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Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 
Regional geologic mapping of digitally enhanced Landsat imagery 
in the southcentral Alborz mountains of northern Iran 
Sima Bagheri 
New Jersey Institute of Technology, Newark, USA 
Ralph W.Kiefer 
University of Wisconsin-Madison, USA 
ABSTRACT: This study evaluates the utility of using Landsat MSS data in regional geologic mapping of linea 
ments. Both conventional image interpretation techniques and digital enhancement techniques were utilized. 
The presence and orientation of lineaments can have great structural significance and a correlation may exist 
between them and zones of weakness characterized by seismic activity and mineral concentrations. The 
lineaments detected on computer-enhanced imagery of the study area exhibited definite trends providing a 
regional view of the geological "grain" of the area. When lineament alignments located by Landsat image 
analysis were plotted, a correlation was found between lineaments detected on the enhanced scene and 
earthquake epicenters, as well as the mapped location of phosphate deposits of the study area. 
1. INTRODUCTION 
Landsat images are widely used in regional geologic 
studies. They are especially useful for displaying 
extended structural elements such as intrusive 
bodies, domes, folded mountain belts, and fault and 
fracture zones. This study is concerned with the 
utilization of Landsat data for the detection of 
geologic lineaments in the southcentral Alborz 
Mountains of northern Iran. The term "lineament", as 
used here, is defined by Siegal and Gillespie (1980), 
as follows: 
Lineament: a two-dimensional geomorphological term 
referring to a mappable, simple or composite 
linear feature of a surface, whose parts are 
aligned in a rectilinear or slightly curvilinear 
relationship and which differs distinctly from the 
patterns of adjacent features and presumably 
reflects a subsurface phenomenon. 
The study area is located in the southcentral part of 
the Alborz Mountains of northern Iran (Figure 1). 
The region is one of high to moderate relief which 
consists of marine sedimentary rocks of Paleozoic and 
Mesozoic ages and volcanic rocks of Tertiary age. 
The primary objective of this research was to 
delineate geological structures by means of digital 
image processing techniques, since the presence and 
orientation of these features may have great 
structural significance and correlation may exist 
between them and seismic activities, as well as 
mineral concentrations. 
The data used here include both film products and 
digital data of four Landsat MSS bands imaged in 
November 1976. The scene is characterized by a 
relatively low sun elevation angle (31°) and a light 
continuous snow cover in the mountainous areas, 
characteristics that are advantageous for mapping and 
interpreting the structural features. A lineament 
map and a rock type classification map were produced 
from the computer enhanced MSS data. These maps were 
compared with an earthquake epicenter map and the 
mapped location of ore deposits (mainly phosphate 
minerals) in order to investigate relationships 
between them. 
2. REGIONAL GEOLOGIC SETTING 
Recent discoveries indicate that the traditional 
concept of Iran as a pair of orogenic belts (the 
Alborz and Zagros Mountains) with a median mass 
between them has been invalid. Nor can central Iran 
be regarded as an eugeosyncline. The only distinct 
ion between the Alborz Mountain and central Iran is 
one of relief and the two areas are structurally and 
stratigraphically very similar (Stocklin, 1968). The 
Bouguer gravity anomaly map conforms with the reg 
ional structural pattern revealing no separation of 
the Alborz as an independent zone from Central Iran. 
The Alborz Mountains are continuation of the Alpine 
type mountains, which are a complex, asymmetric belt 
of folded and faulted rocks. The Alpine orogeny of 
the Iranian ranges is characterized by the absence of 
nappes present in the European Alps which extend over 
a width of 1200 km (Stocklin, 1968). The compressive 
stress of Alpine orogeny results in thrusts and high- 
angle reverse faults in the central Alborz and a wide 
range of fold systems throughout the mountain chain. 
These structural features are surface manifestations 
of underlying faults, joints, folds, lithologic 
contacts or other geologic discontinuities and are 
expressed as lineaments of different dimensions on 
Landsat imagery. An understanding of these features 
and their significance in the regional geologic 
framework is essential in analyzing both earthquake 
prone areas and mineral potential locations of the 
Alborz Mountains. 
Physiographically the range is divided into three 
segments—Western, Central and Eastern Alborz—with 
the central part subdivided into seven lithostruct- 
ural units (Gansser & Huber, 1962). The study area 
is 3500 sq-km in size and is located between Karaj 
River to the west and Damavand volcano to the east 
and includes the following units of the southern 
Central Zone: (1) the Tertiary Central Zone, (2) the 
Southern Paleozoic-Mesozoic Zone and (3) the Southern 
Tertiary Zone. 
3. METHODOLOGY 
Two methods of analysis were utilized, visual image 
interpretation and computer-assisted interpretation.