Correction of the Calculation Formula of Stratum True Thickness in the Measured Geological Section

Abstract:

The леоновский’s stratum true thickness formula is widely accepted and used by lots of geologists, but some problems still exist. Based on the actual situation, the calculation formula of stratum thickness was deduced, the range of the stratum thickness value and the influence of angle error were analyzed, and the problems of zero data, negative data and negative thickness of the stratum thickness were discussed. Finally, the case study was carried out to verify it. The results are obtained as follows: ①the леоновский’s formula only contains two kinds of field measurement and omits one kind of field measurement, so the calculation formula of stratum thickness is corrected; ②the range of F-data of stratum thickness is 0~1,and the F-data has different variation characteristics in three field survey situations respectively, but the maximum values are all obtained when the stratum dip direction is nearly vertical to the ground slope where the measure line passes, and the minimum values are all obtained when the stratum dip direction is nearly parallel to the ground slope where the measure line passes; ③the error influence of true dip angle, slope angle as well as the acute angle between the guiding line direction and the stratum strike has different variation characteristics in three field conditions, but both the true dip angle and the slope angle error have the greatest influence on the thickness calculation when the stratum trend is nearly parallel to the ground slope direction where the measure line passes, meanwhile, the acute angle between the guiding line direction and the stratum strike has the greatest influence on the stratum thickness when the acute angle is smallest; ④When the measure line is the translation line, the stratum thickness is zero; the concept of the negative stratum thickness only has its sense in the modified form of леоновский’s formula, which just indicates that the measure line crosses from the upper stratum surface to the lower stratum surface; the negative data of the calculation using the леоновский’s formula is caused by that the леоновский’s formula lacks one kind of field measurement, and the negative data isn’t equal to the negative thickness; the calculated values of the corrected formula are all positive values, which are in line with the objective reality, meanwhile it can be used to calculate the total stratum thickness combining with the structural analysis. The above knowledge has a guiding role in the selection of field measured profile and guiding line direction as well as the calculation of indoor stratum thickness and total thickness, and has an important value in the scientific research and production based on stratigraphic knowledge.

Key words:measured geological section;the true thickness of the stratum;error analysis