Hemipelagic sediment

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Hemipelagic sediment, or hemipelagite, is a type of marine sediment that consists of clay and silt-sized grains that are terrigenous and some biogenic material derived from the landmass nearest the deposits or from organisms living in the water. [1] [2] Hemipelagic sediments are deposited on continental shelves and continental rises, and differ from pelagic sediment compositionally. Pelagic sediment is composed of primarily biogenic material from organisms living in the water column or on the seafloor and contains little to no terrigenous material. [1] Terrigenous material includes minerals from the lithosphere like feldspar or quartz. Volcanism on land, wind blown sediments as well as particulates discharged from rivers can contribute to Hemipelagic deposits. [3] These deposits can be used to qualify climatic changes and identify changes in sediment provenances. [4] [5]

Contents

Deposition

Hemipelagic sediment dispersal is mainly controlled by fluvial discharge. [3] Dispersal rate is influenced by sea-level variations which change the proximity of river mouths to oceanic basins and by oceanographic phenomena like currents. [3] Sea-level variations are caused by the earth's natural oscillation between glacial and interglacial periods. [6] For example, a low average sea level would occur during a glacial period as more water is held in ice caps. In addition, underwater landslides called turbidity currents can transport hemipelagic sediment from the continental slope to the continental rise and form a turbidite sequence. [7] [8]

Typically, hemipelagic sediment is transported to the continental slope in suspension from river mouths but can be transported by the wind. [3] The rate of deposition of hemipelagic sediment is higher than pelagic sediment but still quite slow. [9] Ordinarily hemipelagic sediments accumulate too rapidly to react chemically with seawater. In most cases, individual grains thus retain characteristics imparted to them in the area where they formed. [9]

Composition

Hemipelagic sediments can be made of a diverse range of elements or mineral types. The composition of Hemipelagic sediment directly depends on the composition of the adjacent land mass and geologic events such as volcanism that influence sediment input into the ocean. [7] [8] Hemipelagic sediments are mainly terrigenous but can also have biological oozes from marine organisms like Radiolarians or Diatoms. Radiolarians are a species of zooplankton that produce silica tests, or shells and Diatoms are photosynthetic organisms that live in the sunlit region of the ocean. [10] Both organisms are visible in the sedimentary rock record. For example, in the Galice Formation in Oregon the hemipelagic sequence was composed of slaty radiolarian argillite with radiolarian chert present as well. [7] [8] The argillite in the Galice Formation was composed of radiolarians, terrigenous and tuffaceous detritus, and hydrothermal sediment. [11] [12] [13]

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<span class="mw-page-title-main">Sedimentary rock</span> Rock formed by the deposition and subsequent cementation of material

Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles to settle in place. The particles that form a sedimentary rock are called sediment, and may be composed of geological detritus (minerals) or biological detritus. The geological detritus originated from weathering and erosion of existing rocks, or from the solidification of molten lava blobs erupted by volcanoes. The geological detritus is transported to the place of deposition by water, wind, ice or mass movement, which are called agents of denudation. Biological detritus was formed by bodies and parts of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on the floor of water bodies. Sedimentation may also occur as dissolved minerals precipitate from water solution.

<span class="mw-page-title-main">Sediment</span> Particulate solid matter that is deposited on the surface of land

Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation; if buried, they may eventually become sandstone and siltstone through lithification.

<span class="mw-page-title-main">Ophiolite</span> Uplifted and exposed oceanic crust

An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks.

<span class="mw-page-title-main">Continental shelf</span> Coastal and oceanic landform

A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island is known as an insular shelf.

The Nevadan orogeny occurred along the western margin of North America during the Middle Jurassic to Early Cretaceous time which is approximately from 155 Ma to 145 Ma. Throughout the duration of this orogeny there were at least two different kinds of orogenic processes occurring. During the early stages of orogenesis an "Andean type" continental magmatic arc developed due to subduction of the Farallon oceanic plate beneath the North American Plate. The latter stages of orogenesis, in contrast, saw multiple oceanic arc terranes accreted onto the western margin of North America in a "Cordilleran type" accretionary orogen. Deformation related to the accretion of these volcanic arc terranes is mostly limited to the western regions of the resulting mountain ranges and is absent from the eastern regions. In addition, the deformation experienced in these mountain ranges is mostly due to the Nevadan orogeny and not other external events such as the more recent Sevier and Laramide Orogenies. It is noted that the Klamath Mountains and the Sierra Nevada share similar stratigraphy indicating that they were both formed by the Nevadan orogeny. In comparison with other orogenic events, it appears that the Nevadan Orogeny occurred rather quickly taking only about 10 million years as compared to hundreds of millions of years for other orogenies around the world.

<span class="mw-page-title-main">Pelagic sediment</span> Fine-grained sediment that accumulates on the floor of the open ocean

Pelagic sediment or pelagite is a fine-grained sediment that accumulates as the result of the settling of particles to the floor of the open ocean, far from land. These particles consist primarily of either the microscopic, calcareous or siliceous shells of phytoplankton or zooplankton; clay-size siliciclastic sediment; or some mixture of these. Trace amounts of meteoric dust and variable amounts of volcanic ash also occur within pelagic sediments. Based upon the composition of the ooze, there are three main types of pelagic sediments: siliceous oozes, calcareous oozes, and red clays.

<span class="mw-page-title-main">Biogenic silica</span> Type of biogenic mineral

Biogenic silica (bSi), also referred to as opal, biogenic opal, or amorphous opaline silica, forms one of the most widespread biogenic minerals. For example, microscopic particles of silica called phytoliths can be found in grasses and other plants.

In oceanography, terrigenous sediments are those derived from the erosion of rocks on land; that is, they are derived from terrestrial environments. Consisting of sand, mud, and silt carried to sea by rivers, their composition is usually related to their source rocks; deposition of these sediments is largely limited to the continental shelf.

<span class="mw-page-title-main">Franciscan Complex</span> Late Mesozoic terrane of heterogeneous rocks in the California Coast Ranges

The Franciscan Complex or Franciscan Assemblage is a geologic term for a late Mesozoic terrane of heterogeneous rocks found throughout the California Coast Ranges, and particularly on the San Francisco Peninsula. It was named by geologist Andrew Lawson, who also named the San Andreas fault that defines the western extent of the assemblage.

<span class="mw-page-title-main">Radiolarite</span> Type of sedimentary rock

Radiolarite is a siliceous, comparatively hard, fine-grained, chert-like, and homogeneous sedimentary rock that is composed predominantly of the microscopic remains of radiolarians. This term is also used for indurated radiolarian oozes and sometimes as a synonym of radiolarian earth. However, radiolarian earth is typically regarded by Earth scientists to be the unconsolidated equivalent of a radiolarite. A radiolarian chert is well-bedded, microcrystalline radiolarite that has a well-developed siliceous cement or groundmass.

<span class="mw-page-title-main">Dropstone</span> Rock fragments found within host rock

Dropstones are isolated fragments of rock found within finer-grained water-deposited sedimentary rocks or pyroclastic beds. They range in size from small pebbles to boulders. The critical distinguishing feature is that there is evidence that they were not transported by normal water currents, but rather dropped in vertically through the air or water column. Such deposition can occur i.e. during a volcanic eruption.

<span class="mw-page-title-main">Marine sediment</span>

Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor. These particles have their origins in soil and rocks and have been transported from the land to the sea, mainly by rivers but also by dust carried by wind and by the flow of glaciers into the sea. Additional deposits come from marine organisms and chemical precipitation in seawater, as well as from underwater volcanoes and meteorite debris.

<span class="mw-page-title-main">Siliceous ooze</span> Biogenic pelagic sediment located on the deep ocean floor

Siliceous ooze is a type of biogenic pelagic sediment located on the deep ocean floor. Siliceous oozes are the least common of the deep sea sediments, and make up approximately 15% of the ocean floor. Oozes are defined as sediments which contain at least 30% skeletal remains of pelagic microorganisms. Siliceous oozes are largely composed of the silica based skeletons of microscopic marine organisms such as diatoms and radiolarians. Other components of siliceous oozes near continental margins may include terrestrially derived silica particles and sponge spicules. Siliceous oozes are composed of skeletons made from opal silica SiO2·nH2O, as opposed to calcareous oozes, which are made from skeletons of calcium carbonate (CaCO3·nH2O) organisms (i.e. coccolithophores). Silica (Si) is a bioessential element and is efficiently recycled in the marine environment through the silica cycle. Distance from land masses, water depth and ocean fertility are all factors that affect the opal silica content in seawater and the presence of siliceous oozes.

<span class="mw-page-title-main">Submarine landslide</span> Landslides that transport sediment across the continental shelf and into the deep ocean

Submarine landslides are marine landslides that transport sediment across the continental shelf and into the deep ocean. A submarine landslide is initiated when the downwards driving stress exceeds the resisting stress of the seafloor slope material, causing movements along one or more concave to planar rupture surfaces. Submarine landslides take place in a variety of different settings, including planes as low as 1°, and can cause significant damage to both life and property. Recent advances have been made in understanding the nature and processes of submarine landslides through the use of sidescan sonar and other seafloor mapping technology.

<span class="mw-page-title-main">Contourite</span> Type of sedimentary deposit

A contourite is a sedimentary deposit commonly formed on continental rise to lower slope settings, although they may occur anywhere that is below storm wave base. Countourites are produced by thermohaline-induced deepwater bottom currents and may be influenced by wind or tidal forces. The geomorphology of contourite deposits is mainly influenced by the deepwater bottom-current velocity, sediment supply, and seafloor topography.

<span class="mw-page-title-main">Geology of Finland</span> Overview of the geology of Finland

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<span class="mw-page-title-main">Geology of Bulgaria</span>

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Madeira Abyssal Plain, also called Madeira Plain, is an abyssal plain situated at the center and deepest part of the Canary Basin. It is a north-northeast to south-southeast elongated basin that almost parallels the Mid-Atlantic Ridge. Its western boundary is marked by a chain of seamounts known as the either Seewarte Seamounts or Atlantis-Great Meteor Seamount Chain. Its eastern boundary is a distinct break of slope that marks the foot of the African Continental Rise. This abyssal plain occupies an area of about 68,000 km2 (26,000 sq mi). Across this basin, slope angles are generally less than 0.01°.

The geology of California is highly complex, with numerous mountain ranges, substantial faulting and tectonic activity, rich natural resources and a history of both ancient and comparatively recent intense geological activity. The area formed as a series of small island arcs, deep-ocean sediments and mafic oceanic crust accreted to the western edge of North America, producing a series of deep basins and high mountain ranges.

Biogenous ooze is a type of marine sediment composed of a high percentage of organic compounds.

References

  1. 1 2 Ochoa, Jesús; Wolak, Jeannette; Gardner, Michael H (2013). "Recognition criteria for distinguishing between hemipelagic and pelagic mudrocks in the characterization of deep-water reservoir heterogeneity". AAPG Bulletin. 97 (10): 1785–803. doi:10.1306/04221312086.
  2. ↑ Stow, D.A.V. (1994). "Deep sea processes of sediment transport and deposition". In Pye, K. (ed.). Sediment Transport and Depositional Processes. London: Blackwell. pp. 257–91.
  3. 1 2 3 4 Aksu, A.E; Yaşar, D; Mudie, P.J (1995). "Origin of late glacial—Holocene hemipelagic sediments in the Aegean Sea: Clay mineralogy and carbonate cementation". Marine Geology. 123 (1–2): 33–59. doi:10.1016/0025-3227(95)80003-T.
  4. ↑ Trentesaux, A; Recourt, P; Bout-Roumazeilles, V; Tribovillard, N (2001). "Carbonate Grain-Size Distribution in Hemipelagic Sediments from a Laser Particle Sizer" (PDF). Journal of Sedimentary Research. 71 (5): 858. doi:10.1306/2DC4096E-0E47-11D7-8643000102C1865D.
  5. ↑ Weedon, G.P (1986). "Hemipelagic shelf sedimentation and climatic cycles: The basal Jurassic (Blue Lias) of South Britain". Earth and Planetary Science Letters. 76 (3–4): 321–35. doi:10.1016/0012-821X(86)90083-X.
  6. ↑ Bierman, P.R.; Montgomery, D.R. (2014). "Geomorphology and Climate". Key Concepts in Geomorphology. W.H. Freeman and Company. p. 443.
  7. 1 2 3 MacDonald, James H; Harper, Gregory D; Zhu, Bin (2006). "Petrology, geochemistry, and provenance of the Galice Formation, Klamath Mountains, Oregon and California". Special Paper 410: Geological Studies in the Klamath Mountains Province, California and Oregon: A volume in honor of William P. Irwin. Vol. 410. pp. 77–101. doi:10.1130/2006.2410(04). ISBN   0-8137-2410-4.
  8. 1 2 3 Snoke, Arthur W; Barnes, Calvin G (2006). "The development of tectonic concepts for the Klamath Mountains province, California and Oregon". Special Paper 410: Geological Studies in the Klamath Mountains Province, California and Oregon: A volume in honor of William P. Irwin. Vol. 410. pp. 1–29. doi:10.1130/2006.2410(01). ISBN   0-8137-2410-4.
  9. 1 2 "Hemipelagic sediment". Encyclopædia Britannica. Retrieved 2010-05-27.
  10. ↑ Miller, C. B.; Wheeler, P.A. (2012). Biological Oceanography (2nd ed.). Wiley. pp. 28, 117–8.
  11. ↑ Harper, Gregory D; Bowman, John R; Kuhns, Roger (1988). "A field, chemical, and stable isotope study of subseafloor metamorphism of the Josephine ophiolite, California-Oregon". Journal of Geophysical Research. 93 (B5): 4625–56. doi:10.1029/JB093iB05p04625.
  12. ↑ Kuhns, Roger J; Baitis, Hart W (1987). "Preliminary study of the Turner Albright Zn-Cu-Ag-Au-Co massive sulfide deposit, Josephine County, Oregon". Economic Geology. 82 (5): 1362. doi:10.2113/gsecongeo.82.5.1362.
  13. ↑ Pinto-Auso, Montserrat; Harper, Gregory D (1985). "Sedimentation, Metallogenesis, and Tectonic Origin of the Basal Galice Formation Overlying the Josephine Ophiolite, Northwestern California". The Journal of Geology. 93 (6): 713–25. doi:10.1086/628998. S2CID   128462112.
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