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Chapter: 2 General physics
    Section: 2.7 Astronomy and geophysics
        SubSection: 2.7.10 The geological timescale

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2.7.10 The geological timescale

In assessing the relative age of rock formations, superposition of uninterrupted and undisturbed strata establishes a stratigraphic sequence (i.e. older below younger), while the thickness of deposition is a guide to the time period of sedimentary accretion. In palaeontology, the presence of fossils from the Cambrian period onwards promotes a correlation between strata in different areas. Geological Periods, collected into palaeontological Era, have been named after the districts in which the rock horizons were classically identified.

A variety of geochronological techniques are available. The most recent past is indicated from dendrochronology (annular growth rings in very old trees), or the examination of a sequence of glacial meltwater varves (upper Pleistocene lacustrine deposits); both methods are related to changes in terrestrial climate and solar excursions. For anthropological specimens less than 1.5 million years old, fluorine dating (Oakley, 1980) may provide relative estimates of contemporaneous age of associated specimens, at least one of which has been dated by independent stratigraphic, cultural or absolute means. Their inter-relation is inferred from chemical measurement of fluorine/phosphate ratios (Glover and Phillips, 1965) of apatite mineral in bone, teeth, antlers, etc. from contiguous horizons.

Absolute age may be computed from the decay of various radioisotopes which occur in specific relationships ‘starting’ from some geomorphological or biological event. Radiocarbon dating relies on a living organism exchanging carbon dioxide at an equilibrium level of 14C/12C until it dies; the level of 14C then decays according to its 5730 year half-life. Dates are reliable to 5% or better but this scale is only useful for events in the last 70 000 years. For earlier events, e.g. in the Tertiary Era, the measurement of 40K/40A ratios in micaceous and volcanic rocks has been notable in assessing the antiquity of fossil remains of very early hominids and anthrapoids found in East Africa. Dating of older (e.g. Palaeozoic) rock formations relies on determining the ratios of longer lived isotopes, e.g. 87Rb/87Sr or various uranium/lead ratios. Estimates of the age of the earth’s crust have been derived from ratios of 206Pb and 207Pb to (nonradiogenic) 204Pb.

(See section 4.6.2 for an exposition of the uranium and thorium radioactive disintegration series.)

Harland and colleagues (1990) developed a chronostratic scale of rock sequences (with data through 1988) which assigns ages with standardised stratigraphic reference points. In the following table, the geological periods are mostly given classic (West) European stage names but some broadly equivalent East European and Asian strata (marked ‘*’) have been included. For more detailed reference there is a useful wall chart by his co-author Smith (1990) based on their book but with some minor revisions.

In the table, the age point for the base bed of most systems has been abstracted from data in Harland et al. (1990).

References

M. J. Glover and G. F. Phillips (1965) J. Appl. Chem., 15, 570–576.
W. B. Harland et al., (1990) A geological time scale 1989, Cambridge University Press.
K. P. Oakley (1980) Relative dating of the fossil hominids of Europe, Bull. Br. Mus. Nat. Hist. 34(1).
A. G. Smith (1990) Wall chart: a geological time scale 1989, Cambridge University Press.

G.F.Phillips

The geological timescale 1989

Age points are expressed in million years; uncertainties are generally around 5 in the last digit

ERA, Period and

Epoch

Bed Base

Duration

       

QUATERNARY

     

HOLOCENE -     post-Glacial

 0.01

  0.01

 

 

 

 

 

 

PLEISTOCENE

 

 1.64

  1.63

 

 

 

 

 

 

TERTIARY = CENOZOIC

 

 

 

PLIOCENE

 

 

 

 

    upper

 Piacenzian

  3.4   1.8 3.6

    lower

 Zanclian

  5.2   1.8

 

 

 

 

 

 

MIOCENE

 Messinian

  6.7   1.5 18

 

 Tortonian

10.4   3.7

 

 

 Serravallian

14.2   3.8

 

 

 Langhian

16.3   2.1

 

 

 Burdigalian

21.5   5.2

 

 

 Aquitanian

23.3   1.8

 

 

 

 

 

 

OLIGOCENE

 Chattian

29.3   6.0 12

 

 Rupelian

35.4   6.1

 

 

 

 

 

 

EOCENE

 Priabonian

38.6   3.2 21

 

 Bartonian

42.1   3.5

 

 

 Lutetian

50.0   7.9

 

 

 Ypresian

56.5   6.5

 

 

 

 

 

 

 

 

 

 

PALAEOCENE 

 Thanetian

60.5   4.0 10

 

 Montian + Danian

65.0

  4.5

 

 

 

 

 

 

 

 

 

 

 

 

SECONDARY = MESOZOIC

 

 

 

upper CRETACEOUS K2

 

 

 

 

Maastrichtian

74.0

  9.0

32

Senonian      

 Campanian

83.0   9.0

 

 Santonian

86.6   3.6

 

 Coniacian

88.5   1.9

 

 

 Turonian

90.4   1.9

 

 

 Cenomanian

97.0   6.6

 

 

 

 

 

 

lower CRETACEOUS K1

 

 

 

 

 Albian

112.0   15.0 49

 

 Aptian

124.5   12.5

 

 

 Barremian

131.8     7.3

 

 

 Necomian

145.6   13.8

 

 

 

 

 

 

upper JURASSIC J3

 

 

 

 

Tithonian     

Purbeckian

Portlandian

 

 

62

152.1  

  6.5

 

Malm

 Kimmeridgian

154.7     2.6

 

 

 Oxfordian

157.1     2.4

 

middle JURASSIC

 Callovian

161.3     4.2

 

J2

 Bathonian

166.1     4.8

 

Dogger

 Bajocian

173.5     7.4

 

 

 Aalenian

178.0     4.5

 

lower JURRASSIC

 Toarcian 187.0     9.0  

J1

 Pliensbachian

194.5     7.5

 

Lias

 Sinemurian

203.5     9.0

 

 

 Hettangian

208.0  

  4.5

 

 

 

 

 

 

upper TRIASSIC

 Rhaetic

209.5     1.5 37

TR3    keuper

 Norian

223.4   13.9

 

 

 *Karnian

235.0   11.6

 

middle TRIASSIC

 *Ladinian

239.5     4.5

 

TR2    Muschelkalk

 *Anisian

241.1     1.6

 

lower TRIASSIC

 Scythian

 

 

 

TR1    Bunter

 *Olenekian

ca 245

 ca

 

 

 

 

 

 

         



ERA, Period and

Epoch

Bed Base

Duration

       
PRIMARY = PALAEOZOIC  

 

 

 

 

 

 

 

upper PERMIAN

Zechstein

256.1

11.0

45

lower PERMIAN

*Kungurian

259.7

3.6

 

Rotliegendes

 *Artinskian

268.8

9.1

 

 

 *Sakmarian

281.5 12.7

 

 

 Asselian

290.0 8.5

 

 

 

 

 

 

upper CARBONIFEROUS = Silesian

 

 

 

NA2

 Stephanian

295.1 5.1 33

 

 Westphalian

311.3 16.2

 

 

 Namurian

322.8 11.5

 

 

 

 

 

 

lower CARBONIFEROUS = Dinantian

 

 

 

NA1

 Viséan

349.5 26.7 40

 Tournaisian

362.5 13.0

 

 

 

 

 

 

upper DEVONIAN

 Famennian

367.0 4.5 46

D3

 Frasnian

377.4 10.4

 

middle

 

 

 

 

    DEVONIAN

 Givetian

380.8 3.4

 

D2

 Eifelian

386.0 5.2

 

lower DEVONIAN

 Emsian

390.4 4.4

 

D1

 Siegenian/Pragian

396.3 5.9

 

 

 Gedinnian/

408.5 12.2

 

 

 Lochkovian

 

 

 

 

 

 

 

 

SILURIAN

 Ludlow

424.0 15.5 30

 

 Wenlock

430.4 6.4

 

 

 Valentian/

439.0 8.6

 

 

 Llandovery

 

 

 

 

 

 

 

 

upper

 

 

 

 

    ORDOVICIAN

 Ashgill

443.1 4.1 71

Bala

 Caradoc

463.9 20.8

 

middle

 

    ORDOVICIAN

 Llandeilo

468.6 4.7

 

Dyfed

 Llanvirn

476.2 7.6

 

lower

 

 

 

 

    ORDOVICIAN

 Arenig

493.0 16.8

 

canadian

Tremadoc

510.0   17.0

 

 

 

 

 

 

upper CAMBRIAN

 Merioneth

517.2 7.2 60

middle

 

 

 

 

    CAMBRIAN

 St Davids

536.0 18.8

 

lower CAMBRIAN

 Lenian/Comley

553.7 17.7

 

Caerfai

 Atdabanian

560   6.3

 

 

 Tommotian

570   10   

 

 

 

 

 

 

 

PROTEROZOIC

 

 

 

 

SINIAN   Neoproterozoic

 

 

230
Pt3  
 

Vendian

 
   

 Poundian

580 10

 

 Wonokan

590 10

 

 Mortensnes

600 10

 

 Smâlfjord 610 10  

 Sturtian

ca 800  190

 

RIPHEAN/HELIKIAN

 Mesoproterozoic

 

 

850

pt2

Karatau

1050 250

 

 

Yurmatin

1350 300

 

 Burzyan

1650
300

 

 

 

 

 

APHEBIAN 

 Palaeoproterozoic

 

 

750

pt1

 Animikean

2200 550

 

 

 Huronian

2400 200

 

 

  AZOIC = ARCHEAN   ca 4500  ca 2100
Crust formations without organic life    


 

 

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