Holocene Marine Research Articles

Sediment recycling during the Holocene marine transgression in Ría de Vigo (NW Iberia): multiproxy evidence and environmental implications

A new multiproxy study of a 155-cm sediment core located in Ría de Vigo (NW Iberia) recording the transgressive and highstand system tract of the Holocene sea-level rise is presented. New data described include grain size, geochemical analyses, high-resolution qualitative/quantitative analyses of pollen, non-pollen palynomorphs and dinoflagellate cysts content, the qualitative evaluation of diatoms at different key levels and the reconsideration of some seismic interpretations. Besides, 14 radiocarbon dates were obtained from shells and pollen extracts. This new evidence revealed that notable changes in the sedimentation rates and the relative abundance of the different types of palynomorphs occurred during the Holocene. The sediment core studied shows anomalous pollen successions, including unexpected Pinus pollen peaks, during the Early and Middle-Holocene. Differential dating revealed that those anomalous successions correspond to conspicuously aged sediment that has inverted pollen chronologies. Thus, these facies may constitute evidence of redeposition of ancient upland sediments, formed above the ancient coastline at different intervals comprised between the end of the Last Glacial Maximum and the early stages of the Lateglacial, which were rich in very resistant pollen types (Pinus). Dinoflagellate cyst records in combination with the non-reworked pollen evidence reveal a reliable climatic seesaw during the Holocene, includingwet stormy periods of prevailing mixed waters, with strong development of Lingulodinium and high accumulation rates in dinoflagellate cysts, which alternate with other sparsely stormy and drier phases, characterised by the coastal upwelling intensification, well-stratified waters, and increases in Bitectatodinium and Spiniferites spp. but low accumulation rates in dinoflagellate cysts. These climatic dynamics, including a millennial drier cool period that occurred just after the Thermal Optimum are consistent with previous evidence obtained in other limnetic systems in the Iberian Peninsula. Furthermore, there is a delay between the two phases with the highest marine contribution to sediment (ca. 11.0-8.2 and ca. 4.0–3.0 cal ka BP) and the subsequent warm stages when the relative sea level stabilises: the Thermal Optimum (8.0–6.0 ka BP) and the 2.5-0.5 ka BP interval, respectively. Changes in Pinus pollen concentrations and grain size recorded in the postglacial sediments suggest that some upland ancient (Lateglacial) pollen evidence might be remobilised, especially during stages of upwelling intensification, and then resedimented in the seabed. Further studies will be needed to determine if the significant differences existing between the Pinus pollen grain sizes respond to climatic variations affecting the region or have been the result of any replacement of pine species in the area. Nonetheless, Pinus pollen evidence almost disappeared with the first signs of anthropisation in the area, and only recovered after the modern repopulations. Our findings open up new possibilities to further our understanding of sediment reworking and recycling mechanisms through the integration of multiproxy studies encompassing pollen, seismic and sedimentary data.

Possible Indication of the Impact of the Storegga Slide Tsunami on the German North Sea Coast around 8150 cal BP

The Storegga slide tsunami (SST) at ca. 8100 ± 100–250 cal BP is known to be the largest tsunami that affected the North Sea during the entire Holocene. Geological traces of tsunami landfall were discovered along the coasts of Norway, Scotland, England, Denmark, the Faroes and Shetland Islands. So far, the German North Sea coast has been considered as being well protected due to the wide continental shelf and predominant shallow water depths, both assumed to dissipate tsunami wave energy significantly, thus hindering SST propagation dynamics. The objective of our research was to clarify if the SST reached the German Bight and if corresponding sediment markers can be found. Our research was based on the in-depth investigation of a 5 m long section of the research core Garding-2 from Eiderstedt Peninsula near Garding in North Frisia known from a previous study. For this, we newly recovered sediment core Garding-2A at exactly the same coring location as core Garding-2. Additionally, high-resolution Direct Push sensing data were collected to gain undisturbed stratigraphic information. Multi-proxy analyses of sediment material (grain size, geochemical, geochronological and microfaunal data) were carried out to reconstruct palaeoenvironmental and palaeogeographical conditions. We identified a high-energy event layer with sedimentological (e.g., erosional unconformity, rip-up clasts, fining-upward), microfaunal (e.g., strongly mixed foraminiferal assemblage) and other features typical of tsunami influence and identical in age with the SST, dated to ca. 8.15 ka cal BP. The event layer was deposited at or maximum ca. 1–1.5 m below the local contemporary relative sea level and several tens of kilometers inland from the coastline within the palaeo-Eider estuarine system beyond the reach of storm surges. Tsunami facies and geochronological data correspond well with SST signatures identified on the nearby island of Rømø. SST candidate deposits identified at Garding represent the southernmost indications of this event in the southeastern North Sea. They give evidence, for the first time, of high-energy tsunami landfall along the German North Sea coast and tsunami impact related to the Storegga slide. SST deposits seem to have been subsequently reworked and redeposited over centuries until the site was affected by the Holocene marine transgression around 7 ka cal BP (7.3–6.5 ka cal BP). Moreover, the transgression initiated energetically and ecologically stable shallow marine conditions within an Eider-related tidal channel, lasting several millennia. It is suggested that the SST was not essentially weakened across the shallow continental shelf of the North Sea, but rather caused tsunami run-up of several meters (Rømø Island) or largely intruded estuarine systems tens of kilometers inland (North Frisia, this study). We, therefore, assume that the southern North Sea coast was generally affected by the SST but sedimentary signals have not yet been identified or have been misinterpreted. Our findings suggest that the German North Sea coast is not protected from tsunami events, as assumed so far, but that tsunamis are also a phenomenon in this region.

Middle Holocene Marine Sedimentation on the Southwestern Coastal Margin in Primorye, Russia

Middle Holocene Marine Sedimentation on the Southwestern Coastal Margin in Primorye, Russia

Paleo-climatic control on recharge and fresh-salt groundwater distribution in the Red River delta plain, Vietnam

Paleo-climatic induced sedimentation controls present-day recharge and the fresh-salt groundwater distribution in Quaternary delta systems. During sea-level highstands, marine clays with saline pore water were deposited and are interbedded with aquifers of coarse-grained sandy fluvial and shallow marine deposits, laid down during lowstands. The low-permeable marine layers may inhibit recent recharge to deeper aquifers, and thereby limit sustainable use of these freshwater resources. This phenomenon has been investigated in the Red River delta plain, using geophysical borehole logging, transient electromagnetic soundings, groundwater chemistry, stable isotope analysis and 3H and 14C dating of groundwater. Results reveal that marine saline pore water is still present in the Holocene marine clays, implying that fresh water has not entered the clays since their deposition. Therefore, recharge within the delta plain is not occurring and the deeper aquifers are hydraulically disconnected from the upper sandy layers. Today, recharge only occurs from the hinterland. Recharge during the last glacial period has flushed saline pore water from Pleistocene marine clays, but these clays were again affected by saline water during the Holocene transgression. The use of the groundwater resources in the delta plain must be adjusted to the present recharge to be sustainable.

Landscape evolution during Holocene transgression of a mid‐latitude low‐relief coastal plain: The southern North Sea

AbstractLow‐relief coastal landscapes are at major risk of rising sea levels, as vertical changes in relative sea level have far‐reaching lateral effects. Integration of a dense 2D grid of seismic reflection data with sedimentological and geotechnical data obtained in two offshore wind farm zones allows detailed documentation of postglacial landforms and environmental change over a 1,021 km2 area in the western sector of the southern North Sea. Following the retreat of Last Glacial Maximum ice sheets from the southern North Sea, the resulting postglacial terrestrial landscape provided a surface for peatland formation as climate started to warm and the water table rose in response to relative sea‐level rise. Southward‐draining fluvial networks formed contemporaneously with the peatlands, and remnants of this terrestrial wetland landscape are buried beneath Holocene marine sediments. Distinctive isolated incisional features and discrete widening of fluvial channels that cut through the peats are interpreted as either tidal ponds or relict tidal channels. These features record the evolution of this landscape through the Early Holocene as marine transgression inundated a low‐relief coastal plain. The erosion of the peatlands observed in the cores, the patchy preservation of the organic wetland landscape, and the lack of preserved barrier systems recorded by the seismic reflection data suggest that the rate of relative sea‐level rise outpaced sediment supply during the Late Postglacial and Early Holocene in this area of the southern North Sea. In a regional context, the southward draining river channels contrast to northward fluvial drainage to the North Sea, pointing to a subtle drainage divide in the palaeolandscape and the presence of a low‐relief land bridge separating the North Sea and the English‐Channel/La Manche during the Early Holocene. The documented scenario of rising sea levels combined with decreasing sediment supply in a low‐relief setting is a situation faced by many global deltas and coastlines, which makes the southern North Sea a crucial archive of coastal landscape change.

Mid-Holocene marine faunas from the Bangkok Clay deposits in Nakhon Nayok, the Central Plain of Thailand.

Based on several field investigations, many molluscan shells and chondrichthyan teeth, together with other invertebrate and actinopterygian remains were found from the marine Bangkok Clay deposits in Ongkharak, Nakhon Nayok, at a depth of ~ 5-7 m below the topsoil surface. Animal macrofossils recovered from these Holocene marine deposits were identified and their chronological context was investigated in order to reconstruct the paleoenvironments of the area at that time. The majority of marine fossils recovered from the site consist of molluscs, with a total of 63 species identified. Other invertebrate species include a stony coral, a mud lobster, barnacles, and a sea urchin. The vertebrates are represented by fish remains, including carcharhinid shark teeth from at least nine species, stingray and trichiurid teeth, and one sciaenid otolith. The molluscan fauna indicates that the paleoenvironments of the area corresponded to intertidal to sublittoral zones, where some areas were mangrove forests and intertidal mudflats. The fish fauna is dominated by the river shark Glyphis, indicating freshwater influences and possibly occasional brackish conditions. The carbon-14 analysis of mollusc and charcoal remains shows that deposition of the marine sediment sequence began during the mid-Holocene, spanning approximately from 8,800 to 5,300 cal yr BP. This study provides in-depth insights into the diversity of fishes, marine molluscs, and other invertebrates from the Bangkok Clay deposits, supporting the existence of a marine transgression onto the Lower Central Plain of Thailand during the mid-Holocene.

Holocene paleoceanographic variability in Robertson Bay, Ross Sea, Antarctica: A marine record of ocean, ice sheet, and climate connectivity

Accelerating ocean-driven basal melting of Antarctic ice shelves in recent decades has implications for sea level rise and global overturning circulation. Here, we reconstruct oceanographic conditions at the confluence of the Ross Sea and the Southern Ocean by analyzing a multi-proxy Holocene marine sedimentary record collected from Robertson Bay. A ramped pyrolysis oxidation radiocarbon age-depth model provides a timeline for glacial behavior and oceanographic changes over the last 6700 years. The diatom assemblage, magnetic susceptibility, grain size, total organic carbon and nitrogen, trace elements, and bulk δ13C are used as proxies for changing ocean and glacial conditions, which we interpret in the context of modern oceanographic measurements.Our record shows evidence of persistent ice cover in the northwestern Ross Sea during the Antarctic mid-Holocene climate optimum (ca. 5 cal kyr BP). Based on this observation, we suggest that meltwater and iceberg discharge associated with ice sheet retreat in the Ross Sea region altered local oceanography during the mid-Holocene. The onset of modern style oceanographic conditions in Robertson Bay occurred at ca. 4 cal kyr BP. Stable late Holocene conditions in are punctuated by a period of enhanced polynya activity and upwelling of nutrient rich Circumpolar Deep Water ca. 0.8 cal kyr BP and an increase in the seasonal duration of sea ice after 0.7 cal kyr BP, during the Little Ice Age. The response of the marine environment in Robertson Bay to mid-Holocene ice sheet retreat and natural climate variability during the last millennium underscores the sensitivity of the Antarctic ice-ocean interface to projected changes in coming decades.

Holocene records of oyster reefs in a shallow semi-enclosed island embayment of the Aegean Sea

A high-resolution survey in the semi-enclosed Kalloni Gulf (Lesvos Island, NE Aegean Sea) revealed a plethora of oyster reef structures. The reefs have a relief of up to 6 m high and a length of 1.4 km at the deepest part (∼17 m) of the surveyed area and are developed in a fine-grained seabed. Acoustic backscatter variations caused by the presence and the type/distribution of different reef structures were mapped, resulting in the identification of four backscatter types. Sub-bottom acoustic information revealed the presence of similar buried features, which were classified in three types according to their characteristics. The seismic stratigraphy also showed the Holocene highstand and the transgressive system tracts as well as a deeper-seated distinct erosional surface with numerous buried channels, most likely corresponding to the surface flooded during the Holocene marine transgression. Starting at around 9700 years BP, the Kalloni paleo-landscape was progressively submerged and gradually transformed into a shallow, land-locked marine environment, allowing the establishment, and thriving of oyster reefs. The buried reefs presumably began to grow during the early stages of the gulf's transgression, whereas most of the modern reefs were developed/maintained by the modern hydrodynamic/sedimentary regime. It is the first time that such a large occurrence of well developed, diachronic oyster reef assemblage has been documented in the transgressive coastal environments of the microtidal Mediterranean Sea, but further research is required to determine the exact mode of their development.

Diatom record the holocene marine facies deposition history in inner bay of Pearl River Estuary, South China

To understand the evolution of river mouth systems under natural and human being forces is a critical task in coastal and marine science studies. We present a new sedimentary record with diatom, grainsize analysis and radiocarbon age dating, recovered from a drilling core in an inner bay of the Pearl River Estuary, South China, in order to describe marine facies depositional history and to examine relative palaeoclimatic and palaeoenvrionmental changes during the Holocene. The occurrence of marine diatoms at ca. 9,000 cal. yr. BP provides marine facies starting point at this core profile in the shoal area, west of the Pearl River Estuary. Three fossil diatom units were distinguished following the early to late Holocene epoch division. The changed diatom bio-facies before and after ca. 8,200 cal. yr. BP, especially in coastal and neritic species relative abundances contrast, offers a diatom floral response to the "8.2 kyr" event. In middle Holocene, enhanced diatom absolute abundances of tropical open-sea water species and increased neritic species number and relative abundances, with more sand fractions, provide evidences of diatom bio-facies response to higher sea-level and strong hydrodynamic clearly. Following the regression, fossil diatom flora experienced a long-term decline after ca. 5,500 cal. yr. BP, until to ca. 1,400 cal. yr. BP. In the past ca. 1,400 years, there has been a clear increase in the absolute abundances and biodiversity of diatoms, along with a greater presence of coarse granularity fractions. This is a strong signal that human activities influenced local environmental change, combined with natural forces.An interesting phenomenon of higher sedimentation rate was observed in three periods as a millennial-scale pulse, at ca. 9,000–8,000 cal. yr. BP, ca. 6,500 - 5,500 cal. yr. BP, and ca. 1,000 - 0 cal. yr. BP. Meanwhile, two periods of lower sedimentation rate over longer time interval occurred during those pulses. Through regional correlation, this study presents a record of deposition after ca. 9,000 cal. yr. BP in Holocene marine facies, provide improved understanding of the west shoal evolution history in Pearl River Estuary, and natural and human being impact on diatom flora and coastal geo-environment in low latitude river mouth systems in Asian Monsoon realm.

Comprehensive molecular-isotopic characterization of archaeal lipids in the Black Sea water column and underlying sediments.

The Black Sea is a permanently anoxic, marine basin serving as model system for the deposition of organic-rich sediments in a highly stratified ocean. In such systems, archaeal lipids are widely used as paleoceanographic and biogeochemical proxies; however, the diverse planktonic and benthic sources as well as their potentially distinct diagenetic fate may complicate their application. To track the flux of archaeal lipids and to constrain their sources and turnover, we quantitatively examined the distributions and stable carbon isotopic compositions (δ13 C) of intact polar lipids (IPLs) and core lipids (CLs) from the upper oxic water column into the underlying sediments, reaching deposits from the last glacial. The distribution of IPLs responded more sensitively to the geochemical zonation than the CLs, with the latter being governed by the deposition from the chemocline. The isotopic composition of archaeal lipids indicates CLs and IPLs in the deep anoxic water column have negligible influence on the sedimentary pool. Archaeol substitutes tetraether lipids as the most abundant IPL in the deep anoxic water column and the lacustrine methanic zone. Its elevated IPL/CL ratios and negative δ13 C values indicate active methane metabolism. Sedimentary CL- and IPL-crenarchaeol were exclusively derived from the water column, as indicated by non-variable δ13 C values that are identical to those in the chemocline and by the low BIT (branched isoprenoid tetraether index). By contrast, insitu production accounts on average for 22% of the sedimentary IPL-GDGT-0 (glycerol dibiphytanyl glycerol tetraether) based on isotopic mass balance using the fermentation product lactate as an endmember for the dissolved substrate pool. Despite the structural similarity, glycosidic crenarchaeol appears to be more recalcitrant in comparison to its non-cycloalkylated counterpart GDGT-0, as indicated by its consistently higher IPL/CL ratio in sediments. The higher TEX86 , CCaT, and GDGT-2/-3 values in glacial sediments could plausibly result from selective turnover of archaeal lipids and/or an archaeal ecology shift during the transition from the glacial lacustrine to the Holocene marine setting. Our in-depth molecular-isotopic examination of archaeal core and intact polar lipids provided new constraints on the sources and fate of archaeal lipids and their applicability in paleoceanographic and biogeochemical studies.

Early Holocene transgression in the central of Svalbard: research results and problems of reconstruction

The report presents the results of the study of Holocene marine sediments and terrace levels in the central part of West Spitsbergen Island. The results of the study showed that the postglacial transgression in the study area reached marks of 30-35 m and 40-45 m in the north and south of the study area, respectively. The early Holocene marine sediments were formed in shallow-water, predominantly ice-sea conditions with an unstable coastline. The sea level retreat was rapid and was accompanied by a general cooling.

Regional variation in Swedish acid sulfate soil microbial communities is influenced by temperature and geochemistry

AbstractAcid sulfate soils are frequently described as the nastiest soils on Earth, and they pose environmental risks associated with their strong acidity and consequential mobilization of toxic metals present in the soils. Within Sweden, acid sulfate soils have been extensively studied around the northern Baltic coastline and have now been found to occur throughout the area below the maximum Holocene marine limit that stretches for some 2000 km from North to South. This study investigated 20 active acid sulfate soils (field tested pH < 4.0) collected throughout this area that were tested for microbial community composition using 16S rRNA gene amplicons, representing a novel study of microbial communities in ripening zones across a broad regional scale. The microbial community compositions exhibited a north (boreal zone) to south (hemiboreal zone) regional divide, primarily within the oxidized zone (pH < 4.0), to a lesser degree in the transition zone (steep pH gradient), while little differences were observed in the reduced zone (near‐neutral pH). For instance, a higher relative abundance of Ktedonobacteraceae was identified in the northern boreal and Gallionellaceae in the southern hemiboreal oxidized zones. In addition, microbial taxa associated with iron and sulfur oxidation and reduction were identified, such as Acidobacteriaceae, Gallionellaceae and Koribacteraceae that have been previously identified in other acid sulfate soils and acid mine drainage settings. The predominant controls of the microbial community differences were the north–south divide indicative of a strong soil‐temperature effect followed by soil zones suggesting an influence of the soils' pH and/or redox conditions.

Growth of the sandy isthmus of tyre and ensuing relocation of its harbors

The renowned Phoenician city of Tyre was settled on a small coastal island from which it resisted invasions and sieges for centuries. In 332 BCE, the city was taken when Alexander-the-Great built a 750 m-long causeway to seize the island. The causeway interrupted longshore sediment transport, forcing sand to accumulate along the causeway, creating a isthmus that today still connects the island to the mainland. This isthmus is no less than 530 m wide and 13 m high. We studied the impact of isthmus growth on city development during Antiquity, by combining archeological data, core stratigraphy, and multibeam bathymetry to track the paleogeographic evolution of the land-facing coast of Tyre, from the Holocene marine transgression up to today. In Phoenician time (900-300 BCE), sea-level markers indicate that relative sea level lied more than 2.5 m below current sea level, defining a 1500 × 600 m rocky island, 450 m longer in the south than the modern rocky headland. Between the island and the mainland, diffracted/refracted waves built a submerged sand bank that rests on eroded transgressive lagoonal clays. Along the mainland-facing coast of Tyre Island, Phoenician walls were built on the emerged end of the sand bank. Middle infrared spectroscopy (MIRS) shows that the sand of the bank and its successor isthmus is made of carbonate clasts (90–100%). 36Sr/37Sr ratios further indicate that these are modern bioclastic sands. Coeval, heterogeneous clay-rich sediments were deposited between the rocky island, and the sand bank. We interpret these as harbor sediments, deposited behind buried and/or submerged Phoenician breakwaters. The sand bank inflated dramatically after the building of Alexander's causeway, rising 5 m during the Hellenistic and Roman periods. It rose another 4 m–8 m in successive stages during Byzantine and Medieval times, up to the 19th century. The rapid growth of the sandy isthmus after 332 BCE led to the demise and burial of the harbors that had been developed along the mainland-facing coast. The Phoenician southern harbor of Tyre appears to have been buried in Roman times during the repurposing of the SE corner of the island for monumental baths. We interpret this repurposing as a response to the growth of the sandy isthmus, and suggest that the northern Phoenician harbor was then relocated to its present position. Subsequent relative sea level rise led to the erosion of the landfill overlying the southern harbor, exposing the formerly buried port on the seafloor.

Sedimentation Processes and the Holocene Evolution of the Indigirka Paleovalley (Coastal Shelf Area of the East Siberian Sea)

Problems of the paleogeographical evolution and changes in sedimentation environment within the Indigirka River paleovalley (the East Siberian Sea) are discussed. Based on the results of geophysical and geological research and a high-resolution study of sediment cores (grain size analysis, geochemistry, macro- and micropaleontology, pollen analysis, radiocarbon dating) the development of the Holocene marine transgression has been reconstructed, sedimentation rates have been calculated, and the basic principles of changes in sedimentation processes have been established.

Holocene geomorphological evolution of a sediment-starved coastal embayment in response to sea level change: Insights from the Qing'ao Embayment, southern China

Aiming to gain a better understanding of the response of sediment-starved coastal systems to the climate-driven sea level change, this study examines the Holocene evolution history of Qing'ao Embayment, southern China, as a case study. Results suggest three distinct stages of the evolution history: Stage 1 (8400–6000 cal yr BP) records an initial sedimentation phase associated with the early Holocene marine transgression into the embayment. Stage 2 (6000–3000 cal yr BP) records early sediment deposition under relatively strong hydrodynamic inshore/open-bay environment during early marine regression. Stage 3 (3000 cal yr BP to present) records two substages: Stage 3a relates to the semi-enclosed bay, intertidal and lagoonal salt marsh facies between 3000 and 1300 cal yr BP, and Stage 3b records the final infilling of the embayment into a lagoonal plain. This evolution model suggests that the rates of sea level change and sediment accretion are the two major controlling factors for the Holocene geomorphological evolution of sediment-starving coastal systems.Comparison of the evolution of Qing'ao embayment with sediment-supply rich large-river estuary/deltas reveals unique features in the response to Holocene sea level change of this sediment-starved embayment: During the early Holocene marine transgression, sediment starts to accumulate in the small embayment around 8400 cal yr BP, hundreds of years later than in large river estuaries. During 8400–6000 cal yr BP, sediment accretion rate remains dramatically lower than sea level rise rate, which results in the quick growth of sediment accommodation space during this stage. Around 6000 cal yr BP, though sea level has remained relatively stable and large-river deltas have been growing for about 1000 years, the sediment-starved embayment was still under shallow marine and/or open bay conditions. At 3000 cal yr BP, shoreline started to prograde in sediment-starved embayment, which is about 3000 years later than large river deltas. Finally, agricultural activity started around 1300 cal yr BP in the embayment, thousands of years later than large river deltas. Limited or minimal fluvial sediment supply to the small embayment has constrained the land expansion during the sea level stabilization since mid-Holocene, and the limited living space might result in the much later agricultural activity in such coastal system.Due to the different balances between sea level change and sediment flux, sediment-starved coasts are expected to be under higher risks than large river deltas. However, earlier and more extensive human activities in large river basins have resulted in the reduction of sediment discharge that heighten the risks of large river deltas against future sea level rise. Thus, more attention should be paid to the coastal sediment supply budgets in the context of the background of rising sea level.

Holocene marine deposits in the Bohai Sea: Depocenters, sediment sources, and oceanic and tectonic influences

The Bohai Sea is a semi-enclosed shallow shelf sea that has undergone a unique sediment source-to-sink process in the past. Despite this, our knowledge about the sediment budget, existence of depocenters and the factors controlling depocenter formation during the Holocene remains limited. This paper aims to address these gaps by estimating the Holocene marine deposit thickness and sediment budget in the Bohai Sea using high-resolution subbottom profiles. The results reveal that the mean thickness of Holocene marine deposits is approximately 7.8 m and a maximum thickness of 28 m was found in Jinzhou Bay. The Highstand System Tracts (HST) have a mean thickness of approximately 5.4 m and a maximum thickness of 25 m observed in the Jinzhou Bay. On the other hand, the Transgressive System Tracts (TST) have a mean thickness of approximately 2.5 m and a maximum thickness of 7 m in the north of the Laizhou Bay. The total accumulation in the Bohai Sea is estimated to be ∼713.97 × 109 tons, consisting of 489.28 × 109 tons from the HST and 224.69 × 109 tons from the TST. Three deposit centers were identified and estimated to be approximately 299 × 109 tons, accounting for approximately 42 % of the total Bohai Sea sediments. The development of Holocene marine deposit centers was mainly influenced by the Tanlu Fault zone and water circulations. Based on preliminary estimates, it is suggested that roughly half of the sediments dispersed from the estuaries are preserved on the Bohai Sea shelf since the maximum flooding (∼7000 cal yr BP). This research provides valuable insights for the post-glacial sedimentary and geomorphic evolution of the Bohai Sea.

Impact of submarine karst sulfur springs on benthic foraminiferal assemblage in sediment of northern Adriatic Sea

PurposeThis work highlights the sedimentary characteristics and the role of submarine sulfur-rich karstic springs in the distribution of benthic foraminifera in the northern part of the Adriatic Sea (Bay of Koper). Little is known about how local conditions such as temperature and sulfur bursts may influence sediment properties, benthic habitat variability, and composition of foraminiferal assemblages. Here we compare the distribution of total and living benthic assemblages in surface sediment samples collected from a funnel-shaped depression created by submarine sulfur springs.Materials and methodsSampling was performed at water depths between 24.6 and 32.2 m in fine-grained sandy silt to silty sand (partially washed). Sedimentological, mineralogical, and geochemical analyses of the sediment were carried out and the distribution of benthic foraminifera living around the springs was studied.Results and discussionIn general, sediment characteristics (i.e., mineralogical, geochemical, and organic content) around the sulfur springs do not show prominent deviations from the marine surface sediment of the area; however, some differences exist among depressions of different depths. Deeper depressions in the lower parts probably extend to older continental sediments of Late Pleistocene age with alluvial features, while shallower depressions were formed entirely in Holocene marine sediments typical of a wider area. Only one of the five samples (M05) contained living foraminifera in sufficient abundance for biocenosis research. The benthic foraminiferal assemblages of moderate diversity are composed of opportunistic species. Elphidium translucens, Ammonia ex gr. tepida, Haynesina depressula, and Porosononion granosum dominate, while A. neobeccarii, Reussella spinulosa, and Textularia bocki are subordinate.ConclusionsThe distribution and diversity of foraminifera in the sediment near sulfur springs can be explained by several factors and their interactions. The intensity of the spring discharge affects the mixing/oxygenation of the sediment, the shape of spring depressions, and the granulometry of the coarser sediment around the springs. Sediment characteristics indicate different types of sediment origin. This is related to and can be explained by the depth of spring depressions.

Influence of sedimentary deposition on the microbial assembly process in Arctic Holocene marine sediments.

The sea-level rise during the Holocene (11-0 ky BP) and its resulting sedimentation and biogeochemical processes may control microbial life in Arctic sediments. To gain further insight into this interaction, we investigated a sediment core (up to 10.7 m below the seafloor) from the Chuckchi Shelf of the western Arctic Ocean using metabarcoding-based sequencing and qPCR to characterize archaeal and bacterial 16S rRNA gene composition and abundance, respectively. We found that Arctic Holocene sediments harbor local microbial communities, reflecting geochemical and paleoclimate separations. The composition of bacterial communities was more diverse than that of archaeal communities, and specifically distinct at the boundary layer of the sulfate-methane transition zone. Enriched cyanobacterial sequences in the Arctic middle Holocene (8-7 ky BP) methanogenic sediments remarkably suggest past cyanobacterial blooms. Bacterial communities were phylogenetically influenced by interactions between dispersal limitation and environmental selection governing community assembly under past oceanographic changes. The relative influence of stochastic and deterministic processes on the bacterial assemblage was primarily determined by dispersal limitation. We have summarized our findings in a conceptual model that revealed how changes in paleoclimate phases cause shifts in ecological succession and the assembly process. In this ecological model, dispersal limitation is an important driving force for progressive succession for bacterial community assembly processes on a geological timescale in the western Arctic Ocean. This enabled a better understanding of the ecological processes that drive the assembly of communities in Holocene sedimentary habitats affected by sea-level rise, such as in the shallow western Arctic shelves.

Socioeconomic roles of Holocene marine shell beads reveal the daily life of composite objects from East Kalimantan, Borneo

Cultural objects composed of composite materials with differing physical properties are often differentially preserved in archaeological records favouring those materials less susceptible to taphonomic processes. Using microscopically observed wear patterns to decipher a model of socioeconomic roles for composite beaded objects, this study examines the rich marine shell bead assemblage excavated from Liang Jon in East Kalimantan, Borneo. Assessment of this 16,700-year sequence provides a unique context for discussing collection, transport, manufacture, and use of marine shell beads; spanning the biogeographical change associated with sea level rise 11,700 years ago creating the island of Borneo. Quantifying differences in bead wear patterning and distribution has revealed changes across 11,000 years of human occupation—detail seldom exposed in Island South East Asian archaeology. Results demonstrate marine species belonging to the families Nassariidae and Cypraeidae were targeted for the manufacture of beads. Whole shells and removed dorsa indicate some onsite manufacture occurred, while patterns of wear and residues including pigments, suggest most beads originated from different varieties of composite objects brought to the site and maintained in different contexts of daily life. Our model reveals a novel picture of Holocene social complexity broadly associated with dated rock art, providing a unique link between parts of the rich archaeological record at the Liang Jon, circumventing popular modes of ethnographic analogy less appropriate for this region.

Quaternary uplift of palaeoshorelines in southwestern Crete: the combined effect of extensional and compressional faulting

We undertake spatio-temporal analysis on sequences of Pleistocene palaeoshorelines in southwestern Crete where deformed Holocene marine notches have predominantly been suggested to be linked to coseismic uplift from the 365 CE Mw > 8 earthquake. Previous investigations into the Holocene notches have been used to infer that the dominant mechanism of uplift may be slip either on a reverse crustal fault or on the subduction interface. However, seismic reflection studies attest to the presence of numerous active offshore extensional faults whose role in the long-term deformation is unclear. The relative contributions of upper-plate extensional and compressional faults to the overall deformation can be assessed through the study of uplifted and deformed Late Quaternary palaeoshorelines. New 36Cl exposure dating on wave-cut platforms and palaeoshoreline mapping are combined with existing age controls to facilitate investigation into the deformed Late Quaternary palaeoshorelines. We observe that the Late Quaternary uplift rates increase from west (0.61 mm/yr) to east (0.83 mm/yr) over ∼20 km, a spatial uplift pattern that is inconsistent with published vertical deformation models of slip solely on the subduction interface or on a reverse crustal fault. Elastic half-space modelling suggests that an offshore extensional fault may also contribute to the uplift. We conclude that a combination of active extensional and compressional faults may be responsible for Late Quaternary uplift across southwestern Crete.