Sedimentary Environment Division by Clayey Water Electrical Conductivity and Grain-Size Analysis: A Case Study of an xz-Borehole in the Western Plain of Bohai Bay, China

Abstract

Fang, J.; Zhang, L.; Liu, Y.; Chen, G.; Yang, S.; Wang, T., and Wang, F., 2020. Sedimentary environment division by clayey water electrical conductivity and grain-size analysis: A case study of an xz-borehole in the western plain of Bohai Bay, China. In: Yang, D.F. and Wang, H. (eds.), Recent Advances in Marine Geology and Environmental Oceanography. Journal of Coastal Research, Special Issue No. 108, pp. 99–103. Coconut Creek (Florida), ISSN 0749-0208.According to the measured value of clayey water electrical conductivity (EC) of xz-borehole core samples from the south bank plain of the Haihe River in Tianjin, the marine and continental strata of the xz-borehole core were divided. From bottom to top, the core represents the regression process of a neritic facies deposit (Zone I), intertidal deposit (Zone II), and continental deposit (Zone III). The hydrodynamic conditions of xz-borehole marine facies, sea–land transitional facies, and terrestrial strata were analyzed by grain-size analysis methods such as probability accumulation curve and CM diagram, and the sedimentary facies were further divided according to sediment grain size and sorting characteristics. Zone I is subdivided into a neritic facies deposit with a finer grain size and hydrodynamic stability (I-1 and I-3), a neritic facies deposit with a coarser grain size and stronger hydrodynamic force (I-2), and a delta front deposit with rapid EC value decline and a coarse grain size (I-4). Zone III, with a low EC value, is subdivided into fine-grained floodplain–flooding plain sediments (III-2) and coarse-grained crevasse splay sediments (III-1). High-energy hydrodynamic events in the deposition process can be accurately identified with grain-size analysis and EC indicators. Therefore, it can make up for the defect that EC cannot further refine the internal sedimentary facies for the marine facies, transitional facies, and continental facies. It has a good effect on the detailed differentiation of sediments and sedimentary facies in the coastal plain, and the identification of sedimentary events.