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CLAY MINERALOGY OF SEDIMENTS IN FRESHWATER MARSH ENVIRONMENTS OF THE MISSISSIPPI RIVER Aparicio, Patricia 1 and Ferrell, Ray E. 2. 1 Departamento de Cristalografía, Mineralogía y Q. Agrícola. Universidad de Seville, Spain. e-mail:patric@cica.es
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CLAY MINERALOGY OF SEDIMENTS IN FRESHWATER MARSH ENVIRONMENTS OF THE MISSISSIPPI RIVERAparicio, Patricia1 and Ferrell, Ray E.2 1 Departamento de Cristalografía, Mineralogía y Q. Agrícola. Universidad de Seville, Spain. e-mail:patric@cica.es 2 Department of Geology and Geophysics. Louisiana State University, Baton Rouge, LA 70803-4101, USA. e-mail: rferrell@lsu.edu
The clay mineral composition of sediments collected from the freshwater marsh in the area of Lake Des Allemands near New Orleans (Louisiana, USA) from a depth of 200 to 300 cm is complex because of the variety of materials derived from the drainage basin and postdepositional alteration.
MATERIALS • Samples from the freshwater marsh in the area of Lake Des Allemands near New Orleans (Louisiana, USA) from a depth between 200-206cm and 290-300cm. • The dark gray samples belong to the Kenner-Allemands soil association. They are typical of the moderately alkaline, fluid clays occurring beneath slightly acid mucks in freshwater marsh environments of the Mississippi River Deltaic Plain.
Sampling Kenner - Des Allemands Association
Kenner - Allemands Association ..moderately alkaline, fluid clays overlain by acid mucks...
METHOLOGY Sample normal settling by centrifugation <2µ fraction <0.2µ fraction K-saturation Mg-saturation air-dried glycerol-dried air-dried EG-solvation XRD-patterns EG-solvation Heat-treatment at 300°C and 550°C 2q correction 1st qualitative result Layer type determination
METHOLOGY 1st qualitative result Layer type determination profile-fitting of Mg-EG patterns Mixed-layered clay mineral identification according to: Moore & Reynolds (1997), Srodon (1984) 2nd qualitative result Mulcalc simulation pattern Clay++ procedure Mulcalc library Assess concordance of experimental and theoretical pattern Qualitative analysis (QR) and Ideal layer percentage of clay minerals Change calculated parameters Bad R2> 0.01 Good R2 ≤ 0.01
9.98 A 16.86 A 3.32 A 4.98 A K-550 12.2 A K-300 9.91 A MgEG 14.5 A 7.2 A MgAD SAMPLE C9, <0.2 micrometers Des Allemands
SAMPLE C9, <2 micrometers Des Allemands 3.34 A 9.98 A 13.9 A 4.99 A Qtz 3.57 A K-550 16.8 A K-300 MgEG 15.34 A MgAD
Des Allemands Mg- saturated Fine Clay Residual Smoothed composite Individual peaks 23 28 Two theta (Cu)
Des Allemands Coarse Clay Residual Individual peaks Smoothed composite 23 28 Two theta (Cu)
actual XRD simulation 9 14 19 24 29 5 Two theta (Cu) “FIT” Mg-saturated Fine Clay (C9)
“FIT” K-saturated Fine Clay (C9) actual XRD simulation 5 9 14 19 24 29 Two theta (Cu)
SUMMARY • The reported differences in the clay assemblages call attention to the complex mineralogy of modern sediments and soils. • The various minerals are all potentially present considering the alteration that may be occurring in the present-day environment and the variability of source materials contributed by the Mississippi River and its tributaries. • Differences in the quantities of vermiculite-like materials in the coarse and fine fractions of samples are ones that could be attributed to hydroxy-interlayer formation by diagenesis and crystallite growth.