A method for restoring paleoclimate factors based on plant community homeostasis

Abstract

This paper provides a method for restoring paleoclimate factors based on plant community homeostasis. This method, which falls within the field of paleoclimate restoration in paleontology and geophysics, focuses on characterizing paleotemperatures and paleoprecipitation. Specifically, it relates to a method for restoring pollen-paleoclimate factors (paleotemperatures and paleoprecipitation) from wells or rock columns, comparing the measured terrestrial pollen species and content with indicators of the climatic conditions required for the reproduction of terrestrial plant species and communities, and incorporating corrections based on paleolatitude insolation and evaporation intensity. This method achieves the restoration of a full-sequence, continuous paleoclimate curve, and the restored paleoclimate factors are more accurate.

Description

Technical Field

[0001] The present invention relates to the fields of paleontology and geophysics, and in particular to a method for recovering spore-pollen paleoclimate factors based on plant community homeostasis. Background Art

[0002] Reference 1: (Xu Qinghai, Xiao Jule, Nakamura Toshio, et al. Quantitative Reconstruction of the Holocene Paleoclimate of the Daihai Basin Using Pollen Data [J]. Marine Geology and Quaternary Geology, 2003.) The distribution of modern pollen abundance in geographic space was converted to a climatic distribution for each representative pollen type. Quadratic or cubic response surface methods were then used to determine the optimal and extreme climatic conditions for each pollen type. The fossil pollen assemblage data were then compared with various pollen-climate response surfaces to determine paleoclimate parameters. The specific steps were: first, the dominant pollen type in the profile was selected and a trend surface model was established. The climatic space containing the topsoil pollen data was then evenly divided into several grids, with each grid node representing a data point. The trend surface was used to determine the percentage content of each node for each pollen type. These pollen type percentage data were then compared as a set of vectors with a set of measured percentage data for the same pollen type in each profile sample. The similarity between the two data sets was calculated, and the one with the greatest similarity was considered to have the same climatic parameter values. However, the pollen-climate response surface (PRS) is a functional relationship between pollen and climate, established based on the responses of vegetation to climate and the environment in its natural state. Since it is currently difficult to find vegetation in its pure natural state, the pollen-climate response surface, based on the relationship between vegetation and climate under human interference, is inevitably subject to some errors and interference.

[0003] Reference 2: (Li Haonan, Wang Chunlian, Liu Chenglin, et al. Early Eocene paleotemperature in the Jiangling Sag: Evidence from anhydrous thenardite fluid inclusions [J]. Acta Geologica Sinica, 2015, 89(11):9.) Compared to rock salt, anhydrous thenardite has the advantages of high hardness, low solubility, and low recrystallization resistance, which is more conducive to the preservation of primary inclusions. In addition, anhydrous thenardite is a representative mineral of warm minerals, and the temperature information contained in its fluid inclusions may have a good relationship with the paleotemperature at that time. For temperature measurement, anhydrous thenardite samples containing only single liquid phase fluid inclusions or only a small amount of gas-liquid two-phase fluid inclusions were selected (the gas-liquid two-phase fluid inclusions were marked and excluded during the temperature measurement process), thereby ensuring the accuracy of the temperature measurement data. This method is highly dependent on the accuracy of the data and the technical technology of the temperature measurement method. In addition, the fluid inclusions can only represent the paleotemperature by measuring the temperature when the fluid is captured by the mineral, which is difficult to truly reflect the atmospheric temperature.

[0004] Reference 3: (Jia Yulian, Fan Yunqi, Shi Yafeng. Method for determining parameters in restoring ancient precipitation in a watershed using the combined water-energy equation and its application—taking the calculation of ancient precipitation in the Holocene hypertherm period of Qinghai Lake as an example [J]. Advances in Water Science. 2001, 12(3):324-330.) Based on the paleolake remains, the paleolake area is determined, the water balance equation for the entire watershed is established, and the paleoprecipitation of the basin is calculated. The combined water and energy balance equation for the entire watershed in a closed lake basin is as follows: using various parameters including surface water vapor pressure, atmospheric temperature, cloud cover, surface reflectivity, surface scattering, astronomical radiation, atmospheric transparency coefficient, latent heat of evaporation, Born ratio, etc., the parameters are obtained by multiple approximations based on the present and the past. The parameter calculation of this method relies heavily on empirical transformation and mathematical analogy, and the large number of parameters involved makes it difficult to apply to ancient geological periods before the Holocene. It is generally only applicable to closed lake basins since the Holocene, and has significant limitations.

[0005] Therefore, how to obtain accurate paleoclimate factors (paleotemperature values, paleoprecipitation) and obtain a continuous paleoclimate change curve is still a problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0006] The present invention provides a method for recovering paleoclimate factors based on plant community steady state, which is used to solve the problem in the prior art that it is difficult to obtain accurate paleoclimate factors (paleotemperature values, paleoprecipitation), and that discrete curves rather than full-sequence continuous climate curves are used.

[0007] The present invention provides a method for restoring sporopollen paleoclimate factors based on plant community homeostasis, comprising:

[0008] Collect the original pollen count data of each type at each depth and convert it into pollen content data of each depth;

[0009] Based on the pollen content data of each depth and the terrestrial pollen temperature-precipitation conversion database, the climate index of each depth is determined, wherein the climate index includes the temperature index and the precipitation index. The temperature index includes the maximum temperature, the minimum temperature and the average temperature, and the precipitation index includes the maximum precipitation, the minimum precipitation and the average precipitation.

[0010] Determine the dominant plant pollen at each depth according to preset rules based on the pollen content data at each depth, determine the dominant plant community to which the dominant plant pollen belongs, and determine the community precipitation coefficient and community temperature coefficient based on the dominant plant community;

[0011] The precipitation index is corrected based on the community precipitation coefficient to obtain the initial paleoprecipitation index of each depth, and the temperature index is corrected based on the community temperature coefficient to obtain the initial paleotemperature index of each depth;

[0012] Determining a sunshine coefficient as a paleotemperature correction multiple based on the paleolatitude of each depth and the initial paleotemperature index of each depth, and determining a final paleotemperature index based on the initial paleotemperature index and the paleotemperature correction multiple;

[0013] Determine an evaporation coefficient as a paleoprecipitation correction factor based on the paleolatitude of each depth and the initial paleoprecipitation index at each depth, and determine a final paleoprecipitation index based on the initial paleoprecipitation index and the paleoprecipitation correction factor;

[0014] The climate sensitivity curve is converted into an astronomical cycle curve, and the periodic changes of the astronomical cycle curve are taken as the trend, combined with the minimum climate and the maximum climate as the reference boundary values, and the average climate as the basic parameter to fit and generate a continuous periodic curve. Among them, the minimum climate includes the minimum temperature and minimum precipitation, the maximum climate includes the maximum temperature and maximum precipitation, and the average climate includes the average temperature and average precipitation.

[0015] According to a method for restoring paleoclimate factors based on plant community steady state provided by the present invention, the temperature index and precipitation index at each depth are determined based on the pollen content data at each depth and the terrestrial pollen temperature-precipitation conversion database, specifically comprising:

[0016] The climate index at each depth was obtained by weighted summing the standard climate index in the terrestrial pollen temperature-precipitation conversion database and the content of each pollen at each depth.

[0017] According to a method for restoring pollen paleoclimate factors based on plant community steady state provided by the present invention, the method of determining the dominant plant pollen at each depth according to preset rules based on the pollen content data at each depth specifically includes:

[0018] For paleolatitudes between 0 and 23.5° south or north, the pollen with the highest proportion of angiosperms was selected as the dominant plant pollen. For paleolatitudes between 23.5 and 66.5° south or north, the pollen with the highest proportion of angiosperms and gymnosperms was selected as the dominant plant pollen. For paleolatitudes between 66.5 and 90° south or north, the pollen with the highest proportion of gymnosperms was selected as the dominant plant pollen.

[0019] According to a method for restoring paleoclimate factors based on plant community steady state provided by the present invention, the precipitation index is corrected based on the community precipitation coefficient to obtain the initial paleoclimate index at each depth, and the temperature index is corrected based on the community temperature coefficient to obtain the initial paleoclimate index at each depth, specifically comprising:

[0020] The initial paleoprecipitation index and initial paleotemperature index at each depth are calculated using the following formula:

[0021] T i =ti +ΔT i , P i =p i +ΔP i

[0022] Among them, T i is the initial paleotemperature index at depth i, t i is the temperature index at depth i, ΔT i is the community temperature coefficient at depth i, T i is the initial precipitation index at depth i, t i is the precipitation index at depth i, ΔP i is the community precipitation coefficient at depth i.

[0023] According to a method for restoring paleoclimate factors based on plant community steady state provided by the present invention, the method comprises determining a sunshine coefficient as a paleotemperature correction multiple based on the paleolatitude of each depth and the initial paleotemperature index of each depth, and determining a final paleotemperature index based on the initial paleotemperature index and the paleotemperature correction multiple, which specifically includes:

[0024] The sunshine coefficient Sun is determined as the paleotemperature correction factor using the following formula:

[0025] 0≤L≤90:

[0026] 0>L>-60:

[0027] -60≥L≥-90:

[0028]

[0029] Among them, L is latitude, with positive values for north latitude and negative values for south latitude, S is the sunshine intensity at each depth, S i is the sunshine intensity at the i-th depth, n is the total number of depths in the drilling pollen sampling, i is the i-th depth among all the drilling pollen sampling depths, T i is the initial paleotemperature index at the i-th depth;

[0030] The final paleotemperature index is equal to the initial paleotemperature index multiplied by the paleotemperature correction factor.

[0031] According to a method for restoring paleoclimate factors based on plant community steady state provided by the present invention, the evaporation coefficient is determined as a paleoprecipitation correction multiple based on the paleolatitude of each depth and the initial paleoprecipitation index of each depth, and the final paleoprecipitation index is determined based on the initial paleoprecipitation index and the paleoprecipitation correction multiple, specifically comprising:

[0032] The evaporation coefficient Eva is determined as the paleoprecipitation correction factor using the following formula:

[0033] 30≤L≤90: E=4827-365.8L+11.846L 2 -0.1577L 3 +7.2×10 -4 L 4

[0034] 0≤L<30: E=1788+36L-6.26L 2 +0.134L 3

[0035] 0>L≥-30: E=1799+62L+1.93L 2 +0.028L 3

[0036] -3>L≥-90: E=19500+1491L+42.51L 2 +0.509L 3 +2.16×10 -3 L 4

[0037]

[0038] Where L is the latitude, with positive values for north latitude and negative values for south latitude, and E is the evaporation at each depth. i is the evaporation at the th depth, n is the total number of depths in the drilling pollen sampling, i is the i-th depth among all the drilling pollen sampling depths, P i is the initial paleoprecipitation index at the i-th depth;

[0039] The final paleoprecipitation index is equal to the initial paleoprecipitation index multiplied by the paleoprecipitation correction factor.

[0040] According to a method for restoring paleoclimate factors based on plant community steady state provided by the present invention, the method of converting a climate sensitivity curve into an astronomical cycle curve specifically includes:

[0041] The climate sensitivity curve is subjected to noise reduction and detrending processing to obtain the preprocessed curve;

[0042] Performing spectrum analysis on the pre-processed curve to generate a frequency spectrum, and selecting a target frequency spectrum of a frequency band corresponding to a 405ka long eccentricity period;

[0043] The target frequency spectrum is filtered using a bandpass filter to generate a filtering curve corresponding to a characteristic peak of a long eccentricity period of the envelope, which is an astronomical cyclotron curve.

[0044] According to the present invention, a method for restoring paleoclimate factors based on plant community homeostasis further comprises:

[0045] Using global temperature change curves and major climate events to conduct trend and event verification, and to determine the relationship between the periodic curve trend and the global climate fitting response;

[0046] Finally, the full sequence of paleotemperature data and curves, as well as paleoprecipitation data and curves of the target well section were obtained.

[0047] The present invention provides a method for restoring paleoclimate factors of pollen based on the steady state of plant communities. The method collects original pollen count data of each type at each depth and converts the data into pollen content data of each depth. Based on the pollen content data of each depth and a terrestrial pollen temperature-precipitation conversion database, the climate index of each depth is determined, wherein the climate index includes a temperature index and a precipitation index, the temperature index includes the highest temperature, the lowest temperature and the average temperature, and the precipitation index includes the maximum precipitation, the minimum precipitation and the average precipitation. Based on the pollen content data of each depth, the dominant plant pollen of each depth is determined according to preset rules, the dominant plant community to which the dominant plant pollen belongs is determined, and based on the dominant plant community, the community precipitation coefficient and the community temperature coefficient are determined. The precipitation index is corrected based on the community precipitation coefficient to obtain the initial paleoprecipitation index of each depth, and the initial paleoprecipitation index of the depth is corrected based on the community temperature coefficient. The temperature index was corrected to obtain the initial paleotemperature index at each depth. The sunshine coefficient was determined as a paleotemperature correction factor based on the paleolatitude and initial paleotemperature index at each depth, and the final paleotemperature index was determined based on the initial paleotemperature index and the paleotemperature correction factor. The evaporation coefficient was determined as a paleoprecipitation correction factor based on the paleolatitude and initial paleoprecipitation index at each depth, and the final paleoprecipitation index was determined based on the initial paleoprecipitation index and the paleoprecipitation correction factor. The climate sensitivity curve was converted into an astronomical cycle curve, and the cyclical changes of the astronomical cycle curve were used as the trend. The minimum and maximum climates were combined as reference boundary values, and the average climate was used as the basic parameter to fit and generate a continuous periodic curve. The minimum climate includes the minimum temperature and minimum precipitation, the maximum climate includes the maximum temperature and maximum precipitation, and the average climate includes the average temperature and average precipitation. This restored a continuous paleoclimate curve, and the restored paleoclimate factors (paleotemperature values and paleoprecipitation) are more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0049] Figure 1 A schematic flow chart of the method for recovering palynological climate factors based on plant community homeostasis provided by the present invention;

[0050] Figure 2 An example table of terrestrial pollen temperature-precipitation conversion provided by the present invention;

[0051] Figure 3 A flow chart of the steps of the palynological paleoclimate restoration method based on plant community homeostasis and paleolatitude sunlight intensity provided by the present invention;

[0052] Figure 4 The spectrum analysis diagram and astronomical orbit parameter diagram for screening the filter frequency band provided by the present invention;

[0053] Figure 5 The present invention provides a graph based on which paleoclimate factors are finally obtained;

[0054] Figure 6 This is a schematic data table of the paleoclimate factors finally obtained provided by the present invention. DETAILED DESCRIPTION

[0055] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0056] Due to the limited accuracy of paleoclimate restoration in existing technologies and the inability to obtain a full sequence of continuous paleoclimate curves, Figures 1-6 The present invention describes the method for restoring paleoclimate factors of palynological plant communities. Figure 1 The present invention provides a schematic flow chart of a method for recovering paleoclimate factors based on plant community homeostasis, which includes:

[0057] Step 110 , collecting original pollen count data of each type at each depth, and converting the data into pollen content data of each type at each depth.

[0058] Specifically, in geological research, cores are drilled at various depths through drilling, and then the types and numbers of pollen in the cores at various depths are analyzed. The paleoclimate factors that need to be generated by the present invention are determined based on the plant pollen in the rock strata. Therefore, plant pollen analysis must be performed on the core samples of each depth sampled by drilling. At each depth, the types of plant pollen contained therein and the number of each type of pollen can be detected. At each depth, the number of each type of pollen is converted into the proportion of each type of pollen to the total number of all pollen, that is, the content data of each pollen at each depth is obtained. For example, assuming the sampling depths are 4000 meters underground, 6000 meters underground, and 7000 meters underground, type A pollen N is detected at 4000 meters underground. A Type B pollen N B C-type pollen N C So the content of Class A pollen at 6000 meters underground is N A / (N A +N B +N C ), the content of Class B pollen at 6000 meters is N B / (N A +N B +N C ), the content of C-type pollen at 6000 meters is N C / (N A +N B +N C ), D-type pollen N was detected at 6000 meters underground D E-type pollen N E F type pollen N F G-type pollen N G So the content of D-type pollen at 6000 meters underground is N D / (N D +N E +N F +N G ), the content of E-type pollen at 6000 meters is N E / (N D +N E +N F +N G ), the content of F-type pollen at 6000 meters is N F / (N D +N E +N F +N G ), the content of G-type pollen at 6000 meters is N G / (N D +N E +N F +N G), and so on, the content of each pollen at each depth can be calculated.

[0059] Step 120, based on the pollen content data of each depth and the terrestrial pollen temperature-precipitation conversion database, determine the climate index of each depth, wherein the climate index includes a temperature index and a precipitation index, the temperature index includes the maximum temperature, the minimum temperature and the average temperature, and the precipitation index includes the maximum precipitation, the minimum precipitation and the average precipitation.

[0060] Specifically, the terrestrial pollen temperature-precipitation conversion database stores the correspondence between standard pollen plants and climate indices, where the climate index includes the temperature index and the precipitation index. The temperature index includes three scalar values: maximum temperature, minimum temperature, and average temperature. The precipitation index also includes three scalar values: maximum precipitation, minimum precipitation, and average precipitation. By referring to the correspondence between the standard pollen plants and the climate index, as well as the pollen content data at each depth, the climate index at each depth can be determined. It should be noted here that the depth actually corresponds to the geological age of the deposition, and determining the climate index at each depth is essentially determining the climate index of each deposition period.

[0061] Step 130, based on the pollen content data of each depth and according to preset rules, determine the dominant plant pollen at each depth, determine the dominant plant community to which the dominant plant pollen belongs, and based on the dominant plant community, determine the community precipitation coefficient and community temperature coefficient.

[0062] Specifically, the dominant plant pollen in each depth can be determined based on the content data of each pollen at each depth, wherein the dominant plant pollen can be the pollen plant with the highest content. The dominant plant pollen is converted into the plant community to which it belongs, that is, the dominant plant community, and then the precipitation coefficient and temperature coefficient of the community are determined based on the dominant plant community. The community precipitation coefficient is used to correct the precipitation index of the corresponding depth, and the community temperature coefficient is used to correct the temperature index of the corresponding depth.

[0063] Step 140: Correct the precipitation index based on the community precipitation coefficient to obtain the initial paleoprecipitation index at each depth; correct the temperature index based on the community temperature coefficient to obtain the initial paleotemperature index at each depth.

[0064] Specifically, the precipitation index of the corresponding depth is corrected using the community precipitation coefficient of each depth. For example, the precipitation index at 5,000 meters underground is corrected using the community precipitation coefficient. Furthermore, the maximum precipitation, minimum precipitation and average precipitation at 5,000 meters underground are corrected using the community precipitation coefficient at 5,000 meters underground. The temperature index of the corresponding depth is also corrected using the community temperature coefficient of each depth. For example, the temperature index at 4,000 meters underground is corrected using the community temperature coefficient at 4,000 meters underground. Furthermore, the maximum temperature, minimum temperature and average temperature at 5,000 meters underground are corrected using the community temperature coefficient at 4,000 meters underground.

[0065] Step 150: Determine a sunshine coefficient as a paleotemperature correction factor based on the paleolatitude of each depth and the initial paleotemperature index at each depth, and determine a final paleotemperature index based on the initial paleotemperature index and the paleotemperature correction factor.

[0066] Specifically, the authors combined temperature and sunshine intensity data at different latitudes over the past 40 million years to determine a sunshine coefficient for each depth. This sunshine coefficient was then used as a paleotemperature correction factor, multiplied by the maximum, minimum, and average temperatures in the initial paleotemperature index at each depth to obtain the final paleotemperature index for each depth. The final paleotemperature index includes the final paleomaximum, final paleominimum, and final paleoaverage temperatures.

[0067] Step 160 : determining an evaporation coefficient as a paleoprecipitation correction factor based on the paleolatitude of each depth and the initial paleoprecipitation index at each depth, and determining a final paleoprecipitation index based on the initial paleoprecipitation index and the paleoprecipitation correction factor.

[0068] Specifically, the evaporation coefficient for each depth was derived by combining precipitation and evaporation intensity data at different latitudes over the past 40 Ma. The evaporation coefficient was then used as a paleoprecipitation correction factor and multiplied by the maximum, minimum, and average precipitation values in the initial paleoprecipitation index at each depth to obtain the final paleoprecipitation index for each depth. The final paleoprecipitation index includes the final paleomaximum, final paleominimum, and final paleoaverage precipitation values.

[0069] Step 170, using the climate sensitivity curve to convert into an astronomical cycle curve, taking the periodic changes of the astronomical cycle curve as a trend, combining the minimum climate and the maximum climate as reference boundary values, and the average climate as a basic parameter, to fit and generate a continuous periodic curve, wherein the minimum climate includes the minimum temperature and minimum precipitation, the maximum climate includes the maximum temperature and maximum precipitation, and the average climate includes the average temperature and average precipitation.

[0070] Specifically, the climate sensitivity curve is converted into an astronomical cycle curve, and the astronomical cycle curve (periodic changes) is used as the trend. The minimum temperature and the maximum temperature are combined as reference boundary values, and the average temperature is used as the basic parameter to fit and generate a continuous temperature periodic (sinusoidal) curve. The minimum precipitation and the maximum precipitation are also combined as reference boundary values, and the average precipitation is used as the basic parameter to fit and generate a continuous precipitation periodic (sinusoidal) curve.

[0071] The present invention provides a method for restoring paleoclimate factors of pollen based on the steady state of plant communities. The method collects original pollen count data of each type at each depth and converts the data into pollen content data of each depth. Based on the pollen content data of each depth and a terrestrial pollen temperature-precipitation conversion database, the climate index of each depth is determined, wherein the climate index includes a temperature index and a precipitation index, the temperature index includes the highest temperature, the lowest temperature and the average temperature, and the precipitation index includes the maximum precipitation, the minimum precipitation and the average precipitation. Based on the pollen content data of each depth, the dominant plant pollen of each depth is determined according to preset rules, the dominant plant community to which the dominant plant pollen belongs is determined, and based on the dominant plant community, the community precipitation coefficient and the community temperature coefficient are determined. The precipitation index is corrected based on the community precipitation coefficient to obtain the initial paleoprecipitation index of each depth, and the initial paleoprecipitation index of the depth is corrected based on the community temperature coefficient. The temperature index was corrected to obtain the initial paleotemperature index at each depth. The sunshine coefficient was determined as a paleotemperature correction factor based on the paleolatitude and initial paleotemperature index at each depth, and the final paleotemperature index was determined based on the initial paleotemperature index and the paleotemperature correction factor. The evaporation coefficient was determined as a paleoprecipitation correction factor based on the paleolatitude and initial paleoprecipitation index at each depth, and the final paleoprecipitation index was determined based on the initial paleoprecipitation index and the paleoprecipitation correction factor. The climate sensitivity curve was converted into an astronomical cycle curve, and the cyclical changes of the astronomical cycle curve were used as the trend. The minimum and maximum climates were combined as reference boundary values, and the average climate was used as the basic parameter to fit and generate a continuous periodic curve. The minimum climate includes the minimum temperature and minimum precipitation, the maximum climate includes the maximum temperature and maximum precipitation, and the average climate includes the average temperature and average precipitation. This restored a continuous paleoclimate curve, and the restored paleoclimate factors (paleotemperature values and paleoprecipitation) are more accurate.

[0072] Based on the above embodiment, in this method, the air temperature index and precipitation index at each depth are determined based on the pollen content data at each depth and the terrestrial pollen air temperature-precipitation conversion database, specifically including:

[0073] The climate index at each depth was obtained by weighted summing the standard climate index in the terrestrial pollen temperature-precipitation conversion database and the content of each pollen at each depth.

[0074] Specifically, Figure 2 This is an example table of terrestrial pollen temperature-precipitation conversion provided by the present invention, Figure 2 This is just a brief example of the temperature and precipitation values corresponding to 19 species of pollen plants. In fact, the terrestrial pollen temperature-precipitation conversion database includes the temperature-precipitation correspondence of hundreds of pollen plants. Due to limited space, only examples are given here. Figure 2 As shown, the maximum precipitation, minimum precipitation, average precipitation, maximum temperature, minimum temperature, and average temperature corresponding to each pollen plant can be obtained. It should be noted here that the temperature and precipitation values indicated by the pollen corresponding to the plant and community in the terrestrial pollen temperature-precipitation conversion database are the temperature and precipitation values when they reproduced.

[0075] For example, at a depth of 5000 meters underground, the content of Class A pollen is R A , the content of Class B spore pollen is R B , the content of C-type pollen is R C , R A +R B +R C = 1, querying the terrestrial pollen temperature-precipitation conversion database shows that the lowest temperature corresponding to type A pollen is T Amin , the maximum temperature is T Amax , the average temperature is T Aaver , the maximum precipitation is P Amax , the minimum precipitation is P Amin , the average precipitation is P Aaver The lowest temperature corresponding to type B pollen is T Bmin , the maximum temperature is T Bmax , the average temperature is T Baver , the maximum precipitation is P Bmax , the minimum precipitation is P Bmin , the average precipitation is P Baver The lowest temperature corresponding to type C pollen is T Cmin , the maximum temperature is T Cmax , the average temperature is T Caver , the maximum precipitation is P Cmax , the minimum precipitation is P Cmin , the average precipitation is P Caver , then the highest temperature at 5000 meters underground is R A ×T Amax +R B ×T Bmax +R C ×T Cmax , the lowest temperature is R A ×T Amin +R B ×T Bmin +R C ×T Cmin, the average temperature is R A ×T Aaver +R B ×T Baver +R C ×T Caver , the maximum precipitation is R A ×P Amax +R B ×P Bmax +R C ×P Cmax , the minimum precipitation is R A ×P Amin +R B ×P Bmin +R C ×P Cmin , the average precipitation is R A ×P Aaver +R B ×P Baver +R C ×P Caver The highest temperature, lowest temperature, average temperature, maximum precipitation, minimum precipitation and average precipitation at 5000 meters underground constitute the climate index at 5000 meters.

[0076] Based on the above embodiment, in this method, determining the dominant plant pollen at each depth according to preset rules based on the pollen content data at each depth specifically includes:

[0077] For paleolatitudes between 0 and 23.5° south or north, the pollen with the highest proportion of angiosperms was selected as the dominant plant pollen. For paleolatitudes between 23.5 and 66.5° south or north, the pollen with the highest proportion of angiosperms and gymnosperms was selected as the dominant plant pollen. For paleolatitudes between 66.5 and 90° south or north, the pollen with the highest proportion of gymnosperms was selected as the dominant plant pollen.

[0078] Specifically, to determine the dominant plant pollen at each depth, it is first necessary to convert the depth into the corresponding paleolatitude. Due to the relative movement of plates in different geological ages, the paleolatitudes corresponding to the deposition of strata at different depths may be offset from the latitude of the current drilling. After determining the paleolatitudes at each depth, its range is determined, and the dominant plant pollen is determined based on this range. For example, when the rock stratum at a depth of 5,000 meters underground was deposited, the paleolatitude was offset 4° southward based on the drilling latitude, and the obtained paleolatitude was 17° north. Then the angiosperm with the highest pollen content among all angiosperm pollen detected at 5,000 meters underground was selected as the dominant plant pollen. The paleolatitude corresponding to the rock stratum at a depth of 7,000 meters underground is 45° north. The pollen with the highest proportion of angiosperms and gymnosperms is converted into the dominant community. The paleolatitude when the rock stratum at a depth of 8,000 meters underground was 80° north. Then the gymnosperm with the highest pollen content among all gymnosperm pollen detected at 8,000 meters underground was selected as the dominant plant pollen.

[0079] Furthermore, the community correction coefficient is calculated as follows:

[0080]

[0081]

[0082] Where ΔT i is the community temperature coefficient at depth i, ΔP i is the precipitation coefficient of the community at depth i, is the proportion of gymnosperm pollen at depth i, is the proportion of angiosperm pollen at depth i, is the proportion of fern pollen at depth i, is the precipitation of the dominant plant community at depth i, is the temperature value of the dominant plant community at depth i. It should be noted here that the precipitation and temperature values of the dominant plant community need to be queried Figure 2 The example table of terrestrial pollen temperature-precipitation conversion provided is as follows: Figure 2 As shown in the figure, it can be seen that each pollen plant also corresponds to the dominant plant temperature and dominant plant precipitation. For example, when the latitude corresponding to the depth i is determined to be between 0 and 23.5° south or north of the ancient latitude, the pollen with the highest proportion of angiosperms at the depth i is selected as the dominant plant pollen Q. Figure 2 Given a terrestrial pollen temperature-precipitation conversion example table, query the dominant plant temperature value and dominant plant precipitation value corresponding to the dominant plant pollen Q, which are used to determine the dominant plant temperature value. and precipitation values for dominant plants When the latitude corresponding to the depth i is determined to be between 23.5° and 66.5° south or north of the paleolatitude, the pollen K with the highest proportion of angiosperms and the pollen L with the highest proportion of gymnosperms at the depth i are comprehensively selected, and the results are obtained by Figure 2 Given a terrestrial pollen temperature-precipitation conversion example table, query the dominant plant temperature value and dominant plant precipitation value corresponding to the dominant plant pollen Q and L, and use the weighted sum method to determine the dominant plant temperature value. and precipitation values for dominant plants When the latitude corresponding to the depth i is determined to be between 66.5° and 90° south or north of the paleolatitude, the pollen with the highest proportion of gymnosperms at the depth i is selected as the dominant plant pollen M. Figure 2 Given a terrestrial pollen temperature-precipitation conversion example table, query the dominant plant temperature value and dominant plant precipitation value corresponding to the dominant plant pollen M, which are used to determine the dominant plant temperature value respectively. and precipitation values for dominant plants

[0083] Based on the above embodiment, in this method, the precipitation index is corrected based on the community precipitation coefficient to obtain the initial paleoprecipitation index of each depth, and the temperature index is corrected based on the community temperature coefficient to obtain the initial paleotemperature index of each depth, which specifically includes:

[0084] The initial paleoprecipitation index and initial paleotemperature index at each depth are calculated using the following formula:

[0085] T i =t i +ΔT i , P i =p i +ΔP i

[0086] Among them, T i is the initial paleotemperature index at depth i, t i is the temperature index at depth i, ΔT i is the community temperature coefficient at depth i, T i is the initial precipitation index at depth i, t i is the precipitation index at depth i, ΔP i is the community precipitation coefficient at depth i.

[0087] Specifically, the initial paleoprecipitation index at each depth is obtained by first correcting the precipitation index at each depth obtained in the above steps with the community precipitation coefficient, and the initial paleoprecipitation index at each depth is obtained. The initial paleotemperature index at each depth is also obtained by first correcting the temperature index at each depth obtained in the above steps with the community temperature coefficient, and the initial paleotemperature index at each depth is obtained. Furthermore, for example, the temperature index at 5000 meters underground is the highest temperature T max , minimum temperature T min , average temperature T aver After the first correction, the initial paleotemperature index is the maximum temperature (T max +ΔT), minimum temperature (T min +ΔT), average temperature (T aver +ΔT), where ΔT is the community temperature coefficient at 5000 meters underground, and the precipitation index at 5000 meters underground is the maximum precipitation P max , minimum precipitation P min , average precipitation P aver After the first correction, the initial paleoprecipitation index is the maximum precipitation (P max +ΔP), minimum precipitation (P min +ΔP), average precipitation (P aver +ΔP), where ΔP is the community precipitation coefficient at 5000 meters underground; and so on, the initial paleoprecipitation index and initial paleotemperature index at each depth are calculated.

[0088] Based on the above embodiment, in this method, the sunshine coefficient is determined as the paleotemperature correction multiple based on the paleolatitude of each depth and the initial paleotemperature index of each depth, and the final paleotemperature index is determined based on the initial paleotemperature index and the paleotemperature correction multiple, which specifically includes:

[0089] The sunshine coefficient Sun is determined as the paleotemperature correction factor using the following formula:

[0090] 0≤L≤90:

[0091] 0>L>-60:

[0092] -60≥L≥-90:

[0093]

[0094] Among them, L is latitude, with positive values for north latitude and negative values for south latitude, S is the sunshine intensity at each depth, S i is the sunshine intensity at the i-th depth, n is the total number of depths in the drilling pollen sampling, i is the i-th depth among all the drilling pollen sampling depths, Ti is the initial paleotemperature index at the i-th depth;

[0095] The final paleotemperature index is equal to the initial paleotemperature index multiplied by the paleotemperature correction factor.

[0096] Specifically, combining the temperature and sunshine intensity data at different latitudes over the past 40 Ma, the calculation formula for the sunshine coefficient (Sun) is as follows:

[0097] The calculation formula of the sunshine intensity S at each depth is based on the latitude L, which is

[0098] 0≤L≤90:

[0099] 0>L>-60:

[0100] -60≥L≥-90:

[0101] It should be noted here that the latitude L here is preferably the paleolatitude. If the paleolatitude is not available, the present latitude (i.e. the latitude of the well where the sample was collected) can also be used directly.

[0102] The final calculation formula for the paleotemperature correction factor is:

[0103]

[0104] Among them, Sun is the sunshine coefficient, S i is the sunlight intensity at depth i, L is the latitude, T i is the initial paleotemperature at depth i.

[0105] Ultimately, the final paleotemperature index at each depth is equal to the initial paleotemperature index at each depth multiplied by the paleotemperature correction factor.

[0106] Based on the above embodiment, in this method, the evaporation coefficient is determined as a paleoprecipitation correction multiple based on the paleolatitude of each depth and the initial paleoprecipitation index at each depth, and the final paleoprecipitation index is determined based on the initial paleoprecipitation index and the paleoprecipitation correction multiple, specifically including:

[0107] The evaporation coefficient Eva is determined as the paleoprecipitation correction factor using the following formula:

[0108] 30≤L≤90: E=4827-365.8L+11.846L 2 -0.1577L 3 +7.2×10 -4 L 4

[0109] 0≤L<30: E=1788+36L-6.26L 2 +0.134L 3

[0110] 0>L≥-30: E=1799+62L+1.93L 2 +0.028L 3

[0111] -3>L≥-90: E=19500+1491L+42.51L 2 +0.509L 3 +2.16×10 -3 L 4

[0112]

[0113] Where L is the latitude, with positive values for north latitude and negative values for south latitude, and E is the evaporation at each depth. i is the evaporation at the i-th depth, n is the total number of depths in the drilling pollen sampling, i is the i-th depth among all the drilling pollen sampling depths, P i is the initial paleoprecipitation index at the i-th depth;

[0114] The final paleoprecipitation index is equal to the initial paleoprecipitation index multiplied by the paleoprecipitation correction factor.

[0115] Specifically, combining the precipitation and evaporation intensity data at different latitudes over the past 40 Ma, the calculation formula for the evaporation coefficient (Eva) is obtained as follows:

[0116] The calculation formula for evaporation E at each depth is based on the latitude L, which is:

[0117] 30≤L≤90: E=4827-365.8L+11.846L 2 -0.1577L 3 +7.2×10 -4 L 4

[0118] 0≤L<30: E=1788+36L-6.26L 2 +0.134L 3

[0119] 0>L≥-30: E=1799+62L+1.93L 2 +0.028L 3

[0120] -3>L≥-90: E=19500+1491L+42.51L 2 +0.509L3 +2.16×10 -3 L 4

[0121] It should be noted here that the latitude L here is preferably the paleolatitude. If the paleolatitude is not available, the present latitude (i.e. the latitude of the well where the sample was collected) can also be used directly.

[0122] The final precipitation correction factor calculation formula is:

[0123]

[0124] Among them, Eva is the evaporation coefficient, E i is the evaporation at depth i, L is the latitude, and Pi is the initial paleoprecipitation at depth i.

[0125] Ultimately, the final paleoprecipitation index at each depth is equal to the initial paleoprecipitation index at each depth multiplied by the paleoprecipitation correction factor.

[0126] Based on the above embodiment, in the method, converting the climate sensitivity curve into an astronomical cycle curve specifically includes:

[0127] The climate sensitivity curve is subjected to noise reduction and detrending processing to obtain the preprocessed curve;

[0128] Performing spectrum analysis on the pre-processed curve to generate a frequency spectrum, and selecting a target frequency spectrum of a frequency band corresponding to a 405ka long eccentricity period;

[0129] The target frequency spectrum is filtered using a bandpass filter to generate a filtering curve corresponding to a characteristic peak of a long eccentricity period of the envelope, which is an astronomical cyclotron curve.

[0130] Specifically, converting the climate sensitivity curve into an astronomical cycle curve includes: ① denoising / detrending the climate sensitivity curve data; ② performing spectrum analysis (Fourier transform) to generate a frequency spectrum, reading frequencies / frequency bands that meet the ratio of the astronomical cycle orbit period, that is, screening frequency characteristic peaks whose wavelength (the inverse of the frequency) ratio meets the long eccentricity period (E): short eccentricity period (e): slope period (O): precession period (P) = 405:99~131:24.5~54:15~24. The present invention selects the most stable 405ka (ka, thousand years) long eccentricity period corresponding frequency band; ③ using bandpass filtering (Bandpass filter) / other filtering methods to filter the denoised climate sensitivity curve to generate a filtered curve (i.e., generate an astronomical cycle curve) that envelops the characteristic peak corresponding to the long eccentricity period.

[0131] Based on the above embodiment, the method further includes:

[0132] Using global temperature change curves and major climate events to conduct trend and event verification, and to determine the relationship between the periodic curve trend and the global climate fitting response;

[0133] Finally, the full sequence of paleotemperature data and curves, as well as paleoprecipitation data and curves of the target well section were obtained.

[0134] Specifically, the trend of the filtering curve is combined with the climate and precipitation data (discrete data with non-equal depth intervals) to perform equal-depth fitting, and finally a continuous curve and corresponding data are formed. The global temperature change curve and major climate events are used to perform trend and event verification, and the relationship between the trend of the restored paleotemperature and paleoprecipitation curves and the global climate fitting response is judged, and finally the full sequence of cyclic paleotemperature and cyclic paleoprecipitation data and curves of the target well section are obtained.

[0135] Based on the above embodiments, Figure 3 The present invention provides a flow chart of the steps of the palynological paleoclimate restoration method based on plant community steady state and paleolatitude sunlight intensity, as shown in FIG. Figure 3 As shown, the key technical points of the present invention are: ① constructing a database corresponding to terrestrial pollen and terrestrial plant climate; ② calculating the paleolatitude sunshine coefficient S and evaporation coefficient E, that is, the calculation formula applicable to all latitudes:

[0136] The relationship between sunshine coefficient S and latitude L is as follows:

[0137] 0≤L≤90:

[0138] 0>L>-60:

[0139] -60≥L≥-90:

[0140] The relationship formula between evaporation coefficient E and latitude L is:

[0141] 30≤L≤90: E=4827-365.8L+11.846L 2 -0.1577L 3 +7.2×10 -4 L 4

[0142] 0≤L<30: E=1788+36L-6.26L 2 +0.134L 3

[0143] 0>L≥-30: E=1799+62L+1.93L 2 +0.028L 3

[0144] -3>L≥-90: E=19500+1491L+42.51L 2 +0.509L 3 +2.16×10 -3 L 4 .

[0145] Figure 4 The spectrum analysis diagram and astronomical orbit parameter diagram for screening the filter frequency band provided by the present invention are as follows: Figure 4 As shown, the horizontal axis is frequency, the vertical axis is cyclonic intensity, the color blocks are bounded by four frequency bands that conform to the ratio of the inverse of the frequency (wavelength), and the upper right corner is a schematic diagram of the Sun-Earth orbit. Figure 5 The present invention provides a graph based on the paleoclimate factors, such as Figure 5 As shown in the figure, there are process and result maps, where GR is the climate sensitivity curve, the six offline curves of ancient temperature changes and precipitation changes are all temperature and precipitation data after the first and second corrections, and the last two columns are the continuous climate curves after fitting. Figure 6 This is a schematic data table of the paleoclimate factors finally obtained provided by the present invention.

[0146] The technical effects of the present invention are as follows:

[0147] 1. The present invention can calculate paleotemperature and paleoprecipitation values for well sections with paleontological pollen test data, and then realize the restoration of the paleoclimate curve of the entire sequence by combining the climate sensitivity curve. Starting from the multi-level control factors of climate change (solar radiation intensity, earth orbit change, plate movement and vegetation coverage), the pollen species and abundance are used as direct entry points, and multi-latitude parameters (plant community, sunshine intensity, evaporation and paleolatitude position) are taken into consideration. This breaks through the thinking barrier of restoring paleotemperature and paleoprecipitation from the perspective of a single pollen category or feature combination, solves the problem of diversification of boundary indicators, and provides a method for quantitative restoration of paleoclimate with higher accuracy. Quantitative calculation of paleoclimate based on paleontological information and geophysical data can more intuitively and scientifically characterize the sedimentary environment and evolution of different geological periods. By clarifying the temperature and precipitation, the provenance erosion-sedimentation transportation and accumulation process can be simulated, the sedimentary phase belt type can be determined, and the picking of key sequence interfaces has important guidance and verification significance. The combination of solar cycles, astronomical cycles and paleontological data is a new attempt in the field of paleoclimate research. It has the advantages of good operability, strong pertinence and high precision. The present invention provides a highly operable mapping process for restoring the paleoclimate of the study area using paleontological data and well logging data, and introduces the working ideas, principles, methods and processes in detail. It is advanced, scientific, practical in exploration and widely applicable, and can be widely used in paleoenvironmental research and geological resource exploration applications.

[0148] 2. Because paleoclimate (paleotemperature and paleoprecipitation) changes directly reflect evolutionary patterns across different timescales, consistent with the fundamental principles of cyclostratigraphy, within a complete sequence, climate, as a key variable, exhibits cyclical evolution from dry and cold to wet and hot. The trend envelope of paleoclimate curves can be used to identify and delineate sequence stratigraphic units of varying degrees. This is particularly sensitive to sudden changes in paleotemperature and paleoprecipitation, i.e., key climate change surfaces. Continuous paleotemperature and paleoprecipitation curves allow for precise identification and tracking of the sudden change range, enabling verification and acquisition of high-precision sequence stratigraphic units for the study area.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for recovering palynological climate factors based on plant community homeostasis, characterized in that: include: Collect the original pollen count data of each type at each depth and convert it into pollen content data of each depth; Based on the pollen content data of each depth and the terrestrial pollen temperature-precipitation conversion database, the climate index of each depth is determined, wherein the climate index includes the temperature index and the precipitation index. The temperature index includes the maximum temperature, the minimum temperature and the average temperature, and the precipitation index includes the maximum precipitation, the minimum precipitation and the average precipitation. Determine the dominant plant pollen at each depth according to preset rules based on the pollen content data at each depth, determine the dominant plant community to which the dominant plant pollen belongs, and determine the community precipitation coefficient and community temperature coefficient based on the dominant plant community; The precipitation index is corrected based on the community precipitation coefficient to obtain the initial paleoprecipitation index of each depth, and the temperature index is corrected based on the community temperature coefficient to obtain the initial paleotemperature index of each depth; Determining a sunshine coefficient as a paleotemperature correction multiple based on the paleolatitude of each depth and the initial paleotemperature index of each depth, and determining a final paleotemperature index based on the initial paleotemperature index and the paleotemperature correction multiple; Determine the evaporation coefficient as the paleoprecipitation correction factor based on the paleolatitude of each depth and the initial paleoprecipitation index of each depth, and determine the final paleoprecipitation index based on the initial paleoprecipitation index and the paleoprecipitation correction factor; specifically include: The evaporation coefficient is determined by the following formula Eva As the paleoprecipitation correction factor: 30≤ L ≤90: 0≤ L ＜30: 0＞ L ≥-30: -3＞ L ≥-90: in, L is the latitude, with positive values for north latitude and negative values for south latitude. is the evaporation at each depth, , n is the total number of depths in the drilling pollen sampling, i The depth of all drilling pollen sampling is i depth, For the i Initial paleoprecipitation index at depth; The final paleoprecipitation index is equal to the initial paleoprecipitation index multiplied by the paleoprecipitation correction factor; The climate sensitivity curve is converted into an astronomical cycle curve, and the periodic changes of the astronomical cycle curve are taken as the trend, combined with the minimum climate and the maximum climate as the reference boundary values, and the average climate as the basic parameter to fit and generate a continuous periodic curve. Among them, the minimum climate includes the minimum temperature and minimum precipitation, the maximum climate includes the maximum temperature and maximum precipitation, and the average climate includes the average temperature and average precipitation.

2. The method for recovering the palynological climate factors based on the steady state of plant communities according to claim 1, wherein The temperature index and precipitation index at each depth are determined based on the pollen content data at each depth and the terrestrial pollen temperature-precipitation conversion database, specifically including: The climate index at each depth was obtained by weighted summing the standard climate index in the terrestrial pollen temperature-precipitation conversion database and the content of each pollen at each depth.

3. The method for recovering the sporopollen paleoclimate factors based on the steady state of plant communities according to claim 1, wherein The method of determining the dominant plant pollen at each depth based on the pollen content data at each depth according to a preset rule specifically includes: For paleolatitudes between 0 and 23.5° south or north, the pollen with the highest proportion of angiosperms was selected as the dominant plant pollen. For paleolatitudes between 23.5 and 66.5° south or north, the pollen with the highest proportion of angiosperms and gymnosperms was selected as the dominant plant pollen. For paleolatitudes between 66.5 and 90° south or north, the pollen with the highest proportion of gymnosperms was selected as the dominant plant pollen.

4. The method for recovering the sporopollen paleoclimate factors based on the steady state of plant communities according to claim 1, wherein The precipitation index is corrected based on the community precipitation coefficient to obtain the initial paleoprecipitation index of each depth, and the temperature index is corrected based on the community temperature coefficient to obtain the initial paleotemperature index of each depth, specifically including: The initial paleoprecipitation index and initial paleotemperature index at each depth are calculated using the following formula: ， in, For depth i The initial paleotemperature index at For depth i The temperature index at For depth i The community temperature coefficient at For depth i Initial precipitation index at For depth i The precipitation index at For depth i The community precipitation coefficient at .

5. The method for recovering the sporopollen paleoclimate factors based on the steady state of plant communities according to claim 1, wherein The determining of the sunshine coefficient as the paleotemperature correction multiple based on the paleolatitude of each depth and the initial paleotemperature index of each depth, and the determining of the final paleotemperature index based on the initial paleotemperature index and the paleotemperature correction multiple, specifically includes: The sunshine coefficient is determined by the following formula Sun As the paleotemperature correction factor: 0≤ L ≤90： 0＞ L ＞-60： -60≥ L ≥-90： in, L is the latitude, with positive values for north latitude and negative values for south latitude. is the sunlight intensity at each depth, n is the total number of depths in the drilling pollen sampling, i The depth of all drilling pollen sampling is i depth, For the i Initial paleotemperature index at depth; The final paleotemperature index is equal to the initial paleotemperature index multiplied by the paleotemperature correction factor.

6. The method for recovering the sporopollen paleoclimate factors based on the steady state of plant communities according to claim 1, wherein The method of converting the climate sensitivity curve into an astronomical cycle curve specifically includes: The climate sensitivity curve is subjected to noise reduction and detrending processing to obtain the preprocessed curve; Performing spectrum analysis on the pre-processed curve to generate a frequency spectrum, and selecting a target frequency spectrum of a frequency band corresponding to a 405ka long eccentricity period; The target frequency spectrum is filtered using a bandpass filter to generate a filtering curve corresponding to a characteristic peak of a long eccentricity period of the envelope, which is an astronomical cyclotron curve.

7. The method for recovering the palynological climate factors based on the steady state of plant communities according to claim 6, wherein: Also includes: Using global temperature change curves and major climate events to conduct trend and event verification, and to determine the relationship between the periodic curve trend and the global climate fitting response; Finally, the full sequence of paleotemperature data and curves, as well as paleoprecipitation data and curves of the target well section were obtained.

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