High Subsidence Rates Research Articles

Tradeoffs in habitat value to maximize natural resource benefits from coastal restoration in a rapidly eroding wetland: is monitoring land area sufficient?

Louisiana contains nearly 40% of estuarine herbaceous wetlands in the contiguous United States, supporting valuable ecosystem services and providing significant economic benefits to the state and the entire United States. However, coastal Louisiana is a hotspot for rapid land loss from factors including hurricanes, land use change, and high subsidence rates contributing to high relative sea‐level rise. The Coastal Protection and Restoration Authority (CPRA) was established after major hurricanes in 2005 to coordinate coastal restoration in Louisiana and develop the Louisiana Coastal Master Plan. The LA Coastal Master Plan uses numerical modeling of multiple scenarios to select a suite of restoration projects based on maximum land area created and flood reduction (as proxies for ecosystem value). Using potential value to aquatic, terrestrial, and social resources, our work compared habitat value of shallow open water areas to emergent wetland. While potential resource benefits varied by emergent wetland salinity type and emergent wetland versus water, they were similar, suggesting that restoration planning based primarily on wetland land area may not achieve the maximum possible ecosystem benefits. After nearly 20 years of integrated restoration planning in coastal Louisiana, a reassessment of restoration planning decision drivers may be beneficial to ensure maximum benefits from coastal restoration. As a result of the Deepwater Horizon oil spill, settlement funds will be a major support to coastal restoration in Louisiana for many years. Assessing potential habitat value to multiple natural and social resources in Louisiana has potential to maximize synergy with large northern Gulf of Mexico restoration programs.

Comparative Analysis of Cage Subsidence in Anterior Cervical Decompression and Fusion: Zero Profile Anchored Spacer (ROI-C) vs. Conventional Cage and Plate Construct.

Background: Anterior cervical discectomy and fusion (ACDF) has been widely performed to treat cervical generative diseases. Cage subsidence is a complication after ACDF. Although it is known that segmental kyphosis, acceleration of adjacent segmental disease, and restenosis may occur due to cages subsidence; however detailed research comparing zero-profile cages (ROI-C) and conventional plate and cage construct (CPC) on cage subsidence has been lacking.Objective: The objectives of this study was to compare the rate of postoperative cage subsidence between zero profile anchored spacer (ROI-C) and conventional cage and plate construct (CPC) and investigate the risk factors associated with cage subsidence following ACDF.Methods: Seventy-four patients with ACDF who received either ROI-C or CPC treatment from October 2013 to August 2018 were included in this retrospective cohort study. Clinical and radiological outcomes and the incidence of cage subsidence at final follow up-were compared between groups. All patients were further categorized into the cage subsidence (CS) and non-cage subsidence (NCS) groups for subgroup analysis.Results: The overall subsidence rate was higher in the ROI-C group than in the CPC group (66.67 vs. 38.46%, P = 0.006). The incidence of cage subsidence was significantly different between groups for multiple-segment surgeries (75 vs. 34.6%, P = 0.003), but not for single-segment surgeries (54.55 vs. 42.30%, P = 0.563). Male sex, operation in multiple segments, using an ROI-C, and over-distraction increased the risk of subsidence. Clinical outcomes and fusion rates were not affected by cage subsidence.Conclusion: ROI-C use resulted in a higher subsidence rate than CPC use in multi-segment ACDF procedures. The male sex, the use of ROI-C, operation in multiple segments, and over-distraction were the most significant factors associated with an increase in the risk of cage subsidence.

Integrating InSAR and deep-learning for modeling and predicting subsidence over the adjacent area of Lake Urmia, Iran

ABSTRACT InSAR processing is vastly used for land deformation monitoring from the space. Machine learning methods are known as strong tools for data modeling as well as predicting. In this study, we are going to model and predict the future behavior of land subsidence by InSAR processing and leveraging deep learning methods over the lands in the vicinity of Lake Urmia (located in the northwest of Iran). Accordingly, Sentinel-1 data over 56 months from November 2014 to June 2019 and small baseline subsets (SBAS) InSAR methods were utilized. Several regions with a high rate of subsidence were identified (maximum monthly subsidence of 13.3 mm). Furthermore, environmental factors affecting subsidence were considered. Therefore, parameters such as rainfall, groundwater, and lake area variations were measured using TRMM, GRACE, and MODIS satellite data, respectively. In order to determine and assess the relation between land deformations and environmental variations, several machine learning methods were implemented. The environmental parameters were used as the input of models and ground deformations as the target to be predicted. Eventually, ground deformations were estimated using multi-layer perceptron (MLP), convolutional neural network (CNN), and long short-term memory (LSTM) networks, in which each network had strengths and weaknesses on different occasions. Thus, by blending the forecast of the three models, a weighted ensemble was constructed, which outperformed the single models and reached the root mean square error (RMSE), mean absolute error (MAE), and standard deviation (SD) of 8.2 mm, 6.4 mm, and ±5.2 mm, respectively. The result indicated that although each single model had proper accuracy, an ensemble model can improve land deformation anticipation using the strength of networks in various conditions.

Results of land subsidence measurement using GPS method in the Jakarta groundwater basin in 2015-2019

The development of population and development activities in big cities in Indonesia, especially in the city of Jakarta and surrounding areas is very rapid. From several land subsidence studies, several factors have been identified that cause land subsidence, namely: excessive groundwater extraction, reduction due to building/infrastructure loads, subsidence due to natural consolidation of soft soil layers, and subsidence due to tectonic forces. At present the exploitation of ground water for industrial and residential needs is at a level that needs attention. Excessive pumping of groundwater will cause a decrease in the quantity of ground water, entry of seawater into the land (sea water intrusion) and land subsidence. Symptoms of the negative impact of land subsidence have been felt in several areas, especially in industrial areas located in the northern part of Jakarta. This land subsidence can be measured by GPS or satellite geodetic method, which have begun to develop in Indonesia in the past two decades. Measurements were made using the radial method at 53 GPS points in 2015 up to 100 measurement points in 2019 in Jakarta Groundwater Basin. The result of these campaign GPS surveys that is northern part of Jakarta relatively had higher subsidence rate than the southern. The largest subsidence almost reached 6.2 cm/year in Muara Baru in northern area which is southern area only suffered an average rate of 1.16 cm/year.

Evaluation of methods for connecting InSAR to a terrestrial reference frame in the Latrobe Valley, Australia

Deformation measurements from satellite-borne synthetic aperture radar interferometry (InSAR) are usually measured relative to an arbitrary reference point (RP) of assumed stability over time. For InSAR rates to be reliably interpreted as uplift or subsidence, they must be connected to a defined Earth-centred terrestrial reference frame (TRF), usually made through GNSS continuously operating reference stations (CORS). We adapt and compare three methods of TRF connection proposed by different studies which we term the single CORS RP (SCRP), plane-fit multiple CORS (PFMC), and the multiple CORS RP (MCRP). We generalise equations for these methods, and importantly, develop equations to propagate InSAR and GNSS uncertainties through the transformation process. This is significant, because it is important to not only estimate the InSAR uncertainties, but also to account for the uncertainties that are introduced when connecting to the CORS so as to better inform our interpretation of the deformation field and the limitation of the measurements. We then test these methods using Sentinel-1 data in the Latrobe Valley, Australia. These results indicate that differences among the three TRF connection methods may be greater than their estimated uncertainties. MCRP appears the most reliable method, although it may be limited in large study areas with sparse CORS due to long wavelength InSAR errors and that gaps and/or steps may appear at the spatial limit from the CORS. SCRP relies on the quality of the single CORS connection, but can be validated by unconnected CORS in the study area. The PFMC method is suited to larger areas undergoing slow, constant deformation covering large spatial extents where there are evenly distributed CORS across the study area. Selecting an optimal method of TRF connection is dependent on local site conditions, CORS network geometry and the characteristics of the deformation field. Hence, the choice of TRF connection method should be carefully considered, because different methods may result in significantly different transformed deformation rates. We confirm slow subsidence across the Latrobe Valley relative to the vertical component of the ITRF2014, with localised high subsidence rates near open cut mining activities. Subsidence of ~ -6 mm/year is observed in the adjacent coastal region which may exacerbate relative sea level rise along the coastline, increasing future risks of coastal inundation.

Spatiotemporal variations in groundwater levels and the impact on land subsidence in CanTho, Vietnam

This study assesses qualitative and quantitative changes in groundwater resources and their impact on land subsidence in Can Tho, Vietnam, from 2000 to 2018. Can Tho city is characterized by scarce water resources and intense industrial, domestic, agricultural, and mining usage, creating water stress. The vertical compaction rates and thus land subsidence, resulting from a head drawdown in three aquifers, were calculated using 1D consolidation of compressible porous media. Experiments were conducted in 16 wells clusters consisting of a total of 48 shallow and deep wells. The three wells from every 16 well clusters from different aquifers, namely the Middle-Upper Pleistocene confined aquifer (qp2-3), the Upper-Pleistocence (qp3), and a well in Holocene (qh), respectively, were examined. The Mann Kendal test with Sen's slope was performed and for most of the wells, negative values of Kendall's tau were found, which indicated decreasing trend of groundwater level. A significant change in groundwater level were also detected during the last eighteen years from 2000 to 2018. The results show significant downward trends of groundwater level for all of the wells of aquifer qp3 and qp2-3 except for a few shallow wells. The trend of this dropdown groundwater level for these deep wells is highly associated with extraction rates. The average subsidence rate of 4.28 cm yr−1 were observed in the study area. Tra Noc Industrial zones (QT8, QT16) showed a high subsidence rate which ranges from 5 to 7 cm yr−1. The calculated subsidence rates indicate the ongoing groundwater overexploitation, which might place Can Tho at risk of increased flooding and saltwater intrusion in the context of climate change and sea-level rise. The findings of this study call for effective policy strategies for sustainable water resource management to limit further land subsidence.

Facies and bed type characteristics of channel‐lobe transition deposits from the Oligocene‐Miocene Tajau Sandstone Member, Kudat Formation, Sabah, Malaysia

Channel‐lobe transition zones (CLTZs) are identified in many modern deep‐water systems, but few exhumed examples have been identified. Exposures of the Oligocene‐Miocene Tajau Sandstone Member (TSM), Kudat Formation, northern Sabah, Malaysia, provides the opportunity to document a CLTZ from an active basin margin. This work provides the first detailed field‐based sedimentological logging to produce a quantitative database on facies, sedimentary structures, bed type, and statistical analysis. This is particularly important to produce a robust stratigraphic framework of the TSM. Sedimentary facies support interpretation of subaqueous sediment density flows, and key features, including scour‐fills, antidunes, and dune‐scale bedforms, suggest changes in gradient and/or flow confinement and the development of hydraulic jumps. Eight bed types are recognized including: (a) tripartite beds with a debrite (BT1), interpreted as hybrid event beds recording downslope flow transformation between turbulent and laminar states; (b) beds with a mixture of depositional, erosional, and bypass features (BT2, BT4, BT5), interpreted as recording the transitions between supercritical and subcritical flow conditions triggered by hydraulic jumps; (c) bipartite beds with a basal massive sandstone overlain by fine‐grained facies (BT3), interpreted as hyperconcentrated flow deposits with evidence of downcurrent flow transformation; (d) bipartite beds with a basal high‐density turbidite sharply overlain by a low‐density turbidite (BT6), interpreted as turbidites with evidence of sediment bypass; (e) basal tractive structures capped by fine‐grained facies as the product of reworking of very coarse‐ to coarse‐grained sediments caused by lateral spreading of turbulent flows; and (f) Bouma Tbcde sequences (BT8) interpreted as high‐to‐low‐density turbidites. Our depositional model for the TSM comprises: (a) an aggradational channel‐lobe transition zone (CLTZs/BTA 1 and BTA 2) which was dominated by hydraulic jumps and sediment bypass; and (b) stacked lobe (i.e., lobe‐axis/BTA 3a, lobe‐off axis/BTA 3b, frontal lobe fringe/BTA 3c, and distal lobe fringe/BTA 3d) located in the northern and southern parts of the study area, which is dominated by tabular, sheet‐like elements bioturbated with the Nereites ichnofacies. The aggradational stacking of CLTZs deposits observed in the TSM may be explained by high subsidence rates combined with high sediment supply rates associated with a tectonically active margin setting.

The role of carbonate factories and sea water chemistry on basin‐wide ramp to high‐relief carbonate platform evolution: Triassic, Nanpanjiang Basin, South China

AbstractThe end‐Permian extinction and its aftermath altered carbonate factories globally for millions of years, but its impact on platform geometries remains poorly understood. Here, the evolution in architecture and composition of two exceptionally exposed platforms in the Nanpanjiang Basin are constrained and compared with geochemical proxies to evaluate controls on platform geometries. Geochemical proxies indicate elevated siliciclastic and nutrient fluxes in the basal Triassic, at the Induan—Olenekian boundary and in the uppermost Olenekian. Cerium/Ce* shifts from high Ce/Ce* values and a lack of Ce anomaly indicating anoxia during the Lower Triassic to a negative Ce anomaly indicating oxygenation in the latest Olenekian and Anisian. Uranium and Mo depletion represents widespread anoxia in the world's oceans in the Early Triassic with progressive oxygenation in the Anisian. Carbonate factories shifted from skeletal in the Late Permian to abiotic and microbial in the Early Triassic before returning to skeletal systems in the Middle Triassic, Anisian coincident with declining anoxia. Margin facies shifted to oolitic grainstone in the Early Triassic with development of giant ooids and extensive marine cements. Anisian margins, in contrast, are boundstone with a diverse skeletal component. The shift in platform architecture from ramp to steep, high‐relief, flat‐topped profiles is decoupled from carbonate compositions having occurred in the Olenekian prior to the onset of basin oxygenation and biotic stabilisation of the margins. A basin‐wide synchronous shift from ramp to high‐relief platforms points to a combination of high subsidence rate and basin starvation coupled with high rates of abiotic and microbial carbonate accumulation and marine cement stabilisation of oolitic margins as the primary causes for margin up‐building. High sea water carbonate saturation resulting from a lack of skeletal sinks for precipitation, and basin anoxia promoting an expanded depth of carbonate supersaturation, probably contributed to marine cement stabilisation of margins that stimulated the shift from ramp to high‐relief platform architecture.

Geomorphology and InSAR-Tracked Surface Displacements in an Ice-Rich Yedoma Landscape

Ice-ridge Yedoma terrain is susceptible to vertical surface displacements by thaw and refreeze of ground ice, and geomorphological processes of mass wasting, erosion and sedimentation. Here we explore the relation between a 3 year data set of InSAR measurements of vertical surface displacements during the thaw season, and geomorphological features in an area in the Indigirka Lowlands, Northeast Siberia. The geomorphology is presented in a geomorphological map, based on interpretation of high resolution visible spectrum satellite imagery, field surveys and available data from paleo-environmental research. The main landforms comprise overlapping drained thaw lake basins and lakes, erosion remnants of Late Pleistocene Yedoma deposits, and a floodplain of a high-sinuosity anastomosing river with ancient river terrace remnants. The spatial distribution of drained thaw lake basins and Yedoma erosion remnants in the study area and its surroundings is influenced by neotectonic movements. The 3 years of InSAR measurement include 2 years of high snowfall and extreme river flooding (2017–2018) and 1 year of modest snowfall, early spring and warm summer (2019). The magnitude of surface displacements varies among the years, and show considerable spatial variation. Distinct spatial clusters of displacement trajectories can be discerned, which relate to geomorphological processes and ground ice conditions. Strong subsidence occurred in particular in 2019. In the wet year of 2017, marked heave occurred at Yedoma plateau surfaces, likely by ice accumulation at the top of the permafrost driven by excess precipitation. The spatial variability of surface displacements is high. This is explored by statistical analysis, and is attributed to the interaction of various processes. Next to ground ice volume change, also sedimentation (peat, colluvial deposition) and shrinkage or swelling of soils with changing water content may have contributed. Tussock tundra areas covered by the extreme 2017 and 2018 spring floods show high subsidence rates and an increase of midsummer thaw depths. We hypothesize that increased flood heights along Siberian lowland rivers potentially induce deeper thaw and subsidence on floodplain margins, and also lowers the drainage thresholds of thaw lakes. Both mechanisms tend to increase floodplain area. This may increase CH4 emission from floodplains, but also may enhance carbon storage in floodplain sedimentary environments.

Long-term investigation of subsidence rate and its environmental effects using the InSAR technique and geospatial analyses

Herein, we examined the subsidence occurring over two main plains for agricultural activities in Qom province in Iran using interferometric synthetic aperture radar (InSAR). ENVISAT-ASAR images from 2003 to 2010 and Sentinel-1A images from 2014 to 2019 were used to produce interferograms and mean velocity maps of subsidence in the line of sight (LOS) direction. Using the analyses in geospatial information science (GIS), the spatial correlations between areas with subsidence and water level drop and agricultural land-uses were explored. The results showed the mean velocity map which revealed 35 and 28 mm/yr of deformation going away in the LOS direction in Jafarabad and Qanvat plains, respectively, between 2003 and 2010 and higher subsidence rates between 2014 and 2019. Moreover, maximum subsidence occurred in the places that had not only a larger water level decline, but also a greater thickness of fine-grained sediments. Finally, the environmental effect of subsidence on the ground, infrastructures and water salinity was examined.

The radiological outcome in lumbar interbody fusion among rheumatoid arthritis patients: a 20-year retrospective study

BackgroundClinical outcomes amongst Rheumatoid Arthritis (RA) patients have shown satisfactory results being reported after lumbar surgery. The increased adoption of the interbody fusion technique has been due to a high fusion rate and less invasive procedures. However, the radiographic outcome for RA patients after receiving interbody fusion has scarcely been addressed in the available literature.MethodsPatients receiving interbody fusion including ALIF, OLIF, and TLIF were examined for implant cage motion and fusion status at two-year follow-up. Parameters for the index correction level including ADH, PDH, WI, SL, FW, and FH were measured and compared at pre-OP, post-OP, and two-year follow-up.ResultsWe enrolled 64 RA patients at 104 levels (mean 64.0 years old, 85.9% female) received lumbar interbody fusion. There were substantial improvement in ADH, PDH, WI, SL, FW, and FH after surgery, with both ADH and PDH having significantly dropped at two-year follow up. The OLIF group suffered from a higher subsidence rate with no significant difference in fusion rate when compared to TLIF. The fusion rate and subsidence rate for all RA patients was 90.4 and 28.8%, respectively.ConclusionsWe revealed the radiographic outcomes of lumbar interbody fusions towards symptomatic lumbar disease in RA patients with good fusion outcome despite the relative high subsidence rate amongst the OLIF group. Those responsible for intra-operative endplate management should be more cautious to avoid post-OP cage subsidence.

From rapid coastal collapse to slow sedimentary recovery: The morphological ups and downs of the modern Po Delta

As is the case with many deltas in the world, the Po Delta (Italy) and its barrier systems have experienced severe modifications over the last century as a consequence of anthropogenic subsidence and river input decrease. The interruption of subsurface fluid withdrawals in the early 1960s created an opportunity to evaluate the effects of the subsequent subsidence decrease along the 11 km of beaches and 45 km of barrier islands of the Po Delta, and improve the understanding of coastal system response to relative sea level rise. To this aim, shoreline and bathymetric multi-decadal dataset were coupled with the local rate of subsidence and classified with a geomorphic - response approach. From 1954-78, a mean shoreline variation of −224 m (−9.34 m y−1) occurred under high rates of subsidence (14–43 mm y−1) with a diffuse process of landward barrier rollover (up to 1124 m), frequently associated with break-up. This phase is evidenced by the diffuse sinking of the shoreface (up to 4 m), the negative upper shoreface sediment budget and the parallel drowning of the cross-shore profiles highlighted by the 1968–2008 bathymetric dataset. Despite the loss of altimetry and shoreline retreat being almost irrecoverable, during the period from 1978 to 1996 and 1996 to 2014 barrier islands experienced a stabilisation in response to a decrease in the subsidence rates down to 6 mm y−1. The mean rates of shoreline changes (−0.25 and + 1.51 m y−1 respectively) are the results of different local behaviour with progressively dominant longshore processes and progradation at the most active fluvial branches. The most recent bathymetric data (2008–2014) confirm this reversal trend, both in the altimetry differences and in the upper shoreface sediment budget. This trend is at odds with signals from many of the world's deltas and represents an important issue for the present and future coastal management and adaptation plans.

Analysis of the Deformation Behavior and Sinkhole Risk in Kerdabad, Iran Using the PS-InSAR Method

The unexpected collapse of land surface due to subsidence is one of the most significant geohazards that threatens human life and infrastructure. Kabudrahang and Famenin are two Iranian plains experiencing several sinkholes due to the characteristics of the underground soil layers and extreme groundwater depletion. In this study, space-based Synthetic Aperture Radar images are used to investigate the ground displacement behavior to examine the feasibility of Sentinel-1 data in detecting precursory deformation proceeding before the sinkhole formation. The selected sinkhole occurred in August 2018 in the vicinity of Kerdabad village in Hamedan province with a 40 m diameter and depth of ~40 m. Time series of the European constellation Sentinel-1 data, spanning from January 2015 to August 2018, is analyzed, and the results revealed a 3 cm annual subsidence (–3 cm/year) along with the line-of-sight direction. Time-series analysis demonstrated that the driving mechanism of the sinkhole formation had a gradual process. Displacement of persistent scatterers (PSs) near the cave area had an acceleration by approaching the sinkhole formation date. In contrast, other areas that are far from the cave area show linear subsidence behavior over time. Additionally, the one-kilometer deformation profile over the cave area indicates a high subsidence rate precisely at the location where the sinkhole was formed later on 20 August 2018.

Delayed subsidence of the Dead Sea shore due to hydro-meteorological changes

Many studies show the sensitivity of our environment to manmade changes, especially the anthropogenic impact on atmospheric and hydrological processes. The effect on Solid Earth processes such as subsidence is less straightforward. Subsidence is usually slow and relates to the interplay of complex hydro-mechanical processes, thus making relations to atmospheric changes difficult to observe. In the Dead Sea (DS) region, however, climatic forcing is strong and over-use of fresh water is massive. An observation period of 3 years was thus sufficient to link the high evaporation (97 cm/year) and the subsequent drop of the Dead Sea lake level (− 110 cm/year), with high subsidence rates of the Earth’s surface (− 15 cm/year). Applying innovative Global Navigation Satellite System (GNSS) techniques, we are able to resolve this subsidence of the “Solid Earth” even on a monthly basis and show that it behaves synchronous to atmospheric and hydrological changes with a time lag of two months. We show that the amplitude and fluctuation period of ground deformation is related to poro-elastic hydro-mechanical soil response to lake level changes. This provides, to our knowledge, a first direct link between shore subsidence, lake-level drop and evaporation.

Space-Time Evolutions of Land Subsidence in the Choushui River Alluvial Fan (Taiwan) from Multiple-Sensor Observations

Land subsidence is a significant problem around the world that can increase the risk of flooding, damage to infrastructure, and economic loss. Hence, the continual monitoring of subsidence is important for early detection, mechanism understanding, countermeasure implementation, and deformation prediction. In this study, we used multiple-sensor observations from the Continuous Global Positioning System (CGPS), the small baseline subset (SBAS) algorithm, interferometric synthetic-aperture radar (InSAR), precise leveling, multi-layer compaction monitoring wells (MLCWs), and groundwater observation wells (GWs) to show the spatial and temporal details of land subsidence in the Choushui River alluvial fan (CRAF), Taiwan, from 1993 to 2019. The results showed that significant land subsidence has occurred along the coastal areas in the CRAF, and most of the inland subsidence areas have also experienced higher subsidence rates (>30 mm/yr). The analysis of subsidence along the Taiwan High Speed Rail (THSR) revealed a newly formed subsidence center between Tuku and Yuanchang Townships in Yunlin, with high subsidence rates ranging from 30 to 70 mm/yr. We propose a map showing, for the first time, the distribution of deep compactions occurring below 300 m depth in the CRAF.

Neogene to Quaternary evolution of carbonate and mixed carbonate-siliciclastic systems along New Caledonia's eastern margin (SW Pacific)

Neogene and Quaternary shallow-water carbonate records surrounding New Caledonia main island, Grande Terre, provide a good example for understanding the stratigraphic architecture of tropical mixed carbonate-siliciclastic systems. Due to a southeastern tilt of the eastern margin, the eastern shelf of Grande Terre has been better preserved from erosion than the western part, favouring the development and preservation of shallow-water carbonates. Based on the integration of bathymetric and seismic data, along with paleoenvironmental and biostratigraphic constraints derived from dredged carbonate rocks, a comprehensive geomorphological and architectural characterization of the offshore eastern margin of Grande Terre has been made. During the Mio-Pliocene, a wide, up to 750 m-thick carbonate build-up developed and extended over at least 350 km from north to south. This Mio-Pliocene build-up, currently lying at 300 to 600 m water depths, is overlain by a Pleistocene-Holocene barrier reef-lagoon complex and associated slope deposits. The switch from aggrading Neogene carbonate banks to backstepping Quaternary platforms likely reflects an increase in accommodation due to a high subsidence rate or to relative sea-level rise, and/or results from a switch in carbonate producers associated with global environmental changes. The internal architecture of the Quaternary barrier reef-lagoon complex is highlighted, especially the development of lowstand siliciclastic prisms alternating with transgressive shallow-water carbonate sequences. This pattern agrees with the reciprocal sedimentation model typically invoked for mixed sedimentary systems. This stratigraphic pattern is well developed in front of the Cap Bayes inlet in the north of our study area, yet it is not observed southward along the eastern margin. This difference suggests that other factors than relative sea-level variations directed the architecture of the margin, such as low terrigenous inputs, lagoon paleo-drainage networks or sediment by-pass towards deep basins.

Two-phase Himalayan extension recorded in the Late Miocene-Pleistocene Gyirong Basin, south Tibet

The Late Miocene-Pleistocene Gyirong Basin in the central Himalaya provides a record of basin evolution in response to tectonic extension within the active Himalaya orogen. The up to ~550-m-thick basin fill can be subdivided, from bottom to top, into four stratigraphic units with distinctly different lithofacies associations: alluvial fan, debris flow, lacustrine-fan delta, and braided river. Analysis of the stratigraphic pattern, provenance, and detrital zircon UPb geochronology of the basin fill indicates significant changes of depositional sources and tectonic boundary conditions through time. The alluvial fan deposits in the Oma sub-basin, which unconformably overlie the Tethyan strata, show northward paleoflow directions, detrital zircon UPb ages >400 Ma, and low subsidence rates. The unconformably overlying debris conglomerates show westward paleoflow directions, younger detrital zircon UPb ages of 15–37 Ma, and high subsidence rates. The abrupt changes in depositional source and tectonic subsidence indicate that the basin evolved from a supradetachment basin related to east-trending northward normal faults in the hanging wall of the South Tibetan Detachment to a rift basin that was mainly controlled by a major north-trending normal fault along the eastern basin margin from ~10–9 Ma onwards. We propose that initial basin formation is the result of N-S extension related to faulting along the South Tibetan Detachment, which was immediately followed by E-W extension of the Himalaya orogen in response to decoupling of the Himalayan crust related to India underthrusting beneath Asia.

Stand-Alone Posterior Expandable Cage Technique for Adjacent Segment Degeneration with Lumbar Spinal Canal Stenosis: A Retrospective Case Series.

Background and Objectives: Symptomatic adjacent segment degeneration (ASD) with lumbar spinal canal stenosis (LSCS) is a common complication after spinal intervention, particularly interbody fusion. Stand-alone posterior expandable cages enable interbody fusion with preservation of the previous operation site, and screw-related complications are avoided. Thus, the aim of this study was to investigate the clinicoradiologic outcomes of stand-alone posterior expandable cages for ASD with LSCS. Materials and Methods: Patients with persistent neurologic symptoms and radiologically confirmed ASD with LSCS were evaluated between January 2011 and December 2016. The five-year follow-up data were used to evaluate the long-term outcomes. The radiologic parameters for sagittal balance, pain control (visual analogue scale), disability (Oswestry Disability Index), and early (peri-operative) and late (implant) complications were evaluated. Results: The data of 19 patients with stand-alone posterior expandable cages were evaluated. Local factors, such as intervertebral and foraminal heights, were significantly corrected (p < 0.01 and p < 0.01, respectively), and revision was not reported. The pain level (p < 0.01) and disability rate (p < 0.01) significantly improved, and the early complication rate was low (n = 2, 10.52%). However, lumbar lordosis (p = 0.62) and sagittal balance (p = 0.80) did not significantly improve. Furthermore, the rates of subsidence (n = 4, 21.05%) and retropulsion (n = 3, 15.79%) were high. Conclusions: A stand-alone expandable cage technique should only be considered for older adults and patients with previous extensive fusion. Although this technique is less invasive, improves the local radiologic factors, and yields favorable clinical outcomes with low revision rates, it does not improve the sagittal balance. For more widespread application, the strength of the cage material and high subsidence rates should be improved.

Long-term radiographic outcomes of expandable versus static cages in transforaminal lumbar interbody fusion.

Potential advantages of using expandable versus static cages during transforaminal lumbar interbody fusion (TLIF) are not fully established. The authors aimed to compare the long-term radiographic outcomes of expandable versus static TLIF cages. A retrospective review of 1- and 2-level TLIFs over a 10-year period with expandable and static cages was performed at the University of California, San Francisco. Patients with posterior column osteotomy (PCO) were subdivided. Fusion assessment, cage subsidence, anterior and posterior disc height, foraminal dimensions, pelvic incidence (PI), segmental lordosis (SL), lumbar lordosis (LL), pelvic incidence-lumbar lordosis mismatch (PI-LL), pelvic tilt (PT), sacral slope (SS), and sagittal vertical axis (SVA) were assessed. A consecutive series of 178 patients (with a total of 210 levels) who underwent TLIF using either static (148 levels) or expandable cages (62 levels) was reviewed. The mean patient age was 60.3 ± 11.5 years and 62.8 ± 14.1 years for the static and expandable cage groups, respectively. The mean follow-up was 42.9 ± 29.4 months for the static cage group and 27.6 ± 14.1 months for the expandable cage group. Within the 1-level TLIF group, the SL and PI-LL improved with statistical significance regardless of whether PCO was performed; however, the static group with PCOs also had statistically significant improvement in LL and SVA. The expandable cage with PCO subgroup had significant improvement in SL only. All of the foraminal parameters improved with statistical significance, regardless of the type of cages used; however, the expandable cage group had greater improvement in disc height restoration. The incidence of cage subsidence was higher in the expandable group (19.7% vs 5.4%, p = 0.0017). Within the expandable group, the unilateral facetectomy-only subgroup had a 5.6 times higher subsidence rate than the PCO subgroup (26.8% vs 4.8%, p = 0.04). Four expandable cages collapsed over time. Expandable TLIF cages may initially restore disc height better than static cages, but they also have higher rates of subsidence. Unilateral facetectomy alone may result in more subsidence with expandable cages than using bilateral PCO, potentially because of insufficient facet release. Although expandable cages may have more power to induce lordosis and restore disc height than static cages, subsidence and endplate violation may negate any significant gains compared to static cages.

Tectonostratigraphic evolution of the new frontier Foram Basin and implications for hydrocarbon potential, Western Desert, Egypt

The Western Desert of Egypt is an important hydrocarbon province as it consists of many petroliferous sedimentary basins. The researchers and petroleum companies are interested in exploring the new frontier sedimentary basins and evaluating their hydrocarbon potential. Given this point of view, the current study attempts to assess the new frontier sedimentary basin in the Western Desert of Egypt, named Foram Basin (FB), using various geophysical and geological methods, including the magnetic, gravity, and seismic methods in addition to the petroleum system and basin analysis modeling. The magnetic data analysis uses various techniques, including power spectrum and source parameter image, total magnetic intensity (TMI), reduction to the pole (RTP), regional-residual separation, and tilt derivative. The used techniques in the interpretation of gravity data include Bouguer gravity, power spectrum, regional-residual separation of Bouguer gravity, tilt derivative of the Bouguer gravity and gravity inversion, and 2D gravity modeling, in addition to the tentative basement depth based on the gravity inversion and 2D gravity modeling for the nine profiles. The main results of these techniques indicate that the main structural trend is NE-SW and the depth to the basement ranges from 1.8 to 5 km comprising two depocenters.Two-thirds of the sedimentary basin fill is a Paleozoic succession and one-third is a Mesozoic-Cenozoic succession. Therefore, the FB is thought to be a Paleozoic basin. The Paleozoic-Mesozoic stratigraphic framework of the FB was classified into six seismic sequences separated by the seven seismic boundaries. The main regional structural trend of the FB is NE-SW, the same trend as that of the Paleozoic Kufra Basin in Libya. In the FB, the major structural trend in the Early Paleozoic is NE-SW, whereas it is E-W in Late Paleozoic. Moreover, in Mesozoic Jurassic time, the dominant trends are E-W and ENE-WSW, and in Middle Cretaceous is ENE-WSW and in Upper Cretaceous are E-W and NE-SW. Regarding the tectonic subsidence rate, the FB passed three tectonic phases. The first tectonic phase has a high subsidence rate that occurred in the Paleozoic, resulting in the deposition of most of the sedimentary succession. The second and third tectonic phases occurred at a relatively low subsidence rate, resulting in the deposition of Mesozoic-Cenozoic deposits. The Paleozoic Silurian Kohla source rock passed the early generation phase in the Early Eocene (50 Ma) and reached a maximum generation rate of 2.77 (mg/gTOC^my) in Late Oligocene (27 Ma) that is considered a very low rate and did not allow for oil expulsion.