Through the research of the research group (Deng Tao et al. ), the main progress and achievements are as follows: (1) Preliminary screening of candidate stratotype profiles in Shanwang period; Collected and accumulated rich and varied paleontological fossil data of Shanwang period; Isotopic chronostratigraphy and magnetostratigraphy were studied, and reference data were obtained. The definition of the bottom boundary of Shanwang stage and the regional comparison of the stage are discussed.
(1) Location of candidate stratotype profile in Shanwang period
Shanwangjie candidate stratotype profile is located in Xiejiahe Village, Yaoshan Township, Shanglin Town, Linqu County, Shandong Province, about 20 kilometers east of Linqu County. The specific locations of the profile are Jiaoyanshan and Laomuqiangou in the south of Shanwang Basin, and the geographical coordinates of the southern starting point of the profile are 36 32 ′ 36 ″ north latitude and118 43 ′ east longitude.
Figure 1 13 Geographical Location Map of Shanwang Basin
Figure 1 14 Location Map of Candidate Strata Profile in Shanwang Period
(2) profile description of candidate stratotypes in Shanwang period
Shanwang basin belongs to a small basin in the hilly area of central Shandong, with uneven basement, so the sediment distribution is uneven and discontinuous. In addition, during the Shanwang period, magmatic activities were frequent, and the later eluvial soil was quite covered, so it was difficult to find a complete and continuous stratigraphic section in the basin. The selected candidate stratotype profile strata are well developed.
Overlying strata Yaoshan Formation
The bottom is grayish yellow and grayish brown basaltic glutenite with loose structure and easy weathering.
Progress and Achievements of Major Dating Strata Research Projects in China (200 1 ~ 2009)
Progress and Achievements of Major Dating Strata Research Projects in China (200 1 ~ 2009)
Niu Shan Formation of Underlying Stratum
1. Blue-gray spotted olivine basalt with columnar joints developed and red weathering crust at the top.
(3) Biological assemblage in Shanwang period
Based on the research of this topic and the data of predecessors, it is revealed that all kinds of organisms are extremely rich and prosperous in the Shanwang stage, mainly including mammals and other vertebrates, paleontology, insects, ancient plants, sporopollen and diatoms.
1. Mammals
Mammals are the most epoch-making category in Shanwang period and play an important role in stratigraphic division and correlation. The evolution characteristics of mammals in Shanwang period are as follows: most families developed in Oligocene have disappeared or almost disappeared; Some new families or subfamilies have appeared, such as butterfly subfamily, bear subfamily, giraffe subfamily, lizard subfamily and so on. During the flourishing period, a large number of new genera appeared, such as Megalodon, Megalodon, Heteroodon, Hemiodon, Hymenoptera, Amphibia and Swine. In the prosperous period, mammals entered a brand-new evolutionary period: rodents really began to be dominated by squirrels and rodents, carnivores were completely replaced by new carnivores, long-nosed animals began to appear, while Chiroptera declined, and ancient strange hoofed animals became extinct. Among rhinoceros, ungulates and equines, only the newly emerging genus Anqima is still common, and ruminants are obviously differentiated. Up to now, the mammal genera and species found and recorded in Shanwang period mainly include Shanwang bat (Chiroptera), Shanwang long-eared bat (rodent) and plesiosaur. China people. Canna in Asia, Diatoms in Shandong, Rodents in Carnivora, Cynoglossus semilaevis in Yang, and Oriental Water Bear. (Pottery-Equisetinae Genus and Species), Gomphotherium sp., Long-nosed, Odd-hoofed Xiejiahe Ancient Tapirs. , Dianthus shanwangensis, Dianthus gracilis, Dianthus bicolor. Bijuu in Shanwang, bijuu in Linquan, China, pettitoes in Shanwang, bijuu in Pan, etc.
2. Paleovertebrate Zoology
There are abundant vertebrate fossils at the peak of mountain, such as juvenile plovers, mountain plovers and great apes. Diatoms China river duck (Sinanas di-atomas) and Qilu bird (Qiluornis taishanensis); Mionatrix diatom, crocodile, a reptile diatom; Amphibians, such as rock carp, wood frog, linqu toad and big webbed bell toad; The fish are linqu, Scottish shad, exotic flat carp and Shanwang shad. Macrobrachium giganteum, Macrobrachium giganteum, Sparus nobilis, Sparus glabratus, Shandong bighead carp, long-breasted cobra, Shandong Siniperca, etc.
3. Insects
The diatomaceous earth layer in Shanwang period contains extremely rich insect fossils, which is rare in the world. Up to now, * * 272 species have been found, belonging to 12 orders, 74 families and 162 genera, of which 49 genera are extinct. In this huge insect fauna, the percentage of the main group is COLEOPTERA 36. 0%, Hymenoptera 33. 8%, Diptera 1 1. 8%, Heteroptera 7. 4%, Odonata 2. 9%, HOMOPTERA 2. 6% and dermatophytes 66.
4. Ancient plants
During the flourishing period, the fossils of ancient plants were also extremely rich. Up to now, 104 genera and 155 species have been found in 50 families. Mainly some temperate plants, including betulaceae, Aceraceae, Rosaceae, Ulmaceae, Juglandaceae, Tiliaceae, Salicaceae and Beech. At the same time, some subtropical evergreen or deciduous broad-leaved plants have also appeared. Such as camphor tree, banyan tree, witch hazel, Liquidambar formosana, Carya cathayensis, Lauraceae, Stachyceae, Sterculiaceae, Rutaceae, Meliaceae, Vitaceae, Sapindaceae, Araliaceae, etc. About 75% species of Shanwang flora can be found in today's living flora; From the subordinate level, 90% of the genera continue to this day.
5. Sporopollen
There are also abundant sporopollen fossils in Shanwang period, and the assemblage is mainly angiosperm pollen, accounting for about 80% of the assemblage. Followed by gymnosperm pollen; The spore content of ferns is sporadic. The combination mainly includes Pinaceae, Fagaceae, betulaceae, Juglandaceae, Ulmaceae, Hamamelidaceae, etc. The important genera are Pinus, Picea, Hemlock, Quercus, Cy-Cy-clobalanopsis, Quercus, Alnus, Betula and Populus. Carya cathayensis, Juglans mandshurica, Pterocarya stenoptera, Ulmus pumila, Zelkova schneideriana, Pterocarya stenoptera and a few Castanopsis plants; In addition, there are some types whose genetic relationship is unknown; In the combination, the pollen content of herbs is low, and only a few molecules of Chenopodiaceae, Gramineae and Polygonaceae are found. The appearance of Shanwang sporopollen assemblage is similar to that of Lengshuigou Formation in Weihe Basin, Shaanxi Province, upper Guantao Formation in Bohai Sea, Huanghai Formation in South Yellow Sea Basin and lower Yancheng Formation in Subei Basin, and the age is from late early Miocene to early middle Miocene.
diatom
There are abundant diatom fossils in Shanwang period, with nearly 100 species and varieties belonging to 18 genus. Similar diatom flora has also been found in Dunhua, Jilin, Shangdu, Huade, Inner Mongolia and Xundian, Yunnan. Compared with the diatoms in North America, Europe and Russia, the age of Shanwang diatom group should belong to Miocene.
(4) isotopic age of Shanwang period
In 1985, the samples of Cenozoic volcanic rocks and Shanwang basin in the middle section of the Tanlu fault were K-Ar isotopic dated by Jin, and it was considered that diatomite rich in fossils in the basin was formed between18.85 ~14.11Ma. This age data is consistent with the age of fossils. Chen Daogong and Peng Zicheng (1985) not only reported the age data of Niu Shan basalt in Linqu, which is consistent with that of gold, but also determined the age of Jiaoyanshan basalt as (18.05 0.55) Ma. The samples of this era were collected under the diatomaceous earth layer of Shanwang Formation, which are rich in fossils and should be close to the bottom of Shanwang Formation or the top of Niu Shan Formation.
(5) Definition of the bottom boundary of Shanwang Stage
According to the comparison of mammals, the Shanwang period in China is equivalent to the Orleans period in Europe, which includes three animal stages (MN3 ~ 5). The lower limit of MN3 in the lowest stage is marked by the first appearance of Anchitherium or euclicket-Odon hamster. It seems that the bottom line of the flourishing period in China should also be marked by the first appearance of these two mammals. But so far, it has not been found in China. Therefore, the bottom boundary of Shanwang stage is still difficult to determine at present. For the Shanwang period, it can be identified according to the biological combination of the characteristics in the above period.
(VI) Regional comparison during the flourishing period of mountain.
According to the comparison, the Shanwang period is roughly equivalent to the Bourdi Garian period in the international stratigraphic table. In China, the lithostratigraphic units in the same period are: Shanwang Formation in Linqu area, Shandong Province; Chetougou Formation in Xining and Huangzhong areas of Qinghai, Xiacaowan Formation and Dongxuanguan Formation in Jiangsu and Anhui areas, etc.