Net Uplift Research Articles

Lithospheric Flexure Controls on Geomorphology, Hydrology, and River Chemistry in the Andean Foreland Basin

AbstractTectonics exerts a strong control over the morphology of Earth's surface that is apparent in active mountain belts. In lowland areas, subtle processes like lithospheric flexure and isostatic rebound can impact Earth surface dynamics, hydrologic connectivity, and topography, suggesting that geomorphic and hydrologic analyses can shed light on underlying lithospheric properties. Here we examine the effect of lithospheric flexure on the geomorphology, hydrology, and river water chemistry of the Rio Bermejo fluvial system in the east Andean foreland basin of northern Argentina. Results show that proximal to the mountain front, foredeep basin subsidence causes sedimentation along a braided channel belt that is superelevated relative to the surrounding flood basin. During floods, water flows from the superelevated channel into the groundwater reservoir, causing a net loss of discharge with distance downstream. Further downstream, forebulge uplift forces channel narrowing, high lateral migration rates, and incision up to 13 m into older river deposits. This incision locally allows groundwater flow into the river, causing a ∼20% increase in river solute load. Groundwater emerges from the forebulge into the backbulge, predominantly as spring‐fed channels. Here, channel migration rates decrease, suggesting a switch from net uplift to subsidence that reduces the depth to the groundwater table. This analysis shows that subtle lithospheric flexure can have significant effects on river channel morphology that determine hydrologic flow paths, and ultimately influence geochemical and ecological patterns. We suggest that these effects may elucidate lithospheric properties that are otherwise inferred from bulk geophysical observations.

Ionospheric Pre‐Sunrise Uplift: Comparison of Sanya Incoherent Scatter Radar Observations and Numerical Simulations

AbstractUsing the high spatial‐temporal resolution electron density profiles observed by the newly built Sanya Incoherent Scatter Radar at Sanya (18.3°N, 109.6°E) in its first 1‐month‐long continuous run with Barker code, we identified a substantial ionospheric pre‐sunrise uplift at low latitudes associated with the upward movement of ions. The uplift mainly occurs during local solar time 01:00–06:00 and is ∼52–240 km with significant night‐to‐night variability. With increasing geomagnetic and/or interplanetary activity, the uplift can have a larger amplitude. Further TIEGCM simulations show that the pre‐sunrise ionospheric uplift is jointly determined by the net effect of ambipolar diffusion, neutral wind, and E × B drift. The neutral wind during 00:00–05:00 usually lifts the ionosphere through equatorward wind. After 02:00, the weakening and/or even the reversal of downward E × B drift, which is not sufficient to offset the net uplift effect of wind and diffusion combination, triggers uplifting.

Modeling Exhaust-Generated Aerodynamic Pressure Loads on Airfield Matting Repair Systems

Airfield matting systems are commonly used for rapid repair of damaged runways to facilitate continuity of critical operations. Under normal service conditions, matting repair systems are subject not only to wheel loads exerted by airfield traffic but also to aerodynamic pressure loads resulting from high-speed, turbulent exhaust plumes produced by jets during taxi and take-off. Matting systems employed by the U.S. Air Force have been tested with respect to wheel loads, but probabilities of failure because of pressure loads produced by jet exhaust have not yet been established. This study presents a numerical approach for preliminary estimation of worst-case matting anchor forces resulting from exhaust-generated pressure loads. Using a two-dimensional computational fluid dynamics model, system behavior is evaluated by means of a parametric study of six system variables, of which the most significant are: (1) distance between engine and matting, (2) depth of cavity openings at matting edges, and (3) engine exhaust velocity. The results demonstrate that matting systems are likely to experience net uplift in typical service scenarios, driven by the combined effects of flow separation and cavity pressurization. Worst-case anchor pull-out forces, computed according to a tributary-area approach, are estimated to fall in the range of 130 lb (581 N) to 979 lb (4,350 N), depending on assumed load-sharing behavior among anchors and the size of the repair site. Field testing of instrumented matting systems during jet taxi and take-off sequences is recommended as the best next step toward understanding system behavior.

Morphodynamics of Bedrock‐Alluvial Rivers Subsequent to Landslide Dam Outburst Floods

AbstractTectonically active mountain regions such as Southwestern China are frequently hit by catastrophic floods caused by the breach of landslide dams. However, how these extreme events influence the morphodynamics of bedrock‐alluvial rivers is not well understood. More specifically, during a landslide dam outburst flood, bedrock can be eroded by intensive transport of sediment (i.e., tools effect), but can also be buried under thick alluvial cover (i.e., cover effect). Here, we implement the MRSAA‐c (Corrected Macro‐Roughness‐based Saltation‐Abrasion‐Alluviation) model to simulate the morphodynamics of bedrock‐alluvial rivers subject to landslide dam outburst flood(s). For a single dam breach event, the evolution of a bedrock‐alluvial river shows different characteristics at different time scales. At flood time scale (within one day), bedrock is eroded by about 10 mm. The landslide deposit then mainly provides a cover effect in the decadal‐century scale, which leads to a net uplift of the bedrock underneath, and thus the formation of a bedrock “bump.” The bedrock profile returns to its initial equilibrium state at a millennial time scale, after the bedrock bump migrates upstream beyond the inlet. When subject to repeated dam breach events, the bedrock‐alluvial river can reach a dynamic equilibrium after sufficient time (tens of thousands of years). The equilibrium is characterized by sharply increased bedrock slope around the dam site, and gently decreased slope downstream. The impact of dam breach events is constrained within a scale of hundreds of kilometers, indicating the existence of a sedimentograph boundary layer.

Interference effect on tsunami generation by segmented seafloor deformations

Most tsunamis are triggered by seismic events, involving an underwater earthquake with a sharp vertical displacement of the seafloor. Generally, seabed deformations are not unipolar, but instead bipolar or even more complex. To model tsunamis generated by segmented seafloor deformations, an analytical model and a numerical model including source kinematics are presented. Specifically, a parametric analysis, varying the number of segments and the relative sizes of each segment, is performed to investigate their influence on the wave generation process. Destructive interference is observed between the free surface waves generated by adjacent segments moving in opposite directions. The relatively large horizontal velocities compared to vertical velocities within the rotating flow generated in the case with two opposing segments correspond to relatively low wave amplitudes and the shift in the location of the largest wave. When the net uplift or subsidence volume is smaller, the associated destructive interference is more pronounced. In addition, a larger number of opposing segments produce a more complex velocity field within the tsunamigenic region, causing more destructive interference on the free surface. The role of destructive interference induced by segmented seabed deformations should be considered in assessing tsunami hazards caused by complex fault ruptures.

Quaternary uplift and fault movement near Waitomo, North Island, New Zealand

ABSTRACT The hill country of west central North Island, west of Te Kuiti and Otorohanga, is recognised to be slowly uplifting and relatively stable. The New Zealand national seismic hazard model shows the area to be in a low-risk zone and the New Zealand active faults database recognises no active faults in the region. However, dated evidence provided by speleothems in a cave near Waitomo indicates the intermittent movement of the Okohua fault from before the Last Interglacial until around 38 kyrs ago. Evidence of older movement along the Waipa Fault near Te Kuiti is also apparent from the vertical displacement of the Ngaroma ignimbrite (1.55 Myrs) by about 150 m in the interval prior to the deposition of the Ongatiti ignimbrite at 1.21 Myrs. Net uplift in the West Waikato Hills and Ranges, by about 0.1 mm/yr in the Late Quaternary, is accommodated in a series of NNE-trending faults and transverse faults, resulting in a staircase of fault-bound blocks rising westwards from Waitomo to the western watershed of the Waipa basin. Geomorphologically fresh cliffed lineaments on the Okohua and Hikurangi faults convey evidence of mid to late Quaternary fault activity.

Retrieving the displacements of the Hutubi (China) underground gas storage during 2003–2020 from multi-track InSAR

Many countries and regions build underground gas storages (UGSs) to regulate the energy demand and supply in different seasons. The Hutubi underground gas storage (HUGS) in Xinjiang province is the largest UGS in China, so it is of great significance to monitor its operation. At present, the researches on the HUGS mainly rely on traditional geodetic monitoring (e.g., in-situ leveling and global navigation satellite system (GNSS)), which has a short time span and low spatial resolution. The whole-domain and long-temporal sequence surface displacements induced by gas recovery (before 2013) and injection/extraction (since 09/06/2013) were seldom reported. In this study, the large-scale background deformation was firstly obtained using the ALOS PALSAR data (2006–2011), and the displacement time series of the HUGS over 2003–2020 was observed by all available Synthetic Aperture Radar (SAR) data from multiple SAR sensors (Envisat ASAR, TerraSAR/TanDEM-X, Sentinel-1). The results show that this area had a long history of slow subsidence (2.2 mm/yr) before 2013. Since 06/2013, the surface of the HUGS showed periodic uplift and subsidence with a net uplift. The average uplift rate in the center was about 7 mm/yr during 08/2013–07/2015 and 13 mm/yr during 03/2015–05/2020. The deformation has a temporal correspondence with the gas extraction/injection process. The accuracy is assessed by the cross-validation of the results of different datasets and the GNSS measurements. The compound dislocation model (CDM) is used to model the dynamic displacements caused by gas injection/extraction in HUGS. This model can reflect the UGS volume changes and the estimated central depth (3499.7 m) and height (108.6 m) of the storage are consistent with the actual central depth (~3585 m) and height (~110 m). We also restore the dynamic change of the pore pressure and the injected gas volume during the 5–7 cycles, on the basis of the linear relations between gas injection volume, pore pressure, and CDM parameters. In 12/2017, the estimated gas inventory of the HUGS is 91.29 × 108 m3, about 4.7% smaller than the real gas inventory of 95.77 × 108 m3. At the end of the seventh injection/extraction cycle, the predicted maximum gas injection volume and pore pressure reached 11.2 billion m3 and 36 MPa, respectively.

Cenozoic structural evolution of the Catalina metamorphic core complex and reassembly of Laramide reverse faults, southeastern Arizona, USA

AbstractThis study investigates the Late Cretaceous through mid-Cenozoic structural evolution of the Catalina core complex and adjacent areas by integrating new geologic mapping, structural analysis, and geochronologic data. Multiple generations of normal faults associated with mid-Cenozoic extensional deformation cut across older reverse faults that formed during the Laramide orogeny. A proposed stepwise, cross-sectional structural reconstruction of mid-Cenozoic extension satisfies surface geologic and reflection seismologic constraints, balances, and indicates that detachment faults played no role in the formation of the core complex and Laramide reverse faults represent major thick-skinned structures.The orientations of the oldest synextensional strata, pre-shortening normal faults, and pre-Cenozoic strata unaffected by Laramide compression indicate that rocks across most of the study area were steeply tilted east since the mid-Cenozoic. Crosscutting relations between faults and synextensional strata reveal that sequential generations of primarily down-to-the-west, mid-Cenozoic normal faults produced the net eastward tilting of ∼60°. Restorations of the balanced cross section demonstrate that Cenozoic normal faults were originally steeply dipping and resulted in an estimated 59 km or 120% extension across the study area. Representative segments of those gently dipping faults are exposed at shallow, intermediate (∼5–10 km), and deep structural levels (∼10–20 km), as distinguished by the nature of deformation in the exhumed footwall, and these segments all restore to high angles, which indicates that they were not listric. Offset on major normal faults does not exceed 11 km, as opposed to tens of kilometers of offset commonly ascribed to “detachment” faults in most interpretations of this and other Cordilleran metamorphic core complexes. Once mid-Cenozoic extension is restored, reverse faults with moderate to steep original dips bound basement-cored uplifts that exhibit significant involvement of basement rocks. Net vertical uplift from all reverse faults is estimated to be 9.4 km, and estimated total shortening was 12 km or 20%. This magnitude of uplift is consistent with the vast exposure of metamorphosed and foliated cover strata in the northeastern and eastern Santa Catalina and Rincon Mountains and with the distribution of subsequently dismembered mid-Cenozoic erosion surfaces along the San Pedro Valley. New and existing geochronologic data constrain the timing of offset on local reverse faults to ca. 75–54 Ma.The thick-skinned style of Laramide shortening in the area is consistent with the structure of surrounding locales. Because detachment faults do not appear to have resulted in the formation of the Catalina core complex, other extensional systems that have been interpreted within the context of detachments may require further structural analyses including identification of crosscutting relations between generations of normal faults and palinspastic reconstructions.

Distribution and evolution of knickpoints along the Layue River, Eastern Himalayan Syntaxis

The longitudinal profile of rivers in active orogenic belts records the competitive process occurring between erosion and uplift, and the knickpoint, as a unique sign, can support this. A series of distinctive knickpoints are distributed at different heights in the basin of the Layue River, which is a tributary located on the northwest side of the Yurlung Tsangpo Basin, China. By combining the stream power erosion model and field investigation, this paper explores the relationship among dams, knickpoints and the normalized steepness index (ksn). In addition to sporadic damming-type knickpoints, a 4 k knickpoint group located in the basin has attracted attention. Using the slope-area analysis method and the integration analysis method, paleo profile reconstruction of 14 tributaries and trunks was carried out to estimate the resulting paleo relief and net uplift. The results show that the topographic relief increases by 35.3–214.3% during the process in which the knickpoint entered into the basin and spread, which is the result of the growth and retreat of the knickpoint. Using the celerity model for the 4 k knickpoint group, 83.3% of the model knickpoints are less than 5 km away from the observed knickpoints, which indicates that the model is suitable for application in the Layue River Basin. And the migration rate of the knickpoint in the Layue Basin is 10.8–51.7 km/Ma at an initial setup time of 1.25–6 Ma.

Climate or tectonics? What controls the spatial-temporal variations in erosion rates across the Eastern Cordillera of Colombia?

Linking the long-term with the short-term exhumation history of a mountain range is vital for understanding the evolution of orogenic topography. Further, erosion rates could be controlled by the variability of climatic and/or tectonic processes over geological time. For example, in the Eastern Cordillera of the Colombian Andes, until recently climate forcing has been hypothesized as the primary driver of rapid Pliocene exhumation rates. In this contribution, we test this climate forcing hypothesis by integrating geomorphic, seismic, geological and published low-temperature thermochronological (Apatite Fission-Track; AFT), and cosmogenic nuclide (CN) data to quantitatively test the correlation of the spatial patterns of exhumation/erosion with either a tectonic or climatic forcing. From a regional perspective, both the long- and short-term erosion rates (derived from AFT and CN data, respectively) have a reasonable correlation with the seismic strain rates and local relief, whereas the contribution of the short-term rainfall patterns to exhumation (and denudation) is either weak or non-existent. For the Eastern Cordillera, tectonism through seismic deformation therefore seems to be a more critical driver of the topographic evolution of the range when compared with the climate variable. To deepen our investigation, we subdivided the study area into six subregions and performed a detailed statistical analysis. In one out of the six subregions (SEC2E), in the Quetame Massif area, short-term rainfall data is well correlated with the computed erosion rates. Nevertheless, the ten-fold difference between the long-term (2.36 km/Myr) and the current (0.27 km/Myr) denudation rates suggest they are strongly decoupled. The remaining five subregions featured varied correlations suggesting that the tectonic-climatic characteristics of each area must be considered and that effective local controls, such as rainfall in subzone SEC2E, cannot be extrapolated to the whole range. Finally, we discuss the tectonic implications of our findings, stressing how tectonic inheritance, typical of inversion orogens such as the Eastern Cordillera, is critical for understanding the spatial variability in exhumation/erosion rates and surface uplift. For instance, we reconstructed the paleoprofiles of four rivers (the Duda, Ariari, Guayuriba, and Guatiquía Rivers), draining the Sumapaz and Chingaza relict landscapes, on the hanging wall of the Servitá Fault, the typical example of an inverted structure. In this way, we evidenced a net surface uplift of at least 1.4 km since the late Miocene, which we speculate primarily controlled by the Servitá Fault. These findings have first-order implications as they provide evidence for Pliocene to Pleistocene landscape rejuvenation driven by tectonically inverted faults.

Uplifted marine terraces on Santa Catalina Island, California, USA

Abstract Marine terraces are widespread along California's coastline, including on all of the Channel Islands, with the possible exception of Santa Catalina. For over a century, the origins of subhorizontal surfaces and gravel deposits on Santa Catalina have been debated, with recent suggestions that Santa Catalina has no marine terraces and is subsiding. We mapped, measured, and described terrace deposits on Santa Catalina Island, including both in situ deposits and distributed gravel float. Rounded gravels and cobbles, locally pholad-bored, are present as float across low-relief surfaces in the Little Harbor area. We also mapped and described the Eagles Nest Gravels, an ∼8-m-thick package overlying a broad bedrock-cut platform at ∼200 m elevation and dipping 3.2° northward. The Eagles Nest Gravels contain rounded cobbles and boulders, many of which contain pholad borings. Two other platforms are inferred from concordant gravels with similar orientations but at lower elevations. Terrace deposits on Santa Catalina truncate underlying lithological units, including a narrow band of fossiliferous Miocene to Pliocene sands. Terrace deposits and gravel lag on Santa Catalina closely resemble older terrace deposits on other California Channel Islands. The terraces on Santa Catalina Island remain undated but document at least 200 m of net uplift, similar to the elevations of undated terraces on the other Channel Islands. While the timing of uplift of Santa Catalina is unclear, analysis of terrace deposits in the Little Harbor area confirms their marine origin and settles the debate regarding the presence of marine terraces on Santa Catalina Island.

Caldera resurgence during the 2018 eruption of Sierra Negra volcano, Gal\xe1pagos Islands

Recent large basaltic eruptions began after only minor surface uplift and seismicity, and resulted in caldera subsidence. In contrast, some eruptions at Galápagos Island volcanoes are preceded by prolonged, large amplitude uplift and elevated seismicity. These systems also display long-term intra-caldera uplift, or resurgence. However, a scarcity of observations has obscured the mechanisms underpinning such behaviour. Here we combine a unique multiparametric dataset to show how the 2018 eruption of Sierra Negra contributed to caldera resurgence. Magma supply to a shallow reservoir drove 6.5 m of pre-eruptive uplift and seismicity over thirteen years, including an Mw5.4 earthquake that triggered the eruption. Although co-eruptive magma withdrawal resulted in 8.5 m of subsidence, net uplift of the inner-caldera on a trapdoor fault resulted in 1.5 m of permanent resurgence. These observations reveal the importance of intra-caldera faulting in affecting resurgence, and the mechanisms of eruption in the absence of well-developed rift systems.

Cretaceous to Recent net continental uplift from paleobiological data: Insights into sub-plate support

AbstractThere are many geoscience problems for which constraining histories of uplift or subsidence of Earth’s surface is of direct or indirect importance, for example reconstructing tectonics, mantle convection, geomorphology, sedimentary and chemical flux, biodiversity, glacio-eustasy, and climate change. The least equivocal constraints on timing and amplitude of vertical motions on geological timescales come from the distribution of rock formed in shallow marine environments. However, obtaining enough observations at sufficiently large spatial and temporal scales (∼100–10,000 km, ca. 1–100 Ma) to constrain histories of regional topographic evolution remains challenging. To address this issue, we adapted modern inventories of paleobiological and paleoenvironmental data to generate a new compilation of >24,000 spot measurements of uplift on all continents and numerous oceanic islands. Uncertainties associated with paleobathymetry, post-deposition compaction, and glacio-eustasy are assessed. The compilation provides self-consistent and, in places, high-resolution (<100-km-length scale, <1 Ma) measurements of Cretaceous to Recent (post-deposition) net uplift across significant tracts of most continents. To illustrate how the database can be used, records from western North America and eastern South America are combined with geophysical observations (e.g., free-air gravity, shear, and Pn-wave tomography) and simple isostatic calculations to determine the origins of topography. We explore how lithospheric thinning and mantle thermal anomalies may generate uplift of the observed wavelengths and amplitudes. The results emphasize the importance of large inventories of paleobiological data for understanding histories of tectonic and mantle convective processes and consequently landscapes, climate, and the environment.

Use of pore pressure data from the Norwegian Continental Shelf to characterize fluid-flow processes in geological timescales

Abstract A dataset with pore pressures from more than 1000 exploration wells has been used to investigate the dynamics of aquifer systems in the Norwegian Continental Shelf (NCS). Variations in aquifer pressures reflect flow of porewater through permeable rocks over geological time. Strongly overpressured regimes are formed within confined aquifers in subsiding areas, where fluid flow out of the aquifer is controlled by vertical seepage. In transitional pressure regimes, fluid flows within permeable beds towards areas with hydrostatic pressures. In the hydrostatic regime, pressure differences result from density differences due to varying formation water salinity and by hydrocarbon columns. An underpressured regime has been encountered in confined aquifers in the platform areas of the Barents Sea, and is related to net uplift and erosion. In the case studies, pressure differences are interpreted in the context of the relevant pressure regime, and with a dynamic approach where segment boundaries and cap rocks are regarded as low-permeability restrictions rather than barriers. The present distribution of pressure regimes was developed over the last few million years due to rapid Pleistocene sedimentation and erosion processes.

Active layer freeze-thaw and water storage dynamics in permafrost environments inferred from InSAR

In cold regions where soils freeze and thaw annually, the ground surface deforms due to the density difference between groundwater and ground ice. Here we mapped thaw subsidence and frost heave signals over the Toolik Lake area on the North Slope of Alaska using 12 ALOS PALSAR Interferometric Synthetic Aperture Radar (InSAR) scenes (2006–2010). For the first time, we jointly analyzed InSAR observations with a large number of soil measurements collected within ~ 100 km of the Toolik Field Station. We found that the InSAR-observed deformation patterns are mainly related to soil water content and the seasonal active layer freeze-thaw (FT) cycle. We did not observe any substantial long-term subsidence trend outside the 2007 Anaktuvuk River Fire scar. This suggests that the magnitude of the maximum annual thaw subsidence did not change much outside the fire zone during the study period. The joint analysis of InSAR and field observations allows us to show that the amplitude of the seasonal thaw subsidence is proportional to the total amount of ice that has melted into liquid water at any given time. We note that topography influences the spatial distribution of soil water content, and the availability of soil water influences the type of vegetation that can grow. As a result, we found that the average seasonal thaw subsidence increases along a geomorphic-ecohydrologic transect with heath vegetation on the drier ridge-tops, tussock tundra on hillslopes, and sedge tundra at the wet lowland riparian zones. In addition, we detected a net uplift between late July and early September, mostly in the wetter riparian zone that experienced a larger seasonal thaw subsidence. Toolik Field Station in-situ records suggest that the air temperature fluctuated around or below freezing in early September during the ALOS PALSAR data acquisition times (at ~ 12 am local time). In this scenario, ice can be formed at the top of the soil, which leads to frost heave in saturated soils. Our results highlight how InSAR can improve our understanding of active layer freeze-thaw and water storage dynamics in permafrost environments.

System-level modeling methodology for capturing the pile cap, helical pile group, and soil interaction under uplift loads

In tall and light structures, such as transmission towers, wind turbines, and light-gauge steel structures, there is an increasing application of pile cap with helical pile foundation systems to resist the uplift loads due to the effects of windstorms and earthquakes. There is a lack of knowledge, published literature, or analysis methods to account for the effects of the pile cap, helical pile group, and soil interactions on the holistic response of the foundations, particularly, for the load conditions creating net uplift loads. In the lack of such, discrete modeling approaches are frequently employed in practice. These approaches isolate each system component and analyze them individually, neglecting the interactions between them. In an attempt to bridge this knowledge gap, this study proposes a system-level modeling methodology for the holistic analysis of pile cap systems in dry soil and static load conditions, while accounting for the effects of interactions between system components and the inherent material nonlinearities. The methodology employs a three-stage process in which the material and interaction properties are calibrated with the experimental benchmark specimens. The failure mechanisms are also experimentally verified based on the relative displacement of the piles. Important modeling considerations are discussed, and experimental benchmark specimens are provided to assist practitioners in accurately performing system-level analyses. The effectiveness of the proposed methodology is discussed, and the responses obtained, including the load–displacement responses, load capacities, and failure modes, are compared with those obtained from the discrete modeling approaches. The results demonstrate that discrete modeling approaches significantly underestimate the load capacity while not accurately predicting the governing behavior and the failure modes.

Syn‐rift delta interfan successions: Archives of sedimentation and basin evolution

AbstractModels that aim to capture the interactions between sediment supply, base level and tectonism recorded in fan delta successions in rift basins have not considered the stratigraphic archive preserved in interfan areas; yet interfan stratigraphy can provide a complementary record to the fan delta axes. The exhumed Early–Middle Pleistocene Kerinitis and Selinous fan deltas, in the hangingwall of the Pyrgaki–Mamoussia (P‐M) Fault, Corinth Rift, Greece, offer an ideal laboratory for the assessment of interfan architecture. Furthermore, using the geometry of adjacent present‐day fan deltas, interfans are classified into three end‐members. The classification is based on their lateral separation, which determines the degree of interfingering of topset, foreset and bottomset deposits. Qualitative (facies, stratal geometries, nature of key surfaces) and quantitative (stratigraphic thickness, bedding dip, palaeocurrents, breakpoint trajectories) data were collected in the field and from unmanned aerial vehicle photogrammetry‐based 3D outcrop models of the exhumed fan delta successions. The ancient Kerinitis–Selinous interfan architectures record: (a) initial westward progradation of the Kerinitis fan delta into the interfan area (Phase 1), (b) subsequent progradation of the Selinous fan delta into the interfan area and asymmetric growth of both fan deltas eastward (Phase 2), (c) stratal interfingering of foresets from both systems (Phase 3), and (d) relative base‐level fall, erosion and reworking of sediments into the interfan area (Phases 4 and 5). The Kerinitis–Selinous interfan evolution is linked to initial net subsidence of the P‐M Fault (Phases 1–3) and subsequent net uplift (Phases 4 and 5) resulting from a northward shift in fault activity. The interfan area provides a more complete stratigraphic record than the proximal axial areas of the fan deltas of the early stages of basin uplift, through higher preservation potential and protracted submergence. Therefore, for the most comprehensive insight into basin evolution, interfan analysis should be undertaken in concert with analysis of the fan delta axes.

Thermotectonic History of the Kluane Ranges and Evolution of the Eastern Denali Fault Zone in Southwestern Yukon, Canada

AbstractExhumation and landscape evolution along strike‐slip fault systems reflect tectonic processes that accommodate and partition deformation in orogenic settings. We present 17 new apatite (U‐Th)/He (He), zircon He, apatite fission‐track (FT), and zircon FT dates from the eastern Denali fault zone (EDFZ) that bounds the Kluane Ranges in Yukon, Canada. The dates elucidate patterns of deformation along the EDFZ. Mean apatite He, apatite FT, zircon He, and zircon FT sample dates range within ~26–4, ~110–12, ~94–28, and ~137–83 Ma, respectively. A new zircon U‐Pb date of 113.9 ± 1.7 Ma (2σ) complements existing geochronology and aids in interpretation of low‐temperature thermochronometry data patterns. Samples ≤2 km southwest of the EDFZ trace yield the youngest thermochronometry dates. Multimethod thermochronometry, zircon He date‐effective U patterns, and thermal history modeling reveal rapid cooling ~95–75 Ma, slow cooling ~75–30 Ma, and renewed rapid cooling ~30 Ma to present. The magnitude of net surface uplift constrained by published paleobotanical data, exhumation, and total surface uplift from ~30 Ma to present are ~1, ~2–6, and ~1–7 km, respectively. Exhumation is highest closest to the EDFZ trace but substantially lower than reported for the central Denali fault zone. We infer exhumation and elevation changes associated with ~95–75 Ma terrane accretion and EDFZ activity, relief degradation from ~75–30 Ma, and ~30 Ma to present exhumation and surface uplift as a response to flat‐slab subduction and transpressional deformation. Integrated results reveal new constraints on landscape evolution within the Kluane Ranges directly tied to the EDFZ during the last ~100 Myr.

Numerical Investigation of Wind Pressure Coefficients for Photovoltaic Arrays Mounted on Building Roofs

The wind pressure distribution on the photovoltaic (PV) array is of great importance to the wind resistance design. The flow field related to the pressure can be influenced significantly by the turbulence induced by the building roof edge (Kopp et al., 2012) and it is essential to consider the building effect during the investigation. However, most CFD (computational fluid dynamics) investigations of wind pressure distribution on the PV array are limited to ground mounted PV array without the building. There is a necessity to extend the application of CFD method to flows around roof-mounted PV array. This study investigated the wind pressure distributions on PV arrays mounted on building roofs by means of Reynolds-averaged Navier-Stokes (RANS) approach using the FLUENT software. Since RANS models are sensitive to the fiow condition, several RANS models are adopted and the most accurate RANS model for predicting this type of flow is identified based on a comparison with the wind tunnel experimental results. The SST Κ-ω model can predict the highest net mean wind uplift located at panels upstream accurately and is further applied for the parameter analysis to facilitate the installation of roof-mounted PV array. Numerical simulations of the wind flow field for wind angles between 0° to 180° were carried out at intervals of 20°, and the resulted net pressure distributions were presented. The influences of tilt angles of the PV array were investigated and the pressure distributions of PV panels were related to the flow field. Moreover, the effects of clearance between the PV array and building roof on the flow fields and pressure distributions of the PV array related to PV array tilt angle are studied.

PORE PRESSURE MODELLING IN A COMPRESSIONAL SETTING: A CASE STUDY FROM ASSAM, NE INDIA

The petroleum‐bearing Assam oil province, NE India, has a complex tectonic history resulting from the Cenozoic collision of the Indian Plate with the Eurasian and Burma Plates. Well data show that there are significant variations in the magnitude and stratigraphic occurrence of overpressures across the foreland basin. In areas which have not been affected by thrust tectonics, analyses of pore pressures in Upper Miocene to Eocene and underlying sequences indicate that overpressures are caused by disequilibrium compaction. Pore pressures were observed to be 25.8–28 MPa over a depth interval of 2259–2382 m and 43–45 MPa between depths of 3820 m and 3994 m. In the adjacent Schuppen (fold‐thrust) belt, multiple overpressure regimes are recognised and disequilibrium compaction is the main cause of the overpressures in both the supra‐thrust and the sub‐thrust successions. Unloading due to uplift and erosion in the supra‐thrust section of the Schuppen belt was quantified using velocity data and the normal compaction trend for shales; net uplift was estimated to total 1000–1600 m with a standard deviation of 250–476 m. Overpressure development in supra‐thrust strata in the Schuppen belt suggests the possible effects of normal burial prior to tectonic deformation, as well as of compaction related to high horizontal stresses resulting from thrusting and associated fold development. Pore pressures in the supra‐thrust section, over a depth interval of 700–1400 m which corresponds to the Oligocene to Upper Miocene succession, were observed to range from 9.6 to 19.5 MPa. The top of the overpressured zone in sub‐thrust strata was observed in the Upper Eocene to Oligocene succession at a depth of 3700 m, in the argillaceous Barail Formation, with pore pressures ranging between 48 MPa and 54 MPa. Pore pressures were estimated using acoustic log data calibrated to measured pressures from Modular Dynamic and Drill Stem Test data. The modelled pore pressures closely correspond to the measured data, supporting the robustness of the model. The numerical parameters defined in this study may be used for future exploration in the region.