Tertiary period


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See also: Geologic Timescale (table)Geologic Timescale
Era Period Epoch Approximate duration
(millions of years)
Approximate number of years ago
(millions of years)

Cenozoic Quaternary Holocene 10,000 years ago to the present  
Pleistocene 2 .
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Tertiary period

(tûr`shēĕr'ē), name for the major portion of the Cenozoic eraCenozoic era
, last major division of geologic time (see Geologic Timescale, table) lasting from 65 million years ago to the present. The Cenozoic is divided into the Tertiary (from 65 million years ago until 2 million years ago) and Quaternary (2 million years ago to the
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, the most recent of the geologic eras (see Geologic TimescaleGeologic Timescale
Era Period Epoch Approximate duration
(millions of years)
Approximate number of years ago
(millions of years)

Cenozoic Quaternary Holocene 10,000 years ago to the present  
Pleistocene 2 .
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, table) from around 26 to 66 million years ago. The name Tertiary was first applied about the middle of the 18th cent. to a layer of deposits, largely unconsolidated sediments, geologically younger than, and overlying, certain other deposits then known as Primary and Secondary. Later (c.1830) a fourth division, the Quaternary, was added. Although these divisions of the earth's crust seemed adequate for the region to which the designations were originally applied (parts of the Alps and plains of Italy), when the same system was later extended to other parts of Europe and to America it proved to be inapplicable. It was realized that one scheme of classification could not be applied universally: The names Primary and Secondary were generally abandoned; Tertiary and Quaternary were, and still are, used, but other geologic literature substitutes other names, including the Palaeogene and Neogene. The main divisions of the Tertiary are the PaleocenePaleocene epoch
, first epoch of the Tertiary period in the Cenozoic era of geologic time (see geologic timescale) between 60 to 66 million years ago. In W North America, the uplift of the Rocky Mts.
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, EoceneEocene epoch
, second epoch of the Tertiary period in the Cenozoic era of geologic time, from approximately 54.9 to 38 million years ago. The Eocene in North America was marked by the submergence of the Great Valley of California and a portion of the Atlantic and Gulf coastal
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, OligoceneOligocene epoch
, third epoch of the Tertiary period in the Cenozoic era of geologic time, lasting from 38 to 24 million years ago. More of North America was dry land during the Oligocene than in the preceding Eocene epoch.
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, MioceneMiocene epoch
, fourth epoch of the Tertiary period in the Cenozoic era of geologic time (see Geologic Timescale, table), lasting from around 24.6 to 5.1 million years ago.
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, and Pliocene epochsPliocene epoch
, fifth epoch of the Cenozoic era of geologic time (see Geologic Timescale, table), from 5.1 to 2 million years ago. By the beginning of the Pliocene, the outlines of North America were almost the same as in recent time.
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. Sometimes the Paleocene is included in the Eocene. At the beginning of the Tertiary, the outlines of the North American continent were very similar to those of today; by the close of the period, Europe also had emerged substantially in its present form. Marine submergences in Europe were moderately extensive, but in North America they never went beyond the Atlantic, Gulf, and Pacific coasts and the lower Mississippi valley. These inundations took place chiefly in the Eocene, Oligocene, and Miocene epochs, the continents being generally emergent in the Pliocene epoch. The Tertiary formations of either unconsolidated sediments or quite soft rocks are widespread. In the Tertiary, Gondwanaland finally split completely apart, and India collided with the Eurasian plate (see plate tectonicsplate tectonics,
theory that unifies many of the features and characteristics of continental drift and seafloor spreading into a coherent model and has revolutionized geologists' understanding of continents, ocean basins, mountains, and earth history.
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). The previously existing mountain ranges of North America were again elevated, the Alps, Pyrenees, Carpathians, and other ranges were formed in Europe, and in Asia the Himalayas arose. Widespread volcanic activity was prevalent. At the beginning of the period the mammals replaced the reptiles as the dominant animals; each epoch was marked by striking developments in mammalian life. Modern types of birds, reptiles, amphibians, fishes, and invertebrates either were already numerous at the beginning of the period or appeared early in its history.
References in periodicals archive ?
Although two-thirds of the total may have survived, only a small fraction of the species on land actually made it through into the Tertiary period, he says.
Water from the Late Precambrian, Permian, and Tertiary periods, for example, had a chemistry similar to today's oceans, the researchers report.
Evidence of the occurrence of a cosmic catastrophe--sometime between the Cretaceous and Tertiary periods some sixty-five million years ago--began to mount in 1980 when geologists at the University of Berkeley in California discovered large amounts of the rare metal iridium, an element more common in outer space than on our planet.
Geologists have much better evidence that a comet or meteorite knocked life for a loop 65 million years ago, at the boundary between the Cretaceous and Tertiary periods.
Iridium has played a primary role in uncovering the drama at the junction between the Cretaceous and Tertiary periods in Earth's history, which geologists call the K-T boundary.
The thin layer of iridium-and-quartz-rich sediment dates to the transition of the Cretaceous and Tertiary periods, which mark the end of the Mesozoic Era and the beginning of the Cenozoic Era.
In recent years, a controversy overprehistoric impacts has been making waves in the scientific community as geologists debate whether a large impact 65 million years ago could possibly have initiated a round of mass extinctions concurrent with the boundary between the Cretaceous and the Tertiary periods (SN: 5/16/87, p.
Because iridium has been found at the geologic boundary between the Cretaceous and Tertiary periods in concentrations exceeding typical iridium levels in the crust, some scientists have speculated that a meteorite had slammed into the earth, spraying the planet with a fine layer of meteoric iridium and other debris.
Kitchell studied various species of marine plankton, or diatoms, and found that those that had adapted to northern climates survived the mass extinction between the Cretaceous and Tertiary periods (65 million years ago), while plankton that had adapted to low- and mid-latitude sites did not.

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