**2. Type section**

In order to reveal the sedimentary characteristics and lithofacies paleogeographic evolution of quartz sandstone in the Member 1 of Suotoushan Formation in the study area, the author measured several sections,The type sections are listed as follows.



4. Gra-white thick bedded fine-grained quartz sandstone Light flesh-red, grayish white thick bedded medium-grained quartz sandstone, occasionally parallel bedded. The upper quartz sandstone is obliquely bedded. Gray argillaceous siltstone about 60cm in the lower part, graygreen mudstone 30–40cm in the middle, and purple red quartz sandstone 50cm thick in the top 48.2m 3. Gray-white thick bedded medium-fine grained quartz sandstone, with 15cm iron bearing fine grained quartz sandstone at the bottom. The upper medium-grained quartz sandstone reaches the industrial standard of silica ore 6.1m —————————————conformable contact—————————————— **Lower strata: Middle Devonian Qingmen Formation (D2***qm***)** 2. Gray-green thin bedded siltstone intermixed with dark gray shale, 3–6cm purplish red argillaceous siltstone at the top, and 1.2m dark gray argillaceous mass at the cross section 1.2m **(2) Measured stratigraphic profile of Yutoushan Formation of Middle Devonian (D2***st***) in Songlinpo, Yiliang County(P6)** Overlying strata: Hongyapo Formation of Middle Devonian (D2*hy*) 24. Purplish-red and gray-green silty mudstone interbedded with grey thin bedded quartz siltfine sandstone. The ratio of the two lithologies is about 1:1 9.77m —————————————conformable contact—————————————— **Member 3 of Suotoushan Formation(D2***st***<sup>3</sup> )** 23. Gray-white thin-medium grained quartz sandstone 1.26m 22. Gray, thin-medium quartz sandstone. The quartz sand layers are interspersed with graygreen and 1–8cm purplish red thin-layer siltstone. From bottom to top, quartz sandstone becomes thinner and siltstone thickens. In the middle and upper part, the ratio of quartz sandstone to gray-green and purple siltstone approaches 1:1 2.84m 21. Light gray thick bed to massive quartz sandstone 5.77m 20. The bottom is gray-white thin bedded fine-grained quartz sandstone(gravels at the bottom), the middle is gray-yellow thin bedded siltstone, the top is gray-green thin bedded mudstone 1.29m —————————————conformable contact—————————————— **Member 2 of Suotoushan Formation(D2***st***<sup>2</sup> )** 19. Gray white thin to medium grained fine-grained quartz sandstone interbedded with mud shale and very thin argillaceous siltstone 1.03m 18. Thick layers of gray-white massive fine grained quartz sandstone. 40cm thick gray-green silty mudstone in the middle and upper part, and it is separated from the next layer by 1–3cm thick gray-green silty mudstone at the top 24.63m 17. Light grey mudstone interbedded with grey white quartz siltstone 0.58m 16. Greyish medium grained quartz sandstone 2.02m 15. Thick gray-white massive fine and medium-grained quartz sandstone 20.73m 14. It is a set of siltstone, quartz sandstone, argillaceous siltstone and silty mudstone assemblage, which can be divided into five parts. The bottom is purplish red siltstone, the middle and lower part is gray white thin bedded quartz sandstone, the middle part is sandwiched with 50cm thick gray white thin bedded argillaceous siltstone, the middle and upper part is purple red thin bedded argillaceous siltstone, the top is gray green thin bedded argillaceous mudstone 5.37m —————————————conformable contact————————— ————— **Member 1 of Suotoushan Formation(D2***st***<sup>1</sup> )** 13. Thick layer of gray-white massive fine grained quartz sandstone 12.4m 12. Light grey thin – mesomorphic fine-grained quartz sandstone bounded by grey-green 5.72m

extremely thin mudstone at the bottom


*Sedimentary Characteristics of the Member 1 of the Middle Devonian Suotoushan Formation… DOI: http://dx.doi.org/10.5772/intechopen.103826*

From the above three representative measured sections, the boundary between top and bottom of Suotoushan Formation is clearly marked and the internal tripartite is extremely obvious, which can be compared regionally (**Figure 2**). The Member 1 of Suotoushan Formation is mainly composed of gray-white medium-thick bedded quartz sandstone with relatively few muddy interbeds, which is a concentrated production layer of high purity quartz sandstone. Many muddy interlayers in Member 2 of Suotoushan Formation, and the quartz sandstone is dark in color and mainly thin bedded, which is not the enrichment layer of high purity quartz sandstone. Although Member 3 of Suotoushan Formation contains more quartz sandstone, there are more mud interlayers, which is not the ideal formation for high purity quartz sandstone production. Therefore, only the sedimentary structure, tectonic characteristics and sedimentary environment of Member 1 of Suotoushan Formation are discussed detailedly in this paper.

## **3. Sediment structure**

Member 1 of Suotoushan Formation in the study area is mainly gray-white medium thick bedded quartz sandstone. Microscopic identification results show that the minerals are mainly medium-fine quartz, with a content of 99% the roundness is subedge, grain support, Moderate sorted, concave-line contact, and the cementation mode is press-inlay – pore type. Field profile shows the Member 1 of Suotoushan Formation is dominated by gray-white medium-thick bedded quartz sandstone with sheet sand body. Parallel bedding (**Figure 3a**) and wash bedding (**Figure 3b**) are extremely well developed. Straight ridge wave-forming marks (**Figure 3c**), small flowing wave marks and exfoliated lineation can be seen on the plane. Skolithos in the vertical plane can also be seen in the Luohanba section (**Figure 3e**). Sedimentological studies show [8, 9] that parallel bedding, wash bedding and wave-forming ripple marks are typical structures of the foreshore wash zone, while small flow ripple marks are products of wave backflow deposition. Therefore, it can be considered that the sedimentary environment of Member 1 of Suotoushan formation is the foreshore zone. The existence of Skolithos [10] also indicates that the sedimentary environment of Member 1 of Suotoushan Formation is dominated by the foreshore zone.

## **4. Grain size analysis**

The grain size distribution characteristics of sedimentary rocks can reflect the hydrodynamic conditions of sedimentation, and the results of grain size analysis are an important means to distinguish the sedimentary environment [11]. Sediment can be transported in three ways in normal traction flow: suspension, saltation, bottom passage or traction. Different sedimentary environments have different transport modes, among which the eolian dune sand and beach sand have narrow grain size interval, saltation is specially developed in general, while the passage is not developed in general and there is a lack of suspension. The biggest characteristic of beach sand is that there is a cut-off point inside the saltation whole, which represents the slight change of wave round-trip energy [11]. The quartz sandstone in the Member 1 of Suotoushan Formation is mostly medium and fine grained quartz sandstone

### **Figure 2.**

*Histogram correlation diagram for the Middle Devonian Suotoushan Formation in Northeastern Yunnan.*

(**Figure 3f**), with excellent sorting, grain support, voidaceous cementation, and void filled by secondary enlarged quartz (**Figure 3g**). Its mineral maturity and structural maturity are extremely high. In order to quantitatively reveal the grain size distribution characteristics of quartz sandstone in the Member 1 of Suotoushan Formation,

*Sedimentary Characteristics of the Member 1 of the Middle Devonian Suotoushan Formation… DOI: http://dx.doi.org/10.5772/intechopen.103826*

**Figure 3.** *Typical sedimentary texture and structure of the Member 1of the Suotoushan Formation.*



*Sedimentary Characteristics of the Member 1 of the Middle Devonian Suotoushan Formation… DOI: http://dx.doi.org/10.5772/intechopen.103826*

seven samples were randomly selected for grain size analysis in this paper (**Table 1**, **Figure 4a–c**).

The results showed that the samples were dominated by fine sand, followed by medium sand, containing a certain proportion of very fine sand, most of which did not contain coarse silt, only one sample detected coarse sand (Y170588006, 6.06per), completely missing gravel particles, silt and clay particles. The separation coefficient (S0) is between 0.78 and 0.92. Comparison sorting coefficient grading standard (Fine: 1–1.23; Good: 1.23–1.41; Medium: 1.41 to 1.74; Poor: 1.74–2.0; Bad: > 2.0) [11], and the

### **Figure 4.**

*Grain size analysis diagram of the quartz sandstone from the Member 1 of the Suotoushan Formation (diagram (d) is after reference [11]) (NPA-Normal probability accumulation).*

sorting degree of the analyzed samples was better than "very good" grade. Standard deviation (σ) can also describe the sorting degree, with most samples ranging from good (0.35–0.50) to excellent (< 0.35). The skewness (SK) values of the samples were 2 near symmetrical (0.10 +0.10), 3 positive skewness (+0.10 +0.30) and 2 polar positive skewness (+3 +1.0), and the grain size peak value was inclined to the fine end. It is generally believed that beach sand is mostly negatively skewed and dune sand is mostly positively skewed [11]. The characteristics of sample skewness of the Member 1 of Suotoushan Formation may be related to the dissolution and fining of quartz particles during diagenesis. Kurtosis mainly describes the convexity of grain size curve, so as to reflect the concentration degree of grain size, and is also an indicator of the degree of sediment sorting. The classification levels are: very wide (< 0.67 =, wide (0.67 0.90), narrow (1.11 1.50), very narrow (1.50 3.00), and very narrow (> 3.0) [11]. The kurtosis of the quartz sand in the Member 1 of Suotoushan Formation is very narrow and the grain size distribution is unusually concentrated, indicating that the quartz sand has undergone very sufficient sorting and transformation, thus laying the foundation of high purity quartz sandstone. Appears above a mountain group quartz sandstone grain size analysis results show that the majority of samples to a single modal nearly normal distribution, the lack of time overall, overall and suspended saltation overall content above 99per, and can distinguish two general, show wave flow and reflow sedimentary characteristics, and the ideal of foreshore with particle size distribution (**Figure 4d**). It should be noted that the internal intercept points of the saltation of quartz sandstone in the Member 1 of Suotoushan Formation are not clear, indicating that the sorting ability of quartz sandstone is close to eolian dune sand and superior to ordinary beach sand. This is also an obvious feature of quartz sand in the Member 1 of Suotoushan Formation, which is different from other quartz sandstone along the shore.


**Table 2.**

*Chemical analysis data of the Member 1 and Member 3 quartz sandstone of the Soutoushan Formation (%).*

*Sedimentary Characteristics of the Member 1 of the Middle Devonian Suotoushan Formation… DOI: http://dx.doi.org/10.5772/intechopen.103826*
