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Ledger Formation
The Ledger Formation or Ledger Dolomite is a geologic formation in Pennsylvania, United States. The Ledger is described as light-gray, locally mottled, massive, pure, coarsely crystalline dolomite. It may be siliceous in the middle part. Type section Named from exposures at Ledger, Pennsylvania, formerly 3 miles northeast of Kinzers, Lancaster County, Pennsylvania.Stose, G.W., and Jonas, A.I., 1922. ''The lower Paleozoic section in southeastern Pennsylvania'', Washington Academy of Sciences, Journal v. 12, no. 5, p. 358-36/ref> Other outcrops At Valley Forge National Historical Park, the visitor center parking lot is built within an old quarry of the Ledger, and the former quarry walls are exposed. The rocks contain stromatolites. In the nearby Port Kennedy Quarry, the Triassic Stockton Formation unconformably overlies the folded Ledger. The Harpers Formation overlies the Ledger Formation due to a thrust fault in small roadside quarry (currently overgrown) on Potte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formation (stratigraphy)
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers. A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness (geology), thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stromatolites
Stromatolites () or stromatoliths () are layered sedimentary formations (microbialite) that are created mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing bacteria, and Pseudomonadota (formerly proteobacteria). These microorganisms produce adhesive compounds that cement sand and other rocky materials to form mineral "microbial mats". In turn, these mats build up layer by layer, growing gradually over time. A stromatolite may grow to a meter or more. Although they are rare today, fossilized stromatolites provide records of ancient life on Earth. Morphology Stromatolites are layered, biochemical, accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains in biofilms (specifically microbial mats), through the action of certain microbial lifeforms, especially cyanobacteria. They exhibit a variety of forms and structures, or morphologies, including conical, stratiform, domal, columnar, and branching ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vulcan Materials Company
Vulcan Materials Company () is an American company based in Birmingham, Alabama. It is principally engaged in the production, distribution and sale of construction materials. Vulcan is the largest producer of construction materials, primarily gravel, crushed stone, and sand, and employs approximately 7,000 people at over 300 facilities. Vulcan serves 20 states, the District of Columbia and Mexico. Vulcan's innovative Crescent Market project led to construction of a large quarry and deep water seaport on the Yucatán Peninsula of Mexico, just south of Cancun. This quarry supplies Tampa, New Orleans, Houston, and Brownsville, Texas, as well as other Gulf coast seaports, with crushed limestone via large 62,000-ton self-discharging ships. History In the late 1980s Vulcan acquired Reed Crushed Stone, near Kentucky. On June 7, 2005, Vulcan completed the sale of its chemicals business, known as Vulcan Chemicals, to Occidental Chemical Corporation. The sale of assets included Vulcan' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lancaster, Pennsylvania
Lancaster, ( ; pdc, Lengeschder) is a city in and the county seat of Lancaster County, Pennsylvania. It is one of the oldest inland cities in the United States. With a population at the 2020 census of 58,039, it ranks 11th in population among Pennsylvania's municipalities. The Lancaster metropolitan area population is 507,766, making it the 104th-largest metropolitan area in the U.S. and second-largest in the South Central Pennsylvania area. The city's primary industries include healthcare, tourism, public administration, manufacturing, and both professional and semi-professional services. Lancaster is a hub of Pennsylvania's Dutch Country. Lancaster is located southwest of Allentown and west of Philadelphia. History Originally called Hickory Town, the city was renamed after the English city of Lancaster by native John Wright. Its symbol, the red rose, is from the House of Lancaster. Lancaster was part of the 1681 Penn's Woods Charter of William Penn, and was laid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pennsylvania Route 23
Pennsylvania Route 23 (PA 23) is an state highway in southeastern Pennsylvania. The route begins at PA 441 in Marietta and heads east to U.S. Route 1 (US 1) at City Avenue on the border of Lower Merion Township and Philadelphia. PA 23 begins at Marietta in Lancaster County and continues east to Lancaster, where it passes through the city on a one-way pair of streets and intersects US 222 and US 30. East of Lancaster, the route runs through agricultural areas in Pennsylvania Dutch Country, serving Leola, New Holland, and Blue Ball, the latter location where it crosses US 322. PA 23 passes through the southern tip of Berks County and serves Morgantown, where a ramp provides access to Interstate 176 (I-176). The route runs through northern Chester County and serves Elverson, Bucktown, Phoenixville, and Valley Forge. PA 23 continues into Montgomery County and intersects US 422 in King of Prussia and US 202 in Bridgeport. The route follows the Schuylkill River to West Consho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
York, Pennsylvania
York ( Pennsylvania Dutch: ''Yarrick''), known as the White Rose City (after the symbol of the House of York), is the county seat of York County, Pennsylvania, United States. It is located in the south-central region of the state. The population within York's city limits was 43,718 at the 2010 census, a 7.0% increase from the 2000 census count of 40,862. When combined with the adjacent boroughs of West York and North York and surrounding Spring Garden, West Manchester, and Springettsbury townships, the population of Greater York was 108,386. York is the 11th largest city in Pennsylvania. History 18th century York, also known as Yorktown in the mid 18th to early 19th centuries, was founded in 1741 by settlers from the Philadelphia region and named for the English city of the same name. By 1777, most of the area residents were of either German or Scots-Irish descent. York was incorporated as a borough on September 24, 1787, and as a city on January 11, 1887. York served ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thrust Fault
A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. If the angle of the fault plane is lower (often less than 15 degrees from the horizontal) and the displacement of the overlying block is large (often in the kilometer range) the fault is called an ''overthrust'' or ''overthrust fault''. Erosion can remove part of the overlying block, creating a ''fenster'' (or ''window'') – when the underlying block is exposed only in a relatively small area. When erosion removes most of the overlying block, leaving island-like remnants resting on the lower block, the remnants are called ''klippen'' (singular ''klippe''). Blind thrust faults If the fault plane terminates before it reaches the Earth's surface, it is referred to as a ''blind thrust'' fault. Because of the lack of surface evidence, blind thr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harpers Formation
The Harpers Formation is a geologic formation in Maryland, Pennsylvania, Virginia, and West Virginia, consisting of schist, phyllite, and shale. It dates back to the early Cambrian period. It is considered part of the Chilhowee Group. Notable exposures The type section is in gorges of the Potomac River and the Shenandoah River at Harpers Ferry, West Virginia. The Harpers Formation overlies the Ledger Formation (dolomite) due to a thrust fault in small roadside quarry (currently overgrown) on Pottery Hill, southwest of York, Pennsylvania. A. J. Stose and G. W. Stose, 1944. ''Geology of the Hanover-York district'', U. S. Geological Survey Professional paper 204. Gallery File:Quartzite (Harpers Formation, Lower Cambrian; Verona, Virginia, USA).jpg, Quartzite sample of Harpers Formation from near Verona, Virginia File:Jefferson Rock, Harpers Ferry, WV - area view.jpg, Harpers Shale by Jefferson Rock in Harpers Ferry, West Virginia Harpers Phyllite Pottery Hill outcrop 2022.jpg, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fold (geology)
In structural geology, a fold is a stack of originally planar surfaces, such as sedimentary strata, that are bent or curved during permanent deformation. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur as single isolated folds or in periodic sets (known as ''fold trains''). Synsedimentary folds are those formed during sedimentary deposition. Folds form under varied conditions of stress, pore pressure, and temperature gradient, as evidenced by their presence in soft sediments, the full spectrum of metamorphic rocks, and even as primary flow structures in some igneous rocks. A set of folds distributed on a regional scale constitutes a fold belt, a common feature of orogenic zones. Folds are commonly formed by shortening of existing layers, but may also be formed as a result of displacement on a non-planar fault (''fault bend fold''), at the tip of a propagating fault (''fault propagation fold''), by differential compaction or due to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unconformity
An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger layer, but the term is used to describe any break in the sedimentary geologic record. The significance of angular unconformity (see below) was shown by James Hutton, who found examples of Hutton's Unconformity at Jedburgh in 1787 and at Siccar Point in 1788. The rocks above an unconformity are younger than the rocks beneath (unless the sequence has been overturned). An unconformity represents time during which no sediments were preserved in a region or were subsequently eroded before the next deposition. The local record for that time interval is missing and geologists must use other clues to discover that part of the geologic history of that area. The interval of geologic time not represented is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stockton Formation
The Triassic Stockton Formation is a mapped bedrock unit in Pennsylvania, New Jersey, and New York. It is named after Stockton, New Jersey, where it was first described. It is laterally equivalent to the New Oxford Formation in the Gettysburg Basin of Pennsylvania and Maryland.Faill, R.T., (2004). The Birdsboro Basin. ''Pennsylvania Geology'' V. 34 n. 4. Description The Stockton is defined as a light-gray to light brown and yellowish medium to coarse grained sandstone and reddish to purplish-brown siltstone and mudstone with shale interbeds; and interbedded argillite. In New Jersey, feldspar pebbly sandstone and conglomerate, and quartz-pebble conglomerate are also mapped. Depositional environment The Stockton is described as a bajada. The sediments were a result of the rifting of Pangea. The sediments came from the southeast from a largely granitic terrane and spread across an even plain. Interfingered with the Stockton, the Lockatong Formation are lake sediments, which grew d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Valley Forge National Historical Park
Valley Forge National Historical Park is the site of the third winter encampment of the Continental Army during the American Revolutionary War, taking place from December 19, 1777, to June 19, 1778. The National Park Service preserves the site and interprets the history of the Valley Forge encampment. Originally Valley Forge State Park, it became a national historical park in 1976. The park contains historical buildings, recreated encampment structures, memorials, museums, and recreation facilities. The park encompasses and is visited by over 1.2 million people each year. Visitors can see restored historic structures, reconstructed structures such as the iconic log huts, and monuments erected by the states from which the Continental soldiers came. Visitor facilities include a visitor center and museum featuring original artifacts, providing a concise introduction to the American Revolution and the Valley Forge encampment. Ranger programs, tours (walking and trolley), and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
