Misplaced Pages

#207792

56-489: The Old Port Formation consists of limestone, sandstone, shale, and chert. The Old Port Formation is divided into several members with varying lithologies , which are (in ascending stratigraphic order): New Creek Member (limestone), Corriganville Member (limestone), Mandata Member (shale), Shriver Member (cherty limestone), and Ridgeley Member (sandstone). Where the Shriver Chert does not occur it may be replaced by

112-420: A laboratory or factory . Mining in a wider sense comprises extraction of any resource (e.g. petroleum , natural gas , salt or even water ) from the earth. Mining of rock and metals has been done since prehistoric times. Modern mining processes involve prospecting for mineral deposits, analysis of the profit potential of a proposed mine, extraction of the desired materials, and finally reclamation of

168-409: A body of water or beneath ice. Unconsolidated surficial materials may also be given a lithology. This is defined by grain size and composition and is often attached to an interpretation of how the unit formed. Surficial lithologies can be given to lacustrine , coastal, fluvial , aeolian , glacial , and recent volcanic deposits, among others. Examples of surficial lithology classifications used by

224-411: A continually-increasing extent of metamorphism. Metamorphic facies are defined by the pressure-temperature fields in which particular minerals form. Additional metamorphic rock names exist, such as greenschist (metamorphosed basalt and other extrusive igneous rock) or quartzite (metamorphosed quartz sand). In igneous and metamorphic rocks, grain size is a measure of the sizes of the crystals in

280-402: A fourth class of rocks alongside igneous, sedimentary, and metamorphic. Rock varies greatly in strength, from quartzites having a tensile strength in excess of 300 MPa to sedimentary rock so soft it can be crumbled with bare fingers (that is, it is friable ). (For comparison, structural steel has a tensile strength of around 350 MPa. ) Relatively soft, easily worked sedimentary rock

336-408: A hand lens, the visible mineralogy is included as part of the description. In the case of sequences possibly including carbonates , calcite - cemented rocks or those with possible calcite veins, it is normal to test for the presence of calcite (or other forms of calcium carbonate ) using dilute hydrochloric acid and looking for effervescence . The mineralogical composition of a rock is one of

392-433: A huge impact on the cultural and technological development of the human race. Rock has been used by humans and other hominids for at least 2.5 million years . Lithic technology marks some of the oldest and continuously used technologies. The mining of rock for its metal content has been one of the most important factors of human advancement, and has progressed at different rates in different places, in part because of

448-671: A massive limestone overlying the Keyser Formation. C. R. Wood first mapped it as part of the Old Port Formation in Pennsylvania. The Licking Creek Limestone of the Helderberg Group was first introduced by F. M. Swartz in 1938, and was described more fully in 1939. The unit consists of layers and nodules of black chert interbedded with light-gray crystalline limestone. The type locality is a bluff on

504-461: A particular depositional environment and may provide information on paleocurrent directions. In metamorphic rocks associated with the deeper levels of fault zones , small scale structures such as asymmetric boudins and microfolds are used to determine the sense of displacement across the zone. In igneous rocks, small-scale structures are mostly observed in lavas such as pahoehoe versus ʻAʻā basaltic flows, and pillows showing eruption within

560-569: A rock describes the relationship between the individual grains or clasts that make up the rock. Sedimentary textures include the degree of sorting , grading , shape and roundness of the clasts. Metamorphic textures include those referring to the timing of growth of large metamorphic minerals relative to a phase of deformation—before deformation porphyroclast —after deformation porphyroblast . Igneous textures include such properties as grain shape, which varies from crystals with ideal crystal shapes ( euhedral ) to irregular crystals (anhedral), whether

616-636: A sample. The colour of a rock or its component parts is a distinctive characteristic of some rocks and is always recorded, sometimes against standard colour charts, such as that produced by the Rock-Color Chart Committee of the Geological Society of America based on the Munsell color system . The fabric of a rock describes the spatial and geometric configuration of all the elements that make it up. In sedimentary rocks

SECTION 10

#1732801579208

672-562: A source area and then transported to the place of deposition by water , wind , ice , mass movement or glaciers (agents of denudation ). About 7.9% of the crust by volume is composed of sedimentary rocks, with 82% of those being shales, while the remainder consists of 6% limestone and 12% sandstone and arkoses . Sedimentary rocks often contain fossils . Sedimentary rocks form under the influence of gravity and typically are deposited in horizontal or near horizontal layers or strata , and may be referred to as stratified rocks. Sediment and

728-432: A summary of the gross physical character of a rock. Examples of lithologies in the second sense include sandstone , slate , basalt , or limestone . Lithology is the basis of subdividing rock sequences into individual lithostratigraphic units for the purposes of mapping and correlation between areas. In certain applications, such as site investigations , lithology is described using a standard terminology such as in

784-713: A texture are referred to as foliated ; the remainders are termed non-foliated. The name of the rock is then determined based on the types of minerals present. Schists are foliated rocks that are primarily composed of lamellar minerals such as micas . A gneiss has visible bands of differing lightness , with a common example being the granite gneiss. Other varieties of foliated rock include slates , phyllites , and mylonite . Familiar examples of non-foliated metamorphic rocks include marble , soapstone , and serpentine . This branch contains quartzite —a metamorphosed form of sandstone —and hornfels . Though most understanding of rocks comes from those of Earth, rocks make up many of

840-664: Is at the town of Ridgeley , Mineral County , West Virginia. The sandstone of the Ridgeley Member has been extensively mined due to its very pure quartz suitable for glass . The glass derived from the sandstone was used for lenses on the Hubble Space Telescope . A separate formation, the Oriskany Sandstone, is a lateral equivalent of the Ridgeley Member, but bounded above and below by unconformities . The Shriver Member, or Shriver Chert,

896-458: Is formed through the cooling and solidification of magma or lava . This magma may be derived from partial melts of pre-existing rocks in either a planet 's mantle or crust . Typically, the melting of rocks is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Igneous rocks are divided into two main categories: Magmas tend to become richer in silica as they rise towards

952-540: Is impractical, they may be classified chemically using the TAS classification . This is based on the total content of silica and alkali metal oxides and other chemical criteria. Sedimentary rocks are further classified by whether they are siliciclastic or carbonate . Siliciclastic sedimentary rocks are then subcategorized based on their grain size distribution and the relative proportions of quartz, feldspar, and lithic (rock) fragments. Carbonate rocks are classified with

1008-505: Is mapped as part of the Old Port Formation. In New Jersey it is mapped as the middle unit of the Oriskany Group. The Mandata Shale of the Helderberg Group was first introduced by F. M. Swartz in 1938, mainly with reference to the overlying Licking Creek Limestone. The type locality is about 0.25 miles south of Mandata , Pennsylvania, on Route 225 . The Corriganville Limestone was first described by J. W. Head in 1972 as part of

1064-410: Is mined extensively in Pennsylvania and Maryland. Lithology The lithology of a rock unit is a description of its physical characteristics visible at outcrop , in hand or core samples , or with low magnification microscopy. Physical characteristics include colour, texture, grain size , and composition. Lithology may refer to either a detailed description of these characteristics, or

1120-494: Is next in importance. About 65% of the Earth's crust by volume consists of igneous rocks. Of these, 66% are basalt and gabbro , 16% are granite, and 17% granodiorite and diorite . Only 0.6% are syenite and 0.3% are ultramafic . The oceanic crust is 99% basalt, which is an igneous rock of mafic composition. Granite and similar rocks, known as granitoids , dominate the continental crust . Sedimentary rocks are formed at

1176-477: Is the diameter of the grains and/or clasts that constitute the rock. These are used to determine which rock naming system to use (e.g., a conglomerate , sandstone , or mudstone ). In the case of sandstones and conglomerates, which cover a wide range of grain sizes, a word describing the grain size range is added to the rock name. Examples are " pebble conglomerate" and "fine quartz arenite ". In rocks in which mineral grains are large enough to be identified using

SECTION 20

#1732801579208

1232-453: Is the study of Earth and its components, including the study of rock formations. Petrology is the study of the character and origin of rocks. Mineralogy is the study of the mineral components that create rocks. The study of rocks and their components has contributed to the geological understanding of Earth's history, the archaeological understanding of human history, and the development of engineering and technology in human society. While

1288-475: The Dunham or Folk classification schemes according to the constituents of the carbonate rock. Metamorphic rock naming can be based on protolith , mineral composition, texture, or metamorphic facies . Naming based on texture and a pelite (e.g., shale , mudrock ) protolith can be used to define slate and phyllite . Texture-based names are schist and gneiss . These textures, from slate to gneiss, define

1344-464: The QAPF classification , which is based on the relative content of quartz , alkali feldspar , plagioclase , and feldspathoid . Special classifications exist for igneous rock of unusual compositions, such as ultramafic rock or carbonatites . Where possible, extrusive igneous rocks are also classified by mineral content using the extrusive QAPF classification, but when determining the mineral composition

1400-408: The U.S. Geological Survey are, "Glacial Till, Loamy ", "Saline Lake Sediment", and "Eolian Sediment, Coarse-Textured (Sand Dunes )". Rock (geology) In geology , rock (or stone ) is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition , and the way in which it is formed. Rocks form

1456-417: The history of geology includes many theories of rocks and their origins that have persisted throughout human history, the study of rocks was developed as a formal science during the 19th century. Plutonism was developed as a theory during this time, and the discovery of radioactive decay in 1896 allowed for the radiocarbon dating of rocks. Understanding of plate tectonics developed in the second half of

1512-399: The 20th century. Rocks are composed primarily of grains of minerals, which are crystalline solids formed from atoms chemically bonded into an orderly structure. Some rocks also contain mineraloids , which are rigid, mineral-like substances, such as volcanic glass , that lack crystalline structure. The types and abundance of minerals in a rock are determined by the manner in which it

1568-442: The Earth's crust, or lava cools on the ground surface or the seabed. Sedimentary rocks are formed by diagenesis and lithification of sediments , which in turn are formed by the weathering , transport, and deposition of existing rocks. Metamorphic rocks are formed when existing rocks are subjected to such high pressures and temperatures that they are transformed without significant melting. Humanity has made use of rocks since

1624-548: The Earth's outer solid layer, the crust , and most of its interior, except for the liquid outer core and pockets of magma in the asthenosphere . The study of rocks involves multiple subdisciplines of geology, including petrology and mineralogy . It may be limited to rocks found on Earth, or it may include planetary geology that studies the rocks of other celestial objects. Rocks are usually grouped into three main groups: igneous rocks , sedimentary rocks and metamorphic rocks . Igneous rocks are formed when magma cools in

1680-467: The Earth's surface, a process called magma differentiation . This occurs both because minerals low in silica crystallize out of the magma as it begins to cool ( Bowen's reaction series ) and because the magma assimilates some of the crustal rock through which it ascends ( country rock ), and crustal rock tends to be high in silica. Silica content is thus the most important chemical criterion for classifying igneous rock. The content of alkali metal oxides

1736-503: The Earth's surface: temperatures greater than 150 to 200 °C and pressures greater than 1500 bars. This occurs, for example, when continental plates collide. Metamorphic rocks compose 27.4% of the crust by volume. The three major classes of metamorphic rock are based upon the formation mechanism. An intrusion of magma that heats the surrounding rock causes contact metamorphism—a temperature-dominated transformation. Pressure metamorphism occurs when sediments are buried deep under

Old Port Formation - Misplaced Pages Continue

1792-879: The European geotechnical standard Eurocode 7 . The naming of a lithology is based on the rock type . The three major rock types are igneous , sedimentary , and metamorphic . Igneous rocks are formed directly from magma , which is a mixture of molten rock, dissolved gases, and solid crystals. Sedimentary rock is formed from mineral or organic particles that collect at the Earth's surface and become lithified . Metamorphic rock forms by recrystallization of existing solid rock under conditions of great heat or pressure. Igneous rocks are further broken into three broad categories. Igneous rock composed of broken rock fragments created directly by volcanic processes ( tephra ) are classified as pyroclastic rock . Pyroclastic rocks are further classified by average fragment ( clast ) size and whether

1848-581: The Helderberg Group in Allegany County , Maryland, as a gray limestone with chert. C. R. Wood first mapped it as part of the Old Port Formation in Pennsylvania. The type locality is a railroad cut 0.3 mi southeast of Corriganville , Alleghany County, Maryland. The New Creek Member was first described by Bowen only as a limestone that is replaced by the Elbow Ridge Sandstone near Hancock , Maryland. Bowen later described it as

1904-649: The Licking Creek Limestone. It was originally combined from the Helderberg Group and Oriskany Group by Conlin and Hoskins in 1962 to form a single Formation with the above members. The Ridgeley Member was first described as a member of the Oriskany Formation by Swartz and others (1913), as a calcareous sandstone which passes into an arenaceous limestone. It is still mapped as part of the Oriskany Group in New Jersey. The type locality

1960-812: The Shriver Member around the type locality of Shriver Ridge. Ostracods are also present in the Shriver Member. The Old Port Formation contains conodonts . Relative age dating of the Old Port places it in the Lower Devonian period. It rests conformably atop the Keyser Formation and usually unconformably below the Needmore Formation or below the Onondaga Formation . Shallow marine. The Ridgeley Member

2016-523: The constituent particles, and particle size . These physical properties are the result of the processes that formed the rocks. Over the course of time, rocks can be transformed from one type into another, as described by a geological model called the rock cycle . This transformation produces three general classes of rock: igneous , sedimentary and metamorphic . Those three classes are subdivided into many groups. There are, however, no hard-and-fast boundaries between allied rocks. By increase or decrease in

2072-496: The earliest humans. This early period, called the Stone Age , saw the development of many stone tools. Stone was then used as a major component in the construction of buildings and early infrastructure . Mining developed to extract rocks from the Earth and obtain the minerals within them, including metals . Modern technology has allowed the development of new human-made rocks and rock-like substances, such as concrete . Geology

2128-606: The earth's surface by the accumulation and cementation of fragments of earlier rocks, minerals, and organisms or as chemical precipitates and organic growths in water ( sedimentation ). This process causes clastic sediments (pieces of rock) or organic particles ( detritus ) to settle and accumulate or for minerals to chemically precipitate ( evaporite ) from a solution . The particulate matter then undergoes compaction and cementation at moderate temperatures and pressures ( diagenesis ). Before being deposited, sediments are formed by weathering of earlier rocks by erosion in

2184-427: The earth, from an ore body, vein or seam . The term also includes the removal of soil. Materials recovered by mining include base metals , precious metals , iron , uranium , coal , diamonds , limestone , oil shale , rock salt , potash , construction aggregate and dimension stone . Mining is required to obtain any material that cannot be grown through agricultural processes, or created artificially in

2240-440: The fragments are mostly individual mineral crystals , particles of volcanic glass , or rock fragments. Further classifications, such as by chemical composition , may also be applied. Igneous rocks that have visible mineral grains ( phaneritic rocks) are classified as intrusive , while those that are glassy or very fine-grained ( aphanitic ) are classified as extrusive rock . Intrusive igneous rocks are usually classified using

2296-402: The ground; pressure is dominant, and temperature plays a smaller role. This is termed burial metamorphism, and it can result in rocks such as jade . Where both heat and pressure play a role, the mechanism is termed regional metamorphism. This is typically found in mountain-building regions. Depending on the structure, metamorphic rocks are divided into two general categories. Those that possess

Old Port Formation - Misplaced Pages Continue

2352-491: The kind of metals available from the rock of a region. Anthropic rock is synthetic or restructured rock formed by human activity. Concrete is recognized as a human-made rock constituted of natural and processed rock and having been developed since Ancient Rome . Rock can also be modified with other substances to develop new forms, such as epoxy granite . Artificial stone has also been developed, such as Coade stone . Geologist James R. Underwood has proposed anthropic rock as

2408-431: The land to prepare it for other uses once mining ceases. Mining processes may create negative impacts on the environment both during the mining operations and for years after mining has ceased. These potential impacts have led to most of the world's nations adopting regulations to manage negative effects of mining operations. Stone tools have been used for millions of years by humans and earlier hominids . The Stone Age

2464-454: The main visible fabric is normally bedding , and the scale and degree of development of the bedding is normally recorded as part of the description. Metamorphic rocks (apart from those created by contact metamorphism ), are characterised by well-developed planar and linear fabrics. Igneous rocks may also have fabrics as a result of flow or the settling out of particular mineral phases during crystallisation, forming cumulates . The texture of

2520-487: The major ways in which it is classified. Igneous rocks are classified by their mineral content whenever practical, using the QAPF classification or special ultramafic or carbonatite classifications. Likewise metamorphic facies, which show the degree to which a rock has been exposed to heat and pressure and are therefore important in classifying metamorphic rocks, are determined by observing the mineral phases that are present in

2576-418: The original rock was formed. This process is called metamorphism , meaning to "change in form". The result is a profound change in physical properties and chemistry of the stone. The original rock, known as the protolith , transforms into other mineral types or other forms of the same minerals, by recrystallization . The temperatures and pressures required for this process are always higher than those found at

2632-425: The particles of clastic sedimentary rocks can be further classified by grain size . The smallest sediments are clay , followed by silt , sand , and gravel . Some systems include cobbles and boulders as measurements. Metamorphic rocks are formed by subjecting any rock type—sedimentary rock, igneous rock or another older metamorphic rock—to different temperature and pressure conditions than those in which

2688-466: The proportions of their minerals, they pass through gradations from one to the other; the distinctive structures of one kind of rock may thus be traced, gradually merging into those of another. Hence the definitions adopted in rock names simply correspond to selected points in a continuously graduated series. Igneous rock (derived from the Latin word igneus, meaning of fire, from ignis meaning fire)

2744-401: The rock shows highly nonuniform crystal sizes (is porphyritic ), or whether grains are aligned (which is described as trachytic texture). Rocks often contain small-scale structures (smaller than the scale of an individual outcrop). In sedimentary rocks this may include sole markings , ripple marks , mudcracks and cross-bedding . These are recorded as they are generally characteristic of

2800-478: The rock. In igneous rock, this is used to determine the rate at which the material cooled: large crystals typically indicate intrusive igneous rock, while small crystals indicate that the rock was extrusive. Metamorphism of rock composed of mostly a single mineral, such as quartzite or marble , may increase grain size ( grain growth ), while metamorphism of sheared rock may decrease grain size (syntectonic recrystallization ). In clastic sedimentary rocks, grain size

2856-481: The south side of Licking Creek , about one mile east of Warren Point , Franklin County , Pennsylvania. See also type localities listed in subsections above. Brachiopods are occasionally abundant (as casts) in the Ridgeley Member. The brachiopods Costispirifer arenosus , Beachia immatura , Leptocoelia flabellites , Metaplasia paucicostata , Plicoplasia tribuarius , and Chonetes hudsonicus are present in

SECTION 50

#1732801579208

2912-621: The universe's celestial bodies. In the Solar System , Mars , Venus , and Mercury are composed of rock, as are many natural satellites , asteroids , and meteoroids . Meteorites that fall to Earth provide evidence of extraterrestrial rocks and their composition. They are typically heavier than rocks on Earth. Asteroid rocks can also be brought to Earth through space missions, such as the Hayabusa mission. Lunar rocks and Martian rocks have also been studied. The use of rock has had

2968-408: Was a period of widespread stone tool usage. Early Stone Age tools were simple implements, such as hammerstones and sharp flakes. Middle Stone Age tools featured sharpened points to be used as projectile points , awls, or scrapers . Late Stone Age tools were developed with craftsmanship and distinct cultural identities. Stone tools were largely superseded by copper and bronze tools following

3024-498: Was first described as a member of the Oriskany Formation by Swartz and others (1913), as dark siliceous shale with much black impure chert in nodules or layers of nodules. It is named after Shriver Ridge (the type locality), Allegany County , Maryland, and was originally mapped as the basal unit of the Oriskany Formation. In Maryland and West Virginia, the Shriver is mapped as part of the Helderberg Group. In central Pennsylvania it

3080-456: Was formed. Most rocks contain silicate minerals , compounds that include silica tetrahedra in their crystal lattice , and account for about one-third of all known mineral species and about 95% of the earth's crust . The proportion of silica in rocks and minerals is a major factor in determining their names and properties. Rocks are classified according to characteristics such as mineral and chemical composition, permeability , texture of

3136-789: Was quarried for construction as early as 4000 BCE in Egypt, and stone was used to build fortifications in Inner Mongolia as early as 2800 BCE. The soft rock, tuff , is common in Italy, and the Romans used it for many buildings and bridges. Limestone was widely used in construction in the Middle Ages in Europe and remained popular into the 20th century. Mining is the extraction of valuable minerals or other geological materials from

#207792