Paleoenvironment reconstruction method based on geological historical records

Abstract

The invention discloses a paleo-environment reconstruction method based on geological historical records, which belongs to the technical field of paleo-geography reconstruction, and is characterized by comprising the following steps: a, obtaining a target geographic position to be subjected to paleo-environment reconstruction; b, well drilling points are marked at the target geographic position, and well drilling sampling is carried out; c, performing component analysis on the obtained gravel sample, and judging the sedimentary environment and sporopollen characteristics of the gravel sample; and d, constructing an ancient environment according to the sedimentary environment to which the gravel sample belongs and sporopollen characteristics. According to the method, the gravel in the geological layer is finely analyzed, so that the sedimentary environment of the geological layer can be more accurately judged, a more reasonable interpretation framework is provided for the magnetic susceptibility data, the magnetic susceptibility analysis accuracy is improved, and the paleoenvironment reconstruction accuracy is further improved.

Description

Technical Field

[0001] This invention relates to the field of paleogeographic reconstruction technology, and in particular to a method for paleoenvironment reconstruction based on geological historical records. Background Technology

[0002] Exploring paleoenvironments in terrestrial strata relies primarily on in-depth sampling and analysis of underground rock layers. This process integrates knowledge and techniques from multiple disciplines, including geology, paleoclimatology, paleontology, and geophysics. Specifically, by analyzing physical, chemical, and biological indicators such as magnetic susceptibility, sediment grain size, and plant pollen content, combined with high-precision dating data, the evolutionary history of paleoenvironments can be reconstructed.

[0003] However, magnetic susceptibility is affected by a variety of factors, such as the type, content and distribution of magnetic minerals in the strata, as well as diagenesis after sedimentation. These factors may interfere with the accurate interpretation of paleoenvironmental changes.

[0004] Chinese patent document CN117214415A, published on December 12, 2023, discloses a method for reconstructing the paleogeographic pattern of sedimentary basins based on geochemical indicators. The method includes the following steps: analyzing the major, trace, and rare earth element components of sampled sedimentary basins to determine the tectonic setting and parent rock lithology of the basin; constraining the determined tectonic setting by analyzing minor components in selected rock fragments from the sampled samples; calculating the heavy mineral assemblage maturity index by analyzing the proportion of heavy mineral components in the sampled samples to determine the sediment transport distance of the basin; determining paleoenvironmental reconstruction indicators of the sedimentary basin using trace element analysis of the sampled samples; combining the sedimentary characteristics of the basin and classifying sedimentary facies to infer the sediment dispersion pattern indicated by stratigraphic indicators within the basin; and reconstructing the paleogeographic pattern of the sedimentary basin by combining the obtained geochemical indicators through a coupling method.

[0005] The patent document discloses a method for reconstructing the paleogeographic patterns of sedimentary basins based on geochemical indicators, which can reconstruct the paleogeographic patterns of sedimentary basins. However, the accuracy of the paleogeographic pattern reconstruction is affected because it cannot perform accurate magnetic susceptibility analysis on geological layers with large age differences. Summary of the Invention

[0006] To overcome the shortcomings of the prior art, this invention provides a paleoenvironment reconstruction method based on geological historical records. By conducting detailed analysis of gravel in geological layers, this invention can more accurately determine the sedimentary environment of geological layers, provide a more reasonable interpretation framework for magnetic susceptibility data, improve the accuracy of magnetic susceptibility analysis, and thus improve the accuracy of paleoenvironment reconstruction.

[0007] This invention is achieved through the following technical solution: A paleoenvironment reconstruction method based on historical geological records, characterized by comprising the following steps: a. Obtain the target geographical location for the paleoenvironment reconstruction to be carried out; b. Mark the drilling points at the target geographical location and conduct drilling sampling; c. Perform compositional analysis on the obtained gravel samples to determine the sedimentary environment and pollen characteristics of the gravel samples; d. Construct paleoenvironments based on the sedimentary environment and pollen characteristics of the gravel samples.

[0008] In step b, drilling sampling refers to sampling at a well depth of 10-15 meters, layer by layer from top to bottom.

[0009] In step c, the component analysis of the obtained gravel sample refers to performing pollen analysis, particle size analysis, magnetic susceptibility analysis, and dating analysis on the gravel sample.

[0010] The magnetic susceptibility analysis refers to weighing and grinding a gravel sample, compacting and fixing the ground gravel sample, and then testing it using a magnetic susceptibility instrument.

[0011] The dating analysis is performed using optically stimulated luminescence dating, electron self-selection resonance dating, amino acid dating, fluoride dating, potassium-argon dating, fission track dating, or obsidian hydration.

[0012] In step c, determining the sedimentary environment of the gravel sample refers to analyzing the gravel composition in geological layers A and B, where the age difference between the geological layers exceeds a preset threshold, using optically stimulated luminescence dating. If the gravel in geological layers A and B exhibits elongated, banded, or dendritic shapes, then geological layers A and B are determined to be river or lake sediments; if the gravel in geological layers A and B does not exhibit elongated, banded, or dendritic shapes, then geological layers A and B are determined to be grassland sediments.

[0013] The mass of the sand and gravel sample is 10-20g, and the particle size after grinding is less than 1mm.

[0014] The pollen analysis involves numbering the gravel samples, drying them, crushing and sieving the dried samples to remove calcium, adding hydrofluoric acid to remove strontium, removing fluoride, filtering through a 5-micron sieve, flotating and concentrating the pollen in a prepared heavy liquid, counting the types and quantities of pollen, and identifying the pollen using pollen morphology charts.

[0015] The removal of calcium refers to removing calcium with a concentration of 10% dilute hydrochloric acid, and the removal of fluoride refers to removing fluoride with a concentration of 37% hydrochloric acid.

[0016] The particle size analysis involves crushing and drying the sand sample, passing hydrogen peroxide through the sample to remove organic matter, adding water after impurities are removed, centrifuging the sample, and aspirating the supernatant until the sample is neutral. Then, 10% hydrochloric acid is added to remove carbonates, followed by rinsing with water and centrifuging again to remove the supernatant. This process is repeated until the sample is neutral. Finally, sodium metaphosphate is added, and the sample is stirred in an ultrasonic vibrator to obtain a suspension, which is then measured using a laser diffraction particle size analyzer.

[0017] The beneficial effects of this invention are mainly reflected in the following aspects: 1. This invention: a) Obtains the target geographical location for paleoenvironment reconstruction; b) Marks drilling points at the target geographical location and performs drilling sampling; c) Performs component analysis on the obtained gravel samples to determine the sedimentary environment and pollen characteristics of the gravel samples; d) Constructs paleoenvironments based on the sedimentary environment and pollen characteristics of the gravel samples. Compared with existing technologies, by performing detailed analysis on the gravel in geological layers, the sedimentary environment of geological layers can be determined more accurately, providing a more reasonable interpretation framework for magnetic susceptibility data, improving the accuracy of magnetic susceptibility analysis, and thus improving the accuracy of paleoenvironment reconstruction.

[0018] 2. In step c of this invention, determining the sedimentary environment of the gravel sample refers to analyzing the gravel composition in geological layers A and B, where the age difference between the geological layers exceeds a preset threshold, using optically stimulated luminescence dating. If the gravel in geological layers A and B exhibits elongated, banded, or dendritic shapes, then geological layers A and B are determined to be river or lake sediments; if the gravel in geological layers A and B does not exhibit elongated, banded, or dendritic shapes, then geological layers A and B are determined to be grassland sediments. During well sampling, when performing magnetic susceptibility analysis on geological layers with significant age differences, the indicative significance of magnetic susceptibility for the environment varies due to different soil-forming conditions. Analyzing the gravel composition in geological layers A and B, where the age difference exceeds a preset threshold, helps improve the accuracy of magnetic susceptibility analysis.

[0019] 3. According to the present invention, the gravel in geological layer A and geological layer B is found to be in the form of long strips, bands or dendrites through dating analysis. This indicates that the magnetic susceptibility of geological layer A and geological layer B is greatly affected by hydrodynamics. Therefore, geological layer A and geological layer B are river and lake sediments, which makes the judgment more accurate and reasonable.

[0020] 4. According to the present invention, the gravel in geological layers A and B does not show long strips, bands or dendrites through dating analysis. This indicates that the magnetic susceptibility of geological layers A and B is greatly affected by precipitation. Therefore, geological layers A and B are grassland sediments, which is a more reasonable and accurate judgment.

[0021] 5. This invention greatly improves the accuracy of paleoenvironment reconstruction by performing pollen analysis, particle size analysis, magnetic susceptibility analysis, and dating analysis on gravel samples. Attached Figure Description

[0022] The present invention will now be further described in detail with reference to the accompanying drawings and specific embodiments: Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0023] Example 1 See Figure 1 A paleoenvironment reconstruction method based on geological historical records includes the following steps: a. Obtain the target geographical location for the paleoenvironment reconstruction to be carried out; b. Mark the drilling points at the target geographical location and conduct drilling sampling; c. Perform compositional analysis on the obtained gravel samples to determine the sedimentary environment and pollen characteristics of the gravel samples; d. Construct paleoenvironments based on the sedimentary environment and pollen characteristics of the gravel samples.

[0024] This embodiment is the most basic implementation method. Compared with the prior art, by conducting a detailed analysis of the gravel in the geological layer, the sedimentary environment of the geological layer can be determined more accurately, providing a more reasonable interpretation framework for the magnetic susceptibility data, improving the accuracy of magnetic susceptibility analysis, and thus improving the accuracy of paleoenvironment reconstruction.

[0025] Example 2 See Figure 1 A paleoenvironment reconstruction method based on geological historical records includes the following steps: a. Obtain the target geographical location for the paleoenvironment reconstruction to be carried out; b. Mark the drilling points at the target geographical location and conduct drilling sampling; c. Perform compositional analysis on the obtained gravel samples to determine the sedimentary environment and pollen characteristics of the gravel samples; d. Construct paleoenvironments based on the sedimentary environment and pollen characteristics of the gravel samples.

[0026] In step b, drilling sampling refers to sampling at a depth of 10 meters, layer by layer from top to bottom.

[0027] In step c, the component analysis of the obtained gravel sample refers to performing pollen analysis, particle size analysis, magnetic susceptibility analysis, and dating analysis on the gravel sample.

[0028] The magnetic susceptibility analysis refers to weighing and grinding a gravel sample, compacting and fixing the ground gravel sample, and then testing it using a magnetic susceptibility instrument.

[0029] The dating analysis was performed using optically stimulated luminescence dating.

[0030] In step c, determining the sedimentary environment of the gravel sample refers to analyzing the gravel composition in geological layers A and B, where the age difference between the geological layers exceeds a preset threshold, using optically stimulated luminescence dating. If the gravel in geological layers A and B exhibits elongated, banded, or dendritic shapes, then geological layers A and B are determined to be river or lake sediments; if the gravel in geological layers A and B does not exhibit elongated, banded, or dendritic shapes, then geological layers A and B are determined to be grassland sediments.

[0031] The mass of the sand and gravel sample taken was 10g, and the particle size after grinding was 0.5mm.

[0032] This embodiment is a preferred implementation. In step c, determining the sedimentary environment of the gravel sample refers to analyzing the gravel composition in geological layers A and B, where the age difference exceeds a preset threshold, using optically stimulated luminescence dating. If the gravel in geological layers A and B exhibits elongated, banded, or dendritic shapes, then geological layers A and B are determined to be river or lake sediments. If the gravel in geological layers A and B does not exhibit elongated, banded, or dendritic shapes, then geological layers A and B are determined to be grassland sediments. During well sampling, when performing magnetic susceptibility analysis on geological layers with significant age differences, the indicative significance of magnetic susceptibility for the environment varies due to different soil-forming conditions. Analyzing the gravel composition in geological layers A and B, where the age difference exceeds a preset threshold, helps improve the accuracy of magnetic susceptibility analysis.

[0033] Example 3 See Figure 1 A paleoenvironment reconstruction method based on geological historical records includes the following steps: a. Obtain the target geographical location for the paleoenvironment reconstruction to be carried out; b. Mark the drilling points at the target geographical location and conduct drilling sampling; c. Perform compositional analysis on the obtained gravel samples to determine the sedimentary environment and pollen characteristics of the gravel samples; d. Construct paleoenvironments based on the sedimentary environment and pollen characteristics of the gravel samples.

[0034] In step b, drilling and sampling refers to sampling at a depth of 12 meters, layer by layer from top to bottom.

[0035] In step c, the component analysis of the obtained gravel sample refers to performing pollen analysis, particle size analysis, magnetic susceptibility analysis, and dating analysis on the gravel sample.

[0036] The magnetic susceptibility analysis refers to weighing and grinding a gravel sample, compacting and fixing the ground gravel sample, and then testing it using a magnetic susceptibility instrument.

[0037] The dating analysis is performed using the electron self-selected resonance dating method.

[0038] In step c, determining the sedimentary environment of the gravel sample refers to analyzing the gravel composition in geological layers A and B, where the age difference between the geological layers exceeds a preset threshold, using optically stimulated luminescence dating. If the gravel in geological layers A and B exhibits elongated, banded, or dendritic shapes, then geological layers A and B are determined to be river or lake sediments; if the gravel in geological layers A and B does not exhibit elongated, banded, or dendritic shapes, then geological layers A and B are determined to be grassland sediments.

[0039] The mass of the sand and gravel sample taken was 15g, and the particle size after grinding was 0.8mm.

[0040] The pollen analysis involves numbering the gravel samples, drying them, crushing and sieving the dried samples to remove calcium, adding hydrofluoric acid to remove strontium, removing fluoride, filtering through a 5-micron sieve, flotating and concentrating the pollen in a prepared heavy liquid, counting the types and quantities of pollen, and identifying the pollen using pollen morphology charts.

[0041] The removal of calcium refers to removing calcium with a concentration of 10% dilute hydrochloric acid, and the removal of fluoride refers to removing fluoride with a concentration of 37% hydrochloric acid.

[0042] This embodiment is another preferred implementation. Through dating analysis, it is found that the gravel in geological layer A and geological layer B is in the form of long strips, bands, or dendritic shapes. This indicates that the magnetic susceptibility of geological layer A and geological layer B is greatly affected by hydrodynamics. Therefore, it is determined that geological layer A and geological layer B are river and lake sediments, which is a more accurate and reasonable judgment.

[0043] Example 4 See Figure 1 A paleoenvironment reconstruction method based on geological historical records includes the following steps: a. Obtain the target geographical location for the paleoenvironment reconstruction to be carried out; b. Mark the drilling points at the target geographical location and conduct drilling sampling; c. Perform compositional analysis on the obtained gravel samples to determine the sedimentary environment and pollen characteristics of the gravel samples; d. Construct paleoenvironments based on the sedimentary environment and pollen characteristics of the gravel samples.

[0044] In step b, drilling sampling refers to sampling at a depth of 15 meters, layer by layer from top to bottom.

[0045] In step c, the component analysis of the obtained gravel sample refers to performing pollen analysis, particle size analysis, magnetic susceptibility analysis, and dating analysis on the gravel sample.

[0046] The magnetic susceptibility analysis refers to weighing and grinding a gravel sample, compacting and fixing the ground gravel sample, and then testing it using a magnetic susceptibility instrument.

[0047] The dating analysis is performed using fission track dating.

[0048] In step c, determining the sedimentary environment of the gravel sample refers to analyzing the gravel composition in geological layers A and B, where the age difference between the geological layers exceeds a preset threshold, using optically stimulated luminescence dating. If the gravel in geological layers A and B exhibits elongated, banded, or dendritic shapes, then geological layers A and B are determined to be river or lake sediments; if the gravel in geological layers A and B does not exhibit elongated, banded, or dendritic shapes, then geological layers A and B are determined to be grassland sediments.

[0049] The mass of the sand and gravel sample was 20g, and the particle size after grinding was 0.6mm.

[0050] The pollen analysis involves numbering the gravel samples, drying them, crushing and sieving the dried samples to remove calcium, adding hydrofluoric acid to remove strontium, removing fluoride, filtering through a 5-micron sieve, flotating and concentrating the pollen in a prepared heavy liquid, counting the types and quantities of pollen, and identifying the pollen using pollen morphology charts.

[0051] The removal of calcium refers to removing calcium with a concentration of 10% dilute hydrochloric acid, and the removal of fluoride refers to removing fluoride with a concentration of 37% hydrochloric acid.

[0052] The particle size analysis involves crushing and drying the sand sample, passing hydrogen peroxide through the sample to remove organic matter, adding water after impurities are removed, centrifuging the sample, and aspirating the supernatant until the sample is neutral. Then, 10% hydrochloric acid is added to remove carbonates, followed by rinsing with water and centrifuging again to remove the supernatant. This process is repeated until the sample is neutral. Finally, sodium metaphosphate is added, and the sample is stirred in an ultrasonic vibrator to obtain a suspension, which is then measured using a laser diffraction particle size analyzer.

[0053] This embodiment is the best implementation method. Through dating analysis, it was found that the gravel in geological layers A and B did not show long strips, bands, or dendritic shapes. This indicates that the magnetic susceptibility of geological layers A and B is greatly affected by precipitation. Therefore, geological layers A and B are judged to be grassland sediments, which is a more reasonable and accurate judgment.

[0054] By conducting pollen analysis, grain size analysis, magnetic susceptibility analysis, and dating analysis on gravel samples, the accuracy of paleoenvironment reconstruction has been greatly improved.

[0055] The invention will now be illustrated with specific examples: In the paleoenvironment reconstruction of site M, staff conducted on-site investigations and collected information on the historical land use of the site. Through comprehensive analysis of the on-site investigations and historical data, areas of human intervention were excluded, such as those that had been dug and filled in. Drilling point No. 1 was marked, and then drilling was carried out using mechanical equipment to a depth of 10-15m. Sampling was carried out from top to bottom in site M, with stratified sampling at 10cm intervals. Four gravel samples were collected from each stratum, with each gravel sample weighing 300g. After collection, the samples were numbered and recorded as follows: for example, gravel sample No. 1, No. 2, No. 3, and No. 4 in section h1; and gravel sample No. 1, No. 2, No. 3, and No. 4 in section h2. Then, the gravel samples from sections h1 and h2 were analyzed for composition.

[0056] When weighing the No. 1 gravel sample from section h1 for pollen analysis, the following specific steps are included: S1. After the No. 1 gravel sample of section h1 is naturally air-dried, it is ground with a grinding pestle. Then, 200g is weighed and placed in a beaker. The beaker and the No. 1 gravel sample of section h1 are numbered. After the sample is loaded, lycopodium spores are added to the beaker as indicator pollen. One lycopodium spore tablet contains 27,637 lycopodium spore pollen grains. S2. Slowly add 10% dilute hydrochloric acid to the beaker, and then heat it in a water bath to promote the reaction between the dilute hydrochloric acid and the carbonate in the No. 1 gravel sample of section h1. After the reaction is complete, add water to the beaker to wash the sample. After standing for 10 hours, remove the upper layer of water, then add water again, stand, remove water, until the liquid in the beaker is neutral. S3. Add hydrofluoric acid to the beaker in small amounts several times while stirring. After the addition is complete, heat in a water bath for 8 hours. Then wash the sample with water and remove the water until the sample is neutral. S4. Add 37% hydrochloric acid to the beaker, heat in a water bath to allow the No. 1 gravel sample in section h1 to react fully and remove fluoride, then wash with water until neutral. S5. Pass the No. 1 sand sample of section h1 in the beaker through a 5-micron sieve to remove impurities. Then pour the No. 1 sand sample of section h1 left on the sieve into a test tube to precipitate. Number the test tubes, and keep the numbers consistent with those of the beaker. S6. Add the prepared heavy liquid to the test tube, stir, and then put it into a centrifuge. After centrifugation, take the upper layer of liquid and pour it into a new beaker. Number the new beaker and keep the number consistent with the original. Then, the pollen was identified using an optical microscope, and the types of pollen that appeared during the identification were photographed, while referring to books and pollen morphology plates.

[0057] When weighing the No. 2 gravel sample from section h1 for particle size analysis, the following specific steps are included: S1. Weigh 5g of the No. 2 gravel sample from section h1 and dry it. S2. Add hydrogen peroxide to the No. 2 gravel sample in section h1. After the hydrogen peroxide reacts fully with the No. 2 gravel sample in section h1, remove the impurities in the No. 2 gravel sample in section h1. Then add water and centrifuge. After centrifuging, remove the supernatant. Continue to add water to wash the sample until the No. 2 gravel sample in section h1 is neutral. S3. Add 10% hydrochloric acid to the No. 2 gravel sample in section h1. After the hydrochloric acid reacts fully with the No. 2 gravel sample in section h1, remove the carbonate in the No. 2 gravel sample in section h1. Then continue to add water to rinse. Centrifuge and remove the supernatant. Repeat washing until the sample is neutral. S4. Add sodium metaphosphate to the No. 2 gravel sample in section h1, and then place it in an ultrasonic vibrator to stir and vibrate to obtain a highly dispersed suspension, which is then measured by a laser diffraction particle size analyzer.

[0058] When weighing the No. 3 gravel sample from section h1 for magnetic susceptibility analysis, the following specific steps are included: S1. Weigh 20g of gravel sample No. 3 from section h1; S2. Grind the weighed No. 3 gravel sample from section h1 to 0.5mm; S3. Place the ground h1 section No. 3 gravel sample into a 2cm*2cm*2cm plastic cubic box, then compact and fix it. Test the h1 section No. 3 gravel sample through a magnetic susceptibility meter. The magnetic susceptibility data selected are the high-frequency magnetic susceptibility, low-frequency magnetic susceptibility and frequency magnetic susceptibility test results of the h1 section No. 3 gravel sample.

[0059] When dating sand and gravel samples, optically stimulated luminescence dating is used for measurement. In step c, determining the sedimentary environment of the gravel sample refers to analyzing the gravel composition in geological layers A and B, where the age difference between the geological layers exceeds a preset threshold, using optically stimulated luminescence dating. If the gravel in geological layers A and B exhibits elongated, banded, or dendritic shapes, then geological layers A and B are determined to be river or lake sediments; if the gravel in geological layers A and B does not exhibit elongated, banded, or dendritic shapes, then geological layers A and B are determined to be grassland sediments.

[0060] When the age difference between geological layers A and B exceeds a preset threshold of 2000 years, the morphology of gravel in both layers will be collected and analyzed simultaneously during the magnetic susceptibility analysis. If the gravel in layer A is elongated, banded, or dendritic, it indicates that the magnetic susceptibility of layer A is greatly affected by the hydrodynamics at that time, and layer A is identified as fluvial or lacustrine sediments. Conversely, if the gravel in layer A does not exhibit elongated, banded, or dendritic shapes, it indicates that the magnetic susceptibility of layer A is greatly affected by the precipitation at that time, and layer A is identified as grassland sediments. Similarly, if the gravel in layer B is elongated, banded, or dendritic, it indicates that the magnetic susceptibility of layer B is greatly affected by the hydrodynamics at that time, and layer B is identified as fluvial or lacustrine sediments. Conversely, if the gravel in layer B does not exhibit elongated, banded, or dendritic shapes, it indicates that the magnetic susceptibility of layer B is greatly affected by the precipitation at that time, and layer B is identified as grassland sediments.

[0061] Finally, when reconstructing the paleoenvironment of site M, we obtained the morphology of the sand and gravel, determined the influencing factors of magnetic susceptibility based on the morphology, and finally derived the sedimentary environment of site M based on a comprehensive analysis of pollen assemblage, magnetic susceptibility characteristics, and grain size parameters.

[0062] In addition, when dating gravel samples, if the age of the gravel sample exceeds the range of the selected dating method, multiple dating methods are used for cross-dating.

[0063] The range of optically stimulated luminescence (OSL) dating is 100a-1Ma, while that of fission track dating is 20ka-100Ma, where 'a' is the unit of residual activity of radioactive elements. The residual activity of radioactive elements in gravel samples is around 2Ma. Therefore, cross-dating using OSL and fission track dating yields the specific year of the gravel sample. Compared to direct fission track dating, where a larger range results in a larger error, cross-dating using OSL and fission track dating provides more accurate and reliable results.

Claims

1. A paleoenvironment reconstruction method based on historical geological records, characterized in that, Includes the following steps: a. Obtain the target geographical location for the paleoenvironment reconstruction to be carried out; b. Mark the drilling points at the target geographical location and conduct drilling sampling; c. Perform compositional analysis on the obtained gravel samples to determine the sedimentary environment and pollen characteristics of the gravel samples; d. Construct paleoenvironments based on the sedimentary environment and pollen characteristics of the gravel samples.

2. The paleoenvironmental reconstruction method based on historical geological records according to claim 1, characterized in that: In step b, drilling sampling refers to sampling at a well depth of 10-15 meters, layer by layer from top to bottom.

3. The paleoenvironment reconstruction method based on historical geological records according to claim 1, characterized in that: In step c, the component analysis of the obtained gravel sample refers to performing pollen analysis, particle size analysis, magnetic susceptibility analysis, and dating analysis on the gravel sample.

4. The paleoenvironment reconstruction method based on historical geological records according to claim 3, characterized in that: The magnetic susceptibility analysis refers to weighing and grinding a gravel sample, compacting and fixing the ground gravel sample, and then testing it using a magnetic susceptibility instrument.

5. The paleoenvironmental reconstruction method based on historical geological records according to claim 3, characterized in that: The dating analysis is performed using optically stimulated luminescence dating, electron self-selection resonance dating, amino acid dating, fluoride dating, potassium-argon dating, fission track dating, or obsidian hydration.

6. The paleoenvironment reconstruction method based on historical geological records according to claim 5, characterized in that: In step c, determining the sedimentary environment of the gravel sample refers to analyzing the gravel composition in geological layers A and B, where the age difference between the geological layers exceeds a preset threshold, using optically stimulated luminescence dating. If the gravel in geological layers A and B exhibits elongated, banded, or dendritic shapes, then geological layers A and B are determined to be river or lake sediments; if the gravel in geological layers A and B does not exhibit elongated, banded, or dendritic shapes, then geological layers A and B are determined to be grassland sediments.

7. The paleoenvironment reconstruction method based on historical geological records according to claim 4, characterized in that: The mass of the sand and gravel sample is 10-20g, and the particle size after grinding is less than 1mm.

8. The paleoenvironmental reconstruction method based on historical geological records according to claim 3, characterized in that: The pollen analysis involves numbering the gravel samples, drying them, crushing and sieving the dried samples to remove calcium, adding hydrofluoric acid to remove strontium, removing fluoride, filtering through a 5-micron sieve, flotating and concentrating the pollen in a prepared heavy liquid, counting the types and quantities of pollen, and identifying the pollen using pollen morphology charts.

9. The paleoenvironmental reconstruction method based on historical geological records according to claim 8, characterized in that: The removal of calcium refers to removing calcium with a concentration of 10% dilute hydrochloric acid, and the removal of fluoride refers to removing fluoride with a concentration of 37% hydrochloric acid.

10. The paleoenvironment reconstruction method based on historical geological records according to claim 3, characterized in that: The particle size analysis involves crushing and drying the sand sample, passing hydrogen peroxide through the sample to remove organic matter, adding water after impurities are removed, centrifuging the sample, and aspirating the supernatant until the sample is neutral. Then, 10% hydrochloric acid is added to remove carbonates, followed by rinsing with water and centrifuging again to remove the supernatant. This process is repeated until the sample is neutral. Finally, sodium metaphosphate is added, and the sample is stirred in an ultrasonic vibrator to obtain a suspension, which is then measured using a laser diffraction particle size analyzer.

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