Engineering Geology

Table 1.1. The geological timescale
Duration of Total from
Eras Periods and systems Derivation of names period (Ma) beginning (Ma)
43
Cainozoic
Quaternary
Recent or Holocene* Holos = complete whole
Glacial or Pleistocene* Pleiston = most 2 or 3 2–3
Tertiary
Pliocene* Pleion = more 9 or 10 12
Miocene*
Meion = less (i.e. less
than in Pliocene) 13 25
Oligocene* Oligos = few 15 40
Eocene* Eos = dawn 20 60
Paleocene* Palaios = old 10 70
The preceding comparative terms refer to the proportions of modern
marine shells occuring as fossils.
Mesozoic Cretaceous Creta = chalk 65 135
Jurassic Jura Mountains 45 180
Triassic Threefold division in Germany 45 225
(New Red Sandstone = desert sandstones of the Triassic period
and part of the Permian)
Palaeozoic Permian Permia, ancient kingdom between the 45 270
Urals and the Volga
Carboniferous Coal (carbon)-bearing 80 350
Devonian
Devon (marine sediments)
(Old Red Sandstone = land sediments of the Devonian period) 50 400
Silurian Silures, Celtic tribe of Welsh borders 40 440
Ordovician Ordovices, Celtic tribe of North Wales 60 500
Cambrian Cambria, Roman name for Wales 100 600
Pre-Cambrian Era
Origin of Earth 5000
*Frequently regarded as epochs or stages, “cene” from kainos = recent.
Chapter 1