Ecology: The Biology of Interactions. 2.13. (Supplement) The Geochronological Scale
To describe the history of life on Earth, one needs a scale that allows the relevant spans of time to be described. How is this history studied? By the sequence of sedimentary rocks. The mutual sequence of the strata is determined by the character of their occurrence and by the composition of the fossils they contain. ...
Ukrainian language (latest version) / Russian language (no longer updated) 2.12. (supplement) The Origin of Life. Preliving Systems
D. Shabanov, M. Kravchenko. Ecology: The Biology of Interactions Chapter 2. Biospherology
2.14. (supplement) Some Stages in the History of Life on Earth
2.13. (supplement) The Geochronological Scale To describe the history of life on Earth, one needs a scale that allows the relevant intervals of time to be described. How is this history studied? By the sequence of sedimentary rocks. The mutual sequence of strata is determined by the character of their bedding and by the composition of the fossils they contain. Many groups of organisms abundant in the past that left well-preserved remains, shells, teeth, scales, and so on, acquire great significance for determining the age of rocks and are called index fossils. The coordinated sequence of rocks of different ages, and of the corresponding intervals in Earth’s history, is called the geochronological scale (Table 2.13.1). Table 2.13.1. The geochronological scale
2.13. (addendum) Geochronological scale To describe the history of life on Earth, it is necessary to have a scale that allows describing the corresponding time intervals. How is this history studied? By the sequence of sedimentary rocks. The mutual sequence of rocks is determined by the nature of their occurrence and the composition of the fossil remains they contain. Numerous groups of organisms in the past that left well-preserved remains (shells, teeth, scales, etc.) are of great importance for determining the age of rocks and are called guide fossils. A consistent sequence of rocks of different ages and the corresponding time intervals of Earth's history is called a geochronological scale (Table 2.13.1). Table 2.13.1. Geochronological scale
Eons
Eras
Periods
Epochs
Boundary (million years)
Phanerozoic
Cenozoic Kz
Quaternary (Anthropogene) Q (A)
Holocene
0
0,0114
Pleistocene
2,59
Neogene N
Pliocene
5,3
Miocene
23
Paleogene P
Oligocene
33,9
Eocene
55,8
Paleocene
65,5
Mesozoic Mz
Chalk K
Late
99,6
Early
145
Yura J
Late
161
Average
176
Early
200
Trias T
Late
228
Average
245
Early
251
Paleozoic Pz
Perm P
Late
Lopingia
260
Guadalupe
270
Early
Cirsium
299
Carboniferous C
Upper
Pennsylvanian
306
Average
318
Lower
Mississippi
359
Devonian D
Late
385
Average
397
Early
416
Silur S
Przhydol
418
Ludlov
423
Венлок
428
Llandovery
444
Ordovician O
Late
461
Average
472
Early
488
Kembriy Ye
Furong
503
Average
510
Early
542
Proterozoic Pr
Neoproterozoic
Ediacaran
630
Cryogenian
850
Toniy
1000
Mesoproterozoic
Steniy
1200
Ectasis
1400
Калімій
1600
Paleoproterozoic
Stateriy
1800
Orozyrius
2050
Ріасій
2300
Sideriy
2500
Archaea Ar
Neoarchean
2800
Mesoproterozoic
3200
Paleoarchean
3600
Eoarchean
3800
Гадей
4570
The geochronological scale is the result of the work of many generations of geologists. First of all, it reflects the sequence of time intervals, their relative age. In the twentieth century, relative dating was supplemented by absolute dating based on estimating the rate of decay of radioactive elements in the rocks under study. It should be noted that the relative scale is more precise and informative than the absolute one. For example, both Acanthostega, the oldest known tetrapod, and Panderichthys, a fish very similar to tetrapods but at the same time unable to have been their ancestor, lived in the Upper Devonian. The age of Panderichthys is 378±10 million years, whereas that of Acanthostega is 360±10 million years. These data are insufficient to assert confidently that Acanthostega lived later. But if it is known that it was found in later strata, lying above, that is sufficient to state confidently that it is younger, even if the absolute age of the rocks is not known at all. Additional materials: Educational model: The Development of Life on Earth
2.12. (supplement) The Origin of Life. Preliving Systems
D. Shabanov, M. Kravchenko. Ecology: The Biology of Interactions Chapter 2. Biospherology
2.14. (supplement) Some Stages in the History of Life on Earth