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A sequence of rock layers that were laid down in the same geological period
A
system
in
stratigraphy
is a sequence of
strata
(rock layers) that were laid down together within the same corresponding
geological period
. The associated period is a
chronological
time
unit
, a part of the
geological time scale
, while the system is a unit of
chronostratigraphy
. Systems are unrelated to
lithostratigraphy
, which subdivides rock layers on their
lithology
. Systems are subdivisions of
erathems
and are themselves divided into
series
and
stages
.
Systems in the geological timescale
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The systems of the
Phanerozoic
were defined during the 19th century, beginning with the
Cretaceous
(by Belgian geologist
Jean d'Omalius d'Halloy
in the
Paris Basin
) and the
Carboniferous
(by British geologists
William Conybeare
and
William Phillips
in 1822). The
Paleozoic
and
Mesozoic
were divided into the currently used systems before the second half of the 19th century, except for a minor revision when the
Ordovician
system was added in 1879.
The
Cenozoic
has seen more recent revisions by the
International Commission on Stratigraphy
. It has been divided into three systems with the
Paleogene
and
Neogene
replacing the former
Tertiary
System though the succeeding
Quaternary
remains. The one-time system names of
Paleocene
,
Eocene
,
Oligocene
,
Miocene
and
Pliocene
are now
series
within the Paleogene and Neogene.
Another recent development is the official division of the
Proterozoic
into systems, which was decided in 2004.
Notes
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]
References
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]
- Gehling, James; Jensen, Soren; Droser, Mary; Myrow, Paul; Narbonne, Guy (March 2001). "Burrowing below the basal Cambrian GSSP, Fortune Head, Newfoundland".
Geological Magazine
.
138
(2): 213?218.
Bibcode
:
2001GeoM..138..213G
.
doi
:
10.1017/S001675680100509X
.
S2CID
131211543
. 1.
- Hedberg, H.D., (editor),
International stratigraphic guide: A guide to stratigraphic classification, terminology, and procedure
, New York, John Wiley and Sons, 1976
- International Stratigraphic Chart
from the
International Commission on Stratigraphy
- USA National Park Service
- Washington State University
Archived
2011-07-26 at the
Wayback Machine
- Web Geological Time Machine
- Eon or Aeon
,
Math Words - An alphabetical index
External links
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]