Application of long-chain alkenones and U_(37)~k values for paleotemperature estimation in the Arctic Chukchi Sea-Bering Sea area

Long-chain alkenones were detected in samples of sea surface sediments from the Chukchi Sea and the Bering Sea areas, the Arctic Pole. The analysis result indicates that C37:3 methylketone is predominate in the long-chain alkenones from the Chukchi and Bering Sea sediments. The abundance of C37 to C39 unsaturated alkenones changes in an order of C37 > C38 > C39. Based on C37 /C38 ratio, the detected organism precursors of the long-chain alkenones are mainly coccolithophrid (Emiliania huxleyi). By the calibration relationship between U37k and U37k indices, the sea surface paleotemperature in these seas is estimated. The estimated values of U37k vary from 4.147℃ to 5.706℃ , with a mean value of 5.092℃.

A METHOD TO ESTIMATE PALEOTEMPERATURE FROM ENVIRONMENTAL PROXIES IN LAKE SEDIMENTSDISSOLVED AND PARTICULATE ORGANIC CARBON IN YANTAI SISHILI BAY AQUICULTURE WATERS——A STUDY ON ZOIGE BASIN IN EASTERN TIBETAN PLATEAU,CHINA

Seeking for an effective method to probe further the relation among Tibetan Plateau, climatic events, and natural environmental changes in the Zoige Basin, we proposed a physical model for the reconstruction of climate and environment and a preliminary application was conducted on the 45 m (about 200 ka BP ), upper part of Core RM (310 m long) drilled in the Zoige Basin (33°57’N, 102°21’E), on the eastern Tibetan Plateau. The results showed that: a) in the Zoige region, the maximum temperature in the period equivalent to Stage 7 in the deep sea stable oxygen record was 2.7℃ higher than that at present; b) Stage 6 temperature was 4.3℃ lower than that at present; c) Stage 5 peak temperature was 5.2℃ higher than that at present; d) Stage 4 average temperature should have been 2-3℃ lower than that at present; and e) Stage 3 temperature differences within the period were more than 4℃. It was found that during Stage 6 (140-160 ka BP) the environment in the Zoige Basin was extraordinary, representing a transition period from warm dry and cold wet to warm wet and cold dry environmental conditions due to the uplift that occurred on the Tibetan Plateau at this period.

PALEOTEMPERATURE BY APATITE FISSION TRACK IN THE ORDOS BASIN, NW CHINA

The effective heating time for apatite fission track ranges from 200 to 300 Ma in the Ordos Basin. The annealing zone in the western margin of the basin is shallow and wide,having its paleotemperature gradient (1. 5-2. 1 ℃ /100m) less than that (1. 9-2. 5 ℃ /100m) of the present time, while the annealing zone in main part of the basin is relatively deep and narrow, having its paleotemperature gradient (3. 8-4. 7℃ /100m) much bigger than that (2. 0-3. 1℃/100m) of the present time. The results of the apatite fission track analysis shows that there are three times tectonothermal events (215 Ma. 135 Ma and 72 Ma) in Ordos basin since late Paleozoic.

Late Holocene brGDGTs-based quantitative paleotemperature reconstruction from lacustrine sediments on the western Tibetan Plateau

We present a quantitative mean annual air temperature(MAAT)record spanning the past 4700 years based on the analysis of branched glycerol dialkyl glycerol tetraethers(brGDGTs)from a sediment core from Xiada Co,an alpine lake on the western Tibetan Plateau(TP).The record indicates a relatively stable and warm MAAT until 2200 cal yr BP;subsequently,the MAAT decreased by~4.4℃ at~2100 cal yr BP and maintained a cooling trend until the present day,with centennial-scale oscillations centered at~800 cal yr BP,~600 cal yr BP,and~190-170 cal yr BP.MAAT decreased abruptly at~500-300 cal yr BP and reached its minimum for the past 4700 years.We assessed the representativeness of our record by comparing it with 15 published paleotemperature records from the TP spanning the past~5000 years.The results show divergent temperature variations,including a gradual cooling trend,a warming trend,and no clear trend.We suggest that these discrepancies could be caused by factors such as the seasonality of the temperature proxies,the length of the freezing season of the lakes,the choice of proxy-temperature calibrations,and chronological errors.Our results highlight the need for more high-quality paleotemperature reconstructions with unambiguous climatic significance,clear seasonality,site-specific calibration,and robust dating,to better understand the processes,trends,and mechanisms of Holocene temperature changes on the TP.

Quantitative reconstruction of the lake water paleotemperature of Daihai Lake, Inner Mongolia,China and its significance in paleoclimate

By measuring Sr/Ca ratios of the ostracod shells (Limnocthere cf. inopinata) in sediments of the Daihai Lake, and combined with Sr2+/Ca2+ ratios of the lake water, this paper obtained paleosalinity of the lake water. Vaporizing experiment of the lake water in laboratory showed that there was a quantitative relationship between salinity and oxygen isotope. Using this relationship, oxygen isotope values of the paleo-lake water were calculated. By measuring the oxygen isotope of the authigenic carbonate in the lake’s sediments, and in combination with the oxygen isotope values of the paleo-lake water, the paleotemperature of the lake water was calculated. Finally, based on these proxies, the paleoclimate in the lake basin was explored.

Distribution of microbial fatty acids and fatty alcohols in soils from an altitude transect of Mt. Jianfengling in Hainan, China: Implication for paleoaltimetry and paleotemperature reconstruction

The temperature gradient along the altitude transect of Mt. Jianfengling provides a good opportunity to establish and evaluate the microbial lipid-based environmental proxies. The soils collected from 14 different altitudes of Mt. Jianfengling contain abundant microbial fatty acids and fatty alcohols, including iso/anteiso fatty acids （i/aC12：0-i[aCl9：0）, 10-Me-C16：0 fatty acid, iso/anteiso fatty alcohols （i/aC13-iC26）, 10-Me-C16：0 fatty alcohol and unsaturated fatty alcohols, which can indicate a strong microbial activity in the Jianfengling soils. The branched and unsaturated fatty alcohols can be only detected when saponifica- tion is performed, implying that these lipids are present as the constituents of bacterial wax esters in the soils. The ratio of aC15/iC15 fatty acids is positively correlated with altitude, suggesting that the decrease in temperature can induce the increase in the relative abundance of anteiso C^5 fatty acid. In contrast, the ratio of aCJiC15 fatty alcohols and of aCjs/nC15 fatty alco- hols both decrease with increased altitude or decreased temperature. Similarly, the ratio of nC18：l/nCi8：0 fatty alcohols also de- creases with decreased temperature, which is opposite to the previous observation that unsaturation of fatty acids in microor- ganism increases in response to decreased temperature. Besides, the average chain length （ACL） of long chain fatty alcohols （C22-C30） from leaf waxes and carbon preference index （CPI） of all n-fatty alcohols are also significantly correlated with alti- tude or mean annual temperature, demonstrating their potential for paleoclimate reconstruction. The correlation of microbial fatty acids and alcohols as well as ACL and CPI of plant wax-derived fatty alcohols with altitude may provide novel ways to reconstruct paleotemperature and paleoaltimetry.

Comparison of paleotemperature reconstructions using microbial tetraether thermometers of the Chinese loess-paleosol sequence for the past 350000 years

The recently proposed global and local calibrations for the mean annual air temperature(MAT) reconstruction on the basis of 5-and 6-methyl brGDGTs have rarely been applied to the Chinese LPS yet, leaving the applicability of these calibrations unclear. Here, we used the improved chromatography method to analyze 198 loess-paleosol samples from the Weinan section in the southern CLP for the past 350 kyr. The 6-methyl brGDGTs comprise a major proportion of total brGDGTs, pointing to alkaline conditions for most soil samples from the Weinan LPS. The decoupled profile variation of MBT′6ME and MBT′_(5ME) suggests their response to different enviromental factors, possibly soil pH(or soil moisture) and temperature, respectively. This discrimination further corraborates that temperature and monsoonal precipitation were not in phase during the last four deglaciations on the CLP. Temperature estimates for the six calibrations tested show similar trends but remarkably differ in amplitudes. The soil moisture appears to affect the global MBT′/CBT calibration, the global MATmr calibration(a calibration based on the multiple linear regression) and the Chinese local SSM(Stepwise Selection Method) calibration, resulting in a significant underestimation of late Holocene temperature. In contrast, the dry climate has no effect on the global MBT′5ME calibration. Of the six calibrations,only the Chinese local SSM calibration and global MATmr calibration produce temperature variation amplitude over the past 350 ka that is consistent with other independent proxy data. The recently proposed local calibrations based on 5-and 6-methyl brGDGTs for North China yield the amplitude of temperature changes that is much larger than the results determined by other approaches.All the six calibrations have their own weakness in the MAT reconstruction, due partly to the inconsistency between the brGDGT distribution in the Weinan LPS and the modern soils used to establish these calibrations.

A new method based on vitrinite reflectance gradient to determine paleotemperature gradient of a petroleum-bearing basin

Based on the Arrhenius equation and Karweil method, a simulation calculation has been made on the thermal maturation of organic matter under a series of assuming paleotem-perature gradients. Results show that there was a positive correlation of vitrinite reflectance gradient with paleotemperature gradient and vitrinite reflectance. According to this, a model

Roadian-Wordian(Middle Permian)Conodont Biostratigraphy,Sedimentary Facies and Paleotemperature Evolution at the Shuixiakou Section,Xikou Area,Southeastern Qinling Region,China

Focusing on the Shuixiakou Section(Xikou area,Zhen’an County,Shaanxi Province,southeastern Qinling region,China),the Roadian-Wordian conodonts are investigated.More than 2000 conodont elements including 6 genera and 14 species have been obtained.Based on these materials,the Guadalupian Jinogondolella nankingensis and J.aserrata zones have been recognized.The Roadian-Wordian boundary is tentatively defined by the first occurrence of J.aserrata in the lower part of UnitⅢin the Shuixiakou Formation.The sedimentary succession of Xikou area records similar sea-level changes to those observed in Laibin area(South China).The 40 m-thick bioclastic limestone of UnitⅣin this section can be correlated with the reefs of Bed 114 in Laibin area.A temperature drop indicated byδ18Oapatite values suggests this Wordian interval coincides with a period of glaciation and global regression.

AN ATTEMPT AT PALEOTEMPERATURE ESTIMATION IN SOUTH CHINA SEA USING TRANSFER FUNCTION

Micropaleontological analysis has been widely applied to paleoenvironmental reconstruction, and the transfer function (TF) method provides a new means of quantitative paleoenvironmental interpretation of micropaleontological data. As the first attempt in China to quantitatively estimate paleotemperature of sea water,

Distribution of tetraether lipids in surface sediments of the northern South China Sea:Implications for TEX_(86) proxies

Archaea have unique glycerol dialkyl glycerol tetraether（GDGT） lipids that can be used to develop paleotemperature proxies such as TEX86.This research is to validate proposed GDGT-proxies for paleotemperature determination in the South China Sea（SCS）.Samples were collected from core-top sediments （0-5 cm） in the northern SCS.Total lipids were extracted to obtain core GDGTs,which were identified and quantified using liquid chromatography-mass spectrometry（LC-MS）.The abundance of isoprenoidal GDGTs（/GDGTs） ranged from 271.5 ng/g dry sediment to 1266.3 ng/g dry sediment,whereas the branched GDGTs（bGDGTs）,supposedly derived from terrestrial sources,ranged from 22.2 ng/g dry sediment to 56.7 ng/g dry sediment.The TEX_（86）-derived sea surface temperatures ranged from 20.9℃in the coast（water depth 〈 160 m） to 27.9℃offshore（water depth 〉 1000 m）.TEX86-derived temperatures near shore（〈 160 m water depth） averaged 23.1±2.5℃（n =4）,which were close to the satellite-derived winter mean sea surface temperature（average 22.6±1.0℃,n = 4）;whereas the TEX_（86）-derived temperatures offshore averaged 27.4±0.3℃（n = 7） and were consistent with the satellite mean annual sea surface temperature（average 26.8±0.4℃,n = 7）.These results suggest that TEX_（86） may record the sea surface mean annual temperature in the open ocean,while it likely records winter sea surface temperature in the shallower water.

Mg/Ca Variation in Planktonic Foraminiferal Tests:Assessing Influence of Salinity and Diagenetic Carbonate Dissolution for Reconstruction of Palaeo-seawater Temperature

Over the past decade,the Mg/Ca ratio in foraminiferal tests has emerged as a valuable paleotemperature proxy.In this study we describe the application of the Mg/Ca paleothermometer with the aim of illustrate its use in the Mediterranean Basin.We value the influence of the salinity and diagenetic carbonate processes besides temperature as an important environmental factor controlling the foraminiferal Mg/Ca.For this purpose 3 species of

Campanian Climatic Change:Isotopic Evidence from Far East,North America,North Atlantic and Western Europe

Paleoclimatic settings have been reconstructed for the Campanian using original oxygenisotopic analyses of well-preserved molluskan and foraminifera shells from Russian Far East, Hokkaido, USA, Belgium and some DSDP holes （95, 98, 102, 390A, and 392A） in North Atlantic. Early Early Campanian climatic optimum has been recognized from data on high bottom shelf water paleotemperatures in middle latitudes of both the western circum-Pacific （to 24.2℃） and the eastern circum-Pacific （to 26.4℃） areas and high bottom shallow water paleotemperatures in high latitudes of the Koryak Upland （22.4-25.5℃）, which agrees with the data on the Campanian Barykovskaya flora in high latitudes （Golovneva and Herman, 1998） and Jonker flora and its equivalents in middle latitudes. Judging from the data on comparatively high bottom shallow water paleotemperature values in high latitudes, South Alaska （19.4℃） and the Koryak Upland （22.4-25.5℃）, we also expect Latest Campauian temperature maximum, which has not been confirmed, however, for low and middle latitudes by neither of isotopic nor paleobotanic data now. Main dimatic tendency during the Campanian （with the exception of Latest Campanian） has been learned from isotopic composition of Campanian aragonitic ammonoid shells from the Hokkaido-South Sakhalin （Krilyon） marine basin. In contrary to Huber＇s et al. （2002） assumption, we expect warm greenhouse conditions during the most part of the Campanian.

Significance of Caucasian Sections for Working out Carbon-Isotope Standard for Upper Permian and Lower Triassic (Induan) and Their Correlation with the Permian of North-Eastern Russia

Data obtained on conodont distribution in the Permian-Triassic Sovetashen Section of Transcaucasia provide further limitations on the age of the carbon-isotopic anomalies discovered by Baud et al. (1989). The significance of Caucasian sections for working out the carbon-isotope standard for the Upper Permian and Lower Triassic (Induan) is shown. Original data on carbon-isotope composition of bivalve and brachiopod shells from Permian sediments of North-Eastern Russia (Omolon and Okhotsk areas) have been obtained, which may be used for their correlation.

Tectonic thermal history and its significance on the formation of oil and gas accumulation and mineral deposit in Ordos Basin

The analyzing data on stratigraphic temperature measurement , thermal conductivity of the strata and radioactive heat production rate show that the present average geothermal gradient in the Ordos Basin is 2.93℃/100 m, and the average heat flow value is 61.78 mW/m2, which belongs to the mesothermal basin, and the value of the present geothermal gradient and heat flow in the east is higher than that in the west. The sandstone radioactive heat production rate of Zhiluo Group in Dongsheng Uranium deposits of Yimeng uplift is obviously higher in the mudstone, indicating that there exists a uranium anomaly. Based on studies of the present thermal field of the basin, the late-Mesozoic paleotemperature and paleogeothermal gradient are determined by using different kinds of paleotemperature methods. According to the anomaly of the late-Mesozoic paleotemperature gradient and magmatic event age, there was a tectonic thermal event in the early Cretaceous epoch of late-Mesozoic. This article rebuilds tectonic thermal history of different tectonic units by thermal history simulation using basin simulating software. The evolution of oil-gas and coal, and accumulation (mineralization) of mineral uranium are all controlled by the tectonic thermal history in the Ordos basin, especially by the tectonic thermal event that happened in the late Mesozoic. For both the gas source rocks of upper Paleozoic group and lower paleozoic group, the gas was largely generated in the early Cretaceous epoch of the late Mesozoic. The main petroleum generation period for Yanchang Group in Triassic system is the early Cretaceous epoch too, and the highest thermal maturity of the coal of Permo-Carboniferous, Triassic, and Jurassic reaches is the early Cretaceous epoch also. Early Cretaceous epoch is still one of the most important mineralizing periods of uranium.

Temperature estimation by oxygen-stable record over the past 200 ka in Zoige basin

According to the evolutionary processes of stable oxygen isotope in lake water, a physical model has been established to calculate paleotemperature and used to quantitatively rebuild the temperature sequences in the past 200 ka in Zoige basin, eastern Tibet. The results show that in the Zoige region the maximum temperature of the period equivalent to stage 7 in deep-sea stable oxygen record was 2.7℃ higher than that of the present; in stage 6, it was 4.3℃ lower and the value of the peak temperature of stage 5 was 5.2℃ higher than the present air temperature; in stage 4, the average temperature was 2-3℃ lower; in stage 3, the curve of the temperature estimated displayed the character of two peaks and one valley, and the value of the temperature difference in the period was above 4℃. Moreover, by comparing the tendency of the curves of paleotemperature calculated and responsive stable oxygen isotope of authicarbonate, we also found that during stage 6 the environment in the Zoige basin was extraordinary, inferring that the stage represented a transition period from warm-dry and cold-wet to warm-wet and cold-dry.

Thermal history of the Sichuan Basin,SW China:Evidence from deep boreholes

The Sichuan Basin is a superimposition basin composed of terrestrial and marine sediments that is well known for its abundant petroleum resources. Thermal history reconstruction using paleogeothermal indicators, including vitrinite reflectahoe and thermochronological data, shows that different structural subsections of the Sichuan Basin have experienced various paleogeothermal episodes since the Paleozoic. The lower structural subsection comprising the Lower Paleozoic to Middle Permian （Pz-P2） successions experienced a high paleogeothermal gradient （23.0-42.6℃/km） at the end of the Middle Permian （P2）, whereas the upper structural subsection comprising Late Permian to Mesozoic strata underwent a relatively lower paleogeothermal gradient （13.2-26.9℃/km） at the beginning of the denudation （Late Cretaceous or Paleocene in the different regions）. During the denudation period, the Sichuan Basin experienced a successive cooling episode. The high paleogeothermal gradient resulted from an intensive thermal event correlated to the Emeishan mantle plume. The heat flow value reached 124.0 mW/m2 in the southwestern basin near the center of the Emeishan large igneous province. The low geothermal gradient episode with heat flow ranging from 31.2 to 70.0 mW/m2 may be related to the foreland basin evolution. The cooling event is a result of the continuous uplift and denudation of the basin.

Evolution of chlorite composition in the Paleogene prototype basin of Jiyang Depression, Shandong, China, and its implication for paleogeothermal gradient

The Dongying Basin, Huimin Basin, and Zhanhua Basin constitute the Jiyang Depression in Shandong Province. They are major oil and gas exploring districts within the depression. Through reconstructions of the paleotemperature of the three basins facilitated with the chlorite geothermometry, the thermal history of the Paleogene prototype basin in Jiyang Depression and its geologic significance were explored. This study reveals that the Si^(4+) component in chlorites reduces gradually as its buried depth increases, while the AI~Ⅳ component increases accordingly. The chlorite type changes from silicon-rich diabantite to silicon-poor ferroamesite and prochlorite. The prochlorite in this district only appears in the deep buried depth, high temperature, and relatively old stratigraphies; while the diabantite appears in the shallower buried, low temperature, and newly formed strata; the ferroamesite exists in the conditions between prochlorite and diabantite formation. The diagenetic temperatures of the chlorites in these Paleogene basins are 171 — 238℃ for the Dongying Basin, 160—202℃ for the Huimin Basin, and 135—180℃ for the Zhanhua Basin. The differences of the chlorite diagenetic temperatures in the three basins were controlled by the duration time of the structural depressing processes. Higher temperature indicates longer depression time. The relationship between the chlorite diagenetic temperature and its buried depth indicates that the average paleogeothermal gradient is about 38.3℃ /km in the Paleogene prototype basin of Jiyang Depression. It was higher than the present geothermal gradient (29—30℃/km). This phenomenon was attributed to the evolution of the structural dynamics in the depression basin.

Innovations and stepwise evolution of CBFs/DREB1s and their regulatory networks in angiosperms

The C-repeat binding factors/dehydrationresponsive element binding protein 1 s(CBFs/DREB1 s)have been identified as major regulators of cold acclimation in many angiosperm plants.However,their origin and evolutionary process associated to cold responsiveness are still lacking.By integrating multi-omics data of genomes,transcriptomes,and CBFs/DREB1 s genome-wide binding profiles,we unveil the origin and evolution of CBFs/DREB1 s and their regulatory network.Gene collinearity and phylogeny analyses show that CBF/DREB1 is an innovation evolved from tandem duplication-derived DREBⅢgene.A subsequent event of e-whole genome duplication led to two CBF/DREB1 archetypes(CladesⅠandⅡ)in ancient angiosperms.In contrast to cold-insensitivity of Clade I and their parent DREBⅢgenes,CladeⅡevolved a further innovation in cold-sensitive response and was stepwise expanded in eudicots and monocots by independent duplications.In geological time,the duplication events were mainly enriched around the Cretaceous-Paleogene(K-Pg)boundary and/or in the Late Cenozoic Ice Age,when the global average temperature significantly decreased.Consequently,the duplicated CBF/DREB1 genes contributed to the rewiring of CBFs/DREB1 s-regulatory network for cold tolerance.Altogether,our results highlight an origin and convergent evolution of CBFs/DREB1 s and their regulatory network probably for angiosperms adaptation to global cooling.

Middle Jurassic climate oscillations from paleosol records of the Sichuan Basin,SW China

The Middle Jurassic is characterized by major plate tectonic changes,variable atmospheric CO_(2)concentrations(pCO_(2)),and climate oscillations in both marine and terrestrial realms.However,the limited evidence from the terrestrial sedimentary records hampers a comprehensive understanding of global climate state in this period.Well-exposed strata of the Shaximiao Formation in the Sichuan Basin,Southwest China,preserve successions of paleosols that offer the possibility of evaluating the terrestrial paleoclimatic changes during the Middle Jurassic(Bajocian to Callovian).A total of 151 paleosol profiles belonging to four paleosol types(Entisol-like,Inceptisol-like,Aridisol-like and argillic Inceptisol-like paleosols)were identified and characterized.The quantitative paleoclimate reconstructions based on the bulk geochemistry of paleosol horizons and depths of carbonate nodules indicate a generally semiarid-subhumid climate alternating with arid-humid and cool/warm-temperate climates during this time interval.This dynamic climate terminated in a dry,subhumid,humid/perhumid and superhumid moisture regime characterized by steppe/wet or rain forest floral provinces.We suggest that these climatic fluctuations may have been related to global geodynamic(e.g.,the fragmentation of Pangea,“megamonsoonal”circulation,and bolide impacts)and regional tectonic uplift(e.g.,the uplift of the Longmenshan Mountains in the South China Block)during the Middle Jurassic.The pCO_(2)estimates suggest relatively low pCO_(2)levels within the range of~100 ppm-~890 ppm during the Bajocian to Callovian.Our results coincide with the threshold for the initiation of glaciation and may help to explain the occurrence of cool intervals in the generally warm Jurassic.These pCO_(2)fluctuations,which coincide with paleotemperature variations in the low paleolatitudes of the Northern Hemisphere,are possibly attributable to global geological events(e.g.,wildfire events,eustatic sea-level oscillations,and the transient development of glaciations)in the Middle Jurassic.