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A new compilation of Bouguer gravity anomaly data has been used, together with forward and inverse modeling, to reappraise the structure, volume, and state of isostasy of the Cornubian batholith of SW England. We show the individual plutons that comprise the batholith are, on average, ∼10–11 km thick, are outward-sloping in their upper 2–3 km, and are underlain by roots which protrude downward into the middle crust. The batholith volume is estimated within the range of 76,367 ± 17,286 km³, significantly larger than previous estimates. Granite outcrops correlate with elevated topography, and mass balance calculations show that the mass deficiency of the granites relative to their host metasedimentary rocks is approximately equal to the mass excess of the topography relative to air. The existence of roots beneath individual plutons is in general agreement with predictions of an Airy model of isostasy and a depth of compensation that is within the crust rather than at the Moho. In addition, a middle crust compensation depth is compatible with the origin of the granites by heating and melting of metasedimentary rocks and with data from experimental rock mechanics which suggest that at the melting temperature and pressure of granite formation, deformation is likely to be plastic and controlled by glide along dislocations. During pluton emplacement the middle crust would, therefore, have acted as a mechanically weak layer, effectively decoupling the topography from any support it might otherwise have received from the lower crust and/or upper mantle. [ABSTRACT FROM AUTHOR]

The elastic thickness parameter was estimated using the mobile correlation technique between the observed isostatic disturbance and the gravity disturbance calculated through direct gravimetric modeling. We computed the vertical flexure value of the crust for a specific elastic thickness using a given topographic dataset. The gravity disturbance due to the topography was determined after the calculation. A grid of values for the elastic thickness parameter was generated. Then, a moving correlation was performed between the observed gravity data (representing actual surface data) and the calculated data from the forward modeling. The optimum elastic thickness of the particular point corresponded to the highest correlation coefficient. The methodology was tested on synthetic data and showed that the synthetic depth closely matched the original depth, including the elastic thickness value. To validate the results, the described procedure was applied to a real dataset from the Barreirinhas Basin, situated in the northeastern region of Brazil. The results show that the obtained crustal depth is highly correlated with the depth from known models. Additionally, we noted that the elastic thickness behaves as expected, decreasing from the continent towards the ocean. Based on the results, this method has the potential to be employed as a direct estimate of crustal depth and elastic thickness for any region.

Afar is undergoing the final stages of continental rifting and hosts the triple junction between the Red Sea, Gulf of Aden, and Main Ethiopian rifts. To better understand the nature of the crust and continental breakup in the region, we calculate teleseismic receiver functions across northeastern Afar and the Danakil microplate, using new data from a regional deployment in Eritrea. We estimate the Moho depth and bulk crustal VP/VS ratio using the H‐κ stacking method. The heterogeneity of our crustal thickness estimates (∼19–35 km) indicates that the Danakil microplate has undergone stretching and crustal thinning. By investigating the relationship between crustal thickness and topographic elevation, we estimate the regional crustal bulk density as ρc ≈ 2,850 ± 20 kg m−3, which is higher than expected, given the crustal thickness of the region. We show that topography is 1.5 ± 0.4 km higher than would be expected due to crustal isostasy alone. We propose that this topography is supported by the same hot mantle upwelling suggested to be responsible for the onset of rifting in East Africa. Uplift is generated due to the presence of a hot thermal anomaly beneath the plate and by thinning of the lithospheric mantle. Our results are consistent with a number of independent constraints on the thermal structure of the asthenospheric and lithospheric mantle. Evidence of melt within the crust is provided by anomalously high VP/VS ratios of >1.9, demonstrating that magma‐assisted extension continues to be important in the final stages of continental breakup. Plain Language Summary: Afar is an area of northern Ethiopia that extends into Eritrea. It hosts three tectonic plate boundaries that are pulling apart from one another (rifting) as continental breakup is occurring. These rifting processes have led to a complicated tectonic history; isolating a small microcontinent (the Danakil) and giving rise to volcanism across the region. To better understand the nature of the crust, we study seismic data to estimate the crustal thickness and the ratio of seismic wave speeds. Our results indicate that the crust shows substantial variation in thickness, meaning that the Danakil microplate has undergone crustal thinning. We use our results to determine that dynamic mantle processes are responsible for supporting the elevation of the region. We also show that partially molten rock (magma) is likely to be present in the crust beneath northeastern Afar and the Danakil microplate, which is evidence that magma assists with continental breakup. Key Points: Receiver functions produce the first estimates of Eritrean bulk crustal propertiesThe crust of Afar and the Danakil microplate is denser than global average and highly heterogeneousEvidence found for melt within crust and for support from hotter mantle propping up topography beneath Afar and the Danakil microplate [ABSTRACT FROM AUTHOR]

Mantle convection plays a fundamental role in driving evolution of oceanic and continental lithosphere. In turn it impacts a broad suite of processes operating at or close to Earth's surface including landscape evolution, glacio‐eustasy, magmatism, and climate. A variety of theoretical approaches now exist to simulate mantle convection. Outputs from such simulations are being used to parameterize models of landscape evolution and basin formation. However, the substantial body of existing simulations has generated a variety of conflicting views on the history of dynamic topography, its evolution and key parameters for modeling mantle flow. The focus of this study is on developing strategies to use large‐scale quantitative stratigraphic observations to assess model predictions and identify simulation parameters that generate realistic predictions of Earth surface evolution. Spot measurements of uplift or subsidence provide useful target observations for models of dynamic topography, but finding areas where tectonics have not also influenced vertical motions is challenging. To address this issue, we use large inventories of stratigraphic data from across North America with contextual geophysical and geodetic data to constrain the regional uplift and subsidence history. We demonstrate that a suite of typical geodynamic simulations struggle to match the amplitude, polarity and timing of observed vertical motions. Building on recent seismological advances, we then explore strategies for understanding patterns of continental uplift and subsidence that incorporate (and test) predicted evolution of the lithosphere, asthenosphere and deep mantle. Our results demonstrate the importance of contributions from the uppermost mantle in driving vertical motions of continental interiors. Key Points: Large‐scale digital inventories of stratigraphic observations used to test predictions from mantle convection simulationsUseful diagnostics include net uplift and subsidence, absolute elevations, paleo‐water depthsUpper mantle thermo‐mechanical evolution—crucial for assessing sub‐plate support—constrained using stratigraphy [ABSTRACT FROM AUTHOR]

We investigated how spatial variations in tidal heating affect Io's isostatic topography at long wavelengths. The long‐wavelength relief is less than the 0.3 km uncertainty in Io's global shape. Assuming Airy isostasy, degree‐2 topography <0.3 km amplitude is only possible if surface heat flux varies spatially by <19% of the mean value. This is consistent with Io's volcano distribution and is possible if tidal heat is generated within and redistributed by a convecting layer underneath the lithosphere. However, that layer would require a viscosity <1010 Pa s. A magma ocean would have low enough viscosity but would not generate enough tidal heat internally. Conversely, assuming Pratt isostasy, we found ∼0.15 km degree‐2 topography is easily achievable. If a magma ocean was present, Airy isostasy would dominate; we therefore conclude that Io is unlikely to possess a magma ocean. Plain Language Summary: As it orbits Jupiter elliptically, the difference in gravitational pull experienced by the moon Io results in tidal heating due to internal friction. Some evidence suggests this heat forms a magma ocean beneath Io's crust. If so, there would be a difference in the amount of heat generated at Io's equator versus its poles and would alter the thickness of Io's crust between the two locales. Assuming the crust has a uniform density, its thickness would be inversely proportional to the tidal heat beneath the crust, which in turn affects the difference in Io's radius at the equator versus at its poles. However, reasonable variation in tidal heating across Io would result in a greater difference in radius than is observed. The difference in observed radius is more likely if variation in tidal heat across Io affects crustal density rather than crustal thickness. Then, it is more likely that Io does not have a magma ocean. Key Points: Long‐wavelength relief implies low spatial variation in Io's tidal heating when assuming Airy isostasyTidal heat produced in a convecting aesthenosphere can reduce spatial variation in tidal heating, but requires prohibitively low viscosityIo's topography is consistent with expected tidal heating spatial variations if thermal expansion drives crustal density variations [ABSTRACT FROM AUTHOR]

The general subject of this article deals with the term salt. Salt deposits usually contain chlorides, sulphates/gypsum, borates, carbonates, etc., that are seemingly part of the same system. Even though this article mainly presents data and observations on chlorides, which are not easily explained by the present paradigm, it should also prove relevant for the formation of sulphates and other types of salts observed in major salt deposits. The paradigm explaining large salt deposits rests on two pillars governing salt formation and salt deformation. Salt formation is thought to occur vis solar evaporation of seawater in restricted basins. Salt deformation and forming of salt diapirs is thought to occur due to gravity-induced movements. Our review presents peer-reviewed and published data and observations from different authors within different disciplines that challenge the present evaporite paradigm. The current theory/paradigm rests on numerous observations and interpretations in support of it. Adding more observational interpretations in support of the paradigm will not nullify even one observation that contradicts or remains unexplained by the theory. The contradicting evidence must be explained within the present paradigm for it to survive. Significant observations of and within salt deposits are presented, as well as visual and geophysical observations of salinity in crusts and mantles in relevant tectonic settings. In our view, the omnipresent salinity observed in the subsurface needs to be understood and included in the description of a new salt formation mechanism in order to fully explain all features presented herein. [ABSTRACT FROM AUTHOR]

Using 31 CMIP6 models we have analyzed projected future Caribbean precipitation. The model mean projection results in a 0.5 mm/day (20%) drying under a SSP5-8.5 scenario for the end of this century over the Caribbean basin. The multi-model spread is large ranging from no drying to a 1 mm/day (40%) reduction in mean precipitation. Eastern and central Pacific warming, resembling an El Niño / positive phase of Pacific Decadal Oscillation (PDO), appears to be the main driver by shifting and weakening the Walker circulation and inducing subsidence over the Caribbean, especially during the wet season (May–November). This applies for the model mean as well as for the inter-model spread. During the dry season (December–April) the southward migration of the Intertropical Convergence Zone (ITCZ) and the advection of dry air from outside the Caribbean seem to be the dominant drivers of the projected drying. Another mechanism that contributes to the drying is the land-sea contrasts that induce divergence/convergence over the Caribbean. The incapability of CMIP6 models to simulate the current tropical Pacific warming and Walker circulation trends questions the reliability of precipitation projections in the Caribbean. Based on our understanding of the physical processes affecting Caribbean drying and on an emergent constraint analysis we state that the future drying in the Caribbean is likely to be weaker than the one projected by CMIP6 models. [ABSTRACT FROM AUTHOR]

Lunar impact basins are critical markers to understand the early bombardment history. This study focuses on isostatic compensation processes at 16 lunar farside basins, exploring how long‐term alteration processes affect estimates of impactor sizes and timing. Using a lithospheric flexure model, we analyze the isostatically compensated gravity signature of these basins. Our approach is based on previously published basin formation models using the iSALE‐2D shock physics code. Here we investigate how isostatic compensation processes alter the gravity signature using models of basin formation as initial conditions. We compare our results with the present day observed gravity data. We assume that isostatic compensation is the result of flexural deformation of the crust‐mantle boundary with varying lithospheric elastic thicknesses. Our results indicate that the effect of isostatic compensation on the gravity signature varies depending on the thermal conditions at the time of impact. We find that despite this variability, the overall influence of isostatic compensation on the gravity signature is generally moderate to minor. Additionally, our analysis is consistent with previous studies that have shown that the elastic thickness varies across the Moon. Our findings contribute to our understanding of the relationship between basin formation and the thermal evolution of the Moon. The variations in elastic thickness found provide nuanced insights into lunar geological processes and improve our understanding of the early history of the Moon. Plain Language Summary: This study addresses the early bombardment history of the Moon, particularly the basin forming asteroid impacts in the first 700 million years. The large crater structures and basins serve as historical markers that make it possible to estimate the size of the cosmic bodies that formed them and to estimate the thermal conditions of the Moon at the time of their formation. As the surface expression of some basins is poorly preserved, making size measurements uncertain, gravity anomalies, caused by subsurface mass displacements and changes in density, are valuable for evaluation. Based on previously published numerical simulations of basin formation, we correlate our results with gravity data from the Gravity Recovery and Interior Laboratory mission. In the period between the formation of the basin and today's observation, isostatic compensation processes probably caused changes that we are trying to reconstruct using models. Our findings emphasize the significant role of lithospheric elasticity, determining whether isostatic compensation occurs locally or regionally. Regarding the lunar farside, we observed spatial variations in elastic thickness, dependent on the cooling history of each basin. Importantly, our study revealed that previously determined impactor sizes exhibit no to minimal change with the introduction of isostatic compensation through our lithospheric flexure model. Key Points: Isostatic compensation: We use the elastic thickness of the lithosphere to account for isostatic compensation in basin formation modelsIsostatic compensation of lunar farside basins varies with impactor size and thermal state, affecting basin's gravity signaturesThe effects of isostatic compensation on the estimated impactor sizes for farside basins are limited [ABSTRACT FROM AUTHOR]

We discuss geological and biotic aspects of the extensive Akchagylian transgression that occurred in the Caspian region of Eurasia near the Plio-Pleistocene transition, in Piacenzian and Gelasian. It is shown that the onset of the Akchagylian marine sedimentation in Western Turkmenistan (ca. 3.2 Ma) preceded that in the Kura Basin (ca. 3.0 Ma). The position of the upper boundary of the Akchagylian remains uncertain (ca. 2.1 or 1.8 Ma). The analyzed biotic content of the Akchagylian includes molluscs, microfossils (pollen, dinocysts, foraminifers), and mammals. It is noted that specific forms of the Akchagylian aquatic biota co-occur with microfossils that clearly indicate a connection with the World Ocean or related seas. The palynology of the Akchagylian time signals a directed cooling in the Pliocene and Early Pleistocene with several warm and humid epochs. The Akchagylian transgression was preceded by a change of a structural-sedimentary pattern of the region. In the latest Miocene and Early Pliocene, a pre-existed longitudinal tectonic zonation of the Caucasian-Caspian segment of the Paratethys gradually changed into clearly transverse tectonic zonation. The latter was manifested in the tectonic uplift of the Greater Caucasus, its northern piedmonts and the Lesser Caucasus, and in the subsidence of the western parts of the South and Middle Caspian basins. The interplay of longitudinal and transverse tectonic features shaped the configuration of the Akchagylian brackish-water basin and controlled thickness of its deposits. It was the transverse zonation that dominated in the thickness pattern. The increasing role of the transverse zonation in the post-Akchagylian time is manifested in the magnitudes and rates of the Quaternary tectonic uplift. These parameters were calculated based on current heights of the top of the Akchagylian marine deposits in different parts of the basin. The highest magnitudes of uplift are found in the Eastern Caucasus (up to 1980 m on the NE slope and about 2500 m in the axial part) and in the west of the Lesser Caucasus in eastern Turkey (up to 1750 m). The maximum level of the Akchagylian transgression is estimated at 40–50 m above the present level of the World Ocean. We show a low probability of connection of the Akchagylian basin with the Mediterranean Sea or the Persian Gulf, and a high probability of its connection with the Arctic Ocean through the northern tributaries of the Kama River and the Pechora Basin in the NE of East European Plain. [ABSTRACT FROM AUTHOR]

The paper presents a new high-resolution (up to decadal) palaeoecological evidence based on detailed AMS radiocarbon dating, plant macrofossils, testate amoebae, loss on ignition, peat humification, elemental and stable isotopic records, obtained from a palsa peatland located in vicinities of Igarka town. This gave us a unique possibility to examine the mid-to late Holocene environmental changes in a poorly investigated area in Yenisei Siberia. The obtained data show that the peatland initiation occurred at about 6350 cal yr BP by paludification of a larch forest in the conditions of climate warming and high surface wetness, possibly, due to permafrost thaw. The first sign of palsa formation occurred about 5360 cal yr BP and coincided with the temperature decrease, wetter and anoxic conditions in peatland. After several phases of uplifts (and relatively dryer conditions) and partial thawing and subsidence of its surface (wetter conditions) between 5360 and 2250 cal yr BP, the continuous rise of the perennial frost mound (up to the height of 5 m) accomplished by drying its surface and colonization by drought-resistant plant species, evidently, encouraged by the climate cooling and permafrost aggradation during the last two millennia. The high-resolution analyses of elemental (C and N) and stable isotope content (δ13C and δ15N) of the peat sequence revealed the strong linkages between the plant composition and mineralization/humification processes. Our multi-proxy study revealed detailed features of peat accumulation patterns driven by multiple interrelated allogenic and autogenic forcings, influencing changes in peat macroelement content and stable isotope composition. [ABSTRACT FROM AUTHOR]

Very Long Period (VLP) signals with periods longer than 2 s may occur during eruptive or quiet phases at volcanoes of all types (shield and stratovolcanoes with calderas, as well as other stratovolcanoes) and are inherently connected to fluid movement within the plumbing system. This is supported by observations at several volcanoes that indicate a correlation between gas emissions and VLPs, as well as deformation episodes due to melt accumulation and migration that are followed by the occurrence of VLPs. Moment tensors of VLPs are usually characterized by large volumetric components of either positive or negative sign along with possibly the presence of single forces that may result from the exchange of linear momentum between the seismic source and the Earth. VLPs may occur during a variety of volcanological processes such as caldera collapse, phreatic eruptions, vulcanian eruptions, strombolian activity, and rockfalls at lava lakes. Physical mechanisms that can generate VLPs include the inflation and deflation of magma chambers and cracks, the movement of gas slugs through conduits, and the restoration of gravitational equilibrium in the plumbing system after explosive degassing or rockfalls in lava lakes. Our understanding of VLPs is expected to greatly improve in the future by the use of new instrumentation, such as Distributed Acoustic Sensing, that will provide a much denser temporal and spatial sampling of the seismic wavefield. This vast quantity of data will then require time efficient and objective processing that can be achieved through the use of machine learning algorithms. [ABSTRACT FROM AUTHOR]

Upper Palaeozoic lacustrine basin deposits not only record local tectonism but are also an archive to evaluate global palaeoclimate changes linked to the Late Palaeozoic Gondwanan ice age. The Tournaisian Horton Group of Nova Scotia, south‐east Canada, accumulated in rift basins following the final accretion of peri‐Gondwanan terranes to the Appalachians. Sedimentology, mineralogy and geochemistry of the well‐exposed sandstones and shales at the classic Blue Beach section (ca 353.5 to 352 Ma) reveal the interplay of local tectonism and global climatic controls on lacustrine sedimentation. The lacustrine depositional environment gradually transitioned from deep water offshore at the base of the section to wave‐dominated and fluvial‐dominated nearshore at the top. Multiple small transgressive–regressive sedimentation cycles have an average 21 ka duration, likely related to Milankovitch cyclicity. Unusually abundant soft‐sediment deformation structures and landslides are the sedimentary responses to frequent earthquakes during the most active phase of rift subsidence. The overall succession shows changes from a shallowing‐up balanced‐filled to an overfilled lacustrine basin. The chemical weathering intensity index and the Th/K ratio show a longer‐term trend from dry and cool conditions low in the section to humid and warm conditions near the top, with rapid change in the transition period. The section records the peak of the global mid‐Tournaisian carbon isotope excursion and the corresponding cooling event (354 Ma to approximately 351 Ma). The sedimentary succession is a response to long‐term and short‐term climatic cycles influencing lake level and sediment supply during the time of maximum rift basin subsidence recorded by the soft‐sediment deformation structures. [ABSTRACT FROM AUTHOR]

Abstract—It is shown that most marsquakes epicenters are located in the zones of extension and fairly high shear stresses associated with deviation of the planet from hydrostatic equilibrium. In this paper, non-hydrostatic stresses in the interior of Venus are calculated for two types of models: an elastic model and a model with a lithosphere of variable thickness (150–500 km) covering a weakened layer that has partially lost its elastic properties. Numerical modeling of the system of elastic equilibrium equations for a gravitating planet is carried out with a step of 1° × 1° degrees in latitude and longitude down to a depth of 480 km, which is the first phase transition in the mantle. The boundary conditions of the problem are the topography and the gravitational field of the planet. In general, the level of nonhydrostatic stress on Venus is not very high. On the surface and in the crust, the highest shear stresses are observed in the region of the Maxwell Montes on Ishtar Terra. Beneath the Maxwell Montes, shear stresses in the crust reach 80 MPa and compressive stresses, 125–150 MPa, depending on the model. Tensile stresses around this area are about 20 MPa. The highest tensile stresses occur in the regions beneath such structures as Lavinia Planitia, Sedna Planitia, and Aino Planitia. [ABSTRACT FROM AUTHOR]

Abstract Mantle convection plays a fundamental role in driving evolution of oceanic and continental lithosphere. In turn it impacts a broad suite of processes operating at or close to Earth's surface including landscape evolution, glacio‐eustasy, magmatism, and climate. A variety of theoretical approaches now exist to simulate mantle convection. Outputs from such simulations are being used to parameterize models of landscape evolution and basin formation. However, the substantial body of existing simulations has generated a variety of conflicting views on the history of dynamic topography, its evolution and key parameters for modeling mantle flow. The focus of this study is on developing strategies to use large‐scale quantitative stratigraphic observations to assess model predictions and identify simulation parameters that generate realistic predictions of Earth surface evolution. Spot measurements of uplift or subsidence provide useful target observations for models of dynamic topography, but finding areas where tectonics have not also influenced vertical motions is challenging. To address this issue, we use large inventories of stratigraphic data from across North America with contextual geophysical and geodetic data to constrain the regional uplift and subsidence history. We demonstrate that a suite of typical geodynamic simulations struggle to match the amplitude, polarity and timing of observed vertical motions. Building on recent seismological advances, we then explore strategies for understanding patterns of continental uplift and subsidence that incorporate (and test) predicted evolution of the lithosphere, asthenosphere and deep mantle. Our results demonstrate the importance of contributions from the uppermost mantle in driving vertical motions of continental interiors.

Abstract We investigated how spatial variations in tidal heating affect Io's isostatic topography at long wavelengths. The long‐wavelength relief is less than the 0.3 km uncertainty in Io's global shape. Assuming Airy isostasy, degree‐2 topography

Tectonic processes resulting from solid Earth dynamics control uplift and generate sediment accommodation space via subsidence. Unraveling the mechanism of basin subsidence elucidates the link between deep Earth and Surface processes. The NW Zagros fold-thrust belt results from the Cenozoic convergence and subsequent collision between the Arabian and Eurasian plates. The associated Neogene foreland basin includes ~4 km of syntectonic nonmarine clastic sediments, suggesting a strongly subsiding basin inconsistent with the adjacent topographic load. To explain such discrepancy, we assessed basin subsidence with respect to the effect of surface load and dynamic topography. The isopach map of the Fatha Formation during the middle Miocene displays a longitudinal depocenter aligned with the orogenic trend. In contrast, the maps of the Injana Formation and Mukdadiya Formation during the late Miocene illustrate a focused depocenter in the southern region of the basin. The rapid subsidence in the south during the late Miocene was coeval with the Afar plume flow northward beyond the Arabia-Eurasia suture zone in the northwestern segment of the Zagros belt. Based on isopach maps, subsidence curves, and reconstructions of flexural profiles, supported by Bouguer anomaly data and maps of dynamic topography and seismic tomography, we argue for a two-stage basin evolution. The Zagros foreland basin subsided due to the load of the surface and the subducting slab during the early-middle Miocene and was later affected by the Neothethys horizontal slab tear propagation during the late Miocene. This tear propagation was associated with a northward mantle flow above the detached segment in the NW and a focussed slab pull on the attached portion of the slab in the SE. [ABSTRACT FROM AUTHOR]

Foreland basins are ideal laboratories to examine and quantify forces that contribute to Earth's topography. The interaction of these driving mechanisms (atmospheric, lithospheric and asthenospheric) affects the accumulation and preservation of strata in marine or terrestrial depocentres. For foreland basins that cover thousands of kilometres along orogens, geodynamic processes or lithospheric structure might differ and/or overlap differently along or across strike. The Magallanes-Austral basin in the southernmost Patagonia serves as a good analogue to analyse the interactions between subcrustal forces and foreland sedimentation. While to the northern part of southern Patagonia, Cenozoic basins were predominantly terrigenous and above sea level; at the southernmost end of Patagonia, sedimentation in the island of Tierra del Fuego was mostly submarine. We analysed in this contribution the southernmost foreland of Patagonia by combining backstripping with reconstruction of flexural and dynamic subsidence. These results were compared with terrestrial records exposed further north of southern Patagonia. We found that, in addition to crustal contributions (as deformation and sedimentation), subcrustal forces are required to accommodate the proximal and distal foreland strata and explain the palaeoenvironmental and subsidence discrepancies that resulted after our analysis. When our models are compared with dynamic topographic curves, strong correlations are observed during the Palaeogene, whereas strong topographic differences occurred in the Neogene. Dynamic topography models in the Neogene have reproduced clear uplift, whereas our residual topography results show equilibrium (close to the orogen) to subsidence values (to the distal foreland). We propose that changes in the lithospheric mantle had to work together with the rest of the tectonics and dynamic forces to match 1-D backstripping and flexural curves. This suggests that foreland basins in southern Patagonia were controlled differently along strike the southern Andes and that crustal deformation, asthenospheric flows and a heterogeneous lithospheric mantle structure affected the Cenozoic basin evolution. [ABSTRACT FROM AUTHOR]

The interplay between climate-forced sea level change, erosional and depositional processes, and flexural isostasy in deep time on passive margin deltas remains poorly understood. We performed a series of conceptual simulations to investigate flexural isostatic responses to high-frequency fluctuations in water and sediment load associated with climatically driven sea level changes. We model a large drainage basin that discharges to a continental margin and produces a large deltaic depocenter, then prescribe synthetic and climatic-driven sea level curves of different frequencies to assess flexural response. Results show that flexural isostatic responses are bidirectional over 100–1000 kyr timescales and are in sync with the magnitude, frequency, and direction of sea level fluctuations and that isostatic adjustments play an important role in driving along-strike and cross-shelf river mouth migration and sediment accumulation. Our findings demonstrate that climate-forced sea level changes produce a feedback mechanism that results in self-sustaining creation of accommodation into which sediment is deposited and plays a major role in delta morphology and stratigraphic architecture. [ABSTRACT FROM AUTHOR]

Thick red clay in northern China contains rich information about the uplifting of the Qinghai–Tibet Plateau, the drying process of Asian inland, the East Asian monsoon changes, and global cooling since 22 Ma. In comparison, the red clay widely distributed in southern China is generally much younger (<1 million years), thus limiting the paleoclimate and paleoenvironment reconstruction over a longer geological time. We conducted a comprehensive magnetic investigation on the Pliocene red clay of the core LQ11, located in the Yangtze Delta, to reveal its paleoclimate and paleoenvironment implications for the eastern China coast. Our results revealed that the Pliocene red clay in the Yangtze Delta has higher S-ratio and lower HIRM (Hard isothermal remanent magnetizations) values than Quaternary vermiculate red clay of hot–humid climate origin in southern China. This indicates a weaker transformation from maghemite to hematite during the process of pedogenesis. The lack of net-like white veins in the Pliocene red clay also indicates a relatively low intensity of pedogenesis. We believe that the Pliocene red clay, which is presently 250 m below the mean sea level, was formed in high-altitude topography before the Quaternary period, where paedogenic intensity was remarkably low. This finding shows rapid tectonic subsidence occurring on the eastern China coast since the late Pliocene and enriches the theoretical research on paleoenvironment reconstruction based on red clay. [ABSTRACT FROM AUTHOR]

It is generally believed that the rapid uplift of the eastern Tibetan Plateau is due to the continuous continental collision between the Indian and Eurasian plates. But the uplift mechanisms of the eastern Tibetan Plateau remain uncertain. The analysis of flexural isostasy can provide new insights into those uplifting mechanisms. In this study, the effective elastic thickness (Te) and load ratio (F) of the lithosphere are estimated around the eastern Tibetan Plateau. The derived Te and F are used to compute flexural isostatic anomalies (FIA) using the theoretical Bouguer admittance method. We find the eastern margin of the Tibetan Plateau is dominated by low Te, high F, and significant negative FIA. Our results suggest that this area has a weak lithosphere with heavy subsurface loadings and crustal mass surpluses. This supports that a middle‐lower crustal channel flow probably underlies this region. [ABSTRACT FROM AUTHOR]

Basin inversion is a process that takes place when a sedimentary basin is subjected to compressional stresses resulting in the reactivation of pre-existing faults and/or the localization of deformation along new reverse faults. The Araripe Basin (NE Brazil) is an example of a Cretaceous intracontinental aborted rift, with its sedimentary infill found at ca. 1000 m altitude, 500 m above the host basement. Post-rift basin inversion has been proposed by previous authors as the cause of this topographic high, but how inversion affected this basin remains a matter of debate, with the following two end-member scenarios: reactivation of pre-existing normal faults leading to local uplift or regional uplift and differential erosion. Neither end-member fully explains the observations from seismic and field data. In this study, we, therefore, conducted analogue models to explore how basin inversion in the Araripe Basin could have taken place. We present two series of crustal-scale brittle–viscous experiments: (i) extension followed by compression without sedimentation, with a variation in divergence and convergence directions (orthogonal or 45 ∘ oblique); and (ii) extension with syn-rift sedimentation followed by compression, with the same variation in rifting and inversion directions. We found that orthogonal rifting without sedimentation forms throughgoing graben boundary faults, whereas oblique rifting initially creates en échelon faults that eventually link up, creating large graben boundary faults. Rift basins with syn-rift sedimentation evolved in a similar fashion; however, sedimentary loading resulted in increased subsidence. During both oblique and orthogonal inversion, most shortening was accommodated along new low-angle reverse faults. Significant intra-graben fault reactivation occurred in all models without syn-rift sedimentation. By contrast, orthogonal inversion of models with syn-rift sedimentation did not reactivate rift faults, whereas only a minor reactivation of rift faults took place during oblique inversion since the sediments strengthened the otherwise weakened basin, thus acting as a buffer during convergence. Based on our modelling results, we propose an alternative scenario for the evolution of the Araripe Basin, involving oblique inversion and the development of low-angle reverse faults, which better fits observations from seismic lines and field data from the region. [ABSTRACT FROM AUTHOR]

The topography of ocean worlds is often used to infer ice shell thicknesses by assuming topography is compensated by a basal root. We systematically test the stability of isostatically compensated topography in ice shells. At short horizontal wavelengths, lithospheric strength can support surface topography, while at long wavelengths, buoyancy forces can support topography at the surface and base of the ice shell over geologic time scales. These behaviors are also seen for Airy isostasy in terrestrial worlds. Contrastingly at intermediate scales, the mechanically weak lower ice shell can inhibit the transfer of buoyancy forces to the surface. Factors such as surface temperature can alter the contribution of lithospheric strength, decreasing the stability of a compensating root. This nuanced understanding of icy shell lithospheres provides crucial insights for interpreting surface features and inferring underlying ice shell thickness, with substantial relevance for upcoming space missions to the Jovian system. Plain Language Summary: Ocean moons have topography on their surfaces that can be used to estimate the thickness of the capping ice shells. In contrast to rocky worlds, the nature of ice shells prevents traditional approaches from being applied. In this study, we use geophysical models to simulate how topography evolves over geologic time. For small features, the stiffness of the ice crust plays a significant role in supporting topography. For larger features, buoyancy forces, like how an iceberg floats, keep topography stable over long periods. In the lower shell near the underlying ocean, the ice is near its melting temperature, which makes it much weaker than the ice nearer the surface. This weakness can prevent the buoyancy forces from reaching the surface for intermediate scale features. Understanding the dynamics of Airy isostasy in ocean worlds can help interpret data collected from space missions, and further our understanding of these icy satellites. Key Points: Distinct behaviors emerge in support of icy shell topography at varying spatial scalesIce shell thickness estimates using Airy isostasy are valid at only long wavelengths [ABSTRACT FROM AUTHOR]

Extensive geophysical databases, covering the UK sector of the North Sea, have been used to gravity layer strip the sedimentary layers down to the base Zechstein so that the gravity response of the Carboniferous and deeper strata can be identified and structurally interpreted. To achieve this, the average bulk density grids for each layer were derived using Gardner's functions derived from well velocity and density logs. The resulting residual gravity response of each layer and the Moho response were then removed from the Free air gravity anomaly to generate the isostatic gravity response of the crust below the base Zechstein. This gravity response was used to re-evaluate the British Geological Survey interpretation over the Mid North Sea High (MNSH) and was able to identify the same crustal structures. Using the tilt derivative method, a positive gravity anomaly was found to parallel the central fracture zone that forms a northern extension of the Dowsing fault zone. This anomaly can be traced north across the MNSH with offsets coinciding with the WSW–ENE basement lineaments. To the south, the southern North Sea basin is well defined by the stratigraphic layer depth and thickness maps as well as the residual gravity maps which identify the structures associated with the low-density Carboniferous Coal Measures. [ABSTRACT FROM AUTHOR]

In this study, an approach using gravity observations utilizing the Least Squares Collocation (LSC) method is developed with the aim of mapping the depth spatial variability of the Mohorovičić discontinuity. This approach is based on a spherical two-layer isostatic model where the exterior gravity field only varies because of the shifting topographic masses and the related isostatic adjustment since it is believed that the Earth's core has a uniform density distribution. Assuming mass conservation between the Moho column of height δR with respect to Rm representing the mean Moho and following a Helmert condensation approach, the relationship between the surface layer density to the potential δT can be obtained and δR can be estimated via LSC from observed values of any functional derived from δT. With such approach, the depth of Moho in the Iranian Plateau is estimated from Trr data generated by GOCO06S model reduced by topography, bathymetry and sediments effects by considering GEBCO2021 and CRUST1.0 models. The needed a-priori assumptions on Rm and the density contrast Δρ are tuned so to obtain the best fit with seismic Moho depths reported by literature. 73 stations were matched with 3 km of standard deviation, which is coherent with the expected accuracy of the benchmark values. The remaining greater discrepancies showed to be clustered in defined areas like the Zagros chain and the reliefs along the Caspian coastline and the East borders.

The effective elastic thickness (EET) of the lithosphere is a measure of the lithosphere's ability to flex under long-term geological and topographic loads. It is often estimated through analyses of gravity and topographic data. The EET has a significant role in regulating the geodynamic evolution of both the continental and oceanic plates. Estimates of EET derived from geophysical data are consistent with rheological models in the oceanic regions. However, there are extensive debates on the estimates of EET and rheological models over the continental areas; differences are probably due to the complex structure and history of the continental plates. For instance, according to one model of continental rheology, popularly known as the 'Jelly Sandwich', the mechanical strength of the lithospheric plate is distributed in the upper crust and the lithospheric mantle. In another model, dubbed as 'Crème Brulee', the lithospheric mantle is weak, and the mechanical strength of the lithosphere is limited to the upper portion of the crust. These model differences have arisen because of inconsistent results obtained using different datasets, e.g. the distribution of earthquakes, EET, gravity anomaly and rheology. This article discusses the evolution of these contrasting models and the critical necessity to resolve the model differences. [ABSTRACT FROM AUTHOR]

A long-wavelength geoidal geometry characterizes the most pronounced features of the Indian Ocean geoid low and the West Pacific and North Atlantic geoid highs. These large geoid undulations (globally roughly within ±100 m) are mainly attributed to a deep mantle structure and large lithospheric density and geometry variations (such as the African superswell), while maximum geoid modifications by a topographic relief of Himalaya and Tibet are up to ~30 m. To enhance the mantle signature in a long-wavelength geoidal geometry, gravimetric, isostatic, and spectral decomposition methods can be applied. In this study, we demonstrate that isostatic schemes yield isostatic geoid models that closely resemble a long-wavelength geoidal geometry. The gravimetric method, on the other hand, modifies the mantle geoid significantly. Further modifications of the mantle geoid by removing gravitational contributions of lithospheric mantle density and lithospheric thickness variations should (optimally) enhance the signature of the deep mantle in the sub-lithospheric mantle geoid. Our results confirm this assumption by revealing (large-scale) positive anomalies in the Central Pacific and along the Atlantic Ocean that are coupled by two negative anomalies in the East Pacific and South Eurasia. A gravimetric method thus better enhances the mantle signature in the geoidal geometry than isostatic and spatial decomposition methods. Nonetheless, our results also indicate the presence of possibly large errors in geoid modelling results that limit their full implementation in gravimetric studies of the Earth's mantle density structure without using tomographic images of the mantle and additional geophysical, geothermal, and geochemical constraints. [ABSTRACT FROM AUTHOR]

Abstract—This paper discusses the results of magnetic variation soundings at two sites in the eastern Arctic, in the Chaun Bay region, at the Pevek and Valkarkai weather stations, by using the ModEM program to perform a three–dimensional (3D) inversion of tippers. The inversion has produced a geoelectric model of the region in a subsurface area of 300 × 300 × 200 km. The moduli of tippers at both sites have values between 0.2 and 0.85, reaching the maximum ones in a period of 1000 s. At the Pevek weather station, the real induction arrow in the Parkinson convention is oriented to the west throughout the range of periods. At the second site, its azimuth changes from 30° to the NE to –30° to the NW as the period of variations increases. Throughout the range of depths, conductive inhomogeneities are located to the west and north of the Chaun folded zone. They extend as a narrow strip under the western and northern coastal parts of the zone at depths of 8–12 km. As the depth increases, they are split into blocks, which reach their maximum size in the horizontal plane at depths ranging between 20 and 30 km. The most prominent among them is the conductive block beneath the southern part of the Chaun Bay. The roots of these blocks are distinguishable at depths of up to 100 km. The Chaun folded zone is represented by a high–resistance block down to a depth of 150 km with an electrical resistivity of more than 1000 Ω m. Comparison of the obtained geoelectric model with the geophysical studies previously conducted here reveals a correlation between the location of conductive formations and the location of weakly positive anomalies in the gravity field in the Bouguer and isostatic reductions in the coastal water area. [ABSTRACT FROM AUTHOR]

Fractional calculus (FC) has recently received increasing attention due to its applications in many fields involving complex and nonlinear systems. However, one of the key challenges in using FC to deal with fractal or multifractal phenomena is how to relate functions to geometries with fractal dimensions. The current paper demonstrates how fractal calculus can be used to represent physical properties such as density defined on fractal geometries that no longer have the Lebesgue additive properties required for ordinary calculus. First, it introduces the recently proposed concept of fractal density, that is, densities defined on fractals and multifractals, and then shows how fractal calculus can be used to describe fractal densities. Finally, the singularity analysis based on fractal density calculation is used to analyze the depth clustering distribution of seismic frequencies around the Moho transition zone in the subduction zone of the Pacific plates and the Tethys collision zones. The results show that three solutions (linear, log-linear, and double log-linear) of a unified differential equation can describe the decay rate of the fractal density of depth clusters at the number (frequencies) of earthquakes. The spatial distribution of the three groups of earthquakes is further divided according to the three attenuation relationships. From north latitude to south latitude, from the North Pacific subduction zone to the Tethys collision zone, and then to the South Pacific subduction zone, the attenuation relationships of the earthquake depth distribution are generally from a linear, to log-linear, to double log-linear pattern. This provides insight into the nonlinearity of the depth distribution of earthquake swarms. [ABSTRACT FROM AUTHOR]

The Earth's synthetic gravitational and density models can be used to validate numerical procedures applied for global (or large-scale regional) gravimetric forward and inverse modeling. Since the Earth's lithospheric structure is better constrained by tomographic surveys than a deep mantle, most existing 3D density models describe only a lithospheric density structure, while 1D density models are typically used to describe a deep mantle density structure below the lithosphere-asthenosphere boundary. The accuracy of currently available lithospheric density models is examined in this study. The error analysis is established to assess the accuracy of modeling the sub-lithospheric mantle geoid while focusing on the largest errors (according to our estimates) that are attributed to lithospheric thickness and lithospheric mantle density uncertainties. Since a forward modeling of the sub-lithospheric mantle geoid also comprises numerical procedures of adding and subtracting gravitational contributions of similar density structures, the error propagation is derived for actual rather than random errors (that are described by the Gauss' error propagation law). Possible systematic errors then either lessen or sum up after applying particular corrections to a geoidal geometry that are attributed to individual lithospheric density structures (such as sediments) or density interfaces (such as a Moho density contrast). The analysis indicates that errors in modeling of the sub-lithospheric mantle geoid attributed to lithospheric thickness and lithospheric mantle density uncertainties could reach several hundreds of meters, particularly at locations with the largest lithospheric thickness under cratonic formations. This numerical finding is important for the calibration and further development of synthetic density models of which mass equals the Earth's total mass (excluding the atmosphere). Consequently, the (long-to-medium wavelength) gravitational field generated by a synthetic density model should closely agree with the Earth's gravitational field. [ABSTRACT FROM AUTHOR]

Using the gravity/GNSS data of 318 stations observed in 2020, this paper optimizes the Bouguer and free-air gravity anomalies around the 2021 Yangbi Ms 6.4 Earthquake, inverses the litho-spheric density structure of the focal area, and obtains the distribution of isostatic additional force borne by the lithosphere. The results show that the Bouguer gravity anomaly in western Yunnan varies from -120 to -360 mGal. As a whole the anomalies are large in the north and small in the south, and the value in the source area of the 2021 Yangbi Ms 6.4 Earthquake is about -260 mGal. Significant lateral differences indicates that the crust around the great earthquake does not belong to a solid and stable tectonic unit. The lithosphere in the source area is basically in equilibrium, indicating that the occurrence of the great event is not relative to the lithospheric equilibrium, but to the differential movement of the crust in the horizontal direction. In addition, we obtain the teleseismic SKS phases of 51 stations. As a whole, the polarization direction of fast wave in western Yunnan is approximately vertical to the maximum gradient change direction of regional Bouguer gravity anomaly that reflects the change of Moho. [ABSTRACT FROM AUTHOR]

The bathymetry is the most superficial layer of the Earth's crust on which it is possible to perform direct measurements. However, it is also well known that water covers more than 70% of the Earth's surface, so an enormous expenditure of acquisition campaigns should be performed to produce a high-resolution map of this layer. Currently exploiting mainly commercial navigation routes, the sea floor coverage with shipborne sounding is only at 11%, and the remaining part is currently modeled by classical interpolation techniques or satellite-based gravity inversion methods. In the present work, a new method to refine bathymetry modeling based on the exploitation of global gravity field models is presented. In the proposed solution, once modeled and removed from the observed gravity field, the gravitational signals related to the deepest structures, a 3D Bayesian inversion algorithm is used to improve the actual knowledge of bathymetry. The proposed inversion method also enables limiting the solution to shipborne sounding measurements in such a way as to improve the seafloor grid where no local, high-quality information is available. Two test cases are discussed in the Mediterranean Sea region. Promising results are presented, opening the possibility of applying an analogous method to refine the bathymetry modeling at larger scales up to the global one. [ABSTRACT FROM AUTHOR]

Black shales may serve as an important source of metals such as Co, Ni, or As, largely due to anoxic to euxinic conditions in association with high concentrations of sulfur leading to efficient scavenging and transport of metals from seawater into the seafloor sediment. We report on an unusual type of Au mineralization newly discovered in Ediacaran trench-slope black shales in the Bohemian Massif, Czech Republic. The Au enrichment is related to the formation of a quartz–sulfide vein system and a progressive evolution of ore-forming fluids with decreasing temperature, from Sb- to As-rich to final precipitation of native gold from silica and Au-bearing low-temperature hydrothermal colloidal solutions. The hydrothermal nature of these solutions is also documented by Li contents and isotope compositions which differ markedly between barren black shales and those carrying significant late-stage quartz-rich veins. The structural relationships and orientation of the associated quartz veins point to a close connection between vein emplacement and high heat flow in response to Ordovician rifting, and breakup of the northern margin of Gondwana, and opening of the Rheic Ocean. This triggered metal and sulfur remobilization, including Au, from the associated Neoproterozoic–Cambrian volcanosedimentary successions. The documented Au mineralization and its association with the Ordovician rift-related magmatic activity is different from the widespread Variscan Au occurrences in the Bohemian Massif. Our study thus provides a new genetic model potentially important for future exploration of Au also in other terrains underlain by a rifted Cadomian basement. [ABSTRACT FROM AUTHOR]

The Eastern Himalayan Syntaxis (EHS) is one of the fastest exhuming regions on Earth since ∼10 Ma, and the mechanism of its fast exhumation is under debate. Different from many other studies based on tectonics‐driven models, we performed analytical analysis and numerical simulations to investigate an erosion‐driven system. Our results show that fast and focused surface erosion alone is able to exhume the lower crust on the timescale of ∼10 Myr. This process leads to the formation of a domal structure, an elevated geothermal gradient, rapid cooling of crustal rocks, and decompression melting in the lower crust. In the upper‐mid crust, the uplift of crustal rocks is caused by isostatic flow driven by pressure gradient, whose rate is limited by the driving erosional forcing. In the mid‐lower crust where decompression melting occurs, rocks entrained in a buoyant diapir experience fast uplift rate exceeding the erosional forcing. Our erosion‐driven model demonstrates an intricate coupling between surface erosion and crustal processes. Positive feedback between surface erosion and rock uplift is possible under certain conditions and crustal diapirism plays a key role in the feedback. Our study shows that both isostatic and diapiric flows play important roles in the uplift and exhumation of crustal rocks in the EHS. We highlight that erosion‐driven crustal diapirism can be one of the missing pieces explaining the evolution of the Eastern Himalayan Syntaxis. Plain Language Summary: Located in southern Tibet, the Eastern Himalayan Syntaxis (EHS) has undergone fast rock exhumation in the past ∼10 million years. Previous studies show that such exhumation can be driven by tectonic or surface processes. In this study, we built a numerical model in which we directly tested how focused surface erosion can cause the crust to deform. We also uses simple math equations to quantify the relationship between surface erosion and crustal deformation. We confirm that crust can flow in response to pressure gradient and buoyancy. The formal type of flow is limited by the surface erosion rate while the latter occurs if the rocks undergo partially melting. The surface erosion and rock uplift can mutually enhance each other, accelerating both rates, if certain conditions are met. Our study highlights that the rapid ascent of partially molten mid‐lower crustal rocks in the form of a diapir. We suggests that crustal flows driven by both pressure gradient and buoyancy are important to understand the evolution of the EHS. Key Points: Analytical and numerical models were performed to study the dynamics of the crustal flow in an erosion‐driven systemSurface erosion generates pressure‐gradient‐driven isostatic flow and buoyancy‐driven diapiric flow in continental crustDiapirism can trigger positive feedback and it can be one of the missing pieces in the evolution of the Eastern Himalayan Syntaxis [ABSTRACT FROM AUTHOR]

We probe the gravitational properties of two neighboring planets, Earth and Venus. To justify a comparison between gravity models of the two planets, spherical harmonic series were considered up to a degree and order of 100. The topography and gravity aspects, including Γ zz (vertical derivative of the vertical component of the gravity field), strike alignment (SA), comb factor (CF), and I2 invariant derived from the Marussi tensor, were calculated for the two planets at specifically selected zones that provided sufficient resolution. From Γzz we discovered that the N-NW edge of Lakshmi Planum does not show any subduction-like features. Its Γzz signature resembles passive continental margins on Earth, like those surrounding the Indian Peninsula. Moreover, according to SA and CF, the Pacific and Philippine-North American Contact Zone on Earth indicates significantly higher level of deformation due to convergent motion of the plates, whereas the deformation level on Venus is significantly smaller and local, when considering an equatorial rifting zone (ERZ) of Venus (between Atla-Beta Regios) as diverging boundaries. The strain mode on the East African Rift system is smaller in comparison with ERZ as its Venusian analog. The topography-I2 analysis suggests a complicated nature of the topographic rise on Beta Regio. We show that specific regions in this volcanic rise are in incipient stages of upward motion, with denser mantle material approaching the surface and thinning the crust, whereas some risen districts show molten and less dense underlying crustal materials. Other elevated districts appear to be due to mantle plumes and local volcanic activities with large density of underlying material. [ABSTRACT FROM AUTHOR]

A hydrodynamic model for small acoustic oscillations in a cloud of stars is built, taking into account the self-consistent gravitational field in equilibrium with a non-zero second correlation moment. It is assumed that the momentum flux density tensor should include the analog of the anisotropic pressure tensor and the second correlation moment of both longitudinal and transverse gravitational field strength. The non-relativistic temporal equation for the second correlation moment of the gravitational field strength is derived from the Einstein equations using the first-order post-Newtonian approximation. One longitudinal and two transverse branches of acoustic oscillations are found in a homogeneous and isotropic star cloud. The requirement for the velocity of transverse oscillations to be zero provides the boundary condition for the stability of the cloud. The critical radius of the spherical cloud of stars is obtained, which is precisely consistent with the virial theorem. [ABSTRACT FROM AUTHOR]

The Mohorovičić discontinuity, often known as the Moho, marks the boundary separating the Earth's crust from the mantle. Techniques such as isostatic-gravity and seismic methods can be used to determine this division. The Moho marks the boundary between the continental and oceanic crust and the upper mantle. Simply put, the Moho acts as a physical/chemical boundary between the mantle and the crust and causes significant changes in geophysical properties such as seismic wave velocity, density, pressure, and temperature (Mooney and Masters, 1998; Martinck, 1994; Bagherbandi, 2011 and Dashtbazi et al., 2023). An accurate and high resolution Moho depth model in fields such as geodesy, geology, geophysics, geodynamic modeling, seismic risk assessment, stress field modeling caused by mantle convection (Li et al., 2018; Behr et al., 2022; Singh and Yadav, 2023; Heilman and Becker, 2022; Hashima et al., 2016; Eshagh et al., 2020; Eshagh, 2015 and Gido et al., 2019), and understanding seismic source mechanisms is important, among other applications (Gido et al., 2019 and Dashtbazi et al., 2023). Furthermore, a reliable Moho model can reveal details of crustal structure that provide valuable insights into the complexities of deeper mantle layers; related to the calculations and detailed examination of gravity, geothermal, geomagnetic models (Stalk et al., 2013). Although there are several Moho models, their accuracy and resolution are insufficient in the complex tectonic geometry of the Makran subduction zone (Brizi et al., 2021 and Heilman and Becker, 2022), because these zones show a complex Moho configuration (Shad Manaman et al., 1390; Taghizadeh Farhamand et al., 2015 and Dashtbazi et al., 2023). As a result, the existing models lack the necessary accuracy for the Makran subduction zone, a region approximately 1000 km long located in southeast Iran and southwest Pakistan (Byrne et al., 1992; Shad Manaman et al., 1390, Penney et al., 2017; Dashtbazi et al., 1398; Dashtbazi. et al., 2023). In geophysical and geodetic studies, hybrid methods are mainly used to determine the Moho depth when seismic data with appropriate distribution and abundance are not available. These techniques include the Parker-Oldenberg method and the Wenning-Mines-Moritz method. In an effort to strengthen the existing Moho depth models in the Makran subduction zone, two distinct models named BC and SC through the integration of gravity (VMM) and seismic (CRUST1.0) data, which are processed through the Butterworth filter, spectral combination approaches and the least squares technique, was developed (Bagherbandi, 2011 and Dashtbazi et al., 2023). The resulting models provide a resolution of 5' x 5' degrees of arc, corresponding to a grid size of 9 x 9 km (Dashtbazi et al., 2023). The accuracy of these models was evaluated against four separate regional and local models. The resulting RMS values were 5.28, 1.55, 4.18, and 1.27 km for the BC model and 5.59, 1.17, 3.74, and 3.04 km for the SC model. Also, the Moho depth model obtained for the west Makran region in Iran significantly improved the accuracy and resolution of the Moho depth models in the studied area. The SC Moho model exhibits improved RMS metrics compared to the combined BC model, so we recommend it as the first priority. While the Moho depth models in our research really bring significant improvements to the existing models of the Makran subduction Moho zone, the integration of more detailed seismic data with SC and BC Moho models can improve the developed model for the Makran subduction zone. In the end, we suggest that a similar approach be adopted for the analysis of the Moho model in the eastern Makran region in Pakistan, which allows a comparative evaluation of the Moho depth and structure between the western and eastern parts in order to obtain a better picture of the Moho depth model of the Makran subduction zone. [ABSTRACT FROM AUTHOR]

The composition of the lower continental crust, as well as its formation, growth, and evolution, remains a fundamental subject to be understood. In this study, we carry out a comparative and integrative analysis of seismic tomographic models, teleseismic receiver function results, and Airy isostasy in order to investigate the properties of the lower continental crust in eastern North America. We extract the depths for Vs of 4.0 km/s, 4.2 km/s, and 4.5 km/s from three selected tomographic models and calculate the differences between the Vs depth contours and the Moho depth defined by receiver functions. We then calculate the Airy isostatic Moho depth and its misfit with the receiver‐function‐defined Moho. Our analysis reveals three key features: (a) the deepening of the Vs depth contours and the strong negative Airy misfit within the U.S. Grenville Province; (b) a seismically faster‐than‐average and compositionally denser‐than‐average lowermost crust in the eastern North American Craton and the Grenville Province; and (c) the thickest, seismically fastest, and densest lowermost crust beneath the southern Grenville Front, the southern Grenville‐Appalachian boundary, and the U.S.‐Canada national border. We suggest that the lower crust of the craton and the Grenville Province has densified through garnet‐forming metamorphic reactions during and after orogenesis, contributing to the widely distributed fast‐velocity layer. The lower crust beneath the tectonic boundaries could have experienced more extensive garnet growth during orogenesis and emplacement of mafic magma. This study provides new constraints on the seismic and compositional properties of the lower crust in eastern North America. Plain Language Summary: The continental crust provides important clues about the formation and evolution of the Earth. However, the dominant composition of the lower part of the continental crust remains enigmatic, especially in the regions where the seismic velocities are significantly faster than the global average. In this paper, we investigate the properties of the lower continental crust in eastern North America by comparatively analyzing two types of data sets: (a) the variations of seismic velocity within the crust and (b) the variations of the crustal thickness. Our comparative and quantitative analysis reveals that the lower crust of the eastern North American Craton and the Grenville Province is seismically faster and compositionally denser than the global average. The thickest, seismically fastest, and compositionally densest lower crust is roughly along the orogenic fronts and the U.S.‐Canada national border. We suggest that garnet growth within the lower crust is a viable mechanism for forming the widely distributed fast‐velocity layer in eastern North America. The lower crust may have been further densified through extensive garnet growth and emplacement of mafic magma at a regional scale. Key Points: A high‐velocity lower continental crust distributes widely in eastern North AmericaThe seismically fastest and densest lower crust is roughly along the orogenic frontsThe lower crust densifies through the metamorphic growth of dense minerals [ABSTRACT FROM AUTHOR]

The Sturtian (720–670 Ma) glacial–interglacial transition period was an important interval for sedimentary manganese metallogenesis, including the Mn oxide deposit in the Otjosondu region in Namibia and Mn carbonate deposits in the Datangpo Formation in the south-eastern Yangtze Platform, South China. During this period, Earth experienced the breakup of Rodinia, the Sturtian glaciation, and the Neoproterozoic oxygenation event. In this study, we investigate scenarios that might have provided geologically and geochemically favorable conditions for Mn metallogenesis. In these scenarios, the global recovery of microorganisms enhanced marine primary productivity and O2 levels of the hydrosphere and atmosphere during the Sturtian glacial–interglacial transition. However, the water column was not completely oxidized, maintaining redox stratification. Transgression–regression cycles or O2-rich downwelling drove the exchange of oxygenated topwater and anoxic deep water in rift-related basins that developed due to Rodinia's breakup. The coupling of these processes precipitated existing dissolved Mn(II) at the margins of basins (Otjosondu region) or at their centers (Yangtze Platform). In the latter case, precursor Mn oxides were further converted into Mn carbonates via the reduction of Mn oxides coupled with organic matter oxidation during early diagenesis. A brief review of Mn metallogenesis in the geological record reveals that Mn metallogenic processes typically occur under geo-environmental conditions that, in concert, produce favorable conditions for Mn sourcing, concentration, and sedimentation. [ABSTRACT FROM AUTHOR]

The Singhbhum Craton, Singhbhum Mobile Belt along its northern, eastern, and western edges, and Chotanagpur Gneissic Complex farther north are all parts of the Precambrian eastern Indian shield. Modern isotope dates and associated geological evidence suggest that these crustal units may be one cratonic block that developed sequentially between 3.55 and 1.00 Ga. The region has always been the focus of numerous geoscientific studies due to its complex evolutionary history and abundant mineralisation. We used the terrestrial gravity data from the Gravity Map Series of India and the EGM2008 global gravity dataset in the Bay of Bengal to model the 3D Moho geometry of the eastern Indian shield and the adjoining Bay of Bengal by inverting the gravity data. The Bouguer gravity data were filtered at several levels before applying the Parker–Oldenburg iterative inversion procedure. The Moho depth measurement is then computed by presuming a constant density contrast. The effects of sediments were eliminated from gravity data by collecting thickness and density details of the sediment from a worldwide sedimentary thickness map CRUST1.0 and applying a correction comparable to the Bouguer correction that uses the density difference of 0.24 g/cm3. Spectral analysis is used to fix a reference depth level and the low-frequency range associated with Moho deflection in the Bouguer anomaly filtered for sedimentary overburden. We subsequently executed the gravity inversion of a basic two-layer structure having a constant density difference of 0.40 g/cm3 across the Moho fixed at an average depth of 35 km. The gravity inversion analysis shows that the Moho depth within the Bay of Bengal is between 18 and 24 km. In the continent, the Moho depth varies from 34 km near the coastline to 38 km towards the Singhbhum Craton and Chhotanagpur Gneiss Complex. In the northern portion of the region, the Moho depth increases to over 40 km underneath the convergence of the Mahanadi–Damodar Gondwana basins and the Ganga foreland basin. [ABSTRACT FROM AUTHOR]

Characterizing the thermophysical properties of the lithosphere is critical for studying its evolution. We determine the elastic thickness of the lithosphere by modeling mass‐related loads and lithospheric deflection and analyzing gravity and topography data. In impact basins region where a mantle plug is present, the correlation between topography and gravity can be low, and the admittance can change quickly, making it difficult to develop accurate models without considering mantle uplift. In this study, we developed a lithospheric loading model for large impact basins that take advantage of a high‐resolution crustal thickness model and does not require the assuming compensation. Since the mantle uplift formed by super‐isostatic adjustment following the impact, the elastic thickness obtained by fitting the observed data reflects the lithospheric temperature at the end of the super‐isostatic process. Sensitivity analysis suggests that modeling the impact‐induced load is critical to reproduce how the mascon is expressed in the correlation and admittance data. Our mantle loading model provides a better fit to the observed admittance spectrum compared to previous research. The larger elastic thicknesses obtained for the Hellas basin indicate a longer duration of mascon formation or a faster cooling of the lithosphere. Models that consider a denser upper crust and an elastic thickness of about 0 km fit the observed admittance of the Utopia basin. The elastic thickness of the Argyre and Isidis basins cannot be precisely inferred without additional constraints on the load ratio. Plain Language Summary: The lithosphere is defined as the outer rigid part of a planet, and its deformation due to applied masses (loading) can be calculated using the deflection equation. Topography and gravity data are used to measure this deformation and constrain the thickness of the elastic shell assumed to represent the lithosphere. However, this approach is difficult to apply to impact basins due to the complex loading process that follows the impact, such as the formation of a mass concentration (mascon) beneath the basin center. In this work, we modeled the mascons as mantle plugs and inferred their structures from a global crustal thickness model. The resulting mantle loading model is applied to large impact basins on Mars. The large elastic thickness inferred for the Hellas basin means the temperature of the lithosphere was low when the mascon formed, indicating that the lithosphere cooled quickly or mascon formation took a long time. The Utopia basin's nearly zero lithosphere thickness means the mascon formed in a relatively high‐temperature situation, causing the lithosphere to be too weak to support the mascon. Key Points: A mantle‐plug loading model based on crustal thickness helps understand the gravity and topography signals of large impact basins on MarsThe elastic thickness inferred for the Hellas basin indicates fast lithosphere cooling or long‐duration mascon formationThe elastic thickness inferred for the Utopia basin is near 0 km when considering a denser upper crust [ABSTRACT FROM AUTHOR]

Evidence of early oceanization during transition from large igneous provinces (LIPs) to new ocean crust is mostly missing in the geological record. Mafic dykes geochemically akin to mid‐ocean ridge basalts (MORBs) occur in late stages of LIPs, but their tectonic role during margin evolution remains poorly constrained. Here we use whole‐rock and high‐resolution clinopyroxene chemistry of two distinct types of mafic dykes from the southeastern Brazilian margin to show that a MORB‐like plumbing system became magmatically active in the central South Atlantic ∼2 Ma after the volcanic peak of the Paraná‐Etendeka Magmatic Province. The LIP basaltic dyke compositions resulted from the mixing between a highly metasomatized lithospheric mantle comprising enriched DMM and Archean contributions. The lack of elemental oscillatory zoning in clinopyroxene crystals suggests that they were produced by a single magma pulse, consistent with the strong magma fluxes in LIPs. In contrast, the MORB‐like dykes, which exhibit strong similarities with South Atlantic MORBs, are interpreted to represent early stages of oceanization deriving from the mixing of enriched asthenospheric melts either with ancient SCLM contributions or small crustal assimilation. The MORB‐like intrusions ascended and cooled rapidly along faults and were fed by numerous magma injections that suggest episodic decompression of the asthenospheric source ∼20 Ma before the birth of central South Atlantic. The combination of subduction‐influenced and MORB‐like dykes is recurrent in ancient and modern rifts globally, suggesting that thinned lithospheric blocks affected by ancient subduction events may become more susceptible to early oceanization in rifted margins. Plain Language Summary: The processes that promote initial formation of new ocean floor, whenever a continent breaks, are still poorly described. In the South Atlantic Ocean case, for example, magnetic registers of oceanic rocks indicate that seafloor boomed ∼20 Ma after the ancient Gondwana continent broke up, creating distinct South American and African plates. However, we know very little about the preliminary steps of "oceanization" of the continental margins during the transition period. In this research, we studied two groups of magmatic rocks located in the Brazilian southeast margin. One of them is geochemically similar to the abundant volcanism that affected Gondwana prior to breakup; the other is akin to South Atlantic seafloor. The later was formed only ∼2 Ma after initial stages of Gondwana breakup. Geochemical signatures and mineralogical textures allowed us to describe how the two types of magmas were formed and how they ascended through the crust. The results and comparisons suggest that ∼20 Ma before the South Atlantic seafloor developed there were localized areas of the continental margins affected by early "oceanization," where ocean floor‐like rocks started forming along weakened continental structures. Such areas were probably more susceptible to breakup because of their more complex previous geological histories. Key Points: Oceanization of the South Atlantic started as early as ∼132 Ma through lithospheric thinning and focused mid‐ocean ridge basalt (MORB)‐like intrusive magmatismMagma dynamics of Paraná‐Etendeka and MORB dykes in the Brazilian margin suggest an intermittent shift toward a passive regime at ∼132 MaThinned lithospheric blocks affected by ancient subduction potentially allow early asthenospheric magma ascent and crustal oceanization [ABSTRACT FROM AUTHOR]

The crustal structure of the Nordland and Troms region, Norway, has received growing scientific attention because (a) the region is one of the most seismically active areas of mainland Norway, and (b) there are differing interpretations of the crustal structure but none of the proposed models simultaneously satisfy gravity, topography and crustal isostasy. At the core of the puzzle is the Lofoten‐Vesterålen archipelago, which exhibits considerable variations in crustal thickness, seemingly inconsistent with the topographic expression along this geomorphic structure. The prevalent view has been that the crust beneath the southern Lofoten is extremely thin (∼20 km). This has recently been disputed. Here, we address this debate by producing new lithospheric models in the region from joint inversion of receiver functions and P‐wave polarizations at 62 seismic stations. Our results are consistent with the regional trends from other models, including a shallow Moho in the southern Lofoten. Moreover, our results detect a low‐velocity layer in the uppermost mantle, which appears to be highly relevant to isostasy in the region. We conclude that the crustal structure in the region may not be as controversial as the recent debate suggested. What appears more urgent to understand is how the concept of isostasy is defined, and how it relates to the layered structure of the lithosphere. In particular, our findings emphasize the importance of conceptualizing the Moho as a transition zone with considerable thickness and internal structural variations, rather than a simple velocity discontinuity. Plain Language Summary: The Nordland and Troms region, Norway, is one of the most seismically active areas of mainland Norway. To understand the occurrence of earthquakes, we need to understand the forces acting on and in the tectonic plate, the lithosphere, which consists of the crust and the underlying lithospheric mantle. One set of forces are caused by the distribution of masses and thereby variations of potential energy within the lithosphere. However, in the study area the structure of the lithosphere and the internal mass distribution is debated. So far, none of the proposed models can satisfactorily explain the geological observations. In particular the crust and topography seem to have a paradoxical relation. To gather more information, we develop another complementary model of the lithospheric structure based on a seismological method not yet applied in the area to this extent. Our new seismological study roughly confirms previous models of the crust. However, the model includes a hitherto unseen structure beneath the crust that may be key to understanding the relationship between topography and crust. This may have general and global implications for lithospheric structure. Key Points: Receiver function inversion in Nordland and Troms, Northern Norway confirms earlier crustal structure modelsTopography in the Lofoten‐Vesterålen archipelago is not isostatically compensated from within the crust and requires additional buoyancyA newly discovered low‐density layer in the uppermost mantle beneath the Lofoten‐Vesterålen archipelago provides the additional buoyancy [ABSTRACT FROM AUTHOR]

We conducted a receiver function (RF) analysis to understand the convergence process in and around the Izu collision zone. We calculated the P‐ and S‐wave RFs and converted them to depth using a three‐dimensional (3D) regional tomography model and regionally estimated near‐surface structure. We detected the Moho of the Philippine Sea Plate and determined its 3D geometry in and around the collision zone. In addition, we considered the 3D seismic velocity model, which was previously determined using seismic tomography, and we complemented a part of the Moho that we did not detect using the RFs. Based on the geometry of the upper surface of the Philippine Sea Plate determined in previous studies, the crust is >35 km thick beneath the Izu Peninsula and collision zone and becomes thinner (<20 km) moving east of the collision zone. Thus, the thick crust along the Izu‐Bonin arc collides, and the thin forearc crust subducts. A stable slip surface was previously assumed to exist at a 15–20 km depth beneath the Izu Peninsula and the collision zone. This study indicates that the surface should exist within the crust of the Philippine Sea Plate. Plain Language Summary: The Philippine Sea Plate subducts beneath the continental plates along its entire length; however, it collides with the Izu collision zone at one point. Little information is available on the three‐dimensional (3D) configuration of the rock layers in and around the collision zone or the mechanisms by which they accommodate relative plate motion. To understand this, we investigated the subsurface structure using seismic waveform data. Based on the results and previously determined structural properties, the geometry of the crust‐mantle boundary (termed the "Moho") of the Philippine Sea Plate was determined. We estimated the crustal thickness of the plate by considering the previously determined geometry of its upper surface. The crust is >35 km thick beneath the Izu Peninsula and the collision zone; however, the crust becomes thinner with increasing distance. Thus, the thick crust collides, and the thin crust subducts. Although the thin crust subducts through the unstable sliding of its upper surface, the upper surface of the thick crust is fixed. Instead, a stable slip was previously assumed to occur at a 15–20 km depth beneath the Izu Peninsula. The results of this study indicate that a stable slip surface exists within the crust of the Philippine Sea Plate. Key Points: The geometry of the Moho of the Philippine Sea Plate was determined around the Izu collision zoneA thick arc crust collides with the continental plate, and a thin forearc crust subducts beneath the plateA stable slip surface beneath the collision zone may exist within the underthrusted crust [ABSTRACT FROM AUTHOR]

The 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. Plain Language Summary: The Charleston, South Carolina seismic zone is the site of an 1886 ∼M7 earthquake and present‐day low‐level seismicity, indicating a need to better understand seismic hazards there. This seismic zone is not located near a plate boundary, so the causes of seismicity are poorly understood. It is, however, associated with a basin that formed during the Mesozoic rifting event that led to the breakup of Pangea. New airborne magnetic data collected over the region provide an unprecedented view of geologic features buried beneath hundreds of meters of sediments including faults, folds, dikes, larger magmatic bodies, and sub‐basins. A set of faults interpreted to have formed during Mesozoic rifting are favorably oriented for reverse slip in the modern stress regime; these faults terminate along interpreted Paleozoic faults. Seismic reflection profiles show evidence of tectonic activity on some of these faults in more recent (Eocene or younger) times, and two of these faults are aligned with Quaternary landforms. The seismic zone also appears to be within a sub‐basin, which could facilitate reverse slip because the sedimentary fill is less dense. Favorably oriented faults and a sub‐basin suggest mechanisms by which features of ancient rift basins might contribute to intraplate earthquake hazards. Key Points: New aeromagnetic data provide an unprecedented view of structures within a large, buried rift basin and associated intraplate seismic zoneReflection, earthquake, and landform data indicate reactivation of Paleozoic and Mesozoic faults in the modern passive margin settingFavorably oriented rift faults and a likely sub‐basin suggest links between ancient rift zones and intraplate seismicity [ABSTRACT FROM AUTHOR]

This paper considers a construction procedure of a satellite reference angular motion in the vicinity of an unstable gravitational equilibrium position. The satellite is stabilized on the reference trajectory by the magnetic coils. The problem is solved in several stages. An optimization problem to be solved by the particle swarm optimization method is formulated at each stage. Cost functions are based on the linearized model analysis. The main stage is the construction of a special reference motion, which provides the minimum control torque projection on the geomagnetic induction vector. Optimal geomagnetic field dipole approximation for a given time interval is considered to reduce tracking errors. The paper compares combinations of different cost functions in terms of the terminal attitude accuracy in the presence of perturbations. [ABSTRACT FROM AUTHOR]

The East Kunlun Shan (EKLS) in northern Tibet occupies boundaries of the low‐relief topography and lower crustal low‐velocity zone in the interior plateau, making it ideal for exploring the relationship of surface deformation with underlying geodynamic processes. We used previous and new apatite (U‐Th)/He data to analyze the exhumation history and pattern throughout the EKLS and link surface deformation to deep structures. Integrated (U‐Th)/He ages reveal the rapid exhumation at 27–25 Ma, due to the coeval orogen‐scale tilting of the EKLS. Along with the crustal structures beneath the EKLS, it is inferred that orogen‐scale tilting is the isostatic response of the nonuniform crustal thickening related to northward injection of the Tibetan lower crust. This study highlights the role of ductile deformation within the lower crust in mountain building in northern Tibet, which shares a similarity with mountain building pattern in the eastern plateau margin. Plain Language Summary: How deep geodynamic process affects shallow crustal deformation in Tibet is one of the key issues in understanding continental dynamics. The East Kunlun Shan (EKLS) defines northern boundaries of low‐relief topography and crustal low‐velocity zone in the interior plateau. In this study, we explore the relationship between surface deformation and underlying geodynamic processes in the EKLS by analyzing the shallow crustal exhumation pattern in conjunction with deep structures. Amounts of apatite (U‐Th)/He ages across the EKLS reveal the late Oligocene orogen‐scale tilting, indicating the involvement of indistinctive shallow crustal shortening in the mountain building process. Such a regional tilting may be the reflection of nonuniform crustal thickening related to the injection of the Tibetan lower crust when considering the crustal structures beneath the EKLS. By comparing the mountain building patterns in the northern and eastern margins of Tibet, we conclude that ductile deformation in the lower crust may be a common phenomenon to mountain building in plateau margins. Key Points: Apatite (U‐Th)/He data reveal the accelerated exhumation at 27‐25 Ma and southward increasing exhumation across the East Kunlun Shan (EKLS)The EKLS has experienced the orogen‐scale tilting during the late OligoceneOrogen‐scale tilting of the EKLS may be the isostatic response of northward injection of the Tibetan weak lower crust [ABSTRACT FROM AUTHOR]

Changes in sediment flux to continental margins are commonly interpreted in terms of tectonic growth of topography or climatic change. Here, we show that variations in sediment yield from orogenic systems, previously considered as resulting from climate change, drainage reorganisation or mantle processes can be explained by intrinsic mechanisms of mountain belt/foreland basin systems naturally evolving during post‐orogenic decay. Numerical modelling indicates an increase of sediment flux leaving the orogenic system synchronous with the cessation of deposition in the foreland basin and the transition from late syn‐ to post‐orogenesis. Experiments highlight the importance of lithospheric flexure that causes the post‐orogenic isostatic rebound of the foreland basin. Erosion of the rebounding foreland basin combined with continued sediment flux from the thrust wedge drives an acceleration in sediment outflux towards continental margins. Sediment budget records in natural settings such as the Northern Pyrenees or Western European Alps also indicate accelerated post‐orogenic sediment delivery to the Bay of Biscay and Rhône Delta respectively. These intrinsic processes that determine sediment yield to continental margins must be accounted for prior to consideration of additional external tectonic or climatic controls. [ABSTRACT FROM AUTHOR]