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Paleocene ­ Accessscience from Mcgraw­Hill Education 4/21/2016 Paleocene ­ AccessScience from McGraw­Hill Education (http://www.accessscience.com/) Paleocene Article by: Haq, Bilal U. Division of Ocean Sciences, National Science Foundation, Arlington, Virginia. Publication year: 2014 DOI: http://dx.doi.org/10.1036/1097­8542.483400 (http://dx.doi.org/10.1036/1097­8542.483400) Content Subdivisions Tectonics, oceans, and climate Life Bibliography Additional Readings The oldest of the seven geological epochs of the Cenozoic Era, and the oldest of the five epochs that make up the Tertiary Period. The Paleocene Epoch represents an interval of geological time (and rocks deposited during that time) from the end of the Cretaceous Period to the beginning of the Eocene Epoch. Recent revisions of the geological time scales place the Paleocene Epoch between 65 to 55 million years before present (MYBP). See also: Cenozoic (/content/cenozoic/118600); Eocene (/content/eocene/236400); Geologic time scale (/content/geologic­time­scale/286500); Tertiary (/content/tertiary/686000) The close of the Cretaceous Period was characterized by the disappearance of many terrestrial and marine animals and plants. The dawn of the Cenozoic in the Paleocene Epoch saw the establishment of new fauna and flora that have evolved into modern biota. The concept of the Paleocene as a separate subdivision of the Tertiary was introduced by the paleobotanist W. P. Schimper in 1874. He observed a distinctive assemblage of plant fossils in the http://www.accessscience.com/content/paleocene/483400 1/8 4/21/2016 Paleocene ­ AccessScience from McGraw­Hill Education lower Eocene nonmarine sediments of the Paris Basin that he separated out as representing an independent epoch. In the older Lyellian classification, this interval was a part of the Eocene Epoch that constituted the oldest part of the Tertiary Period. The Paleocene deposits had lateral equivalents bearing early Tertiary mammals and were devoid of remains of dinosaurs, which had become extinct at the end of the Cretaceous Period. Schimper also noticed that the Paleocene flora contained numerous components that are now typical of Northern Hemisphere, in contrast to the Cretaceous when Southern Hemispheric floras prevailed. Subdivisions Modern schemes of the Paleocene subdivide it into Lower and Upper series, and their formal equivalents, the Danian and Selandian stages. Some authors prefer to use a threefold subdivision of the Paleocene, adding the Thanetian at the top. The older, Danian lithofacies generally tend to be calcium carbonate–rich (pure chalk in the Danian type area), whereas the younger, Selandian and Thanetian facies have greater land­derived components and are more siliciclastic (sand, sandstone, marl). See also: Chalk (/content/chalk/124200); Facies (geology) (/content/facies­geology/250000); Marl (/content/marl/407400); Sand (/content/sand/600600); Sandstone (/content/sandstone/600900) The Danian Stage was proposed by the French geologist E. Desor in 1847 with its type locality near Copenhagen, Denmark. Desor, however, regarded the Danian to be the youngest stage of the Cretaceous. He equated the Danian Chalk and Limestone at the Danish type localities of Faxe and Stevns Klint to the uppermost Cretaceous strata of the Paris Basin largely on the basis of similarities in lithology and the contained echinoidal fauna. It was not until 1897 that another French scientist, A. de Grossouvre, suggested that it would make more sense to place the upper limit of the Mesozoic at the base of the Danian and a major extinction level where ammonites, belemnites, rudistids, and dinosaurs disappeared. The Russian geologist P. Bezrukov in 1934 was the first to actually assign the Danian to the Tertiary, based on paleontological studies in the Ural River sections. In the 1960s the Danian Stage was formally placed in the lowermost Paleocene when it was demonstrated that these strata lacked diagnostic ammonites typical of the Late Cretaceous and contained a microfauna with greater affinity to those of the Tertiary. A major faunal break and hiatus below the Danian and equivalent strata in many sections in the world reinforced its definite Tertiary character. The Selandian Stage was also defined based on sections in Zealand, near Copenhagen, by the Danish stratigrapher A. Rosenkrantz in 1924. Rosenkrantz, however, did not designate a formal type section for the stage. Later workers have amended the concept of standard Selandian to include all of the temporal equivalent interval of the Late Paleocene series, although the debate about the lithostratigraphic continuity within these sections continues. This stage is, nevertheless, preferable to the previously used upper Paleocene standard stage of Thanetian, which spans only the very upper part of Late Paleocene. Regional subdivisions of the Paleocene include the Montian Stage, proposed by G. Dewalque in 1868, with a type locality near Mons, Belgium. Like the Danian, the Montian Stage has also been a subject of much discussion. It is now considered to be temporally equivalent to the youngest part of Danian and older part of Selandian (Fig. 1). The Thanetian Stage in Britain was based on the marine Thanet Sands of the Isle of Thanet in Kent. It was first raised to a stage level by E. Renevier in 1873 and is time­equivalent to the upper part of Selandian. The Landenian Stage was proposed by A. Dumont in 1839. It also has its type locality in Belgium and is often used in northwestern http://www.accessscience.com/content/paleocene/483400 2/8 4/21/2016 Paleocene ­ AccessScience from McGraw­Hill Education Europe as a stage younger than the Montian. Detailed studies have shown the Belgian Landenian also is equivalent to the British Thanetian. In the United States the Gulf coast Paleocene subdivisions include the Midwayan and the older part of the Sabinian stages. The base of the Midwayan shows a major faunal and lithological hiatus. In California, local stratigraphers have often used the Ynezian Stage to represent an informal equivalent of the upper Paleocene. In the former Soviet Union, the Kachinian Stage has been shown to encompass much of the Paleocene, extending slightly into the earliest Eocene. In New Zealand, the Teurian Stage spans most of the Paleocene, with the overlying Waipawan Stage ranging into the youngest Eocene. In Australia, the Late Paleocene strata are sometimes ascribed to the regional Wangerripian Stage. Paleontologists working with vertebrate fossils have often used their own informal age classifications for assemblage associations. In North American, they subdivide the Paleocene into the Puercan, Torrejonian, and Tiffanian ages, whereas in Europe the terms Dano­Montian and Cernayasian have often been used to span the Paleocene in vertebrate paleontological literature. See also: Stratigraphy (/content/stratigraphy/659000) Fig. 1 Standard Paleocene stages and their temporal equivalents in Europe, North America, and New Zealand. Tectonics, oceans, and climate Several major tectonic events that began in the Mesozoic continued into the Paleocene. For example, the Laramide Orogeny that influenced deformation and uplift in the North American Rocky Mountains in the Mesozoic continued into the Paleocene as a series of diastrophic movements, which ended abruptly in the early Eocene. See also: Orogeny (/content/orogeny/476700) On the ocean floor the most notable tectonic events were the separation of the Seychelles from the rapidly northward­moving Indian plate in the early Paleocene, and the initiation of sea­floor spreading in the Norwegian­ Greenland Sea, between North America and Greenland in the late Paleocene. The Indian plate had broken away from eastern Gondwanaland in the Late Cretaceous and started moving relatively rapidly northward some 80 MYA. In the early Paleocene, the spreading ridge between Madagascar and India jumped northeastward toward India. This initiated the spreading between India and the Seychelles Platform and the formation of the Chagos­Laccadive transform ridge. During the Paleocene Epoch, the Indian plate continued its rapid flight across the eastern Tethys Ocean, the ancestral seaway that occupied the position of the modern northern Indian Ocean, to eventually collide with the Asian mainland in the mid­Eocene around 50 MYA. In the Paleocene, the eastern Tethys was also characterized by http://www.accessscience.com/content/paleocene/483400 3/8 4/21/2016 Paleocene ­ AccessScience from McGraw­Hill Education another very active transform, the Ninetyeast Ridge. This ridge was formed when the Indian plate moved over a fixed mantle plume hot spot in the Late Cretaceous. See also: Plate tectonics (/content/plate­tectonics/527000) The lower­latitude shallow­water seas, as exemplified by the Tethys seaway, received thick deposits of calcium carbonates during the Paleocene. However, the seaway became progressively narrower and shallower, and the nature of carbonate accumulation changed correspondingly. The sedimentary record of the Paleocene in the northwestern Atlantic indicates that a relatively calm regime of predominantly calcareous sediments typical of the Late Cretaceous was largely replaced by facies that represents more vigorous bottom waters that packed great erosive power due to increased convective overturn and dynamic ocean bottom currents. Although the deep­water connection between the North and South Atlantic was already established by the Early Paleocene, the South Atlantic sedimentary record indicates that in this basin the extensive erosion on the sea floor did not begin until
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