scholarly journals “Continuous” Backstepping of Holocene Coastal Barrier Systems into Incised Valleys: Insights from the Ofanto and Carapelle-Cervaro Valleys

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1799
Author(s):  
Vincenzo De Santis ◽  
Massimo Caldara ◽  
Luigi Pennetta
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Sediment Supply ◽  
Seismic Facies ◽  
Time Interval ◽  
Coastal Barrier ◽  
Incised Valleys ◽  
The Mediterranean

Two recently recognised incised valleys in the Manfredonia Gulf are described. The first (CCV) is correlated with the current Carapelle and Cervaro streams. The second (OSFV) is correlated mostly with the current Ofanto River. Six seismic facies and seven unconformity-bounded seismic units have been identified, which infilled CCV and OSFV. In CCV, during the sea-level ranges from −29 to −18 and from −18 to −4.7 m b.s.l., two barrier/spit-backbarrier systems formed in the most landward sector of the valley. The lower system was attributed to a time interval between 9.2 ka BP and ca. 8.3 ka BP, chronologically constrained by the ZS2 borehole. In OSFV, during the sea level ranges from −39 to −29, and from −29 and to −18 m b.s.l., two beach/spit-backbarrier systems, arranged in a “continuous” landward backstepping pattern, formed. The phase that contributed most to the beach/spit-backbarrier systems formation is that which is coeval with the formation of the sapropel S1 in the Mediterranean. The conservation of barrier/spit-backbarrier systems arranged in a “continuous” landward backstepping pattern, is due to a strong and continued sediment supply that occurred during the sapropel S1 formation, coupled with low-gradient settings and a regime of slow sea-level rise.

Autogenic progradation of Bayhead deltas during sea-level rise wIthin incised valleys : theory, experiment and field examples    

2021 ◽  
Author(s):  
Laure Guerit ◽  
Brady Foreman ◽  
Chen Chen ◽  
Chris Paola ◽  
Sébastien Castelltort
Keyword(s):  
Sediment Transport ◽  
Sea Level Rise ◽  
Sea Level ◽  
Large Scale ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Surface Evolution ◽  
Sequence Stratigraphic ◽  
Incised Valleys ◽  
The Trinity

<p>The evolution of sedimentary landscapes is primary driven by the interplay between the rate of accommodation creation A, controlled by sea-level and subsidence, and the rate of sediment supply S, controlled by erosion and sediment transport. In simple terms, the balance between A and S can be used to predict periods of progradation (when sediment supply exceeds accommodation) and periods of retrogradation (when accommodation exceeds sediment supply). However, a growing list of observations show that internal feedbacks within the sediment transport system can generate large-scale, autogenic stratigraphic patterns that are not anticipated by the A/S theory. These observations call for a reanalysis of several sequence stratigraphic precepts that assume a deterministic relationship between external forcings and stratigraphic products. Here, we focus on the filling of incised valleys during constant sea-level rise, and by a constant sediment flux. We develop a simple conceptual model of valley filling and we show that the classic sequence stratigraphic phenomenon of bayhead deltaic systems can be generated by purely autogenic progradation during the late stage of valley flooding. This transient “auto-advance” event results from a strong decrease of in-valley accommodation as base-level rises towards the valley apex. To test this model, we build a laboratory experiment that successfully reproduces the dynamics predicted by the model. Finally, we apply our model to two similar field examples, the Trinity and Brazos rivers incised valleys (Texas, USA). There systems are broadly similar in dimension and sea-level history but were filled at different sediment rates. We propose that this led to auto-advance event in the Trinity River valley while no advance is observed in the Brazos system. We thus show by conceptual, experimental and natural examples that auto-advance can produce out-of-sequence regressive bayhead diastems during highstands similar to a transient change in allogenic forcing. Combined with other recent studies, our findings support the idea that meso-scale autogenic patterns are ubiquitous in the fluvio-deltaic record, and need to be more extensively incorporated into reconstructions of Earth surface evolution and reservoir models.</p>

scholarly journals Contributions of Organic and Mineral Matter to Vertical Accretion in Tidal Wetlands across a Chesapeake Bay Subestuary

2021 ◽  
Vol 9 (7) ◽  
pp. 751
Author(s):  
Jenny R. Allen ◽  
Jeffrey C. Cornwell ◽  
Andrew H. Baldwin
Keyword(s):  
Organic Matter ◽  
Sea Level Rise ◽  
Chesapeake Bay ◽  
Sea Level ◽  
210Pb Dating ◽  
Sediment Supply ◽  
Mineral Matter ◽  
Tidal Wetlands ◽  
Vertical Accretion ◽  
Inorganic Matter

Persistence of tidal wetlands under conditions of sea level rise depends on vertical accretion of organic and inorganic matter, which vary in their relative abundance across estuarine gradients. We examined the relative contribution of organic and inorganic matter to vertical soil accretion using lead-210 (210Pb) dating of soil cores collected in tidal wetlands spanning a tidal freshwater to brackish gradient across a Chesapeake Bay subestuary. Only 8 out of the 15 subsites had accretion rates higher than relative sea level rise for the area, with the lowest rates of accretion found in oligohaline marshes in the middle of the subestuary. The mass accumulation of organic and inorganic matter was similar and related (R2 = 0.37). However, owing to its lower density, organic matter contributed 1.5–3 times more toward vertical accretion than inorganic matter. Furthermore, water/porespace associated with organic matter accounted for 82%–94% of the total vertical accretion. These findings demonstrate the key role of organic matter in the persistence of coastal wetlands with low mineral sediment supply, particularly mid-estuary oligohaline marshes.

Feasibility of sedimentation strategies for the Mekong delta to counterbalance relative sea-level rise

2021 ◽  
Author(s):  
Frances E. Dunn ◽  
Philip S. J. Minderhoud
Keyword(s):  
Land Use ◽  
Sea Level Rise ◽  
Sea Level ◽  
Mekong Delta ◽  
Sediment Deposition ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Relative Sea Level ◽  
Fluvial Sediment ◽  
Relative Sea Level Rise

<p>As one of the largest deltas in the world, the Mekong delta is home to over 17 million people and supports internationally important agriculture. Recently deposited sediment compacts and causes subsidence in deltas, so they require regular sediment input to maintain elevation relative to sea level. These processes are complicated by human activities, which prevent sediment deposition indirectly through reducing fluvial sediment supply and directly through the construction of flood defence infrastructure on deltas, impeding floods which deliver sediment to the land. Additionally, anthropogenic activities increase the rate of subsidence through the extraction of groundwater and other land-use practices.</p><p>This research shows the potential for fluvial sediment delivery to compensate for sea-level rise and subsidence in the Mekong delta over the 21st century. We use detailed elevation data and subsidence scenarios in combination with regional sea-level rise and fluvial sediment flux projections to quantify the potential for maintaining elevation relative to sea level in the Mekong delta. We present four examples of localised sedimentation scenarios in specific areas, for which we quantified the potential effectiveness of fluvial sediment deposition for offsetting relative sea-level rise. The presented sediment-based adaptation strategies are complicated by existing land use, therefore a change in water and sediment management is required to effectively use natural resources and employ these adaptation methods. The presented approach could be an exemplar to assess sedimentation strategy feasibility in other delta systems worldwide that are under threat from sea-level rise.</p>

scholarly journals Holocene sea level and climate interactions on wet dune slack evolution in SW Portugal: A model for future scenarios?

The Holocene ◽  
2018 ◽  
Vol 29 (1) ◽  
pp. 26-44 ◽  
Author(s):  
Manel Leira ◽  
Maria C Freitas ◽  
Tania Ferreira ◽  
Anabela Cruces ◽  
Simon Connor ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Environmental Changes ◽  
Sediment Accumulation ◽  
High Energy ◽  
Sediment Supply ◽  
Dune Slack ◽  
Ecological Stability ◽  
The Holocene ◽  
Climate Interactions

We examine the Holocene environmental changes in a wet dune slack of the Portuguese coast, Poço do Barbarroxa de Baixo. Lithology, organic matter, biological proxies and high-resolution chronology provide estimations of sediment accumulation rates and changes in environmental conditions in relation to sea-level change and climate variability during the Holocene. Results show that the wet dune slack was formed 7.5 cal. ka BP, contemporaneous with the last stages of the rapid sea-level rise. This depositional environment formed under frequent freshwater flooding and water ponding that allowed the development and post-mortem accumulation of abundant plant remains. The wetland evolved into mostly palustrine conditions over the next 2000 years, until a phase of stabilization in relative sea-level rise, when sedimentation rates slowed down to 0.04 mm yr−1, between 5.3 and 2.5 cal. ka BP. Later, about 0.8 cal. ka BP, high-energy events, likely due to enhanced storminess and more frequent onshore winds, caused the collapse of the foredune above the wetlands’ seaward margin. The delicate balance between hydrology (controlled by sea-level rise and climate change), sediment supply and storminess modulates the habitat’s resilience and ecological stability. This underpins the relevance of integrating past records in coastal wet dune slacks management in a scenario of constant adaptation processes.

scholarly journals Supplemental Material: Detrital signals of coastal erosion and fluvial sediment supply during glacio-eustatic sea-level rise, Southern California, USA

2021 ◽  
Author(s):  
Glenn Sharman ◽  
et al.
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Erosion ◽  
Southern California ◽  
Mixture Modeling ◽  
Sediment Supply ◽  
Analytical Methodology ◽  
Fluvial Sediment ◽  
Icp Ms ◽  
Data Tables

Sample summary, LA-ICP-MS data tables, sources of Cretaceous-Paleogene forearc data, Peninsular Ranges batholith zircon U-Pb ages, mixture modeling results, and U-Pb analytical methodology.<br>

scholarly journals Fluvial Sediment Supply and Relative Sea-Level Rise

2019 ◽  
pp. 103-126
Author(s):  
Stephen E. Darby ◽  
Kwasi Appeaning Addo ◽  
Sugata Hazra ◽  
Md. Munsur Rahman ◽  
Robert J. Nicholls
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Sediment Supply ◽  
Relative Sea Level ◽  
Fluvial Sediment ◽  
Relative Sea Level Rise

scholarly journals Biogeomorphic modeling to assess resilience of tidal marsh restoration to sea level rise and sediment supply

2021 ◽  
Author(s):  
Olivier Gourgue ◽  
Jim van Belzen ◽  
Christian Schwarz ◽  
Wouter Vandenbruwaene ◽  
Joris Vanlede ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Tidal Marsh ◽  
Model Performance ◽  
Suspended Sediments ◽  
Sediment Supply ◽  
Tidal Marshes ◽  
Marsh Restoration ◽  
Tidal Marsh Restoration ◽  
Increasing Demand

Abstract. There is an increasing demand for creation and restoration of tidal marshes around the world, as they provide highly valued ecosystem services. Yet, tidal marshes are strongly vulnerable to factors such as sea level rise and declining sediment supply. How fast the restored ecosystem develops, how resilient it is to sea level rise, and how this can be steered by restoration design, are key questions that are typically challenging to assess. In this paper, we apply a biogeomorphic model to a planned tidal marsh restoration by dike breaching. Our modeling approach integrates tidal hydrodynamics, sediment transport and vegetation dynamics, accounting for relevant fine-scale flow-vegetation interactions (less than 1 m2) and their impact on vegetation and landform development at the landscape scale (several km2) and on the long term (several decades). Our model performance is positively evaluated against observations of vegetation and geomorphic development in adjacent tidal marshes. Model scenarios demonstrate that the restored tidal marsh can keep pace with realistic rates of sea level rise and that its resilience is more sensitive to the availability of suspended sediments than to the rate of sea level rise. We further demonstrate that restoration design options can steer marsh resilience, as it affects the rates and spatial patterns of biogeomorphic development. By varying the width of two dike breaches, which serve as tidal inlets to the restored marsh, we show that a larger difference in the width of the two inlets leads to more diversity in restored habitats. This study showcases that biogeomorphic modeling can support management choices in restoration design to optimize tidal marsh development towards sustainable restoration goals.

scholarly journals Supplemental Material: Detrital signals of coastal erosion and fluvial sediment supply during glacio-eustatic sea-level rise, Southern California, USA

2021 ◽  
Author(s):  
Glenn Sharman ◽  
et al.
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Erosion ◽  
Southern California ◽  
Mixture Modeling ◽  
Sediment Supply ◽  
Analytical Methodology ◽  
Fluvial Sediment ◽  
Icp Ms ◽  
Data Tables

Sample summary, LA-ICP-MS data tables, sources of Cretaceous-Paleogene forearc data, Peninsular Ranges batholith zircon U-Pb ages, mixture modeling results, and U-Pb analytical methodology.<br>

scholarly journals Outer- to inner-shelf response to stepped sea-level rise: Insights from incised valleys and submerged shorelines

2019 ◽  
Vol 416 ◽  
pp. 105979 ◽  
Author(s):  
L. Pretorius ◽  
A.N. Green ◽  
J.A.G. Cooper ◽  
A. Hahn ◽  
M. Zabel
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Inner Shelf ◽  
Incised Valleys
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