Holocene evolution of mud depocentres on a high-energy, low-accumulation shelf (NW Iberia)

2009 ◽  
Vol 72 (3) ◽  
pp. 325-336 ◽  
Author(s):  
Hendrik Lantzsch ◽  
Till J.J. Hanebuth ◽  
Vera B. Bender
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Sediment Traps ◽  
High Energy ◽  
Sediment Supply ◽  
Material Source ◽  
The Holocene ◽  
Accommodation Space ◽  
Catchment Areas ◽  
The Individual

AbstractThe high-energy, low-accumulation NW Iberian shelf features three confined Holocene mud depocentres. Here, we show that the evolution of such depocentres follows successive steps. The flooding of inner shelf zones and river catchment areas by the late deglacial sea-level rise provided the precondition for shelf mud deposition. Following this, the Holocene deceleration of the sea-level rise caused a rapid refill of the accommodation space within river valleys. Subsequently, the export of major amounts of fines was initiated. The initial onset and loci of shelf mud deposition were related to deposition-favouring conditions in mid-shelf position or to the presence of morphological highs, which act as sediment traps by providing protection against stronger hydrodynamic energy. The detailed reconstruction of the Holocene depocentre evolution shows for the first time that the expansion of such shelf mud deposits cannot only occur by linear growth off the associated sediment source. Rather, they might develop around centres that are fully disconnected from the source of original sediment supply, and expand later into specific directions. Based on these differences and on the connection of the individual mud depocentres to the material source we propose a conceptual subdivision of the group “mid-shelf mud depocentres”.

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 Architecture of the Holocene Rhine-Meuse delta (the Netherlands) - A result of changing external controls

2007 ◽  
Vol 86 (1) ◽  
pp. 23-54 ◽  
Author(s):  
M.J.P. Gouw ◽  
G. Erkens
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Cross Sections ◽  
Single Channel ◽  
Temporal Trends ◽  
Sediment Supply ◽  
Relative Importance ◽  
The Holocene ◽  
Time Control ◽  
Lithological Composition

AbstractThe Holocene Rhine-Meuse delta is formed under the influence of sea-level rise, tectonics, and variations in discharge and sediment supply. This paper aims to determine the relative importance of these external controls to improve our understanding of the evolution of the Rhine-Meuse fluvio-deltaic system. To do this, the geological and lithological composition of the fluvio-deltaic wedge has to be known in detail, both in space and time. This study presents five cross-valley sections in the Holocene Rhine-Meuse delta, based on almost 2000 shallow borings. Over 130 14C dates provide detailed time control and are used to draw time lines in the sections. Distinct spatio-temporal trends in the composition of the Holocene fluvio-deltaic wedge were found. In the upstream delta, the Holocene succession is characterised by stacked channel belts encased in clastic flood basin deposits through which several palaeo-A-horizon levels are traceable. In a downstream direction, the fluvio-deltaic wedge thickens from 3 to 7 m. The Holocene succession in the downstream cross sections formed from <8000 cal yr BP onwards and is characterised by single channel belts encased in organic flood basin deposits. The main part of the organic beds accumulated between 6000 and 3000 cal yr BP. After 3000 cal yr BP, clastic deposition dominated throughout the delta, indicating an increase in the area of clastic sedimentation. The Holocene fluvio-deltaic wedge is subdivided into three segments based on the relative importance of eustatic sea-level rise, subsidence, and upstream controls (discharge and sediment supply). Before 5000 cal yr BP, eustatic sea-level rise controlled the build-up of the wedge. After eustatic sea-level rise ceased, subsidence was dominant from 5000 to 3000 cal yr BP. From 3000 cal yr BP onwards, increased sediment supply and discharge from the hinterland controlled the formation of the fluvio-deltaic wedge. A significant part of the present-day Rhine-Meuse fluvio-deltaic wedge aggraded after eustatic sea-level rise ceased. We therefore conclude that external controls other than eustatic sea-level rise were also of major importance for the formation of the fluvio-deltaic wedge. Because this is probably true for other aggrading fluvial systems at continental margins as well, all external controls should be addressed to when interpreting (ancient) fluvio-deltaic successions.

Stratigraphic organisation of a composite macrotidal wedge: the Holocene sedimentary infilling of the Mont-Saint-Michel Bay (NW France)

2010 ◽  
Vol 181 (2) ◽  
pp. 99-113 ◽  
Author(s):  
Bernadette Tessier ◽  
Isabelle Billeaud ◽  
Patrick Lesueur
Keyword(s):  
Sea Level ◽  
High Energy ◽  
Sediment Supply ◽  
Estuarine System ◽  
The Holocene ◽  
The North ◽  
Most Significant Change ◽  
Main Component ◽  
The Impact ◽  
Main Factor

Abstract The Mont-Saint-Michel Bay (NW France) is a composite macrotidal environment that was filled up in the course of the Holocene transgression and sea-level highstand. Three main sub-environments constitute the present-day landscape of the bay: 1) a wide embayment with extensive mud to sandflats in the south, 2) a sandy to muddy channel-and-shoal estuarine system in the east, 3) a wave-dominated sandy coast composed of beach and dune barrier in the north. The Holocene infill of this composite macrotidal basin has been studied thanks to a set of vibrocores and VHR seismic data. The main results are summarized as follows: the TST is composed by a low-energy aggradational unit in the axis of the estuarine valley, and by high-energy sediment bodies (tidal dunes and banks) outside the valley; the HST (post 6500 yr B.P.) constitutes the main component of the infill. In the north, it is characterised by an aggradational unit made of back-barrier tidal lagoonal infill successions. In the embayment, it is represented by an aggradational unit composed of tidal-flat deposits. In the estuarine axis, the HST is constituted by a sand-dominated tidal channel-and-shoal belt. The rate of the Holocene sea-level rise appears to be the main factor of control of the infill architecture of the Mont-Saint-Michel Bay since the most significant change occurred around 6500 yr B.P. when the transgression slowed down. The interaction between hydrodynamic agents and sediment supply exerts as well a key control, especially during the late Holocene, when transgression is slow. The impact of climate changes is recorded in the infill during this period. The rocky substrate hypsometry should be considered also as a major forcing parameter as it determines the potential of preservation of the infill in relation with the depth of ravinement by tidal currents.

scholarly journals Holocene sedimentation offshore Southeast Vietnam based on geophysical interpretation and sediment composition analysis

2021 ◽  
Vol 43 (3) ◽  
Author(s):  
Long Hoang Van ◽  
Thanh Nguyen Tien ◽  
Tuan Vu Tat ◽  
Tung Nguyen Thanh ◽  
Anh Nguyen Lam ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
High Energy ◽  
Heavy Minerals ◽  
Energy Conditions ◽  
Composition Analysis ◽  
The Holocene ◽  
Sedimentary Evolution ◽  
New Findings ◽  
Holocene Sea Level

Offshore Southeast (SE) Vietnam is considered a transition zone, with the sedimentary evolution of this area controlled by land-sea interactions, especially by the Holocene sea-level rise. This study presents some new findings regarding Holocene sedimentation and its linkage to the heavy mineral placers within the study area based on high-resolution seismic interpretation and sediment analysis. Our obtained results show that the Holocene sediments directly overlie the Late Pleistocene sedimentary formation, from which they are separated by an erosional/unconformity surface (R­1­ seismic reflector). Sediments deposited in the Early (~11.7-8.2kyr BP), Middle-Late (8.2kyr BP-present-day) Holocene sub-epochs correspond to the Transgressive and Highstand System tracts, which were closely controlled by the three stages of Holocene sea-level rise. The recent sediments distributed on the seafloor are dominated by sand and gravelly sand, demonstrating high-energy conditions, while the heavy minerals are rich in ilmenite and zircon. Most of these are concentrated along the present shoreline zones, but we do not exclude their accumulation in the paleo-shoreline and incised channels. Two ilmenite dispersion halos (1st and 2nd order) and one zircon dispersion halo (1st order) suggest that ilmenite and zircon are the most dominant heavy minerals while gold is only observed locally. The minerals were potentially derived from the weathering products of the Triassic-Cretaceous ilmenite-, zircon-, and gold-bearing granite and granitoid in central Vietnam.

scholarly journals The role of sea-level changes in the evolution of coastal barriers – An example from the southwestern Baltic Sea

The Holocene ◽  
2020 ◽  
pp. 095968362098170
Author(s):  
Reinhard Lampe ◽  
Matthias Lampe
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Sediment Supply ◽  
Sea Level Changes ◽  
Climate Fluctuations ◽  
The Past ◽  
Basic Model ◽  
Accommodation Space ◽  
Evolution Scheme

According to a basic model, the formation of the coastal barriers in the southwestern Baltic can be divided into four evolutionary stages which are characterized by different rates of sea-level rise and varying relations between sediment supply and accommodation space. This model is tested using the example of a strandplain of the island Usedom, along with a local sea-level curve that reflects even smaller fluctuations of the water table and a detailed chronostratigraphy based on OSL measurements that allows the correlation of the morphodynamics with specific climatic phases. The resulting evolution scheme generally confirms the basic model but the timing of the stages depends on the inherited relief and has to be adjusted locally. A comparison with barriers from the W and SW Baltic region shows that the development during the past 5000 years was controlled by climate fluctuations which caused minor variations of the rather stable sea level and consequential changes in sediment supply, accommodation space and foredune deposition. Progradation decline can mainly be related to cool and windy climate phases which centered around 4.2, 2.8, 1.1, and 0.3 ka b2k, while increasing progradation correlated with warmer climate around 3.5, 2.0, and 0.9 ka b2k. The climate warming and the increasing sea-level rise in the recent past, however, led to shrinking progradation rates and may indicate a critical point beyond which the main progradation trend of the past turns into erosion.

scholarly journals Holocene coastal landscape development in response to rising sea level in the Central Wadden Sea coastal region

2021 ◽  
Vol 100 ◽  
Author(s):  
Martina Karle ◽  
Friederike Bungenstock ◽  
Achim Wehrmann
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Wadden Sea ◽  
Sediment Supply ◽  
Sea Level Changes ◽  
Landscape Development ◽  
Coastal Landscape ◽  
The Holocene ◽  
Depositional Processes ◽  
Holocene Sea Level

Abstract The Holocene sea-level rise has led to significant changes in present-day coastal zones through multifold retrogradational and slightly progradational displacements of the mainland coastline. During the course of this postglacial transgression, sediments characteristic of coastal environments accumulated first in palaeovalleys of the pre-Holocene landscape and later on the subsequently developed coastal plain. Based on a compilation of sedimentological, lithological and litho-chronostratigraphical data of more than 1200 sediment cores, we generated four palaeogeographic maps of the coastal zone of the central Wadden Sea to document with a high spatial resolution the landscape changes during characteristic phases of the Holocene sea-level rise, i.e. the periods 8600–6500 cal BP, 6500–2700 cal BP, 2700–1500 cal BP and 1500–1000 cal BP. Along three cross-sections, representing different hydrodynamic conditions and exposure, we exemplify how the Holocene landscape development and sedimentary facies types are controlled by the local palaeorelief, sea-level changes, sediment supply, accommodation space, the morphodynamic impact of channel shifts, and their erosion base. This leads to a better understanding of main factors controlling the local depositional processes of the coastal landscape along the central Wadden Sea during the Holocene transgression.

scholarly journals The Holocene depositional history of the IJzer palaeovalley (Western Belgian coastal plain) with reference to the factors controlling the formation of intercalated peat beds

2000 ◽  
Vol 2 (1-2) ◽  
pp. 39-72 ◽  
Author(s):  
Cecile BAETEMAN
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Sediment Supply ◽  
Sedimentary Sequence ◽  
Channel Network ◽  
Depositional History ◽  
The Holocene ◽  
Sea Level Fluctuations ◽  
Coastal Deposits ◽  
The Many

Detailed stratigraphic and sedimentological work, together with radiocarbon datings of the Holocene coastal deposits in the IJzer palaeovalley was performed in order to document the formation of the sedimentary sequence in relation to the controlling factors, to reveal the stratigraphical significance of intercalated peat beds, and to reconstruct the depositional history. Because of the many controversies relating to these topics, the Belgian literature has been reviewed. An initial rapid sea-level rise prior to ca. 7800 cal BP resulted in a rapid shift of the facies belts across the palaeovalley and was associated with rapid filling with no formation of intercalated peat beds. A deceleration in the rate of the sea-level rise with sufficient sediment supply produced rapid facies changes registered as frequent alternations of mud, peat and gyttja in the sedimentary sequence deposited between ca. 7800 and 6000 cal BP. The facies changes are determined by a sedimentological control related to the tidal channel and creek network, and not by sea-level fluctuations. Periods of peat growth lasted longer and the lateral extension became more widespread as deceleration of the sea-level rise and filling of the plain continued. This was associated with progradation of the shoreface from ca. 6000 cal BP onwards. Tidal conditions returned to the area from ca. 4000 cal BP onwards. This return was accompanied by erosion and landward migration of the shoreface and channel network. This study demonstrates that the tripartite stratigraphy using Dunkerque and Calais as units should be abandoned in favour of lithological and sedimentological descriptions and age determinations together with environmental interpretation.

scholarly journals RELATIONSHIP BETWEEN SEQUENCE STRATIGRAPHY AND RELATIVE SEA-LEVEL CHANGES

2017 ◽  
Vol 1 (2) ◽  
pp. 38
Author(s):  
Jamaluddin . ◽  
Romuald Sohores ◽  
Muhammad Fawzy Ismullah
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Sequence Stratigraphy ◽  
Sedimentation Rate ◽  
Sediment Supply ◽  
Maximum Point ◽  
Sea Level Changes ◽  
Highstand System Tract ◽  
Accommodation Space ◽  
System Tract

The continuous sea-level rise will result in conditions where the level of accommodation space is greater than that of sediment supply produced undertransgression conditions. When the sea level reaches its maximum point, the sedimentation rate will exceed the sea level rise and aggrades becomes more dominant progradation will result in new Highstand System Tract (HST) condition. Keyword: Accommodation, Sea level changes, Sedimentation, Sequence, Stratigraphy

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.

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