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CLAY MINERALOGY OF SEDIMENTS IN FRESHWATER MARSH ENVIRONMENTS
OF THE MISSISSIPPI RIVER
Aparicio, Patricia1 and Ferrell, Ray E.2
1 Departamento de Cristalografía, Mineralogía y Q. Agrícola. Universidad de Seville, Spain.
e-mail:[email protected] Department of Geology and Geophysics. Louisiana
State University, Baton Rouge, LA 70803-4101, USA. e-mail: [email protected]
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...
METHOLOGYSample
<2µ fraction <0.2µ fraction
normal settling by centrifugation
K-saturation
air-dried
glycerol-dried
EG-solvation
air-dried
EG-solvationHeat-treatment
at 300°C and 550°C
XRD-patterns
2 correction
Layer type determination 1st qualitative result
Mg-saturation
METHOLOGYLayer type determination
1st qualitative result
profile-fitting of Mg-EG patterns
Mixed-layered clay mineral identification according to: Moore & Reynolds (1997), Srodon (1984)
Mulcalc simulation pattern
Mulcalc libraryClay++ procedure
2nd qualitative result
Qualitative analysis (QR) and
Ideal layer percentage of clay minerals
BadR2> 0.01
Assess concordance of experimental and theoretical pattern
Change calculated parameters GoodR2 ≤ 0.01
SAMPLE C9, <0.2 micrometers
Des Allemands
MgAD
K-550
K-300
MgEG
3.32 A4.98 A
9.98 A
7.2 A
14.5 A
16.86 A
12.2 A
9.91 A
K-550
K-300
3.34 A
MgAD
MgEG
13.9 A
9.98 A
4.99 A Qtz 3.57 A
15.34 A
16.8 A
SAMPLE C9, <2 micrometers
Des Allemands
Des Allemands Mg- saturated Fine Clay
23 28
Residual
Smoothed composite
Individual peaks
Two theta (Cu)
Des Allemands Coarse Clay
23 28
Residual
Smoothed composite
Individual
peaks
Two theta (Cu)
“FIT” Mg-saturated Fine Clay (C9)
0
1000
2000
3000
4000
5000
6000
simulation
actual XRD
5 29Two theta (Cu)
9 14 19 24
0
500
1000
1500
2000
2500
3000
“FIT” K-saturated Fine Clay (C9)
5 29Two theta (Cu)
9 14 19 24
simulation
actual XRD
Mg-saturated finer clay
0,0
10,0
20,0
30,0
40,0
50,0
C1 (200-206 cm)
C6 (250-270 cm)
C7 (270-280 cm)
C8 (280-290 cm)
C9 (290-300 cm)
RESULTS - Simulated minerals
K-saturated finer clay
0,0
10,0
20,0
30,0
40,0
50,0C1 (200-206 cm)
C6 (250-270 cm)
C7 (270-280 cm)
C8 (280-290 cm)
C9 (290-300 cm)
RESULTS - Simulated minerals
K-saturated <2µm
0%
20%
40%
60%
80%
100%
C1 C2 C3 C5 C6 C8 C9
Q
V
Ch
Sm
I
K
RESULTS-Ideal layersMg-saturated <2µm
0%
20%
40%
60%
80%
100%
C1 C2 C3 C5 C6 C8 C9
Q
V
Ch
Sm
I
K
Mg-saturated coarse clay
0,0
5,0
10,0
15,0
20,0
25,0
C1 (200-206 cm)
C6 (250-270 cm)
C7 (270-280 cm)
C8 (280-290 cm)
C9 (290-300 cm)
RESULTS - Simulated minerals
K-saturated coarse clay
0,05,0
10,015,020,025,030,0
Chlorit
eIlli
te
Kaolin
ite
R0 illi
te (0
,5)/s
mec
tite
R0 sm
ectite
(0,7
)/illit
e
R0 sm
ectite
(0,9
)/illit
e
R1 sm
ectite
(0,7
)/illit
e
R1 sm
ectite
(0,9
)/illit
e
R0 ve
rmicu
lite (0
,8)/i
llite
R1 illi
te (0
,6)/v
ermicu
lite
Quartz
Smecti
te
Verm
iculite
C1 (200-206 cm)
C6 (250-270 cm)
C7 (270-280 cm)
C8 (280-290 cm)
C9 (290-300 cm)
RESULTS - Simulated minerals
Mg-saturated <0.2µm
0%
20%
40%
60%
80%
100%
C1 C6 C7 C8 C9
V
Ch
Sm
I
K
K-saturated <0,2µm
0%
20%
40%
60%
80%
100%
C1 C6 C7 C8 C9
V
Ch
Sm
I
K
RESULTS - Ideal layers
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.