Development and controlling factors of shale lithofacies cycles in a continental rift basin: A case study of Es4u in the Boxing Subsag of Dongying Sag, Bohai Bay Basin, China

The shale of the upper Es4 formation (Es 4 u ), deposited during Eocene in Boxing Subsag Dongying Sag, is a typical set lime-rich lacustrine continental rift basin. Through logging data interpretation, core and thin section observations, geochemical elements [obtained by X radial fluorescence (XRF) mud logging] analysis, development controlling factors lithofacies cycles Es were analyzed. results show that 22 types with characteristics are developed , indicating sedimentary environments, such as lower lakeshore (LL) slope zone; upper, middle, shallow-lake zones; semi-deep-lake deep-lake zone. Lithofacies three scales recognized : small-scale indicated alternate two lithofacies, mesoscale repetition associations or regular variation multiple large-scale well curves, which have average thickness approximately 0.4, 5, 35 m, respectively. According to vertical astronomical parameters cycles, periodic change long eccentricity has close relationship cycle, closely relative precession related cycle. However, short correlates poorly cycles. climate reflected quite distinct from actual basin paleoclimatic (e.g., Rb/Sr Sr/Cu), paleoclimate was greatly influenced paleogeological conditions. For Subsag, 55% stratigraphic record dominantly controlled 45% Affected conditions, different superimposition patterns, just found repetitive vertically. These findings suggest product driving mechanism (Milankovitch forcing) local apparently marine evidently Milankovitch Therefore, should be comprehensively analyzed under background paleoclimate.