What are the types of strata?

The main types of Quaternary terrestrial strata are as follows.

(1) moraine layer

Concentrated in the western stratigraphic area, all of them are mountain glacier accumulation type. The moraine layers in Tianshan, Altai, West Kunlun, East Kunlun and Qilian are generally controlled by dating data. Most moraine layers from Himalaya, Minshan and Longmenshan to northwest Yunnan lack dating data, but the standard of geomorphology and stratigraphic relationship can be compared. Under mountain glaciers, there are glacial deposits or lake deposits infiltrated by glacial water, such as "Chengdu Clay" in the western margin of Sichuan Basin and "Yumen Formation" mud gravel layer in Hexi Corridor. The moraine in the eastern stratigraphic area is a controversial issue. Modern glaciologists believe that Li Siguang (1937, 1940, 1975) named Lushan moraine, Dagu moraine and Poyang moraine. Therefore, they still have the scientific significance of paleoclimatology and stratigraphic correlation. Their interlayer relationship with reticulated red soil can explain the influence of climate cycle during glacial and interglacial periods. The moraine in China started from the late Early Pleistocene to the late Late Pleistocene, which is roughly equivalent to the four major ice ages in Europe (Zhou Shangzhe, Li Jijun, Li Shijie, 199 1) and earlier "moraine" (such as Xigeda Formation in Xichang area).

(2) Loess and Gobi gravel layers

Loess is a aeolian sediment, and its provenance is the distribution area of Tarim, Hexi Corridor, Beishan, Alashan to Mongolia desert and Gobi gravel layer. Loess is mainly distributed in the Loess Plateau, but there are also a lot of loess and secondary loess in the strata of Northeast China, North China and even the middle and lower reaches of the Yangtze River, among which Mentougou area in Beijing was named Malan Loess in the Late Pleistocene. Quaternary loess is about 200 meters thick. Paleomagnetic dating data show that there are 2.5 ~ 1.2 horses in Wucheng loess, 1.20 ~ 0. 10 in Lishi loess and 0.10 ~ 0/0 in Malan loess, among which Lishi loess is. There is loess of Xia Shu Formation in the middle and lower reaches of the Yangtze River, which interacts with paleosol layer to form SO/L1—S14/L1/WL1—WS4/WL4 sequences, showing the climatic cycle synchronized with the deep-sea oxygen isotope sequence (Liu Dongsheng, 1999). Ding Zhongli, Liu Dongsheng,1989; Liu Dongsheng et al., 2000).

(3) the accumulation of grindstones

The accumulation of molasses is the material record of orogeny. The Western Regions in the northern margin of Kunlun Mountain and the northern and southern margins of Tianshan Mountain are typical representatives. Although it was first located in Dushanzi (Huang et al., 1947) in the southern margin of Junggar Basin, the most developed area is the southwestern margin of Tarim Basin, which consists of conglomerate with a thickness of several hundred meters to 3,000 meters. Kang Sulac conglomerate on the north side of West Kunlun Mountain and Yumen Formation in Hexi Corridor are synchronous strata, which contain Sanmenma, the first Quaternary fossil belt marker fossil in China. The bottom boundary of dating data is late Pliocene and the upper boundary is Sanmenxia. Gravel beds in this period were widely developed around the Qinghai-Tibet Plateau, such as Gongba Formation in the northern Himalayas, Qigequan Formation in Qaidam Basin, Dayi Formation in the western margin of Sichuan Basin and Xigeda Formation in Xichang area, but the thickness was several hundred meters, which was not the maximum thickness of Xiyu Formation in the northern margin of the plateau. The molasses accumulation in this period shows that the Qinghai-Tibet Plateau uplifted most violently at 1.20 ~ 1.50 Ma, which had a great influence on the middle and eastern strata, causing the Pliocene-Early Pleistocene strata to dip downward ("Sanmen Movement" was at the top of Sanmen Formation), the lacustrine Nihewan Formation in Nihewan Basin suddenly ended, and the strata in the late early Pleistocene and middle Pleistocene were missing. The late Pleistocene Xu Jiayao Formation was unconformity or pseudo-conformity overlying Nihewan Formation. This stratigraphic record shows that the modern geomorphic pattern of China, including the formation of large water system in the east-west direction, was laid before 1.20 ~ 1.50 Ma.

(4) Reticular laterite

This is a red soil layer with wormlike spots or stripes. It is generally believed that all red soils are weathering crusts formed in hot and humid climate (Xi Fancheng, 1965, 1982). Although this name originally refers to the red soil layer (Li Siguang, 1937) above the "Dagu moraine layer" in Lushan area, it is widely distributed in the stratigraphic division of South China and the middle and lower reaches of the Yangtze River, and its distribution area can reach Xichang area (Bingcaogang Formation) in the west. Typical development zones are in Jiangxi, Zhejiang and Guangxi. Jinxian Formation in southern Jiangxi (upper and lower parts), Zhijiang Formation in Zhejiang and Tangxi Formation can be regarded as reticulated red soil and reticulated red soil respectively. According to the latest paleomagnetic dating data (Xie Shucheng et al., 2003), it developed from the early middle Pleistocene to the early late Pleistocene (Xu Jiayao period), and its peak periods were 0.06 ~ 0. 14ma and 0.40~0.90ma respectively. The generalized red soil includes Pliocene "hippie red soil" and even Holocene "micro-developed" red soil. From Pliocene to early Quaternary, generalized red soil developed in the north, and then the red soil area moved to the south, among which reticulated red soil was the most characteristic (Huang Zhenguo, Zhang Weiqiang, Chen Junhong, 1999). Dating data provide the time frame of climate cycle of reticular laterite between Lushan moraine and Dagu moraine and reticular laterite between Dagu moraine and Poyang moraine, which are equivalent to glacial period and interglacial period respectively.

(5) Cave accumulation

It is widely developed in the central stratigraphic area and the eastern stratigraphic area (rarely studied in the western stratigraphic area). Cave sediments occupy a special position in the Quaternary in China. Many famous ancient human fossils and associated fauna are preserved in this kind of sediments, such as Homo erectus (Middle-Middle Pleistocene), Neanderthals and Neanderthals (Late Pleistocene) in Zhoukoudian, Beijing. Nanjing Homo erectus in Huludong, Nanjing (early Middle Pleistocene); The earliest hominid fossils in China were found in Wushan Cave, Sichuan, with a paleomagnetic age of 2.0 1 ~ 2.04 Ma. These cave deposits have generally gone through different glacial and interglacial stages, and the climate characteristics of strata containing human and animal fossils are also different. The fossil layer accumulated in Wushan Cave is a calcareous breccia layer, and the sporopollen shows that the climate is warm and humid. Homo erectus was born in the reddish brown clay layer, corresponding to the MIS 16 Ice Age or the Ganci Ice Age. Homo erectus was born in the breccia with gray layer, corresponding to the temperate interglacial period or M/Ganci interglacial period (Liu Jinling and Wang Weiming, 2003). The caves in the cave are accumulated in the loose limestone breccia layer, ranging from 14C to 18000 years, and the caves in the countryside are man-made for 25000 years, which undoubtedly experienced the last great ice age. However, there are southern molecules in mammals, which indicates that the interglacial mild climate of the Great Ice Age is also included. There are many caves in our country and there will be more new discoveries. One disadvantage of cave accumulation is that there are no continuous long sections, such as Zhoukoudian time zone and cave time zone, which need to be searched at the same time.

(6) Volcanic rocks

Quaternary volcanic rocks are mainly basalt, mainly distributed in Qinghai-Tibet, western Yunnan, Northeast China, Lei Qiong, Penghu and other places. There are basalts and andesites from late Pleistocene to Holocene in Qiangtang-Kunlun area in the northern Qinghai-Tibet Plateau, including alkaline and ultraalkaline deep mantle rocks. It is a mystery to be solved that such mantle rocks should be produced in the tensile environment under the background of the overall tectonic compression of the Qinghai-Tibet Plateau. Quaternary and Neogene basalts in northeast China constitute a unified eruption sequence, which is called plateau basalt, and its origin may be a huge East Asian mantle plume (Deng et al., 1996). However, the distribution area of Quaternary basalt has been obviously reduced, and the small volcanic eruption in Wudalianchi has created a series of bonsai craters, which is beneficial to viewing. According to research, there are three acts of Quaternary volcanic activity (Liu Jiaqi,1988; Liu Jiaqi and Liu Qiang, 2000). Tengchong volcanic rocks in western Yunnan contain many andesite and dacite components. Penghu basalt also constitutes a unified sequence with Neogene, which is characterized by more olivine basalt components. Basalt in Zhanjiang and Haikou interacts with pyroclastic rocks and other sedimentary layers, and there are systematic dating data.

(7) Other special sediments

The most famous is the glass meteorite (Leigongmo) layer from Leizhou to the South China Sea, and the Leigongmo layer of Beihai Formation with 0.6 ~ 0.7 Ma was also found in the deep-sea section of the South China Sea, which has become a meaningful marker layer and is of great value in the correlation of marine and continental strata. The earliest Leigong Mill was discovered in Guangxi by Zhang (1927), a pioneer of geology in China. The use of the name Lei Gongmo was related to astronomical factors at that time. Later, it was found in Guangdong, Hainan, Nanhai and Taiwan Province. Among them, the Leigongmo Formation in the middle Pleistocene in Lei Qiong has fission track dating data of 0.60~0.70ma and paleomagnetic data of 0.70ma, and in recent years, data of about 0.80ma or 0.83ma have been obtained in South China and South China Sea (Zhu Zhaoyu et al., 2001; , et al., 2000), in which the glass meteorite with drilling depth of 42.50m in OPP 1 143 in the South China Sea is the most accurate, and the meteorite age is 0.78ma (Wang, Tian Jun and Cheng Xinrong, 200 1). Considering that the oxygen isotope dating data of the underlying horizon is 0.75ma, the age of the meteorite horizon should be 0. In addition, the Zhaili Formation (or Yangliuqing Formation) in the middle Pleistocene in Hebei Plain contains four layers of micro-glass fused stone, and the dating data of thermoluminescence and uranium series method is 0.54±0.08ma (Li Dingrong et al., 1982), which indicates that the distribution area of glass meteorites may not be limited to the south, but the dating data is relatively new, and whether it is the product of different periods and different genesis or the dating error needs to be verified. In a word, about 0.60ma to 0.80ma is the formation period of China glass-ceramics meteorite, which crossed the boundary of 0.73ma in early and middle Pleistocene. Similar events have been found in Thailand, the Philippines, Australia, the eastern edge of Africa and Madagascar (Xu et al.,1983; Glass,1982; Schnetzler et al., 1993), and pointed out that "the original source crater of Asian-Australian micro-glass meteorite" is located in the Indian Ocean (Schnetzler et al.,1993; Wan Tianfeng et al., 1999). The meteorite impact at the triple junction of the Indian Ocean Ridge and the Red Sea caused the Indian plate to move northward, which promoted the dramatic uplift of the Qinghai-Tibet Plateau (Ge Xiaohong et al., 2004). At present, it is known that the single particle diameter of glass meteorites in this period is mostly less than 1mm, and those that reach or exceed 1mm are only found in the South China Sea and Hebei Plain. It should be that the distribution range has not been completely determined, and the horizon and period have yet to be analyzed. So whether the impact event is one or more phases, and whether the impact center is one or more, there is still room for research. Its stratigraphic correlation and regional tectonic significance deserve further study.

The ash layer of ancient human fire remains, the ash layer formed by natural fire and the deposition of carbon chips are all indicators of the dry-wet cycle of human culture and ancient climate.

(8) deposition of rivers and lakes

This is the most widely distributed type in Quaternary strata in China, and it is also one of the main objects to study the continuous stratigraphic section. Most of the stratigraphic areas in the west are deposited by rivers and lakes in interior drainage. Because there is no big river, the terrace profile is not developed, but lake sediments are widely developed, with the lake profiles in Qaidam Basin and Tarim Basin being the most continuous. An important type of lake deposits in western stratigraphic areas is gypsum-salt deposits, which contain important mineral and biological resources. Therefore, detailed stratigraphic division and dating data are important basis for stratigraphic division and correlation (Zheng Jin equation,1989; Wang You Li et al, 200 1). Abundant potash deposits were found in the Daer Formation of Lop Nur from late Pleistocene to Holocene, which contained a single species of foraminifera, which seems to indicate that there are residual wandering basins in Tarim Basin since Neogene. The fluvial facies and lacustrine facies deposits in the central and eastern stratigraphic areas are the focus of Quaternary stratigraphic research. Most of them are located in the sedimentary area of outflow water system, and river terraces are developed. The stratotype of the six time zones from Gongwangling to Sarawusu is terrace profile, and the red soil profiles in the middle and lower reaches of the Yangtze River and South China are mostly terraces. Most of these terrace profiles were formed in the late Early Pleistocene (1.20 ~ 1.50). Early Pleistocene lacustrine strata in central and eastern China are famous at home and abroad for their important cultural remains, ancient human fossils and abundant mammalian fossils, such as Nihewan fauna of Nihewan Formation in North China, where Xiaochangliang site, Mid-Levels site and "new culture layer" have been found. There are famous Yuanmou fossils in Yuanmou Formation of Yunnan. In addition, the lacustrine deposits (Sanmen Formation and Nihewan Formation) in the Wei Fen Basin and Sanggan River graben belt produced the marine fossil belt Evolutononion shanxiense (foraminifera) -sinocyprida impressa (Ostracoda), which caused a heated discussion on land-sea interaction. These Hu Guang facies strata stopped suddenly in the late Early Pleistocene, especially in the period of 1.20 ~ 1.50 Ma, and were covered by late unconformity or pseudo-conformity fluvial facies strata (Zhang Zonghu, 199 1), reflecting an important paleogeographic event (Sanmen Movement). In North China (Beijing Plain and Hebei Plain), there is a set of very special early Pleistocene fluvial-lacustrine strata (Xiadian Formation or Gu 'an Formation), which are extremely thick fleshy red argillaceous cemented gravels and gravel layers, interacting with "chicken manure" or rusty red clay layers and sand layers, showing a "strongly weathered" appearance, but containing several Guang Hai-style and shallow-water marine interlayers. This stratum is not only like the molasse of Xiyu Formation in the west, but also like Nihewan Formation in Yanqing, the eastern end of Sanggan Graben. Is the red-yellow mottled clay in it somewhat similar to the red soil in the south? Whether it is the product of the peak season of southeast monsoon needs to be studied.

2. Marine and land-sea alternating strata

The main types of Quaternary marine and land-sea alternating strata are as follows.

(1) Deep-sea argillaceous deposits

With the completion of hole ODP 1 143 in the South China Sea, the Quaternary sedimentary sequence with a thickness of about 100 m and its oxygen isotope stages, biological and abiotic marker layers have been clarified. In the range of 2.0 ~ 0. 12ma, eight marker layers are divided (Wang et al., 2000; , Jianzhilou, 200 1) and MIS 1-85 climate period (Wang, Tian Jun, Cheng Xinrong, 2001; Zhao et al; Jane et al., 200 1), set a close comparison standard for China. In addition, a biomarker layer of 0. 12ma was obtained in the deep sea area of Okinawa Trough in the East China Sea (Cang Shu Crick et al.,1989; Wang Naiwen, Xu, 2003).

(2) Sediment deposition in shallow sea and land-sea interaction.

Widely distributed in the continental shelf area and coastal plains and deltas in the eastern seas. The QC2 hole 1 10m formation (Yingdeng, 1989) in the South Yellow Sea contains several sand-mud sedimentary cycles and 12 sedimentary assemblages. The real shallow sea deposits are only the surface since the end of Holocene, and the following are the land-sea interactive deposits of coastal, coastal, lake and even river facies. The paleomagnetism and isotopic stages of the hole are detailed, and the lower, middle and upper Pleistocene and Holocene groups are clearly divided, which can be compared with the QC 1 hole, QC4 hole and QC5 hole in Nantong-Lianyungang area. At the bottom of the hole before 1.80ma, there are tropical and subtropical foraminifera Asterorotalia, and all the above layers are cold temperate or wide temperate genera and species. The Quaternary of the East China Sea Shelf is called the East China Sea Group, with a thickness of about 350m, which is deposited by sand and mud, but it has not been carefully divided.

Hebei plain is dominated by terrestrial facies, with multiple marine interlayers. In the early Holocene, there was a warm-temperate foraminifera pseudocharophyta. The Lower Liaohe Plain is similar to the Hebei Plain. Before 1.8ma, there were warm-water species of ammonia snails in the Yangtze River Delta and Shanghai, and there were warm-water species of Pseudocharophyta in the late Pleistocene or early Holocene. Other cold-temperate and wide-temperate genera and species have synchronous bioclimatic cycles with Hebei Plain.

(3) Debris deposition in tropical Guang Hai.

Sand shale (Zuolan Formation) from early Pleistocene to early middle Pleistocene and glutenite with lenticular reef limestone in late middle Pleistocene in western and southern Taiwan Province Province (

The Jishan Formation is several thousand meters thick, and the super-thick conglomerate in the upper part ends the history of Guang Hai facies deposition in Taiwan Province Province, marking an important tectonic movement of the island uplift in Taiwan Province Province. This Middle Pleistocene movement obviously lagged behind the intense uplift of the Qinghai-Tibet Plateau for about 500,000 years. Whether this is the lag effect of the latter or the regional movement of the South China Sea remains to be proved.

(4) Tropical reefs and bioclastic limestone.

From Miocene to Holocene, the Xisha Islands were dominated by reef limestone, but the sedimentary thickness gradually became thinner. The thickness of limestone in early Pleistocene is 150m, 70m and 40m in middle Pleistocene and late Pleistocene respectively, and only 10m m in Holocene. There are reef limestone in the coastal area of Taiwan Province Province from late middle Pleistocene to Holocene, and the thickness is not large.