The Stratigraphic Column

The sequence of rocks formed during geological time may be represented by the stratigraphic column which lists them in their order of age: the oldest rocks are at the base of the column and the youngest at the top.

Rocks are grouped by age into broad Periods and Epochs, most of which are named after the areas where they were first studied, many of these being in Britain. They are characterised by distinctive assemblies of rock types and tectonic episodes and reflect identifiable periods in the Earth's history. Epochs are subdivided into finer and finer units, often having only local significance. In order to help understand geological models, the table below gives the basic stratigraphic column, showing the divisions of geological time, together with the age of important global scale events. The dates of the naming of the divisions are also given to help illustrate the way the stratigraphic column was developed by geologists, mainly throughout the nineteenth century.

Eion Era Period Epoch

Approximate
duration and
Cumulative Age
(106y or Ma)

Mountain Building Orogenies

(Europe)(N.America)
PHANERO-
ZOIC
('evident life')
CENOZOIC
('recent life' 1841)
Qaternary

Holocene (1885)
or Recent (1833)
(last 10,000yrs)
Pleistocene (1839)

           Present

0.01 
1.8           1.8

                Coast Ranges
(himalayan)

(Neogene 1853)

Tertiary

(Palaeogene    1866)  

Pliocene (1833)
Miocene (1833)

3.5
18.5        23.8
Oligocene (1854)
Eocene (1833)
Palaeocene (1874)
9.9
63.7
42.5          65

 

Alpine                    Laramide

MESOZOIC
('middle life' 1841)

Cretaceous (1822)
Jurasic (11795)
Triasic (1834)
Each of these Periods is devided into numerous Epochs which can be recognised throughout the world 77
63.7
24.5         248.2

Navadan

PALAEOZOIC
('ancient life' 1838)

Permian
Carboniferous (1822)
Devonian (1837)

Silurian (1835)
Ordovician (1879)
Cambrian (1835)

42
64
63

26
52
50            545

PRE
PHANERO-
ZOIC
(or PRE
CAMBRIAN)

PROTERO-
ZOIC

 

Edicarian (1982)

 

All rocks older than Palaeozoic can be collectively descrobed as PRECAMBRIAN

Many Precambrian rocks are severely deformed and metamorphosed, but large areas of undesturbed Precambrian strata are known.
Epochs than can be correlated throughout the world have not been defined.
c. 1910   c. 2500
ARCHEAN

 

c. 2100

c. 4600