Environment change of Sihu Lake in the past 450 years, southern China

In recent years, climate and environment changes since the Little Ice Age have become a focus in modern research. The paper selected the sediment (77 cm) of Sihu Lake, which was located in Guilin, southern China, as the research object and analyzed the karst wetland environmental changes within nearly 450 years. According to the vertical profile of indicators and geochemical elements in sediment core, the regional environmental evolution was divided into four stages. The former two stages were mainly influenced by Little Ice Age (1562–1895). The third stage climate has changed slowly. The fourth stage was mainly affected by human activities and global warming. The factor analysis of geochemical elements indicated that karst wetland regional environmental change was affected by four major factors. In the 53–77 cm stage (1562–1703), F1 (erosion factor), F2 (watershed runoff and diagenesis factor) and F3 (regional background factor) were reduced, indicating that it was in cold and dry stage of Little Ice Age. In the 20–53 cm stage (1703–1895), F1 and F2 increased, indicating that it was in cold and wet stage of Little Ice Age. In the 4–20 cm stage (1895–1987), F1, F2 and F4 (human activity factor) increased slowly, indicating that the climate was affected by global warming and more precipitation. In the 0–4 cm stage (1987–2007), F1 and F2 reduced and F4 increased, indicating the reduced precipitation, rising temperature and more impact of human activities. In addition, it was proposed that the Little Ice Age in Guilin District in southern China started in the 1560s and lasted until the 1895s or so.     

Environmental evolution and hydrodynamic process of Dongping Lake in Shandong Province, China, over the past 150 years

Sporopollen, when recorded in the sedimentary record, is a characterization factor of vegetation over geological time of an area; the grain-size characteristics are direct reflection of the hydrodynamic conditions. Based on analyses of high-time resolution sporopollen and grain size of a 55-cm-long sediment core of Dongping Lake, it is shown that the sedimentary environment and hydrodynamic processes of Dongping Lake have seen significant changes over the past 150 years. From 1855 to 1865, the lake is in a hydrostatic depositional environment, where submerged plants were in great abundance, emergent and floating-leaved aquatic plants were comparatively fewer, and reworked sporopollen fossils were not observed. These indicate a weak and stable hydrodynamic condition during this stage. However, fluctuation of Mz, amounts of clay and silt were present, which may be due to high volumes of sediments around Dongping Lake basin transported into Dongping Lake via the Yellow River during the early lake-forming stages. From 1865 to 1922, the lake is in a backswamp depositional environment, where aquatic plants are nearly nonexistent, appearing occasionally in some layers with relatively low abundance. Fern spores show a twofold increase in occurrence and reworked sporopollen fossils are frequently identified. All of these indicate a strong hydrodynamic condition and frequent environmental change. Grain-size characteristics also support this interpretation. From 1922 to 1961, aquatic plants appeared at the upper layers of this zone at relatively low amounts, and reworked sporopollen fossils were frequently identified. Grain-size characteristics show an obvious change in grain-size distribution, indicating a strong hydrodynamic condition and unstable depositional environment. These relationships were attributed to a backswamp depositional environment. From 1961 to 2007, Dongping Lake is in a hydrostatic depositional environment, where the hydrodynamic condition is weak and stable. Evidence for this is shown by a remarkable increase in submerged plants, a rapid decrease in fern spores, and occasional appearances of reworked sporopollen fossils in the lower part of the zone. However, grain-size characteristics reveal that fluctuation of Mz, amounts of clay, silt and sand are noticeable and frequent, which may be mainly related to impacts of ever-enhancing human activities in recent years.     

Streamflow changes and its influencing factors in the mainstream of the Songhua River basin,Northeast China over the past 50 years

The Songhua River plays a key role in the national development of China, owing to its unique natural condition and resources. Recent changes in the streamflow in the Songhua River are important with regard to local sustainable development and management under the background of global warming and aggravating soil erosion. In order to detect changes in the streamflow, two streamflow series from 1955 to 2004 (observed at the Harbin and Jiamusi stations) in the mainstream of Songhua River basin were obtained, and methods of statistical analysis, wavelet transform, and double mass analysis were employed to analyze the data. Reasons for the changes to the streamflow are discussed with respect to natural and man-made drivers. The results show the following: (1) From 1955 to 2004, the streamflow series present obvious declining trends. (2) The streamflow series followed the pattern of a wet–dry–wet–dry cycle pattern over the past 50 years. In the mainstream of Songhua River, wet years mainly occurred during the periods of 1955–1966 and 1984–1993, while dry years mainly occurred in the 1970s and after 2000. (3) Within the 50-year scale, the streamflow series appeared in the main periods of circa 33-, 13- and 4-year, in which the 33-year periodicity is the strongest. (4) Precipitation and temperature directly influenced the streamflow in the mainstream of the basin. The discharge was positively correlated with the precipitation and negatively correlated with the temperature. In addition, human activity was another important driving factor for streamflow change. (5) In the mainstream of Songhua River basin, the influences on streamflow can be divided into three periods: 1955–1976, 1977–1997, and 1998–2004. In the first period climate change played a dominant role, and during the latter two periods human influences were enhanced significantly.     

Study on rainfall variations in the middle part of Inner Mongolia,China during the past 43 years

The study area, the middle part of Inner Mongolia including Hohhot city, Baotou city, Wulanchabu city, Ordos city, Bayannaoer city and Wuhai city, is one of typical eco-geographical transition zones in China. Using monthly precipitation data (1961–2003) from 45 meteorological stations in the study area, this paper analyzes characteristics and tendencies of annual and seasonal rainfall variations, and reveals multi-time scales structures of these time series through wavelet analyses; also, the periods of annual and seasonal precipitation series are identified, and the periodical oscillations and points of abrupt change at the principal period scale are discovered. The results show that annual precipitation varies in a large range, and has an ascending tendency at an increasing rate of 1.482 mm/10a; the multi-time scales periodical oscillations are clear; differences in tendencies, ranges and decadal precipitation anomalies exist within each decade during 1961–2000. The seasonal allocation of overall annual precipitation is extremely uneven; in terms of tendencies of seasonal precipitation, winter and spring have upward trends while summer and autumn have downward tendencies; distinctions in tendencies, ranges and decadal precipitation anomalies among each seasons are in existence within each decade during 1961–2000. The periodical oscillations of each seasonal precipitation time series are also evident. The research results not only provide convincing evidence for global climate change research, but also facilitate the understanding of specific natural process and pattern to make steps to rehabilitate and reconstruct vegetation, and contribute to fulfill the sustainability of water management.     

Climate and environmental changes over the past 150 years inferred from the sediments of Chaiwopu Lake, central Tianshan Mountains, northwest China

We used a 55-cm sediment core from shallow Chaiwopu Lake in the central Tianshan Mountains of Xinjiang, northwest China, to investigate climate and environmental changes in this arid region over the past ~150 years. The core was dated using ¹³⁷Cs. We compared temporal changes in several sediment variables with recent meteorological and tree-ring records. Organic matter had a positive correlation with the Palmer Drought Severity Index in the central Tianshan Mountains, and the δ¹³C of organic matter had a positive correlation with regional temperature. We applied constrained incremental sum-of-squares cluster analysis to element concentrations in the core and identified three distinct zones: (1) 55–46 cm, ~1860–1910, (2) 46–26 cm, ~1910–1952, and (3) 26–0 cm, 1952–present. Between 1880 and 1910 AD, following the Little Ice Age (LIA), the sediment environment was relatively stable, climate was cold and dry, and the lake water displayed high salinity, in contrast to conditions during the LIA. During the LIA, westerlies carried more water vapor into Central Asia when the North Atlantic Oscillation was in a negative phase, and encountered the enhanced Siberia High, which probably led to increased precipitation. In the period 1910–1950 AD, the lake was shallow and the regional climate was unstable, with high temperatures and humidity. In the last ~15–20 years, human activities caused an increase in sediment magnetic susceptibility, and heavy metal and total phosphorus concentrations in the sediment were substantially enriched. Mean annual temperature displays a warming trend over the past 50 years, and the lowest temperature was observed in the 1950s. There has been an increase in annual total precipitation since the 1990s. The combined influences of climate and human activity on the lake environment during this period were faithfully recorded in sediments of Chaiwopu Lake. This study provides a scientific basis for environmental management and protection.     

High-resolution sedimentary record of lead in the coastal mud of the East China Sea in the past one hundred and fifty years

In the East China Sea （ECS）, there are some mud areas, including the south coastal mud area, the north coastal mud area, and the mud area to the southwest of Cheju Island. X-ray fluorescence （XRF） techniques and Thermal Ionization Mass Spectrometry （TIMS） were used to study the high-resolution sedimentary record of Pb concentrations and Pb stable isotopic compositions in the past one hundred and fifty years in the coastal mud of the ECS. Pb concentrations of a ^210Pb dating S5 core in the study area have increased rapidly since 1980, and reached the maximal value with 65.08 μg/g in 2000, corresponding to the fast economic development of China since the implementation of the ＂Reform and Open Policy＂ in 1978; ^206Pb/^207Pb ratios generally had stabilized at 1.195 from 1860 to 1966, and decreased gradually from 1966 to 2000, indicating that the anthropogenic source Pb contribution to the ECS has increased gradually since 1966, especially since 1980. Pb concentrations decreased distinctly from 2000 to 2003 and ^206Pb/^207Pb ratios increased from 2001 to 2003, corresponding closely to the ban of lead gasoline from 2000 in China. From 1950 to 2003, there occurred four distinct decrease events of ^206Pb/^207Pb, possibly responding to the Changjiang River （Yangtze River） catastrophic floods in 1998, 1991, 1981 and 1954; from 1860 to 1966, there were two decrease periods of ^206Pb/^207Pb, which may respond to the catastrophic floods of Changjiang River in 1931 and 1935, and 1870. As a result of the erosion and drowning by the catastrophic floods, the anthropogenic lead accumulated in soil and water environments over a long period of time was brought into the Changjiang River, then part of them was finally transported into the ECS, which leads to changes in Pb stable isotopic composition.     

New volcanological and volatile data provide strong support for the continuous existence of Galápagos Islands over the past 17 million years

The first systematic rock sampling of volcanoes along the Galápagos hotspot tracks (the aseismic Cocos, Carnegie, Malpelo and Coiba ridges and adjacent seamounts) in the area between the Galápagos Islands and Central and South America was carried out on R/V Sonne cruise 144-3. Guyot-shaped seamounts, paleo-beach or intertidal wave-cut platform deposits, the structure and texture of volcanic rocks, and low sulfur contents of fresh glasses dredged at these volcanoes imply that ocean islands existed continuously above the Galápagos hotspot for at least the past 17 million years. These new data significantly extend the time period over which the unique endemic Galápagos fauna could have evolved, providing a complete solution to the long-standing enigma of the evolution of Galápagos land and marine iguanas.     

REE Geochemistry of Loess in Xinjiang ,China

The total rare-earth element values(ΣREE)of loess in the Xinjiang region vary over a range of 128-200 ppm ,with an average of 153ppm .The average REE content of loess lies between the earth‘s crust (155ppm) and sedimentary rocks(151ppm).The Xinjiang loess,with the REE distribu-tion patterns characterized by negative slopes ,is rich in the Ce-family elements, and has a distribu-tion pattern characteristic of sedimentary rocks.The North Xinjiang loess is relatively depleted in Tb,but rich in Yb and Lu.The South Xinjiang loess is relatively rich in light rare-earth elements.This is full proof that the Xinjiang loess comes partly from weathered materials(clay rock,sandstone)in the region studied.The REE distribution patterns in the Xinjiang loess are similar to those in the precipitated dust and Aeolian sand,indicating the same material source.The REE distribution pat-terns in the Xinjiang loess are also similar to those in loess from the middle Yellow River Valley,China and Taskent,the former USSR.This implies that loesses of the three locations(Xinjiang,the mid-dle Yellow River Valley and Taskent) come from a common material source.But the REE patterns in the Xinjiang loess are different from those in wall rocks (volcanic rock,K-bearing volcanic rock).Generally ,LREE/HREE,Eu/Eu* and Ce/Ce* ratios reflect the features of parent materials of loess,indicating that the parent rocks were probably in the early stage of alkaline weathering and the weathered materials existed in an oxidation environment with basic mediums under arid-climatic conditions before transport.As a result,the migration ability of the REE is weak.     

U-Pb Ages of the Late Early Cretaceous Magmatic Rocks in the Zhalantun Area of Inner Mongolia

A great deal of early-to-mid Early Cretaceous magmatic activities have been recorded in the Zhalantun area of Inner Mongolia,while the late Early to Late Cretaceous magmatic rocks have been barely reported(Guo et al.,2018;Zhang Xiangxin et al.,2017).At present,only a few Late Cretaceous magmatic activities were reported in the Arongqi area,such as volcanic rocks of the Gushanzhen Formation.However,the Gushanzhen Formation lacks accurate isotopic age,and contemporaneous intrusive rocks has not been reported yet.In this work,we collected the volcanic rocks from the Gushanzhen Formation and contemporaneous intrusive rocks in the Zhanlantun and nearby,and aim to figure out the formation ages of volcanic rocks of the Gushanzhen Formation and accompanied intrusive rocks by analyzing zircon U-Pb isotopes(Fig.1).     

Hydrogeochemical characteristics of groundwater and pore-water and the paleoenvironmental evolution in the past 3.10 Ma in the Xiong’an New Area,North China

The groundwater level has been continuously decreasing due to climate change and long-time overexploitation in the Xiong’an New Area, North China, which caused the enhanced mixing of groundwater in different aquifers and significant changes in regional groundwater chemistry characteristics. In this study, groundwater and sediment pore-water in drilling cores obtained from a 600 m borehole were investigated to evaluate hydrogeochemical processes in shallow and deep aquifers and paleo-environmental evolution in the past ca. 3.10 Ma. Results showed that there was no obvious change overall in chemical composition along the direction of groundwater runoff, but different hydrochemical processes occurred in shallow and deep groundwater in the vertical direction. Shallow groundwater (< 150 m) in the Xiong’an New Area was characterized by high salinity (TDS > 1000 mg/L) and high concentrations of Mn and Fe, while deep groundwater had better water quality with lower salinity. The high TDS values mostly occurred in aquifers with depth < 70 m and >500 m below land surface. Water isotopes showed that aquifer pore-water mostly originated from meteoric water under the influence of evaporation, and aquitard pore-water belonged to Paleo meteoric water. In addition, the evolution of the paleoclimate since 3.10 Ma BP was reconstructed, and four climate periods were determined by the δ¹⁸O profiles of pore-water and sporopollen records from sediments at different depths. It can be inferred that the Quaternary Pleistocene (0.78–2.58 Ma BP) was dominated by the cold and dry climate of the glacial period, with three interglacial intervals of warm and humid climate. What’s more, this study demonstrates the possibilities of the applications of pore-water on the hydrogeochemical study and further supports the finding that pore-water could retain the feature of paleo-sedimentary water.© 2021 China Geology Editorial Office.     

A Comparison of the Geochemical Features of Some Loess Sections in New Zealand and China

A comparison of the geochemical features of loesses of New Zealand and China indicates that the distributions of the elements and their variations reflect the fluctuations of climate which can be compared with the oxygen isotope stages and glacial periods.New Zialand loess is different in source from Chinese loess.Therefore ,some differences are also noticed in their chemical compositions .Loess accumulation in New Zealand is later than that in China.Because of more rainfall in New Zealand and different distributions of loess the elements in loess have suffered stronger leaching than in China.     

Biomarkers in the Molar Tooth （MT）-Bearing Limestones in the Jilin-Liaoning Area of China

The origin of Molar Tooth (MT) carbonates has been argued for more than 100 years, which are a kind of Proterozoic carbonates especially composed of microsparite with ptygmatically folded and sheet-like structures. Biomarkers detected in the microcalcsparite from the Wanlong and Xingmincun formations in the Jilin-Liaoning area showed there are abundant normal alkanes, isoprenoids, hopanes, steranes, alkylmethylcyclohexanes, and alkyleyclohexanes, indicating a diversity of biological source: long-chain isoprenoids, the major components of chlorophyll, such as C19, C20, a kind of major biomarkers synthesized early by isoprenoid monomers; hopanes a type of characteristic biomarkers from prokaryote, such as archaebacteria and cyanobacteria; sterane a biomarker for eukaryote; and two kinds of alkanes with C17, C18 as the main peaks representing aquatic bacteria and with C23, C24 as the main peaks representing fungi, respectively. Biomarker analysis showed that MT is the result of bacterial and algal activities, which is a kind of organisms between aerobic and anaerobic bacteria, reproducing well in normal or slightly saline sea water under weak oxidation-reduction conditions, resulting in rapid deposition of calcite as microsparite clue to some mechanisms.     

Mineral Composition of Loess—Paleosol Samples from the Loess Plateau of China and Its Environmental Significance

34samples of loess-paleosol from the Luochuan and Xifeng sections in the Loess Plateau,northern China were eparated into sand,silt and clay fractions and analyzed for their mineral compositions.The results indicate that there is almost no difference between loess and paleosol in mineral composition.Major mineral species are quartz,mica,feldspar and chlorite,accounting for about 88-92% of the total;other minerals are kandite,smectite,vermiculite and a few heavy minerals.The calcite,magnetite and hematite were not taken into consideration because of their removal in the process of sample preparation.The main difference with respect to the mineral composition of samples collected from different sections and different statigraphic levels lies in the amount and grain size of minerals hosted.Comparisons between the Luochuan section and the Xifeng section,between paleosol and loess and between the upper part and the lower part of some paleosol layers show that the formers contain less feldspar but more mica and vermiculite and are finer in grain size,indicating the co-occurrence of both biochemical weathering process responsible for mineral change and physical weathering process leading to grain-size change during the soil-forming processes.This result favours such an explanation of the soil-forming mechanism that loess deposition and paleosol development occurred synchronously,though the rate of soil formation was greater than that of loess deposition,thus leading to soil development.     

Groundwater level fluctuation in the Waimea Plains, New Zealand: changes in a coastal aquifer within the last 30 years

Data for the Waimea Plains, New Zealand indicate that the lower confined groundwater aquifer is hydraulically homogeneous and that shallow groundwater levels inland are affected mostly by anthropogenic processes, while those near the coast are affected more by sea level variation. Analysis of long-term data for New Zealand indicates that sea level has increased continuously, but trends are not spatially uniform. Results from non-parametric trend analysis show that rising trends for groundwater levels are predominant in the shallow aquifer both inland on the Waimea Plains and, for recent years, near the coast, while decreasing trends are evident in the underlying confined aquifer near the coast. Groundwater level change in the shallow aquifer appears to be more affected by climate change than the lower confined aquifer. Correlation analysis indicated that groundwater levels are more affected by rainfall during the rainy season than the dry season and more influenced by rainfall inland than near the coast. Groundwater level declines in the lower confined aquifer near the coast, which has its major recharge area inland in the catchment, may be substantially affected by groundwater abstraction in inland areas as well as sea level variation, but there are little evidences of seawater intrusion. Meanwhile, groundwater recharge over the catchment area has great influence on rising groundwater levels in the shallow aquifer and its recharge is estimated to be 417.8 mm/year using chloride concentrations of precipitation and groundwater.     

Characteristics of the changes in tropical cyclones influencing the South Korean region over the recent 10 years (2001–2010)

Through the investigation of tropical cyclone (TC) characteristics related to climate change, this study found that the frequency of TCs occurring over the Western North Pacific has recently decreased slightly, while their average intensity has increased. The number of overall TCs that passed within the vicinity of South Korea has also been reduced, but the number of strong typhoons in the area, those with maximum wind speeds of more than 44 m/s, has significantly increased. These changes are closely related to the following phenomena. (1) The average genesis region of TCs that influence South Korea has moved eastward. Accordingly, the TCs tend to strengthen as they move westward for long distances along the Intertropical Convergence Zone (ITCZ) trade easterlies and the southern boundary of the North Pacific Subtropical High (NPSH). (2) The NPSH and Asia Monsoon trough, which are known to affect TC tracks, have extended to the northwest and southeast. This has caused TCs that travel to higher latitudes and curve back toward the Korean Peninsula to become more frequent. (3) TCs have approached the Korean Peninsula without hitting land. In addition, the sea surface temperature became higher than it was before. These factors have caused TCs to maintain their strength or become stronger than before.     

Functional Spectral Analysis of Paleoclimatic Evolution in Lanzhou Area over the Last 15 ka

In this paper, we make use of the functional spectral analysis to infer the periodicity of paleoelimate in the Hongzuisi section since about 15 ka. Through combined analysis of organic carbon isotope and CaCO3 content, the law of paleoclimatic evolution of the Hongzuisi section is obtained. There were climatic changes from 10 ka to about 0.1 ka over the last 15 ka. Among these cycles, the cycle of several ka is most remarkable. The result indicates that functional spectral analysis is helpful for paleoclimatic study, which can provide useful information about paleoclimatic reconstruction and future forecast.     

Monitoring climate variability over the past 116 years in coral oxygen isotopes from Ningaloo Reef, Western Australia

 116-year record of coral skeletal δ¹⁸O is presented from a colony of Porites lutea from Ningaloo Reef, western Australia. Interannual variability of sea-surface temperatures (SST) inferred from skeletal δ¹⁸O is dominated by a 9.5-year period, and may constitute a characteristic signal of the Leeuwin Current. On long-terms coral skeletal δ¹⁸O indicates a near-continuous increase of SST at Ningaloo Reef over one century. The skeletal δ¹⁸O time series was checked for the presence of seasonal cooling events resulting from major volcanic eruptions. An ∼1  °C cooling is evident following the eruption of Pinatubo in 1991, which reproduces the results of previous investigations. However, only weak or no signals can be related to the eruptions of Krakatau (1883) and Agung (1963). Received: 9 November 1998 / Accepted: 12 April 1999     

Correlation of the largest craters,stratigraphic impact signatures,and extinction events over the past 250 Myr

The six largest known impact craters of the last 250 Myr(≥70 km in diameter),which are capable of causing significant environmental damage,coincide with four times of recognized extinction events at 36(with 2 craters),66,and 145 Myr ago,and possibly with two provisional extinction events at 168 and215 Myr ago.These impact cratering events are accompanied by layers in the geologic record interpreted as impact ejecta.Chance occurrences of impacts and extinctions can be rejected at confidence levels of99.96%(for 4 impact/extinctions)to 99.99%(for 6 impact/extinctions).These results argue that several extinction events over the last 250 Myr may be related to the effects of large-body impacts.