关键词: 化学元素, 沉积环境, 伽马能谱, 细粒沉积, 层序

Abstract: Integrating the geochemical elements, sedimentary environment restoration indicators, lithology and gamma spectroscopy logging response, we studied the fine shale sedimentary sequence on the Es₄s-Es₃x of Jiyang Depression, and the results show that, during the formation process of fine-grained sedimentary sequence, the sequence boundary, affected by depositional environment and depositional effects, displays characteristics as follows:high supply of detritus source, high abundances of Ti, Fe, Al, Na, K, Co, Cr, Cd and Mn, low content of carbonate rocks, Ca elements and sapropel group, and great variations in sedimentary structures and paleoenvironmental indicators of scour surface and cross-bedding which represent strong hydrodynamic conditions. Parasequence group often represents a process of large scale progradation and retrogradation, with great value segment of TOC or Sr corresponding with the transformed surface. Due to small particles, slow deposition process, and abundant organic matter, the fine-grained sediments have strong adsorption on K, U, Th and other radioactive elements, which contributes to the enrichment of these radioactive elements, and better performance of GR logging on fine shale resolution than other lithologies. The GR logging response bears obvious longitudinal regulationand is of good contrast tracking feature on the Es₄s-Es₃x of Jiyang Depression, so we can use the vertical evolution of GR curve to contrast and trace the fine-grained sedimentary sequence in the whole region.

Key words: chemical elements, depositional environment, gamma spectroscopy, fine deposition, sequence