Postglacial Marine Transgression Research Articles

Litho- and chronostratigraphy of holocene sedimentary successions preserved in Lake Illawarra, NSW, Australia

Using a Holocene barrier estuary, Lake Illawarra, New South Wales, Australia, as an example, a detailed litho- and chrono-stratigraphy of the Holocene estuarine deposits has been investigated. Forty kilometres of seismic surveys, 61 vibracores, supplemented by auger drill holes and trenches, and faunal analysis were used in this study. A detailed chronology of the infilling of the barrier estuary has been established using 121 aspartic acid derived ages and 14 radiocarbon ages. The results provide a detailed chronology for the deposition of marine transgressive deposits between ca. 8 and 5 ka years ago. Barrier growth, initiated with rising sea levels during the post-glacial marine transgression and subsequent Holocene sea level highstand, resulted in the development of a low-energy back-barrier depositional environment from ca. 5 ka years ago, and fluvial progradation into the present Lake Illawarra basin from ca. 2 ka years ago. The results from Lake Illawarra indicate that the generalised evolution of the barrier estuary occurred in five geomorphologically distinct phases associated with rising sea levels following the last glacial maximum and the subsequent Holocene sea level highstand.

Successive foraminiferal faunas and inferred palaeoenvironments associated with the postglacial (Holocene) marine transgression, Gulf St Vincent, South Australia

Gulf St Vincent is one of a pair of elongate, triangular, shallow water embayments into the southern coast of continental Australia. From the southern floor of this embayment, within a shallow basin-like depression where present-day water depth is about 40 m, vibracore SV23 recovered c. 4 m of late Quaternary sediments. The uppermost 1.5 m of this core comprises postglacial (Holocene) marine deposits; six radiocarbon ages for the interval 64-130 cm downcore are all around 10 000 cal. yr BP, while two for 18-24 cm are several thousand years younger. Radiocarbon analysis of an oyster shell at 154 cm yielded a minimum age of c. 37 000 cal. yr BP. Well-preserved benthic foraminifera are abundant in all the recovered sediments. The early phase of Holocene marine sedimentation in Gulf St Vincent was marked by the development of a marginal marine, perhaps lacustrine to estuarine environment, as signified by the presence of oogonia, gypsum crystals and the foraminifera Miliolinella labiosa and Elphidium cf. articulatum. Development of seagrass meadows followed; these were inhabited by Nubecularia lucifuga and Discorbis dimidiatus. As the marine transgression proceeded, the environment remained somewhat restricted, as indicated by Ammonia beccarii, but numbers of this species declined giving way to Massilina milletti as conditions began to resemble those of the modern Gulf St Vincent. Culmination of the transgression provided the conditions necessary for the dominance of Ammobaculites reophaciformis and Flintina triquetra. A. reophaciformis and F triquetra therefore record the final episode of the transgression and transition to the modern, deeper water environment. At several lower horizons they also occur as conspicuous spikes, equivalent to their modern abundance. These spikes, which coincide with equivalent decreased numbers of A. beccarii, are interpreted to represent downward bioturbation of the overlying deeper water sediment.

Aminostratigraphy of Two Holocene Wave-Dominated Barrier Estuaries in Southeastern Australia

An aminostratigraphy of Lake Illawarra and St Georges Basin, two wave-dominated barrier estuaries in southeastern Australia, has been derived on the basis of the extent of aspartic acid racemisation in the Holocene fossil molluscs Anadara trapezia and Notospisula trigonella. Relative ages were also assigned to Late Pleistocene fossil molluscs on the basis of the extent of racemisation of the slower racemising amino acids valine, leucine, and proline. Aminostratigraphy indicates that remnant Last Interglacial deposits within both incised valleys form a substrate over which Holocene estuarine sediments have been deposited and form a core for the Holocene barrier. Results from this study also indicate that the early geomorphological evolution of wave-dominated barrier estuaries formed in broad and relatively shallow, incised valleys is different from previously published models of Holocene barrier estuary evolution that explain successions in narrow, drowned valleys. Divergence from previous models is seen with the deposition of a near-basinwide shell-rich transgressive sandsheet deposited as rising sea levels breached remnants of Last Interglacial barriers during the most recent postglacial marine transgression (PMT; ca. 12,000–7000 Cal BP). Subsequent development of the estuaries follows the previously developed models with the Holocene barrier and central mud basin accumulating over the initial transgressive sandsheet. The aminostratigraphic framework derived from this study will serve as a geochronological template for future studies in wave-dominated barrier estuaries on the southeast coast of Australia.

ESTRATIGRAFIA E EVOLUÇÃO DA BARREIRA HOLOCÊNICA DO RIO GRANDE DO SUL NO TRECHO TRAMANDAÍ-CIDREIRA

A barreira costeira de idade holocênica (sistema barreira-laguna IV), no Rio Grande do Sul, não evoluiu de um modo uniforme nos últimos 6 – 5 ka, ao longo dos seus 620km de extensão. O segmento da barreira investigado neste trabalho situa-se entre dois outros segmentos, um ao norte e outro ao sul, onde a barreira holocênica apresenta um caráter regressivo e transgressivo, respectivamente. Com base em dados morfológicos, litológicos de sub-superfície, datações por 14C e simulações de evolução costeira, foi definida uma natureza transgressiva para este segmento da barreira, porém não uniforme ao longo de seus 30 km de extensão, e estabelecida a sua cronologia evolutiva. Em Tramandaí, a barreira permaneceu relativamente estável nos últimos 6 – 5ka, enquanto que em Jardim do Éden e Cidreira a barreira apresentou um comportamento dominantemente transgressivo. Estas diferenças evolutivas são atribuídas a fatores locais que influenciaram no balanço de sedimentos. Como principal fator local é destacada a declividade diferenciada dos substratos da barreira em Tramandaí (0,062°), Jardim do Éden (0,067°) e Cidreira (0,069°), a qual, por sua vez, influenciou nas taxas de translação da barreira durante a elevação do nível do mar, e na energia das ondas incidentes no sistema praial.

Holocene Sea Level Fluctuations and the Sedimentary Evolution of a Barrier Estuary: Lake Illawarra, New South Wales, Australia

Abstract Lithostratigraphy of the Holocene Lake Illawarra barrier estuary on the New South Wales coast, Australia, adds details to previous models of barrier estuary evolution. Establishment of a detailed chronology, with the use of 121 aspartic acid–derived ages and six radiocarbon ages, has allowed the definition of a five-stage geomorphic model for the infill of the barrier estuary. A broad incised valley formed during the sea level lowstand represents the initial stage. Stage two is represented by a basal transgressive marine sand sheet deposited in response to rising sea levels associated with the last postglacial marine transgression, which inundated the shallow incised valley ca. 8000–7500 years ago. This feature is not present in the deeper and narrower incised valleys used to establish previous barrier estuary models. The more open marine conditions, with a diverse assemblage of estuarine and marine mollusc species, persisted until ca. 5000 years ago when the barrier started to become emergent an...

Holocene evolution of Itapeva Lake, Rio Grande do Sul, Brazil: Palynomorphs C org, N, and S records

Holocene coastal environmental changes are interpreted from a 590 cm long core taken from Itapeva Lake in the northern coastal plain, Rio Grande do Sul, Brazil. The sediment core is radiocarbon dated at 211 cm depth (6460±40 yr B.P.) and studied by geochemistry and palynomorph analyses. The Pleistocene–Holocene boundary is predicted at the top of a glauconitic sand layer at 330 cm depth. On the basis of C org, N, S, and palynomorph data, it is possible to distinguish four zones related to the Holocene transgression–regression cycle, as well as proxies for the salinity trends and organic matter source. The start of Zone 1 represents the oldest Holocene sedimentary record in the core. Palynomorphs reveal a marsh environment with a freshwater influence. In Zone 2, Operculoclinium centrocarpum and high S values indicate brackish water and reflect a Holocene sea-level rise related to the postglacial marine transgression. The high amount of Cyperaceae pollen grains and a significant C org increase in Zone 3 indicate a typical marsh environment with episodes of marine water that reflect a regression phase. Salvinia natans (L) All. and Cyperaceae pollen grains are the most significant palynomorphs in Zone 4, which characterizes a freshwater marsh.

Late Quaternary landscape evolution in the Keep River region, northwestern Australia

This paper evaluates the Late Quaternary chronostratigraphic context of archaeological sites in the Keep River region, Northern Territory, Australia. Cosmogenic dating, luminescence dating and sediment characterisation reveal sedimentary processes commencing from erosion of the escarpment and plateaux source through temporary storage in sand sheets, to final deposition in alluvial floodplains. Erosion of the sandstone plateaux (∼5 mm ka −1) and escarpment faces (probably ∼50–100 mm ka −1) provide the main sediment source for the adjacent sand sheets which have evolved over the past 100,000 years as the product of ongoing cycles of accumulation and denudation. The rate of sediment accumulation is lowest near the escarpments on the low-energy sediment-limited sand sheets (<100 mm ka −1) and greatest near the main streams (>400 mm ka −1) that have more numerous sediment sources. Collectively, luminescence ages indicate an apparent increase in sediment accumulation rate in the sand sheets from ∼100 mm ka −1 in the late Pleistocene to over 200 mm ka −1 in the Holocene. This most likely reflects enhanced monsoonal activity following postglacial marine transgression. Palaeosol horizons in the creek profile distinguished by sediment mottling mark potentially significant palaeoenvironmental and palaeoclimatic changes during the Quaternary.

Barrier evolution and placer formation at Bujuru southern Brazil

This paper demonstrates the link between the evolution of a coastal barrier in southern Brazil during the Late Holocene and the formation of a large volume of eolian disseminated heavy mineral deposits. Our data set is based on an earlier heavy mineral prospecting campaign (1991) and on 10 new shallow vibrocores, 2–5 m long. The model presented has three main steps of barrier evolution. The first step is the recycling of coastal plain deposits during the Postglacial Marine Transgression, which ended at 5.6 ka when heavy minerals were incorporated into beach and washover facies of a transgressive barrier. The second step is the shoreward retreat of the barrier, under a slow and small sea-level fall, during the last 5.6 ka. This second step eroded and recycled sediments from the Pleistocene substrate, which acted as an extra source of heavy minerals. Heavy minerals were concentrated in backshore deposits by wave action during barrier recession. The third step is the erosion and transport of backshore sands by onshore winds into an inter-barrier depression in the form of transgressive dune deposits. These deposits contain an average of 4.66±1.02% disseminated heavy minerals (1494 samples). This eolian placer deposit has started to form 1 ka ago and is still under formation.

Geomorphological evidence for a Pleistocene barrier at Matakana Island, Bay of Plenty, New Zealand

New Zealand's largest barrier island, Matakana Island, consists of an elongate coastal sand barrier of Holocene age that encloses Tauranga Harbour and adjoins an area of Pleistocene terraces and terrace remnants. The lowest Pleistocene terrace is well preserved, with a degraded marine cliff, vestiges of shore‐parallel relict foredunes, and a parabolic dune. These hitherto unrecognised coastal landforms are analogous to those of the Holocene barrier and indicate that a prograded coastal plain underlies the terrace. The original landforms of the coastal plain are now mainly below sea level but survived the postglacial marine transgression because at least 12 m of tephra accumulated on the surface, preserving the topography, albeit in a subdued form. In a separate area of the island, the present morphology may reflect the former presence of large parabolic dunes of Pleistocene age. Morphological evidence indicates that coastal processes shaped the island during both Pleistocene and Holocene times, and that the Holocene barrier is welded to a Pleistocene “proto‐barrier”.

Stratigraphy and Holocene evolution of a regressive barrier in south Brazil

The Paranaguá coastal plain is a 600 km2 barrier system located in south Brazil (25° 30′ S) and is largely made up of Pleistocene and Holocene beach ridges. Sea level history in the area is characterized by a gradual, 3.5 m sea level fall in the last 5000 years. Several reverse-circulation drill logs from the Pleistocene and Holocene sectors allowed for the definition of a general morphostratigraphic model of the coastal plain, which proposes the staking of at least two generations of marine deposits upon continental and paleo-estuarine sediments. Analysis of shallow vibro-cores and exposures along back-barrier creeks indicates the existence of four transgressive (estuarine, estuarine channel, overwash and flood-tidal delta) and three regressive (beachface, nearshore and upper shoreface) sedimentary facies in the Holocene section of the coastal plain. The morphostratigraphy suggests that barrier emplacement took place at the last stages of the post-glacial marine transgression, when the back-barrier estuary was squeezed in between the Pleistocene and Holocene barriers. Holocene barrier progradation was significant in both the shore-normal and longshore direction, and was apparently very swift in the last thousand years corresponding to a period when sea level fell by 1.5 m, and when about half of the present barrier volume was accumulated. Higher progradation rates are ascribed to the arrival of sediment yielded by an active littoral drift system, which appears to have eroded large extents of several Holocene barriers along 100 km of coastline.

Relative stability on a tectonically active coast: paleoenvironment during the last 7000 years at Lake Kohangapiripiri, Wellington, New Zealand

Abstract Lake Kohangapiripiri is a small coastal lake in Fitzroy Bay, Wellington, New Zealand. It is situated in a tectonically active area that has well-documented records of co-seismic uplift. The lake is separated from the sea by a gravel barrier and is partially surrounded by wave-cut cliffs, indicating that it was once an inlet. Lake sediments were analysed to determine the age of the marine to freshwater transition believed to have taken place as a result of recent uplift. Diatoms, particle size, organic carbon and radiocarbon data indicate changes in barrier height, water depth, and marginal wetland occurrence. The data also provide evidence that the lake has been freshwater for 7000 years. We propose that a large barrier has been in place between the lake and sea at least since the culmination of the post glacial marine transgression ca. 7000 years ago. Comparison of the lake record with Holocene earthquake records from surrounding locations, shows that the sedimentary environment of the lake has been relatively insensitive to sudden changes in base level and disturbance of the catchment. Previous studies have identified earthquake-related features in lake sediments. However, this study provides an example of a lacustrine environment subjected to large co-seismic uplift events that does not record conclusive evidence of the events.

Evolution of Holocene coastal environments near Robe, southeastern South Australia

Abstract Coastal Robe Range, and adjacent Woakwine Range, situated 10–15 km inland, are the most southwesterly and youngest of a series of parallel, low altitude, Pleistocene beach-dune barriers in southeastern South Australia. In the early Holocene, the post-glacial marine transgression flooded the Robe–Woakwine Corridor, thus forming a shallow back-barrier lagoon, open to the Southern Ocean near the present towns of Robe and Beachport. Marine to lagoonal, bioclastic, carbonate-quartz sedimentation prevailed within the corridor from ca. 7500–2000 yr BP. Along the seaward side of Robe Range, transgressive sands were deposited initially as ephemeral sand flats, but were mostly redistributed as coastal dunes, which today remain active and blanket the Pleistocene core of the range. Sand was also transported along the coast and deposited within the protected embayments of Guichen and Rivoli Bays, in the form of prograded beach ridge plains, eventually isolating the back-barrier lagoon from the open ocean. Sediment aggradation within the lagoon, cessation of marine influence and regional uplift of 0.7 m during the Holocene, combined to transform the corridor to a lacustrine landscape. Fossil molluscs, foraminifera and ostracods are diagnostic of successive palaeo-environments, and thus signify stages in the rapid geomorphic evolution of the coastal Robe–Woakwine Corridor.

Sedimentary environment and acid potential of the pyritic sediments in a sand barrier estuarine system, eastern Australia.

Three cores of Holocene sediments were investigated from an infilled sand barrier estuary, eastern Australia. The estuary formed as a result of drowning of the previous river valley following the postglacial marine transgression. The sedimentary environments evolved over time at the investigated site from a saline prodelta to a less saline delta front to fresh flood overbank sedimentation. Both prodelta and delta front sediments contained large amounts of pyrite, but pyrite accumulation was limited in the riverine flood overbank sediments. The accumulation of pyrite in the estuarine sediments appears to have been controlled by the combined effect of sedimentation rate and the supply of organic matter, while palaeowater salinity relating to the supply of sulfate ion did not limit pyrite accumulation except for the top 1 metre of the freshwater sediments. The degree of pyritization (DOP) of the investigated estuarine sediments is comparable to that of aerobic marine sediments (Raiswell et al., 1988), although the concentrations of organic C, reactive Fe and pyrite-S were much greater. This may be attributed to higher availability of organic matter and reactive Fe compounds, and consequently pyrite-S enrichment in an embayed estuary than in the open sea. Owing to the presence of large amounts of pyrite, the investigated estuarine sediments posed great acid potential upon the oxidation of pyrite. In general, increasing pyrite concentration in the sediments resulted in increasing acid potential, but this was also accompanied by an increase in self-neutralizing and buffering capacity (NBC) of the sediments although the finely-grained prodelta sediments tended to have greater NBC values than did the coarser delta front sediments on an equivalent pyrite concentration.

Development of the middle creek delta plain, Narrabeen Lagoon, NSW

Abstract Middle Creek drains 26 per cent of the total Narrabeen Lagoon catchment and has formed a 1.6 km‐long delta plain where the channel debouches into the coastal lake. The upper delta plain is characterised solely by fluvial landforms because reworking by lateral migration, cutoffs, channel widening and floodplain stripping has totally eroded the previously existing delta landforms. A combination of lateral and vertical accretion has formed a floodplain characterised by point bars, cutoffs, levees, backswamps and floodplain ridges. The lower delta plain consists of landward retreating silt jetties, an enlarging straight channel, and a subaqueous delta comprising an arcuate river‐mouth bar, delta front and pro‐delta. Extensive landfill was used to stabilise the silt jetties and prevent a channel avulsion through the southern silt jetty during the 1960s. The whole delta plain has formed over the last 6000–7000 years, since the stabilisation of sea level following the postglacial marine transgression, b...

Late Weichselian to early Holocene subaqueous dune formation and burial off the North Sea Northumberland coast

High resolution seismic profiles from the North Sea, 20 km off Northumberland, have shown the presence of a 25 km 2 subaqueous dune field buried beneath Holocene marine mud. The dunes are composed of fine to medium sand with occasional pebbles and have heights ranging from 0.5 m to 5.5 m and spacings from 100 m to 600 m. Most larger dunes (> 2 m high) have their steeper slopes facing to the south and internal reflectors representing foreset bedding that dips to the south, suggesting dominant southward sand transport. The dunes are inferred to have been produced by tidal currents of between 1.00 and 1.50 m/s in a shallow water tidal embayment or large estuary during the initial stages of the post-glacial marine transgression in the area, sometime between about 10,700 and 9700 yr B.P. Burial of the dunes occurred when the dimensions of the tidal embayment were increased, tidal current velocities reduced beneath the threshold for dune formation and finer-grained sediment was deposited. The tops of the dunes were eroded and a deflation surface formed before burial.

Composition, distribution and origin of surficial salts in the Vestfold Hills, East Antarctica

A regional chemical boundary termed the ‘salt line’, in the Vestfold Hills of East Antarctica, has been investigated using X-ray diffraction and electron probe analyses of surficial salts, and conductivity of surficial sediments. West of the salt line, halite and thenardite are abundant. These salts are derived from dispersal of marine aerosols, saturation of sediment by seawater during postglacial marine transgression, and glacial dispersal of salt-saturated fjord bottom sediments. East of the salt line, subglacial calcium carbonates and salts formed by chemical weathering of their substrates occur. Chemically and morphologically diverse minerals form the weathering products. They include two minerals not found previously in Antarctica, dypingite and hydromagnesite, and the first confirmed occurrence of brushite.

Studies of Land Bridges and the Migration of Men and Other Animals along Them. Late Pleistocene Unconformity of the Tsushima and Korea Straits Revealed by Seismic Reflection Profiles.

Four major seismic sequences (A, B, C, and pre Quaternary basement) and a major seismic sequence boundary (Reflector T) of an erosional unconformity were recognized in the Tsushima and Korea Straits as a result of shallow seismic stratigraphy. Subsequent sequences A, B, and C were interpreted as recent post-glacial marine transgression sequence, pre glacial marine regressive sequence, and Pleistocene pre-glacial sequence with topmost marine transgressive sequence, respectively.We estimate that the Reflector T was probably formed by an erosion due to subaerial exposure of the sequence (sequences B or C or the basement) lying immediately below the Reflector T during the last glacial period (LGP) of isotopic stage 2. The existence of the erosional unconformity, the Reflector T, suggests that the Tsushima and Korea Straits were land and the Korean Peninsula was connected with the Japanese Islands during the LGP.

Simulation of large-scale coastal change using a morphological behaviour model

Quantitative simulation of large-scale coastal behaviour (LSCB) is possible using a model based only on principles of sand-mass conservation and geometric rules for shoreface and active sand-body morphology. Dynamic processes are subsumed into a set of parameters that define the geometry of the active cross-shore profile which in turn can represent an entire coastal cell. The parameters, together with a set of local behaviour rules governing adjustments at discrete points along the profile, provide a simple formulation that is constrained by sediment mass balance to yield emergent, numerical solutions for profile kinematics. The emergent qualities of this shoreface-translation model are exemplified in simulation experiments on changes to sand deposits on the southeastern Australian coast and shelf during the post-glacial marine transgression. In another example, the model is used to simulate LSCB over engineering time scales at an idiosyncratic site. Both examples illustrate the over-riding importance of small residual sand movements that accumulate through time to cause LSCB. In comparison to gross sand movements, the residuals are too small to measure directly or predict on the basis of available theory. Exploratory (inverse) simulation provides a quantitative method for side stepping these limitations. The shoreface-translation model therefore is used as a tool to explore possible forms of coastal behaviour through an approach that incorporates available data along with theoretical considerations. Validation is not strictly possible for this type of inverse approach, so the degree to which a simulation reproduces observed features in nature is a measure of its success.

Vertical tectonic movement in northeastern Marlborough: Stratigraphic, radiocarbon, and paleoecological data from Holocene estuaries

Abstract Height and age information from Holocene estuarine deposits along the northeastern Marlborough coast provide a database to evaluate coastal vertical tectonics. These data are related to the postglacial marine transgression and coastal geomorphic features formed since the culmination of sea‐level rise. Four tectonic domains are recognised. The Wairau domain is characterised by subsidence at rates over 4 mm/yr. About 60% of this subsidence is tectonic and may be related to Marlborough Sounds subsidence, and 40% is a result of compaction. The Vernon Fault at the south side of the lower Wairau plain separates the Wairau domain from the high‐standing Vernon domain. The Awatere Fault marks the southern boundary between the Vernon domain and the Grassmere domain, which extends from the Awatere River valley to Mussel Point. Slight uplift (c. 1 m in 6500 yr) characterises the Grassmere domain, based on data obtained from Blind River, Lake Grassmere, and, to a lesser extent, from Awatere River fluvial terraces. The north‐trending London Hill Fault reaches the coast at Mussel Point and coincides with the boundary between the Grassmere and Cape Campbell domains. The latter is characterised by rapid uplift (16 m in c. 6500 yr). No late Quaternary traces are known on the London Hill Fault, but the data presented are indicative of Holocene activity.

The Torres Reefs, North Queensland, Australia ?strong tidal flows a modern control on their growth

High resolution seismic data from Torres Strait off northern Australia provide the first insights into the development of the striking platform reefs of the region. In the southern part of Torres Strait, where the sea floor is shallow and featureless, the Torres Reefs have developed as long, narrow platforms parallel to very strong east-west flowing tidal currents. The reefs have expanded since the end of the post-glacial marine transgression (approximately 6000 years ago) through preferential growth at each end of their platforms. In these localized areas sheltered from the strong tidal currents, patch reefs have developed. Sediments swept from the reef margin and the inter-reef channels are deposited in these current lee areas at the ends of the reefs. The combination of the patch reefs and reefal sediments provides the essentials for extension of the platform reefs. The seismic data confirm that modern reef expansion is occurring without there being a high substrate for coral colonization. The evolutionary sequence from an uncolonized seafloor to a mature platform reef envisages a synchronous process of patch reef development and sediment accumulation.