Magma and Limestone Met at America's Second Tallest Cliff: Notch Peak, Utah

[Music] foreign [Music] holy smokes friends it just doesn't get much better than this welcome to the house range of western Utah more specifically uh this peak up here Notch Peak which is a little under 10 000 feet but you can see how sheer that huge Cliff is up there and that uh from the reading I did that is the perhaps the second tallest sheer vertical cliff in the U.S outside of El Capitan in North America pretty awesome thanks for joining me geology Professor Sean Wilson it's one of my favorite places to explore geology it's just it's vast it's desolate there's no one out here um there's no you know like there's just no civilization for the most part um it's just this really Stark landscape where the geology can just take front and center stage and just really Pop um this is an area along the house range where we get this big dramatic escarpment um as a product of faulting Basin and Range extension pushing this Mountainside up while this Valley back down here has dropped down so really impressive uh topographic expression here probably looking at a good mile or so 5000 feet or more between the summit of Notch Peak and the valley floor just behind me um so let's start with some investigation here I think there's some really cool things to look at here I think probably the the two main units that kind of pop out here are the gray um layered rocks in the distance that make up Notch Peak and then closer here in the Middle Ground are these vibrant pink rocks which do not appear to have much layering to them now I thought I was gonna have to hike up a little ways to get a good exposure of them I can see a nice little outcrop over here that what I was planning on walking to but then I started walking up the wash and lo and behold the rocks are right here and so I only had to walk maybe 100 yards from the truck so this was quite fortuitous and I think these exposures here in the Gully are just as good as anything I might see further up the way so let's take a look at these let's start with the pink rocks and see if we can decipher these a bit so these pink rocks are crystalline you might be able to see a few little sparklies there um they look to lack for the most part any sort of layering to them in places at least here as you come down um they're more coarsely crystalline so we've got big beautiful pink uh potassium feldspark crystals and some white quartz in here and then as we work our way down that grades into a little bit darker unit more salt and pepper looking these are hopefully you've guessed correctly intrusive igneous rocks with a texture that allows me to see the visible crystals in them so these would be grenadic rocks I think this is probably a nice true granite or pretty close the one down here is probably a granodiorite maybe even a diorite so these are granitic rocks that formed as magma was underground Cooling and crystallizing some more beautiful pegmatite zones here with the pink feldspars and the white quartz and this little kind of pod right here um so we can see the pink rocks continuing along this way we can also see looking up there's more pink rocks here extending this way and I've been up there before but these pink rocks here out in the distance are the same so that's our that's one of our units here and then we have these gray rocks which are lining the wash here the same gray rocks that make up the high point there of Notch Peak let's take a look at these well actually they're going to look different here so those gray rocks out in the distance are Cambrian age limestones mostly limestones so carbonate rocks that formed at the bottom of the ocean and again this is where geology is so incredible and so just striking that rocks that formed probably hundreds if not a few thousands of feet below sea level are now forming the highest point in this region nearly a full two miles above sea level so those are the gray limestones we can see fragments of them here in the wash some of them have the same nice layering that you see up the way there but what we want to look at here is what the gray rocks look like here and this is just a tremendously instructive and awesome outcrop so what we're seeing here is some of the pink granitic Rock and then the gray and white Limestone or what we think might be the Limestone the Cambrian age unit but you can see there's a intrusion of the magma cutting right across the layers here so technically we would call this a dyke and you can see a little sandwich there of the gray and white rocks sitting in between those two zones if we come over here to this end of the outcrop we can see a much more vertical contact here with the granite on the right and the sedimentary rocks the Limestone here on the left just really I mean these are these are classic textbook examples of what we might see now as we look at these striped rocks here in front of us they they look different than the rocks in the wash a little bit and that should make sense because these rocks are in contact or close proximity to these pink granites so these gray carbonates these gray limestones have literally been baked cooked not just the heat but fluids moving through them has caused them to change character to some degree and so this white material here which was originally a tiny microorganisms and Shelly particles in the Limestone has been partially recrystallized into calcite so the calcite exoskeletons has been partially recrystallized so we might even call this a marble if we wanted to it still fizzes it still has the same composition but its texture has changed dramatically and that's the main unit we see right along here but the contact between the pink granite and the baked underlying Cambrian sedimentary rocks is just really striking here's another interesting relationship here where we've got a little bit of the limestone in here surrounded by the granite then we have a little offshoot of the Granite that intrudes forming a bit of a diet almost a sill because it actually is parallel to the layering here into um those units there and again with the afternoon lighting it's just it's just fabulous it's it really is probably world class um in terms of displaying these intrusive relationships so again pink Granite on top the Cambrian units below what's interesting here and what might be a little bit confusing is you're like well wait a minute the pink Granite was the magma shouldn't it be on the bottom instead of the Limestone and um we just can't see far enough into the subsurface I have a diagram that I think will help explain that a little bit so there is more of the Granite below this section of limestone here is more or less a a little lens or a a small layer roughly sitting in and amongst with all the the magma here and you actually see this in a lot of places in this area so if you come out to painter Springs or just get up against the mountain Frontier in the house range you'll likely see some similar uh relationships but just so cool the zebra it's almost like zebra striped Rock and then you get these nice beautiful sharp contacts with the pink Granite along its margin and then this is another spot where it looks like it's been very much recrystallized I think the dark layers um these I don't think these are going to Fizz a little bit so these are probably areas of the Limestone that had a little bit different composition maybe a little bit more silica or church in them I'm not exactly sure but we can see that they've definitely been cooked and uh metamorphose contact metamorphism right along their margins there so let's go down to the clipboard oh one more view I mean the lighting's just it's just too good I need to probably just sit here in silence and take it in um fantastic and this intrusion has been dated um it's Jurassic in age about 170 million years I was thinking about that earlier and wondering um you know you get these Jurassic intrusions throughout Nevada obviously in the Sierras of California but I'm wondering if this is and it probably isn't but I wonder if this is the Eastward most Jurassic intrusion into North America I suppose there may be some in Arizona that go a little bit further east but this would have to be among the most Eastward intrusions caused by that subduction event and the generation of magma during the Jurassic okay so again um just beautiful this here we have almost a sandwich so here's what I was talking about a little layer of the Cambrian rocks so you can see it running back through there so we have Granite below okay intrusive igneous rock we have Granite above and then we just have a little sandwich of a little leftover chunk of the Cambrian rocks so these magmas were intruding in places parallel to the layers forming Sills we saw a couple of dikes back there but it looks like at least here a lot of the intrusive activity was parallel to the layering in the um in the Cambrian rocks in the limestones so okay back to the clipboard so here's hopefully this is somewhat helpful here's a diagram I threw together just a minute ago um let's see if we can make sense it's just a simple cross-section highly simplified west to east here's Notch Peak up here I wrote the actual elevation 9658 feet I'll add the meters in there as well it's all made of these Cambrian mostly limestones there may be a tiny bit of ordovician rocks along the top but let's just collectively call it Cambrian it's all tilted to the east so you have this very steep West face that forms this big huge continuous Cliff but the east side is more of a what we call a dip slope it it dips very gradually back down to the east then near the base of the cliff or in the the middle ground as we looked uh towards the mountain front there we see we have lots of this pink uh intrusive rock the granite or granodiorite but then we have just these little lenses and pieces left over of the Cambrian um limestones that are left here and that's kind of what we're seeing with some of these outcrops I've showed you little sandwich structures there might be places where um the magma actually cuts into it I try to draw a little tiny dike pushing up into the the limestones there sorry about the bad artwork and then of course everything's bounded on the on the west with this large normal fault that's uplifted the house range so this would evolve so we if we put together the whole sequence of events our oldest unit here or these Cambrian limestones deposited uh on the edge of North America but under hundreds if not a few thousand feet of water so these shallow to deep water limestones and then our next event fast forwarding quite a bit would be into the Jurassic period so these units would have originally been flat lying horizontal the magmas intrude into them in a variety of ways and then the whole thing get and this would have happened underground and then the whole thing gets exposed and shoved up to the surface by Basin and Range extension and this large normal fault here along the western boundary of the house range so just fantastic and spectacular I'm obviously giddy I hope you are too um just beautiful country beautiful geology here in the house range so I hope you enjoyed that thanks for joining me uh feel free to like share subscribe all those things are helpful just trying to promote geologic education get people excited about getting outside looking at rocks and Landscapes and learning um also if you want to donate there's ways to do that there's a thanks button the bottom right of the viewer at the bottom right of the what you're looking at right now and then under each video description there's a PayPal link and then there's also um a donate button on the banner of my home page so thanks again for joining me from the spectacular and beautiful house range of western Utah here in the Basin and Range province

Channel: Shawn Willsey

Views: 58,632

Keywords: shawn willsey, geology of utah, notch peak, jurassic intrusion, painter springs, notch peak geology, house range utah, cambrian geology, basin and range

Id: strox6p35wk

Length: 15min 17sec (917 seconds)

Published: Sat Sep 16 2023