Talk:Geologic time scale/Archive 2
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Any citation for the term "epoch" as meaning a span (rather than moment) of time?
The article uses the word epoch to mean a span of time less than an era. In chronology, the term specifies a specific moment in time. Using the latter definition, the current favourite proposed epoch for the Anthropocene is 1950; the epoch for the Holocene is "approximately 11,650 cal years before present". Wiktionary gives both senses (though five of the six use the 'moment' meaning). So I expected to find here a source for the 'time span' meaning, but failed to find it. Under #Terminology, we have Eons are divided into eras,[2] which are in turn divided into periods,[3] epochs and ages.
No citation is given for 'epochs' or 'ages'.
Citation 2 above [Chapter 9 of Stratigraphic Guide] just says a. Definition. The series is a chronostratigraphic unit ranking above a stage and below a system. The geochronologic equivalent of a series is an epoch.
I don't have Citation 3 [the AGI Glossary of geology] but it is curious that we have citations for eras and periods, but not for epochs and ages (and don't even mention 'series'. Nor 'stage' nor 'system', for that matter.).
Would someone rectify, please? --John Maynard Friedman (talk) 11:48, 1 February 2022 (UTC)
- I found it surprisingly difficult to find a clear definition - I note that both Epoch (geology) and Age (geology) unhelpfully redirect to this page. I think that this source should cover this, both for "epochs" and "ages", even if it doesn't go into any detail about the latter. Mikenorton (talk) 12:55, 1 February 2022 (UTC)
- I suggest it would be a good idea to expand the #Terminology section to define and explain all these terms. That really needs some subject expertise that I don't have. I don't think that just whacking in a citation arbitrarily will do. --John Maynard Friedman (talk) 17:21, 1 February 2022 (UTC)
- This is what I was looking for. It contains everything that we need to write a more comprehensive terminology section as you suggest. I will do my best to get around to doing this, if nobody else gets there first. Mikenorton (talk) 17:41, 1 February 2022 (UTC)
- Hi @Mikenorton I've started work on writing a much more comprehensive terminology Draft: GeologicTimeScale Terminology and am happy to take the lead on this. If you have time and feel like helping out that would be much appreciated and would speed up the process. Given I'm planning a substantial rewrite I thought it would be easier to write a draft first and then replace the current terminology section on this page. Jarred C Lloyd (talk) 05:47, 2 April 2022 (UTC)
- Good news, I keep getting involved in other things. Currently away and with little opportunity to edit, so will hopefully take a look on my return, thanks, Mikenorton (talk) 14:38, 2 April 2022 (UTC)
- In passing, I was surprised to see this in the ICS item to which you linked @Mikenorton: An eonothem is a chronostratigraphic unit greater than an erathem. The geochronologic equivalent is an eon. Three eonothems are generally recognized, from older to younger, the Archean, Proterozoic and Phanerozoic eonothems. The combined first two are usually referred to as the Precambrian. - it rather ignores the Hadean and equates just the combined Archaean and Proterozoic eon(othem)s with the Precambrian; a definition from an august body at odds with the general understanding of the supereon and indeed with its own published chart. A simple error on the part of ICS? cheers Geopersona (talk) 07:18, 26 April 2022 (UTC)
- I think that may be a deliberate omission of the Hadean in that definition by the ICS as they are only talking about the formally defined eonothems/eons. As you point out the general use of pre-Cambrian includes the Hadean (as does their latest chart [although both are still informal as indicated by italics]), but neither are formal chronostratigraphic names/terms. The better definition which I've used in this revision of the article I'm working on, is "Informally, the time before the Cambrian is often referred to as the pre-Cambrian or Precambrian (Supereon)". Jarred C Lloyd (talk) 07:46, 26 April 2022 (UTC)
- There are plainly nuances here - I'm leaving a clearer exposition of all this in your hands. thanks Geopersona (talk) 08:02, 26 April 2022 (UTC)
- I think that may be a deliberate omission of the Hadean in that definition by the ICS as they are only talking about the formally defined eonothems/eons. As you point out the general use of pre-Cambrian includes the Hadean (as does their latest chart [although both are still informal as indicated by italics]), but neither are formal chronostratigraphic names/terms. The better definition which I've used in this revision of the article I'm working on, is "Informally, the time before the Cambrian is often referred to as the pre-Cambrian or Precambrian (Supereon)". Jarred C Lloyd (talk) 07:46, 26 April 2022 (UTC)
- In passing, I was surprised to see this in the ICS item to which you linked @Mikenorton: An eonothem is a chronostratigraphic unit greater than an erathem. The geochronologic equivalent is an eon. Three eonothems are generally recognized, from older to younger, the Archean, Proterozoic and Phanerozoic eonothems. The combined first two are usually referred to as the Precambrian. - it rather ignores the Hadean and equates just the combined Archaean and Proterozoic eon(othem)s with the Precambrian; a definition from an august body at odds with the general understanding of the supereon and indeed with its own published chart. A simple error on the part of ICS? cheers Geopersona (talk) 07:18, 26 April 2022 (UTC)
- Good news, I keep getting involved in other things. Currently away and with little opportunity to edit, so will hopefully take a look on my return, thanks, Mikenorton (talk) 14:38, 2 April 2022 (UTC)
- Hi @Mikenorton I've started work on writing a much more comprehensive terminology Draft: GeologicTimeScale Terminology and am happy to take the lead on this. If you have time and feel like helping out that would be much appreciated and would speed up the process. Given I'm planning a substantial rewrite I thought it would be easier to write a draft first and then replace the current terminology section on this page. Jarred C Lloyd (talk) 05:47, 2 April 2022 (UTC)
- This is what I was looking for. It contains everything that we need to write a more comprehensive terminology section as you suggest. I will do my best to get around to doing this, if nobody else gets there first. Mikenorton (talk) 17:41, 1 February 2022 (UTC)