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Analytical Model for the Palaeoenvironmental Evolution of the Nihewan Beds
Author(s) -
Jun Yue,
Qizhong Wen
Publication year - 1991
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/j.1755-6724.1991.mp4001007.x
Subject(s) - alkalinity , geology , pleistocene , base (topology) , mineralogy , chemistry , paleontology , mathematics , mathematical analysis , organic chemistry
In this paper, the evolutional characteristics of palaeoclimate and oxidation‐reduction conditions as well as acidity‐alkalinity environment are discussed by means of the step‐regression, cluster, optimal partitioning and correlation analyses of CaCO 3 , C / P 2 O 5 , Fe 2+ / Fe 3+ , pH and Eh values, taking the Xiaodukou section in the Nihewan basin as an example. The CaCO 3 , C / P 2 O 5 and pH were calculated respectively using the optimal partitioning method. Thus five cold zones and six warm zones as well as five reduction and six oxidation zones were distinguished. Then the inductive method was used to produce four numerical groups: 8.10, 8.3–8.4, 8.6–8.7 and 8.9–8.97. The above‐mentioned results are respectively based on CaCO 3 content, C/ P 2 O 5 and pH values. From Fig. 3, Tables 1 and 2 it can be seen that the Nihewan Beds were formed mainly under a reduction and slightly alkaline environment of cold climate, with pH values of 8.3–8.4. Fig. 3 shows that bed 35 is approximately near the boundary between the Brunhes and Matuyama polarity epochs, 0.73 Ma in age; bed 26 is roughly near the Jaramillo event (base), 0.97 Ma in age; bed 18 coincides roughly with the magnetostratigraphic boundary of 2.00 Ma (?). Bed 13 may be the Pleistocene‐Pliocene boundary, 2.48 Ma in age. Thus geochemical zones I, ?, IH and IV include respectively cold zones 1; 2 and 3; 4; and 5.