GEO 101 1st EditionExam # 2 Study GuideGeology 101 Test 2 Study GuideTerms: Weathering: Generation of detritus via rock disintegrationDeposition: Settling out of the transporting fluidErosion: Removal of sediment grains from rockBreccia:- Coarse Clastics – Composed of Gravel Sized Clasts - Comprised of angular fragmentso Angularity indicates a lack of transport processingo Deposited relatively close to sourceConglomerate- Coarse Clastics – Composed of Gravel Sized Clasts - Comprised of rounded gravelo Indicates water transport Clasts bang together forcefully in flowing water Collisions round angular corners and edges of clastso Conglomerates are deposited at a distance from the sourceShale - Fine Clastics – Composed of silt and clayo Silt-sized sediments are lithified to form siltstoneo Clay-sized particles form shaleo Fine clastics are deposited in quieter waters Floodplains, lagoons, mudflats, deltas, deep-water basins Organic-rich shales are the source of petroleumSedimentary Structures- Features imparted to sediments at or near depositiono Layeringo Surface features on layerso Arrangement of grains- Help decipher conditions at or near time of deposition- Sedimentary rocks are usually layered or “stratified” o Arranged in planar, close-to-horizontal “beds”o Bedding is often laterally continuous for long distanceso Beds are often similar in composition, color and texture- Bedding reflects changing conditions during deposition- These can be changes in…o Energy conditions, and hence, grain sizeo Disturbance by organisms- Bedding may also reflect non-deposition or erosion- A series of beds are referred to as strata- Formation: Strata recognized on a regional scale- Geologic maps display the distribution of formationso i.e. Coconino Formation - Water flowing over loose sediment creates bedforms- Bedforms are linked to flow velocity and sediment sizeo Ripples, cm-scale ridges, and troughs, indicate flow Asymmetric ripples – Unidirectional flow Symmetric ripples – Wave oscillation Ripples are commonly preserved in sedimentary rocksSandstone - Sandstone – Clastic rock made of sand-sized particleso Forms in many depositional settingso Quartz is, by far, the dominant mineral in sandstoneso Sandstone varieties: Arkose – Contains abundant feldspar (pink color) Quartz sandstone – Almost pure quartzDigenesis - Change that occurs to make sediments into sedimentary rocks o Lithificationo Sedimentation Stratification - Layering - The formation of layering in a sedimentary rock Depositional Environments - What type o environment would you find coal? Metamorphism Metamorphism- 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 inlandSlaty Cleavage- Types of foliated textureso Slaty Cleavage: Planar surfaces along which rocks split DullestSchistosity - Types of foliated textureso Schistosity: Platy minerals exhibit layered structure  ShinyFoliation - 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 shapes4 Grades of Metamorphism Agents 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 occursPyroclastic Debris: Extruded