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Cretasaidd Gweler hefyd | Cyfeiriadau | Llywiogolygu

Nodiadau daearegCyfnodau daearegol


CyfnoddaearegddaearCPJwrasiggorgyfnodCainosöigddifodiannaubywyddinosoriaidJean d'Omalius d'HalloyWlad Belg1822StratigraffegDaeareg












Cretasaidd




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Cyfnod Cretasaidd
145.5–65.5 miliwn o flynyddoedd yn ôl

PreЄ

Є

O

S

D

C

P

T

J

K

Pg

N




Cyfartaledd O2 yn yr atmosffêr

ca. 30 Cyfaint %[1]
(150 % o lefel a geir heddiw)

Cyfartaledd CO2 yn yr atmosffêr

ca. 1700 rhan / miliwn[2]
(6 wedi'i luosi gyda'r lefel fodern (cyn-ddiwydiannol))

Cyfartaledd tymheredd yr wyneb

ca. 18 °C[3]
(4 °C uwch na'r lefel heddiw)


Prif ddigwyddiadau'r cyfnod


gweld • trafod • golygu




M
e
s
o
s
ö
i
g

 

Jwrasig

 

Paleogen

C
y
n
n
a
r

H
w
y
r

Beriasaidd

Valangiaidd

Hauterivian

Baremaidd

Aptaidd

Albaidd

Cenomanaidd

Turonaidd

Coniasaidd

Santonaidd

Campanaidd

Maastrichtaidd

 

 

 

 















C
r
e
t
a
s
a
i
d
d









































Llinell amser bras o brif ddigwyddiadau'r cyfnod Cretasaidd.
Graddfa: miliynau o flynyddoedd yn ôl.


Cyfnod mewn daeareg yw'r Cretasaidd. Cyfeiria at y ddaear yn ystod y cyfnod rhwng 145±4 a 66 miliwn o flynyddoedd (Ma) yn ôl (CP). Mae'n dilyn y cyfnod Jwrasig yn y gorgyfnod Cainosöig.


Nodir diwedd y cyfnod Cretasaidd gan un o ddifodiannau mawr bywyd, gan gynnwys diflaniad y dinosoriaid. Cyflwynwyd y cyfnod gan Jean d'Omalius d'Halloy, daearegwr o Wlad Belg, yn 1822[4]. Bellach arolygir cyfnodau daeareg gan Gomisiwn Rhyngwladol Stratigraffeg[5], is-bwyllgor Undeb Rhyngwladol Gwyddorau Daeareg[6].




Golygfa ddychmygol o'r cyfnod Cretasaidd. (Sefydliad Smithsonian, 1977)




Diagram i ddangos gwahanu Pangaea a symudiad y cyfandiroedd hynafol i'w safle presennol (gwaelod y llun). Mae'r rhif ar waelod pob map yn cyfeirio at 'miliwn o flynyddoedd cyn y presennol'.




Gweler hefyd |


  • Yr uwchgyfandiroedd: Gondwana, Lawrasia a Pangaea.

  • Gweler hefyd y cyfnodau: Permaidd, Triasig, Jwrasig a'r Cretasaidd.


Cyfeiriadau |




  1. ↑ Image:Sauerstoffgehalt-1000mj.svg


  2. ↑ Image:Phanerozoic Carbon Dioxide.png


  3. ↑ Image:All palaeotemps.png


  4. ↑ (Ffrangeg) d’Halloy, d’O., J.-J. (1822). Observations sur un essai de carte géologique de la France, des Pays-Bas, et des contrées voisines. Annales des Mines ... 7: 353–376. O tudalen 373: "La troisième, qui correspond à ce qu'on a déja appelé formation de la craie, sera désigné par le nom de terrain crétacé."


  5. ↑ Comisiwn Rhyngwladol Stratigraffeg (ICS) http://www.stratigraphy.org/


  6. ↑ Undeb Rhyngwladol Gwyddorau Daeareg (IUGS) http://www.iugs.org/










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