Late Quaternary Sea-level Fluctuations Research Articles

Deciphering the role of late Quaternary sea level fluctuations in controlling the sedimentation in the Brahmaputra Plains

Continent-continent collision between Eurasian and the Indian plate during the Cenozoic period lead to the formation of the Himalayan Mountain chain and the development of the Indus-Ganga-Brahmaputra foreland basin to the south. Complex climate-tectonic interactions in this orogenic belt are responsible for the rapid erosion and filling of the Indus-Ganga-Brahmaputra foreland basin with the eroded materials. This study based on geomorphic mapping, lithofacies analysis, and geochemical (Strontium-Neodymium i.e., SrNd analysis) provenance characterization, as well as optically stimulated luminescence (OSL) ages, provides a dated sedimentation framework for the western Assam lowland areas. The dated relict fan surface lies ~40 m above mean sea level (msl), is incised and forms a regional valley terrace T1 composed of meandering channel deposits. Modern braided rivers flow on the T0 surface. The findings suggest that the alluvial fan is composed of three distinct lithofacies associations and aggraded during 27 to 3 ka. The bottom-most gravelly-sandy facies indicates progradation of the fan during the last glacial maximum (LGM), owing to the increased gradient of the Himalaya bound rivers. The middle facies is a sheet flood deposit which formed during the Latest Pleostocene-early Holocene period with rising sea level and increasing precipitation. During the Mid-Late Holocene, the uppermost facies is deposited as rivers lost their gradient in response to high sea level stand, resulting in inland sedimentation within muddy meandering channels. Our analysis found that falling sea level during the late Holocene was associated with greater precipitation and allowed the river to incise, to form gullies over the fan surface and form the valley terrace T1. The SrNd isotope fingerprints have been used to identify varying fan sediment sources in the Himalaya's southern front (i.e., Lesser and Higher Himalaya) as a function of changing monsoon conditions.

OSL and radiocarbon dating of a core from the Bohai Sea in China and implication for Late Quaternary transgression pattern

The Bohai Sea is a semi-enclosed continental shelf sea in northern China. Three transgression layers have been identified from the Late Quaternary strata in the western Bohai Sea and the coastal regions, which provide critical information on Late Quaternary sea-level fluctuations and landscape development. The three transgression layers were previously assigned to Marine Isotope Stage (MIS) 1 (transgression 1, T1), MIS 3 (T2) and MIS 5 (T3), respectively, mainly based on 14C dating. However, this chronological framework aroused an enigma that the regional sea level in MIS 3 was even higher than that of MIS 5, conflicting with the context of global sea-level pattern. In order to clarify this issue, here quartz optically stimulated luminescence (OSL) dating (four samples) was used to constrain the T2 chronology of borehole TJC-1 from the western Bohai Sea. Radiocarbon samples (eight) of peaty sediments were also measured for reference and comparison. All the four OSL samples showed saturation ages of >80 ka, suggesting that the T2 layer should have formed at least in MIS 5, instead of in MIS 3. Radiocarbon ages in T2 should have been severely underestimated, with a saturation age range of 22–30 cal ka BP, similar to all the previous published radiocarbon ages. The renewed OSL chronological framework for Late Quaternary transgressions in the western Bohai Sea is in better compliance with the history of global sea-level change.

Late Quaternary deep marine sediment records off southern Africa

Abstract High-resolution mapping, sampling and analysis of upper Quaternary southern African continental margin sediments recovered from beyond the Last Glacial Maximum shoreline (>130 m water depth) have expanded our understanding of how marine and terrestrial records are linked over glacial-interglacial climatic cycles. This paper synthesises data currently available from the deep seafloor around southern Africa and, specifically, core sites that demonstrate terrestrial sedimentological connectivity. Several proxies and case studies reveal the evolution of depositional systems, palaeoceanography and palaeoclimate over the last 191 kyr. Hydroacoustic mapping and investigations of submarine canyons have been carried out primarily on the eastern and southwestern margins, while palaeoceanographic productivity and microfossil assemblages have been applied most extensively on the western marine and southern Agulhas Bank. Studies on the western margin indicate that enhanced productivity, less oxygenated bottom waters and reduced marine faunal diversity in the transition to glacial periods, while glacial terminations are associated with reduced productivity and more oxygenated bottom waters. These changes, linked to palaeoceanography and late Quaternary sea-level fluctuations, influence the sedimentary record and sedimentation rates. On the eastern margin, sediment fluxes applied as proxies for rainfall offshore of the Great Kei, Umzimvubu, Limpopo and Zambezi rivers indicate that the southern African climate responds to changes in orbitally-modulated insolation and in particular, to the ~23 kyr precessional cycle, where the proxy records keep pace with this and then diverge at ~80 to 70 kyr. Since the penultimate glacial (Marine Isotope Stage/MIS 6), more humid conditions observed in southern Africa, as the Northern Hemisphere entered phases of rapid cooling, were potentially driven by a combination of warming in the Agulhas Current and shifts of the subtropical anticyclones. Broadly, the sedimentary records reviewed suggest fluctuations in climate and oceanographic circulation that are strongly correlated with the global benthic δ18O record, suggesting sensitivity to high-latitude forcing, and a strong influence of late Quaternary glacial-interglacial cycles despite these marine sites being far-removed from terrestrial environments.

Late Quaternary uplift and sea level fluctuations along the Tyrrhenian margin of Basilicata - northern Calabria (southern Italy): New constraints from raised paleoshorelines

New analyses of marine terraces in the Tyrrhenian Sea margin of Basilicata - northern Calabria (southern Italy) have been carried out. In the study area, c. 25 km in length, an impressive flight of marine terraces occurs, with the highest terraces reaching ~160 m a.s.l. Detailed geomorphological-stratigraphical analyses on remnants of paleoshorelines located within 60 m a.s.l. have shown that the rocky coast of the investigated coastal stretch has been affected by multiple relative sea-level fluctuations, during which reworking of older shorelines has occurred. Dating of the coral Cladocora caespitosa and speleothems, either predating or postdating single paleoshorelines, has allowed the construction of a chronological framework for the identified relative sea-level markers, and their correlation with MIS 7, MIS 6e and distinct peaks of MIS 5. A mean uplift rate of c. 0.25 mm/y since the Last Interglacial has been quantified, one order of magnitude larger than previous estimates. The uplift rate value has been used to infer the elevations of MIS 5a, 5c and 6e sea level peaks, which are higher than those reported in most sea level curves worldwide, although consistent with several findings from the western Mediterranean. Our results demonstrate that a mere sequential correlation may be misleading in the interpretation of flights of marine terraces and indicates that multiple age controls are crucial to unravelling the complex interaction between uplift and sea-level fluctuations in uplifted coastal areas. The reconstructed MIS 5a, 5c and 6e sea level paleo-elevations, besides contributing to the assessment of late Quaternary sea-level fluctuations in the Mediterranean Sea, may contribute to constrain coeval ice sheets volume variations.

Past connections with the mainland structure patterns of insular species richness in a continental-shelf archipelago (Aegean Sea, Greece).

Recent research in island biogeography has highlighted the important role of late Quaternary sea‐level fluctuations in shaping biogeographic patterns in insular systems but focused on oceanic systems. Through this study, we aim investigate how late Quaternary sea‐level fluctuations shaped species richness patterns in continental‐shelf island systems. Focusing on the Aegean archipelago, we first compiled maps of the area's geography using published data, under three sea‐level stands: (a) current; (b) median sea‐level over the last nine glacial–interglacial cycles (MSL); and (c) Last Glacial Maximum (LGM). We gathered taxon–island occurrences for multiple chorotypes of angiosperms, butterflies, centipedes, and reptiles. We investigated the impact of present‐day and past geographic settings on chorological groups by analyzing island species–area relationships (ISARs) and using generalized linear mixed models (GLMMs) selection based on multiple metrics of goodness of fit. Our results confirm that the Aegean's geography has changed dramatically since the LGM, whereas the MSL only modestly differs from the present configuration. Apart for centipedes, paleogeographic changes affected both native and endemic species diversity through altering connections between land‐bridge islands and the mainland. On land‐bridge islands, we detected over‐representation of native species and under‐representation of endemics. Unlike oceanic islands, sea‐level‐driven increase of isolation and area contraction did not strongly shape patterns of species richness. Furthermore, the LGM configurations rather than the MSL configuration shaped patterns of endemic species richness. This suggests that even short episodes of increased connectivity with continental populations are sufficient to counteract the genetic differentiation of insular populations. On the other hand, the over‐representation of native nonendemic species on land‐bridge islands reflected MSL rather than LGM mainland connections. Our study shows that in terms of processes affecting species richness patterns, continental archipelagos differ fundamentally from oceanic systems because episodic connections with the mainland have profound effects on the biota of land‐bridge islands.

Comments on: “Anatomy of a late quaternary carbonate island: Constraints on timing and magnitude of sea-level fluctuations, West Caicos, Turks and Caicos Islands, BWI” by Kerans et al. [Quat Sci. Rev. 205 (2019), 193–223

We comment on interpretations of the evolution of late Pleistocene geology on West Caicos Island, Caicos Platform, B.W.I. by Kerans et al. (2019), which omits our documentation of the interrelationship of carbonate facies in outcrop and in boreholes (Dravis and Wanless, 2017). We further disagree with their geochronological dating assumptions/results that are the basis for interpreting late Quaternary sea-level fluctuations.

Late Quaternary coastal evolution and aeolian sedimentation in the tectonically-active southern Atacama Desert, Chile

Analyses of aeolianites and associated dune, surficial carbonate and marine terrace sediments from north-central Chile (27° 54′ S) yield a record of environmental change for the coastal southern Atacama Desert spanning at least the last glacial-interglacial cycle. Optically stimulated luminescence dating indicates phases of aeolian dune construction at around 130, 111–98, 77–69 and 41–28ka. Thin-section and stable carbon and oxygen isotope analyses suggest a predominantly marine sediment source for the three oldest dune phases. Aeolianites appear to have accumulated mainly from tectonically-uplifted interglacial marine sediments that were deflated during windier and/or stormier intervals. Bedding orientations indicate that sand-transporting winds varied in direction from S-ESE during MIS 5e and WNW-ESE during MIS 5c-5a. Winds from the southeast quadrant are unusual today in this region of the Atacama, suggesting either major shifts in atmospheric circulation or topographic airflow modification. Thin-section evidence indicates that the aeolianites were cemented by two phases of vadose carbonate, tentatively linked to wetter periods around 70 and 45ka. Tectonic uplift in the area has proceeded at an average rate of 305–542mmkyr−1. The study illustrates the complexity of understanding onshore-offshore sediment fluxes in the context of Late Quaternary sea-level fluctuations for an area undergoing rapid tectonic uplift.

Postglacial sediment deposition along a mixed carbonate-siliciclastic margin: New constraints from the drowned shelf-edge reefs of the Great Barrier Reef, Australia

A seismic stratigraphy analysis was conducted at two sites, Hydrographers and Noggin passages, separated by about 540km on the shelf-edge of the central Great Barrier Reef (GBR), Australia. We used recently available seismic and bathymetry data and a new synthesis of downhole logs and lithological, petrophysical and radiometric data from cores recovered by the Integrated Ocean Drilling Program Expedition 325 (Great Barrier Reef Environmental Changes). We compared the stratigraphy of both sites, identifying a full depositional sequence with deposits from at least 28ka BP to ~7ka BP, bounded by two marine flooding surfaces. Within this sequence, each systems tract is represented by unique depositional features characteristic of the shelf-edge systems. Despite the broad environmental and geomorphic similarities between the two sites, differences in postglacial reef development were remarkable. These contrasts can be explained as a result of: (1) local antecedent substrate variations and (2) the interplay of shelf physiography with Late Quaternary sea level fluctuations, which favoured changes in biological production and sediment flux as the palaeo-shoreline evolved from linear to complex during intermediate sea levels. During these intermediate sea levels, the northern estuarine coast and its steep substrate at shelf-edge locations contrasted strongly with the protected palaeo-lagoons and the extensive, gentle marginal terraces found at the southern central GBR. This setting enhanced the regional differences in sediment transport and reef development through the last transgression. The conceptual model presented here provides a broader depositional framework and improves the understanding of the main processes controlling the spatial and temporal depositional patterns on the shelf-edge of mixed siliciclastic-carbonate margins.

Morphology of Salina offshore (Southern Tyrrhenian Sea)

ABSTRACTIn this paper, we present the first complete morphological map of the Salina offshore at a scale of 1:100,000. The submarine flanks of the Salina edifice extend down to −650 to −1300 m, are steep and characterized by an uneven morphology due to the presence of volcanic and erosive-depositional features. The volcanic features cover ∼30% of the submarine portion and include volcanic cones and bedrock outcrops. The remaining ∼70% is affected by a wide series of erosive-depositional features. Among these, features related to Late Quaternary sea level fluctuations comprise the insular shelf surrounding the island and overlying submarine terraced depositional sequences. Mass-wasting features include landslide scars, channels, fan-shaped deposits and waveforms. The presented map provides useful insights for a better understanding of the morphological evolution of the edifice

Morphology of Lipari offshore (Southern Tyrrhenian Sea)

High-resolution multibeam bathymetry was recently collected around Lipari, the largest and most densely populated island of the Aeolian Archipelago (Southern Tyrrhenian Sea). The data were acquired within the context of marine geological studies performed in the area over the last 10 years. We present the first detailed morphological map of the Lipari offshore at 1:100,000 scale (Main Map). A rugged morphology characterizes the submarine portions of Lipari volcano, reflecting both volcanic and erosive-depositional processes. The volcanic features include cones, lava flows and bedrock outcrops. Erosive-depositional features include an insular shelf topped by submarine depositional terraces related to Late-Quaternary sea-level fluctuations, as well as landslide scars, channelized features, fan-shaped deposits and wavy bedforms. The different distribution of volcanic and erosive-depositional features on the various sectors of Lipari is mainly related to the older age of the western flank with respect to the eastern one. The map also provides insights for a first marine geohazard assessment of this active volcanic area.

Submarine structure of Vulcano volcano (Aeolian Islands) revealed by high-resolution bathymetry and seismo-acoustic data

A new definition of the morpho-structural submarine setting of the Vulcano volcano is presented based on the integration of multibeam swath bathymetry, high-resolution seismic profiles and sea-floor sampling. A number of unknown volcanic features have been mapped on the submarine flanks of Vulcano Island as volcanic outcrops and isolated cones. For most of them a relatively old age is suggested (especially to the west of the island), while evidence of relatively recent volcanic activity characterizes the north-eastern submarine sector, offshore Vulcanello. The morphology and distribution of these features, either aligned along NNW–SSE trends or radially elongated, suggest the prevalence of regional structural control or local stresses related to the volcano structure, respectively, in the different sectors of the volcanic edifice. Shallow-water (< 120 mbsl) insular shelves, related to wave action during Late Quaternary sea-level fluctuations, were recognized in correspondence of the oldest sectors of the edifice, while they are lacking in the younger sectors. Beyond the shelf edge, a strong increase of slope gradients characterizes the submarine flanks, promoting the formation of erosive-depositional and mass-wasting features at different scale, such as landslide scars, gullies, headless channelized features, crescent-shaped bedforms and volcaniclastic fans. In particular, two large volcaniclastic fans were identified on the north-eastern and south-western flanks, where marine retrogressive processes are very active and sediment is funnelled from the coasts to the foot of the volcano. These fans are created by the gradual stacking of gravity flows fed by repeated small- and medium-scale mass-wasting events, instead of being related to large-scale flank instability events. The lack of large-scale lateral collapse on the submarine flanks of Vulcano volcano has been related to the morpho-structural and volcano-tectonic setting of the volcanic edifice, characterized by the occurrence of summit caldera collapses limiting its total height and by the absence of well-defined rift zones. ► The submarine portions of Vulcano account for ≈ 85% of its areal extent. ► Multibeam and seismic data show new details of the submarine flanks. ► Interacting constructional and erosive-depositional processes are documented. ► Insular shelf development gives constraints on the evolution of the edifice. ► No large-scale lateral collapse deposits have been recognized on submarine flanks.

Late Quaternary evolution of macrotidal Kimpo tidal flat, Kyonggi Bay, west coast of Korea

Up to 32 m thick late Quaternary deposits are developed in the Kimpo tidal flat, Kyonggi Bay, west coast of Korea. The deposits consist of six lithofacies units that are grouped into three unconformity-bounded sequences, which formed in response to late Quaternary sea-level fluctuations. The lowermost sequence (S3) consists of late Pleistocene fluvial deposits (Unit VI) and overlying tidal deposits (Unit V). Unit VI is interpreted to have formed in a meandering channel and associated floodplain environment. Weak pedoturbation characterizing the upper part of Unit VI suggests that pedogenesis occurred prior to initial transgression. Well-developed tidal rhythmicities in Unit V indicate that tidal sedimentation prevailed during the first marine inundation. Intermediate sequence (S2) is composed of late Pleistocene fluvial deposits (Unit IV) and overlying tidal deposits (Unit III). Depositional environments of Unit IV and Unit III are similar to those of Unit VI and Unit V, respectively. Upper parts of Unit IV and Unit III are variably indurated and pedoturbated, suggesting prolonged subaerial exposure. The uppermost sequence (S1) consists of early Holocene sphaerosiderite-rich marsh deposits (Unit II) and overlying middle to late Holocene tidal deposits (Unit I). Pervasive occurrence of similar tidal rhythmites in both Holocene and late Pleistocene tidal deposits indicates that tidal environment recurred over several sea-level cycles. Age dates and stratigraphic position indicate that Holocene tidal deposits were formed since 7–8 ka BP. Given the validity of age dates, however, timing of late Pleistocene tidal deposits is controversial in the light of eustatic sea-level curves. Considering tectonically stable condition of study area, the elevation of the late Pleistocene tidal deposits is too high to fit the curves. Elucidation of the exact timing of the tidal deposits requires more independent age controls as well as further understanding on the tectonic regime of the west coast of Korea.

Aeolianite and barrier dune construction spanning the last two glacial–interglacial cycles from the southern Cape coast, South Africa

The southern Cape region of South Africa has extensive coastal aeolianites and barrier dunes. Whilst previously reported, limited knowledge of their age has precluded an understanding of their relationship with the climatic and sea-level fluctuations that have taken place during the Late Quaternary. Sedimentological and geomorphological studies combined with an optical dating programme reveal aeolianite development and barrier dune construction spanning at least the last two glacial–interglacial cycles. Aeolianite deposition has occurred on the southern Cape coast at ca 67–80, 88–90, 104–128, 160–189 and >200 ka before the present. Using this and other published data coupled with a better understanding of Late Quaternary sea-level fluctuations and palaeocoastline configurations, it is concluded that these depositional phases appear to be controlled by interglacial and subsequent interstadial sea-level high stands. These marine transgressions and regressions allowed onshore carbonate-rich sediment movement and subsequent aeolian reworking to occur at similar points in the landscape on a number of occasions. The lack of carbonates in more recent dunes (Oxygen Isotope Stages 1/2 and 4/5) is attributed not to leaching but to changes to carbonate production in the sediment source area caused by increased terrigenous material and/or changes in the balance between the warm Agulhas and nutrient-rich Benguela ocean currents.

Timing and distribution of calciturbidites around a deeply submerged carbonate platform in a seismically active setting (Pedro Bank, Northern Nicaragua Rise, Caribbean Sea)

The sedimentological study of thirteen sediment cores from the periplatform setting surrounding Pedro Bank (Northern Nicaragua Rise, Caribbean Sea) shows that during the last 300 ka turbidite deposition is controlled by at least four factors: (1) late Quaternary sea level fluctuations, (2) prolific fine-grained sediment production and export resulting in oversteepening of the upper slope environment, (3) the proximity to the bank margin, and (4) local slope and seafloor morphology. The most intriguing finding of this study is the paucity of turbidites, with only 101 turbidites in 13 cores in this tectonically active setting near the Caribbean plate boundary. Throughout the last 300 ka, the frequency of turbidite input during interglacial stages is three times higher than during glacial stages. Also it is obvious that changes in sea level influence the timing of turbidite deposition. This is especially evident during the transgressions resulting in rapid renewed bank-top flooding, subsequent neritic sediment overproduction, and offbank export. The flooding event during each transgression is usually recorded by the onset of turbidite deposition at various sites along several platform-to-basin transects in down- and upcurrent slope settings. Overall, however, more turbidites are deposited during the regressive rather than the transgressive phases in sea level, probably as a result of sediment reorganisation on the slope resulting in slope failure. Five cores show "highstand bundling" of calciturbidites, i.e. higher number of turbidites during highstands than during lowstands in sea level.

Contrasting facies patterns in subtropical and temperate continental slope sediments: inferences from east Australian late Quaternary records

Abstract Studies of latest Quaternary continental slope sediments at two localities on the east Australian margin have revealed markedly different responses to late Quaternary sea level fluctuations. Offshore of Noosa, in the sub-tropics, the sediment is predominantly a mixture of fine metastable carbonate, siliciclastic material, and pelagic carbonate. Important features of the stratigraphy include a siliciclastic-dominated facies deposited relatively slowly during the last glacial lowstand (sedimentation rate ≤8 cm/ka), and a calcareous facies, rich in metastable carbonate, deposited more rapidly during the late post-glacial transgression (sedimentation rates 15–24 cm/ka). Highstand and transgressive sedimentation rates are greater than lowstand rates by a factor of 2.5–6 due to increased shelf carbonate productivity after flooding of the mid-shelf. Off Sydney, in temperate latitudes, continental slope sediment is largely a mixture of fine siliciclastic material and pelagic carbonate. Mean sedimentation rates range from 2 to 5 cm/ka over the last four oxygen isotope stages, with mean glacial/interstadial rates higher than Holocene rates by a factor of ∼1.36. This largely reflects the transfer of siliciclastic mud from the shelf to the slope during sea level regression. In both localities, facies changes on the slope are not related to specific sea level states (e.g. lowstand facies, transgressive facies, etc.), but reflect instead the interaction of changing sea level with shelf morphology.

Lowermost Amazon River: evidence of late Quaternary sea-level fluctuations in a complex hydrodynamic system

Abstract Sedimentological, geochemical, and high-resolution seismic studies on the lowermost Amazon River (Xingu Mouth–Macapa–Estreitos de Breves) allow reconstruction of the sediment dynamics of this large river system in response to late Quaternary sea-level changes. Areas of sediment transport and deposition on an older river bottom are delineated by seismic reflectors and are related to inundation and incision caused by late Quaternary rising and falling of sea level. Older substrates have been identified as the Alter do Chao Formation (Cretaceous) and the Barreiras Formation (Tertiary). The initial AMS-radiocarbon dates yielded late Pleistocene to Holocene ages, and indicate a high sedimentation rate (0.6 cm/yr) for the last 800 yr. Three stages in the late Quaternary evolution of the Amazon mouth system can be distinguished: (i) relative sea-level fall, probably related to the Last Glacial Maximum with channel incision; (ii) deposition and consolidation of mud found near Afua during relative sea-level rise between late Pleistocene and middle Holocene, corresponding to the “freshwater lake” or the evolution of large floodplain areas in Amazonia; and (iii) stable sea-level conditions since 6000 yr BP resulting in the modern pattern of deposition and erosion, controlled by complex interactions of fluvial and oceanic processes.

Palynological study of the Late Quaternary of Loyalty Basin (SW Pacific)

Palynological studies have been carried out on two cores from the Loyalty Basin, one near the New Caledonia shore (KK 231) and the other near Lifou Island (KK 88). The sediments under consideration cover the interval from the Last Interglacial to the Holocene. All the samples revealed the mixing of continental and marine palynomorphs varying with carbonate sediment variations that are themselves correlated with the Late Quaternary sea level fluctuations. Dinoflagellate cysts and foraminifera are the dominant components of the marine fraction. Dinoflagellate cysts reached their maximum abundance during the high sea-level of the Last Interglacial, while foraminifera were most abundant during the onset of the Holocene transgression. Changes in the continental palynomorphs can also be observed; these seem to be linked to sea-level variations, modifying conditions of production, transport and deposition, and to the effects of climatic changes on the community structure of terrestrial vegetation.

Sea level control of stacked late Quaternary coastal sequences, central Great Barrier Reef

ABSTRACTLithofacies analysis, pollen assemblages and radiocarbon age dates of 20 stratigraphic drill holes are used to develop an evolutionary history for late Quaternary sedimentation in two coastal embayments landward of the central Great Barrier Reef. Different physiographic settings of the embayments result in two contrasting styles of sedimentary sequence: (a) an exposed, moderate energy, beach barrier‐lagoon system (Wyvuri Embayment) and (b) a protected, low energy, muddy inlet fill sequence (Mutchero Inlet). Despite sharp contrast in sequence style, similar depositional cycles occur in both embayments in response to late Quaternary sea level fluctuations including: (1) a last interglacial highstand (+2 m; c. 125 000 yr bp) beach barrier (Wyvuri); (2) an early to mid‐Holocene (8000–6100 yr bp) transgressive beach barrier‐lagoon (Wyvuri) and estuarine infill (Mutchero); and (3) mid‐Holocene to present highstand beach barrier (Wyvuri) and estuarine (Mutchero) progradation. Preservation of such cycles in the stratigraphic record would produce a series of vertically stacked and offset linear barrier sands surrounded by lagoonal mud and fine grained shoreface sediment juxtaposed to muddy, estuarine infills.Sea level elevations are well recorded by the upward transition from Rhizophora‐dominated intertidal mangrove mud to freshwater swamp (clearly identified by pollen analysis) and by the basal contacts of beach barrier sediments which sharply overlie the upper shoreface. Transgressive sedimentation is interrupted in both embayments by a constructional beach barrier (Wyvuri) and abbreviated progradation (Mutchero) corresponding to a — 5 m pause in relative sea level rise at c. 6800 yr bp. Sea level control of fine scale coastal sedimentation patterns is beginning to be widely recognized and provides an accurate analogue for stacked ancient sequences.

Rates of tectonic uplift in the Corinth and Megara Basins, central Greece

We present evidence of the rates of late Quaternary tectonic uplift that have affected parts of central Greece during this period of active extension and basin formation. Dual lines of evidence indicate upper Pleistocene to Holocene uplift rates of the order of 0.3 mm yr−1 for the Corinth and Megara basins. First, U‐series disequilibrium ages of Acropora sp. corals from uplifted marine sediments are used to derive minimum average rates of vertical displacement since deposition. Second, the geometries of cyclical transgressive sequences and of erosional terraces are consistent with the radiometric evidence and the known history of late Quaternary sea level fluctuations. Two types of uplift are distinguished on the basis of structural relationships: (1) fault block rotation about a horizontal axis (tilting) in response to footwall uplift on the active normal fault bounding the Alkyonides Gulf and (2) a more regional uplift which affects the Corinth Basin and Peloponnesos to the south. The results of U‐series dating are discussed in the light of initial 234U/238U activity ratios, derived from the coral samples, which are higher than for average marine waters (1.17–1.31 compared to 1.14). These values may be related to a variable freshwater input to the structurally confined Gulf of Corinth or, alternatively, they may reflect a previously higher global 234U/238U activity ratio in marine waters, or post‐mortem enrichment in 234U, although the mechanism of the latter is not yet understood.

Clastic sequences developed during late Quaternary glacio-eustatic sea-level fluctuations on a passive margin: Example from the inner continental shelf near Barnegat Inlet, New Jersey: Discussion and reply

Clastic sequences developed during late Quaternary glacio-eustatic sea-level fluctuations on a passive margin: Example from the inner continental shelf near Barnegat Inlet, New Jersey: Discussion and reply