Relations between clay mineralogy and depositional environment in the Atchafalaya basin and Terrebonne Marsh areas, south-central Louisiana

Conference · Sat Sep 01 04:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:5920220

Stewart, K D ^[1]; Patrick, D M ^[2]

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1. Texaco, Inc., New Orleans, LA (USA)
2. Univ. of Southern Mississippi, Hattiesburg (USA)

The analyses of nearly 200 vibracore samples taken from Holocene sediments in south-central Louisiana revealed strong statistical relations between clay mineral composition and depositional environment and lithology The samples selected for study were representative of the major depositional environments, which are: backswamp, channel fill, crevasse channel, inland swamp, interdistributary bay, lacustrine or lacustrine delta, marsh, and natural levee. The dominant clay minerals from most to least abundant in both the Atchafalaya basin and Terrebonne Marsh areas were: smectite (70%), illite (18%), kaolinite (10%), and chlorite (1%). The higher concentrations of smectite occurred in the inland swamp (86%) and backswamp (83%), and the lower concentrations were found in the crevasse channel (44%) and lacustrine delta (58%). Generally, the percent smectite was inversely proportional to the relative depositional energy of the environment. The percent illite ranged from a low of 8 in the inland swamp to a high of 37 in the crevasse channel. Kaolinite was most abundant in the lacustrine delta (14%), and least abundant in the inland swamp (5%). Chlorite was 2% or less in most environments; however, the crevasse channel exhibited a concentration of 8%. In terms of lithology, the highest concentration of smectite (78%) occurred in deposits classed as clay, and the lowest (46%) occurred in organic-rich clay. Clay and organic-rich clay, respectively, also exhibited the lowest and highest concentrations of both illite and kaolinite. The high smectite content is attributable to the low energy of the clay deposits, while the low concentrations of smectite in both organic-rich and peat material are due to instability of smectite in low pH environments.

• OSTI ID: 5920220
• Report Number(s): CONF-9010204--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Journal Volume: 74:9
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALLUVIAL DEPOSITS
ALUMINIUM COMPOUNDS
ALUMINIUM SILICATES
CENOZOIC ERA
CLAYS
DEPOSITION
DRILL CORES
ENERGY SOURCES
FEDERAL REGION VI
FOSSIL FUELS
FUELS
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
GEOLOGY
ILLITE
KAOLINITE
LITHOLOGY
LOUISIANA
MINERALS
NORTH AMERICA
ORGANIC MATTER
OXYGEN COMPOUNDS
PEAT
PH VALUE
QUATERNARY PERIOD
SEDIMENTARY BASINS
SEDIMENTS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SMECTITE
STRATIGRAPHY
USA