New palaeoclimatic insights on the Late Cretaceous environments of Mongolia based on the isotope data (δ^13C,δ^18O) of dinosaur eggshells and pedogenic carbonates from Bayn Dzak section

Isotopic data obtained from the dinosaur eggshells and pedogenic nodules(pedonodules)are interpreted in terms of palaeoclimatology.The material studied originated from the Bayn Dzak locality,Southern Gobi Aimak,Mongolia,having Late Cretaceous(Campanian)age.Stratigraphically the Bayn Dzak locality belongs to the Djadokhta Formation.All the present data(lithology,type of paleosols,FPS-profiles,geochemistry),and the isotopic characteristics of the selected samples show unequivocally that the environments of the Bayn Dzak area in Late Cretaceous(Campanian)time were warm to summer-hot,seasonally dry.Wet seasons(most probably,which took place in the winter time)were not longer than two months with not more than 400 mm precipitation per year.The distribution of isotope data in the dinosaur eggshells show the main relation,which is the dependence ofδ^13C andδ^18O values,i.e.specimens with heavy carbon isotope ratios are characterized by lighter oxygen isotope composition and conversely.Thus,theδ^13C andδ^18O values of the dinosaur eggshells display a clear positive correlation.It may be consequent both with the difference of the isotope composition of diet of the egg-lying animals modified by physicochemical isotope fractionation due to metabolism and changes in the isotope environment,and/or diagenetic alteration of the eggshell carbonate.Obtained isotopic data on the studied dinosaur eggshell fragments and the soil carbonates lend support to our assumption that diagenesis did not play significant role in changing the isotopic values.The distribution ofδ^13C andδ^18O values in eggshells and in pedogenic carbonates shows the visible opposite dependencies.

Differential response of radial growth and δ^(13)C in Qinghai spruce(Picea crassifolia) to climate change on the southern and northern slopes of the Qilian Mountains in Northwest China

Tree radial growth can have significantly differ-ent responses to climate change depending on the environ-ment.To elucidate the effects of climate on radial growth and stable carbon isotope(δ^(13)C)fractionation of Qing-hai spruce(Picea crassifolia),a widely distributed native conifer in northwestern China in different environments,we developed chronologies for tree-ring widths and δ^(13)C in trees on the southern and northern slopes of the Qilian Mountains,and analysed the relationship between these tree-ring variables and major climatic factors.Tree-ring widths were strongly influenced by climatic factors early in the growing season,and the radial growth in trees on the northern slopes was more sensitive to climate than in trees on the southern.Tree-ring δ^(13)C was more sensitive to climate than radial growth.δ^(13)C fractionation was mainly influenced by summer temperature and precipitation early in the growing season.Stomatal conductance more strongly limited stable carbon isotope fractionation in tree rings than photosynthetic rate did.The response between tree rings and climate in mountains gradually weakened as climate warmed.Changes in radial growth and stable carbon isotope fractionation of P.crassifolia in response to climate in the Qilian Mountains may be further complicated by continued climate change.

黑云杉林大气CO_2稳定同位素组成δ^(13)C,δ^(18)O的分析

研究CO2稳定同位素特征可以揭示光合、呼吸作用等众多信息,从而有助于了解生态系统与环境之间的碳循环过程。利用大气CO2浓度及其稳定同位素的测定资料,分析稳定同位素比1δ3C、1δ8O,发现两者具有相似的时空分布特征。主要表现在1δ3C和1δ8O在冠层内具有明显的垂直变化趋势,冠层上部重同位素含量较高,而底部含量较低。从时间变化看,1δ3C和1δ8O在午后到日落具有较高的水平,而凌晨,1δ3C和1δ8O较低。运用Keeling图法分析1δ3C、1δ8O和CO2浓度的关系,发现1δ3C值主要受光合和呼吸作用影响,与CO2浓度的高低密切相关;而1δ8O的变化比较复杂,因为1δ8O除受光合、呼吸强度影响外,还取决于环境空气湿度。

Stable carbon and oxygen isotopes of four planktonic foraminiferal species from core-top sediments of the Indonesian throughflow region and their significance

Horizontal and vertical distributions of δ^18 and δ^13 were investigated in shells of four planktonic foraminiferal species, Globigerinoides ruber, Globigerinoides sacculifer, Pulleniatina obliquiloculata and Neogloboquedrina dutertrei, from a total of 62 core-top sediment samples from the Indonesian throughflow region. Results were compared to modern hydrologic conditions in order to explore potential of proxies in reconstructing fluvial discharge and upper ocean water column characteristics in this region. Our results show that, in the Makassar Strait, both of depleted δ^18 and δ^13 of these four species were linked to freshwater input. In the Bali Sea,however, depleted δ^18 and δ^13 for these species may be due to different reasons. Depleted δ^18 was a result of freshwater input and as well influenced by along-shore currents while depleted δ^13 was more likely due to the Java-Sumatra upwelling. Comparison of shell δ^18 records and hydrographic data of World Ocean Atlas 2005 suggests that G. ruber and G. sacculifer calcify within the mixed-layer, respectively at 0–50 m and 20–75 m water depth, and P. obliquiloculata and N. dutertrei within the upper thermocline, both at 75–125 m water depth. N.dutertrei calcifies at slightly deeper water depth than P. obliquiloculata does. In general, δ^13 values of both G.ruber and G. sacculifer are larger than those of P. obliquiloculata and N. dutertrei at all sites, possibly related to depth habitats of these species and vertical distribution of nutrients in the Indonesian throughflow region.

Stable oxygen and carbon isotopes from the planktonic foraminifera Neogloboquadrina pachyderma in the Western Arctic surface sediments:Implications for water mass distribution

Neogloboquadrina pachyderma is the most abundant planktonic foraminifera species found in the modern polar oceans. The δ^18O and δ^13C of N. pachyderma from the Western Arctic Ocean sediments were analyzed to reveal the implications of the proxies to environmental changes. The δ^18O from N. pachyderma in the Chukchi Sea reflect the water mass distribution in this area. Heavier δ^18O values were found along the Anadyr Current （AC） and lighter values in the central and eastern Chukchi Sea..These may reflect the freshwater signal from the Alaska Coastal Current （ACC） and Bering Sea Shelf Water （BSSW）. The light δ^18O signature in the high Arctic basin comes from the freshwater stored in the Arctic surface layer. The δ^18O distribution pattern in the Chukchi Sea is also influenced by the current system. High primary productivity along the AC results in heavy δ^18O. The relatively low primary productivity and the freshwater component from the BSSW and ACC may be the reason for this light δ^13C signal in the central and eastern Chukchi Sea. Our data reveal the importance of well ventilated Pacific Water through the Chukchi Sea into the Arctic Ocean.

若尔盖盆地RM孔自生碳酸盐δ^(18)Ο、δ^(13)C记录所揭示的环境演化特征

利用湖泊自生碳酸盐δ１８Ο、δ１３Ｃ指标，研究了青藏高原东部边缘若尔盖盆地９０万年来的环境演化特征，划分了２３个气候阶段，并与黄土记录及深海记录进行了比较。结果显示，各记录９０万年来气候演化阶段及变化趋势具有较好的可比性，但环境特点也存在较大的差异。表明９０万年来若尔盖地区气候变化具有全球一致性的同时也存在有明显的区域特征。ＲＭ孔记录显示在２３、１７、１２等阶段暖而不湿，而１８、１６等阶段冷而不干，钻孔记录揭示的６阶段环境特征也是不同于其它任何记录。另外，在７００—４８０ｋａＢ．Ｐ．时段气候以冷湿暖干为主，明显不同于此时段前后各期的气候特征，也与黄土高原黄土—古土壤系列所揭示的冷干暖湿型气候格局形成鲜明的对照，显示了明显的区域特征。

Use of δ^(18)O, δ^(13)C and NO_(3)^(-) to identify hydrogeochemical processes related to contamination in an aquifer located in central Mexico

In this work,an isotopic analysis of δ^(18)O,δ^(13)C,and NO_(3)^(-) concentrations was carried out to identify the origin and the processes related to the contamination of an aquifer located in the state of Guanajuato,Mexico.The research identified the possible sources of δ^(13)C in groundwater.During groundwater flow,CO_(2) participates in different hydrogeochemical reactions in which the dissolution of carbonates or biochemical processes related to biodegradation stand out.Isotopic data of δ^(13)C,δ^(18)O,and the hydrogeochemical behavior of NO_(3)^(-) and HCO_(3)^(-) in water,in addition to isotopic data and the chemical composition of limestones in the study area,were determined to establish the isotopic signature and the processes undergone by the rocks.The isotopic signature of rock and water samples indicated that metamorphic limestones contributed with carbon dioxide to deep groundwater,while in the upper aquifer,bacterial metabolic reactions during nitrification–denitrification could modify the isotopic signature of δ^(13)C in some wells,although atmospheric contribution also plays a role.The modification of the carbon isotopic component is related to the precipitation of calcite in specific regions of the study area,input of atmospheric CO_(2),and soil(e.g.the possible participation of C4-type plants in the assimilation-release of carbon).This process is not confirmed or completely ruled out in this study since agriculture is excessively developed throughout the region.The joint interpretation of isotopic values and the hydrogeochemical behavior of major and conservative elements help in identifying possible pollution processes in which different carbon sources are related.

Isotopes (¹³C and ¹⁸O) Geochemistry of Lower Triassic Montney Formation, Northeastern British Columbia, Western Canada

Oxygen isotope (δ18O) serves as paleothermometer, and provides paleotemperature for carbonates. δ18O signature was used to estimate the temperature of fractionation of dolomite and calcite in Montney Formation, empirically calculated to have precipitated, between approximately 13°C to ±33°C during Triassic time in northeastern British Columbia, Western Canada Sedimentary Basin (WCSB). Measurements of stable isotopes (δ13C and δ18O) fractionation, supported by quantitative X-ray diffraction evidence, and whole-rock geochemical characterization of the Triassic Montney Formation indicates the presence of calcite, dolomite, magnesium, carbon and other elements. Results from isotopic signature obtained from bulk calcite and bulk dolomite from this study indicates depleted δ13CPDB (-2.18‰ to -8.46‰) and depleted δ18OPDB (-3.54‰ to -16.15‰), which is interpreted in relation to oxidation of organic matter during diagenesis. Diagenetic modification of dolomitized very fine-grained, silty-sandstone of the Montney Formation may have occurred in stages of progressive oxidation and reduction reactions involving chemical elements such as Fe, which manifest in mineral form as pyrite, particularly, during early burial diagenesis. Such mineralogical changes evident in this study from petrography and SEM, includes cementation, authigenic quartz overgrowth and mineral replacement involving calcite and dolomite, which are typical of diagenesis. High concentration of chemical elements in the Montney Formation?-Ca and Mg indicates dolomitization. It is interpreted herein, that calcite may have been precipitated into the interstitial pore space of the intergranular matrix of very fine-grained silty-sandstone of the Montney Formation as cement by a complex mechanism resulting in the interlocking of grains.

美国东南部边缘磷成因期与海洋δ^(13)C和δ^(18)O记录的联系

美国东南部边缘磷成因期与海洋δ￣（１３）Ｃ和δ￣（１８）Ｏ记录的联系ＤａｖｉｄＪ．Ｍａｌｌｉｎｓｏｎ等海洋一大气储库中ＣＯ２的生物迁移在地质年代中受磷的可利用性限制。因此，为了推断出关于碳的生物地球化学循环和潜在的气候控制，了解整个地质时代中磷通量是...

塔里木盆地南缘沉积物磁化率、δ^(13)C与粒度及其气候环境意义

本文研究表明, 塔里木盆地南缘湖沼相沉积物质量磁化率与碳酸盐δ13C呈正相关关系, 与粒度参数中 0 56~35 57μm各组分呈显著负相关, 其中同 17 83 ~31 70μm部分负相关性最为显著; 与 56 37~224 4μm之间各组分显著正相关, 其中与 70 96~200μm各组分正相关性最为显著。其气候环境背景与意义表现为: 在寒冷期中, δ13C偏轻, 相对湿度和植被盖度增加, 地表侵蚀减弱, 只有较细物质才能向湖泊沼泽搬运加积, 地表氧化环境减弱, 磁化率减小; 而在温暖期中, 则相反。在区域对比基础上, 根据上述指标将近 4 0ka以来此地区气候环境变化划分了 8个阶段。本文的各种指标 (特别是粒度指标 ) 与GreenlandGISP2冰芯δ18O记录之间有很好的吻合, 表明研究区近 4 0ka以来的气候与环境变化可能具有全球背景。

基于耳石δ13C和δ18O的黄、渤海秋季小黄鱼补充群体的种群划分

关于小黄鱼的种群划分问题,从20世纪50年代至今一直存在争议。以往研究海洋鱼类种群划分的方法主要有标记重捕法、渔获量分析法、寄生虫标记法、形态表型量度特征法、分子生物学法和钙质结构元素指纹法等,而这些方法在细节的表述方面有各自的局限性。本研究采用稳定同位素质谱分析技术,分析了黄、渤海渔业资源调查中92尾小黄鱼(Larimichthys polyactis)的左矢耳石样品中δ^13C和δ^18O的值,并对每尾小黄鱼耳石δ^13C和δ^18O的值进行聚类分析。结果显示,我国黄、渤海秋季小黄鱼早期补充群体可划分为4个种群,即渤海黄海北部种群、黄海中部种群、黄海南部离岸种群和黄海南部沿岸种群。其中,黄海南部离岸种群和其他3个种群没有站位交叉现象。对聚类分析的结果进行判别分析,得出渤海黄海北部种群的判别成功率为75.9%,黄海中部种群的判别成功率为80.0%,黄海南部离岸种群判别成功率为81.0%,黄海南部沿岸种群判别成功率为95.5%,总体判别成功率为82.6%。首次将黄海南部种群细分为了黄海南部离岸种群和黄海南部沿岸种群,且2种群之间很少有站位的交叉现象。

广西横县六景吉维特期腕足类Rhynchospirifer和Stringocephalus的环境元素和稳定同位素生物效应

利用现代生物学研究模式,对比了吉维特期不同层位中原地埋藏的Rhynchospirifer属壳体次生层(纤维层)与其围岩之间元素和碳、氧稳定同位素变化,探讨了不同时期同属腕足类的古环境元素和稳定同位素生物效应及其变化趋势;通过对比同层位Rhynchospirifer属和Stringocephalus属化石壳体次生层及其围岩之间的元素变化,探讨了同时期、同生境不同属腕足类的古环境元素生物效应。当环境元素含量发生变化时,Rhynchospirifer因其对各元素生态幅和耐受限度的差异而并不完全对环境中各化学因子的变化产生一致性的响应,而当跨越牙形石Lowervarcus和Middlevarcus亚带后,其属内适应性变异造成属内特异性选择发生一定程度的变化。Stringocephalus和Rhynchospirifer对其耐受限度较小的Al,K,Sc,Co等元素保持较高的属内有效性和特异性选择;对其耐受限度和生理有效性中等、可被其他元素替代的Mn,P,Ni,Cu等元素,其特异性选择有限,并可能与有效性原则和丰度作用相叠加;对于生态幅较宽的V,Cr,Sr,Pb等元素,属内的特异性选择弱化。当与同时期生态龛比邻属种对比时,彼此的生态幅发生部分重叠,部分元素如Mg,Na,As,Pb等的含量甚至较不同时期同属生物更加接近。Rhynchospirifer壳体次生层与其围岩碳、氧同位素比值分别保持着较好的同步性和一致性,即不存在碳、氧同位素生物效应。

C、H、O稳定同位素在树木植株不同部位的分馏规律研究

采用同位素比率质谱仪分别测定了树木不同部位的δ^(13)C、δ^(18)O和δ^(2)H值。结果表明:δ^(13)C值在研究树种植株不同部位的变化相对最小,其次是δ^(18)O值,δ^(2)H值最大。对于橡胶木、铁刀木和羊蹄甲3个树种,C和O元素是实现其木材产地稳定同位素溯源较理想的元素。

Unexpectedly low δ^(13)C in leaves,branches,stems and roots of three acacia species growing in hyper-arid environments

Aims In plant eco-physiology,less negative(enriched)carbon 13(^(13)C)in the leaves indicates conditions of reducing leaf gas exchange through stomata,e.g.under drought.In addition,^(13)C is expected to be less negative in non-photosynthetic tissues as compared with leaves.However,these relationships inδ^(13)C from leaves(photosynthetic organs)to branches,stems and roots(non-photosynthetic organs)are rarely tested across multiple closely related tree species,multiple compartments,or in trees growing under extreme heat and drought.Methods We measured leaf-to-root^(13)C in three closely related desert acacia species(Acacia tortilis,A.raddiana and A.pachyceras).We measuredδ^(13)C in leaf tissues from mature trees in southern Israel.In parallel,a 7-year irrigation experiment with 0.5,1.0 or 4.0 L day1 was conducted in an experimental orchard.At the end of the experiment,growth parameters andδ^(13)C were measured in leaves,branches,stems and roots.Important Findings Theδ^(13)C in leaf tissues sampled from mature trees was ca.-27‰,far more depleted than expected from a desert tree growing in one of the Earth's driest and hottest environments.Across acacia species and compartments,δ^(13)C was not enriched at all irrigation levels(-28‰to ca.-27‰),confirming our measurements in the mature trees.Among compartments,leafδ^(13)C was unexpectedly similar to branch and rootδ^(13)C,and surprisingly,even less negative than stemδ^(13)C.The highly depleted leafδ^(13)C suggests that these trees have high stomatai gas exchange,despite growing in extremely dry habitats.The lack ofδ^(13)C enrichment in nonphotosynthetic tissues might be related to the seasonal coupling of growth of leaves and heterotrophic tissues.

长江流域水体稳定同位素分馏特征及碳水循环

岩溶碳循环具有快速的动力学反应过程,对环境变化敏感,水循环可影响岩溶碳循环的两个驱动因子(水和CO_(2)),是岩溶碳循环的重要影响因素。通过2016年6月和10月长江干流、主要支流、水库、湖泊的采样测试,分析了δD、δ^(18)O、无机碳含量和同位素分馏特征及控制因素,揭示了长江流域水循环对岩溶碳循环的影响特征。结果表明:长江流域水体δD和δ^(18)O的空间变化表现出大陆效应、纬度效应和海拔效应,并随降雨的季节性变化而变化;无机碳主要源自碳酸盐岩风化,δ^(13)C DIC值主要受碳酸风化碳酸盐岩和硫酸/硝酸风化碳酸盐岩对HCO-3的贡献比例控制。长江流域水文过程可显著影响岩溶碳循环,上游冻土区土壤冻结时,幔源和大气源CO_(2)参与碳酸盐岩风化使δ^(13)C DIC值显著增加;夏秋季季风期降雨爆发,降水导致δD和δ^(18)O急剧下降,同时利于土壤CO_(2)累积和碳同位素值下降,并使得水体δD、δ^(18)O和δ^(13)C DIC值均下降;水文过程可影响“生物碳泵”作用,平水期“生物碳泵”作用更强,水库的分层效应也更显著。

南海西沙群岛现代鳞砗磲内外层壳体稳定碳、氧同位素变化特征及其影响因素

砗磲具有清晰的生长纹层,是记录热带海洋气候变化的良好载体,其壳体δ^(18)O、δ^(13)C已广泛应用于第四纪古气候研究。然而,目前大多数研究主要集中在内层壳体,关于外层壳体的研究十分稀少。本研究通过对采自南海西沙群岛浪花礁一个现代鳞砗磲的内外层壳体进行月分辨率δ^(18)O、δ^(13)C测试和内壳日生长纹层扫描,分析内外层壳体δ^(18)O和δ^(13)C的变化特征及其影响因素。结果显示该砗磲外壳δ^(18)O比内壳δ^(18)O更加偏正,但是两者都具有十分相似的变化特征,主要受到海表面温度的控制,表明砗磲内外层壳体δ^(18)O能够可靠地指示气候环境的变化。砗磲内外层壳体δ^(13)C存在较大的差异,其中内壳δ^(13)C具有明显的年周期变化。通过对比分析砗磲内壳δ^(13)C与日生长速率、气候环境参数,发现内壳δ^(13)C的季节变化主要与初级生产力和砗磲自身生命活动有关。砗磲外壳δ^(13)C相对于内壳δ^(13)C较为偏负,表现出持续下降的趋势,且无季节性变化,这可能是由采样路径偏离最大生长轴导致的。

陕南石笋稳定同位素记录中的古气候和古季风信息

采自陕西省柞水县的石笋给出了过去 750a来的高分辨率气候记录以及全新世和80～ 330ka之间的低分辨率的气候变化。定年方法使用了石笋生长纹层计数法、2 10 Pb法和TIMS2 30 Th法。分析了石笋中δ18O和δ13C的气候含义 ,认为当δ18O和δ13C值变重时 ,指示干热的气候组合 ,当δ18O和δ13C值同时变轻时 ,指示湿冷的气候组合。在长时间尺度δ18O值的变化以反映温度变化为主 ,δ13C值的变化反映湿度变化为主。当δ18O变轻 ,而δ13C变重时 ,指示干冷气候。这时期的夏季风很弱而冬季风很强 ,相反 ,当δ18O变重 ,而δ13C变轻时 ,指示湿热气候 ,表明夏季风很强 ,冬季风很弱。过去 750a的记录中分为 :公元 12 50～ 152 0年的温暖中世纪 (MedievalWarmPeriod) ,公元 152 0～ 182 0年的湿冷小冰期 (LittleIceAge)和公元 182 0年以来的温热期。全新世的气候在 4 0 0 0a左右有一显著的变化。在此时之前的温度低于全新世的平均气温 ,而在此之后的温度高于全新世的平均气温。全新世气候记录可细分为 18个不同的时期。

贵州荔波董歌洞D3石笋碳氧稳定同位素及微量元素记录的环境变化

通过对贵州荔波董歌洞D3石笋一系列的TIMSU系法测年以及碳氧稳定同位素分析 ,取得了连续 90 .0～ 16 0 .0ka气候变化高分辨率的同位素记录。表明石笋氧同位素记录和海洋同位素记录一样 ,也可以明显地按峰、谷划分为MIS5c,MIS5d ,MIS5e及MIS6多个气候阶段 ,界线年龄分别为 :5c/ 5d为 110 .0kaBP ,5d/ 5e为 12 0 .0kaBP ,5e/ 6为 12 9.2kaBP。在由冰盛期的 6阶段到间冰期的 5e,δ18O值由偏重的谷底至偏轻的峰顶的跃变 ,代表冰期旋回之间由冷到暖的快速转变。此外 ,δ13 C值也同样自谷底至峰顶的快速变化 ,说明生态环境也随气候环境的迅速变化而变化。系统的微量元素分析表明 ,Si,Al,Sr,P ,F等均表现出由冰盛期 6阶段至间冰期 5e阶段最大幅度的迅速变化 ,在间冰期 ,微量元素记录变化幅度较小 ,变化波形与δ13 C记录更为相似 ,研究表明 ,这些微量元素与δ13 C记录一样也可以作为岩溶区生态环境重建的代用指标。

高放射性废物深地质处置库预选场址深部花岗岩的同位素地球化学

评价高放射性废物深地质处置库安全性能的一个重要方面是研究处置库的远场地球化学环境 ;矿物和岩石同位素地球化学研究可以较客观地重现矿物、岩石形成时的古环境及其演化历史。对中国第一个高放射性废物处置库预选场深部花岗岩不同深度裂隙充填矿物 (方解石、石英 )的 C、O同位素 ,Rb- Sr同位素及铀系核素的研究表明预选场深部花岗岩可分为四种不同的地球化学环境 :1浅部 (0～ 15 0 m ) ,其填隙矿物的δ1 8O(SMOW) =12 .1‰～ 13.0‰ ,δ1 3C(PDB) =- 9.5‰～ - 10 .1‰ ,δ87Sr=- 3.2 4‰～ - 1.0 9‰ ,填隙矿物形成于低温流体环境 ,为大气降水补给。 2中—上部 (15 0～ 35 0 m) ,δ1 8O(SMOW) =13.3‰～ 18.0‰ ,δ87Sr≈ 0 ,δ1 3C(PDB) =- 11.2‰～- 10 .5‰ ,填隙矿物形成时其流体来源较复杂 ,为大气降水和盆地卤水的混合流体 ,且处于弱还原环境 ;铀系核素活度数据也显示此区段地下水环境相对稳定 ,未受到现代大气降水或地下水的影响。 3中—下部花岗岩 (35 0～5 5 0 m) ,填隙矿物形成时的环境由两种不同性质的地下水控制 ,但深部地球化学环境相对稳定。 4深部 (>5 5 0 m) ,岩性相对稳定 ,地下水—花岗岩的反应处于稳定的长期平衡状态。这种地球化学环境对于高放射性废物的永久处置是有利的。

试论块状白云岩的混合水成因模式

通过沉积相、岩石学、矿物学、氧碳同位素和微量元素特征研究,证明块状白云岩的混合水白云石化作用是一个包括交代、重结晶调整和溶蚀充填作用的复杂水-岩反应过程,提出块状白云岩的混合水成因模式。白云石化过程主要受混合水带的孔隙水盐度变化控制,在侧向加积变浅的浅海碳酸盐沉积体系中,混合水带由陆向海方向迁移引起的孔隙水盐度由高向低变化,是控制白云石化过程的水文动力因素。