利用天然热发光划分和对比碳酸盐岩层

热发光方法在地质学中的应用,只是近年来才迅速、广泛地发展起来的。目前已用于地质年龄测定、考古学、地层对比、岩相古地理、矿床学、地质温度计、构造活动、变质作用、陨石以及月岩研究等方面,并且都取得了一定的效果。

SUBDIVISION AND CORRELATION OF CARBONATE ROCK LAYERS BY MEANS OF NATURAL THERMOLUMINESCENCE

How to subdivide and correlate the rock layers correctly is an important but difficult task encountered frequently in geology.Through the investigation of five cross section related to the Triassic Jialing River formation of southern Sichuan, the authors discuss the feasibility to subdivide and correlate the carbonate rock layers by using natural thermoluminescence.The Triassic Jialing River formation is chiefly composed of carbonate rocks and evaporites. Further subdivision of the lower G2 and upper G1 into seven layers - layer A, B, C, D, E, P and G is suggested in accordance with practical requirements.The use of natural thermoluminescence in subdividing and correlating rock layers is based upon the regularity in the distribution of glow intensity in the carbonate rocks. By correlating and analysing a great number of glow intensity of rock samples it is observed that layers A, C, B, G present a stronger intensity than layers B, D and F. Among the formers, layer A seems to be the strongest with the nature of higher temperature peak, while layer G appears to be also strong in intensity but with medium temperature peak. It is well known that thermoluminescence intensity depends upon the nature of stratigraphic horizons (i.e. the age of the rock). In the same horizon, however, the changes of NT intensity are affected by lithology and composition of chemical elements.Using the regularity shown by NT intensity distribution, the authors have redi-vided the five cross-sections mentioned above. As a result it is noticed that for two sections among them the data on which the field subdivision is based appear to agree closely with the thermoluminescene data, while for the other two both data differ slightly and for the last section a great disagreement exists due to both the facies change occurring in layer B of this section and the lacking of key bed, so there is no way of subdividing it in the field. By analysing the features of NT, however, layer B can be satisfactorily separated, thereby, the subdivision of the entire section into layers agrees more exactly with the actual conditions.Summing up, the application of thermoluminescence in subdividing and correlating the layers occurring in areas under investigation has proved to be an invaluable method.