International Archives of the Photogrammetry, Remote Sensing 
  
    
    
  
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Figure 6. Stream drainage pattern of the study area 
  
  
  
2.4 Vegetation anomalies 
Figure 7 shows extracted vegetation density using the 
Normalized Vegetation Difference Index (NDVI) method in 
Idrisi (Idrisi, 1997). 
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Figure 7. Vegetation anomalies with overlaid 
water bodies 
Vegetation makes geological interpretation difficult since it 
camouflages the land. Nevertheless, it gives us some important 
information about geological structures. For instance, vegetation 
types and density develop depending on geological structures. 
Thus, vegetation patterns are used as clues. Vegetation cannot 
grow in basalt, salt, or marble areas. This information is used for 
petrographic interpretation (Drury 2001; Pandey, 1987; Prost, 
1994; Ray, 1960). 
Vegetation anomalies can indicate fault lines, drainage patterns, 
and boundaries of foliated rock formations. For instance, the 
clustering of vegetation along valleys, 
vegetation around water bodies, and sudden changes in the 
area's geomorphology give us important information about the 
geological structures of the land surface, particularly about faults 
(Drury, 2001; Pandey, 1987; Prost, 1994; Ray, 1960). 
the appearance of 
and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004 
3. ANALYSIS OF UNDERLYING ROCKS IN IMAGERY 
Topography and geomorphology are controlled by geological 
structures and by erosional characteristics of the underlying 
rocks. Rocks can be recognized by the textural expressions of 
the surface in imagery. 
3.1 Carbonate rocks 
In humid environments, the dissolving and collapsing of 
carbonate rocks produce karst topography, which is readily 
recognized by a distinctive pitted surface. Faulting and stream 
erosion may obscure the expression of karst topography. 
3.2 Clastic sedimentary rocks 
The study area is most probably formed from clastic sedimentary 
rocks, primarily sandstones and shales. This is recognized from 
stratification that forms asymmetric ridges, called cuestas and 
hogbacks, where the rocks are dipping. Flat-lying clastic rocks 
form mesas, terraces, and associated erosional scarps. The 
absence of karst topography generally distinguishes clastic 
terrain from carbonate terrain in humid regions. 
3.3 Volcanic rocks 
Volcanic rocks form irregular flows associated with cinder cones 
or eroded volcanic necks. Because of erosion and deformation, 
older volcanic terrains lack these distinctive features. These 
kinds of volcanic rocks cannot be seen in our study area since 
our study area has a regular homogeneous dendritic stream 
drainage pattern that indicates sedimentary rocks. 
3.4 Alluvial and coastal rocks 
This category shows low relief characteristics, a uniform bright 
signature of heavily vegetated floodplains, and dark signatures 
of calm water in meandering streams. However, our study area 
reveals slight lineaments and dendritic drainage anomalies of a 
sedimentary geological structure. 
3.5 Melange rocks 
Melange refers to rocks formed in subduction zones as a mixture 
of clastic sediments and oceanic crustal and mantle rocks. Rock 
fragments of a wide range of sizes, up to kilometers in length, 
are enclosed in a matrix of clay. Erosion of these rocks produces 
an irregular, rounded terrain with unsystematic drainage 
patterns. Stratification and individual rock fragments cannot be 
seen in our image because of the scale. 
3.6 Metamorphic rocks 
When sedimentary rocks have been metamorphosed to slate, 
quartzite and schist, metamorphic rocks occur. The original 
stratification is not recognizable in our study image. Strongly 
dissected metamorphic terrain has high relief and angular ridges 
that distinguish it from the low relief and rounded appearance 0 
melange terrain. Foliation trends are not discernible in our study 
image. Also, crystallization that indicates metomorphizm cannot 
be seen in our image. 
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