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Revisions to the relative time scale have occurred since the late 1700s. The numerically calibrated geologic time scale has been continuously refined since approximately the 1930s (e.g., ... Geologic time is finely subdivided through most of the Phanerozoic (see Harland et al., 1990 for details), but most of the finer...
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www.geo.ucalgary.ca/~macrae/timescale/timescale.html
www.geo.ucalgary.ca/~macrae/timescale/timescale.html
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The Phanerozoic eon is further subdivided into three eras: the Paleozoic, Mesozoic, and Cenozoic. These subdivisions were devised on the basis of fossil and geologic evidence of global change. The Earth has changed dramatically during the Phanerozoic. ... Return to Geologic Time Homepage...
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humanorigins.si.edu/faq/gt/gt_scale.html
humanorigins.si.edu/faq/gt/gt_scale.html
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Earth's history is subdivided into eons, ... Fossils are fundamental to the geologic time scale. The names of most of the eons and eras end in zoic, because these time intervals are often recognized on the basis of animal life. Rocks formed during the Proterozoic Eon may have fossils of relative simple organisms,
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pubs.usgs.gov/gip/fossils/scale.html
pubs.usgs.gov/gip/fossils/scale.html
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There are two main classification systems, being those of chronostratigraphy, and that of geologic time. ... The concept of a geological time-scale has been evolving since the middle of the 18th century. ... These periods were further subdivided into epochs (See the page on Periods for more detail about these divisions).
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www.bbm.me.uk/portsdown/PH_740_geoTime.htm
www.bbm.me.uk/portsdown/PH_740_geoTime.htm
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Each era within an ordinal reference system may be subdivided into an ordered sequence of sub-eras, ... The GeoSciML Geologic Timescale model and encoding is described in detail in the paper A formal model for the geologic time scale and global stratotype section and point, compatible with geospatial information...
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www.seegrid.csiro.au/twiki/bin/view/CGIModel/GeologicTi...
www.seegrid.csiro.au/twiki/bin/view/CGIModel/GeologicTime
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By 1890 an essentially modern geologic timescale had been established on the basis of the unique paleontology of the different systems of strata. ...
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people.hofstra.edu/faculty/J_B_Bennington/137notes/time...
people.hofstra.edu/faculty/J_B_Bennington/137notes/timescale.html
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Note that chronologically, fossil succession was well and independently established long before Darwin's evolutionary theory was proposed in 1859. Fossil succession and the geologic time scale are constrained by the observed order of the stratigraphy -- basically geometry -- not by evolutionary theory.
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www.talkorigins.org/faqs/dating.html
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The geological timescale is subject to fine-tuning a) as time-stratigraphic boundaries become formally fixed in sediments/rocks by international agreement, ... Periods of the Paleozoic and Mesozoic eras are further subdivided into epochs, ages and chrons on the basis of included fossils. Subdivision of the Proterozoic...
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eesc.columbia.edu/courses/v1010/timescale.html
eesc.columbia.edu/courses/v1010/timescale.html
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For example, in North America the Lower Cambrian is referred to as the Waucoban series that is then subdivided into zones based on trilobites. The same timespan is ... The commission's most recent work is described in the 2004 geologic time scale of Gradstein et al. (ISBN 0521786738), and is used as the basis of this page...
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en.allexperts.com/e/g/ge/geologic_time_scale.htm
en.allexperts.com/e/g/ge/geologic_time_scale.htm
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