HOME

TheInfoList



OR:

Shallow water marine environment refers to the
neritic The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...
marine environment A marine habitat is a habitat that supports marine life. Marine life depends in some way on the saltwater that is in the sea (the term ''marine'' comes from the Latin ''mare'', meaning sea or ocean). A habitat is an ecological or environmen ...
between the
shore A coast (coastline, shoreline, seashore) is the land next to the sea or the line that forms the boundary between the land and the ocean or a lake. Coasts are influenced by the topography of the surrounding landscape and by aquatic erosion, su ...
and the shelf break. This environment is characterized by oceanic, geological and biological conditions, as described below, and water in this environment is shallow and clear, allowing the formation of different sedimentary structures, carbonate rocks, coral reefs, and allowing certain organisms to survive and become fossils.


Sediment

The
sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...
itself is often composed of
limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...
, which forms readily in shallow, warm, calm waters. While siliciclastic and carbonaceous sediments can coexist, shallow marine environments can also contain only one or the other. Shallow water
marine sediment Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor. These particles either have their origins in soil and Rock (geology), rocks and have been Sediment transport, ...
primarily features larger
grain size Grain size (or particle size) is the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. This is different from the crystallite size, which ...
s because smaller grains have washed out to deeper water. Within carbonaceous sedimentary rock, evaporite minerals such as gypsum, anhydrite, and halite may be present. The most common evaporite minerals found within modern and ancient deposits are gypsum, anhydrite, and halite. These minerals can occur as crystalline layers, isolated crystals, or clusters of crystals. Approximately 75% of surface sediments are in shallow marine environments, holding most
Phanerozoic The Phanerozoic is the current and the latest of the four eon (geology), geologic eons in the Earth's geologic time scale, covering the time period from 538.8 million years ago to the present. It is the eon during which abundant animal and ...
and
Precambrian The Precambrian ( ; or pre-Cambrian, sometimes abbreviated pC, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of t ...
sedimentary rock. This is visible in the North American and Caribbean regions. However, shallow marine sediment quantity varies significantly over geologic time due to supercontinent breakup and shifting tectonic plate processes.


Sedimentary Structures


Shallow Marine Environments

Shallow marine environments are characterized by various types of sedimentary structures, including: *
Graded Bedding In geology, a graded bed is a bed characterized by a systematic change in grain or clast size from bottom to top of the bed. Most commonly this takes the form of normal grading, with coarser sediments at the base, which grade upward into progre ...
: characterized by a vertical gradation in grain size, with the smallest grains at the top * Ripples: the smallest bedform type *
Dunes A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, flat ...
: larger and similar in shape to ripples


Carbonaceous Rocks in SMEs

Carbonaceous sedimentary rock in SMEs contain significant amounts of non-skeletal matter along with siliciclastic or chemical constituents and can exhibit a range of sedimentary structures, including: * Cross stratification: a layering structure found in gravel, sand, and coarse silt-sized sediment, characterized by distinct layers that are steeply inclined to the underlying surface. * Desiccation cracks: cracks formed by the drying of newly deposited mud in sub-aerial climates. * Flame structures: mud shaped like flames that intrude into the overlying layer of rock. * Convolute Folds: sediment folded into irregular anticlines and/or synclines. *
Flutes The flute is a member of a family of musical instruments in the woodwind group. Like all woodwinds, flutes are aerophones, producing sound with a vibrating column of air. Flutes produce sound when the player's air flows across an opening. In th ...
: outstretched ridges that are rounded at one end and flared at the other. * Groove casts: outstretched, almost straight grooves in sediment caused by the dragging of an object. * Chevron structures: a v-shaped type of groove cast, resulting from stress applied in two or more directions, found on the bottoms of beds deposited in shallow water environments. *
Syneresis crack Syneresis cracks (also known as subaqueous shrinkage cracks) are a sedimentary structure developed by the shrinkage of sediment without desiccation – not to be confused with desiccation cracks. Syneresis is the expulsion of a liquid from a ge ...
s: cracks formed by other than by sub-aerial climate exposure, including contraction by clay clumping, contraction from settling during faulting, smectitic clay compaction from dewatering due to a salinity change in surrounding water, compaction dewatering under sediment causing injection from below or collapsing from above, and tensional opening due to down-sloping of a surface mud layer. * Fenestrae: open or partially filled spaces occupied by different sediment or cement


Water composition


Characteristics

Shallow marine environments are typically characterized by clear and shallow water. The distributional patterns of marine organisms in these environments can be used to define different types of shallow marine environments based on temperature, which can also provide insights into past patterns in
Paleolithic The Paleolithic or Palaeolithic ( years ago) ( ), also called the Old Stone Age (), is a period in human prehistory that is distinguished by the original development of stone tools, and which represents almost the entire period of human prehist ...
zones. The boundaries between different shallow marine environment types in terms of climatic zones are not always agreed upon. However, three major criteria are used to define SME types: faunal provinces, faunal elements, and
latitude In geography, latitude is a geographic coordinate system, geographic coordinate that specifies the north-south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from −90° at t ...
.


Carbonate factory zones

Carbon dioxide is removed from the atmosphere when it dissolves in seawater and turns into
carbonic acid Carbonic acid is a chemical compound with the chemical formula . The molecule rapidly converts to water and carbon dioxide in the presence of water. However, in the absence of water, it is quite stable at room temperature. The interconversion ...
. The acid then weathers rocks, creating bicarbonate and other ions.
Calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...
is a precipitate from calcium and the bicarbonate ions, while the carbon is precipitates as limestone. Many shallow marine environments are associated with carbonate factory zones, where processes that remove from the water change bicarbonate ions into carbonate ions, supporting lime precipitation. These processes include increasing temperature, intense evaporation, and mixing water that is high in and low in calcium cations with
seawater Seawater, or sea water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has approximat ...
.


Changes in limestone composition over geologic time

Over geologic time, the composition of limestone has changed from
calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...
-rich to
aragonite Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (), the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation fr ...
-rich. This change is influenced by the presence of
magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...
ions, which can inhibit calcite precipitation. Aragonite and calcite have the same chemical formula but a different crystal system, although aragonite is less prone to magnesium inhibition. Changes in the Mg/Ca ratio over geologic time, influenced by seafloor spreading and tectonic plate movement, have also increased aragonite abundance.


Organisms

Shallow marine environments, particularly the
intertidal zone The intertidal zone or foreshore is the area above water level at low tide and underwater at high tide; in other words, it is the part of the littoral zone within the tidal range. This area can include several types of habitats with various ...
, are home to a diverse range of organisms, including
starfish Starfish or sea stars are Star polygon, star-shaped echinoderms belonging to the class (biology), class Asteroidea (). Common usage frequently finds these names being also applied to brittle star, ophiuroids, which are correctly referred to ...
,
sea anemone Sea anemones ( ) are a group of predation, predatory marine invertebrates constituting the order (biology), order Actiniaria. Because of their colourful appearance, they are named after the ''Anemone'', a terrestrial flowering plant. Sea anemone ...
s,
sponge Sponges or sea sponges are primarily marine invertebrates of the animal phylum Porifera (; meaning 'pore bearer'), a basal clade and a sister taxon of the diploblasts. They are sessile filter feeders that are bound to the seabed, and a ...
s,
marine worm Any worm that lives in a ocean, marine environment (biophysical), environment is considered a sea or marine worm. Marine worms are found in several different phylum (biology), phyla, including the Platyhelminthes, Nematoda, Annelida (segmented ...
s,
clam Clam is a common name for several kinds of bivalve mollusc. The word is often applied only to those that are deemed edible and live as infauna, spending most of their lives halfway buried in the sand of the sea floor or riverbeds. Clams h ...
s,
mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and Freshwater bivalve, freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other ...
s, predatory
crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...
s,
barnacle Barnacles are arthropods of the subclass (taxonomy), subclass Cirripedia in the subphylum Crustacean, Crustacea. They are related to crabs and lobsters, with similar Nauplius (larva), nauplius larvae. Barnacles are exclusively marine invertebra ...
s and small
fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
.


Hydrozoa and microinvertebrates

Hydrozoa Hydrozoa (hydrozoans; from Ancient Greek ('; "water") and ('; "animals")) is a taxonomy (biology), taxonomic class (biology), class of individually very small, predatory animals, some solitary and some colonial, most of which inhabit saline wat ...
, also known as hydroids, inhabit SMEs and feed on surrounding
algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
and
zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...
. Species of
isopods Isopoda is an Order (biology), order of crustaceans. Members of this group are called isopods and include both Aquatic animal, aquatic species and Terrestrial animal, terrestrial species such as woodlice. All have rigid, segmented exoskeletons ...
and
amphipods Amphipoda () is an order (biology), order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods () range in size from and are mostly detritivores or scavengers. There are more than 10,700 amphip ...
are found in intertidal zones, creating complex burrows and surface tracks in the sediment.
Brittle star Brittle stars, serpent stars, or ophiuroids (; ; referring to the serpent-like arms of the brittle star) are echinoderms in the class Ophiuroidea, closely related to starfish. They crawl across the sea floor using their flexible arms for locomot ...
s may bury themselves in sediment with their arms exposed.


Carbonate reefs

SMEs are characterized by carbonate reefs, which support many species. Estimates suggest that
coral reef A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in group ...
s alone may host between 1-9 million species. The three main types of reef formations are: * Fringing Reefs: attached to the shore * Barrier Reefs: separated from the mainland by a lagoon * Atoll Reefs: ring-shaped reefs surrounding a lagoon


Reef Organisms

Organisms that inhabit these reefs include
red algae Red algae, or Rhodophyta (, ; ), make up one of the oldest groups of eukaryotic algae. The Rhodophyta comprises one of the largest Phylum, phyla of algae, containing over 7,000 recognized species within over 900 Genus, genera amidst ongoing taxon ...
,
green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...
,
bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...
s and
echinoderm An echinoderm () is any animal of the phylum Echinodermata (), which includes starfish, brittle stars, sea urchins, sand dollars and sea cucumbers, as well as the sessile sea lilies or "stone lilies". While bilaterally symmetrical as ...
s. Many of these organisms contribute to reef formation. Furthermore,
unicellular A unicellular organism, also known as a single-celled organism, is an organism that consists of a single cell, unlike a multicellular organism that consists of multiple cells. Organisms fall into two general categories: prokaryotic organisms and ...
dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...
s live in coral tissues, engaging in a mutualistic relationship where they provide corals with essential organic molecules.


Fossils

The majority of the fossil record has been discovered in lithified SMEs, which were once home to diverse organisms. Many of these fossils date to periods when much of the Earth was covered in shallow seas. Several types of fossils can be found in these environments, including: * Skolithos Ichnofacies: vertical, cylindrical, or U-shaped burrows created by organisms for protection. These are classified as trace fossils. * Glossifungites Ichnofacies: vertical, cylindrical, U-shaped, or tear-shaped borings or burrows created by organisms such as shrimp, crabs, worms, and bivalves. These are also classified as trace fossils. *
Stromatolite Stromatolites ( ) or stromatoliths () are layered Sedimentary rock, sedimentary formation of rocks, formations (microbialite) that are created mainly by Photosynthesis, photosynthetic microorganisms such as cyanobacteria, sulfate-reducing micr ...
s: laminated sedimentary structures formed when
cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...
create microbial mats, trapping clay, silt sediment, and organic materials. These mats eventually lithify, embedding fossils.


See also

* Tides in marginal seas


References

{{reflist


External links


Example of marine fossil - Burgess Shale
Oceans