Sand Influx Research Articles

Storminess reconstruction in the northeastern Baltic Sea region over the past 7600 years based on aeolian sand influx into coastal bogs

This study aims to reconstruct the changes in storminess during the past 7600 years in the northeastern Baltic Sea region. For storminess reconstructions, aeolian sand influx (ASI) in coastal peat bog deposits was applied as an indicator of the past storminess. We analyzed cores from four peat bogs in the western and northern coastal areas of Estonia: the cores from Hiiumaa N, Hiiumaa SW, Saaremaa and Juminda study sites covered the past 3700, 3750, 2400, and 8400 years, respectively. The sediment chronologies were established using 36 14C dates. Image-analysis method ( ImageJ) was used to count and measure the grain size of all sand particles at every centimeter to gain high-resolution ASI records. Although minor site-to-site variations exist, all four ASI records were in general consistent, suggesting that stormier periods occurred around 7300, 6600, 5900, 4600, 3600, 2900, 2400, 2100, and 1600 cal yr BP and over the last 1200 years. The results and comparisons with other storminess and climate studies indicate a shift in climatic conditions around 2500 cal yr BP when stormy periods became more frequent. The ASI values were also high during the last millennium, suggesting either higher storminess or more suitable transport mechanisms for sand into the coastal bogs: the niveo-aeolian transport mode could have been favored in winters, especially during the Little Ice Age, and human impact on landscapes has probably increased over the past centuries.

Foredune-ridge development along an urban pocket beach, Montrose dunes natural area, Southwestern Lake Michigan

While foredune geomorphology has been studied along many Great Lakes coastlines, little attention has been given to the development and evolution of foredune ridges along engineered ‘pocket’ beaches, which are common along many urban lakefronts of the region. This paper reports on the recent morphodynamics of Montrose Beach, the largest of Chicago’s engineered coastal embayments, with emphasis on its ‘Dunes Natural Area.’ A post-2020 period of beach recovery occurred after 2013–2020 lake-level rise of >1.5 m, which was accompanied by shoreline recession and overwash-induced backshore accretion. The influx of sand into the urban embayment during this time facilitated post-2020 beach recovery with lake-level fall. This phase of beach expansion was marked by the formation of three distinct, parallel berm lines that have become vegetated and functioned as focal points for eolian accretion. Undisturbed by grooming and other beach-management activities, the Dunes Natural Area continues to be influenced by lake-level changes and storms. Vegetative establishment and eolian sand trapping upon disconnect from active reworking along the shoreline have increased the expression of linear topographic highs. Seasonal ridgelines along natural beach environments, including barrier spits, tend to undergo reworking prior to such stabilization. Insights from Montrose Beach provide coastal managers with up-to-date information on important geomorphic developments at Chicago’s most popular beach destination, whose Dunes Natural Area provides habitat for the endangered Great Lakes piping plover. Understanding its geomorphic trajectory can help inform coastal resiliency planning, here and elsewhere, to protect valuable ecosystems and infrastructure within the urban coastal landscape.

Uncertainty in measuring the role of climate change on debris-flow triggering on volcanoes - bulk-density, temperature and moisture analysis at Unzen Volcano (Japan)

As climate change creeps into the 21st century, the intensity of debris flows due to heavy and concentrated rainfall has increased in mountainous regions of Japan and East Asia. However, the relationship between climate change and an increase in debris flows is likely to be non-linear. Rainwater infiltrates more quickly into porous material, and the lack of vegetation cover increases evaporation and the temperature of surface sediments. In addition, periodic gully collapses bring fresh layers of porous material that increase the distance between the surface and the vadose zone. Therefore, to understand the relationship between volcanic debris flows (or lahars), parameters such as density, porosity, temperature, and moisture retention must be captured in detail in both time and space. The aim of this paper is to assess the role of loose, coarse, and porous sediments in lahar triggering. The present study was conducted at Unzen volcano in the Tansandani Guly between 31 May and 1 June 2023, 30 years after the last eruption. The dacite material is composed of a matrix of sand and coarse sand mixed with larger fractions and blocks, therefore traditional density measurement methods could not be applied, and a photogrammetric based method was used. In the field, sets of SfM-MVS photographs were taken before and after digging a hole in the sediments so that the measured mass could be compared to the volume of the hole in the sediments. After the sediments were dried, the dry and wet density, bulk density and porosity of the sample were calculated. When compared to the temperature data collected in the field, the following results were obtained: (1) The porosity of the volcanic material was highest in the lower reaches, followed by the upper reaches, and lowest in the middle reaches. This may be because fine sand washed out of the upstream area by rainfall is currently stored in the midstream area, which may facilitate debris flow generation. In addition, the downstream area has a high porosity, which may be due to the surrounding vegetation preventing the influx of new fine sand from the channel wall. (2) Because of the higher porosity and the lack of organic matter and vegetation cover, the increase in temperature acts more directly on the decrease in water content than in mountainous areas. Consequently, empirical equations for the potential for mudslides in volcanic areas with respect to surface temperature and soil moisture need to be developed for hazard and disaster risk management purposes.

State of the shoreline since Hurricane Sandy: Summary of changes at New Jersey Beach Profile Network (NJBPN) sites

Following the devastating impacts from Hurricane Sandy in October 2012, Congress passed Public Law 113-2 in January 2013 which provided the funding for the U.S. Army Corps of Engineers (USACE) to restore authorized federal coastal storm risk management projects in New Jersey to their original design templates. Between 2013 and 2016, approximately 28.3 million cubic yards of sand were used to rebuild the beaches and dunes along 92.7 miles of the 127-mile Atlantic Ocean shoreline (an average of 283,290 cubic yards per mile). Between 2017 and 2019, initial federal beachfill had been completed at the northern Ocean County beaches (an additional 11 million cubic yards). A review of the changes to the New Jersey Beach Profile Network (NJBPN) locations indicates that this influx of sand benefitted nearly all shorelines as well as former erosion hot spots. Examples are provided from each of the four counties (Monmouth, Ocean, Atlantic, Cape May) to show trends in profile volume and shoreline position. State support of beach nourishment continues through the efforts of the New Jersey Department of Environmental Protection and its Office of Coastal Engineering.

Evaluation of formation susceptibility and sand production potential in an offshore field, Niger Delta Basin, Nigeria

Wellbore instability and sand production are all common challenges in the Niger Delta oil province, resulting in high drilling and production cost as well as damage to oil facilities. The vulnerability of lithologic formations to wellbore instability and resultant sand production is investigated in the four delineated reservoirs of the “Areo” field, western part of Niger Delta Basin. The foundation for establishing the geomechanical properties in this study was a 1-dimensional mechanical earth model, using gamma ray (GR), density (RHOB), compressional slowness (DTC), and shear slowness (DTS) logs. Within the Areo oil field, two wells (well 001 and well 002) were correlated. The evaluated formations are still primarily composed of compacted shale and unconsolidated sandstone, with reservoir sand units exhibiting lower elastic and rock strength properties than shale units. High compressibility and porosity make sand more brittle, while low compressibility and porosity make shale stiffer due to high moduli. The maximum force that can be applied to a shale unit without causing it to fail is 17.23 MPa, which is the maximum average rock strength of the shale. It means that shale requires more vertical stress or pressure than sand does in order to deform it (15.06 MPa). The three sand prediction approaches used in the analysis of sand production predictions have cut-off values that are higher than the average values of the formations. The Schlumberger sand production index method (S/I) indicates that the reservoir has potential for sand influx in the two wells, with the average of the four reservoirs studied in wells 001 and 002 being 1.55 × 1012 psi and 1.14 × 1012 psi respectively. However, when a formation's sand production index is less than 1.24 × 1012 psi, as it is in this study, the formation is likely to produce sand. These findings support the notion that the defined sandstone units are highly unconsolidated and have a high potential for producing sands; therefore, sand control techniques must be factored into process optimization and cost reduction plans.

Predicting Sanding Potential Using Empirical Method in “Ebendo” Field, Niger Delta, Nigeria

Sand formations represent a large fraction of oil and/or gas reservoirs in the world, hence it becomes imperative to determine the competency of the reservoirs to produce sand-free hydrocarbon. This informed the empirical technique adopted in this study to evaluate elastic parameters such as shear modulus (G), bulk compressibility (Cb), shear modulus to bulk compressibility (G/Cb) ratio and Unconfined Compressive Strength (UCS) to determine sand influx in the “Ebendo” Field, Niger Delta, Nigeria. To achieve this goal, seven (7) hydrocarbon-bearing sand units with thicknesses ranging from 12.51 to 48.63 m were identified at depth range of 1884.79 - 3350.15 m across the four (4) wells. These elastic parameters were estimated at the interval of interest. The range of values obtained for G/Cb ratio in EBD (01 and 02) is 1.49 × 1012 - 5.40 × 1012 psi2 while the range of values for G/Cb ratio in EBD (04 and 06) is 0.06 × 1012 - 0.41 × 1012 psi2. This result suggests that EBD (01 and 02) have no potential to sanding while EBD (04 and 06) have a high probability of sanding when compared to the threshold value of 0.8 × 1012 psi2. The production history of the “Ebendo” Field also correlates with the findings of this study. The low values of UCS in EBD (04 and 06) also agrees with the observation. Thus, this study has shown the efficacy of using empirical method as a quick approach to predicting sand production in the “Ebendo” Field and this technique could be used in other fields with similar geological setting.

Conceptual evolution and practice of sand management

This paper focuses on understanding the conceptual evolution and practice of sand management through six stages. The geomechanical mechanisms leading to sand production are presented at different scales for comprehensive conceptualization. The concept of “conservatism” is assumed when analyzing passive and active methods for sand control and in the models and approaches to the sanding risk. There is a strong relationship between oil prices and publications (papers) about sand management and sand control. At its core, sand management considers sand production not as a problem but as a phenomenon that demands an intensive study of the genesis and mechanism of sanding. However, the risk assessment must be considered instead of avoiding sand influx as sand control currently does. This paper illustrates how the focus of technical literature and practices has adjusted its questions about sand management through different stages of understanding. Therefore, this paper helps the technical community understand sand management from its historical conceptualization and its relationship with multiple external factors.

Tectonostratigraphic evolution of a rift basin and corresponding source-to-sink systems: Implications for the western Bohai Bay Basin, North China

The Bohai Bay Basin, a typical intracontinental rift basin, records East Asia's kinematic plate history during the Cenozoic. The rifting process was driven by the counterclockwise rotation in the direction of the Pacific Plate subduction. From the early Eocene to the Oligocene, the rifting process can be divided into three stages: extension initiation, peak extension, and post-extension. The corresponding rifting rate was calculated based on 40Ar-39Ar data. Then, the provenance area evolution of the above three rifting stages was established by combining the detrital zircon U–Pb data and heavy mineral assemblage data (ZTR, GZi, and ATi). According to the results calculated by 40Ar/39Ar analysis, the topography of the sink area in the western Bohai bay basin was characterized by moderately rising subsidence rates (100 m/Ma) during the extension initiation stage (Paleocene-Early Eocene), when surface drainage was restricted to a limited area with steep channel slopes. During this stage, referring to the core description and seismic interpretation results, the fan delta distributes most of the sediment, most of which migrates from the proximal region. Until the peak extension stage, the source-sink system develops as the rate of subsidence increases (200 m/Ma), making the sink area larger, and this period involves multiple types of pathways, including synsedimentary faults and erosional valleys. Sediments from Taihang Massif and Jiaoliao Massif infill the subsidence zone at the distal end. Then, in the post-extension stage, the source-sink systems involve a multi-provenance area (i.e., sourcing from both proximal and distal areas), a large sink area, and a gentle channel gradient due to a decrease in subsidence rate (60–80 m/Ma). Catchment relief, sediment migration distance, and average fault displacement were used, and these parameters were related to the sediment supply (Qs) for the three rifting stages. We find that during extension initiation and peak extension, the source-to-sink systems show a high amount of sand influx (Qsand/) and that the ratio Qsand/Qs total shows a proportional relationship with catchment relief and average fault displacement; this relationship is inversely proportional to the catchment-unit area. Also, according to the types of pathways, we classified the source-to-sink systems during this period into three types, steep eroded pathway (Type-I S2S), gentle slope developed with several boundary faults (Type-II S2S), steep slope with observably eroded valleys or fault-troughs (Type-III S2S). The ratio of Qsand/Qs is only related to the sediment migration distance and average fault displacement in the post-extension stage. Besides the above three types of source-to-sink systems, we found that multi-stage faults developed along the slope (Type-IV S2S) predominated during this stage.

DETERMINATION OF GEOMECHANICAL ROCK PROPERTY IN THE ESTIMATION OF SANDING IN FIELD “A” IN CENTRAL NIGER DELTA

Well logs data from four wells were analysed for determining the petrophysical and geomechanical properties of two reservoirs in the study area. The parameters derived from these properties were used to predict the likelihood of the occurrence of sanding in the reservoirs of interest. Five sand production methods were used in predicting sanding in the reservoirs of interest. The results obtained from these sand prediction methods all showed that the reservoirs were not likely to produce sanding during drilling exploration and production. Reservoir geomechanical study has a significant role that cannot be neglected in the development of various hydrocarbon exploitation procedures, such as in the exploration and production, drilling and field development phase. The role of geomechanical properties have great impact on the drill bit selection, optimization of well trajectory placement, casing design, wellbore stability analysis, safe mud weight window (SMWW) prediction and sand production. Sand production is a serious problem widely existing in oil/gas production. The problems resulting from sand influx include abrasion of downhole tubular/casing, subsurface safety valve and surface equipment, casing/tubing buckling, failure of casing or liners from removal of surrounding formation, compaction and erosion; and loss of production caused by sand bridging in tubing and/or flow lines.

Acid-based cement slurry with controllable properties

Intensive occurrence of sand related problems in wells diminishes oil flow rate and leads to heavy expenses on production and equipment maintenance. Hard geological factors on field bedding, heterogeneity of reservoir porosity and permeability, strict constraints on physicochemical property of oil and produced water restrict the efficient application of several available methods and technologies for sand control. The increasing densification of sand related problems at late stages of development gives rise to implementation of different type of workover. There exist several backfilling compositions with a number of draw-backs to control sand influx from the reservoir into the well. With the purpose to work out more effective technology to ensure the consolidation of reservoir there was developed a new grouting mortar. This slurry contains cement, hydrated aluminum silicate and 7-8% hydrochloric acid solution. Barrier of grouting mortar has high resistance and adhesive characteristics and penetrates much deeper into pores increasing consolidation efficiency.

Aeolian dune accommodation space for Holocene Wadi Channel Avulsion Strata, Wahiba Dune Field, Oman

Geomorphic evolution of the Wahiba Dune Field, Oman, during the Quaternary has occurred within a set of boundary conditions that include climatic forcing of fluvial, aeolian and eustatic cycles within an active tectonic basin. Because of basin down-warping and sediment transport into the basin, evolution of the geomorphic surface has been accompanied by the generation of a distinctive stratigraphic record. The coupled geomorphic and stratigraphic record of the northeastern portion of the dune field illustrates wadi-aeolian interactions, in which a channel avulsion, likely initiated during a flood, scoured through the interdune corridor between linear dunes. Interdune outcrops (7 m thick) consist of a lower interval interpreted as deposited by ephemeral fluvial flow, but an upper interval consists of six fining-upward units, each of which is interpreted to represent a flood event that culminated in ponding followed by desiccation. Luminescence dating indicates that the channel remained open for 2–3 ka during the Holocene, but ground-penetrating radar imaging shows that dunes encroached into the channel between floods and suggests that the transition from ephemeral flow to ponding resulted from dune damming. Maximum channel width and length are unknown, but width was greater than the current interdune area, and a speculative extended channel course is identified. Subsequently, interdune strata and linear dunes were buried by crescentic dunes sourced by an influx of sand with wadi affinity. The resultant complex stratigraphic architecture illustrates the role of existing surface topography in providing local geomorphic accommodation space for short-lived, concentrated patterns of sedimentation.

Protocol for sand control screen design of production wells for clayey silt hydrate reservoirs: A case study

AbstractThe process of extracting natural gas from gas hydrate‐bearing sediments (GHBS) may yield significant sand influx due to the metastable nature of GHBS. Selecting appropriate sand control media is vital to addressing the challenges caused by excessive sand production. This study proposes a protocol called holding coarse expelling fine particles (HCEFP) for sand control design. The protocol aims to provide a new optimization method for screen mesh size selection for clayey silt hydrate reservoirs. Detailed optimizing procedures of proper candidate screen mesh sizes in hydrate exploitation well in clayey silt hydrate reservoirs are depicted based on the HCEFP. Then, the site W18, which is located in the Shenhu area of the northern South China Sea, is taken as an example to illustrate the optimization procedure for screen mesh size selection. The results reveal that complete solid retention via a standalone screen is rarely beneficial as high clay contents can adversely affect wellbore productivity due to excessive plugging. Screen aperture size selection for clayey silt hydrate wells should strike a balance between retaining coarser particles and avoiding screen blockage by the relatively fine particles. Furthermore, longitudinal heterogeneity of the PSDs also increases the difficulties associated with sand control design. Multistage sand control optimization is necessary in hydrate production wells. For Site W18, we recommend that the entire production interval can be divided into two subintervals for multistage sand control operations.

Application of image analysis technique for measurement of sand grains in sediments

This paper provides a methodological protocol for measuring diameter and other properties of mineral sand grains using an image analysis technique. The aeolian sand influx (ASI) from coastal bogs has been used to reconstruct changes in the past storminess. However, concentrations of sand grains in peat deposits, from which the ASI is calculated, tend to be low, and sieving and laser diffractometry cannot be applied. Manual counting of sands under microscope is time-consuming and less efficient because of possible human errors. This paper describes a protocol for an image analysis method used in our recent paper (Vandel et al. 2019) that overcomes those issues in sand grain measurements. After preliminary sample preparations, including loss-on-ignition and chemical pretreatments, this study uses ImageJ - a semi-automated image processing program – to analyze images captured under microscope. With proper sample size selection, pre-treatment, image capturing and image analysis settings in ImageJ described in this paper, the approach proved to be:•objective and efficient for analysing grain-size distribution even with low concentrations of sands in samples,•increasing reliability of the measurement and providing reproducible results by avoiding manual measuring processes, and•non-destructive and enabling further analyses on mineral composition and other properties of sand grains.

Biofilm microfacies in phosphoritic units of the Neoproterozoic Halkal Shale, Bhima basin, South India

The phosphatic bands of the Halkal Shale of the Neoproterozoic Bhima Basin, record an anoxic paleoenvironment, where only a few episodic depositional events introduced oxygen. In thin-sections, five distinct microfacies, caused by biofilms colonizing the ancient sea floor, can be distinguished. The microfacies document that low sedimentation rate allowed growth of biomass-rich laminae sets, whereas episodic influx of sand led to stacks of organic laminae alternating with fine sandy interlayers. Such depositional events may have also caused local rupture of biofilms and the release of small biofilm roll-ups and clasts. The ancient biofilms led to precipitation of phosphorous and iron-rich minerals and likely contributed to phosphorite formation. In modern equivalent environments, sea floor-colonizing biofilms include a high abundance of sulfide oxidizing and sulphate reducing bacteria.

Reconstruction of past storminess: Evaluation of an indicator approach using aeolian mineral grains buried in peat deposits, Estonia

This study aims to evaluate a reconstruction method of past storminess using aeolian sand influx (ASI) in peat deposits. We use high-resolution records of ASI from four peat bogs along the Estonian coast and compare those with local instrumentally-recorded storminess data since 1920 AD and with historical climatic records around the Baltic Sea over the last two centuries. Potential effects of local changes in forest cover and anthropogenic disturbances on the ASI signals are also evaluated with historical maps available for the study sites. Diameter of all sand grains >65 μm is measured with an image analysis system to detect temporal changes in the grain-size distribution. Our results demonstrate two major periods of high ASI over the last centuries in the region: during the 19th century and since the 1950s with highest values in 1980–2000 AD. Cross-correlations between the changes in ASI and the instrumentally-recorded storm days during the last century are positive and significant. High ASI values recorded during the 19th century correspond to the positive NAO indices and high cyclonic activity reconstructed in southern Sweden. We find that sand grains <250 μm in diameter add additional information for detecting changes in storminess. Temporal shifts in grain-size distribution and median diameter of mineral grains occur in every core, showing changes in the source materials through time.

Stratigraphic Revision of the Miocene Trealla Limestone (cape Range, Western Australia): Implications For Australasian Foraminiferal Biostratigraphy

AbstractOutcrops of Miocene coral-rich limestones mapped as Trealla Limestone are widespread along the coast of north-west Western Australia. Despite their central importance in Australian Miocene stratigraphy, the age of these outcrops is poorly constrained as they were only dated in their type area, and as the age assignation was based only on off-centred sections of sparse planktonic foraminifera and a broad correlation based on larger benthic foraminiferal species.This study aims to refine the dating of the Trealla Limestone in its type area, and to provide the first dating of outcrops located elsewhere in the Cape Range Anticline. Results are based on microscopic observations made on large acetate peels, which allowed the observation of numerous planktonic foraminifera, and also of serial sections of species.The coral-rich deposits mapped as “Trealla Limestone” can be divided into three age-based units in the Cape Range Anticline: (1) upper Burdigalian, (2) Langhian to lower Serravallian, and (3) Serravallian. This revised stratigraphic framework provides a standard for future correlations with sections located elsewhere in Australia. The Trealla Limestone at its type section on Mt Lefroy contains mainly upper Burdigalian strata of the mid-neritic zone, with the top of the formation marked by an erosion surface. It may in part be equivalent to the Tulki Limestone mapped elsewhere in the anticline. Further north in the anticline, the Trealla Limestone ranges stratigraphically higher into the Langhian and Serravallian in shallower water facies. An influx of quartz sand in the Cape Range Anticline, probably indicative of a wetter environment in the hinterland to the east, started during or after the Serravallian.This study also brings new insight into the environmental and stratigraphic ranges of larger benthic foraminifera from north-west Western Australia. Austrotrillina asmariensis was recorded above levels with Orbulina universa. This suggests that the species has a more extended stratigraphic range in this area than in Asia. A re-examination of the soritids reveals that Marginopora, previously recorded here, is not present in the deposits. Borelis is replaced by Flosculinella after the end of the Te Letter Stage, a zone based on larger benthic foraminifera recognized throughout the Indo-West Pacific region. The morphology of Flosculinella may be environmentally controlled, with the most globular specimens more abundant in protected and shallow environments. Finally, Cycloclypeus from the Cape Range Anticline had a similar bathymetric range to its modern analogue found in the lower part of the photic zone, as indicated by its co-occurrence with minute planktonic foraminifera.

Decadal variability of north-eastern Atlantic storminess at the mid-Holocene: New inferences from a record of wind-blown sand, western Denmark

Abstract Disentangling the external and internal forcing responsible for the variability of the Earth's climate and associated extreme events over the Holocene is crucial for producing reliable scenarios of adaptation to the effects of ongoing climate change. At mid-latitudes, significant relationships between westerly storminess, solar activity and internal atmospheric and oceanic modes of variability have been repeatedly evidenced to exist over millennial and centennial time scales. However, at shorter (decadal) scale, it is still challenging to establish clear control links between the forcing mechanisms and the spatio-temporal variability of past extra-tropical storms. This probably owes to the existence of complex multi-scale relationships and feedback loops, as well as to the difficulty of producing proxy-records of sufficiently high-resolution and wide spatial significance. Here we present a reconstruction of westerly storminess in western Denmark between 4840 and 2300 yrs. cal. B·P. Past-storminess is retrieved from an organic-rich sedimentary succession by combining markers of aeolian sand influx, μ-XRF geochemistry and plant macrofossils. Particular focus is paid to the c. 4840–4350 yrs. cal. B·P. period for which our record is characterized by a pluri-annual resolution. We evidence concurrent pluri-decadal shifts in storminess and humidity regime at our site that we interpret as relocations of the mean westerly storm-track over the North-Atlantic. The signal is dominated by ≈ 90, ≈ 50–80 and ≈ 35-yr periods, evoking possible links with solar activity, the North-Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO) and the Atlantic Meridional Overturning Circulation (AMOC) modes of variability, respectively. The ≈ 35-yr periodicity found in our record is especially strong and stationary, suggesting that storminess could have been closely linked with the AMOC over the study period. Our records of storminess indeed show some great similarities with a record of deep overflow of a branch of the AMOC. Opposite to some model outputs, the strength of the AMOC seems to have often co-varied with storminess at pluri-decadal scales over the study period. We also find periods of high storminess activity to be significantly correlated with solar minima and relative pluri-decadal lows in the NAO. We suggest that small lowering in the strength of the NAO in an otherwise positive NAO context may have caused southward relocations of the mean westerly storm-track from subpolar latitudes to northern Europe. This invites to reconsider the importance given to using the NAO as a binary index. Finally, an attempt is made to explore the temporal lead-lag relationships between storminess and different potential forcing agents such as the Total Solar Irradiance, the NAO and the AMOC. Unfortunately, the insufficient chronological precision of the proxy-records available for the TSI, the NAO and the AMOC over the study period prevents us from deriving any robust interpretations regarding potential teleconnections at a decadal-scale between past north-Atlantic westerly storminess activity, solar forcing, the NAO and north-Atlantic surface and deep oceanic circulation.

Medieval fan aggradation in the wetland fringe of Lake Shkodra, Albania

The analysis of sediment cores and auger holes from the wetland fringe of Lake Shkodra were used to interpret Late Holocene shoreline fluctuations in northwestern Albania. Dry bulk density, organic carbon, magnetic susceptibility, particle size determination, sediment composition, X-ray diffraction, and AMS 14C dating provide the basis for interpretation. The Kir River may have sourced the 50 km2 Late Pleistocene-Holocene Shtoj alluvial fan at the terminus of the 372 km2 Kir River drainage basin on the western slopes of the Bjeshkët e Namuna Mountains. However, the Kir River has not transected the fan since at least the first century BC. The vertical succession of facies in sediment cores from peat to lacustrine clay and then to over 1.1 m of alluvial silt and sand documents an expansion, then contraction of the lake to its current size after 1390 cal yr BP. Sand influx off the fan is attributed to sheetflow, rill, or gullying related to increased anthropogenic activity across the fan during Medieval time. Archaeological surveys support abandonment of hill fort dwellings for the plain around 500 CE. Since 1390 cal yr BP, the Lake Shkodra shoreline has fluctuated at least 1.5 km to the east of the present shoreline.

Tidal Flat Depositional Response to Neotectonic Cyclic Uplift and Subsidence (1–2 m) as Superimposed on Latest-Holocene Net Sea Level Rise (1.0 m/ka) in a Large Shallow Mesotidal Wave-Dominated Estuary, Willapa Bay, Washington, USA

The late-Holocene record of tidal flat deposition in the large shallow Willapa Bay estuary (43 km in length), located in the Columbia River Littoral Cell (CRLC) system (160 km length), was investigated with new vibracores (n=30) and gouge cores (n=8), reaching 2–5 m depth subsurface. Reversing up-core trends of muddy sand to peaty mud deposits in marginal tidal flat settings demonstrate episodic submergence events resulting from cyclic tectonic uplift and subsidence (1–2 m) in the Cascadia subduction zone. These short-term reversals are superimposed on longer-term trends of overall sediment coarsening-up, which represent the transgression of higher-energy sandy tidal flats over pre-existing lower-energy tidal flat mud and peaty mud deposits in late-Holocene time. Fining-up trends associated with channel lateral migration and accretionary bank deposition occurred only infrequently in the broad intertidal flats of Willapa Bay. Vibracores and gouge cores were dated by 14C (n=16) and paleo-subsidence event contacts (n=17). Vibracore median probability 14C ages ranged from 0 to 6,992 yr BP and averaged 2,174 yr BP. Dated sample ages and corresponding depths of tidal flat deposits yield net sedimentation rates of 0.9–1.2 m ka-1, depending on the averaging methods used. Net sedimentation rates in the intertidal flat settings (~1.0 m ka-1) are comparable to the rate of net sea level rise (~1.0 m ka-1), as based on dated paleo-tidal marsh deposits in Willapa Bay. Reported modern inputs of river sand (total=1.77x104 m3 yr-1), from the three small rivers that flow into Willapa Bay, fall well short of the estimated increasing accommodation space (1.9x105 m3 yr-1) in the intertidal (MLLW-MHHW) setting (1.9x108 m2 surface area) during the last 3 ka, or 3.0 m of sea level rise. The under-supply of tributary sand permitted the influx of littoral sand (1.1x105 m3 yr-1) into Willapa Bay, as based on the net sedimentation rate (~1.0 m ka-1) and textural composition (average 60 % littoral sand) in analyzed core sections (n=179). The long-term littoral sand sink in Willapa Bay’s intertidal setting (55 % of total estuary area) is estimated to be about 5 % of the Columbia River supply of sand to the CRLC system, and about 30% relative to the littoral sand accumulated in barrier spits and beach plains during late-Holocene time. A 2.0 m rise in future sea level could yield a littoral sand sink of 2.2x108 m3 in the Willapa Bay intertidal setting, resulting in an equivalent shoreline retreat of 600 m along a 50 km distance of the barrier spit and beach plains that are located adjacent to the Willapa Bay tidal inlet. Willapa Bay serves as proxy for potential littoral sand sinks in other shallow mesotidal estuary-barrier-beach systems around the world following future global sea level rise.

Quartz grains reveal sedimentary palaeoenvironment and past storm events: A case study from eastern Baltic

Sediment record collected from the coastal lake serves as a powerful tool for reconstructing changes in palaeoenvironment and understanding the potential signals of past storminess. In this study, we use several proxies from sediment of the Holocene Thermal Maximum at coastal Lake Lilaste, Latvia. We focus on surface texture of quartz grains from the mineral inorganic fraction as indicators of depositional environments. We then use this as a proxy for potential storm transport and combine with information on granulometry, diatom stratigraphy and chronology to answer the question whether flux of quartz grains in the lake originated from the sea or from the land. Analyses in a binocular and scanning electron microscope reveal that most of the investigated quartz grains originate from dwelling in the seawater and wave action in the nearshore zone. Grains representing very energetic subaqueous environment similar to storm events are also present. Terrestrial record is of minor significance and visible through occurrence of aeolian quartz grains.During drier and colder conditions, an influx of sand with aeolian imprint was delivered to the lake between 8500 and 7800 cal yr BP. Marine and terrestrial conditions alternated between 7800 and 6000 cal yr BP. Storm-induced grains were likely deposited three times: at 7300 cal yr BP, 6600–6400 cal yr BP, and 6200–6000 cal yr BP. Overall stable marine environmental conditions prevailed between 6000 and 4000 cal yr BP except of the last portion of terrestrial-induced sediment at 4100 cal yr BP.