High-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method and system

Abstract

The invention belongs to the technical field of deep-time atmosphere carbon dioxide isotope composition estimation, and particularly relates to a high-resolution deep-time atmosphere carbon dioxide isotope composition estimation method and system, and the method comprises the steps: S100, reconstructing the global surface average temperature based on the atmosphere carbon dioxide concentration pCO2; s200, calculating the relative content of carbonate ions and bicarbonate radical ions in the marine carbonate system; s300, determining a fractionation coefficient; s400, determining a difference value V of carbon isotopes of the carbonatite and surrounding seawater in the carbonatite deposition process on the basis of the carbon isotope difference of the carpopods and the carbonatite; according to the method, carbonate rocks which generally exist in geological history and are continuously deposited on time are selected as a tool for atmospheric carbon dioxide isotope reconstruction, and the atmospheric carbon dioxide isotope is reconstructed through quantitative evaluation of the geological history ocean surface layer temperature, the ocean carbonate rock salt content and the fractionation effect during formation of the carbonate rocks. And the atmospheric carbon dioxide isotope composition in the deep-time geological historical evolution process can be accurately calculated.

Description

Technical Field

[0001] This invention belongs to the field of deep-time atmospheric carbon dioxide carbon isotope composition estimation technology, and particularly relates to a high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method and system. Background Technology

[0002] Deep-time atmospheric CO2 carbon isotope reconstruction refers to the use of information from the geological record to infer and reconstruct the changes in the carbon isotopic composition of atmospheric carbon dioxide (CO2) over a timescale of millions or even hundreds of millions of years, especially the δ¹²⁺ ions. 13 The historical changes of C. Generally, we use δ. 13 The C value describes the sample. 13 C / 12 The degree of deviation of C from the standard is expressed in ‰ (parts per thousand). Deep-time atmospheric CO2 carbon isotope reconstruction has significant scientific value. For example, it can be used to understand climate-carbon cycle feedback mechanisms, constrain carbon cycle and climate models, study the background of biological evolution and extinction events, and predict future climate risks. Ultimately, it can use geological evidence to infer the isotopic characteristics and variation trajectory of ancient atmospheric CO2, clarify the Earth's carbon cycle and paleoclimate evolution, and serve to understand today's and future anthropogenic carbon emissions and global change issues.

[0003] Currently, the main technologies for deep-time atmospheric carbon dioxide carbon isotope reconstruction include the following:

[0004] (1) Reconstruction method based on carbon isotope characteristics of carbonate rocks (i.e., I-δ) 13 C carb );

[0005] It analyzes and statistically analyzes the current atmospheric carbon isotope values ​​(δ¹²). 13 C CO2 The difference ε between the carbon isotope values ​​of the newly deposited carbonate rocks and the carbon isotope values ​​of the deep-seated carbonate rocks is then measured. 13 C carb(t) This allows for the reconstruction of deep-time atmospheric carbon dioxide carbon isotope values, i.e., δ¹². 13 C CO2(t) =δ 13 C carb(t) -ε.

[0006] (2) Reconstruction method based on organic carbon isotopes in plant tissues (II-δ) 13 C plant )

[0007] By analyzing the correlation between organic carbon isotopes in modern plant tissues and atmospheric carbon dioxide isotopes, it fitted a linear correlation between the two, i.e., δ... 13 C plant =a*(δ 13 C CO2 )-b, where a and b are constants; then based on the measured carbon isotope composition of plant tissue (δ) 13 C plant Estimate δ 13 C CO2 .

[0008] (3) Inorganic carbon isotope estimation method based on marine paleontological fossils (III-δ) 13 C fossil )

[0009] This method estimates atmospheric carbon dioxide carbon isotopes based on the carbon cycle pathway from the atmosphere to seawater to marine shellfish, taking into account the influence of deep-sea temperature on isotopic fractionation during the carbon cycle.

[0010] However, these techniques have the following problems in estimating the carbon isotopic composition of carbon dioxide:

[0011] (1)Ⅰ-δ 13 C carb Technology in δ 13 C CO2 The fractionation parameter ε was introduced during the estimation process. In practical estimations, ε is often treated as a constant of 8‰. However, temperature is the main factor affecting the variation of this parameter. Laboratory measurements show that ε varies from 7‰ to 11‰. In paleogeological periods, the global average surface temperature often fluctuated by more than 10℃. Therefore, the depth δ 13 C CO2 During the reconstruction process, if ε is set to a certain value, the reconstructed δ 13 C CO2 The error could be greater than 4‰, and such results are almost meaningless in deep paleoclimate and carbon cycle studies due to the excessive error.

[0012] (2)Ⅱ-δ 13 C plant In δ 13 C CO2 The estimation process is based on the linear relationship between carbon isotopes of plant and atmospheric carbon dioxide. This fitting formula is primarily based on contemporary environmental conditions. In reality, the carbon isotopes of different plant tissues (such as roots, stems, leaves, or organic matter mixtures) vary considerably, and δ... 13 C plant and δ 13 C CO2The relationship is also significantly influenced by temperature, humidity, and atmospheric carbon dioxide concentration. Deep-seated paleoclimates experienced conditions of high carbon dioxide concentrations (e.g., pCO2 > 3000 ppm, compared to modern pCO2 = 400 ppm) and drastic temperature changes, therefore δ... 13 C plant and δ 13 C CO2 The actual correlation between the two varies greatly, and the current fitted linear function is insufficient to accurately estimate the depth-time δ. 13 C CO2 .

[0013] (3)Ⅲ-δ 13 C fossil Based on the carbon cycle pathway in the atmosphere-seawater-marine shellfish, this study quantitatively evaluates the isotopic fractionation effect during this process using δ¹⁸Optometry. 13 C CO2 The reconstruction is underway; however, the current estimation process has the following problems:

[0014] ① The carbonate system in the deep ocean lacks precise quantitative evaluation, such as the commonly used setting of bicarbonate (HCO3-) - ) and (CO3) 2- Setting the concentration of ) to a constant value is clearly impractical;

[0015] ② During the process of marine organisms using inorganic carbon in seawater to form their shells, there may be a fractionation of carbon isotopes, that is, the inorganic carbon isotopes of the formed shells may differ from those of the surrounding seawater.

[0016] ③ Deep-sedimentary rocks are relatively poor in fossils and often lack continuous temporal constraints. These issues make δ¹⁸O fossils reconstructed from marine shell fossils... 13 C CO2 The data has too large an error and is discontinuous.

[0017] In view of this, the present invention provides a high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method, aiming to overcome the technical bottlenecks in the existing deep-time carbon isotope reconstruction process, such as low resolution, time discontinuity, and insufficient accuracy, and to achieve high-precision and continuous estimation of deep-time atmospheric carbon dioxide carbon isotope composition. This is of great strategic significance for revealing the co-evolution law of the Earth's deep-time carbon cycle-climate system, assessing current and future global change trends, supporting resource and energy strategic layout, and promoting innovation in Earth science and technology. Summary of the Invention

[0018] The purpose of this invention is to address the aforementioned technical problems by providing a high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method and system. This method selects carbonate rocks, which are ubiquitous in geological history and have been deposited continuously over time, as a tool for atmospheric carbon dioxide isotope reconstruction. Through quantitative evaluation of geological history ocean surface temperature, marine carbonate content, and fractionation during carbonate rock formation, the atmospheric carbon dioxide isotope composition during deep-time geological history evolution can be accurately calculated.

[0019] In view of this, the present invention provides a high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method, comprising the following steps:

[0020] S100, reconstructing the global average surface temperature based on atmospheric carbon dioxide concentration pCO2;

[0021] S200, calculates the relative content of carbonate ions and bicarbonate ions in a marine carbonate system;

[0022] S300, the fractionation coefficient is determined based on the calculation results in steps S100 and S200;

[0023] S400, based on the difference in carbon isotopes between brachiopods and carbonate rocks, determines the difference in carbon isotopes between carbonate rocks and surrounding seawater during the deposition of carbonate rocks.

[0024] S500, Estimate δ based on the parameters determined in steps S100 to S400. 13 C CO2 .

[0025] Furthermore, in step S100, the global average surface temperature T(t) is calculated according to the following formula:

[0026]

[0027] Where T(t) represents the global average surface temperature at time t;

[0028] h is a time-dependent factor used to characterize the enhanced climate sensitivity during cold periods;

[0029] μ is the climate sensitivity coefficient, which represents the response of temperature to a doubling of atmospheric carbon dioxide concentration under current solar radiation intensity and paleogeographic conditions.

[0030] pCO2(t) represents the atmospheric carbon dioxide concentration at time t.

[0031] Furthermore, in step S200,

[0032] The relative content of bicarbonate ions f([HCO3-)) in the marine carbonate system is calculated according to the following formula I. - ]):

[0033] f([HCO3 - ])=[HCO3 - ] / DIC (Ⅰ);

[0034] The relative content of carbonate ions f([CO3]) in the marine carbonate system was calculated according to Formula II. 2- ]):

[0035] f([CO3 2- ])=[CO3 2- ] / DIC (Ⅱ);

[0036] Among them, [HCO3] - [HCO3] represents the concentration of bicarbonate ions in a seawater carbonate system. - ];

[0037] DIC is the total inorganic carbon content of the ocean in the seawater carbonate system;

[0038] CO3 2- [ ] represents the carbonate ion concentration in the seawater carbonate system.

[0039] Furthermore, in step S200:

[0040] Based on the known atmospheric carbon dioxide concentration pCO2, the carbon dioxide content [CO2] in the seawater of the marine carbonate system was quantitatively calculated using Henry's Law.

[0041] Based on the total alkalinity (ALK) and the concentration of calcium ions in the ocean [Ca] 2+ The relationship between these parameters is used to obtain the value of total marine alkalinity (ALK).

[0042] After obtaining the values ​​of carbon dioxide [CO2] and total alkalinity (ALK) in seawater, the concentration of bicarbonate ions [HCO3] is determined based on the relationships between various parameters within the seawater carbonate system. - ], carbonate ion concentration [CO3 2- The values ​​of four parameters: ocean pH, total inorganic carbon (DIC), and ocean pH.

[0043] Furthermore, in step S300: the fractionation coefficient between carbon dioxide and DIC needs to be determined based on the calculation results in steps S100 and S200. Fractionation coefficient between bicarbonate ions and carbon dioxide and the fractionation coefficient between carbonate ions and carbon dioxide.

[0044] Furthermore, based on the reconstructed average surface temperature T in step S100 and the calculated f([HCO3]2) in step S200... - ]) and f([CO3 2- ]) Calculate and Three fractionation coefficients.

[0045] Furthermore, in step S300, and The three fractionation coefficients are calculated as follows:

[0046]

[0047] Furthermore, the difference value V represents the difference between the average carbon isotope values ​​of carbonate rocks and brachiopod fossils in the same sedimentary stratum.

[0048] Furthermore, in step S500, δ is estimated according to the following formula. 13 C CO2 Value:

[0049]

[0050] Where, δ 13 C CaCO3 This represents the stable carbon isotope composition of carbonate rocks, which was obtained through laboratory instrumentation.

[0051] A high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation system is provided, wherein the deep-time atmospheric carbon dioxide carbon isotope composition estimation system uses the aforementioned high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method to estimate the deep-time atmospheric carbon dioxide carbon isotope composition.

[0052] The beneficial effects of this invention are:

[0053] 1. High resolution and good data continuity: This invention selects carbonate rocks as the research object. Carbonate rocks are a type of sediment that is widely distributed in geological history, has a relatively continuous deposition time, and is well preserved. This avoids the limitations of discontinuous distribution of plant fossils, scarcity of marine shell fossils, and interruption of time constraints. It can obtain atmospheric CO2 carbon isotope composition data with high temporal resolution, complete sequence, and wide spatial applicability. Therefore, the high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method described in this invention has the advantages of high resolution and good data continuity at deep-time scale.

[0054] 2. High accuracy and reliability of estimation results: The method of this invention achieves high accuracy and reliability in δ... 13 C CO2In the estimation process, the fractionation parameter ε is no longer simplified to a constant. Instead, it dynamically and quantitatively corrects the key factors affecting the fractionation effect by combining changes in ocean surface temperature during geological history, the evolution of the composition of the marine carbonate system, and the isotopic fractionation effect during the formation of carbonate rocks. This overcomes the problem of neglecting environmental changes in traditional methods, which leads to inaccuracies in the δ-parameter. 13 C CO2 The problem of excessive error was ultimately effectively addressed by improving δ. 13 C CO2 The accuracy and reliability of the estimation results;

[0055] 3. It can achieve accurate estimation of atmospheric CO2 carbon isotopes in a wider range of geological history stages and different environmental backgrounds: Through carbonate rock records and comprehensive parameter correction, this invention has the ability to cope with high pCO2 concentration fluctuations in paleogeological periods and extreme warm or glacial environments. It can be applied to accurate reconstruction under extreme climate backgrounds and can achieve accurate estimation of atmospheric CO2 carbon isotopes in a wider range of geological history stages and different environmental backgrounds.

[0056] 4. High versatility and wide application range: Carbonate rocks are widely distributed and have diverse sedimentary environments. Therefore, the high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method described in this invention can be applied to the deep-time atmospheric carbon dioxide carbon isotope composition estimation in various regions such as ancient continental margin sedimentary areas, open ocean basins and shallow sea platforms, and high-latitude extreme climate zones. It meets the needs of deep-time atmospheric CO2 carbon isotope composition estimation in multiple locations, periods, and scales, and can provide support for multiple fields such as paleoclimate, paleooceanography, paleoecology, and geological resource surveys. Attached Figure Description

[0057] Figure 1 This is a schematic diagram of the process of the high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method described in this invention;

[0058] Figure 2 This is a comparison of carbon isotope values ​​between carbonate rocks and brachiopod fossils in this invention;

[0059] Figure 3 This is a comparison chart of the deep-time atmospheric carbon dioxide carbon isotope composition estimated according to the method provided in this invention and the deep-time atmospheric carbon dioxide carbon isotope composition calculated using biological shell fossils.

[0060] Figure 4 This is a comparison chart of the global average surface temperature estimated according to the method provided in this invention and the paleotemperature estimated based on oxygen isotopes from biological shell fossils. Detailed Implementation

[0061] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0062] It should be noted that, in this application, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0063] This invention provides a high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method. This method selects carbonate rocks that are ubiquitous in geological history and have been deposited continuously over time as a tool for atmospheric carbon dioxide isotope reconstruction. Through quantitative evaluation of geological history ocean surface temperature, marine carbonate content, and fractionation during carbonate rock formation, the atmospheric carbon dioxide isotope composition during deep-time geological history evolution can be accurately calculated.

[0064] like Figure 1 As shown, a high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method includes the following steps:

[0065] S100, reconstructing the global average surface temperature based on atmospheric carbon dioxide concentration (pCO2);

[0066] S200, calculates the relative content of carbonate ions and bicarbonate ions in a marine carbonate system;

[0067] S300, the fractionation coefficient is determined based on the calculation results in steps S100 and S200;

[0068] S400, based on the difference in carbon isotopes between brachiopods and carbonate rocks, determines the difference in carbon isotopes between carbonate rocks and surrounding seawater during the deposition of carbonate rocks.

[0069] S500, Estimate δ based on the parameters determined in steps S100 to S400. 13 C CO2 .

[0070] Specifically, in step S100, the global average surface temperature T(t) is calculated according to the following formula:

[0071]

[0072] Where T(t) represents the global average surface temperature at time t (million years ago);

[0073] h (=1~2) is a time-dependent factor used to characterize the enhanced climate sensitivity during cold periods;

[0074] μ is the climate sensitivity coefficient, which represents the response of temperature to a doubling of atmospheric carbon dioxide concentration under current solar radiation intensity and paleogeographic conditions.

[0075] pCO2(t) represents the atmospheric carbon dioxide concentration at time t (million years ago).

[0076] As will be understood by those skilled in the art, in this invention, the atmospheric carbon dioxide concentration at different times is known and can be directly obtained through methods such as ice core bubble measurement, boron isotope proxy (δ¹¹B method), paleoplant stomatal method, combined carbonate composition and stable isotope method, geochemical-numerical model inversion method, or by consulting publicly available databases and literature data, and is used as the input parameter of this invention to estimate the global average surface temperature T(t) at time t (millions of years ago).

[0077] In addition, in the above step S100, the time dependence factor h is usually set to a range of 1 to 2. Generally, the larger h is, the stronger the climate sensitivity. The specific value of h can be determined through empirical inversion and calibration. The climate sensitivity coefficient μ can be determined by combining the results of modern climate sensitivity research, paleoclimate proxy data inversion and numerical simulation correction. Its value range can be dynamically adjusted according to the specific geological period and paleogeographic background.

[0078] Specifically, in step S200, we generally assume that:

[0079] The seawater carbonate system mainly includes the carbon dioxide content ([CO2]) and bicarbonate ion concentration ([HCO3]) in seawater. - ]), carbonate ion concentration ([CO3) 2- ]), ocean pH, total inorganic carbon (DIC), and total alkalinity (ALK).

[0080] Furthermore, it is known to those skilled in the art that the seawater carbonate system is a closed, coupled chemical equilibrium system, in which there are definite mathematical and physical relationships between its various parameters, mainly determined by the carbonate-bicarbonate-carbon dioxide balance, the conservation of total alkalinity, and the conservation of mass. For example, the total inorganic carbon content (DIC) of the ocean = the carbon dioxide content in the seawater ([CO2]) + the concentration of bicarbonate ions ([HCO3]). - ])+ carbonate ion concentration ([CO3 2- Therefore, when we know any two of the above six parameters, we can substitute them into the equilibrium equation and conservation relationship, solve the system of equations, and determine the other four parameters. The detailed calculation process can be found in relevant materials and will not be elaborated here.

[0081] In step S200 of this invention, the carbon dioxide content ([CO2]) in seawater can be quantitatively calculated using Henry's Law based on the known atmospheric carbon dioxide concentration (pCO2). The specific calculation formula is as follows:

[0082] [CO2]=k H (T,S)×pCO2;

[0083] [CO2] represents the carbon dioxide content in seawater;

[0084] k H (T,S) represents the Henry coefficient;

[0085] pCO2 is the atmospheric carbon dioxide concentration (or partial pressure).

[0086] Furthermore, based on the above, the carbon dioxide content ([CO2]) in the seawater of the seawater carbonate system can be obtained. If another parameter can be obtained, the other four parameters can be determined.

[0087] In this invention, the design first obtains the total alkalinity (ALK) of the ocean, and then determines four other parameters based on the carbon dioxide content ([CO2]) in the seawater and the total alkalinity (ALK).

[0088] Specifically, marine total alkalinity (ALK) is obtained based on ALK and the concentration of marine calcium ions ([Ca2+]). 2+ The relationship between ]) is used to achieve this, and the specific process is as follows:

[0089] First use M ca The total calcium content in the ocean is expressed in F. W,sil F W,carb F b,carb Let represent the weathering rate of silicate rocks, the weathering rate of carbonate rocks, and the deposition rate of carbonate rocks, respectively. Then, these parameters have the following relationship:

[0090]

[0091] Where, α (=10.8×10 12 (mol / yr) is a constant representing the equilibrium flux under the initial steady state;

[0092] K sp *(=4.3×10 -7 () represents the solubility product of calcite under specific conditions;

[0093] [Ca 2+ [Represents the calcium ion concentration per unit mass of seawater (=M)] ca / M oc M oc The mass of seawater is approximately 1.4 × 10⁻⁶. 21 kg).

[0094] Through the above ALK, M ca F W,sil F W,carb F b,carb The value of total alkalinity (ALK) in the ocean can be calculated by combining the equations relating the relationships between them.

[0095] Furthermore, after obtaining the values ​​of carbon dioxide content ([CO2]) and total alkalinity (ALK) in seawater, the concentration of bicarbonate ions ([HCO3]) can be determined based on the mathematical and physical relationships between the parameters within the seawater carbonate system. - ]), carbonate ion concentration ([CO3) 2- The values ​​of four parameters—ocean pH, total inorganic carbon (DIC), and total marine pH—were obtained, and further derived:

[0096] f([HCO3 - ])=[HCO3 - ] / DIC, f([CO3 2- ])=[CO3 2- ] / DIC;

[0097] Wherein, f([HCO3 - The bicarbonate ion content represents the proportion of bicarbonate ions in the total inorganic carbon in a carbonate system, i.e., the relative content of bicarbonate ions in a marine carbonate system.

[0098] f([CO3 2- The value represents the proportion of carbonate ions in the total inorganic carbon in a carbonate system, i.e., the relative content of carbonate ions in a marine carbonate system.

[0099] Furthermore, in step S300, the fractionation of marine carbon cycle isotopes mainly manifests as fractionation between carbon dioxide and DIC, between bicarbonate ions and carbon dioxide, and between carbonate ions and carbon dioxide, which can be expressed as follows: and

[0100] Furthermore, these three fractionation coefficients are functions of temperature, based on the global average surface temperature T reconstructed in step S100 and f([HCO3]2) calculated in step S200. - ]) and f([CO3 2- It can be calculated that and Three fractionation coefficients:

[0101]

[0102] Furthermore, in step S400, considering that the carbonate rock precipitation process is affected by marine biological activity and organic matter oxidation, resulting in differences in carbon isotopes with the surrounding seawater, this design defines the difference value as V.

[0103] Furthermore, in order to determine the V value, this design selects an ancient organism (brachiopod) as a reference. Brachiopods are considered not to undergo fractionation during the precipitation of seawater carbonate ions. Therefore, the shells of this brachiopod are considered to be the main proxy indicator of seawater carbon isotopes. The V value can be obtained by the difference in carbon isotopes between the brachiopod and the carbonate rocks.

[0104] As some examples of the present invention, the V value can be calculated by the difference between the carbon isotopes of marine shell fossils (Brachiopod) and carbonate rocks. Specifically, in this application, it can be obtained by... Figure 2 The difference value V is obtained by calculating the average value of the comparison between the two, that is, the difference value V is the difference between the average carbon isotope values ​​of carbonate rocks and brachiopod fossils in the same sedimentary stratum.

[0105] Data comparison revealed a difference of V≈1.3‰.

[0106] Furthermore, in step S500, δ is estimated according to the following formula. 13 C CO2 Value:

[0107]

[0108] Where, δ 13 C CaCO3 Carbonate rock ( CaCO3 The stable carbon isotope composition of ) can be directly determined using laboratory instruments.

[0109] Furthermore, the present invention also provides a high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation system, wherein the deep-time atmospheric carbon dioxide carbon isotope composition estimation system uses the high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method to estimate the deep-time atmospheric carbon dioxide carbon isotope composition.

[0110] The high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method provided by this invention has the following advantages and positive effects compared with existing deep-time atmospheric carbon dioxide isotope reconstruction techniques:

[0111] 1. High resolution and good data continuity: This invention selects carbonate rocks as the research object. Carbonate rocks are a type of sediment that is widely distributed in geological history, has a relatively continuous deposition time, and is well preserved. This avoids the limitations of discontinuous distribution of plant fossils, scarcity of marine shell fossils, and interruption of time constraints. It can obtain atmospheric CO2 carbon isotope composition data with high temporal resolution, complete sequence, and wide spatial applicability. Therefore, the high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method described in this invention has the advantages of high resolution and good data continuity at deep-time scale.

[0112] 2. High accuracy and reliability of estimation results: The method of this invention achieves high accuracy and reliability in δ... 13 C CO2 In the estimation process, the fractionation parameter ε is no longer simplified to a constant. Instead, it dynamically and quantitatively corrects the key factors affecting the fractionation effect by combining changes in ocean surface temperature during geological history, the evolution of the composition of the marine carbonate system, and the isotopic fractionation effect during the formation of carbonate rocks. This overcomes the problem of neglecting environmental changes in traditional methods, which leads to inaccuracies in the δ-parameter. 13 C CO2 The problem of excessive error was ultimately effectively addressed by improving δ. 13 C CO2 The accuracy and reliability of the estimation results;

[0113] 3. It can achieve accurate estimation of atmospheric CO2 carbon isotopes in a wider range of geological history stages and different environmental backgrounds: Through carbonate rock records and comprehensive parameter correction, this invention has the ability to cope with high pCO2 concentration fluctuations in paleogeological periods and extreme warm or glacial environments. It can be applied to accurate reconstruction under extreme climate backgrounds and can achieve accurate estimation of atmospheric CO2 carbon isotopes in a wider range of geological history stages and different environmental backgrounds.

[0114] 4. High versatility and wide application range: Carbonate rocks are widely distributed and have diverse sedimentary environments. Therefore, the high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method described in this invention can be applied to the deep-time atmospheric carbon dioxide carbon isotope composition estimation in various regions such as ancient continental margin sedimentary areas, open ocean basins and shallow sea platforms, and high-latitude extreme climate zones. It meets the needs of deep-time atmospheric CO2 carbon isotope composition estimation in multiple locations, periods, and scales, and can provide support for multiple fields such as paleoclimate, paleooceanography, paleoecology, and geological resource surveys.

[0115] The following specific examples illustrate the method for estimating atmospheric carbon dioxide carbon isotope composition at high resolution depth according to the present invention:

[0116] (1) First, based on the known atmospheric carbon dioxide concentration (pCO2), and considering the relationship between Earth's surface temperature, carbon dioxide content, solar photometric evolution, and paleogeographic changes, the global average surface temperature T(t) is calculated using the following formula:

[0117]

[0118] Where T(t) represents the global average surface temperature at time t (million years ago);

[0119] h (=1~2) is a time-dependent factor used to characterize the enhanced climate sensitivity during cold periods;

[0120] μ (≈4) is the climate sensitivity coefficient, which represents the response of temperature to a doubling of atmospheric carbon dioxide concentration under current solar radiation intensity and paleogeographic conditions;

[0121] pCO2(t) represents the atmospheric carbon dioxide concentration at time t (million years ago).

[0122] To verify the accuracy of the temperature estimation achieved by this method, the temperature estimated by the above method was compared with the paleotemperature (~183 Ma) estimated based on oxygen isotopes from biological shell fossils. The results are as follows: Figure 4 As shown, by Figure 4 It can be seen that the paleotemperatures reconstructed by these two methods show a high degree of fit in terms of evolutionary trends.

[0123] (2) Calculate the relative contents of carbonate ions and bicarbonate ions in the marine carbonate system.

[0124] In this design, pCO2 is known, and [CO2] can be calculated using Henry's Law; therefore, another parameter is needed. The design selects total marine alkalinity ALK, which is based on ALK and the concentration of marine calcium ions ([Ca... 2+ The relationship between ]) is used to calculate:

[0125] First use Mca The total calcium content in the ocean is expressed in F. W,sil F W,carb F b,carb Let represent the weathering rate of silicate rocks, the weathering rate of carbonate rocks, and the deposition rate of carbonate rocks, respectively. Then, these parameters have the following relationship:

[0126]

[0127] Where, α (=10.8×10 12 (mol / yr) is a constant representing the equilibrium flux under the initial steady state;

[0128] K sp *(=4.3×10 -7 () represents the solubility product of calcite under specific conditions;

[0129] [Ca 2+ [Represents the calcium ion concentration per unit mass of seawater (=M)] ca / M oc M oc The mass of seawater is approximately 1.4 × 10⁻⁶. 21 kg).

[0130] Through the above ALK, M ca F W,sil F W,carb F b,carb The value of total alkalinity (ALK) in the ocean can be calculated by combining the equations relating the relationships between them.

[0131] Furthermore, after obtaining the values ​​of carbon dioxide content ([CO2]) and total alkalinity (ALK) in seawater, the concentration of bicarbonate ions ([HCO3]) can be determined based on the mathematical and physical relationships between the parameters within the seawater carbonate system. - ]), carbonate ion concentration ([CO3) 2- The values ​​of four parameters—ocean pH, total inorganic carbon (DIC), and total marine pH—were obtained, and further derived:

[0132] f([HCO3 - ])=[HCO3 - ] / DIC, f([CO3 2- ])=[CO3 2- ] / DIC;

[0133] Wherein, f([HCO3 - The bicarbonate ion content represents the proportion of bicarbonate ions in the total inorganic carbon in a carbonate system, i.e., the relative content of bicarbonate ions in a marine carbonate system.

[0134] f([CO3 2- The value represents the proportion of carbonate ions in the total inorganic carbon in a carbonate system, i.e., the relative content of carbonate ions in a marine carbonate system.

[0135] (3) Determination of fractionation coefficients: The fractionation of marine carbon cycle isotopes is mainly manifested in the fractionation between carbon dioxide and DIC, between bicarbonate ions and carbon dioxide, and between carbonate ions and carbon dioxide, which can be expressed as follows: and These three fractionation coefficients are functions of temperature, based on the temperature T reconstructed in step S100 and f([HCO3]2) calculated in step S200. - ]) and f([CO3 2- Three parameters can be calculated:

[0136]

[0137] (4) Determination of the differences in carbon isotopes between carbonate rocks and surrounding seawater during carbonate rock deposition:

[0138] To determine the V value, this design selects a brachiopod as a reference. Brachiopods are considered not to undergo fractionation during the precipitation of seawater carbonate ions. Therefore, the shells of this brachiopod are considered as the main proxy indicator of seawater carbon isotopes. The V value can be obtained by the difference in carbon isotopes between the brachiopod and the carbonate rock. Through data comparison, the difference between the two is found to be V≈1.3‰.

[0139] (5)δ 13 C CO2 Final estimate:

[0140] By determining the above parameters, δ can be accurately estimated. 13 C CO2 ,Right now:

[0141]

[0142] (6) Comparison of atmospheric carbon dioxide carbon isotopes reconstructed from carbonate rocks and brachiopod fossils. The comparison results are shown in […]. Figure 2 ,according to Figure 2 It can be known that:

[0143] First, there are certain deviations in the estimation results of atmospheric carbon dioxide carbon isotope composition reconstructed based on carbonate rocks and brachiopod fossils. In particular, the estimation results of atmospheric carbon dioxide carbon isotope composition reconstructed based on carbonate rocks are generally higher than those reconstructed based on brachiopod fossils.

[0144] Second, despite the absolute value deviations, the estimated atmospheric carbon dioxide carbon isotope composition based on carbonate rocks and brachiopod fossils generally shows synchronous fluctuations.

[0145] (7) The deep-time atmospheric carbon dioxide carbon isotope composition estimated according to the method provided in this invention is compared with the traditional deep-time atmospheric carbon dioxide carbon isotope composition calculated using biological shell fossils to obtain the following results: Figure 3 The comparison revealed that the deep-time atmospheric carbon dioxide carbon isotope composition results estimated by the present invention based on carbonate rocks are highly consistent with the traditional deep-time atmospheric carbon dioxide carbon isotope composition results calculated using biological shell fossils. Furthermore, the deep-time atmospheric carbon dioxide carbon isotope composition results estimated by the method provided by the present invention have higher resolution and better data continuity.

[0146] In summary, this invention uses carbonate rocks, which are commonly found in deep-time Earth, as the object of reconstruction of atmospheric carbon dioxide carbon isotopes. During the reconstruction process, the influence of marine carbonate systems and fractionation effects on carbon isotope composition is taken into account, providing a high-resolution reconstruction method for deep-time atmospheric carbon dioxide isotopes.

[0147] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A high-resolution, deep-time atmospheric carbon dioxide carbon isotope composition estimation method, characterized in that, Including the following steps: S100, reconstructing the global average surface temperature based on atmospheric carbon dioxide concentration pCO2; S200, calculates the relative content of carbonate ions and bicarbonate ions in a marine carbonate system; S300, the fractionation coefficient is determined based on the calculation results in steps S100 and S200; S400, based on the difference in carbon isotopes between brachiopods and carbonate rocks, determines the difference in carbon isotopes between carbonate rocks and surrounding seawater during the deposition of carbonate rocks. S500, Estimate δ based on the parameters determined in steps S100 to S400. 13 C CO2 .

2. The high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method according to claim 1, characterized in that, In step S100, the global average surface temperature T(t) is calculated according to the following formula: Where T(t) represents the global average surface temperature at time t; h is a time-dependent factor used to characterize the enhanced climate sensitivity during cold periods; μ is the climate sensitivity coefficient, which represents the response of temperature to a doubling of atmospheric carbon dioxide concentration under current solar radiation intensity and paleogeographic conditions. pCO2(t) represents the atmospheric carbon dioxide concentration at time t.

3. The high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method according to claim 1, characterized in that, In step S200, The relative content of bicarbonate ions f([HCO3-)) in the marine carbonate system is calculated according to the following formula I. - ]): f([HCO3 - ])=[HCO3 - ] / DIC (Ⅰ); The relative content of carbonate ions f([CO3]) in the marine carbonate system was calculated according to Formula II. 2- ]): f([CO3 2- ])=[CO3 2- ] / DIC (Ⅱ); Among them, [HCO3] - [HCO3] represents the concentration of bicarbonate ions in a seawater carbonate system. - ]; DIC is the total inorganic carbon content of the ocean in the seawater carbonate system; CO3 2- [ ] represents the carbonate ion concentration in the seawater carbonate system.

4. The high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method according to claim 3, characterized in that, In step S200: Based on the known atmospheric carbon dioxide concentration pCO2, the carbon dioxide content [CO2] in the seawater of the marine carbonate system was quantitatively calculated using Henry's Law. Based on the total alkalinity (ALK) and the concentration of calcium ions in the ocean [Ca] 2+ The relationship between these parameters is used to obtain the value of total marine alkalinity (ALK). After obtaining the values ​​of carbon dioxide [CO2] and total alkalinity (ALK) in seawater, the concentration of bicarbonate ions [HCO3] is determined based on the relationships between various parameters within the seawater carbonate system. - ], carbonate ion concentration [CO3 2- The values ​​of four parameters: ocean pH, total inorganic carbon (DIC), and ocean pH.

5. The high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method according to claim 1, characterized in that, In step S300: the fractionation coefficient between carbon dioxide and DIC needs to be determined based on the calculation results in steps S100 and S200. Fractionation coefficient between bicarbonate ions and carbon dioxide and the fractionation coefficient between carbonate ions and carbon dioxide.

6. The high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method according to claim 5, characterized in that, Based on the reconstructed average surface temperature T in step S100 and the calculated f([HCO3]2) in step S200 - ]) and f([CO3 2- ]) Calculate and Three fractionation coefficients.

7. The high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method according to claim 6, characterized in that, In step S300, and The three fractionation coefficients are calculated as follows:

8. The high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method according to claim 1, characterized in that, The difference value V is the difference between the average carbon isotope values ​​of carbonate rocks and brachiopod fossils in the same sedimentary stratum.

9. The high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method according to claim 1, characterized in that, In step S500, δ is estimated according to the following formula. 13 C CO2 Value: Where, δ 13 C CaCO3 This represents the stable carbon isotope composition of carbonate rocks, which was obtained through laboratory instrumentation.

10. A high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation system, characterized in that, The deep-time atmospheric carbon dioxide carbon isotope composition estimation system uses the high-resolution deep-time atmospheric carbon dioxide carbon isotope composition estimation method described in any one of claims 1 to 9 to estimate the deep-time atmospheric carbon dioxide carbon isotope composition.

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