250 1. 1. Krolenko 



Experimental seismic studies by the reflected methods were carried out 

 on a small scale in 1950-1952 in the western part of the Kerch peninsula 

 and in territory adjoining from the west to Feodosiya. This work showed 

 that where the anticline crests produced by diapiric and crypto diapiric 

 structures are separated by narrow and deep synclinal depressions, the use 

 of seismic exploration involves considerable difficulties in correlating these 

 reflections. In many profiles the crestal sections are characterized by irregular 

 readings, by different orientation of the co-phasal axes and by the so-called 

 "blind zones" with almost complete absence of reflecting horizons. In the 

 peripheral parts of the structures on the limbs and in the synclines, where 

 the layers slope relatively gently, the record of reflections is perfectly 

 satisfactory. 



As a result of processing the method of seismic exploration of the western 

 part of the Kerch peninsula in 1954, considerable improvements were obtain- 

 ed in the quality of the recorded seismograms. The Avork showed a certain 

 lack of correspondence of the structural plan of the Tertiary and Meso- 

 zoic deposits and an increase in the angle of dip of rocks with depth. 

 Due to the absence of continuous, correlatable horizons, the construc- 

 tions were made by using two arbitrary seismic horizons: M (stratigra- 

 phically related to the top of the upper Kerleutskian horizon) and C^ 

 (corresponding to the Upper Cretaceous sediments (^^)). The accuracy 

 of the constructions was conditioned mainly by the quality in the 

 initial data. It was, therefore, at its least in the hinges of the anticlines, 

 found by the strongly folded rocks with large angles of dip (up to 

 70-80°). 



The seismic profiles showed all the culminations including those which 

 were kno\Mi previously, and those shown by the loop method: Ul'yanovskaia, 

 Shirokovskaia and Yuzhno Andreevskaia^^^). The closures of the structures 

 formed by the arbitrary seismic horizon M in the overwhelming majority of 

 cases coincide "vvith the closures mapped by the loop method or are slightly 

 displaced. Thus, under the conditions existing on the Kerch peninsula on the 

 limbs of the folds there is a correspondence between the structure contours 

 nf the seismic exploration and the isonormals of the loop method. The absence 

 of reflecting areas in the closures of the intensively dislocated folds is easily 

 made up by the data of electrical explorations, i.e. the methods are comphmen- 

 tary to one another, giving a continuous section of observation without 

 "blind zones". This is very important in interpreting geophysical material 

 and should be remembered when planning and carrying out field work. 



The loop method, as shown above, successfully depicts local cvilminations 

 of axial plunge and secondary complications on the limbs. It explains the 



