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"...conceived as a visual poem that reflects on the coexistence of permanence and impermanence as a universal human condition rooted in our existences and bodies, as well as in objects, images, and interpretations."

Afterimage includes contemporary and historical experimentations in photography and film, spatial interventions, paintings, and sculptures, and explores the intersections of fragmented iconographies, mutable materials, perceptual memories, and morphing bodies.

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curated by Bartolomeo Pietromarchi and Alessandro Rabottini

Francis Alÿs, Francesco Arena, Stefano Arienti, Benni Bosetto, Mario Cresci, June Crespo, Thomas Demand, Paolo Gioli, Massimo Grimaldi, Bronwyn Katz, Esther Kläs, Oliver Laric, Tala Madani, Anna Maria Maiolino, Marisa Merz, Luca Maria Patella, Hana Miletić, Luca Monterastelli, Frida Orupabo, Pietro Roccasalva, Mario Schifano, Elisa Sighicelli, Paloma Varga Weisz, Danh Vo, Dominique White, He Xiangyu.

A major international group show features 26 international artists from different generations and includes newly commissioned pieces and site-specific installations, historical works belonging to the MAXXI Collection together with monographic rooms, with works spanning from the 1960s to the present day. Afterimage is a meditation upon memory and metamorphosis and looks at the unpredictable forms - both material and metaphorical - in which what has vanished silently endures within spaces, bodies, and meanings.
The title of the show refers to the optical illusion of the residual image, which happens when a visual stimulus generates an impression on the retina that remains even after the stimulus has disappeared, as happens, for example, with the camera flash.

conceived as a visual poem that reflects on the coexistence of permanence and impermanence as a universal human condition rooted in our existences and bodies, as well as in objects, images, and interpretations.

The viewers explore the 15 rooms of the museum and its passages, and to establish intuitive and spontaneous associations between the works, the architecture of Palazzo Ardinghelli, and the history of L'Aquila, a city that daily testifies to the need to remember and the impetus to transformation and that continuously manifests how the principle of metamorphosis contains that which has been and generates what will be.

Encom passing a wide variety of media, Afterimage includes contemporary and historical experimentations in photography and film, spatial interventions, paintings, and sculptures, and explores the intersections of fragmented iconographies, mutable materials, perceptual memories, and morphing bodies.

The exhibition set-up refrains from the concept of "sections" in favor of four narrative paths that cross the rooms, suggesting a formal and immaterial architecture within the physical architecture of the museum. These constellations of meanings are Material and Memory, The Mutable Image, The Body Disclosed, and Inner Architecture.

other events of the Afterimage cycle

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curated by Bartolomeo Pietromarchi and Alessandro Rabottini Francis Alÿs, Francesco Arena, Stefano Arienti, Benni Bosetto, Mario Cresci, June Crespo, Thomas Demand, Paolo Gioli, Massimo Grimaldi, Bronwyn Katz, Esther Kläs, Oliver Laric, Tala Madani, Anna Maria Maiolino, Marisa Merz, Luca Maria Patella, Hana Miletić, Luca Monterastelli, Frida Orupabo, Pietro Roccasalva, Mario Schifano, Elisa Sighicelli, Paloma Varga Weisz, Danh Vo, Dominique White, He Xiangyu.

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Until October, the most Mike Winkelmann - the digital artist known as Beeple - had ever sold a print for was $100.

Today, an NFT of his work sold for $69 million at Christie's. The sale positions him "among the top three most valuable living artists," according to the auction house.

The record-smashing NFT sale comes after months of increasingly valuable auctions. In October, Winkelmann sold his first series of NFTs, with a pair going for $66,666.66 each. In December, he sold a series of works for $3.5 million total. And last month, one of the NFTs that originally sold for $66,666.66 was resold for $6.6 million.

"I do view this as the next chapter of art history."

NFTs, or non-fungible tokens, are unique files that live on a blockchain and are able to verify ownership of a work of digital art. Buyers typically get limited rights to display the digital artwork they represent, but in many ways, they're just buying bragging rights and an asset they may be able to resell later. The technology has absolutely exploded over the past few weeks - and Winkelmann, more than anyone else, has been at the forefront of its rapid rise.

"He showed us this collage, and that was my eureka moment when I knew this was going to be extremely important," Noah Davis, a specialist in post-war and contemporary art at Christie's, told The Verge. "It was just so monumental and so indicative of what NFTs can do."

A few factors explain why Beeple's work has become so valuable. For one, he's developed a large fan base, with around 2.5 million followers across social channels. And he's famously prolific: as part of a project called "Everydays," Winkelmann creates and publishes a new digital artwork every day. The project is now in its 14th year.

At the same time, NFTs have blown up over the past month and - for the moment, at least - are being seen by many as the way digital art will be acquired and traded going forward. For collectors who believe that's true, the escalating prices are nothing compared to what NFTs will be worth down the road, when the rest of the world has caught onto their value.

Christie's is also a legitimizing force for both Winkelmann's art and NFTs as a technology. The 255-year-old auction house has sold some of the most famous paintings in history, from the only known portrait of Shakespeare created during his lifetime to the last-discovered painting by Leonardo da Vinci.

What's an NFT?

NFTs allow you to buy and sell ownership of unique digital items and keep track of who owns them using the blockchain. NFT stands for "non-fungible token," and it can technically contain anything digital, including drawings, animated GIFs, songs, or items in video games. An NFT can either be one of a kind, like a real-life painting, or one copy of many, like trading cards, but the blockchain keeps track of who has ownership of the file.

NFTs have been making headlines lately, some selling for millions of dollars, with high-profile memes like Nyan Cat and the "deal with it" sunglasses being put up for auction. There's also a lot of discussion about the massive electricity use and environmental impacts of NFTs.If you (understandably) still have questions, you can read through our NFT FAQ.

Combine that with Winkelmann already being at the forefront of NFT sales, and today's auction was destined to set records.

"I do view this as the next chapter of art history," Winkelmann said. "Now there is a way to collect digital art."

The piece that was sold, Everydays: The First 5000 Days, is a collage of Winkelmann's work starting at the beginning of the project, when he was posting somewhat crude sketches. It runs through years of evolving digital shapes and sceneries up through the beginning of this year, when he was posting extremely crude political illustrations.

The auction's winner doesn't get much: a digital file, mostly, plus some vague rights to present the image. But Winkelmann expects to work with the buyer to find various ways to display the piece physically, whether that's on a TV in their house or projected onto "the side of a fucking building" at Art Basel.

There's already been pushback against the rise of NFTs. Plenty of works of questionable artistic value are being sold at hype-driven auctions. Artists' works have allegedly been stolen and auctioned off as authentic. And many artists are concerned about the climate impact of art sales that rely on blockchain technology, which is notoriously inefficient by design. (Winkelmann said he plans to buy carbon offset for all his NFTs going forward so that their impact is a net positive.)

Those who are early to the space think the tech is here to stay. Pablo Rodriguez-Fraile, the collector who bought a Beeple for $66,666 and resold it for 100 times that just four months later, started collecting digital art a year ago and co-founded the Museum of Crypto Art in part to display his growing collection. He sees Winkelmann's rising sale prices as a way of proving to the public that the technology matters.

"I really thought it was the right catalyst."

"The reason I did that sale was in no way shape or form for the money," Rodriguez-Fraile said. "I really thought it was the right catalyst to signal the validation of what's happening in the industry."

At Christie's, Davis plans to work with more digital artists to auction NFTs. With a growing crop of smaller marketplaces and countless number of NFTs being created daily, he sees Christie's role as helping to promote the space in an "extremely thoughtful" way.

"We have more responsibility than we've ever had in any collecting category as arbiters of the items that we're selling," Davis said.

The plan isn't to pull more traditional artists into the digital world (a Jeff Koons NFT isn't next on the list, Davis joked), but to work with established digital artists to explore their "alternative art history."

Rodriguez-Fraile believes that the next wave of artists and collectors will come to see NFTs as simply the way art is bought and sold.

"I'm confident it's not a hype thing," he said. "It's the catalyst for a generation."

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Mike Winkelmann, aka the digital artist Beeple, smashed records with a Christie's auction of an NFT collage of the first 5,000 entries in his "Everydays" series.

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Mad Dog Jones - REPLICATOR, A Multi-Generational NFT | Phillips

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REPLICATOR is an NFT experience comprising seven unique generations of artworks. Bid now through April 23.

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Backdated NFT/ Cryptokitty Display Hardware Wallet Replica (Celestial Cyber Dimension)

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Backdated NFT/ Cryptokitty Display Hardware Wallet Replica (Celestial Cyber Dimension)

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opensea.io needs to review the security of your connection before proceeding.

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Erosion causing island in Canada's north to disappear

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Time-lapse video of bluff erosion on Barter Island, Alaska

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biogeochemical cycles: the pathways for movement and transformations of chemical elements or molecules within or among the biotic and abiotic components of the Earth System as a result of biological, physical, geological, and chemical processes.

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5 Weathering, Erosion, and Sedimentary Rocks

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5 Weathering, Erosion, and Sedimentary Rocks

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https://opengeology.org/textbook/5-weathering-erosion-and-sedimentary-rocks/

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Announcement: Chapter quizzes are not working as of summer 2023.
By the end of this chapter, students will be able to:

Describe how water is an integral part of all sedimentary rock formation

Explain how chemical and mechanical weathering turn bedrock into sediment

Differentiate the two main categories of sedimentary rocks : clastic rock formed from pieces of weathered bedrock; and chemical rock that precipitates out of solution by organic or inorganic means

Explain the importance of sedimentary structures and analysis of depositional environments, and how they provide insight into the Earth's history

Sedimentary rock and the processes that create it, which include weathering, erosion, and lithification, are an integral part of understanding Earth Science. This is because the majority of the Earth's surface is made up of sedimentary rocks and their common predecessor, sediments. Even though sedimentary rocks can form in drastically different ways, their origin and creation have one thing in common, water.

5.1 The Unique Properties of Water

Water plays a role in the formation of most sedimentary rock. It is one of the main agents involved in creating the minerals in chemical sedimentary rock. It also is a weathering and erosion agent, producing the grains that become detrital sedimentary rock. Several special properties make water an especially unique substance, and integral to the production of sediments and sedimentary rock.

The water molecule consists of two hydrogen atoms covalently bonded to one oxygen atom arranged in a specific and important geometry. The two hydrogen atoms are separated by an angle of about 105 degrees, and both are located to one side of the oxygen atom. This atomic arrangement, with the positively charged hydrogens on one side and negatively charged oxygen on the other side, gives the water molecule a property called polarity . Resembling a battery or a magnet, the molecule's positive-negative architecture leads to a whole suite of unique properties.

Polarity allows water molecules to stick to other substances. This is called . Water is also attracted to itself, a property called , which leads to water's most common form in the air, a droplet. Cohesion is responsible for creating surface tension, which various insects use to walk on water by distributing their weight across the surface.

The fact that water is attracted to itself leads to another important property, one that is extremely rare in the natural world-the liquid form is denser than the solid form. The polarity of water creates a special type of weak bonding called hydrogen bonds . Hydrogen bonds allow the molecules in liquid water to sit close together. Water is densest at 4°C and is less dense above and below that temperature. As water solidifies into ice, the molecules must move apart in order to fit into the crystal lattice, causing water to expand and become less dense as it freezes. Because of this, ice floats and water at 4 o C sinks, which keeps the oceans liquid and prevents them from freezing solid from the bottom up. This unique property of water keeps Earth, the water planet, habitable.

Even more critical for supporting life, water remains liquid over a very large range of temperatures, which is also a result of cohesion. Hydrogen bonding allows liquid water can absorb high amounts of energy before turning into vapor or gas. The wide range across which water remains a liquid, 0°C-100°C (32°F-212°F), is rarely exhibited in other substances. Without this high boiling point, liquid water as we know it would be constricted to narrow temperature zones on Earth, instead water is found from pole to pole. Further, water is the only substance that exists in all three phases, solid, liquid, and gas in Earth's surface environments.

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5.2 Weathering and Erosion

Bedrock refers to the solid rock that makes up the Earth's outer crust. Weathering is a process that turns bedrock into smaller particles, called sediment. Mechanical weathering includes pressure expansion, frost wedging, root wedging, and salt expansion. Chemical weathering includes carbonic acid and hydrolysis, dissolution, and oxidation.

Erosion is a mechanical process, usually driven by water, wind, gravity, or ice, which transports sediment (and soil) from the place of weathering. Liquid water is the main agent of erosion. Gravity and mass wasting processes (see Chapter 10, Mass Wasting) move rocks and sediment to new locations. Gravity and ice, in the form of glaciers (see Chapter 14, Glaciers), move large rock fragments as well as fine sediment.

Erosion resistance is important in the creation of distinctive geological features. This is well-demonstrated in the cliffs of the Grand Canyon. The cliffs are made of rock left standing after less resistant materials have weathered and eroded away. Rocks with different levels of erosion resistance also create the unique-looking features called hoodoos in Bryce Canyon National Park and Goblin Valley State Park in Utah.

5.2.1 Mechanical Weathering

Pressure Expansion

Bedrock buried deep within the Earth is under high pressure and temperature. When uplift and erosion brings bedrock to the surface, its temperature drops slowly, while its pressure drops immediately. The sudden pressure drop causes the rock to rapidly expand and crack; this is called pressure expansion. Sheeting or exfoliation is when the rock surface spalls off in layers. Spheroidal weathering is a type of exfoliation that produces rounded features and is caused when chemical weathering moves along joints in the bedrock.

Frost Wedging

Frost wedging, also called ice wedging, uses the power of expanding ice to break apart rocks. Water works its way into various cracks, voids, and crevices. As the water freezes, it expands with great force, exploiting any weaknesses. When ice melts, the liquid water moves further into the widened spaces. Repeated cycles of freezing and melting eventually pry the rocks apart. The cycles can occur daily when fluctuations of temperature between day and night go from freezing to melting.

Root Wedging

Like frost wedging, root wedging happens when plant roots work themselves into cracks, prying the bedrock apart as they grow. Occasionally these roots may become fossilized. is the term for these roots preserved in the rock record. Tunneling organisms such as earthworms, termites, and ants are biological agents that induce weathering similar to root wedging.

Salt Expansion

Salt expansion, which works similarly to frost wedging, occurs in areas of high evaporation or near-marine environments. Evaporation causes salts to precipitate out of solution and grow and expand into cracks in rock. Salt expansion is one of the causes of , a series of holes in a rock. Tafonis, cracks, and holes are weak points that become susceptible to increased weathering. Another phenomena that occurs when salt water evaporates can leave behind a square imprint preserved in a soft sediment, called a h opper crystal.

5.2.2 Chemical Weathering

Carbonic Acid and Hydrolysis

Carbonic acid (H ₂CO ₃) forms when carbon dioxide, the fifth-most abundant gas in the atmosphere, dissolves in water. This happens naturally in clouds, which is why precipitation is normally slightly acidic. Carbonic acid is an important agent in two chemical weathering reactions, hydrolysis and dissolution.

Hydrolysis occurs via two types of reactions. In one reaction, water molecules ionize into positively charged H+1 and OH −1 ions and replace mineral cations in the crystal lattice. In another type of hydrolysis, carbonic acid molecules react directly with minerals, especially those containing silicon and aluminum (i.e. Feldspars), to form molecules of clay minerals.

Hydrolysis is the main process that breaks down silicate rock and creates clay minerals. The following is a hydrolysis reaction that occurs when silica-rich feldspar encounters carbonic acid to produce water-soluble clay and other ions:

Clay minerals are platy silicates or phyllosilicates (see Chapter 3, Minerals) similar to micas, and are the main components of very fine-grained sediment. The dissolved substances may later precipitate into chemical sedimentary rocks like evaporite and limestone, as well as amorphous silica or chert nodules.

Dissolution

Dissolution is a hydrolysis reaction that dissolves minerals in bedrock and leaves the ions in solution, usually in water. Some evaporites and carbonates, like salt and calcite, are more prone to this reaction; however, all minerals can be dissolved. Non-acidic water, having a neutral pH of 7, will dissolve any mineral, although it may happen very slowly. Water with higher levels of acid, naturally or man-made, dissolves rocks at a higher rate. Liquid water is normally slightly acidic due to the presence of carbonic acid and free H+ ions. Natural rainwater can be highly acidic, with pH levels as low as 2. Dissolution can be enhanced by a biological agent, such as when organisms like lichen and bacteria release organic acids onto the rocks they are attached to. Regions with high humidity (airborne moisture) and precipitation experience more dissolution due to greater contact time between rocks and water.

The Goldich Dissolution Series shows chemical weathering rates are associated to crystallization rankings in the Bowen's Reaction Series (see Chapter 4, Igneous Rock and Volcanic Processes). Minerals at the top of the Bowen series crystallize under high temperatures and pressures, and chemically weather at a faster rate than minerals ranked at the bottom. Quartz, a felsic mineral that crystallizes at 700°C, is very resistant to chemical weathering. High crystallization-point mafic minerals, such as olivine and pyroxene (1,250°C), weather relatively rapidly and more completely. Olivine and pyroxene are rarely found as end products of weathering because they tend to break down into elemental ions.

Dissolution is also noteworthy for the special geological features it creates. In places with abundant carbonate bedrock, dissolution weathering can produce a karst topography characterized by sinkholes or caves (see Chapter 10, Mass Wasting).

Three commonly found minerals are produced by iron-oxidation reactions: red or grey hematite, brown goethite (pronounced "GUR-tite"), and yellow limonite. These iron oxides coat and bind mineral grains together into sedimentary rocks in a process called cementation, and often give these rocks a dominant color. They color the rock layers of the Colorado Plateau, as well as Zion, Arches, and Grand Canyon National Parks. These oxides can permeate a rock that is rich in iron-bearing minerals or can be a coating that forms in cavities or fractures. When the minerals replacing existing minerals in bedrock are resistant to weathering, iron concretions may occur in the rock. When bedrock is replaced by weaker oxides, this process commonly results in void spaces and weakness throughout the rock mass and often leaves hollows on exposed rock surfaces.

5.2.3 Erosion

Erosion is a mechanical process, usually driven by water, gravity, (see Chapter 10), wind, or ice (see Chapter 14) that removes sediment from the place of weathering. Liquid water is the main agent of erosion.

Erosion resistance is important in the creation of distinctive geological features. This is well demonstrated in the cliffs of the Grand Canyon. The cliffs are made of rock left standing after less resistant materials have weathered and eroded away. Rocks with different levels erosion resistant also create the unique-looking features called hoodoos in Bryce Canyon National Park and Goblin Valley State Park in Utah.

5.2.4. Soil

Soil is a combination of air, water, minerals, and organic matter that forms at the transition between biosphere and geosphere. Soil is made when weathering breaks down bedrock and turns it into sediment. If erosion does not remove the sediment significantly, organisms can access the mineral content of the sediments. These organisms turn minerals, water, and atmospheric gases into organic substances that contribute to the soil.

Soil is an important reservoir for organic components necessary for plants, animals, and microorganisms to live. The organic component of soil, called , is a rich source of bioavailable nitrogen. Nitrogen is the most common element in the atmosphere, but it exists in a form most life forms are unable to use. Special bacteria found only in soil provide most nitrogen compounds that are usable, bioavailable, by life forms.

These nitrogen-fixing bacteria absorb nitrogen from the atmosphere and convert it into nitrogen compounds. These compounds are absorbed by plants and used to make DNA, amino acids, and enzymes. Animals obtain bioavailable nitrogen by eating plants, and this is the source of most of the nitrogen used by life. That nitrogen is an essential component of proteins and DNA. Soils range from poor to rich, depending on the amount of humus they contain. Soil productivity is determined by water and nutrient content. Freshly created volcanic soils, called andisols, and clay-rich soils that hold nutrients and water are examples of productive soils.

O Horizon: The top horizon is a thin layer of predominantly organic material, such as leaves, twigs, and other plant parts that are actively decaying into humus.

A Horizon: The next layer, called , consists of humus mixed with mineral sediment. As precipitation soaks down through this layer, it leaches out soluble chemicals. In wet climates with heavy precipitation this leaching out produces a separate layer called horizon E, the leaching or eluviation zone.

B Horizon: Also called , this layer consists of sediment mixed with humus removed from the upper layers. The subsoil is where mineral sediment is chemically weathered. The amount of organic material and degree of weathering decrease with depth. The upper subsoil zone, called , is a porous mixture of humus and highly weathered sediment. In the lower zone, saprolite, scant organic material is mixed with largely unaltered parent rock.

R Horizon: The final layer consists of unweathered, parent and fragments.

The prairie soils and native plants are well adapted to a relatively dry climate. With government encouragement, settlers moved in to homestead the region. They plowed vast areas of prairie into long, straight rows and planted grain. The plowing broke up the stable soil profile and destroyed the natural grasses and plants, which had long roots that anchored the soil layers. The grains they planted had shallower root systems and were plowed up every year, which made the soil prone to erosion. The plowed furrows were aligned in straight rows running downhill, which favored erosion and loss of topsoil.

The local climate does not produce sufficient precipitation to support non-native grain crops, so the farmers drilled wells and over-pumped water from the underground aquifers. The grain crops failed due to lack of water, leaving bare soil that was stripped from the ground by the prairie winds. Particles of midwestern prairie soil were deposited along the east coast and as far away as Europe. Huge dust storms called black blizzards made life unbearable, and the once-hopeful homesteaders left in droves. The setting for John Steinbeck's famous novel and John Ford's film, The Grapes of Wrath, is Oklahoma during this time. The lingering question is whether we have learned the lessons of the dust bowl, to avoid creating it again.

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Sedimentary rock is classified into two main categories: clastic and chemical. Clastic or detrital sedimentary rocks are made from pieces of bedrock, sediment, derived primarily by mechanical weathering. Clastic rocks may also include chemically weathered sediment. Clastic rocks are classified by grain shape, , and . Chemical sedimentary rocks are precipitated from water saturated with dissolved minerals. Chemical rocks are classified mainly by composition of minerals in the rock.

5.3.1 Lithification and Diagenesis

Lithification turns loose sediment grains, created by weathering and transported by erosion, into clastic sedimentary rock via three interconnected steps. Deposition happens when friction and gravity overcome the forces driving sediment transport, allowing sediment to accumulate. Compaction occurs when material continues to accumulate on top of the sediment layer, squeezing the grains together and driving out water. The mechanical compaction is aided by weak attractive forces between the smaller grains of sediment. Groundwater typically carries cementing agents into the sediment. These minerals, such as calcite, amorphous silica, or oxides, may have a different composition than the sediment grains. Cementation is the process of cementing minerals coating the sediment grains and gluing them together into a fused rock.

Diagenesis is an accompanying process to lithification and is a low-temperature form of rock metamorphism (see Chapter 6, Metamorphic Rock). During diagenesis, sediments are chemically altered by heat and pressure. A classic example is aragonite (CaCO ₃), a form of calcium carbonate that makes up most organic shells. When lithified aragonite undergoes diagenesis, the aragonite reverts to calcite (CaCO ₃), which has the same chemical formula but a different crystalline structure. In sedimentary rock containing calcite and magnesium (Mg), diagenesis may transform the two minerals into dolomite (CaMg(CO ₃) ₂). Diagenesis may also reduce the pore space, or open volume, between sedimentary rock grains. The processes of cementation, compaction, and ultimately lithification occur within the realm of diagenesis, which includes the processes that turn organic material into fossils.

5.3.2 Detrital Sedimentary Rocks (Clastic)

Detrital or sedimentary rocks consist of preexisting sediment pieces that comes from weathered bedrock. Most of this is mechanically weathered sediment, although some clasts may be pieces of chemical rocks. This creates some overlap between the two categories, since clastic sedimentary rocks may include chemical sediments. Detrital or clastic rocks are classified and named based on their grain size.

Sorting and Rounding

Sorting describes the range of grain sizes within sediment or sedimentary rock. Geologists use the term " well sorted " to describe a narrow range of grain sizes, and "poorly sorted" for a wide range of grain sizes (see figure). It is important to note that soil engineers use similar terms with opposite definitions; well graded sediment consists of a variety of grain sizes, and poorly graded sediment has roughly the same grain sizes.

Composition and provenance

Composition describes the mineral components found in sediment or sedimentary rock and may be influenced by local geology, like source rock and hydrology. Other than clay, most sediment components are easily determined by visual inspection (see Chapter 3, Minerals). The most commonly found sediment mineral is quartz because of its low chemical reactivity and high hardness, making it resistant to weathering, and its ubiquitous occurrence in continental bedrock. Other commonly found sediment grains include feldspar and lithic fragments. Lithic fragments are pieces of fine-grained bedrock, and include mud chips, volcanic clasts, or pieces of slate.

Geologists use provenance to discern the original source of sediment or sedimentary rock. Provenance is determined by analyzing mineral composition and types of fossils present, as well as textural features like sorting and rounding. Provenance is important for describing tectonic history, visualizing paleogeographic formations, unraveling an area's geologic history, or reconstructing past supercontinents.

In quartz sandstone, sometimes called quartz arenite (SiO ₂), provenance may be determined using a rare, durable clast mineral called zircon (ZrSiO ₄). Zircon, or zirconium silicate, contains traces of uranium, which can be used for age-dating the source bedrock that contributed sediment to the lithified sandstone rock (see Chapter 7, Geologic Time).

Classification of Clastic Rocks

Clastic rocks are classified according to the grain size of their sediment. Coarse-grained rocks contain clasts with a predominant grain size larger than sand. Typically, smaller sediment grains, collectively called groundmass or matrix, fill in much of the volume between the larger clasts, and hold the clasts together. Conglomerates are rocks containing coarse rounded clasts, and breccias contain angular clasts (see figure). Both conglomerates and breccias are usually poorly sorted.

Medium-grained rocks composed mainly of sand are called , or sometimes arenite if well sorted. Sediment grains in sandstone can having a wide variety of mineral compositions, roundness, and sorting. Some sandstone names indicate the rock's mineral composition. Quartz sandstone contains predominantly quartz sediment grains. Arkose is sandstone with significant amounts of feldspar, usually greater than 25%. Sandstone that contains feldspar, which weathers more quickly than quartz, is useful for analyzing the local geologic history. Greywack e is a term with conflicting definitions. Greywacke may refer to sandstone with a muddy matrix, or sandstone with many lithic fragments (small rock pieces).

Fine-grained rocks include mudstone, shale, siltstone, and claystone. Mudstone is a general term for rocks made of sediment grains smaller than sand (less than 2 mm). Rocks that are , meaning they separate into thin sheets, are called shale. Rocks exclusively composed of silt or clay sediment, are called siltstone or claystone, respectively. These last two rock types are rarer than mudstone or shale.

Rock types found as a mixture between the main classifications, may be named using the less-common component as a descriptor. For example, a rock containing some silt but mostly rounded sand and gravel is called silty conglomerate. Sand-rich rock containing minor amounts of clay is called clayey sandstone.

5.3.3. Chemical, Biochemical, and Organic

Biochemical sedimentary rocks are formed from shells and bodies of underwater organisms. The living organisms extract chemical components from the water and use them to build shells and other body parts. The components include aragonite, a mineral similar to and commonly replaced by calcite, and silica.

Inorganic chemical

Inorganic chemical sedimentary rocks are formed when minerals precipitate out of an aqueous solution, usually due to water evaporation. The precipitate minerals form various salts known as evaporites. For example, the Bonneville Salt Flats in Utah flood with winter rains and dry out every summer, leaving behind salts such as and . The deposition order of evaporites deposit is opposite to their solubility order, i.e. as water evaporates and increases the mineral concentration in solution, less soluble minerals precipitate out sooner than the highly soluble minerals. The deposition order and saturation percentages are depicted in the table, bearing in mind the process in nature may vary from laboratory derived values.

Calcium carbonate-saturated water precipitates porous masses of calcite called . Tufa can form near degassing water and in saline lakes. Waterfalls downstream of springs often precipitate tufa as the turbulent water enhances degassing of carbon dioxide, which makes calcite less soluble and causes it to precipitate. Saline lakes concentrate calcium carbonate from a combination of wave action causing degassing, springs in the lakebed, and evaporation. In salty Mono Lake in California, tufa towers were exposed after water was diverted and lowered the lake levels.

Cave deposits like stalactites and stalagmites are another form of chemical precipitation of calcite, in a form called travertine . Calcite slowly precipitates from water to form the travertine, which often shows banding. This process is similar to the mineral growth on faucets in your home sink or shower that comes from hard (mineral rich) water. Travertine also forms at hot springs such as Mammoth Hot Spring in Yellowstone National Park.

Chert, another commonly found chemical sedimentary rock, is usually produced from silica (SiO ₂) precipitated from groundwater. Silica is highly insoluble on the surface of Earth, which is why quartz is so resistant to chemical weathering. Water deep underground is subjected to higher pressures and temperatures, which helps dissolve silica into an aqueous solution. As the groundwater rises toward or emerges at the surface the silica precipitates out, often as a cementing agent or into nodules. For example, the bases of the geysers in Yellowstone National Park are surrounded by silica deposits called geyserite or sinter. The silica is dissolved in water that is thermally heated by a relatively deep magma source. Chert can also form biochemically and is discussed in the Biochemical subsection. Chert has many synonyms, some of which may have gem value such as jasper, flint, onyx, and agate, due to subtle differences in colors, striping, etc., but chert is the more general term used by geologists for the entire group.

Biochemical

This biochemical extraction and secretion is the main process for forming limestone, the most commonly occurring, non-clastic sedimentary rock. Limestone is mostly made of calcite (CaCO ₃) and sometimes includes dolomite (CaMg(CO ₃) ₂), a close relative. Solid calcite reacts with hydrochloric acid by effervescing or fizzing. Dolomite only reacts to hydrochloric acid when ground into a powder, which can be done by scratching the rock surface (see Chapter 3, Minerals).

Limestone occurs in many forms, most of which originate from biological processes. Entire coral reefs and their ecosystems can be preserved in exquisite detail in limestone rock (see figure). Fossiliferous limestone contains many visible fossils. A type of limestone called originates from beach sands made predominantly of shells that were then lithified. Coquina is composed of loosely-cemented shells and shell fragments. You can find beaches like this in modern tropical environments, such as the Bahamas. contains high concentrations of shells from a microorganism called a coccolithophore. , also known as microscopic calcite mud, is a very fine-grained limestone containing microfossils that can only be seen using a microscope.

Under the right conditions, intact pieces of organic material or material derived from organic sources, is preserved in the geologic record. Although not derived from sediment, this lithified organic material is associated with sedimentary strata and created by similar processes-burial, compaction, and diagenesis. C Deposits of these fuels develop in areas where organic material collects in large quantities. Lush swamplands can create conditions conducive to coal formation. Shallow-water, organic material-rich marine sediment can become highly productive petroleum and natural gas deposits. See Chapter 16, Energy and Mineral Resources, for a more in-depth look at these fossil-derived energy sources.

Classification of Chemical Sedimentary Rocks

In contrast to detrital sediment, chemical, biochemical, and organic sedimentary rocks are classified based on mineral composition. Most of these are monomineralic, composed of a single mineral, so the rock name is usually associated with the identifying mineral. Chemical sedimentary rocks consisting of halite are called rock salt. Rocks made of Limestone (calcite) is an exception, having elaborate subclassifications and even two competing classification methods: Folk Classification and Dunham Classification. The Folk Classification deals with rock grains and usually requires a specialized, petrographic microscope. The Dunham Classification is based on rock texture, which is visible to the naked eye or using a hand lens and is easier for field applications. Most carbonate geologists use the Dunham system.

Sedimentary rock identification chart

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5.4 Sedimentary Structures

Sedimentary structures are visible textures or arrangements of sediments within a rock. Geologists use these structures to interpret the processes that made the rock and the environment in which it formed. They use uniformitarianism to usually compare sedimentary structures formed in modern environments to lithified counterparts in ancient rocks. Below is a summary discussion of common sedimentary structures that are useful for interpretations in the rock record.

5.4.1. Bedding Planes

The most basic sedimentary structure is bedding planes, the planes that separate the layers or strata in sedimentary and some volcanic rocks. Visible in exposed outcroppings, each bedding plane indicates a change in sediment deposition conditions. This change may be subtle. For example, if a section of underlying sediment firms up, this may be enough to create a form a layer that is dissimilar from the overlying sediment. Each layer is called a bed, or stratum, the most basic unit of stratigraphy , the study of sedimentary layering.

As would be expected, bed thickness can indicate sediment deposition quantity and timing. Technically, a bed is a bedding plane thicker than 1 cm (0.4 in) and the smallest mappable unit. A layer thinner than 1 cm (0.4 in) is called a lamina. Varves are bedding planes created when laminae and beds are deposited in repetitive cycles, typically daily or seasonally. Varves are valuable geologic records of climatic histories, especially those found in lakes and glacial deposits.

5.4.2. Graded Bedding

Graded bedding refers to a sequence of increasingly coarse- or fine-grained sediment layers. Graded bedding often develops when sediment deposition occurs in an environment of decreasing energy. A Bouma sequence is graded bedding observed in clastic rock called turbidite. Bouma sequence beds are formed by offshore sediment gravity flows, which are underwater flows of sediment. These subsea density flows begin when sediment is stirred up by an energetic process and becomes a dense slurry of mixed grains. The sediment flow courses downward through submarine channels and canyons due to gravity acting on the density difference between the denser slurry and less dense surrounding seawater. As the flow reaches deeper ocean basins it slows down, loses energy, and deposits sediment in a Bouma sequence of coarse grains first, followed by increasingly finer grains (see figure).

5.4.3. Flow Regime and Bedforms

In fluid systems, such as moving water or wind, sand is the most easily transported and deposited sediment grain. Smaller particles like silt and clay are less movable by fluid systems because the tiny grains are chemically attracted to each other and stick to the underlying sediment. Under higher flow rates, the fine silt and clay sediment tends to stay in place and the larger sand grains get picked up and moved.

Bedforms are sedimentary structures created by fluid systems working on sandy sediment. Grain size, flow velocity, and flow regime or pattern interact to produce bedforms having unique, identifiable physical characteristics. Flow regimes are divided into upper and lower regimes, which are further divided into uppermost, upper, lower, and lowermost parts. The table below shows bedforms and their associated flow regimes. For example, the dunes bedform is created in the upper part of the lower flow regime.

Plane beds created in the lower flow regime are like bedding planes, on a smaller scale. The flat, parallel layers form as sandy sediment piles and move on top of layers below. Even non-flowing fluid systems, such as lakes, can produce sediment plane beds. Plane beds in the upper flow regime are created by fast-flowing fluids. They may look identical to lower-flow-regime beds; however, they typically show parting lineations, slight alignments of grains in rows and swaths, caused by high sediment transport rates that only occur in upper flow regimes.

First scientifically described by Hertha Ayrton, ripple shapes are determined by flow type and can be straight-crested, sinuous, or complex. Asymmetrical ripples form in a unidirectional flow. Symmetrical ripples are the result of an oscillating back-and-forth flow typical of intertidal swash zones. Climbing ripples are created from high sedimentation rates and appear as overlapping layers of ripple shapes (see figure).

Dunes are very large and prominent versions of ripples, and typical examples of large cross bedding. Cross bedding happens when ripples or dunes pile atop one another, interrupting, and/or cutting into the underlying layers. Desert sand dunes are probably the first image conjured up by this category of bedform.

British geologist Agnold (1941) considered only Barchan and linear Seif dunes as the only true dune forms. Other workers have recognized transverse and star dunes as well as parabolic and linear dunes anchored by plants that are common in coastal areas as other types of dunes.

In tidal locations with strong in-and-out flows, dunes can develop in opposite directions. This produces a feature called herringbone cross bedding.

5.4.4. Bioturbation

5.4.5. Mudcracks

occur in clay-rich sediment that is submerged underwater and later dries out. Water fills voids in the clay's crystalline structure, causing the sediment grains to swell. When this waterlogged sediment begins to dry out, the clay grains shrink. The sediment layer forms deep polygonal cracks with tapered openings toward the surface, which can be seen in profile. The cracks fill with new sediment and become visible veins running through the lithified rock. These dried-out clay beds are a major source of mud chips, small fragments of mud or shale, which commonly become inclusions in sandstone and conglomerate. What makes this sedimentary structure so important to geologists, is they only form in certain depositional environments-such as tidal flats that form underwater and are later exposed to air. Syneresis cracks are similar in appearance to mudcracks but much rarer; they are formed when subaqueous (underwater) clay sediment shrinks.

5.4.6. Sole Marks

Sole marks are small features typically found in river deposits. They form at the base of a bed, the sole, and on top of the underlying bed. They can indicate several things about the deposition conditions, such as flow direction or stratigraphic up-direction (see Geopetal Structures section). Flute casts or scour marks are grooves carved out by the forces of fluid flow and sediment loads. The upstream part of the flow creates steep grooves and downstream the grooves are shallower. The grooves subsequently become filled by overlying sediment, creating a cast of the original hollow.

Formed similarly to flute casts but with a more regular and aligned shape, groove casts are produced by larger clasts or debris carried along in the water that scrape across the sediment layer. Tool marks come from objects like sticks carried in the fluid downstream or embossed into the sediment layer, leaving a depression that later fills with new sediment.

Load casts, an example of soft-sediment deformation , are small indentations made by an overlying layer of coarse sediment grains or clasts intruding into a softer, finer-grained sediment layer.

5.4.7. Raindrop Impressions

5.4.8. Imbrication

Imbrication is a stack of large and usually flat clasts-cobbles, gravels, mud chips, etc.-that are aligned in the direction of fluid flow. The clasts may be stacked in rows, with their edges dipping down and flat surfaces aligned to face the flow (see figure). Or their flat surfaces may be parallel to the layer and long axes aligned with flow. Imbrications are useful for analyzing paleocurrents, or currents found in the geologic past, especially in alluvial deposits.

5.4.9. Geopetal Structures

Vugs: Small voids in the rock that usually become filled during diagenesis. If the void is partially filled or filled in stages, it serves as a permanent record of a level bubble, frozen in time.

Cross bedding - In places where ripples or dunes pile on top of one another, where one cross bed interrupts and/or cuts another below, this shows a cross-cutting relationship that indicates up direction.

Ripples, dunes: Sometimes the ripples are preserved well enough to differentiate between the crests (top) and troughs (bottom).

Fossils: Body fossils in life position, meaning the body parts are not scattered or broken, and trace fossils like footprints (see figure) can provide an up direction. Intact fossilized coral reefs are excellent up indicators because of their large size and easily distinguishable top and bottom. Index fossils, such as ammonites, can be used to age date strata and determine up direction based on relative rock ages.

Vesicles - Lava flows eliminate gas upwards. An increase of vesicles toward the top of the flow indicates up.

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5.5 Depositional Environments

5.5.1. Marine

Marine depositional environments are completely and constantly submerged in seawater. Their depositional characteristics are largely dependent on the depth of water with two notable exceptions, submarine fans and turbidites.

Abyssal sedimentary rocks form on the abyssal plain . The plain encompasses relatively flat ocean floor with some minor topographical features, called abyssal hills. These small seafloor mounts range 100 m to 20 km in diameter, and are possibly created by extension. Most abyssal plains do not experience significant fluid movement, so sedimentary rock formed there are very fine grained.

There are three categories of abyssal sediment. Calcareous oozes consist of calcite-rich plankton shells that have fallen to the ocean floor. An example of this type of sediment is chalk. Siliceous oozes are also made of plankton debris, but these organisms build their shells using silica or hydrated silica. In some cases such as with diatomaceous earth, sediment is deposited below the calcite compensation depth , a depth where calcite solubility increases. Any calcite-based shells are dissolved, leaving only silica-based shells. Chert is another common rock formed from these types of sediment. These two types of abyssal sediment are also classified as biochemical in origin. (see BIOCHEMICAL section).

The third sediment type is pelagic clay. Very fine-grained clay particles, typically brown or red, descend through the water column very slowly. Pelagic clay deposition occurs in areas of remote open ocean, where there is little plankton accumulation.

Two notable exceptions to the fine-grained nature of abyssal sediment are submarine fan and deposits. Submarine fans occur offshore at the base of large river systems. They are initiated during times of low sea level, as strong river currents carve submarine canyons into the continental shelf. When sea levels rise, sediment accumulates on the shelf typically forming large, fan-shaped floodplains called deltas. Periodically, the sediment is disturbed creating dense slurries that flush down the underwater canyons in large gravity-induced events called turbidites. The submarine fan is formed by a network of turbidites that deposit their sediment loads as the slope decreases, much like what happens above-water at alluvial fans and deltas. This sudden flushing transports coarser sediment to the ocean floor where they are otherwise uncommon. Turbidites are also the typical origin of graded Bouma sequences. (see Chapter 5, Weathering, Erosion, and Sedimentary Rock).

Continental Slope

Lower shoreface

Upper shoreface

5.5.2. Transitional coastline environments

Transitional environments, more often called shoreline or coastline environments, are zones of complex interactions caused by ocean water hitting land. The sediment preservation potential is very high in these environments because deposition often occurs on the continental shelf and underwater. Shoreline environments are an important source of hydrocarbon deposits (petroleum, natural gas).

The study of shoreline depositional environments is called sequence stratigraphy . Sequence stratigraphy examines depositional changes and 3D architectures associated with rising and falling sea levels, which is the main force at work in shoreline deposits. These sea-level fluctuations come from the daily tides, as well as climate changes and plate tectonics. A steady rise in sea level relative to the shoreline is called transgression . Regression is the opposite, a relative drop in sea level. Some common components of shoreline environments are littoral zones, tidal flats, reefs, lagoons, and deltas. For a more in-depth look at these environments, see Chapter 12, Coastlines.

Tidal Flats

Tidal flats, or mud flats, are sedimentary environments that are regularly flooded and drained by ocean tides. Tidal flats have large areas of fine-grained sediment but may also contain coarser sands. Tidal flat deposits typically contain gradational sediments and may include multi-directional ripple marks. Mudcracks are also commonly seen due to the sediment being regularly exposed to air during low tides; the combination of mudcracks and ripple marks is distinctive to tidal flats.

Tidal water carries in sediment, sometimes focusing the flow through a narrow opening called a tidal inlet. Tidal channels, creek channels influenced by tides, can also focus tidally-induced flow. Areas of higher flow like inlets and tidal channels feature coarser grain sizes and larger ripples, which in some cases can develop into dunes.

Reefs, which most people would immediately associate with tropical coral reefs found in the oceans, are not only made by living things. Natural buildups of sand or rock can also create reefs, similar to barrier islands. Geologically speaking, a reef is any topographically-elevated feature on the continental shelf, located oceanward of and separate from the beach. The term reef can also be applied to terrestrial (atop the continental crust) features. Capitol Reef National Park in Utah contains a topographic barrier, a reef, called the Waterpocket Fold.

Most reefs, now and in the geologic past, originate from the biological processes of living organisms. The growth habits of coral reefs provide geologists important information about the past. The hard structures in coral reefs are built by soft-bodied marine organisms, which continually add new material and enlarge the reef over time. Under certain conditions, when the land beneath a reef is subsiding, the coral reef may grow around and through existing sediment, holding the sediment in place, and thus preserving the record of environmental and geological condition around it.

Sediment found in coral reefs is typically fine-grained, mostly carbonate, and tends to deposit between the intact coral skeletons. Water with high levels of silt or clay particles can inhibit the reef growth because coral organisms require sunlight to thrive; they host symbiotic algae called zooxanthellae that provide the coral with nourishment via photosynthesis. Inorganic reef structures have much more variable compositions. Reefs have a big impact on sediment deposition in lagoon environments since they are natural storm breaks, wave and storm buffers, which allows fine grains to settle and accumulate.

Reefs are found around shorelines and islands; coral reefs are particularly common in tropical locations. Reefs are also found around features known as , which is the base of an ocean island left standing underwater after the upper part is eroded away by waves. Examples include the Emperor Seamounts, formed millions of years ago over the Hawaiian Hotspot. Reefs live and grow along the upper edge of these flat-topped seamounts. If the reef builds up above sea level and completely encircles the top of the seamount, it is called a coral-ringed atoll. If the reef is submerged, due to erosion, subsidence, or sea level rise, the seamount-reef structure is called a guyot.

Deltas are organized by the dominant process that controls their shape: tide-dominated, wave-dominated, or river-dominated. Wave-dominated deltas generally have smooth coastlines and beach-ridges on the land that represent previous shorelines. The Nile River delta is a wave-dominated type. (see figure).

The Mississippi River delta is a river-dominated delta. shaped by levees along the river and its distributaries that confine the flow forming a shape called a birdfoot delta. Other times the tides or the waves can be a bigger factor, and can reshape the delta in various ways.

A tide-dominated delta is dominated by tidal currents. During flood stages when rivers have lots of water available, it develops distributaries that are separated by sand bars and sand ridges. The tidal delta of the Ganges River is the largest delta in the world.

5.5.3. Terrestrial

Terrestrial depositional environments are diverse. Water is a major factor in these environments, in liquid or frozen states, or even when it is lacking (arid conditions).

Fluvial (river) systems are formed by water flowing in channels over the land. They generally come in two main varieties: meandering or braided. In meandering streams, the flow carries sediment grains via a single channel that wanders back and forth across the floodplain. The floodplain sediment away from the channel is mostly fine grained material that only gets deposited during floods.

Braided fluvial systems generally contain coarser sediment grains, and form a complicated series of intertwined channels that flow around gravel and sand bars ( see Chapter 11, Water).

A distinctive characteristic of systems is the intermittent flow of water. Alluvial deposits are common in arid places with little soil development. Lithified alluvial beds are the primary basin-filling rock found throughout the Basin and Range region of the western United States. The most distinctive alluvial sedimentary deposit is the alluvial fan, a large cone of sediment formed by streams flowing out of dry mountain valleys into a wider and more open dry area. Alluvial sediments are typically poorly sorted and coarse grained, and often found near playa lakes or aeolian deposits ( see Chapter 13, Deserts).

Lacustrine

Lake systems and deposits, called lacustrine, form via processes somewhat similar to marine deposits, but on a much smaller scale. Lacustrine deposits are found in lakes in a wide variety of locations. Lake Baikal in southeast Siberia (Russia) is in a tectonic basin. Crater Lake (Oregon) sits in a volcanic caldera. The Great Lakes (northern United States) came from glacially carved and deposited sediment. Ancient Lake Bonneville (Utah) formed in a pluvial setting that during a climate that was relatively wetter and cooler than that of modern Utah. Oxbow lakes, named for their curved shape, originated in fluvial floodplains. Lacustrine sediment tends to be very fine grained and thinly laminated, with only minor contributions from wind-blown, current, and tidal deposits. When lakes dry out or evaporation outpaces precipitation, playas form. Playa deposits resemble those of normal lake deposits but contain more evaporite minerals. Certain tidal flats can have playa-type deposits as well.

With sufficient sediment influx, aeolian systems can potentially form large dunes in dry or wet conditions. The figure shows dune features and various types. British geologist Ralph A. Bagnold (1896-1990) considered only Barchan and linear Seif dunes as the only true dune forms. Other scientists recognize transverse, star, parabolic, and linear dune types. Parabolic and linear dunes grow from sand anchored by plants and are common in coastal areas.

Compacted layers of wind-blown sediment is known as . Loess commonly starts as finely ground up rock flour created by glaciers. Such deposits cover thousands of square miles in the Midwestern United States. Loess may also form in desert regions ( see Chapter 13). Silt for the Loess Plateau in China came from the Gobi Desert in China and Mongolia.

Glacial sedimentation is very diverse, and generally consists of the most poorly-sorted sediment deposits found in nature. The main clast type is called diamictite, which literally means two sizes, referring to the unsorted mix of large and small rock fragments found in glacial deposits. Many glacial tills, glacially derived diamictites, include very finely-pulverized rock flour along with giant erratic boulders. The surfaces of larger clasts typically have striations from the rubbing, scraping, and polishing of surfaces by abrasion during the movement of glacial ice. Glacial systems are so large and produce so much sediment, they frequently create multiple, individualized depositional environments, such as fluvial, deltaic, lacustrine, pluvial, alluvial, and/or aeolian ( see Chapter 14, Glaciers).

In addition to mineral composition and lithification process, geologists also classify sedimentary rock by its depositional characteristics, collectively called facies or lithofacies. Sedimentary facies consist of physical, chemical, and/or biological properties, including relative changes in these properties in adjacent beds of the same layer or geological age. Geologists analyze sedimentary rock facies to interpret the original deposition environment, as well as disruptive geological events that may have occurred after the rock layers were established.

Biological facies are remnants (coal, diatomaceous earth) or evidence (fossils) of living organisms. Index fossils, fossilized life forms specific to a particular environment and/or geologic time period, are an example of biological facies. The horizontal assemblage and vertical distribution of fossils are particularly useful for studying species evolution because transgression, deposition, burial, and compaction processes happen over a considerable geologic time range.

Fossil assemblages that show evolutionary changes greatly enhance our interpretation of Earth's ancient history by illustrating the correlation between stratigraphic sequence and geologic time scale. During the Middle Cambrian period (see Chapter 7, Geologic Time), regions around the Grand Canyon experienced marine transgression in a southeasterly direction (relative to current maps). This shift of the shoreline is reflected in the Tapeats Sandstone beach facies, Bright Angle Shale near-offshore mud facies, and Muav Limestone far-offshore facies. Marine organisms had plenty of time to evolve and adapt to their slowly changing environment; these changes are reflected in the biological facies, which show older life forms in the western regions of the canyon and younger life forms in the east.

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Sedimentary rocks are grouped into two main categories: clastic (detrital) and chemical. Clastic (detrital) rocks are made of mineral clasts or sediment that lithifies into solid material. Sediment is produced by the mechanical or chemical weathering of bedrock and transported away from the source via erosion. Sediment that is deposited, buried, compacted, and sometimes cemented becomes clastic rock. Clastic rocks are classified by grain size; for example sandstone is made of sand-sized particles. Chemical sedimentary rocks comes from minerals precipitated out an aqueous solution and is classified according to mineral composition. The chemical sedimentary rock limestone is made of calcium carbonate. Sedimentary structures have textures and shapes that give insight on depositional histories. Depositional environments depend mainly on fluid transport systems and encompass a wide variety of underwater and above ground conditions. Geologists analyze depositional conditions, sedimentary structures, and rock records to interpret the paleogeographic history of a region.

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3. Ayrton, H., 1910, The origin and growth of ripple-mark: Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character, v. 84, no. 571, p. 285-310.

4. Bagnold, R.A., 1941, The physics of blown sand and desert dunes: Methum, London, UK, p. 265.

5. Blatt, H., Middleton, G.V., and Murray, R., 1980, Origin of Sedimentary Rocks: Prentice-Hall, Inc., Englewood Cliffs, New Jersey, USA.

6. Bouma, A.H., Kuenen, P.H., and Shepard, F.P., 1962, Sedimentology of some flysch deposits: a graphic approach to facies interpretation: Elsevier Amsterdam.

7. Cant, D.J., 1982, Fluvial facies models and their application:

8. Dickinson, W.R., and Suczek, C.A., 1979, Plate tectonics and sandstone compositions: AAPG Bull., v. 63, no. 12, p. 2164-2182.

9. Dunham, R.J., 1962, Classification of carbonate rocks according to depositional textures:

10. Eisma, D., 1998, Intertidal deposits: River mouths, tidal flats, and coastal lagoons: CRC Marine Science, Taylor & Francis, CRC Marine Science.

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17. Longman, M.W., 1981, A process approach to recognizing facies of reef complexes:

18. Mckee, E.D., and Weir, G.W., 1953, Terminology for stratification and cross-stratification in sedimentary rocks: Geol. Soc. Am. Bull., v. 64, no. 4, p. 381-390.

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20. Nichols, M.M., Biggs, R.B., and Davies, R.A.Jr., 1985, Estuaries, in Coastal Sedimentary Environments: Springer-Verlag: New York, p. 77-173.

21. Normark, W.R., 1978, Fan valleys, channels, and depositional lobes on modern submarine fans: characters for recognition of sandy turbidite environments: AAPG Bull., v. 62, no. 6, p. 912-931.

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23. Plummer, P.S., and Gostin, V.A., 1981, Shrinkage cracks: desiccation or synaeresis? J. Sediment. Res., v. 51, no. 4.

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26. Stow, D.A.V., Faugères, J.-C., Viana, A., and Gonthier, E., 1998, Fossil contourites: a critical review: Sediment. Geol., v. 115, no. 1-4, p. 3-31.

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29. Wentworth, C.K., 1922, A scale of grade and class terms for clastic sediments: J. Geol., v. 30, no. 5, p. 377-392.

30. Yin, D., Peakall, J., Parsons, D., Chen, Z., Averill, H.M., Wignall, P., and Best, J., 2016, Bedform genesis in bedrock substrates: Insights into formative processes from a new experimental approach and the importance of suspension-dominated abrasion: Geomorphology, v. 255, p. 26-38.

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5 Weathering, Erosion, and Sedimentary Rocks

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Announcement: Chapter quizzes are not working as of summer 2023.

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4 September 2021 - 6 February 2022
Beit Wing Curators | Donal Maguire and Dr Brendan Rooney Happily supported by Key Capital
"No one creates. The artist assembles memories." - Jack B. Yeats
If you or your company wish to support our exhibition programme, our Development team will be delighted to speak with you about sponsorship or making a donation. Please call +353 (0) 1 632 5541 to speak to a member of the team.
Coinciding with the 150 th anniversary of the birth of one of Ireland's most important artists, this exhibition explores the role of memory in Jack B. Yeats' life and work. From his earliest forays into oil painting, Yeats was unusually reliant on memory and retrospection. Memories of childhood in Sligo inspired many of his works, and particular motifs - music and horses prominent among them - recur in his paintings. In a selection of oil paintings spanning more than 40 years, view places and people Yeats remembered, his observations of humanity, and reflections on life and loss in his later years.

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4 September 2021 - 6 February 2022 Beit Wing Curators | Donal Maguire and Dr Brendan Rooney Happily supported by Key Capital "No one creates. The artist assembles memories." - Jack B. Yeats If you or your company wish to support our exhibition programme, our Development team will be delighted to speak with you about sponsorship or making a donation.

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Featuring more than 90 recent works by over 40 artists, 'Memory Palace' seeked to inspire reflections on the forms and themes of memory.

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Curated by Susanna Greeves and Susan May
11 July - 2 September 2018
White Cube Bermondsey

Autobiographical - Featuring Franz Ackermann, Etel Adnan, George Baselitz, Tracey Emin, Gilbert & George, Magnus Plessen, Raqib Shaw, Christine Ay Tjoe and Liu Wei

As history began to be defined as a discipline, so the sense grew that memory was subjective and concerned with the inner life. During the Enlightenment and Romantic period, the concept of memory emerged as something personal and bound up with identity. In modern times, mass media forms such as reality TV, exposés and chat shows have made ubiquitous the disclosure of personal histories. Art is an ideal medium for the intimate and confessional, lending itself to diaristic and autobiographical forms. As these artists show, all experience can be manifest in art, whether captured in the moment or recollected in tranquillity.

Traces - Featuring Darren Almond, Miroslaw Balka, Antony Gormley, Andreas Gursky, David Hammons, Mona Hatoum, Runa Islam, Rachel Kneebone, Ibrahim Mahama, Virginia Overton, Jeff Wall and He Xiangyu

We can think of an artwork as a memory of the gestures or actions that produced it: the record of a line, a brushstroke, a thumb in wet clay. In a cast, an impression or a print, a memory is anchored through an indexical relationship with the subject: the artwork and that which it has touched. In its inception, photography was also felt to have a direct existential relationship with the subject, a quasi-magical capturing of the essence. Now, in our digital age, it is perceived as unreliable and easily manipulated: just as our understanding has grown that memory can be false, unreliable or partial.

Transcription - Featuring Cerith Wyn Evans, Christian Marclay, Harland Miller, Sarah Morris, Eddie Peake and Jessica Rankin

The Memory Palace technique develops the skill of committing to memory without making an external record. However, the idea of memory has been indivisible from the means of recording it since Plato defined the concept using the metaphor of memory as a wax tablet. As memory is equated with inscription, so too is forgetting with erasure. Transcribing memories is a means of sharing them, and of declaring them, whether in the form of an inscription on stone or a graffiti tag. These artists use text in a variety of ways and show how other forms of notation can record the memory of sound or movement.

Collective - Featuring Sergej Jensen, Elad Lassry, Jac Leirner, Christian Marclay, Josiah McElheny, Beatriz Milhazes, Gabriel Orozco, Damián Ortego, Haim Steinbach and Fred Tomaselli

The material world offers a vital framework for the formation of collective memory. The everyday objects that surround us and products we consume, the pop culture images and major news events that are part of our shared experience, merge to create our group consciousness. It is a form of memory that resides not in an individual mind but in a common realm. These artists summon collective memory, drawing on the power of the recognisable or shared events and familiar objects.

Sensory - Featuring Ellen Altfest, Cerith Wyn Evans, Robert Irwin, Imi Knoebel, Liza Lou and Virginia Overton

We think of memory as located in the mind, yet Aristotle noted the physical basis of memory, overlooked by Plato in his emphasis on the visual. To psychologists, sensory memory is a short-term impression registered through the senses without conscious control. For Proust, the sensory basis of memory resided in all the senses but sight: hearing, smell, taste, touch. He distinguished voluntary from involuntary memory; the latter may be triggered by a sensory experience, which summons uninvited a flood of recollection, sensation and emotion beyond the reach of intellect or visual memory. These artworks focus our attention on perceptual phenomena of light or colour, or appeal to our senses of touch and even smell.
'Memory Palace' continues at White Cube Mason's Yard until Saturday 15 September 2018. Download Exhibition Guide

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White Cube - Gallery Exhibitions - Memory Palace

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'Memory Palace' was a major group exhibition extending across White Cube's London galleries in Bermondsey and Mason's Yard. Featuring more than 90 recent works by over 40 artists, 'Memory Palace' seeked to inspire reflections on the forms and themes of memory. The exhibition's

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A group exhibition featuring selected work by artists Tara Donovan, Tom Friedman, Robert Gober and Mark Manders. Memory and Obsession brings together new and important works by four leading international artists who make sculpture and drawing. By looking at their individual approaches to making art, the exhibition reveals a shared tendency towards the obsessive and a collective interest in personal histories.

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A broad grouping of contemporary works that attempt to capture a sense of memory through fading or disintegrating imagery. These works are often, but not always, figurative, and many are inspired by Gerhard Richter’s paintings. While the category is primarily comprised of paintings, it also includes highly stylized photography and video works that evoke the passage of time and memories both personal and collective.

# data[].attributes.attachment_link.readable_text
A broad grouping of contemporary works that attempt to capture a sense of memory through fading or disintegrating imagery. These works are often, but not always, figurative, and many are inspired by Gerhard Richter 's paintings. While the category is primarily comprised of paintings, it also includes highly stylized photography and video works that evoke the passage of time and memories both personal and collective.

# data[].attributes.attachment_link.description
A broad grouping of contemporary works that attempt to capture a sense of memory through fading or disintegrating imagery. These works are often, but not always, figurative, and many are inspired by Gerhard Richter's paintings. While the category is primarily comprised of paintings, it also includes highly stylized photography and video works that evoke the passage of time and memories both personal and collective.

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Art | Memory | Place was a year-long programme of talks and events taking place over the course of 2015-16 in the context of the 'decade of centenaries.' Focusing on artists whose work addresses themes relating to memory and place, the purpose of this programme was to broaden and deepen the current discussion about the subject of remembrance and commemoration and to take account of such work.

Many artists are creating work that is concerned with memory and the past but does not necessarily take the form of a memorial or a commemorative gesture. Such work may arise out of the imperative of the artist rather than in response to an event or a public commission. Artists, critical writers and researchers are also articulating their ideas about the significance and meaning of such practice. The purpose of this programme was to broaden and deepen the current discussion about the subject of remembrance and commemoration to take account of such work.

The Art | Memory | Place programme was launched in October 2015 and ran throughout 2016, focusing on the role of art and artists whose work addresses the subject of memory.

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Art | Memory | Place was a year-long programme of talks and events taking place over the course of 2015-16 in the context of the 'decade of centenaries.' Focusing on artists whose work addresses themes relating to memory and place, the purpose of this programme was to broaden and deepen the current discussion about the [...]

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From Generation to Generation: Inherited Memory and Contemporary Art

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From Generation to Generation: Inherited Memory and Contemporary Art

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There are many forms of memory: memories of events we have experienced, memories we have heard as family stories and from popular culture, even memories of an imagined future. The twenty-four artists in From Generation to Generation: Inherited Memory and Contemporary Art work with memories that are not their own.

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The CJM | From Generation to Generation: Inherited Memory and Contemporary Art

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From Generation to Generation: Inherited Memory and Contemporary Art presents work by twenty-four artists who grapple with memories that are not their own. There are many forms of memory: memories we have experienced, memories we have heard as family stories and from popular culture, even memories f…

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https://www.bookdepository.com/Empathic-Vision/9780804751711

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whitney biennial visual arts letterpress prints multidisciplinary artist speech acts phaidon monument lab political guggenheim fellowship museum

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Everything Else Has Failed! Don't You Think It's Time For Love? by Sharon Hayes | Tate