Feature Papers in Quaternary

The Western Pacific Warm Pool (WP), with the highest sea surface temperature (SST) in the world, has strong impacts on the drought variations in Eurasia. However, since the little ice age (1250–1850, LIA), the co-climatic drought pattern due to WP warming in Eurasia remains unclear. This is a long-term warming background for the current warming period (CWP). In this paper, we use both instrumental data and 1625 tree-ring width records from Eurasia to investigate the drought patterns in both modern and historical periods. This study revealed two seesaw precipitation patterns, namely the Central Asia–Mongolia (CAMO) and Northern Europe–Southern Europe (NESE) patterns. When the Western Pacific Warm Pool sea surface temperature (WPSST) is high, precipitation increases in Central Asia and Northern Europe, and decreases in Mongolia and southern Europe. When the positive (negative) phase event of the El Niño–Southern Oscillation (ENSO) occurs, the WPSST is reduced (increased), and the decreases (increases) of precipitation in Central Asia and Northern Europe and the increases (decreases) in precipitation in Mongolia and southern Europe are more obvious. The CAMO dipole has been strengthened since the LIA. The CAMO dipole is positively correlated with solar radiation and Northern Hemisphere temperature, and negatively correlated with Pacific decadal oscillations (PDO). Full article

We studied twelve late Holocene organic deposits in West-Frisia, The Netherlands. Pollen, spores, non-pollen palynomorphs, mosses, other botanical macrofossils and insect remains were recorded for reconstructions of changing environmental conditions. Eastern West-Frisia was a cultivated landscape during the Bronze Age, but it became a freshwater wetland in the Late Bronze Age. In most of our sites, radiocarbon dates show that time transgressive inundation of soils preceded the climate shift at 850 cal BC for several centuries. We suggest that solar forcing of climate change may have delivered the final push to the inundation and depopulation of West-Frisia, which had already commenced several centuries before, due to sealevel rise. We did not find evidence for significant Bronze Age tree growth in West-Frisia before the inundations. Vegetation successions in the new wetlands developed from shallow mineral-rich freshwater to rich-fen vegetation. Subsequently poor fen vegetation with birch and pine developed, and the natural succession led to ombrotrophic raised bog vegetation. Complete successions from shallow, mineral-rich lakes to raised bog lasted between 1000 and 1500 calendar years. We hypothesize that medieval drainage and reclamation became possible only when the mires of West-Frisia had reached the raised bog stage. Reclamation of raised bogs by medieval farmers (drainage, eutrophication, peat digging) caused compaction, oxidation and loss of the upper part of the peat deposit. Seeds of salt-tolerant and salt-demanding plant species indicate that the medieval sites were inundated during storm surges with brackish or salt water, which triggered the farmers to build artificial mounds and, later, dikes. Under mounds and dikes, peat deposits remained protected against further decay. With our data we deliver a long-term perspective on contemporary ecosystem dynamics of freshwater wetlands, relevant for nature conservation and future climate change. Full article

In this article, I show how an Ultisol, representative of a globally-important group of soils with clay-rich subsoils, low base saturation, and low fertility, in the central Waikato region in northern North Island, can be evaluated using soil stratigraphy and tephrochronology to answer challenging questions about its genesis, age and classification. The Kainui soil, a Typic Kandiudult (Soil Taxonomy) and Buried-granular Yellow Ultic Soil (New Zealand Soil Classification), occurs on low rolling hills of Mid-Quaternary age mainly in the Hamilton lowlands in, and north and northeast of, Hamilton city. It is a composite, multi-layered tephra-derived soil consisting of two distinct parts, upper and lower. The upper part is a coverbed typically c. 0.4–0.7 m in thickness (c. 0.6 m on average) comprising numerous late Quaternary rhyolitic and andesitic tephras that have been accumulating incrementally since c. 50 ka (the age of Rotoehu Ash at the coverbed’s base) whilst simultaneously being pedogenically altered (i.e., forming soil horizons) via developmental upbuilding pedogenesis during Marine Oxygen Isotope Stages (MOIS) 3-1. Any original depositional (fall) bedding has been almost entirely masked by pedogenic alteration. Sediments in lakes aged c. 20 ka adjacent to the low hills have preserved around 40 separate, thin, macroscopic tephra-fall beds mainly rhyolitic in composition, and equivalent subaerial deposits together form the upper c. 30 cm of the coverbed. Okareka (c. 21.8 ka), Okaia (c. 28.6 ka), Tāhuna (c. 39.3 ka) and (especially) Rotoehu tephras make up the bulk of the lower c. 30 cm of the coverbed. Tephra admixing has occurred throughout the coverbed because of soil upbuilding processes. Moderately well drained, this upper profile is dominated by halloysite (not allophane) in the clay fraction because of limited desilication. In contrast, Otorohanga soils, on rolling hills to the south of Hamilton, are formed in equivalent but thicker (>c. 0.8 m) late Quaternary tephras ≤c. 50 ka that are somewhat more andesitic although predominantly rhyolitic overall. These deeper soils are well drained with strong desilication and thus are allophanic, generating Typic Hapludands. Ubiquitous redox features, together with short-lived contemporary reduction observed in the lower coverbed of a Kainui soil profile, indicate that the Kainui soil in general is likely to be saturated by perching for several days, or near saturation for several months, each year. The perching occurs because the coverbed overlies a slowly-permeable, buried, clay-rich paleosol on upper Hamilton Ash beds, >c. 50 ka in age, which makes up the lower part of the two-storeyed Kainui soil. The coverbed-paleosol boundary is a lithologic discontinuity (unconformity). Irregular in shape, it represents a tree-overturn paleosurface that may be c. 74 ka in age (MOIS 5/4 boundary). The buried paleosol is markedly altered and halloysitic with relict clay skins (forming paleo-argillic and/or paleo-kandic horizons) and redoximorphic features. It is inferred to have formed via developmental upbuilding pedogenesis during the Last Interglacial (MOIS 5e). The entire Hamilton Ash sequence, c. 3 m in thickness and overlain unconformably by Rotoehu Ash and underlain by c. 340-ka Rangitawa Tephra at the base, represents a thick composite (accretionary) set of clayey, welded paleosols developed by upbuilding pedogenesis from MOIS 10 to 5. Full article

Science-based information on historical fire frequency is lacking for longleaf pine sandhills. We undertook a high-resolution macroscopic charcoal and geochemical analysis of sediment cores recovered from three depression marshes located within a longleaf pine sandhill ecosystem in Florida, USA. A ~1500-year fire history reconstructed from >1.5 m length peat cores analyzed at decadal to multi-decadal resolution revealed abundant macroscopic charcoal particles at nearly all sampling intervals, suggesting that fire occurred near the sites for almost all decades represented in the deposit. This result supported previous hypotheses of a frequent natural fire return interval for Florida’s longleaf pine sandhills and suggested that management decisions for this ecosystem should continue to focus on the frequent prescription of controlled burns. Our research also demonstrated that some of Florida’s depression marshes contain a >3000-year archive of organic-rich peat. Bulk elemental carbon and nitrogen data and stable carbon isotope analysis of the deposits at two of the three study sites suggested persistently wet soils. Soil data from the third site suggested that drying and peat oxidation occurred periodically. These depression marshes rapidly sink carbon, with measured sequestration rates on the order of 16 to 56 g m⁻² yr⁻¹. Our research demonstrated that Florida’s depression marshes provide an untapped record of paleoenvironmental information. Full article

At 37°24′ N 22°8′ E, the Megalopolis Basin lies in the central Peloponnese Peninsula, southwestern Greece. In the Megalopolis Basin at ~350 m amsl, the Paleolithic site, Marathousa 1, sits within a palustrine/lacustrine clastic package between Lignite Seams III and II, that both likely correlate with interglacial periods. At Marathousa 1, immediately below Lignite Seam III, lies a clayey-silty sand layer with a horizon rich in molluscs ranging from ~20–40 cm thick. About 0.8–1.3 m below the shell-rich horizon (SRH), lacustrine silty to muddy sands rich in organic matter yielded Paleolithic lithic artefacts associated with Middle Pleistocene fauna, some with cut marks and possible bone knapping, found within palustrine/lacustrine clastic deposits. Since ESR (electron spin resonance) can date teeth and molluscs aged >2 Ma, two bivalve samples, AM66 and AM65, five subsamples from a cervid molar, AT39, and one subsample from another cervid molar, AT68, were independently dated by ESR from Marathousa 1. To calculate the ages, time-averaged cosmic and time- and volumetrically-averaged sedimentary dose rates were calculated using past water depths and sedimentation rates as determined from paleontological and geological criteria. Found in the SRH in Layer UA2, AM66 and AM65 averaged 488 ± 37 ka, which correlates with MIS 13a. Because the bivalves sat stratigraphically above the artefacts and mammalian fossils, their ages constrain the ESR ages for the teeth deposited below. Lying on the unconformity at the base of Layer UA3c with UA4, and its correlative unconformity at the Layer UB4c/UB5 boundary, sat the dated teeth from large mammals. Because the bones in the Palaeoloxodon antiquus skeleton lay in quasi-anatomical association, the likelihood for fossil reworking on the Layer UB3c/UB4 surface is low. Isochron analysis suggests that using a U uptake model with p = 2 provides the most accurate ages for AT39. With p = 2, AT39 dates to 503 ± 13 ka, while AT68 dates to 512 ± 34 ka. Nonetheless, two to three more teeth and molluscs should be dated to confirm these ages, when more samples suitable for ESR dating are found. Both tooth ages correlate well with early MIS 13, an interglacial period with cooler mean global temperatures compared to MIS 11 or 9. Assuming that the archaeological site formed in one event, rather than as a palimpsest, the data suggest that hominins processed elephant and other faunal carcasses along the shores of a shallow lake or marsh in the Megalopolis Basin at 503 ± 12 ka. Between the two horizons dated here, their sedimentation rate averaged 4.8 ± 1.8 to 7.8 ± 2.9 cm/ka. Full article

Despite the societal importance of extreme hydroclimate events, few palaeoenvironmental studies of Scandinavian lake sediments have investigated flood occurrences. Here we present a flood history based on lithological, geochemical and mineral magnetic records of a Holocene sediment sequence collected from contourite drift deposits in Lake Storsjön (63.12° N, 14.37° E). After the last deglaciation, the lake began to form around 9800 cal yr BP, but glacial activity persisted in the catchment for ~250 years. Element concentrations and mineral magnetic properties of the sediments indicate relatively stable sedimentation conditions during the Holocene. However, human impact in the form of expanding agriculture is evident from about 1100 cal yr BP, and intensified in the 20th century. Black layers containing iron sulphide appear irregularly throughout the sequence. The increased influx of organic matter during flood events led to decomposition and oxygen consumption, and eventually to anoxic conditions in the interstitial water preserving these layers. Elevated frequencies of black layer occurrence between 3600 and 1800 cal yr BP reflect vegetation changes in the catchment as well as large-scale climatic change. Soil erosion during snowmelt flood events increased with a tree line descent since the onset of the neoglacial period (~4000 cal yr BP). The peak in black layer occurrence coincides with a prominent solar minimum ~2600 cal yr BP, which may have accentuated the observed pattern due to the prevalence of a negative NAO index, a longer snow accumulation period and consequently stronger snowmelt floods. Full article