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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. • Holocene marine accumulation in the Bohai Sea is estimated to be ∼713.97 × 109 tons. • Accumulation in HST is of ∼489.28 × 109 tons and that in TST is of ∼224.69 × 109 tons. • Three depocenters were identified and account for ∼42 % of the total accumulation. • Roughly half of the sediments were preserved on the shelf over the past 7000 years. [ABSTRACT FROM AUTHOR]

This paper documents the history of vegetation assemblage in Honghe Wetland (NE China) during the last 6200 years. Vegetation changes were reconstructed based on high-resolution plant macrofossil analysis of sedimentary sequence obtained from Honghe National Nature Reserve located in Sanjiang Plain, in conjunction with Accelerator Mass Spectrometry (AMS) 14 C radiocarbon data. Results indicate that plant macrofossil composition of Honghe wetland ecosystem are dynamic and have undergone several significant changes. Around 2500 cal yr BP, plant composition transited from Equisetum fluviatile community to Carex lasiocarpa - Drepanocladus aduncus community, and then following by Drepanocladus aduncus community at 460 cal yr BP. Another major vegetation changes occurred at 220 cal yr BP, transitioning to Carex sp. community. By comparison between the plant macrofossil assemblages and the climate changes during the last 6200 cal yr BP, we suggest that ASM (Asian summer monsoon) is the main driving force for the vegetation succession before the impacts of human activities. Since some restoration programs have been undertaken at Honghe wetland, thus our results can provide valuable baseline data for assessment of the practicability and suitability of the former restoration plan and the further designing of conservation management and restoration targets. Since the vegetation composition of Honghe wetland is pronouncedly sensitive to water level, it can be inferred that wetland ecosystem can be restored to near-natural condition through the effective management and restoration by controlling the water source of the wetland. [ABSTRACT FROM AUTHOR]

It is widely accepted that climate has a strong impact and exerts important feedbacks on erosional processes and sediment transport mechanisms. However, the extent at which climate influences erosion is still a matter of debate. In this paper we test whether frost-cracking processes and related temperature variations can influence the sediment production and surface erosion in a small catchment situated in the eastern Italian Alps. To this extent, we first present a geomorphic map of the region that we complement with published 10 Be-based denudation rates. We then apply a preexisting heat-flow model in order to analyze the variations of the frost-cracking intensity (FCI) in the study area, which could have controlled the sediment production in the basin. Finally, we compare the model results with the pattern of denudation rates and Quaternary deposits in the geomorphic map. The model results, combined with field observations, mapping, and quantitative geomorphic analyses, reveal that frost-cracking processes have had a primary role in the production of sediment where the intensity of sediment supply has been dictated and limited by the combined effect of temperature variations and conditions of bedrock preservation. These results highlight the importance of a yet poorly understood process for the production of sediment in mountain areas. [ABSTRACT FROM AUTHOR]

In tropical Africa, Late Pleistocene-Holocene climatic fluctuations heavily impacted the continental hydro-systems. The timing and magnitude of 'African Humid Period' hydrological dynamics (AHP; ~14.8 to ~5.5 ka BP) are not yet fully understood due to the extreme variability in African geomorphic patterns and the complex network of past air convergence boundary shifts. The investigation of the functioning of specific hydro-sedimentary basins is needed to improve our knowledge on the AHP spatial and chronological patterns over the continent. In this paper we present a revised Holocene lake level curve of Lake Abhe: an endorheic basin situated in the Afar Depression at the northern extremity of the East African Rift System (EARS). Located at the boundary of the Red Sea and the Indian and Atlantic Oceans' air moisture mass fluxes, the Lake Abhe watershed represents a system sensitive to changes in Northeast African hydro-climate. Based on numerous littoral lacustrine geomorphic features and 53 related radiocarbon ages on stromatolites and nearshore deposits, we have defined the main Holocene lake highstands proposing a detailed paleo-shoreline record. The first rise in water level is dated to ~11.1 ka cal. BP, while the Maximal Holocene Highstand Shoreline (~420 m a.s.l.) was rapidly reached around ~10 ka cal. BP. Evidence of the impact of the 8.2 ka North Atlantic cooling event is recognized with slow lake level regression until ~8.3 ka cal. BP and with an abrupt drop at ~8 ka cal. BP. The resurgence of humid conditions was recorded from ~7.7 ka cal. BP to ~4.6 ka cal. BP. Radiocarbon ages on littoral materials allow us to propose a Holocene subsidence rate of the Abhe basin axial valley. Furthermore, multiphase sill overflow incisions towards the downstream Hanle basin and transient fluvial connectivity with the upstream Ziway-Shala basin, indicate strong geomorphic controls on lake highstand elevations. In summary, Lake Abhe Holocene fluctuations are the result of combined hydro-climatic, tectonic and local geomorphic controls. However, the confrontation with others East African basins allows us to discuss the transport of moisture masses dynamics into the northern EARS during the Holocene. [ABSTRACT FROM AUTHOR]

Coastal morphodynamics and environmental changes have been obviously altered by global warming, sea-level fluctuations, and human activities. Palynological analysis is one of the most important tools for providing information on vegetation, climate, and environmental change, which can be relatively sensitive indicators of human activity during the Holocene. However, Holocene coastal morphodynamics and palynological evidence from the Pearl River Delta and coastal areas has not been sufficiently studied. In this paper, we carry out analyses using detailed grain-size and palynological records of pollen, spores, freshwater algae, and marine dinoflagellate cysts from Borehole QZK13 in the Pearl River Estuary (PRE), southern China. The results show information relating coastal morphodynamics, vegetation evolution, climate changes, and anthropogenic activities during the Holocene based on radiocarbon chronology. In general, the PRE experienced marine transgressive processes; sea-level and the coastline tended to migrate landward between 10,700 and 4250 cal yr BP. Meanwhile, abundant arboreal pollen (mainly Castanopsis , Quercus -evergreen, Oleaceae, and Castanea) and small amounts of non-arboreal pollen (mainly Poaceae, Cyperaceae, and Artemisia) were observed in Borehole QZK13, which suggests that subtropical evergreen broadleaved forests were distributed throughout the PRE and adjacent areas, and relatively warm and moist climatic conditions were present during the early-middle Holocene. After that, there were relatively cool and wet climatic conditions, and marine regressive processes occurred in the PRE during the Late Holocene (ca. 4250–960 cal yr BP) indicated by an abrupt increase in aquatic herbs and Dicranopteris. Moreover, we hypothesize that the Neolithic "cultural fault" in the PRE is likely related to frequent storm surges induced by extreme typhoon events that occurred ca. 3000–2700 yr BP. • Grain size, pollen, spores, freshwater algae and dinoflagellate cysts from the Pearl River Estuary were investigated. • Three major phases shown by palynological results were corresponding to the changes in vegetation and climate. • We hypothesized that the Neolithic "cultural fault" is probably related to the storm surges induced by extreme typhoon events. • Natural vegetation cover has suffered large-scale destruction by ancient humans during the Late Holocene. [ABSTRACT FROM AUTHOR]

Palaeomeanders are characteristic features of meandering river floodplains. Some were abandoned several millennia ago and can be used as evidence for past fluvial patterns. Despite many observations of changes undergone by meandering rivers, little is known about long-term morphological adjustment of meanders. This paper reports on investigations conducted in two reaches located in the middle valley of the Cher River (northwestern Europe, France) to examine the readjustments of lowland meanders during the second half of the Holocene. The aim of our study was to provide new insights into the complex dynamics that control low-energy meandering rivers. LiDAR DEM spatial analyses coupled with geophysical surveys and observations of sediments enabled the identification and dating of thirteen palaeomeanders embedded in coarse sediments (sand and gravel) while the whole floodplain is covered by silty overbank deposits. Sedimentological, geochemical and pollen analyses combined with radiocarbon and OSL dating allowed us to reconstruct the chronology of the cutoff and the filling of palaeochannels. No palaeochannels older than ca 6000 yr cal. BP, and no palaeochannels younger than the eleventh–thirteenth centuries cal. AD were identified. This allowed us to distinguish two periods of meandering processes. (1) Our observations demonstrate the multi-millennia persistence of an active meandering pattern in a context of land use changes (ca 6000 yr cal. BP-eleventh–thirteenth centuries cal. AD). The preserved mobility of the river can be mainly interpreted as the result of the low cohesiveness of the bank material. Too few fine sediments were delivered during the proto-historical and historical periods to help stabilize the river course. (2) Following the eleventh–thirteenth centuries cal. AD, the fluvial system underwent a laterally stable phase. The many medieval and modern hydraulic engineering works reduced the specific stream power and prevented lateral erosion. The drastic decrease in the river's capacity to generate new meanders resulted in the disappearance of floodplain lakes and loss of habitat diversity. [ABSTRACT FROM AUTHOR]