Sediments - Group 1 2024 PDF

SEDIMENTS Acula, Albores Alivio, Bantiles Baya, Dialde Peñaflor, Vinzon  KEY CONCEPTS Sediments are loose accumulations of particulate material. The depth and composition of marine sediments tell us of relatively recent events in the ocean basin above. The most abundant sediments are te...

SEDIMENTS Acula, Albores Alivio, Bantiles Baya, Dialde Peñaflor, Vinzon  KEY CONCEPTS Sediments are loose accumulations of particulate material. The depth and composition of marine sediments tell us of relatively recent events in the ocean basin above. The most abundant sediments are terrigenous (from land) and biogenous (from once-living things). Marine sediments have been uplifted and exposed on land. Arizona’s Grand Canyon is made of marine sediment, as is the top of the world’s highest mountain. Because marine sediments are usually subducted along with the seabed on which they lie, the oldest sediments are relatively young—rarely older than 180 million years. Table of Contents Ocean Sediments Sediments are 01 vary greatly in appearance 02 classified by particle size Sediments may Neritic Sediments 03 be classified by source 04 overlie continental margins Pelagic Sediments Researchers 05 vary in composition and 06 and Geologists thickness Historical records 07 and Economical Significance WHAT ARE SEDIMENTS? 01 Ocean Sediments Vary Greatly in Appearance Ripples on the sediment beneath the Sediment near Brittle stars and their swift Antarctic Circum- the crest of the tracks on the continental polar Current in the Mid-Atlantic slope off the coast of northern Drake Ridge. New England. Passage. 01 Ocean Sediments Vary Greatly in Appearance The deep sediments of the Sohm Abyssal Plain in the North Atlantic south of Nova Scotia have buried the base of this seamount. This seismic profile shows the depth of the sediments above the geological base of the seamount to be more than 1.8 kilometers (1.1 miles). 02 Sediments vary in Particle Size Most Sediments are made of: sand, silt and clay. As sediments travel, they get sorted by size: finer grains travel farther than coarser grains. Cohesiveness of smaller particles is important in determining whether they will be eroded and transported.  02 Sediments vary in Particle Size Well-sorted sediments occur in an environment where energy fluctuates within narrow limits. A layer of sediment can contain particles of similar size, or it can be a Poorly sorted sediments form in mixture of different-sized particles. environments where energy fluctuates over a wide spectrum. Sediments with a mixture of sizes are poorly sorted sediments. Sorting is a https://geologyistheway.com/sedimentary/sorting/ function of the energy of the environment—the exposure of that area to the action of waves, tides, and currents. 03 Sediments may be classified by source Another way to classify marine sediments is by their origin. Such a scheme was first proposed in 1891 by Sir John Murray and A. F. Renard after a thorough study of sediments collected during the Challenger expedition. This scheme separates sediments into four categories by source: terrigenous, biogenous, hydrogenous (also called authigenic), and cosmogenous. 03 Sediments may be classified by source Terrigenous Sediments Come from Land Terrigenous Sediments (terra, “Earth”; generare, “to produce”) They originate on the continents or islands from erosion, volcanic eruptions, and blown dust. Terrigenous sediments are part of a slow and massive cycle. Over the great span of geologic time, mountains rise as plates collide, fuse, and subduct. The mountains erode. The resulting sediments are transported to the sea by wind and water, where they collect on the seafloor. The sediments travel with the plate and are either uplifted or subducted. The material is made into mountains. The cycle begins a new. 03 Sediments may be classified by source Biogenous Sediments (bio, “life”; generare, “to produce”) form from the Remains of Marine Organisms https://geo.libretexts.org/Bookshelves/Oceanography/Introduction_to_Oceanography_%28Webb%29/12%3A_O cean_Sediments/12.03%3A_Biogenous_Sediments  03 Sediments may be classified by source Hydrogenous sediments (hydro, “water”; generare, “to produce”) are minerals that have precipitated directly from seawater. The most obvious hydrogenous sediments are manganese nodules, which litter some deep sea-beds, and phosphorite nodules, seen along some continental margins. Hydrogenous sediments are also called authigenic sediments (authis, “in place, on the spot”) because they were formed in the place they now occupy. Image Source: https://www.sciencedirect.com/science/article/abs/pii/S1572548008002133 03 Sediments may be classified by source Cosmogenous Sediments Come from Space Cosmogenous sediments (cosmos, “universe”; generare, “to produce”), which are of extraterrestrial origin, are the least abundant. These sediments are typically greatly diluted by other sediment components and rarely constitute more than a few parts per million of the total sediment in any layer. Scientists believe that cosmogenous sediments come from https://www.sciencedirect.com/science/article/abs/p two major sources: interplanetary dust that falls constantly ii/S1572548008002133 into the top of the atmosphere and rare impacts by large asteroids and comets. 03 Sediments may be classified by source Marine Sediments Are Usually Combinations of Terrigenous and Biogenous Deposits Continental shelf sediments— called neritic sediments (neritos; of the coast)— consist primarily of terrigenous material. Sediments of the slope, rise, and a deep-ocean floor that originates in the ocean are called pelagic sediments (pelagios; of the sea). 04 Neretic Sediments Overlie Continental Margins Neritic sediments are primarily terrigenous, originating from land. These sediments are eroded and transported by streams into the ocean. They are typically found over continental margins and play a crucial role in shaping ocean floor characteristics. The primary components include sand, silt, and clay, which vary in size and origin. Terrigenous Source: Eroded materials from land. Transport Mechanism: Carried by rivers and streams to the ocean. Location: Found over continental margins. Primary Components: Sand: Larger particles. Silt: Medium-sized particles. Clay: Smallest particles. Redirect notice. (n.d.-c). https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.researchgate.net%2Ffigure%2FPhotographs-of-turbidite-layers-showingneritic-sediment-grains-from-Pedro-Bank-A- andB_fig3_225918808&psig=AOvVaw3JY7319Q55ooCgNxLP76bx&ust=1728819253181000&source=images&cd=vfe&opi=89978449&ved=0CBQQjRxqFwoTCPjxkN3fiIkDFQAAAAAdAAAAABAE  04 Neretic Sediments Overlie Continental Margins Currents and wave action are key in distributing sediments along coastlines. Currents carry sand and larger particles, while wave action moves finer silts and clays to deeper waters. This results in an orderly sorting of particles: Larger grains settle near the coast. Smaller grains accumulate further out. When currents are too weak for wave action to affect sediment, the finest particles may remain suspended or settle on the deep ocean floor. The general pattern of sediments on the ocean floor  04 Neretic Sediments Overlie Continental Margins Biogenic Contributions to Sediments Neritic sediments also Coccolithophores produce contain significant coccoliths, small plates Other contributors include radiolaria and biological material. essential in the formation of diatoms, which are single-celled algae Foraminiferans are calcareous oozes, which are amoeba-like organisms prevalent in high-latitude regions. generally absent at depths contributing to biogenic below 4,500 meters due to sediments. dissolution. A foraminiferan, an Coccoliths, individual Radiolaria, another Shells of diatoms, single- amoeba-like animal plates of coccolithophores, siliceous ooze-former celled algae a form of planktonic algae. 04 Neretic Sediments Overlie Continental Margins Shelf deposits are significantly influenced by sea Researchers suspended over an level fluctuations. During ice ages, when sea levels iceberg take samples of the dust and gravel scraped off a nearby drop, continental shelves can become exposed, continent by the iceberg’s parent glacier. affecting sediment distribution. This results in several important effects: Direct Transport: Rivers can transport sediments directly to the continental slope. Turbidity Currents: These currents move sediments quickly into deeper ocean areas, disrupting typical sorting. Glacial Influence: Glaciers can carry various particle sizes, creating poorly sorted deposits when they melt. Understanding these processes is crucial for comprehending sediment dynamics on continental margins. 04 Neretic Sediments Overlie Continental Margins Sediment accumulation rates vary significantly across regions. Key points include: High Accumulation Rates: Near large rivers, sediments can accumulate at rates of up to 1 meter every 1,000 years. Estuarine Trapping: Many estuaries trap sediment, preventing it from reaching the continental shelf. Lithification Process: Over time, neritic sediments can undergo lithification, transforming into sedimentary rock through: An example of lithified sediment is Mount - Compaction: Pressure from overlying sediments Everest, which is primarily composed of compresses deeper layers. marine limestone formed from ancient - Cementation: Minerals precipitate from water ocean sediments. and bind sediments together. 05 PELAGIC SEDIMENTS VARY IN COMPOSITION AND THICKNESS QUICK RECALL: Oceanic Zone The thickness of Pelagic Sediments are highly variable the composition and thickness also vary Pelagic with location: Zone thickest on the abyssal plains thinnest (or absent) on the oceanic ridges https://es.pinterest.com/pin/understanding-the-differences-between-benthic- and-pelagic-zones-science-struck--1078119598272385085/ 05 PELAGIC SEDIMENTS VARY IN COMPOSITION AND THICKNESS HOW IS PELAGIC SEDIMENTS FORMED? Due to Turbidity Currents the dense mixture of sediments flow down deep sea floor by gravity 05 PELAGIC SEDIMENTS VARY IN COMPOSITION AND THICKNESS HOW ARE PELAGIC SEDIMENTS FORMED? Due to water and wind currents and settle slowly in deep ocean floor Microscopic waterborne particles and tiny bits of windborne dust and volcanic ash settle slowly to the deep-ocean floor, forming fine brown, olive-colored, or reddish clays. https://www.google.com/url?sa=i&url=https%3A%2F%2Fslideplayer.com%2Fslide%2F10772066%2F&psig=AOvVaw1K7HLyjtNQRaB5KfSu- Xdi&ust=1728824720311000&source=images&cd=vfe&opi=89978449&ved=0CBQQjRxqFwoTCKiQi430iIkDFQAAAAAdAAAAABAJ  05 PELAGIC SEDIMENTS VARY IN COMPOSITION AND THICKNESS HOW IS PELAGIC SEDIMENTS FORMED? From the rigid remains of living creatures that formed Oozes Deep-ocean sediment containing at least 30% biogenous material is called an ooze. The organisms that contribute their remains to deep-sea oozes are small, singlecelled, drifting, plantlike organisms and the single-celled animals that feed on them. The silica-rich residues give rise to siliceous ooze; the calcium-containing material to calcareous ooze Redirect notice. (n.d.-b). https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.sciencedirect.com%2Ftopics%2Fearth-and-planetary- sciences%2Fpelagicsediment&psig=AOvVaw2z8QJqFh14UAMvngpaK3TF&ust=1728815167897000&source=images&cd=vfe&opi=89978449&ved=0CBQQjRxqFwoTCIj-h8HQiIkDFQAAAAAdAAAAABAE 05 PELAGIC SEDIMENTS VARY IN COMPOSITION AND THICKNESS TYPES OF OOZE Small drifting mollusks called Calcareous ooze forms pteropods, and tiny algae mainly from shells of the known as coccolithophores amoebalike foraminifera 05 PELAGIC SEDIMENTS VARY IN COMPOSITION AND THICKNESS TYPES OF OOZE Radiolarian Oozes occur in Siliceous (silicon-containing) equatorial regions, most ooze is formed from the hard notably in the zone of equatorial upwelling west of parts of another amoeba- South America. like animal, the beautiful glassy radiolarian , and from single-celled algae called diatoms. Diatom ooze is most common in the deep-ocean basins Covering about 14% of the surrounding Antarctica because deep-ocean floor’s surface , it strong ocean currents and predominates at greater seasonal upwelling in this area depths and in colder polar support large populations of regions. diatoms. General Pattern of Sediments on the Ocean Floor 05 PELAGIC SEDIMENTS VARY IN COMPOSITION AND THICKNESS How could such tiny particles fall quickly enough to avoid great horizontal displacement? This involves their compression into fecal pellets. They are much larger than the tiny individual skeletons of diatoms, foraminifera, and other plantlike organisms that they consumed, so they fall much faster, reaching the deep-ocean floor in about 2 weeks. Some deep-sea oozes have been uplifted by geological processes and are now visible on land. The white calcareous chalk cliffs of Dover are partially lithified deposits composed largely of foraminifera and coccolithophores. Diatomaceous earth, fine-grained siliceous deposits, are mined from other deposits. This fossil material is a valued component in flat paints, pool and spa filters, and mildly abrasive car and tooth polishes. 05 PELAGIC SEDIMENTS VARY IN COMPOSITION AND THICKNESS HYDROGENOUS MATERIALS PRECIPITATE OUT OF SEAWATER ITSELF Hydrogenous sediments are associated with terrigenous or biogenous sediments and rarely form sediments by themselves. Most originate from chemical reactions that occur on particles of the dominant sediment. The most famous are manganese nodules, which were discovered by the hardworking crew of HMS Challenger. The nodules consist primarily of They form in ways not fully manganese and iron oxides and understood by marine chemists, contain small amounts of cobalt, “growing” at an average rate of 1 nickel, chromium, copper, to 10 millimeters (0.04–0.4 inch) per molybdenum, and zinc. million years. 05 PELAGIC SEDIMENTS VARY IN COMPOSITION AND THICKNESS Though most are irregular lumps the size of a potato, some nodules may exceed 1 meter (3.3 feet) in diameter and often form around nuclei such as sharks’ teeth, bits of bone, microscopic alga and animal skeletons, and tiny crystals. Bacterial activity may play a role in the development of a nodule. Around 20 - 50% of the Pacific Ocean floor may be strewn with nodules. WHY DON’T THESE HEAVY LUMPS DISAPPEAR UNDER THE CONSTANT RAIN OF ACCUMULATING SEDIMENT? Possibly the continuous churning of the underlying sediment by creatures living there keeps the dense lumps on the surface, or perhaps slow currents in areas of nodule accumulation waft particulate sediments away. 05 PELAGIC SEDIMENTS VARY IN COMPOSITION AND THICKNESS EVAPORITES ARE AN IMPORTANT GROUP OF HYDROGENOUS DEPOSITS Evaporites include many salts important to humanity. These salts precipitate as water evaporates from isolated arms of the ocean or from landlocked seas or lakes. They are forming today in the Gulf of California, the Red Sea, and the Persian Gulf. The first evaporites to precipitate as water’s salinity increases are the carbonates, such as: Calcium carbonate from which limestone is formed Calcium sulfate gives rise to gypsum Evaporated crystals of sodium chloride form table salt Deposition of such a thick evaporite layer would have required evaporation of an arm of the ocean over a long period of time. 05 PELAGIC SEDIMENTS VARY IN COMPOSITION AND THICKNESS Geology students inspect the base of a thick layer of rock gypsum in Colorado. This rock probably formed by the lithification of evaporites left behind as a shallow inland sea dried up. 05 PELAGIC SEDIMENTS VARY IN COMPOSITION AND THICKNESS OOLITE SANDS FORM WHEN CALCIUM CARBONATE PRECIPITATES FROM SEAWATER These white, rounded grains are called ooliths (oon; egg) because they resemble fish eggs. Oolite sands, sands composed of ooliths, are abundant in many warm, shallow waters such as those of the Bahama Banks. A small decrease in the acidity of seawater, or an increase in its temperature, can cause calcium carbonate to precipitate from water of normal salinity. 06 Geologists use Specialized Tools to study Ocean Sediments Weighted wax- tipped poles HMS Challenger scientist used these to collect sediment samples Deep water cameras Camera attached on a cable and triggered by a trip wire 06 Geologists use Specialized Tools to study Ocean Sediments Clamshell sediment sampler For shallow samples A device used to collect surface sediment samples from the ocean floor 06 Geologists use Specialized Tools to study Ocean Sediments A device capable of punching through as much as 25 meters of sediment and returning an intact plug of material. Core 06 Researchers have mapped the Distribution of Ocean Sediments JOIDES Resolution The deep-sea drilling ship operated by the Joint Oceano-graphic Institutions for Deep Earth Sampling. The rig can drill to a depth of 9,150 meters (30,000 feet) below sea level. Helped verify the theory of plate tectonics, shed light on the evolution of life-forms, and helped researchers decipher the history of changes in Earth’s climate over the past 100,000 years. 06 Researchers have mapped the Distribution of Ocean Sediments 07 Sediments Are Historical Records of Ocean Processes In 1899, the British geologist William Johnson Sollas theorized that deep- sea deposits could reveal much of the planet’s history. 07 Sediments Are Historical Records of Ocean Processes In the era before plate tectonics theory, the deep-ocean bottom was thought to be a calm, changeless place, where an unbroken accumulation of sediment could be probed to discover the entire history of the ocean. 07 Sediments Are Historical Records of Ocean Processes The center of an ocean basin should contain the thickest layers of sediment, yet the ridged mid-Atlantic bottom was nearly naked. 07 Sediments Are Historical Records of Ocean Processes There didn’t seem to be any difference in the nature of the overlying seawater that could account for the variations in thickness and composition of the sediments across the bottom of the Atlantic. Oozes were particularly mysterious: The organisms that form oozes grow well at the surface of the middle Atlantic floor. Credit | Image: Unsplash 07 Sediments Are Historical Records of Ocean Processes Deep-sea sediment record is ultimately destroyed in the subduction process. Deep-sea sediments using seafloor samples, cores obtained by deep drilling, and continuous seismic profiling have demonstrated that these deposits contain a remarkable record of relatively recent ocean history. 07 Sediments Are Historical Records of Ocean Processes The analysis of layered sedimentary deposits, whether in the ocean or on land, represents the discipline of stratigraphy. Deep-sea stratigraphy analyzes variations in the composition of rocks, microfossils, depositional patterns, and geochemical and physical characteristics to identify sediment layers, determine their age, and study past changes in ocean and atmospheric conditions. 07 Sediments Are Historical Records of Ocean Processes These sorts of studies and the advent of deep- sea drilling have given rise to the emerging science of paleoceanography. Early attempts to analyze ocean and climate history from deep-sea sediments began in the 1930s and continued into the 1950s with the availability of sediment cores. Modern paleoceanographic studies use the same features as before but benefit from a better understanding of their significance and the use of seismic imaging to examine deposits over large areas. 07 Marine Sediments Are Economically Important In 2010, an estimated 39% of the world’s crude oil and 35% of its natural gas were extracted from the sedimentary deposits of continental shelves and continental rises. Deposits within the sediments of continental margins account for about one third of the world’s estimated oil and gas reserves. Natural gas is burned off during exploration in the North Sea. 07 Marine Sediments Are Economically Important In 2005, over $550 million worth of sand and gravel was extracted from the ocean, accounting for about 1% of global demand. There has also been interest in commercially mining manganese nodules containing significant amounts of manganese, iron, and other important chemical elements. Due to their high iron content, there is a proposal to rename them ferromanganese nodules. THANK YOU GROUP 1