Rocks under the Microscope Zone II Versions EN1 Vol 5 (3) 2020
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Carbonate micrograph dataset of Feixianguan Formation in the northwestern margin of Upper Yangtze
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Abstract & Keywords
Abstract: Carbonate platform-basin facies developed during the Early Triassic Feixianguan Formation in the northwestern margin of the Upper Yangtze. Studies of rock characteristics (such as structure and formation) under a microscope provide intuitive evidence for research on the sedimentary environment and biological resuscitation in the Early Triassic following the mass extinction during the Late Permian. In this study, we selected four field sections of the Lower Triassic Feixianguan Formation, in the open platform, the platform margin, and the pre-platform slope-basin multiphase belt in the northwestern Upper Yangtze, from which common slices were systematically sampled and made. Photomicrographs of the slices were taken to systematically display the type, mineral composition, structure, formation, paleontology, and diagenesis of the rock sections. This dataset consists of two parts, including a total of 1,082 polarizing micrographs of 330 rock samples from the four geological sections and a sheet information table. The dataset provides basic material for research on the Early Triassic paleoclimate, paleoenvironment, and paleontological resuscitation or research on the sedimentary differentiation of different facies in this period. It also provides data support for oil and gas surveys on these particular strata.
Keywords: northwestern margin of Upper Yangtze; Lower Triassic Feixianguan Formation; carbonate rock; biological extinction; micro-atlas
Dataset Profile
TitleA carbonate micrograph dataset of the Feixianguan Formation in the northwestern margin of Upper Yangtze
Data authorsChai Hanbing, Xing Fengcun, Gu Qiang, Chen Xiaoquan, Zhou Shaopeng
Data corresponding authorXing Fengcun (xingfengcun@163.com)
Time rangeThe rock samples were collected between 2013 and 2017 from strata whose stratigraphic age was attributed to the Early Triassic. The polarizing microscopic photos of the rock flakes were taken in 2019.
Geographical scopeChengkou County, Chongqing City; Jiuyuan Town, Wanyuan City, Sichuan Province; Tongjiang County, Bazhong City, Sichuan Province; Jiangyou City, Sichuan Province
Polarized microscope resolution1280 × 960 pixels or 800 × 600 pixels
Data volume1.49 GB
Data format*.docx; *.xlsx
Data service systemhttp://dx.doi.org/10.11922/sciencedb.j00001.00021
Dataset compositionThis dataset consists of two parts, including a total of 1,082 polarizing micrographs of 330 rock samples from four geological sections and a sheet information table. The first part includes: 260 polarizing micrographs of 56 rock samples from the Huangdidong Section in Chengkou County, Chongqing (HDD); 158 polarizing micrographs of 66 rock samples from Jiuyuan Town Section in Wanyuan City, Sichuan Province (DST); 262 polarizing micrographs of 91 rock samples from Jiaoshutang Section in Tongjiang County, Bazhong City, Sichuan Province (JST); and 402 polarizing micrographs of 117 rock samples from Yudongzi Section in Jiangyou City, Sichuan Province (YDZ). The second part includes an Excel sheet (with a data volume of 53 KB) that records basic information and identification data for the rock samples.
1.   Introduction
The world’s largest biological extinction event occurred at the end of the Permian[1-2]. This was followed by the formation of the Early Triassic, which brought with it ocean acidification[3-4], strong fluctuations in the carbon cycle[5], stagnant oceans[6], the development of storms[7], aragonite seas[8], microbial outbreaks[9], oolitic factories[8], wrong time phases[7,10-11], and other special sedimentary environments and sedimentary records. The sediment structure and tectonics are the direct result of this special period.
The northwestern margin of the Upper Yangtze is an important area in the study of the mass extinction of organisms during the Late Permian. Carbonate platforms developed during this period[12-13], and many large gas fields have been discovered in the marginal areas of these platforms[14-15].
Previous researchers have carried out a substantial amount of geochemical and paleontological research on the cause of this mass extinction event, the biological recovery, and the environmental changes. However, there is a lack of basic geological research in this area, and the basic petrological data that is freely available either at home or abroad is very scarce. This research also needs strong support from thin section data under a polarized light microscope and other geological evidence.
It is within this context that this study has conducted a systematic observation, involving analysis under the microscope, of different platform areas of the Feixianguan Formation. This is more conducive to interpreting the characteristics and responses of the sedimentary environment in this special period. For this reason, four sections from different platform areas in the northwestern margin of the Upper Yangtze have been selected. Based on field system sampling and sample delivery, the platform, the platform margin and the pre-platform slope-basin area of ​​the Lower Triassic were carried out. The thin slices were identified under the microscope, and a carbonate microscopic image dataset was formed.
2.   Data collection and processing
2.1   Data collection
After researching the existing literature and undertaking a number of field surveys, four sections from different platform margins in the northwestern margin of the Upper Yangtze were selected: Huangdi Cave in Chengkou County, Chongqing (HDD); Jiuyuan Town, Wanyuan City, Sichuan Province (DST); Jiaoshutang, Tongjiang County, Bazhong, Sichuan Province (JST); and Yudongzi of Jiangyou City, Sichuan Province (YDZ). The locations of these sites are shown in Figure 1. A systematic sample collection was carried out, which included 56 rock samples from the HDD section, 66 from DST, 91 from JST, and 117 from YDZ section. Common thin section samples were sent as the field samples. The methods of photographing and collecting information from the thin slices were uniformly implemented in accordance with the “Rock Microscopic Image Topics” standards. This system collects rock microscopic images and obtains relevant information about the thin slices through systematic observation, analysis, and identification. The description of the thin slices and the naming of the sedimentary rocks were based on the standards determined by “Special Topics on Rock Microscopic Images”[16].


Figure 1   Location of the Feixianguan Formation field profile (modified from Xing Fengcun et al.[13])
2.2   Processing method
The sheet preparation was carried out using two-thirds of the coverslip, and to effectively distinguish between dolomite and calcite, the remaining one third was stained with Alizarin Red. Observation under the microscope was completed in the Sedimentary Geology Laboratory of the Institute of Sedimentary Geology at the Chengdu University of Technology. A Nikon LV100 P0L polarizing microscope was used, under test conditions of 25°C and 50% humidity.
3.   Sample description
This dataset is composed of two parts: the slice photo dataset and the slice identification report.
The specific stratum units and the rock slices contained in the four geological sections from which the rock slices were collected are shown in Table 1.
Table 1   Profile information of Feixianguan Formation in northwestern margin of Upper Yangtze
EraGroup nameSection codeSection nameNumber of slicesNumber of micrographs
Early TriassicFeixianguan FormationHDDSection of Huangdidong, Chengkou County, Chongqing56260
DSTSection of Jiuyuan Town, Wanyuan City, Sichuan Province66158
JSTSection of Jiaoshutang, Tongjiang County, Bazhong City, Sichuan Province91262
YDZSection of Yudongzi Section, Jiangyou City, Sichuan Province117402
The entire slice photo dataset consists of polarized light micrographs of 330 rock slices. For each rock slice there is one cross-polarized photomicrograph and one single-polarized photomicrograph from the same field of view. The color of the photomicrograph is consistent with the color observed with the naked eye using a polarizing microscope. The composition and identification in the microscopic image and the description in the report are the same.
Numbering principle: slice number + m + digital serial number of the camera field of view + “+ or –”. If multiple slices of the sheet numbered YDZ2-22-1 were taken, they have been marked as YDZ2-22-1m1–, YDZ2-22-1m1+; YDZ2-22-1m2–, YDZ2-22-1m2+, YDZ2-22-1m3–, YDZ2-22-1m3+; etc. The third-to-last m is the abbreviation of the micrograph, – is single polarization, and + is cross polarization (Figure 2).
Figure 2   Example of the microscopic image dataset
YDZ2-22-1m1– Bright crystal oolitic limestoneYDZ2-22-1m2– Bright crystal oolitic limestone
YDZ2-22-1m1+ Bright crystal oolitic limestoneYDZ2-22-1m2+ Bright crystal oolitic limestone
Magnification and scale position: the appropriate magnification was selected in relation to the size of the particles, in accordance with the principle that the image should clearly be recognized. The scale of the debris is placed in the lower right corner, with the units (in μm) shown by a red solid line on a white background.
The resolution of the photomicrographs are 1280 × 960 and 800 × 600 pixels, and the images were saved in PNG format.
The thin section appraisal report consists of a carbonate rock appraisal table, which contains micrite limestone, ultrafine crystalline limestone, oolitic limestone, and bioclastic ash in the four measurement sections mentioned above. Basic and lithological feature information, the classification and naming of rock slices, such as rock, internal clastic limestone, dolomite, dolomitic limestone, oolitic dolomite. The data description includes the rock name, the carbonate particle type, the structure, and the diagenesis and has been refined in various ways.
Table 2 is the header of the sheet identification report data. The slice information has been comprehensively analyzed and includes the serial number, the original number of the slice, the rock type, the rock name, its grain structure or residual grain structure, its recrystallized structure, and its fixed biological structure or residual biological structure, along with a supplementary description and sample information. Table 3 is a summary table of the rock types and the lithological information contained in the dataset.
Table 2   Data header of the flake identification report
Serial numberOriginal sheet numberRocksRocks (choose one of the two)Image numberParticle structure or residual particle structureRecrystallized structureFixed biological structure or residual biological structureSupplementary descriptionSample information
Carbonate particle typeType of interstitialInterstitial contentParticle support relationship>2mm
Particle support relationship
Grain sizeGrain structureGrain self-shape degreeMain sessile organism typesBiological structureBiological construction type
(Field observation)
Dunham
classification
Zeng Yunfu ClassificationParticle typeParticle contentTotal particle contentParticle sizeParticle sortingParticle preservation degree>2mm particle contentSpecial particlesCement fabricDeposition structureSedimentary structureDiagenesisotherPublication IDLocationsample/Profile latitudesample/Longitude of sectionGrouperaFlake owner
Table 3   Summary table of the rock types with their lithology information
RocksRock TypeQuantity
LimestoneMicrite limestone29
Microcrystalline limestone92
Microcrystalline ultrafine crystalline limestone14
Micrite-Fine limestone4
Micrite-Fine-medium limestone1
Very Fine crystalline limestone20
Very Fine-Fine limestone2
Fine crystalline limestone27
Oolitic limestone47
Bioclastic limestone17
Internal clastic limestone12
With Dolomitic limestone18
Dolomitic limestone12
DolomitesMicrocrystalline dolomite7
Very Fine crystal dolomite3
Micrite-very Fine dolomite1
Very Fine-Fine dolomite1
Oolitic dolomite6
Sandy dolomite1
Gray dolomite16
4.   Quality control and assessment
The thickness of the rock flake samples meets national and international standards. The photomicrographs are high-definition and contain no differences in color. Automatic exposure and automatic white balance were used in the process of microscope shooting to ensure consistency between the color in the system photos and the color observed by the naked eye. The two resolutions of the photomicrographs (1280 × 960 and 800 × 600) are due to the use of two different microscopes. The images have been saved in PNG format, which ensures the reliability of the quality and clarity of the photomicrographs. To meet industry standards, the identification under the microscope was based on the “Identification of Rock Thin Sections” SY/T5368-2000; the identification criteria used are shown in Table 4. To ensure the quality of the data, the data sheet information was checked and verified many times after the observation and identification of the slice.
Table 4   Appraisal basis classification standard table
TypesUse standardSupplement
Grain sizeZeng Yunfu[17](1986)Mud crystal, microcrystal, very fine crystal, fine crystal, medium crystal, coarse crystal, giant crystal
Grain structureFridedman[18](1965)Isogranular structure, porphyritic structure, embedded crystal structure
Grain self-shape degreeFridedman[18](1965)Self-form, semi-self-form, other form
Grain preservation degreeYu Suyu[19](1992)Self-shape, semi-self-shape, gravel-level other-shape, powder-level other-shape
SortingJerram[20](2001)Excellent sorting, good sorting, better sorting, sorting, etc., poor sorting
Biological structureZengYunfu[17](1986)Skeleton structure, barrier structure, bonding structure
5.   Value and significance
This dataset shows the microscopic features of different sedimentary facies from this special period, and it provides first-hand data for the long, slow biological recovery and reconstruction of the ecosystem in the Early Triassic.
Sedimentary facies is the material manifestation of the sedimentary environment, which includes all the characteristics (such as the petrological, geophysical, geochemical, and paleontological characteristics) of the sediments formed in the sedimentary environment. This dataset directly provides features such as petrology and paleontology that provide basic geological support in the recording and evolution of the Early Triassic sedimentary environment. It can also be used for further analysis of the E
arly Triassic microfacies and can provide reference information regarding the ecological environment of paleontological evolution.
6.   Usage notes
The data format of this dataset is straightforward, but attention should be paid to the following two points when using the data:
(1) All the slices that appear in the dataset are stored in the research group of Associate Professor Xing Fengcun of the Chengdu University of Technology. If the micrographs provided in the above dataset do not meet the requirements of further research, please contact the author of this article to apply for further use of these flakes.
(2) If you wish simply to use the image set, it can be download directly from the database; however, if you need to solve further scientific problems relating to geosciences, you will need to combine the geographic location provided in the data information table, as well as the geological age and structural background of the rock formation. Let’s start the analysis.
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Data citation
CHAI HB, XING FC, GU Q, et al. Carbonate micrograph dataset of Feixianguan Formation in northwestern margin of Upper Yangtze. Science Data Bank, 2020. (2020-05-09). DOI: 10.11922/sciencedb.j00001.00021.
Article and author information
How to cite this article
CHAI HB, XING FC, GU Q, et al. Carbonate micrograph dataset of Feixianguan Formation in northwestern margin of Upper Yangtze. China Science Data , 2020, 5(3). (2020-09-01). DOI: 10.11922/csdata.2020.0007.zh.
Chai Hanbing
Mainly responsible for the work: thin slice photo identification, paper writing.
from Nanchong City, Sichuan Province, master's degree, research field of sedimentology.
Xing Fengcun
Mainly responsible for work: field planning design, data set design, thesis guidance.
xingfengcun@163.com
from Jinzhou City, Liaoning Province, Ph.D., associate professor, research interests include sedimentology, petroleum reservoir geology, sequence stratigraphy, etc.
Gu Qiang
Mainly responsible for the work: thin slice photography, data sorting.
from Deyang City, Sichuan Province, master's degree, research field in sedimentology.
Chen Xiaoquan
Mainly responsible for work: field survey and sampling.
from Deyang City, Sichuan Province, PhD student, research field in sedimentology.
Zhou Shaopeng
Mainly responsible for work: field survey and sampling.
from Ziyang City, Sichuan Province, master's degree, research field of sedimentology.
Publication records
Published: Sept. 3, 2020 ( VersionsEN1
Released: March 23, 2020 ( VersionsZH3
Published: Sept. 3, 2020 ( VersionsZH5
References
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