DE (W8)

• siliciclastic sediments are formed from the weathering of preexisting rocks, and chemical and biological sediments are formed through chemical processes and the activities of organisms
• Sedimentary rocks are formed through weathering, erosion, transportation, and deposition processes.
• Physical and chemical weathering weaken rocks and produce sediment particles
• Sediment particles are transported and deposited, forming layers of sedimentary rocks
• Siliciclastic Sediments form clastic particles that range in size from boulders to sand, silt, and clay. Their composition varies based on the intensity of weathering and the stability of minerals
• Chemical sediments precipitate from dissolved ions in water bodies.
• Biological sediments result from mineral precipitation by organisms or their shells/skeletons.
• Microorganisms can facilitate mineral precipitation, even away from their bodies
• Chemical weathering weakens rocks, increasing susceptibility to fragmentation while physical weathering produces smaller fragments, exposing more surface area to chemical weathering.
• the shape of particles determined by natural breakage along bedding planes and fractures in the parent rock.
• Siliciclastic sediments contain a mixture of minerals, including quartz, partly altered fragments like feldspar, and newly formed clay minerals.
• Organisms like mollusks and corals contribute shells or skeletons, directly controlling mineral precipitation while some organisms indirectly facilitate mineral precipitation, altering their environment.
• Deposition occurs when current velocity decreases, causing particles to settle.
• Particle settling velocity depends on size and density, with larger particles settling faster.
• Current strength determines the size of particles deposited in a particular place: Strong currents deposit gravel, moderate currents deposit sand, and weak currents deposit mud composed of fine particles like silt and clay.
• Sorting refers to the tendency of variations in current velocity to segregate sediments according to size.
• Chemical and biological sedimentation in oceans is driven by precipitation rather than gravity.
• Sediments tend to accumulate in depressions in Earth's crust.
• Depressions are formed by subsidence, where a broad area of the crust sinks relative to the surrounding crust.
• Sedimentary basins are regions where the combination of sedimentation and subsidence has led to the formation of sedimentary rocks.
• Sedimentary basins are primary sources of oil and natural gas.
• Rift Basins form within continents during plate separation as a result of stretching, thinning, and heating of the lithosphere and are characterized by deep, narrow rift valleys with thick successions of sedimentary and igneous rocks.
• Thermal Subsidence Basins form during later stages of plate separation due to the cooling of thinned lithosphere which leads to subsidence below sea level where accumulated sediments from erosion of adjacent land, forms continental shelves.
• Flexural Basines develop at convergent plate boundaries where one plate overrides the other. The overriding plate's weight causes the underlying plate to bend or flex downward, creating a basin.
• Types of Sedimentary Environments include: Continental Environments (Lakes, rivers, deserts, and glaciers.), Shoreline Environments (Deltas, beaches, and tidal flats.) and Marine Environments (Deep sea, continental shelf, and organic reefs.)
• Factors that effect Sedimentary Environments include: Transport Agents like Water, wind, ice, and tidal currents, the Climate, Biological Processes and the Geographic Location and Plate Tectonic Setting which Influences sediment sources and basin formation.
• Continental Sedimentary Environments include: Lake Environments, Alluvial Environments (river channels, floodplains, and wetlands), Desert Environments and Glacial Environments (transitional alluvial environments form at glacier borders.)
• Shoreline Sedimentary Environments include: Delta Environments, Tidal Flat Environments and Beach Environments:
• Marine Sedimentary Environments: Continental Shelfs, Organic Reefs, Continental Margins and Slopes and Deep-Sea Environments (Including abyssal plains, mid-ocean ridges, and lower continental slopes; accumulation of carbonate sediments from plankton shells.)
• Siliciclastic Sedimentary Environments: are dominated by siliciclastic sediments derived from land and encompass continental as well as transitional shoreline and certain marine regions.
• terrigenous sediments are primarily composed of minerals from land-based weathering.
• • Carbonate Environments are Found in marine settings with sediments primarily composed of calcium carbonate secreted by organisms.
• Siliceous Environments: Deep-sea environments with sediments made of silica shells from planktonic organisms.
• Evaporite Environments: Formed by rapid evaporation of seawater, leading to precipitation of salts like gypsum and halite.
• Some siliciclastic sediment ends up in terrestrial sedimentary environments, while most chemical and biological sediments are deposited in ocean basins, with some in lakes and wetlands.
• Once deposited on the ocean floor, sediments become trapped, making the deep seafloor the ultimate sedimentary basin.
• Over time, sediments are buried under new layers, subjected to increasing temperatures, pressures, and chemical changes.
• Diagenesis refers to the physical and chemical changes sediments undergo as they are buried deeper in the Earth's crust. These changes continue until the sediment or sedimentary rock is exposed to weathering or undergoes metamorphism due to extreme heat and pressure.
• Buried sediments are exposed to groundwater rich in dissolved minerals. Minerals can precipitate in the pores between sediment particles, binding them together in a process called cementation
• Compaction is a major physical diagenetic change, leading to a decrease in volume and porosity of sediment. It occurs as sediment particles are squeezed closer together by the weight of overlying sediments.