GEOLOGICAL STRUCTURE OF THE PRE-JURASSIC BASEMENT OF THE CENTRAL PART OF THE KRASNOLENINSKY SWELL IN THE LIGHT OF NEW GEOLOGICAL AND GEOPHYSICAL DATA

Author(s):  
D. A. Sidorov ◽  
◽  
L. V. Lapina ◽  
N. V. Kholmanskikh ◽  
D. V. Emelyanov ◽  
...  

The article reviews features of the pre-Jurassic geological structure of the Krasnoleninsky Swell, located on the western edge of the West Siberian petroleum basin. New geological and geophysical materials are presented enabling significant clarifification of the relationships pattern between Precambrian, Paleozoic and Triassic formation complexes. The stratification of the pre-Jurassic section is based on previously known age determinations and datings made in recent years by high-precision methods. The analysis of mode of occurrence of Pre-Jurassic rock complexes is based on the interpretation of seismic materials and gravity and magnetic data. The proposed model of the Krasnoleninsky Swell pre-Jurassic basement is characterized by the significantly reduced volume of pre-Cambrian formations due to the expansion of the Paleozoic complexes area, local Paleozoic depressions at the base of the Yem-Yegovskaya and Kamennaya peaks and linear zones of development of Triassic terrigenous-volcanogenic rocks on the Talinskaya Terrace and in the Palyanovsky trough have been identified. The conclusion is made about the long and complex history of the basement structure formation in the zone of collision junction of divergent Ural and Central-West Siberian folded systems.

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 87-96 ◽  
Author(s):  
Nicole Debeglia ◽  
Jacques Corpel

A new method has been developed for the automatic and general interpretation of gravity and magnetic data. This technique, based on the analysis of 3-D analytic signal derivatives, involves as few assumptions as possible on the magnetization or density properties and on the geometry of the structures. It is therefore particularly well suited to preliminary interpretation and model initialization. Processing the derivatives of the analytic signal amplitude, instead of the original analytic signal amplitude, gives a more efficient separation of anomalies caused by close structures. Moreover, gravity and magnetic data can be taken into account by the same procedure merely through using the gravity vertical gradient. The main advantage of derivatives, however, is that any source geometry can be considered as the sum of only two types of model: contact and thin‐dike models. In a first step, depths are estimated using a double interpretation of the analytic signal amplitude function for these two basic models. Second, the most suitable solution is defined at each estimation location through analysis of the vertical and horizontal gradients. Practical implementation of the method involves accurate frequency‐domain algorithms for computing derivatives with an automatic control of noise effects by appropriate filtering and upward continuation operations. Tests on theoretical magnetic fields give good depth evaluations for derivative orders ranging from 0 to 3. For actual magnetic data with borehole controls, the first and second derivatives seem to provide the most satisfactory depth estimations.


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