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As others before him, Folk proposed a classification for sandstones based on the relative abundances of quartz (Q), feldspars (F), and rock fragments (R). These are the main poles of the classification diagram. To define the clan name one must normalize the sum of abundances of quartz, feldspars and rock fragments to 100%.
Depending on the structure, metamorphic rocks are divided into two general categories. Those that possess 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 ...
The inclusion of the moraine illustrates how land-based rocks and sediment are carried by ice. Erratics provide an important tool in characterizing the directions of glacier flows, which are routinely reconstructed used on a combination of moraines, eskers, drumlins, meltwater channels and similar data. Erratic distributions and glacial till ...
Craters are very useful in relative dating; as a general rule, the younger a planetary surface is, the fewer craters it has. If long-term cratering rates are known to enough precision, crude absolute dates can be applied based on craters alone; however, cratering rates outside the Earth-Moon system are poorly known. [8]
Solidified lava flow in Hawaii Sedimentary layers in Badlands National Park, South Dakota Metamorphic rock, Nunavut, Canada. Geology (from Ancient Greek γῆ (gê) 'earth' and λoγία () 'study of, discourse') [1] [2] is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. [3]
The following is a list of rock types recognized by geologists.There is no agreed number of specific types of rock. Any unique combination of chemical composition, mineralogy, grain size, texture, or other distinguishing characteristics can describe a rock type.
A sequence of fossil-bearing sedimentary rocks can be subdivided on the basis of the occurrence of particular fossil taxa. A unit defined in this way is known as a biostratigraphic unit, generally shortened to biozone. [6] The five commonly used types of biozone are assemblage, range, abundance, interval and lineage zones. [7]
A facies encompasses all the characteristics of a rock including its chemical, physical, and biological features that distinguish it from adjacent rock. [ 2 ] The term "facies" was introduced by the Swiss geologist Amanz Gressly in 1838 and was part of his significant contribution to the foundations of modern stratigraphy , [ 3 ] which replaced ...