Principle of Geological Reconstruction

Basic Principal of Geological Reconstruction

Geological reconstruction is a process to describe geological phenomenon consisted of topography, geological structure and lithology. Basic principal in geological reconstruction that is having topographical data that can be obtained by topographical survey or DEM data that is available in many sources, geological structure and lithology. Geological structure identification is very important aspect in studying geology. Aspect related to geological structures is landform on surface. Landform classification uses the main principal about morphological formation referring to geological processes either endogenous or exogenous.

**Figure 1.** Geological Reconstruction PrincipalFigure 1. Geological Reconstruction Principal

Analysis of Geological Structure

Geological structure is resulted of tectonic activities in the past time including relative structures that are fault and fold, complex structure that are igneous rocks and more complex structure that is mountainous landscape. Structures in regional scale relate to geological condition and the effects to landscape and the effects to material in surface processes (Harvey, 2012). There are 3 types of geological structure that can be identified in the field that are contact plane of boundary among the rocks, primary structure of structure in developing rocks alongside the formation process and secondary structure formed of the force after formation process in the rocks (Sapiie & Harsolumakso, 2006).
Geological structure like joint, fold, fault, and drainage pattern are evidences of structural landforms that can be an initial indication against deformation. Explanation about deformation can be seen on this post. Material in a ductile layer will raise the fold among rock bed planes because material is not easily broken or is called fold, however once the rock layers are composed of brittle, then will raise cracks separating rocks in two parts namely fault.

**Figure 2.** Types of general fold (Thompson & Turk, 1997)
Figure 2. Types of general fold (Thompson & Turk, 1997)

**Figure 3.** Characteristics of fault blocks (Twiss & Moores, 1992)
Figure 3. Characteristics of fault blocks (Twiss & Moores, 1992)

Identification of geological structural can be conducted through an approach towards one geological aspect namely lineament. Lineament can be an indicator to the existence of joint, fault and fold. Lineament can be the boundary of linear or curvilinear that have relation with fault, joint, line weakness and other geomorphological features. Lineament identification can be conducted through some formed characteristics such as straight drainage, valley, parallel surface depression, vegetation types, elevation and topography change (Hung et al, 2005).

Analysis of Landform and Drainage Pattern

Landform is the composition of earth surface and every physical appearance resulted of natural process that has distinctive shape and can be recognized through terrain properties and characteristic (Bates & Jackson, 1987). Extrinsic and intrinstic factors have role to create and change landforms on earth. Landform is a final result resulted of natural surface interaction with rocks (Gupta, 2018). Landform has connectivity towards structural geomorphology on earth. Landform formed is affected by 3 factors that are structure, process, and time. Structure is a main factor in landform formation because it depends on lithological structure so it can be said as structural landform. Variations of earth surface shapes related to active tectonic structure interacting with geomorphic process and produce topography in a region namely tectonic landorm. Topography has role to show boundary between two landforms. Elements of tectonic landform become be very important in identifying and mapping active tectonic structure such as drainage pattern and lineament.
Drainage patterns resulted of erosion process can represent characteristic of rock types and geological structure in a landscape. Drainage pattern can show the strength of topography composed from various rock materials and soil gradient.

**Figure 4.** Types of drainage patterns (Tarbuck et al, 2013)
Figure 4. Types of drainage patterns (Tarbuck et al, 2013)

Analysis of Lithology

The most simple categorization of rock types or lithology is based on the event or formation process divided into 3 main groups that are igneous rocks, sedimentary rocks and metamorphic rocks. These rock types has gained different formation processes and the igneous rock is earliest formed of the process of cooling and freezing of magma. Sedimentary rock is from sediment of material on earth and in sea and has gained a lot of processes like transportation and erosion. Metamorphic rock is a rock that has gained the change of high pressure and temperature.

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