Abstract:

The Paleozoic in Jiyang depression can be divided into three super-sequences and 14 third-order sequences by using sequence stratigraphy theory and cycle analysis of datum level,combining with drilling, seismic and logging methods. The super-sequences are the Mantou formation-Liangjiashan formation (A), the Xiamajiagou formation-Badou formation (B) and the Benxi formation-Shiqianfeng formation (C). According to calibration of sequences in regional seismic profiles, an isochronic framework of the Paleozoic sequence stratigraphy in Jiyang depression is established through tracing and interpreting the four super-sequence boundaries. The three super-sequences are clear in logging-constrained inverse profiles, showing low, high and low impedances from bottom to top,respectively. The main identification marks of sequence boundaries are unconformable surfaces, scouring surfaces of rivers, surfaces showing abrupt changes of litho-electric properties and color, of which unconformable surfaces are super-sequence boundaries, while others are boundaries of third-order sequences. Standards for dividing seismic sequences are defined and a sedimentation model is developed for the Paleozoic sequence stratigraphy in Jiyang depression

Key words: Jiyang depression, Paleozoic, sequence stratigraphy, sedimentary system