Answer the following question: Information:  - Carbon (from "coal") is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalentmaking four electrons available to form covalent chemical bonds. Three isotopes occur naturally, C and C being stable, while C is a radioactive isotope, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity.  - The Eocene Epoch, lasting from , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch. The start of the Eocene is marked by a brief period in which the concentration of the carbon isotope C in the atmosphere was exceptionally low in comparison with the more common isotope C. The end is set at a major extinction event called the "Grande Coupure" (the "Great Break" in continuity) or the EoceneOligocene extinction event, which may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay. As with other geologic periods, the strata that define the start and end of the epoch are well identified, though their exact dates are slightly uncertain.  - The Phanerozoic Eon (British English Phanærozoic) is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers million years to the present, and began with the Cambrian Period when diverse hard-shelled animals first appeared. Its name was derived from the Ancient Greek words (phanerós) and (z), meaning "visible life", since it was once believed that life began in the Cambrian, the first period of this eon. The time before the Phanerozoic, called the "Precambrian" supereon, is now divided into the Hadean, Archaean and Proterozoic eons.  - The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period million years ago (Mya) to the beginning of the Paleogene Period Mya. It is the last period of the Mesozoic Era. The Cretaceous Period is usually abbreviated K, for its German translation "Kreide" (chalk).  - Isotopes are variants of a particular chemical element which differ in neutron number. All isotopes of a given element have the same number of protons in each atom. The term isotope is formed from the Greek roots isos ( "equal") and topos ( "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table.  - The Miocene is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words (', less) and (', new) and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene Epoch and is followed by the Pliocene Epoch.  - An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp change in the diversity and abundance of multicellular organisms. It occurs when the rate of extinction increases with respect to the rate of speciation. Because the majority of diversity and biomass on Earth is microbial, and thus difficult to measure, recorded extinction events affect the easily observed, biologically complex component of the biosphere rather than the total diversity and abundance of life.  - Sir Charles Lyell, 1st Baronet, (14 November 1797  22 February 1875) was a British lawyer and the foremost geologist of his day. He is best known as the author of "Principles of Geology", which popularized James Hutton's concepts of uniformitarianismthe idea that the Earth was shaped by the same processes still in operation today. "Principles of Geology" also challenged theories popularized by Georges Cuvier, which were the most accepted and circulated ideas about geology in England at the time.  - A bolide (French via Latin from the Greek  "bolís", "missile") is an extremely bright meteor, especially one that explodes in the atmosphere. In astronomy, it refers to a fireball about as bright as the full moon, and it is generally considered a synonym of a fireball. In geology, a bolide is a very large impactor.  - The Paleocene or Palaeocene, the "old recent", is a geologic epoch that lasted from about . It is the first epoch of the Paleogene Period in the modern Cenozoic Era. As with many geologic periods, the strata that define the epoch's beginning and end are well identified, but the exact ages remain uncertain.  - The Paleogene (or ; also spelled Palaeogene or Palæogene; informally Lower Tertiary) is a geologic period and system that spans 43 million years from the end of the Cretaceous Period million years ago (Mya) to the beginning of the Neogene Period Mya. It is the beginning of the Cenozoic Era of the present Phanerozoic Eon. The Paleogene is most notable for being the time during which mammals diversified from relatively small, simple forms into a large group of diverse animals in the wake of the CretaceousPaleogene extinction event that ended the preceding Cretaceous Period.   - The Pliocene (also Pleiocene) Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58 million years BP. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch. Prior to the 2009 revision of the geologic time scale, which placed the four most recent major glaciations entirely within the Pleistocene, the Pliocene also included the Gelasian stage, which lasted from 2.588 to 1.806 million years ago, and is now included in the Pleistocene.  - An era is a span of time marked by character, events, changes on earth, etc. When used in science, for example geology, an "era" denotes a clearly defined period of time of arbitrary but well-defined length, such as for example the Mesozoic Era frozen m 252 Ma66 Ma, delimited by a start event and an end event. When used in social history, eras may for example denote a period of some monarch's reign. In colloquial language, eras denote longer spans of time, before and after which the practices or fashions change to a significant degree. When era is extended to a calendar system, it is known as a calendar era. In Sanskrit or Indian culture eras are known as yugas.  - The transition between the end of the Eocene and the beginning of the Oligocene is marked by large-scale extinction and floral and faunal turnover (although minor in comparison to the largest mass extinctions). Most of the affected organisms were marine or aquatic in nature. They included the last of the ancient cetaceans, the Archaeoceti.  - Animals are multicellular, eukaryotic organisms of the kingdom Animalia (also called Metazoa). The animal kingdom emerged as a basal clade within Apoikozoa as a sister of the choanoflagellates. Sponges are the most basal clade of animals. Animals are motile, meaning they can move spontaneously and independently at some point in their lives. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later in their lives. All animals are heterotrophs: they must ingest other organisms or their products for sustenance.  - Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a "backbone" or "spine"), derived from the notochord. This includes all animals apart from the subphylum Vertebrata. Familiar examples of invertebrates include insects; crabs, lobsters and their kin; snails, clams, octopuses and their kin; starfish, sea-urchins and their kin; and worms.  - The Oligocene / losin / ( symbol OG ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( 33.9 ± 0.1 to 23.03 ± 0.05 Ma ) . As with other older geologic periods , the rock beds that define the epoch are well identified but the exact dates of the start and end of the epoch are slightly uncertain . The name Oligocene comes from the Greek  ( oligos , few ) and  ( kainos , new ) , and refers to the sparsity of extant forms of molluscs . The Oligocene is preceded by the Eocene Epoch and is followed by the Miocene Epoch . The Oligocene is the third and final epoch of the Paleogene Period . The Oligocene is often considered an important time of transition , a link between the archaic world of the tropical Eocene and the more modern ecosystems of the Miocene . Major changes during the Oligocene included a global expansion of grasslands , and a regression of tropical broad leaf forests to the equatorial belt . The start of the Oligocene is marked by a notable extinction event called the Grande Coupure ; it featured the replacement of European fauna with Asian fauna , except for the endemic rodent and marsupial families . By contrast , the Oligocene -- Miocene boundary is not set at an easily identified worldwide event but rather at regional boundaries between the warmer late Oligocene and the relatively cooler Miocene .  - Tertiary is the former term for the geologic period from 66 million to 2.58 million years ago, a time span that lies between the superseded Secondary period and the Quaternary. The Tertiary is no longer recognized as a formal unit by the International Commission on Stratigraphy, but the word is still widely used. The traditional span of the Tertiary has been divided between the Paleogene and Neogene Periods and extends to the first stage of the Pleistocene Epoch, the Gelasian age.  The period began with the demise of the non-avian dinosaurs in the CretaceousPaleogene extinction event, at the start of the Cenozoic Era, and extended to the beginning of the Quaternary glaciation at the end of the Pliocene Epoch.  - The Cenozoic Era (also Cænozoic, Caenozoic or Cainozoic ; meaning "new life", from Greek "kainos" "new", and "zoe" "life") is the current and most recent of the three Phanerozoic geological eras, following the Mesozoic Era and covering the period from 66 million years ago to present day.  - The Neogene is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period million years ago (Mya) to the beginning of the present Quaternary Period Mya. The Neogene is sub-divided into two epochs, the earlier Miocene and the later Pliocene. Some geologists assert that the Neogene cannot be clearly delineated from the modern geological period, the Quaternary.    What entity does 'oligocene' has the relation 'instance of' with?
Answer:
geological epoch