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Abstract Continuous coastal erosion has been observed on the shoreline of major river deltas worldwide as a result of relative sea level rise and anthropogenic impacts. However, the relative contribution of sea-level rise on deltaic coastline retreat (i. e. separately from anthropogenic interference) has not been clearly defined, due to a lack of research on naturally developing deltas. The Parnaíba River Delta, located on the NE Brazilian coast is one of the few examples of a river delta that is still developing in almost natural conditions in contrast to many heavily impacted deltas worldwide. The wave- and tide-dominated delta is subjected to delta switching processes with two active distributaries in the east and remnant tidal channels in the west. To address the decadal evolution of the delta in terms of suspended sediment transport and shoreline changes remote sensing techniques applied on orbital sensors were used. Satellite images from LANDSAT missions 2 to 8 were used to assess shoreline change between 1972 and 2016. Moreover, maps of suspended sediment concentration calculated from water leaving reflectance revealed the importance of Parnaíba River as major sediment supplier for the adjacent coast. Sufficient sediment supply from the Parnaíba River (PR) maintains shoreline stability and progradation of the delta in the region of the distributaries despite of a reservoir located 700 km upstream, which is supplied by only 25% of the drainage basin. Westward longshore drift of the sediment yielded by the Parnaíba River is an important transporting agent distributing river sediment along the coast. During ebb-phase, the PR discharge pushes the suspended sediment plume as far as 10 km offshore and the runoff forms a hydrodynamic barrier preventing alongshore transport of sediment from the east to the west part of the delta shoreline. During flood-phase and high tide, the river sediment plume is pushed shoreward by tidal forces and westward by longshore currents. A high turbidity zone extends from the river-mouth plume of the main distributary to the western tidal channels. Turbid water enters the tidal channels during flood-phase and leaves during ebb-phase. Coastal accretion or stability characterizes the eastern active part of the delta while moderate erosion prevails in the western abandoned part damped by the westward directed longshore sediment transport from the PR mouth. Highlights • Rivers are the major sediment suppliers to coastlines, especially for river deltas. • Sea-level rise and anthropogenic impacts are considered the major causes for coastline retreat worldwide. • Major river deltas of the world suffering of severe coastal erosion and shoreline retreat. • Satellite image is an important tool for short term (decadal) shoreline change mapping. • How does sea level rise affects a naturally developing delta? [ABSTRACT FROM AUTHOR]

The late Pleistocene–Holocene stratigraphic architecture on the steep and narrow shelf off Nha Trang, central Vietnam has been explored by high resolution seismic profiles integrated with sediment core data. Sequence stratigraphic results reveal five major seismic units and three bounding surfaces which are composed of two distinctive sequences. Those sequences are bounded by two regional unconformities (SB1, SB2) which have been formed in respond to different sea-level regimes. The revealed relict beach–ridge deposits at water depth of about ∼130 m below the present water depth indicate that the Last Glacial Lowstand (LGM) sea-level in this area was lower than in neighboring areas and it probably resulted from subsidence due to high sedimentation rate and/or neotectonic movements of the East Vietnam Fault System. The late Pleistocene high amplitude of sea-level change during a long fourth-order and superimposed by shorter fifth-order cycle is the principal factor in reorganizing the formation of the Nha Trang continental shelf sequence. Other local controlling factors as fluctuations in sediment supply, morphological variations of the LGM surface, subsidence rate and hydrodynamic conditions provided the distinctive features of the Nha Trang shelf sequence stratigraphic model in comparison with neighboring other areas. [ABSTRACT FROM AUTHOR]

Highlights: [•] The Tarfaya basin sediments were deposited in a passive margin tectonic setting. [•] The Tarfaya basin sediments were originated from felsic source rocks. [•] The Tarfaya basin sediments demonstrate a change in provenance over time. [ABSTRACT FROM AUTHOR]

Regressive siliciclastic deposits from the central Sunda Shelf (Southeast Asia) were investigated by seismic surveying and sediment coring. High-resolution stratigraphy is favoured by the low shelf gradient and by a strong and focused sediment supply during periods of lower sea level. Three types of regressive deposits formed over the past fifty thousand years can be distinguished: (1) thick lens-shaped clinoform sediment ‘bodies’ up to 30 km wide which fill gentle depressions; (2) thin horizontally bedded deposits between the lens-shaped ‘bodies’; and (3) a thick progradation sediment wedge on the outer shelf and upper slope. The sediment cores reached the upper part of the regressive deposits and contain a regressive–transgressive succession of terrestrial, tidal and shallow-marine sediment facies. The lens-shaped sediment ‘bodies’ are interpreted as regressive deposits detached from each other, probably reflecting the interplay of low morphological gradient and minor sea-level fluctuations during Marine Isotope Stage 3, which resulted in the reduction of accommodation space and local depositional stacking. The Late Pleistocene sedimentation on the outer shelf was partly controlled by differential subsidence of the margin or by wave and wind-induced current action. [Copyright &y& Elsevier]

In this study, 11 CBERS 2B and 1 LANDSAT 5-TM satellite images from 2008 were used to estimate the suspended sediment concentration and the total suspended sediment load of the Parnaíba River (NE-Brazil). The calculation of the amount of sediment in suspension was performed using Tassan’s algorithm, which was originally developed for use on LANDSAT 5-TM images; therefore, the CBERS 2B images were spectrally calibrated using LANDSAT 5-TM at-satellite radiance. The application of atmospheric correction to the images was necessary to account for meteorological influence on the spectral data prior to the calculation of the suspended sediment concentration. Three types of dark object subtraction and the 6S model were tested, and one type of dark object subtraction was chosen as the appropriate atmospheric correction method. Tassan’s algorithm requires in situ calibration; therefore, suspended sediment concentrations measured in water samples from the Parnaíba River mouth were used to calibrate the algorithm. The results revealed that the variation of suspended sediment concentration was strongly influenced by seasonal precipitation. In 2008, the suspended sediment released by the Parnaíba River was approximately 2.54 × 10 6 tons. The discharged sediment formed a sediment plume on the inner continental shelf. The extension of the plume depended on the specific hydrodynamic conditions that were forced mainly by the strength of river runoff, longshore currents, tidal currents and amplitudes, and wind and wave climate. [ABSTRACT FROM AUTHOR]

• Micaceous, limonites and opaque heavy minerals are useful diagnostic features. • Lim, Lim-Mi-Chl, Opq/Lim-Chl-Tur, Opq-Tur-(Ep-Zr) and Opq-Amp-(Ep) heavy minerals provinces distinguished on the shelf. • Mineral groups: Lim-Chl, Amp-Ep, and Opq-Tur-Zr are attributed to specific source areas and dominant transport paths. • Dominant sediment transport from the Mekong River over the continental shelf is southwestward. • Vast mixing zone of different modern and relict sediments is east of the Mekong River mouth. The continental shelf off southern Vietnam is relatively well studied regarding the dominant transport paths of bulk and fine-grained sediments discharged by the Mekong River. Thus, this region is particularly suitable for testing the applicability of heavy mineral analysis in determining the extent and origin of the sandy fraction of continental shelf deposits supplied mainly by a large river and their distribution over the adjacent extensive shelf. The fine sand fraction of 105 sediment samples from the Mekong River Delta and neighbouring continental shelf is investigated, applying two approaches: i) considering only the transparent non-micaceous mineral assemblage and ii) considering all the identified heavy minerals. The geological complexity of the source areas and local dominance of micaceous and non-transparent heavy minerals require the inclusion of all heavy mineral components when interpreting sediment provenance and dominant transport paths. The most diagnostic heavy minerals, amphibole, chlorite, epidote, limonite, opaques, tourmaline and zircon, are used for this purpose. The investigated continental shelf can be divided into two main regions characterised by various heavy mineral assemblages, namely, SW and NE off the Mekong River Delta. The south-western region is dominated by chlorite and limonite, indicating prevailing southward sediment transport from the Mekong River, whereas the north-eastern region is characterised by amphibole, epidote, opaques, tourmaline and zircon, indicating various sources from SE Vietnam and relict sediments partly covering the continental shelf. Between the two main regions, a large mixing zone is found where sediments from all sources are present, including Mekong River sediments transported eastward. [ABSTRACT FROM AUTHOR]

The Parnaíba River Delta (PRD) is the second major delta in NE Brazil and occupies approximately 100 km of the Brazilian equatorial coast. This delta is highly asymmetric due to a large tidal channel complex in the western portion that has at present time no natural connection to the Parnaíba River (PR) and the actual PR mouth in the eastern part of the PRD. A sedimentological, stratigraphic, and mineralogical study was performed on vibracores acquired in late Holocene sediments from the PRD to investigate how this environment developed during the Holocene. The core acquired in the western portion of the delta (VC-10/16) contains a medium sand layer with fluvial facies between depths of 1.50 and 0.52 m, dated by the radiocarbon method at 4.057 ± 22 BP. However, above a depth of 0.52 m, a transition to silt with tidal channel facies and higher organic matter contents (OM) and calcium carbonate (CaCO 3) is observed. Moreover, a fining-upward trend was also observed in the other four cores located farther west, and the mineral assemblage at the bases of these cores has strong similarities with cores collected in the eastern portion of the PRD (VC-07/16) in the main channel of the PR. However, the core-tops show significant variations in the assemblage of the key minerals (cordierite, cummingtonite, and garnet), indicating that in the past, the PR was connected to the western portion of the delta. The sedimentary provenance and the variations in the depositional environment indicate that a lobe switching process changed the main channel's course and caused the isolation of the delta's western portion during the late Holocene. During this period, the main channel ran through the western portion, and the large tidal channels of the delta are the ancient main channels that were abandoned during the lobe switching process probably caused by tectonics influence. • Mineral assemblages to identify delta lobe switching. • Parnaíba River Delta sedimentology and evolution during Holocene. • Vibrocores in shallow sediments. • Age dating, compositional and textural features of sediments. [ABSTRACT FROM AUTHOR]

Abstract: Variations in clay mineral composition of sediment cores from the margin and continental slope of the Sunda Shelf (southern South China Sea, SE Asia) covering the past 17,000 yr reflect changing influences of sediment sources together with clay mineral partitioning processes in shallow waters. We identify the deglacial sea level rise as the principal factor driving these changes. During the late glacial, high values of kaolinite are interpreted to reflect a higher contribution of clays from soils that have formed on the exposed Sunda Shelf and in the southern archipelagos of Indonesia. At this time core sites were located in close proximity to the mouths of the Sunda Shelf palaeo-drainage systems on the emerged shelf (“Sundaland”). The progressive landward displacement of the coastline and breakdown of these vast drainage systems during deglaciation led to a decrease in influence of the kaolinite-rich southern sources. When the coastline had retreated closely to its present-day position in mid-Holocene times, the former dominance of southern sources was replaced by a stronger influence of illite-rich sources (e.g. Borneo). The overriding control of sea level changes on the clay mineral distribution patterns precludes a definite climatic interpretation of clay mineral data in terms of climatic/monsoonal changes in such highly dynamic sedimentary environment. [Copyright &y& Elsevier]