Talk:Isograd

Plane of . . .

I'm not a geologist, but in the opening definition "surface" seems more likely than "plane". Normally in scientific usage a plane is flat. Musiconeologist (talk) 17:31, 25 August 2021 (UTC)

Update: The OED definition uses surface as do all its examples, so I've now changed it.Musiconeologist (talk) 18:16, 25 August 2021 (UTC)

References in introduction

I've made the first paragraph more explanatory using information from the articles for the various technical terms it uses. But I had to keep its three references together at the end, as I don't have access to the books. I think it would be sensible to check whether they can now be moved to the specific points where they're relevant. Musiconeologist (talk) 22:32, 25 August 2021 (UTC)

Lines on maps of metamorphic terranes

There are several issues with the second paragraph of the article as it stands. Safely fixing them requires more knowledge of geology than I have.

• Metamorphic terranes: This needs a link, but the Terrane article appears to be about a different usage of the term so either is not the appropriate place, or needs clarifying so that it is.
• (or landscapes underlain by metamorphic rocks): unclear whether this is an explanation (that is, . . .) or an alternative (or of . . .)
• An isograd has just been defined as a surface, but now refers to a line.
• the first occurrence of garnet is confusing. First in what respect? Presumably as one moves across the map into a region containing garnet, and then other index minerals, but on first reading I imagined moving vertically into the rock until one finds garnet, then somehow relating this to a line on the map. I think something like the garnet isograd represents the boundary between areas which do and do not contain garnet would be better.

I'd like to add a sentence immediately after the existing definition similar to one of the following, but worded so as to accurately represent the usage within geology:

• The line where this surface and the upper surface of the bedrock intersect is also commonly referred to as an isograd.
• The line where this surface intersects a horizontal section through the rock is also commonly called an isograd.

Alternatively I could just trust the OED definition and change surface to surface or line in the first paragraph, though this would be slightly less specific about what the line on a map represents.

Musiconeologist (talk) 18:01, 26 August 2021 (UTC)