Pet-518 Elements Of Geology

Pet-518 Elements of Geology Course content

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Definition, significance and basic disciplines. Earth as a dynamic terrestrial planet: Its shape, composition, surface relief, origin and age. Introduction to minerals, rocks and fossils. Definitions, method of study , description and classification of rock forming minerals and major rock types, rock cycle. Weathering and Soil. Sedimentary rocks and their classification. Basic concept of stratigraphy and sedimentation. Sedimentary environment and stratigraphic sequences. Basic concepts in geodynamics; interior model of earth. lithosphere and plate tectonic. Deformation of rocks: Classification of Fold, Fault and Unconformities. Geological Time Scale and significance of Fossils

Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology Course content

1. An Introduction to Geology 2. Matter and Minerals 3. Earth's Interior 4. Kind of Rocks and Rock Cycle 5. Igneous & Metamorphic rocks 6. Weathering , Mass Wasting and Soil 7. Sedimentary Environments 8. Sedimentary Rocks 9. Principles of Stratigraphy and Sedimentation 10. Crustal Deformation including Plate Tectonics 11. Deformational features of rocks 12. Classification of Fold Fault and Unconformities. 13. Geological Time Scale 14. Fossils and Fossilization 15. Mountain Building and the Evolution of Continents

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University of Karachi

Pet-518 Elements of Geology View of the Planet Earth

• Definition of Geology: •

Geology is classically defined as the study of the Earth.

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Geology is the study of the Earth, the materials of which it is made, the structure of those materials, and the processes acting upon them.

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It also includes the study of the organisms which inhabit our planet.

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A very important part of geology is the study of how Earth’s materials, structures, processes and organisms have changed over time.

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University of Karachi

Pet-518 Elements of Geology Some Discipline of Geology

• Mineralogy - formation, chemical and physical properties, and classification of minerals • Petrology - formation, properties, and classification of rocks • Sedimentology - genesis, transport, and deposition of sediment, and the formation of sedimentary rocks • Structural geology - deformation of earth materials and resulting geologic structures • Tectonics - regional to global-scale deformation and structures resulting from interactions among pieces of the Earth's rigid outer layer, or lithosphere • Geomorphology - processes of landform evolution and landscape development • Hydrogeology - interrelationships of water and geologic materials and processes Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology The two broad areas of the science of geology

• (1) Physical geology, is the study of Earth materials and structures; the processes and forces that act upon them; and how these materials, structures, processes, and forces have changed over time.

• (2) Historical geology, which seeks to understand the origin of Earth and its development through time. The relationship between people and the natural environment is an important focus of geology. This includes natural hazards, resources, and human influences on geologic processes Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology Physical geology

• Earth materials

atoms, chemicals, metals, oil, gas, rocks, minerals, salt, gems, coal, sand, gravel, clay, soil, atmosphere, hydrosphere, organisms, etc. How do Earth materials affect people? building materials, fuels, soil to grow food, salt for food, jewelry, we are made of Earth materials

• Earth processes

earthquakes, volcanic eruptions, floods, continental drift, weather, climate, landslides, subsidence and collapse, tides, geysers, erosion, etc. Any geologic processes recently in the news? How do these processes affect people?

Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology Historical Geology

• How old is the Earth? •

4.5 to 4.6 billion years (4,500,000,000 to 4,600,000,000 years) Determined through radiometric dating (Uranium, Thorium). Using an instrument called a mass spectrometer.

• Multicellular life •

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did not appear until about 1 billion years ago. Before this, 3 billion years ago single celled life only. Hard parts like shells don't appear until 600 million years ago. (Trilobites)

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University of Karachi

Pet-518 Elements of Geology Earth at a Glance

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University of Karachi

Pet-518 Elements of Geology Introduction to Historical Geology

• Historical Geology is the study of changes to Earth and life in time and space.

• I. Time • A. How much time? •

Oldest meteorites and oldest moon rocks are 4.6 old,4,600,000,000 years.

billion years

• Oldest rocks found so far on Earth are zircon grains from a sandstone in western Australia, dated at 4.1 to 4.2 bilion years old. •

Previously, the oldest Earth rocks were 3.96 billion years old, from the Northwest Territories of Canada.

• B. How do we know? • Radioactive materials serve as geologic clocks. • Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology Introduction to Historical Geology

• C. What happened on the Earth during this long period of time? •

Many natural events:

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meteorite impacts volcanic eruptions and lava flows mountain building earthquakes erosion slow movement of continents (plate tectonics) formation and destruction of ocean basins (plate tectonics) – glaciations climatic changes • • • •

All of these natural events are still going on today We see evidence in the rock record that these events have been occurring for a long time. Geologists call this uniformitarianism. The physical laws governing the universe operate uniformly through time.

Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology Introduction to Historical Geology •

James Hutton (1726-1797) believed that

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"the past history of our globe must be explained by what can be seen to be happening now."

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Some events which occurred in the past, and left a record in the rocks, ARE NOT OCCURRING TODAY, or have not occurred in the human lifespan:

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Huge meteorite imapcts Large glacial ice sheets Other events occur so slowly that they are difficult to measure: Plate Tectonics - sea floor spreading, continental drift Erosion of mountain ranges Still other events are short lived but very catastrophic: Volcanic eruptions Earthquakes Floods Mudflows, avalanches, etc (mass wasting) Evidence of all of these events is preserved in the geologic record.

Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology Geologic record

• D. What do you mean by geologic record? • The geologic record consists of rock units, each of which records some event or series of events that occurred in the past.

• What are rocks? – Rocks are defined as aggregates of one or more minerals.

• What are minerals? – – – – –

naturally occurring inorganic solids definite chemical composition characteristic internal crystal structure (arrangement of atoms in lattice)

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University of Karachi

Pet-518 Elements of Geology Course content Geologic record

• E. How do rocks form? • By cooling, hardening, and crystallizing from hot, molten lava – Igneous rocks • By forming from the compaction and cementation of sediments – Terrigenous, clastic or detrital sedimentary rocks • By forming from the precipitation of dissolved chemicals in water – Chemical and biochemical sedimentary rocks

• By forming from accumulated organic matter – Organic sedimentary rocks (coals)

• By the alteration of pre-existing igneous or sedimentary rocks by heat and pressure – Metamorphic rocks

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University of Karachi

Pet-518 Elements of Geology Fundamental principles of Geology

• Most sedimentary rocks occur in the form of layers called beds or strata. • Each layer is the result of the deposition of sediment during some natural event (such as a flood or storm). • A. Steno's Laws Named for Nicholaus Steno • • • • • • •

Principle of Superposition Oldest rocks on the bottom Younger rocks on top Principle of Original Horizontality Sediments are deposited in flat layers Principle of Original Lateral Continuity Sediments are deposited over a large area in a continuous sheet

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University of Karachi

Pet-518 Elements of Geology Other basic principles of Geology

• Principle of intrusive relationships • •

The intrusion is younger than the rocks it cuts.

• Principle of cross-cutting relationships • •

The fault is younger than the rocks it cuts.

• Principle of components or inclusions • • • • • •

Note the irregular erosional surface. This is an unconformity. The clasts (in the bed above the unconformity) are derived from the underlying (older) bed. The gravel clasts are older than the layer which contains them. The layer containing the gravel must be younger than the layer from which the clasts originate.

Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology •

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Principle of Superposition Sometimes papers pile up on my desk for several weeks before I have time to put them away. The oldest papers are at the bottom of the pile, the most recent additions near the top. The lowermost objects must be placed first. Rocks are no different. This is simple idea behind the principle of superposition.

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When we examine a series of undisturbed sedimentary rock layers we assume the rocks at the bottom of the stack are the oldest and the rocks at the top are the youngest (Fig. ).

Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology Principle of Original Horizontality

• Sedimentary rocks are deposited in nearly horizontal layers (beds; Fig. ). If layers are no longer horizontal they must have undergone deformation after formation. The majority of sedimentary rocks are deposited under water. They may be pushed above sea level and tilted during the formation of mountains. These processes expose rocks to weathering and erosion that serves to erase parts of the geologic record as rock units are worn away.

Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology Course content • •

Superposition: A lies below B so A must be the oldest unit. Original horizontality: A, B, and C must have been deposited as horizontal layers. Because they have the same orientation we can probably consider them a discrete group that experienced a similar geologic history

Original horizontality: Because A, B, and C are more steeply tilted than the overlying units they must have been uplifted and tilted early in the history of the region. A, B, and C were subjected to weathering and erosion at Earth's surface. A relatively flat land surface was formed by erosion. A significant time interval may have passed while erosion occurred. This eroded surface is known as an unconformity and is the physical expression of a gap in time. An unconformity occurs when no beds are deposited or when part of the rock record is removed by erosion

Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology •

Course content Superposition: D must have been deposited after C as it overlies B and C. Original horizontality: D was deposited as a horizontal bed. Cross-cutting: D must be younger than B and C because it cuts across the underlying layers.

Original horizontality: D is no longer horizontal so it must have been slightly tilted after formation. This would also have increased the inclination of layers A, B, and C.

Cross-cutting: All layers A through D are cut by the younger igneous pluton. The pluton contains inclusions of layers B and C, further indication that it must have formed subsequent to the deposition of those beds. We have no evidence to tell us whether E formed before or after D was tilted

Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology Course content • • •

D and E were subjected to weathering and erosion at Earth's surface. A relatively flat land surface was formed by erosion. A second unconfomity surface is formed.

Superposition: Layers F and G must have been deposited after E because they lie atop all other units. Original horizontality: F and G were deposited as horizontal beds. Cross-cutting: F must be younger than D and E because it cuts across the underlying units. The river carved a valley through the upper part of G.

Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology Principle of fossil succession •

Fossils occur in a consistent vertical order in sedimentary rocks all over the world.

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(William"Strata Bill" Smith, late 1700's, England).

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This principle is valid and does not depend on any pre-existing ideas of evolution.

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(In fact, Charles Darwin's ideas on evolution did not appear until 50 years later - 1858).

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Geologists interpret fossil succession to be the result of evolution - the natural appearance and disappearance of species through time.

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University of Karachi

Pet-518 Elements of Geology Geological time Scale

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Pet-518 Elements of Geology The Rock Cycle and Geological Cycle

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Pet-518 Elements of Geology Course content

Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology Course content

Department of Petroleum Technology

University of Karachi

Pet-518 Elements of Geology PRESENT IS KEY TO THE PAST PRESENT IS KEY TO THE PAST

• The "present is key to the past" is a simple but important statement in paleontology. Paleontologists look at present day organisms to help interpret fossils. "Paleo" means old and "onto" means life. Present day organisms help us to understand the life and environment of past organisms. Department of Petroleum Technology

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Pet-518 Elements of Geology Kinds of Rocks

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Pet-518 Elements of Geology Course content

Department of Petroleum Technology

University of Karachi