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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 Berwickshire in 1788, both in Scotland. 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disconformity
An unconformity is a buried erosion surface, erosional or non-depositional surface separating two Rock (geology), rock masses or Stratum, 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 rocks, 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 Berwickshire in 1788, both in Scotland. The rocks above an unconformity Law of superposition, are younger than the rocks beneath (unless the sequence has been overturned). An unconformity represents Geologic time, 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 m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hutton's Unconformity
Hutton's Unconformity is a name given to various notable geological sites in Scotland identified by the 18th-century Scottish geologist James Hutton as places where the junction between two types of rock formations can be seen. This geological phenomenon marks the location where rock formations created at different times and by different processes adjoin. For Hutton, such an unconformity provided evidence for his Plutonist theories of uniformitarianism and the age of Earth. An unconformity is a break in the normal progression of sedimentary deposits, where newer deposits are laid on top of older. The example Hutton discovered is known as an angular unconformity in which a sharp change in younging direction can be seen in the orientation of bedding planes. The younging direction points ''from'' the oldest bed, to the ''youngest'' bed in the sequence of sedimentary beds. In his search, Hutton and colleagues examined rock outcrops and cliffs, both riverside and sea, and found se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sedimentary Rocks
Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedimentation is any process that causes these particles to settle in place. Geological detritus originates from weathering and erosion of existing rocks, or from the solidification of molten lava blobs erupted by volcanoes. The geological detritus is transported to the place of deposition by water, wind, ice or mass movement, which are called agents of denudation. Biological detritus is formed by bodies and parts (mainly shells) of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on the floor of water bodies ( marine snow). Sedimentation may also occur when dissolved minerals precipitate from water solution. The sedimentary rock cover of the continents of the Earth's crust is extensive (73% of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Siccar Point
Siccar Point is a rocky promontory in the county of Berwickshire on the east coast of Scotland. It is famous in the history of geology for Hutton's Unconformity found in 1788, which James Hutton regarded as conclusive proof of his uniformitarian theory of geological development. History Siccar Point was the site of a dun, or small hill fort, in the territory of the ancient Britons. Siccar Point is now in the parish of Cockburnspath but was formerly in the parish of Old Cambus, from which the ancient parish church of St Helen's Chapel survives as a ruin about one kilometre to the west of the point. The church is built in a Romanesque style, in a mixture of Old Red Sandstone believed to have been quarried from the nearby Greenheugh Bay and of the greywacke rock also used in the drystone dyke forming the field boundaries. It is likely that the medieval village of Old Cambus was nearer to Siccar Point than the extant hamlet of Old Cambus. To the south of the point twenti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geologic Time
The geologic time scale or geological time scale (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (a scientific branch of geology that aims to determine the age of rocks). It is used primarily by Earth scientists (including geologists, paleontologists, geophysicists, geochemists, and paleoclimatologists) to describe the timing and relationships of events in geologic history. The time scale has been developed through the study of rock layers and the observation of their relationships and identifying features such as lithologies, paleomagnetic properties, and fossils. The definition of standardised international units of geological time is the responsibility of the International Commission on Stratigraphy (ICS), a constituent body of the International Union of Geological Sciences (IUGS), whose primary objective is to precisely de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erosion Surface
In geology and geomorphology, an erosion surface is a surface of rock (geology), rock or regolith that was formed by erosion and not by construction (e.g. lava flows, sediment deposition) nor fault (geology), fault displacement. Erosional surfaces within the Lithostratigraphy#Stratigraphic relationship, stratigraphic record are known as unconformity, unconformities, but not all unconformities are buried erosion surfaces. Erosion surfaces vary in scale and can be formed on a mountain range or a rock. Particularly large and flat erosion surfaces receive the names of peneplain, wikt:paleoplain, paleoplain, planation surface or pediplain. An example of erosion surface is road surface erosion which is caused by natural and anthropogenic factors. Erosion surface can be measured through direct, contact measurement methods and indirect, non-contact measurement methods. Road surface erosion Just like mountains and rocks, erosion can also occur on unsealed roads due to natural and Human im ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relative Dating
Relative dating is the science of determining the relative order of past events (i.e., the age of an object in comparison to another), without necessarily determining their absolute age (i.e., estimated age). In geology, rock or superficial deposits, fossils and lithologies can be used to correlate one stratigraphic column with another. Prior to the discovery of radiometric dating in the early 20th century, which provided a means of absolute dating, archaeologists and geologists used relative dating to determine ages of materials. Though relative dating can only determine the ''sequential order'' in which a series of events occurred, not ''when'' they occurred, it remains a useful technique. Relative dating by biostratigraphy is the preferred method in paleontology and is, in some respects, more accurate. The Law of Superposition, which states that older layers will be deeper in a site than more recent layers, was the summary outcome of 'relative dating' as observed in g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diastem
In geology, a diastem is a short interruption in sedimentation with little or no erosion. They can also be described as very short unconformities (more precisely as very short paraconformities). In 1917, Joseph Barrell estimated the rate of deposition of succession from the available radiometric age. His outcrops showed that the strata accumulation was at the rate of thousands of years per foot rather than hundreds. He stated that diastems are universal in sedimentary rocks and explained them as a product of fluctuation of base level. Definition The International Commission on Stratigraphy defines a diastem as " short interruption in deposition with little or no erosion before resumption of sedimentation". Duration Studies indicate that the time gap represented in diastems ranges from a few hundred to a few thousand years in shelf settings as well as throughout the Paleozoic The Paleozoic ( , , ; or Palaeozoic) Era is the first of three Era (geology), geological eras of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jedburgh
Jedburgh ( ; ; or ) is a town and former royal burgh in the Scottish Borders and the traditional county town of the Shires of Scotland, historic county of Roxburghshire. History Jedburgh began as ''Jedworð'', the "worth" or enclosed settlement on the Jed. Later the more familiar word "burgh" was substituted for this, though the original name survives as Jeddart/Jethart. Bishop Ecgred of Lindisfarne founded a church at Jedburgh in the 9th century, and King David I of Scotland made it a priory between 1118 and 1138, housing Augustinians, Augustinian monks from Beauvais in France. The abbey was founded in 1147, but border wars with England in the 16th century left it a ruin. The deeply religious Scottish king Malcolm IV of Scotland, Malcolm IV died at Jedburgh in 1165, aged 24. His death is thought to have been caused by Paget's disease of bone. David I built a Jedburgh Castle, castle at Jedburgh, and in 1174 it was one of five fortresses ceded to England. It was an occasiona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
