| The Kalpin thrust tectonic system is the result of India-Asia collision and intracontinent orogeny, which is an important part of the foreland fold-thrust zone (belt) in the southwestern Tien Shan. It is greatly significant for the research on geological structural features, tectonic deformation, distribution and mechanism of folds and faults of the Tien Shan. Unfortunately, because of the adverse nature condition, complicated topography and poor transport facilites, the field investigation is difficult so that the research level degree of its tectonic deformation is low. Not come singly but a pairs, under the influence of steep terrain of the foreland thrust zone, the seismic information of the upper lithostratigraphy is almost blank. The field survey at attitude of bedding won't work without great river breaking the fold mountains. There will be more uncertainty only useing the limited stratigraphic data from geologic maps. The high resolution satellite image technique and digital photographic methods are new approaches to study the tectonic deformation and attitude of surface bedding, which can help solve the problems above.Firstly, based on the processing and analysis of the Landsat 7 ETM+ multispectral image and SPOT-5 Pan, the interpretation and field investigation of three typical sites (named Xikeer,Bachulinkuang,Wulangtage)have been done about the bedded geomorphologic surfaces, the location and distribution of active tectonics. It is testified to be feasible for using the ETM+ and SPOT-5 Pan fused image to interpret the late tectonic deformation of the thrust tectonic system, especially fit to the tectonic area with sparse vegetation, preserved tectonic geomorphology and inconvenient transportation. At the same time, interpretation symbols of tectonic deformation are summarized such as shadow, texture and hue symbol; stratum symbol; distribution and size of alluvial and proluvial fan symbol; gully and river system symbol.These symbols are used to interpret the fused image of the other area and get some preliminary determinations of late tectonic deformation of the Kalpin thrust tetonic system.The determinations are as follows:1) There are bedded geomorphologic surfaces composed of gobi gravel of different times, which reflects that the deformation of the thrust faults is the main deformation style of the Kalpin thrust tectonic system.2)Bedded geomorphologic surfaces are generally divided into five episodes, which shows the activity of faults in several times.3) Most of fault scarps are continually wavily distributed on the middle top of the alluvial and proluvial fan, which corresponds to characteristics of the low-angle thrust fault; 4) There are young terraces near the outlets of Quaternary neonatal folds, which reveals late Quaternary activity of the neonatal folds.Secondly, high-resolution satellite IRS-P5 stereo pairs are used to extract the Digital Elevation Model (DEM) which is perpendicular to strike of the fold mountains. The horizontal Root Mean Square (RMS) of the DEM is less than 2 meters,the vertical is less than 5 meters .Then the IRS-P5 Digital Orthophoto Map is made with the input from generated DEM. In order to accurately extract the stratigraphic boundary and classify strata, GeoEye-1 multispectral images downloaded from Google Earth must be matched to rectified P5 images. And then the points will be selected in every stratum at the locations of ridge and valley, stratum with different colors and stable attitudes. The strike and dip of bedding are programming calculated in the matlab system using the three-dimension coordinates of the points. With the help of GPS, the field survey shows that the measurement error of surface bedding attitude is less than 6 degree, and 85% is less than 4 degree, and the RMS of dipangel is less than 3 degree, which can be accepted. Because the digital photogrammetry method based on high-resolution satellite images is less affected by natural conditions, it makes up for the lack of surface bedding attitude and has some referential value for other similar areas.At last, according to the stratigraphic attitude and its thickness, a geological cross-section of the Kalpin fold-thrust belt is constructed using the fault-propagation fold model and some other data such as topographic and geological data, the faults and folds morphology evidence through field survey, seismic reflection profiles and so on. The present-day length of the section is 72km, and the original length of the restored section is 113 km, Tthat is to say, the restored section yields a crustal shortening of 41km, and the shortening rate is 36.3%. If the initial time of tectonic deformation is about 2.5 Ma B.P, the shortening rate of the Kalpin thrust tectonic zone is 16.4mm/a, which reflects its intensity of tectonic deformation to a certain extent. The result indicates that the surface stratigraphic attitude which is gotten from the IRS-P5 stereo pairs and GeoEye-1 imagine, can provide trustworthy data to constrain deep seismic data, ascertain shallow tectonic features, and calculate crustal shortening. |
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