589
Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986
Application of remote sensing in the field of experimental tectonics
J. Dehandschutter
Royal Museum of Central Africa, Tervuren, Belgium
ABSTRACT : Geological documents of often display systematic arrangements of linear structural elements. The
basic geometric configuration is a rhomb divided by its short diagonal. Various classes of geological structures
repeatedly occupy the same position inside the basic rhomb. Examples are seen on remote sensing documents of
both brittle and ductile tectonic domains in the Andes and in Central Africa. Photoelastic.stress analyses
implemented on homogeneous plates and on others cut by vertical discontinuities the elastic properties of which
are different from those in the interior of the plate, suggest that several factors determine the geometric
position of lineaments and structures. The rhombic pattern of intersecting discontinuities is one factor of
lower order. Directions of vertical faulting inside the blocks and oblique-slip rotational strain inside the
lineaments are predicted.
1 INTRODUCTION
The results presented here stem from conventional
analyses of Landsat MSS imagery. Emphasis was put on
the possible geological and economic significance of
lineaments (Dehandschutter & Lavreau 1985). The latter
are defined according to Hobbs' classic definition
(Hobbs 1911).
Frequency diagrams issued by students of linears and
lineaments from various parts of the world often show
a remarkable similarity in the mutual angular relation
ships between several groups of lineaments and in their
trerids. Two sets generally occupy sub-latitudinal po
sitions, while two others strike in a sub-meridional
sense. A regional representative example selected from
a survey over Shaba (Zaire) and northern Zambia is
shown in fig. la. Figure lb depicts the very compa
rable situation in the Eastern Cordillera of Colombia,
South America. Dividing each of the regions in dis
tinct areas results in diagrams revealing a strong
positive correlation between one meridional and one
latitudinal set. We may separate one eastern conjugate
pair from a western one (fig.la,c).On the scale of the
area does in most cases one pair of sets largely sub
due the other pair.
In plan view is this basic geometrical configura
tion translated into the picture of a rhomb divided
by its short diagonal (fig. Id). There is only limited
three-dimensional control on the attitudes of the
sensed structures and lineaments. It is tentatively
assumed that the straight lineaments which are inde
pendent of topography, extent sub-vertically. The
basic rhomb offers an hypothetical framework in which
some large geological structures, i.e. rifts, plateau-
uplifts, subsiding areas, oblique-slip sedimentary
basins, fit in some characteristic spatial relation
ship. This relationship is recognised on various con
tinents and underlying causative processes might have
been operative during widely separated orogenic cycles.
2 SPATIAL RELATIONSHIPS
Geological structures can, for all practical purposes,
be subdivided in three distinct classes according to
the particular stress regime that prevails at the time
of creation of the structure. It is furthermore con
venient to limit the discussion to the major groups
of structures, i.e. structures respectively related
to vertical or horizontal compression taking along
the third class, oblique compression, within any one
of the former major classes.
CENTRAL AFRICA N N COLOMBIA
Figure 1. Representative examples of frequency dia
grams (A,B,C); basic rhombic configuration (D).
2.1 Structures related to vertical compression
Rifts, normal faults, dilatancy
The conjugate couple of (sub)r”eridional-(sub)latitudi
nal lineaments appears clearly in downfaulted areas
and/or areas under extensional strain.
Examples abound in the Central- and East-African
rift belt (fig. 2a). The long axis of Lake Tanganyika
is W from north close to and influenced by the NW-SE
Precambrian Ubende trend. Both sets of lineaments
constitute a western conjugate pair. Close to the
NE-SW Precambrian Kibara lineament trend, the long
axis projects east from north : the eastern couple.
Observations of this kind are made on the Karroo
rifts of Zambia (Luangwa, where the well known
