CN114324819A - Method for extracting high-resolution ancient climate index in wind dust accumulation sample - Google Patents
Method for extracting high-resolution ancient climate index in wind dust accumulation sample Download PDFInfo
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Abstract
The invention provides a method for extracting high-resolution ancient climate indexes in a wind dust accumulation sample, which can be used for quickly scanning, sampling, analyzing and testing wind dust accumulation elements and magnetic susceptibility indexes. According to the method, continuous columnar samples are obtained in an outcrop sampling mode, the magnetic susceptibility and the element index are synchronously obtained by using a core scanner, and the connection between every two columnar samples is completed by adopting magnetic susceptibility comparison, so that a continuous and high-resolution wind-dust accumulation ancient climate index sequence is finally obtained. According to the method, the continuous columnar sample with the outcrop section is adopted, the discontinuity problems existing in wind dust accumulation, drilling sampling and each-time splicing are solved, the interval powder sample is collected in situ, the continuous columnar sample age scale is accurately controlled, the scanning element indexes which accurately reflect wind in winter and summer seasons can be obtained, and a new method is provided for extracting the high-resolution ancient climate indexes in the wind dust accumulation sample.
Description
Technical Field
The invention belongs to the technical field of ancient climate index extraction and analysis, and particularly relates to a method for extracting a high-resolution ancient climate index from a wind dust accumulation sample.
Background
Understanding the paleoclimate changes during geological history is crucial to dealing with present global warming and predicting future climate changes. The basic means for ancient climate change research is to extract a substitute index capable of reflecting climate change from various geological records. At present, with the development of a plurality of drilling plans for oceans and continents, the core scanning analysis technology is rapidly developed and applied. The core rapid scanning element analysis system developed based on the X fluorescence spectrum (XRF) analysis technology can perform in-situ, continuous and high-resolution element and magnetic susceptibility index analysis (Croudace et al, 2006), and provides great technical support for obtaining ancient climate substitute indexes.
Wind dust accumulation is an undisturbed subsurface sediment formed after dust is carried by wind, and is formed by seasonal alternation of low latitude ocean carrying water vapor circulation and high latitude siberian high pressure carrying wind dust circulation in a monsoon environment (Liudongsheng et al, 1985; Pye, 1995; Guogong, 2010; 2017). China loess plateau has continuous wind and dust accumulation for two hundred and twenty thousand years, and is a unique continental facies ancient climate record with one hundred-thousand year resolution ratio in the world since the new generation.
The conventional sampling method is to take powder samples one by one at a certain interval (e.g. 10cm or 2.5cm), and the median particle size as shown in fig. 4 and 5 is the result of the conventional sampling method. With the continuous and deep research of the wind dust accumulation record, the requirement on the sampling resolution ratio is gradually increased, and the sampling resolution ratio below 1cm is at least required to meet the requirement of century-thousand year scale paleoclimate research. However, the formation of wind-dust accretions is influenced by topography and local formation, so that the collection of wind-dust accretion continuously scanned samples is difficult to use drilling coring technology as well as marine and lake facies deposits. In addition, due to the characteristics that the fine particles accumulated by the wind dust are different from other sediment samples in terms of looseness, fragility, easy collapse and the like, a rapid scanning sampling and analysis testing method for the element and magnetic susceptibility indexes is urgently needed to be established.
The invention patent with the patent application number of CN202110294450.6 in the prior art discloses an analysis method for the change of a continuous sediment paleoclimate substitute index tashengmu, which effectively describes the information characteristics of the talogeno gyru, further analyzes the paleoclimate background experienced in the process of forming a deposition section, and provides a basic technical support for deep analysis of the difference existing in paleoclimate area comparison and promotion of global change research. The invention clearly analyzes the amplitude and degree of the paleoclimatic relative change process on the section; the method is relatively simple and clear to separate a plurality of volunteers, and plays an important role in analyzing the influence of external factors such as paleoclimate and controlling the influence. The method solves the problems that the validity of paleoclimate information is strongly interfered, the accuracy of paleoclimate reconstruction result analysis is influenced and global comparison research is carried out due to the superposition of the talaroid gyrus and the autogenous gyrus in the comprehensive information of paleoclimate substitute indexes in the prior art, but the patent does not solve the problems of difficult sampling and the like and does not provide a method for rapidly scanning, sampling, analyzing and testing the element and magnetic susceptibility indexes.
Disclosure of Invention
In order to overcome the technical problems in the prior art, the invention provides a method for extracting high-resolution paleoclimatic indexes in a wind dust accumulation sample, which can be used for quickly scanning, sampling, analyzing and testing wind dust accumulation elements and magnetic susceptibility indexes. According to the method, continuous columnar samples are obtained in an outcrop sampling mode, the magnetic susceptibility and the element index are synchronously obtained by using a core scanner, and the connection between every two columnar samples is completed by adopting magnetic susceptibility comparison, so that a continuous and high-resolution wind-dust accumulation ancient climate index sequence is finally obtained.
In order to achieve the above purpose, the invention adopts the following technical scheme: a method for extracting high-resolution paleoclimate indexes in a wind dust accumulation sample specifically comprises the following steps:
(1) acquiring a wind dust accumulation columnar sample in the field;
(2) sampling the columnar sample;
(3) acquiring element and continuous magnetic susceptibility data by using a rock core scanner;
(4) comparing the magnetic susceptibility of the two adjacent columnar sample repeated layers to realize the splicing of continuous scanning data;
(5) taking powder samples on the columnar sample at the same interval and sequentially testing the mass magnetic susceptibility and the particle size sequence of the powder samples;
(6) comparing the obtained ratio of each continuous scanning element sequence with the mass magnetic susceptibility and the granularity sequence of the powder samples collected at the original position intervals in the step (5) to obtain an ancient climate element index capable of reflecting the change of the summer season wind and the winter season wind;
(7) obtaining an age scale of a continuous scanning sequence by a susceptibility interpolation method, and finally obtaining a wind dust accumulation high-resolution continuous scanning time sequence;
and the steps (1) to (7) are sequentially carried out according to the sequence.
Preferably, in the step (1), a probe groove perpendicular to the deposition direction of the stratum is excavated in the region where the wind dust is accumulated.
In any of the above schemes, preferably, the specific method in step (1) is: and excavating sampling probe grooves perpendicular to the stratum development direction, wherein the depth of each probe groove is 1-1.4m, the width of each probe groove is 0.8-1m, the vertical depth is marked on the sampling wall of the probe groove at fixed intervals from the initial probe groove of 0m to the sampling end position, and the sampling top and bottom positions of the columnar samples are marked in each probe groove.
In any of the above schemes, preferably, each of the probe grooves has a depth of 1m and a width of 0.8 m.
In any of the above schemes, preferably, each of the probe grooves has a depth of 1.4m and a width of 1 m.
In any of the above schemes, preferably, each of the probe grooves has a depth of 1.2m and a width of 1 m.
In any of the above solutions, it is preferable to mark vertical depths on the sampling wall of the probe groove starting from the starting probe groove at 0m and at intervals of 0.2m up to the sampling end position.
In any of the above solutions, it is preferable to mark vertical depths on the sampling wall of the probe groove starting from the starting probe groove at 0m and at intervals of 0.1m up to the sampling end position.
In any of the above embodiments, it is preferable that the step (2) of sampling the columnar sample is preceded by filling the crack in the sampling region with a glue.
In any of the above schemes, preferably, in the step (2), the columnar samples are obtained by using a U-shaped stainless steel groove, and 8% -12% of repeated layers exist between adjacent columnar samples.
In any of the above embodiments, it is preferred that there are 8% repeat horizons between adjacent columnar patterns.
In any of the above embodiments, it is preferred that there are 10% repeat levels between adjacent columnar patterns.
In any of the above embodiments, it is preferred that there are 12% repeat horizons between adjacent columnar patterns.
In any of the above schemes, preferably, the specific method of step (2) is:
(2.1) carving a columnar sample outline along the sampling position on the probing groove sampling wall in the step (1), then cutting the columnar sample along the outline, and buckling a U-shaped stainless steel groove on the columnar sample connected to the probing groove wall;
(2.2) marking the serial number of the columnar sample, the top direction and the top-bottom depth meter number on the U-shaped stainless steel groove;
and (2.3) chiseling down the joint of the columnar sample and the wall of the detection groove to take out the columnar sample, and wrapping and sealing the columnar sample.
In any of the above schemes, preferably, the U-shaped stainless steel groove is of a concave structure, and the U-shaped stainless steel groove is of a hollow structure.
In any of the above schemes, preferably, the upper part of the U-shaped stainless steel groove is arranged in an open manner, and two ends of the U-shaped stainless steel groove are not closed.
In any of the above schemes, preferably, the U-shaped stainless steel trough includes a bottom plate, and two sides of the bottom plate are vertically connected with side plates.
In any one of the above schemes, preferably, the upper end of the side plate is provided with a knife edge part, and the knife edge part is arranged in a triangle shape.
In any of the above schemes, preferably, the inner diameter between the two side plates is 70-90mm, the heights of the two side plates are the same, and the thickness of a single side plate is 2 mm.
In any of the above embodiments, the inner diameter between the two side plates is preferably 70 mm.
In any of the above embodiments, the inner diameter between the two side plates is preferably 80 mm.
In any of the above embodiments, the inner diameter between the two side plates is preferably 90 mm.
In any of the above schemes, preferably, the outer side of at least one side plate is provided with a scale mark.
In any of the above embodiments, the step (3) may be preceded by a step of pretreating the obtained columnar sample, and the specific pretreatment method is: and cutting a cylindrical sample into a flat scanning surface along the long axis direction, wherein pits and cracks with the width larger than 1mm cannot appear on the surface of the cylindrical sample.
In any of the above schemes, preferably, the XRF element scanning is performed at a scanning resolution of 1mm and a scanning time of 50s in the step (3); after the XRF elemental scan is complete, a volume susceptibility scan is performed at the same scan position with a resolution of 1 cm.
In any of the above schemes, preferably, the specific method for performing continuous scan data stitching in step (4) is as follows: and comparing the peak-valley of the scanning magnetic susceptibility data of the repeated section between two adjacent columnar samples to accurately splice the scanning magnetic susceptibility and element data of the next columnar sample to the front tail end, and corresponding the scanning position data to the depth meters of the columnar samples to obtain the scanning magnetic susceptibility and element data on the depth sequence.
In any of the above embodiments, it is preferable that in the step (5), powder samples are taken at intervals of 2 to 3cm on the surface of the columnar sample and the powder samples are tested for mass magnetic susceptibility and particle size index.
In any of the above embodiments, it is preferable that in the step (5), the powder samples are taken at 2cm intervals on the columnar sample and the powder samples are tested for mass magnetic susceptibility and particle size index.
In any of the above embodiments, it is preferable that in the step (5), the powder samples are taken at intervals of 2.5cm on the columnar sample and the powder samples are tested for mass magnetic susceptibility and particle size index.
In any of the above embodiments, it is preferable that in the step (5), powder samples are taken at 3cm intervals on the columnar sample and the powder samples are tested for mass magnetic susceptibility and particle size index.
In any of the above schemes, preferably, the mass magnetic susceptibility detection method is: taking a powder sample, packaging the powder sample into a regular sphere by using weighing paper, placing the regular sphere on a susceptibility meter, testing the susceptibility at a low-frequency gear, detecting three times, taking an average value as a result, and dividing the susceptibility value by an accurate mass number to obtain mass susceptibility data.
In any of the above embodiments, preferably, the particle size analysis method is: taking a powder sample, and sequentially adding H under the heating condition2O2Adding deionized water and an HCl solution, and standing; removing the supernatant, adding a sodium hexametaphosphate solution, and performing ultrasonic dispersion; after being taken outPerforming particle size analysis on a laser particle size analyzer; and carrying out statistical analysis on the obtained percentage results under all the particle sizes to obtain the median particle size of the sample.
In any of the above schemes, preferably, in the step (6), the ratio of each of the obtained continuous scanning element sequences is subjected to a sliding average to obtain the same resolution as the scanning magnetic susceptibility sequence and the powder sample particle size sequence taken at the in-situ intervals, and then the correlation analysis is performed on the variation trend.
In any of the above schemes, preferably, when the comparison in step (6) is performed, the element ratio sequence having a correlation with the scanning magnetic susceptibility sequence of more than 80% is an index reflecting the change of wind in summer season, and the element ratio sequence having a correlation with the grain size sequence of more than 80% is an index reflecting the change of wind in winter season.
In any of the above schemes, preferably, in the step (7), the mass magnetic susceptibility sequence of the spaced powder sample is subjected to peak-valley matching with an existing ancient geomagnetic chronological scale, the age of the sampling horizon is determined, and then the scanning magnetic susceptibility and the element sequence are inserted into the magnetic susceptibility sequence of the spaced powder sample, so as to obtain the chronological scale of the scanning magnetic susceptibility and the element sequence.
The invention provides a method for extracting high-resolution ancient climate indexes in a wind dust accumulation sample, which can be used for quickly scanning, sampling, analyzing and testing wind dust accumulation elements and magnetic susceptibility indexes. According to the method, continuous columnar samples are obtained in an outcrop sampling mode, the magnetic susceptibility and the element index are synchronously obtained by using a core scanner, and the connection between every two columnar samples is completed by adopting magnetic susceptibility comparison, so that a continuous and high-resolution wind-dust accumulation ancient climate index sequence is finally obtained. According to the method, the continuous columnar sample with the outcrop section is adopted, the discontinuity problems existing in wind dust accumulation, drilling sampling and each-time splicing are solved, the interval powder sample is collected in situ, the continuous columnar sample age scale is accurately controlled, the scanning element indexes which accurately reflect wind in winter and summer seasons can be obtained, and a new method is provided for extracting the high-resolution ancient climate indexes in the wind dust accumulation sample.
The invention has the beneficial effects that:
the invention discloses a method for extracting high-resolution ancient climate indexes in a wind dust accumulation sample, which comprises the steps of firstly excavating a probe groove vertical to the stratum deposition direction in a wind dust accumulation exposed area; obtaining columnar samples by using a U-shaped stainless steel groove, wherein repeated layers are arranged among the columnar samples; pre-treating the obtained columnar sample to perform continuous magnetic susceptibility and element scanning; acquiring scanning magnetic susceptibility and element data by using a rock core scanner; comparing the magnetic susceptibility of the repeated positions of two adjacent columnar samples to realize the splicing of spliced continuous scanning data of each sample; taking powder samples on the surface of the columnar sample at fixed intervals and obtaining interval mass magnetic susceptibility and a granularity sequence; comparing the obtained ratio of each continuous scanning element sequence with the in-situ interval mass magnetic susceptibility and the granularity sequence to obtain an ancient climate element index capable of reflecting the change of the summer season wind and the winter season wind; obtaining an age scale of the continuous scanning sequence by a susceptibility interpolation method; finally, a wind dust accumulation high-resolution continuous scanning time sequence is obtained.
According to the method, the continuous columnar sample is taken by adopting the section outcrop, the discontinuity problems existing in wind dust accumulation, drilling sampling and each-time splicing are solved, the interval powder sample is collected in situ, the age scale of the continuous columnar sample is accurately controlled, the scanning element indexes which accurately reflect wind in winter and summer seasons can be obtained, and a new method is provided for extracting the high-resolution ancient climate indexes in the wind dust accumulation sample.
Drawings
FIG. 1 is a diagram of a field exploration groove excavation and columnar sample collection position of the method for extracting high-resolution paleoclimate indexes in a wind dust accumulation sample according to the present invention;
FIG. 2 is a schematic structural diagram of a U-shaped stainless steel sampling tank of the method for extracting high-resolution paleoclimatic indexes in a wind dust accumulation sample;
FIG. 3 is a sampling flow of a columnar sample of the method for extracting high-resolution paleoclimate indexes in a wind dust accumulation sample according to the present invention;
FIG. 4 is a result graph of scanning element winter-summer season wind index (Si/K, Fe/K) in a wind-dust accumulation sample in Tianshui of Gansu obtained by the method for extracting high-resolution ancient climate index in a wind-dust accumulation sample of the present invention;
FIG. 5 is a graph showing the results of scanning element winter/summer season wind indicators (Si/Ti, Rb/K) in a wind dust accumulation sample in Gansu region obtained by the method for extracting high-resolution paleo-climate indicators in a wind dust accumulation sample according to the present invention;
wherein, the meaning of each reference number in the figure is as follows:
1. the cutting tool comprises a bottom plate, 2, side plates, 3, a knife edge part, 4, a connecting column, 5 and a connecting groove.
Detailed Description
In order that the present invention may be more clearly understood, the following description and the accompanying drawings are provided for further explanation and explanation.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.
The core scanner used in the invention is manufactured by Cox company, and has the model of Itrax, Cr light pipe (30kV and 50mA), the scanning resolution is 2mm, and the scanning time is 20 s. The susceptibility meter used was Bartington MS 3. The laser particle sizer used was Beckman LS 13320.
Example one
A method for extracting high-resolution paleoclimate indexes in a wind dust accumulation sample comprises the following steps in sequence:
(1) and acquiring the wind dust accumulation columnar sample in the field. And excavating a series of sampling probe grooves perpendicular to the development direction of the stratum, wherein the depth of each probe groove is 1-1.5m, the width of each probe groove is 0.6-1m, the vertical depth of each probe groove is marked on the sampling wall of each probe groove from 0m to 0.1m at intervals until the sampling end position, and the sampling top and bottom positions of the columnar sample are marked in each probe groove, as shown in figure 1.
(2) And obtaining a columnar sample by using a U-shaped stainless steel groove. The cracks in the sampling area are filled with a gel transparent glass gel to ensure that the columnar sample is not broken and broken during sampling. And (3) a sampling knife is used for engraving a columnar sample outline along the sampling position on the groove detecting sampling wall in the step (1), then a cutting machine is used for cutting the columnar sample along the outline, the columnar sample connected to the wall of the groove detecting sampling wall is buckled with a U-shaped stainless steel groove, and the structure of the U-shaped stainless steel groove is shown in figure 2. The number of the column sample, the top direction and the top-bottom depth meter are marked on the U-shaped stainless steel groove. And (3) chiseling the joint of the columnar sample and the probing groove wall by using a cutting machine and an iron chisel to take out the columnar sample, wrapping and sealing the columnar sample by using absorbent paper and anti-collision wrapping paper for facilitating transportation, and firstly, engraving the outline of the columnar sample → cutting the columnar sample → buckling a U-shaped stainless steel groove → numbering and packaging and sealing as shown in figure 3.
(3) And continuously scanning the test sample for pretreatment. And processing the columnar sample to form a flat scanning surface, and ensuring that pits and cracks with the width larger than 1mm cannot appear on the surface of the columnar sample. During processing, cutting is carried out in the direction parallel to the long axis of the columnar sample, so that test errors caused by mixing of different layers are avoided.
(4) And acquiring continuous scanning magnetic susceptibility and element data by using a core scanner. Firstly, a special scale is arranged on one side of the columnar sample in a direction parallel to the long axis, the main scale of the special scale is 1cm, the auxiliary scale of the special scale is 0.5cm, a plastic insulating tape is pasted on the tail end of the sample, and then surface scanning is carried out to obtain a surface image of the columnar sample. The position of the start and end of the surface scan is recorded, and the exact distance in meters from the top of the sample at the start of the scan and the exact meters at the bottom of the sample at the end of the scan are recorded. And removing the graduated scale on one side of the columnar sample, and covering a Mylar film on the surface of the columnar sample to prevent the XRF detector from being polluted. XRF elemental scans were then performed at 1mm scan resolution for 50s scan duration. After the XRF elemental scan is complete, a volume susceptibility scan is performed at the same scan position with a resolution of 1 cm. The volume magnetic susceptibility scan result is obtained from the difference between the magnetic susceptibility value of the sample above the sample and the magnetic susceptibility value of the sample surface.
(5) And splicing continuous scanning data. And comparing the peak-valley of the scanning magnetic susceptibility data of the repeated section between two adjacent columnar samples to accurately splice the scanning magnetic susceptibility and element data of the next columnar sample to the front tail end, and corresponding the scanning position data to the depth meters of the columnar samples to obtain the scanning magnetic susceptibility and element data on the depth sequence.
(6) And taking powder samples on the columnar samples at intervals of 2.5cm and testing the mass magnetic susceptibility and the granularity index of the powder samples.
First, mass magnetic susceptibility analysis of the powder samples was performed: taking 10g of sample, packaging the sample into a regular sphere by using weighing paper, placing the regular sphere on a susceptibility meter, measuring the susceptibility at a low frequency (1SI) gear, taking an average value for three times as a result, and dividing the susceptibility value by an accurate mass number to obtain mass susceptibility data.
The particle size analysis method comprises the following steps: taking 0.2g of sample, adding 30% H under heating at 140 deg.C2O220ml of solution is added to remove organic matter, and 20ml of 1mol/LHCl solution is added to remove secondary carbonate. 500ml of deionized water was added to the above treated sample and allowed to stand for at least 24 hours. And (3) removing the supernatant, adding 0.05mol/L sodium hexametaphosphate solution, and performing ultrasonic dispersion for 10 min. And taking out the particles and then carrying out particle size analysis on a laser particle size analyzer. And carrying out statistical analysis on the obtained percentage results under all the particle sizes to obtain the median particle size of the sample.
(7) And obtaining the ancient climate element index capable of reflecting the change of the wind in the summer and the wind in the winter.
And (3) obtaining the resolution ratio of each obtained continuous scanning element sequence which is the same as the scanning magnetic susceptibility sequence and the in-situ 2.5cm interval powder sample particle size sequence through a sliding average, and then carrying out correlation analysis on the change trends of the scanning magnetic susceptibility sequence and the in-situ 2.5cm interval powder sample particle size sequence, wherein the element ratio sequence which has the correlation with the scanning magnetic susceptibility sequence of more than 80 percent is an index for reflecting the change of summer season wind, and the element ratio sequence which has the correlation with the particle size sequence of more than 80 percent is an index for reflecting the change of winter season wind.
(8) An age scale of a sequence of consecutive scans is obtained.
On the basis of an ancient geomagnetic chronograph scale established by predecessors, a 2.5cm interval powder sample mass magnetic susceptibility sequence is matched with the chronograph scale of predecessors in a peak-valley mode, the chronograph of a sampling horizon is determined, and then scanning magnetic susceptibility and element sequences are inserted into the 2.5cm magnetic susceptibility sequence to obtain the chronograph scale of scanning magnetic susceptibility and element sequences.
Example two
The method for extracting the high-resolution ancient climate indexes in the wind dust accumulation sample is adopted to analyze the wind dust accumulation sample in the Tianshui area of Gansu, and the specific method is as follows:
(1) and obtaining the columnar sample in the field.
A series of sampling probe grooves are excavated in the direction perpendicular to the stratum development direction, the depth of each probe groove is 1m, the width of each probe groove is 0.8m, the vertical depth of each probe groove is marked on the sampling wall of each probe groove at intervals of 0.1m from the initial probe groove to the position 2.3m away from the sampling end position, and the sampling top and bottom positions of the columnar samples are marked in each probe groove.
(2) And obtaining a columnar sample by using a U-shaped stainless steel groove.
The cracks in the sampled area were first filled with glue to ensure that the column did not break and fracture when sampled. And (3) engraving a columnar sample outline along the sampling position on the groove detecting sampling wall in the step (1) by using a sampling cutter, then cutting the columnar sample along the outline by using a cutting machine, and buckling the columnar sample connected to the wall of the groove detecting sampling wall with a U-shaped stainless steel groove. The serial number of the columnar sample, the top direction and the top-bottom depth meter are marked on the U-shaped groove. And chiseling the joint of the columnar sample and the wall of the detection groove by using a cutting machine and an iron chisel to take out the columnar sample, and wrapping and sealing the columnar sample by using absorbent paper and anti-collision wrapping paper so as to facilitate transportation.
(3) And continuously scanning the test sample for pretreatment.
And cutting the columnar sample by a zirconia ceramic knife in a direction parallel to the long axis of the columnar sample to form a flat scanning surface, and sealing pits with height difference of more than 5cm and cracks with width of more than 1mm by using insulating tapes with the same width.
(4) And acquiring continuous scanning magnetic susceptibility and element data by using a core scanner.
Firstly, a special scale (a common scale fixed on a columnar sample) is arranged on one side of the columnar sample in a direction parallel to a long axis, the main scale of the scale is 1cm, the auxiliary scale of the scale is 0.5cm, a plastic insulating tape is pasted on the tail end of the sample, and then surface scanning is carried out to obtain a surface image of the columnar sample. The position of the start and end of the scan of the surface is recorded, and the exact distance in meters from the top of the sample at the start of the scan and the exact meters from the bottom of the sample at the end of the scan are recorded. And removing the graduated scale on one side of the columnar sample, and covering a Mylar film on the surface of the columnar sample to prevent the XRF detector from being polluted. XRF elemental scans were then performed at 2mm scan resolution for 20s scan duration. After the XRF elemental scan is complete, a volume susceptibility scan is performed at the same scan position with a resolution of 1 cm. The volume magnetic susceptibility scan result is obtained from the difference between the magnetic susceptibility value of the sample above the sample and the magnetic susceptibility value of the sample surface.
(5) And splicing continuous scanning data.
And (3) carrying out peak-valley comparison on the scanning magnetic susceptibility data of the repeated section between two adjacent columnar samples so as to accurately splice the scanning magnetic susceptibility and element data of the next columnar sample to the front tail end, and corresponding the scanning position data to the depth meter number of the columnar sample so as to obtain a scanning magnetic susceptibility and element depth sequence of 2.3m, as shown in a in figure 4.
(6) And taking powder samples at 2.5cm intervals on the columnar samples with the magnetic susceptibility and element scanning completed and testing the mass magnetic susceptibility and the granularity index of the powder samples.
Firstly, analyzing the mass magnetic susceptibility of a powder sample, taking 2g (plus or minus 0.001g) of the sample, packaging the sample into a regular cube by using a cube-shaped plastic box, placing the regular cube on a susceptibility meter, measuring the magnetic susceptibility at a low-frequency gear, taking an average value for three times as a result, and dividing the magnetic susceptibility value by an accurate mass number to obtain mass magnetic susceptibility data.
The particle size analysis method comprises the following steps: taking 0.02g of sample, adding 30% H under heating at 140 DEG C2O220ml of the solution is used for removing organic matters, and 20ml of 1mol/L HCl solution is added for removing secondary carbonate. 500ml of deionized water was added to the above treated sample and allowed to stand for at least 48 hours. And (3) removing the supernatant, adding 0.05mol/L sodium hexametaphosphate solution, and performing ultrasonic dispersion for 10 min. And taking out the particles and then carrying out particle size analysis on a laser particle size analyzer. The percentage results obtained for each particle size were statistically analyzed to obtain the median particle size of the sample, as shown by d in fig. 4.
(7) And obtaining the ancient climate element index capable of reflecting the change of the wind in the summer and the wind in the winter.
And obtaining the resolution ratio of each obtained continuous scanning element sequence which is the same as the scanning magnetic susceptibility sequence and the in-situ 2.5cm interval powder sample particle size sequence through the sliding average, and then carrying out correlation analysis on the variation trend of the scanning magnetic susceptibility sequence and the in-situ 2.5cm interval powder sample particle size sequence to obtain an element ratio sequence with the correlation of more than 80% with the scanning magnetic susceptibility sequence, namely Rb/K which is 82%. Rb/K is therefore an index reflecting the change in the summer wind, as shown by b in FIG. 4. The sequence of the ratio of the elements having a correlation of greater than 80% with the sequence of the particle sizes is Si/Ti, 89%. Therefore, Si/Ti is an index reflecting the change in winter and season, as shown by c in FIG. 4.
(8) Obtaining an age scale of the sequence of consecutive scans.
On the basis of the ancient geomagnetic chronograph ruler established by predecessors (Guo et al, 2002), peak-valley matching is carried out on a 2.5cm interval powder sample mass magnetic susceptibility sequence and the ancient geomagnetic chronograph ruler of predecessors, the era of a sampling horizon is determined, and then the scanning magnetic susceptibility and the element sequence are inserted into the 2.5cm magnetic susceptibility sequence to obtain the ancient chronograph ruler of the scanning magnetic susceptibility and the element sequence, as shown in fig. 4.
EXAMPLE III
The method for extracting the high-resolution ancient climate index in the wind dust accumulation sample is adopted to analyze the wind dust accumulation sample in the Longxi region, and the specific method is as follows:
(1) and obtaining the columnar sample in the field. A series of sampling probe grooves are excavated in the direction perpendicular to the stratum development direction, the depth of each probe groove is 1.4m, the width of each probe groove is 1m, the vertical depth of each probe groove is marked on the sampling wall of each probe groove at intervals of 0.1m from the initial probe groove to the position 4m from the sampling end position, and the sampling top and bottom positions of the columnar samples are marked in each probe groove.
(2) And obtaining a columnar sample by using a U-shaped stainless steel groove.
The cracks in the sampled area were first filled with glue to ensure that the column did not break and fracture when sampled. And (3) engraving a columnar sample outline along the sampling position on the groove detecting sampling wall in the step (1) by using a sampling cutter, then cutting the columnar sample along the outline by using a cutting machine, and buckling the columnar sample connected to the wall of the groove detecting sampling wall with a U-shaped stainless steel groove. The serial number of the columnar sample, the top direction and the top-bottom depth meter are marked on the U-shaped groove. And chiseling the joint of the columnar sample and the wall of the detection groove by using a cutting machine and an iron chisel to take out the columnar sample, and wrapping and sealing the columnar sample by using absorbent paper and anti-collision wrapping paper so as to facilitate transportation.
(3) And continuously scanning the test sample for pretreatment.
And cutting the columnar sample by a zirconia ceramic knife in a direction parallel to the long axis of the columnar sample to form a flat scanning surface, and sealing pits with height difference of more than 5cm and cracks with width of more than 1mm by using insulating tapes with the same width.
(4) And acquiring continuous scanning magnetic susceptibility and element data by using a core scanner.
Firstly, a special scale is arranged on one side of the columnar sample in a direction parallel to the long axis, a plastic insulating tape is pasted at the tail end of the sample, and then surface scanning is carried out to obtain a surface image of the columnar sample. The position of the start and end of the surface scan is recorded, and the exact distance in meters from the top of the sample at the start of the scan and the exact meters at the bottom of the sample at the end of the scan are recorded. And removing the graduated scale on one side of the columnar sample, and covering a Mylar film on the surface of the columnar sample to prevent the XRF detector from being polluted. XRF elemental scans were then performed at 2mm scan resolution for 20s scan duration. After the end of (2mm scan resolution, 20s scan duration), a volume susceptibility scan was performed at the same scan position with a resolution of 1 cm. The volume magnetic susceptibility scan result is obtained from the difference between the magnetic susceptibility value over the sample and the magnetic susceptibility value of the sample surface, as shown in a in fig. 5.
(5) And splicing continuous scanning data.
And comparing the peak-valley of the scanning magnetic susceptibility data of the repeated section between two adjacent columnar samples to accurately splice the scanning magnetic susceptibility and element data of the next columnar sample to the front tail end, and corresponding the scanning position data to the depth meter number of the columnar sample to obtain a scanning magnetic susceptibility and element depth sequence of 4 m.
(6) And taking powder samples at 2.5cm intervals on the columnar samples with the magnetic susceptibility and element scanning completed and testing the mass magnetic susceptibility and the granularity index of the powder samples.
Firstly, analyzing the mass magnetic susceptibility of a powder sample, taking 5g (plus or minus 0.001g) of the sample, packaging the sample into a regular cube by using a cube-shaped plastic box, placing the regular cube on a susceptibility meter, measuring the magnetic susceptibility at a low-frequency gear, taking an average value for three times as a result, and dividing the magnetic susceptibility value by an accurate mass number to obtain mass magnetic susceptibility data.
The particle size analysis method comprises the following steps: taking 0.01g of sample, adding 30% H under heating at 140 deg.C2O220ml of the solution is used for removing organic matters, and 10ml of 1mol/L HCl solution is added for removing secondary carbonate. 450ml of deionized water was added to the above treated sample and left for 24 hours. And (3) removing the supernatant, adding 0.04mol/L sodium hexametaphosphate solution, and performing ultrasonic dispersion for 10 min. And taking out the particles and then carrying out particle size analysis on a laser particle size analyzer. The percentage results obtained for each particle size were statistically analyzed to obtain the median particle size of the sample, the results are shown as d in fig. 5.
(7) And obtaining the ancient climate element index capable of reflecting the change of the wind in the summer and the wind in the winter.
And obtaining the resolution ratio of each obtained continuous scanning element sequence which is the same as the scanning magnetic susceptibility sequence and the in-situ 2.5cm interval powder sample particle size sequence through the sliding average, and then carrying out correlation analysis on the variation trend of the scanning magnetic susceptibility sequence and the in-situ 2.5cm interval powder sample particle size sequence to obtain an element ratio sequence which has the correlation with the scanning magnetic susceptibility sequence of more than 80% and is Fe/K which is 84%. Therefore Fe/K is an index reflecting the change of the summer wind, and the result is shown as b in FIG. 5. The element ratio sequence with a correlation of more than 80% with the particle size sequence is Si/Ti, which is 90%. Therefore, Si/Ti is an index reflecting the change in winter and season, and the result is shown as c in FIG. 5.
(8) Obtaining an age scale of the sequence of consecutive scans.
On the basis of the ancient geomagnetic chronograph ruler established by predecessors (Guo et al, 2002), peak-valley matching is carried out on a 2.5cm interval powder sample mass magnetic susceptibility sequence and the ancient geomagnetic chronograph ruler of predecessors, the era of a sampling horizon is determined, and then the scanning magnetic susceptibility and the element sequence are inserted into the 2.5cm magnetic susceptibility sequence to obtain the ancient chronograph ruler of the scanning magnetic susceptibility and the element sequence, as shown in fig. 5.
Example four
The U-shaped stainless steel tank used in the method for extracting the high-resolution paleoclimatic indexes in the wind dust accumulation sample has a concave structure and a hollow structure as shown in figure 2. The length of the U-shaped stainless steel groove is not limited and can be set according to the requirement. The upper part of the U-shaped stainless steel groove is arranged in an open manner, and the two ends of the U-shaped stainless steel groove are not closed. The U-shaped stainless steel groove specifically comprises a bottom plate 1, and side plates 2 are vertically connected to two sides of the bottom plate 1. The upper end of the side plate 2 is detachably connected with a knife edge part 3, the upper end of the knife edge part 3 is arranged in a right-angled triangle or an equilateral triangle,
the inner diameter L between the two side plates 2 is 80mm, the heights H of the two side plates 2 are the same, H is set to be 40mm, and the thickness of a single side plate 2 is 2 mm. The outer sides of the two side plates are provided with scale marks, the main scale is 1cm, and the auxiliary scale is 0.5 cm.
EXAMPLE five
The U-shaped stainless steel groove used in the method for extracting the high-resolution paleoclimatic indexes in the wind dust accumulation sample is similar to that of the embodiment, except that the lower end of the blade part 3 is provided with the connecting column 4, the side plate 2 is provided with the connecting groove 5 which is relatively matched with the connecting column, when the U-shaped stainless steel groove needs to be buckled on the columnar sample, in order to accelerate the buckling speed, the bottom end of the blade part 3 is fixed at the upper part of the connecting groove 5 of the side plate 2 through the connecting column 4, and the upper part of the blade part 3 is a sharp-pointed end, so that the effect of cutting the side wall of the columnar sample can be achieved while the speed is accelerated, and redundant soil samples can be removed.
Of course, in the later packaging process or the maintenance process of the U-shaped stainless steel groove, the blade part 3 can be pulled out from the connecting groove 5 for the safety of workers.
It should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. A method for extracting high-resolution paleoclimate indexes in a wind dust accumulation sample is characterized by comprising the following steps:
(1) acquiring a wind dust accumulation columnar sample in the field;
(2) sampling the columnar sample;
(3) acquiring element and continuous magnetic susceptibility data by using a rock core scanner;
(4) comparing the magnetic susceptibility of the two adjacent columnar sample repeated layers to realize the splicing of continuous scanning data;
(5) taking powder samples on the columnar sample at the same interval and sequentially testing the mass magnetic susceptibility and the particle size sequence of the powder samples;
(6) comparing the obtained ratio of each continuous scanning element sequence with the mass magnetic susceptibility and the granularity sequence of the powder samples collected at the original position intervals in the step (5) to obtain an ancient climate element index capable of reflecting the change of the summer season wind and the winter season wind;
(7) obtaining an age scale of a continuous scanning sequence by a susceptibility interpolation method, and finally obtaining a wind dust accumulation high-resolution continuous scanning time sequence;
and the steps (1) to (7) are sequentially carried out according to the sequence.
2. The method for extracting the high-resolution paleo-climate indicator in the wind dust accumulation sample as claimed in claim 1, wherein in the step (1), a probe perpendicular to the direction of formation deposition is excavated in the region where the wind dust accumulation is exposed.
3. The method for extracting the high-resolution paleo-climate index in the wind dust accumulation sample as claimed in claim 1, wherein the specific method in step (1) is as follows: and excavating sampling probe grooves perpendicular to the stratum development direction, wherein the depth of each probe groove is 1-1.4m, the width of each probe groove is 0.8-1m, the vertical depth is marked on the sampling wall of the probe groove at fixed intervals from the initial probe groove of 0m to the sampling end position, and the sampling top and bottom positions of the columnar samples are marked in each probe groove.
4. The method for extracting the high-resolution paleo-climate index in the wind dust accumulation sample as claimed in claim 1, wherein the step (2) is to use a U-shaped stainless steel tank to obtain the columnar samples, and the adjacent columnar samples have 8% -12% of repeated layers.
5. The method for extracting the high-resolution paleo-climate index in the wind dust accumulation sample as claimed in claim 1, wherein the specific method of the step (2) is as follows:
(2.1) carving a columnar sample outline along the sampling position on the probing groove sampling wall in the step (1), then cutting the columnar sample along the outline, and buckling a U-shaped stainless steel groove on the columnar sample connected to the probing groove wall;
(2.2) marking the serial number of the columnar sample, the top direction and the top-bottom depth meter number on the U-shaped stainless steel groove;
and (2.3) chiseling down the joint of the columnar sample and the wall of the detection groove to take out the columnar sample, and wrapping and sealing the columnar sample.
6. The method for extracting high-resolution paleo-climate indicator in the wind dust accumulation sample as claimed in claim 1, wherein the scanning in step (3) is performed with XRF element scanning at 1mm scanning resolution for 50s scanning time; after the XRF elemental scan is complete, a volume susceptibility scan is performed at the same scan position with a resolution of 1 cm.
7. The method for extracting the high-resolution paleo-climate index in the wind dust accumulation sample as claimed in claim 1, wherein the specific method for performing the continuous scanning data stitching in the step (4) is as follows: and comparing the peak-valley of the scanning magnetic susceptibility data of the repeated section between two adjacent columnar samples to accurately splice the scanning magnetic susceptibility and element data of the next columnar sample to the front tail end, and corresponding the scanning position data to the depth meters of the columnar samples to obtain the scanning magnetic susceptibility and element data on the depth sequence.
8. The method for extracting high-resolution paleo-climate indicators from wind dust accumulation samples as claimed in claim 1, wherein in step (5), powder samples are taken at intervals of 2-3cm on the surface of the columnar sample and the powder samples are tested for mass magnetic susceptibility and particle size indicators.
9. The method for extracting the high-resolution paleo-climate indicator in the wind dust accumulation sample as claimed in claim 1, wherein the ratio of each of the obtained continuous scanning element sequences in step (6) is subjected to a sliding average to obtain the same resolution as the scanning magnetic susceptibility sequence and the powder sample particle size sequence taken at the in-situ interval, and then the correlation analysis is performed on the variation trend.
10. The method for extracting high-resolution paleo-climate indicator in wind dust accumulation sample as claimed in claim 1, wherein in step (7), the mass magnetic susceptibility sequence of the interval powder sample is matched with the existing paleogeomagnetism chronometer to determine the chronology of the sampling horizon, and then the scanning magnetic susceptibility and the element sequence are inserted into the magnetic susceptibility sequence of the interval powder sample to obtain the chronometer of the scanning magnetic susceptibility and the element sequence.
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