| Typical basin | Characteristics of shale | Characteristics of mudstone | Chang-7
Member in the
Ordos Basin | Black, micro wavy, flat, lenticular laminated, with square fish scale fossils, deep lake environment, insufficient supply of
terrigenous debris, low deposition rate, seasonal laminae
developed, felsic-clay and organic matter structure, the
aggregate of pyrite, collophane and clay arranged
directionally, the average TOC of 13.81% | Greyish green-greyish black, massive and graded bedding, containing ostracods, bivalves, and plant stems and leaves, pre-delta and shore shallow lake environment or gravity flow, high deposition rate, high silt content, multiple beddings
developed due to transformation of hydrodynamics and benthic organisms, the average TOC of 3.75% | Qingshankou
Formation in the
Songliao Basin | Dark black, clayey shale and silty shale, high clay content,
low quartz content, carbonate mineral content of 8.41%,
high pyrite content (5.3%), TOC of 0.11%-8.76% (with
an average of 3.41%), semi-deep to deep lake facies | Gray-dark gray, silty mudstone, clayey mudstone, low clay content, high content of terrigenous debris, low pyrite content, high siderite content, TOC of 0.39%-4.62% (with an average of 1.98%), shore shallow lake facies and pre-delta facies | Lucaogou
Formation in
Jimsar Sag, the
Junggar Basin | Dark gray-black, dolomitic (limy) shale, horizontal laminar structure, continuous distribution of organic matter along
the beddings, the average TOC of 6.1%, semi-deep
lake to deep lake low-energy environment | Dark gray-light gray, mainly silt-bearing mudstone, massive structure, some with biological disturbance structure, organic matter not observed or weakly oriented, the average TOC of 3.2%, shallow lake to shore shallow lake environment | Shahejie
Formation in
Dongying Sag,
the Bohai
Bay Basin | Black-greyish black, with well-developed laminations, mostly in lamelliform, composed of organic-rich argillaceous laminae and clay laminae, with TOC of 3.8%-6.0%, long-term hypoxic deep-water environment, salinity, and temperature caused
the persistent density stratification of lake water | Gray-dark gray, uniformly massive, macroscopically unbedded, mixture of felsic minerals, clay minerals and cryptocrystalline carbonate minerals, TOC of 1.3%-2.0%, the water becomes lighter and shallower without stratification, circulating oxygen- weak reducing environment with enhanced terrestrial input | Second member of
Kongdian Forma-
tion, Cangdong
Sag, the Bohai
Bay Basin | Thin section observation shows that the laminae of various components such as argillaceous-calcareous-felsic-analcime- organic matter are frequently superimposed, and the laminae are all straight and fine, which are formed by seasonal variations, TOC of 2.32%-9.23% (with an average of 4.87%) | Mainly gray and dark gray thick layers, uniformly massive structure; felsic particles, micrite or microcrystalline carbonate minerals, clay minerals, etc. can be observed, which are
relatively uniform and irregularly mixed in thin sections.
TOC of 0.14%-8.41% (with an average of 3.07%) |
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