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This work assessed the geologic history of the currently defined eons and eras of the pre-Cambrian, [note 2] and the proposals in the "Geological Time Scale" books 2004, [74] 2012, [5] and 2020. [75] Their recommend revisions [ 4 ] of the pre-Cryogenian geologic time scale were (changes from the current scale [v2023/09] are italicised):
Index fossils must have a short vertical range, wide geographic distribution and rapid evolutionary trends. Another term, "zone fossil", is used when the fossil has all the characters stated above except wide geographical distribution; thus, they correlate the surrounding rock to a biozone rather than a specific time period.
The oldest large angiosperm trees are known from the Turonian (c. 90 Mya) of New Jersey, with the trunk having a preserved diameter of 1.8 metres (5.9 ft) and an estimated height of 50 metres (160 ft). [89] During the Cretaceous, ferns in the order Polypodiales, which make up 80% of living fern species, would also begin to diversify. [90]
The Maastrichtian (/ m ɑː ˈ s t r ɪ k t i ə n / mahss-TRIK-tee-ən) is, in the International Commission on Stratigraphy (ICS) geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interval from .
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after creta, the Latin word for the white limestone known as chalk.
During the Cretaceous, the dominant group of living fishes, the teleosts, first achieved ascendency over their holostean forebears. [81] The aquatic toothed bird Hesperornis is the only known Cretaceous bird whose remains are found with any frequency in North America. [82] Near the end of the Cretaceous, the Western Interior Seaway began to ...
Palaeogeography of the Earth in Aptian. The Aptian is an age in the geologic timescale or a stage in the stratigraphic column.It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), approximately.
The ice age was probably not as long-lasting as once thought; study of oxygen isotopes in fossil brachiopods shows that it was probably no longer than 0.5 to 1.5 million years. [41] The event was preceded by a fall in atmospheric carbon dioxide (from 7000ppm to 4400ppm) which selectively affected the shallow seas where most organisms lived.