GEOLOGICAL AGE OF ROCKS AND LAYERS

GEOLOGICAL AGE OF ROCKS AND LAYERS

In the descriptions of rocks and deposits, it is important to define their geological age. This is because it makes it easier to find similar deposits in other areas, especially the neighboring ones. This also applies to deposits of precious stones.

Division of the history of the Earth
he was

(Era)

System

(Period)

Branch

(Age)

Age in million years
Kenozoic quaternary holocene

Pleistocene

1.8
tertiary pliocen

miocene

oligocen

eocen

paleocen

65
Mezozoiczna chalk upper

lower

140
jura upper (Ore)

median (dogger) lower (lias)

145
trias top (kajper)

middle (shell limestone)

bottom (variegated sandstone)

230
Paleozoic perm top (Zechstein)

bottom (red algae)

280
carbon top

bottom

345
dewon top

middle

bottom

395
sylur top

middle

bottom

435
ordowik top

middle

bottom

500
chamber top

middle

bottom

570
Proterozoic 2600
Archaic 3600
The rise of the earth 4600 (?)

Presence of fossils in rocks, that is, the fossilized remains of organisms, is of great importance for comparing the age of rocks. Especially these species of animals and plants, who lived shortly, but in large areas they are of great value to a geologist. Based on fossils found only in a given period (index fossils) rocks, they contain can be easily identified as being of equal age even then, when they occur in distant areas. Fossils are used to determine the relative age of rocks, which is the basis for the division of the history of the Earth into eras, geological periods and epochs. Physico-chemical methods, involving the study of radioactive isotopes present in rocks, the absolute age of minerals and rocks is determined. This research shows, that the duration of geological eras was very different. The Cenozoic era lasted over 60 min years, Mesozoic - approx 170 million years, paleozoicza — 340 min years. The oldest eras - Proterozoic and Archaic - lasted much longer, because approx 5000 min years.