Quaternary International最新文献

With its numerous environmental archives stored in lake and peat sediments and relatively low human pressure, the Lake Onega region in eastern Fennoscandia is regarded as a particularly promising area for studying past changes in vegetation and climate since the Lateglacial period. The 885-cm-long sediment core RZ19 (62°27′53″N, 34°26′4″E) was collected from Razlomnoe Peat on the northern shore of Lake Onega in 2019, radiocarbon-dated and analysed for pollen and cryptogam spores. The age-depth model suggests continuous sedimentation since ca. 11,800 a BP (all ages given in years (a) or kiloyears (ka) before present (BP) with BP referring to 1950 CE). The results of pollen analysis and pollen-based biome reconstruction show rapid afforestation of the area in the Early Holocene, although the scores of the tundra biome remain relatively high prior to ca. 11,450 a BP, suggesting that the vegetation was likely more open than today. Between 8300 and 8000 a BP, Betula sect. Albae shows a marked increase in pollen percentage, while Pinus sylvestris experiences a marked decrease. These changes coinciding with the 8.2 ka BP cooling event indicate less favourable conditions for Scots pine while being beneficial for fast-growing birch. The transition from the Early to Middle Holocene (i.e. from Greenlandian to Northgrippian) is marked by an increase in pollen productivity, spread of Picea and further afforestation of the area. The decrease in arboreal and Picea pollen percentages and the abrupt increase in landscape openness after ca. 4000 a BP mark the onset of the Late Holocene (i.e. Northgrippian-Meghalayan transition) and likely reflect the combined effect of insolation-induced temperature decrease and associated paludification and forest retreat rather than a decrease in atmospheric precipitation and/or spread of Late Neolithic agriculture.

The sustainability of dry regions has become a key issue for global development. Their natural and cultural landscapes are facing threats resulting from ongoing global changes. This paper presents an overview of geomorphological, climatic-environmental, and archaeological studies in the hyper-arid eastern Tarim Basin (Lop Nur), northwest China, a world-renowned crossroad for early east-west communications, to provide a scientific foundation for sustaining its nature-culture heritage. The late Quaternary landscape changes in the Lop Nur region are characterised by cycles between oases and yardang deserts, shaping the extensive aeolian landform. Archaeological evidence suggests humans’ adaptation and resilience to today what are viewed as inhospitable environments since the late Pleistocene by exploiting the diverse range of oasis resources, movement, and encouraging adjacent populations to diversify their subsistence base. Settlement- and regional-scale deterioration of available water resources, affected by environmental and climatic dynamics, caused the eventual abandonment. Periodic occupation and abandonment in the Lop Nur region accompanying oasis-desert/yardang environment cycles provide important lessons for present-day policymakers to contextualise the relationship between human communities and fragile ecosystems. The open-air sites in the Lop Nur region represent the best-preserved oasis-desert civilisation, suffering cultural history losses. We propose the urgent necessity to establish a transdisciplinary database, construct a master chronological framework of settlement, and integrate the culture-nature heritage within the network of the Silk Roads. The scientific management of river networks is also critical for protecting those riverine cultural relics. The site- and group-level management of heritage needs to be adapted to the projected changes in climate and environment.

Long-lasting drought records can provide valuable insights into the history of hydroclimate change in central China, but meteorological records are too short to capture long-term variability of the humidity. In this study, we established a tree-ring width chronology of Pinus armandii Franch in the Funiu Mountains region of central China. Correlation analyses showed that tree radial growths were mainly limited by hydrothermal combination in May–June. The results of the moving correlation analysis further showed that the response relationship between tree growth and relative humidity in May–June (RH_MJ) was the most stable. This relationship has been reconstructed since 1863. The variance of the reconstructed RH_MJ was explained by 41.7% (40.6% after adjusting for degrees of freedom). Over the past 158 years, there were 3 wet periods and 4 dry periods. The spectral analysis revealed that the reconstructed RH_MJ exhibited quasi-periods of 2-4a and 31.6a, and cross-spectrum analysis showed that the reconstructed RH_MJ may be related to ENSO, PDO, solar activity and the East Asian summer monsoon. The spatial correlation analysis revealed that the reconstructed RH_MJ accurately depicted the fluctuations in humidity within the Huanghe-Huaihe Plain. Furthermore, the reconstructed RH_MJ exhibited a strong negative correlation with the sea surface temperature (SST) of the subtropical North Pacific, while it displayed a highly significant positive correlation with the SST of the eastern equatorial Pacific from the previous May to the current April. This also indicated a possible link between humidity fluctuations in the Huanghe-Huaihe Plain and the Pacific internal variability in climate system. Therefore, this research aims to expand and complement the existing meteorological records, providing important reference significance for forest management, agriculture, and animal husbandry.

Humans have had profound and environmentally changing impacts on land cover, and China has many examples of this. It has been recognised for some time that middle to late Holocene forests in China have undergone changes that are best described as due to human impacts. Hence the Holocene has seen sometimes gradual and sometimes abrupt changes from forest dynamics driven by natural forces to those dominated by human impacts. This leads to a conclusion that it is often difficult to disentangle natural and anthropogenic controls on forest composition. In many cases records show minor changes in the early Holocene giving way to intense changes as agriculture expanded. The two earliest centres of extensive forest changes from 6 to 5 kyr BP were in the middle to lower Yellow and lower Yangtze valleys, where millet and rice agriculture developed. Major forest clearing was later in other areas, including the Pearl River valley, Northeast China and Yunnan. Forest clearing for agriculture was widespread in eastern China by 2 kyr BP. Where data is available it seems that initial clearing took place in valleys adjacent to rivers, presumably because these were the preferred living places for early farmers. Then gradually spread to nearby slopes. New approaches and technologies were needed to achieve this. The records show that north east China, north of the Liao River, and the mountains of central China were amongst the last places to record forest clearing, in some cases just within the last few hundred years, or not at all.

The mid-Pliocene warm period (MPWP) during 3.3–3.0 Ma has been defined as a potential analog for future climate warming with atmospheric CO₂ concentration higher than the modern level. However, the migration of the East Asian summer monsoon (EASM) rain belt during this period is still controversial, which hinders our understanding of the future environmental changes in China. Two periods, Pleistocene interglacials (with atmospheric CO₂ ∼280 ppmv) and mid-Pliocene (with atmospheric CO₂ ∼450 ppmv) were selected to study the changes of regional humidity and the EASM edge location as high CO₂ forcing. The results show a relatively drier and warmer climate prevails in the area and the edge of the EASM retreated eastward. Our study supports that the edge of the EASM will eastward retreat in the future and the CLP will get drier and warmer with increasing atmospheric CO₂ concentration can be expected.

The Dalangsonggou (DLSG) fault is an internal fault within the Sichuan–Yunnan block, located on the southern side of the Garzê–Yushu fault. On the basis of geological and geomorphological surveys, we estimated the Holocene activity of the DLSG fault. We excavated two trenches and identified two paleoseismic events by analyzing the stratigraphic deformation and radiocarbon dating results of the faulted strata. The occurrence times of these events were determined to be 8420–8346 and 4612–5045 cal BP. The time elapsed since the latest earthquake, which exceeds 4500 years, indicates strong risk of occurrence of a large earthquake on the DLSG fault. Furthermore, the recurrence interval of large earthquakes on the DLSG fault is much longer than that of earthquakes on the Garzê–Yushu fault. Thus, the DLSG fault conducts only regulating effects in terms of regional tectonic deformation compared to the dominant impact of the Garzê–Yushu fault, which is a boundary fault of the block.

Fire is an essential component of the landscapes and forests of the Pacific Northwest, including the temperate rainforests of the Olympic Peninsula. Previous fire history reconstructions from the peninsula show that fire return intervals varied throughout the postglacial period, primarily in response to climatic changes and corresponding shifts in vegetation. However, much less is known about the fire history of the low-elevation forests of the Olympic Peninsula and the role of cultural fire regimes in these environments. The purpose of this study was to reconstruct the paleoenvironmental history of a low-elevation study site, Beaver Lake, located in the northwestern part of the peninsula. Using macroscopic charcoal, pollen, and sedimentological analyses of a ca. 3440-year-long record, we reconstructed a high-resolution record that shows fire activity was remarkably high during the late Holocene for an area considered part of a temperate rainforest. However, patterns of burning varied throughout the record, with the first third (ca. 3440 to 2350 cal yr BP) and last third (ca. 800 cal yr BP to the present day) recording much higher amounts of fire activity compared to the middle portion (ca. 2350 to 800 cal yr BP), which recorded very little fire activity. Larger and/or more severe fires that likely burned during multi-year droughts correlate with peaks in magnetic susceptibility and pollen trends that indicate substantial geomorphic responses and successional changes in forest structure following these events. Cooler temperatures and a wetter climate, indicated by nearby glacial advancements, may have staved off fire activity during the period of low fire activity. Cultural burning by the Indigenous tribes of the Olympic Peninsula likely contributed to the observed fire activity at Beaver Lake as nearby prairies were managed for resource procurement, indicated in particular by an increase in herbaceous morphotype charcoal during the past 800 years.

The connection of the Southern Ocean and Eastern Equatorial Pacific (EEP) has been used to explain the presence of an old, respired water mass into the Eastern Tropical North Pacific (ETNP) and Eastern North Pacific (ENP) during deglaciation. This water mass and its geochemical properties are transported along the thermocline via subsurface and intermediate circulation. Some questions remain regarding an intermediate water mass with old and less ventilated characteristics in the eastern Pacific because certain sedimentary records of δ¹³C, δ¹⁸O, and Δ¹⁴C in benthic foraminifera have failed to prove its presence. The top-down hypothesis has been proposed to explain the absence of this carbon isotopic signal in benthic and its presence in planktonic foraminifera in the EEP. To prove this hypothesis in the ETNP, oxygen and carbon isotopic compositions were determined for Neogloboquadrina dutertrei in a core collected at 700 m depth over the Magdalena margin, Mexico. From these new data, a reconstruction of the water column structure and the change in ocean circulation at the thermocline level during deglaciation was inferred. N. dutertrei δ¹⁸O values in the ETNP and those from Globigerina bulloides in the ENP, similar to those of N. dutertrei in the EEP, suggest that the tropical water mass extended as far as 32 °N. Specifically, N. dutertrei δ¹⁸O values were more positive in the Heinrich Stadial-1 (HS-1) and Younger Dryas (YD) than the Bolling Allerod-Antarctic Cold Reversal (BA-ACR) and Early Holocene (EH) suggesting the presence of a saline water mass with origin in the EEP. N. dutertrei δ¹³C depleted values during the HS-1 and YD suggested the presence of a water mass with old and respired carbon. This is consistent with the salinification or “spicy” inferred from δ¹⁸O for the ETNP. These isotopic findings in N. dutertrei corroborate the existence of a tropical water mass that probably originated in the Southern Ocean. Additionally, the present data do not support the top-down hypothesis.

Fundamental insight into the long-term ‘geoecohydrological’ dynamics of rivers and floodplains is required for their sustainable management. To study these dynamics, a multi-proxy approach is essential. While suitable proxies are available for reconstructing floodplain geomorphology and past vegetation, the suitability of the available proxies for past hydrology to reconstruct floodplain wetness has not yet been evaluated. In this study, we apply a multi-proxy analysis combining testate amoebae and several geochemical proxies for decomposition (humification, carbon and nitrogen stable isotopes), in comparison to sedimentological (stratigraphy, loss on ignition) and palaeobotanical records, to obtain independent hydrological reconstructions of alluvial floodplains in contrasting environmental settings to explore the suitability of the available proxies for past hydrology to reconstruct floodplain wetness.

This study concludes that testate amoebae cannot provide a continuous and reliable hydrological reconstruction, as they are insufficiently preserved in alluvial peat deposits. In addition, mineral particles within the tests size range hamper the analysis in mineral-dominated sediment units. As organic matter decomposition is low when water tables are high and vice versa, we expected the decomposition proxies to reflect the hydrological conditions. While the amount of humic acids appears to depend mainly on the substrate rather than the decomposition of the organic matter in it, the analyses of carbon and nitrogen stable isotopes provide promising results, for both peat and non-peat deposits.

In this work, we present new biostratigraphic and paleoecological data from the Mignone River valley, located in the central sector of the Tyrrhenian Sea margin and part of the wider Tarquinia basin, and cores in the area of Rome. By combining the new paleontological information with a review of the extant literature, we re-examine the stratigraphic architecture of the Pliocene succession in the central sector of the northwestern Tyrrhenian Sea margin, spanning the Zanclean (MPl1; 5.33–5.08 Ma) through the early Piacenzian (MPl4b; 3.57–3.31 Ma), and of the following Pleistocene transgressive-regressive sequence, comprising the Gelasian (MPl6; 2.59–1.81 Ma) through the Santernian (MPl1; 1.81–1.5 Ma).

We propose a revision of the paleogeographic evolution of the central Tyrrhenian Sea basins throughout the Pliocene-Lower Pleistocene interval, by coherently framing it within the chronology of the volcanic phases that occurred in this region. In particular, our reconstruction points toward the presence of a single Transgressive-Regressive (T-R) sequence starting with the Zanclean reflooding of the Mediterranean after the Messinian Salinity Crisis and ending in the Piacenzian, as opposed to the previously proposed occurrence of two depositional T-R sequences separated by an erosional phase affecting part of the Globorotalia puncticulata biozone.