Talk:Santos Basin

bear trap??

On 12 January 2013, an IP added the two words "bear trap" to the article without further explanation: "The Santos Basin is an ... offshore bear trap pre-salt basin." I've not been able to find any indication anywhere that "bear trap" is a term commonly (or even infrequently) used by petroleum geologists to qualify or describe a particular type of basin. Bear Trap Basin is, however, the name of a mountain bike trail in California, so this may simply be a joke. Unless someone can clarify that this term is somehow relevant to oil resources, I will drop these two words from the article soon, as they do not seem to add useful information. Piperh (talk) 18:12, 23 October 2013 (UTC)

radioactive shales

There is a reference to radioactive shales, that seems odd to me, why would shales be radioactive? ϢereSpielChequers 06:06, 5 December 2017 (UTC)

I have removed the word "radioactive". If someone wants to restore it it needs context and more detail, such as what sort of radioactivity and by what mechanism. ϢereSpielChequers 08:09, 21 May 2020 (UTC)

Hello, I didn't see this message in 2017. What is "odd" about radioactive shales? The radioactive minerals in shales is how shales are identified using Gamma ray logging. E.g. see here. @WereSpielChequers: Tisquesusa (talk) 12:56, 21 May 2020 (UTC)

Hi Tisquesusa, I've come across radiometric dating before, so I'm familiar with the concept of background radiation, though I didn't know that shales were more radioactive than other sedimentary rocks. But for a particular bed of shale to be described as radioactive, I would expect something that had made it more radioactive than ordinary shale, maybe not a nuclear leak or Oklo, but something that had made it notably more radioactive than ordinary shale. ϢereSpielChequers 13:32, 21 May 2020 (UTC)

It is the radioactive isotopes in clay minerals that causes this, of course it is not at the same level as nuclear radiation levels, but it is an essential property of certain shales to measure them in borehole logging. The use of "highly radioactive shales" would be thus relative to other shales, not relative to levels of radiation in general. Notably is in those cases defined by the detection method, and when writing about a geologic feature it is common language, it may surprise you, but someone accustomed to shale lithologies and petroleum exploration, as is the main focus of the offshore Santos Basin, should not be surprised by those terms. It is a matter of familiarity with the subject. It would be a bit awkward to explain that "radioactive shales are not as radioactive as you, the reader who is used to read about nuclear physics, may find not so radioactive", right? But good you ask these questions, because that is the only way to learn about these things. Cheers, Tisquesusa (talk) 13:42, 21 May 2020 (UTC)

In general, all shales have a low level of radioactivite bigger than others sedimentary rocks like sandstones and carbonates. But it is only a background radioactivite, due the presence of low levels of potassium 40 (mainly), aside minor levels of thorium and uranium. But some shales may be more radioactives than the ordinary shales, mainly those with a high content of organic mather, and geologist call them "radioactive shales". They are the main oil generation rocks in sedimentary basins. For more details, see: https://petrowiki.org/Gamma_ray_logs GeoPotinga (talk) 21:56, 23 May 2020 (UTC)

Thanks GeoPotinga, that makes sense to me. If these particular shales are "radioactive shales" could you put your explanation in as a footnote or perhaps link to an article that explains this? ϢereSpielChequers 10:06, 24 May 2020 (UTC)