamorphism during collisions between the Intermontane superterrane (including the Yukon‐Tanana terrane) and Laurentia (Early to Middle Jurassic), and between the Insular superterrane and Laurentia (Middle to Late Jurassic). Our study suggests that collision between the Yukon‐Tanana terrane and the Laurentian margin began no earlier than ∼205 Ma.

Has the impact flux of small and large asteroids varied through time on Mars, the Earth and the Moon?

The impact flux over the last 3 Ga in the inner Solar System is commonly assumed to be constant through time due to insufficient data to warrant a different choice for this range of time. However, asteroid break-up events in the main belt may have been responsible for cratering spikes over the last ∼2 Ga on the Earth-Moon system. Due to its proximity with the main asteroid belt, i.e., the main impactors reservoir, Mars is at the outpost of these events with respect to the other inner planets. We investigate here, from automatic crater identification, the possible variations of the size frequency distributions of impactors from the record of small craters of 521 impact craters larger than 20 km in diameter. We show that 49 craters (out of the 521) correspond to the complete crater population of this size formed over the last 600 Ma. Our results on Mars show that the flux of both small (> 5 m) and large asteroids (> 1 km) are coupled, does not vary between each other over the last 600 Ma. Existing data sets for large craters on the Earth and the Moon are analyzed and compared to our results on Mars. On Earth, we infer the formation location of a set of impact craters thanks to plate tectonic reconstruction and show that a cluster of craters formed during the Ordovician period, about 470 Ma ago, appears to be a preservation bias. On the Moon, the late increase seen in the crater age signal can be due to the uncertain calibration method used to date those impacts (i.e. rock abundance in lunar impact ejecta), and other calibrations are consistent with a constant crater production rate. We conclude to a coupling of the crater production rate between kilometer-size craters (∼100 m asteroids) and down to ∼100 m in diameter (∼5 m asteroids) in the inner Solar System. This is consistent with the traditional model for delivering asteroids to planet-crossing obits: the Yarkovsky effect slowly pushes the large debris from asteroid break-ups towards orbital resonances while smaller debris are grinded through collisional cascades. This suggests that the long-term impact flux of asteroids > 5 m is most likely constant over the last 600 Ma, and that the influence of past asteroid break-ups in the cratering rate for D > 100 m is limited or inexistent.

Overview on GPlates: focus on plate reconstruction

Plate tectonic reconstructions have been employed in geosciences since 1970s, in the context of hydrocarbon exploration, regional geology and paleobiology. Such studies have given valuable inputs for climate and geodynamic computations, present-day mantle structure, models of plate motion, and the interpretation of the drift of hotspots, true polar wander (TPW), sea level and stratigraphic signals. However, geodynamic models generated in the past by incorporating global plate tectonic reconstructions have limitations. To overcome this, GPlates software brings forward a new era of interactive plate tectonic reconstruction software integrated with GIS databases that incorporates a wide variety of geological and geophysical data. Besides modelling tectonic and crustal evolution, GPlates has also been used in visualizing paleogeography and paleobathymetry, in understanding deep carbon cycle, subduction zone initiation, mantle evolution, investigating earthquakes and predicting future supercontinents. the software has been widely used in hydrocarbon exploration along the passive conjugate margins such as from the margins of South America and Africa and has provided promising results in acquiring new and more reliable prospecting criteria for petroleum systems. Additionally, it has become an integral tool for paleolatitude calculations, modelling of paleoclimate and paleoenvironment. This article reviews key plate reconstructions that have been carried out using GPlates, the typical constraints and the set of input parameters.

Latitudinal land–sea distributions and global surface albedo since the Cretaceous

We estimate global surface albedo from the areal proportion of land to sea in climatically-significant latitudinal belts at ten million-year intervals for the Late Cretaceous and Cenozoic (120 million years ago to Present) using modern plate tectonic reconstructions and a composite apparent polar path designed to minimize known biases in the determination of paleolatitude. We find that global surface albedo stayed almost constant until it shifted 30% higher to the modern value of around 0.15 with the inception of the Late Cenozoic Ice Age 34 million years ago, reflecting polar ice-albedo amplification of global cooling resulting from the reduction of greenhouse gases below a critical threshold, most probably as the culmination of enhanced CO 2 weathering consumption of continental mafic rocks in the tropical humid belt. The contribution from cloud cover toward a planetary albedo is unclear in the absence of measurable proxies but might eventually be gauged from the role cloudiness evidently plays in maintaining radiative balance with the increasing land bias between northern and southern hemispheres over the Cenozoic. • Changes in land–sea area were small in equatorial and polar climate belts from 120 Ma • Land area decreased in temperate belts and increased in subtropical arid belts • Global surface albedo was low from 120 to 40 Ma and shifted to modern value by 30 Ma • Increase in surface albedo due to polar ice cover with Late Cenozoic Ice Age at 34 Ma • Ice age reflects polar amplification of global cooling triggered by drawdown of CO 2

PetroChron Antarctica: A Geological Database for Interdisciplinary Use

AbstractWe present PetroChron Antarctica, a new relational database including petrological, geochemical and geochronological data sets along with computed rock properties from geological samples across Antarctica. The database contains whole‐rock geochemistry with major/trace element and isotope analyses, geochronology from multiple isotopic systems and minerals for given samples, as well as an internally consistent rock classification based on chemical analysis and derived rock properties (i.e., chemical indices, density, p‐velocity, and heat production). A broad range of meta‐information such as geographic location, petrology, mineralogy, age statistics and significance are also included and can be used to filter and assess the quality of the data. Currently, the database contains 11,559 entries representing 10,056 unique samples with varying amounts of geochemical and geochronological data. The distribution of rock types is dominated by mafic (36%) and felsic (33%) compositions, followed by intermediate (22%) and ultramafic (9%) compositions. Maps of age distribution and isotopic composition highlight major episodes of tectonic and thermal activity that define well known crustal heterogeneities across the continent, with the oldest rocks preserved in East Antarctica and more juvenile lithosphere characterizing West Antarctica. PetroChron Antarctica allows spatial and temporal variations in geology to be explored at the continental scale and integrated with other Earth‐cryosphere‐biosphere‐ocean data sets. As such, it provides a powerful resource ready for diverse applications including plate tectonic reconstructions, geological/geophysical maps, geothermal heat flow models, lithospheric and glacial isostasy, geomorphology, ice sheet reconstructions, biodiversity evolution, and oceanography.

Morphotectonic signatures and revised timing of opening of the Andaman Backarc Basin, Northeast Indian Ocean

The Andaman Backarc Basin is believed to have been formed by the present episode of seafloor spreading in the Andaman Sea, separating the Alcock Rise in the north (Burmese Plate) and the Sewell Rise in the south (Sunda Plate). The geophysical investigations carried out so far in this basin provided detailed information on the morphotectonic signatures of its central sector, however, such understanding of the eastern sector is still awaited. Those studies also inferred continual seafloor spreading in the Andaman Backarc Basin starting from 4.0 Ma, however, some of the subsequent studies, based on deep water sedimentation, postulated an episodic seafloor spreading responsible for the formation of the Andaman Backarc Basin. To address these problems, we revisited the morphotectonic signatures and evolution of the Andaman Backarc Basin using a new set of multibeam bathymetry and magnetic data from the central and eastern sectors of the Andaman Backarc Basin, complemented by the existing geophysical data from the central sector. Our updated bathymetry map of the newly surveyed northernmost segment (referred as Segment D), is characterized by the presence of a well-defined rift valley, with an along-axis gentle dip from the east to the west. The segment D is also characterized by the absence of significant magnetic anomalies, as in the case of segment C, corroborating the concept of replacement of layer 2A by a sill-sediment-metasedimentary layer, in a sedimented spreading centre. Further, our revisit to the magnetic anomaly identifications suggests that the magnetic anomalies over the segment B of the Andaman Backarc Basin can reasonably be explained in terms of continual seafloor spreading from chron C3An.1ny (5.894 Ma) till the present (0.0 Ma). Based on these identifications of magnetic anomalies and the plate tectonic reconstructions, we revise the age of opening of the Andaman Backarc Basin from 4.0 Ma to ~5.9 Ma.

Carbonatites and Global Tectonics

Carbonatites have formed for at least the past three billion years. But over the past 700 My the incidence of carbonatites have significantly increased. We compile an updated list of 609 carbonatite occurrences and plot 387 of known age on plate tectonic reconstructions. Plate reconstructions from Devonian to present show that 75% of carbonatites are emplaced within 600 km of craton edges. Carbonatites are also associated with large igneous provinces, orogenies, and rift zones, suggesting that carbonatite magmatism is restricted to discrete geotectonic environments that can overlap in space and time. Temporal constraints indicate carbonatites and related magmas may form an ephemeral but significant flux of carbon between the mantle and atmosphere.

Earth history events shaped the evolution of uneven biodiversity across tropical moist forests

Far from a uniform band, the biodiversity found across Earth's tropical moist forests varies widely between the high diversity of the Neotropics and Indomalaya and the relatively lower diversity of the Afrotropics. Explanations for this variation across different regions, the "pantropical diversity disparity" (PDD), remain contentious, due to difficulty teasing apart the effects of contemporary climate and paleoenvironmental history. Here, we assess the ubiquity of the PDD in over 150,000 species of terrestrial plants and vertebrates and investigate the relationship between the present-day climate and patterns of species richness. We then investigate the consequences of paleoenvironmental dynamics on the emergence of biodiversity gradients using a spatially explicit model of diversification coupled with paleoenvironmental and plate tectonic reconstructions. Contemporary climate is insufficient in explaining the PDD; instead, a simple model of diversification and temperature niche evolution coupled with paleoaridity constraints is successful in reproducing the variation in species richness and phylogenetic diversity seen repeatedly among plant and animal taxa, suggesting a prevalent role of paleoenvironmental dynamics in combination with niche conservatism. The model indicates that high biodiversity in Neotropical and Indomalayan moist forests is driven by complex macroevolutionary dynamics associated with mountain uplift. In contrast, lower diversity in Afrotropical forests is associated with lower speciation rates and higher extinction rates driven by sustained aridification over the Cenozoic. Our analyses provide a mechanistic understanding of the emergence of uneven diversity in tropical moist forests across 110 Ma of Earth's history, highlighting the importance of deep-time paleoenvironmental legacies in determining biodiversity patterns.

Papanin Ridge and Ojin Rise Seamounts (Northwest Pacific): Dual Hotspot Tracks Formed by the Shatsky Plume

AbstractAlthough previous findings support an origin of the Shatsky Rise igneous plateau (Northwest Pacific) through interaction of a mantle plume with a mid‐ocean ridge triple junction, the evidence for the involvement of a mantle plume is equivocal. The identification of an intraplate hotspot track emanating from the plateau could solve this controversy. Here we present major and trace element geochemical data from two different bathymetric features that emanate from the youngest end of Shatsky Rise: Papanin Ridge and the Ojin Rise Seamount province. Combining our results with plate tectonic reconstructions, we conclude that Papanin Ridge represents a hotspot track formed by plume‐ridge interaction. Whereas the southwestern part was formed along the path of the retreating Pacific‐Farallon‐Izanagi triple junction, the northeastern part was built by preferential drainage into its Pacific‐Farallon branch. In contrast, the Ojin Rise Seamounts formed as a true intraplate hotspot track of the Shatsky plume tail. Our wide‐ranging study reveals systematic spatial geochemical variations, consistent with a lithospheric thickness control on magma composition derived from melting a heterogeneous plume source. The recognition of two hotspot tracks and in particular of the Ojin Rise Seamounts as an intraplate hotspot track that is directly linked to Shatsky plateau volcanism both in terms of geochemistry and plate tectonic reconstructions confirms the long‐disputed involvement of a mantle plume for the formation of Shatsky Rise.

Multiple melt source origin of the Line Islands (Pacific Ocean)

Abstract The Line Islands volcanic chain in the central Pacific Ocean exhibits many characteristics of a hotspot-generated seamount chain; however, the lack of a predictable age progression has stymied previous models for the origin of this feature. We combined plate-tectonic reconstructions with seamount age dates and available geochemistry to develop a new model that involves multiple melt regions and multiple melt delivery styles to explain the spatial and temporal history of the Line Islands system. Our model identifies a new melt source region (Larson melt region at ~17°S, ~125°W) that contributed to the formation of the Line Islands, as well as the Mid-Pacific Mountains and possibly the Pukapuka Ridge.

Investigating the Plate Kinematics of the Bay of Biscay Using Deformable Plate Tectonic Models

AbstractThe plate kinematics of the Iberian plate and their implications on the plate tectonic evolution of the Bay of Biscay during rifting and subsequent opening of the southern North Atlantic continue to be topics of scientific discussion and debate. Constrained by previous plate reconstruction, geophysical, and geological studies, deformable plate tectonic reconstructions of the Bay of Biscay‐Parentis rift system are created in this study using the GPlates software. These deformable plate models are used to investigate the kinematics of the Landes High, Le Danois High, and Ebro Block previously recognized as independent continental blocks within deformable regions. A comparison between results calculated via deformable plate models with previously published and newly presented gravity inversion crustal thickness estimates provided a good metric for delineating the most probable plate kinematic scenario for the Bay of Biscay‐Parentis system and investigating the effect of the plate kinematic scenarios on the present‐day structure. The preferred plate kinematic model implies a transtensional Bay of Biscay‐Parentis rift system from the Jurassic to Early Cretaceous, with the onset of significant crustal thinning initiating during the Late Jurassic (∼150 Ma) induced by the motion of the Landes High and its interplay with the Ebro Block. Aside from demonstrating the role of the Landes High and its suggested interplay with structural inheritance on the deformation experienced within the Bay of Biscay, the timing and orientation of regional stress directions, and the velocities induced by the preferred deformable model provide good comparisons with previously calculated subsidence rates.