Talk:Basin Groups

Proposed deletion

"Basin group" is not a recognized geology time period for the Moon. If anything, this is an informal term that is rarely if ever used. Perhaps someone could give me a good reason for keeping this article? If not, I will be inclined to put it up for deltion. Lunokhod 12:11, 14 January 2007 (UTC)

• It is part of the geological time line, and we need some name or another for it. Keep. Anthony Appleyard 16:12, 14 January 2007 (UTC)

We need to emphasize that this is an outdated "era" that is not used by lunar geologists anymore. I'll try to look into the history of this, but I suspect it went out of style in 1970 when lunar samples were used to date the Imbrium and Nectaris basins. If you look at lunar geologic timescale, you'll see that there is no basin group. A possible solution is to merge this article with lunar geologic timescale, and mention that at one time, the Imbrian and Nectaris eras (more or less, according to the dates given) was referred to as "basin group". Also, Hadeon is not used for the Moon, this is a terrestrial term, so I'm going to remove these references from the Nectarian and lower imbrian topics. Lunokhod 16:58, 14 January 2007 (UTC)

• We still need a continuous series of named periods from the formation of the Moon (by the Theia collision) to the present day. Anthony Appleyard 23:52, 14 January 2007 (UTC)

If you look at lunar geologic timescale, you will see that it contains a continuous series of named periods from 4.5 to 0 Ga. Lunokhod 09:49, 15 January 2007 (UTC)

• It appears that Basin Groups was used for Late Pre-Nectarian time. Take a look at the GeoWhen database and

Harland, Walter Brian , et al. (1989) A Geologic Time Scale 1989 Cambridge University Press, Cambridge, UK, Fig. 1.7 on page 10, available via Google books, which shows both Basin Groups and Cryptic. Unfortunately the textual discussion is not available as part of the Google offering. I do realize that at present these subdivisions remain more theoretical than real, as many lunar deposits are still just lumped together as Pre-Imbrian age materials, which may account for the absence of mention of Basin Groups in Wilhelms' book and Martel's article. --Bejnar 03:10, 16 January 2007 (UTC)

• Basin Groups is a division of c:a 6-7 Lunar geology time intervals. It cannot be removed. As a Terran geology time intervals it will soon be obsolete, and replaced by something like Late CEE era and Early LHB, but it will still be occurring as an obsolete time subdivision, and the article is therefore still relevant. It would be very improper to remove Basin Groups. Rursus 14:40, 20 January 2007 (UTC)

Basin groups (1-9) (as wel as the cryptic) are subdivisions of the Pre-Nectarian. They are informal (as opposed to the Pre-Necatian), and have never been used on any USGS geologic map. See the discussion on the AfD. The confusion arises becuase Harland et al. (1989) decided to "paste" the lunar geologic time scale into the terrestrial one for the Hadean. In their book, they advocate using Pre-Nectarian, Necarian, and Lower Imbrian. However, when you look at their figure, they did not include the Pre-Nectarian, but only gave the informal subdivisions of this era! This is almost certainty a typo in their figure, as it appears to be inconsistent with their text. All occurences of "Basin Groups" when it is NOT a subdivision of the Pre-Necarian (as on the web sites posted above) have simply reproduced a typographic error. Please read the book and see for yourself! Lunokhod 15:05, 20 January 2007 (UTC)

But Harland is a (terran) geologist, while the Basin Groups (1-9) are selenological concepts, whether formal or not. And they're used. Maybe we can properly degrade Basin Groups from being a geochron, to an obsolete geochron, but Basin Groups are still a scientific concept. In 100 years it might be as obsolete as the geochrons Primary and Secondary, but still valid as geology historical notion. Rursus 15:45, 20 January 2007 (UTC)

Regarding Cryptic - it can't properly be regarded as a chron - it's "defined" from what we don't know, and by many examples, such a term won't usually survive the expansion of science and humankind. It's a pretty poetic variant of the label Unknown. Rursus 15:39, 20 January 2007 (UTC)

Quality

Subjectively: since I made my last comment in the Basin Group deletion discussion, the article seems to have been considerably improved. It looks good to me – mirroring our discussion of lack of validness and support as a geochron from its first geochron user Harland. Shouldn't we consider deleting the deletion proposal? Rursus 11:44, 27 January 2007 (UTC)

I am still for at least a merger of Cryptic era and Basin Groups into both Hadean eon and Pre-Nectarian. I just can't see how either of these articles will ever become more developed than they are now. I still maintain that that use of Basin Groups is not common among terrestrial geologists, and at best is an instance of bad science that was incorporated into an otherwise respectable book. Lunokhod 11:54, 27 January 2007 (UTC)

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