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Nigeria's free digital learning hub. Videos, lecture notes, practice questions and leaderboards aligned with CCMAS, NBTE, NCCE, WAEC, NECO, IJMB and JAMB curricula.
Geology · 300 Level
This is the complete lecture note for GEY 305 Fundamentals of Sedimentary Flows and Facies, prepared for Geology students at 300 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 Course code: GEY 305 Course title: Fundamentals of Sedimentary Flows and Facies. Units: 2 Units List of Series Series 1: Fundamentals of Sedimentary Flows and Facies Series 2: Depositional Environments: Marine and Continental Systems Series 3: Classification and Analysis of Sedimentary Settings Series 4: Paleoenvironmental Criteria and Sedimentation Controls Series 5: Stratigraphy and Evolution of African Sedimentary Basins 1.1 Properties of Sedimentary Flows - 1.1.1 Definition and types of flows (e.g., laminar, turbulent) - 1.1.2 Flow dynamics and energy conditions - 1.1.3 Bed forms and their relationship to flow properties 1.2 Sedimentary Facies and Walther’s Law - 1.2.1 Definition of facies and their characteristics - 1.2.2 Walther’s Law of Facies: concept and applications - 1.2.3 Facies models in depositional environments 1.3 Controls on Sedimentation - 1.3.1 Physical controls (climate, tectonics, relief) - 1.3.2 Chemical controls (composition, diagenesis) - 1.3.3 Biological controls (organisms, bioturbation) 1.4 Significance of Flows and Facies in Basin Analysis - 1.4.1 Facies interpretation in stratigraphy - 1.4.2 Application to African sedimentary basins
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS - 1.4.3 Economic implications (resources linked to facies) Series 1: Introduction to Sedimentary Flows and Facies Introduction Sedimentary rocks tell the story of Earth’s past, recording the movement of water, wind, and ice across landscapes and oceans. To interpret these stories, geologists must first understand how sedimentary flows (movements of fluids such as water or air that transport sediments) shape the ground and how facies (distinct bodies of rock with specific characteristics reflecting their depositional environment) preserve evidence of these processes. This Series sets the foundation for the course by equipping you with the essential concepts needed to recognise and analyse the building blocks of sedimentary environments. The aim of this Series is to introduce you to the fundamental properties of sedimentary flows and facies, and to enable you to evaluate their significance in interpreting depositional environments and basin evolution. We shall commence this Series by examining the properties of sedimentary flows, including their dynamics and the bed forms they produce. Next, we will explore the concept of sedimentary facies and Walther’s Law, highlighting how facies relationships provide insights into depositional settings. Following that, we will consider the physical, chemical, and biological controls that influence sedimentation patterns. Finally, we will wrap up by discussing the broader significance of flows and facies in basin analysis, with particular reference to African sedimentary basins and their economic implications. Series Learning Outcomes Upon completing this Series, you should be able to: - SLO 2.1 define the different types of sedimentary flows and describe their key properties, - SLO 2.2 explain how flow dynamics influence the formation of bed forms, - SLO 2.3 define sedimentary facies and illustrate the principles of Walther’s Law, - SLO 2.4 analyse the role of physical, chemical, and biological controls on sedimentation, - SLO 2.5 evaluate the significance of flows and facies in stratigraphic interpretation and basin analysis.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1.1 Properties of Sedimentary Flows Sedimentary flows are the driving forces behind the transport and deposition of sediments. By studying their properties, geologists can interpret past environments and predict how sediments accumulate in basins. In this Part, we shall explore the types of flows, their dynamics, and the bed forms they produce. 1.1.1 Definition and types of flows A sedimentary flow is the movement of a fluid such as water, air, or ice that carries and deposits sediment particles. These flows vary in energy, velocity, and behaviour, which in turn determine the nature of the deposits they create. The two primary types are: - Laminar flow: a flow in which fluid particles move in parallel layers with minimal mixing. It is typical of low-energy environments such as slow-moving water. - Turbulent flow: a flow characterised by chaotic mixing and eddies, common in rivers, deltas, and storm-driven marine settings. Fill in the blank: A flow in which fluid particles move in parallel layers with minimal mixing is called .
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.1: Comparison of laminar and turbulent flows 1.1.2 Flow dynamics and energy conditions The dynamics of flow refer to how velocity, depth, and slope interact to control sediment transport. High-energy flows can carry larger particles such as gravel, while low-energy flows deposit finer materials like silt and clay. Energy conditions are crucial in determining depositional environments. For example, braided rivers with high energy deposit coarse sediments, while meandering rivers with lower energy deposit finer sediments. Fill in the blank: High-energy flows are capable of transporting ______ particles, while low-energy flows deposit finer materials.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Sediment Deposition vs. Flow Energy Flow Level Description of Flow Sediment Size & Rock Examples Very Low Still or Slack Water (e.g., deep ocean, lakes, lagoons) Clay, Silt (Mudstone, Shale) Low–Medium Gentle Currents (e.g., slow-moving rivers, continental shelves) Sand (Sandstone) Medium–High Strong Currents (e.g., mountain streams, floods, surf zones) Gravel, Pebbles (Conglomerate) Very High Rapid or Torrential Flow (e.g., flash floods, tsunamis, glacial outwash) Cobbles, Boulders (Massive Breccia) Table 1.1: Relationship between flow energy and sediment size 1.1.3 Bed forms and their relationship to flow properties Bed forms are structures created on the sediment surface by flowing water or wind. They provide clues about flow velocity and direction. Common bed forms include: - Ripples: small undulations formed under gentle currents. - Dunes: larger structures formed under stronger currents. - Plane beds: flat surfaces formed under very high or very low flow velocities. These bed forms are preserved in sedimentary rocks and serve as indicators of past flow conditions. Fill in the blank: Small undulations formed under gentle currents are known as .
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Plate 1.1: Examples of bed forms in a river environment Pilot questions 1.1 1. Which type of flow is characterised by chaotic mixing and eddies? 2. What sediment size is typically deposited in low-energy environments? 3. Name two common bed forms created by flowing water. 4. What does the presence of ripples in a rock sequence indicate about past flow conditions? 5. How do braided rivers differ from meandering rivers in terms of energy and sediment deposition? 1.2 Sedimentary Facies and Walther’s Law
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Sedimentary facies are fundamental to interpreting depositional environments. They provide a window into the processes that shaped ancient landscapes and basins. In this Part, we shall define facies, examine Walther’s Law, and explore how facies models are applied in geological studies. 1.2.1 Definition of facies and their characteristics A sedimentary facies is a body of rock with specific characteristics that reflect the conditions of deposition. These characteristics may include grain size, sedimentary structures, fossil content, and mineral composition. Facies are used to reconstruct past environments and to correlate rock units across regions. Facies can be classified into different types such as lithofacies (based on rock properties), biofacies (based on fossil content), and chronofacies (based on time of deposition). Each type provides unique insights into depositional history. Fill in the blank: A body of rock with specific characteristics that reflect the conditions of deposition is called a .
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