Palaeoenvironmental periodisms of middle Eocene terrestrial sediments in Bohai Bay Basin, eastern China, and their implications for organic matter accumulation

2020 ◽  
Vol 112 ◽  
pp. 104060
Author(s):  
Di Chen ◽  
Xiongqi Pang ◽  
Youwei Wang ◽  
Yuexia Dong ◽  
Fujie Jiang ◽  
...  
Keyword(s):  
Organic Matter ◽  
Middle Eocene ◽  
Eastern China ◽  
Bohai Bay ◽  
Bohai Bay Basin ◽  
Organic Matter Accumulation ◽  
Terrestrial Sediments

Sedimentary deformation features as evidence for paleoseismic events in the middle Eocene in the Dongying Depression of the southern Bohai Bay Basin, eastern China

2020 ◽  
Vol 57 (8) ◽  
pp. 954-970
Author(s):  
Zhongshuai Hou ◽  
Shiyue Chen ◽  
Shun Zhang ◽  
Huaiyu Yang
Keyword(s):  
Middle Eocene ◽  
Eastern China ◽  
Active Faults ◽  
Bohai Bay ◽  
Bohai Bay Basin ◽  
The North ◽  
Dongying Depression ◽  
Gravity Flows ◽  
Tectonically Active ◽  
Deformation Features

Cores from the middle Eocene sediments of the Dongying Depression of the southern Bohai Bay Basin in east China yield various kinds of sedimentary deformation structures. They include microfolds, load casts, flame structures, ball-and-pillow structures, load-cast ripples, pinch-and-swell structures, boudinage structures, sand dikes, microfaults, and cataclastic breccias. Gravity flows, including turbidites and debris flows, also occur in the study area. The deformation layers can be divided into plastic deformation and brittle deformation types. These develop in a succession composed mainly of dark finely laminated and massive mudstone interbedded with thin sandstones and carbonate rocks that accumulated in a low-energy semi-deep to deep lacustrine environment in a tectonically active setting. Considering the facies attributes in the study area, intrinsically possible trigger mechanisms such as rapid sediment loading and storm currents are absent. Thus, the sedimentary deformation features should be induced by seismic activity, and the same with the gravity flows. These seismites are interpreted to have originated from earthquakes with magnitudes exceeding M 5.6. Basin-controlling faults in the north border of Dongying Depression give rise to the occurrence of seismites. The increasing occurrence frequency of seismites from Es4u to Es3l corresponds with the increase in the activity velocity of the basin-controlling faults. Compared with the seismites developed in other fault depressions in the Bohai Bay Basin, seismites developed in the Dongying Depression are relatively smaller scale and are dominated by microfault layers, relatively more cohesive sediments, and greater distance between seismites and active faults results in the occurrence of these features.

scholarly journals Characteristics of nanopores in terrestrial low-maturity shale based on organic-inorganic interactions: A case study on the Shahejie Formation shale in the southern Bohai Bay Basin, Eastern China

2020 ◽  
Vol 600 (1) ◽  
pp. 012007
Author(s):  
Fu Deliang ◽  
Sun Lina ◽  
Xu Guosheng ◽  
Liang Haoran ◽  
Zhang Chen ◽  
...  
Keyword(s):  
Organic Matter ◽  
Surface Area ◽  
Pore Diameter ◽  
Eastern China ◽  
Bet Surface Area ◽  
Bohai Bay ◽  
Bohai Bay Basin ◽  
Pore Characteristics ◽  
Inorganic Matter ◽  
Shahejie Formation

Abstract In this study, the influence of organic matter and inorganic matter on the pore structure of the Shahejie Formation (E2-3S) shale in the Bohai Bay Basin, was analysed. The pore characteristics, including the BET surface area, BJH adsorption cumulative volume and average pore diameter of the original samples, extracted samples, H2O2-treated samples and kerogen samples, were analysed with low-pressure N2 adsorption experiment. The study showed that the soluble organic matter in low-maturity shale blocked a certain number of pores, which mainly had pore sizes below 5 nm. The solid organic matter mainly formed pore diameters of 1-2 nm and pore diameters larger than 10 nm. A large amount inorganic pore diameter in the ranges of less than 0.8 nm, 1-2 nm, and 2.3-20 nm was blocked by solid organic matter. The micropores formed by minerals were much more abundant than those formed by organic matter in the terrestrial low-maturity shale. The symbiotic relationship between the minerals and the organic matter led to a decrease in the specific surface area and pore volume of the terrestrial low-maturity shale.

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