Even though it is well accepted that the Earth's surface topography has been affected by mantle-convection induced dynamic topography, its magnitude and time-dependence remain controversial. The ...dynamic influence to topographic change along continental margins is particularly difficult to unravel, because their stratigraphic record is dominated by tectonic subsidence caused by rifting. We follow a three-fold approach to estimate dynamic topographic change along passive margins based on a set of seven global mantle convection models. We first demonstrate that a geodynamic forward model that includes adiabatic and viscous heating in addition to internal heating from radiogenic sources, and a mantle viscosity profile with a gradual increase in viscosity below the mantle transition zone, provides a greatly improved match to the spectral range of residual topography end-members as compared with previous models at very long wavelengths (spherical degrees 2–3). We then combine global sea level estimates with predicted surface dynamic topography to evaluate the match between predicted continental flooding patterns and published paleo-coastlines by comparing predicted versus geologically reconstructed land fractions and spatial overlaps of flooded regions for individual continents since 140Ma. Modelled versus geologically reconstructed land fractions match within 10% for most models, and the spatial overlaps of inundated regions are mostly between 85% and 100% for the Cenozoic, dropping to about 75–100% in the Cretaceous. Regions that have been strongly affected by mantle plumes are generally not captured well in our models, as plumes are suppressed in most of them, and our models with dynamically evolving plumes do not replicate the location and timing of observed plume products. We categorise the evolution of modelled dynamic topography in both continental interiors and along passive margins using cluster analysis to investigate how clusters of similar dynamic topography time series are distributed spatially. A subdivision of four clusters is found to best reveal end-members of dynamic topography evolution along passive margins and their hinterlands, differentiating topographic stability, long-term pronounced subsidence, initial stability over a dynamic high followed by moderate subsidence and regions that are relatively proximal to subduction zones with varied dynamic topography histories. Along passive continental margins the most commonly observed process is a gradual motion from dynamic highs towards lows during the fragmentation of Pangea, reflecting the location of many passive margins now over slabs sinking in the lower mantle. Our best-fit model results in up to 500 (±150) m of total dynamic subsidence of continental interiors while along passive margins the maximum predicted dynamic topographic change over 140millionyears is about 350 (±150) m of subsidence. Models with plumes exhibit clusters of transient passive margin uplift of about 200±200m, but are mainly characterised by long-term subsidence of up to 400m. The good overall match between predicted dynamic topography to geologically mapped paleo-coastlines makes a convincing case that mantle-driven topographic change is a critical component of relative sea level change, and indeed the main driving force for generating the observed geometries and timings of large-scale continental inundation through time.
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•We model the dynamic topography of passive margins since the Cretaceous.•Predicted and geologically mapped paleo-coastlines match well overall.•The most common topographic change since 140Ma is about 350 (±150) m of subsidence.•Models with plumes exhibit clusters of passive margin uplift of about 200±200m.
Southern Tunisia is known to be less deformed and simpler than its neighboring Atlassic domain to the north. This area is complex and basin evolution in the Southern Chotts‐Jeffara (SCJ) basin is ...debated. In this paper we combined surface and subsurface data with low temperature thermochronology (LTT) to reinvestigate the tectono‐sedimentary evolution of the SCJ basin from Permian to Jurassic. We reconstruct the present‐day architecture of the SCJ basin along two regional sections. In these sections, we focused mainly on regional thickness variations and on internal reflections interpreted from seismic data. We observe three structural elements: (a) A Paleozoic culmination, oriented E‐W, capped by Mid‐Upper Triassic deposits; (b) the Tebaga of Medenine (ToM), a culmination also oriented E‐W but located ∼50 km north of the Paleozoic culmination; and (c) A Triassic culmination in the eastern part of the area, oriented NW‐SE. We note the absence of major normal faults along the sections. The LTT data we present are the first published in this area and allow to reconstruct the timing and magnitude of vertical movements. These data prove: (a) exhumation at ∼230 Ma of the Permian and Lower Triassic units associated with the onset of the ToM removing locally about 900 m of pre‐Cretaceous sediments; and (b) the development of the Triassic culmination ∼180 Ma removing 2000 m of pre‐Cretaceous sediments in the Jebel Rehach. This study demonstrates that vertical movements in the SCJ basin are controlled by long‐wavelength processes developed essentially in shortening regimes.
Key Points
Two large scale cross sections accross the Southern Chotts‐Jeffara basin allowed to interpret multiscale architecture of the basin
The basin deformation is controled by the implacement of anticlines and basin related to successive shortening regimes
Outcrop observations, seismic‐well interpretation and low temperature thermochronology data allow to reconstruct the evolution of the basin
The mid-Tyrrhenian coast is the most complex volcano-tectonic sector in the Mediterranean basin. Here the vertical ground movements (VGMs) due to the interaction between extensive tectonic processes ...and volcano-tectonic activities have a significant impact on both past and future sea-level evolution. This area represents the youngest basin of the western Mediterranean and it hosts one of the most active volcanic districts, formed by the Campi Flegrei and Vesuvius volcanoes, which are worldwide known for the vertical ground movements accompanying their volcanic activity since the Late Pleistocene. The short-lived alternation of subsidence and uplift has induced great changes in inland areas and abrupt coastal landscape transformations since that time. This study aimed to spatially constrain the magnitude of the vertical displacements which significantly affected this coastal sector during the last millennia. We then reconstructed the multiple relative sea-level oscillations that occurred during the Late-Quaternary by developing a comprehensive WebGIS of sea-level index and limiting points (https://dist.altervista.org/seaproxy/). This includes newly produced sea-level data from recent marine surveys, which were coupled to previously available data standardized according to the recent international guidelines for RSL studies. This allowed producing a multiproxy dataset composed of depositional, erosional, biological, and archaeological sea-level markers, in this very complex Mediterranean area. The collected sea-level data were further compared with a number of geophysical predictions in order to disentangle the different components which influenced the sea-level evolution. Moreover, the tectonic rates derived from the available MIS 5e sea-level data were used to shift the LIG elevations vertically and backwards in time in order to constrain the Last Interglacial RSLs to certain levels depending on the areas. Finally, we used GIS techniques to spatially constrain the coastal sectors more vulnerable to the coupled effects of future sea-level rise and VGMs in the next decades.
•Reconstruction of Late Quaternary sea-level oscillations in the mid-Thyrrenian area.•Development of a WebGIS of sea-level data in the mid-Thyrrenian area.•Definition of Vertical ground movements due to volcano-tectonic activities.•Holocene vertical displacements by comparing sea-level data and GIA models.•Long-term tectonic rates from MIS 5e sea-level data.
The vast majority of our country’s road bridges were built at least three decades ago, faults and alterations being produced over time. To operate safely it is necessary to determine the degree of ...stability and the precautions needed. This paper presents the analysis of vertical movements for such an bridge, determined by topographic methods in order to establish the proper conditions under which it can be further exploited.
SUMMARY
The spatiotemporal evolution of drought is often modulated by climate and watershed characteristics. While numerous drought studies using space geodesy have been conducted in Yunnan, the ...scarcity and limited sensitivity of observation instruments have hindered the development of watershed-scale drought analyses. This study aims to accurately characterize hydrological droughts within three watersheds in Yunnan from 2011 January to 2021 May by a Global Navigation Satellite System (GNSS) inversion constrained by Gravity Recovery and Climate Experiment (GRACE) data. Initially, we employed Variational Bayesian Independent Component Analysis to reconstruct the 3-D crustal deformations at 43 GNSS stations resulting from hydrological loadings. We then computed the time-series of vertical displacements caused by GRACE Mascon water products. Subsequently, utilizing the method of least squares, we derived the scaling factors between the vertical crustal displacements (VCD) obtained from GNSS observations and the synthetic displacements derived from GRACE data. By combing scaling-factor-adjusted VCDs derived from GRACE with the GNSS data, we have obtained accurate estimates of water storage for three Yunnan watersheds. Finally, we identified drought events characterized by abnormal decreases in water storage and used climatological methods to quantitatively describe the severity, extent and recovery of these drought extremes. Additionally, we evaluated the influence of various earth elastic structures on the scaling factors, and demonstrated their advantageous contribution to aligning GNSS and GRACE observations. In conclusion, our study introduces a novel approach to integrate GNSS and GRACE retrievals, allowing for accurate characterization of droughts in data-scarce regions, which cannot be achieved by GNSS or GRACE individually. Moreover, our results underscore the potential benefits of watershed-scale drought monitoring and analysis for effective water resource management.
Rheological heterogeneities in the lithosphere have first order control on the topographical expression of tectonic processes. Pre-existing orogenic suture zones localise extensional deformation ...resulting in asymmetric basins. Such crustal geometries are often in contrast with the more symmetric regional lithospheric structure observed beneath extensional basins. We study such (a)symmetries and their controlling parameters by conducting a series of 2D thermo-mechanical numerical experiments of the extension of an overthickened, hot lithosphere that contains a weakness zone. The modelling shows that syn-rift subsidence is low to moderate creating asymmetric half grabens where extension migrates in space and time, grouped in an overall symmetrical appearance on a larger scale. The initial lithospheric mantle asymmetry is attenuated by the lateral heat conduction and further dynamic evolution of the thermal anomaly during the “post-rift” phase, resulting in differential vertical movements of the crust including additional 2–3 km subsidence in the basin centre. The modelling shows that the initial crustal and lithospheric thicknesses, rate of extension and surface processes strongly control the thermo-mechanical evolution of the extensional system. The numerical modelling yields new insights into the mechanics of coupling between near-surface kinematics and the evolution of deep lithospheric structure in the Pannonian basin and the Aegean, two of Europe's largest back-arc systems.
•Spatial and temporal migration of extension is observed in numerical models and nature.•Rheological heterogeneities control variable subsidence rates.•Surface processes control syn-rift and post-rift basin subsidence and uplift.•Extension rate controls lithospheric and crustal thinning.•Symmetry of extensional system changes during basin evolution.
Ground deformations are among the main volcanic phenomena occurring within the caldera system and presently recorded at different volcanoes worldwide including the Campi Flegrei active caldera ...(southern Italy). A new stratigraphic, sedimentological and paleontological survey carried out in the central sector of the Campi Flegrei caldera both along the already known La Starza succession and through a new excavated tunnel provided new insights into the ground movement episodes occurred in the last 15 kyr. This study, which has also benefited of unpublished boreholes stratigraphic data, shows that the most uplifted sector of the Campi Flegrei caldera, presently marked by the morphological structure of the La Starza cliff close to the Pozzuoli coastline, was characterized by a complex sedimentary evolution. It results from different phases of alternating marine transgressions and regressions, the latter marked by both continental volcanic and/or palustrine/lacustrine sediments. These alternations result from the interplay between (i) subsidence and uplift episodes of the caldera floor and (ii) sea level variations during the Holocene. A rest period of volcanism accompanied by a sea level rise determined a significant submersion phase in about 3000 years between 8.59 and 5.5 ka. This phase was defined by a sea level with a maximum water depth value of 60–80 m and a late stage recording significant episodes of ground movements. Subsequently, between 5.5 and 3.5 ka, a ground uplift of about 100 m occurred, with short subsidence around 4.5 ka following the Plinian Agnano-Monte Spina eruption. The net vertical displacement represents the recorded deformation linked with a volcanism period in which ~2.5 km3 of magma were erupted by different vents within the caldera. It is worth to note as the general trend of ground movement through the time indicates a similarity in the pattern, beyond its scale.
•New geological data about ground movement of Campi Flegrei caldera in the last 15 kyr•The studied marine succession indicates alternating transgressions and regressions.•Subsidence and uplift episodes of the caldera were reconstructed.
Obtaining a precise velocity field of the Earth's surface is critical for probing Earth's tectonic movements. In this contribution we construct a precise vertical velocity field with high-spatial ...resolution for the Tibetan Plateau (TP) and its surrounding areas using both 113 continuous and 969 campaign GPS time series over the period 2008 to 2019. Specifically, we compared the statistical distribution of residual continuous GPS time series to find the optimal regional surface mass loading (SML) models. The optimal modeled nontectonic displacements were used to correct these campaign GPS time series to reduce their scatter and accordingly improve the precision of the uplift rate estimates. The results showed that we could reduce the root mean square (RMS) on the vertical coordinate time series by more than 75% of the campaign GPS stations. We computed and removed vertical deformation due to horizontal strain rates obtained from GPS time series, and discussed dynamic sources (mantle dynamic topography, isostatic adjustment, and flexural loading) that drive the residual vertical tectonic motion. The study presents the most recent surface kinematic constraints for comprehending the dynamic sources of tectonic uplift or subsidence between and within tectonic units.
Plain Language Summary: Movements of the Tibetan Plateau (TP) have a profound impact on adjacent areas. We collected all available GPS data to determine a precise vertical velocity field with high-spatial resolution. We make use of optimal surface mass loading (SML) models to improve estimation accuracy of campaign GPS stations, including an estimate of the vertical movement caused by the horizontal tectonic motions. We combine geological and geophysical data with our vertical velocity field to understand the dynamic sources of uplift or subsidence between and within tectonic units of the TP.
•We obtain a high spatial resolution vertical velocities over the TP.•Regional optimal surface mass loadings can reduce the scatter of most campaign GPS.•New vertical velocities provide the latest surface kinematic constraint of the TP.
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