TWO QUANTITATIVE METHODS FOR CONSTRUCTING BIOSTRATIGRAPHIC COMPOSITE SEQUENCE:A CASE STUDY OF CARBONIFEROUS BIOSTRATIGRAPHY IN SOUTH CHINA
One of the important goals of biostratigraphy is to construct a global or regional biostratigraphic composite sequence that can be used as the reference of correlation.The traditional method to construct the composite sequence is to evaluate the sequences qualitatively and empirically based on a few main sections,while the quantitative stratigraphy methods provide a routine to analyze and compile fossil taxa from a large number of stratigraphic sections and construct a more widely adapted composite sequence.In this paper,two quantitative stratigraphic methods,Ranking and Scaling(RASC)and Constrained Optimization(CONOP),are introduced to a study on the fusulinid and conodont bioevent sequences in the Carboniferous stratigraphic framework of China.Altogether,25 marine sections dominated by conodont and fusulinid fossils from South China were compiled.RASC and CONOP were applied to the datasets to quantitatively evaluate the observed records for the first occurrence datum of all the fossils,and establish the result sequences.The result sequences were compared with the empirical sequence of Carboniferous conodonts and fusulinids of China.The results show that for the sharing bioevents,the RASC and CONOP result sequences present very high correlation,with a high Spearman's correlation coefficient(ρ)value of 0.9826.The ρ values between the two result sequences and the empirical sequence are also high,both higher than 0.97.The causes for the differences between RASC and CONOP result sequences lie on three main aspects:the different superposition philosophies,the bioevent relations they mainly based on,and the influence from the dataset.The reason for the differences between the quantitative result sequences and the empirical sequence is that the empirical sequence focuses more on the direct relations of fossils on the main sections,while the quantitative sequences synthesize all the relations in usually a large number of sections.The composite sequence obtained by both qualitative and quantitative methods need to be deeply analyzed and utilized before application.
quantitative stratigraphyRASCCONOPindex fossilconodontsfusulinidsSouth China
万方数据
维普
