JournalTOCs

Geo-Marine Letters
Journal Prestige (SJR): 0.658

Citation Impact (citeScore): 2
Number of Followers: 6

Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1432-1157 - ISSN (Online) 0276-0460
Published by Springer-Verlag

[2469 journals]

Origin of Asian dust reconstructed from the Eu anomaly in the Hanon
paleo-maar sediment of Jeju Island, Korea
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  Abstract: Abstract In downwind regions, Asian dust fluxes are influenced by aridity and expansion of the source area, as well as by the frequency of dust storms associated with the predominant westerly jet and East Asian winter monsoon (EAWM). This study investigated the origin of Asian dust, and factors affecting its intensity, through analysis of the Hanon paleo-maar sediment of Jeju Island, Korea, using the Eu anomaly as a dust proxy. Trachybasalt (as an end-member) normalization pattern from the Hanon sediment core showed that the (Eu/Eu*)trachybasalt values were lower (0.85 on average) from the pre-Last Glacial Maximum (Late Pleistocene, 32.8–25.9 ka) to the early deglacial period (16.8–14.8 ka), indicating that most of the dust originated from the Gobi Desert. During the late deglacial period (14.5–11.6 ka), the (Eu/Eu*)trachybasalt increased to 0.88 on average, which indicated a gradual change in Asian dust origin toward the Taklimakan Desert and a consequently higher (Eu/Eu*)trachybasalt (> 0.9) during the Holocene period (after 10.2 ka). Asian dust proportion in the Hanon sediment core was around 20–70% during the last glacial period (32.8–11.6 ka), but decreased to 10–30% during the Holocene as the East Asian summer monsoon (EASM) expanded toward north and northeast China. Consequently, provenance changes in dust transport indicate that Asian dust flux associated with the surface EAWM intensity is overall greater during the last glacial period, while the dust transported via the upper level westerly jet could reach the study region during the Holocene.
  PubDate: 2022-04-19
Mobilized shear strengths of Mississippi River Delta Front sediments
during submarine landslides
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  PubDate: 2022-03-22
Characteristics of rare earth elements in the surface sediments of
Southwest Indian Ridge: implication of grain size for the identification
of hydrothermal activity
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  Abstract: Abstract The characteristics of rare earth elements (REEs) in mid-ocean ridge (MOR) sediments are important indicators of hydrothermal activity. However, these sediments generally have multiple sources and different grain sizes, resulting in variations of the REE characteristics in bulk sediment samples, which create difficulties when interpreting the results. We studied the characteristics of REEs in sediments with different grain sizes collected proximal, a moderate distance, and distal to hydrothermal fields located on the Southwest Indian Ridge (SWIR). The results show that > 250 μm sediments comprised abundant local debris (especially in proximal sediments) and hydrothermal components with minor Fe–Mn oxides and hydroxides, while < 250 μm sediments comprised higher contents of hydrothermal components, Fe–Mn (hydr)oxides, and terrigenous dust. The REE features of > 250 μm sediments were significantly controlled by local mafic and ultramafic debris (heavy REE enrichment), while hydrothermal components, calcareous ooze, and Fe–Mn oxides played a more important role in the features of the 74–250 μm sediment REEs (light REE enrichment and negative Ce anomaly). The REE characteristics of the < 74 μm sediments were partially controlled by the occurrence of Mn oxides and eolian dust. With decreasing grain size, the sediments generally exhibited increasing negative Ce anomalies, probably the result of adsorption of REE onto hydrothermal Fe oxyhydroxides. In addition, with increasing distance from the hydrothermal fields, the influence of the hydrothermal components on the REE features decreased. The relative contributions of material source components to the sediments and feasible grain size for the identification of hydrothermal contribution were discriminated by the δEu–(Gd/Yb)N diagram. Overall, our results showed that the REE features of 74–250 μm MOR sediments are the most feasible for the identification of potential hydrothermal activity in studied segments.
  PubDate: 2022-02-21
  DOI: 10.1007/s00367-022-00729-8
An examination of dimensionless variables in sediment threshold studies
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  Abstract: Abstract Shields dimensionless stress and particle Reynolds number have been used since their introduction into sediment threshold studies. They do not separate forcing and resisting quantities so that both shear velocity and particle grain size occur in each. This study considers two different combinations of those traditional parameters to give two dimensionless variables, a dimensionless grain size independent of flow, and a dimensionless shear stress independent of the size. Considering observed data from various sources, the scatter around the new dimensionless threshold curve was found to be less than around the traditional Shields form. Simple explicit rational approximations were obtained between the new dimensionless stress and dimensionless grain size. They describe experimental results better than arbitrary formulae for the traditional Shields parameter. That, with the separation of flow and resistance, makes the solution of practical problems simpler.
  PubDate: 2022-02-20
  DOI: 10.1007/s00367-022-00730-1
Correction to: Bedform evolution and dynamics of a geostrophic
current‑swept shelf, northern KwaZulu‑Natal, South Africa
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  PubDate: 2022-01-19
  DOI: 10.1007/s00367-022-00728-9
Evolution of fluid flow and carbonate recrystallization rates in deep-sea
sediments of the Equatorial Pacific
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  Abstract: Abstract Fluid flow and carbonate recrystallization rates of deep-sea sediments from eight locations in the Equatorial Eastern Pacific were determined by using δ44/40Ca values of pore water and corresponding sediments. The studied drill sites of IODP Exp. 320/321 are located along a transect of decreasing crustal age and reveal different characteristic pore water depth profiles. The younger sites show an overall isotopic equilibration with the sediment in the upper part of the sedimentary column. In the lower part, the δ44/40Ca of the pore water increases back to seawater-like values at the sediment/basalt interface, forming a bulge-shaped pore water profile. The magnitude of the δ44/40Ca pore water bulge decreases with increasing age of the oceanic crust and sediment cover, resulting in seawater-like δ44/40Ca values throughout the sedimentary column in the oldest Sites U1331 and U1332. These findings indicate a seawater-like fluid input from the underlying crust into the sediment. Thus, after sedimentation, carbonate recrystallization processes start to enrich the pore water in 40Ca, and after a time of carbonate recrystallization and cooling of oceanic crust, a flow of seawater-like fluid starts to move upwards through the sedimentary column, enriching the pore water with 44Ca. We established a carbonate recrystallization and fluid flow model to quantify these processes. Our determined carbonate recrystallization rates between 0.000013e(−t/15.5) and 0.00038e(−t/100.5) and fluid flow rates in the range of 0.42–19 m*Myr−1 indicate that the fluid flow within the investigated sites of IODP Exp. 320/321 depends on the sedimentary composition and location of the specific site, especially the proximity to a recharge or discharge site of a hydrothermal convection cell.
  PubDate: 2022-01-12
  DOI: 10.1007/s00367-021-00720-9
Sediment budget of a cuspate shoreline and its influence on spit
development—Lagoa dos Patos, Brazil
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  Abstract: Abstract The coastal sediment budget is an essential tool to understand erosion/accretion patterns along coastlines and to predict future changes. This work is one of the first approaches of a coastal sediment budget study in a cuspate shoreline covering the whole embayment-spit system. Taking this into consideration, this study aims to estimate the main longshore sediment transport patterns and propose a conceptual model of the regional sediment budget of the lagoon cuspate shoreline (Lagoa dos Patos-Brazil), while also analyzing its influence on the spit development. To do so, representative wind conditions (direction and speed) were used to force a validated lagoon wave model utilizing the process-based modeling suite Delft3D. The potential longshore sediment transport was computed along widely distributed cross-sections, based on representative wave cases, and the annual sediment budget was estimated. The results showed a pattern of inter-related source and storage areas along the bay beaches and the occurrence of short-term nodal zones (convergent and divergent), which have an important control on the regional sediment budget of the coast. The central littoral cells of the embayments behave as temporary sediment storage areas, while the southern littoral cells act as sources of sediments to the spits. The findings of this study demonstrate the important control that short-term nodal zones have on the annual coastal sediment budget of complex coastline shapes and, the importance of the budget of the adjacent updrift cell to the sediment supply for the spits.
  PubDate: 2022-01-12
  DOI: 10.1007/s00367-021-00724-5
Detection of a hot 137Cs particle in marine sediments from Norway:
potential implication for 137Cs dating
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  Abstract: Abstract An anomalous value in the 137Cs record from a marine sediment core in Veafjord, Norway, appears to be due to the presence of a micron-size hot radioactive particle. The 137Cs concentration in a subsample from the surficial 0–1 cm sediment slice was over 3 times higher than in the adjoining slice and double that in a concentration peak significantly deeper in the core dating from the period of Chernobyl fallout. To determine the cause of the anomaly, the sample was divided into two equal parts each of which were then reanalysed. Whereas one had a normal concentration similar to that of the adjoining slice, the concentration in the other was now over 5 times higher. Analyses of three further splits of the high activity subsamples followed a similar pattern with one part having a normal concentration, and the other a concentration that nearly doubled each time. The results are consistent with the presence of a hot 137Cs particle embedded in the sediment matrix. Its activity was estimated to be 15 ± 2 mBq. Possible sources are fallout from the 1986 Chernobyl accident or marine discharges from UK nuclear installations in the 1970s. The delayed input of such a particle into the sedimentary record highlights the need for care in using 137Cs records for dating sediment accumulations in areas open to contamination from these or similar sources.
  PubDate: 2021-12-26
  DOI: 10.1007/s00367-021-00727-2
Bedform evolution and dynamics of a geostrophic current-swept shelf,
northern KwaZulu-Natal, South Africa
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  Abstract: Abstract When compared to tide-dominated shelves, shelves swept by geostrophic flows are relatively understudied, yet geostrophic currents have the potential to construct substantial current-generated shelf bedforms. This paper examines the evolution of a series of bedforms encountered along the narrow Agulhas Current-swept northern KwaZulu-Natal shelf. Their evolution is placed in the context of progressive current impingement and variation in flows associated with the postglacial transgression and culminating in the present-day highstand. Ultra-high resolution seismic reflection, multibeam, side-scan sonar and single beam data sets reveal several bedform scales and morphologies; wave ripples and shoreface-connected ridges are associated only with the inner shelf, and 2D and 3D very large dunes are more cosmopolitan and span the entire shelf sector. The inner shelf is marked by rock outcrop (aeolianite), surrounded by sandy sediment, grading seaward into sediment starved bedforms associated with bioclastic gravels. Where sufficient sediment exists in local depocenters, very large dunes form discontinuous fields along the outer shelf. The seismic stratigraphy of the outer shelf reflects the effects of postglacial flooding by rising sea levels and increasing current impingement by the Agulhas Current. The Holocene wave ravinement surface is overlain by flat-lying strata (early dune development and dune amalgamation with first current exposure), in turn covered by hummocky, sub-horizontal aggrading beds (amalgamation), overlain by inclined cross-bedded packages (lee faces of the bedforms formed during migration and full current interaction). Morphometric analyses show that for both the inner and outer shelf, no relationships exist between water depth, wavelength and spacing. Height to spacing (H/L) relationships are weak but nevertheless show a broadly positive trend. Bedform heights are lower on the inner shelf compared to the outer shelf, but bedform spacing is greater on the inner shelf, with a 40% overlap in H/L indices observed between the two areas. The departures in overlap can be linked to the competing offshore Agulhas Current and the inshore wave-dominated processes. Bedforms of the inner shelf plot below the global H/L mean and can be related to the more infrequent incursions of the Agulhas Current core. At the time of survey, the Agulhas Current was likely situated well offshore, resulting in reduced current activity in the survey area resulting in rounding of the dune crests, degradation of the dune crests and trough infilling. On the outer shelf, the H/L values plot above the mean global trend, suggesting vertical accretion due to the faster currents. Crest rounding and downlapping of the upstream lee faces onto the downstream stoss faces indicate dune degradation, which is related to a seaward location of the Agulhas Current at the time of survey.
  PubDate: 2021-12-07
  DOI: 10.1007/s00367-021-00722-7
Sequence stratigraphy in the Algoa and Gamtoos basins (South Africa): a
shoreline’s journey since the Middle Mesozoic
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  Abstract: Abstract Basin evolution models are dependent on high-quality subsurface data, normally obtained during hydrocarbon exploration activities. The limited exploration, to-date, has impeded the understanding of the geological evolution of the offshore Algoa and Gamtoos half-graben basins in the southern Cape region of South Africa. To reconstruct the main geological events of the area since the Early Jurassic, vintage borehole and seismic data as well as key outcrop observations were integrated. Using this combined dataset, we generated contemporary gross depositional environment models, as well as tested the applicability of different sequence stratigraphic models for these late Gondwana basins. The studied stratigraphic interval contains syn- and post-rift systems that were impacted by marine processes, especially in the distal hanging walls of these compartmentalized half-graben basins. Sedimentation within these depocenters primarily occurred above the hanging walls, while the footwalls formed regions of basement highs. The geological characteristics of the studied succession prevent the application of the depositional sequence or tectonic system tracts models in the syn-rift succession. Because subaerial unconformities (SUs) in the distal syn-rift sequence are not detectable, a diachronous, northward advancement of the shoreline (relative sea level rise) until the late Valanginian can be postulated. The observations in the syn-rift sequence, which is bound by a basal SU, followed by third- and fourth-order transgressive and regressive cycles and a second-order maximum flooding surface at the top, can be explained with a modified genetic sequence model. In the transitional to drift phase interval, from Hauterivian to Holocene, the successions are bound by SUs and their correlative conformities. In the successions without evidence for subaerial exposure, flooding surfaces could be used as sequence-bounding stratigraphic contacts. This study reaffirms the notion that while the sequence stratigraphic concept is model-independent, sequence models are sensitive to depositional scale.
  PubDate: 2021-12-04
  DOI: 10.1007/s00367-021-00721-8
Detecting the effects of rapid tectonically induced subsidence on Mayotte
Island since 2018 on beach and reef morphology, and implications for
coastal vulnerability to marine flooding
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  Abstract: Abstract Subsidence is a widespread phenomenon on the world’s coasts. Mayotte, a coral reef-fringed archipelago in the SW Indian Ocean, experienced, in 2018 and 2019, 32 earthquakes with a recorded magnitude > 5 sourced by magmatic extraction from a deep reservoir 40–60 km east of the archipelago. This crisis resulted in island subsidence of up to 0.2 m. Profile measurements of three beaches in 2019–2021, referenced to benchmarks adjusted for subsidence, did not show any notable morphological change when compared to earlier profiles obtained in 2006/2008. This suggests that the rapid but limited subsidence has not significantly affected these systems, excluding eventual ecological repercussions that are not investigated here. Profile changes reflect seasonal variations in monsoon and trade-wind wave energy, and additionally the effect of local mild terrigenous sediment inputs. The sea-level rise caused by subsidence is, however, leading to more frequent spring high-tide flooding of some low back-beach areas and roads on the densely populated northeastern shores of the archipelago, the zone most affected by this tectonic movement. The case of Mayotte is interesting inasmuch as the subsidence caused by a distant submarine volcanic event has not been abrupt as in tectonically active areas nor continuous as in subsidence related, for instance, to glacio-isostatic readjustment, to continuous natural sediment compaction, or to anthropogenic loading. The crisis has been relatively quiescent since July 2021. Continuous monitoring will be needed to see how subsidence will eventually further affect the beach-reef flat systems of Mayotte.
  PubDate: 2021-12-03
  DOI: 10.1007/s00367-021-00725-4
Palaeoenvironmental context and significance of ferruginous tubular
bioforms and other authigenic mineral formations in source-to-sink
sedimentary systems
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  Abstract: Abstract Surficial sediments on the seafloor from passive continental margins can provide insight into recent Late Quaternary sedimentary dynamics acting over offshore sedimentary systems. This work focuses on the study of some particular ferruginous tubular structures resembling bioforms (FTB) located in the distal Galician Continental Margin (NW Iberian Margin) at water depths between ~ 1550 and ~ 2200 m. The characterisation of these structures made it possible to study in depth their formation environment and subsequent sedimentary evolution during the Late Pleistocene and Holocene. The FTB consist of goethite with a framboidal texture. They were interpreted as formed by an initial pyrite precipitation in reducing microenvironments conditioned by the activity of sediment-dwelling organisms during the early diagenesis. This is followed by the oxidation of pyrite by a combination of hydrothermal fluids and erosional processes, which triggers the formation of the framboidal oxyhydroxides. The data allowed obtaining a comprehensive understanding of the environmental context and the significance of these ferruginous tubules, as there are no previous studies in the scientific literature that describe these structures in a source-to-sink sedimentary system.
  PubDate: 2021-12-03
  DOI: 10.1007/s00367-021-00726-3
The active tectonic structures along the southern margin of Lesvos Island,
related to the seismic activity of July 2017, Aegean Sea, Greece
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  Abstract: Abstract Hydrographic survey of the southeastern coastal margin of Lesvos Island (Greece) was conducted in January 2018 by R/V METEOR. The main morphological characteristic of the southern margin of Lesvos Island is a sub-parallel to the coast elongated basin, 30 km long, 5–10 km wide, and 700 m deep. It is interrupted by an oblique NW–SE narrow channel of 650 m depth, which separates the adjacent platform areas surrounding the longitudinal basin. The northern margin of the basin is abrupt with morphological slopes of more than 10°, following the major WNW-ESE normal fault surface, running along the coastal zone, with an overall throw of more than 800 m. In contrast, the southern margin shows a gradual slope increase from 1° to 5°, where several shallow sub-bottom profiles across the basin have indicated the existence of some minor WNW-ESE normal faults and one reverse/strike-slip fault zone, with throws of a few up to 13 m. However, the NW–SE narrow channel intersecting the basin is bounded by two sub-vertical fault zones with sinistral strike-slip motion and throws of more than 150 m. The above structure was reflected in the mainshock of magnitude 6.3 (12/6/2017), corresponding to a WNW-ESE normal fault dipping to the SSW and the two major aftershocks of magnitude 5.2 and 5.0 corresponding to the two sub-parallel NW–SE sinistral strike-slip faults of the channel. This active deformation comprising WNW-ESE normal faults and NW–SE or NE-SW strike-slip faults is compatible with the area’s overall tectonic frame at the eastern margin of the Aegean microplate.
  PubDate: 2021-11-09
  DOI: 10.1007/s00367-021-00723-6
Improved feature extraction in seismic data: multi-attribute study from
principal component analysis
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  Abstract: Abstract Seismic attribute analysis is the most effective method to predict geological features from seismic images. However, using a single attribute for the purpose may reduce the prediction quality. Therefore, integrating multiple attributes becomes significant and has the potential to decipher the finer details. The present study uses the principal component analysis to carry out a multi-attribute study for long offset (5 km) seismic data from the Krishna-Godavari basin, Eastern Margin of India, so as to improve the seismic image and aid in feature extraction. The colour composites developed for the seismic data indicate improved continuity in reflectors in stratigraphic attributes analysis and better resolution of the faults and migration pathways in structural attributes analysis.
  PubDate: 2021-10-02
  DOI: 10.1007/s00367-021-00719-2
The morphodynamics of transverse dunes on the coast of South Africa
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  Abstract: Abstract Transverse sand dunes located within the supratidal zones of beaches are a significant geomorphic feature along sand-dominated coasts worldwide and are generated by strong alongshore winds in areas of high sediment availability. Transverse dunes are present along the South African coast, and these are known to migrate dynamically in response to wind forcing. However, the detailed dynamics of individual dune systems along the same coastal stretch have not been compared to one another, and the relationship of transverse dunes to their hosting beach systems has also not been examined. This study examines the properties and dynamics of transverse supratidal dunes from three systems along the coast of South Africa, using remote sensing methods. Results show that, although the underlying beach system appears to be relatively stable over the time period of analysis, there is a dominant aeolian-driven migration of transverse dunes towards the northeast, following prevailing wind direction, countered by less dominant movement to the southwest. There are also considerable variations in calculated annual dune migration rates between adjacent systems, between summer and winter seasons, and between dunes within a single site. This highlights that, although beach and dune landforms can be conceptually considered as part of the same sediment system, there is not a clear relationship between phases of beach aggradation and phases of dune aggradation. Instead, a primary control appears to be beachface erosion by waves that reduces beach width and influences dune morphodynamics, independent of sediment supply.
  PubDate: 2021-09-30
  DOI: 10.1007/s00367-021-00717-4
Sedimentological evidence for seiching in a swell-dominated headland-bay
system: Table Bay, Western Cape, South Africa
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  Abstract: Abstract Table Bay, South Africa, is a typical headland-bay system with a shoreline that can be described by a logarithmic spiral. A peculiarity and unique feature of Table Bay is the juxtaposition of Robben Island opposite its headland. As a consequence, the bathymetry defines an ellipsoidal basin which was postulated to potentially resonate in the form of long-period standing waves (seiches). One aim of this study, therefore, was to investigate whether any evidence for such resonant oscillations could be detected in the geomorphology and sediment distribution patterns. Indeed, the ellipsoidal shape of the basin can be framed by two converging log-spirals with their centres located opposite each other, one off Robben Island and the other on the Cape Town side of the bay. The so-called apex line, which divides the two spirals into equal parts is aligned SW–NE, i.e. more or less parallel to the direction of ocean wave propagation. The distribution patterns of all sedimentary parameters were found to be characterised by a strikingly similar trend to either side of the apex line. This supports the hypothesis that the basin of Table Bay appears to resonate in the form of a mode 1 standing wave, with the node positioned above the apex line in the centre of the bay. The maximum period of such a standing wave was calculated to be around 37 min. The study demonstrates that large-scale sediment distribution patterns can reveal the existence of specific hydrodynamic processes in coastal embayments. It is recommended that this phenomenon be investigated in greater detail aimed at verifying the existence of resonant oscillations in Table Bay and, in the event, at establishing its precise nature and trigger mechanism.
  PubDate: 2021-09-18
  DOI: 10.1007/s00367-021-00718-3
Environmental implications of the distribution and physical
characteristics of surface sediments in the northern Persian Gulf
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  Abstract: Abstract The Persian Gulf (PG) is a marginal sea with unique geomorphology and ocean currents, as well as various sub-basins with specific sediment characteristics. In this study, grain size distribution and microscopic examination of coarse-grained particles of 52 surface sediments of the Iranian part of the PG were performed to assess the distribution and physical characteristics of surface sediments and their link to the environmental conditions. Results showed that the seafloor of the middle parts of the PG bottom is covered by silt and sandy silt with a coarsening trend from shallower to deeper waters. At the NW part (submerged Arvand Delta) and the SE part (Strait of Hormoz) of the PG, however, coarser grains of silty sand, and locally, gravelly muddy sand dominate. High-energy density-driven bottom current leaving the PG from channelized deeper areas is likely responsible for removing fine grains, resulting in the accumulation of very poorly to poorly sorted coarse sediments (shell fragments and relict particles) in the deep bottom areas. This hard bottom, in turn, provides a proper surface for some epifaunal communities such as corals and foraminifera. The Iranian offshore basins, on the other hand, are dominated by well to moderately sorted silt to fine sand terrigenous particles. These finer sediments contain a relatively high organic matter with high pellet contents. Altogether, the sedimentation regime of the basin is under the influence of complex hydrodynamic conditions, different bottom materials (relict and bioclasts), the proportion of terrigenous components, complex bottom topography and climate.
  PubDate: 2021-09-10
  DOI: 10.1007/s00367-021-00716-5
Sedimentology and structure of a Holocene slump deposit on the continental
slope off Baja California, Mexico
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  Abstract: Abstract A marine sediment core located off the southernmost part of the Baja California Peninsula, NE Pacific, is analyzed to investigate a submarine mass failure. We examine the lithofacies and sedimentary structures, the total organic (TOC) and inorganic (TIC) carbon, the grain size composition, and the degree of fragmentation in foraminifera tests. The core BB03 consists of five lithostratigraphic units, from bottom to top, U1 to U5. Radiocarbon dating (AMS 14C) indicates that this sequence is inverted, where the deepest strata U1–U2 date at ~ 4,162 cal yr BP, U3–U4 at ~ 14,406 cal yr BP, and the shallower strata U5 at ~ 18,759–19,445 cal yr BP. Analysis of core and multibeam bathymetric data evidenced a submarine mass failure of the slump type, characterized by abruptly inverted layers with soft-sediment deformation structures. The event’s timing is constrained both with AMS 14C and the well-known stratigraphic identification of laminated or bioturbated layers in this highly productive upwelling zone. The event occurred during the Late Holocene as constrained by a maximum age of ~ 4,000 years. Although there is no explicit evidence on the cause of the submarine slump, the geomorphic characteristics and the close spatial connection with other submarine mass failures suggest a close relationship with the Tosco-Abreojos fault having acted either as a preconditioning factor or as a triggering mechanism. Finally, this study represents one of the few studies of submarine mass failures at the NE Tropical Pacific margin, aiming to identify how the transported sediments interact with the regional morphology and the formation of modern seafloor structures.
  PubDate: 2021-09-08
  DOI: 10.1007/s00367-021-00713-8
Hurricane Matthew in 2100: effects of extreme sea level rise scenarios on
a highly valued coastal area (Palm Beach, FL, USA)
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  Abstract: Abstract Sea-level rise represents a severe hazard for populations living within low-elevation coastal zones and is already largely affecting coastal communities worldwide. As sea level continues to rise following unabated greenhouse gas emissions, the exposure of coastal communities to inundation and erosion will increase exponentially. These impacts will be further magnified under extreme storm conditions. In this paper, we focus on one of the most valuable coastal real estate markets globally (Palm Beach, FL). We use XBeach, an open-source hydro and morphodynamic model, to assess the impact of a major tropical cyclone (Hurricane Matthew, 2016) under three different sea-level scenarios. The first scenario (modern sea level) serves as a baseline against which other model runs are evaluated. The other two runs use different 2100 sea-level projections, localized to the study site: (i) IPCC RCP 8.5 (0.83 m by 2100) and (ii) same as (i), but including enhanced Antarctic ice loss (1.62 m by 2100). Our results show that the effective doubling of future sea level under heightened Antarctic ice loss amplifies flow velocity and wave height, leading to a 46% increase in eroded beach volume and the overtopping of coastal protection structures. This further exacerbates the vulnerability of coastal properties on the island, leading to significant increases in parcel inundation.
  PubDate: 2021-09-08
  DOI: 10.1007/s00367-021-00715-6
Analytical solutions of one-line model to shoreline change on a coast
bounded by solid boundaries
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  Abstract: Abstract This study introduces new analytical solutions for the one-line model of shoreline change on bounded coast whose both ends are fixed by the coastal structures or rocky cliffs (solid boundaries). A general analytical solution describing shoreline evolution on the bounded coast with the arbitrary initial shape of beach fill/cut is introduced. Subsequently, several shaped types of initial shorelines, such as trapezoid rectangle, and triangle are considered. The new solutions for the bounded coast (finite coast) were compared with the underlying analytical solutions, which describe shoreline evolution on an infinite coast. This shows the distinct differences in the cases without and with solid boundaries. The solid boundaries lead the shoreline to the equilibrium stage more quickly at a certain position instead of slow and 0 of the case without solid boundaries. The relationship showing the decaying process of sediment in the beach fill portion is presented. Results also highlight that when the value of L*, the ratio of bounded coast length to the width of beach fill portion, is large enough, the shoreline evolution of the cases without solid boundaries is asymptotic even at a large t*. Furthermore, the relationship between the dimensionless decay time, t*, and the dimensionless total length of the adjacent coasts to the beach fill portion is also provided, LS*, If LS* is large, then the t* is large and vice versa. The solutions proposed in this study have not been verified with the measured data, which could be a disadvantage. However, the derived solutions could be very useful and beneficial for preliminary design, education practices, and beach nourishment (beach fill), or the recovery of coastal morphology after the severe damages induced by natural disasters (beach cut).
  PubDate: 2021-08-28
  DOI: 10.1007/s00367-021-00714-7