GEO 101 1st Edition Lecture 10 Outline of Last Lecture 1. Clastic Sedimentary Rocks 2. Biochemical and Organic Rocks 3. Chemical Sedimentary Rocks 4. Sedimentary Structures5. Bedforms6. Bed-Surface Markings7. Depositional EnvironmentsOutline of Current Lecture 1. Sedimentary Basins 2. Diagenesis3. Metamorphic rocks a. Metamorphism b. Agents of Metamorphism c. Metamorphic Textures d. Metamorphic Rocks e. 3 Types of Metamorphic Environments f. Metamorphism and Plate Tectonics Current LectureSedimentary Basins- Sediments vary in thickness across Earth’s surfaceo Thin to zero edge where non-sedimentary rocks outcropo Thicken to 10 to 20+km in sedimentary basins- Subsidence – Sinking of the land during sedimentationso Due to crustal flexure and faultingo Compounded by the weight of added sediments- Basins are important locations for natural resourceso Coalo Petroleumo Natural Gaso Uranium- Basins form where tectonic activity creates spaceo Rift Basins: Divergent (pull-apart) plate boundariesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute. Crust thins by stretching and rotational normal faulting Thinned crust subsides Sediment fills the down-dropped basino Passive Margin Basins: Non-plate-boundary continental edge Underlain by crust thinned by pervious rifting Thinned curst subsides as it coolso Intercontinental Basins: Interiors far from margins Results from differential thermal subsidence May be linked to failed crustal riftso Foreland Basins: Craton side of collisional mountain belt Flexure of the crust from loading creates a downwarp Fills with debris eroded off of the mountains- Sea-level changeso Sedimentary deposition is strongly linked to sea levelo Changes in sea level are commonplace geologically Depositional belts shift landward or seaward in response Layers of strata record deepening or shallowing upwardo Transgression: Flooding due to sea-level rise Sediment belts shift landward; strata “deepen” upwardo Regression: Exposure due to sea level fall Depositional belts shift seaward; strata “shallow upward” Regression tied to erosion; less likely to be preservedo Sea-level rise and fall creates a predictable patternDiagenesis- Physical, chemical, and biological changes to sedimento Bioturbationo Lithificationo Dissolutiono Mineral precipitation- Temps between burial and metamorphism (~300 °C)- Integrates changes across the entire sediment historyMetamorphic RocksMetamorphism- Formed by increase in temperatures and/or pressures from:o Igneous rockso Sedimentary rockso Other metamorphic rocks- Low-to high-grade- Rocks remain solidAgents of Metamorphism- 1.) Heato Recrystallization results in new, stable mineralso 2 sources Heat from magma Geothermal gradient- 2.) Pressure and Stresso Increase with deptho Forces applied in all directions- 3.) Fluidso Water and other volatileso Enhance migration of ionso Recrystallization of existing mineralso Where does the water come from? Pore spaces of sedimentary rocks Fractures in igneous rocks Hydrated minerals- 4.) Parent Rocko Minerals determines degree to which change occursMetamorphic Textures- Texture: Size, shape, and arrangement of mineral grains- Foliation: Planar arrangement of mineral grainso Parallel alignment of platy and/or elongated mineralso Compositional banding- Foliation forms by:o Rotation of platy and/or elongated mineralso Recrystallization of mineralso Changing shape of grains into elongated shapes- Types of foliated textureso Slaty Cleavage: Planar surfaces along which rocks split Dullesto Schistosity: Platy minerals exhibit layered structure  Shinyo Gneissic: Minerals segregate, distinctively banded All of the dark crystals line up with each other, and light crystals line up with each other, and you see distinct bands- Other metamorphic textureso Nonfoliated Minimal deformation Equidimensional crystalso Porphyroblasitc textures Large grains surrounded by fine-grained matrixMetamorphic Rocks- Foliated Rockso Slate Fine-grained Slaty cleavage Low-grade metamorphism of shaleo Phyllite Minerals not large enough to be identified Glossy sheen and wavy surfaceso Schist Medium-to coarse-grained Micas predominate Schistosity textureo Gneiss Medium-to coarse-grained Banded appearance High-grade metamorphic- Nonfoliated Rockso Marble Coarse, crystalline Calcite or dolomiteo Quartzite Metamorphism of quartz-rich sandstone Quartz grains interlocking3 Types of Metamorphic Environments- 1.) Contact (or thermal) Metamorphismo Increase temperature from intruding magmao Zone of alteration (aureole) forms in rock surrounding magma- 2.) Hydrothermal Metamorphismo Chemical alteration caused when hot, ion-rich fluids circulate through crackso Widespread along Mid-Ocean Ridges- 3.) Regional (or dynamothermal) Metamorphismo Associated with mountain buildingMetamorphism and Plate Tectonics- Continent-Continent Collisionso Edges of plate deformso Major mountains – Alps, Himalayas, and Appalachians are metamorphic- Subduction Zoneso Linear belts of metamorphic rocks High-pressure, low-temperature zones nearest to the trench High-temperature, low-pressure zones further