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11.
Camilla L. Würtzen Alvar Braathen Miquel Poyatos-Moré Mark J. Mulrooney Lina H. Line Ivar Midtkandal 《Basin Research》2023,35(2):705-743
Fault throw gradients create transverse folding, and this can influence accommodation creation and sedimentary routing and infill patterns in extensional half-graben basin. The Fanja half-graben basin (Oman) offers an excellent outcrop of an alluvial fan succession displaying cyclical stacking and basin-scale growth-fold patterns. These unique conditions allow for an investigation of fault-timing and accommodation development related to fault-transverse folding. Our study combines geological mapping, structural analysis, sedimentary logging and correlation, and bulk mineralogical compositions. Mapping reveals that the basin is bounded by a regional-scale fault, with local depocentres changing position in response to transverse syncline and anticline development ascribed to fault-displacement gradients. The alluvial Qahlah Formation (Late Cretaceous) is unconformably overlying the Semail Ophiolite, and is in turn overlain by the marine Jafnayn Formation (Late Palaeocene). Facies and stratigraphic analysis allows for subdivision of the Qahlah Formation into four informal units, from base to top: (i) laterite in topographic depressions of the ophiolite, (ii) greenish pebbly sandstones, deriving from axially draining braided streams deposited in the low-relief half-graben basin. This green Qahlah grades vertically into the red Qahlah, formed by alluvial fanglomerates and floodplain mudstones, with drainage patterns changing from fault-transverse to fault-parallel with increasing distance to the main fault. The red Qahlah can be divided into (iii) the Wadi al Theepa member, found in a western basin depocentre, with higher immaturity and sand: mud ratio, suggesting a more proximal source, and (iv) the Al Batah member, located in the eastern part of the basin. The latter shows better sorting, a lower sand: mud ratio, and more prominent graded sub-units. It also shows eastward expansion from an orthogonal monocline, ascribed to accommodation developed in a relay ramp. Changes in sedimentary facies and depositional patterns are consistent with differential mineralogical composition. The Green Qahlah is composed of quartz and lithic mafic rock fragments, sourced from the ophiolite and schists of the metamorphic basement. The Red Qahlah is composed of chert and kaolinite sourced from the Hawasina Nappe succession in the footwall of the master fault. These changes in source area are linked to unroofing of fault-footwalls and domal structures during the extensional collapse of the Semail Ophiolite. The novelty of this study resides in linking sedimentology and fault-displacement events controlling fault-perpendicular folding, and its influence on depocentre generation and stratigraphic architecture. This is an approach seldom considered in seismic analysis, and rarely analysed in outcrop studies, thus placing the results from this study among the key outcrop-based contributions to the field. 相似文献
12.
The Nile Delta of Egypt is known for its large irrigated area supplied with water diverted from the Nile River, with a limited use of groundwater, largely for domestic and industrial use. Official statistics for the whole delta indicate that there are a few thousand individual wells used for agriculture by a population of over 2 million farmers. This study, however, shows that a phenomenon of groundwater development for irrigation has been unfolding over the last few years, largely below the radar of managers and researchers. A survey was carried out in the central part of the delta with the objective of (1) uncovering the actual situation of groundwater use in this part of the delta and (2) speculating on its implications. The results of the survey pointed to a recent and booming tube-well drilling industry, with well densities in some parts reaching one well every 2 ha. The development of groundwater abstraction in the central delta is strongly linked to inadequate and/or untimely availability of surface water in the canals. A technical, economic, and management characterization of wells complements the study, showing a continuum between purely private/individual ownership of wells and collective investments and management. Lastly, the article explores the implications of unchecked abstraction at the farm, local and delta scales. 相似文献
13.
Roy H. Gabrielsen Jan Inge Faleide Christophe Pascal Alvar Braathen Johan Petter Nystuen Bernd Etzelmuller Sejal O'Donnell 《Marine and Petroleum Geology》2010
The regional resultant stress field of the northeastern North Atlantic has shifted significantly throughout the Phanerozoic. In Fennoscandian parts of the Caledonian orogen, mountain building, which was characterized by NW-SE contraction (reference to present North), was followed by a collapse with transport both parallel and transverse to the mountain chain. The Late Palaeozoic – Mesozoic saw several stages of E-W to NW-SE extension, varying in time and position. Local episodes of inversion are traceable in some cases, particularly in connection with deep-seated and long-lived zones of weakness. The Cenozoic has to a larger degree been affected by compression, including folding and basin inversion. Again some of the more pronounced effects of local inversion are related to pre-existing fault systems. Neogene uplift of the western mountainous area in Scandinavia can be unravelled by potential field study, AFT data and reflection seismic sections. Assuming that the region is close to isostatic equilibrium, the uplifted areas must be supported at depth by substantial volumes of low-density material within the crust or the mantle, close to the crust/mantle interface or close to the lithosphere/asthenosphere interfaces. 相似文献
14.
15.
Ingrid Anell Valentin Zuchuat Anna Daniela Rhnert Aleksandra Smyrak‐Sikora Simon Buckley Gareth Lord Harmon Maher Ivar Midtkandal Kei Ogata Snorre Olaussen Per T. Osmundsen Alvar Braathen 《Basin Research》2021,33(1):478-512
The study describes the depositional development and sediment partitioning in a prograding paralic Triassic succession. The deposits are associated with the advance of large prism‐scale clinoforms across a shallower platform area. Approaching the platform, the limited accommodation and associated relative higher rates of deposition generated straighter clinoforms with lower foreset angles. The vertical restriction across the platform is interpreted to have amplified the tidal signature. Sediment was redistributed from the coast into increasingly sandy delta‐front deposits, compared to offshore equivalents. The deposits comprise extensive compound dune fields of amalgamated and increasingly clean sandbodies up‐section. Rapid deposition of significant amounts of sand led to differential subsidence and growth‐faulting in the delta front, with downthrown fault blocks further amplifying the tidal energy through funnelling. A mixed‐energy environment created along‐strike variability along the delta front with sedimentation governing process‐regime. Areas of lower sedimentation were reworked by wave and storm‐action, whereas high sedimentation rates preserved fluvially dominated mouth bars. A major transgression, however, favoured tidally dominated deposits also in these areas, attributed to increasing rugosity of the coastline. Formation of an extensive subaqueous platform between the coast and delta front dampened incoming wave energy, and tidally dominated deposits dominate the near‐shore successions. Meanwhile formation of wave‐built sand‐bars atop the platform attest to continued wave influence. The strong tidal regime led to the development of a heterolithic near‐shore tidally dominated channel system, and sandier fluvial channels up‐river. The highly meandering tidal channels incising the subaqueous platform form kilometre wide successions of inclined heterolithic stratification. The fluvially dominated channels which govern deposition on the delta plain are narrower and slightly less deep, straighter, generally symmetric and filled with cleaner sands. This study provides important insight into tidal amplification and sand redistribution during shallowing on a wide shelf, along with along‐strike process‐regime variability resulting from variations in sediment influx. 相似文献
16.
Unravelling the complex structure of a benthic community: A multiscale-multianalytical approach to an estuarine sandflat 总被引：1，自引：0，他引：1
Luis Gimnez Caterina Dimitriadis Alvar Carranza Ana Ins Borthagaray Marcel Rodríguez 《Estuarine, Coastal and Shelf Science》2006,68(3-4):462
We evaluated scale-dependent patterns of distribution of sandflat macroinfauna of a coastal lagoon, using different analytical approaches. The sampled area was divided into three sectors (outer, inner-north, inner-south) containing small promontories. At each side of the promontories we defined stations in a line transect across the sandflat. Thus, we evaluated sediment characteristics and macroinfaunal responses to sectors, orientations and intertidal levels; animal–sediment relationships were also studied. At a large scale, there was a clear pattern of sediment composition and macroinfaunal abundance. While the outer sector had medium to coarse sands, reflecting the high hydrodynamic conditions existing near the lagoon entrance, the inner sectors showed sandy and muddy sediments. Most species were in low abundances at the outer sector. At small scale, macroinfaunal abundance and species richness decreased sharply towards the upper sandflat level. Also at small scale, sediment composition limited the maximal densities reached by all species, with exception of the deposit-feeding polychaetes. Thus, the macroinfaunal community at muddy sediments was dominated by burrowing deposit-feeders, while all species peaked in sandy sediments. Our results suggest that physical factors shaping macroinfaunal communities operate at different scales and are better detected using several analytical approaches. Large scale patterns, associated with along-shore variations in disturbance by currents, were detected as changes in the mean abundance of macroinfauna. Small scale patterns, related to sediment characteristics, were observed as changes in maximal densities of macroinfauna. Small scale patterns, associated with the level of inundation of the sandflats, were detected through changes in the abundance and presence of macroinfauna. The evaluation of the role of the physical conditions on communities must involve the use of several sampling and analytical approaches. 相似文献
17.
Aleksandra Smyrak-Sikora Per Terje Osmundsen Alvar Braathen Kei Ogata Ingrid Anell Mark J. Mulrooney Valentin Zuchuat 《Basin Research》2020,32(5):949-978
World-class examples of fault-controlled growth basins with associated syn-kinematic sedimentary fill are developed in Upper Triassic prodelta to delta-front deposits exposed at Kvalpynten, SW Edgeøya in East Svalbard. They are interpreted to have interacted with north-westerly progradation of a regional delta system. The syn-kinematic successions consist of 4 to 5 coarsening-upward units spanning from offshore mudstones to subtidal heterolithic bars and compound tidal dunes, which were blanketed by regional, post-kinematic sandstone sheets deposited as laterally continuous, subaqueous tidal dune fields. The rate of growth faulting is reflected in the distribution of accommodation, which governs sedimentary architecture and stacking patterns within the coarsening-upward units. Fully compartmentalized basins (12, 200–800 m wide and c. 150 m high grabens and half grabens) are characterized by syn-kinematic sedimentary infill. These grabens and half-grabens are separated by 60–150 m high horsts composed of pro-delta to distal delta-front mudstones. Grabens host tabular tidal dunes (sandwaves), whereas half-grabens bound by listric faults (mainly south-dipping) consist of wedge-shaped, rotated strata with erosive boundaries proximal to the uplifted fault block crests. Heterolithic tidal bars (sand ridges) occur in narrow half-grabens, showing migration oblique to the faults, up the dipslope. Structureless sandstone wedges and localized subaqueous slumps that formed in response to collapse of the block crests were only documented in half-grabens. Late-kinematic deposition during the final stages of faulting occurred in partly compartmentalized basins, filled with variably thick sets of continuous sandstone belts (compound tidal dunes). 相似文献
18.
An assessment of the non-market value of the ecosystem services provided by the Catalan coastal zone,Spain 总被引：1，自引：0，他引：1
Jorge Brenner José A. Jiménez Rafael Sardá Alvar Garola 《Ocean & Coastal Management》2010,53(1):27-38
A spatial value transfer analysis was performed to generate baseline estimates of the value of ecosystem services in the coastal zone of Catalonia, Spain. The study used the best available conceptual frameworks, data sources, and analytical techniques to generate non-market monetary value estimates that can be used to identify scarce ecosystem services among competing coastal uses. The approach focused on natural and seminatural, terrestrial and marine systems, which provide essential services that are not considered in current economic markets. Results show that in 2004 a substantial economic value of $3,195 million USD/yr was delivered to local citizens by surrounding ecosystems. In a spatially explicit manner, the approach illustrates the contribution made by natural environmental systems to the well being of communities in the coastal zone of Catalonia. It is hoped that this study will highlight the need to consider these coastal systems in future management strategies to ensure their proper maintenance and conservation. 相似文献
19.
Gordon E. Sarty László L. Kiss Richard Huziak Lionel J. J. Catalan Diane Luciuk Timothy R. Crawford David J. Lane Roger D. Pickard Thomas A. Grzybowski Pere Closas Helen Johnston David Balam Kinwah Wu 《Monthly notices of the Royal Astronomical Society》2009,392(3):1242-1252
The high-mass X-ray binary RX J0146.9+6121, with optical counterpart LS I+61°235 (V831 Cas), is an intriguing system on the outskirts of the open cluster NGC 663. It contains the slowest Be type X-ray pulsar known with a pulse period of around 1400 s and, primarily from the study of variation in the emission line profile of Hα, it is known to have a Be decretion disc with a one-armed density wave period of approximately 1240 d. Here we present the results of an extensive photometric campaign, supplemented with optical spectroscopy, aimed at measuring short time-scale periodicities. We find three significant periodicities in the photometric data at, in order of statistical significance, 0.34, 0.67 and 0.10 d. We give arguments to support the interpretation that the 0.34 and 0.10 d periods could be due to stellar oscillations of the B-type primary star and that the 0.67 d period is the spin period of the Be star with a spin axis inclination of 23+10 −8 degrees. We measured a systemic velocity of −37.0 ± 4.3 km s−1 confirming that LS I+61°235 has a high probability of membership in the young cluster NGC 663 from which the system's age can be estimated as 20–25 Myr. From archival RXTE All Sky Monitor (ASM) data we further find 'super' X-ray outbursts roughly every 450 d. If these super outbursts are caused by the alignment of the compact star with the one-armed decretion disc enhancement, then the orbital period is approximately 330 d. 相似文献
20.
Beyene G.Haile Urszula Czarniecka Kelai Xi Aleksandra Smyrak-Sikora Jens Jahren Alvar Braathen Helge Hellevang 《地学前缘(英文版)》2019,10(2):629-649
Sedimentary basins containing igneous intrusions within sedimentary reservoir units represent an important risk in petroleum exploration. The Upper Triassic to Lower Jurassic sediments at Wilhelm?ya(Svalbard) contains reservoir heterogeneity as a result of sill emplacement and represent a unique case study to better understand the effect of magmatic intrusions on the general burial diagenesis of siliciclastic sediments. Sills develop contact metamorphic aureoles by conduction as presented in many earlier studies. However, there is significant impact of localized hydrothermal circulation systems affecting reservoir sediments at considerable distance from the sill intrusions. Dolerite sill intrusions in the studied area are of limited vertical extent(～12 m thick), but created localized hydrothermal convection cells affecting sediments at considerable distance(more than five times the thickness of the sill)from the intrusions. We present evidence that the sedimentary sequence can be divided into two units:(1) the bulk poorly lithified sediment with a maximum burial temperature much lower than 60-70 ℃,and(2) thinner intervals outside the contact zone that have experienced hydrothermal temperatures(around 140 ℃). The main diagenetic alteration associated with normal burial diagenesis is minor mechanical plastic deformation of ductile grains such as mica. Mineral grain contacts show no evidence of pressure dissolution and the vitrinite reflectance suggests a maximum temperature of ～40 ℃. Contrary to this, part of the sediment, preferentially along calcite cemented flow baffles, show evidence of hydrothermal alteration. These hydrothermally altered sediment sections are characterized by recrystallized carbonate cemented intervals. Further, the hydrothermal solutions have resulted in localized sericitization(illitization) of feldspars, albitization of both K-feldspar and plagioclase and the formation of fibrous illite nucleated on kaolinite. These observations suggest hydrothermal alteration at T 120-140 ℃ at distances considerably further away than expected from sill heat dissipation by conduction only, which commonly affect sediments about twice the thickness of the sill intrusion. We propose that carbonate-cemented sections acted as flow baffles already during the hydrothermal fluid mobility and controlled the migration pathways of the buoyant hot fluids. Significant hydrothermally induced diagenetic alterations affecting the porosity and hence reservoir quality was not noted in the noncarbonate-cemented reservoir intervals. 相似文献