sedimentary rock
Sedimentary rocks are types of rock (geology), rock formed by the cementation (geology), cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or de ...
that is composed either wholly or almost entirely of the transported, abraded, and mechanically sorted fragments of
mollusks
Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The num ...
,
trilobite
Trilobites (; meaning "three-lobed entities") are extinction, extinct marine arthropods that form the class (biology), class Trilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most succ ...
s,
brachiopod
Brachiopods (), phylum (biology), phylum Brachiopoda, are a phylum of animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear e ...
s, or other
invertebrate
Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordata, chordate s ...
s. The term ''coquina'' comes from the Spanish word for " cockle" and "shellfish".
For a sediment to be considered to be a coquina, the particles composing it should average or greater in size. Coquina can vary in hardness from poorly to moderately cemented. Incompletely consolidated and poorly cemented coquinas are considered grainstones in the
Dunham classification
The Dunham classification system for Carbonate minerals, carbonate sedimentary rocks was originally devised by Robert J. Dunham (1924–1994) in 1962, and subsequently modified by Embry and Klovan in 1971 to include coarse-grained limestones and ...
system for carbonate sedimentary rocks. A well-cemented coquina is classified as a biosparite (fossiliferous limestone) according to the Folk classification of sedimentary rocks.
Coquinas accumulate in high-energy marine and lacustrine environments where currents and waves result in the vigorous winnowing, abrasion, fracturing, and sorting of the shells that compose them. As a result, they typically exhibit well-developed bedding or
cross-bedding
In geology, cross-bedding, also known as cross-stratification, is layering within a stratum and at an angle to the main bedding plane. The sedimentary structures which result are roughly horizontal units composed of inclined layers. The origina ...
, close packing, and good orientation of the shell fragments. The high-energy marine or lacustrine environments associated with coquinas include beaches, shallow submarine raised banks, swift tidal channels, and barrier bars.
Composition and distribution
Coquina is composed mainly of the
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...
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 ...
, often including some
phosphate
Phosphates are the naturally occurring form of the element phosphorus.
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthop ...
, in the form of
seashell
A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer usually created by an animal or organism that lives in the sea. Most seashells are made by Mollusca, mollusks, such as snails, clams, and oysters ...
s or
coral
Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important Coral ...
. Coquinas dating from the
Devonian
The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...
period through to the much more recent
Pleistocene
The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
epoch are a common find all over the world, with the depositional requirements to form a coquina being a common thing in many marine
facies
In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...
.
History and use
Australia
Adjacent to Shark Bay Road beginning southeast of Denham is an approximately long stretch of coastline composed of billions of tiny shells of the Shark Bay cockle ( Fragum erugatum), averaging less than in length. The shell deposit, between thick, has compacted and cemented in some areas into solid masses of limestone that formerly was quarried and cut into blocks used in local construction.
St Andrew's
Anglican
Anglicanism, also known as Episcopalianism in some countries, is a Western Christianity, Western Christian tradition which developed from the practices, liturgy, and identity of the Church of England following the English Reformation, in the ...
Church, the Old Pearler Restaurant, and parts of the Shark Bay Hotel in
Shark Bay
Shark Bay () is a World Heritage Site in the Gascoyne region of Western Australia. The area is located approximately north of Perth, on the westernmost point of the Australian continent.
UNESCO's listing of Shark Bay as a World Heritage S ...
were built from coquina shell blocks. The church, built in 1954, has walls infilled with coquina shell blocks between a light steel frame and a shell facing, while the Old Pearler was built in 1974–1977 with buttressed coquina shell block walls.
Brazil
Recently discovered petroleum-bearing formations off the coast of northeastern Brazil hold coquina reservoirs of oil. The coquinas are generally heterogeneous in their porosity and permeability, but like other lacustrine carbonates, they are uncommonly reservoirs. Corbett et al. (2015) in their discussion of the reservoirs say the finding of the Badejo Field (
Campos Basin
The Campos Basin is one of 12 coastal sedimentary basins of Brazil. It spans both onshore and offshore parts of the South Atlantic with the onshore part located near Rio de Janeiro. The basin originated in Neocomian stage of the Cretaceous peri ...
) in 1975 was the first hydrocarbon discovery in the coquinas of the Lagoa Feia, followed by that of the Pampo and Linguado Fields in 1978. The coquinas of the Morro do Chaves Formation were formed by non-marine bivalves and
ostracod
Ostracods, or ostracodes, are a Class (biology), class of the crustacean, Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 33,000 species (only 13,000 of which are extant taxon, extant) have been identified,Brandão, S.N.; Antoni ...
s. The shells of the bivalves, which lived in shallow oxygenated water, were transported and deposited as washout over stream fans and beaches by storms and long-shore drift.
The palynological record of coquinas of the Sergipe-Alagoas Basin has been analyzed and the sediments dated to the late Barremian age; the results suggest a marine and/or brackish environment. Daniel Thompson (2013) asserts that the coquinas of the Morro do Chaves Formation include a wide range of marine mollusca characteristic of brackish environmental conditions, suggesting periodic marine ingression during the
Early Cretaceous
The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...
.
According to a paper by Senira Kattah published in ''The Sedimentary Record'', the discovery of the Lula Field by
Petrobras
Petróleo Brasileiro S.A., better known by and Trade name, trading as the portmanteau Petrobras (), is a Brazilian state-owned enterprise, majority state-owned multinational corporation in the petroleum industry headquartered in Rio de Janeiro. ...
and partners in 2006 opened petroleum exploration in the Barremian/
Aptian
The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...
pre-salt play in the offshore Santos and Campos basins, and consequently deeper coquina reservoirs have become important targets. He says the two main reservoir targets recognized for the pre-salt within the study areas are: "late rift coquinas, lacustrine
facies
In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...
deposited at the Late Barremian to Early Aptian, and the younger rift/sag microbial limestones deposited during the Aptian, just before the establishment of the major evaporitic sag basin between South America and Africa." There are abundant beds of coquina in the Outer High of the
Santos Basin
The Santos Basin () is an approximately large mostly offshore sedimentary basin. It is located in the south Atlantic Ocean, some southeast of Santos, São Paulo, Santos, Brazil. The basin is one of the Brazilian basins to have resulted from th ...
, similar to those from the neighboring Campos. Pre-salt stratigraphy of the Santos Basin shows lacustrine sediments composed of coarse pelecypod (bivalve) coquina during the Barremian and Aptian sag phase of the
continental crust
Continental crust is the layer of igneous, metamorphic, and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as '' continental shelves''. This layer is sometimes called '' si ...
subsidence.
Florida
Coquina deposits in Florida occur mostly along the eastern coast of the peninsula. This coquina is named the
Anastasia Formation
The Anastasia Formation is a geologic formation deposited in Florida during the Late Pleistocene epoch.
Age
Period (geology), Period : Quaternary
Epoch (geology), Epoch: Pleistocene ~2.558 to 0.012 Mya (unit), mya, calculates to a period of
Nort ...
Palm Beach County
Palm Beach County is a county in the southeastern part of Florida, located in the Miami metropolitan area. It is Florida's third-most populous county after Miami-Dade County and Broward County and the 24th-most populous in the United States, wi ...
Pleistocene
The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
The Nature Conservancy
The Nature Conservancy (TNC) is a global environmental organization headquartered in Arlington, Virginia, United States. it works via affiliates or branches in 79 countries and territories, as well as across every state in the US.
Founded in ...
, in Martin County.
Still occasionally quarried or mined, and used as a building stone in
Florida
Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
for over 400 years, coquina forms the walls of the Castillo in St. Augustine. The stone made a very good material for building forts, particularly those built during the period of heavy cannon use. Because of coquina's softness, cannonballs would sink into, rather than shatter or puncture the walls. The first Saint Augustine lighthouse, built by the Spanish, was also made of coquina.
Coquina was used as building stone in St. Augustine as early as 1598 for construction of a powder house. This was the beginning of a building tradition that extended into the 1930s along Florida's Atlantic Coast. In the St. Augustine vicinity, the Castillo de San Marcos, Fort Matanzas, the old city gates, the
Cathedral
A cathedral is a church (building), church that contains the of a bishop, thus serving as the central church of a diocese, Annual conferences within Methodism, conference, or episcopate. Churches with the function of "cathedral" are usually s ...
, Spanish and British Period residential structures, property line walls and tombs were constructed of coquina quarried on Anastasia Island. To the south in New Smyrna, a large storehouse and wharf were constructed of coquina at the 1770s Andrew Turnbull colony. Around 1816, John Addison constructed a kitchen house of coquina on his plantation on the Tomoka River. The material was also used in the construction of sugar mill buildings on sugar plantations in the 1820s and 1830s. Examples are the Bulow, Dunlawton and New Smyrna sugar mills. In these early structures, the porous coquina was protected by lime plaster. With the exception of a few residences that have been restored in St. Augustine, the coquina masonry of these structures is today exposed to the elements and is slowly deteriorating.
Mexico
Overlying the fossiliferous sands and sandy clays of the upper San Fernando River in northeastern Mexico is a bed of coquina limestone dating probably to the
Cenozoic
The Cenozoic Era ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterized by the dominance of mammals, insects, birds and angiosperms (flowering plants). It is the latest of three g ...
era. Coquina deposits also occur in the
Baja California
Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...
peninsula, including submerged "reefs". So-called coquina "reefs" occur at Punta Borrascosa, San Felipe and Coloraditos on the northeast coast of Baja California. These have been uranium-thorium dated to the Pleistocene epoch, with an age estimated at 130,000 ybp. Semi-continuous coquina
outcrop
An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth and other terrestrial planets.
Features
Outcrops do not cover the majority of the Earth's land surface because in most p ...
s have been found east of Puerto Peñasco, in the shallow subtidal zone or partly submerged under intertidal sands.
Other Pleistocene outcrops occur along both coastlines of the upper
Gulf of California
The Gulf of California (), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Vermejo''), is a marginal sea of the Pacific Ocean that separates the Baja California peninsula from ...
. On the Vizcaino Peninsula of western Baja California, the informally named " Tivela stultorum" coquina is abundant in shells of the Pismo clam. Until analysis of the shells by U-series and amino-acids methods is concluded, this marine transgression is assigned an approximate age of 200,000 ybp. Outcrops in Bahía de San Hipolito and Bahía de Asunción are loosely consolidated, sandy beachrock a few meters thick, found above present mean sea level.
The ancient Maya built their city of Toniná in the highlands of what is now
Chiapas
Chiapas, officially the Free and Sovereign State of Chiapas, is one of the states that make up the Political divisions of Mexico, 32 federal entities of Mexico. It comprises Municipalities of Chiapas, 124 municipalities and its capital and large ...
in southern Mexico using native rocks to construct its
masonry
Masonry is the craft of building a structure with brick, stone, or similar material, including mortar plastering which are often laid in, bound, and pasted together by mortar (masonry), mortar. The term ''masonry'' can also refer to the buildin ...
buildings, among them large coquina
flagstone
Flagstone (flag) is a generic flat Rock (geology), stone, sometimes cut in regular rectangular or square shape and usually used for Sidewalk, paving slabs or walkways, patios, flooring, fences and roofing. It may be used for memorials, headstone ...
s from which they made blocks and bricks for floors, walls, and stairways.
North Carolina
Coquina has a very limited distribution in southeastern
North Carolina
North Carolina ( ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It is bordered by Virginia to the north, the Atlantic Ocean to the east, South Carolina to the south, Georgia (U.S. stat ...
. The best known outcrop is located in New Hanover County, near Fort Fisher, along the southern tip of North Carolina's coast. It is one of the few naturally occurring outcrops in the
coastal plain
A coastal plain (also coastal plains, coastal lowland, coastal lowlands) is an area of flat, low-lying land adjacent to a sea coast. A fall line commonly marks the border between a coastal plain and an upland area.
Formation
Coastal plains can f ...
region of North Carolina, described as “a low-relief plain underlain by beds of shallow-marine, estuarine, shoreline, and fluvial sediments" in ''The Geology of the Carolinas''. These sediments were deposited during numerous episodes of sea level rise and fall over hundreds of thousands of years. The coastlines of the Tidewater region of North Carolina change constantly in response to wind and wave action, sedimentary deposition, tidal movements, and changes in sea level. Although the inner coastal plain is considered to be more stable, the coastal plain was inundated by repeated marine transgressions due to fluctuating sea levels during the late
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58Clear Springs Plantation near
New Bern
New Bern, formerly Newbern, is a city in Craven County, North Carolina, United States, and its county seat. It had a population of 31,291 at the 2020 United States census, 2020 census. It is located at the confluence of the Neuse River, Neuse a ...
plantation house
A plantation house is the main house of a plantation, often a substantial farmhouse, which often serves as a symbol for the plantation as a whole. Plantation houses in the Southern United States and in other areas are known as quite grand and ...
on the lower
Cape Fear River
The Cape Fear River is a blackwater river in east-central North Carolina. It flows into the Atlantic Ocean near Cape Fear, from which it takes its name. The river is formed at the confluence of the Haw River and the Deep River in the town of ...
was built of locally quarried coquina. The house that once stood on a vast tract of land directly across the river from Orton was described by local historian and author James Sprunt as "the grandest colonial residence of the Cape Fear". Sprunt compared Sedgeley Abbey in dimensions and appearance to the two-story, cellared, Governor Dudley mansion that still stands in Wilmington. Like many southern plantations, Sedgeley Abbey was abandoned after the
Civil War
A civil war is a war between organized groups within the same Sovereign state, state (or country). The aim of one side may be to take control of the country or a region, to achieve independence for a region, or to change government policies.J ...
. The vacant house was demolished in the 1870s and the coquina rubble was burned and spread on the fields as fertilizer. A cellar eight feet deep carved into solid coquina was located during archaeological investigations on the site of the former
plantation
Plantations are farms specializing in cash crops, usually mainly planting a single crop, with perhaps ancillary areas for vegetables for eating and so on. Plantations, centered on a plantation house, grow crops including cotton, cannabis, tob ...
quarrying
A quarry is a type of open-pit mine in which dimension stone, rock, construction aggregate, riprap, sand, gravel, or slate is excavated from the ground. The operation of quarries is regulated in some jurisdictions to manage their s ...
is no longer permitted in the
World Heritage Site
World Heritage Sites are landmarks and areas with legal protection under an treaty, international treaty administered by UNESCO for having cultural, historical, or scientific significance. The sites are judged to contain "cultural and natural ...
.
When first quarried, coquina is extremely soft. This softness makes it very easy to remove from the quarry and cut into shape. However, the stone is also at first much too soft to be used for building. In order to be used as a building material, the stone is left out to dry for approximately one to three years, which causes the stone to harden into a usable, but still comparatively soft, form.
Coquina has also been used as a source of paving material. It is usually poorly cemented and easily breaks into component shell or coral fragments, which can be substituted for
gravel
Gravel () is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentation, sedimentary and erosion, erosive geological processes; it is also produced in large quantities commercially as crushed stone.
Gr ...
or crushed harder rocks. In the 1930s, large-scale mining of coquina for use in highway construction began at Fort Fisher in North Carolina. Large pieces of coquina of unusual shape are sometimes used as landscape decoration.
Because coquina often includes a component of
phosphate
Phosphates are the naturally occurring form of the element phosphorus.
In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthop ...
, it is sometimes mined for use as
fertilizer
A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Man ...
Palm Beach County, Florida
Palm Beach County is a county in the southeastern part of Florida, located in the Miami metropolitan area. It is Florida's third-most populous county after Miami-Dade County, Florida, Miami-Dade County and Broward County, Florida, Broward County ...
Shropshire
Shropshire (; abbreviated SalopAlso used officially as the name of the county from 1974–1980. The demonym for inhabitants of the county "Salopian" derives from this name.) is a Ceremonial counties of England, ceremonial county in the West M ...
Ukraine
Ukraine is a country in Eastern Europe. It is the List of European countries by area, second-largest country in Europe after Russia, which Russia–Ukraine border, borders it to the east and northeast. Ukraine also borders Belarus to the nor ...
Flagler County, Florida
Flagler County is a county located in the northeastern portion of the U.S. state of Florida. As of the 2020 census, the population was 115,378. Its county seat is Bunnell, and the largest city is Palm Coast. Created in 1917 from portions of ...