Chapter 4

Beach Deposits

Composed of what is locally available, most composed of quartz sand that is made available to the coast and rivers and subsequently transported by wave action.

Glacial Deposits

Consist of poorly-sorted (boulder to clay sized) sediment that was deposited by glaciers during the most recent glacial period when glaciers covered the continental shelf in high-latitude regions. Ice rafting currently occurring around Greenland and Antarctica. Sediment is trapped in ice sheets that break off the main ice sheet and drift out to sea where the ice melts and deposits the carried sediment.

Neritic

Located on the continental shelf and in shallow waters near islands. Generally coarser grained.

hydrogenous sediments

Manganese Nodules, Phosphates, Carbonates, evaporites and Metal Sulfides are all examples of what?

Pelagic Biogenous Deposits.

Siliceous Ooze and Calcareous Ooze

Wentworth scale and sorting

Texture is described based on what 2 things?

Grain size

The average size of the grains of material in a sample. Also known as fragment or particle size.

Algae

primarily aquatic, eukaryotic, photosynthetic organisms ranging in size from microscopic shells to large organisms like kelp.

Silica and calcium carbonate

What are the most common chemical compounds in biogenous sediments.

Calcite Compensation Depth

(CCD) The depth at which the amount of calcite (CaCCO3) produced by the organisms in the overlying water column is equal to the amount of calcite the water column can dissolve. No calcite deposition occurs below this depth, which, in most parts of the ocean, is at a depth of 4500 meters (15,000 feet).

biogenous sediments

(Living organisms) hard part remains of once-living organisms. - The hard parts of organisms ranging in size from microscopic algae to fish and whales settle to the ocean floor upon death of the organism. -In terms of volume, these sediments are the 2nd most abundant. But they cover the most oceanic surface area.

hydrogenous sediments

(Minerals dissolved in water) is derived directly from seawater as the dissolved minerals precipitate.

Cosmogenous Sediments

(Outer-space) are of extraterrestrial origin. - These are rare but provide a wealth of information concerning the history of universe. -Two types. 1. Microscopic spherules 2. Macroscopic meteor debris

Lithogenous Sediment

(Weathered rock from land) - Generated from preexisting rocks and minerals that originate on the continents or islands from erosion, volcanic eruptions, or wind-blown dust. - Also referred to as terrigenous sediments.

Quartz

- Although the composition of these sediments is extremely varied, the most common is what?

High

- High or Low- energy currents move sediment constantly within this region.

Low

- High or Low-energy currents move finer particles to the deep-ocean basin.

Large

- What size particles are deposited in high-energy environments?

Small

- What size particles are deposited in low-energy environments. In general, sediments become finer as distance from shore increases.

Productivity

-Biogenous sediment is common in the pelagic environment. But the distribution of it is dependent on three factors. 1.____________: The number of organisms present in the surface water. When productivity is high, biogenous oozes may develop. When it is low, there are not enough organisms to produce ooze.

Destruction

-Biogenous sediment is common in the pelagic environment. But the distribution of it is dependent on three factors. 2. ______________: Some skeletal remains (tests) dissolve in seawater, when this occurs, biogenous sediments will not accumulate.

Dilution

-Biogenous sediment is common in the pelagic environment. But the distribution of it is dependent on three factors. 3. ____________: Deposition of other sediments decrease the percentage of biogenous sediments. Most often occurs due to the input of lithogenous sediment in neritic environments. Therefore, biogenous oozes are uncommon along the continental margins.

Appalachian Mountains

-The sand on our beaches comes partially from where?

Microscopic spherules

1. ________ spherules: Small masses composed of silicate rock material formed from impact events on Earth or other planets the blow crustal material into space. This is termed tektites which then falls to Earth. Some contain iron and nickel. 90% are destroyed as they fall through the atmosphere, but it is estimated that 300,000 metric tons of this material reaches earth's surface every year.

Sediment texture

1: The Wentworth scale of grain size which classifies particles based on their size. - Sediment size is proportional to the energy needed to deposit sediments. - Large particles are deposited in high-energy environments. - Small particles are deposited in low-energy environments. In general, sediments become finer as distance from shore increases. 2: Sorting Measures the uniformity of grain sizes. - Sediment deposits that consist of one sized particle are said to be well-sorted. - This indicates that the energy that moved the sediment remained consistent over a long period. Example: Coastal sand dune. - Sediment deposits that consist of more than one particle size are said to be poorly-sorted. - This indicates that energy that moved the sediments varied greatly. Example: Glacial deposits.

Wentworth

1: The ________ scale of grain size which classifies particles based on their size. - Sediment size is proportional to the energy needed to deposit sediments.

Macroscopic meteor

2. __________ __________ debris: Very rare but typically associated with impact sites. Meteorites are composed of silicate rock or iron and nickels.

Sorting

2: _______ Measures the uniformity of grain sizes. - Sediment deposits that consist of one sized particle are said to be well-sorted. - This indicates that the energy that moved the sediment remained consistent over a long period. Example: Coastal sand dune. - Sediment deposits that consist of more than one particle size are said to be poorly-sorted. - This indicates that energy that moved the sediments varied greatly. Example: Glacial deposits.

Ooze

A pelagic sediment containing at last 30% skeletal remains of pelagic organism, the balance being clay minerals. Oozes are further defined by the chemical composition of the organic remains (siliceous or calcareous) and by their characteristic organisms.

Sorting

A texture of sediments, where a well-sorted sediment is characterized by having great uniformity of grain sizes.

Neretic Biogenous Sediments

Carbonate Deposits and Stromatolites

Carbonate Deposits

Carbonate minerals contain CO3^2- in their chemical formula. -Rocks containing calcite are called limestones. -Can form as marine shells accumulate or by precipitating directly from seawater. - Modern limestone deposits are forming in shallow, warm-waters such as the Bahama Banks and Great Barrier Reef (Australia) -Ancient limestone deposits can be found worldwide and many are the bedrock of continental areas such as Florida, Kentucky, Michigan, and Colorado. -This indicates a marine environment of deposition.

Abyssal Clay

Clay contains at least 70% fine, clay-sized particles that originated on land. Transported great lengths by wind or ocean currents and deposited on the ocean floor. Typically contain oxidized iron resulting in a red-brown to tan color. Estimates indicate it takes 1,000 years for a 2mm layer of abyssal clay to settle on the plains. The predominance of abyssal clays in the abyssal plains is due to the absence of other material that would normally settle to the ocean floor.

Macroscopic

Large enough to be seen without a microscope (including shells, bones, and teeth) rare in most areas except tropical locations.

Stromatolites

Lobate structures consisting of layers of carbonate that usually form in shallow, warm, hypersaline waters. -Produced by cyanobacteria which trap fine-grained sediment in a mucous mat. - As subsequent layers of algae form near the surface, the structure builds. -Commonly found in rocks between 1 and 3 billion years old. - Suggests that conditions were conducive for Stromatolites developed in early Earth's history.

Tests

Microscopic shells

diatoms and radiolarians

Most of the silica in biogenous ooze is from microscopic _______ (algae) and _________ (Protozoans)

Texture

One of the most important properties of lithogenous sediments is the what?

Sediments

Particles of organic or inorganic origin that accumulate in loose form.

Turbidite Deposits

Recall turbidity currents. When this material reaches the base of the continental rise, the material fans out, resulting in deep-sea fan deposits called Turbidite, this deposit exhibits graded bedding.

Continental Shelf Deposits

Relic (left behind) deposited along the coastal region when sea level was lower and have not been covered by other sediments in the past 3,000 to 7,000 years. Cover approximately 70% of the continental shelf area.

Manganese Nodules

Rounded, hard deposits of manganese, iron, and other metals with a diameter of 2-8 inches.

Greatest

The greatest or least quantity of lithogenous sediments is found along the edges of the continents.

Pelagic

The open ocean environment, which is divided into the neritic province (water depth 0 to 200 meters or 656 feet) and the oceanic province (water depth greater than 200 meters or 656 feet). Typically finer grained, the source of these sediments include volcanoes, windblown dust, and sediment from deep-ocean currents.

Paleoceanography

The study of historical changes of shapes and positions of the continents and oceans.

Calcareous Ooze

This ooze contains at 30% of the remains of calcareous organisms. - Calcium carbonate dissolves at different rates at different depths in the ocean. - Warm water is usually saturated with calcium carbonate. Therefore, it does not dissolve and calcareous oozes develop. - Cold water contains greater amounts of CO2 generating carbonic acid which dissolves calcim carbonate easily. - Higher pressures also accelerate this dissolution. - The depth at which pressure and CO2 levels are sufficient to dissolve calcium carbonate is called lysocline. Average depth at 13,1000 feet. - Below this depth, calcium carbonate dissolves at an increasing rate with increasing depth until the calcium compensation depth is reached. -Very little calcium carbonate is contained in sediment below the CCD on average is 15,000 feet below sea level.

Siliceous Ooze

This ooze contains at least 30% of the remains of silica-test organisms. -Since ocean water is under saturated with silica at all depths, siliceous oozes will only develop in areas of high biological productivity of silica-test organisms. -Without this high productivity (large number of organisms), the silica remains (tests) would dissolve as they settle to the ocean floor or while they are on the ocean floor.

Microscopic

Too small to be identified without the use of a microscope. The hard parts of an organisms (tests) sink after the organism dies. When this material accumulates, the sediment deposit is termed and ooze. Those that contribute to biogenous sediment typically include Algae and Protozoan.

Most

Volumetrically these are the most or least abundant sediments.

Radiolarians

are planktonic, single celled protozoan with long spikes or rays of silica. Do not photosynthesize and typically possess well-developed symmetry and are referred to as living snowflakes of the sea. - The accumulation of diatoms, radiolarians and other silica organisms produces siliceous ooze.

Coccolithophores

are planktonic, single-celled algae made of thin plates (20 to 30 plates) which overlap to produce a spherical test. Photosynthetic. When this material lithifies, chalk is formed.

Diatoms

need abundant of sunlight to generate food and are therefore found only in the upper sunlit surface waters. - Composted of two parts that fit together like a petri dish, their tests are perforated with small holes to allow nutrients to pass in and waste to pass out. Most are free floating (planktonic). When these oozes lithify, diatomaceous earth is generated.

Foraminifers

or forams are planktonic, single-celled protozoans. Non-photosynthetic, range from micro to macroscopic, resemble shells that can be found at the beach. These generate calcareous ooze.

Protozoan

single celled, eukaryotic organisms that are not photosynthetic.