Coarse-grained Sand Research Articles

Sediment material potential of Bone River as a prevention of silting and flood of Bone River estuary, Gorontalo

Bone River Estuary acts as a connecting lane between the three rivers (Bolango River, Bone River, and Tamalate River) with Tomini Bay. There is a port activity of goods located right on the river estuary, which is potentially disrupted due to the silting and can cause flood. This situation will undoubtedly disrupt port transportation routes and affect the economic condition of Gorontalo. The aim of this research is to identify the potential of sediment utilization at the downstream of the Bone River as an effort to prevent siltation at the estuary of river Bone, Gorontalo and to prevent flood. The method used in this research is field observation which includes observation of the morphological condition of research location and sampling. Samples will then be processed by means of sieving, separation, and classification of Sphericity sediment material by referring to zoning classification and Sneed and Folk classification. The result of histogram data showed that the sediment material was dominated by coarse sand size and grain size distribution dominated by coarse sand with size of phi is 0, on sediment data showed generally very leptokurtic with skewed skill or highly skewed.

Correlation of upper Miocene–Pliocene Lake Pannon deposits across the Drava Basin, Croatia and Hungary

Upper Miocene to Pliocene (Pannonian) sediments of the Pannonian Basin System accumulated in the brackish Lake Pannon and the fluvial feeder systems, between 11.6-2.6 Ma. Their stratigraphic subdivision has been problematic for a long time due to the laterally prograding architecture of the basin fill and the historically independently evolving stratigraphic schemes of the neighbouring countries. We correlated the lithostratigraphic units of the Lake Pannon deposits between Hungary and Croatia in the Drava Basin, using lithological, sedimentological and palaeontological data from boreholes and outcrops, and seismic correlation. The Croatica and Medvedski breg formations in Croatia correspond to the Endrőd Fm. in Hungary, comprising shallow to deep water, open lacustrine, calcareous to argillaceous marls. The Andraševec fm. in Croatia corresponds to the Szolnok and Algyő Fms. in Hungary, consisting of sandstones and siltstones of turbidite systems and of clay marls deposited on the shelf-break slope. The Nova Gradiška fm. in Croatia is an equivalent of the Újfalu Fm. in Hungary, built up of a variety of lithologies, including sand, silt, clay and huminitic clay, deposited in deltaic environments. The Pluska fm. in Croatia corresponds to the Zagyva Fm. in Hungary, consisting of variegated clays, silts, sands and lignites, deposited in alluvial and fluvial environments. Coarse-grained (sand, gravel) basal layers are assigned to the Kálla and Békés Fms. and the Sveti Matej member of the Croatica fm. Coarse-grained intercalations within the deep-water marls belong to the Dorozsma Member of the Endrőd Fm. in Hungary, and to the Bačun member of the Medvedski breg fm. in Croatia. Sediment transport and lateral accretion of the shelf edge in the Drava Basin took place from the N, NW, and W, to the S, SE, and E, respectively. According to the biostratigraphic and chronostratigraphic analyses, the oldest shelf-break slopes in the Mura Basin are more than 8 Ma old, whereas the youngest ones in the southeasternmost part of the Drava Basin may be Pliocene in age (younger than 5.3 Ma). Thus, the 180 km long and at least 700 m deep Drava Basin was transformed into a fluvial plain during the last 3.5 million years of the Miocene.

Residual Sediments of the Vema Fracture Zone, Central Atlantic

The Vema Fracture Zone orthogonally intersecting the Mid-Atlantic Ridge along 11° N is a complex tectono-sedimentary system, through which bottom water is transferred from the western to the eastern Atlantic. The southern surrounding of the fault valley is an extended (about 320 km) transverse ridge. At the early stages of the Vema System evolution, the ridge was located at shallow depths in the photosynthesis zone, which led to the formation of extensive biogenic carbonate buildups on its surface. Spreading, general sinking of the system, and associated movements along faults caused disintegration of ultramafic basement and bioherms with subsequent fractionation of colluvial–pelagic sediments and their eastward transport by bottom currents. The formation of coarse-grained residual sands completely devoid of pelitic material is associated with the high flow rates of Antarctic bottom waters. The presence of rounded pebbles of organogenic limestones and ultramafic rocks with traces of bioproductivity indicates that clastic material was transferred over a few hundred kilometers.

Statistical Characterisation of tropical seagrass bed sediment and adjacent unvegetated sediment in Lae-Lae Island of Makassar (Indonesia)

The statistical characteristic of sediment is useful in interpretation of the past or future processes acting on the sediments. This paper reports the statistical characteristic of small island sediment taken from seagrass bed and adjacent unvegetated area. Surface sediment samples were collected from four sites using a sediment corer (PVC pipe with a diameter of 6 cm and a length of 15 cm) and dry sieved in the laboratory to determine grain size distribution. The grain size measurement in mm were converted into the phi (§) unit before calculating the statistical parameters of the sediment including mean grain size, sorting, skewness, and kurtosis using a GRADISTAT (a grain size distribution and statistics package for the analysis of unconsolidated sediments). The results show that both seagrass bed sediments and adjacent unvegetated sediments in the study site are characterized by medium to coarse-grained sand fractions, mostly poorly sorted, symmetrical to very coarse skewed, and have platykurtic, mesokurtic, and leptokurtic kurtosis. These findings highlight the practical use of grain size analysis to classify sedimentary environments and elucidate transport dynamics in the Lae-Lae Island.

Patterns in diversity and composition of the microbenthos of subarctic intertidal beaches with different morphodynamics

Diversity and composition of benthic diatom algae and ciliates were studied at several beaches along the White and Barents seas: from highly exposed, reflective beaches with coarse-grained sands to sheltered, dissipative silty-sandy flats. For diatoms, the epipelic to epipsammic species abundance ratio was significantly correlated with the beach index and mean particle size, while neither α-diversity measures nor mean cell length were related to beach properties. In contrast, most of the characteristics of ciliate assemblages (diversity, total abundance and biomass, mean individual weight and percentage of karyorelictids) demonstrated a strong correlation to beach properties, remaining low at exposed beaches but increasing sharply in more sheltered conditions. β-diversity did not correlate with beach properties for either diatoms or ciliates. We suggest that wave action and sediment properties are the main drivers controlling the diversity and composition of the intertidal microbenthos. Diatoms and ciliates, however, demonstrated divergent response to these factors. Epipelic and epipsammic diatoms exhibited 2 different strategies to adapt to their environments and therefore were complementarily distributed along the environmental gradient and compensated for each other in diversity. Most ciliates demonstrated a similar mode of habitat selection but differed in their degree of tolerance. Euryporal (including mesoporal) species were relatively tolerant to wave action and therefore occurred under a wide range of beach conditions, though their abundance and diversity were highest in fine, relatively stable sediments on sheltered beaches, whereas the specific interstitial (i.e. genuine microporal) species were mostly restricted to only these habitats.

Sediment distribution along the fluvial to marine transition zone of the Dong Nai River System, southern Vietnam

Studies on the sediment distribution along the fluvial to marine transition zone are rare and have focused on large-scale systems. Here, we report a case study from the Dong Nai River System (DNRS), a small-scale, tide-dominated river delta from southern Vietnam. The study is based on 80 channel bed sediment samples, together with channel depth, temperature, and salinity measurements, identification of mangroves and mollusks, and grain-size analysis. Year-round meter-scale water-level fluctuations due to tides are present across the entire study area, whereas saline-water intrusion affects the entire studied part of the Vam Co Dong–Vam Co River and the majority of the studied part of the Dong Nai–Soai Rap River. The sediment distribution of both channels highlights the presence of a downstream area characterized by soft mud indicating active deposition, and upstream areas characterized by sand and gravel sediments with abundant bedrock clasts and other evidence of the extremely limited sedimentation (e.g., encrusting biostructures, borings, coating, and agglutinated mats). The coarser-grained sand and gravel are likely reworked from local bedrock and transported for short distances as also suggested by their angularity and the similarities with Pleistocene sedimentary and igneous rocks in the study area. The sediment of the DNRS is overall coarser and muddier than the sediment of the Mekong, likely reflecting the smaller scale of this system, the lower discharge, and the local sediment supply from the bedrock.

Diagenesis and its controls on reservoir quality of the Tambar oil field, Norwegian North Sea

A study of the diagenetic evolution of the Late Jurassic sandstones of the shallow marine facies in the Tambar oil field, Norwegian North Sea was carried out to understand its controls on reservoir quality. Core samples and a set of wireline logs obtained from three wells were used to carry out petrographic studies including light optics and scanning electron microscopy, well log analysis, fluid inclusions, X-ray diffraction (XRD) for whole rock samples, clay mineral extracts and stable isotopes. The Tambar reservoir sandstones range mainly from siltstone to fine-grained sandstones, exclusively arkoses cemented mainly by microcrystalline quartz, euhedral quartz overgrowth, dolomite cement, illite and chlorite. Early diagenetic/eodigenetic minerals include pyrite, calcite, and microcrystalline quartz and late diagenetic/mesodiagenetic minerals include quartz overgrowth, dolomite, illite and chlorite. The δ18O values of dolomite cement in the Tambar sandstone reservoir range from −11.77‰ to −3.57‰ PDB, while the δ13C values of the dolomite cement are from −5.07‰ to −1.12‰ PDB. Homogenization temperature for fluid inclusions trapped in authigenic quartz fall between 130 °C and 169 °C. The reservoir quality is controlled mainly by early formed grain-coating microcrystalline quartz that precipitated from the dissolution of sponge spicules which significantly inhibits quartz overgrowth precipitation. Oil emplacement do not show significant control on reservoir quality because considerable quartz cementation has taken place before the onset of major oil charge. Only the coarse-grained sands show a correlation between quartz cement volume and water saturation. However, the interpreted temperature for dolomite cementation is significantly higher for water leg-suggested effect of oil emplacement on the late dolomite. Understanding these controls on the reservoir quality will enhance the exploration strategy for the Tambar oil field.

Podzols on Esker in the Northern Taiga Zone of the Kola Peninsula

This study presents a genetic characteristic of iron-illuvial podzols formed on an esker composed of coarse-grained and medium-grained sands, including the gravel–pebble fractions with boulders. We have revealed quantitative differences in the composition and properties of iron-illuvial podzols on the esker as compared to iron-illuvial podzols formed on sandy moraines under similar bioclimatic conditions. These differences are related to the topography and specific lithological composition of rocks in the esker. Fluvioglacial deposits are usually described without their specification into intraglacial deposits, forming esker, and periglacial deposits formed beyond the glacier. However, this is insufficient, taking into account the differences in the topography and rocks of eskers.

A three-dimensional stratigraphic model of the Mississippi River Delta, USA: implications for river deltaic hydrogeology

A three-dimensional stratigraphic model was constructed of the upper 50 m of the Mississippi River Delta, southeastern USA. The model is used to understand hydrogeological connections among the Mississippi River, adjacent interdistributary bays and groundwater systems, and to understand how stratigraphic settings affect potential anthropically induced subsidence and erosion in the region. This study uses 619 geotechnical borings throughout the area along with the multiple-indicator natural neighbor (MINN) interpolation method to construct the model. Based on available data, the study focused on the Mississippi River reach from Head of Passes (river mouth) to Jesuit Bend (108 km upstream), covering an area of approximately 1,800 km2 and ranging in elevation from 3 to −46 m. The model shows typical basal coarse-grained sand bodies overlain by 10-m-thick blanket clay, which is interbedded frequently with silty and sandy sediments and occasionally with peat and organic clay. Sands are most abundant between elevations −10 and −35 m. The Mississippi River main channel incises the underlying sands, thereby providing pathways for river–groundwater exchange. Increased hydrologic loads may propagate along the flow paths potentially giving rise to high pore-water pressure and a resultant increase in land subsidence and thus local erosion of natural and local flood-control levees. This method of analysis may apply to other deltaic regions similarly subject to anthropically accelerated subsidence and erosion.

Stratigraphic evolution of the Nakdong River valley in response to late Quaternary sea-level changes

Sequence analysis using borehole samples and high-resolution seismic data in the Nakdong River valley yielded a good example of a river-valley sequence influenced by the complex interplay between the bottom morphology of the steep paleo-valley, varying sediment supply, and Holocene sea-level change associated with coastal currents. The late Quaternary stratigraphic sequence in the Nakdong River Estuary, approximately 60–70 m thick, forms a high-frequency sequence consisting of a set of lowstand, transgressive, and highstand systems tracts that corresponds to a fifth-order (20 ka) sea-level cycle. Four main depositional systems, including ten sedimentary facies, constitute these systems tracts: fluvial, estuarine, coastal/shoreface, and deltaic. The lowstand systems tract (LST), consisting of gravelly sand, forms a fluvial depositional system (Unit I) which fills the thalweg of river valley mainly developed before 12 ka. The transgressive systems tract (TST), showing a succession of retrograding or backstepping depositional arrangements, can be divided into two depositional systems (Unit II and III). The riverine sediments were trapped within the paleo-estuary, forming an estuarine depositional system (Unit II) developed between 12 and 7 ka. As the transgression continued, the coarse sediments were deposited and redistributed by coastal processes, resulting in coastal/shoreface depositional system (Unit III). It is characterized by an isolated sand body and thin sand veneer. The HST is composed of deltaic depositional system including delta plain, delta front, and prodelta (Unit IV). During the delta progradation, most coarse-grained sands derived from the river were deposited in the lower delta plain and delta front, forming sand bars and shoals less than 15 m deep. The remaining fine-grained sediments were transported further offshore in a suspension mode and deposited in the inner shelf off the present river mouth, forming a subaqueous prodelta. Radiocarbon and optically stimulated luminescence (OSL) dating suggest that the Holocene deltaic system was initiated by aggradational and progradational stacking patterns at approximately 8 ka during the last stage of decelerated sea-level rise, and was then followed by a prograding clinoform after the highest sea level at approximately 7 ka.

HYDROGEOPHYSICAL DELINEATION OF PROLIFIC GROUNDWATER AQUIFER AROUND STUDENTS’ HOSTELS IN FUPRE CAMPUS, NIGERIA

Electrical resistivity survey was conducted around Students’ Hostels in FUPRE to delineate prolific aquifer for potable water to serve the teeming population of staff and students. Five vertical electrical soundings (VES) using Schlumberger electrode configuration with a maximum current electrode spread of 300m were employed for data acquisition. WINRESIST software was employed to execute the iteration and inversion processes of computing resistivities, depths and thicknesses of the various layers and the curve types. Results indicate that the area is characterized by 4 distinct geoelectric layers inferred differently at the VES locations. Two potential groundwater aquifer zones are delineated. The unconfined shallow aquifer zones found at VES 1, 3, 4 and 5 locations have shallow overburden depth ranging between 3.7-19.3m and coarse-grained sand columns with thicknesses ranging between 2.8-17.7m while the confined deep aquifer zone found at VES 2 location coincides with deep overburden layer at a depth of 42.6m and coarse-grained sand column with appreciable thickness of 19.1m. These results suggest that boreholes for sustainable groundwater supply around the Students’ Hostels should be sited at VES 2 location and screened at a depth ≥40.0m. However, aquifers at VES 1, 3, 4 and 5 have potentials for groundwater but are vulnerable to contamination. It is recommenced that electrical resistivity and hydrogeological surveys should be conducted at different locations in FUPRE, before any borehole(s) are drilled, to delineate the appropriate aquifer for potable groundwater supply and to avoid possible contamination.

Moisture variations in Lacustrine−eolian sequence from the Hunshandake sandy land associated with the East Asian Summer Monsoon changes since the late Pleistocene

Paleoclimate records currently lack sufficient geographic detail to understand the spatiotemporal evolution of East Asian Summer Monsoon (EASM) rain belt since the late Pleistocene. In particular, there is no consensus on whether the EASM rain belt reached its modern northern limit by the early Holocene. Here, we present inferred moisture variations from a multi-parameter, absolute-dated lacustrine−eolian sequence from northern China that date back to the late Pleistocene (∼14 ka BP or thousand years ago). We observed a sharp transition towards wet conditions at the onset of the Holocene Epoch. Maximum wet climate occurred here during ∼11.3–8.5 ka. The climate remained predominantly wet until ∼4.2 ka, then it became progressively drier. We observed alternating organic-rich, fine-grained lake deposits and organic-depleted, coarse-grained eolian sand layers during ∼14−7 ka. These layers correspond to sedimentation associated with the Allerød, Younger Dryas (YD), post YD warming, pre-Boreal oscillation (PBO), early Holocene and 8.2 ka event. We interpreted the orbital scale moisture variation at our study site to the changes in insolation, assigning these abrupt and short-lived changes during the late Pleistocene−Holocene transition to a persistent teleconnection between the North Atlantic and east Asian climate zones.

An automated testing device for continuous measurement of the hysteretic water retention curve of granular media

The water retention curve (WRC), representing an important key for the modelling of hydro-mechanical behaviour of unsaturated soils, is still not fully understood, because it originates from microscopic hydraulic and capillary phenomena. Furthermore, its experimental measurement, especially for cyclic drainage and imbibition paths, is challenging and time-consuming. In this contribution, a recently developed low-cost easy-to-use miniature testing device for the investigation of the WRC of unsaturated granular soils, such as coarse-grained sand and a packing of glass beads, is presented. With the help of the new device, that can be controlled by a Raspberry Pi single-board computer, the hysteretic WRC can be investigated in a conventional macroscopic approach by plotting the macroscopic specimen degree of saturation versus measured matric suction. The test set-up allows an automatic measurement of the WRC which is measured continuously following a programmed test procedure. In addition to the technical realisation of the new device, this contribution focuses on macroscopic results of water retention tests. Moreover, the testing device has been designed in a miniaturised size, in order to obtain microscopic insights into the phase distribution during cyclic drainage and imbibition paths with the help of computed tomography in future applications.

Geochemistry and petrography of beach sands along the western coast of Ghana: implications for provenance and tectonic settings

The paleoweathering, provenance, and tectonic setting of sediments of the western coast of Ghana were unraveled using the geochemistry of 29 beach sands, which are characterized by coarse-, medium-, and fine-grained sizes. The coarse-grained beach sands contain higher SiO2 content (2.9-96 wt.%) than the medium-grained (4.9-94 wt.%) and fine-grained (16.1-90.7 wt.%) sands, implying that the increase in grain size is related to the increase in SiO2 content. Al2O3 and CaO concentrations are higher in the fine- and medium-grained sands than the coarse-grained sands. The beach sands are compositionally immature based on the index of compositional variable values (1.17-141) and Th/Sc versus Zr/Sc diagram although they have high SiO2/Al2O3 values. The high SiO2/ Al2O3 is not indicative of the weathering conditions of the coastal sediments in the area. The sands are chemically unaltered clastic materials of first cycle regime that still have their labile minerals retained in them very close to the sediment source based on the chemical index of alteration values, plagioclase index of alteration values, and A-CN-K and A-CNK-FM ternary diagrams. The total rare earth elements (ΣREE) content increases with decreasing grain size. However, there are some discrepancies where some coarsegrained samples have high ΣREE content. This suggests that apart from the grain size, the provenance of the sediments has direct control over their geochemical composition. The correlation of the rare earth elements patterns of the beach sands with those of adjacent source rocks points to felsic sources for their derivation. The felsic (granodioritic composition) igneous suites of the Paleoproterozoic Birimian highland rocks adjacent to the beach sediments in the western coast are possibly the source rocks of the beach sands. Rifting in the continents is the tectonic regime probably during the Paleoproterozoic times responsible for deposition of the beach sands in the western coast of Ghana.

SEASONAL SOIL FREEZING IMPACT ON FOUNDATIONS OF BUILDINGS (LIQUEFIED HYDROCARBON DEPOT TERMINAL)

The paper presents the analysis of the influence of seasonal freezing and thawing of clay soils on structural deformation. Studies are performed at the construction site of liquefied hy-drocarbon depot terminal. Additional surveys are carried out after the winter construction peri-od. In autumn and winter, loam was frozen at the base of the foundations. In spring and sum-mer, pit soils were soaked with meltand storm-water. On the pit walls erosion developed tie-in flows of meltwater at the bottom of the pit, which led to significant deviations from the de-sign position of the erected depot foundations, which were dismantled, and the concrete prepa-ration for retaining walls was destroyed almost everywhere. The study shows that the subsidence properties of loams degrade after soaking. It is there-fore unnecessary to reduce drawdown of designed and partially executed expensive measures. Initially, under the ground horizontal depots and retaining walls pile foundations are con-structed. Finally, foundations are erected in open pits with a depth of 4.0–5.8 m of monolithic reinforced concrete on a natural base. For the latter option, the project requires a large amount of excavation works at the open pit with a volume of about 10 thousand cubic meters and re-placing them by the same volume of compacted coarse-grained marble sand and gravel. It is shown that the most efficient and reliable option are pile foundations with a high grillage and also effective anti-rubble measures developed in TSUAB. In the pile variant, it is proposed to use piles 8 and 9 m long with a permissible load of 250 kN and 260 kN, respectively. The de-veloped proposals can be applied in the construction of the 2nd stage of the depot terminal.

Soil moisture dynamics modelling of a reclaimed upland in the early post-construction period

Mine reclamation landscapes typically comprise layers of mine waste materials such as tailings sands, capped with a cover soil. In addition to the arrangement and placement of these materials, their hydraulic properties govern the performance of the built system. Soil evolution due to freeze–thaw cycling can result in dramatically altered soil hydraulic properties compared to the as-built material. Therefore, prediction of present and future hydrologic behaviour relies on understanding the nature and magnitude of this change and the elapsed time associated with stabilization. This research quantifies the transient hydraulic properties of mine reclamation materials at a constructed upland within a reclaimed watershed, and models the effect of this evolution on the partitioning of soil moisture between evaporation and groundwater recharge. Soil moisture dynamics were simulated using HYDRUS-1D for the ice-free period two, three, and five years after construction. A capillary barrier between the fine-grained cover soil and coarse-grained tailings sand regulated percolation past the interface. Soil evolution of the cover soil was responsible for an increase in saturated hydraulic conductivity by an order of magnitude, decrease in air-entry pressure by a factor of 4, and decrease in the van Genuchten n parameter by a factor of 2. The altered soil hydraulic properties associated with the weathered cover soil ultimately resulted in a 64% increase in groundwater recharge as a consequence of the capillary barrier weakening. The cover soil exhibited minor spatial heterogeneity in soil hydraulic properties, and did not contribute substantial uncertainty to the estimates of groundwater recharge and evaporation. Cover soil thickness exerted a strong influence on the partitioning of soil moisture. Reclaimed uplands will provide the most recharge to downgradient ecosystems in the period following the completion of soil evolution (~4 years) but preceding substantial vegetation development.

Sedimentology and facies analysis of ancient sand ridges: Jurassic Rogn Formation, Trøndelag Platform, offshore Norway

Sand ridges represent a common type of sedimentary bedform of modern shelves seldom used as analogues to interpret isolated marine sandbodies recognised in the subsurface. Lack of extended literature on outcrop and subsurface examples limits the possibility for their recognition and seems one of the reason behind this underrepresentation. The Draugen discovery made in the early 80's represents an unicum in the Trøndelag Platform, offshore Norway. After more than 30 years the Froan Basin and Frøya High area are still underexplored and the Late Jurassic Rogn Fm play not well understood. Predicting reservoir distribution, and its internal architecture and properties requires the understanding of factors controlling sedimentation (e.g. palaeocirculation, depositional processes). North-south elongated sandbodies pertaining to the Rogn Formation are recognised in the Froan Basin and Frøya High encased within thick shaly deposits. Sandbodies develop above a ravinement or flooding surface (i.e. Callovian Unconformity) of regional extent where local depressions occur with a non-erosional concave-up top. Depressions representing the depositional loci for the accumulation of sand and development of the ridge. The presence of eastward and westward dipping reflections within the sandbodies allows identifying their large-scale architectures. Sediments form coarsening-upward vertical units characterised by a shaly base evolving upwards to medium- and coarse-grained sand forming tabular and trough cross strata. Locally, a fining upward trend characterised by plane-parallel stratification and coarse-grained massive layers is recognised. Sediments results well organised and sorted, which positively affects final porosity and permeability with values up to 30% and 6 Darcy, respectively - typical values for many sand ridges. Accordingly, sand ridges encased within thick shaly deposits can form stratigraphic traps with the potential for large hydrocarbon accumulations. The aim of the present study is to help the understanding of distribution, and internal architectures and properties of the Rogn Fm in the Trøndelag Platform.

Extreme wave events recorded in sedimentary archives of the Geropotamos River (north-central Crete, Greece)

Recent tsunami events have shown that tsunamis may propagate far inland by entering rivers mouths and may cause massive damage along the river banks. However, so far, only a few studies have been conducted such a search for studying tsunami signals in incised valley systems along the Mediterranean coasts although the tsunami hazard is high. The island of Crete is known to have been affected several times by strong tsunamis, e. g., by the AD 365 and the Late Bronze Age (LBA) Santorini tsunamis. The narrow Geropotamos River valley, distinctly incised into local bedrock and located at the northern coast of Crete and fully exposed to the Cretan Sea, was selected as a promising natural setting to search for palaeotsunami signatures in fluvial sedimentary archives. Based on a multi-electrode geoelectrical survey and a set of sediment cores, we investigated the event-geochronostratigraphic record of both the Geropotamos River mouth area and the river valley ca. 1 km upstream by means of sedimentological, geo-chemical, geochronological, geomorphological, and micropalaeontological methods. The sedimentary environment towards the present-day river mouth is dominated by (fluvio-)lagoonal muds since the mid- Holocene. These lagoonal sediments are intersected by six coarse-grained sand layers each representing an extreme wave event (EWE). EWE layers are up to several decimetres thick and are characterized by an allochthonous foraminiferal assemblage comprising shallow marine to open marine species. Also ca. 1 km further upstream, the sedimentary record revealed grain size and microfossil evidence of two high-energy events showing a clear marine imprint. Based on this, we suggest inundation from the seaside that reached minimum 1 km inland and left EWE signatures in a presently inactive external bank position of the Geropotamos River. Considering the sedimentary characteristics, the local wind and wave climate of the Cretan Sea, and the overall geomorphological setting, we interpret these EWE layers as tsunami- related. A major hiatus identified in the Geropotamos River mouth sediments seems to be related to the LBA Santorini tsunami as can be inferred based on local age-depth relations. The LBA tsunami is known to have severely hit the northern coast of Crete. However, the hiatus may also reflect changes in the subsidence rate and the local accommodation space architecture. The youngest EWE signal in the Geropotamos River archive appears to have been caused by the AD 365 tsunami event. Candidate deposits for both tsunami deposits were identified ca. 1 km further inland. Evidence of EWE impact documents channelling and acceleration effects of intruding water masses caused by the narrow and steeply incised Geropotamos River valley in an upstream direction. Further geochronological studies based on OSL dating are necessary for a reliable age control of these EWE candidate layers.

Effect of sand texture on nest quality and mating success in a fish with parental care

Nest quality is an important aspect of courtship and mate choice, offering females direct benefits through offspring survival and, if it reflects male genetic quality, also indirect ones. Nest characteristics may thus affect both male mating success and reproductive success. Using the sand goby, where males build nests by covering mussel shells or stones in sand, we tested the role of nest material in male nest site choice, nest construction, and female mate choice. We examined the effect of sand texture (coarse or fine, depending on grain size) in two different settings: (A) when the male was free to choose between nest sites in different sand textures and other males were absent, and (B) when the male was denied a choice of sand texture and another male was present behind a partition. In (B), we also examined the effects of sand texture on female preference. In (A), males took up nest sites equally often in coarse and fine sand, but nests built in fine sand had greater sand cover. In (B), there was no difference in nest sand cover, but a greater number of males, and in particular males that weighed less and had been assigned coarse sand, refrained from building a nest at all. This suggests that sand texture does affect nest building in sand gobies, manifesting itself directly through nest sand cover, or indirectly through failure to build a nest. Moreover, we found that females preferred to spawn in well-covered nests regardless of sand texture. Nests offer eggs and offspring protection from predators and inclement weather, but building material may affect both the properties of the nest and the quality of the construction. Here, we presented male sand gobies with nest sites in either fine-grained or coarse-grained sand, assessed the sand cover of the nest, and allowed females to spawn. We found that grain size influenced the amount of sand cover on the nest and affected the fraction of males that refrained from building a nest. Female spawning decision depended on the amount of sand cover, but neither males nor females expressed a preference for sand texture. Our results show that nest material is an important but indirect aspect of mating success, which may influence habitat utilization in the wild.

Makran continental margin sedimentation during the Late Holocene

Sedimentation in the Makran active margin is governed by a complex interaction of atmospheric, tectonics, and hydrodynamic setting of the northern flank of the Gulf of Oman. The mixed clastic carbonate sediments in the tectonically and hydrodynamically active environment have complicated the distribution pattern. The region is suffering from basic sedimentological data, and specifically, the sedimentation history of the Holocene deposits has been rarely studied in the Iranian coast. To deal with this deficiency, surface and core sediment samples from the Iranian continental shelf and upper slope of the Gulf of Oman have been studied using standard sedimentological techniques. The overall sediment distribution pattern demonstrates that the grain size gradually decreases from the shoreline to the deeper zones. However, some medium- to coarse-grained sand patches can be found in the deeper parts, especially in the middle part of the studied area that can be related to sediment supply of ephemeral rivers discharging into the sea in rainy seasons and (or) high-energy events (i.e., turbidites and tsunamis during the Holocene). Several horizons of the coarse-grained detrital sediments are detectable in the upper slope sediment cores. The coarse-grained materials are received from the hinterland during flash floods and could be accumulated due to mass wasting events. The elevated amount of organic materials in the upper slope indicates a deficit of dissolved oxygen that leads to preservation of organic materials in the bottom sediments.