Talk:Chalk Group

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I have added a section on the petroleum geology of the North sea chalk, I will expand this as time allows

A.Foum

The capitalization, i.e. "Upper Chalk" is deliberate. Please don't change it.

Dlloyd 09:11, 28 Jul 2004 (UTC)


http://www.bbm.me.uk/portsdown/PH_743_Chalk.htm says...

As described in stratigraphy, the Chalk of the Britain has been divided into 3 Provinces, the 'Northern', the 'Southern', and the 'Transitional'. These geographical classifications replace the old age-based units of 'Upper', 'Middle' and 'Lower' - which are, however, still used informally.

Now with the creation of the Southern England Chalk Formation page this can be a much more technical article about how Chalk is formed -- Any Geologists :) as I don't feel qualified to do this --Davelane 16:49, 1 Jan 2005 (UTC)

This article is close to Good Article level, if some one is prepared to propose and repair! GB 10:42, 4 July 2007 (UTC)

It is not. It is very confusing in its terminology and the division in paragraphs should be clearer too. Some points that need urgent attention:
  • Is the Chalk a formation (as the title suggests) or a group (as appears from the text about its subdivisions) or even something else (somewhere it is called a series)? When describing a lithostratigraphic unit we should at least have the lithostratigraphic definitions clear.
  • If you describe lithostratigraphy, an essential point is to name the units immediately above and below the one described. It could even go in a template. Yet it is lacking.
  • It is said that the Chalk is "most prominently" found in England. That is an Anglocentric POV and should be removed, because chalk is also a lithology.
  • It is not clear with which other formations the Chalk is correlated, for example in Northern France, the low countries or in Germany. Do they have the same lithology? What is different and why?
  • The article lacks a good paleogeographic description.
  • The Chalk is called an important reservoir unit. Yet, further in the text, it is called a seal. It cannot be both, so which is it?
  • It should be made clear that there are two definitions of the word chalk: a lithology and a lithostratigraphic unit.
Unfortunately, I have no literature here on the lithostratigraphy of England. I can guess that the Chalk is a group, since it is divided into formations. As for the rest I would say the article needs a thorough revision by an expert. Best regards all, Woodwalker (talk) 15:20, 31 May 2008 (UTC)
I have to agree with a lot of what Woodwalker says. The Chalk is problematic, it's generally defined lithostratigraphically and this rock type continues across the Cretaceous/Tertiary boundary into the overlying Danian so we can't even refer to it as Cretaceous. There is an agreed nomenclature used in the offshore areas and quite a lot of this has been included here, however, it dosen't fit in with the rest of the article, which describes it from an onshore exposure perspective.
To answer two of Woodwalker's points,
  • it does act as both seal and reservoir due to variations in the distribution of the permeable allochthonous chalks. The Joanne oifield has a Tor chalk reservoir, the neighbouring Jade gas condensate field has a slightly older Hod chalk top seal.
  • The article actually says that the chalk "appears" most prominently in England, for which I read "is exposed"; this just needs rewording to both clarify and include the equally dramatic exposures on the other side of the channel.
An overall correlation diagram showing how the onshore exposures in the UK, France, Belgium, Netherlands & Germany fit in with the sequences defined offshore would be extremely useful. Mikenorton (talk) 16:26, 31 May 2008 (UTC)
Thanks for your fast reply Mike. Your first answer should be incorporated in the text, it clearifies the confusing reservoir/seal stuff. Your second answer: I know that at least in the low countries and Germany, the group/formation (?? I assume group but am not sure) has a different name. No surprise there, because the British Geologic Survey has no influence on lithostratigraphic names outside the UK... As far as I know (I am not sure about France) the name "Chalk" is therefore in a lithostratigraphic sense restricted to England. That its age is not only Cretaceous, is no problem and a common feature of larger lithostratigraphic units (that's why there is a difference between lithostratigraphy and chronostratigraphy I guess). To the point: I think this article should only refer to the Chalk unit in the UK, and mention its correlation with similar units in France and elsewhere. The article on chalk (the lithology) can then mention all exposures across the world. Woodwalker (talk) 18:54, 31 May 2008 (UTC)

Terminology: formations[edit]

This article refers to the Chalk Group appearing in England in three formations: Upper, Middle and Lower. However the image of The Needles is captioned as being part of the Southern England Chalk Formation, with no reference to any of the previous three terms. Also the article Southern England Chalk Formation itself makes no reference to the three terms, nor even indeed to the term Group. This is confusing (at least it is to a non-geologist like myself), and I think requires explanation on both articles. PaleCloudedWhite (talk) 08:28, 20 January 2012 (UTC)

I've adddressed some of this by using the modern terms and made reference to various earlier one which will remain 'at large' for years to come. Further work required here to help clarify what is a confusing situation with stratigraphic names changing so frequently - hopefully we're now enetring a period of stability! cheers Geopersona (talk) 08:23, 17 February 2012 (UTC)

Would it be possible, as part of the further work required, to address the definition of 'provinces', and how they relate to the Group? At the moment it isn't clear which way the hierarchy works - in the introduction it states that the Chalk Group in England forms part of a wider 'province', thus implying that 'group' is a subdivision of 'province', whereas later in the body of the text, the relationship is the other way round (and to add to the confusion, according to the Geological unit article, 'province' isn't a recognised unit - only Supergroup and Formation are named as being the relevant larger and smaller units relating to Group). PaleCloudedWhite (talk) 19:20, 18 February 2012 (UTC)

Useful conversation, helping the article become clearer. In fact 'province' is not a part of the stratigraphical hierarchy, it is a geographical descriptor; it defines different areas within which the rock sequence has been laid down and which may have - indeed do have, in this case - differing sequences (reflecting different depositional histories) even though all of the rocks are lumped together within the same stratigraphic group. Does that help? (See Province#Geology - though that description might be made clearer) cheers Geopersona (talk) 06:32, 19 February 2012 (UTC)

Yes that does help, thanks. It wasn't clear to me before, but I can see now (I hope I have got this right!) that different geological units are applied to strata according to how the strata relate to each other temporally within a depositional sequence. Of course, that means that different units also relate to one another spatially, simply because the strata are deposited one on top of another, but their spatial relationships are not the basis for how they are classified. So 'Formation' and 'Group' etc are temporally-based terms referring to layers within a sequence, whereas 'Province' is a spatially-based term referring to a particular spatial extent of those layers. Is that right? PaleCloudedWhite (talk) 21:17, 19 February 2012 (UTC)

Indeed! It can become confusing because as our knowledge of geological processes and more importantly, of depositional and erosional histories increases so we are better able to make correlations in both time and space between different 'units' of rock, and as a result, associate these rock units (temporally) into different groups, formations and so forth and (spatially) into various provinces etc. Often new names are conceived, at other times old names are co-opted - in any case earlier associations remain in the literature for years, decades, centuries even, waiting to trap the unwary! I guess a role for the interested Wikipedian is to guide others through this maze. I'm currently doing battle with the 'Southern England Chalk Formation' which seems to have proliferated through dozens of Wiki articles. I am unable to find any original reference to it ever having existed though. This phrase appears to be a fiction which has arisen from a Chalk formation described from southern England, getting mention in the 1911 edition of Encyclopaedia Britannica (see http://www.archive.org/stream/encyclopaediabrit05chisrich#page/806/mode/2up/search/chalk) - a publication which in 2012 has so many shortcomings yet nevertheless has been copied wholesale into innumerable Wikipedia articles. The term 'formation' appears to have been understood in the modern sense of a defined rock unit by wikipedia authors, unaware that it was more loosely defined back then - indeed the word, like so many others, has a tightly defined modern scientific meaning but also a much looser general one; senses which are often mixed to the detriment of understanding. Geopersona (talk) 06:07, 20 February 2012 (UTC)

Yes, I had noticed you had tackled a few of the pages which linked to 'Southern England Chalk Formation' - perhaps you had noticed my own sandbox in that list, as recently I've been chipping away at a gestating 'Geography of Dorset' article (following the discussion which took place at Geology of Dorset a while back), and I had also adopted 'Southern England Chalk Formation' as an accepted term, until I read around a bit and found 'Chalk Group', and realised something wasn't quite right! So these recent discussions have been helpful for me in a particular way regarding my writing of 'Geography of Dorset', as well as more generally. (Incidentally if you have a look at my sandbox and see any glaring errors, feel free to correct them). As a minor contribution to this article, I've slightly re-worded the first sentence, eliminating the "this is the name of" wording - I can recall a discussion ages ago at the WikiProject Plants talk page when it was decided that these kind of introductory sentences ("X is the name applied to a type of Y") were somewhat superfluous, and better replaced by just stating that "X is a type of Y". However, if I have missed some subtlety of geological description, just revert my edit. Cheers, PaleCloudedWhite (talk) 22:06, 20 February 2012 (UTC)

No you've not missed anything, I can be a bit over-wordy sometimes. There's always some tweaking to be done regarding style. Did you notice that I'd thought further about the 'Southern England Chalk Formation' article and considered that there is a place for an article describing the assemblage of landforms which rocks of the Chalk Group give rise to in southern and eastern England? Provided that is, that it does not contain the potentially confusing word 'formation' in its title. Geopersona (talk) 06:38, 21 February 2012 (UTC)

Yes I had noticed your proposal, but hadn't had time to formulate a proper reply. I have now however - it's at the 'SECF' talk page. PaleCloudedWhite (talk) 09:14, 21 February 2012 (UTC)