used Landsat 7 images and applied several
data enhancement techniques using Univariate and
Multivariate statistics. He used Minimum Noise Fraction
(MNF) and Principal Component Analysis (PCA) and then
supervised classification was used to test their effectiveness
and to establish differences between different deposits and
detect the Pliocene clay deposits.
Van der Meer (1999)
explained the reflectance spectra for three groups of the clay
minerals (
Fig. 2
). The spectrum of montmorillonite is typical
for water – rich mineral, showing strong absorption bands
near 1.4 and 1.9
l
m, and an additional band near 2.2
l
m.
Absorption features of illites are generally broader and less
well defined where it shows broad water absorption features
near 1.4 and 1.9
l
m, and additional Al-hydroxyl features at
2.2, 2.3 and 2.4
l
m. Illite and muscovite have absorption
bands near 2.35 and 2.45
l
m, which are lacking in the mont-
morillonite spectrum. Kaolinite has well-known double
absorption near 2.2
l
m, and an additional hydroxyl feature
at 1.4
l
m