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Coastline is a crucial dynamic transitional zone between land and open water that gets stressed by many environmental elements, which calls for monitoring sustainability. A case study from the southern Iraqi coast represents a dynamic environment experiencing instability due to active erosional and depositional processes. This study uses multitemporal bathymetric maps and geotechnic sediment characteristics to evaluate the stability of the Iraqi coastline in the northwestern Arabian/Persian Gulf. Erosion is the dominant threat, with an average shoreline retreat of − 3.48 m/year over the past 53 years. The construction of the Grand Faw Port has mitigated some erosion by blocking tidal currents and waves. This study underscores the necessity for robust coastal management strategies that encourage the development of sustainable coastal development practices, including the construction of groin walls, native reed planting, restoration of sediment pathways, and legislation for ship movement control in commercial shipping areas, to protect Iraq's coastline. [ABSTRACT FROM AUTHOR]

The Rare Earth Elements (REEs) in limestones and dolostones that develop on isolated oceanic islands, like the Cayman Islands, were acquired from the seawater in which they formed and various diagenetic processes that led to their lithification and, in some cases, pervasive dolomitization. Modern sediments from North Sound, Grand Cayman, contain up to 30.93 ppm ∑REEs and 45.23 ppm ∑REEs + Y, whereas modern corals contain up to 2.30 ppm ∑REEs and 3.65 ppm ∑REEs + Y. The limestones and dolostones in the Brac Formation (late Oligocene), the Cayman Formation (Miocene), and Ironshore Formation (Pleistocene) generally contain <7 ppm and <10 ppm, ∑REEs and ∑REEs + Y, respectively. In contrast, the Pedro Castle Formation (Pliocene) contains up to 14.18 ppm ∑REEs and 20.81 ppm ∑REEs + Y. The Distribution Coefficients for the REEs from the modern Cayman corals are similar to those determined for corals elsewhere in the world. In the modern sediments from North Sound there is a high correlation between the ∑REEs + Y and Fe and Al but a low correlation with Na and Mn. In contrast, the correlation between the ∑REEs + Y and other elements in the limestones of the Ironshore Formation and dolostones/limestones of the Brac Formation and Cayman Formation is low. The light REEs were >Limit of Quantification (LoQ) in most samples, whereas the medium REEs and heavy REEs were commonly

Despite extensive research, the environmental and temporal significance of microbial lamination is still ambiguous because of the complexity of the parameters that control its development. A 13 year monitored record of modern fast-accreting calcite stromatolites (mean 14 mm year−1) from artificial substrates installed in rapid flow in the River Piedra (north-east Spain) allows comparison of the sedimentological attributes of successive six-month depositional packages with the known climatic, hydrophysical and hydrochemical parameters of the depositional system. The stromatolites are formed of dense, porous and macrocrystalline composite laminae. The dense and porous composite laminae, which are composed of two to eight laminae consisting largely of calcified cyanobacteria, are characterized by: (i) dense composite laminae, up to 15 mm thick, mostly with successive dense laminae and minor alternating dense and porous laminae; and (ii) porous composite laminae, up to 12 mm thick, consisting mainly of porous laminae alternating with thinner dense laminae. Most of the dense composite laminae formed during the warm periods (April to September), whereas most of the porous composite laminae developed in the cool periods (October to March). Each dense and porous composite lamina represents up to or slightly longer than six months. The alternation of these two types of composite laminae parallels seasonal changes in temperature. The dense and porous laminae result from shorter (for example, intraseasonal) variations in temperature, insolation and hydrological conditions. The macrocrystalline laminae, with crystals >100 μm long, occur isolated and grouped into composite laminae up to 1·7 mm thick. Their occurrence suggests the absence or poor development of microbial mats over periods of weeks to several months. Thus, stromatolite lamination can record different-order, periodic and non-periodic changes in the magnitude of environmental parameters over a single year. These results hold important implications for the temporal and environmental interpretation of lamination in microbial structures. [ABSTRACT FROM AUTHOR]

Abstract: The Ironshore Formation on Grand Cayman consists of six unconformity-bounded units (A to F) that developed in response to repeated transgressive–regressive cycles during the Middle to Late Pleistocene. Corals and matrices in limestones from the Rogers Wreck Point (RWP), offshore George Town (GT), and western onshore (WO) areas are characterized by complex diagenetic fabrics that reflect marine (bioerosion, micrite envelopes, internal sediments, fibrous high-Mg calcite, acicular aragonite, isopachous prismatic calcite cements), freshwater phreatic (circumgranular cements, even/random blocky calcite cements), and vadose (meniscus calcite cements, blocky calcite cements) diagenesis. Throughout these limestones, the matrices have undergone more meteoric diagenetic alteration than the corals. Overall, however, no systematic stratigraphic patterns exist to the distribution of these diagenetic fabrics and it is generally impossible to link the different phases of diagenesis with specific unconformities that cap each unit. These heterogenous patterns of diagenetic features can be attributed to many intrinsic and extrinsic factors, including the original compositions of the different components in the limestones, the porosity and permeability of the substrate, the nature of the diagenetic fluids, climate, and the duration of exposure during each lowstand. Integration of available data, however, indicates that maximum diagenesis took place during the lowstands denoted by the unconformities at the top of Unit C (Marine Isotope Stage 7) and Unit D (Marine Isotope Stage 5e) when long periods of exposure were accompanied by wet climates with high annual rainfalls. [Copyright &y& Elsevier]

The Chatham Islands, at the eastern end of the Chatham Rise in the South-west Pacific, are the emergent part of a Late Cretaceous to Cenozoic stratovolcano complex that is variably covered with limestones and fossiliferous tuffs. Most of these deposits accumulated in relatively shallow, high-energy, tide-influenced palaeoenvironments with deposition punctuated by periods of deeper-water pelagic accumulation. Carbonate components in these neritic deposits are biogenic and dominated by molluscs and bryozoans - a heterozoan assemblage. The widespread Middle to Late Eocene Matanginui Limestone contains local photozoan elements such as large benthonic foraminifera (especially Asterocyclina) and calcareous green algae, reflecting the general Palaeogene sub-tropical oceanographic setting. More localized Late Eocene to Oligocene deposits (Te One Limestone) as well as Pliocene carbonates (Onoua Limestone) are, however, wholly heterozoan and confirm a generally cooler-water oceanographic setting, similar to today. Early sea floor diagenesis is interpreted to have removed most aragonite components (infaunal bivalves and epifaunal gastropods). Lack of aragonite resulted in the absence of intergranular calcite cementation during subaerial exposure, such that most carbonates are friable or unlithified. Cementation is, however, present at nodular hardground-firmground caps to metre-scale cycles. Such cements are microcrystalline or micrometre-thick isopachous circumgranular rinds with insufficient definitive attributes to pinpoint their environment of formation. The overall palaeoenvironment of deposition is interpreted as mesotrophic, resulting in part from upwelling about the Chatham volcanic massif and in part from nutrient element delivery from the adjacent volcanic terrane and coeval volcanism. Biotic diversity in tuffs is two to three times that in limestones, supporting the notion of especially high nutrient availability during periods of volcanism. These mid-latitude deposits are strikingly different from their low-latitude, tropical, photozoan counterparts in the volcanic island-coral reef ecosystem. Ground water seepage and fluvial runoff attenuate coral growth and promote microbial carbonate precipitation in these warm-water settings. In contrast, nutrients from the same sources feed the system in the Chatham Islands cool-water setting, promoting active heterozoan carbonate sedimentation. [ABSTRACT FROM AUTHOR]

A distinct lens of marine sand, up to 90 cm thick, confined vertically by peat, is found in the upper fill of a closed freshwater back-barrier lagoon on the southeast Australian coast. Coring of the deposit suggests it extends continuously up to 600 m inland and tapers landward rising to ~1.6 m above principle datum. In places the sand is overlain by accumulations of organic-rich silt that contain charophytes, indicating re-establishment of lagoon conditions. Hypotheses considered for the deposition of the sandsheet are higher Holocene sea level, storms and tsunami. Ground-penetrating radar transects of the seaward dune system suggest a penecontemporaneous erosional contact between a series of truncated pre-event dunes and several small overlying post-event dunes. Dating the sandsheet was problematic but it is confined to the last 800 years. The young age combined with a lack of associated beach deposits and evidence of wave scouring suggest that a higher sealevel hypothesis is unlikely. This sand lens is attributed to a large-scale washover event from the southeast. Based on comparisons with modern storm deposits from the same coast and sedimentological diagnostic criteria derived from studies of modern storm- and tsunami-deposited sandsheets, it is concluded that this sand deposit is the product of a short-lived, large-scale overwash event attributed to a late-Holocene tsunami. [ABSTRACT FROM AUTHOR]

The Lower Permian (Artinskian to Sakmarian) Pebbley Beach Formation (PBF) of the southernmost Sydney Basin in New South Wales, Australia, records sediment accumulation in shallow marine to coastal environments at the close of the Late Palaeozoic Gondwanan ice age. This paper presents a sequence stratigraphic re-evaluation of the upper half of the unit based on the integration of sedimentology and ichnology. Ten facies are recognized, separated into two facies associations. Facies Association A (seven facies) comprises variably bioturbated siltstones and sandstones with marine body fossils, interpreted as recording sediment accumulation in open marine environments ranging from lower offshore to middle shoreface water depths. Evidence of deltaic influence is seen in several Association A facies. Facies Association B (three facies) comprises mainly heterolithic, interlaminated and thinly interbedded sandstone and siltstone with some thicker intervals of dark grey, organic-rich mudstone, some units clearly filling incised channel forms. These facies are interpreted as the deposits of estuarine channels and basins. Throughout the upper half of the formation, erosion surfaces with several metres relief abruptly separate open marine facies of Association A (below) from estuarine facies of Association B (above). Vertical facies changes imply significant basinward shift of environment across these surfaces, and lowering of relative sea level in the order of 50 m. These surfaces can be traced over several kilometres along depositional strike, and are defined as sequence boundaries. On this basis, at least nine sequences have been recognized in the upper half of the formation, each of which is < 10 m thick, condensed, incomplete and top-truncated. Sequences contain little if any record of the lowstand systems tract, a more substantial transgressive systems tract and a highstand systems tract that is erosionally truncated (or in some cases, missing). This distinctive stacking pattern (which suggests a dominance of retrogradation and progradation over aggradation) and the implied relative sea-level drop across sequence boundaries of tens of metres are remarkably similar to some other studies of continental margin successions formed under the Neogene icehouse climatic regime. Accordingly, it is suggested that the stratigraphic architecture of the PBF was a result of an Icehouse climate regime characterized by repeated, high-amplitude cycles of relative sea-level change. [ABSTRACT FROM AUTHOR]

DNA was extracted from water and sediment samples taken from soda lakes of the Kenyan-Tanzanian Rift Valley. DNA was also extracted from microbial enrichment cultures of sediment samples. 16S rRNA genes were amplified by the polymerase chain reaction and microbial diversity was studied using denaturing gradient gel electrophoresis (DGGE) of 16S rDNA amplicons. Cloning and sequencing of single DGGE bands showed that they usually contained mixed amplicons. Several of the amplicon sequences had high identities, up to 99%, with 16S rRNA genes of organisms previously isolated from soda lakes, while others were only distantly related, with identities as low as 82%. Phylogenetic analysis of the sequenced amplicons indicated that sequences were related to the haloarchaeal, Bacillus/Clostridium, Rhodobacterium/Thioalcalovibrio/ Methylobacter, and Cytophaga/Flavobacterium/Bacteroides (CFB) groups and the enterobacteria/Aeromonas/Vibrio part of the γ3 subdivision of the Proteobacteria. [ABSTRACT FROM AUTHOR]

Abstract The Eocene-Oligocene boundary in eastern Turkey has generally been considered conformable with no break in sedimentation. To the west of Malatya in eastern Turkey, however, the Eocene-Oligocene boundary is located between the Asartepe Member of the Darende Formation (Eocene) and the overlying Muratlı Formation (Rupellian-early Chattian). Analysis of the strata below the boundary shows that fossil evidence of the Priabonian stage is missing and that the sediments just below the boundary contain numerous Microcodium. Although the precise origin of Microcodium is open to debate, it is generally agreed that they formed as a result of calcification of roots of terrestrial plants. The morphologically diverse array of Microcodium (types (1), (2), and (3); that are up to 1660 μm in diameter) found in the Asartepe Member, provides clear evidence that terrestrial plants were established before the sediments in the overlying Muratlı Formation were deposited. This study demonstrates that the presence of Microcodium can highlight the presence of a paraconformity in an otherwise conformable succession of shallow-water sediments. [ABSTRACT FROM AUTHOR]

Sediment records left by coastal hazards (e.g. tsunami and/or storms) may shed light on the sedimentary and hydrodynamic processes happening during such events. Modern onshore and offshore sediment samples were compared with the 2004 Indian Ocean Tsunami, three palaeotsunami and a 2007 storm deposit from Phra Thong Island, Thailand, to determine provenance relationships between these coastal overwash deposits. Sedimentological and stratigraphic characteristics are generally inadequate to discriminate tsunami and storm deposits so a statistical approach (including cluster analysis, principal component analysis and discriminant function analysis) was used based on grain size, mineralogy and trace element geochemistry. The mineral content and trace element geochemistry are statistically inadequate to distinguish the provenance of the modern storm and tsunami deposits at this site, but the mean grain size can potentially discriminate these overwash deposits. The 2007 storm surge deposits were most likely sourced from the onshore sediment environment whereas all four tsunami units statistically differ from each other indicating diverse sediment sources. Our statistical analyses suggest that the 2004 tsunami deposit was mainly derived from nearshore marine sediments. The uppermost palaeotsunami deposit was possibly derived from both onshore and nearshore materials while the lower palaeotsunami deposits showed no clear evidence of their sediment sources. Such complexity raises questions about the origin of the sediments in the tsunami and storm deposits and strongly suggests that local context and palaeogeography are important aspects that cannot be ignored in tsunami provenance studies. [ABSTRACT FROM AUTHOR]

Understanding landscape evolution on geological time scales has become increasingly important in the light of recent climate warming and intensified land use. Uranium isotopes ((234U/238U) activity ratios) can be used to reconstruct catchment-wide erosion from fine-grained detrital matter, as the lighter nuclide 234U is lost from grains <63 μm into surrounding pore space in a weathering profile, during transportation, and after final deposition. Thus, (234U/238U) activity ratios are a measure for the time elapsed since comminution of bedrock into detrital sediment. When applied to detrital grains in sedimentary deposits, the comminution age allows derivation of past variations in sediment residence time, i.e. the amount of time for which sediments are stored on hillslopes and transported. Loss of 234U is mainly attributed to recoil of 234Th during α-decay of 238U. However, mobilisation of 234U is also controlled by preferential oxidation and leaching of 234U from detrital grains. Further considerations are required concerning the sediment mineralogy and uranium bound to authigenic or endogenic matter. Here, we extend the discussion about the controls on previously published (234U/238U) activity ratios and uranium concentrations of detrital matter along a 5.43 m-long, Late Glacial to Holocene sedimentary record from Lake Ohrid (North Macedonia, Albania). Lake Ohrid is chosen to study how erosion responds to anthropogenic disturbances and climate variability, which are common through the Late Pleistocene and Holocene in the Mediterranean Region. We compared uranium concentration and isotope data to redox-sensitive, mineralogical and biogeochemical proxies. Mineralogical and biogeochemical data show no control on uranium concentration and (234U/238U) activity ratios. Rock magnetic redox proxies indicate uranium mobilisation from detrital matter in more oxic environments. No correlation between (234U/238U) activity ratios and rock magnetic data is observed, which implies that the redox environment has no control on the isotope signal. Monte Carlo simulations reveal that post-depositional preferential mobilisation of 234U has only negligible impact on the calculated sediment residence times. Our model implies that pre-depositional leaching can results in shorter sediment residence times but low (234U/238U) activity ratios during cold and dry intervals imply that recoil is likely the main processes explaining loss of 234U from the detrital grain. This is explained by the time scales studied herein in (>10,000 years), during which preferential leaching is seen to be not significant. [ABSTRACT FROM AUTHOR]