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38-633: The Parachucla Formation was defined in 1908 by Earle Sloan as "weakly lithified shales and mudstones, olive-grey to dark-greenish-grey in color, that crop out on the Savannah River ". In 1988, Paul Huddlestun added calcareous beds that underlay Sloan's Parachucla Formation to the formation, calling the new addition the Tiger Leap Member, and the original formation defined by Sloan the Porters Landing Member. In 2001, Weems and Edwards removed

76-472: A Oxydactylus species), and a small rhinocerus (possibly a species of Diceratherium ). Most of the land vertebrate fossils in the White Spring Local Fauna are teeth or post-cranial bones of smaller animals. Semi-articulated skeletons of larger mammals have been found at one location along the exposure. It is believed that the land vertebrate bones were carried into a delta or coastal lagoon by

114-481: A marine crocodile , an alligator, a tortoise , and three snakes (a blind snake and two species of boas ). The fossils of three sirenians ( Crenatosiren olseni , Dioplotherium manigaulti and a Metaxytherium species) have been found at those sites (White Springs is the holotype site for C. olseni ). Rodents in the White Springs Local Fauna include species of the eomyid Arikareeomys and

152-545: A broad littoral zone to a narrow band of vegetation. Marshes and wet meadows are at particular risk. For the purposes of naval operations, the US Navy divides the littoral zone in the ways shown on the diagram at the top of this article. The US Army Corps of Engineers and the US Environmental Protection Agency have their own definitions, which have legal implications. The UK Ministry of Defence defines

190-573: A fairly consistent thickness along most of the north-south line in coastal Georgia, 30 feet (9.1 m) thick in Effingham County, then 40 feet (12 m) to 46 feet (14 m) from Richmond Hill to Cumberland Island. The formation thins rapidly south of Cumberland Island, being only 10 feet (3.0 m) thick near the St. Marys River. The Parachucla Formation in Georgia appears to be narrow. No indication of

228-405: A narrow or broad fringing wetland, with extensive areas of aquatic plants sorted by their tolerance to different water depths. Typically, four zones are recognized, from higher to lower on the shore: wooded wetland, wet meadow , marsh and aquatic vegetation . The relative areas of these four types depends not only on the profile of the shoreline, but upon past water levels. The area of wet meadow

266-417: A narrow, almost homogenous, eulittoral strip, often marked by the presence of barnacles . Exposed sites show a wider extension and are often divided into further zones. For more on this, see intertidal ecology . The sublittoral zone starts immediately below the eulittoral zone. This zone is permanently covered with seawater and is approximately equivalent to the neritic zone . In physical oceanography ,

304-544: A river before burial. The dinoflagellates Sumatradinium soucouyantiae , Chordosphaeridium cantharellus , and Exochosphaeridium insigne are typical of the Parachucla Formation in Georgia. Cribroperidinium species are also common. Sixty-five taxa of invertebrates have been identified in the Porters Landing Member of the Parachucla Formation at the White Springs exposure in north Florida. Included in these are

342-466: A small fraction of total lake areas. Because the littoral zone is important for many recreational and industrial purposes, it is often severely affected by many human activities that increase nutrient loading, spread invasive species, cause acidification and climate change , and produce increased fluctuations in water level. Littoral zones are both more negatively affected by human activity and less intensively studied than offshore waters. Conservation of

380-413: Is a stub . You can help Misplaced Pages by expanding it . This sedimentology article is a stub . You can help Misplaced Pages by expanding it . Littoral zone The littoral zone , also called litoral or nearshore , is the part of a sea , lake , or river that is close to the shore . In coastal ecology , the littoral zone includes the intertidal zone extending from the high water mark (which

418-403: Is a process of porosity destruction through compaction and cementation . Lithification includes all the processes which convert unconsolidated sediments into sedimentary rocks . Petrifaction , though often used as a synonym, is more specifically used to describe the replacement of organic material by silica in the formation of fossils . This article about geological processes

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456-457: Is often attracted to shorelines, and settlement often disrupts breeding habitats for littoral zone species. For example, many turtles are killed on roads when they leave the water to lay their eggs in upland sites. Fish can be negatively affected by docks and retaining walls which remove breeding habitat in shallow water. Some shoreline communities even deliberately try to remove wetlands since they may interfere with activities like swimming. Overall,

494-567: Is overlain in part by the Marks Head Formation . The Parachula Formation trends deeper from north to south. In Effingham County , near the Savannah River, the top of the formation is 163 feet (50 m) below sea level . On Cumberland Island , it is 420 feet (130 m), and next to the St. Marys River , 423 feet (129 m) below sea level. The formation (or Porters Landing Member) maintains

532-497: Is particularly dependent upon past water levels; in general, the area of wet meadows along lakes and rivers increases with natural water level fluctuations. Many of the animals in lakes and rivers are dependent upon the wetlands of littoral zones, since the rooted plants provide habitat and food. Hence, a large and productive littoral zone is considered an important characteristic of a healthy lake or river. Littoral zones are at particular risk for two reasons. First, human settlement

570-405: Is rarely inundated), to coastal areas that are permanently submerged — known as the foreshore — and the terms are often used interchangeably. However, the geographical meaning of littoral zone extends well beyond the intertidal zone to include all neritic waters within the bounds of continental shelves . The word littoral may be used both as a noun and as an adjective . It derives from

608-526: The Arikareean stage of the late Oligocene epoch. The fossils of the White Springs Local Fauna have been collected from sites on an approximately 10 km long stretch along the Suwannee River where the Parachucla Formation is exposed. The local fauna includes a number of fossils of near-shore marine and land vertebrates, including 9 sharks, 5 rays, 14 bony fish , 6 reptiles, and 27 mammals. The reptiles include

646-524: The Latin noun litus, litoris , meaning "shore". (The doubled t is a late-medieval innovation, and the word is sometimes seen in the more classical-looking spelling litoral .) The term has no single definition. What is regarded as the full extent of the littoral zone, and the way the littoral zone is divided into subregions, varies in different contexts. For lakes, the littoral zone is the nearshore habitat where photosynthetically active radiation penetrates to

684-530: The Minnesota Department of Natural Resources defines littoral as that portion of the lake that is less than 15 feet in depth. Such fixed-depth definitions often do not accurately represent the true ecological zonation, but are sometimes used because they are simple measurements to make bathymetric maps or when there are no measurements of light penetration. The littoral zone comprises an estimated 78% of Earth's total lake area. The littoral zone may form

722-423: The cricetid Leidymys genera, the squirrels Protosciurus and Nototamias , and three species of geomyid rodents. Other small land mammals in the White Springs Local Fauna include a lagomorph ( Palaeolagus or Megalagus ), two bats, and a marsupial. Larger mammals include a horse ( Miohippus or Anchippus texanus ), an oreodont ( Mesoredon floridensis ), three different camelids (including

760-475: The pelagic zone often rely heavily on resources from the littoral zone. Littoral areas of ponds and lakes are typically better oxygenated, structurally more complex, and afford more abundant and diverse food resources than do profundal sediments. All these factors lead to a high diversity of insects and very complex trophic interactions. The great lakes of the world represent a global heritage of surface freshwater and aquatic biodiversity. Species lists for 14 of

798-434: The sublittoral zone . The supralittoral zone (also called the splash , spray or supratidal zone ) is the area above the spring high tide line that is regularly splashed, but not submerged by ocean water. Seawater penetrates these elevated areas only during storms with high tides. Organisms that live here must cope with exposure to fresh water from rain, cold, heat, dryness and predation by land animals and seabirds. At

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836-426: The Parachucla Formation exposure at White Springs in northern Florida yielded age estimates of 23.9 to 24.7 Million years ago (Ma). Shells from the formation exposure at Porters Landing in northern Georgia yielded age estimates of 19.4 to 20.5 Ma. The Parachucla Formation (Porters Landing Member) in northern Florida is associated with the White Springs Local Fauna, consisting of fossils of 57 vertebrate species from

874-915: The Porters Landing Member strata found along the Savannah River, is the only known occurrence of the Parachucla Formation in Florida. The Parachucla Formation is the lowest unit of the Hawthorn Group in Georgia. The Parachucla Formation also grades into the Chattahoochee Formation in southwest Georgia and the eastern panhandle of Florida. Off the Georgia coast, the Parachucla grades into the Cooper Formation . The Tiger Leap and Porters Landing members appear to be separated by an unconformity . Clam shells ( Ostrea normalis ) from two locations were tested for age using Strontium isotope stratigraphy . Shells from

912-539: The Tiger Leap Member from the Parachucla Formation, raising it in rank to the Tiger Leap Formation and dropping the Porters Landing Member name. Other authors continue to use the Huddlestun definition, which includes the Tiger Leap Member in the formation. The Parachucla Formation (or the Porters Landing Member of the formation, depending on definition), is a quartz sand and clay structure lacking fossils, formed in

950-502: The bivalves Chlamys acanikos and Ostrea normalis and the barnacles Concavus crassostrictola , Balanus reflexus and a species of Solidobalanus . Lithification Lithification (from the Ancient Greek word lithos meaning 'rock' and the Latin -derived suffix -ific ) is the process in which sediments compact under pressure , expel connate fluids , and gradually become solid rock. Essentially, lithification

988-710: The formation (or Porters Landing Member) was found in bore holes in Evans County , to the west of Richmond Hill, or at Fort Pulaski , to the east. The siliciclastic beds of the Parachucla Formation resemble those of the equivalent Penney Farms Formation in Florida, but the Penney Farms Formation has carbonate beds which are not found in the Parachucla. Exposed strata along the Suwannee River near White Springs in Hamilton County, Florida , which correlate with

1026-539: The lake bottom in sufficient quantities to support photosynthesis. The use of the term also varies from one part of the world to another, and between different disciplines. For example, military commanders speak of the littoral in ways that are quite different from the definition used by marine biologists . The adjacency of water gives a number of distinctive characteristics to littoral regions. The erosive power of water results in particular types of landforms , such as sand dunes , and estuaries . The natural movement of

1064-710: The late Aquitanian stage of the early Miocene period. It lies above the Tiger Leap Formation (or Tiger Leap Member of the Parachucla Formation), a chalky, shelly sand structure with phosphate and microfossils, which formed in the Oligocene epoch. The Tiger Leap unit is underlain in part by the Suwannee Limestone , the Lazaretto Creek Formation , and other unnamed units. The Parachucla Formation

1102-403: The littoral along the coast is called the littoral drift . Biologically, the ready availability of water enables a greater variety of plant and animal life, and particularly the formation of extensive wetlands . In addition, the additional local humidity due to evaporation usually creates a microclimate supporting unique types of organisms. In oceanography and marine biology , the idea of

1140-423: The littoral zone is extended roughly to the edge of the continental shelf . Starting from the shoreline, the littoral zone begins at the spray region just above the high tide mark. From here, it moves to the intertidal region between the high and low water marks, and then out as far as the edge of the continental shelf . These three subregions are called, in order, the supralittoral zone , the eulittoral zone , and

1178-420: The presence of human settlement has a demonstrated negative impact upon adjoining wetlands. An equally serious problem is the tendency to stabilize lake or river levels with dams. Dams removed the spring flood, which carries nutrients into littoral zones and reduces the natural fluctuation of water levels upon which many wetland plants and animals depend. Hence, over time, dams can reduce the area of wetland from

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1216-484: The remarkable biodiversity and biotic integrity of large lakes will require better integration of littoral zones into our understanding of lake ecosystem functioning and focused efforts to alleviate human impacts along the shoreline. In freshwater situations, the littoral zone is the nearshore habitat where photosynthetically active radiation penetrates to the lake bottom in sufficient quantities to support photosynthesis. Sometimes other definitions are used. For example,

1254-466: The spring low tide line, which is rarely not inundated. It is alternately exposed and submerged once or twice daily. Organisms living here must be able to withstand the varying conditions of temperature, light, and salinity. Despite this, productivity is high in this zone. The wave action and turbulence of recurring tides shape and reform cliffs, gaps and caves, offering a huge range of habitats for sedentary organisms. Protected rocky shorelines usually show

1292-404: The sublittoral zone refers to coastal regions with significant tidal flows and energy dissipation, including non-linear flows, internal waves , river outflows and oceanic fronts. In practice, this typically extends to the edge of the continental shelf , with depths around 200 meters. In marine biology, the sublittoral zone refers to the areas where sunlight reaches the ocean floor, that is, where

1330-444: The sublittoral zone. Within the sublittoral, marine biologists also identify the following: Shallower regions of the sublittoral zone, extending not far from the shore, are sometimes referred to as the subtidal zone . Many vertebrates (e.g., mammals, waterfowl, reptiles) and invertebrates (insects, etc.) use both the littoral zone as well as the terrestrial ecosystem for food and habitat. Biota that are commonly assumed to reside in

1368-403: The top of this area, patches of dark lichens can appear as crusts on rocks. Some types of periwinkles , Neritidae and detritus feeding Isopoda commonly inhabit the lower supralittoral. The eulittoral zone (also called the midlittoral or mediolittoral zone ) is the intertidal zone , known also as the foreshore . It extends from the spring high tide line, which is rarely inundated, to

1406-585: The water is never so deep as to take it out of the photic zone . This results in high primary production and makes the sublittoral zone the location of the majority of sea life. As in physical oceanography, this zone typically extends to the edge of the continental shelf . The benthic zone in the sublittoral is much more stable than in the intertidal zone; temperature, water pressure, and the amount of sunlight remain fairly constant. Sublittoral corals do not have to deal with as much change as intertidal corals. Corals can live in both zones, but they are more common in

1444-416: The world's largest lakes reveal that 15% of the global diversity (the total number of species) of freshwater fishes, 9% of non-insect freshwater invertebrate diversity, and 2% of aquatic insect diversity live in this handful of lakes. The vast majority (more than 93%) of species inhabit the shallow, nearshore littoral zone, and 72% are completely restricted to the littoral zone, even though littoral habitats are

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