Regional tectonic characteristics of Mesozoic-Cenozoic sedimentary basins in Henan and its adjacent areas

The study area is located between N30°~ 38° and E 108 ~ 120, with a total area of about 1 100,000 km2, including 40 MSS images (table1), of which about 70% is covered by Quaternary period. It is a preliminary attempt to comprehensively study Mesozoic and Cenozoic oil-bearing sedimentary basins covered by large-scale remote sensing images, and there is no mature experience and ready-made methods at home and abroad to learn from, which is very difficult. However, by giving full play to the macro and real characteristics of remote sensing images, we can get a lot of useful indirect geological information by analyzing the micro-geomorphic landscape, the distribution pattern of water system and the distribution law of vegetation, as well as the different reflectivity of underground geological structures reflected in the surface spectrum due to related factors. These indirect geological information, through the comprehensive analysis and verification of drilling geological and geophysical data and various related characteristics in the peripheral outcrop area, can become important evidence to understand the underground geological law.

Table 1 index table of MSS satellite movies in the study area

I. Overview of regional geological background

The main body of the study area is located in the south of North China Plain, which belongs to the middle of the second subsidence zone of the giant Neocathaysian tectonic system in eastern China and the southern margin of North China block. Southwest Shandong uplift in the northeast, Taihang Mountain and Dabie Mountain uplift in the northwest, southwest and south (Figure 1).

In the early Caledonian cycle, the North China block was relatively stable, and a set of sedimentary formations dominated by platform carbonate rocks developed. From the end of the cycle to the beginning of the Hercynian tectonic cycle, the block rose and suffered long-term erosion. In the middle and late Hercynian tectonic cycle, it sank again and deposited a set of marine and continental sandstone and mudstone strata, which was also the main coal-forming period in North China. At the end of Permian and the beginning of Triassic, Indosinian movement spread to this area, forming a series of wide and gentle folds near east-west, further uplifting the crust, and gradually turning into a brand-new tectonic development period with fault block activity as the main form, which is the geological background for the formation and development of Mesozoic and Cenozoic sedimentary basins in this area.

Figure 1 Distribution Map of Structural System in Henan and Its Adjacent Areas

Second, the image characteristics and its preliminary geological analysis

(a) The macroscopic characteristics of the image and the corresponding geological and geophysical background.

It can be seen from the overview map of China/KLOC-0: 6 million black-and-white images that the study area is a giant ring with gray and light gray tones, and its long axis is northeast or nearly north-south, partially extending to the Bohai Sea (Figure 2). Macroscopically, it has a unified feature, and the gray level tends to become lighter from west to east. On the 1:500000 MSS color mosaic, it is light green to light red. On the gray background above, it shows the structural characteristics of a huge hidden point mixed with a northwest belt image. They are intertwined to form a complex pattern with rich colors. Seen from the Moho depth profile, this area is just on the third step rising from west to east (Figure 3), with an average depth of about 35km. From the contour map of crustal depth, there are secondary ups and downs traps with NW strike (Figure 4). No matter from the whole or its internal structure, it has similar characteristics with the image structure of this area. Judging from the gravity field, the gravity field in the area is NNE or nearly NNE, and its value rises from west to east, that is, Xinye and Nanyang are -60 mg, and Biyang and Changyuan are -50 mg. Puyang-40mg, Yongcheng-30mg, Lianyungang in the east-10/0mg. This is related to the uplift of Moho from west to east. Therefore, the image not only shows all kinds of information on the ground, but also shows geological information from the deep crust.

Fig. 2 Schematic diagram of macro-structure interpretation of satellite photos in Henan and its adjacent areas.

Figure 3 Lanzhou-Dalian Moho section

Equivalent map of crustal thickness in eastern China.

(2) Interpretation and analysis of linear images

Interpretation and statistical characteristics of 1. linear images

Linear images (linear features and linear trajectories) are the most easily captured schlieren structural features in image analysis and interpretation. The following discussion mainly focuses on image features that extend over 50km.

Interpretation marks of linear images in Quaternary coverage area (1), which mainly include: ① the boundaries of different regional tones (or grayscales). Such as the Lanliao fault, which consists of dark colors on the east side and bright colors on the west side; (2) The boundary of different shadow structures. For example, the south side of Suxian-Shangqiu fault is composed of a dark coarse variegated texture and the north side is composed of a light fine variegated texture; (3) The boundary between different shadow structures and different regional tones. For example, the north side of Nanzhao-Liyang fault is dendritic shadow structure, and the south side is gray plane tone; ④ Linear boundary of linear water system or large water body. For example, the Hongze Lake-Taiqian fault zone, a dark belt image composed of Hongze Lake, Roman Lake, Weishan Lake and Dongping Lake, spread to the northwest, and so on.

Fig. 5 Interpretation map of remote sensing geological structure in Henan and its adjacent areas

1-main linear structure (obvious image features); 2- second-order linear structure (obvious image features); 3- General linear structure (image features are hidden); 4- strip structure; 5- Barrier graben structure; 6-ring structure reflected by dark image; 7— Ring structure reflected by light-colored images; 8— Ring structure of speckle shadow reflection; 9- Lake; 10- River

According to the above signs, the linear images in the area are comprehensively analyzed and interpreted. A total of 76 linear images/kloc-0 were interpreted, including 27 obvious images, 8 obvious images/kloc-0, and 68 hidden images. In addition, the band or broadband images with obvious macro performance but unclear specific boundaries are also preliminarily interpreted (Figure 5).

(2) Statistically, taking 10 as the swing interval, the extension directions of the above linear images are divided into 18 groups. Among them, 60 ~ 69, 320 ~ 329 and 330 ~ 339 are the highest, which are 28, 18 and 16 respectively (Figure 6). The results are highly similar to the relative values of fault statistics provided by seismic exploration and peripheral ground investigation in this area over the years.

Fig. 6 (a) Rose diagram of linear image trend of satellite images in Henan and its adjacent areas (b) Rose diagram of plane trend of ground fault structure in western Henan.

2. The relationship between linear image and structural plane

The seismic and gravity and magnetic data of outcrop area and overburden area show that the linear images reflected by remote sensing images of different scales in this area are mostly the reflection of faults, fault zones or geological structural plane elements below the surface and overburden. The surface nature is a vivid record of these factors, and the coverage area is an indirect result reflected by factors such as surface micro-landform, water system, humidity, soil and vegetation. Although the genetic mechanism of some problems has not been fully revealed, it is a certain feature in the form of physical fields (thermal field, gravity field, magnetic field and stress field, etc.). ) and geochemical field (alteration, mineralization, groundwater alternating zone, etc. Therefore, it is reasonable to regard linear images as structural plane elements, weak zones and fault zones with a certain depth on the surface or underground.

3. Preliminary matching between the surface features of structural plane and linear structure.

The field investigation of the surface characteristics of (1) discontinuities in western and southwestern Henan shows that the orientation and probability of linear images are very similar to the statistical results of fractured discontinuities in outcrop areas. This is true for regional comparison, and so is the corresponding regional comparison. This is obviously an objective response to the internal laws.

Structural plane or fracture structural plane refers to the discontinuous interface in the geological tectonic stress field, which is the superimposed record of the stress field in the crust, and its scale and nature depend on the size and characteristics of the stress field. In the field investigation, several groups of fracture structural plane data of 1 10 were collected. Among them, about 30 groups have uncertain properties, stretching group 1 1, compression group 3 1, and the rest are torsion or compression. In more than 80 groups of data whose properties have been determined, extensiveness accounts for about 14%, compressibility accounts for about 39%, and torsion or compression-torsion accounts for about 47%.

(2) The preliminary matching of linear structures is as described above. Linear image is the reflection of geological structural plane at a certain depth on the surface or underground, and structural plane is the structural product in a specific stress field. It is natural to explore the process from the results and even reshape the characteristics of the tectonic stress field, which will be discussed below. The regional investigation report of Nanyang and Xuchang shows that the compressive stress in the north-south direction is the earliest controlling factor for the formation of the structure in this area. It originated in the Lvliang period, but it still appeared in the Caledonian period. During the field investigation in the southern margin of Taihang Mountain in Jiyuan area, northwest Henan Province, the author collected that there was an obvious east-west knee fold in front of Taihang Mountain, which was composed of Sinian, Cambrian and Triassic, and the southern wing was accompanied by a huge northward dip reverse fault (occurrence 7 ∠ 60), which extended from east to west 10 km, with serious mineralization and local granodiorite veins interspersed among it. Judging from the gentle north wing and steep south wing of the knee fold and its relationship with the northward dip reverse fault (Figure 7), it is undoubtedly the result of Taihang Mountain pushing southward. Judging from the strata involved in the fold, it was caused by Indosinian period or subsequent movement. Therefore, there are naturally two groups of conjugate shear structural planes, NE30 and NW330.

Fig. 7 Schematic diagram of deconvolution of Bayi Reservoir in Zi Ling, Jiyuan.

If the above structural features are combined with two wide and slow negative structures, Kaifeng and Xinyang, which are distributed in the east-west direction in this area, a complete north-south compressive stress pattern can be obtained in this area since Mesozoic.

In the late stage of the above process, that is, in the early and middle period of Yanshan tectonic cycle, the eastern part of Chinese mainland was influenced by the anticlockwise twisting of the Chinese mainland and the Pacific basement in the north-south direction, forming a huge "polygonal" structural system, that is, the Neocathaysian structure. It strongly controlled the formation of Mesozoic sedimentary basins in this area, such as Dongpu sag. Because Dongpu sag is controlled by Lanliao fault on its east side, Lanliao fault, like Tanlu fault in the east and Zijingguan fault in the west, is one of the main structural elements of New China. It also matches the torsional, compressive, tensile and counterclockwise structural surfaces of NE50, NW 330 ~ 340 and NW 290 ~ 300. Under the action of these structural planes, the North China block has formed rhombic blocks with different sizes. Later, the obvious east-west compressive stress field and corresponding structural plane were formed in this area. For example, a wide and gentle Lu Yi-Xincai negative structural belt extending in the north-south direction, a pair of conjugate shear structural planes of Ne 50 ~ 60, NW 300 ~ 365, 438+00, and a nearly east-west tracing fault. These faults make the fault blocks divided by the previous structures extend in the north-south direction, thus further deepening and expanding the Mesozoic sedimentary basin. During the Cenozoic Himalayan movement, the NE-SW compressive stress reappeared, forming NW-trending nose structures, some NW-trending fold structures and tracking faults around NE45 in the basin. A typical example controlled by it is the old Yellow River in Lankao-Dongping County (see Figure 6 on page 36). The fault structure has remained active until modern times (after 1855).

Therefore, the criss-crossing linear structures in this area, in addition to the pre-Paleozoic structural relics, also overlap the Mesozoic and Cenozoic multi-stage structural elements (see Figure 9).

(3) Interpretation and analysis of ring structure

The main interpretation marks of 1. ring (circle) image

(1) The abnormal tone of deep and dark is characterized by the abnormal tone of dark ring or circle on the light background, such as the abnormal tone of circle between Xunxian and Neihuang. Abnormal bright ring or round tone on dark background, such as abnormal bright tone in Nanyang.

(2) The abnormal display of schlieren structure is the abnormal display of another schlieren structure under the background of one schlieren structure. For example, the coarse variegated circular shadow structure between Zhengzhou and Pueraria lobata (the background is the fine variegated shadow structure).

(3) Circular or annular anomalies caused by water circulation or meandering, such as light-colored circular images in Lankao area (Figure 4 on page 35).

2. Geophysical field analysis of ring (circle) image.

According to the above interpretation marks, 133 annular images were preliminarily interpreted in the whole region (see Figure 5). Among them, there are 54 light-colored ring images and 6 variegated ring images. Like linear structures, these annular images are indirect reflections of geological structures or geophysical fields on remote sensing images. For example, the circular image of Zhengzhou-Changge mentioned above, which is composed of rough and mottled shadow structure, is caused by the dense broad-leaved paulownia forest on the ground, and the distribution of different vegetation is obviously restricted by geology, water quality and soil conditions. Another example is the annular image between Tanghe and Biyang, which is completely consistent with the position and shape of the -40 milligal gravity trap line and basically consistent with Biyang Basin. Through the superposition of gravity data and image interpretation map, it is found that 28 of the 82 rings (circles) covered by gravity data are consistent with gravity anomaly traps, with a coincidence rate of 34%. Superimposed with regional aeromagnetic data, it also has a high coincidence rate. These phenomena show that the ring image has a certain corresponding relationship with geophysical field and underground geological structure. In northern Henan, bright circular images are mostly consistent with low gravity. These bright circular images are generally modern depressions, and most of them are filled with Quaternary sediments with high reflectivity. Therefore, a bright ring (circle) shape is formed on the remote sensing image. And this low pressure coincides with low gravity. This reflects the ups and downs of landforms from different angles, and satisfactorily explains why the basins delineated by gravity data can be clearly reflected in satellite photos.

Thirdly, the relationship between linear structure and Mesozoic and Cenozoic sedimentary basins.

Distribution characteristics of Mesozoic and Cenozoic sedimentary basins in (1)

The spatial distribution of sedimentary basins in this area is regular.

1. The change of basin azimuth arrangement

If the N32 and N34 second lines (namely Xiangfan-Xinyang-Hefei North, Luonan-Xuchang-Yongcheng) are taken as boundaries, the whole area can be divided into three areas: north, middle and south. Weihe Graben, Sanmenxia Basin, Xiangcheng Basin, Lushi Basin, Luoyang Basin and Yichuan Basin. The northern zone has been transformed from west to east into the east-west Luoyang Basin (the main part) and Zhongmu Depression. Then it evolved into northeast Tangyin Graben, Dongpu Depression, Chengwu Depression (main body) and Jining Fault Depression. There are other characteristics of Luxi uplift, so I won't go into details here. From west to east, the middle zone is Waxuezi Basin, Wulichuan Basin, Xixia Basin, Xiaguan Basin, Liu Shan Basin, Liguanqiao Depression, Xiangcheng Depression, Wuyang Depression and Rendian Basin in the northwest. (Of course, there are occasional northeast basins) to Shenqiu sag and Huangchuan Gushi sag near the east-west, and then to Linquan sag, Sixian sag, Dazhuang sag and Liu Quan sag in the northeast. On the other hand, the southern belt has another feature, that is, on the basis of the northeast depression (such as Shizhu syncline, Jong Li syncline, Huaguoping syncline, Jianghan basin and buried hill depression, Wangjiang depression, etc.), there are NW-trending faults and basins in the middle, such as Jingmen fault depression and Hanshui fault depression. (See Figure 8).

Fig. 8 Schematic diagram of basin (depression or depression) distribution in the study area

1-Xiangcheng basin; 2- Lushi basin; 3- Waxuezi Basin; 4- Tantou Basin; 5- Songxian Basin; 6- Yichuan Basin; 7- Dajindian Basin; 8- Liu Shan Basin; 9- Ma Shiping Basin; 10-Xiaguan Basin; 11-Xixia basin; 12- Zhechuan basin; 13- Banqiao basin; 14- shigun river basin; 15— Rendian Basin; 16- Tongbai basin; 17-Quanshu sag; 18— Jurong sag; 19— Sujiazui bulge; 20-Ren Dong uplift; 21-Muyang fault depression; 22— Banpu sag; 23— Trench depression; 24— Taoyuan Depression; 25— Laiwu sag

2. Changes of basin types

From west to east, the whole area from single basin, such as Linfen, Xiangcheng and Xixia, to composite basin, such as Zhongmu sag, Lu Yi sag, Shenqiu sag, Runan sag, Linquan sag and Jianghan basin, to unidirectional basin, composite basin (such as Taoyuan and Qianshan sag, the east of Sixian sag), to composite basin (such as northern Jiangsu), and from north to south, the law is from west to east. The central belt has changed from NW-trending basins (such as Wulichuan Basin, Xixia Basin and Rendian Basin) to NW-trending and NE-trending composite basins with east-west characteristics. The former is Nanxiang Basin and Zhoukou Depression, and the latter is Luoshan-Huangchuan Depression. Then gradually transition from east-west to east-west and northeast composite basins. The former has Hefei Depression, especially in the north, while the latter has Subei Basin. The southern belt has changed from a northeast unidirectional basin such as Lichuan syncline and Huaguoping syncline to a northwest, northeast and east-west composite basin, such as Qianjiang Depression and its adjacent northern Hubei area. Then it turns into one-way basins in Northeast China, such as Wangjiang and Buried Hill Depression (Figure 8). The spatial distribution characteristics of the above basins clearly show that the formation and development of various basins in this area are the result of multi-stage and multi-structural factors. According to the analysis of existing data, there have been at least four times superposition of tectonic stress fields in this area since Mesozoic.

(2) The relationship between linear structure and the formation of Mesozoic and Cenozoic sedimentary basins.

As mentioned above, the boundaries of sedimentary basins (depressions or depressions) in the area are mostly straight lines or broken lines, which is obviously the result of the combination or compound control of one or more linear (fault) structures. Judging from the formation time of sedimentary basins, it seems that there is a trend from west to east and from north to south from old to new. The sedimentary basins in the early Mesozoic are mostly distributed in the northwest corner of the study area, and their extension directions are northwest and east-west. The former includes Shuanghuashu Basin, Wulichuan Basin, Miping Sag, Ma Shiping Basin and Liu Shan Basin. The latter includes Luoyang basin, Jiyuan basin and Du Ying sub-depression, which is related to the east-west structure of N-S compression in Indosinian period. This connection lasted until the middle and late Jurassic. Since then, NE-trending and NW-trending sedimentary basins (depressions or depressions) or fault blocks have begun to appear in this area. These basins or sub-depressions include Dongpu Depression, East Lu Yi Sub-depression and Biyang Depression. Fault blocks include Jingmen fault depression and Hanshui fault depression. This is related to the north-south coupling of Yanshan movement. Under the above-mentioned structural background, the east-west compression formed the Shangshui-Xinxian north-south negative structural belt and some composite sedimentary basins. Such as Lu Yi sag, Shenqiu sag and Runan-Linquan sag. Since the Himalayan movement, due to the compression from NE-SW direction, NW folds, nose bulges and various fault noses have been produced in some strata of the above sedimentary basins, and NE-trending (about NE45) tracer faults have been exposed in the periphery. The front section of Lankao-Taitai of the Yellow River diverted at 1855 is the result of its control (see Figure 6 on page 38).

4. A preliminary study on the Mesozoic-Cenozoic tectonic development model.

(1) A preliminary discussion on the formation mechanism of Mesozoic and Cenozoic sedimentary basins.

The temporal and spatial manifestations of sedimentary basins in this area are closely related to tectonics in different periods, and this relationship has become the basis for analyzing the formation mechanism of basins. The Triassic (North)-Jurassic (South) basin in this area is the reaction of two negative tectonic belts (synclines) formed during the Indosinian movement, that is, the structural elements perpendicular to the principal compressive stress axis. There are two groups of conjugate torsional structural planes near Ne 30° ~ NW 330°. Although it did not play a controlling role in the early stage of this sedimentary period, it had an important potential impact on the occurrence and development of sedimentary basins later. In the early and middle Mesozoic, under the action of strong north-south couple and east-west compressive stress, local tracing-type tensile cracks appeared in the northwest and near east-west, forming a number of Cretaceous-Paleogene composite basins with current structural characteristics and reflecting the early structural elements to varying degrees, which can be clearly seen from the distribution map of Mesozoic and Cenozoic sedimentary basins (Figure 8).

(2) Preliminary discussion on the structural development model of Mesozoic and Cenozoic.

Regionally, the study area is a part of the crustal extension zone in eastern China, but it has its own stress characteristics as a whole: on the basis of the east-west wide and gentle folds formed by the north-south compression, various structural lines formed by the north-south couple action are superimposed in the early and middle period of Yanshan cycle. In the middle and late Yanshan cycle, various east-west compressional tectonic lines are superimposed. At this time, due to the east-west compression, the north-south extension is caused, and various structural planes (including early structural planes) within the stress range open and slide under the action of gravity, thus promoting the formation and expansion of sedimentary basins. The Himalayan tectonic cycle was compressed in the NE-SW direction, leaving some NW-trending weak folds, nose-shaped uplift and some matching fault structures in the Paleogene and its previous strata (see Figure 9).

Fig. 9 Schematic diagram of superposition of structural elements in different periods

Verb (abbreviation of verb) is beneficial to oil-bearing basins and suggestions for future exploration and deployment.

As mentioned above, there were three large east-west negative (syncline) tectonic belts in this area in the early Mesozoic, which may be the product of Indosinian movement. From north to south, there are Jiyang-Kaifeng-Fengxian Belt, Nanyang-Banqiao-Fuyang Belt and Huangchuan-Hefei Belt. As far as the three zones are concerned, their formation is advancing from north to south, so the northern zone was formed early and deposited in Triassic. The middle zone is the second, and a small amount of Triassic-Jurassic exists. The southern belt is relatively late, dominated by Jurassic. The characteristics of the three zones are migration from north to south and from west to east. Later, on the basis of the above three belts, two large-scale negative (syncline) structural belts in the north-south direction were superimposed, namely the Jiyang-Nanyang belt in the west and the Lankao-Xincai belt in the east. Under the influence of nearly east-west tracing faults, these two negative structural belts deposited thick Cretaceous and Paleogene. Zhongmu-Huangkou sag, Nanxiang basin and Zhoukou sag are located at the intersection of the above two negative structural belts, which are rich in source rocks (especially Zhoukou sag) and controlled by NNE faults. Therefore, apart from Nanyang sag and Biyang sag, regional exploration in Zhoukou sag and Zhongmu-Huangkou sag should be strengthened to find new oil fields as soon as possible.

The above is an outline discussion from the perspective of tectonic development through the interpretation of satellite photos. In the future, on the one hand, the research on the sedimentary-tectonic system of Mesozoic and Cenozoic basins will be strengthened, and the above favorable oil-bearing basins (depressions) will be evaluated in detail; On the other hand, using the characteristics of remote sensing information, the key areas are interpreted and analyzed in depth, and the basic laws of oil and gas formation in key areas are explored, so as to play the greatest role of remote sensing technology in expanding oil areas and discovering new oil fields.

refer to

Henan bureau of geology and mineral resources. Structural system and seismogram description in henan province. Beijing: Geological Publishing House, 1980.

Henan bureau of geology and mineral resources. Description of Neogene bedrock geological map in Henan Province. Beijing: Geological Publishing House, 1980.

Shandong bureau of geology and mineral resources. Geological map description of tertiary bedrock in Shandong Province. Beijing: Geological Publishing House, 1985.

Institute of Geography, China Academy of Sciences. Description of geomorphologic map of Huang-Huai-Hai Plain. Beijing: China Map Publishing House, 1985.