1. Thickness of sand body and limestone in benxi formation.
In this period, the thickness of sand body is very small, mostly less than 5 m, and generally speaking, the thickness in the central and northern parts is large, with continuous distribution and flaky sand. There are isolated island-like thick sand bodies in Ningwu-Xinzhou, Beijing-Huairou, Langfang-Cangzhou, Jinan-Laiwu and Dongying-Weifang. The sand layer in the south is small in thickness and mostly distributed on isolated islands. Generally speaking, benxi formation limestone is thick in the east and thin in the west. Except Linfen-Changzhi-Handan-Kaifeng-Pingdingshan in the southwest of the study area, most of them are distributed, and the cumulative thickness is generally 2 ~ 10m. Tianjin-Tanggu in the northeast and Tancheng-Linyi in the southeast are two sedimentary centers of limestone, with total thickness exceeding 30m and 50m respectively.
2. Thickness of sand body and limestone of Taiyuan Formation
Compared with benxi formation, the thickness of sand body in this period increased obviously, generally 10~30m ~ 30m, showing the characteristics of being thick in the northeast and thin in the southwest. In the vast area north of Changzhi-Heze-Xuzhou, the thickness of sand bodies is more than 20m, and they are distributed in a continuous sheet shape. The thickness of sand bodies in Xinglong-Langfang-Renqiu-Cangzhou-Tangshan in the northeast and Jinan-Zibo-Jining-Linyi in the southeast is more than 40m. In the southwest, sand bodies are mostly around 10 meter.
The limestone of Taiyuan Formation is widely distributed in the whole region, and the cumulative thickness is generally 5 ~ 30m. At this time, there are still two limestone sedimentary centers, among which the northeast sedimentary center is still in Bazhou-Tianjin-Tanggu area, but the scope and thickness have increased to more than 30m, which shows the inheritance and development of limestone sedimentary center in benxi formation. The sedimentary center in the southeast moved southward to Zhoukou-Huaibei-Huainan area, and its range and thickness also increased, reaching more than 50 m. Generally speaking, the limestone in this group is thick in the east and thin in the west, and the limestone in Pingshuo-Baoding-Cangzhou-Dongying area is thinner than 5m, which divides the limestone in Taiyuan Group into two major sedimentary areas: north and south.
3. Sand body thickness of Shanxi Formation
The sand bodies of this group are typical banded, and the thickness is generally 10~20m ~ 20m. Among them, there is a sandstone belt running through the north and south in the west, extending from Datong to Xinzhou-Yangquan area. Divided into four small branches extending southwest, south and southeast respectively; There is also a sandstone belt extending to the southeast in Beijing-Langfang-Tianjin in the east. In addition, sand bodies are also distributed in the northern uplift edges such as Pingquan and Chaoyang in the northeast.
During the decline period, the northern part of the sand body was banded, but the sedimentary boundary of the northern part of the sand body moved south, and Datong, Xinglong, Pingquan and Chaoyang in the north lacked sand body deposits. In most areas south of Changzhi-Handan-Jinan in south-central China, due to the enhancement of lateral continuity, sand bodies are mat-shaped. The sand body is usually 10~20m ~ 20m thick, and it is more than 60m thick in some areas such as Liaocheng, Xuzhou and Huaibei.
4. Thickness of sand body of lower stone box group
During the rising period of this group, the sand bodies are obviously banded, and most of them extend to the south or southeast. Generally, the thickness is 30 ~ 50m, and it is greater than 100 m in Chaoyang area of northeast China. The distribution position of banded sand bodies is basically consistent with the position of stratum thickness zone. One is a giant sandstone belt, which runs through the west from Datong to Yangquan, then forks and extends to Pingyao-Huozhou and Shijiazhuang-Linqing-Jinan respectively. The other two sandstone belts extend from Beijing to Tangshan and from Chaoyang to Jinzhou respectively.
The thickness of sand body is obviously reduced in the upper and lower stages, usually 10~30m ~ 30m. The distribution pattern of sand bodies is basically consistent with the rising period, except that the sandstone belt in Chaoyang-Jinzhou area stops moving during the rising period in the northeast.
5. Thickness of sand body of Upper Stone Box Group
The sand body of this group is as thick as its local layer, generally 100 ~ 200 m, and the thickness of Luohe-Zhumadian area in the southwest reaches 280m. The sand bodies of this group are widely distributed in the whole area, but there are still banded structures, and the distribution position of each sand body banded is basically the same as that of Xiashihezi Group.
The similarity of sand body distribution in different periods since Shanxi period reflects the obvious inheritance of late Paleozoic sedimentary paleogeography in the study area.