The stratigraphic evolution of a large back-barrier lagoon system with a non-migrating barrier

Benallack, Keegan; Green, Andrew N.; Humphries, Marc; Cooper, J. Andrew G.; Dladla, N.N.; Finch, Jemma

doi:10.1016/j.margeo.2016.05.001

Cited by 39 publications

(43 citation statements)

References 28 publications

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“…Sitoe et al (2014) dated local lacustrine sediments between 1200 and 1400 yrs BP, which are confirmed by Holmgren et al (2012) at ages between 845 and 1020 yrs BP recorded in Lake Nhauhache. In addition, Gomes et al (2017) and Benallack et al (2016) also reported similar stepped sea level conditions in the Santa Lucia estuary, about 400 km to the south. Based on this information, the closing of inlets may have occurred between 910 and 1400 yrs BP, creating sufficient conditions to prevent the entrance of tidal prisms into the sheltered lacustrine systems.…”

Section: Dune Topographic Profilesmentioning

confidence: 57%

Aeolian dynamics of transgressive dunefields on the southern Mozambique coast, Africa

Miguel

Castro

2018

Earth Surf Processes Landf

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A relatively unknown coastal zone of southern Mozambique in Africa is covered by vast mobile and stabilized dunefields. The aeolian dynamics of these transgressive dunefields are studied based on mobility and stability models, statistical analysis of climate data and topographic profiles. Detailed analyses of regional winds, rainfall records, atmospheric temperature records and annual monitoring of dune migration rates helped to find reliable data about instantaneous aeolian sand transport rates, wind drift potential, dune mobility and dune migration rates. The data obtained suggest that the coastal transgressive dunefields are controlled by the southeast winds, availability of loose sediments on the beach, the presence of headland boundary between Maputo and Gaza provinces and the appropriate deposition spaces between the coastline and lacustrine‐lagoon systems. Two distinctive segments of transgressive dunefields were identified in the region studied, including the northern segment of Maputo province with active (mobile) and semi‐vegetated dunes that migrate 23 m/yr landward, and Gaza province dunefields with stabilized (vegetated) and semi‐vegetated dunes. The data obtained in this research have considerable potential to make a valuable contribution to the study of coastal dunefields. Copyright © 2018 John Wiley & Sons, Ltd.

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Section: Dune Topographic Profilesmentioning

confidence: 57%

Aeolian dynamics of transgressive dunefields on the southern Mozambique coast, Africa

Miguel

Castro

2018

Earth Surf Processes Landf

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“…The record of Holocene sedimentation in St Lucia, the Mkhuze River and Mfolozi River/Lake subsequently by fluvial erosional processes associated with marine regression events has been recorded by Turner and Plater (2004), Grenfell et al (2010), Neumann et al (2010); Benallack et al (2016), Humphries et al (2016) and Gomes et al (2017). Sediment probes, core borehole drilling and seismic profiling have revealed the thickness of the proto-lake deposits and delineated bedrock valleys beneath the bed of the St Lucia waterbody.…”

Section: Geological Evolution and Sedimentationmentioning

confidence: 92%

“…The age distribution and relief of the beach ridge sets, supported by new dated sea-level index point, is compared with published Holocene relative sea-level curves for the eastern coast of South Africa (after Ramsay, 1995, 1996, Compton, 2001, Ramsay and Cooper, 2002, Botha et al, 2013. The depositional context is supported by St Lucia lake sedimentation records (Benallack et al, 2016 and the geochronological framework of dune formation pulses against the coastal barrier and sand remobilization on the coastal plain (Porat and Botha, 2008). The interpretation can be evaluated against palaeo-environmental records from lacustrine settings in the adjacent Mfabeni fen (Baker et al, 2014) and nearby Lake Eteza (Neumann et al, 2010).…”

Section: Introductionmentioning

confidence: 93%

“…A channel system up to 40 m deep was mapped by Hill (1975), Van Heerden (1987 and Sydow and van Heerden (1988). Recent high resolution seismic profiling by Benallack et al (2016) mapped a more intricate network of narrow channels incised into bedrock mapped that have been correlated with the long-lived marine channel that linked the proto-North Lake with the sea near Leven Point (Fig. 2).…”

Section: Geological Evolution and Sedimentationmentioning

confidence: 99%

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Beach ridge sets reflect the late Holocene evolution of the St Lucia estuarine lake system, South Africa

et al. 2018

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Sets of sandy beach ridges and intervening swales define shoreline sections of the shallow St Lucia wetland system within the iSimangaliso Wetland Park, World Heritage Site in northern KwaZulu-Natal province, South Africa. The sets comprise 3-10 beach ridges, the most prominent being 80-150 m wide and rising 0.5-2 m above the adjacent swales. The highest beach ridge crests elevated 3.2-4.6 m above mean sea level are furthest from the present shoreline and the lowest ridges, rising about 0.5 m above the swales, occur closest to the present mean lake level shoreline. This investigation assesses the genesis of the sandy beach ridges on five strand plain remnants within the estuarine lake. The ridges were topographically surveyed and their ages estimated using optically stimulated luminescence (OSL) dating. OSL dating reveals that the oldest beach ridge formed around 6,240 years ago, with a sequence of beach ridges having accumulated during the period ~4,000 to 1,500 years ago

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“…Regional geological map of the Maputaland coastal plain (from data of Watkeys et al, ) showing the location of major paleochannels and former drainage outlets associated with prominent coastal lakes (Benallack et al, ; Green, ; Wright et al, ).…”

Section: Methodsmentioning

confidence: 99%

Transport of Radium and Nutrients Through Eastern South African Beaches

et al. 2019

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Submarine groundwater discharge (SGD) plays a critical role in coastal and ocean biogeochemistry. Elucidating spatially and temporally heterogeneous SGD fluxes is difficult. Here we use radium isotopes to explore the external sources and mixing regime along the eastern coast of South Africa. We demonstrate that the long‐lived radium isotope compositions are controlled by low inputs of low‐ and high‐salinity terrestrial groundwater. While activities of 228Ra and 226Ra in beach porewaters are similar to coastal waters, 224Ra is enriched by inputs of 228Th from coastal seawater. Porewater ages, based on the production of 224Ra from 228Th, range from 0.3 to 2.3 days, indicating rapid flushing of the beach system. Unlike radium, however, nutrients follow a more complex pathway. We hypothesize that high total dissolved nitrogen (TDN) and phosphorus concentrations in beach porewaters (TDN ranges from 1 to >700 μM) and the coastal ocean (TDN ranges from 1 to >40 μM) are derived from a source not enriched in radium. We speculate that this source is terrestrial water flowing below the dune barrier at depths exceeding our beach sampling depths. This water likely flows upward through breaches in the confining layer into the beach or enters the ocean directly through paleochannels. The presence of high nutrient concentrations in the coastal ocean unaccompanied by high 228Ra activities leads to the hypothesis of this additional nutrient source. These combined inputs may be of considerable importance to the coastal ecology of southeastern Africa, an oligotrophic ecosystem dominated by the nutrient‐poor Agulhas Current.

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The stratigraphic evolution of a large back-barrier lagoon system with a non-migrating barrier

Cited by 39 publications

References 28 publications

Aeolian dynamics of transgressive dunefields on the southern Mozambique coast, Africa

Aeolian dynamics of transgressive dunefields on the southern Mozambique coast, Africa

Beach ridge sets reflect the late Holocene evolution of the St Lucia estuarine lake system, South Africa

Transport of Radium and Nutrients Through Eastern South African Beaches

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