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In the transformation from tidal systems to freshwater coastal landscapes, plants act as eco‐engineering species that reduce hydrodynamics and trap sediment, but nature and timing of the mechanisms of land creation along estuaries remains unclear. This article focuses on the Old Rhine estuary (The Netherlands) to show the importance of vegetation in coastal landscape evolution, predominantly regarding tidal basin filling and overbank morphology. This estuary hosted the main outflow channel of the river Rhine between ca 6500 to 2000 cal bp, and was constrained by peat during most of its existence. This study reconstructs its geological evolution, by correlating newly integrated geological data and new field records to varying conditions. Numerical modelling was performed to test the inferred mechanisms. It was found that floodbasin vegetation and resulting organic accumulation strongly accelerated back‐barrier infill, by minimizing tidal influence. After tidal and wave transport had already sufficiently filled the back‐barrier basin, reed rapidly expanded from its edges under brackish conditions, as shown by diatom analysis and datings. Reed growth provided a positive infilling feedback by reducing tidal flow and tidal prism, accelerating basin infilling. New radiocarbon dates show that large‐scale crevassing along the Old Rhine River – driven by tidal backwater effect – only started as nutrient‐rich river water transformed the floodbasin into an Alder carr in a next phase of estuary evolution. Such less dense vegetation promotes crevassing as sediments are more easily transported into the floodbasin. As river discharge increased and estuary mouth infilling progressed, crevasse activity diminished around 3800 to 3000 cal bp, likely due to a reduced tidal backwater effect. The insights from this data‐rich Holocene study showcase the dominant role that vegetation may have in the long‐term evolution of coastal wetlands. It provides clues for effective use of vegetation in vulnerable wetland landscapes to steer sedimentation patterns to strategically adapt to rising water levels. [ABSTRACT FROM AUTHOR]

ABSTRACT In the Northern Hemisphere, the Younger Dryas cooling occurred between 12.8 and 11.7 ka bp. This cooling is thought to have been the result of an abrupt change in atmospheric and oceanic circulations. One of the hypotheses explaining such a change suggests that just before the onset of the Younger Dryas cooling, multiple airbursts/impacts occurred over the Northern Hemisphere. We studied the late Pleistocene sediments from the Netherlands and Belgium to check whether a sudden short event might have taken place just before the onset of the Younger Dryas cooling. The geochemical features revealed suggest that such events might have occurred. The presence of products of biomass burning is suggested on the basis of trace element features of sediments from the lower Younger Dryas boundary. The presence of a volcanic component and a component resulting from extensive biomass burning in the sediments of c. 12.9 ka bp are indicated on the basis of trace element features. The volcanic component may be related to the Laacher See volcano eruption, whereas the cause of the extensive biomass burning remains unclear. [ABSTRACT FROM AUTHOR]

Lake sediment records from the Weerterbos region, in the southern Netherlands, were studied to reconstruct summer temperature and environmental changes during the Weichselian Lateglacial Interstadial. A sediment core obtained from a small lacustrine basin was analysed for multiple proxies, including lithological changes, oxygen isotopes of bulk carbonates, pollen and chironomids. It was found that the oxygen isotope record differed strongly from the other proxies. Based on a comparison with three additional lake sediment records from the same region, it emerged that the oxygen isotope records were strongly affected by local environmental conditions, impeding the distinction of a regional palaeoclimate signal. The chironomid-inferred July air temperature reconstruction produced inferred interstadial temperatures ranging between ∼15° and 18° C, largely consistent with previously published results from the northern part of the Netherlands. A temporary regressive phase in the pollen record, which can be tentatively correlated with the Older Dryas, preceded the expansion of birch woodland. Despite differences between the four pollen records from the Weerterbos region, a comparable regressive vegetation phase that was possibly the result of a shift to drier conditions could be discerned in all of the profiles. In addition, a temporary temperature decline of ∼1.5° C was inferred from the chironomid record during this regressive phase. The multi-proxy approach used here enabled a direct comparison of inferred changes in temperature, vegetation and environmental conditions at an individual site, while the multi-site approach provided insight into the factors influencing the pollen and isotope records from these small-scale depressions. [ABSTRACT FROM AUTHOR]

Peat and gyttja (organic lake sediment) are important indicators for past environmental conditions; they form in areas where the supply of clastic sediment is insufficient to fill the accommodation space. Previous studies of delta sediments, however, have focused mainly on clastic deposits, whereas organics have received only minimal attention. Identification of organic facies can be of value for understanding delta formation as it provides insight into, for example, palaeoenvironmental conditions and compaction susceptibility of these layers. Currently, however, field characteristics of organics are not well-documented for the full range of facies present in delta plains. In this study, a field method - a classification key - for identifying organic facies in delta plains was developed based on concisely described organic facies in selected cores from the Rhine-Meuse delta, The Netherlands. This method was tested on archived borehole descriptions of the diachronous basal peat layer in the distal Holocene Rhine-Meuse delta; this was done by means of a semi-automated procedure to select and classify samples from a database. The resulting data set was used for mapping organic facies in the basal peat layer by means of indicator kriging and inverse distance weighting. The resulting facies distribution map shows consistent and geologically meaningful patterns, which were interpreted in terms of hydrological regimes. The formation of the basal peat layer, which marks the onset of Holocene aggradation, has been controlled by marine-dominated, fluvial-dominated and seepage-dominated environments. Before 9000 cal yr bp, marine processes influenced the initial stage of organic accumulation in the western part of The Netherlands. After 9000 cal yr bp, on the flanks of topographical higher regions, seepage-dominated mesotrophic organic facies characterized the onset of accumulation. Simultaneously, nutrient-rich organic facies could develop in the Rhine-Meuse valley: gyttja formed in the sediment-limited Meuse realm, whereas reed peat accumulated in the Rhine realm, indicating lower water depths and thus a higher elevated surface level. It is concluded that the classification key for identifying organic facies is a strong tool to better recognize peat and gyttja types on the basis of macroscopic field characteristics. Application of the key on archived boreholes also proved to be feasible. Identification of organic facies and determination of their spatial distribution at delta scale, as is shown in this study, contributes to understanding delta evolution. [ABSTRACT FROM AUTHOR]

Three distal tephra layers or cryptotephras have been detected within a sedimentary sequence from the Netherlands that spans the last glacial-interglacial transition. Geochemical analyses identify one as the Vedde Ash, which represents the southernmost discovery of this mid-Younger Dryas tephra so far. This tephra was found as a distinct horizon in three different cores sampled within the basin. The remaining two tephras have not been geochemically 'fingerprinted', partly due to low concentrations and uneven distributions of shards within the sequences sampled. Nevertheless, there is the potential for tracing these tephra layers throughout the Netherlands and into other parts of continental Europe. Accordingly, the possibilities for precise correlation of Dutch palaeoenvironmental records with other continental, marine and ice-core records from the North Atlantic region are highlighted. [ABSTRACT FROM AUTHOR]

Environmental changes were reconstructed from Lateglacial calcareous gyttja deposits at Gulickshof, southern Netherlands. Analyses of pollen, fresh-water mollusca, stable isotopes and geo-chemistry were performed and the combined evidence was put into a chronostratigraphic framework based on regional biostratigraphy and accelerator mass spectrometry radiocarbon dating. The pollen diagram showed vegetation development from the Bølling interstadial into the Late Dryas stadial within 2.9 m of lacustrine deposits. Early in the Allerød, around 11 900 BP, the composition of aquatic taxa and stable isotopes of calcium carbonate changed significantly. It appears that the final melting of relic ground-ice and subsequent re-establishment of the hydrological cell early in the Allerød were responsible for these changes. Later in the Allerød, around 11 250 BP, the disappearance of molluscs, changes in vegetation and isotope composition all point to colder climate conditions attributable to the Gerzensee oscillation. The combination of different lines of evidence in these types of deposits proves to be an excellent tool for unravelling climate and environmental signals. [ABSTRACT FROM AUTHOR]

Abstract: Pollen diagrams of Alpine Late-glacial calcareous lake deposits show several extensions of Betula. The geochronology of these extensions cannot be based on radiocarbon dating due to reservoir effects of such lakes on the radiocarbon ages. A robust geochronology can be based on the oxygen isotope stratigraphy. Additionally, recognition of 12,920 calBP LST in the sediment cores provides a secure time marker. The combined results of pollen, macro-remains and stable isotope analyses of the Gasserplatz cores point to a correlation of the Betula extensions with the oscillations in the oxygen isotope curve and are related to global climatic oscillations. This is sustained by the correlation of the Gasserplatz isotope oscillations with the oscillations as registered in the Greenland ice cores. Comparison of the results of the Gasserplatz cores with the results of similar Alpine lake deposits makes clear that the fluctuations in the Betula curve are not a local but a regional phenomenon. [Copyright &y& Elsevier]

In the Netherlands, several proxies of climate change during the Last Glacial-Interglacial Transition (LGIT) (c. 14,700 to 11,700 b2k) have been investigated in detail over the last few decades. The present paper presents two tree-ring chronologies LETR-A (n = 16, timespan 106 rings) and LETR-B (n = 24, timespan 201 rings) from in situ subfossil pine remains (Pinus sylvestris) discovered at Leusden-Den Treek in the Netherlands that date from the Bølling-Allerød interstadial (GI-1). Using a multiproxy approach (both abiotic and biotic), it was possible to study local woodland development in detail as part of long-term environmental change. Moreover, the trees opened up possibilities for dendrochronological and dendroclimatological research. The tree-ring series show the occurrence of two successive phases of pine woodland development, which were 14C dated with high precision and calibrated using the recent IntCal20 14C calibration curve: 13,450–13,396 to 13,370–13,316 calBP (series LETR-A) and 12,952–12,937 to 12,754–12,739 calBP (series LETR-B). At the north-western boundary of its ecotone, Pinus was highly sensitive to climate change during the latter part of GI-1 and the transition to GS-1. The inability to set fruit and the disappearance of the pine woodland within decades before and after c. 12,745 calBP is interpreted as the vegetational response to abrupt climate deterioration at the start of the Younger Dryas (12,807 ± 12 cal BP). • A multiproxy analysis of a waterlogged Usselo paleosol reveals late Allerød to Younger Dryas environmental change in high detail. • Two precisely dated tree-ring chronologies over the Allerød-Younger Dryas Transition reflect climate sensitivity of Pinus sylvestris. • Pine woodland disappeared after 12,745 calBP as a delayed response to the abrupt climate change at the start of the Younger Dryas. [ABSTRACT FROM AUTHOR]

The controversial Younger Dryas impact hypothesis suggests that at the onset of the Younger Dryas an extraterrestrial impact over North America caused a global catastrophe. The main evidence for this impact--after the other markers proved to be neither reproducible nor consistent with an impact--is the alleged occurrence of several nanodiamond polymorphs, including the proposed presence of lonsdaleite, a shock polymorph of diamond. We examined the Usselo soil horizon at Geldrop-Aalsterhut (The Netherlands), which formed during the Allerød/Early Younger Dryas and would have captured such impact material. Our accelerator mass spectrometry radiocarbon dates of 14 individual charcoal particles are internally consistent and show that wildfires occurred well after the proposed impact. In addition we present evidence for the occurrence of cubic diamond in glass-like carbon. No lonsdaleite was found. The relation of the cubic nanodiamonds to glass-like carbon, which is produced during wildfires, suggests that these nanodiamonds might have formed after, rather than at the onset of, the Younger Dryas. Our analysis thus provides no support for the Younger Dryas impact hypothesis.