Strat and Sedi test #2 Flashcards

Wearing away of hard parts by other organisms burrowing or boring through them - barnacles, worms, mollusks

a combustible black or dark brown rock consisting mainly of carbonized plant matter, found mainly in underground lake low oxygen environments.

A fossil fuel that occurs in underground deposits, composed of a liquid mixture of hydrocarbons, water, and sulfur

the process by which colloidal (i.e. clay-size) particles join together

equal mixture of sand and mud, 50/50

Describes minor mud layers within sandy deposits. Primarily sand, mud lenses injected within it.

greenish-gray mineral found in greensand which is found in shallow sea (marine) environments.

tracks of walking animals, trails of worms, burrows of molluscs and crustaceans.

Coasts with a tidal range of 2-4 metres

Sand accumulates when there is an obstruction across the wind path. The more sand gets collected, the steeper the slope will be.

A dark, rusty-brown coating of iron oxide and magnesium oxide that accumulates on the surface of the rock.

the disturbance of sedimentary deposits by living organisms

A broad, flat area of desert covered with wind-swept sand with little or no vegetative cover

In Canada. They important because of the huge amounts of fossils deposited here. In the deltas slide.

a crescent-shaped accumulation of sand and gravel deposited on the inside of a meander

Washover is the sediment deposited by overwash. Overwash is a regional and recurring process responsible for large-scale coastal change in low-profile coastal areas

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Small lenses of sand in muddy beds which occur when sand is trapped in troughs in the mud as sand waves migrate across a muddy substrate.

Two closely related forms of stratification that are generally attributed to the action of oscillating (wave-generated) currents or combined (oscillating and unidirectional) flows.

The bulge of sand formed at the seaward mouth of tidal inlets as a result of interaction between tidal currents and waves.

Temporary shallow evaporate lakes that form in flat "playas" on the valley floors

Basic Stratigraphic Principles or Laws: Principle of Superposition: In an undisturbed sequence of sedimentary rocks, the oldest rocks are at the bottom, and the youngest are at the top. Principle of Original Horizontality: Sedimentary layers are initially deposited horizontally or nearly horizontally. Principle of Lateral Continuity: Sedimentary layers extend laterally in all directions until they thin out or grade into a different sediment type. Principle of Cross-Cutting Relationships: Any feature that cuts across a rock or sediment must be younger than the rock or sediment it cuts across. Principle of Inclusions: An inclusion within a rock layer must be older than the layer containing it. Principle of Faunal Succession: Fossils succeed one another in a definite and determinable order, allowing them to be used to correlate the ages of rocks.

Meandering streams migrate laterally over time due to erosion on the outer bank of a bend and deposition on the inner bank. This process, called lateral migration, causes the meander to migrate downstream gradually. In preserved rock records of meandering streams, vertical grain size patterns typically exhibit fining-upward sequences. This means that at the base of a bed, you would expect to find coarser-grained sediment, such as sand or gravel, which represents higher energy conditions. Towards the top of the bed, finer-grained sediment like silt and clay would dominate, indicating lower energy conditions. Sedimentary structures and fossils found in each bed may include:Coarser-grained layers: Cross-bedding, ripple marks, and occasional fossilized remains of aquatic organisms adapted to faster-flowing water.Finer-grained layers: Mudcracks, ripple marks, and fossilized remains of organisms adapted to quieter, more stagnant water conditions.

Meandering Streams: Characterized by a single, sinuous channel with smooth, curved banks. They typically have finer-grained sediment, occasional point bars, and exhibit lateral migration over time. (Sands and muds more prevalent), may have levees, floodplain deposits and point bar deposits. Braided Streams: Composed of multiple interwoven channels separated by bars and islands. Braided streams tend to have coarser-grained sediment, abundant gravel bars, and exhibit frequent channel switching. (normal grading, gravel bars)

Sediment provenance can be determined by analyzing sedimentary structures, mineral composition, grain size distribution, and fossil content of fluvial deposits. Comparison of these characteristics with known source areas can help identify the likely sediment source.

Rivers with meandering or braided channels in environments conducive to fossil preservation, such as floodplains or low-energy depositional environments, are where one might expect to find dinosaur bones. This is because such environments offer conditions for burial and fossilization of dinosaur remains.

Sediments in Petrified Forest National Park were deposited during the Late Triassic Period in an ancient floodplain environment. Rivers transported sediments from nearby mountains and deposited them in low-energy environments such as lakes, swamps, and floodplains. Over time, burial and subsequent mineralization processes led to the formation of petrified wood.

Repeated layers of sands and shales in meandering river outcrops are often attributed to cyclical variations in sediment transport and deposition. Seasonal changes in river discharge, along with periodic floods, can lead to alternating deposition of coarser-grained sands during higher flow periods and finer-grained shales during lower flow periods. This cyclical pattern results in the repeated stacking of sand and shale layers observed in meandering river outcrops.

Oil shales form in sedimentary environments where organic-rich material, such as algae and plankton, accumulates in anoxic (oxygen-deprived) conditions, such as shallow marine basins or ancient lakes. Over time, burial and heat from geothermal processes cause the organic matter to undergo thermal decomposition, converting it into kerogen, a precursor to crude oil. This process typically occurs over millions of years.

Thermally stratified lakes have distinct layers of water that do not mix due to differences in temperature and density. During the warmer months, a lake's surface waters heat up and form a layer known as the epilimnion, while colder, denser water forms the hypolimnion below. Varved sediments form in these lakes when seasonal changes, such as temperature fluctuations, cause variations in sediment deposition rates. Each layer of sediment deposited annually, or varve, represents a distinct seasonal cycle, typically consisting of coarser sediments from spring runoff and finer sediments from summer/fall deposition

Mono Lake is renowned for its unique ecosystem and geological features. Some notable aspects include: High alkalinity and salinity due to the lack of an outlet, resulting in the formation of tufa towers and other carbonate deposits.

The sediments of Bryce Canyon were primarily deposited during the Cenozoic Era as fluvial and lacustrine deposits in an ancient lake system. Over time, uplift and erosion sculpted these sedimentary rocks into the intricate hoodoos and spires that characterize Bryce Canyon National Park.

Ancient saline lakes, such as those found in arid regions like the Middle East, have been potential sources of oil due to the presence of organic-rich sediments deposited in anoxic conditions. Over geologic time, the organic matter in these sediments undergoes thermal maturation, leading to the generation and accumulation of hydrocarbons, including oil and gas.

Temperate lakes undergo seasonal changes influenced by factors such as temperature, light availability, and nutrient levels. Common seasonal changes include: Spring: Ice melt and increased water temperatures lead to mixing and nutrient influx, promoting primary productivity. Summer: Warm surface waters stratify, with higher nutrient concentrations in deeper, cooler waters. Algal blooms may occur. Fall: Cooling temperatures lead to lake mixing and turnover, redistributing oxygen and nutrients. Winter: Cold temperatures may cause surface ice formation, limiting light penetration and primary productivity.

Playa lakes are shallow, temporary bodies of water found in arid and semiarid regions. They are typically fed by ephemeral streams and rainfall, with no outlet drainage. Sediments associated with playa lakes include evaporites such as gypsum and halite, as well as siliciclastic sediments like silt and clay. Playa sediments often exhibit characteristics of desiccation and mudcracks due to periodic drying.

The "race track" playa lake in Death Valley is special because of its mysterious phenomenon where large rocks seemingly move across the playa surface, leaving trails behind them. This phenomenon has puzzled scientists for decades. It is now believed that a combination of rare conditions, including thin sheets of ice forming on the playa surface during winter rains and strong winds, may be responsible for moving the rocks. However, this explanation is still not entirely confirmed.

Cross-bedding: Inclined layers of sediment deposited by wind action, typically inclined in the direction of wind migration. Wind Ripples: Small-scale undulations formed on the surface of sand or silt beds due to wind action. Loess Deposits: Fine-grained, wind-blown sediment (silt or clay) that forms extensive blankets of homogeneous material.

What's unusual about these dunes is their brilliant white color and composition, primarily consisting of gypsum crystals. The white sand dunes of White Sands, New Mexico, formed as a result of the weathering and erosion of nearby gypsum-rich deposits in the surrounding mountains, particularly the San Andres and Sacramento Mountains. Gypsum crystals are water-soluble and are typically dissolved and transported away by water. However, in the case of White Sands, the area is arid, and the gypsum crystals are left behind as the water evaporates, forming the characteristic white sand dunes.

Sand dunes form through the interaction of wind, sediment supply, and topography. The process typically involves: Wind picking up loose sand grains and carrying them over a surface. Sand grains being deposited when wind velocity decreases due to obstacles or changes in terrain. Accumulation of sand grains in areas of lower wind energy, such as the leeward side of obstacles or along the base of dunes. Migration of dunes over time due to continued wind action, leading to the formation of various dune types such as barchan, transverse, and longitudinal dunes.

The sands in the Navajo Formation, found in the southwestern United States, were primarily derived from eroded sedimentary rocks of the ancestral Rocky Mountains and other uplifted regions during the late Jurassic Period. These sands were transported by wind and deposited in an ancient desert environment, forming the characteristic cross-bedded sandstone units of the Navajo Formation.

Cross-bedding in aeolian deposits typically inclines in the direction of the prevailing wind during deposition. By examining the orientation of cross-bed sets, geologists can infer the direction of paleo-winds during the time of deposition. (where the bottom tail is facing)

Sand dunes in outcrops can be identified by their characteristic cross-bedding, inclined layers of sediment, and overall geometrical shape resembling modern dunes. The presence of features such as ripple marks, ventifacts, and yardangs may also indicate aeolian deposition.

An erg is a vast area of desert covered with sand dunes. Sedimentary grains found in an erg predominantly include sand-sized particles, often composed of quartz, feldspar, and other minerals resistant to weathering. These grains are typically well-sorted and rounded due to prolonged aeolian transport.

Sedimentary environments in Zion National Park include: Fluvial environments: Formed by rivers and streams, characterized by channels, floodplains, and associated sedimentary structures such as cross-bedding and channel fills. Aeolian environments: Represented by sandstone formations with cross-bedding and other aeolian sedimentary structures indicative of ancient dunes. Lacustrine environments: Deposits from ancient lakes, including fine-grained sediments such as mudstones and shales. Alluvial fan and debris flow deposits: Formed by the deposition of sediment transported by gravity down the slopes of the surrounding mountains, characterized by poorly sorted conglomerates and breccias.

Delta Plain: The land area of the delta, characterized by distributary channels, floodplains, and wetlands. Delta Front: The seaward edge of the delta, where distributary channels deposit sediment into the marine environment. Deltaic Channels: Channels within the delta that carry sediment and water from the river mouth to the delta front. Prodelta: The offshore area beyond the delta front, where fine-grained sediments settle out of suspension. Mouth Bars: Sedimentary deposits formed at the mouth of distributary channels, often composed of coarse-grained sediment. Distributary Channels: Branching channels that carry sediment-laden water from the main river channel to the delta front.

Deltas are classified based on the dominant processes shaping their morphology and sediment distribution. The three end-member delta classifications are:Arcuate (or fan-shaped) deltas: Formed when sediment is dispersed over a broad area, typically in regions with moderate tidal influence and wave energy.Bird's-foot deltas: Characterized by elongated distributary channels extending seaward, resembling the toes of a bird's foot. These deltas typically form in areas with strong tidal currents and minimal wave energy.Cuspate deltas: Composed of sharply pointed protrusions extending seaward, often in regions with strong wave energy and minimal tidal influence.

Deltaic progradation refers to the outward extension of a delta into a body of water, driven by sediment deposition at the delta front. Vertical facies trends in a delta deposit typically show a coarsening-upward succession, with finer-grained sediments deposited offshore (prodelta), transitioning to coarser-grained sediments in delta front and delta plain environments.

Delta Plain: Characterized by fluvial and lacustrine deposits, including sandstones, mudstones, and coal seams. Delta Channels: Channels containing coarse-grained sediments such as sand and gravel, often displaying cross-bedding and channel-fill structures. Delta Front: Accumulation of fine- to medium-grained sands, with occasional gravel deposits, grading seaward into mouth bars composed of coarse-grained sediments. Prodelta: Deposits of fine-grained sediments such as mudstones and shales, accumulating in offshore environments. Offshore Clays: Fine-grained sediments deposited beyond the delta front in deeper marine settings.

Delta Plain: Mudstones, sandstones, coal seams. Delta Channels: Sandstones, conglomerates. Delta Front: Sandstones, siltstones, occasional conglomerates. Prodelta: Mudstones, shales. Mouth Bars: Sandstones, conglomerates.

Channels in deltas can switch due to changes in sediment supply, river avulsion events, shifts in the main river channel, or changes in sea level. In the case of the Mississippi Delta, channel switching has been influenced by human activities such as river engineering and levee construction, as well as natural processes such as sediment deposition and subsidence.

Factors such as sediment supply, river discharge, wave energy, tidal currents, and sea level fluctuations determine the overall shape and depositional properties of a delta. Sediment transport and deposition patterns are influenced by these processes, shaping the morphology of the delta over time.

Active deltaic systems play a crucial role in sediment delivery to coastal areas, nutrient cycling, habitat creation, and shoreline stabilization. Understanding ancient deltaic systems provides insights into past environmental conditions, sedimentary processes, and paleogeography.

Progradation results in a coarsening-up succession, with finer-grained sediments deposited farther offshore and coarser-grained sediments accumulating closer to the delta front and delta plain.

Deltaic systems are highly vulnerable to sea level rise due to their low-lying coastal locations and subsidence. Rising sea levels can lead to increased erosion, saltwater intrusion into freshwater systems, loss of habitat, and increased flood risk for coastal communities.

Coal deposition typically occurs in deltaic plain environments where organic-rich material accumulates in swamps and marshes. Peat formation and burial under sedimentary deposits lead to coal formation over geologic time.

Deltas in outcrop can be recognized by their characteristic sedimentary structures such as cross-bedding, inclined layers, and lateral facies changes. Distinctive lithologies and sedimentary features indicative of fluvial, lacustrine, and marine environments can help identify deltaic deposits.

Flocculation refers to the aggregation of clay particles into larger clumps or flocs, facilitated by the presence of ions or organic matter in the water. Flocculated clay particles settle out of suspension more rapidly, leading to their deposition in sedimentary environments such as lakes, estuaries, and deltaic systems.

Clean sands are typically deposited in high-energy environments such as beaches, dunes, and braided river channels where there is minimal fine-grained sediment supply to interfere with sand deposition. Transport by wind or water helps to sort and deposit the sand grains.

Sedimentary structures associated with deltas include cross-bedding, ripple marks, mudcracks, channel-fill deposits, levees, point bars, and deltaic foresets. These structures reflect the dynamic interplay of fluvial, lacustrine, and marine processes within deltaic environments.

West Coast Beaches: Typically characterized by narrow beaches, steep cliffs, and high-energy wave action. Sediment supply is often limited, resulting in coarser-grained sand and gravel beaches. Beaches on the west coast are directly exposed to the open ocean and are more susceptible to erosion from wave action and coastal storms. East Coast Barrier Islands: Barrier islands are elongated, narrow strips of land parallel to the mainland coast, separated by shallow lagoons or estuaries. These islands serve as natural buffers, protecting the mainland from wave energy and storm surges. Barrier islands are dynamic systems constantly reshaped by waves, tides, and sediment transport processes.

Longshore drift is the process by which sediment is transported along the coastline parallel to the shoreline due to the action of waves approaching at an angle. It occurs when waves break at an angle to the shore, carrying sediment along the beach in a zigzag pattern. Longshore drift is a significant mechanism for sediment transport along sandy coastlines, contributing to beach erosion and accretion.

Erosion of clastic coast cliffs contributes sediment to the sand budgets of beaches by supplying sand and gravel that is transported along the coastline through longshore drift. As cliffs erode, sediment is released and transported by waves and currents, replenishing nearby beaches and maintaining sediment balance.

Barrier Island: Sub-environments include dune systems, tidal inlets, back-barrier lagoons, marshes, and ebb tidal deltas. Beach: Sub-environments include foreshore (intertidal zone), backshore (above high tide), nearshore (submerged zone), and offshore bar.

In response to transgression (sea level rise), barrier island facies models may include: Back-barrier lagoon deposits: Fine-grained sediments such as muds and silts deposited in low-energy, protected areas behind the barrier islands. Barrier island beach deposits: Coarse-grained sediments such as sands and gravels deposited on the seaward side of the barrier islands by wave action. Ebb tidal delta deposits: Coarse-grained sediments deposited at the mouth of tidal inlets by ebb tidal currents.

(Please imagine a visual representation of a cross-section showing the barrier island, back-barrier lagoon, beach, dunes, and offshore bar.)*****

An ebb tidal delta is a deposit of sediment located offshore from a tidal inlet, formed by the deposition of sediment carried by ebb tidal currents. Ebb tidal deltas play a crucial role in barrier island systems by stabilizing tidal inlets, providing sediment to maintain barrier island integrity, and influencing the morphology of adjacent beaches and estuarine environments.

Littoral cells are coastal compartments characterized by the movement of sediment within a distinct area along the coastline. The width of beaches within littoral cells is influenced by factors such as sediment supply, wave energy, and coastal morphology. Wider beaches are typically associated with higher sediment supply and lower wave energy, whereas narrower beaches may result from limited sediment availability or increased wave erosion.

The primary source of beach sands in South Carolina is the erosion and weathering of ancient Appalachian Mountains and Piedmont bedrock. Rivers transport sediment from these upland regions to the coast, where it is redistributed along beaches by longshore drift and wave action.

Barrier island roll over refers to the landward migration or repositioning of barrier islands in response to sea level rise, storms, and sediment supply changes. Peat and oysters can be found outcropping on the front beach of barrier islands due to their growth and accumulation in low-energy environments such as back-barrier lagoons and marshes.

Over the last 18,000 years, barrier island systems have responded to sea level rise through landward migration, vertical accretion, and sediment redistribution. During periods of rising sea levels, barrier islands may migrate landward to maintain their position relative to the shoreline, while sediment supply from rivers and coastal processes helps to build and maintain island elevation.

The history of hurricanes on barrier islands can be determined through sedimentological, geomorphological, and paleoenvironmental analyses. Evidence such as storm deposits, overwash fans, and changes in sediment composition can provide insights into the frequency, intensity, and impact of past hurricane events on barrier island systems.

The tidal range, or difference between high tide and low tide, influences the morphology of barrier islands by affecting sediment transport, erosion, and deposition processes. Macro-tidal environments with large tidal ranges may experience greater erosion and sediment redistribution, making it rare for barrier islands to develop in these settings.

Changes in sediment load can affect sea level by influencing sedimentation rates, subsidence, and erosion processes in coastal environments. Tectonic processes such as sediment compaction and uplift can be influenced by sedimentation, but they are not directly controlled by it.

Barrier island systems primarily develop on passive plate margins due to the presence of wide continental shelves, moderate wave energy, and ample sediment supply. These conditions promote the formation and maintenance of barrier islands over geologic time scales.

Deltas are economically important as they provide fertile agricultural lands, serve as locations for urban development and industrial activities, support diverse ecosystems, and act as natural buffers against storm surges and coastal erosion.

Biological structures such as dune grasses (e.g., American beach grass) help stabilize the dune line of barrier islands by trapping sand and promoting dune accretion. Their extensive root systems bind sand particles together, preventing erosion and providing habitat for other coastal plants and wildlife.

Summer beach profiles are typically wider and flatter, with more gently sloping foreshore areas and higher sand accumulation due to reduced wave energy and longer periods of calm weather. In contrast, winter beach profiles are narrower and steeper, with more pronounced beach slopes and lower sand accumulation, resulting from higher wave energy and storm activity.

Plants in coastal estuaries play a crucial role in sediment deposition by trapping and stabilizing sediment with their roots and stems. Their dense root systems reduce water flow velocities, allowing suspended sediment to settle out and accumulate, leading to the formation of marshes and mudflats.

Sedimentary structures found in coastal estuaries include mudcracks, ripple marks, cross-bedding, and bioturbation features such as burrows and tracks. These structures reflect the dynamic interplay of fluvial, tidal, and wave processes within estuarine environments.

A typical stratigraphic column associated with coastal estuaries may include layers of mud, silt, sand, and organic-rich sediments such as peat or marsh deposits. These layers represent the depositional history of the estuary, with variations in sediment composition and structure reflecting changes in environmental conditions over time.

Estuaries are considered as a type of reverse delta because they exhibit characteristics opposite to those of typical river deltas. While river deltas prograde seaward, building landforms into the ocean, estuaries form inland as a result of sea level rise flooding river valleys, resulting in the deposition of sediment and the formation of brackish water habitats.

Progradation of marsh sediments occurs when the accumulation of organic-rich sediment outpaces the rate of sea level rise, leading to the expansion of marshes and tidal flats landward. This process is facilitated by the trapping and accumulation of sediment by marsh vegetation, which helps build and stabilize marsh platforms.

Coastal estuaries are biologically diverse ecosystems that serve as critical habitats for a wide range of plant and animal species. They also provide important ecological functions such as nutrient cycling, sediment trapping, and shoreline stabilization. Geologically, estuaries are dynamic environments where sedimentation processes influence coastal morphology and stratigraphy.

Coastal estuaries can be associated with the formation of natural gas deposits, particularly methane, through microbial decomposition of organic matter in anaerobic sediments. These deposits, known as biogenic gas accumulations, represent a potential energy resource.

Riverine Flow: Freshwater discharge from rivers carrying sediment-laden water into the delta, characterized by low salinity and high sediment concentration. Tidal Flow: Oscillatory movement of water driven by tidal forces, causing water to flow in and out of the delta, influencing sediment transport and distribution. Wave-Driven Flow: Movement of water induced by wave action, redistributing sediment along the shoreline and affecting delta morphology. Differences in Water Density: Riverine flow has the lowest density due to freshwater input, tidal flow has intermediate density influenced by mixing of freshwater and seawater, while wave-driven flow has the highest density due to wave energy.

Tidal sand ridges are largest during spring tides when tidal range is at its maximum. This is because higher tidal ranges result in greater water movement and sediment transport, leading to the formation of larger and more pronounced sand ridges.

Components: Marshes, mudflats, tidal channels, and mangrove swamps. Biological Remains: Marsh grasses, mangrove trees, burrowing organisms, and microbial mats.

Upper Delta Plain: Fine-grained sediments such as muds, silts, and clays, often with abundant organic matter. Lower Delta Plain: Coarser-grained sediments such as sands and gravels, with interbedded muds and organic-rich layers. Subaqueous Delta: Coarse-grained sediments including sands, gravels, and conglomerates, deposited offshore in deeper marine environments.

Deltas can be found worldwide in regions where rivers discharge sediment into coastal or marine environments. Common locations include river mouths, coastal plains, and regions with extensive wetlands and marshes.

Skolithos and Cruziana: Associated with shallow marine environments. Zoophycos: Found in deeper marine environments. Thalassinoides: Common in nearshore and offshore marine settings.

Glauconite is a greenish mineral commonly found in marine sedimentary rocks, particularly in shallow marine environments such as continental shelves and margins. It forms through the alteration of clay minerals in the presence of organic matter and reducing conditions.

Sediment from continental shelf environments can be transported to abyssal plains through various mechanisms, including turbidity currents, gravity flows, and suspension settling. These processes are often triggered by sediment overloading, slope instability, or submarine mass movements.

Storms: High-energy events associated with strong winds, waves, and precipitation. Storms can create bedforms such as hummocky cross-stratification, storm beds, and erosional scours due to intense wave action and sediment reworking. Tides: Tidal currents generate bedforms such as tidal ridges, ripples, and sand waves due to the cyclic movement of water caused by gravitational forces between the Earth, Moon, and Sun.

Strat and Sedi test #2

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