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:patric@cica.es2 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...

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.