Statistical Analysis of Dispersion and Geochemical Patterns of Sedimentary System ...
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Table 1 Average grain-size parameters (in 1» of the sediment types for the northern South
China Sea
Type Description
Mean size Standard Skewness Sample
deviation
size
Il
Silt and clay with very fine sand
7.95
2.12
-0.35
66
I2
Silt and clay with fine sand
7.49
1.96
-0.30
134
13
Silt and clay with medium and
7.17
2.24
-0.36
96
fine sand
III
Poorly sorted clayey fine sand
5.36
2.80
0.40
174
II2
Poorly sorted medium-fine sand
4.20
2.86
-0.71
141
with fine gravel and clay
lIIl
Gravel-bearing coarse-medium
1.91
1.85
1.36
66
sand, very well sorted
III2
Gravel-bearing sand and clay,
3.14
3.79
0.65
46
very poorly sorted
~
~
~
Type 1-1
Type 1-2
Type 1-3
30
30
30
20
20
20
10
10
10
Type 11-1
Type 11-2
30
30
20
20
10
10
40
30
30
20
20
10
10
Fig.3 Histograms of grain-size distributions of sediment types
ICD=O.5 for the 7 clusters given by the logratio procedure; this means that on average the within-cluster distance is half of the inter-cluster distance. For the cluster analysis of raw data, however, the best classification yields 22 clusters with
ICD=O.71, or the classification of 9 clusters with ICD=O.74. The logratio procedure improved the classification remarkably.