Talk:Geologic time scale

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)

Dates in 'Proposed Precambrian Timeline' section
I was about to change the Precambrian/Cambrian boundary dates (of which there are 3 occurrences) from 541 Ma to 539 Ma in accordance with the recently published ICS chart (as featured elsewhere in this article and many others) but then wondered if this section is intended in full to describe the situation in 2012 in which case it might be appropriate, if confusing, to retain the 541 figure as part of the proposals set out at that time. The section as a whole perhaps needs updating from the perspective of April 2022. Geopersona (talk) 06:42, 26 April 2022 (UTC)


 * Good pick up @Geopersona as in my above reply (about eons), I'm working on revising this entire article. Because I'm making some substantial revisions I've been drafting it on my user page so I don't break this one for now. I'll make sure I adjust the dates in a sensible way for this. If you feel like helping out or providing some commentary on it, pop it on here and I'll be sure to look into it. Jarred C Lloyd (talk) 07:56, 26 April 2022 (UTC)
 * Yes, sounds good to me - good luck! cheers Geopersona (talk) 08:02, 26 April 2022 (UTC)
 * The entire Proposal section has been deleted. Why? 2601:441:4900:A6E0:91A4:2688:B6B:98E5 (talk) 02:10, 9 July 2022 (UTC)
 * I think it was archived: a perfectly normal procedure. Feline Hymnic (talk) 09:18, 9 July 2022 (UTC)
 * If the proposal section that is being referred to was "Proposed Precambrian timeline", it has not been deleted but actually expanded within the section Geologic_time_scale section, which includes the previous content, Anthropocene, and another proposal for the Precambrian of the ICC. Jarred C Lloyd (talk) 12:39, 11 July 2022 (UTC)

Revision of article
To those who are interested (@Geopersona, @Mikenorton, @Benniboi01, @User:GeoWriter?, please ignore if not interested) I've drafted a substantial revision to this article intially spurred on by the commentary above by @User:John Maynard Friedman. I drafted it seperately from this page as I have been making a lot of edits and it was easier to build upon the existing article content this way. I'd like to try elevate this article quality rating. This revision can be found here.

I've also made a new figure to replace the "clock" lead image to try adress previous criticism and have a more senisble progression (I do find a circle to be an odd representation of a linear timeline). I'm not "attached" to this figure and can retain the current circle if other editors prefer it. I've only got the final section (about non-Earth geologic time scales) to finish writing, and copyedit to fix spelling errors etc. The final section will incorporate the times (in the Hadean) I removed from the main table of geologic time that are non-Earth divisions as IMO these are conflating Earth's geologic time scale and the Moon's geologic time scale in an article spefically about Earth's geotime.

It would be much appreciated if I could have a second pair of eyes run over the draft, comment on layout (order of sections), comment on the newer lead image, suggest improvements (i.e. point out critical flaws) they think need to be made before incorporatating it into this main article etc. I'll start incorporating the changes from next Thursday (Aus time) when I return from field work. Jarred C Lloyd (talk) 07:18, 4 May 2022 (UTC)


 * At first glance, looking good. I won't be able to do a proper comparison until I get back from my current trip and can look at them side by side on a large screen, rather than the tablet I've got with me. Mikenorton (talk) 13:18, 4 May 2022 (UTC)


 * I just took a look and I have one issue with it at the moment (aside from minor formatting issues which aren't really that important). I think it might be better if we change the bulleted list in the "terminology" section into prose, since a lot of those terms don't make sense to me to include in a list format like that. Otherwise, I think the draft is pretty solid. I especially like the new "principles" section, as it provides a nice way to link pages that are otherwise rarely mentioned elsewhere, while also providing some new info. Benniboi01 (talk) 16:29, 7 May 2022 (UTC)
 * I've removed the bullet point formatting as per your suggestion, as they were written in prose anyway. I had the bulleted list originally to clearly delineate linked concepts and key concepts, but I think they are clear enough as I have them now anyway. What minor formatting issues are you eluding to? I've likely just missed them in my drafting process. Jarred C Lloyd (talk) 01:55, 12 May 2022 (UTC)

Any objections to me implementing the revised article (see here) and lead image? I've only got a tiny bit to add in the last section of the draft on Non-Earth based geologic time scales. It's a substantial rewrite of the page and I want to give a final heads up before I implement it. Obviously formatting/style may need to be adjusted afterwards if I've missed something or parts don't fit the MOS. Jarred C Lloyd (talk) 05:32, 25 May 2022 (UTC)

Personally, I really miss the horizontal time scale that presented Earth's geologic time at different scales, as seen in this revision (dated 18 May 2021—perhaps it also appears in later revisions, but there have been a lot of changes to the page since then). I find it the most readable and easily scanned version for just getting a sense of whole the epochs unfold across eons, etc. Is there anyway to bring that version back somewhere? I'm sorry I haven't followed the discussions that led to its disappearance, but I get frustrated everytime I return to this page to look up information about specific epochs, because I found that earlier version much more fun and easy to search than what I has appeared since. Thomascantor (talk) 15:27, 25 November 2022 (UTC)


 * @Thomascantor do you mean the multiple scale horizontal time scale that is in the Terminology section of the revision you have linked? if so, it is still in the article, but at the end of the Modern International Timescale subsection of the History section. I moved it when I revised the article to better separate the themes of a given section. Jarred C Lloyd (talk) 22:56, 25 November 2022 (UTC)
 * Ah, I see it now. Thanks, Jarred C Lloyd, for the clarification and help. Thomascantor (talk) 21:50, 28 November 2023 (UTC)

Merging the geological timeline articles? Geologic time scale - Timeline of the evolutionary history of life - Timeline of human evolution
I am interested in the past of Earth and life, a fan of extinct lifeforms, but I am not an expert in any relevant field, i.e. I am not a professional geologist, palaeontologist, palaeoclimatologist or something like that.

Nevertheless, while browsing articles, I found this article to significantly overlap with Timeline of the evolutionary history of life and at least partially with Timeline of human evolution. Thus I propose merging this article with Timeline of the evolutionary history of life and refocusing Timeline of human evolution towards Hominidae or at least primate evolution specific dates. Of course, the first Bilateria represent an important milestone, but such milestones can be explained in this article or Timeline of the evolutionary history of life in my opinion. PragmaFisch (talk) 17:11, 11 November 2023 (UTC)


 * You apparently don't understand the timescale. Evolutionary and geological are very different. --Fama Clamosa (talk) 19:26, 11 November 2023 (UTC)
 * I do see the point - however, Geologic time scale contains quite a lot of information on life and its evolution, too. Might that be better suited to Timeline of the evolutionary history of life? Also, I love Geologic time scale most because the scrollable timetable with the common colours and explanations etc. which provides an excellent overview. Maybe this at least could be incorporated into Timeline of the evolutionary history of life? PragmaFisch (talk) 19:34, 11 November 2023 (UTC)
 * Oppose Despite some extent of overlap given their geological natures, geologic time scale and timeline of the evolutionary history of life are two different concepts, the former focusing on the stratigraphic side and the latter focusing on the paleobiological side. Merging the two pages would result in an excessively long page. They both can overlap in discussing stratigraphic ranges of life forms, but for the geologic time scale page, it's not the main topic. PrimalMustelid (talk) 19:01, 12 November 2023 (UTC)
 * I would be opposed to merging the two, as the only real overlap seems to be the fact that they both use the same division of deep time and the fact that the timeline on this article also has some information on what was happening at the time, also pertaining to life that existed. The topics they cover (those being stratigraphic and paleobiological) are quite far apart, and merging them together would result in a much messier article than either of the two seperate ones. The Morrison Man (talk) 15:57, 13 November 2023 (UTC)
 * Oppose - the timelines each have a different scope: geological development of Earth, lifeforms, human lifeform; each of which needs its own chronological reckoning.  &mdash; The Transhumanist   11:16, 30 April 2024 (UTC)


 * Oppose - There is inevitably some overlap between the timelines but any sort of combined timeline would not, in my view, do any of the topics justice. Mikenorton (talk) 13:49, 30 April 2024 (UTC)
 * Oppose - While there is some overlap due to the nature of how geological time is defined and how biologicial evolution in inherently linked with geologic processes, merging of the two articles would not do either topic justice. As it stands, I believe both articles are able to elaborate on their specific topics in better detail and with greater cohesion and readability than a merged article would be able to do.  Jarred C Lloyd (talk) 12:11, 1 May 2024 (UTC)