Developmental characteristics and geological significance of the bentonite in the Upper Ordovician Wufeng - Lower Silurian Longmaxi Formation in eastern Sichuan Basin, SW China
WANG Yuman,LI Xinjing,WANG Hao,JIANG Shan,CHEN Bo,MA Jie,DAI Bing
Table 3 Main geological characteristics of the Longmaxi Formation bentonite-rich members outcropped on sections and encountered in wells in the Eastern Sichuan Basin and adjacent areas.
Section/well Thickness/m GR/cps Lithology
③ ④ ⑤ ③ ④ ⑤ ③ ④
Datianba
section in
Xiushan		 1.20 1.02 0.10 262-297 220-260 216-220 Siliceous shale, containing
3 bentonite beds 0.5 to
1.0 cm thick each		 Siliceous shale, containing
2 bentonite beds, 1 to
3 cm thick each
Hongyanxi
section in
Longshan		 Absent 1.00 0.10-0.12 308-380 235 Absent Carbon-bearing siliceous shale, containing 2 bentonite beds,
2 to 3 cm thick each
Sanhu section
in Laifeng		 0.21 Doesn’t
crop out		 Doesn’t
crop out		 324-353 Carbonaceous shale intercalated with bentonite Doesn’t crop out
Guanwu
section
in Hefeng		 Absent 1.10 0.10 144-157 308 Absent Thin-bedded argillaceous and siliceous mixed shale intercalated with 8 bentonite beds 2
to 3 cm thick each
Well HY1 Absent 1.20 0.10 194-234 220 Absent Carbonaceous shale intercalated with bentonite
Maoba section
in Lichuan		 0.15 Vegetation covered 0.10 198-218 Carbonaceous shale, containing 4 bentonite beds 0.5 to
2.0 cm each		 Vegetation covered
Well LY1 0.15-
0.20		 1.30 0.10 210-222 204-259 223 Carbonaceous shale intercalated with bentonite Carbonaceous shale intercalated with bentonite
Bailu section
in Wuxi		 0.30 1.10 0.05-0.10 281-282 252-285 253 Moderate-bedded siliceous shale intercalated with
bentonite		 Carbonaceous and siliceous shale intercalated with
bentonite
Bayu section
in Daozhen		 0.90 Not
observed		 0.07 284-338 226-238 Moderate-bedded siliceous shale, containing 4 bentonite beds 1cm thick each Not observed
Huangcao
section in
Wulong		 1.10 Not outcropped Not outcropped 266-455 Thin-bedded siliceous shale and carbonaceous shale, containing 5 bentonite beds 0.5
to 2.0 cm each		 Doesn’t crop out