Talk:Period (geology)
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I am new to this kind of exchange. I was searching for translations from my native German to English and found discrepancies in the naming of geological periods from Europe to North-America. However I found the following periods for North-American, not listed in the article:
Cretaceous is can be split in Upper Cretaceous and Comanchean (lower Cretaceous)
Proterozoic is not divided into periods, so the epochs, Keweenawan, Beltian, Huronian and Grand Canyon can be shown as subdivisions, though I could not find a time-line behind them
Achreozoic (as Proterozoic) is not split into periods and the epochs Timiskaming, Keewatin and Vishnu can be shown in this place.
Thus I would change the table as shown below:
|-----------|-------------------| |Cretaceous | Upper Cretaceous | | |-------------------| | | Comanchean | | | (Lower Cretaceous | |-----------|-------------------|
|-----------|-------------------|-----------------| |Proteozoic | not |Keweenawan Beltian | | | divided |Huronian Grand Canyon | |-----------| into |---------------------------| |Archeozoic | periods | Timiskaming | | | | Keewatin Vishnu | |-------------------------------------------------|
Unfortunatley, I did not note down the time-line, when I found these periods, but will mend this next time I sign in.
[edit] Assumptions?
There are many assumptions in this article regarding the references to the geological column which are put forward as facts. This is still theoretical as are all the dates. The geological column exists nowhere in the world! This article should be noted as being based on generally accepted, but unproven, theories. Refer definition empirical science and please apply.
If you are using fossils to date the rock layers and then using rock layer to date the fossils: isn't this circular reasoning? —Preceding unsigned comment added by 75.21.154.222 (talk) 13:10, 6 January 2008 (UTC)
- No. Fossils are used to delineate relative ages i.e. which rock layers were laid down before which other rock layers. This is not the same as absolute dating (e.g. radiometric dating, or similar), i.e. how many years ago in absolute time were those rock layers laid down. Badgerpatrol (talk) 07:55, 17 March 2008 (UTC)
