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1. Geomorphological signs.
Such as fault cliffs, fault triangles, staggered ridges, sudden changes in mountains and plains, beaded lakes, depressions, strip distribution of springs, sharp turns of water systems, waterfalls, and water falls.
Wait. 2. Construct signs.
1) Any linear or surface geological body extending along strike is abruptly interrupted or staggered along strike.
2) the occurrence of fault fracture zones, such as tectonic lenses, fault breccias, etc.; (3) The appearance of cross-section and cross-sectional structure, such as the fault plane, friction surface, rubbing crystal, step, scratch marks, etc.; (4) The occurrence of fault influence zones, such as tectonic strengthening zones and rock strata occurrence.
Abrupt changes, sudden appearance of joints, splitting and chemical belts, sharp increase of small folds, extrusion and crushing, traction structure, etc.; 3. Stratigraphic markers.
Duplication and absence of strata.
4. Magmatic activity and mineralization.
Mineralized zones or silicified alteration zones are distributed in a linear manner, and the occurrence of ring-shaped and radial rock walls, etc.
5. Rapid changes in lithofacies and thickness.
Sharp thickening of lithofacies and thickness is often caused by faults.
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Geological bodies such as strata,, and veins are suddenly interrupted or staggered in the plane or profile.
Repeating or missing strata, which is a common phenomenon of normal faults or reverse faults that are roughly parallel to the stratigraphic trend, in the case of the fault tendency and stratigraphic tendency, or the same tendencies but the fault dip angle is less than the stratigraphic dip angle, the stratigraphic repetition indicates that it is a normal fault, and the stratum is missing, it is a reverse fault.
Abrasion marks, the traces left by the friction of two rocks on the fault plane, can be used to identify the direction of movement of the two disks and determine the nature of the fault.
Traction construction. During the fault movement, the local arc bending caused by the drag of the rock strata near the fault generally indicates the relative direction of movement of the plate.
The presence of fault breccia, which is composed of two rock fragments of the fault, and the occurrence of powdery fault mud milled by fault movement, indicates the existence of a fault in the area.
In addition, the presence of faults can be identified based on geomorphological features such as faulted ridges, fault cliffs, and abrupt changes in the direction of water systems.
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Field identification of folds: folds are generally weathered and eroded after formation, and the anticline core is prone to weathering and destruction due to joint development, which may form valley lowlands, while the oblique core may form ridges. In the field, most of the rock formations are not well exposed due to denudation and damage, and cannot be directly observed.
Observations should be made perpendicular to the strike of the strata, and fold structures can be concluded when the strata are repeated and symmetrically distributed.
Field identification of faults: mainly look at scratch marks, that is, traces of dense micro-fine grooves with a certain direction on the fault plane. Touch it in the direction of the scratch, and feel that the smooth direction is the sliding direction of the other plate.
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There are a lot, look at the stratum mark, geomorphological mark, rock fracture discontinuity, the lack of strata, etc., the elements of the fault are also an important sign to identify the fault, the fault has a section, the upper wall and the lower wall three elements, the identification of the three elements can be preliminarily identified, and then confirmed by other signs to assist in confirmation.
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1. Geological bodies such as strata,, and ore veins are suddenly interrupted or staggered on the megaplane or profile of the side cavity.
2. Repeat or lack of strata, which is a common phenomenon of normal faults or reverse faults that are roughly parallel to the stratum trend, in the case of the fault tendency and stratigraphic tendency, or the same tendency of the two but the fault dip angle is less than the stratum dip angle, the stratum repeat indicates that it is a normal fault, and the stratum is missing.
3. Friction marks, the traces left by the friction between the two rocks on the fault plane, can be used to identify the direction of movement of the two disks and determine the nature of the fault
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Markers to identify active faults are:
a. Geology: the latest sediments on the surface of the staggered active fault zone, the material structure is loose, there is a phenomenon of active faults, and there are fault steep ridges and ground fissures on the surface.
b. Geomorphology: The two sides of the active fault are often the parts of the water system where the geomorphic units are directly connected: for strike-slip faults; 1. A series of river valleys of the river system move synchronously in the same direction; 2. The main fault controls the trend of the main river channel, and the undesirable geological phenomenon is linear and densely distributed.
Ten. 6. How to determine the relative geological age of sedimentary rocks?
The determination of the relative geological age of rocks (bodies) is based on three methods: stratigraphic sequence law, biological evolution law and contact relationship between geological bodies
a. The original occurrence of sedimentary rocks without the influence of tectonic deformation should be horizontal or approximately horizontal. And the rock layer formed first is below, and the rock layer formed later is above.
b. The law of biological evolution is due to the continuous development and evolution of organisms from low to high, from simple to complex. Therefore, the relationship between the old and the new of the rock layer can be judged according to the biological fossils preserved in the rock layer.
c. The contact relationship between geological bodies is judged according to the unconformity contact between sedimentary rock layers. The formation time of the rock strata with the same lithology as the bottom conglomerate on the unconformity is earlier, and the formation time of the rock strata that is consistent with the occurrence of the angular Qixiao conglomerate is later.
If the rock layer is in sedimentary contact with the magmatic rock, the sedimentary rock is formed later, and if the rock layer is in intrusive contact with the magmatic rock, the dull conjunct rock is formed earlier.
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A fault is a fault that moves significantly up and down or left and right along the fault plane (zone) and the rock layers on both sides. The fracture surface is called the "fault plane", and the rock blocks on both sides are called the "disk". If the fault plane is tilted, the plate above the fault plane is called the "upper plate", and the lower plate is called the "lower plate".
If the fault plane is upright, it is often indicated by the direction, such as the east or west plate, the left or right plate. According to the relative movement of the two disks of the fault, it can be divided into normal fault, reverse fault and translational fault. The scale of the fault varies, after the occurrence of the first in Tangshan in 1976, we can see there that the original flat road has become bumpy, up and down staggered 60 70 cm, and the horizontal staggered distance is larger, reaching 120 cm, or even 250 cm, so that the trees that were originally lined up next to the boulevard are broken and staggered into two discontinuous rows.
The largest vertical dislocation between the two sides was set in Alaska** in 1899 in the United States, setting a record of 141 meters. Faults also exist on the seafloor, such as the eastern Pacific submarine plateau, which is separated by more than a dozen faults in an east-west direction, each extending 1,600 kilometers east-west. Faults will form peculiar landscapes, such as Huashan Mountain, which was formed due to the rise of the Qinling Mountains, which is a fault mountain famous for its steepness, and the descending side is filled with sediment brought by flowing water, resulting in the fertile field of the Qinchuan River for 800 miles.
On the east coast of Taiwan, the majestic coastal cliffs are also a miracle created by the Great Fault. However, faults will also bring harm, it is an important cause of the best, so the factor of faults must be considered in engineering construction and water conservancy construction.
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Faults can be classified according to the relative motion of two points on the fault line that were originally adjacent to each other in the fault movement.
1. Strike sliding fault: the movement is only in the horizontal direction and parallel to the fault plane. Strike-slip faults are further divided into right-slip and left-slip faults.
2. Inclined sliding faults: The relative movement of rising and falling along the fault plane is a inclined sliding fault. A tendency-slip fault that moves downward relative to the lower wall is a normal fault.
3. Thrust fault: When the dip angle of the fault plane is less than or equal to 45°, and the upper wall moves upward relative to the lower wall, it is called thrust fault, and if the dip angle of the fault plane is greater than 45°, it is called a reverse fault.
4. Oblique sliding fault: The relative movement direction of the two disks is between the trending sliding fault and the inclined sliding fault, which is called an oblique sliding fault.
5. Fault drop and flat fault: The relative displacement between the two disks of the fault is often called fault drop and flat fault. Drop reflects vertical displacement, while Flat Error reflects horizontal displacement. The faults mentioned above all have a common feature of movement, that is, the structure of the two disks remains parallel during the movement.
6. Rotating fault: There is twisting and rotation between two adjacent blocks, and such a fault is called a rotating fault or a shear fault.
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First of all, you have to know.
Faults are mainly divided into two types: normal faults and reverse faults, and the characteristics of the layers are judged by learning the representation of faults.
Answer: whether it is a positive fault or an inverse fault; Then, the upper and lower walls are judged according to the values of the corresponding point contours (or the depth of the strata) of the two disks in the direction perpendicular to the strike of the fault.
Discriminant method: 1. If it is a normal fault, the plate with a large absolute value of the contour (depth in front of the negative sign below the altitude) or the depth of the formation is the upper wall (descending plate, rising or falling is relative position), and the other plate is the lower plate (rising plate).
2. If it is a reverse fault, the one with a large absolute value of the contour or the deep stratum is the lower plate (descending plate), and the other plate is the upper plate (rising plate).
Below is the actual geological map, made in CAD, with the normal fault on the left and the reverse fault on the right.
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Faults can be classified into three types: normal faults, reverse faults, and translational faults. (Normal fault: the previous disc is relatively down.)
The lower wall is a fault that rises relatively up. Considerable layers on both sides of it are separated from each other. It is mainly formed by the action of tension and gravity.
Reverse fault: a fault with a relative rise in the upper wall and a relative decline in the lower wall, which is mainly formed by the action of horizontal compressive force. Horizontal inference faults:
The two disks of the fault are oriented along the fault plane for horizontal relative displacement, and the fault plane is steep and straight, also known as translational fault. Such faults are formed by strong horizontal compression.
Answer: Figure 3 is the reverse fault, (receiving extrusion, D and D are misaligned, the upper wall rises, and DOS is the upper wall), and Figure 4 is the positive fault. After receiving the pull force, T and T are torn, misaligned, and the upper plate falls.
TPC is the upper plate. Judging the upper and lower plates according to the vertical direction, the upper plate is the upper plate, and the lower plate is the lower plate. It's simple.
Note that the barriers and the grabens are not judged in this way. It shouldn't be high school geography, right? If you don't understand, keep asking.
Thank you. China National Geographic team A Zhe will answer for you.
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Both normal and reverse faults are represented by different symbols
Look at the arrows of the fault and the direction of the small **.
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The upper and lower falling are positive faults, and the upper and lower falling are reverse faults!
Field identification of folds: folds are generally weathered and eroded after formation, and the anticline core is prone to weathering and destruction due to joint development, which may form valley lowlands, while the oblique core may form ridges. In the field, most of the rock formations are not well exposed due to denudation and damage, and cannot be directly observed. >>>More
Answers]: a, d
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