tag:blogger.com,1999:blog-8693614218792476252.post4448128113121955429..comments2024-03-09T08:06:26.066-08:00Comments on Looking For Detachment: Mapping Upside Down?Silver Foxhttp://www.blogger.com/profile/03131032620978696727noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-8693614218792476252.post-51289625946743267802008-10-29T08:47:00.000-07:002008-10-29T08:47:00.000-07:00Howard, thanks for the alternate explanation - and...Howard, thanks for the alternate explanation - and that's something I didn't realize about the oil patch. In this particular case, I think the section was first described on the ground, and that there hadn't been any drilling for oil. It's possible the oldtimers doing the section had worked elsewhere in the oilfields, though. I'll ask if I see them sometime in the next year or two.<BR/><BR/>I've done a fair amount of drilling for minerals in my time, but our sections have usually been described on the surface first, so are in the usual order - and also, the drilled intervals aren't hardly ever deeper than 2000 feet!Silver Foxhttps://www.blogger.com/profile/03131032620978696727noreply@blogger.comtag:blogger.com,1999:blog-8693614218792476252.post-55278560909793462592008-10-28T19:56:00.000-07:002008-10-28T19:56:00.000-07:00Another possible(?) explanation:Maybe the section ...Another possible(?) explanation:<BR/><BR/>Maybe the section was described by an oilfield geologist! We're used to looking at beds from the surface downward, in the order they are penetrated by a drill bit. Though it is of course stratigraphically backward, it's a common practice in the oilfield, especially when doing informal mapping and naming/numbering of units. It's counterintuitive to say "the 1st unit we penetrated was unit 4, the 2nd was unit 3, the 3rd was unit 2...".<BR/><BR/>Perhaps your section was mapped by someone who was trying to compare the outcrop section to his/her subsurface work, and numbered the units to coincide with an informal subsurface nomenclature that had been developed.<BR/><BR/>I can think of a couple of examples of this upside-down terminology coming into common use. Here in the Alberta basin, early workers nicknamed the oil-producing Devonian rocks "D1" (Wabamun Fm/Gp), "D2" (Nisku Fm.) and "D3" (Leduc Fm.). They were numbered in the order of penetration (youngest to oldest). Similarly, a project I'm currently working on, in SE Saskatchewan, has units labelled "M1, M2, M3" from the top down.<BR/><BR/>Cheers,<BR/>--Howard (geologist, Calgary, AB, Canada)Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-8693614218792476252.post-87088645445821429992008-10-05T18:11:00.000-07:002008-10-05T18:11:00.000-07:00Hmmm... that would really screw things up in the G...Hmmm... that would really screw things up in the Grand Canyon. I would have to re-learn the section. The Redwall Limestone would end up above the Navajo Sandstone, for one thing. And maybe the Chinle would be first? Or should we do it alphabetically from the top down??!Silver Foxhttps://www.blogger.com/profile/03131032620978696727noreply@blogger.comtag:blogger.com,1999:blog-8693614218792476252.post-46257756527242483932008-10-05T08:30:00.000-07:002008-10-05T08:30:00.000-07:00This reminds me of one of our student's exam howle...This reminds me of one of our student's exam howlers ...<BR/>[Superposition:] a very simple concept ... continued to confuse many geologists of the past as it was firstly believed that the rocks were placed in some form of alphabetical order.Anonymousnoreply@blogger.com