Sea Level Change

Ce document représente un guide pratique de pétrologie sédimentaire expérimentale pour les étudiants régulièrement inscrit en troisième année de géologie ainsi que pour les passionnés du domaine. Il permet de faire acquérir les connaissances de bases aux étudiants afin que ces derniers soient bien préparés lors des sessions d'examens.

We have generated a new high‐resolution record of variations in planktonic foraminiferal oxygen isotopes (δ18O) and Mg/Ca from a sediment core (IMAGES 97‐2141) in the Sulu Sea located in the Philippine archipelago of western tropical Pacific. This record reveals distinct, suborbital‐scale δ18O changes, most notably during Marine Isotope Stage 3 (MIS3) (∼30,000 to 60,000 years B.P.). The amplitudes of these δ18O fluctuations (0.4 to 0.7‰) exceed that which can be attributed to sea level changes and must be due to changes in sea surface conditions. In the same interval, variations in planktonic foraminifera Mg/Ca suggest that suborbital surface ocean temperature variations of 1 to 1.5°C in the Sulu Sea were not in phase with δ18O. Combined, this evidence indicates that the MIS3 millennial δ18O events in the Sulu Sea were primarily the result of changes in surface water salinity, which today is directly related to the East Asian Monsoon (EAM) and its influence on the balance between su...

Bungonia Caves are renowned for their high levels of foul air. As early as 1900 a report by Oliver Trickett (Trickett, O., 1901) mentions the presence of foul air which prevented the full exploration of “Bungonia Cave” (now known as Grill Cave B-44). During 1923, foul air caused Ayre and Jones along with others, to mount a concentrated effort to excavate the
Efflux (B67). The work being initially financed by the Goulburn Chamber of Commerce. This was the first of many attempts to drain the sumps of water and thus flush foul air from the lower passages of some caves.

Certainly one could spend much time researching reports by these early speleologists who ventured deep into the unknown cavities of this subterranean world. Many were driven back by the effects of foul air, others undertook scientific studies to try and determine the source of the gasses. Possibly the first to study foul air was Burke during the early 1950’s. He collected air samples from Drum Cave and Putrid Pit and analysed them with a Haldane gas analysis unit. Over the years thousands of gas samples have been taken by numerous researchers and their analysis recorded. Study and speculation on the origin of the cave atmospheres has been a contentious issue for many years and no doubt will continue to be a hot subject for many
years to come given the complexity of possible scenarios which differ from cave to cave. One should also bear in mind that not every cave at Bungonia contains foul air and levels in those which do, may change from day to day or even in a shorter time frame. However potentially lethal concentrations of foul air have been recorded in isolated pockets of a few caves.

One may well ask; what exactly is foul air, how is it life threatening to humans, where do the gasses come from, how can I detect it without sophisticated equipment and what are some basic safety tips? This chapter will cover these questions in layman terms so that the average caver can have an appreciation of the hazards they may face below ground at Bungonia.

Like most ice caps and glaciers worldwide, Icelandic glaciers are losing mass and retreating as a result of a warming climate. Here, the evolution of Vatnajökull ice cap, Iceland, from 1980-2300 is simulated by one-way coupling of Regional Climate Models (RCMs) with the Parallel Ice Flow Model (PISM). For reanalysis data, we rely on HARMONIE simulations forced by ERA-interim, which have previously been evaluated over Vatnajökull. For future climate conditions we rely on available Coordinated Regional Downscaling Experiment (CORDEX) simulations under the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios.

The surface and bed topograhy of Vatnajökull, Hofsjökull and Langjökull ice caps have been constructed from GPS and radioecho surveys (Björnsson, 1986, 1988, Björnsson et al., 2006a) and mass balance measurements conducted over the last 9 to 18 years (Björnsson et al. 1998, 2002, 2006; Sigurðsson 1989- 2004). A degree-day mass balance model, using records of meteorological stations away from the glaciers, was calibrated against the observations of winter and summer balance (Jóhannesson et al., 1995; Jóhannesson, 1997). We used ...

The effects of human activities and sea-level changes on the spatial and temporal behaviour of the coupled mechanism of salt-water and freshwater flow through the Godavari Delta of India were analysed. The density driven salt-water intrusion process was simulated with the use of a SUTRA (Saturated-Unsaturated TRAnsport) model. Physical parameters, initial heads, and boundary conditions of the delta were defined on the basis of available field data, and an areal, steady-state groundwater model was constructed to calibrate the observed head values corresponding to the initial development phase of the aquifer. Initial and boundary conditions determined from the areal calibration were used to evaluate steady-state, hydraulic heads. Consequently, the initial position of the hydraulic head distribution was calibrated under steady-state conditions. The changes of initial hydraulic distribution, under discharge and recharge conditions, were calculated, and the present-day position of the interface was predicted. The present-day distribution of hydraulic head was estimated via a 20-year simulation. The results indicate that a considerable advance in seawater intrusion can be expected in the coastal aquifer if current rates of groundwater exploitation continue and an important part of the freshwater from the river is channelled from the reservoir for irrigation, industrial and domestic purposes. Key words salt water intrusion; numerical modelling; SUTRA model; impacts of sea-level change; climate change impacts; Godavari Delta, India Modélisation numérique de l'intrusion d'eau saline, due aux activités humaines et à la variation du niveau de la mer, dans le delta du fleuve Godavari en Inde Résumé Cet article présente l'analyse des effets, d'une part des activités humaines et d'autre part des variations du niveau de la mer, sur l'évolution spatiale et temporelle des flux d'eau salée et d'eau douce dans le delta du fleuve Godavari en Inde. Le processus d'intrusion saline, régi par la densité, a été simulé avec le modèle SUTRA (de l'anglais Saturated-Unsaturated TRAnsport). Les paramètres physiques, les conditions initiales et les conditions aux limites du delta ont été identifiées à partir de données de terrain disponibles, et un modèle hydrogéologique régional permanent a été construit pour caler les caractéristiques de l'aquifère lors de l'initialisation. Les conditions initiales et limites déterminées à partir du calage régional ont permis d'évaluer en conditions permanentes les zones de front. Par conséquent la distribution initiale des zones de front hydraulique a été calée en conditions permanentes. Les changements de cette distribution initiale, sous conditions de vidange et de recharge, ont été calculés et l'évolution de la position actuelle de l'interface a été prédite grâce à une simulation sur 20 ans. Les résultats indiquent qu'une progression importante de l'intrusion marine dans l'aquifère côtier peut être attendue si les taux actuels d'exploitation de l'eau souterraine perdurent et si une proportion importante de l'eau douce des cours d'eau est détournée pour satisfaire l'irrigation et les usages industriels et domestiques. Mots clefs intrusion d'eau saline; modélisation numérique; modèle SUTRA; impacts du changement du niveau de la mer; impacts du changement climatique; delta du Godavari, Inde Open for discussion until I February 2003

During the detailed excavations of ancient Caesarea, Israel, East Mediterranean, 64 coastal water wells have been examined that date from the early Roman period (with the oldest occurring in the 1st century AD), up to the end of the Crusader period (mid-13th century AD). The depths of these coastal water wells establish the position of the ancient water table and therefore the position of sea level for the first century AD up to 1300 AD. The connection between the coastal water table and changes in sea level has been established from modern observations in several wells on time scales of days and months and this is used to reconstruct sea level during historical time. The results indicate that during the Byzantine period, sea level at Caesarea was higher by about 30 cm than today. The Late Moslem and Crusader data shows greater fluctuations but the data sets are also much smaller than for the earlier periods. The consistency of the data indicates that the near-coastal well data from Caesarea provides a reliable indicator of sea-level change, with an accuracy of about 10 -15 cm. These results are consistent with observations for earlier periods and, with comparisons to model-predicted glacio-hydro isostatic sea-level change, indicate that ocean volumes have been constant for much of the past 2000 years. The well data is also consistent with an absence of significant vertical tectonic movement of the coast at Caesarea over about 2000 years.

Variations of magnetic mineral concentrations in shallow marine environments appear to be in tune with a depth index derived from facies cyclicity. Two platforms (Latemar and Monte Agnello, Southern Alps, Italy) were chosen to verify this idea. No magnetic data could be collected from Monte Agnello because of the strong dolomitization of the buildup. In the Latemar the magnetic signal appears related to aeolian dust, while facies ranking seems a proxy for sea level changes. Facies ranking and magnetic parameters result uncorrelated even if their spectra are similar. This suggests that two independent global proxies are beating at the same frequencies, and implicates climate variations as part of the cause of the Latemar carbonate cyclicity. Lastly, facies analysis revealed the growth history of the so far unknown Agnello platform and a consistent microbial contribution for the formation of Latemar platform (especially in the slopes).

A data archeology exercise was carried out on sea level observations recorded during the transit of Venus across the Sun observed in 1874 from Saint Paul Island (38°41′S, 77°31 E) in the southern Indian Ocean. Historical (1874) and recent (1994–2009) sea level observations were assembled into a consistent time series. A thorough check of the data and its precise geodetic connection to the same datum was only possible thanks to the recent installation of new technologies (GPS buoy and radar water level sensor) and leveling campaigns. The estimated rate of relative sea level change, spanning the last 135 years at Saint Paul Island, was not significantly different from zero (−0.1 ± 0.3 mm yr−1), a value which could be reconciled with estimates of global average sea level rise for the 20th century assuming the DORIS vertical velocity estimate at Amsterdam Island (100 km distant) could be applied to correct for the land motion at the tide gauge. Considering the scarcity of long‐term sea ...

The problem of correcting the tide gauge records for the vertical land motion upon which the gauges are settled has only been partially solved. At best, the analyses so far have included model corrections for one of the many processes that can affect the land stability, namely the Glacial-Isostatic Adjustment (GIA). An alternative approach is to measure (rather than to model) the rates of vertical land motion at the tide gauges by means of space geodesy. A dedicated GPS processing strategy is implemented to correct the tide gauges records, and thus to obtain a GPS-corrected set of 'absolute' or geocentric sea level trends. The results show a reduced dispersion of the estimated sea level trends after application of the GPS corrections. They reveal that the reference frame implementation is now achieved within the millimetre accuracy on a weekly basis. Regardless of the application, whether local or global, we have shown that GPS data analysis have reached the maturity to provide useful information to separate land motion from oceanic processes recorded by the tide gauges or to correct these latter. For comparison purposes, we computed the global average of sea level change according to Douglas (2001) rules, whose estimate is 1.84 ± 0.35 mm/yr after correction for the GIA effect (Peltier 2001). We obtain a value of 1.31 ± 0.30 mm/yr, a value which appears to resolve the 'sea level enigma' .

In the Red Sea the haline flux is negative throughout the year and its contribution is secondary compared to thermal flux. At the northern region, from October to March, the thermal buoyancy flux is more negative compared to central and southern regions. As a response to the pressure gradient generated by this negative buoyancy flux in winter, a NNW surface current will be induced. During this time, the winds over the southern Red Sea are from SSE. The two forcing factors; buoyancy flux and the wind stress will reinforce the NNW flow. During summer, from June to September, there is a reverse pattern of buoyancy flux to that of winter i.e. a positive buoyancy flux in the north and negative in the central and southern regions. This buoyancy pattern will generate a pressure gradient towards the south resulting in a SSE flow. During this time the winds over the Red Sea are from NNW. The two forcing; pressure gradient towards the south and the NNW winds will favour each other to induce S...

ABSTRACTWe analyzed the latest Early Cretaceous to Miocene sections (∼110–7 Ma) in 11 New Jersey and Delaware onshore coreholes (Ocean Drilling Program Legs 150X and 174AX). Fifteen to seventeen Late Cretaceous and 39–40 Cenozoic sequence boundaries were identified on the basis of physical and temporal breaks. Within‐sequence changes follow predictable patterns with thin transgressive and thick regressive highstand systems tracts. The few lowstands encountered provide critical constraints on the range of sea‐level fall. We estimated paleowater depths by integrating lithofacies and biofacies analyses and determined ages using integrated biostratigraphy and strontium isotopic stratigraphy. These datasets were backstripped to provide a sea‐level estimate for the past ∼100 Myr. Large river systems affected New Jersey during the Cretaceous and latest Oligocene–Miocene. Facies evolved through eight depositional phases controlled by changes in accommodation, long‐term sea level, and sedime...

The present work aims to study the microfacies, depositional environment, and foraminiferal biostratigraphy of the Upper Miocene Benghazi Formation at the As Sahabi area in Ajdabyiah Trough, eastern Sirt Basin. It has been measured, described, and sampled from the type section at the P53 locality. Seventeen samples have been collected and subjected to both petrographic thin sections analysis and a foraminiferal investigation. Lithologically, the Benghazi Formation in the study area is dominated by carbonates, siliciclastics, and evaporites. The biogenic components of the examined Benghazi Formation consist of microfossils (planktic foraminifera, larger foraminifera, small benthic foraminifera, bryozoans, ostracods and bony fish teeth), whereas the macrofossil content includes bivalves, gastropods, echinoids, barnacles, coral, and coralline red algae (rhodolith algae). Detailed analyses of lithology, paleontology, and petrography of the Benghazi Formation led to the discrimination of eight sedimentary microfacies types forming four shallowing-upward cycles and one deepening-upward cycle. These facies include one type of clastic facies (F1: claystone) and seven types of grain-supported carbonate facies (F2: sandy algal dolomitic packstone, F3: ostracodal pelletal limestone, F4: gypsified bioskeletal limestone, F5: sandy bioclastic floatstone, F6: gypsiferous fossiliferous limestone, F7: sandy foraminiferal-bioclastic packstone, F8: planktic foraminiferalargillaceous packstone). They have accumulated in a range of depositional environments from continental lacustrine setting to marine inner shelf (open lagoon, restricted lagoon, and shoal) and middle shelf environments. Taxonomically, a total of 49 species belonging to 27 genera of foraminifera were identified. Their stratigraphic distribution allowed the establishment of two successive biozones, the late Tortonian Neogloboquadrina humerosa/Nq. acostaensis concurrent rang Zone and the Tortonian-Messinian Borelis melo melo total rang Zone. This study also discussed the local paleogeographic distribution of the Middle to Late Miocene marker Borelis melo melo from various Libyan sections.

We examine the change in terminus positions of glaciers flowing into the western Ross Sea, Antarctica, between 71°S and 78°S as a proxy for changes in snowfall and/or summer air temperature. This coastline's major glaciers terminate in ice tongues, which are particularly sensitive to changes in flow rate and calving. Using historic maps and satellite imagery spanning 60 yr (A.D. 1955-2015), the terminus positions, ice speed, calving rates, and ice front advance and retreat rates for 34 glaciers are documented. Additionally, changes in regional ice flow speed from 2008 to 2014 are examined. No significant spatial or temporal patterns of terminus position, flow speed, or calving emerged, implying that the conditions associated with ice tongue stability are unchanged. A weak trend of advance may be present in the northernmost part of the coast, consistent with estimates of increased snow accumulation and glacier mass balance in that region. The stability of these glaciers over the past half century contrasts sharply with the rapidly shrinking glaciers of the Antarctic Peninsula and suggests that no significant climate change, as manifest in glacier change, has reached this region of Antarctica.

Analyses of over 6600 km of reflection seismic profiles on the northern continental margin of the South China Sea permit the recognition of four Quaternary high-frequency type 1 sequences of the 4th order, deposited during the past ca. 690 kyr. At the present-day shelf edge, only lowstand systems tracts characterised by a prograding clinoformal internal reflection pattern are preserved. The prograding complexes can be considered as regressive units accumulated during relative sea-level falls. They exhibit internal discontinuities which might point to minor sea-level fluctuations of the 5th order. A preliminary regional relative sea-level curve for the past 630 kyr is established using the present positions of the delta fronts mapped. The neotectonics curve derived by subtracting eustatic sea-level changes from the relative sea-level curve shows that the depths of the delta fronts today are controlled primarily by regional tectonic movements and the global sea-level. Our seismo-stratigraphic interpretation documents that the area off Hong Kong and around the Dongsha Islands experienced two uplift episodes during the past 5 ma, namely at the Miocene/Pliocene boundary and at the end of the lower Middle Pleistocene, respectively. These uplift events which are centred on the Dongsha Rise led to its subaerial exposure and to the erosion of the Pliocene and most of the Pleistocene strata. The change from thermal subsidence of the continental margin initiated at the end of the drift phase to the phase of magmato-tectonic uplift was caused by a reorientation of the tectonic regime. The Recent depositional environment on the northern continental margin of the South China Sea is dominated by sediment accumulation within the inner shelf and the Zhujiang (Pearl River) estuary. The outer shelf and upper slope, especially around the Dongsha Islands, are characterised by bypass of terrigenous material. The sedimentary column in the deepsea basin has a thickness of more than 2 km and comprises 14 depositional units starting with terrestrial rift deposits. It overlies oceanic as well as transitional crust.

In the Piedmont region (NW Italy) between the SW Alps (Paleozoic -Mesozoic) and the hills of the Langhe domain (Tertiary) there is an extensive flood plain (1.790 km 2 ) consisting of a series of overlapped alluvial fans originated by the quaternary geological activity produced by the evolution of several rivers which drain the Alps. These alluvial deposits overlap a Tertiary sedimentary succession through a series of erosional unconformity surfaces. The quaternary deposits highlight a variable thickness ranging from 80 to 100 m in the foothills of the mountains up to a few meters in the more distal portion of the plain. In these deposits there are several unconfined aquifers which are not interconnected from the hydraulic point of view due to the deep fluvial incisions that reach the underlying tertiary substrate. This plain is intensively populated and lot o f villages and farms characterize the landscape. In the overall area it is present an intensive agricultural and livestock activity predominantly represented by crops of wheat and corn and farms of cattle and pigs. All these activities require a considerable amount of groundwater which is withdrawn from the quaternary aquifers by means of thousands of water wells. The groundwater quality is strongly influenced by the content of nitrates and manganese. The nitrates are certainly linked to pollution due to agricultural activities and livestock and increase along the groundwater flow lines. The manganese content is quite high in the foothills of the mountains and in some restricted areas of the plain and appears to be linked to the natural lithological composition of the aquifers. Dans la région du Piémont (nord-ouest de l'Italie) entre les Alpes SW (Paléozoïque -Mésozoïque) et les collines du domaine Langhe (Tertiaire), il est une vaste plaine d'inondation (1.790 km

The Pliensbachian-Toarcian transition was characterised by a drastic turnover from a cool climate to a period of rapid global warming. While the warming associated with the Early Toarcian Oceanic Anoxic Event is rather well-studied, the cause, intensity and extent of the preceding cooling in the late Pliensbachian are still discussed. Occurrences of glendonite play an important role in this debate, since glendonite is a pseudomorph after the cryophilic carbonate mineral ikaite. This study describes the first glendonite-bearing carbonate concretions from South Germany (Buttenheim clay pit, northern Franconian Alb), which represent the southernmost glendonite occurrence in the late Pliensbachian documented so far. Based on petrographical and sedimentological investigations as well as stable isotope analyses it is concluded that a low temperature was the main factor for ikaite formation in the studied section, suggesting that the late Pliensbachian cooling had a more far-reaching impact on the temperature of the European epicontinental sea than previously assumed. To explain the low temperatures required for ikaite precipitation, a model for the sea-ice driven formation of cold bottom-water masses on the continental shelf is proposed. The occurrence of several layers containing reworked hiatus concretions in the studied outcrop is interpreted as the result of recurrent sea-level falls caused by multiple glacial pulses characterising the overall cool climate in the late Pliensbachian.

In 2009, the IGMI (Italian Geographic Military Institute) defined a new geodetic reference frame (ETRF2000) based on the new Italian geodetic reference frame RDN (Rete Dinamica Nazionale), a network consisting of about 100 permanent GNSS stations homogeneously distributed throughout the Italian peninsula. A key characteristic of the RDN network is its dynamic nature: the coordinates of the GNSS stations will be computed periodically to take into account the natural changes of the crustal surface. To date, a first computation of the RDN has been implemented during January 2009 by the IGMI using a dataset of 28 Julian Days and the Bernese scientific software. For the validation of the network, other Analysis Centers have been involved in the computation using the same software. One of these Analysis Centers is the Dept. DISTART (University of Bologna) that for this computation has used tree different software packages. This paper presents dataprocessing results for the same dataset (k...

Paleoecological reconstructions of Holocene sea-level changes in Argentinean coastal regions were based mainly on ecological data gathered from other regions, as there was a lack of information on modern estuarine diatom distributions. The aim of the present work was to assess the spatial variation of diatom assemblages in two representative estuaries of Argentina in order to gather ecological information for paleoecological reconstructions in the region. The two selected estuaries have different geomorphologic features and salinity regimes: Mar Chiquita Lagoon is shallow, which prevents the development of a stable salinity gradient as it occurs in the Queque´n Grande River. Surface sediment samples were taken from selected stations representative of the environmental gradient from the inlet to the inner reaches of both estuaries. Cluster analysis defined three diatom zones at Mar Chiquita: marine/brackish assemblages dominate the inlet (zone I), where salinity, tidal range and current speed are higher. The brackish/freshwater tychoplankton Staurosira construens var. venter and Staurosirella pinnata dominate the inner lagoon (zone II), where environmental conditions are very variable and concentrations of suspended sediments are higher. Brackish/freshwater euryhaline diatoms dominate the headwaters (zone III). On the other hand, the Queque´n Grande River was divided into three diatom zones: coastal taxa are distributed at the inlet (zone I), while the middle estuary (zone II) is dominated by brackish/freshwater euryhaline taxa. At the upper estuary region (zone III), freshwater diatoms dominate, and the halophobous Nitzschia denticula increased in abundance values. Diatom distributions were most closely related to the salinity gradient at Queque´n Grande River than at Mar Chiquita Lagoon. Fossil data of a sequence from Mar Chiquita Lagoon (Las Gallinas Creek) were compared to the modern data set in order to search for analogies between fossil and modern diatom assemblages. DCA results showed that fossil diatom assemblages have modern counterparts. Most diatom assemblages of Las Gallinas Creek fall within Mar Chiquita zone III, representing a shallow brackish/freshwater environment, with low salinity fluctuations ($1-9&) and no tidal influence. Therefore, our modern diatom data provide useful analogs to interpret paleoenvironments in the region.

The Barremian–Early Cenomanian Bjarni Formation on the Labrador Shelf overlies rift-related volcanic rocks of the Alexis Formation or Paleozoic or Precambrian basement. Seismic sections show that it accumulated in tectonically deforming rift basins trending NW-SE. We sedimentologically logged all available conventional core from 9 wells, assessed sediment sources by point counting and bulk geochemistry of sandstones, and examined diagenetic features. Most sediments are lacustrine, fluvial or alluvial fan, or at the top of the formation, marginal marine. Some of the marginal marine facies appear tidal, others show dominance of river flood supply. Sandstones are arkosic, but show differences in petrology and geochemistry from south to north. As in correlative rocks of the Scotian basin, Ti is unusually abundant and Ca particularly low. Sediments appear to have been supplied locally. Diagenetic kaolinite is present in places. Diagenetic siderite is concentrated at abrupt changes in sed...

During Leg 101, the inaugural leg of the Ocean Drilling Program, the JOIDES Resolution drilled 19 holes at 11 sites in the Bahamas. Grids of high-resolution seismic profiles provided information crucial for both site selection and re gional stratigraphic interpretations. The first major scientific objective was to understand the long-term evolution of the bank-and-basin pattern that currently characterizes the Bahamas archipelago. Drilling and seismic surveys have indi cated considerable platform expansion and retreat rather than stationary upward growth. Upbuilding in the Late Juras sic-Early Cretaceous was followed by drowning and retreat in the mid-Cretaceous and by renewed expansion in the Ce nozoic. At Site 627 on the southern Blake Plateau, the stratigraphic succession consists of shallow-water platform car bonates/evaporites (late Albian), marly limestones of a mixed terrigenous/carbonate shelf (latest Albian-middle Cenomanian), carbonate ooze of an oceanic plateau (Campanian-Miocene), and finally the turbidite apron of an ad vancing platform (Neogene). The top of the upper Albian shallow-water platform is characterized seismically by an acoustic unconformity, an amplitude contrast, and a velocity transition (from 2.8 to 4.2 km/s). Jump correlation of a similar acoustic horizon underlying the Straits of Florida (Site 626) with the Great Isaac 1 well on Great Bahama Bank approximately 60 km away suggests that deep-water carbonates in the Straits are also underlain by a mid-Cretaceous shallow-water platform. Delineating the evolution of platform flanks was the second major scientific objective of Leg 101. Modern facies belts were traced back through the Neogene record in two slope transects. A gentle (2°-3°) slope (north of Little Ba hama Bank) is characterized by fine-grained sediments and erosional gullies. Coarse material bypasses the slope in tur bidity currents and is deposited on debris aprons. With an increase of slope angle to 10°-12° (southeastern Exuma Sound), the zone of maximum accumulation shifts from the slope to the debris apron, probably because of increased turbidity-current activity. Slumps, debris flows, and turbidites are unusually abundant in the lower and middle Miocene sections and are probably caused by tectonic activity (the "Abaco event") superimposed on long-term slope evolution. Detailed stratigraphy of the two slope transects supports "highstand shedding," the concept that maximum input of platform sediment to the deep sea occurs during highstands rather than lowstands of sea level. Pleistocene glacial peri ods as well as postulated eustatic lowstands in the Messinian and Pliocene correspond to hiatuses or intervals of slow sedimentation on platform flanks, and perhaps to karst horizons on the platform tops. Diagenesis of periplatform ooze is rapid. Both high-magnesium calcite and aragonite decrease with depth, and dolo mite precipitates. However, lithification is discontinuous and incomplete to burial depths in excess of 200 mbsf and ages of 10-15 Ma.

Ashmore Trough in the western Gulf of Papua (GoP) represents an outstanding modern example of a tropical mixed siliciclastic‐carbonate depositional system where significant masses of both river‐borne silicates and bank‐derived neritic carbonates accumulate. In this study, we examine how benthic foraminiferal populations within Ashmore Trough vary in response to sea level–driven paleoenvironmental changes, particularly organic matter and sediment supply. Two 11.3‐m‐long piston cores and a trigger core were collected from the slope of Ashmore Trough and dated using radiocarbon and oxygen isotope measurements of planktic foraminifera. Relative abundances, principal component analyses, and cluster analyses of benthic foraminiferal assemblages in sediment samples identify three distinct assemblages whose proportions changed over time. Assemblage 1, with high abundances of Uvigerina peregrina and Bolivina robusta, dominated between ∼83 and 70 ka (early regression); assemblage 2, with high...

Eustasy is a key parameter to understand sedimentary sequences on continental margins and to reconstruct continental ice volume in the Cenozoic, but timing and magnitude of global sea level changes remain controversial, especially for the Miocene Epoch. We analyzed sediment cores recovered from the Marion Plateau, offshore northeastern Australia, during Ocean Drilling Program (ODP) Leg 194 to define the mechanisms and timing of sequence formation on mixed carbonate-siliciclastic margins, and to estimate the amplitude of Miocene eustatic adjustments. We identified sequence boundaries on seismic reflection lines, significantly revised the existing biostratigraphic age models, and investigated the sedimentary response to sea-level changes across the Marion Plateau. We subdivided the Miocene sediments into three sequence sets comprising a set of prograding clinoforms, a muddy prograding carbonate ramp evolving into an aggrading platform, and a lowstand ramp evolving into a backstepping ramp. We recognized eight individual sequences dated at 18.

The Indonesian island of Sulawesi occupies a central position withim the biogeographically complex region known as Wallacea. Its fauna is characterised by a lugh rate of endemism and a patchwork distribution of taxa within the island. The grasshopper genus Chituura is a good example having at least ten endemic species with predominantly parapatric distributions. It can be used as a model for determining the origins of Sulawesi taxa and the within-island evolution that has led to the present patterns of distribution. Here we present a phylogenetic hypothesis for 28 individuals within the genus, including individuals of one species from Java and two from the Moluccas, based on DNA sequences of the mitochondrial cytochrome oxidase 1 gene. Frequent sequence heteroplasmy was observed. The phylogenetic hypothesis is consistent with recent interpretations of the geological history of Sulawesi suggesting separate evolution on the island for 7-14 Myr, possibly since South Sulawesi was connected to Borneo. Within the island, the pattern of genetic divergence is dominated by a strong correlation with geographic distance, with exceptions indicating past or present barriers to dispersal. Colonisation of the Moluccas from North or Central Sulawesi is implied. Levels of genetic divergence are compared with distribution patterns of colour morphs and with possible effects of tectonic movements in the Cenozoic, or Pleistocene climatic, vegetational and sea-level changes.

This paper deals with the depositional sequences that occur within the uppermost part of the Plio -Pleistocene Periadriatic basin fill in the southern Marche region, central Italy. The succession is an Early Pleistocene, easterly dipping clastic wedge showing an overall shallowing trend from slope clays to shallow-marine and non-marine deposits comprising two major sequences, namely Q mb and Q mc . Analysis has provided new insights into: (i) the nature of sedimentary facies and facies associations occurring within the upper part of Q mb and Q mc ; (ii) the gradual contact within Q mb between regressive littoral deposits (RLD) and underlying deep-marine blue clays; (iii) the composite origin of the Emilian surface, which is a widespread erosional unconformity separating Q mb from Q mc ; (iv) the cyclothemic pattern of Q mc , composed of downstepping, small-scale depositional sequences; (v) the role played by synsedimentary uplift on the stacking pattern of small-scale sequences and their internal architecture. Up to three small-scale depositional sequences have been recognised within Q mc (Q mc1 , Q mc2 and Q mc3 ). They are up to 50 m thick and defined by previously unrecorded, lower-rank, regionally extensive surfaces. Facies organization indicates that, as a rule, in ascending stratigraphic order each small-scale sequence may includes a distinctive basal unconformity surface that can be traced from incised valleys to associated interfluves, an incised-valley fill, a transgressive surface of marine erosion, a transgressive systems tract, a highstand systems tract, a regressive surface of marine erosion and an attached falling stage systems tract. In proximal positions, the small-scale sequences are dominated by transgressive and highstand systems tracts with incisedvalley fills and falling stage systems tracts absent or volumetrically much less significant. In relatively basinward locations, where the regressive surfaces of marine erosion converge with the lower sequence boundary, the falling stage systems tract may represent the entire depositional sequence. High-frequency sequences display a distinctive stacking pattern and form a tectonically induced forced regressive sequence set underlain by a composite, tectonically enhanced regressive surface of marine erosion formed by the lateral connection of lower-rank sequence boundaries.

There may be differences between this version and the published version. You are advised to consult the published version if you wish to cite from it. Deposited on 3 August 2021 Enlighten -Research publications by members of the University of Glasgow

An effort has been made to assemble a data set on the evolution of coastal morphology of the West Iberian Continental Margin in Portugal, which has occurred since the Last Glacial Maximum. In this integrated review a particular attention was given to the analyses of coastline shaping phenomena on different time scales. Several overlapping processes such as shore erosion, local sediment supply rate, climatic changes, anthropic impacts and mean sea level rise (MSLR) were identi®ed and their combined effects assessed. The eustatic see level rise appears as a principal factor in shaping the shore line contour until mid Holocene. Since then, the non eustatic factors namely the terrigenous sediment supply rate and the dynamics of barriers and spits systems became dominant in the evolution of the near shore morphology. Since the 15th century AD, the anthropogenic activities, namely deforestation and land cultivation contributed decisively to the positive sedimentary balance in the Portuguese coastal zone. Finally, the multiple damming of the major rivers in 20th century and exploitation of sand and gravel from the river beds led to the sediment starving of the coastal zone and generalized shore line retreat.

Changes in the Earth's water cycle can be estimated by analyzing sea surface salinity. This variable reflects the balance between precipitation and evaporation over the ocean, since the upper layers of the ocean are the most sensitive to atmosphere-ocean interactions. In situ measurements lack spatial and temporal synopticity and are typically acquired at few meters below the surface. Satellite measurements, on the contrary, are synoptic, repetitive and acquired at the surface. Here we show that the satellite-derived sea surface salinity measurements evidence an intensification of the water cycle (the freshest waters become fresher and vice-versa) which is not observed at the in-situ nearsurface salinity measurements. The largest positive differences between surface and near-surface salinity trends are located over regions characterized by a decrease in the mixed layer depth and the sea surface wind speed, and an increase in sea surface temperature, which is consistent with an increased stratification of the water column due to global warming. These results highlight the crucial importance of using satellites to unveil critical changes on ocean-atmosphere fluxes. About 85% of the Evaporation (E) and 77% of the Precipitation (P) occurs over the ocean 1,2 . Both processes produce changes in sea surface salinity (SSS) leading to positive (evaporation) and negative (precipitation) anomalies. In a global warming scenario, the global water cycle is expected to be intensified and is a cause of great concern, because of its profound socioeconomic impacts throughout the globe. Monitoring the SSS to assess the intensification of the water cycle is proposed in Yu et al. and references therein, as an alternative to directly measure E and P since these components can only be estimated with limited accuracy. However, there is still some controversy as to whether the salinity is changing at the same rate as the water cycle does , as the impact of the changes in E-P fluxes, meltwater runoff, and ocean warming on the salinity is not completely understood . Moreover, the number of available salinity measurements has been historically scarce and limited to some specific ocean regions . Since 2000, the global array of temperature and salinity floats provided by the Argo system 20 , besides other permanent or routine observation systems, have contributed to further the knowledge on ocean salinity related processes. More recently, since 2010, SSS measurements are also available from space , increasing the monitoring capability of this Essential Climate Variable. One of the main differences between satellite and in situ salinity measurements is that the latter are typically acquired at a few meters depth (5-10 m), thus monitoring the near surface salinity (NSS), while the former are providing measurements at the top cm layer of the ocean, thus monitoring the actual SSS. Differences between the SSS and NSS are due to the vertical stratification of the ocean upper layers. Whereas vertical stratification in temperature has been extensively studied over the past several decades , upper-ocean salinity stratification studies were only initiated in recent years, mostly motivated by the analysis of satellitederived SSS data . The ocean salinity stratification results from a complex combination of various mechanisms such as precipitation, oceanic advection and mixing conditions, as well as fresh water input from rivers runoff, melting of sea ice and removal of freshwater through evaporation. Although negative salinity anomalies have been shown and studied in cases of rainfall , river runoff and sea-ice melting , there is a limited

Sequence boundaries defined by regional unconformities in mixed carbonate/siliciclastic sediments have a variable duration from the margin to the interior of the Florida Platform. Factors controlling the timing and duration of these unconformities include a combination of global (eustatic) and regional mechanisms (sediment supply, current intensification). Integrated chronostratigraphies developed from a transect of continuous cores in the south-central interior to the southern margin of the Florida Platform show an increase in duration of the hiatal gaps along correlative sequence boundaries toward the platform edge. Two sequence boundaries are correlated across the south Florida Platform and mark formation contacts. The lower sequence boundary (SB-A) marks the Suwannee Limestone/Arcadia Formation contact and is of significantly less duration in the platform interior (southwest peninsular Florida, ϳ2.0 m.y.) than at the south platform margin (middle Florida Keys, ϳ8.1 m.y.). The hiatal gap along the upper sequence boundary (SB-B), marking the Arcadia Formation overlain by Miocene-Pliocene sediments that vary in age and composition regionally, records the same increase from the central part of the platform (southwest Florida, Arcadia Fm/Peace River Fm, ϳ1.6 m.y.) to the south platform edge (lower Florida Keys, Arcadia Fm/Stock Island Fm, ϳ11.5 m.y.). Eustatic fluctuations affected the relative sedimentation rates of the mixed sediments in the platform interior and at the margin. Most notably, the large eustatic fall at the end of the Early Oligocene terminated carbonate deposition of the Suwannee Limestone (SB-A). Sediment accumulation on the platform interior was more temporally continuous than at the margin because of greater siliciclastic input from the north. The strengthening of marine currents beginning in the Middle Miocene limited sediment accumulation across the southern platform margin (SB-B) and possibly caused erosion of the margin carbonates, increasing the duration of the hiatal gap on top of the Arcadia Formation.

A Cariaco Basin pollen record shows the development of tropical salt marshes during marine isotope stage 3. Rapid and abrupt expansions of salt marsh vegetation in tropical South America are associated with north Atlantic Heinrich Events stadials (HE-stadials). Intervals of salt marsh expansion have an internal structure, which consists of a recurrent alternation of species that starts with pollen increments of Chenopodiaceae, that are followed by increments of grasses, and subsequently by increments of Cyperaceae. This pattern suggests a successional process that is determined by the close relationship between sea-level and plant community dynamics. The salt tolerant Chenopodiaceae, indicate hypersaline intertidal environments, which were most likely promoted by extremely dry atmospheric conditions. Rapid sea-level rise characterizes the onset of HE-stadials, causing the continued recruitment of pioneer species, which are the only ones tolerating rapid rates of disturbance. Once sea-level rise decelerates, marsh plants are able to trap and stabilize sediments, favouring the establishment of more competitive species. These results add to the scarce knowledge on the dynamics of tropical salt marsh ecosystems, and provide independent paleoclimatic evidence on sea-level changes following Antarctic climate variability.

A dense grid of ice-penetrating radar sections acquired over Pine Island Glacier, West Antarctica has revealed a network of sinuous subglacial channels, typically 500 m to 3 km wide, and up to 200 m high, in the ice-shelf base. These subglacial channels develop while the ice is floating and result from melting at the base of the ice shelf. Above the apex of most channels, the radar shows isolated reflections from within the ice shelf. Comparison of the radar data with acoustic data obtained using an autonomous submersible, confirms that these echoes arise from open basal crevasses 50-100 m wide aligned with the subglacial channels and penetrating up to 1/3 of the ice thickness. Analogous sets of surface crevasses appear on the ridges between the basal channels. We suggest that both sets of crevasses were formed during the melting of the subglacial channels as a response to vertical flexing of the ice shelf toward the hydrostatic condition. Finite element modeling of stresses produced after the formation of idealized basal channels indicates that the stresses generated have the correct pattern and, if the channels were formed sufficiently rapidly, would have sufficient magnitude to explain the formation of the observed basal and surface crevasse sets. We conclude that ice-shelf basal melting plays a role in determining patterns of surface and basal crevassing. Increased delivery of warm ocean water into the sub-ice shelf cavity may therefore cause not only thinning but also structural weakening of the ice shelf, perhaps, as a prelude to eventual collapse.

Elevated arsenic in Bengal Basin aquifers threatens human health. Most deep (>150 m) groundwater in Pleistocene aquifers is low in arsenic; however higher concentrations have been reported in the southwest border region. Here, we establish that this extensive arsenic contamination at depth is not associated with well failure. A combination of geochemistry and flow modeling constrains the factors that contribute to arsenic contamination at depth in this region. Deep groundwater in the affected area is younger (2.0 ± 0.6 kyr) than deep, low‐arsenic groundwater elsewhere (12.0 ± 4.0 kyr) based on radiocarbon. Stratigraphic data indicate pre‐Holocene deposition of the contaminated aquifers, but few low‐permeability strata. Numerical modeling indicates that this stratigraphic anomaly permits a natural flow system that transports shallow groundwater to depth. Thus, in areas lacking low‐permeability layers, arsenic contamination can occur in pre‐Holocene aquifers and is probably not an ...

Borehole logs and 3D seismic data are used to determine the characteristics of a polygonal fault system (PFS) in the Albian Westgate Formation in western Saskatchewan and eastern Alberta. The basal Upper Cretaceous formation is a siliceous siltstone to mudstone deposited in the Western Interior Seaway beneath the Great Plains of North America. The faulted zone is layerbound within the ∼80 m thick Westgate Formation at Swift Current, Saskatchewan. Most faulting occurs along grabens approximately 125 m wide and 10 m deep. The grabens are interconnected, have random strike directions, and lengths up to 800 m. The continuous depositional environment of the Westgate Formation enables timing and compacted sediment thickness estimates for the PFS initiation. The faults appear to have started in ∼15 m or more of compacted sediment within the first 270 000 years of the 1.5 Myr Westgate Formation interval. Polygonal faulting may result from smectite illitization, subsequent bed dissolution, and polygonal fault formation in overlying beds. Mapping the seismic data in intervals above the Westgate shows relief above the graben through Santonian time. Interpreting the seismic dataset and accompanying wellbore data has resulted in a simple model of graben formation post-Turonian time that could induce fracturing in shallower Second White Speckled Shale Formation strata. Wellbore data interpretations from Alberta and Saskatchewan show that the PFS identified at Swift Current may range across a large area. The implications for an extensive PFS identification in the Lower Cretaceous Westgate Formation and homotaxially equivalent Mowry Shale across central North America are discussed.

The study area Gullebi Field is located on the southern edge of concession NC7A in the southcentral part of the intracratonic Ghadames Basin in northwestern Libya. The Tahara Formation which consists of sandstone and siltstone with shale and iron-rich streaks interbedding is considered the main productive horizon in the study area. The stratigraphic framework identified from the analysis and interpretation of the subsurface data for the Late Devonian Tahara Formation, within the Gullebi Field, allow for the recognition of seven ( ) lithofacies based on core and wireline-log data which is; (1) dark grey micaceous bioturbated shale (offshore basinal marine environment), (2) parallel laminated silty sandstone and silty shale (deltaic complex environment), ( ) varicolored silty shale and bioturbated iron-rich shale (lagoonal to river influences environment), ( ) bioturbated sand and shale (beach environment), ( ) interlaminated shale and silty sandstone (coastal plain environment), ( ) massive sandstone and gravel (fluvial; river channel environment), ( ) rippled and fossiliferous sandstone (deltaic-beach environment). The Tahara sandstones can be classified as quartzarenites and sublitharenite in terms of their modal composition. Quartz grains constitute of an average about (86%) of the total sand grains, sparse feldspar grains account for about (2%) and rock fragments of an average (11%). Two types of porosity are recognized in the Tahara sandstones: (1) primary intergranular porosity (2) secondary porosity; dissolution of unstable grains was the dominant process to create secondary porosity. The diagenetic processes and their products may be identified to shed light on the sandstone quality variation of the Tahara Formation. A composite paragenetic sequence explaining diagenetic events through time for the Tahara sandstone of Gullebi Field can be proposed. Based on petrography data, identified diagenetic constituents, and proposed paragenetic sequence, three (3) possible reservoir quality types or associations can be identified for the Tahara sandstones in the Gullebi Field which are: 1-Good quality type of the Tahara sandstone was found to be associated with beach and deltaic complex lithofacies. 2-Medium quality type of the Tahara sandstone was found to be associated with fluvial channellithofacies. 3-Poor quality type of the Tahara sandstone was found to be associated with the lagoonal, coastal plain, and offshore marine lithofacies. The use of a diagenetic sequence integrated with depositional lithofacies represents an initial step in predicting regions of maximum enhanced and preserved porosity on the assessment of reservoir quality in the Tahara sandstones of the Gullebi Field.

Positive deviations from linear sea-level trends represent important climate signals if they are persistent and geographically widespread. This paper documents rapid sea-level rise reconstructed from sedimentary records obtained from salt marshes in the Southwest Pacific region (Tasmania and New Zealand). A new late Holocene relative sea-level record from eastern Tasmania was dated by AMS 14 C (conventional, high precision and bomb-spike), 137 Cs, 210 Pb, stable Pb isotopic ratios, trace metals, pollen and charcoal analyses. Palaeosea-level positions were determined by foraminiferal analyses. Relative sea level in Tasmania was within half a metre of present sea level for much of the last 6000 yr. Between 1900 and 1950 relative sea level rose at an average rate of 4.2 ± 0.1 mm/yr. During the latter half of the 20th century the reconstructed rate of relative sea-level rise was 0.7 ± 0.6 mm/yr. Our study is consistent with a similar pattern of relative sea-level change recently reconstructed for southern New Zealand. The change in the rate of sea-level rise in the SW Pacific during the early 20th century was larger than in the North Atlantic and could suggest that northern hemisphere landbased ice was the most significant melt source for global sea-level rise.

Owing to proximity of the North Atlantic Stream and the shelf, the Andøya biota are assumed to have responded rapidly to climatic changes taking place after the Weichselian glaciation. Palynological, macrofossil, loss‐on‐ignition, tephra and 14C data from three sites at the northern part of the island of Andøya were studied. The period 12 300–11 950 cal. yr BP was characterized by polar desert vegetation, and 11 950–11 050 cal. yr BP by a moisture‐demanding predominantly low‐arctic Oxyria vegetation. During the period 11 050–10 650 cal. yr BP, there was a climatic amelioration towards a sub‐arctic climate and heaths dominated by Empetrum. After 10 650 cal. yr BP the Oxyria vegetation disappeared. As early as about 10 800 cal. yr BP the bryozoan Cristatella mucedo indicated a climate sufficient for Betula woodland. However, tree birch did not establish until 10 420–10 250 cal. yr BP, indicating a time‐lag for the formation of Betula ecotypes adapted to the oceanic climate of Andøya. ...

The southern portion of the Venice lagoon contains a relatively thick (up to 20 m) Holocene sedimentary body that represents a detailed record of the formation and evolution of the lagoon. New very highresolution (VHR) seismic profiles provided a detailed investigation on depositional geometries, internal bounding surfaces and stratal relationships. These informations, combined with core analysis, allowed the identification of large-to medium-scale sedimentary structures (e.g. dunes, point bars), the corresponding sedimentary environment, and of retrogradational and progradational trends. In addition, the availability of dense seismic network produced a 3D reconstruction of the southern lagoon and the recognition of the along-strike and dip variability of the stratal architecture. Three main seismic units (H1-H3), separated by key stratal surfaces (S1-S3), form the Holocene succession in the southern Venice lagoon. This succession is bounded at the base by the Pleistocene/ Holocene boundary (the surface S1), which consists of a surface of subaerial exposure locally subjected to river incision. The lower part of the Holocene succession (up to 13 m thick) consists of incised valley fills passing upward into lagoon and then shallow-marine sediments (Unit H1), and therefore shows a deepening-upward trend and a retrogradational stacking pattern. A prograding delta and adjacent shorelines, showing internal clinoforms downlapping onto the top of Unit H1 (the surface S2), form the middle part of the Holocene succession (Unit H2, up to 7.5 m thick). Unit H2 is interpreted as a result of a regressive phase started about 6 kyr BP and continued until recent time. The upper part of the Holocene succession (Unit H3) consists of lagoonal deposits, including tidal channel and tidal and subtidal flat sediments, that abruptly overlie Unit H2. Unit H3 is thought to represent a drowning of the area primarily due to human interventions that created rivers diversion and consequent delta abandonment during historical time.

The outcrops of the Oxfordian La Manga Formation at Bardas Blancas, Neuquén Basin, west-central Argentina, allow the recognition of six different depositional facies (A to F) on the basis of sedimentological analysis, taphonomic attributes and microfacies studies. These depositional facies correspond to outer ramp (A), middle ramp (B), inner ramp-oolitic shoal (C), inner ramp margin (patch reef) (D), lagoon deposits (E), and a paleokarst surface (F). Outer ramp deposits which are not completely represented, consist of greyish carbonate beds, where the fabric of the shell beds (gryphaeids) reflects the action of waves and currents. Middle ramp deposits consist of a packstone-grainstone lithofacies indicating the importance of storm processes and is dominated by ooids, intraclasts, pelecypods, echinoderms and gastropods which accumulated on a middle-ramp storm-dominated shoreface. Trace fossils belong to the Skolithos and Cruziana Ichnofacies characterizing the upper, lower and middle shoreface setting respectively. The inner ramp deposits consist of oolitic grainstones and subordinate packstones shoal with a small sponge bioherm at the base. Different types of ooids, peloids and coated grains are abundant, as well as skeletal fragments of molluscs, echinoderms and corals. Lithofacies and microfacies studies suggest a high energy and shallow-water depositional setting. The inner ramp margin deposits consist of reef core facies, fore and back reef facies characterized by a scleractinian community of relatively low generic diversity. The rich associated fauna consists of bivalves, echinoids, serpulids, bryozoans, dasycladacean algae and cyanophytes, as well as foraminifers and ostracods. The growth forms of the corals are indicative of shallow well illuminated water. Both the back and fore reef deposits suggest intensive reworking by storm waves or currents. The lagoon deposits consist of bioclastic and peloidal wackestones as well as bioclastic-intraclastic packstones which accumulated on a lagoon under intermittently agitated water in a shallow subtidal to intertidal settings. A stratiform breccia with both matrix and clasts supported fabrics is interpreted as paleokarst. The clasts are derived from the rocks of oolitic shoal and inner ramp margin (patch reef). The six depositional facies are included into a major organizational framework of three third-order depositional sequences (DS-1, DS-2, DS-3) mainly represented by transgressive and highstand systems tracts stages with sequence boundaries of regional importance. The general depositional evolution is here related to the slow subsidence experienced during the Oxfordian-earliest Sedimentary Geology 195 (2007)

Coastal lagoons and dunes are of great ecological importance, not only for providing habitats for rare flora and fauna, but also for protecting coastal areas from rising sea levels and storms, etc. Even though these features are unique for sustainable development and are extremely important to the natural environment and economy, they are one of the most vulnerable and threatened ecosystems due to their small size. The western coasts of Naxos (central Aegean Sea) represent an example of such phenomena, with various wetlands bordered by low-lying sand dunes. The aim of our study is to assess the vulnerability and pressures of the western coasts of Naxos Isl. by taking into consideration both natural and anthropogenic factors. We used a variety of approaches for the environmental and geomorphological study of the coastal zone to achieve this goal, including: (a) study of aerial photography from 1960 until today, (b) systematic seasonal aerial monitoring by drone, since 2015, (c) use of DGPS for the mapping of the coastal zone and for obtaining detailed topographic sections, and (d) dune mapping. Our findings reveal the vulnerability of the western coasts of Naxos due to sea level rise, tectonic subsidence, and a variety of anthropogenic pressures, such as uncontrolled parking, vegetation uprooting, sand extractions, and heavy touristic traffic. Therefore, the protection of the sand dunes, their restoration where they have been eroded, the definition of a zone of control, and restriction of human activities must be a key priority.

Iceberg calving at glacier termini results in mass loss from ice sheets, but the associated fracture mechanics is often poorly represented using simplistic (empirical or elementary mechanics-based) failure criteria. Here, we propose an advanced Mohr-Coulomb failure criterion that drives cracking based on the visco-elastic stress state in ice. This criterion is implemented in a phase field fracture framework, and finite element simulations are conducted to determine the critical conditions that can trigger ice cliff collapse. Results demonstrate that fast-moving glaciers with negligible basal friction are prone to tensile failure causing crevasse propagation far away from the ice front, while slow-moving glaciers with significant basal friction are likely to exhibit shear failure near the ice front. Results also indicate that seawater pressure plays a major role in modulating cliff failure. For land terminating glaciers, full thickness cliff failure is observed if the glacier exceeds a critical height, dependent on cohesive strength 𝜏 c (H ≈ 120 m for 𝜏 c = 0.5 MPa). For marine-terminating glaciers, ice cliff failure occurs if a critical glacier free-board (Hh w) is exceeded, with ice slumping only observed above the ocean-water height; for 𝜏 c = 0.5 MPa, the model-predicted critical free-board is Hh w ≈ 215 m, which is in good agreement with field observations. While the critical free-board height is larger than that predicted by some previous models, we cannot conclude that marine ice cliff instability is less likely because we do not include other failure processes such as hydrofracture of basal crevasses and plastic necking.

Los estuarios presentes en entornos mesomareales muestran con cierta asiduidad situaciones de eutrofización de sus aguas, debido principalmente, a la oclusión de su desembocadura mediante una flecha de arena. Estos estuarios aparecen usualmente en medios con una energía moderada del oleaje, y se encuentran definidos por un canal formado sobre una flecha, donde, las corrientes mareales se aceleran, . En estos ambientes se suceden estacionalmente importantes periodos de cierre y apertura de la bocana del estuario, así como procesos de erosión y acreción de las playas colindantes. Los procesos sedimentarios y la morfología del estuario del río Guadiaro, están relacionados con la acción combinada de las corrientes mareales y de las corrientes inducidas por el oleaje. La influencia relativa de ambas, provoca una migración compleja de la bocana y de las barras. El cierre de la bocana del estuario coincide con la migración natural de la flecha y épocas de mínimo caudal del río durante periodos de estiaje, facilitando así la deposición de la arena. La influencia del bajo caudal del río junto a la escasa renovación de aguas y a su alta carga orgánica, causa la eutrofización del estuario, generando así aguas anóxicas que ocasionan la muerte de importantes especies de flora y fauna. El incremento de los vertidos al río, procedentes de los núcleos urbanos situados aguas arriba (ya que la urbanización de Sotogrande, sita en la misma desembocadura, posee depuradora), añade un factor negativo determinante en la calidad de las aguas, . Además, este proceso de eutrofización de las aguas lleva implícito una generación de gases con un fuerte y desagradable olor para las urbanizaciones colindantes. Su estratégica situación en la vertiente migratoria oriental del Estrecho de Gibraltar propicia la presencia de una rica variedad de aves migratorias y estacionales, que encuentran es estos ecosistemas zonas de descanso en sus largos viajes septentrionales. Las condiciones ambientales naturales de la zona se ven afectadas en gran medida en función del cierre de la desembocadura del río por el avance de la flecha hacia el espigón de encauzamiento. En consecuencia de estos problemas sociales y medioambientales, el Ministerio de Medio Ambiente ha actuado con anterioridad, efectuando dragados de la bocana y otras actuaciones blandas encaminadas a solventar esta problemática (Muñoz-Pérez et al., 2000). El principal objetivo de este artículo es la investigación de las tendencias evolutivas del comportamiento de la flecha Variabilidad espacio-temporal de la flecha del río Guadiaro JORGE ROMÁN SIERRA (*), MARINA NAVARRO (**), JUAN JOSÉ MUÑOZ PÉREZ (**) y BEGOÑA TEJEDOR (**) SPATIAL AND TEMPORAL VARIABILITY IN THE SPIF OF GUADIARO RIVER

The problem of the world greatest lake, the Caspian Sea, level changes attracts the increased attention due to its environmental consequences and unique natural characteristics. Despite the huge number of studies aimed to explain the reasons of the sea level variations the underlying mechanism has not yet been clarified. The important question is to what extent the CSL variability is linked to changes in the global climate system and to what extent it can be explained by internal natural variations in the Caspian regional hydrological system. In this study an evidence of a link between the El Niño/Southern Oscillation phenomenon and changes of the Caspian Sea level is presented. This link was also found to be dominating in numerical experiments with the ECHAM4 atmospheric general circulation model on the 20th century climate.