Episodes Of Erosion Research Articles

Sub ablative Er: YAG laser irradiation on surface roughness of eroded dental enamel.

This study evaluated the effects of Er:YAG laser irradiation applied at varying pulse repetition rate on the surface roughness of eroded enamel. Bovine enamel slabs (n = 10) were embedded in polyester resin, ground, and polished. To erosive challenges, specimens were immersed two times per day in 20mL of concentrated orange juice (pH = 3.84) under agitation, during a two-day period. Specimens were randomly assigned to irradiation with the Er:YAG laser (focused mode, pulse energy of 60 mJ and energy density of 3.79 J/cm(2) ) operating at 1, 2, 3, or 4 Hz. The control group was left nonirradiated. Surface roughness measurements were recorded post erosion-like formation and further erosive episodes by a profilometer and observed through atomic force microscopy (AFM). Analysis of variance revealed that the control group showed the lowest surface roughness, while laser-irradiated substrates did not differ from each other following post erosion-like lesion formation. According to analysis of covariance, at further erosive episodes, the control group demonstrated lower surface roughness (P > 0.05), than any of the irradiated groups (P < 0.05). The pulse repetition rate of the Er:YAG laser did not affect roughness of dental enamel eroded. The AFM images showed that the specimens irradiated by the Er:YAG laser at 1 Hz presented a less rough surface than those irradiated at 2, 3, and 4 Hz.

Displaced/re-worked rhodolith deposits infilling parts of a complex Miocene multistorey submarine channel: A case history from the Sassari area (Sardinia, Italy)

In the Sassari area (north-western Sardinia, Italy), the Miocene Porto Torres sub-basin sequences represent the complex multistorey mixed carbonate-siliciclastic submarine feature called the Sassari Channel. During the late Burdigalian–early Serravallian, repeated terrigenous supplies from uplifted Paleozoic crystalline substrata fed the Sassari Channel system by means of turbidity and locally hyper-concentrated turbidity flows. Shelfal areas were the source of terrigenous clasts, but open shelf rhodalgal/foramol carbonate areas were very productive and largely also contributed to the channel infilling. Re-worked sands and skeletal debris were discontinuously re-sedimented offshore as pure terrigenous, mixed and/or carbonate deposits. Major sediment supply was introduced between the latest Burdigalian and the start of the middle Langhian, during which a large amount of carbonate, mixed and siliciclastic sediments reached the Porto Torres Basin (Sassari Channel I). Contributions from shallow proximal source areas typify the lower intervals (Unit A) in marginal sectors of the channel. Upward, these evolve into autochthonous rhodolith deposits, winnowed by strong currents in relatively shallow well lit settings within a complex network of narrow tidally-controlled channels (Unit D) locally bearing coral assemblages. Conversely, re-sedimented rhodoliths from the Units B and C accumulated under conditions of higher turbidity. In deeper parts of the channel taxonomically diversified rhodoliths point to the mixing of re-deposited skeletal components from different relatively deep bathmetric settings. In the latest early Langhian, major re-sedimentation episodes, resulting in large prograding bodies (Unit D), triggered by repeated regression pulses in a frame of persistent still stand. During these episodes photophile assemblages dwelled in the elevated margin sectors of the channel. A significant latest early Langhian drop in relative sea-level resulted in impressive mass flows involving early cemented channel-margin and levee blocks and culminated in the formation of major erosional surface (ER-E). Such events seemingly correlate with the long-term global cooling trend of the mid-Miocene climatic transition. Episodes of middle Langhian re-sedimentation concluded with the channel abandon phase after which new erosive episodes followed. Overall, this led to a shift in the Sassari Channel II, with phases presumably started during the earlymost Serravallian, subsequent to the major sea-level drop at the Langhian–Serravallian boundary.

Transverse versus longitudinal extension in the foredeep-peripheral bulge system: Role of Cretaceous structural inheritances during early Miocene extensional faulting in inner central Apennines belt

This study reports on the Rocca di Cave extensional fault system, which is located in the Prenestini Mountains (Central Italy) of the Apennines fold-and-thrust belt and presently represents the oldest exposure of early orogenic foreland fault system of the Apennines. This fault system was oriented perpendicular to the strike of the foredeep-peripheral bulge system, indicating that the onset of convergence was marked by a foredeep-parallel extension, instead of the commonly observed foredeep-perpendicular stretching associated with lithosphere flexuring. The studied fault system is formed by a 10 km long and 2 km wide E-W elongated area that includes two mutually orthogonal sets of faults oriented about E-W and N-S, respectively. E-W and, mainly, N-S striking faults developed during a preorogenic (Santonian to Campanian in age) E-W oriented extension kinematics, which caused first uplift and erosion and then drowning of the Cretaceous carbonate platform and the onset of a pelagic environment. Both fault sets were later reactivated in the early Miocene, when the area was forming part of the foreland region ahead of the eastward migrating Apennines fold-and-thrust belt and was undergoing local N-S oriented, i.e., foredeep-parallel, stretching. This extensional stage implied the sedimentation of hundreds of meters of synkinematic strata in the northern block of the Rocca di Cave Fault System, coevally with episodes of subaerial erosion in areas of the southern block. Further extensional and right-lateral reactivation of inherited faults occurred in the late Miocene, during the progressive incorporation of the area into the Apennines belt.

Morphostratigraphical correlation of river terraces in the central part of the Bohemian Massif with the European stratigraphical classification of the QuaternarY

The results of geomorphological research, focused on identification of larger remains of fluvial terrace sedimentary sequences in the Želivka, Sázava, Berounka, Vltava and Labe river-drainage basins in the Bohemian Massif, are presented. The terrace flights are characterised by a variable structure which is conditioned by the bedrock and drainage-network configuration created prior to the Pleistocene. They are formed by the specific hydrodynamic processes during the Quaternary. A series of transverse-valley profiles and longitudinal profiles have been constructed. This has enabled the differentiation of seven main terrace surfaces underlain by Quaternary fluvial sediments. However, the uppermost levels are underlain by Neogene-age deposits that comprise both fluvial and fluvio-lacustrine sediments at altitudes up to 135 m above the present valley floor. The Quaternary incision of the Sázava and Vltava valleys reaches an average depth of over 100 m. This was induced by neotectonic uplift of the Bohemian Massif. The terrace flights include incised meanders and bends, most of which formed during the Middle Pleistocene. Based on the currently accepted Quaternary chronostratigraphical scheme, the terrace system throughout the Bohemian Massif is mostly of Middle and Late Pleistocene age that is the period from the Cromerian Complex to the Weichselian stages of the NW European scheme. A marked erosional episode, that pre-dates the accumulation of terrace I sediments, occurred at the end of the Early Pleistocene Subseries. Older levels of fluvial sediments in the central part of the Bohemian Massif, occupying higher topographical positions, previously classified as of Pliocene age, are now considered to date from the Early Pleistocene. <b>Morfostratigrafická korelace říčních teras střední části Českého masivu s evropskou stratigrafickou klasifikací kvartéru</b> Říční terasy Želivky, Sázavy, Berounky, Vltavy a Labe mají ve střední části Českého masivu rozmanitou strukturu, která vznikala specifickými morfostrukturními a hydrodynamickými procesy při vývoji údolní sítě v mladším kenozoiku. Geomorfologický výzkum reliktů fluviálních sedimentů v těchto údolích umožnil rozlišit sedm kvartérních akumulačních teras (Tabulka 1) a dvě úrovně fluviálních a fluvio-lakustrinních sedimentů neogenního stáří. Relikty předkvarterních uloženin se vyskytují až 135 m nad současnými dny říčních údolí střední části Českého masivu. Erozivní zahloubení této antecedentní a epigenetické říční sítě bylo podmíněno neotektonickými zdvihy a během kvartéru dosáhlo více než 100 m. Charakteristické zakleslé meandry a ohyby říčních údolí vznikaly převážně ve středním pleistocénu. Podle současného statigrafického členění kvartéru se systém říčních akumulačních teras v údolích střední části Českého masivu vytvořil zejména ve středním a mladém pleistocénu, a to od Cromerského komplexu do Viselského období. Erozní procesy před vznikem říční akumulační terasy I probíhaly koncem staršího pleistocénu. Je také ukázáno, že dynamiku fluviálních procesů je vhodné studovat ve vztahu ke zvětrávání, denudaci, erozi a svahovým pohybům v kvartéru.

Holocene evolution of Phra Thong's beach-ridge plain (Thailand) — Chronology, processes and driving factors

Beach-ridge plains are a common morphological element of coastal areas all over the world. While morphological depressions of beach-ridge plains (swales) may function as archives for deposits of extreme wave events, the ridges are not only used as an indicator for coastal evolution but also to reconstruct the processes that are responsible for their formation. In this study, the morphological, sedimentary and chronological structure of the beach-ridge plain on Phra Thong Island was used as an archive for the temporally and spatially complex pattern of shoreline changes during the Holocene. The presence of three spatio-temporal ridge-plain units separated by episodes of shoreline erosion and characterised by varying directions and rates of shoreline progradation, reveals six distinct phases of island evolution within the last 6000years. Unit I was deposited during phase 1 (5500–4000years ago) with high progradation rates of 2.1–2.5m/year. Subsequent to a short episode of erosion during phase 2 (4000–3800years ago), fast shoreline progradation at a rate of 2.7m/year (unit IIa) occurred once again in phase 3 (3800–3300years ago). After 3300years ago, the sedimentation rate decreased to less than 1m/year, resulting in the formation of unit IIb during phase 4 (3300–1500years ago). In phase 5, between 1500 and 800years ago, ridge-plain formation was once more interrupted by significant shoreline erosion. Finally, over most of the last 800years, during phase 6, slow shoreline progradation led to the formation of unit III. This evolution is best explained by the interaction of long-term sea-level change, wave climate, episodic events (tsunamis and storms) and local sediment supply. However, the linkage of successive ridge and swale formation, changing progradation rates and switch-over between phases of erosion and deposition with its trigger mechanisms remains speculative, since (i) the processes involved vary locally and are poorly understood for Phra Thong Island, and (ii) even our comparably large dataset cannot reconstruct the complex spatial and temporal pattern of shoreline evolution without significant uncertainties. This implies that interpretations of ridge plains based on small datasets might be too generalised to capture the real complexity of the system and, as a consequence, might lead to incorrect conclusions about palaeoenvironmental conditions.

A universal meteorological method to identify potential risk of wind erosion on heavy-textured soils

Abstract The climate of Central Europe, mainly winter seasons with no snow cover at lower altitudes and a spring drought as well, might cause erosion events on heavy-textured soils. The aim of this paper is to define a universal method to identify the potential risk of wind erosion on heavy-textured soils. The categorization of potential wind erosion risk due to meteorological conditions is based on: (i) an evaluation of the number of freeze-thaw episodes forming bare soil surfaces during the cold period of year; and (ii), an evaluation of the number of days with wet soil surfaces during the cold period of year. In the period 2001–2012 (from November to March), episodes with temperature changes from positive to negative and vice versa (thaw-freeze and freeze-thaw cycles) and the effects of wet soil surfaces in connection with aggregate disintegration, are identified. The data are spatially interpolated by GIS tools for areas in the Czech Republic with heavy-textured soils. Blending critical categories is used to locate potential risks. The level of risk is divided into six classes. Those areas identified as potentially most vulnerable are the same localities where the highest number of erosive episodes on heavy-textured soils was documented.

Growth of the atrial septum after Amplatzer device closure of atrial septal defects in young children.

Trans-catheter closure of atrial septal defects (ASD) with the Amplatzer Septal Occluder (ASO) device is safe and effective, but concern over erosions has increased. Devices are placed in growing children but septal growth after ASOs is ill-defined. Understanding the device relationship to cardiac structures as a child grows may help us understand erosions. To define (1) how preprocedural septal measurements change after ASO and (2) the effect of somatic growth on these dimensions. Data were collected retrospectively. Echocardiograms were reviewed and rims measured prior to ASO, immediately after ASO, and at follow-up. Demographic, procedural and device data were collected. Thirty-three patients were enrolled; mean age 5.2 ± 3.2 years with 4.0 ± 2.2 years follow-up. All septal measurements decreased after ASO. Thirty-one of 33 devices (94%) contacted the aortic root after ASO; all remained in contact at follow-up with only the IVC rim growing significantly over time. Change in BSA predicted an asymmetric septal growth with increases in superior (P = 0.01) and IVC (P = 0.005) rims and no increase in aortic or AVV rims. No episodes of erosion occurred. ASDs in young children are not central in the septum, but proximate to the aorta. After ASO, the device remains in close proximity to the aorta. With somatic growth, the septum grows asymmetrically, and device position relative to the aorta is constant. Our study was not powered to detect rare serious adverse events such as erosion, but aortic rims were consistently zero and yet no events occurred.

Geotemporal vectors of coastal geomorphological change interacting with National Park Service management policy at Great Kills Park, Gateway National Recreation Area, USA

The trend and episodes of erosion at Great Kills Park, part of the National Park Service, are products of the origin of the park's location and the impact of a negative sediment budget. Management response to the impacts of erosion is somewhat limited by National Park Service philosophy, but some options remain because the negative sediment budget is a product of barriers to sediment transport updrift of the Park. The erosional situation is exacerbated by an exposure of an antecedent backmarsh feature within the Park that is affecting the inshore pattern of incident waves. Recent monitoring data indicate planform conformity to an updrift log-spiral erosional bluff that extends downdrift to a site with beach and dune features. Despite a general net negative sediment budget in the profile, the dune feature is increasing in volume as it shifts inland, fitting models of foredune development. Seasonal monitoring of the topography records that storms cause a stepwise inland displacement of an updrift portion of the Park and a more linear displacement in the downdrift portion. Among the options consistent with management policy responding to the negative sediment budget issue is an opportunity to work within the scale of the small sediment transport cell and backpass sediment toward the updrift margin of the cell.

A self‐limiting bank erosion mechanism? inferring temporal variations in bank form and skin drag from high resolution topographic data

AbstractFluvial bank erosion rates are often quantified by assuming that the erosion rate is a function of the excess (above a critical threshold) boundary shear stress applied by the flow. Research has shown that the form roughness induced by natural topographic bank features, such as slumps, spurs and embayments, is the dominant component of the spatially‐averaged total shear stress, meaning that form roughness provides an important control on bank erosion rates. However, measuring the relative components of the total shear stress for a natural system is not straightforward. In this work we use the method of Kean and Smith to partition the form and skin drag components of river bank roughness using a time series (2005–2011) of high‐resolution topographic surveys of an eroding bank of the Cecina River in central Italy. This method approximates the form drag component of the roughness along a longitudinal bank profile as a series of user‐defined Gaussian curves. The extracted metrics are used in conjunction with an estimate of the outer region flow velocity to partition the form and skin drag components of the total boundary shear stress according to the Kean and Smith analytical solution. The relative magnitude of the form and skin shear stress at each survey date is analysed alongside DEMs of difference to reveal that intense episodes of erosion are followed by periods of quiescence. We show that this is due to the protection offered by increased form drag roughness following erosion. We conceptualise the dynamic feedbacks that exist between river discharge, bank erosion processes and bank form roughness, into a simple model of the self‐limiting nature of river bank erosion. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Cretaceous–Cenozoic sedimentary budgets of the Southern Mozambique Basin: Implications for uplift history of the South African Plateau

In this study, data from 41 wells were used to quantify the evolution of the sedimentary budget in the Southern Mozambique passive margin basin, with a high temporal resolution for the Cenozoic period. We found that the drainage areas, which supplied sediments to the Southern Mozambique Basin, were eroded in two episodes. The first, of Mid–Late Cretaceous in age, is concordant with both thermochronological datation and sedimentary fluxes estimated by other studies in the Namibian and South African and Northern Mozambique margins. This erosion episode ended when the African surface, as defined by Burke and Gunnel (2008), had become flat and low-lying over most of the South African Plateau by ∼65Ma. Carbonate sediment deposition became more important in the shallow waters of the Mozambique basin after that time. The second erosion episode began at ∼23Ma and is likely due to an uplift event of the North-eastern part of the South African Plateau. It seems that the Limpopo catchment and the whole area sourcing the studied basin have inherited their present relief from two epeirogenic uplift pulses of Late Cretaceous and Miocene ages.

Neogene terrestrial sediments: a record of the post-obduction history of New Caledonia

The poorly studied iron-rich terrestrial sediments, referred to as the Fluvio-lacustrine Formation, that crop out in the southern part of the Grande Terre of New Caledonia document the last 25 Ma of the geological history of the island. The age of this formation, which is mainly derived from the erosion of an ultramafic regolith, is not tightly constrained yet; however, it has recorded several episodes of post-obduction erosion and sedimentary infill preceded and followed by weathering and reactivated erosion. A correlation with early Miocene slab break-off, which may have triggered a first stage of erosion marked by coarse conglomerate, is suggested. Thereafter, sediments filled topographic lows and were in turn weathered during an interval of tectonic quiescence. Finally, Holocene sea-level drop and southward tilt of southern New Caledonia, owing to the involvement of eastern Australian Plate in the New Hebrides (Vanuatu) subduction zone, locally changed the drainage pattern and deeply eroded the sediments.

The eastern flank of the Merapi volcano (Central Java, Indonesia): Architecture and implications of volcaniclastic deposits

Merapi volcano in central Java Island is considered to be the most active and dangerous andesitic volcano in Indonesia. The volcanic history of Merapi volcano is complex, and often perturbed by frequent episodes of eruptive edifice building and subsequent erosion and collapse. In this paper, we present a detailed field, literature, and GIS-study of the well-preserved eastern flank of Merapi, which has been spared from major eruptions, in order to reconstruct the geologic and geomorphic history of the edifice. Here, the most recent deposits arise from the remobilization of the old volcanic materials by lahar, gravitational collapse of massive lava flow and local landslide processes.In this study, we describe the specific deposits and subsequent alteration and removal processes. The stratigraphic analysis was performed with respect to the distinct phases of construction due to eruptions and dismantling of the volcano by erosion, gravitational collapse and the associated local to distal re-sedimentation. Based on GIS analysis and field surveys, a drainage network anomaly was detected in two main rivers, the Soka and the Brambang Rivers. We infer that an apex fan of volcaniclastic material was deposited into a central paleo-Pusur river and explains the abnormal divergence of the rivers. A new lithological 3D conceptual model is proposed based on the characterization of the lithological facies and their temporal and spatial evolution along the eastern flank of Merapi volcano.

Multiscale, finite-frequency P and S tomography of the upper mantle in the southwestern Fennoscandian Shield

We image the P- and S-wave structure of the upper mantle in southwestern Scandinavia using a wavelet-based, multiscale parametrization and finite-frequency theory to model wave propagation. Relative traveltime residuals of direct P and S waves are measured in a high- and low-frequency band and are corrected for crustal structure using a detailed model for the study area. A range of resolution tests are used to find optimal damping values not only for variations in V P and V S separately, but also for perturbations in their ratio V P /V S . The tests show that features down to a size of 100 (150)km can be well resolved in the P (S) tomography. To ease comparison with previous studies we also perform ray-theoretical multiscale tomographies, and to test the degree of vertical smearing we evaluate different parametrizations in the vertical direction (wavelet-based multiscale and convolutional quelling). Our finite-frequency, multiscale images of variations in V P and V S confirm the existence of low velocities below southern Norway and Denmark and high velocities beneath the shield proper in Sweden, as seen in previous studies, but add more details to this simplified picture. The low velocities below southern Norway and Denmark are confined to a channel-like structure at about 100–200km depth, and the lateral transition from low to high velocities follows zones of Carboniferous-Permian extension and magmatism very closely. A deeper low-velocity anomaly below central southern Norway emerges from the channel at 150km depth and extends to a depth of 350km. In the Swedish area we infer high-velocity anomalies in V P and V S , and negative anomalies in V P /V S that indicate a strongly depleted mantle. We propose that the episodic erosion and convective removal of an originally thick mantle lithosphere below southern Norway to its current thickness of about 100km could have been a trigger for episodic uplift in the Mesozoic and Cenozoic.

Rifting to drifting transition of the Southwest Subbasin of the South China Sea

Continental rupturing process and related dynamics on the onset of seafloor spreading remain poorly understood in the opening of the South China Sea. To constrain the timing and cause of major tectonic events, we focus on the rifting-to-drifting transition of the Southwest Subbasin, which has very wide extended continental margins. By carefully interpreting rifting structures and carbonate platforms and reefs, we distinguished two major unconformities, i.e., the breakup unconformity (BRU) and the mid-Miocene unconformity, in the two conjugate margins of the Southwest Subbasin. The age of the BRU in our study area is near the Oligocene/Miocene boundary (~23 Ma). Pre-stack depth migration of a recently acquired multichannel reflection seismic profile reveals complex structures and strong lateral velocity variations associated with a 3.5 km thick syn-rifting sequence developed right at the continent-ocean boundary (COB) of the Southwest Subbasin. This syn-rifting sequence is bounded landwards by a large seaward dipping fault, and tapers out seawards. An erosional truncation, which represents the mid-Miocene unconformity landwards but the older breakup unconformity on the seaward side, occurred at the top of this sequence. The overall transitional deformation style from the rifting to drifting suggests a successive episode of rifting, faulting, compression, tilting, and erosion at the COB during the crustal thinning and mantle upwelling. Localized thick syn-rifting deposition and early deposition beneath the BRU in the oceanic domain exist only at the seaward concave part of the COB, indicating discrete rifting and seafloor spreading prior to the buildup of a unified spreading center for the entire subbasin.

Nanoscratch testing for the assessment of enamel demineralization under conditions simulating wine erosion.

Erosive tooth wear and dentinal hypersensitivity are common problems affecting professional wine tasters. By using nanoscratch testing, the aim of this in vitro study was to assess enamel softening under conditions simulating 10 one-minute episodes of wine erosion. Ten enamel specimens were bathed in artificial saliva for 2 hours before being eroded for 10 episodes, with each episode comprising one minute of wine erosion followed by one minute of remineralization in artificial saliva. Nanoscratches were placed with a spherical tip (20 μm radius) in a nanoindenter under a load of 100 mN at baseline (stage 1), after a one-erosion episode (stage 2) and after 10-erosion episodes (stage 3). There were significant effects of erosion stages on both scratch depth (p<0.001) and surface roughness (p<0.001). Post hoc tests showed significant differences in both scratch depths and surface roughness between stages 1 and 3 (p<0.001), and between stages 2 and 3 (p<0.01). Enamel softening occurs at an early stage of wine tasting, emphasizing the need to implement early preventive strategies in professional wine tasters. Further research elucidating the fundamental mechanisms involved in early stages of erosion has the potential to lead to development of more effective preventive strategies.

Anatomy of a subduction complex: architecture of the Franciscan Complex, California, at multiple length and time scales

The Franciscan Complex of California records over 150 million years of continuous E-dipping subduction that terminated with conversion to a dextral transform plate boundary. The Franciscan comprises mélange and coherent units forming a stack of thrust nappes, with significant along-strike variability, and downward-decreasing metamorphic grade and accretion ages. The Franciscan records progressive subduction, accretion, metamorphism, and exhumation, spanning the extended period of subduction, rather than events superimposed on pre-existing stratigraphy. High-pressure (HP) metamorphic rocks lack a thermal overprint, indicating continuity of subduction from subduction initiation at ca. 165 Ma to termination at ca. 25 Ma. Accretionary periods may have alternated with episodes of subduction erosion that removed some previously accreted material, but the complex collectively reflects a net addition of material to the upper plate. Mélanges (serpentinite and siliciclastic matrix) with exotic blocks have sedimentary origins as submarine mass transport deposits, whereas mélanges formed by tectonism comprise disrupted ocean plate stratigraphy and lack exotic blocks. The former are interbedded with and grade into coherent siliciclastic units. Palaeomegathrust horizons, separating nappes accreted at different times, appear restricted to narrow zones of <100 m thickness. Exhumation of Franciscan units, both coherent and mélange, was accommodated by significant extension of the hanging wall and cross-sectional extrusion. The amount of total exhumation, as well as exhumation since subduction termination, needs to be considered when comparing Franciscan architecture to modern and ancient subduction complexes. Equal dextral separation of folded Franciscan nappes and late Cenozoic (post-subduction) units across strands of the (post-subduction) San Andreas fault system shows that the folding of nappes took place prior to subduction termination. Dextral separation of similar clastic sedimentary suites in the Franciscan and the coeval Great Valley Group forearc basin is approximately that of the San Andreas fault system, precluding major syn-subduction strike-slip displacement within the Franciscan.

Reconstruction of Holocene patterns of change in a High Arctic coastal landscape, Southern Sassenfjorden, Svalbard

Abrupt shifts in sediment supply, relative sea level, permafrost regime, glacier state, snow cover and sea ice conditions associated with Holocene climate changes control processes operating on High Arctic coasts and make reconstructions of their past evolution a significant research challenge. This study attempts to describe the development of the coastal zone in southern Sassenfjorden, Svalbard, throughout the Holocene focusing on the styles of adjustment to major landscape changes. Five marine terraces (MT1-5) are identified and assessed. Spatial and chronological analysis suggests that the highest terrace, MT5, is pre-LGM (Last Glacial Maximum) and that MT4-3 underwent rapid uplift (151 and 11.4mm/year, respectively) shortly prior to 11 061±174cal.yrBP and became fully terrestrial by 9100years ago (as indicated by emergence rates) during the Holocene Thermal Maximum (HTM). Uplift rates for MT2-1 slowed to 5 and 2mm/year, respectively, with suggested emergence between 7200 and 6800cal.yrBP. A final 2m uplift of the relict alluvial plain probably happened during the Medieval Warm Period (1200–950cal.yrBP). Most recent coastal development (AD 1912–2012) is characterised by episodes of coastal erosion on the cliff and progradation of the Nøiselva delta. Interactions between sea ice, snow cover, permafrost, wind and wave regimes are assessed to understand their implications on future coastal development in a warming climate.

Dispersion modeling of particulate matter containing hexavalent chromium during high winds in southern Iraq

The aim of this paper is to describe a scientific methodology (i.e., the combination of different well-established modeling techniques) and its application to a real case scenario of contaminated dust emissions in high winds. This scenario addresses potential air pollution problems at the water treatment plant (WTP) at Qarmat-Ali, Basra, Iraq, during 2003. Workplace practices at the WTP before 2003 resulted in sodium dichromate contamination in the area. Looting at the site in early 2003 also contributed to this contamination. Individuals who were assigned to provide security at the site in 2003 have claimed adverse health effects caused by exposure to dust containing hexavalent chromium [Cr(VI)]. This report presents our modeling study with respect to these claims in relation to (1) amount of Cr(VI) present in the soil, (2) wind erosion episodes, and (3) possible long-term (e.g., annual average) Cr(VI) concentrations inhaled by different people while at the site. Our modeling approach included (1) the analysis of Cr(VI) soil measurements to assess the degree of contamination in different areas of the plant at different times; (2) the use of DUSTRAN model equations to calculate the emission rate of particulate matter (PM) less than 10 µm in diameter (PM10) during high-wind episodes; (3) the use of the U.S. Environmental Protection Agency (EPA) AERMOD modeling system to estimate Cr(VI) concentrations at the site; and (4) the calculation of modeling results in the form of both contour lines of average Cr(VI) concentrations at the site, and specific concentration values for selected individuals, based upon their recollection of their visits to the site.Implications: The assessment of individual exposure to contaminated dust during high-wind episodes requires a combination of modeling tools and the calculation of concentration impacts at precise locations and times. We have combined several state-of-the art simulation algorithms to provide a credible methodology for assessing individual exposure. The methodology has been applied to an actual case where exposure was claimed by individuals.

Evolution of topography of post-Devonian Scandinavia: Effects and rates of erosion

The mechanisms and timing of mountain growth in Scandinavia remain enigmatic given that the region has not been involved in active orogenesis since the Devonian and in any large-scale tectonic activities after the NE Atlantic breakup during the early Cenozoic. In this study we combine analysis of the vertical motions of the region caused by (dominantly) glacial erosion during the Quaternary with Apatite Fission Track (AFT) analysis of rocks from the area. Using numerical models, we first quantify how fluvial and glacial erosion carved out the fjords and valleys to a depth of 2km below the paleosurfaces. This erosional episode represents a major local weight loss and results in up to a 0.8-km uplift of rocks and up to a 0.5-km rise of local topography. These estimates only marginally depend on the effective elastic thickness of the lithosphere and thus are robust. We show then that no correlation exists between sample altitude and published AFT data, but that a correlation does exist between AFT age and the depth below our constructed pre-glacial summit surface. This correlation demonstrates the robustness of the numerical erosional model, quantifies average erosion rates during Carboniferous–Cretaceous at <10m/My, and outlines the regions of western Scandinavia (Lofoten and Bergen areas and Møre–Trøndelag fault complex) with atypical Mesozoic–Cenozoic evolution, probably related to regional tectonic activities.

Reprint of: Impacts of Mayan land use on Laguna Tuspán watershed (Petén, Guatemala) as seen through clay and ostracode analysis

Most of the cities built by the Mayas in the Petén area, in the Central Yucatán Peninsula, were abandoned 1200 to 1000 years ago. The phenomenon is sometimes un-appropriately called “the collapse of the Maya civilization”. Its main causes are still debated, ranging from climatic according to the occurrence of severe or modest droughts, to societal in the form of environmental mismanagement of the environment. In both processes, it is inferred that stress triggered the formation in many Petén lake sediments of erosional clay deposits, known as ’Maya clays’.This work presents a high resolution, multi-proxy study of ’Maya clays’ in lacustrine sediments from Laguna Tuspán, near the archaeological site of La Joyanca. Micropaleontological (ostracodes), mineralogical (clay minerals) and geochemical (bulk elemental composition and stable isotopes in organic carbon) records reveal three different phases of soil erosion throughout the last 5300 years. The oldest phase from 5281 to 2998 cal yr BP (i.e. 3331 - 1048 BC) is characterized by successive natural and moderate soil erosion deposits which follow climatic variations recorded in the American tropical belt. The time interval between 2998 and 1281 cal yr BP (i.e. 1048 BC and AD 661) contains four distinct erosional layers which, according to clay mineralogy, are indicative of both increased erosion of the regolith and strong soil loss. The most recent, also the most massive, deposit of Maya clay ends around 1281 cal yr BP (AD 661), that is some 200 years before the so-called ’Maya collapse’ in the Petén area. Recent archeological fieldwork studies indicate that a population mobility took place into the city of La Joyanca from its hinterland by the early Late Classic Period (ca. AD 600), that is, at the end or just after this erosion episode, and well before the occurrence of the Terminal Classic-Postclassic (AD 800-1250) drastic climatic changes. Shifts in environmental management by the local society and timing of urbanization may explain environmental changes better than droughts per se.