At the second meeting of the International Quaternary Federation (1932), it was proposed that the Quaternary period should be divided into four stages: early Pleistocene, middle Pleistocene, late Pleistocene and Holocene based on biostratigraphy. Among them, the early-middle Pleistocene boundary (Q2/Q 1) is divided into early Pleistocene fauna, in which the Pleistocene endemic genera account for the majority, while there are a few Neogene residual species and a few extant species. The Middle Pleistocene fauna includes a large number of Pleistocene endemic species, as well as a large number of existing species, and there may be a few tertiary residual species. According to this standard, the early-middle Pleistocene boundary is generally set at about 0.78Ma, 1973. Wenner-Graeme, chairman of the International Stratigraphic Committee, recommended the paleomagnetic distribution (B)/ Songshan (M) boundary as the early-middle Pleistocene boundary, and its time is also about 0.78Ma, which is basically consistent with the biostratigraphic boundary. The boundary between Middle Pleistocene and Late Pleistocene (Q3/Q2), the late Pleistocene fauna includes a large number of living species, only a few Pleistocene endemic species, and no Neogene remnant species. The stratigraphic boundary is about 0. 100 Ma.
1940, the Soviet branch of the International Quaternary Federation further compared this scheme with the ice age in the Alps (Table 2. 1).
Table 2. 1 Comparison between alpine glaciers and Quaternary biostratigraphic stages
(According to Xia 1997)
These two schemes are still popular today. In China, the former is mainly used for Quaternary division, but the ice age is not widely used as a scheme for Quaternary division.
Quaternary geologists in western Europe established a Quaternary staging model based on the periglacial sedimentary characteristics of northwest Europe and the existence of warm animals and plants during the interglacial period, combined with isotope and paleomagnetic dating, which is now widely used in northwest Europe (Table 2.2).
Table 2.2 Quaternary Staging Table of Northwest Europe
(According to Lin Jingxing 1984)
In recent years, with the in-depth study of oxygen isotope dating of loess, ice core and deep sea, the internal division of Quaternary Pleistocene has been further compared. Richmond thinks that the boundary between the 5th and 6th phases of deep-sea oxygen isotope and the last high sea level time in Bahamas and New Guinea is the boundary between the Middle Pleistocene and the Late Pleistocene, and the time is approximately 0.15 ~ 0.13ma; The lower limit of Late Pleistocene was placed at the beginning of the last interglacial period, and the time was about 0. 14 ~ 0. 13 Ma, which was consistent with the lower limit of the fifth stage of deep-sea oxygen isotope and the paleosol layer S 1 in the loess profile.
The loess-paleosol time scale is comparable to the paleoclimate change in the oxygen isotope stage of deep-sea sediments and polar ice cores, and has become one of the three pillars of global climate change research. The deep aeolian loess accumulated on the Loess Plateau in China can be classified into 33 layers of paleosol (S0-S32) and 33 layers of loess (L 1-L33) from top to bottom. L2-L 15 is the middle Pleistocene Lishi loess, S 15-L33 is the early Pleistocene Wucheng loess, and the Neogene clay is below it.
The noun (Noun's abbreviation) W.Rutter( 1992) has also clearly pointed out that the stratigraphic structure, magnetic susceptibility curve and grain size curve of China loess show that the paleoclimate evolution history recorded by China loess is closely related to global climate change, and the earth orbit change may be the driving mechanism of loess-paleosoil superposition, which provides sufficient basis for the establishment of the time scale of loess profile orbit order adjustment.
Liu Dongsheng et al. (2000), Ding Zhongli et al. (1994) and Liu Jiaqi et al. (2000), based on the fact that there are obvious Milankovic orbital periods in both loess strata and deep-sea oxygen isotope records, respectively, compared the sequence profile of Baoji loess-paleosol with the internationally recognized deep-sea oxygen isotope curve, and carried out the Quaternary stratigraphic correlation of China, a symbol of climate change. The age scale corresponding to the marine isotope stage (MIS) in the deep sea (hole DSDP607 and hole DSDP677) since 2.60Ma has been obtained (see Figure 2. 1).
At present, the Quaternary of the international stratigraphic table is usually divided into Pleistocene and Holocene. But the Pleistocene is divided into Calabrian period, Sicilian period and Lenient period, which is actually three points. China and many other countries have adopted a three-point plan:
2.3. 1. 1 Early Pleistocene (Nihewan period) (Qp 1)/ Middle Pleistocene (Zhoukoudian period) (Qp2) boundary.
The boundary between the early Pleistocene (QP 1) and the middle Pleistocene (Qp2) is usually drawn on the transition boundary between the forward period of Boujon and the reverse period of Songshan (B/M), and the time is 0.78Ma, which is equivalent to the order of magnitude of deep-sea oxygen isotope 19/20. The bottom boundary of L8 layer or S7 in loess section is just the bottom boundary of Zhoukoudian Formation and Nihewan section.
The boundary between the Early Pleistocene (Qp 1)/ Middle Pleistocene (Qp2) and the Quaternary bottom boundary (Qp 1) belongs to the Early Pleistocene (Qp 1), which has a long geological history (2.60~0.78Ma). At present, there is little research on how to further divide. It is suggested that the early Pleistocene (), the middle and early Pleistocene () and the late and early Pleistocene () can be divided by the paleomagnetism Jaramillo (time limit is 0.97Ma) and Oldo-vai (time limit is 1.87Ma).
2.3. 1.2 Middle Pleistocene (Zhoukoudian period) (Qp2)/ Late Pleistocene (Sarawusu period) (Qp3)
The boundary between the Middle Pleistocene (QP2) and the Late Pleistocene (Qp3) was drawn at the beginning of the last interglacial period, that is, 0. 128Ma, which is equivalent to the beginning of the deep-sea oxygen isotope stage 5e. Since then, the largest transgression has occurred in the world since the Quaternary. The loess stratum in China is bounded by S 1/L2, with Zhoukoudian Formation as the top boundary and Salawusu Formation as the bottom boundary.
2.3. 1.3 Late Pleistocene (Sarawusu period) (Qp3)/ Holocene (Qh) boundary
For many years, people have called this geological history the Holocene since 10000a. Since this period, the natural and biological world has been modernized, and the climate has been warming since the late ice age, ending the sudden cold event of young fairy wood. According to the newly published data, this event ended around 1 1050a, while W.Dansgaard and others measured it before 10700a. A Hubbard, according to the research results in Scotland, the new fairy tree event is about12900 ~11008.
The Holocene started after the New Fairy Tree Incident, and its age was about 1 1000. Emiliani defined 1 period as Holocene according to the oxygen isotope values of foraminifera crustaceans in deep sea cores. China is bounded by Holocene paleosol (S0) and late Pleistocene Malan loess (L 1), and loess accumulation is relatively common and stable, which is also the top boundary of the Salawusu Formation, and its time limit is generally 1 1000a. The bottom age of Holocene given by Qingfeng lacustrine sedimentary profile in Jianhu, Jiangsu Province is 14C, which is 10085a (without calendar age correction).
To sum up, China and many other countries believe that the boundary between late Pleistocene (QP3) and Holocene (Qh) is set at 1 1000a.