Search

Temperature changes in the middle reaches of the Yangtze River (MRYR) have affected more than one billion people. In contrast to the warming trend in the Northern Hemisphere (NH), there was a sustained cooling trend of mean annual temperatures in the MRYR from 1930s to 1980s. Due to long-term mean annual temperature record has so far been lacking in the MRYR, it remains unclear to what extent regional peculiarities reflect region-specific internal climate variability or differences in driving mechanisms. Here, we present a reconstruction of temperature variability over the MRYR for the period CE 800-1998 using a laminated stalagmite (HS4) from Heshang cave, Yichang region, China. Observations of Heshang cave suggest that the growth of HS4 stalagmite is mainly affected by the temperature because of the stability of dripping water composition. Based on a significant positive correlation between the growth rate and the observed temperature, we reconstructed the mean annual temperature (MAT) for Yichang region with an explained variance of 39.8%, the correlation in interdecadal scale (10-yr low pass) was significantly improved (r=0.86). The new MAT reconstruction shows an almost similar trend with existing low resolution mean annual temperature records from historical document, which confirms the credibility of the reconstruction. Four warm (800s-880s, 1260-1450s, 1650s-1800s, 1900s-1950s) and three cold (890s-1250s, 1460s-1640s, 1810s-1890s) period were identified in MAT record. Our reconstruction shows a significant cooling in the MRYR during the MCA period, which may differ from previous NH temperature records. We suggested that the unique temperature variation in the MRYR may be driven by El Niño-Southern Oscillation (ENSO), as there was a significant positive correlation between MAT record and ENSO over the past 1200 years on the multidecadal scale. When sea surface temperatures in the eastern Pacific rise, so do temperatures in the MRYR, and vice versa. Our study provided the longest mean annual temperature record in the MRYR, and we also highlight that ENSO may be related to the temperature variation of the East Asian monsoon region, which has generally been ignored in past studies.

There is a great need for the reconstruction of independent El Nino Southern Oscillation (ENSO) from different archives and locations to provide a robust understanding of its driving and feedback mechanisms on long time scales. Though tree-ring cellulose δ18O (δ18OTR) records from the East Asian monsoon (EAM) region of China have the potential to reconstruct ENSO on an annual time scale, δ18OTR ENSO signals may be masked by local climate effects since any individual δ18OTR record is influenced by both large-scale atmospheric circulation and local climate. Few attempts have been made to reduce the uncertainties of the reconstructed ENSO index by δ18OTR records from the EAM region of China by ensemble data analysis. In this study, twelve published δ18OTR records spanning over 100 years (1902–2003 CE) have been collected and processed using principal component analysis (PCA). The first principal component (PC1) extracted from the δ18OTR records shows a positive/negative relationship with the annual Nino 3.4 index/southern oscillation index (SOI), with correlation coefficients higher than those between single δ18OTR record and the Nino 3.4 index/SOI, suggesting the ENSO signal is improved by PCA. A 31-year running correlation on PC1- Nino 3.4 index/SOI reveals an increasingly stronger correlation between δ18OTR and ENSO since the last century, inferring that, in the EAM region, the δ18OTR-ENSO correlation may become much stronger under continuous global warming in the future. Spectrum and spatial correlation analysis further support the idea that PC1 responds to ENSO. The significant relationships between observational precipitation δ18O and Nino 3.4 SST anomaly and PC1 from 1973–2003 CE suggest that precipitation δ18O is a key link to connect δ18OTR with ENSO. This study shows the advantage of ensemble data analysis on δ18OTR records in EAM region of China, which could better extract ENSO signals and reduce the uncertainties of reconstructed ENSO variations by individual δ18OTR records from the EAM region of China. It provides an alternative independent annual indicator for ENSO reconstruction on long time scales when more δ18OTR records from this region are extended in the near future.

Modern precipitation variability over East China is known to be characterized by meridional tripole and dipole structures, linked to atmosphere and ocean dynamics. As the instrumental data may be influenced by anthropogenic global warming, it is unclear whether the physical mechanism underlying the tripole and dipole pattern have remained constant since the pre-industrial period. Here we investigate spatiotemporal precipitation variability over the past 1150 years using three high-resolution stalagmite δ18O records from southern, central and northern China. Principal component analysis results suggest that the first principal component, reflecting large-scale Asian monsoon strength, is closely linked to solar variability. The second and third principal components, which reflect rainfall, reveal tripole and dipole patterns that persist over the last millennium and are driven by the Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO). We find that interactions between the monsoon, PDO, and AMO influence spatiotemporal rainfall patterns in East China.

Understanding the sources and biogeochemical processing of dissolved organic matter (DOM) and nutrients within large rivers is vital to carbon cycling and water management. However, there remains great uncertainty regarding aquatic DOM composition and source proportioning resulting from spatial-temporal heterogeneity. In this study, multiple techniques were applied to track riverine DOM and nutrients over different flow regimes along the middle reach of the Yangtze River. Combined with nitrate dual isotopes, three different organic sources have been identified including terrestrial humic substances, “non-natural” terrestrial humic substances associated with the input of urban sewage, and tyrosine-like substances related to microbiological activities. The higher aromatic degree of DOM, higher \({{\delta }}^{18}{\text{O}}_{{\text{N}\text{O}}_{3}}\), and lighter \({{\delta }}^{15}{\text{N}}_{{\text{N}\text{O}}_{3}}\) signals in the rainy season suggested that soil erosion by intensive monsoon rainfall was the main factor for the release of carbon and nitrogen. During the dry season, nitrate from soil solution in the riparian zone with denitrification and inputs of urban sewage might be responsible for the enrichment of \({{\delta }}^{15}{\text{N}}_{{\text{N}\text{O}}_{3}}\) and higher tyrosine-like substances. At the spatial scale, the same terrestrial DOM was observed between the distal surface water in the Three Gorge Reservoir and the outlet, which was mainly caused by the density currents inducing water intrusion in the reservoir. An ever increasing proportion of tyrosine-like substances longitudinally indicated the cumulative intensity of human activities was becoming stronger along the mainstream. The study advances our evaluation of different carbon and nitrogen in sources in the Yangtze River and provides insights into the management of large monsoonal rivers.

Stalagmites provide one of the few high-quality proxy records of the Thailand monsoon. The Namjang (NJ) cave (19°40′30″N, 98°12′12″E; 923 m a.s.l.), which is situated in the data-scarce region of northwestern Thailand, serves as a unique and important site that offers great potential for multi-proxy climate reconstruction. We present new data on stable oxygen isotopic (δ18O) compositions and growth rates of aragonite stalagmites based on an in situ cave and climate monitoring study performed between August 2012 and October 2013. The dominant factors that control the variations in the δ18O values of rainfall, drip water, and modern aragonite precipitate as well as the variations in the modern speleothem deposition rates and drip water hydrochemical properties were determined to correctly interpret the climatic signals of the parameters that are derived from speleothems. The intraseasonal variations in rainfall δ18O values were faithfully recorded from cave drip water isotopic signals. The monthly mean values of δ18O in cave drip water were lower in the rainy season and higher in the dry seasons and shifted from approximately − 4 in the early rainy months to approximately − 6‰ in the late rainy months. These variations have implications for the use of speleothem δ18O from the NJ cave as a proxy of the seasonal variations in monsoon rainfall δ18O and changes in moisture source trajectories. The deposition rates of modern speleothem deposits are primarily controlled by drip water flow rates, which are linked to the amount of water recharge in the cave during the summer monsoon season. There was a significant correlation between the drip rate and amount of carbonate precipitation for the drip sites NJ-1 (r = 0.54, p < 0.040) and NJ-1202 (r = 0.76, p < 0.004). Combinations of different parameters and proxies from this area could provide the potential for the further development of multi-proxy climate reconstructions over different time scales.

To estimate the parameters of the model of option pricing based on the model of rough fractional stochastic volatility (RFSV), we have carried out the empirical analysis during our study on the pricing of SSE 50ETF options in China. First, we have estimated the parameters of option pricing model by adopting the Monte Carlo simulation. Subsequently, we have empirically examined the pricing performance of the RFSV model by adopting the SSE 50ETF option price from January 2019 to December 2020. Our research findings indicate that by leveraging the RFSV model, we are able to attain a more accurate and stable level of option pricing than the conventional Black–Scholes (B-S) model on constant volatility. The errors of option pricing incurred by the B-S model proved to be larger and exhibited higher volatility, revealing the significant impact imposed by stochastic volatility on option pricing.

The concentration of trace elements such as Ni, Co, and Cu in a stalagmite is determined by (i) the amount of these elements present in so-called organic-metal complexes (OMCs) that trap the ionic forms of such elements in the dripwater, and (ii) the amount that is able to decay from the OMCs into the aqueous phase, from where the elements can adsorb to the growing stalagmite surface (and remain captured within the stalagmite crystal structure). A statistical treatment of the decay of a population of trace element ions from OMCs allow us to model the rates at which the dripwater dropped from the roof of the cave on to the stalagmite’s surface. The problem is however made challenging due to: (i) the lack of reliable monitoring data that quantifies the relationship between OMC trace metal ion concentration and stalagmite trace metal ion concentration, and (ii) the presence of chronological uncertainties in our estimates of trace element concentrations at past time points from the depth-based measurements along the stalagmite. We present here a semi-heuristic, semi-theoretical approach that estimates dripwater rates using a theoretical model based on the population-level chemical kinetics of trace element decay from OMCs, and a heuristic choice of calibration data sets based on precipitation and temperature from nearby weather station data. Our approach is applied to trace metal data from the Heshang Cave in southeastern China, and we are able to reconstruct a driprate proxy time series — a first quantitative hydrological proxy record presented along with well-defined estimates of uncertainty.

With their merits of precise dating and sensitivity to climate changes, laminated stalagmites are an important terrestrial archive for reconstructions of paleohydrological changes. In particular, the Ca isotope composition (δ44/42Ca) of the Heshang Cave stalagmite has been documented to record a precipitation decrease during the 8.2 ka event in central China. As an extension, this study directly compares near-annual resolution δ44/42Ca data with an instrumental precipitation record to evaluate the fidelity of δ44/42Ca as a paleohydrologic proxy on annual to decade timescales. Over the period 1881–2001 AD, the δ44/42Ca values correlate significantly with both precipitation from a nearby weather station and the dryness/wetness index in the middle Yangtze River, with a stronger correlation on decadal smoothed data. These results clearly show that the δ44/42Ca ratio from stalagmites is an effective proxy for paleohydrological changes on a decadal timescale. More study is encouraged to refine understanding of stalagmite Ca isotope ratios and hydrological conditions and their application in paleohydrologic reconstructions.

Acid rain has the potential to significantly impact the quantity and quality of dissolved organic matter (DOM) leached from soil to groundwater. Yet, to date, the effects of acid rain have not been investigated in karstic systems, which are expected to strongly buffer the pH of atmospheric rainfall. This study presents a nine-year DOM fluorescence dataset from a karst unsaturated zone collected from two drip sites (HS4, HS6) in Heshang Cave, southern China between 2005 and 2014. Cross-correlograms show that fluorescence intensity of both dripwaters lagged behind rainfall by ∼1 year (∼11 months lag for HS4, and ∼13 months for HS6), whereas drip rates responded quite quickly to rainfall (0 months lag for HS4, and ∼3 months for HS6), based on optimal correlation coefficients. The rapid response of drip rates to rainfall is related to the change of reservoir head pressure in summer, associated with higher rainfall. In winter, low rainfall has a limited effect on head pressure, and drip rates gradually slow to a constant value associated with base flow from the overlying reservoir- this effect being most evident on inter-annual timescales (R2 = 0.80 for HS4 and R2 = 0.86 for HS6, n = 9, p

Studies have shown that stable isotope [oxygen (O) and carbon (C)] composition of mammal tooth enamel can provide information on a region's paleoclimate and paleoecology. Stable isotope analysis has been used to investigate the impact of the Qinghai–Tibetan Plateau uplift on the development and strength of the Asian monsoon. However, due to sparse data from southern China, a region dominated by the East Asian monsoon, O and C isotope analysis of mammal tooth enamel has been unable to fully inform on the impact of the monsoon environment in the region. Here, we present the results of the analysis of stable isotopes on a set of cervid tooth enamel from late Middle Pleistocene Tantang Cave in Bubing Basin, Guangxi, southern China and compare them with comparable isotope data from nearby early Early Pleistocene Mohui and middle Early Pleistocene Sanhe Caves. The results of the oxygen isotope analysis indicates that Tantang Cave (−8.70‰ to −6.39‰) is similar to Mohui Cave (−8.71‰ to −6.34‰), with both sites being more negative than Sanhe Cave (−4.77‰ to −1.20‰). We suggest the East Asian summer monsoon was stronger during the Tantang and Mohui mammal occupations and weaker during the lifetime of the Sanhe mammals. This result is indirectly corroborated by vertebrate paleontological evidence. Murid rodents, implying an open grassland and somewhat drier climate, are found in great numbers in Sanhe. The carbon isotope results from Tantang (−17.70‰ to −10.26‰), Mohui (−15.27‰ to −12.51‰), and Sanhe (−16.63‰ to −14.71‰) overlap extensively suggesting these various faunas primarily lived in a closed forest environment. The implications of these findings from stable isotope studies from Tantang are discussed in their broader context.

The Permian-Triassic (P-Tr) crisis was the largest mass extinction of the Phanerozoic and eliminated over 90% of marine species. However, the nature of marine productivity changes during the crisis is a matter of on-going debate. Here, thermoluminescence (TL) measurements from 144 bulk carbonate samples from Meishan (South China) show two levels of variation in TL peak intensities at ~270 °C. The first-order variation is characterized by a rapid, nearly three-fold increase. A secondary variation is interpreted to record periodic fluctuations on a Milankovitch scale (~20-kyr rhythm). The periodic variations of TL are negatively correlated with Mn concentrations, suggesting primary productivity is a key factor controlling the TL peak intensity by photo-reduction of particulate Mn in the presence of organic matter. Therefore, the periodic fluctuations of TL were likely controlled by primary productivity changes on orbital timescales. A significant rise of TL peak intensities across the P-Tr boundary represents the rapid increase of dissolved Mn associated with enhanced marine productivity and/or oceanic anoxia.

Previous research has shown a strong persistence for direct teleconnections between the East Asian summer monsoon (EASM) and high northern latitude climate variability during the last glacial and deglaciation, in particular between monsoon weakening and a reduced Atlantic meridional overturning circulation (AMOC). However, less attention has been paid to EASM strengthening as the AMOC was reinvigorated following peak Northern Hemisphere (NH) cooling. Moreover, climate model simulations have suggested a strong role for Antarctic meltwater discharge in modulating northward heat transport and hence NH warming, yet the degree to which Southern Hemisphere (SH) climate anomalies impacted the Asian monsoon region is still unclear. Here we present a new stalagmite oxygen-isotope record from the EASM affected region of central China, which documents two prominent stages of increased 18 O-depleted moisture delivery to the region through the transition from Heinrich Stadial 1 (HS1) to the Bolling–Allerod (B–A) interstadial; this is in general agreement with the other monsoonal records from both NH and SH mid to low latitudes. Through novel comparisons with a recent iceberg-rafted debris (IRD) record from the Southern Ocean, we propose that the two-stage EASM intensification observed in our speleothem records were linked with two massive Antarctic icesheet discharge (AID) events at ∼16.0 ka and ∼14.7 ka, immediately following the peak HS1 stadial event. Notably, the large increase in EASM intensity at the beginning of the HS1/B–A transition (∼16 ka) is relatively muted in the NH higher latitudes, and better aligns with the changes observed in the SH, indicating the Antarctic and Southern Ocean perturbations could have an active role in driving the initial EASM strengthening at this time. Indeed, Antarctic freshwater input to the Southern Ocean during these AID events would have cooled the surrounding surface waters and caused an expansion of sea ice, restricting the southern extent of the SH westerlies. Moreover, increased meltwater flux during IRD events would have freshened Antarctic Intermediate Water, leading to the increased formation of North Atlantic Deep Water and enhanced North Atlantic subsurface heat release, and causing a strengthening of the AMOC during the HS1-Bolling transition. The result of this sequence-of-events would have been warming in the North Atlantic whilst at the same time cooling in the Antarctic. The ensuing interhemispheric temperature gradient would have acted to push the ITCZ northward, weakening the Australian–Indonesian summer monsoon (AISM) whilst intensifying the EASM.

The 8.2 ka BP event could provide important information for predicting abrupt climate change in the future. Although published records show that the East Asian monsoon area responded to the 8.2 ka BP event, there is no high-resolution quantitative reconstructed climate record in this area. In this study, a reconstructed 10-year moving average annual rainfall record in southwest China during the 8.2 ka BP event is presented by comparing two high-resolution stalagmite δ18O records from Dongge cave and Heshang cave. This decade-scale rainfall reconstruction is based on a central-scale model and is confirmed by inter-annual monitoring records, which show a significant positive correlation between the regional mean annual rainfall and the drip water annual average δ18O difference from two caves along the same monsoon moisture transport pathway from May 2011 to April 2014. Similar trends between the reconstructed rainfall and the stalagmite Mg ∕ Ca record, another proxy of rainfall, during the 8.2 ka BP period further increase the confidence of the quantification of the rainfall record. The reconstructed record shows that the mean annual rainfall in southwest China during the central 8.2 ka BP event is less than that of present (1950–1990) by ∼ 200 mm and decreased by ∼ 350 mm in ∼ 70 years experiencing an extreme drying period lasting for ∼ 50 years. Comparison of the reconstructed rainfall record in southwest China with Greenland ice core δ18O and δ15N records suggests that the reduced rainfall in southwest China during the 8.2 ka BP period was coupled with Greenland cooling with a possible response rate of 110 ± 30 mm °C−1.

Thailand has been regarded as a transition zone between the Indian and western North Pacific monsoons which produce most of the precipitation in this area and sustain large-scale agricultural activities. Their different moisture sources and associated transport trajectories could result in distinguishable seasonal variations in rainfall oxygen isotopes (δ18O). Knowledge about seasonal variability in Thailand monsoon could facilitate agricultural water management and improve our understanding of the Asian monsoon system. In this study, a detailed examination of the intra-seasonal variability of tree-ring cellulose δ18O in teak trees from Northwestern Thailand was performed. The results show clear intra-seasonal variability in cellulose δ18O, with heavier values in the early rainy season and much lighter values in the later rainy season. Climate correlation analysis indicates that there is a significant and positive correlation between sub-seasonal variation in cellulose δ18O and rainfall δ18O. A weak and negative correlation with relative humidity (RH) has also been identified. However, there is no relation between intra-seasonal variation in cellulose and that of the amount of rainfall. These results imply that intra-seasonal variability of cellulose δ18O in teak trees from Northwestern Thailand may inherit such variability in rainfall δ18O and might be slightly shaded by RH. The spatial correlations with large-scale precipitation in the Merged Analysis (CMAP) and Outgoing Longwave Radiation (OLR) data sets indicated seasonal changes in moisture origin and may potentially be used to explore long-term monsoon climate variability on a seasonal scale in subtropical Southeast Asia.

The Last Glacial Maximum (LGM), defined as the period between 23 and 19 ka, is considered a key climatic period with conditions in great contrast to the present. Study of this period may reveal aspects of global ice-sheet sensitivity to regional and global climate change which is critical in understanding climate teleconnections and feedback mechanisms. A stalagmite record from Linglong cave, Central China, in combination with other high-resolution stalagmite records from Southwest China and East China existing on the same moisture transport pathway allows a reconstruction of rainfall patterns during the LGM by making use of the δ18O differences between stalagmite records. The rainfall around both Southwest and Central East China show a prominent change centered at ~24 ka corresponding to the H2 event, one of the Heinrich events related to North Atlantic ice-rafting. Also, in Central East China around the periods at 22 and 20 ka, the rainfall is lower than the average during the whole LGM, while around 23, 21 and 19 ka the rainfall is higher than the average, which is opposite to the rainfall variation in Southwest China. This apparent dipole rainfall pattern during the LGM is similar to the modern East Asian Summer Monsoon （EASM） rainfall distribution observed during weak monsoon periods, suggesting a much weaker EASM with its front moving less far north during the LGM than at present, which may link to North Atlantic climate and shifting of the Intertropical Convergence Zone (ITCZ). Power spectral analysis reveals that the rainfall variations in Southwest China are mainly controlled by a cycle of ~1000-yr, while in Central East China, it is mainly controlled by cycles of ~1800-yr and ~ 1300 yr, which are all possible solar activity cycles, suggesting that the EASM rainfall on long term scales is dominated by external forces.

A δ44Ca curve from shells of the planktonic foraminifera Globigerinoides sacculifer in calcareous biogenic oozes has been extracted from the Nintyeast Ridge in the Indian Ocean since 300 ka. By combining terrigenous inputs (e.g., grain size, magnetic susceptibility, and turbidite frequency) with the oceanic productivity (e.g., biogenic content and Neogloboquadrina dutertrei content), it is found that the curve’s variations are closely related to the historical evolution of the oceanic calcium cycle. The δ44Ca value is in lower tendency and has small oscillation during Marine Isotope Stage (MIS) 6, when the supply of terrigenous detrital is highest. In contrast, during MIS 3, 5 and 7, the δ44Ca values are in higher tendency, and their fluctuations are consistent with the variations of the productivity proxies. These results suggest that the calcium isotopes are mainly influenced by the input of the Himalayan erosion products to the northern Indian Ocean. In addition, the developmental stages of calcareous planktons may have a secondary impact on the fluctuations of the calcium isotope ratio of sea water.

The Ediacaran Doushantuo Formation (ca. 635–551 Ma) deposited immediately after the last Neoproterozoic glaciations and recorded the most prominent negative excursions of carbonate carbon isotopic composition (δ13Ccarb). These excursions have been interpreted as a result of widespread remineralization of a large dissolved organic carbon (DOC) reservoir in the Ediacaran deep oceans. However, there is no direct evidence so far found in rocks for the proposed DOC reservoir, which devalues such an interpretation. Here, we conducted a detailed study on the glow-curves characteristics and signal origins of spurious thermoluminescence (TL) of the Doushantuo Formation at Jiulongwan in Yangtze Gorges area, South China, through sequential tests under CO2, N2 and air. Spurious TL intensities for test samples before and after removing soluble organic matter via accelerated solvent extraction (ASE) are nearly identical. Further, significant positive correlation between the spurious TL intensity and total inorganic carbon (TIC) content (R 2=0.7) indicate that the Doushantuo spurious TL with the characteristic peak at 393.5 °C from the sequential test is chemiluminescence (CL) which is derived from the oxidation of a type of non-volatile organic matter strongly associated with carbonate mineral lattice (termed as “X-OM”). A most likely explanation is that the X-OM is a type of dissolved organic matter which co-precipitated with carbonate minerals into sediments in the Ediacaran Doushantuo Ocean. Furthermore, a significant exponential negative correlation (R 2=0.55) is observed between the CL data and the isotopic difference between carbonate and coexisting bulk organic matter (i.e., Δ13Ccarb-org, a proxy for remineralization degree of DOC reservoir in proposed DOC hypothesis), suggesting that the X-OM was derived from the oxidation of the DOC reservoir in the Ediacaran Ocean. We thus propose that the X-OM and its CL detected in our study may have recorded the evolution of the possible DOC reservoir in the Ediacaran Doushantuo Ocean. If this is correct, the stratigraphic variations of the CL intensity in the Doushantuo Formation at Jiulongwan support the pulsed oxidation of the DOC reservoir in the Ediacaran Ocean. Our findings indicate that the CL derived from the oxidation of non-volatile organic matter which is strongly associated with carbonate mineral lattices in rocks may provide a feasible approach for probing the evolution of DOC reservoir in the ancient oceans, thus likely provide direct geological evidence for the development of oceanic DOC reservoir in geological times.

尝试利用二次离子质谱(SIMS)技术, 采用国家一级标样(GBW04481)Oka方解石和美国威斯康星大学标样UWC - 3方解石, 对长江中游清江和尚洞洞穴碳酸盐沉积物HS4石笋的8.3 ka BP时段(236.3~235.6 cm)进行了季节分辨率的 δ 18 O原位分析, 探讨了利用季节分辨SIMS δ 18 O所呈现出的年际旋回对石笋进行相对定年的可能性; 并通过SIMS法与常规法 δ 18 O值的比较, 分析了两者间偏差产生的可能原因. 以Oka作外标, 利用Cameca IMS 1280离子探针在3个工作日内对UWC-3进行了氧同位素分析, 获得的测量结果( δ 18 O VPDB =-17.85‰±0.22‰, 1SD)与其推荐值( δ 18 O VPDB =-17.83‰±0.08‰)在误差范围内一致, 说明仪器稳定性良好、测试方法可靠. 用SIMS法获得的HS4石笋 δ 18 O季节分辨率记录, 则呈现出较为显著的年际旋回特征, 其旋回总数与同段石笋Mg/Ca比及石笋反光微层图像中所呈现出的年层总数一致, 有望为不具备清晰年纹层石笋的相对定年提供一个新的方法. 与常规法 δ 18 O分析结果相比, HS4石笋SIMS法 δ 18 O值系统偏负0.90‰, 且季节性差异增大, 其主要原因可能是缘于样品中细微裂隙、孔洞和包裹体的存在, 同时亦不排除石笋中有机质的存在对SIMS δ 18 O值可能造成的影响, 说明要获得与常规法 δ 18 O值相符的SIMS δ 18 O值记录, 石笋样品的致密度和纯净度均至关重要.

Extreme hydrologic events such as storms and floods have the potential to severely impact modern human society. However, the frequency of storms and their underlying mechanisms are limited by a paucity of suitable proxies, especially in inland areas. Here we present a record of speleothem magnetic minerals to reconstruct paleoprecipitation, including storms, in the eastern Asian monsoon area over the last 8.6 ky. The geophysical parameter IRMsoft-flux represents the flux of soil-derived magnetic minerals preserved in stalagmite HS4, which we correlate with rainfall amount and intensity. IRMsoft-flux exhibits relatively higher values before 6.7 ky and after 3.4 ky and lower values in the intervening period, consistent with regional hydrological changes observed in independent records. Abrupt enhancements in the flux of pedogenic magnetite in the stalagmite agree well with the timing of known regional paleofloods and with equatorial El Nino-Southern Oscillation (ENSO) patterns, documenting the occurrence of ENSO-related storms in the Holocene. Spectral power analyses reveal that the storms occur on a significant 500-y cycle, coincident with periodic solar activity and ENSO variance, showing that reinforced (subdued) storms in central China correspond to reduced (increased) solar activity and amplified (damped) ENSO. Thus, the magnetic minerals in speleothem HS4 preserve a record of the cyclic storms controlled by the coupled atmosphere-oceanic circulation driven by solar activity.

Organic matter preserved in speleothems has the potential to reflect the changes of the overlying vegetation and soil ecosystem. Here we report the first near 50-yr-resolution acid-soluble organic matter (ASOM) carbon isotope (δ 13 C ASOM ) sequence derived from a laminated stalagmite (HS-4) spanning the last 9 ky in Heshang Cave, central China. The δ 13 C ASOM values vary between − 25.8‰ and − 22.0‰, with lower values from 9 to 4 ka BP and less negative values from 4 to 0 ka BP. We postulate that the δ 13 C ASOM sequence is mainly controlled by temperature and water balance. Temperature could affect both vegetation physiology and microbial degradation in soil horizons. The influence of temperature on the δ 13 C ASOM is supported by the negative correlation ( r = − 0.48, p 13 C ASOM record and the paleotemperature record in the nearby Dajiuhu peatland. The water balance can affect the retention time of organic matter in soils. Under drier conditions, the soil organic matter will be retained longer and is more likely to be biologically degraded, resulting in more negative δ 13 C ASOM values. Our results reveal that δ 13 C ASOM in speleothems has the potential to reflect the response of vegetation and/or soil processes to paleoclimate changes.

Northern Thailand is the most flood-prone region in Thailand during the Indian Ocean Dipole (IOD) and El Nino-Southern Oscillation (ENSO) events. An annual growth rate profile covering the period from 1622 to 2008 AD was derived from the laminated stalagmite NJ-0901 from this area. By comparing stalagmite NJ-0901 to a contemporaneous stalagmite from the same cave and correlating the growth rate of NJ-0901 with meteorological data from the most recent 100 years, the stalagmite record proved to be a paleoclimate proxy of Thailand monsoon (TM) rainfall. This is the first annually laminated speleothem record that has been traced back four centuries. This record provided a long-term perspective and a valuable insight into TM rainfall and allowed us to investigate variations in the monsoon activity that was associated with IOD and ENSO. Our results indicate that both IOD and ENSO are significant climate modes that impact TM rainfall, but the effect of the interaction IOD and ENSO on TM rainfall remains unclear.

An improved synchronous fluorimetric method for the determination of dissolved organic matter in cave drip water, by adding ascorbic acid, is described. The method is based on the redox reaction between ascorbic acid and the electron-withdrawing constituents in dissolved organic matter. The results show that adding ascorbic acid can quench the minor peaks, at 200–300 nm, but does not affect the intensity of the main peaks at 300–500 nm. In addition, adding ascorbic acid can maintain relatively high and constant fluorescence intensity over a wide pH range (9-4).

Asian monsoon records are widely documented, but specific proxies of monsoonal rainfall are limited. We present here two new independent proxy records from peatland and stalagmite archives that indicate a high degree of concordance between monsoon-driven hydrological changes occurring since the last deglaciation in a broad region of central China. The wet periods elevated the water table in the Dajiuhu peatland, as recorded by reduced mass accumulation rates of hopanoids, biomarkers for aerobic microbes, confirmed by molecular phylogenic analyses. The hopanoid-based reconstruction is supported by the first report of the environmental magnetism parameter ARM/SIRM (anhysteretic remanent magnetization / saturation isothermal remanent magnetization; ratio of fine magnetic particles to total ferrimagnetic particles) in a stalagmite from Heshang Cave in central China. Heavy rainfall resulted in the enhanced transport of coarse particles to the cave and thus low ARM/SIRM values in the stalagmite. The hydrological conditions inferred from the two records reveal three relatively long wet periods in central China: 13–11.5 k.y. ago, 9.5–7.0 k.y. ago, and 3.0–1.5 k.y. ago. Archaeological evidence for the hydrological impacts on regional populations comes from the observation that temporal shifts among six distinctive cultures of the Neolithic Period to the Iron Age in central China occurred during wet periods or flood episodes. Spatiotemporal distributions of >1600 prehistoric settlement sites correlate with the proxy-inferred fluctuating hydrological conditions, with enhanced flooding risk forcing major relocations of human settlements away from riparian zones.

Thermoluminescence (TL) in marine carbonate has been proposed as a potential proxy for reconstruction of paleoceanography history, and has already been used in defining the Quaternary environment. However, its availability in the geological time scale, such as Permian, is still on debate. The mass extinction event caused by drastic changes of global marine environment in Middle-Late Permian provides a typical example to testify the applicability of this proxy. Here we measured the natural thermoluminescence of the carbonate-dominating marine sediments collected from the strata through the Guadalupian-Lopingian mass extinction boundary (G/LB) in the Penglaitan Section in Laibin, Guangxi, China. Our results reveal that TL intensities of carbonate are much higher than those of siliceous rocks, which indicates that the carbonate is the main contributor to the TL. The variation of TL intensities are related with Mn and Fe contents in the carbonate lattices while high Mn and low Fe (e.g., high Mn/Fe ratio) in carbonate will release stronger TL. Due to the better storage of carbonate lattices for original information of Mn and Fe in seawater, thermoluminescence of carbonate-dominating sediments/rocks could sensitively reflect marine environment and biological productivity in geological time scale.

a b s t r a c t Analyses of marine carbon isotope profiles have provided much of our current understanding of the evolution of Earth surface environments, particularly in the latter portion of the Proterozoic Eon. Earlier Mesoproterozoic successions, however, have received comparatively little attention due to the relatively subdued nature of carbon isotope variation. In this study, we present high-resolution isotopic profiles from three sections in the Yanshan Basin, North China craton that, combined, comprise the entirety of the early Mesoproterozoic (1600-1400 Ma, Calymmian period) Jixian Group. High-resolution profiles of both carbonate and organic carbon provide critical data for global comparison and permit us to better con- strain both the pattern and origin of isotopic variation in the Mesoproterozoic. Marine carbonate rocks of the Jixian Group show generally muted isotopic variation with average values near 0‰, consistent with previous observations from the early Mesoproterozoic. Data furthermore record an increase in isotopic variation through the succession that is interpreted to reflect a long-term decrease in pCO2 and, conse- quently, in the isotopic buffering capacity of marine dissolved inorganic carbon (DIC). By contrast, the isotopic composition of marine organic matter suggests facies-dependent differences in carbon cycling. Organic carbon compositions suggest a dominance of autotrophic carbon fixation and aerobic decom- position in shallow-water environments, and increased remineralization by anaerobic heterotrophs in deeper-water environments. Correlation between organic carbon composition and depositional environ- ment are interpreted to reflect differences in carbon cycling within benthic microbial mats under low oxygen conditions and dynamically maintained stratification of marine waters.

We present the first study of Ca isotope cycling in a natural cave system, with measurements of bedrock, dripwater and recently formed carbonate, coupled to a first stalagmite time-series spanning the 8.2 kyr event. Dripwaters at Heshang Cave (Central China; 30°27′N, 110°25′E) are isotopically heavy relative to the dolomite bedrock, the result of prior calcite precipitation (PCP) occurring earlier in the drip flow path. A simple Rayleigh fractionation model quantifies the extent of PCP in the modern environment at 36% Ca removal. The observed in situ calcium isotope fractionation factor between dripwater and carbonate is Δ 44 / 42 Ca = − 0.63 ± 0.03 ‰ and does not vary during the annual cycle. Measurements of speleothem carbonate spanning the 8.2 kyr event show the response of Ca isotopes to changing climate. δ44/42Ca increases by 0.35‰ at the onset of the event, coeval with changes in δ18O and Mg/Ca, and remains high for 80 yr. This change is explained by decreased rainfall leading to increased PCP; an interpretation supported by established PCP proxies (Mg/Ca, Sr/Ca and Ba/Ca). Ca isotopes indicate that PCP increased to 60% Ca removal during the event, which, from application of a simple box model, suggests mean annual rainfall decreased by approximately a third in Central China during the 8.2 kyr event. The response of Ca isotopes across this event demonstrates their potential for the assessment of past conditions, including past dripwater flow rates and rainfall.

The major processes responsible for the interplay of hydrothermal influence and paleo-depositional environments (paleoproductivity and plaeoredox condition) on the accumulation of organic matters can be better understood by integrating lithological and geochemical characteristics of samples from the well exposed Late Permian sediments in the Dalong Formation of the Shangsi Section, Northwest Sichuan Basin, South China: 1) The content of total organic carbon (TOC) ranging from 0.16% to 14.6% is closely related with the host lithology and high TOC contents prone to occur in intervals of siliceous rocks, dark shales, and laminated limestones that developed in deepwater intra-basin environments; 2) Non-detrital component elements and ratios (after Ti-normalized), e.g. Cuxs, Vxs / (Vxs + Nixs), for all samples and their correlations with TOC contents imprint the control of paleoproductivity level and paleoredox condition on the accumulation of TOC contents; 3) Characteristics such as original contents of Al, Fe, Mn, Th, U and their non-detrital origin values, non-biogenic contribution values (TiO2-normalized) of various elements, and the North America Shale Composite (NASC)-normalized Rare Earth Element (REE) Patterns of chert and shale samples are analyzed and compared to that of world average shales, classic hydrothermal and biogenic cherts, indicating hydrothermal contribution to siliceous rocks formation in the Dalong Formation of the Shangsi Section. Together with the discovery of volcanic ashes and bentonites in the Dalong Formation of the Shangsi Section, a new model has been proposed to explain the relationships of the hydrothermal activities and the organic matter accumulation process in the siliceous rocks in the Dalong Formation of the Shangsi Section: Hydrothermal contribution could cause a bio-thriving in surface water by providing nutrient elements and lead to a high primary productivity; With the organic matters sinking down, the anaerobic and anoxic conditions would control the organic matter accumulation during deposition and early diagenesis stage, which can imprint the organic carbon-rich siliceous rocks formation and the origin of high quality marine source rocks for hydrocarbon.

Evaluating the pre-Jurassic marine source rocks in China has been difficult because these rocks are generally too high- or over-maturated for most traditional methods to work. As to the remaining parameter TOC (%), its lower limit for recognizing the carbonate source rocks in China has been in dispute. Nineteen Phanerozoic sections in the Middle-Upper Yangtze Platform and the Guizhou-Hunan-Guangxi Basin have been studied in search for a different approach to complementing the traditional evaluation method for these source rocks. We have applied a geobiological approach to tracing the organic carbon (OC) output and accumulation from the living stage (primary productivity) to the post-mortem deposited remains, and finally to the preserved burial organics. Four biological and geological parameters are employed to represent the OC of the three stages. A series of proxies of these parameters are discussed and integrated to establish a geobiological evaluation system independent of TOC and other traditional methods. Here we use the Guangyuan section in Sichuan as an example for the geobiological evaluation. Our results indicate that in the argillaceous rocks, the geobiological parameters show the qualified source rocks in accordance with high TOC values; but in the carbonates, the good source rocks delineated by the geobiological parameters have a wide range of TOC, from 0.03% to 1.59%, mostly

In order to investigate how lipids in cave water respond to seasonal climate change, drip water samples were collected from 2006 to 2008 in Heshang Cave, central China for fatty acid analysis. These lipids are abundant in the drip water. Their compositions are dominated by lower-molecular-weight nC16:0, nC18:0 and nC14:0 acids, together with mono-unsaturated nC18:1, nC16:1 and nC14:1. Analysis of one water sample revealed marked differences between the dissolved and particulate fractions. The dissolved fraction contains total fatty acids one order of magnitude higher than that of the particulate fraction. The distributional patterns of the fatty acids suggest that microbes living in the overlying soils and/or groundwater system contribute most fatty acids to the drip water. This 2-a monitoring experiment reveals that the abundance of mono-unsaturated fatty acids relative to the saturated homologues (nC16:1/nC16:0 and nC18:1/nC18:0) relate inversely to the changes of synchronous external air temperature. Higher values occur under cold conditions (winter/spring), while lower values appear in warm intervals (summer). Further studies are needed to elucidate the dynamic processes by which the external temperature affects fatty acids in drip water and to confirm the potential application of fatty acid ratios such as nC16:1/nC16:0 and nC18:1/nC18:0 in paleotemperature reconstructions.

Stalagmite growth rates are usually considered to reflect changes in paleoclimate and paleoenvironment. However, how exactly growth rates are affected by climate and environment is still unclear. We launched a monitoring and modeling program that lasted approximately 4 years on two active drip sites in Heshang Cave, central China. We collected comprehensive quantitative data on growth rates, cave temperature, CO2 concentration, drip rate and drip-water chemistry to better understand the relationship between stalagmite growth and cave environment. By laying out glass substrates, we successfully grew stalagmite calcite crystals with rhombic characteristics, and quantified growth rates by measuring the long and short axes of calcite crystals under a microscope. Combined with coeval environmental data, we explicitly examined the roles of cave temperature, drip rate and drip-water chemistry in controlling the micro-scale growth of stalagmite calcite. Results show that growth of stalagmite calcite crystals at two drip sites exhibited similar seasonal variations − generally faster in the summer months, at ∼3 μm d−1, and slower during the late winter to early spring, at ∼1.5 μm d−1. Variations in calcite growth rates were mainly determined by changes in cave temperature, with the growth rate increasing by 8.1%/°C and 6.6%/°C at the two locations. This indicates the potential use of stalagmite growth rates as a seasonal-resolution paleo-temperature proxy in some ventilated caves. On the other hand, the effect of drip rate and drip-water Ca2+ and SIC values on growth rates were not significant.

A method was proposed for the determination of trace iron released from sulfides in geological samples.Iron was extracted and spectrophotometry measured by sulphosalicylic acid after sulfides were oxidized by sodium hypochlorite.The results show that 30% of sodium hypochlorite soaking the sample for more than 40 hours could transform iron sulfides completely into colloidal ferric hydroxide,which can be easily extracted by the sulphosalicylic acid solution.We integrate the selective sepatation,enrichment and determination of iron in the procedure to make the method simple and suitable for determination of iron sulfides in geological samples.

The internal-electrolysis (IE) process can be used as pretreatment to improve the biodegradability of yeast wastewater. The water before and after IE pretreatment was analyzed by UV, GPC, GC-MS to determine the changes in its chemical composition. The mechanism on the improvement of biodegradability by the IE process was discussed in two aspects according to the changes of chemical composition. (i) Some reactions occurred during the IE process, such as hydrolytic reaction, cracking, and redox reaction. Thus, the cyclic structure opened and changed into chains, and the macromolecular compounds were spilt to small molecule substances. All these reactions tended to simplify the structure of molecules and increase the donating electron groups so as to improve the biodegradability. (ii) The small molecule acids and alcohols in raw water or produced by the internal electrolysis process could be removed through volatilization and electrochemical adhesion, which was conducive to the removal of COD and the improvement of biodegradability of yeast wastewater.

A new method to estimate paleotemperature change is reported in this article. The authors successfully exploit the Xe/Ar ratio trapped in the fluid inclusion of stalagmites for reconstructing climatic evolution since the Last Glacial Maximum (LGM), in the middle reaches of the Yangtze River, where the East Asian monsoon prevails. A logarithmic expression namely ln( C Xe/ C Ar) proves to be bound up with warm/cold cycles. The δ 13 C and Mg/Ca curves drawn from the investigated stalagmites mostly follow the fluctuation of regional paleotemperature, but may be overprinted by other climatic signals. This study clearly states that among the diverse proxies, the Xe/Ar ratio recorded in the fluid inclusion is probably the best indicator, constantly mirroring the temperature variation. The ln( C Xe/ C Ar) profile on the whole shows an identification with those curves oscillating essentially between the warm and cold phases. After integrating the noble gas profile with the δ 13 C and Mg/Ca signals, the authors underline eight warm/cold cyclothems developed in the region under study since LGM. The pattern of the climate variation displayed by the integration is reasonable for interpreting the regional environment evolution during the last 20,000 years.

Hydrocarbon source rocks are characterized by the hydrocarbon discharge, and the alteration and variation in organic compositions and organic content due to the enhanced thermal maturation. These variations throw constraints on the application of the conventional inversion evaluation of hydrocarbon potential by assessing the residual organic matter left in source rocks. Geobiology, probing the interaction between the life system and the earth system, provides new principles in deciphering the whole dynamic processes related to the organic evolution history from living biomass to organic burial. Geobiological subdisciplines, including molecular geobiology, geomicrobiology, geoecology and biogeochemistry, offer new methodology and techniques to estimate the paleoproductivity, depositional organics and organic burial capacity and their components. Geobiofacies, newly proposed herein, is terminologized to define the geobiological dynamic processes through the combination of biofacies with organic facies and sedimentary facies, and expressed by the biohabitat types, paleoproductivity, depositional and preserved organics. Geobiofacies is identified as a useful means to create the geobiological evaluation system, which in turn rectifies the conventional evaluation system for the marine source rocks.

© 2015 Elsevier Ltd. Several recent studies have used records of the radiocarbon (14C) bomb peak in speleothems to inversely model the soil a 14CO2 and the age distribution of soil organic material (SOM) above caves, in part to investigate the potential of speleothems as sensitive records of past SOM dynamics. The results of these modeling studies have suggested that soil CO2 at karst sites is derived primarily from the decomposition of SOM with turnover times on the order of decades to centuries. This result is in stark contrast with observations of soil a 14CO2 at non-karst sites, which indicate that soil CO2 is derived primarily from root respiration and decomposition of SOM with much shorter turnover times. This discrepancy suggests that SOM in karst settings may have a very different age distribution than sites that have been studied previously and/or that soil CO2 is not the main source of speleothem carbon. To help resolve this discrepancy, we present an improved inverse model which we use to estimate the age of CO2 above several caves. We also present results from a detailed case study of soil carbon dynamics at Heshang Cave, China. This work demonstrates that SOM in karst sites may be much older than SOM in non-karst soils that have been studied previously, but that CO2 produced in the shallow soil zone is unlikely to be the main source of speleothem carbon. A review of the literature suggests that the most likely explanation for the aforementioned discrepancy is that decomposition of down-washed SOM in the vadose zone is the dominant source of speleothem carbon.

We report the presence of clear annual cycles in trace-element (Mg/Ca, Sr/Ca, Ba/Ca, and U/Ca) and stable-isotope (δ18O and δ13C) composition in an annually banded stalagmite from Heshang Cave, Hubei Province, China (30.44°N, 110.42°E). Through a combination of micromilling and in situ analysis (LA-MC-CPMS), we measured geochemical variations across 16 annual growth bands, to assess their potential as seasonal resolution paleomonsoon proxies. To facilitate comparison with modern climatic and environmental data we created composite annual cycles for each proxy by stacking 6 well-defined years. Speleothem δ18O variations (- 10.8‰ to - 8.5‰) are controlled by seasonal variations in temperature and drip-water δ18O which lead to maximum values during May, around the time of summer monsoon onset. This provides a chronological marker which can be used to constrain the timing of the other geochemical cycles. The composite cycles reveal a strong positive correlation between Mg/Ca, Sr/Ca, Ba/Ca, and δ13C values in the micromilled section (R2 = 0.65-0.98), with minimum values occurring around May. Maximum U/Ca values occur at the same time. We present simple models which show that these correlations, as well as the observed ranges of Mg/Ca (14.1 to 22.4 mmol/mol), Sr/Ca (0.2 to 0.4 mmol/mol), and δ13C (- 12.5 ‰ to - 10.7-), may be fully explained by progressive CO2 degassing and calcite precipitation from an initially saturated solution. Using realistic initial conditions for Heshang Cave (T = 18 °C, Mg/Casolution = 0.84 mol/mol, Sr/Casolution = 0.69 mmol/mol, δ13CTDIC = - 16.75‰), we find that the observed relationships can be produced by using DMg = 0.016 and DSr = 0.30, within the range of expected values. The model suggests that the fraction of Ca removed from the solution ranges from 0 to 30% to produce the observed seasonal cycles. This variation may be due to two related processes which occur during drier periods: (1) increased prior precipitation of calcite in the epikarst or on the cave ceiling, and/or (2) a greater degree of CO2 degassing and calcite precipitation on stalagmite surfaces when drip-rates are lower. Both mechanisms would have the effect of enriching speleothem Mg/Ca, Sr/Ca, Ba/Ca, and δ13C values during drier periods. Past variations in Heshang carbonate chemistry may therefore be useful as seasonal resolution proxies for past rainfall. © 2006 Elsevier B.V. All rights reserved.

Despite considerable work on other trace elements, the incorporation of dissolved silicon from cave waters into speleothems has not been previously investigated. In this study, the controls on dissolved Si in cave waters and on adsorbed Si in resulting speleothems are therefore investigated. Bedrock (dolomite), soil water, dripping water, and cave carbonates were retrieved from Heshang Cave situated in the central Yangtze valley of China and were subjected to analysis of dissolved Si content (plus accompanying Ca and Fe analyses). Soil waters have Si/Ca of 45.5 mmol/mol, compared to only 3.2 mmol/mol in the dolomite bedrock, demonstrating that >80% of the dissolved Si must come from dissolution of silicate minerals in the soil. Drip waters have a dissolved Si concentration of ≈4.2 μg/mL, similar to that in the overlying soil water. Actively growing cave carbonates have a Si/Ca of 0.075 mmol/mol suggesting a partition coefficient for incorporation of dissolved silicon of 0.0014, in good agreement with previous laboratory studies. Extrapolating the results of these laboratory studies to the cave environment suggests that changes in Si/Ca in cave carbonates are likely to be primarily controlled by changes in drip-water Si/Ca. The drip-water Si/Ca will, in turn, be controlled by the rate of wind-blown silicate supply; by soil weathering rates; by rainfall dilution; and by precipitation of calcite. The general expectation is that these effects combine to produce high Si/Ca in speleothems during times of low rainfall. A δ18O record from a Heshang Cave stalagmite which grew between 20 and 11 thousand years ago allows these controls to be tested. Correlation of high Si/Ca with high δ18O demonstrates that regional rainfall exerts significant (but not complete) control on speleothem Si/Ca. With further understanding, speleothem Si/Ca may provide a proxy for past rainfall to complement existing proxies such as δ18O and Mg/Ca. Copyright © 2005 Elsevier Ltd.

Lipid extracts from a 61.7-cm-long subtropical stalagmite in southern China, spanning the period of ca. 10,000–21,000 yr ago as constrained by U–Th dating, were analyzed using gas chromatography–mass spectrometry. The higher plants and microorganisms in the overlying soils contribute a proportion of n-alkanes identified in the stalagmite. The occurrence of LMW (lower molecular weight) n-alkanols and n-alkan-2-ones in the stalagmite was mainly related to the soil microorganisms. We suggest that HMW (higher molecular weight) n-alkanols and n-alkan-2-ones identified in the stalagmite originate from soil organics and reflect input from contemporary vegetation. Shifts in the ratio of LMW to HMW n-alkanols or n-alkan-2-ones indicative of the variation of soil ecosystems (e.g., microbial degradation of organic matter and/or the relative abundance of soil microorganisms to higher plants) are comparable with the subtropical alkenone-SST (sea surface temperature) record of the same period. The similar trends seen in the δ13C data and the lipid parameters in this stalagmite imply that the overlying soil ecosystem response to climate might be responsible for the variation of δ13C values.

Through a combined analysis of sedimentary characteristics, C and O isotopes, Mg and Sr trace elements of a stalagmite from Heshang Cave, Hubei, with uranium-series dating, alaeopalaeoclimatic and palaeoenvironmental information from 19.0ka to 6.9ka in the Hubei area is obtained. The Average resolution is 17a, and the local resolution is 7a. The following results are obtained: (1) from 19.0-16.6 kaBP: C and O isotope is lighter, the climate is cold and wet; (2) 16.6-11.1 kaBP: C, O isotope is a little heavy, temperature rises, rainfall is inclined to be little; (3) 11.1-10.3 kaBP: an excursion during dry and hot period responds to Younger Dryas Event; (4) 10.3-6.9 kaBP: C, O isotope is lighter, but Mg/Sr value is bigger, which shows temperature is continuing rising and rainfall is greater. These reflect the variation tends from wet-cold climate, to dry-hot climate, and to wet-warm climate in history, and some climatic variation trends of thousand years and hundred years cycle are got.

A stalagmite in Qingjiang, Hubei, has yielded the records of hydrogen and oxygen as well as carbon isotopic changes and provided a climate history of 9000 years. The hydrogen isotopic ratio in fluid inclusions and the oxygen isotopic ratio in stalagmite calcite are controlled by meteoric water, which is in response to ambient temperature or precipitation amount. The carbon isotopic ratio, sensitive to the nature of vegetation, also can be used to reconstruct the climate history. The carbon-14 and U-series dated stalagmite records reveal that climate oscillated in the middle reach of Yangtze river over the past 9000 years: (1) 9.0-6.5 kaBP, a cooler and more humid condition; (2) 6.5-4.0 kaBP, with warmer and drier weather; (3) 4.0-2.0 kaBP, cold weather with heavy precipitation, and (4) 2.0 kaBP to present, tendency to be warmer and drier.

A period of cooling in the North Atlantic region 8,200 years ago affected climate throughout the Northern Hemisphere. A speleothem record from central China indicates that a dry period lasting 150 years was associated with the 8,200 year event. An abrupt cooling event in the North Atlantic region 8,200 years ago affected climate throughout the Northern Hemisphere1,2,3. The event is well constrained in Greenland ice cores3, but lack of resolution in records from other regions has challenged our understanding of the timing and nature of the associated teleconnections. Speleothem records from East Asia have suggested monsoonal changes associated with the 8,200 year event, but the nature of these changes remains controversial1,2. Here we assess changes in East Asian precipitation during the event from a sub-annually resolved stalagmite record from central China. Using δ18O and Mg/Ca measurements of the speleothem carbonate, we show that climate dried significantly about 8,200 years ago. Based on our annual-layer-counted chronology, we show that the dry event lasted 150 years, with a central period of pronounced aridity that lasted 70 years. The duration and evolution of the event is indistinguishable from that observed in the Greenland ice cores. We therefore conclude that an effective and rapid atmospheric teleconnection exists between the North Atlantic and the monsoon system in warm climates similar to today’s.

Author(s): Hu, Chaoyong; Henderson, Gideon; Huang, Junhua; Chen, Zhenghong; Johnson, Kathleen | Abstract: Heshang Cave is situated in central China (30°27’N, 110°25’E; 294 m) in the middle reaches of the Yangtze Valley, a region strongly impacted by the East Asian Monsoon. It contains large annually-laminated Holocene and late Pleistocene stalagmites which capture past monsoon behaviour with seasonal resolution, and could enhance understanding of the amplitude and frequency of monsoon behaviour in different climate states. In this paper, we present results of a 3-year monitoring programme at Heshang. T loggers outside the cave agree closely with T data from nearby meteorological stations. T at the site of growth of the largest recovered stalagmite averages 18°C (identical to mean annual T outside the cave) with a seasonal amplitude of 5oC (about one fifth of the external cycle). Rainfall measurements from a station 3 km from the cave indicate strong summer monsoon rain in 2004 and 2005, but rather weaker summer rain (by ≈30%) in 2006. Drip rate at the monitoring site has a base flow of 14 drips/minute and shows a sharp increase to ≈40 drips/minute early in the summer rains of 2004 and 2005, followed by a gradual return to base-flow as the monsoon weakens. This abrupt change presumably represents threshold behaviour in the hydrological system. This threshold is not passed in 2006 and there is no abrupt increase in drip rate, indicating the sensitivity of this site (and presumably of speleothem chemistry in this cave) to monsoon rainfall. Results are also reported from a 10-month deployment of a Stalagmate drip counter, and for CO2 levels in Heshang Cave. Overall, this monitoring work represents an essential dataset for interpretation of the chemistry of drip waters, of carbonates grown on glass slides and, ultimately, of long speleothem records of past climate from Heshang Cave.

A reconstruction of Holocene rainfall is presented for southwest China — an area prone to drought and flooding due to variability in the East Asian monsoon. The reconstruction is derived by comparing a new high-resolution stalagmite δ 18 O record with an existing record from the same moisture transport pathway. The new record is from Heshang Cave (30°27′N, 110°25′E; 294 m) and shows no sign of kinetic or evaporative effects so can be reliably interpreted as a record of local rainfall composition and temperature. Heshang lies 600 km downwind from Dongge Cave which has a published high-resolution δ 18 O record (Wang, Y.J., Cheng, H., Edwards, R.L., He, Y.Q., Kong, X.G., An, Z.S., Wu, J.Y., Kelly, M.J., Dykoski, C.A., Li, X.D., 2005. The Holocene Asian monsoon: links to solar changes and North Atlantic climate. Science 308, 854–857). By differencing co-eval δ 18 O values for the two caves, secondary controls on δ 18 O (e.g. moisture source, moisture transport, non-local rainfall, temperature) are circumvented and the resulting Δ δ 18 O signal is controlled directly by the amount of rain falling between the two sites. This is confirmed by comparison with rainfall data from the instrumental record, which also allows a calibration of the Δ δ 18 O proxy. The calibrated Δ δ 18 O record provides a quantitative history of rainfall in southwest China which demonstrates that rainfall was 8% higher than today during the Holocene climatic optimum (≈ 6 ka), but only 3% higher during the early Holocene. Significant multi-centennial variability also occurred, with notable dry periods at 8.2 ka, 4.8–4.1 ka, 3.7–3.1 ka, 1.4–1.0 ka and during the Little Ice Age. This Holocene rainfall record provides a good target with which to test climate models. The approach used here, of combining stalagmite records from more than one location, will also allow quantification of rainfall patterns for past times in other regions.