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TERTIARY SYSTEM - PLIOCENE SERIES - Mounds Gravel (Lafayette Formation) - ferruginous, chert gravel, max of 60 ft. EOCENE SERIES - Wilcox Group - includes Holly Springs Formation - x - bedded sandstone, clay and gravel, max of 1200 ft.; Ackerman Formation - clay with lens of sand and gravel, max of 100ft. PALEOCENE SERIES - Midway Group - includes Porters Creek Clay - bentonitic clay, max of 200 ft.; Clayton Formation - marl, fossiliferous, calcareous, limonitic, glauconitic sand and clay, max of 20 ft.,
State Missouri
Geologic age Phanerozoic | Cenozoic | Tertiary | Paleocene Eocene(?) Oligocene(?) Miocene(?) Pliocene-Early(?) Pliocene-Middle(?) Pliocene-Late
Primary rock type sandstone
Secondary rock type clay or mud
Other rock types gravel; sand
Lithologic constituents
Unconsolidated > Coarse-detrital > Sand (Bed)
Unconsolidated > Fine-detrital > Clay (Bed)
Unconsolidated > Coarse-detrital > Gravel (Bed)
Unconsolidated > Marl (Bed)marl refers to loosley consolidated calcareous clays, silts and sands containing glauconite
Unconsolidated > Coarse-detrital > Sand (Lense)
Map references
Middendorf, M. A., and others, 2003, Geologic Map of Missouri: Missouri Geological Survey. Scale 1:500K
Unit references
Howe, W. B. and Koenig, 1961, The Stratigraphic Succession in Missouri: Missouri Geological Survey and Water Resources, Vol XL. 2nd Series.
Counties Dunklin - Scott - Stoddard