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Geology · 200 Level
This is the complete lecture note for GEY 210 Introduction to Structural Geology, prepared for Geology students at 200 Level. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS GEY 210: Introduction to Structural Geology and Geological Map Interpretation (2 Units C: LH 15; PH 45) Course Code: GEY 210 Course Title: Introduction to Structural Geology and Geological Map Interpretation Course Unit: 2 Units C Series 1: Fundamental Geological Structures – Folds, Faults, Foliations, and Joints Series 2: Contours, Contouring, and Topographic Map Reading Series 3: Preparation and Interpretation of Base Maps Series 4: Geological Map Interpretation – Folds, Faults, and Unconformities Series 5: Recognition of Igneous Intrusions and Structural Features on Maps Series 1 Fundamental Geological Structures – Folds, Faults, Foliations, and Joints • Part 1.1: Folds and their characteristics • 1.1.1 Types of folds • 1.1.2 Recognition of folds in the field and on maps • Part 1.2: Faults and related structures • 1.2.1 Types of faults • 1.2.2 Determination of fault throw from maps • Part 1.3: Foliations and joints • 1.3.1 Nature and types of foliations • 1.3.2 Classification and significance of joints
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Introduction Geological structures such as folds, faults, foliations, and joints are among the most fundamental features studied in structural geology. They record the deformation history of rocks and provide insights into tectonic processes that have shaped the Earth’s crust. Recognising and interpreting these structures is essential for geologists, particularly when preparing and analysing geological maps. The aim of this Series is to introduce you to the basic types and characteristics of folds, faults, foliations, and joints, and to equip you with the skills needed to recognise and interpret them both in the field and on maps. We shall commence this Series by examining folds, their types, and how they can be recognised in the field and on maps. Next, we will move on to faults, considering their types and how to determine fault throw from maps. Finally, we will conclude with foliations and joints, exploring their nature, classification, and geological significance. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1 define folds and classify their main types, • SLO 1.2 demonstrate how folds can be recognised in the field and on maps, • SLO 1.3 describe different types of faults and explain their characteristics, • SLO 1.4 apply methods to determine the throw of faults from geological maps, • SLO 1.5 explain the nature and types of foliations in rocks, and • SLO 1.6 classify joints and evaluate their geological significance. 1.1 Folds And Their Characteristics 1.1.1 Types of folds A fold is a bend or curve in rock layers that results from stress, usually compression, acting on the Earth’s crust. Folds occur when originally flat strata are deformed into wave-like structures. They are important because they reveal past tectonic forces and can influence the distribution of natural resources such as oil, gas, and minerals. Folds are classified into several types based on their geometry: • Anticline: An upward arching fold with the oldest rocks at the core. • Syncline: A downward trough-like fold with the youngest rocks at the core. • Monocline: A step-like fold where strata dip in one direction. • Recumbent fold: A fold with limbs nearly horizontal due to intense deformation.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Fill in the blank: An upward arching fold with the oldest rocks at the core is called an ______. Figure 1.1 Types of folds 1.1.2 Recognition of folds in the field and on maps Recognising folds involves observing the orientation of rock layers in the field and interpreting their patterns on geological maps. In the field, folds can be identified by curved bedding planes, repetition of strata, and changes in dip direction. On maps, folds are recognised by the arrangement of outcrop patterns: • Anticlines show outward-dipping strata with older rocks at the centre. • Synclines show inward-dipping strata with younger rocks at the centre. • Axial traces, which mark the hinge line of folds, often appear as curved lines on maps. Fill in the blank: On a geological map, a syncline is recognised by strata dipping ______ the fold axis. Plate 1.2 Recognition of folds on geological maps
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Pilot questions 1.1 1. Define a fold and explain how it forms. 2. Distinguish between anticline and syncline. 3. What is a monocline and how does it differ from other folds? 4. How can folds be recognised in the field? 5. What features on a geological map indicate the presence of a fold? 1.2 Faults And Related Structures 1.2.1 Types of faults A fault is a fracture or zone of weakness in the Earth’s crust along which movement has occurred. Faults are important because they record tectonic stresses and can influence landscape development, groundwater flow, and the occurrence of earthquakes. Faults are classified based on the relative movement of rock blocks:
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS • Normal fault: Formed when the hanging wall moves downward relative to the footwall due to tensional forces. • Reverse fault: Formed when the hanging wall moves upward relative to the footwall due to compressional forces. • Thrust fault: A low-angle reverse fault where the hanging wall is pushed over the footwall. • Strike-slip fault: Movement is horizontal, with blocks sliding past each other. These can be right-lateral or left-lateral depending on the direction of displacement. Fill in the blank: A fault where the hanging wall moves downward relative to the footwall is called a ______ fault. Figure 1.3 Types of faults 1.2.2 Determination of fault throw from maps Fault throw refers to the vertical displacement between the hanging wall and footwall across a fault. Determining fault throw from geological maps involves measuring the vertical separation of stratigraphic units displaced by the fault. On maps, faults are represented by lines that cut across rock units. By comparing the relative positions of the same rock layers on either side of the fault, geologists can calculate the amount of displacement. For example, if a limestone bed is offset vertically by 50 metres, the fault throw is 50 metres.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Fill in the blank: The vertical displacement between the hanging wall and footwall across a fault is known as the fault ______. Plate 1.4 Determination of fault throw from geological maps Pilot questions 1.2 1. Define a fault and explain its geological significance. 2. Distinguish between normal and reverse faults. 3. What is the difference between a thrust fault and a reverse fault? 4. How can strike-slip faults be recognised? 5. What is fault throw and how is it determined from maps?
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1.3 Foliations And Joints 1.3.1 Nature and types of foliations Foliation is the planar arrangement of mineral grains or structural features within a rock, often resulting from deformation and metamorphism. It reflects the alignment of minerals under directed pressure and is a key indicator of tectonic processes. Types of foliations include: • Slaty cleavage: Fine-grained foliation typical of slate, where rocks split easily into thin sheets. • Schistosity: Coarser foliation in schist, marked by visible alignment of platy minerals such as mica. • Gneissic banding: Alternating light and dark mineral bands in gneiss, reflecting segregation of mineral types. Foliation is significant because it records the stress history of rocks and influences their mechanical behaviour. Fill in the blank: Alternating light and dark mineral bands in gneiss are referred to as ______ banding. Figure 1.5 Types of foliations
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