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Sandy shorelines occupy ca. 80% of the coast of Mozambique, South Africa and Namibia. A geomorphological classification of sandy shorelines in the subcontinent identifies twelve major categories in four sub-regional coastal systems. The behaviour of each of the major shoreline types under rising sea level is outlined based on geological principles together with observations of former shorelines preserved onshore and on the continental shelf. Human adaptation strategies regarding shoreline change involve a binary choice (hold the shoreline in place or permit it to fluctuate) and these exert an equally important control on sandy shoreline response in the medium term as does sea-level rise itself. It is anticipated that densely urbanised sandy shorelines will be stabilised by coastal defences involving both capital works and ongoing maintenance that will be accompanied by deterioration and ultimate loss/replacement of the natural ecosystem. In contrast, currently undeveloped, natural shorelines will be permitted to adjust and will, as a consequence, survive and continue to deliver ecosystem services. The major challenge for climate-change adaptation lies in those lightly urbanised coastal areas where relatively small numbers of property owners may be, or perceive themselves to be, at risk of economic loss from shoreline change. In such cases the choice is between preserving those property interests (through sea defences) and preserving the sandy shoreline and its human and ecosystem services (via retreat). [ABSTRACT FROM AUTHOR]

The Namibian inner continental shelf immediately north of the Orange River delta is sediment-poor, dominated by outcrop of metamorphic basement with a scarcity of sandy cover. Using a combination of high and very-high resolution geophysical tools and drill cores, an examination of the evolution of the inner shelf stratigraphy and geomorphology shows persistent antecedent bedrock controls throughout the Pleistocene. The bedrock of the inner shelf comprises schists, in places overlain by Eocene sandstones, over which a subaerial unconformity (H1) formed in the late Oligocene. H1 was repeatedly re-occupied during succeeding transgressive/regressive cycles, creating a backstop for erosion/sedimentation and creating a repeating topography on which transgressions took place. Apart from localised development of Miocene phosphatic limestones, little sediment has since accumulated. Large-scale karst weathering of the limestones reflects several periods of subaerial exposure most recently during the Quaternary lowstands of sea level including MIS 2 and 1. Thin Quaternary cover, housed within depressions on the H1 surface is predominantly preserved in the lee of bedrock ridges, behind which shallow and occasionally hypersaline lagoonal conditions developed. These preserved back-barrier sedimentary sequences developed post-MIS 5 (previous phases were either eroded/weathered or not deposited). Dolomite precipitation occurred when sea-level stabilised at −75 m 37,000 cal BP and restricted lagoonal conditions prevailed. Currently, there are very limited MIS 2/1 deposits preserved above H1. The absence of thick sand cover, adjacent to and downdrift of the Orange River delta, suggests that the onshore diversion of sand that currently supplies the Namib Sand Sea also operated during lower sea levels, related to the bedrock control and lack of accommodation in surface H1. This persistent onshore diversion of sediment throughout the Quaternary has implications for sediment source as well as budget calculations for the Namib Sand Sea. • Seismic stratigraphy of the sediment starved inner shelf of Hottentot's Bay, Namibia. • Reveal inherited erosional subaerial unconformity, with palaeo-lagoon. • Multiple phases of lowstand karst development. • Shelf depth limits erosion and encourages sediment bypass. • Sediment export to the Namib Sand Sea at lowstand. [ABSTRACT FROM AUTHOR]

Beachrock may be considered a reliable indicator of sea level, in addition to a reliable and recognizable source for onshore movement of beachrock clasts by overwash processes associated with extreme events. Key to this is its geomorphology and preservation potential, both of which are poorly understood. Here we examine the processes and deposits associated with beachrock breakdown from Camurupim, NE Brazil and compare its preservation to beachrocks found on continental shelves in South Africa. We study a prominent and continuous 50–60 m-wide beachrock complex that crops out along a 10 km stretch of coastline, and which mostly comprises 1.5 to 2 m-thick trough-crossbedded sandstones. These have generated large joint-bounded blocks that have been transported landwards under extreme energy conditions (based on numerical modelling and comparisons to the contemporary wave climate). Tabular clasts have accumulated as isolated, very coarse boulders on the seaward margin, small clasts in various topographic traps, boulder ridges with large landward- and seaward-dipping clasts on the uppermost part of the outcrop, and subaqueous and subaerial washover fans. Isolated fine meso-boulders emplaced during extreme waves (H s = ca. 12 m) exhibit fitted textures and pressure-solution contacts, pointing to subsequent rocking and shaking. Smaller clasts in boulder ridges and overwash settings are initially liberated and transported by waves within the annual-decadal frequency spectrum, deposited on the high points of the outcrop. Subsequent movement during less extreme wave action progressively transports the clasts across the surface, where they are often trapped in the fitted fabric on top of the platform. Our breakdown model and overall beachrock preservation scheme is consistent with reported seismic signatures of submerged Holocene beachrock shorelines. Beachrock preservation during transgression is strongly influenced by the original sedimentary facies; thick, trough-crossbedded joint-bound clasts preserve the former shoreline. Clasts from the planar units accumulate as washover fans to landwards of the ridge. [ABSTRACT FROM AUTHOR]

The morphology of Lake St Lucia, Africa's largest estuary, has been strongly influenced by antecedent topography throughout its Quaternary evolution. The 5 × 20 km southern basin is bounded to landward by a 50 m-high Early/Mid-Pleistocene dune ridge and to seaward by a 100 m-high Late Pleistocene/Holocene dune barrier. Nine seismic units (A-I) are identified in the enclosed basin, along with two regionally developed sequence boundaries (SB1 and SB2) and two tidal ravinement surfaces (tRS1 and tRS2). The lowermost sequence boundary (SB1) is related to regional late-Pliocene hinterland uplift. SB2 is related to the last glacial maximum (LGM) when sea levels fell ∼130 m below present. Lowstand fluvial sediments occupy the base of both SB1 and SB2 incisions. Thick central basin deposits dominate the valley fills, more so in the Pliocene age valleys, the occurrence and thickness of which is attributed to sheltering by a seaward barrier-dune system as well as to the low gradient settings. Prograding tidal bedforms occupy the minor incisions formed within the tidal ravinement surfaces, marking the onset of lagoonal conditions in the area. The system is capped by lagoonal deposits, deposited above tidal flats. A series of prograding spits mark the early stages of lagoonal segmentation in the Holocene. The preservation of only one incision and fill sequence prior to the development of an LGM-aged valley succession is attributed to geological inheritance whereby older valleys were repeatedly re-incised by younger valleys throughout the Pleistocene, causing partial preservation of Pleistocene fills up to the most recent cycle. The older fill remnant relates to a larger magnitude base level fall prior to the Quaternary, which survived erosion during subsequent sea-level falls. Adjacent topography in the form of rocky cliffs and the seaward fronting barrier limit the accommodation space in which infilling material can be hosted outside the major valley network. The competent basement rock into which these valleys have incised protected lowstand fluvial sediments from subsequent tidal ravinement. [ABSTRACT FROM AUTHOR]

Abstract Rapid cementation (<5 years) of beachrock is reported from the wave-dominated, microtidal coastline of Durban, South Africa. The beachrock is developing at mean sea level on a steep (10°–30°), reflective beach prone to periodic erosion by high-energy wave action; the most recent erosional event resulted in retrogradation of the beach by up to 10 m landward of the beachrock outcrop discussed in this study. Transmitted light microscopy and scanning electron micrographs show the precipitation of two dominant cement types which are linked to the beachface morphodynamics. During the accreted beach phase, when the locus of beachrock formation lay well landward of the beachface in the undersaturated upper intertidal to supra tidal backbeach, meniscus cements were precipitated. Following a period of erosion, associated with a landward shift of the beachface, the incipient beachrock was then exposed to saturated conditions which promoted growth of acicular cements. Contemporary beachrock cementation occurred very rapidly (<5 years) between significant erosional events. The observed cement textures record short-term beach progradation and retrogradation but are similar to those typically associated with longer-term regression and transgression. Highlights • Rapid cementation on a steep, high energy beach, South Africa • Variation in beachrock cement driven by migration of beach • Changes in sea level not necessary to force changes in cement type • Beach morpho-dynamics are critical when discussing cement changes in beachrock. [ABSTRACT FROM AUTHOR]

Abstract Sea-level change around southern Africa (southern Namibia, South Africa, southern Mozambique) since Termination I has been quantified using a variety of indicators. Existing and new data are reviewed to provide a baseline for future studies and identify key research needs and opportunities in the region. While the southern African records broadly agree with other far-field records, detailed Holocene records present as-yet unresolved discrepancies with glacial isostatic adjustment (GIA) model predictions. Two domains, the west coast and east coast are considered. Radiocarbon dated saltmarsh facies and marine shells in life position provide the basis for the west coast sea-level curve back to 9 ka BP. Given the age and elevation uncertainties, a Mid-Holocene highstand of +2 to +4 m is suggested between 7.3 and 6 ka BP, as are several Late Holocene oscillations of <1 m amplitude. On the east coast, fewer data are available for the Mid to Late Holocene (post 7 ka BP) compared to the west, but many submerged indicators are available back to 13 ka BP. Reappraisal of existing data suggests a sea-level curve similar to that of the west coast. In both instances, the resolution of existing sea-level index points is neither sufficient to accurately constrain the magnitude and timing of the peak highstand nor the existence of minor inferred subsequent oscillations. Between 13 and 7 cal ka BP chronological and geomorphological evidence (submerged shoreline complexes) suggest several alternating periods of slow and rapid sea-level change. Despite abundant data, the indicator resolution to quantify these changes remains elusive. Highlights • Sea-level data from southern Namibia, South Africa, and southern Mozambique since Termination I is reviewed and assessed. • Offshore data provide age control on seismic stratigraphic units consistent with a stepped eustatic sea-level rise. • Existing sea-level data have insufficient resolution to accurately define the Holocene highstand. [ABSTRACT FROM AUTHOR]

Barrier/lagoon systems occupy a significant part of the world's coast. They are diverse in size, morphology, geological and oceanographic setting, and morphodynamic behaviour. Understanding the behaviour of barriers at 10 1 to 10 2  year and 10 1 to 10 2  km scales (mesoscale) is an important scientific and societal goal, not least because of the preponderance of intensive coastal development in a time of global climate change. Such understanding presents significant challenges. Challenges in describing mesoscale system behaviour relate largely to the incomplete evidence base of (i) morphological change in system components, (ii) dynamic and internal forcing factors (drivers) and (iii) geological constraints. These shortcomings curtail the development of baseline datasets against which to test models. Understanding observed changes and thereby predicting future behavioural patterns demands assumptions and simplifications regarding the linkages between initial state, dynamic drivers, system feedbacks and a multiplicity of geological constraints that are often location-specific. The record of mesoscale change is improving with the acquisition of long-term morphological datasets. Advances in technology and chronological control mean that geological investigations can now provide decadal to century-scale temporal resolution of morphological change. In addition, exploratory modelling is improving understanding of the influence of various dynamic and geological factors. Straightforward linking of dynamic forcing and response is seldom able to account for observed mesoscale behaviour. Geological factors exert a significant or even dominant control on barrier behaviour at decadal to century timescales. Whereas these geological controls can be quantified to some extent by detailed investigations of contemporary barrier/lagoon morphology and constituent materials, underlying geology and topography and sediment supply, in all but a few locations, such data are absent. This sets an unavoidable constraint on efforts to quantitatively predict the future behaviour of barrier systems, which are strongly site-specific in terms of their geological setting and morphology. Geological controls exist in a network of interactions that individually and collectively influence mesoscale barrier behaviour. Dominant, first-order controls are: • Basement slope; • Basement irregularity and erodibility; • External sediment supply; • Orientation; and • Shoreline lithification (beachrock and aeolianite) An important intermediate level of geological control is exerted by shoreface morphology. Shorefaces are themselves influenced by underlying geological factors, but they are dynamic at longer timescales than barriers. Geological influences are in most cases unquantified and are usually disregarded when conceptualizing and modelling barrier evolution. Consideration of the geological influences is, however, essential in efforts to predict future behaviour at mesoscale (management) timescales. [ABSTRACT FROM AUTHOR]

Beachrock is present in deep, stable sections of a mixed sand and gravel beach at Whitepark Bay (55 o 14′N) on the paraglacial coast of Northern Ireland. The beachrock was revealed following progressive and extreme beach erosion during two particularly stormy winters (2013/14 and 2014/15). It occurs as large (up to 1 m diameter, 0.2 m thick), rounded, disc-shaped concretions in which original beach bedding structures are preserved. Both sand and gravel beach facies are cemented. The cements are similar to those of tropical beachrocks and comprise an initial thin micrite rim, and subsequent grain rims of aragonitic needles. The cementation is attributed to saturation of beach groundwater with calcium carbonate sourced from adjacent Cretaceous chalk outcrop in cliffs behind the beach and dunes. The micrite rims suggest microbial activity in the initial cementation, possibly by scavenging from chalk and skeletal carbonate grains. Subsequent aragonite rims were formed through degassing of CO 2 aided by tidal water level fluctuations. Despite similar cementation processes to low latitude beachrocks, only isolated concretions occur rather than extensive shore-parallel outcrops. Conditions necessary for cementation (and ultimately preservation) in this cold temperate and paraglacial setting include long-term beach stability, a carbonate source (in this case, adjacent chalk cliffs and stream sapping) and tidal water level fluctuations. Bacterial activity may initiate calcite precipitation. Following extreme storms and with progressive shoreline retreat prompted by rising sea levels, increased reporting of cold-water beachrocks is to be expected as formerly stable sections of beaches are exposed to wave action. [ABSTRACT FROM AUTHOR]

The sedimentary record in large marine embayments holds important information on Holocene environmental and sea-level changes. This paper investigates the evolution of a large subtropical marine embayment, Maputo Bay, in southern Mozambique. Using a combination of sediment cores, stable isotope data, seismic reflection profiling and 14 C dating, we show complex back-barrier changes during the Holocene and link these to stepped rises in sea level. Our data reveal a sea-level “slowstand” followed by an abrupt rise that we correlate with the 8.2 ka global rise in sea level. Sedimentological, isotope and seismic evidence point to a subsequent slowstand interspersed by two punctuated rises in sea level that formed clear tidal ravinement surfaces. Sedimentary changes in the embayment are primarily forced by sea-level change, whereby tidal ravinement surfaces sandwich normal regressive packages formed via marginal progradation and shallowing of the system during “slow-” or still-stands. Large marine embayment systems hold great potential in unravelling relative sea-level change. Axiomatically, this reduces their utility as archives of climate-change. [ABSTRACT FROM AUTHOR]

In an era of global rising sea level, quantifying future shoreline behaviour is a key societal concern. The potential for dramatic shoreline change via overstepping or barrier disintegration on barrier-lagoon coasts as a result of future rapid sea level rise has been considered by various authors, but documented examples of barrier overstepping generally involve either coarse grain sizes or early diagenesis as beachrock. Where overstepping has been inferred, the overstepped barrier is seldom preserved. Using high resolution seismic data we describe the mid-Holocene overstepping of a sandy coastal barrier system and subsequent geomorphological changes that ultimately transformed it into a strandplain fronted by a muddy shoreface. This complete change in character is interpreted in the context of rapid sea level rise (tentatively linked to the 8.2 ka event) during which the former sandy shoreface-barrier was overstepped and decoupled from the contemporary shoreline, leaving the latter sand-starved. Upon overstepping, the wave-influenced shoreline was displaced rapidly to the landward margin of the former lagoon. Preservation of the overstepped uncohesive sandy barrier is attributed to the relatively wave-sheltered location, rapid sea level rise and rapid burial by shoreface sediments. This situation provides an insight into the conditions under which overstepping occurs, and thereby, the future response of barrier-lagoon systems to predicted rapid rates of future sea level rise. [ABSTRACT FROM AUTHOR]

Projections of an increase in drought frequency and intensity over the next century are expected to have severe implications for a number of globally important coastal ecosystems. In this paper, we present geochemical data from three sediment cores extracted from the main depositional basins of Lake St Lucia, Africa's largest estuarine system. Lake St Lucia is subject to extreme natural variations in salinity. The sedimentary record documents the evolution of the system from a relatively deep-water, open lagoon to a confined, shallow estuarine lake that today is highly sensitive to changes in freshwater supply. This is particularly evident in the northern portions of the system, where the presence of distinct halite-enriched horizons document episodes of prolonged drought. The lateral persistence of these halite layers, as revealed by seismic profiling, point to a system-wide onset of desiccation associated with a major shift in the regional hydroclimate. The most severe drought events identified, which may have lasted several years, occur at ~ 1100 and 1750 cal year BP, and are associated with known peaks in El Niño frequency and intensity. Our analyses suggest that past cycles of desiccation and hyper-salinity have been controlled by climatic changes related to ENSO intensification. This study provides a valuable new record from a key ENSO-sensitive region of the Southern Hemisphere. Our findings have important relevance for understanding ENSO variability across the Indo-Pacific region and the influence exerted on systems sensitive to changes in moisture balance. [ABSTRACT FROM AUTHOR]

Using a suite of ultra-high resolution geophysical tools, remote operated vehicle dives, legacy cores, and isolated grab samples, we demonstrate at a regional shelf scale, the influence of antecedent geology (basement topography, shelf gradient and submerged shoreline features) on the evolving transgressive shelf stratigraphy of a subaqueous delta. The unconsolidated uppermost delta occurs as isolated remnants scattered across the low-gradient shelf. Seismic data reveal across-shelf heterogeneity in bedrock elevation, with prominent bedrock highs and depressions and several well-preserved aeolianite palaeo-shoreline complexes at water depths of −100, −60 and − 40 m. Analysis of bathymetric and seismic data demonstrates that these pre-existing shoreline complexes exert an overarching control on the distribution patterns of i) deltaic sediments, where they abut the landward flank of the shoreline form, acting as a barrier to seaward dispersal, and ii) shoreface sediments which remain sequestered on the mid-shelf on the seaward flank of the shoreline complex, hampering the landward translation of the shoreface in step with rising sea levels. Moreover, sediment distribution/accumulation is further constrained where elevated portions of the basement topography provide little to no accommodation, and act as zones of sediment bypass, and adjacent basement depressions accommodate sediment to seaward. The gentle antecedent slope, coupled with the gentle shoreline trajectory mediated transgressive erosion directly to landward. This is reinforced where local inflections in the wave ravinement profile form due to the presence of palaeo-shoreline complexes, aiding in the ultimate preservation of these submerged delta facets in the palaeo-shoreline lee. This study shows that low antecedent gradients, and palaeo-shoreline features, lead to development of transgressive coastal profiles that are predisposed to delta overstepping. The pre-existing basement topography and palaeo-shorelines constrain the positioning and morphology of the delta. We suggest that antecedent conditioning has partitioned accommodation for delta accumulation and moderated wave ravinement associated with transgression since the Last Glacial Maximum (LGM). The geological framework has acted as a recurring primary control on the geomorphic evolution of the submarine delta and shelf. • Seismic stratigraphy of the Thukela continental shelf • Reveal several submerged deltaic depocenters and shorelines • Show bedrock highs control depocenter positioning and preservation • Delta morphology and stratigraphy influenced by palaeo-shorelines • Palaeo-shorelines restrict ability for shoreface to migrate with rising sea level [ABSTRACT FROM AUTHOR]

Lake St Lucia, the largest estuarine system in Africa, is enclosed by a 120 m-high compound Quaternary barrier-dune system in northern KwaZulu-Natal, South Africa. It comprises several discrete sedimentary basins within a single shallow back-barrier water body. This paper reports the first very-high-resolution seismic study of the system. Seven seismic units (A–G) are identified and interpreted based on their geometry, acoustic properties and a sediment coring programme. The units are bounded by regionally developed sequence boundaries and lower order unconformity surfaces corresponding to bay and tidal ravinement and hiatus surfaces. The lowermost subaerial unconformity formed during regression related to late-Pliocene hinterland uplift. Initial infilling of this surface in the proximal areas reflects estuarine sedimentation in a mixed wave- and tide-dominated system during the subsequent lowstand and early transgressive systems tracts, overlain by prograding highstand deltaic deposits that developed as sea-levels began to stabilise. Distally, this cycle of sedimentation is initially reflected by the infilling of a similar estuarine system that gradually transitioned to a back-barrier lagoon. Superimposed stillstands drove imbalances in the rate of sediment supply and accommodation space, and this, coupled with the development of an early barrier complex, caused lagoon aggradation and shallowing. A second similar trend is repeated for the recent postglacial sea-level cycle. There appears to be no preservation of the intervening Pleistocene cycles of erosion and deposition. The system is capped by estuarine-lacustrine deposits. The onset of lower energy estuarine-lake conditions began ~ 6235 cal BP in North Lake and started earlier in the proximal False Bay owing to sheltering by the antecedent barrier of a rocky peninsula. This study reveals a markedly different evolutionary history in adjacent basins of the same back-barrier system during two full sea-level cycles. These are attributed to a long established, non-migrating barrier, and to the influence of antecedent conditions on the system response to transgression. Unlike the US Atlantic margin, where migrating barriers truncate the infilling sequences, the main stratigraphic unconformities within each fill sequence correspond to tidal and bay ravinement surfaces. [ABSTRACT FROM AUTHOR]

This study examines both the inlet dynamics, recorded in the back-barrier stratigraphy of Kosi Bay, and the competing effects of waterbody segmentation on along-strike changes in the character and nature of an incised valley fill at Kosi Bay, South Africa. The Kosi Bay system comprises four interconnected lakes (Lake Makhawulani, Lake Mpungwini, Lake Nhlange and Lake Amanzimnyama) subject to varying degrees of marine influence. Formerly, the system's only connection to the ocean was through the Bhanga Nek palaeo-inlet. The location of this system behind a continuous coastal barrier predisposes it to excellent archives of environmental change related to changing sea-level and sediment supply. In this context, two cores were extracted from the system (KB2 and KB4), together with over 150 km of seismic reflection profiling, as well as AMS radiocarbon analyses and legacy data in order to present a new stratigraphic evolution model for this back-barrier system. A total of 5 seismic units were imaged (Units A-E). A major unconformity surface (SB), characterised by broad u-shaped incised valleys, incises the underlying unconsolidated sandy acoustic basement (Unit A). Unit B forms as thickly developed central basin deposits, partially infilling the incised valleys. Two forms of prograding spits are evident -Unit C1 progrades from the palaeo-highs of the valley interfluves into the nearest available accommodation space and Unit C2 progrades from the margins of the system into the basin. These are separated by an erosional surface (T-RS) formed by migrating tidal channels as sea-level rose and marine waters entered the system during the Holocene. Unit C2 spits are in turn associated with slump deposits formed on the steepest part of the margins (Unit D) that were dated to 2900 ± 165 cal. BP. The unusual depth of Surface T-RS is attributed to (1) limited sediment supply during sea-level rise, (2) the presence of easily erodible fine sediments in which this surface erodes and (3) a larger tidal prism when the Bhanga Nek inlet was still open and system segmentation by Units C2 and D had not yet occurred. Unit E caps the stratigraphy and is interpreted as lacustrine fines with a thin layer of acoustically transparent material (gyttja) on top. The deposition of Unit E signifies the closure of the system to the ocean and the overall shift from an estuarine/lagoon environment to a lacustrine one. Recalibrated AMS dates place the system closure to between 3160 and 2900 cal. BP, coeval with the formation of the prograding marginal spits and waterbody segmentation (Unit C2). Along-strike variation in the timing of the basin infilling, attributed to changes to the inlet functioning coupled to the segmentation of the waterbody, is characteristic of this area. At 1450 cal. BP, a new tidal inlet formed to the north of Lake Makhawulani, where impounded waters were diverted via a low point in the back-barrier coastal dune cordon. The formation of this inlet suggests a prolonged period of back-barrier flooding until a low point in the barrier was breached during the Holocene sea-level highstand of 1.5 m. Such inlet development and along-strike back flooding of incised valleys is an unusual attribute of coastal waterbodies of South Africa. • LGM-age incision into unconsolidated Kosi Bay Formation sediments. • Limited sediment supplied to the area during transgressing sea levels. • Post-LGM homogenous central basin fills only partially fill incised valleys. • Development of wind-driven spits signifying early stages of lagoonal segmentation. • Along-strike variation in the timing of the basin infilling. [ABSTRACT FROM AUTHOR]

Smith, A.M, Green, A.N, Cooper, J.A.G. et al., 2014. Cliff-top storm deposits (55-63m amsl) from Morgan Bay, South Africa. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 349-353, ISSN 0749-0208. Cliff-top storm deposits (CTSDs) occur south of Morgan Bay, South Africa at elevations varying from ±55- to 63m. These occur as a ±10m-wide horizontal fringe of shell breccia mixed into a very thin (>15cm) sandy soil on the cliff top platform. Visually it is evident that the shell breccia is of various ages. Comparisons with proven wave breccia from this area indicate the same source. We suggest that this breccia was deposited as fall-out from wave and wind-borne plumes produced by wave bores striking the cliff base. These bores would likely have been produced by waves at least ~40m in height. Alternative interpretations, such as a perched marine desposit or tsunamiite are rejected in favour of CTSDs produced by multiple large wave events. [ABSTRACT FROM AUTHOR]

The Holocene evolution of one of Africa's largest estuaries, Lake St Lucia on the east coast of South Africa, is examined and juxtaposed with previous and contemporary management practices aimed at fixing the estuary state at a single point along the system's overall evolutionary pathway. The estuary has been heavily altered over the course of the last century, mostly through mouth management activities aimed at maintaining a direct connection with the ocean. Based on a high-resolution seismic reflection dataset, LiDAR and bathymetry data of the lake system, together with palaeontological (foraminifera and diatoms) and sulfur isotope geochemical data from three long (14–16 m) piston cores, we investigate the system-wide and coeval evolution of the three different sub-basins (False Bay, North Lake and South Lake) that comprise the current estuarine lake system. The northern and southern sections of the system evolved independently of each other since the Last Glacial Maximum, with each area responding differently to early sea-level forcings. In North Lake, the lagoon evolved from fully estuarine (8300 cal. BP) to a restricted lagoon with occasional marine incursions, steadily decreasing tidal prism and the development of marginal spits by wind-driven lagoonal waves. The tidal inlet closed approximately 6200 cal. BP and fluvial conditions became more dominant as main back-barrier conditions became attuned to fluvial supply. Similar conditions prevailed in the adjacent False Bay basin, albeit with an earlier onset due to sheltering by prominent bedrock peninsulas. In contrast, South Lake evolved from a fully estuarine system (9500 cal. BP) with a persistent ocean connection, to a segmented system with a diminished tidal connection by 5500 cal. BP. The inlet sealed at this point and an isolated back barrier system developed. This prompted the system-wide impoundment of waters causing back-barrier flooding and in situ drowning of bayhead deltas and segmenting spits. By 2000 cal. BP, these areas had flooded sufficiently to connect over a bedrock high that had diverted the initial palaeo-valleys to the north and south. A new, single lagoon, representative of the modern-day system formed, with a new marine connection to the modern day Mfolozi River and contemporary estuary. Periodic desiccation of the lake sub-basins since this point has been apparent. Given the complex management plans implemented to stop excess sedimentation, hypersaline events, and the continuation of "normal" lake levels, this is at odds with the natural system's evolution to a pan or wetland-type state. This geological background should be key to informing management plans that work within the natural evolutionary trajectory of the system, as opposed to attempting to maintain an unattainable status quo. • Examine the Holocene evolution of Lake St Lucia. • Reveal complex back-barrier evolution of two separate systems. • Place evolution in context of sea level and climate forcing. • Juxtapose system evolution with management plans. [ABSTRACT FROM AUTHOR]

Cooper, J.A.G., Green, A.N. and Smith, A.M. 2013. BARDEX II: Vertical stacking of multiple highstand shoreline deposits from the Cretaceous to the present: facies development and preservation. A sequence of vertically stacked shoreline facies exposed by unprecedented water level lowering in Lake St Lucia, South Africa, records multiple occupation of the same shoreline (5-6m amsl) on at least eight occasions since the late Cretaceous. The sequence involves a basal wave-cut surface that is the outcrop of a regional unconformity cut into Late Cretaceous siltstone with occasional borings, representing a hardground (Facies 1). This is succeeded by a limestone unit indicative of sedimentation in a region of low terrigenous input quite different to today. This commences with a 10cm-thick unit comprising corals and giant clams that colonised the hardground as a shallow reef (Facies 2). The reef has an erosional upper surface that is overlain by a 30-50cm thick coquina (Facies 3) with characteristic sand-lined branching burrows, representing a coarse clastic beach unit. This is equated with the Uloa Formation of Miocene/Pliocene age. This unit has in turn been colonised by a patchy development of a coral reef of a single species, representing a renewed phase of reef development (Facies 4). The reef and the underlying Facies 3 have been waveplaned and eroded to form an erosional rocky shoreline with small potholes on a shore platform. The potholes are encrusted with barnacles and oysters to form a distinctive unit (Facies 5). The oysters and barnacles are encrusted with red algae suggesting a slight subsequent rise in sea level which is also associated with the formation of an erosional notch and a higher level shore platform with several small erosional gullies (Facies 6). These gullies are in turn encrusted by thick accumulations of serpulid worm tubes (Facies 7) into which two subsequent notches have been cut by wave action. The shorelines preserved represent a succession of sea level highstands within a few metres of the contemporary sea level since Late Cretaceous times. They survived intervening sea level lowerings and fluvial incision by virtue of their location on an interfluve between adjacent incised valleys. Early cementation would have also been key to their preservation. Each shoreline facies was in turn influenced by the antecedent conditions imparted by the preceding shoreline as well as the contemporaneous conditions of sediment supply, sea level change and the surrounding palaeogeography. The presence of limestone and the absence of clasts or storm beach deposits suggests a protected coastline. The intermittent occurrence of coral and the reduced coral assemblage suggests that the water may not always have been fully marine. [ABSTRACT FROM AUTHOR]

Bond, J., Green, A.N., Cooper, J.A.G. and Humphries, M.S., 2013. Seasonal and episodic variability in the morphodynamics of an ephemeral inlet, Zinkwazi Estuary, South Africa. The inlet dynamics of estuary and lake systems with ephemeral inlets have been little studied compared to systems with semi-permanent tidal inlets. Here we document the meso-scale dynamics of a barrier and its associated ephemeral inlet. The inlet is typically open during the rainy season and experiences closure during winter low flow periods. It does not migrate. The inlet is formed by fluvial overtopping of the barrier and when active, forms a small delta seaward of the channel and a small flood tide delta in the back-barrier. The tidal prism is insufficient to maintain the inlet and it is quickly sealed through wave-reworking of sand from the ephemeral delta when fluvial discharge diminishes. During a large ocean swell event coupled with abnormally high tides in 2007, a departure from this seasonal behaviour occurred. The barrier migrated 100 m landwards and formed a gently (1.74°) seaward dipping sand sheet. Whereas the barrier had previously been narrow, it was widened by 80 m and rose 1.5 m in elevation. A breach later occurred and rapidly migrated northwards, establishing a significantly deeper inlet. This closed following wave reworking of a large ephemeral delta. Since then the barrier has maintained its landward position yet the inlet has continued to function as it did prior to the storm surge. This episodic barrier retreat appears to represent crossing of a morphodynamic threshold that triggered historically unprecedented rates of barrier rollover, creating a new set of inlet morphodynamic processes. These were short-lived and the system appears to have reverted to the typical seasonal morphodynamic processes despite such rapid rollover. [ABSTRACT FROM AUTHOR]

Abstract: Two sequence boundaries are recognised in seismic data collected from the narrow northern KwaZulu-Natal continental shelf. These correspond to late Cretaceous and latest Pleistocene–Last Glacial Maximum (LGM) periods of sea-level fall where fluvial incision into the shelf resulted in several incised valleys having formed. In both examples, the ensuing transgressive valley fills document an evolution from fluvially dominant sedimentation to classic backbarrier estuarine conditions. Central estuary basin sedimentation is most prominent within each fill and is separated from the underlying fluvial sediments by bayline ravinement processes. Tidal-ravinement surfaces separate the upper estuarine sequences from barrier and shoreface deposition, most easily observed in the latest Pleistocene/Holocene valley fills where a Holocene unconsolidated sediment wedge overlies the estuarine fill. The wedge itself is characterised by two packages of sediment separated by a regionally occurring wave/shoreface transgressive ravinement surface which crops out as a semi-indurated shell hash in the mid to outer shelf. Late Cretaceous examples are capped by deposits exhibiting oblique parallel to wavy reflectors interpreted as increasingly energetic deposits analogous to flood-tide deltaic sedimentation. Valley incision and fill are linked to two onshore coastal lake systems, Lake Sibaya and Lake St Lucia and appear to be the product of barrier breaching and fluvial re-adjustment to baseline shifting of these systems during forced regression. Lake St Lucia exhibits a composite palaeo-drainage channel where both sequence boundaries merge within the lake margins. Lake Sibaya has two distinct palaeo-channels for each sequence boundary episode, a late Cretaceous channel which fed a small incised valley within which a modern day submarine canyon is located, the other an LGM channel directed in towards the head of Wright Canyon, the subsequent input of sediment causing this canyon to breach furthest into the shelf than any other canyon in the area. Offshore of Lake St Lucia, the most proximal portions of the associated Leven Canyon occupy the mid shelf and are underlain by Lake St Lucia palaeo-drainage channels of LGM age where erosion along the initial LGM palaeo-channel has occurred. Freshwater exchange between the shelf and the fringing lake system has resulted in the development of sinuous features of Leven Canyon which have eroded in a downslope-fluvial like manner, thus occupying palaeo-drainage lows as erosive flows were entrained. Models proposed here indicate that 1) the limited accommodation space offered by a narrow continental shelf may allow for a greater preservation potential of wave-dominated estuarine facies; 2) the seismic expression of these fills may vary, yet still satisfy similar sedimentological conditions and 3) antecedent valley topography increases the preservation potential of these valley fills by providing a preferred space in which to re-incise and then fill during sea-level rise. [Copyright &y& Elsevier]

Richards Bay is part of a back-barrier lagoon fronted by high coastal dunes on the NE, Indian Ocean coast of South Africa. In the early 1970s, a berm was constructed, dividing the original Mhlathuze Estuary into two separate systems; the Richards Bay Harbour and the new Mhlathuze Estuary. This study investigates the stratigraphic evolution of the incised valley system and bayhead delta in the Richards Bay Harbour segment. Seven seismic units (Units 1–7) were imaged. A single regionally developed sequence boundary (SB) along with two tidal ravinement surfaces (tRS1 and tRS2) were identified. Surface SB is associated with the LGM lowstand which developed when sea levels were ~ 130 m below present, until ~18,000 year BP. Cretaceous age siltstones (Unit 1) form the basement. Transgressive material overlying SB (Unit 2) reflects the filling of an incised valley located in the middle segment of a wave-dominated back-barrier system. It is overlain by a bayhead delta (Unit 3), the geometry and seismic signature of which indicate alternating periods of aggradation/progradation and backstepping. The behaviour is attributed to episodic jumps in sea-level, and is tentatively (on the basis of elevations in relation to the regional sea-level curve) linked to periods of rapidly rising sea-level (8.2 ka event and Meltwater Pulse (MWP)-1d). These intervals of rapidly rising sea-level, combined with relatively low gradient settings facilitated backstepping of the delta. Fills (Unit 4) occur within minor incisions along the delta top. These are interpreted as distributary channels that fed sediment to the seaward edge of the bayhead delta system. Elongated mounds on the seafloor (Unit 5) are interpreted as spoil from contemporary port dredging. Slump deposits (Unit 6) along the delta front are attributed to a combination of oversteepening of the delta by dredging, as well as deposition of modern sediments brought into the system by tidal currents. The system is capped by fine-grained, tidally redistributed and deposited sediments (Unit 7) which were possibly sourced from older organic material of an indeterminate source. This site is especially sensitive to episodic rates of sea-level change due to the relatively small Glacial Isostatic Adjustments (GIA) during the postglacial transgression and the flat antecedent gradients of both the subaerial unconformity and the overlying tidal ravinement. • Stratigraphic evolution of incised valley systems underlying Richards Bay Harbour. • Aggrading, prograding and backstepping bayhead delta into underlying incised valleys. • Pulses of rapidly rising sea levels — 8.2 ka event and Meltwater pulse (MWP)-1d. • Low topographic gradients sensitive to abrupt sea level rises. • Small Glacial Isostatic Adjustments (GIA) during postglacial transgression. [ABSTRACT FROM AUTHOR]

Abstract: Samples collected from the shelf-edge wedge using surface grab samples and the Jago submersible constrain the KwaZulu-Natal shelf-edge wedge to a late Pliocene age on the basis of the absence of Gephyrocapsa oceanica s.l. and Discoaster brouweri, and the presence of Calcidiscus macintyrei. This correlates with proposed Tertiary sea-level curves for southern Africa and indicates relative sea-level fall during the late Pliocene coupled with hinterland uplift. Exposed failure scarps in the upper portions of submarine canyons yield sediment samples of early Pleistocene ages, indicating the uppermost age of deposition of clinoform topsets exposed in the scarp walls. Partially consolidated, interbedded silty and sandy deposits of similar age outcrop in the thalweg of Leven canyon at a depth of 150m. These sediments provide an upper age limit of the shelf-edge wedge of early Pleistocene, giving a sedimentation rate of this wedge of 162–309m/Ma. The distribution of widespread basal-most Pleistocene sediments on the upper slope indicates that these sediments escaped major reworking during sea-level falls associated with Pleistocene glaciations and remain as relict upper slope veneers. The absence of more recent sediments suggests that this area has been a zone of sediment bypass or starvation since the early Pleistocene. Areas where younger sediments mantle deposits of early Pleistocene ages represent areas of offshore bedload parting, re-distributing younger Holocene sediment offshore and downslope. [Copyright &y& Elsevier]

Although blowouts in sand dunes have been extensively studied elsewhere, little is known about those within the Holocene dune fields of the Maputaland coastal margin in KwaZulu-Natal, on the east coast of South Africa. Research in this paper involved measuring, describing and analysing wind flow patterns at a single blowout near Mabibi and related the results to the wind dynamics. From this, a preliminary hypothesis of blowout formation was made. Topographic steering through both the logarithmic spiral form of the bay adjacent to the blowout and the morphology of the dune had a significant influence on wind patterns in both pre- and post-frontal wind conditions. As the blowout widens, further channelling accelerated a jet around the headland, which would ultimately result in complete breakthrough of the dune, leaving a small isolated residual dune fragment, cut off by a mobile arc of sand. The paper concluded that such blowouts are characteristically formed under highly negative beach budgets, and that blowout formation along this coast is more likely at sites in the proximity of rocky headlands. [ABSTRACT FROM AUTHOR]

In the context of rising sea levels, wave-dominated coasts and deltas are among the most threatened of coastal landforms. The study of submerged deltas, in tandem with other drowned wave-dominated shoreline sequences, can shed light on the long-term coastal behaviour of these threatened shorelines when subject to high-end scenarios of relative sea-level rise. Using ultra high-resolution seismic reflection data and gravity core samples, this paper investigates the post-glacial stratigraphic development and architecture of the shelf off southern Mozambique. We document several well-preserved beachrock/aeolianite palaeo-shoreline complexes from water depths of −100, −75 and −60 m, interpreted as representing the positions of former sea-level slowstands or stillstands. These overlie the regional subaerial unconformity associated with the last glacial maximum and are linked to two phases of deltaic deposition. Pro-deltaic deposits on the outer shelf were linked with the period of sea-level stability attributed to the −100 m shoreline, while proximal delta front deposits on the inner- to mid-shelf are linked to a slowstand evident in the local sea level record at −40 m. Well-developed lower delta plain facies overlie both shoreline and delta front facies and show evidence of strong channelisation during normal regression of the delta. These are overlain across the shelf by isolated and stranded pieces of the now relict shoreface, trapped to seaward by the shoreline complexes. The more proximal parts of the shelf are in turn overlain by fluvial-derived muddy facies of the current prodeltas of the area. The preservation of shoreline and delta deposits was enhanced by intervening rapid increments in sea-level rise associated with meltwater pulses 1A (−100 m) and 1B,(−60 m) though the preservation of the −75 shoreline feature, in spite of modest rates of Older Dryas base-level change, points toward other factors such as rapid cementation as dominant in this instance. The region's high sediment supply exerted a primary control on shelf preservation by dampening the erosive extent of wave-ravinement. Variations in antecedent gradient are responsible for much of the documented along-shelf and down-dip depositional variability: low-gradient settings promoted the development of broad coastal plains and strongly wave-dominated deltaic facies, while steeper areas of the shelf favoured the development of coastal landforms in relatively narrow complexes fronted by deep-water deltaic deposits. Steeper areas of the shelf also tend be characterised by an embayed along-coast profile that locally mitigates wave-energy, reinforcing the influence of inherited gradient. Once preserved, drowned coastal barriers introduced an additional geological control as post-glacial sediment became trapped between these features on the outer shelf. The dispersal of modern sediments is strongly influenced by the hydrodynamic regime Delagoa Bight, under which fluvial muds are transported northeastward along the shelf by a persistent inner-mid shelf counter-current. A considerable proportion of the modern sediment budget is lost off-shelf where the shelf narrows. This study shows that low antecedent gradients foster gentle coastal profiles predisposed to delta overstepping. Though local topographic knickpoints can aid in preserving the delta during submergence, they do not buffer the delta from the general effects of inundation which include drowning of the delta top. Once overstepped, the former delta can be overlain by distal deltaic sediments associated with the higher sea level and associated fluvial and oceanographic forcing quite different from earlier phases of delta construction. • Submerged shorelines and wave-dominated deltas of the Limpopo shelf are investigated. • Shorelines and deltas formed by slowstands at −100 m, −75 m, −60 m and −40 m. • Steep zones form narrow shorelines vs the updrift strandplains of flatter slopes. • Large portions of the delta plain are submerged and preserved. • In-situ drowning of landforms linked to MWPs and flat regional antecedent gradient. [ABSTRACT FROM AUTHOR]

Few stratigraphic models of continental shelves incorporate the process of geostrophic current-sweeping, consequently its role in the stratigraphic record is often overlooked. We examine the narrow, current-swept Eastern Cape shelf of South Africa using a combination of geophysical techniques, seafloor sampling and video observations and interpret the role of current action on the transgressive stratigraphy of this steep subtropical shelf. During the Last Glacial Maximum, fluvial valleys incised the acoustic basement rocks. During the subsequent transgression, two distinct shorelines were formed and preserved at −105 m and − 60 m. Their development and preservation is linked to (i) high sediment supply from adjacent fluvial sources, (ii) early diagenesis and (iii) alternating sea-level stillstands and periods of rapid sea-level rise during melt water pulses 1A and 1B, respectively. The deeper shoreline formed in a sandy, wide coastal plain setting with limited bedrock influence, whereas the shallower shoreline comprised alternating rock headlands and embayments like the contemporary coast. Differences in antecedent topography and geology are responsible for the temporal variability in shoreline type; coastal squeeze is exacerbated with increasing bedrock control as the shoreline migrates landward Between the two shoreline complexes, in the mid-shelf, the transgressive stratigraphy records initial valley infill by progradation of coast-parallel sandy spits. These are capped by a stiff lagoonal mud deposited as ongoing sea-level rise overspilled the valley interfluves, onlapping the adjacent aeolianites. The uppermost stratigraphy comprises mounds of rhodoliths which interfinger with a sandy inner to middle shelf highstand wedge. After sea-level reached its present position ca 7.4 ka yr BP, the shelf became subject to reworking by the high-energy geostrophic Agulhas Current. This has had the following major effects on the shelf stratigraphy: 1. The topographic relief of the cemented palaeo-shorelines has been emphasised by removal of the post-transgressive cover; and 2. The shelf no longer acts as a depocenter; instead, the seabed consists of rhodoliths, gravel streamers, bedrock or gravel hash of the wave ravinement surface. Given the necessary antecedent conditions such as accommodation, sediment supply and favourable diagenetic climate, prominent shorelines can form and be preserved on the shelf. Strong current sweeping emphasises these morphological features on subtropical shelves. • Palaeo-lagoons, inlets and barrier islands mark a − 100 m palaeo-shoreline. • Barrier complexes formed within embayments mark a − 60 m palaeo-shoreline. • Rhodolith accumulations, gravel streamers and bedrock exposure signify current-dominated conditions. • Current sweeping began ~7000 BP. • Contemporary morphology reflects relict influences like sea level stillstands, and meltwater pulses. [ABSTRACT FROM AUTHOR]

This paper investigates the interplay between allocyclic controls and antecedent topography in the evolution of submerged coastal landforms, including a back-stepped delta. Using high-resolution tools, we examine the wave-dominated Thukela shelf, and define the major seismic units. Key features identified comprise incised valleys scoured into bedrock, that have overspilled to form lagoons at depths of 50 m. These are in turn overlain by two prograding and backstepped sandy delta systems at 40 m and 32 m depth respectively. The deltas interfinger with muddy prodelta deposits and are truncated by the Holocene ravinement, overlain by the contemporary prodelta of the Thukela River system. A bedrock high separates two physically separate strato-morphological zones; landward a sediment stripped, steep and shallow nearshore zone, and seaward a gentle zone downdip where the deltaic accumulations are sited. Delta development was favoured during sea-level stillstands at −40 m and −32 m respectively. The step-back of the deltas corresponds to sharp increases in the rate of sea-level rise associated with meltwater pulses. The overall gentle palaeo-bathymetric gradient has moderated erosion associated with rising sea level, preserving a sandy back-stepping delta and a draping mud clinoform. Submerged delta positioning relates to underlying incised valleys, suggesting a synchronous transgressive evolution of the drainage and the delta. Incised valley network positioning is further governed by Late Pliocene aged growth-faults in the basement rocks. The geological framework has acted as a recurring primary control to the geomorphic evolution of the area, partitioning accommodation for sediment accumulation and moderating the efficiency of ravinement. • Antecedent geology is a first order control in delta construction and preservation. • Delta construction favoured in swell shadow of bedrock highs. • Gentle palaeo-bathymetry mediates erosion associated with transgression. • Faults in bedrock control position of incised valley network. [ABSTRACT FROM AUTHOR]

Fluid flow features can be used to delineate the migration pathways of fluid from gas sources to the present-day seafloor. A quantitative and qualitative study of these features can reveal linkages between modern mass wasting processes, submarine geomorphology and fluid dynamics in the sub-strata. This study examines 2219 pockmarks from the seafloor of the western margin of South Africa, located in the gas-rich Orange Basin. High resolution bathymetry and 2D seismic reflection data reveal multiple pockmarks which are the manifestation of fluid migration from an Aptian gas reservoir in the basin's drift succession. Six units (Seismic Facies 1–6) and five unconformity surfaces (Surface A–E) are defined, and fluid flow features are studied within the context of this seismic stratigraphy. The fluid migration process formed blowout pipes and brightened reflectors and occured via four mechanisms (Case 1–4). Gas pipes may have cut through the stratigraphy in a near vertical fashion to terminate on the seafloor as pockmarks (Case 1). Peculiar vertical-lateral stepping of gas pipes along seismic units, dominated by lateral flow, comprised Case 2. Case 3 encompassed the termination of gas pipes along stratigraphic boundaries associated with changes in lithology. Lastly, Case 4 involved the migration of fluid along pipes and into palaeo-canyon channels. Using a hydrological extraction technique, the pockmarks are quantified for density, depth and distribution. There appears to be three distinct regions of pockmark occurrences (Zone A–C). Zones A and C are densely populated by pockmarks, whereas Zone B expresses fewer pockmark features. Pockmark morphologies include circular, elongate, crescentic, composite and stringed-types. The diversity in pockmark morphology reflects the local effects of bottom currents. This study show how fluid-flow features may control mass wasting and the development of distinctive seafloor morphologies such as submarine canyons. • Fluid migration pathways of the southern Orange Basin are examined in detail within the host sedimentary succession. • Gas pipes are the most prominent feature and either cut across the stratigraphy or show a stepping pattern. • A total of 2219 pockmarks are quantified using hydrological extraction techniques. • Pockmark morphologies include circular, elongate, crescentic, composite and stringed-types. • A fluid flow model is proposed showing idealised mechanisms for fluid migration within the southern Orange Basin. [ABSTRACT FROM AUTHOR]

Shorelines respond to rising sea-level through processes such as erosion, landward migration and in-situ drowning (i.e. overstepping). Submerged and preserved shorelines on the continental shelf play a key role in examining coastal response to rising sea levels as they provide important information on how modern shorelines may evolve in time and space within the context of changing climate and post-glacial sea-level rise. This study identifies and assesses the response of a continental shelf to stepped rises in sea level with particular focus on the stepwise evolution of incised valleys and shorelines from the shelf-edge to the inner shelf. Multibeam bathymetry from the mid-outer allows for the analysis of seafloor morphology, including the Protea Banks Reef (a palaeo-shoreline complex), and the adjacent incised, sediment starved continental shelf. Six seismic units and intervening surfaces are identified using interpretations from sub-bottom profiles, these include the incised acoustic basement, variable incised valley fill successions, aeolianite ridges and post-transgressive shoreface and associated sediments that withstood wave ravinement processes. The incised valleys of the outer-shelf are manifested as distinctive seafloor depressions, filled at their bases by fluvial deposits overlain, in the unfilled valley, by deposits derived from cascading subaqueous dunes which comprise the upper-most post-transgressive sediments. A core intersecting the dune material yields a maximum age of deposition of 1191–1263 cal yr BP (68% range), synchronous with a period of higher than present sea-levels in the region suggesting reworking and redistribution of coastal sediment as shelf sediment post-transgression. During the stepped rises in sea level, the shoreface has disconnected from the contemporary shoreline and is preserved by means of topographic barriers formed by antecedent topography as relict shoreface deposits. We provide a new perspective of shoreline response to stepped rises in sea level by integrating the seismic architecture of incised valley fills and shorelines across the continental shelf thus allowing for the assessment of variation in rates of relative sea-level rise since the last glacial maximum. • Unfilled incised-valleys result of reduced sediment supply or rapid increases in rate of sea-level rise. • Aeolianite barriers provide antecedent controls on the preservation of disconnected shoreface deposits. • Preservation of palaeo-shorelines by overstepping is related to the ensuing meltwater pulses 1A and 1B. • During these stepped rises in sea level, several shoreface disconnections from the adjacent shoreline occurred. • Reduced sediment supply during shoreline construction may lead to overstepping of low-gradient coastal areas. [ABSTRACT FROM AUTHOR]

Elongate, rock-framed Santa Catarina Island partly encloses a low-energy marine embayment that communicates with the ocean via narrow, rock-bounded inlets with ebb and flood-tide deltas. The bay shoreline consists of low-energy sandy beaches, strandplains, mangroves and bayhead deltas while the exposed Atlantic shoreline comprises a series of headland-embayment littoral cells in a linked, north-directed longshore drift system. New and previously published seismic stratigraphic investigations enable assessment of the palaeogeographic/geomorphic evolution of the area since the early Holocene. At a sea level of ca. −50 m a sandy mainland-attached shoreline complex (dune and beach) developed on a coastal plain setting some 6–7 km offshore of the present shoreline. North of the island, a barrier island and tombolo were formed in a coastal re-entrant adjacent to the northern entrance to Florianopolis Bay. The open coast beach/dune system was overstepped by rapid sea-level rise during MWP-1B whereas the barrier island and tombolo continued to accrete until MWP-1C when they too were overstepped. The back-island embayment contains up to 40 m of sediment overlying an irregular bedrock surface. It was initially flooded during MWP-1C and the early muddy sedimentation suggests a distal, sheltered marine embayment. The subsequent development of many large bioherms on bedrock and mud suggests a change to more fully marine conditions as sea-level continued to rise. In the North Bay, these were subsequently enveloped by tidal dunes migrating north from the mid-bay. The vertical stacking of 3-D and 2-D sandy bedforms suggests that a tidal strait had developed with strong tidal currents radiating from a constriction in the vicinity of modern Florianopolis City. The strong tidal currents may be linked to the Holocene sea-level high that is well documented for this region. A fall in sea level from this highstand, coupled with accumulation of tidal strait sediments, reduced the tidal prism and strength of tidal currents in the bay. At the same time, regressive beachridge plains developed in open coast and bay environments. This coincided with development of the contemporary tidal inlet complexes at the north and south outlets of the bay. As a consequence, the upper surface of the tidal strait sand deposits experienced tidal ravinement and the bay switched to a sheltered back-barrier environment dominated by deposition of mud and silt which blanket the contemporary bay floor. The tidal inlets sequestered sand from the littoral drift system in ebb and flood-tide deltas, which created breaks in the longshore drift system, causing littoral sediment to accumulate at the north of the island in a series of spits, and promoting strandplain development south of the island. • First seismic exploration reveals contrasting shoreline complexes in the region of Santa Catarina Island. • At -50 m a regional sandy shoreline complex developed in a coastal plain setting, removed from bedrock influences. • Open coast beach/dune system thought to be overstepped by rapid sea-level rise during MWP-1B. • A large back-island embayment was flooded during MWP-1C, forming a tidal straight inshore of Santa Catarina Island. • Modern highstand reworked pre-existing sediment and created tidal inlet-associated sand bodies adjacent to the bedrock island. [ABSTRACT FROM AUTHOR]

• Direct footwall gradient – diamond grade relationship. • Indirect wavecut platform-diamond grade relationship. • Inherited structural control on footwall morphology. • Offshore placer exploration target ranking methodology developed. • Data integration. The linear beaches of Mining Area 1 (MA1) on Namibia's south-western coastline host the onshore portion of the world's largest diamond placer deposit. These beaches have been actively mined for over 80 years but land-based mining methods are close to reaching their practical limit on this vigorous wave-dominated coast. Seismic data and sparse sampling data confirm that the linear beach deposits continue offshore onto the inner shelf, which is characterised by a number of erosional nick-points and wave-cut platforms developed over the bedrock topography. This environment constitutes a techno-economic challenge and a target ranking methodology is required for economic development of the offshore extension of the deposit. Detailed analysis of the historical onshore mining dataset (including footwall elevation survey data, diamond grade information and detailed geological mapping and modelling), was integrated with newly acquired geophysical data that spans the onshore and offshore sectors of the deposit. This shows that relative diamond grade is controlled by the gradient of the bedrock and the wave-cut platform width. An inherited structural control on bedrock gradient is also shown. The direct gradient-grade and indirect platform width-grade relationships can be extended to the offshore realm and used as target ranking criteria. These results greatly aid risk mitigation of decision making against the backdrop of techno-economic challenges associated with developing and mining the nearshore extension of the placer. [ABSTRACT FROM AUTHOR]

The inner continental shelf (0–50 m water depth) off Santa Catarina, southern Brazil was investigated using seismic stratigraphic methods to identify and interpret the major seismic stratigraphic units and to reconstruct the late Quaternary evolution of the inner shelf and coast. The stratigraphy comprises a bedrock basement overlain by a thick (> 30 m) unit that comprises, in the distal portion, laminated muds and sands, and in the coast-proximal zone, offlapping deltaic deposits, whose upper surface has been reworked to form alongshore-prograding barrier spits. Deposition of this unit is tentatively attributed to sea levels (− 20 m MSL) during the late Pleistocene (MIS 5a, or 5c). A normal fault in the muddy units with a vertical offset of 3.5 m indicates episodic tectonic activity. Cut into this unit is a profusion of incised valleys, associated with sea level fall ultimately to − 120 m at the last glacial maximum (LGM). The associated subaerial unconformity is only preserved close to shore, where it has escaped subsequent wave ravinement. This, coupled with the well-preserved incised valleys implies the underlying substrate to be weakly cohesive material (mud). The incised valleys display a variety of infilling sediments interpreted variously as basal fluvial sediments, estuarine basin infill muds and marginal bar or barrier-associated sands deposited during the postglacial marine transgression. During a sea level stillstand at ca. -50 m, a 3.5 km-wide planar surface was cut into the unconsolidated coastal plain sediments forming a terrace on which a thick sequence of sands accumulated. This unit is regionally developed and the acoustic signature implies it to comprise littoral sand including a large aeolianite component. The accumulation of sand on this mainland beach/dune system is attributed to establishment of a mature littoral system with strong longshore drift. The fact that it rests on an erosional surface that truncates incised valleys, suggests the unit to be Holocene in age. It is interpreted to have been deposited during a still stand in the Holocene and to have undergone aggradation and cementation until it was overstepped by sea-level rise. Its surface and the coastal plain to landward were then subject to wave ravinement and a thin (ca. 5–6 m) layer of modern marine sands was deposited on the eroded surface. Sea-level rise continued to the regional glacio-isostatic highstand of ca. 5.5 m, after which regressive strandplains developed in response to a renewed mature longshore drift system similar to that prevailing during the − 50 m stillstand of sea level. In the intervening period, rapid shoreline translation over the low gradient surface inhibited the development of the longshore transport system. The three shoreline systems identified show marked differences that relate to sea level change and the influence of the underlying topography. Shoreline 1 (Pleistocene highstand) developed by localised wave-reworking of delta deposits and involved a series of alongshore-prograding barrier spits on a shoreline of alternating high-relief bedrock and littoral sands in coastal re-entrants. Shoreline 2 (− 50 m) was a major accumulation of beach and dune sand deposited as a mainland-attached beach dune system on a low-lying coastal plain environment. Shoreline 3 (the modern coast) comprises a series of headland-embayment beaches, strandplains and transgressive dunes with a strong bedrock control and a well-developed longshore drift system delivering sediment northward. [ABSTRACT FROM AUTHOR]

Patient-reported outcome (PRO) collection and intervention improves disease outcomes. In our urban public hospital radiation oncology department, we created a digital "care companion" (CC) program embedded in the health system electronic medical record (EMR) to provide breast cancer (BC) radiation therapy (RT) patient education and collect PRO. We hypothesized that CC would be used by a majority of patients who had activated the mobile EMR app. A multidisciplinary team (physicians, nurses, and information technology) oversaw CC. Because the EMR did not have an existing CC module for RT, we created a first-of-its-kind program using established and validated content. CC included weekly education, PROs at multiple timepoints during and after RT, reminder messages, and videos. Patients were eligible for the program if they had a diagnosis of BC undergoing RT, were English-literate, and had a smartphone. All patients received usual care consisting of paper-based educational materials before RT start. Patients were enrolled in CC through the EMR before the first RT fraction and instructed to download the mobile EMR app. PROs came from two source surveys: 1) National Cancer Institute PRO-CTCAE Custom Survey of 36 questions relevant to BC, and 2) EORTC-QLQ BR23 comprising 23 BC-related items. Patients completed skin reaction and pain scales weekly during RT. Educational materials were "tasked" to patients during and after RT. Reminder messages were sent by email. Nurses also verbally reminded patients about CC during clinic visits. CC ended 90 days after RT. We measured monthly patient Engagement and Task Compliance. "Engagement" is percentage of patients interacting with a task and either skipping or completing it within a specific time window (1 week for PRO surveys, 3 days for other tasks). "Task compliance" is the percentage of a specific assigned educational or PRO task that is completed each month. A total of 56 BC patients were enrolled in CC from 9/6/2023 to 2/28/2024; 40 completed the program and 16 remain enrolled. Median age was 58 years (range = 29-85). 89% of enrolled patients activated the EMR chart by app or web browser. Engagement was 21.6% on average per month (range = 6 to 38%). Average monthly task compliance ranged from 2% (for PRO-CTCAE) to 6% (for Skin and Pain scales), with monthly high of 19% in January (skin/pain scales). Throughout our hospitals, patient logins to the EMR chart after activating an account remain low at 10-11% monthly. In our urban public hospital population, a novel patient-facing BC care companion EMR program had low engagement in its first six months, despite most patients activating their EMR chart. Digital interventions suffer from high dropout or disengagement. To improve usage, next steps include demonstrating CC task completion to patients in clinic, changing automatic reminders to be text-based, and surveys to understand patient reasons for disengagement. PROs will be reported after longer follow up. [ABSTRACT FROM AUTHOR]

Jackson, D.W.T.., Cooper, J.A.G., Green, A.N., 2014. A preliminary classification of sand dunes of the KwaZulu-Natal coast. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 718-722, ISSN 0749-0208. The 550 km-long KwaZulu-Natal coast broadly divides into a bedrock-framed southern section and northern coastal plain section, each of approximately equal length. Seven types of coastal dune are identified on this coast: estuary barrier dunes; mainland beach foredunes; prograded beachridge dunes; headland bypass dunes; transverse dune fields; parabolic/migrating dunefield; and climbing dunes. The development and distribution of the various dune forms is more strongly controlled by the geological setting, than the aerodynamic regime. [ABSTRACT FROM AUTHOR]

The diverse lagoons and coastal lakes along the east coast of South Africa occupy incised valleys that were flooded during the rise and subsequent stabilisation of relative sea-level during the Holocene. Sedimentary deposits contained within these waterbodies provide an opportunity to investigate complex hydrological and sedimentological processes, and examine sea-level controls governing system geomorphic evolution. In this paper, we combine diatom and sulfur isotope analyses from two sediment cores extracted from the northern sub-basins of Lake St Lucia, a large shallow estuarine lake that is today largely isolated from direct ocean influence behind a Holocene-Pleistocene barrier complex. Analyses allow the reconstruction of hydrological changes associated with the geomorphic development of the system over the mid-to late Holocene. The sedimentary sequences indicate that St Lucia was a shallow, partially enclosed estuary/embayment dominated by strong tidal flows prior to ∼6200 cal. BP. Infilling was initiated when sea-level rise slowed and stabilised around present day levels, resulting in the accumulation of fine-grained sediment behind an emergent proto-barrier. Diatom assemblages, dominated by marine benthic and epiphytic species, reveal a system structured by marine water influx and characterised by marsh and tidal flat habitats until ∼4550 cal. BP. A shift in the biological community at ∼4550 cal. BP is linked to the development of a back-barrier water body that supported a brackish community. Marine planktonics and enrichments in δ 34 S suggest recurrent, large-scale barrier inundation events during this time, coincident with a mid-Holocene sea-level highstand. Periodic marine incursions associated with episodes of enhanced storminess and overwash remained prevalent until ∼1200 cal. BP, when further barrier construction ultimately isolated the northern basins from the ocean. This study provides the first reconstruction of the palaeohydrological environment at Lake St Lucia and highlights the long-term geomorphic controls that have shaped the recent evolution and natural dynamics of the system. Unlike most coastal lake systems, this system is particularly effective as an archive of geomorphological change. Systems driven by back-barrier modifications, such as Lake St Lucia, highlight how geomorphological changes driven by sediment-supply, climate and sea level can be distributed unevenly over several isolated back-barrier basins. [ABSTRACT FROM AUTHOR]