Alluvial Fan Research Articles

Paleovolcanology, geochemistry, and zircon U-Pb-Hf isotopes of the volcano-sedimentary sequences from the Ediacaran Campo Alegre-Corupá Basin, southern Brazil: Linking volcanism and tectonics during Western Gondwana consolidation

The Campo Alegre-Corupá Basin (CACB) records a well-documented sequence of volcano-sedimentary episodes associated with specific periods of crustal extension during the late-convergent to post-collisional tectonic stages of the consolidation of Western Gondwana. Two main volcano-sedimentary stages were detailed through stratigraphic and lithofaciological studies, combined with whole-rock geochemistry and zircon U-Pb-Hf analysis, resulting in a more complete understanding of the tectono-magmatic cycles and volcanological evolution of the CACB. During the Basin Stage (605–590 Ma), regional collisional tectonics was responsible for initiating the basin as a syn-orogenic rift, during which the sedimentary cycle progressed from alluvial fans at the northern limit of the basin to braided rivers and into a lake to the south. U-Pb geochronology and Lu-Hf isotope signatures of detrital zircon revealed that the sediments were mainly derived from the Paleoproterozoic basement of the Luis Alves Terrane, which constitutes the direct basement of the CACB, with contributions from the nearby Piên Magmatic Arc and possibly from the Curitiba Terrane to the North. The sedimentary strata were progressively covered by transitional to mildly alkaline OIB-like basalts, occurring mostly as lava flows with structural aspects suggestive of subaqueous to subaerial environments, interbedded with trachydacites and surge-like pyroclastic deposits. Large volumes of widespread and densely-welded to rheomorphic ignimbrite sheets within the CACB attest to a second infilling period corresponding to the Caldera Stage (583–577 Ma). This stage was inaugurated by the outpouring of trachytic and very subordinated IAB-like basaltic lava flows at ∼583 Ma. The caldera eruption seems to have been initiated by the production of pumiceous fallouts during an early Plinian-like period of decompression of shallow magma chambers at ∼580 Ma, during which the rift-related structural framework of the Basin Stage probably controlled the collapse of a graben-like caldera. Compositional and isotopic signatures suggest lithospheric mantle sources for the magmas from both volcanic stages and support a connection between basic-intermediate and silicic rocks from both bimodal associations. They also suggest a cogenetic nature between the silicic rocks from the Caldera Stage and the A-type granitoids from the nearby plutonic Graciosa Province.

Spatial and temporal distribution of sinuous ridges in southeastern Terra Sabaea and the northern region of Hellas Planitia, Mars☆

Sinuous ridges are an important yet understudied component of Mars' hydrologic history. We have produced a map of sinuous ridges, valleys and channels, and tectonic ridges across southeastern Terra Sabaea and into northern Hellas Planitia (10°-45° S, 35°-80° E) using a CTX mosaic. Although we mapped different types of ridges and negative relief features, the focus of this paper are the sinuous ridges. We present here a new dataset of sinuous ridges that includes basic morphometry (e.g., length, width, sinuosity), morphology, and the types of terrains they are located on. We chose our region of interest because it includes surface ages spanning Mars' geologic history, with emphasis on Noachian and Hesperian terrains. The shift from either a warm and wet or a cold and icy environment to our modern cold and dry climate occurred towards the end of the Noachian and into the Hesperian, a critical temporal window to characterize fluvial landforms.Our CTX-based mapping significantly improved the documentation of fluvial landforms within the study region, with over an order of magnitude increase in the number of valley networks and channels, and nearly 1700 sinuous ridges. Sinuous ridges are found in concentrated settings, with the majority (∼80%) located within impact craters and relatively few (∼20%) on the intercrater plains. Fluvial features are prevalent on Early and Middle Noachian-aged terrain but are relatively rare in the Late Noachian, signifying a shift in fluvial activity that likely led to a decrease in channel incision and subsequent inversion of relief. A subset of sinuous ridges—radial ridges in high-elevation, degraded craters— are possible records of ancient proglacial lakes. The youngest sinuous ridges are associated with intracrater alluvial fans in a narrow zone (∼12°S to 30°S and ∼ 62°E to 77°E). These formed in the Late Hesperian into the Amazonian, reflecting a later epoch of punctuated fluvial events driven by pre-existing topography and solar insolation.

Impact of faulting in depocentres development, facies assemblages, drainage patterns, and provenance in continental half‐graben basins: An example from the Fanja Basin of Oman

AbstractFault 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.

Facies analysis, depositional activity, and internal structure of sieve deposits on an active alluvial fan

AbstractSieve lobes typically appear in gravel‐rich and matrix‐poor alluvial fans. Despite being extensively studied, the sieve‐lobe facies has been defined largely based on qualitative field observations without quantitative sedimentological analyses. Additionally, depositional activity of sieve lobes has not been monitored over extended periods (monthly to annually) and not directly associated with specific precipitation triggers. Furthermore, the internal geometry of sieve‐lobe built alluvial fans has not yet been imaged by subsurface methods. We performed a multi‐method analysis of sieve lobes in the Julian Alps (NW Slovenia) on an alpine alluvial fan composed of carbonate gravels. We performed a detailed textural and structural sedimentological analysis of 11 recent sieve lobes differing in size and age. A three‐year aerial survey of the alluvial fan surface with a small unmanned aircraft and photogrammetric modelling was used to detect active sieve‐lobe evolution. Detected sieve‐lobe formation events and volumetric surface changes were paired with triggering precipitation events. Ground‐penetrating radar (GPR) profiling depicted the geometry of the sieve‐lobe built alluvial fan. The sieve‐lobe facies consists of over 80% poorly sorted, open‐framework gravels and less than 2% mud. Lobes exhibit downward coarsening and increase in clast mean size. These textural and structural characteristics are present in all sieve lobes regardless of their age and size. Sieve lobes form with a sub‐annual frequency, usually following 24 h rainfall events exceeding 50 mm. Over 1000 m3 of sediment was deposited during these events. The GPR profiles confirm that the studied alluvial fan is formed predominantly by stacked sieve lobes. Quantitative sedimentary analysis of sieve lobes, monitoring of their recent evolution, and depiction of their subsurface geometry—demonstrated in this study—reinforce the challenged concept that sieve lobes are one of the main building blocks of alluvial fans. This work also demonstrates that, under specific conditions, sieving may become the dominant alluvial fan‐forming process.

Mapping regional subsidence rate from electricity consumption-based groundwater extraction

Study regionChoushui River alluvial fan in central Taiwan. Study focusExcessive land subsidence is occurring in the Choushui alluvial fan, Taiwan. Groundwater pumping in the region is not monitored so pumping volumes are estimated from information based on electricity consumption. Groundwater pumping data alone cannot be used to accurately estimate the spatial rate and distribution of subsidence due to the low spatial correlation between estimated pumping volumes and subsidence from heterogeneous geologic materials. Time-dependent spatial regression is a reliable tool for estimating the spatial distribution of annual rate of subsidence based on spatial mapping of pumped groundwater volumes and monitored land subsidence. New hydrological insights for the regionEstimates of pumping quantities indicate that the locations of subsidence from overexploitation of groundwater from the underlying aquifer system is not always spatially correlated with major pumping areas or with the observed locations of maximum water-level drawdown. Considering time-dependent spatial regression models, the average RMSE of annual subsidence is 0.65 cm for the Choushui alluvial fan, indicating the high level of correlation between measured and estimated subsidence. These findings show that annual subsidence can be reliably estimated and predicted under the field pumping conditions of the study site. The influences of reduced withdrawals based on the relation between annual subsidence and pumping volumes can be evaluated for improved best management practices.

Preservation of Organic Matter in Aqueous Deposits and Soils Across the Mars‐Analog Qaidam Basin, NW China: Implications for Biosignature Detection on Mars

AbstractA variety of aqueous deposits and soils from gullies, fluvial channels, mountain slopes, alluvial fans, playas, polygons, and yardangs have been found on Mars. However, the occurrence of sedimentary organic matter (SOM) in these landscapes under hyperarid and strongly radiative conditions has yet to be fully assessed. With various desiccated landforms analogous to those on Mars, the Qaidam Basin in northwestern China is considered a promising hyperarid Martian analog. Here, aqueous deposits and soils from nine landforms across the extremely dry northwestern Qaidam and from four landforms across the dry southeastern Qaidam were sampled and investigated. Our results reveal that landform and moisture are important controls on organic carbon distribution across the Qaidam Basin, while sedimentary origin has a dominant effect in the extremely dry northwestern Qaidam. Combined with previous studies, low organic carbon contents of soils in the extremely dry northwestern Qaidam suggest possibly low rates of microbial carbon input and of organic carbon degradation in Mars‐like environments. High organic carbon contents of aqueous deposits together with increasing trends along rivers indicate preservation of relic SOM and possibly slow degradation rates of organic matter as compared to their exposure timescale. Moreover, soils from the distal alluvial fan are found to favor the concentration of pedogenic organic carbon as compared to those from other landforms in the dry southeastern Qaidam and from all landforms in the extremely dry northwest. This suggests that subsoils in the distal fans are promising candidate targets for biosignature detection on Mars.

An Oligocene-Miocene intermontane narrow lowland in the central Tibetan Plateau: Insights from provenance analysis and palynological record of a Cenozoic sedimentary succession

• The Niubao Formation in the Avengco Basin, the western part of the BNSZ, was deposited during Oligocene-Miocene with bidirectional sources. • The Oligocene-Miocene paleoelevation of the Avengco Basin was 3090-3290 m. • A 3 km high intermontane lowland on the BNSZ were formed during the Oligo-Miocene. • This intermontane lowland was probably formed by the reactivation of thrust belts and cloud extend westward to the Avengco Basin. A series of Cenozoic basins are distributed along the Bangong-Nujiang suture zone and amalgamate into an east-west trending topographic lowland. The reconstruction of the formation process for the lowland is critical to understanding the evolution of the Tibetan Plateau and paleoclimate. Here we present results from sedimentology, zircon U-Pb ages, and palynological records of the Niubao Formation in the Avengco Basin, the western part of central Tibet. The Niubao Formation consists of conglomerate, sandstone, siltstone, marl, and limestone, which were deposited in alluvial fan and shallow lake. The palynological assemblages suggest that the Niubao Formation in the Avengco Basin was deposited during the Oligocene-Miocene. Provenance analyses suggest that the Niubao Formation can have bidirectional sources, including the Southern Qiangtang terrane and/or Bangong-Nujiang suture zone in the north and the Northern Lhasa terrane in the south. By using the co-existence approach, palynological records from the Niubao Formation yielded a paleoelevation of 3090-3290 m after temperature and lapse rate correction, which was 1-2 km lower than those of the Lhasa and Qiangtang terranes during the Oligocene-Miocene. Based on the above observations and previous studies from the coeval sediments of the Lunpola and Nima Basins in central Tibet, we propose that the intermontane lowland along the Bangong-Nujiang suture zone was formed as a whole during the Oligocene at the latest and extended to the Avengco Basin in the west.

System response of an interlayered deposit with a localized graben deformation in the Northridge earthquake

The Wynne Avenue site in the California San Fernando Valley was analyzed using two-dimensional (2D) nonlinear dynamic analyses (NDAs) with geostatistical subsurface modeling to interpret key mechanisms contributing to a 12-m-wide graben deformation with vertical offsets of 10–20 cm in the 1994 Northridge earthquake. In-situ data from borings and cone penetration tests (CPTs), joined with geological interpretations of the distal alluvial fan deposition, delineate interlayered silty sand lenses within a typically fine-grained soil stratigraphy. The NDAs used the PM4Sand and PM4Silt constitutive models with the FLAC finite difference program. NDAs with uniform properties for distinct soil zones closely reproduced the observed graben. However, stochastic NDAs, modeled with sequential Gaussian simulations (SGS) for conditional random field realizations of critical zones, often obscured the expected graben. The ability of the stochastic NDAs to model the graben was further reduced when SGS was performed collectively over two distinct soil zones. The NDAs provide new insights on the causal mechanisms of liquefaction-induced ground oscillations and lurching, that were not easily deduced from common one-dimensional (1D) liquefaction vulnerability indices (LVIs) and Newmark sliding-block analyses. This case study demonstrates the capabilities of system-level NDAs for modeling localized ground deformation patterns, but also highlights cautionary nuances for their implementation with data-driven stochastic subsurface modeling.

Initiation and Development of the Late Cenozoic Uplift of Daluo Mountains, Northeastern Margin of the Tibetan Plateau

AbstractDaluo Mountains lie at front of the arcuate tectonic belt at the northeastern margin of the Tibetan Plateau, and are the landform boundary zone between the active Tibetan Plateau and the stable North China Craton. Studying of the late Cenozoic uplift evolution of Daluo Mountains is important for understanding the expansion mechanism of the northeastern margin of the Tibetan Plateau and its influence on the western North China Craton. In this study, the late Cenozoic uplift of Daluo Mountains is constructed from the development of the late Cenozoic alluvial fan around Daluo Mountains. The entire sedimentary sequence and framework of the fan was revealed by the newly obtained drilling core data. The cosmogenic nuclide, optically stimulated luminescence, and detrital zircon U‐Pb dating results provide new evidences for discussion about the initial timing of the late Cenozoic uplift of Daluo Mountains and the key stages of uplift during the Pleistocene. The late Cenozoic alluvial fan at front of Daluo Mountains overlies a set of fluvial‐facies strata; therefore, development of the alluvial‐fan marks the start of late Cenozoic uplift of Daluo Mountains. The timing of this event can be constrained to ∼4.64 Ma. Two extensive gravel layers (dated to ca. 0.76–0.6 Ma and ∼0.05 Ma) developed during the Pleistocene, indicating two episodes of considerable uplift. This study provides a new time scale for the uplift and expansion of the arcuate tectonic belt at the northeastern margin of the Tibetan Plateau.

Airborne geophysical method images fast paths for managed recharge of California’s groundwater

Given the substantial groundwater level declines in the Central Valley of California, there is an urgent need to supplement the recharge of the groundwater systems by implementing managed aquifer recharge. With approximately 170 km3 (140 million acre-feet) of available groundwater storage space, water deemed to be excess during wet years could be spread on the ground surface at selected locations allowing it to move downward to recharge the underlying aquifer system. Along the eastern edge of the Central Valley there are large paleovalleys that can act as fast paths expediting the downward movement of water. These paleovalleys, incised and then filled with coarse-grained materials—sand, gravel, cobbles—at the end of the last glacial period, are referred to as incised valley fill (IVF) deposits. An IVF deposit has been mapped at one location in the Kings River alluvial fan, with others proposed to exist in the fans of major rivers. If located, these deposits would be optimal sites for managed recharge. In this study, we assessed the use of a helicopter-deployed geophysical method to efficiently locate IVF deposits throughout the Central Valley. We acquired 542 line-kilometers of airborne electromagnetic (AEM) data in the Kings River alluvial fan, with dense line-spacing over the Kings River IVF deposit which had been mapped as ∼2 km wide, extending over 20 km into the Central Valley, from the ground surface to a depth of 30 m. The IVF deposit was unambiguously imaged in the AEM data as an extensive linear feature that was more electrically resistive than the surrounding materials due to the high percentage of coarse-grained sediments. This study provides the evidence to support the rapid adoption of the AEM method to locate IVF deposits along the eastern edge of the Central Valley. These deposits provide valuable natural infrastructure for recharging California’s groundwater.

사천 선상지 ‘새미’의 이용 실태 및 가치 고찰

This study is about the story of ‘Saemi’, existing in the Sacheon Alluvial fan area. Saemi is a local word for Dumbeong, which is the traditional water irrigation facilities in this area that could be formed according to the geographical characteristics of a Alluvial fan site. In the meantime, although Saemi has been an important source of water, related research has been mainly done from an ecological point of view. Accordingly, the researcher paid attention to the functional aspects of Saemi itself, grasped its location, distribution status, and usage including the construction method, and considered its intrinsic value through classification and characteristic analysis of Saemi. As a result of five field surveys from September 2021 to October 2022, 129 Saemies remained in the Sacheon alluvial fan area. According to the structure and shape, Saemi could be divided into basic type, complex type, and buried type. The basic type was subdivided into bucket-type and stairs-type along with the complex type, and the buried type was subdivided into all buried-type and some buried-type. Saemies were mainly distributed at the distal end of the Sacheon alluvial fan site, individual Saemies were built on farmland, and common Saemies were usually built along roadsides adjacent to villages. The reason why the Saemies are concentrated at the distal end is the geographical characteristics of the alluvial fan where the water underflows. Saemi was an important multifunctional water supply source equivalent to the main water source for people at the distal end of the pond who did not receive a stable supply of water from the reservoir. Saemi was at the center of the underground water irrigation network agricultural system in the Sacheon alluvial fan area according to the principles of ‘bbaeim(drop out)’ and ‘gaepim(pooling)’ It has provided a foundation for establishing itself as an appropriate technology in this area. Such Saemi contributed to the rural landscape and agricultural biodiversity through its own system and served as a public interest function. It is necessary to know, conserve, manage, and continuously utilize the value of this Saemi as an agricultural heritage.

Alluvial fans at Cala Gonone (Sardinia), a fast developing touristic village: origins, hazards and potential risks

The study area of Cala Gonone in NE Sardinia (Italy) consists of a wide terraced re-entrance/valley crowned inland by carbonate hills and, near the coast bounded laterally and partly floored by thin basaltic lava lying over carbonate bedrock. In this re-entrance, several inland alluvial fans (500 m length by 700 m wide) have developed, and a local ~ 30 m high, about 10 m wide (thick), 400 m long scarp body-remnant of semi-consolidated alluvial fan deposits is exposed along the coast. The fans experience depositional events mostly developed during the late Pleistocene. They although nowadays dormant may be reactivated by major rainstorms during strong climate changes. In these last few decades, the touristic village of Cala Gonone has been rapidly expanding over the mid to lower parts of two coalescing alluvial fans (Stadium and Gustui) and along the coastal marine scarp edge (Palmasera alluvial fan system). The village thus may become exposed to natural hazards if extreme climatic conditions may re-occur. Moreover, rock falls and the instability of the costal scarp due to wave erosion may add addition hazards for habitations built near the scarp crest and visitors to the frontal replenished beach. As commonly occurring elsewhere since antiquity, the risk perception of such events is low because of the centennial, millennial of longer recurrence. Such perception does not negate the hazards but a long event recurrence may be accepted as a reasonable risk for the human’s activity. Nevertheless, serious consideration should be given to potential problems and plan and build for amelioration and defense. The evidence of what environmentally did and could still happen in the Cala Gonone and similar other area is in part clearly imprinted on the landscape: geology, geomorphology, and relative details in the stratigraphy and sedimentology of the deposits.

Understanding of groundwater evolution through chemical and age dating information in the Yongding River alluvial fan in Beijing

Groundwater plays important roles in human community development and the urbanization process as the results of global environmental change and rapid population growth. A clear understanding of the vertical and horizontal spatial distribution characteristics of groundwater and sediment is the premise of efficient groundwater resource management and utilization in alluvial plains. To explore the evolution process of groundwater and the distribution of sediment in the Yongding River (YDR) alluvial fan, a typical profile from Mentougou to Fengheying was chosen to conduct an extensive hydrogeological investigation with multiple hydrochemical, isotopic, and age dating analyses, which represents one of the most typical hydrogeological units in the YDR alluvial fan. The analysis results show that (i) along the profile, the water’s chemistry type gradually changes from HCO3-Ca·Mg to HCO3-Na. The contents of coarse grain gradually decrease while fine particles regularly increase. Also, a similar evolution trend is found in the vertical direction. (ii) The annual renewable rate of groundwater is > 10% in the upper fan, 2%–8% nearby Daxing, and < 2% in Fengheying. (iii) In the proximal fan area, the average flow velocity of the single and double layer is about 65 m yr−1 and of approximately 18.9 m yr−1. From the mid fan to distal fan, the value of velocity and hydraulic conductivity decreases from 12.4 m yr−1 to 3.75 m yr−1 and from 8.54 m yr−1 to 0.64 m yr−1, respectively. (iv) The 14C analysis results indicate that the age of shallow and deep groundwater ranges from 5a to 60a and from 4000a to 12000a, respectively. The groundwater age increases with depth in the vertical direction and increases from northwest to southeast along in the alluvial fan in the horizontal direction. Understanding the evolution process of sediment and hydrochemistry in the YDR alluvial fan provides a valuable reference for groundwater resource development, utilization, and pollution prevention in the alluvial fan.

Facies association and sequence stratigraphic analysis of the lower Cretaceous Bima Formation in Yola arm of the Upper Benue Trough, Northeastern Nigeria

The Lower Cretaceous Bima Formation is the oldest sedimentary rock in the Upper Benue Trough. This research is aimed at understanding the facies, facies association, and sequence stratigraphic framework of the continental Bima Formation. Detail field mapping, lithostratigraphic studies, petrography, and paleocurrent analysis revealed that the formation is composed of three facies associations; gravel facies association FAI (gravelly dominated), sandstone facies association FAII (sand-sandstones dominated), and fine-grained facies association FAIII and four facies successions; proximal alluvial fan facies succession, braided river facies succession, fluvio-lacustrine facies succession, and flood plain facies association. The Bima Formation is punctuated by three major bounding surfaces, these provide the means of subdividing the Bima Formation into four depositional sequences namely; SQ1, SQ2, SQ3, and SQ4. Four system tracts were also identified within the Bima Formation; aggradational and high accommodation system tracts represent positive accommodation/sediments supply, and low accommodation system tract-A and B suggest negative accommodation/sediment supply. The overall sedimentation processes in the Bima Formation are controlled by climate, tectonic subsidence, and uplift. The paleocurrent data from the northern part of the study area suggest a unidirectional flow in NNW while the southern part of the study area shows SSW direction.

Sinjar Anticline Northwest of Iraq: A Tectonic Geomorphological Study

The Sinjar Anticline (Mountain) is an outstanding structural and geomorphic feature in the northwestern part of Iraq. The anticline is a double plunging with almost E – W trend dividing the gently rolling plain in which it is developed into two parts, Al-Jazira Plain in the south and Rabi’a Plain in the north. The Sinjar anticline is asymmetrical with steeper northern limb (45 – 80)° and gentler southern limb (15 – 25)°, its length is about 80 km, whereas the width ranges between (9.25 – 12. 5) km. The oldest exposed rocks belong to the Shiranish Formation, whereas the youngest rocks belong to the Fatha Formation. Different geomorphological and structural forms were observed through interpretation of satellite images, geological and topographical maps of different scales, beside field observations. Among those forms are: Abandoned alluvial fans, radial, inclined, and cross-shaped valleys, whale-back shape, wind gaps, and parasitic folds. All these forms are good indications about the lateral growth of the anticline. Neotectonic measurements were carried to estimate the rates of upward and downward movements. These estimations were performed by measuring the elevation of the contact between the Fatha (Middle Miocene) and Injana (Late Miocene) formations at different selected locations on both sides of the anticline. Keywords: Sinjar anticline, lateral growth, neotectonic movements, wind gap, abandoned alluvial fans

Geology, geomorphology and geochronology of the coseismic? Emad Deh rock avalanche associated with a growing anticline and a rising salt diapir, Zagros Mountains, Iran

This work documents for the first time the prehistoric, but morphologically pristine, Emad Deh rock avalanche of the Zagros Mountains. The ca. 420 Mm3 rock avalanche was initiated as a rockslide on a dip slope affecting a weak unit of marls with interbedded limestones overlain by a thick and competent limestone formation. The slope is located on the northern limb of the growing Gavbast Anticline and at the edge of the inflating Gavbast Dome, related to a buried salt diapir of Hormuz salt. The unconfined rock avalanche deposits, covering 32 km2, were accumulated on coalescing alluvial fans and a floodplain environment. The depositional lobe shows sectors with distinctive morphological features attributable to the variable flow-depositional behavior of the debris stream, controlled by the nature of the substrate: (1) proximal continuous breccia flanked by levees; (2) intermediate depression; and (3) flat-topped polygonal hills and conical hills. A morphometric and spatial distribution analysis has been performed with the 550 conical hills (hummocks) mapped in the distal sector. The rock avalanche, with 914 m of maximal height drop (H) and 9280 m of runout (L), displays an extraordinarily high mobility (H/L index of 0.09), that can be attributed to the combined effect of dynamic rock fragmentation and basal lubrication by the soft substrate in the floodplain. Relief rejuvenation and slope over-steepening related to the growth of the anticline and the inflation of the Gavbast Dome are considered the main long-term preparatory factors that shifted the slope to a state of marginal stability. The slope failure was likely triggered by a large M ≥ 6.5–7 earthquake at ca. 5.4 ka, as indicated by OSL ages obtained from folded alluvium situated just beneath the rock avalanche deposit. The source of the earthquake was probably a blind reverse fault situated beneath the asymmetric Gavbast Anticline, as support the structural and geomorphic features of the fold. The identification and dating of large coseismic landslides in the Zagros Mountains, where large earthquakes are rarely accompanied by primary surface ruptures, could help to improve both landslide and seismic hazard assessments.

The Paraná River in the argentine plain: A review of its evolution and contemporary characteristics

This paper discusses the geological evolution of the Paraná River in Corrientes Province, located inside the Mesopotamic Argentine region, and reviews the principal geomorphological and hydro-sedimentological characteristics of this outstanding fluvial system.Active lateral migration of the Paraná River inside its large alluvial fan, which covers the north-western portion of Corrientes Province, reveals a structural control related to the separation and breakup of Gondwana. The lowlands now present in this region receive only pluvial input and constitute one of the largest wetlands in South America, the Esteros del Iberá.The best exposed geological units in Corrientes Province are the Ituzaingó Formation (Plio-Pleistocene) that is a fluvial deposit associated with evolution of the Paraná River, and the Toropí-Yupoí Formation (Pleistocene), a younger palustrine fill generated by deposition of aeolian sediment over the underlying fluvial sands.The present planform pattern of the Paraná River in Corrientes Province is anabranching with several types of bar that occupy more than 30% of the channel surface. The bed sediment is predominantly medium to fine sand with the dominant bedform being dunes, which thus also dominate its subsurface sedimentary architecture.The suspended sediment concentration of the Paraná River downstream from its confluence with the Paraguay River (its main tributary) is asymmetric across the channel width, with higher concentrations towards the west due to the much higher input of sediment from the Paraguay River, which in turn receives most of its suspended sediment from the Bermejo River. At Corrientes City, suspended sediment concentration shows extremes ranging from 1 to 616 mg L−1 on the eastern margin and from 8 to 1271 mg L−1 on the western margin. Mixing between the Paraná and Paraguay rivers flows may take more than 600 km downstream before full mixing is achieved, with the mixing processes at the junction being determined by the discharge (momentum) ratio between the two confluent rivers, topographically-driven flows and the possible influence of density driven underflows at their interface. The confluence area between the Paraná and Paraguay rivers is characterized by a large scour that is ∼30 m deep, with its deepest location being at the mouth of the Paraguay River where the channel narrows due to local bedrock control.Due to the different elevation of the Paraná River margins in the region downstream of the confluence, the contemporary floodplain is developed extensively only on the western margin. This floodplain can also be considered as proximal (flooded yearly) or distal (flooded only during extraordinary events) in its geomorphic character. Most of the headwaters of small tributaries in this part of the Paraná River basin are located in wetlands. In these wetlands, the channel beds are characterized by fine sediment consisting of silt and cohesive clays, and where the suspended sediment has a high proportion of organic matter.

Well hydraulics in wedge-shaped aquifer: Unsteady Darcian flow model revisited by lagging theory

Pumping events are often conducted in the alluvial fan due to its considerable amount of water; If pumping events occur in the nearby vicinity of the streams, it will inevitably influence the complex microbial ecosystems in both the river and the aquifer, induce the issue of water rights permits, and affect the development of the water resource management. Therefore, it becomes necessary to accurately predict groundwater flow as a result of pumping in the wedge-shaped aquifer. In this paper, we propose an analytical solution to describe the drawdown distribution and the stream depletion rate (SDR) due to pumping in a wedge-shaped aquifer, which represents the shape of the alluvial fan bounded by two streams. Moreover, we adopt the lagging theory into the model by introducing two lagging parameters in Darcy’s law to allow the water flow and the hydraulic gradient to occur at different times. This measure facilitates the reflection of the inertial force because of a higher pumping rate and the microstructural interaction resulting from the water transfer between the primary pores and secondary pores (e.g., dead-end pores and very-small pores). It leads to the predicted result being closer to reality when these effects are profound. We found that the drawdown and SDR curves will behave like waves when the flux lagging dominates. The SDR value can be over unit due to the additional recharge driven by inertial force; the drawdown and SDR acts more like an unconfined or dual-porosity flow if storage lagging governs the system. Moreover, lagging parameters have the largest effect on drawdown and SDR when the times are close to the corresponding values of lagging parameters. The case of wedge-shaped domain bounded by two impervious barriers is considered to further explore the boundary effects on aquifer response to pumping.

Late Pleistocene slip rate and subsurface fault-plane geometry of the Latgan Fold (Bole Basin, North Tian Shan, NW China) derived from a deformed cosmogenically dated alluvial fan

Deformed alluvial fans can indicate the subsurface fault-plane geometry of thrusts. Numerous seismic profiles have illustrated the subsurface fault-plane geometry of thrusts in the Tian Shan piedmonts. However, due to a lack of seismic profiles, the subsurface fault-plane geometry in the Tian Shan is not well-known. This paper focuses on a thrust-related anticline in the eastern Kusongmuxiek Fault (KF), the Latgan Anticline (LA), located in the southern margin of the Bole Basin, northern Tian Shan. Five alluvial fan surfaces, A1-A5 from young to old, are determined along the Dilike River. We used the alluvial fan surfaces and fault attitude to determinate the subsurface fault-plane geometry of the Latgan Fault. The geometric model reveals that the Latgan Fault can be divided into three segments: an upper ramp with a dip of 55°S, a central listric fault, and a lower ramp with a dip of 31°S. The abandonment age of the A4 surface based on its cosmogenic 10Be concentrations and use of a kinematic model of a listric fault fold reveal that the fault dip-slip rate is c. 0.5 mm/a, and the horizontal crustal shortening rate is c. 0.4 mm/a during the Pleistocene. The vertical incision rates of the Dilike River are 0.5–0.6 mm/a in the uplifted area and 0.2 mm/a in the non-uplifted area. This difference may be the result of tectonic uplift. Our field and remote sensing observations and the geometric characteristics of the eastern Keguqin Mountains piedmont thrusts indicate fault propagation into the basin via thick-skinned tectonics. The LA crustal shortening rate and previous studies indicate that the crustal shortening rates of the Bole, Borohoro, and Turfan Units are ~1.7–2.0 mm/a, >4.0 mm/a, and 3.2–4.4 mm/a, respectively. The lower shortening rate of the Bole Unit and higher shortening rates of the Borohoro and Turfan Units indicate that the Bole Unit is the lowest crustal shortening rate unit in the northern Tian Shan.

Maize experiment in a traditional Zuni agroecosystem: nutrient composition

ABSTRACT Maize has sustained the Zuni and other peoples of the arid American Southwest for more than four millennia. In Zuni dryland agriculture, fields on alluvial fans and other valley-edge landforms are managed to receive supplemental water and nutrients by retaining storm runoff and associated sediment and organic material transported from adjoining uplands. An experiment with Zuni blue maize (Zea mays L.) and commercial hybrid maize was conducted in two Zuni fields to study traditional maize and its productivity as part of a larger study of Zuni agroecosystems. Following a closely related paper on maize growth and productivity, studies of maize nutrient composition and quality are presented here. More nutrient differences occurred between Zuni and hybrid maize than between runoff and other treatments. Zuni grain had higher concentrations of more nutrients than hybrid maize, and for several elements, there was an inverse pattern in grain vs. leaf nutrient concentration between cultivars. Zuni grain had a higher N (protein) concentration than hybrid maize, and a higher proportion of N in grain vs. leaf, indicating an ability to partition more N and other nutrients into grain. Parallel differences in maize and soil N and P were found between the two fields, though the cultivars had different P content patterns. Overall, agronomically sufficient concentrations of most nutrients were present across cultivars and treatments. Long-term production and nutrient management of maize grown without conventional irrigation or fertilization reflect a traditional agroecosystem that incorporates sustainable practices intended to maintain productivity with conservation of soil and water resources.