Orogenic Structures Research Articles

Slowing Convergence Controls on Orogeny: A Three‐Stage Evolution of the Cenozoic India‐Asia Collision

AbstractThe Cenozoic India‐Asia convergence represents the most well‐documented case of long‐lived orogeny, characterized by slowing plate convergence and complex deformation across the collisional margin, from crustal burial, exhumation and thrusting in the Himalaya, to thickening of southern Tibet. Here, we use a thermo‐mechanical computational model to show the controls of decelerating convergence on the lithospheric and orogenic structures during prolonged collision. Constant convergence velocity models, bracketing the India‐Asia convergence velocity, illustrate two rheological end‐members, a fast‐convergence orogeny dominated by lithospheric underthrusting and crustal burial and exhumation, and a slow convergence orogeny dominated by fold‐and‐thrusting and no lithospheric underthrusting. In contrast, models simulating the decelerating India‐Asia convergence history show a unique evolutionary path. The initial structures formed at fast convergence are subsequently destabilized as convergence decreases below ∼5 cm yr−1, and the structural style transitions from crustal burial and exhumation, and thickening to outwards compression along a frontal fold‐and‐thrust belt, progressively underthrusted by the subducting lithosphere. As the convergence decreases below ∼3 cm yr−1, the reduced compression cannot sustain the plateau height and crustal thickness, inducing collapse of the orogen interiors and the diapiric ascent of buried crust. These models show a three‐stage orogeny: fast thickening with crustal exhumation, widening along a frontal and fold‐and‐thrust belt, and internal collapse and extension. Similar to structuring of the Himalaya‐southern Tibet, with the early rise of the southern Tibetan Plateau to the Himalayan crystallines formation, to the later thrust belt expansion and internal doming, reconcile with the three‐stages orogeny, emphasizing the role of slowing convergence on orogenies.

Devonian-Mississippian magmatism related to extensional collapse in Svalbard: implications for radiating dyke swarms.

Despite extensive studies of the Mesozoic-Cenozoic magmatic history of Svalbard, little has been done on the Paleozoic magmatism due to fewer available outcrops. 2D seismic reflection data were used to study magmatic intrusions in the subsurface of eastern Svalbard. This work presents seismic evidence for west-dipping, Middle Devonian-Mississippian sills in eastern Spitsbergen, Svalbard. The sills crosscut a late Neoproterozoic Timanian thrust system, which was reworked during Caledonian contraction. The sills are unconformably overlain by relatively undeformed Pennsylvanian-Mesozoic sedimentary rocks and crosscut by Cretaceous dykes of the High Arctic Large Igneous Province. The sills probably intruded along extensional fractures during post-Caledonian reactivation-overprinting of the late Neoproterozoic thrust system. Kimberlitic accessory minerals in exposed contemporaneous intrusions and the chemical composition of chromium spinel grains in Upper Triassic sedimentary rocks in Svalbard suggest that the Middle Devonian-Mississippian intrusions in eastern Spitsbergen show affinities with diamond-rich kimberlites in northwestern Russia. Overall, the sills were emplaced during a regional episode of extension-related Devonian-Carboniferous magmatism in the Northern Hemisphere including the Kola-Dnieper and Yakutsk-Vilyui large igneous provinces. This work presents the first evidence for extensive Middle Devonian-Mississippian magmatism in Svalbard. These intrusions may be part of the Kola-Dnieper Large Igneous Province and intruded parallel to preexisting, Proterozoic-early Paleozoic orogenic structures. Their strike is inconsistent with a source from a potential mantle plume center in the eastern Barents Sea. Thus, the radiating emplacement pattern of the magmatic intrusions of the Kola-Dnieper Large Igneous Province are not the product of plume-related uplift but of structural inheritance. A similar line of reasoning is successfully applied to intrusions of the Yakutsk-Vilyui and High Arctic large igneous provinces.

From Orogeny to Rifting: The Role of Inherited Structures During the Formation of the South China Sea

AbstractMany of the world's rifts and rifted margins have developed within former orogens. The South China Sea (SCS) formed during Cenozoic rifting by utilizing pre‐existing orogenic structures, like thrust faults, thickened crust, and corresponding thermal weaknesses. The mechanisms explaining how inherited structures influence the spatiotemporal evolution of a rift remain a topic of on‐going research. Here, we explore the impact of orogenic inheritance on rift evolution through a numerical forward model that reproduces geodynamic and landscape evolution processes. By imposing time‐dependent phases of shortening and extension, we model rifted margin formation that is consistent with the available geological and geophysical observations of the SCS. Our numerical models allow us to identify thrust faults that are reactivated as normal faults during extensional phases. Not all pre‐existing thrust faults, however, undergo full reactivation, as their behavior is influenced by variations in lithospheric strength and the pre‐existing structural discontinuities. We further show that inherited orogenic structures compete with each other during extensional reactivation and ultimately govern the location of continental breakup. Our results provide valuable insights into the broader implications of inherited orogenic structures and how they affect subsequent rift system evolution.

Inverted metamorphic gradient in the Zanhuang nappe/thrust system, north China indicates large-scale thrust stacking in an Archean Orogen

We report a dramatic inverted metamorphic gradient across an Archean suture zone in the North China craton. The upper plate of the suture experienced metamorphic conditions of 650–700 °C/7–11 kbar, whereas the lower plate experienced temperatures of 500–600 °C, and pressures of 4-6 kbar, rising slightly in the frontal thrusts of the orogen. Importantly, we show that metamorphic conditions drop from 11 kbar/700 °C to 4 kbar/500 °C over a mere 1 km across-strike, representing a depth difference of almost 20 km across the frontal thrust fault. P-T trajectories derived from the upper plate record decompression, whereas those from the lower plate record a prograde path with increasing temperature. We show that the inverted metamorphic gradient formed during emplacement of thrust sheets during an Archean arc/continent collision, accommodating horizontal transport of at least hundreds of kilometers 2.5 billion years ago. Peclet number analysis shows that the inverted gradient formed with a thrusting rate of ∼ 30 mm/yr, consistent with modern analogues. This finding enhances our understanding of Archean tectonics and highlights similar convergence rates and thermal structure of orogens between Archean and modern examples.

In situ Rb–Sr geochronology of slickensides reveals reactivation of cratonic margins post-Gondwana assembly

Assessing the time-strain evolution of orogenic structures is a crucial but difficult task, especially for upper-crust structures where the deformation conditions are often below the closing temperature of the main geochronometers. Conventional Rb–Sr and total fusion 40Ar/39Ar techniques are insufficient to spatially-resolve distinct microstructures, such as inherited and recrystallized micas associated with fault zones developed under low to medium-temperature conditions. Here we present in situ Rb–Sr geochronology of fine-grained micas from fault-related rocks of the São Francisco Craton margin, in the Southern Espinhaço Range (SE Brazil), to investigate the timing and effects of fault reactivation at the dawn of Gondwana assembly. Fine-grained muscovite and biotite from slickensides yield Rb–Sr isochron ages spanning 500–450 Ma associated to thrust faults reactivation. This tectonic reactivation is coeval with brittle-ductile deformation of marbles in the footwall of the main regional thrust zones. These novel mica Rb–Sr ages indicate that thrust reactivation was 30–80 Ma younger than the last regional metamorphic event related to collisional deformation in the Araçuaí Orogen, coinciding with the timing of post-collisional magmatism and a fluid flow event in the cratonic margin. We envisage that fault reactivation in the São Francisco Craton margin might be associated with thermal post–orogenic relaxation due to gravitational collapse of the Araçuaí Orogen, with gravity-driven mass transport from the orogenic core causing compressive reactivation in the external fold-thrust-belt. These new results indicate that the Brasiliano thrust fronts remained active throughout the main interval of biogeochemical development in the Ediacaran–Cambrian transition post-Gondwana assembly.

Provenance composition and evolution of marine black shales in the Yangtze platform from Ediacaran to Silurian

Provenance is important in understanding the evolution of geological structure and the coupling of the basin-mountain system. Although many geochemical data document the three sets of marine black shales (Ediacaran to Silurian) in the Yangtze Platform, the evolution characteristics of their sediment sources remain unclear. We gather a huge database from 307 published papers totaling 12,342 analyzed samples to establish provenance. Pearson correlation coefficient and multivariate statistical analyses were performed to establish the element and mineral links in the black shale. Nine immobile elemental ratios (Ti/Th, Th/Sc, Cr/Th, Ti/Zr, Sc/Ta, Ti/Nb, Sc/La, Zr/Sc, and La/Ti) were employed to indicate provenance. The results show that the black shales of the Longmaxi and Niutitang formations are relatively enriched in redox sensitive and productivity related elements such as V, Cr, Mo, U, Co, Ni, Cu, Zn, and Ba. The use of provenance analysis proxies, including V, Cr, Mo, Ce, Fe, P, Ba, Cu, Ni, and Si, should be approached with caution due to the potential interference of marine authigenic components. The three black shales have provenance compositions that gradually extend from intermediate to felsic from the Doushantuo to the Niutitang to the Longmaxi shale. This difference in provenance is a response to the Pan-African and Kwangsian orogenic structures which are likely to impact the paleomarine environment by variable biotrophic element inputs.

The orogenic bridge theory: towards a predictive tool for past and future plate tectonics

Wegener’s Continental Drift Theory has laid the foundations of modern plate tectonics. However, despite decades of work and studies around the globe, modern plate tectonics still does not explain all the datasets acquired up to now and is well overdue for a major update. We propose a new theory, the orogenic bridge theory, which partly builds on the Continental Drift Theory and modern plate tectonics and reconciles them with the idea put forward by a competing theory, the Land Bridge Theory (or Isthmian Links). The orogenic bridge theory states that the style of continental rifting is directly controlled by preexisting orogenic structures. On the one hand, preexisting orogens trending parallel to an opening rift facilitate breakup and rift propagation and control the strike and geometry of rift-related structures. This endmember has already been broadly studied worldwide. On the other hand, orogens oriented orthogonal (or highly oblique) to the opening rift will act as strong barriers forcing the rift to step, therefore delaying or impeding breakup and rift propagation and localizing the formation of major-offset transform faults. In the present contribution, we review the evidence in favor of a correlation between rift-orthogonal orogens and major transforms and discuss some of the main implications of the orogenic bridge theory.

Impact of rift history on the structural style of intracontinental rift-inversion orogens

Abstract Although many collisional orogens form after subduction of oceanic lithosphere between two continents, some orogens result from strain localization within a continent via inversion of structures inherited from continental rifting. Intracontinental rift-inversion orogens exhibit a range of structural styles, but the underlying causes of such variability have not been extensively explored. We use numerical models of intracontinental rift inversion to investigate the impact of parameters including rift structure, rift duration, post-rift cooling, and convergence velocity on orogen structure. Our models reproduce the natural variability of rift-inversion orogens and can be categorized using three endmember styles: asymmetric underthrusting (AU), distributed thickening (DT), and localized polarity flip (PF). Inversion of narrow rifts tends to produce orogens with more localized deformation (styles AU and PF) than those resulting from wide rifts. However, multiple combinations of the parameters we investigated can produce the same structural style. Thus, our models indicate no unique relationship between orogenic structure and the conditions prior to and during inversion. Because the style of rift-inversion orogenesis is highly contingent upon the rift history prior to inversion, knowing the geologic history that preceded rift inversion is essential for translating orogenic structure into the processes that produced that structure.

Features of the Geological Structure and Polymetallic Mineralization of the Uspensky (Central Kazakhstan) and Dalnegorsky (Far East) Ore Districts

Polymetallic deposits of lead and zinc are of great importance in the economy of the developed countries of the world. Kazakhstan is among the world leading countries in terms of reserves and production of lead and zinc. There are large ore regions with polymetallic mineralization; these are the deposits of the Atasu and Uspensky ore regions in Central Kazakhstan. The former are genetically related to the final (taphrogenic) phase of the development of the large orogenic structure in the Central Kazakhstan (the Devonian volcano-plutonic belt), with the period of Late Frasnian-Famenian-Early Carboniferous formations of thick carbonate and carbonate-terrigenous sediments, including significant reserves of stratiform lead-zinc ores. Polymetallic mineralization of the Uspensky zone is singled out as an independent genetic Alaygyr type, and the tectonic nature of the ore-bearing Uspensky zone, as well as mineralization of this type, is still the subject of constant discussions. In this regard, the comparative characteristics of the Dalnegorsky and Uspensky ore regions, which have certain similarities in geodynamics, magmatism and metallogeny, are of great importance not only for solving the issues of the general patterns of formation, factors and criteria for controlling lead-zinc mineralization but also for an objective assessment of the ore potential of these and similar areas with polymetallic mineralization. Research methods: comparative analysis of the results of petrographic, chemical and mineralogical studies of ores enclosing near-ore metasomatically altered rocks and intrusions of different age and composition.

DEEP STRUCTURE AND FORMATION MODEL OF CONTINENTAL CRUST OF THE VERKHOYANSK FOLD- AND-THRUST BELT IN THE LATE MESOZOIC

The article considers the geological framework of a large orogenic structure in northeastern Eurasia - the Verkhoyansk fold-and-thrust belt (VFTB), formed in the Late Mesozoic on the eastern margin of the Siberian craton. Zoning of geopotential fields and the authors' interpretation of frequency-energetic characteristics along the 3-DV reference geo-physical profile provided the basis for modeling the deep structure of the VFTB and adjacent structures of the Siberian craton. There were identified structural zones of different geodynamic nature: the outer zone of the fold belt, underlain by the dropped margin of the craton; the inner zone of the VFTB with the oceanic crust at the base; the rear-zone structures formed by the Verkhoyansk complex in the subduction zone of the Uyandina-Yasachnaya island arc. In the Earth's crust of the VFTB there are distinguished two layers of approximately equal thickness: the lower one comprises a duplex system of complexes of the oceanic crust, and the upper one is built up by formations of the Verkhoyansk terrigenous complex, which have also undergone folding and duplexing. In parallel with thrusting of the upper terrigenous layer over the craton in the zone of collision between the VFTB structures and the Siberian craton margin there also occurred subduction of the lower layer of the VFTB under its margin. This led to an increase in thickness of the craton's crust by 5-10 km from below. The development of the Uyandina-Yasachnaya island arc system comprises two stages associated with blocking of the subduction zone and its transition towards the Oimyakon Ocean, which increased its area and complicated the structure. The paleosubduction zones and blocking structures are well-traced on the deep sections of reference seismic profiles.

Rift Basins and Intraplate Earthquakes: New High‐Resolution Aeromagnetic Data Provide Insights Into Buried Structures of the Charleston, South Carolina Seismic Zone

AbstractThe delineation of faults that pose seismic risk in intraplate seismic zones and the mapping of features associated with failed rift basins can help our understanding of links between the two. We use new high‐resolution aeromagnetic data, previous borehole sample information, and reprocessed seismic reflection profiles to image subsurface structures and evaluate recent fault activity within the Charleston seismic zone, the associated Mesozoic South Georgia rift basin, and surrounds. The new aeromagnetic data provide an unprecedented view of buried basement structures. NE‐ and NW‐trending lineaments of various lengths throughout the survey area are interpreted as Paleozoic orogenic structures and Mesozoic dikes, respectively. Within the rift basin, 15‐ to 20‐km long ESE‐trending lineaments are associated with faults in pre‐Cretaceous strata of the reflection data and are interpreted as Mesozoic rift structures. Various intersections and terminations of interpreted faults suggest rift‐related reactivation of Paleozoic faults and corresponding inheritance for Mesozoic structures. The reflection data show that several Paleozoic and Mesozoic faults are associated with deformation in Cretaceous and younger sediments, suggesting reactivation in the more recent passive margin setting. Two of these faults, one NE‐striking and one ESE‐striking, are coincident with surficial landforms, suggesting Quaternary slip; the ESE‐striking fault is also well‐aligned with a plan‐view offset in modern seismicity. A favorable orientation for reverse motion on ESE‐striking Mesozoic faults, a possible sub‐basin, and potentially weakened lithosphere are failed rift basin features that may influence intraplate seismicity within the Charleston seismic zone.

Structural control of Mesozoic orogens on SE Asia Basin opening

• Intrinsic relationship between Sundaland crustal inherited structures, and subsequent deformation through time since the Mesozoic. • The main rifting necking zones follow former sutures, and the direction of opening is perpendicular to them. • Counter Regional Normal Faults often reactivate former thrust faults and plutons boundaries. • Distal low angle normal faults mostly ocean dipping are dependant to the thermal state and boundary stress conditions. • Rifting of the Cenozoic basins was triggered and conditioned by the crustal collapse of Mesozoic orogens. A comparative study of basement structures, basins geometry and evolution, around SE Asia, highlights an intrinsic relationship between crustal inherited structures, and deformation through time from the Late Mesozoic to the Present. The present continental margin developed alongside of a large magmatic arc active from the Permian to the middle of the Cretaceous subsequently stretched during the Cenozoic. The Permo-Triassic crustal configuration was affected by a regional compression during the middle to late Cretaceous which appears to be mostly radial to the horse-shoe shape of the magmatic belt, and is best imaged by large regional shear zones, broad folds and densely distributed shear joints. A subsequent extension perpendicular to the margin followed in the Paleogene, which is firstly marked by an early stretching characterized by block faulting, dykes, and parallel extensional joint. We observed that the main necking zones follow former sutures, and the direction of opening is interestingly also perpendicular to them. The following thinning phase initiated with only minor discrepancies in the timing of initiation from E to W of SE Asia, marked by large crustal tilted blocks underlining a first thinning of the crust. This event was dominated by the occurrence of low angle normal faults bounding basins which capture most of the clastics derived from the formerly uplifted magmatic arc. These faults are frequently continent-dipping (counter-regional). Rooted into the lower crust, they often reactivate former thrust faults and plutons boundaries on the edges of the Mesozoic magmatic arc. Therefore, a link with the relaxation of the Late Mesozoic thickened crust is invoked. In a later stage, rifting developed across the outer edges of the previously thinned crust, outside the magmatic arc and up to the final continent-ocean boundary (COB of the South China Sea in the East and the Andaman Sea to the West). It is marked by distal low angle normal faults mostly ocean dipping (regional) that do not seem to be sensitive to margin fabric but more dependant to the thermal state and boundary stress conditions. Therefore, the pattern of basin structure and development seems conditioned by the intrinsic crustal configuration of SE Asia, specifically by the Triassic and Cretaceous orogenic structures (suture, crustal faults, and crustal thickness variations). The Late Mesozoic margins were indeed characterized by thickened crust which may have undergone collapse just before the onset of rifting sensus stricto . As a consequence, the general dip direction of these major crustal boundaries was often preserved during the Cenozoic extension that affected the marginal regions. Where the crustal thinning was strong enough, the fault plane dipped oceanward as a result from the crust/mantle relative motion. It is proposed that the rifting of the Cenozoic basins was triggered and conditioned by the relaxation of the orogens that assembled Sunda Plate in the past.

Advances in the understanding of multi-scale and coupled evolution of orogens, sedimentary basins and the underlying lithosphere

The integrated understanding of processes and mechanisms driving the coupled evolution of orogens and sedimentary basins and the underlying lithosphere-mantle system, requires a multi-scale temporal and spatial approach that crosses the traditional boundaries of disciplines and methodologies. While analysing the sedimentary infill we need to account for the characteristics and variations of the exhumation, evolving topography and external forcing in the source area, and the complexity of a transport system that is often characterized by a massive unidirectional sediment influx during moments of activity at tipping points or gateways. Such an influx can often span across multiple depocenters and sedimentary basins and is conditioned by an evolving structural geometry that can migrate in time, directly related to the evolving lithospheric structure in orogens that are influenced by their inherited rheology. Depocenters can be fed from multiple directions, while having an endemic or endorheic character during key evolutionary moments. The thermal structure and its variability in continental and oceanic domains conditions the rheology and subsequent structural evolution of the orogens, subduction zones and sedimentary basins, with significant consequences for understanding societally relevant issues. Quantifying basin deposition requires analysing the sediment transport network that can often span multiple interacting orogenic and sedimentary systems, where understanding the allogenic or autogenic nature of sedimentary processes can be significantly enhanced by knowing the inherited and evolving structural and tectonic parameters. Such sedimentary quantification is important for understanding the orogenic structure and the evolution of subduction systems, that include mechanisms such as cycles of burial-exhumation, formation of highly arcuate orogens and timings of nappe stacking events. Deriving processes in orogen - sedimentary basins systems also requires testing process-oriented hypotheses by focused studies in well-known natural laboratories, such as the examples from the Pannonian-Carpathians - Alps - Dinarides system and its analogues used by the numerous contributions in the special Global and Planetary Change issue entitled Understanding the multi-scale and coupled evolution of orogens, sedimentary basins and their underlying lithosphere , whose significance is explained in our review. • Integrated understanding of processes and mechanisms driving the coupled evolution of orogens and sedimentary basins. • Quantifying deposition requires analysing sediment transport across multiple interacting orogenic and sedimentary basins. • Quantifying sedimentary basins is important for understanding the orogenic structure and the evolution of subduction systems. • Testing process-oriented hypotheses in well-known natural laboratories, such the Pannonian - Carpathians - Alps - Dinarides.

U-Pb age of the 2016 Amatrice earthquake causative fault (Mt. Gorzano, Italy) and paleo-fluid circulation during seismic cycles inferred from inter- and co-seismic calcite

The Mt. Gorzano Fault (MGF) is a major seismically active extensional fault of the central Apennines, responsible for the destructive Mw 6.0 Amatrice earthquake in 2016. The MGF developed during post-orogenic extensional tectonics, generating a continental basin in the hanging wall. The age of the onset of the MGF and the relationship among faulting, fluid circulation, and the seismic cycles are unknown. We investigate these issues by studying the footwall damage zone of the MGF (exhumed from ~2-3 km depth), where extensional structures and related mineralizations cut and partially overprint the pre-existing compressional orogenic fabric. Structural and geochemical analyses (REE, O, C and clumped isotopes) combined with U-Pb dating of calcite mineralizations show that extensional deformation along the MGF began at least ~2.5 Myr ago. Its activity has continued to the present-day with a mean slip rate of ~0.9 mm/yr, consistent with other seismically active extensional faults of the central Apennines. During Apennine contractional tectonics, orogenic structures and tectonic overburden hindered the ascent of deep fluids, which, therefore, may have been progressively overpressured. We postulate that such overpressure occasionally or cyclically triggered impulsive deformation (earthquakes). During the subsequent extensional phase (younger ~2.5 Ma), pre- or co-seismic crustal dilation opened pathways for the ascent of deep mineralizing fluids, which impregnated the fault damage zone and may have triggered earthquakes. The crustal reservoir of carbonate-rich fluids nowadays is the source of water for the Acquasanta thermal springs close to the Mt. Gorzano seismic area.

Neogene kinematics of the Giudicarie Belt and eastern Southern Alpine orogenic front (northern Italy)

Abstract. Neogene indentation of the Adriatic plate into Europe led to major modifications of the Alpine orogenic structures and style of deformation in the Eastern and Southern Alps. The Giudicarie Belt is a prime example of this, as it offsets the entire Alpine orogenic edifice; its activity has been kinematically linked to strike-slip faulting and lateral extrusion of the Eastern Alps. Remaining questions on the exact role of this fold-and-thrust belt in the structure of the Alpine orogen at depth necessitate a quantitative analysis of the shortening, kinematics, and depth of decoupling beneath the Giudicarie Belt and adjacent parts of the Southern Alps. Tectonic balancing of a network of seven cross sections through the Giudicarie Belt parallel to the local NNW–SSE shortening direction reveals that this belt comprises two kinematic domains that accommodated different amounts of shortening during overlapping times. These two domains are separated by the NW–SE-oriented strike-slip Trento-Cles–Schio-Vicenza fault system, which offsets the Southern Alpine orogenic front in the south and merges with the Northern Giudicarie Fault in the north. The SW kinematic domain (Val Trompia sector) accommodated at least ∼ 18 km of Late Oligocene to Early Miocene shortening. Since the Middle Miocene, this domain experienced at least ∼ 12–22 km shortening, whereas the NE kinematic domain accommodated at least ∼ 25–35 km shortening. Together, these domains contributed an estimated minimum of ∼ 40–47 km of sinistral strike-slip motion along the Northern Giudicarie Fault, implying that most offset of the Periadriatic Fault is due to Late Oligocene to Neogene indentation of the Adriatic plate into the Eastern Alps. Moreover, the faults linking the Giudicarie Belt with the Northern Giudicarie Fault reach ∼ 15–20 km depth, indicating a thick-skinned tectonic style of deformation. These fault detachments may also connect at depth with a lower crustal Adriatic wedge that protruded north of the Periadriatic Fault and are responsible for N–S shortening and eastward, orogen-parallel escape of deeply exhumed units in the Tauern Window. Finally, the E–W lateral variation of shortening across the Giudicarie Belt indicates internal deformation and lateral variation in strength of the Adriatic indenter related to Permian–Mesozoic tectonic structures and paleogeographic zones.

Three-dimensional shear velocity structure of the Mauléon and Arzacq Basins (Western Pyrenees)

We present a 3-D shear wave velocity model of the Mauléon and Arzacq Basins from the surface down to 10 km depth, inverted from phase velocity maps at periods between 2 and 9 s. These phase velocity maps were obtained by analyzing coherent surface wave fronts extracted from ambient seismic noise recorded by the large-N Maupasacq seismic array with a matched filtering approach. This new model is in good agreement with a local earthquake tomography study performed on the same acquisition dataset. Our passive imaging models reveal the upper crustal architecture of the Mauléon and Arzacq Basins, with new details on the basement and its relationship with the overlying sedimentary cover. Combining these new tomographic images with surface and subsurface geological information allows us to trace major orogenic structures from the surface down to the basement. In the basin, the models image the first-order basin architecture with a kilometric resolution. At depth, high velocity anomalies suggest the presence of dense deep crustal and mantle rocks in the hanging wall of north-vergent Pyrenean Thrusts. These high velocity anomalies spatially coincide with a positive gravity anomaly in the western Mauléon Basin. In addition, our models reveal major changes from the Chaînons Béarnais to the western Mauléon Basin across a set of orogen-perpendicular structures, the Saison and the Barlanès transfer zones. These changes reflect the along-strike variation of the orogenic evolution that led to the preservation of the former rifted domain and its underlying mantle in the orogenic wedge of the Western Pyrenees. We discuss the implications of these results for the 3-D architecture of the Mauléon Basin and its underlying basement.

Two Cases of COVID-19 in Adults who Vape

In 2019, a severe acute respiratory disease with coupled multiple organ pathologies, namely, Coronavirus Disease 2019 (COVID-19), emerged. The lungs and other organs in this disease exhibit glass-like (hyaline) tissue pathologies with iron oxide deposits, which mimics rock-related mineralization. The impact of significant geological and geophysical perturbations on aberrant mineralization in living organisms has not been explored. Many Indigenous Knowledge systems posit that unseen forces emitted by orogenic structures and modulated by geophysical dynamics play a significant role in health. Here, it is proposed that carbon dioxide-rich water-lithospheric ferromagnesian silicates interactions generate aberrant lithospheric long-wavelength magnetic anomalies (LWMA) via serpentinization, during geologic periods with polar ice melt-induced hydrosphere redistribution, increased atmospheric carbon dioxide, and weakened geomagnetic field intensity. Here, it is also proposed that COVID-19 in humans (and animals) is a pathogenic manifestation of aberrant LWMA-induced magnetic catalysis of silicate/carbonate-like-iron oxides minerals from tissues (carbon-based molecules), gases (dioxygen and carbon dioxide) and metals (iron, magnesium, silicon), and coronavirus from the genome (endogenous viruses), with the virus capable of replication and limited transmission. These COVID-19-LWMAs are generated in tectonic plates with degraded Proterozoic bedrocks and are linked to the refertilization of iron oxides-silicate/carbonate rocks. Thus, severe COVID-19 outbreaks are/will predominately occur on the Eurasian and North American tectonic plates and governed by the diurnal, semiannual (equinoctial maxima, solstitial minima) and quasi-biannual oscillations of the geomagnetic magnetic field intensity (analogous to a vibrating drum head). Furthermore, abnormally high ferromagnetic iron content in humans is the unifying determinant for COVID-19-induced morbidity and mortality.

Neogene to recent evolution of the Southern Gulf of Mexico basin: Tectonic controls on deep‐water sediment dispersal systems

AbstractNewly available two‐dimensional (2D) and limited three‐dimensional (3D) reflection seismic data coupled with publicly available well and core data were used to generate the first comprehensive regional basin evolution model for the deep‐water Neogene to recent southern Gulf of Mexico (GoM). This evolution is presented in the context of contemporaneous onshore tectonic drivers and predecessor basin tectonic history. Dynamic uplift to the west in North America, transpression to the south and tectonically influenced salt tectonics to the east served to collapse the margins of the southern Gulf of Mexico Basin throughout the late Neogene and into the modern. This collapse and salt inflation served to shut off efficient sediment transport into the axial deep basin. Newly developed nearshore extensional accommodation along both the western margin of the basin and salt‐rooted orogenic structures to the south and east appear to have baffled coarser‐caliber sediment input from southern (Mexican) sediment sources into the deep Gulf of Mexico Basin beginning in the late Miocene. This sequence is recorded in the southern GoM basin by a transition from large early–mid Miocene submarine channel belts to late Miocene–recent sediment wave fields and mass transport deposits. Improved resolution of new 2D and 3D subsurface seismic reflection data shows that sediment waves of the southern Gulf of Mexico are supercritical bedforms, long wavelength antidunes and cyclic steps, not contourites. These supercritical bedforms are among the most spatially expansive and morphologically largest documented globally. The location and evolution of these bedforms appears closely tied to the tectonically driven history of margin collapse, salt inflation and the starving of the deep basin of coarse‐grained sediment. Cumulatively, the tectonic drivers that intuitively should have increased sediment flux into the deep southern Gulf of Mexico acted to ‘pinch off’ the basin, starving it of sediment supplied from southern sediment sources.

The U–Pb Age of Detrital Zircons from Paleozoic Sedimentary Sequences of the Southwestern Siberian Platform as Evidence of Paleoproterozoic and Early Paleozoic Orogenic Events

This work presents the results of the isotope dating of detrital zircons from sandstones of the Bratsk (O3), Kezhemskaya (S1), and Baeronovka (C1) formations of the sedimentary cover of the southwestern part of the Siberian Platform. It was established that Paleoproterozoic igneous and metamorphic complexes of the Siberian Platform basement with ages of 2.00–1.85 Ga were the dominant source of the clastic material. The Central Asian Orogenic Belt, namely, rock complexes with age of 490–450 Ma, was a second important source of the clastic material. Furthermore, it was noted that the age spectra obtained for detrital zircons from rocks of the Siberian Platform sedimentary cover reflect two global orogenic events: the Paleoproterozoic one, which is responsible for the formation of the most ancient cratons, including the Siberian one, and the Early Paleozoic one, marking the beginning of the development of one of the largest orogenic structures of the world (Central Asian Orogenic Belt).

Tectonically controlled carbonate-seated maar-diatreme volcanoes: The case of the Volsci Volcanic Field, central Italy

Quaternary carbonate-seated maar-diatremes in the Volsci Range are one of the most intriguing products of the west-directed subduction of the Adriatic slab that drove the development of the Apennine mountain belt in Central Italy. The Volsci Volcanic Field is characterized by phreatomagmatic surge deposits, rich in accidental carbonate lithics, and subordinate Strombolian scoria fall deposits and lava flows, locally sourced from some tens of monogenetic eruptive centers (at least fifty tuff rings and scoria cones). We investigate the subsurface maar-diatreme processes in terms of relationships between faulting and explosive magma-water interaction, as well as the distribution pattern of the eruptive centers. With this aim, we present the following new data: i) description of the fold-and-thrust belt structure and associated eruptive centers, ii) componentry of volcanic rock-types, iii) determination of grain-size, degrees of whiteness and roundness of carbonate lithic inclusions, iv) micropaleontological analysis of carbonate lithics. We show that the clustering of eruptive centers is controlled by tectonic features. A first order control is tentatively related to crustal laceration and deep magma injection along a ENE-trending Quaternary lateral tear in the slab and to Mesozoic rift-related normal faults. A second-order control is provided by orogenic structures (mainly thrust and extensional faults). In particular, magma-water explosive interaction occurred at multiple levels (< 2.3 km depth), depending on the structural and hydrogeologic setting of the Albian-Cenomanian carbonates, which are intersected by high-angle faults. The progressive comminution, rounding and whitening of entrained carbonate lithics allow us to trace multistage diatreme processes. Finally, our study bears implications on volcanic hazard assessment in the region.