Subsidence

In Great Britain, gypsum karst is widespread in the Late Permian (Zechstein) gypsum of north-eastern England. Here and offshore, a well-developed palacokarst with large breccia pipes was formed by dissolution of the underlying Permian gypsum. Farther south, around Ripon, the same rocks are still being dissolved, forming an actively evolving phreatic gypsum-maze cave system. This is indicated by the presence of numerous active subsidence hollows and sulphate-rich springs. In the English Midlands, gypsum karst is locally developed in the Triassic deposits south of Derby and Nottingham. Where gypsum is present, its fast rate of dissolution and the collapse of overlying strata lead to difficult civil-engineering and construction conditions; these can be further aggravated by water abstraction. Salt (halite) occurs within British Permian and Triassic strata, and has a long history of exploitation. The main salt fields are in central England and the coastal areas of northwest and northeast England. In central England, saline springs indicate that rapid, active dissolution occurs that can cause subsidence problems. In the past, subsidence was aggravated by shallow mining and the uncontrolled extraction of vast amounts of brine. This has now almost stopped, but there is a legacy of unstable buried salt karst, formed by both natural and induced dissolution. The buried salt karst occurs at depths ranging from about 40 m to 130 m; above these depths, the overlying strata are foundered and brecciated. In the salt areas, construction and development are hampered by both abandoned mines and by natural or induced brine runs, with their associated unstable ground.

In the United Kingdom Permian and Triassic halite (rock salt) deposits have been affected by natural and artificial dissolution producing karstic landforms and subsidence. Brine springs from the Triassic salt have been exploited since Roman times, or possibly earlier, indicating prolonged natural dissolution. Medieval salt extraction in England is indicated by the of place names ending in “wich” indicating brine spring exploitation at Northwich, Middlewich, Nantwich and Droitwich. Later, Victorian brine extraction in these areas accentuated salt karst development causing severe subsidence problems that remain a legacy. The salt was also mined, but the mines flooded and consequent brine extraction caused the workings to collapse, resulting in catastrophic surface subsidence. Legislation was enacted to pay for the damage and a levy is still charged for salt extraction. Some salt mines are still collapsing and the re-establishment of the post-brine extraction hydrogeological regimes means that salt springs may again flow causing further dissolution and potential collapse.

Las técnicas geofísicas se pueden emplear para entender las características físicas del subsuelo en áreas densamente pobladas, donde los asentamientos urbanos presentan problemas estructurales. Un ejemplo interesante se presenta en esta investigación, donde se aplica en tres dimensiones el método de Tomografía de Resistividad Eléctrica (TRE-3D) empleando arreglos alternativos que permiten investigar el subsuelo bajo las construcciones afectadas. Se estudia un pequeño barrio compuesto por un bloque de casas dentro del pueblo de San Antonio Tecomitl. El área se encuentra hacia la planicie de la Sierra del Chichinautzin, en el límite sur de la Cuenca de México. Este asentamiento sufre de fuertes daños estructurales debido a fracturamientos y hundimientos en el subsuelo. El método TRE-3D se realizó para caracterizar el subsuelo bajo este complejo urbano. Se utilizó un arreglo de resistividad especial (geometría de ‹herradura') empleando una combinación de arreglos en "L", los métodos ecuatorial -dipolo y de Mínimo de Acoplamiento para ‹ iluminar ' en su totalidad el subsuelo que se encuentra debajo de la manzana de casas. Los modelos de resistividad calculados presentan un patrón de valores de alta resistividad, que coincide con las viviendas afectadas. Tal rasgo parece extenderse más allá de los límites de la región estudiada, y es probablemente parte de un sistema de fracturas más complejas. Es muy probable que las fracturas se produjeron debido al suelo pobremente consolidado, el cual es parte de una zona de transición; la intensa extracción de agua, que forman vacíos en el la existencia de fallas regionales de mayor extensión y profundidad que podrían controlar Palabras clave: tomografía de resistividad eléctrica 3-D, Geofísica urbana, fracturamientos, hundimientos.

The fast development of wireless sensor networks and MEMS make it possible to set up today real-time wireless geotechnical monitoring. To handle interferences and noises from the output data, Kalman filter can be selected as a method to achieve a more realistic estimate of the observations. In this paper, a one-day wireless measurement using accelerometers and inclinometers was deployed on top of a tunnel section under construction in order to monitor ground subsidence. The normal vectors of the sensors were firstly obtained with the help of rotation matrices, and then be projected to the plane of longitudinal section, by which the dip angles over time would be obtained via a trigonometric function. Finally, a centralized Kalman filter was applied to estimate the tilt angles of the sensor nodes based on the data from the embedded accelerometer and the inclinometer. Comparing the results from two sensor nodes deployed away and on the track respectively, the passing of the tunnel boring machine can be identified from unusual performances. Using this method, the ground settlement due to excavation can be measured and a real-time monitoring of ground subsidence can be realized.

A new graphical technique is developed that takes advantage of time-subsidence data collected from either traditional extensometer installations or from newer technologies such as fixed-station global positioning systems or interferometric synthetic aperture radar imagery, to accurately estimate storage properties of the aquifer and vertical hydraulic conductivity of semi-confining units. Semi-log plots of time-compaction data are highly diagnostic with the straight-line portion of the plot reflecting the specific storage of the semi-confining unit. Calculation of compaction during one-log cycle of time from these plots can be used in a simple analytical expression based on the Cooper-Jacob technique to accurately calculate specific storage of the semi-confining units. In addition, these semi-log plots can be used to identify when the pressure transient has migrated through the confining layer into the unpumped aquifer, precluding the need for additional piezometers within the unpumped aquifer or within the semi-confining units as is necessary in the Neuman and Witherspoon method. Numerical simulations are used to evaluate the accuracy of the new technique. The technique was applied to time-drawdown and time-compaction data collected near Franklin Virginia, within the Potomac aquifers of the Coastal Plain, and shows that the method can be easily applied to estimate the inelastic skeletal specific storage of this aquifer system.

An analytical method has been developed to predict the location, depth and size of caverns created at the interface between salt and overlying formations. A governing hyperbolic equation is used in a statistical analysis of the ground survey data to determine the cavern location, maximum subsidence, maximum surface slope and surface curvature under the sub-critical and critical conditions. The regression produces a set of subsidence components and a representative profile of the surface subsidence under sub-critical and critical conditions. Finite difference analyses using FLAC code correlate the subsidence components with the cavern size and depth under a variety of strengths and deformation moduli of the overburden. Set of empirical equations correlates these subsidence components with the cavern configurations and overburden properties, and hence allows prediction of cavern configurations from the subsidence components.

The lower part of the Carboniferous Shannon Basin of Western Ireland contains a deep-water succession which exceeds 1200 m in thickness that comprises five lithologically different units deposited within a confined, relatively narrow basin: (i) a calciclastic debris-flow and turbidite unit formed by resedimentation from nearby carbonate platforms, (ii) a siliciclastic black shale succession with former source potential which onlaps basin margins (Clare Shales), (iii) a sandstone-dominated turbidite formation, controlled by ponded accommodation and deposited axially in the basin (Ross Formation), (iv) a mudstone-rich turbidite-bearing succession, which onlaps basin margins (lower Gull Island Formation), and (v) a mudstone-dominated prograding slope succession (upper Gull Island Formation and lower Tullig Cyclothem), which grades transitionally upwards into deltaic deposits. The top unit records progradation at a time when basin differential subsidence had diminished significantly and local basin topography did not control deposition. The two upper mudstone-dominated units are different in terms of both sandstone content and their genetic significance within the overall basin-fill, and their potential relevance as reservoir analogues. The lower part of the Gull Island Formation contains three principal facies associations: (a) shallow turbidite channels and sheets representing channel margin and levee deposits, (b) mud-rich slumps, and (c) less than 1 m thick, rare, hemipelagic shales. More than 75% is deformed by soft-sediment deformation, but only to a smaller degree affecting sandstone units. The turbidites record transport to the ENE, along the axis of the basin, while the slumps were derived from an unstable northern slope and transported transversely into the basin towards the southeast. The distribution of turbidite sandstone and slumps is inversely proportional. Sandstones decrease in importance away from the basin axis as slumps increase in number and thickness. The lower part of the Gull Island Formation is interpreted to record progressive fill of a deep basin controlled by local, healed slope accommodation with onlap/sidelap of the basin margins. The instability resulted from a combination of fault-controlled differential subsidence between basin margin and basin axis, and high rates of sedimentation. The upper part of the Gull Island Formation is entirely dominated by mudstones, which grade upwards into siltstones. It contains rare, up to 15 m thick, isolated channels filled by turbidites, showing transport towards the east. The upper part records easterly progradation of a deepwater slope genetically tied to overlying deltaic deposits, and controlled by regional accommodation. The contrasts between the lower and upper parts of the Gull Island Formation show that onlapping/sidelapping turbidite successions have reservoir potential near basin axes, but that prograding deep-water slopes are less likely to have reservoir potential of significance. A suggested regional downlap surface between the two parts is a significant break and marker in terms of reservoir potential.

The Microgravity technique consists of measuring minute variations in the gravitational pull of the Earth and interpreting the presence of voids/cavities from these readings. Gravity variations arising from such features are virtually undetectable by conventional gravity investigation methods as their resultant anomalies are superimposed upon much larger variations generated by changes in height, latitude and the regional geological environment.

A quantitative method for assessing sinkhole susceptibility and hazard has been developed and independently tested in an evaporite karst of NE Spain. Three genetic types of sinkholes have been mapped: 947 small cover-collapse sinkholes, 23 large collapse sinkholes and 24 large subsidence depressions. By analysing the statistical relationships between the sinkholes and the potential conditioning factors, susceptibility models have been developed. These were evaluated using several strategies that have allowed us to assess quantitatively the quality of the models. The best susceptibility model for the small collapse sinkholes was transformed into a hazard map by considering the frequency and average size of an independent population of new occurrences. The susceptibility and hazard models obtained indicate that it is possible to produce reasonably good predictions on the distribution and frequency of sinkholes in the study area.

Various approaches to the widespread problem of the hydroconsolidation and subsidence of loess have been suggested. These include considerations of rheology, thermodynamics, phase movements, particle packing, interparticle bonding, pore structure and distribution, catastrophe theory, topology, and simple structural frameworks. Chinese, North American and most European investigators tend to concentrate on mechanisms of loess collapse. The Russian literature, however, retains an extra dimension. Two approaches, the 'syngenetic' and the 'epigenetic' approach, to the formation of subsiding loess have been defined in the literature. Most investigators follow a syngenetic approach which appears to be a consequence of the aeolian idea of loess deposition. Some Russian writers, in contrast, promote an epigenetic approach in which collapsibility can develop in an originally noncollapsible material, which can then suffer from hydroconsolidation and subsidence. The basis of the phenomenon is a change in the packing structure of the major loess particles, and this can be modelled using simple Monte Carlo methods to develop appropriate structures. This paper aims to review the work done on this important subject. Serious investigation of hydroconsolidation and subsidence of loess began in the early nineteen-forties, fifty years ago, and this has been reported in a piecemeal manner. A detailed, critical review of this diverse work is now overdue and this is presented herein in the light of recent work in the United Kingdom. An attempt is made to describe the process in a phenomenological and a structural sense. Inherent in this, the role of N. Ya Denisov as 'subsidence pioneer' is considered.

During the Keuper, the Paris Basin was an intracratonic sedimentary basin ®lled by continental deposits. Using paleo-environmental, isopach and paleo-altitude maps, we estimate the variations of accommodation rate at the scale of stratigraphic minor hemi-cycle (1±3 Ma). An analysis of the short-and long-wavelength accommodation variations allows us to assess the relative in¯uence of tectonics, eustasy and sediment supply on the stratigraphic record. Our data suggest a pattern of subsidence along three trends: E±W in the Carnian, E±W to NNE± SSW in the Norian and NE±SW in the Norian±Rhaetian. During the Keuper, the Paris Basin accurately records the different phases of the opening of the Tethys Ocean associated with a rotation of the extension direction. The Norian cycle could thus re¯ect the intraplate stresses in a transitional period between the Triassic and the Liassic. q

Regional-scale faulting, particularly in strike-slip tectonic regimes, is a relatively poorly constrained factor in the formation of caldera volcanoes. To examine interactions between structures associated with regional-tectonic strike-slip deformation and volcano-tectonic caldera subsidence, we made scaled analogue models. Tabular (sill-like) inclusions of creamed honey in a sand/gypsum mix replicated shallow-level granitic magma chambers in the brittle upper crust. Lateral motion of a base plate sited below half the sand/gypsum pack allowed simulation of regional strike-slip deformation. Our experiments modelled: (1) strike-slip deformation of a homogeneous brittle medium; (2) strike-slip deformation of a brittle medium containing a passive magma reservoir; (3) caldera collapse into sill-like magma reservoirs without regional strike-slip deformation; and (4) caldera collapse into sill-like magma reservoirs after regional strike-slip deformation. Our results show that whilst the magma chamber shape principally influences the development and geometry of volcano-tectonic collapse structures, regional-tectonic strike-slip faults (Riedel shears and Y-shears) may affect a caldera’s structural evolution in two main ways. Firstly, regional strike-slip faults above the magma chamber may form a pre-collapse structural grain that is exploited and reactivated during subsidence. Our experiments show that such faults may preferentially reactivate where tangential to the collapse area and coincident with the chamber margins. In this case, volcano-tectonic extension in the caldera periphery tends to localise on regional-tectonic faults that lie just outside the chamber margins. In addition, volcano tectonic reverse faults may link with and reactivate pre-collapse regional-tectonic faults that lie just inside the chamber margins. Secondly, where regional-tectonic strike-slip faults define corners in the magma chamber margin, they may halt the propagation of volcano-tectonic reverse faults. The experiments also highlight the potential difficulties in assessing the relative contributions of volcano-tectonic and regional-tectonic subsidence processes to the final caldera structure seen in the field. Disruption of the pre-collapse surface by regional-tectonic faulting was preserved during coherent volcano-tectonic subsidence to produce a caldera floor of differentially-subsided fault blocks. Without definitive evidence for syn-eruptive growth faulting, thickness changes in caldera fill across such regional-tectonic fault blocks in nature could be mistaken as evidence for piecemeal volcano-tectonic collapse.

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For guidance on relationships between caving depth and surface subsidence, a comprehensive database was developed after an exhaustive search of published data from cave mining operations from around the world. The distribution of data was found to largely focus on caving angles and macro deformations; very little empirical data exists on the extent and magnitudes of smaller surface displacements. The data clearly show that caving-induced surface deformations tend to be discontinuous and asymmetric due to large movements around the cave controlled by geologic structures, rock mass heterogeneity and topographic effects. The data also show that as undercut depth increases for a given extraction volume, the magnitude and extent of the caved zone on surface decreases. However, numerical modeling indicates that this is only the case for macro deformations and the extent of smaller displacements actually increases as a function of undercut depth. The results presented caution against relying on existing empirical design charts for estimates of caving-induced subsidence where small strain subsidence is of concern, as the data being relied upon does not properly extrapolate beyond the macro deformations (i.e., caving angles) that make up the majority of the observations. The findings also suggest that the extent and magnitudes of subsidence may be underestimated if the analysis adopted neglects the influence of geological structures and assumes symmetrical surface displacements above the undercut.

Plusieurs études multidisciplinaires ont été effectuées sur les couches riches en matière organique (MO) de la Formation Bahloul. Nos études de terrain et les synthèses géologiques, géochimiques, isotopiques et minéralogiques disponibles ont permis d'apporter des précisions nouvelles d'ordre paléogéographique et paléocéanographique. Ces données ont contribué à l'élaboration d'un modèle de dépôt sous une zone à minimum d'oxygène (ZMO) dans des bassins marins profonds et subsidents de type bathyal, où se sont accumulées et préservées d'importantes quantités de MO (jusqu'à 18,7 % de COT). Le présent modèle a permis la corrélation de la Formation Bahloul à d'autres coupes de référence à l'échelle globale, ce qui permet de mettre en évidence que le d 13 C mesuré sur MO serait un meilleur outil de corrélation que le d 13 C mesuré sur carbonates pour reconnaître la limite Cénomanien/Turonien. Mots clés Formation Bahloul ; Géochimie ; Stratigraphie ; EAO-2 ; Cénomanien-Turonien ; matière organique; modèle de dépôt.

, and the origin of unconformity-bounded depositional sequences. Mar. Geol., 97: 35-56. Unconformity-bounded depositional sequences represent the fundamental building blocks of sedimentary successions. They are typically characterized by onlap at the base and by offlap at the top, and they tend to be markedly asymmetrical, with onlap accounting for a larger part of any cycle of sedimentation than offlap. Offlap cannot be attributed solely to erosional truncation, but instead implies that sequence boundaries develop over a finite interval of time. Depositional sequences are commonly associated with a cyclic arrangement of facies, but transgressive-regressive cycles are out of phase with respect to sequence boundaries, which in down-dip locations are both overlain and underlain by progradational deposits, and hence form during times of regression of the shoreline. These observations are used to develop some ideas about the origin of unconformity-bounded sequences, with reference to the inter-related roles of changes in depositional base level and sediment supply. In particular, it is shown than onlap and offlap are due to lateral migration of a "line of critical bypassing", defined so as to incorporate the effects of sediment loading and compaction as well as the rate of change of elevation with respect to sea level. Downward shifts in onlap may be achieved by either an increase in the rate of eustatic fall or a decrease in the rate of tectonic subsidence, and it is premature to assume that eustatic and tectonic controls on sea level may be distinguished solely on the basis of the frequency of depositional cyclicity. Small shifts in the position of onlap can also be produced by changes in sediment supply, and more attention needs to be paid to the influence of sediment supply in the development of minor boundaries. Unconformities related to eustatic fluctuations are thought to correspond approximately to times of relatively rapid sea-level fall (inflection points), but questions remain about the existence of possible leads and lags of up to ~ cycle, and hence about the degree to which sequence boundaries of eustatic origin may vary in age both within a given basin and from one basin to another.

Surprisingly few natural hydrocarbon seeps have been identified in Australia's offshore basins despite studies spanning thirty years. Early studies of natural hydrocarbon seepage around the Australian margin were generally based on the geochemical analysis of stranded bitumens, water column geochemical ‘sniffer’ sampling, synthetic aperture radar or airborne laser fluorosensor. Later studies involved the integration of these remote sensing and geochemical techniques with multi-channel and shallow seismic. A review of these earlier studies indicates that many seepage interpretations need to be re-evaluated and that previous data sets, when placed in a global context, often represent normal background hydrocarbon levels. Low Recent burial and subsidence rates are not favourable for high rates of seepage. There are also difficulties in proving seepage on high energy, shallow carbonate shelves, where seabed features may be rapidly re-worked and modern marine signatures are overprinted on authigenic seep carbonates. Thus, the relatively few sites of proven natural hydrocarbon seepage in Australia's offshore sedimentary basins can be reconciled relative to their geological occurrences and the dominantly passive margin setting. Active thermogenic methane seepage on the Yampi Shelf, the only proven documented occurrence in Australia, is driven by deposition of a thick Late Tertiary carbonate succession and Late Miocene tectonic reactivation. Therefore, to increase the success of detecting and correctly interpreting natural hydrocarbon seepage, data need to be analysed and integrated within the context of the local geological setting, and with an understanding of what is observed globally.

Archaeologists assessed eight Native American sites on Louisiana’s Gulf Coast for the effects of the MC252 Deepwater Horizon oil spill of 2010. Crude oil and dispersant used during the cleanup response were detected in redeposited shoreline midden and intact archaeological contexts. The proximate impacts on the archaeological record include contamination of artifacts, ecofacts, and samples, with the potential for long-term impacts on radiocarbon dating and archaeometry. Pretreatment can mitigate the effects of contaminants on radiocarbon dating and elemental analyses. Other analytical methods, such as absorbed pottery residue analysis, are more adversely effected by a combination of crude oil and dispersant. Integrated cultural resources management planning should take into account the potential effects of an oil spill on archaeological sites, and the increased time and cost expenditures for field and lab research in hazardous conditions and with contaminated collections.

Single-pair differential synthetic aperture radar interferometry (DInSAR) as well as more advanced methods, such as persistent scatterer interferometry (PSI), allow vertical displacements to be detected at the sub-centimeter level. Since 2014 free SAR data-Sentinel-1-have been collected systematically under the COPERNICUS program at a high temporal resolution and with global coverage. Such an open-access policy greatly helps build a wide user-community and develop diverse SAR-based applications. In this study conventional single-pair DInSAR and the PSI techniques were employed to monitor the vertical displacements of the newly constructed D8 highway, more specifically the part passing through thě Ceské Středohoří Mountains, where, during highway construction, a massive landslide occurred in June 2013. For both DInSAR and PSI, free Sentinel-1 radar data were used; moreover, the conventional single-pair DInSAR workflow was processed using freely available SNAP software. Results from the radar interferometry were validated using in situ techniques, such as geodetic measurements, 3D inclinometers, and laser scanning. Both approaches proved their ability to achieve reliable results in detecting vertical displacement "hotspots". Additionally, in terms of absolute values, the PSI interferometry corresponds very well with the in situ measurements. This study also shows that open-source solutions (free data and SW) provided under the COPERNICUS program bring a great potential for monitoring vertical displacements.

Calatayud in NE Spain is an historically important city built on recent alluvial deposits underlain by gypsum and other soluble rocks. Since its foundation by the Muslims in 716 AD, the city development has been strongly influenced by geohazards including flooding, subsidence and slope movements. Most of the flooding problems have been mitigated by diversion of the local drainage. However, dissolution of the evaporite bedrock in the urban areas continually causes subsidence and triggers rock-falls from the gypsum cliffs ...

Conventional sequence stratigraphy has been developed primarily for passive-margin basins. Despite the conceptual advances within the last 30 years, a suitable model for rift basins has not yet been devised. Many authors have attempted to adapt the passive-margin model to all other tectonic settings, including rifts, despite the fundamental differences in terms of the mechanisms controlling the formation and evolution of these sedimentary basins. Passive margins have their stratigraphic framework controlled largely by cyclic sea-level fluctuations superimposed on long-term thermal subsidence. By contrast, rift basins have their accommodation history strongly related to their mechanical subsidence regime, with episodic pulses of extension that create space for sediment accumulation at very fast rates. Stages of rapid mechanical subsidence are typically followed by longer periods of tectonic quiescence, when sediment supply gradually consumes and fills the available accommodation. This cyclicity results in depositional sequences that display overall progradational trends and coarsening-upward vertical stacking patterns. Sequence boundaries are often marked by sharp flooding surfaces related to the transgression of lacustrine or marine systems in response to rapid tectonic subsidence and the consequent 'instantaneous' generation of accommodation. As such, a typical rift depositional sequence starts with a flooding surface overlain by a relatively thin transgressive systems tract and a much better developed highstand systems tract. A renewed subsidence pulse leads to the drowning of the previous deposits and the start of a new depositional sequence. The strong asymmetry of the base-level curve resembles the shape of glacio-eustatic cycles, with fast transgressions followed by longer term regressions, although at potentially different temporal scales.

The burial of a basement sequence enriched in heat producing elements during thermal subsidence following rifting produces two concomitant changes in the thermal structure of the crust. Firstly, the burial of the enriched layer produces high geothermal gradients in the overlying sedimentary succession, with the high gradients propagating down into, but not through, the enriched basement sequence. Secondly, the lithospheric thickening that drives thermal subsidence reduces the heat flowing into the deeper crust from the mantle. Because the process of thermal subsidence promotes burial, it naturally increases the depth extent of the high geothermal gradients in the upper crust, potentially inducing significant temperature increases in the mid-upper crust during burial. The lowering of the thermal gradients in the deep crust accompanying burial severely limits the temperature changes affecting the Moho; potentially allowing Moho cooling while the mid-upper crust heats. These effects can promote high geothermal gradient (>40°C/km) metamorphism in the mid-upper crust without inducing significant melting in the lower crust, providing the basement heat production contributes > ∼70 mW m−2 to the surface heat flow and that the horizontal length scale for the basement heat production anomaly is > ∼50 km. These conditions appear to be met in several Australian intermediate- to high-temperature, low-pressure metamorphic terranes where the thermal causes of metamorphism have hitherto remained enigmatic. One of these terrains, the Mt. Painter province in the northern Flinders Ranges, South Australia, is used to illustrate some of the attributes of the model.

Sinkholes usually have a higher probability of occurrence and a greater genetic diversity in evaporite terrains than in carbonate karst areas. This is because evaporites have a higher solubility and, commonly, a lower mechanical strength. Subsidence damage resulting from evaporite dissolution generates substantial losses throughout the world, but the causes are only well understood in a few areas. To deal with these hazards, a phased approach is needed for sinkhole identification, investigation, prediction, and mitigation. Identification techniques include field surveys and geomorphological mapping combined with accounts from local people and historical sources. Detailed sinkhole maps can be constructed from sequential historical maps, recent topographical maps, and digital elevation models (DEMs) complemented with building-damage surveying, remote sensing, and high-resolution geodetic surveys. On a more detailed level, information from exposed paleosubsidence features (paleokarst), speleological explorations, geophysical investigations, trenching, dating techniques, and boreholes may help in investigating dissolution and subsidence features. Information on the hydrogeological pathways including caves, springs, and swallow holes are particularly important especially when corroborated by tracer tests. These diverse data sources make a valuable database—the karst inventory. From this dataset, sinkhole susceptibility zonations (relative probability) may be produced based on the spatial distribution of the features and good knowledge of the local geology. Sinkhole distribution can be investigated by spatial distribution analysis techniques including studies of preferential elongation, alignment, and nearest neighbor analysis. More objective susceptibility models may be obtained by analyzing the statistical relationships between the known sinkholes and the conditioning factors. Chronological information on sinkhole formation is required to estimate the probability of occurrence of sinkholes (number of sinkholes/km2 year). Such spatial and temporal predictions, frequently derived from limited records and based on the assumption that past sinkhole activity may be extrapolated to the future, are non-corroborated hypotheses. Validation methods allow us to assess the predictive capability of the susceptibility maps and to transform them into probability maps. Avoiding the most hazardous areas by preventive planning is the safest strategy for development in sinkhole-prone areas. Corrective measures could be applied to reduce the dissolution activity and subsidence processes. A more practical solution for safe development is to reduce the vulnerability of the structures by using subsidence-proof designs.

Analysis of more than 900 wireline logs indicates that the Middle Devonian Marcellus Formation encompasses two thirdorder transgressive-regressive (T-R) sequences, MSS1 and MSS2, in ascending order. Compositional elements of the Marcellus Formation crucial to the successful development of this emerging shale gas play, including quartz, clay, carbonate, pyrite, and organic carbon, vary predictably within the proposed sequencestratigraphic framework. Thickness trends of Marcellus T-R sequences and lithostratigraphic units reflect the interplay of Acadian thrust-load-induced subsidence, short-term base-level fluctuations, and recurrent basement structures. Rapid thickening of both T-R sequences, especially MSS2, toward the northeastern region of the basin preserves a record of greater accommodation space and proximity to clastic sources early in the Acadian orogeny. However, local variations in T-R sequence thickness in the western, more distal, area of the basin may reflect the reactivation of inherited Eocambrian basement structures, including the Rome trough and northwest-striking cross-structural discontinuities, induced by Acadian plate convergence. Episodes of block displacement locally warped the basin into northeast-southwest-trending regions of starved sedimentation and/or erosion adjacent to depocenters in which regressive systems tract deposits were ponded. Block movement

Fossil forests, buried in growth position in a geological instant (T° assemblages) are far more abundant in Pennsylvanian successions than in any other part of the geological record. In this review paper, we evaluate the fundamental controls on the origin of these phenomena, investigate the taphonomic biases that influence their composition, and summarize their palaeoecological significance. Following earlier workers, we highlight that high rates of burial and accommodation are essential for the formation and preservation of T° assemblages. Contexts especially favourable for their origin include ashfalls proximal to volcanic centres, coastal plains drowned by relative sea-level rise, and fluvial environments such as channel bars, crevasse splays, and distributary lobes. Long-term preservation requires high rates of subsidence. Consequently, the vast majority of Palaeozoic T° assemblages are confined to wetland settings at, or close to, sea level, whereas drylands are poorly represented and uplands rarely sampled, if ever. However, this is not the only major bias in the fossil record; taphonomic processes selectively preserve plants dependent on their anatomy and stature, and on groundwater chemistry. Thus, although T° assemblages offer unrivalled insights into the nature of ancient forests (whole-plant reconstructions, tree density, canopy height, productivity, plant hydraulics, cohort dynamics, spatial heterogeneity, ecological gradients, tree-sediment interactions, and animal-plant interactions, to name but a few), it is naive to believe they provide 'photographic snapshots' of palaeoecosystems. None the less, careful taphonomic analysis of T° assemblages offers the potential for a nuanced understanding of these evocative phenomena, and much remains to be learned from these important palaeoecological resources.

The Tellian foreland in Algeria represents a part of the southern Tethyan margin during the Mesozoic. Its tectonic evolution includes a rifting stage during the Triassic and Liassic times characterised by tilted blocks and early diapiric events during the Liassic, a post-rift regime from Middle Jurassic up to the Late Cretaceous and basin inversion during the Tertiary related to the African and European plates convergence.

The present paper entails the petrographic characterization on limited coal samples drawn from the Tarakan basin, Eastern Kalimantan, Indonesia. These coals contain a high concentration of huminite which, in turn, is dominated by telohuminite. As a result of telohuminite content they have high GI and TPI values. They contain, low concentrations of liptinite and inertinite macerals. The dominant microlithotype is vitrite. Based on the macerals and microlithotypes of these coals, their paleodepositional environment has been reconstructed. Accordingly it is deciphered that these coals have originated under telmatic condition. There was predominance of wood derived tissues and increased subsidence rate prevailed in the basin. Moreover, during the time of their evolution, there were alternate phases of oxic and anoxic moor conditions with intermittent moderate to high flooding in the basin.

A B S T R A C T Ground subsidence and sinkhole collapse are phenomena affecting regions of karst geology worldwide. The rapid development of such phenomena around the Dead Sea in the last four decades poses a major geological hazard to the local population, agriculture and industry. Nonetheless many aspects of this hazard are still incompletely described and understood, especially on the eastern Dead Sea shore. In this work, we present a first low altitude (< 150 m above ground) aerial photogrammetric survey with a Helikite Balloon at the sinkhole area of Ghor Al-Haditha, Jordan. We provide a detailed qualitative and quantitative analysis of a new, high resolution digital surface model (5 cm px −1) and orthophoto of this area (2.1 km 2). We also outline the factors affecting the quality and accuracy of this approach. Our analysis reveals a kilometer-scale sinuous depression bound partly by flexure and partly by non-tectonic faults. The estimated minimum volume loss of this subsided zone is 1.83 • 10 6 m 3 with an average subsidence rate of 0.21 m yr −1 over the last 25 years. Sinkholes in the surveyed area are localized mainly within this depression. The sinkholes are commonly elliptically shaped (mean eccentricity 1.31) and clustered (nearest neighbor ratio 0.69). Their morphologies and orientations depend on the type of sediment they form in: in mud, sinkholes have a low depth to diameter ratio (0.14) and a long-axis azimuth of NNE–NE. In alluvium, sinkholes have a higher ratio (0.4) and are orientated NNW–N. From field work, we identify actively evolving artesian springs and channelized, sediment-laden groundwater flows that appear locally in the main depression. Consequently, subrosion, i.e. subsurface mechanical erosion, is identified as a key physical process, in addition to dissolution, behind the subsidence and sinkhole hazard. Furthermore, satellite image analysis links the development of the sinuous depression and sinkhole formation at Ghor Al-Haditha to preferential groundwater flow paths along ancient and current wadi riverbeds.

Multiple sinkhole susceptibility models have been generated in three study areas of the Ebro Valley evaporite karst (NE Spain) applying different methods (nearest neighbour distance, sinkhole density, heuristic scoring system and probabilistic analysis) for each sinkhole type separately (cover collapse sinkholes, cover and bedrock collapse sinkholes and cover and bedrock sagging sinkholes). The quantitative and independent evaluation of the predictive capability of the models reveals that: (1) The most reliable susceptibility models are those derived from the nearest neighbour distance and sinkhole density. These models can be generated in a simple and rapid way from detailed geomorphological maps. (2) The reliability of the nearest neighbour distance and density models is conditioned by the degree of clustering of the sinkholes. Consequently, the karst areas in which sinkholes show a higher clustering are a priori more favourable for predicting new occurrences. The predictive capability of the best models obtained in this research is significantly higher (12.5-82.5%) than that of the heuristic sinkhole susceptibility model incorporated into the General Urban Plan for the municipality of Zaragoza. Although the probabilistic approach provides lower quality results than the methods based on sinkhole proximity and density, it helps to identify the most significant factors and select the most effective mitigation strategies and may be applied to model susceptibility in different future scenarios.

The Indonesian Throughflow (ITF) is a critical part of the global thermohaline conveyor. It plays a key role in transporting heat from the equatorial Pacific (the Indo-Pacific Warm Pool) to the Indian Ocean and exerts a major control on global climate. The complex tectonic history of the Indonesian Archipelago, a result of continued northward motion and impingement of the Australasian Plate into the Southeast Asian part of the Eurasian Plate, makes it difficult to reconstruct long-term (i.e., million year) ITF history from sites within the archipelago. The best areas to investigate ITF history are downstream in the Indian Ocean, either in the deep ocean away from strong tectonic deformation or along proximal passive margins that are directly under the influence of the ITF. Although previous Ocean Drilling Program and Deep Sea Drilling Project deepwater cores recovered in the Indian Ocean have been used to chart Indo-Pacific Warm Pool influence and, by proxy, ITF variability, these sections lack direct biogeographic and sedimentological evidence of the ITF. International Ocean Discovery Program Expedition 356 will drill a transect of cores over 10° latitude on the northwest shelf (NWS) of Australia to obtain a 5 m.y. record of ITF, Indo-Pacific Warm Pool, and climate evolution that has the potential to match orbital-scale deep-sea records in its resolution. Coring the NWS will reveal a detailed shallow-water history of ITF variability and its relationship to climate. It will allow us to understand the history of the Australian monsoon and its variability, a system whose genesis is thought to be related to the initiation of the East Asian monsoon and is hypothesized to have been in place since the Pliocene or earlier. It also will lead to a better understanding of the nature and timing of the development of aridity on the Australian continent.
Detailed paleobathymetric and stratigraphic data from the transect will also allow subsidence curves to be constructed to constrain the spatial and temporal patterns of vertical motions caused by the interaction between plate motion and convection within the Earth’s mantle, known as dynamic topography. The NWS is an ideal location to study this phenomenon because it is positioned on the fastest moving continent since the Eocene, on the edge of the degree two geoid anomaly. Accurate subsidence analyses over 10° of latitude can resolve whether northern Australia is moving with/over a time-transient or long-term stationary downwelling within the mantle, thereby vastly improving our understanding of deep-Earth dynamics and their impact on surficial processes

Gypsum dissolves relatively quickly and gypsum karst can evolve on a rapid time scale that may be accelerated by human induced change, often resulting in severe subsidence damage. The area close to Inandık stream in Central Anato-lia, Turkey, is affected by subsidence in two ways: formation of collapse sinkholes on agricultural land and progressive subsidence in Inandık village that has damaged buildings. This study focuses on these subsidence phenomena. Seven large sinkholes were formed on a terrace where episodic incision of the fluvial system has led to reduced thickness and mechanical strength of the cavity roof; a process that also increases the hydraulic gradient and enhances cavity development in the terrace area. These processes formed a sinkhole-prone terrace surface. The other subsidence phenomena, which have increased progressively in the last decade, relate to human activity in Inandık village. Water consumption increased after domestic water service systems were installed in houses in 2007, and in 2012 a sewer system was built in the village. Due to cracks and breakage, leaking water from buildings and sewer pipes infiltrated the gypsum substratum, resulting in dissolution of the bedrock and superficial cavity formation, as shown by GPR and borehole data. The process leading to subsidence caused severe damage to buildings. Consequently, it was decided to relocate the village three km south of its current location because of the high level of damage.

Extraction of a large volume of ore during block caving can lead to the formation of significant surface subsidence. Current knowledge of the mechanisms that control subsidence development is limited as are our subsidence prediction capabilities. Mining experience suggests that, among other contributing factors, geological structures play a particularly important role in subsidence development. A conceptual modeling study has been undertaken to evaluate the significance of geological structure on surface subsidence. A hybrid finite/discrete element technique incorporating a coupled elasto-plastic fracture mechanics constitutive criterion is adopted; this allows physically realistic modeling of block caving through simulation of the transition from a continuum to a discontinuum. Numerical experiments presented emphasize the importance of joint orientation and fault location on mechanisms of subsidence development and the governing role of geological structure in defining the degree of surface subsidence asymmetry.

1] Svalbard is an anomalous, subaerial part of the Barents Shelf, Northeast Atlantic Ocean. In this study, we performed both, one-and two-dimensional subsidence analyses based on basin structure, water depth, and thermochronology, to quantify and date the phases of uplift affecting Svalbard during the Cenozoic. Svalbard has experienced two phases of uplift, from >36 to~10 Ma, and since~10 Ma, similar in timing to uplift phases identified in Greenland, Scandinavia, and the Barents Shelf. Total uplift across much of the Central Tertiary Basin of Svalbard is >1.5 km and exceeds 2.5 km in parts of the West Spitsbergen Foldbelt (WSFB). Uplift from >36 to~10 Ma accounts for the greatest part of the vertical motion and like the younger phase reduces in magnitude towards the east. Flexural rigidity of the lithosphere is estimated to be low (Te % 5 km), so that post-36 Ma erosion of the WSFB contributes little to the uplift, whose permanent nature and proximity to the synchronous Yermak Plateau favors a link to regional magmatic underplating. Plume dynamic support and flexural unloading along the western transform plate margin can be ruled out as influences on vertical motions. Since~10 Ma renewed uplift, generating the modern topography may be linked to thermal erosion of the mantle lithosphere under Svalbard. We suggest that a likely cause of much of the surface uplift is the northward propagation of the Knipovich Ridge to establish continuous seafloor spreading through the Fram Strait after~10 Ma.

The conflict between energy supply and the environment is one of the critical issues of our time. and geothermal energy, often touted as plentiful and environmentally benign, has received a measure of attention as one possible answer to the problem.

Field examples from the Pliocene to Pleistocene succession of the Crotone Basin document the variability of stratal architecture in syntectonic units deposited in normal fault-bounded basins. Relatively thick trangressive intervals are common within these successions, as shown in the Zinga 2, Zinga 3 and Strongoli stratal units. Transgressive packages are formed by lagoonal mudstones that are abruptly overlain by shoreface sandstones. Aggradational highstand shallow-marine packages are typical of the lower Pliocene succession in half-graben basins. These deposits resulted from balanced conditions between the rate of sediment supply and the rate of creation of accommodation. Relatively thick forced regressive deposits are common within basins during phases where the accommodation-supply ratio is low (e.g. the middle Pleistocene San Mauro Sandstone). These deposits, influenced by growth faulting and folding, recorded baselevel lowering linked to glacio-eustasy. A complex stratal architecture may be the consequence of the alternation between tectonic subsidence and uplift (e.g. the Serra Piani stratal unit). Such variations are thought to be related to the onset of an earliest mid-Pliocene transpressional tectonic phase. The studied deposits, therefore, show a marked tectonic control that strongly influenced their stratal architecture. These examples represent interesting cases of sequence-stratigraphic analysis in growth-faulted contexts.

Groundmagnetic was used to investigate the cause of the subsidence at an Abandoned Local Government Secretariat, Ogbomoso, Southwestern Nigeria with a view to determining whether the sinking and cracks in the plasterworks experienced at the Eastern side of the study area is due to subsurface features or insufficient use of building materials. The study took place at an Abandoned Local Government Secretariat Ogbomoso, Southwestern Nigeria which falls within latitude 08 0 09 ′ 50.6 ″ -08 0 09 ′ 55.9 ″ and longitude 004 0 15 ′ 36.1 ″ -004 0 15 ′ 42.3 ″ . Proton Precision Magnetometer model GSM-19T was used to carry out the geophysical survey along four traverses in East-West and North-South directions. The traverses length ranges from 70m to 150m with inter station spacing of 10m. The results were presented as groundmagnetic profiles of varying magnetic intensities, groundmagnetic contoured map and groundmagnetic surface map. The basement topography was obtained from the profiles using half-width of the amplitude method. Areas with high magnetic values are the competent zones for construction while areas with low magnetic values are the weak zones. The quantitative interpretation gave the overburden thickness to the top of the magnetic basement rock as varied between 7.0m to 13.0m. Interpretation of groundmagnetic data revealed that the weak zones present at the Southeastern, Eastern and Northeastern part of the study area are the cause for the subsidence that occurred towards the Eastern side of the building. Contrary to the opinion of people that the building contractor used inferior building materials for the construction, we found out that half of the building is constructed on either collapse tunnel, fault or fracture which resulted into the sinking and new cracks in plasterworks experienced at the Eastern part of the abandoned Local Government secretariat.

A newly discovered phreatic cave system is described from Permian gypsum at Houtsay Quarry in the Vale of Eden, Cumbria. This is believed to be the first time gypsum caves have been described from England; the system has now been removed by quarrying. The cave system developed along joint
and bedding intersections and chambers up to 6m across were present. Some of the more important gypsum deposits in England are described and evidence is given to suggest that gypsum caves and buried gypsum karst occur elsewhere in the country. They occur within soft, readily eroded  sequences of strata and their presence is largely confined to low drift-covered areas.

Publié le 29 avril 2022 sur https://archeorient.hypotheses.org/18350.
Les ruines du brise-lame principal du port forment les façades ouest et sud du port extérieur. Les blocs de couronnement de cet ouvrage culminent aujourd’hui à -2.5 à -3.5 m sous le niveau actuel de la mer. Par ailleurs, les ruines d’une plateforme submergée à l’intérieur du port extérieur sont à -5 m sous le niveau actuel de la mer. Si on relevait ces niveaux de 6 m, le brise-lame culminerait donc à environ +3 m au-dessus du niveau actuel de la mer et la plateforme serait à +1 m. Ces deux niveaux seraient alors corrects pour un brise-lame et pour un quai. La question est donc de savoir comment une subsidence de 6 m a pu se produire dans le port extérieur, avec une subsidence de seulement 1 m dans le port central.
Après avoir acté que la surélévation du niveau de la mer depuis 2000 ans est d’environ 0.50 m, des chercheurs ont commencé par évoquer l’option tectonique selon laquelle une faille nord-sud située à la limite entre le port extérieur et le port central serait le plan de rupture d’un effondrement tectonique du port extérieur, mais cette option est rejetée aujourd’hui par Galili (2021).
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In the Neoarchaean intracratonic basin of the Kaapvaal craton, between approximately 2640 Ma and 2516 Ma, two successive stromatolitic carbonate platforms developed. Deposition started with the Schmidtsdrif Subgroup, which is probably oldest in the southwestern part of the basin, and which contains stromatolitic carbonates, siliciclastic sediments and minor lava flows. Subsequently, the Nauga formation carbonates were deposited on peritidal flats located to the southwest and were drowned during a transgression of the Transvaal Supergroup epeiric sea, around 2550 Ma ago. This transgression led to the development of a carbonate platform in the areas of the preserved Transvaal and Griqualand West basins, which persisted for 30-50 Ma. During this time, shales were deposited over the Nauga Formation carbonates in the southwestern portion of the epeiric sea. A subsequent period of basin subsidence led to drowning of the stromatolitic platform and to sedimentation of chemical, iron-rich silica precipitates of the banded iron formations (BIF) over the entire basin. Carbonate precipitation in the Archaean was largely due to chemical and lesser biogenic processes, with stromatolites and ocean water composition playing an important role. The stromatolitic carbonates in the preserved Griqualand West and Transvaal basins are subdivided into several formations, based on the depositional facies, reflected by stromatolite morphology, and on intraformational unconformities; interbedded tuffs and available radiometric age data do not yet permit detailed correlation of units from the two basins. Thorough dolomitisation of most formations took place at different post-depo-sitional stages, but mainly during early diagenesis. Partial silicification was the result of diagenetic and weathering processes. Karstification of the carbonate rocks was related to periods of exposure to subaerial conditions and to percolation of groundwater. Such periods occurred locally at the time of carbonate and BIF deposition. Main karstification, however, probably took place during an erosional period between approximately 2430 Ma and 2320 Ma.

Groundwater resources are under stress in many regions of the world and the future water supply for many populations, particularly in the driest places on Earth, is threatened. Future climatic conditions and population growth are expected to intensify the problem. Understanding the factors that control groundwater storage variation is crucial to mitigate its adverse consequences. In this work, we apply satellite-based measurements of ground deformation over the Tertiary detritic aquifer of Madrid (TDAM), Central Spain, to infer the spatiotemporal evolution of water levels and estimate groundwater storage variations. Specifically, we use Persistent Scatterer Interferometry (PSI) data during the period 1992-2010 and piezometric time series on 19 well sites covering the period 1997-2010 to build groundwater level maps and quantify groundwater storage variations. Our results reveal that groundwater storage loss occurred in two different periods, 1992-1999 and 2005-2010 and was mainly concentrated in a region of ~200 km 2. The presence of more compressible materials in that region combined with a long continuous water extraction can explain this volumetric deficit. This study illustrates how the combination of PSI and piezometric data can be used to detect small aquifers affected by groundwater storage loss helping to improve their sustainable management.