Exotic W: Plutons

trying to be positive trying to be uh mature about this this is take two we just did a bunch of thank yous it's the holiday time everything was going very well here in the front porch it's a beautiful afternoon and um as soon as i was ready to start the thing blurped and went away and i tried everything i turned the phone off i went back turned it back on multiple times everybody was still in the live chat and i said we're gonna have to start a new stream we've done this a couple times before so it doesn't phase me quite as much as it did before but if you're watching this in replay form and this is the beginning of this pluton show you're gonna have to wait just a couple minutes because i want everybody to from the old stream to find us on the new stream so the local time is 208 and we will begin this program on plutons at 2 15 and just keep our fingers crossed that we won't have another problem 2 15 will be the top of the program uh mere seven minutes from now so hopefully that will give us enough time to gather people so thank you i see we have 138 140 150 coming over now would you mind a couple of you going back to the old stream and helping people find us if that's possible and wow thank you this is a program on plutons we will begin momentarily at 215 local time seven minutes from now you are welcome to come back sunday morning 9 a.m baja bc actually these two shows kind of work together so this is kind of uh i'm not sure how much we'll get into it with baja bc but we'll introduce baja bc to those that don't know about it before we quit today if we are allowed to continue here my goodness so i think in the the five minutes that i have i want to do a couple of quick thank yous that i just did before but i i want to just share that beautiful work so thank you to pat and karen miller in yakima who sent these beautiful handcrafted pens made out of green stone one of these is for chris mattinson the professor who was in my backyard a few weekends ago [Music] a pink one is for liz i'm going quickly because i already did this 15 minutes worth this is a brand new fruitcake from vinman's bakery you've got to love it in downtown ellensburg jeff i didn't really need another one i was kind of half kidding but now that you've made it a custom made fruitcake number two for me this one's a little different i almost don't want to do anything to it it's so perfect but i don't know maybe sunday we'll have a slice together and i'll i'll give some thought on how to do that but thank you jeff i thanked bonnie from bellevue for the wonderful gift card to vinman's bakery i thanked julie from prosser for these chucker cherries to be used as props for uh plutons in the fruitcake in fact i think it was in mid bite of a chucker cherry acting as a pluton my neighbors down the street uh thank you andres and shirley thank you for the wonderful christmas cookies holiday cookies i really got to stay away from cookies like that i don't want to balloon back up thank you to larry and lake oswego for the beautiful gift card for from cornerstone pizza in ellensburg we will use your gift card tonight we're celebrating a few things here in the house and from wire gold i know that you saw in the previous live stream but i want to thank wire gold for his beautiful samples wiregold lives in snohomish and he's been collecting for more than 20 years and he has some beautiful mount stewart batholith samples and some other things as well that was rushed and quick but hey i hope you can understand let me get my laptop re-connected we have more than 400 that have made the switch that old stream i guess is going away i don't such a shame but um yep there's one person still at the old stream so 400 people uh jumped uh jump ship to the to the new stream so i'm grateful 440. i don't know if it's on my end i guess i gotta if i do a lot more live streaming in 2021 i guess i need a new system i guess i need to be hardwired and everything else and a bunch of you have been very kind with your advice but if it's not me and it's youtube then i don't feel so bad and it's just kind of like whatever that's it's pure magic that i can even do this but regardless of how much planning and rehearsal and everything else getting everything just right and turning stuff off turning it back on still have major problems so so my watch says 214 could you give me one minute please uh to get my heart rate down just a little bit and just to think about the topic today and we shall begin more than 500 now that's good okay so here's to you for uh working hard on your end to find this new stream and uh let's pray to whoever needs to be prayed to to make sure that this stream doesn't go away here thank you we'll start in one minute well a pleasant good afternoon to you all welcome and thank you for joining us here in the front porch on a beautiful friday afternoon here in ellensburg washington we still don't have snow on the ground here in town we do have up on the ridges and we continue with our exotic terrain series both this afternoon and sunday morning it's baja bc weekend and we've been waiting a long time to deal with this i've been teasing baja bc throughout the fall when we started this series and i'd like to start by reminding you of the two main reasons that i've been doing this live stream series on exotic terrains a to z main reason number one is that every morning and i'm not exaggerating every morning when i walk down the stairs heading towards the north from my neighborhood i see the stewart range if if the clouds allow and i always have conflicting feelings this is 30 years now of conflicting feelings part of me goes god that is a beautiful mountain range and i'm so lucky to live in a valley that has that view every morning the stuart range in mount stewart to the north of town a beautiful jagged teton-like skyline it's amazing but my other thought almost simultaneously is i still haven't sat down and learned the exotic terrains of northern washington of the north cascades and beyond mount stewart i'm pointing to the north now beyond mount stewart is this complicated fruitcake of exotic terrains and i never have sat down to figure it all out and i haven't because i know it's not going to take me just a couple hours to figure it out i need to have a sustained effort to try to learn even the basics about all the exotic terrains that are up in the pacific northwest's north cascades exotic terrain country the crystalline core et cetera well i feel very good i feel very good for the first time after 30 years of living here and teaching here as a geology instructor i know the basics now and you would have thought that i'd have this long ago but i i didn't and i do now the other reason i've done this exotic terrain series this fall is because i'm part of a collaboration with three research scientists who are going to spend the next few years with their graduate students from purdue purdue university nevada reno and san jose state those professors are michael eddie stacia gordon and bob miller they're going to be working in this area and mike in particular is going to work with a lot of plutons and so this topic this weekend we've only really looked at one pluton so far right that's the mount stewart pluton the mount stewart batholith but this area is just absolutely riddled with plutons and it was my choice it was my choice for this a to z series to assemble the fruitcake the best we could up in alaska yukon british columbia northern washington fruitcake exotic terrains stacina quinelli everything else right and we've ignored the plutons we've ignored the plutons and i thought that was a smart move and i still do think it was a smart move i don't see how we can study the fruit fruit cake if there's all this stuff interrupting it but here we are towards the end of the alphabet and we are finally ready to deal with the complication because we've made the fruitcake i mean i tried to disassemble it and then put it back together and restore the fruitcake last time didn't work so well if you recall but if we're having plutons invade the fruitcake we've got to have the fruitcake to start with don't we and we have done that by now we have assembled piece by piece sometimes in groups these complicated areas in northern washington and crossing over into southern british columbia so what are the goals then today one main goal is to realize that mount stewart pluton the mount stewart batholith is just one of hundreds and hundreds of plutons and so i want to plug mount stewart which we decided long ago was 96 to 91 million year old granitic material pluton that's just one of hundreds and hundreds of plutons of that same rough vintage and i want to plug mount stewart into a more regional story and ask some significant questions that are still unresolved but also share some exciting work that's been done over the last 20 30 years that i find interesting and hopefully you will too okay he goes to the introductory folder let's see what's inside oh yeah oh it's i'm getting nostalgic now man this is way back in september when i was outdoors and we didn't have plutons then we didn't even i didn't even know the details of these terrains back then but we've done a fair amount learning each constituent within the fruitcake and putting them in at different times and realizing that there's an oceanic history for much of this no plutons here even here in the north cascades we've looked at this a number of times i keep adding colors and different names and strike slip faults the straight creek fault and these other faults as well the melange belts was my our most recent visit to the fruitcake it's all assembled now we're waiting for something next to happen recall please that the only pluton that we looked at was the mount stewart batholith and here it is offset i've showed this to you more than once offset by the straight creek fault 100 miles of offset a dextral strike slip fault with the western side of the fault moving north between 50 and 35 million years ago last time if you recall that we're still just trying to get into it here last time we looked at one scientific paper by sandra wilde and others 2006 a 15 year old paper and the whole point of that session last time called restoring the fruitcake was to try to put the fruitcake back together as it was a hundred million years ago by taking all of the strike slip faults that have been mapped over the last 100 years most of them's dextrol might add most of them right lateral and restore each of those guys and our centerpiece was this map here which i held as a freeze frame so i won't do it again necessarily right now but we realized that many of the northern washington and even southern bc terrains were a hundred million years ago according to that paper in southern oregon in northern california and we took things that are in today's northern washington and restored them a hundred million years ago using known strike slip faults and we got a bunch of that stuff down and connected it with places in northern california and maybe you felt like hey that's pretty significant like wow we move things like 500 miles to the south or 300 miles to the south or in the case of rengelia maybe more than 500 miles to the south feeling pretty good about ourselves well today we're going to move things more than that this is the minimum amount of translation that if you are talking about north cascades terrains and the main point from last time was you have to have hundreds of miles of northward translation of a bunch of these terrains just based on the known strike slip faults that we have in the north cascades and into bc case closed no discussion you you just you just can't have zero uh northward translation we already made that point in the last session oh you need it maybe you need it so we said today there's this columbian payment that separates these terrains in northern washington with some of the known terrains in southern oregon let's say but if we go back in time again this is last show we move the northern guys to back to where they came from and we can connect them up with exotic terrains uh down in southern oregon northern california okay that's where we left things we had a functional live stream then do we still i guess we do we have more than 600 now that's good i'm done with the introduction and notice we didn't talk about plutons even last time because we don't know any plutons well let's change that let's go to folder one which is new stuff this isn't folder one but i'm reminding from day one we reminded ourselves that most of our drama was going to happen between 250 million years so right off the bat i want to establish that there are plenty of plutons in the pacific northwest that are younger than 50. we don't care about them today if i do a live stream series on the most recent 50 million years in 2021 we will be very interested in those plutons but we're not interested today we are interested in the plutons that hover around 100 million years ago daddy's freelancing already daddy's freelancing already you notice i don't have my wireless microphone i decided maybe i have a stronger sound and a stronger voice just using the mic on the camera we'll see so i get confused with early mid and late jurassic and so i always have to refer to my little uh uh envelope and as we've done a number of sessions now and we will again today the main interest is quote unquote the main event a hundred million years ago the mid cretaceous if you get into this exotic terrain reading or learning or whatever in different forms the mid that phrase mid cretaceous keeps coming up well they're basically talking about ish 100 million years ago and i did a couple of zoom calls on wednesday not something i normally do but i wanted to visit for this show i wanted to visit with basil t coff back in madison wisconsin and john garver who teaches at union college they both had long careers involved in these terrains and they both reinforced they've seen a little bit of our stuff not a whole lot that's fine they're very busy so i don't think they realized how hard i was hitting the 100 million year old event but basil in particular is like saying i think the future work is going to continue to have people looking very carefully at this 100 million year whatever happened at that time so our first major message is we want plutons on either side age-wise of the mid-cretaceous you know 20 million years younger 20 million years older so if you're curious what pluton first of all if you're curious what a pluton is i guess we got work to do but if you feel comfortable with what a pluton is or a bunch of plutons together of batholith we want to look at batholiths or plutons that are between 120 and 80 million years ish okay that's our topic so now i'm ready to go to folder number one and i've showed you this before this is a map from bob hildebrand and i'll be talking a fair amount about bob today bob has been incredibly prolific in the last 15 years and one of the most impressive things that he does is create these absolutely stunning looking maps i don't know how he does it and i don't know how many how much time goes into every one of these maps but this map should look somewhat familiar to you plutons different ages we're mostly interested today in now we're gonna have a different color scheme of course i have to create my own color scheme some sort of egotistical person i don't know you know everybody has a different color scheme but notice we do have there's mount stewart and the mount stewart pluton which ages which ranges in age from 96 to 91 million years old are you got your bearing ellensburg washington's down here this is looking familiar isn't it it's kind of familiar here's the the stuff that went down the geologic elevator and came back up that's stacia gordon country uh the metal we had all that sediment coming in we'll come back to the metal on sunday morning so there's plenty of plutons here just in northern washington just in the north cascades but i'm saying we don't care about most of them we don't care about these or these or these i guess that are undated we just want those plutons mid cretaceous ish 120 to 80. so right off the bat you can see just in northern washington mount stewart did not act alone was not an invasion by itself speaking of wish i got an email from kyle kyle i don't know where you live but thank you for this kyle uh kind of played off the idea i kept saying these plutons are eating up from below they're invading the crush from below so here's kyle attention earth people this is an invasion of the plutons terrains versus invasive basalts cascades british columbia baja featuring professor nick zettner with bijou the cat oh that's right the old stream had bijou the cat and uh the new stream that i just started because we like the old one so beijia is going to end up on the cutting room floor that's too bad thank you kyle for that so you have seen this before that i've already showed you that there's this incredible belt of plutonic material stretching from northern washington mount stewart's at the very southern tip of this thing you're going to hear this a lot today coast plutonic complex up through western bc crossing through the yukon getting up into alaska we really have three batholis that we're featuring today and this is one of them the coast plutonic complex of british columbia but we're just getting we're just getting started here uh are we yeah we are this is not looking at plutons but it's trying to reinforce i like it it's from one of those roadside of southern british columbia books it kind of shows our area that we've been studying very carefully the northern cascades of washington we're just kind of showing that that can content continues whoa so plenty of the geology including the plutons are going to continue across the border in a general way so they're not showing our straight creek fault of course but this is a regional story you're kind of feeling that now i think from me this is this is not an isolated event tiny mount stewart the tiny mount stewart pluton what do i want to do here hang on i thought i had these organized ah yeah i'll do i'll do this and then i'll and then i'll move on to the next little phase here i think i've shown you this one too but this is an even more complicated map where i took my colored pencils out and just showed mount stewart all these guys we know that they're not all the same age we know that some of these plutons are very young now if you're guessing you're new to us you're not sure what a pluton is think a blob of magma in the subsurface liquid magma a big pool of it cartoonishly just a big room of of orange liquid magma okay and if we cool that off we're gonna form a plutonic igneous rock so it was liquid it's not plutonic rock yet it's just magma but if we cool that off we cool that magma chamber off in the dark and we we turn it to stone it becomes a pluton and if there's a lot of these plutons dozens and dozens of them kind of together we call that a batholith so batholith is more of kind of a size term a quantity term a whole bunch of individual plutons together is a batholith okay i want to cut to something quickly i mentioned those three plutons where are they pluton if the drinking word is pluton you're screwed by the way so a bunch of plutons together batholith here are the three batholiths to study today let me slow down and give you a chance we just looked at this one a little bit here's the straight creek fault this is obviously me drawing on some sort of whatever so we have our offset our 100 miles offset of this is pretty much the crystalline core so another major message our crystalline core which had the stuff that was dropped more than 20 miles into the crust and then brought back up there's so much plutonic material there that we're lumping that in with this massive coast plutonic complex the cpc and again mount stewart is just the the southernmost little dot i mean it barely even shows up on this map so maybe that's new to you that mount stewart is not an isolated thing it's part of this incredible welt or family of plutons known as the coast plutonic complex mostly in canada in british columbia and then further south we have an american batholith and we have a mexican batholith so we got canada u.s and mexico i promised we were going to be far-reaching at some point well here we are so at least in the u.s in geology most people know about the sierra nevada batholith making up much of eastern california and that's the same baffle lift that we you have used in the past remember we had a piercing point to measure the 300 miles of offset recently in the last police boy ambulance boy in the last 18 million years we've had 300 miles of offset on the san andreas fault but this is the pluton that we're talking about today that also is not alone so this guy is a mid-cretaceous batholith you're starting to see it major mid-cretaceous batholith major mid-cretaceous batholith and another one the peninsular ranges batholith which is mostly in mexico baja california mexico but there is some of the peninsular ranges batholith in socal in southern california approaching los angeles these we're going to be comparing and contrasting between these three basilisks and somehow saying something significant about the american west okay i'm really improving here i had a plan but i'm junking it in real time uh this i forget where i got it but is showing a little bit more alaska down to central mexico peninsula ranges baffle this year nevada batholith they're not labeling it but here's our coast range pluto a co coast plutonic complex now there's the idaho baffles we're going to ignore it today there's some other battle lists we're going to ignore them they don't have the right age or a couple other things there's reason to ignore them okay well let's get to the improv then oh i'll do it this way so we now know where these three major batholiths are we all know that they're generally mid-cretaceous and you know that's between 120 and 80 million years train boy what are you imagining created all this magma in the neighborhood of 100 million years ago why do we have all this magma do you have a mechanism in mind now you're a fan of geology so you've done reading you've taken geology classes possibly what is is there a conventional answer to that is there a new answer to that the answer is yes and yes and this is going to sound familiar to the current siglock show that we did a month ago here is the main mechanism that today it's the majority opinion about at least the sierra nevada batholith and for many also the view for these other two major batholis as well in the mid cretaceous you've got it in mind maybe you've already typed it down it's this it's that sometime during the mid-cretaceous let's say our window of time that we care about again today 120 to 80. we had a major ocean plate in the pacific ocean most people call it the fairlawn plate depending on what time you're talking about and that big ocean plate is eastward subducting subducting towards the east diving underneath north america and diving to the east and this is subduction of course the process of subduction almost everybody here knows what that is it's taking one tectonic plate and sending it underneath another uh many view this as a pulling mechanism that once you get this stuff down deep then you're just pulling on the rest of this ocean plate so instead of cramming the ocean plate underneath you're kind of once you get it underneath you're you're pulling it and almost gravitationally pulling it i don't know what i'm talking about now by the way but this is the general mechanism to create a bunch of plutonic material and if you cool that off it becomes plutons and if there's a hell of a lot of it sorry patrick it becomes a batholith this is what most people have in mind for the sierra nevada bathulet here's another picture of the same thing by the way it's not just this subduction generated eastward subduction creating the batholith the sierra nevada batholith in california there's other features that go along with this as well this is known as the california triad three things together is telling us that we have eastward subduction and a creationary wedge which we've talked about before i think i've shown you this cartoon a few times a four arc basin this is the basin you cross before you get to the ark haha okay so this is geology 101 as it's been taught forever including by moi that's french do i need to show you this one i showed you this i don't know last weekend just what i said right eastward subduction major plate applicable to many batholiths or large plutons around the world but are there other ways that mother nature creates plutons is it always a subduction story to me that's the first interesting question of today are we sure these guys are from subduction and if we're sure they're from subduction are they from eastward subduction where we had ocean plate coming west to east and diving beneath now i've already tipped my hand a little bit haven't i especially recently i keep saying if there's a bunch of strike slip faults that means we have oblique subduction that means we have major times in our geologic past along the west coast of north america where we did not have an ocean plate coming head on but we had an oblique subduction in some cases an ocean plate heading true north that's coming more sunday than it is today but let's just go ahead and go back to the basic question i'm asking right now why do we have incredible batholiths all about the same time along the west coast of north america is it simply [Applause] an eastward subduction story and oh by the way they're going to stop at 80 million years ago the sierra nevada batholith in particular but others as well they just stop the plutons just stop the magma hardens and there's models like this one saying well we we stop we change the angle of the subducting plate and so we no longer have magmas here we have them further east that's never set well with me by the way but we don't need to go there today we're ignoring the rocky mountains all together today okay i think now i'll finish out i know the major next major thing i want to do but let's just finish out this little introductory folder so here's one of our bath lists today the sierra nevada here's just the northern tip in california of the peninsula ranges batholith then we got some kind of no man's land here in the mojave that's kind of a puzzle for a number of reasons [Applause] same kind of map there's our sierra nevada batholith that abruptly stops because of strike slip faulting down in southern california much younger than our strike slip faulting by the way and then our peninsula ranges i'm just trying to kind of just let this sink in a little bit with you we have some video field reports today one from shirley in tahoe lake tahoe area and she's not going to take us into the plutonic rock of the sierra nevada mountains but she will give us a quick little tour of some stuff that's from older exotic terrain times quinella cash creek remember in the foothills i think i know you'll enjoy that from shirley and then i just grabbed this this is also from bob hildebrand uh just up in the squamish area so we're back up in british columbia just showing all the the plutons of various ages you know bob's pretty famous for that kind of visual sense he's so good visually that's folder number one what's next it's about to get wild are you ready about to get wild are we doing okay by the way on this new stream i keep seeing comments come by so i assume i assume we're functional but i'd like to just take a second if you don't mind okay todd's with us tom john saber dale lars dan i'm gonna keep going until i see a female name mardine okay good okay there's more than one possibility for creating a lot of pluton material so let's open our mind up for just a second we don't have to be aggressive we don't have to be angry we don't have to be ah the old guard is all they don't know what they're talking about us new guy look at me i'm not a new look us new guys we've got these new ideas you know now we're not doing that but let's just think worldwide of other places that we're generating large volumes of magma so we have talked about this to this point today correct and that's probably what you had in mind i'm guessing for our plutons here in the american west now you know the concept of a deep mantle plume and a geologic hot spot and a moving plate over the top we're generating large volumes of magma in that situation i'm not saying that's the story for these battleless today but just hang with me please and also in the middle of the atlantic ocean floor or the east pacific rise we have the opposite we don't have collision we don't have one plate moving we've got a divergence we have two plates going away from each other and we're generating large volumes of magma there of course these are different chemistries there's lots of differences between this but i'm just trying to think very basically about how the world creates large volumes of magma and so far in my teaching i've presented this in fact pretty early in the quarter i kind of do this with my students and say here are the three ways that plate tectonics creates large volumes of magma i've never done this so this is brand new to me and it's not particularly common for geologists to embrace the idea or even know about it it's a pretty new idea although i think it's been in the literature in minor amounts over the years but it is a major pluton generator even a batholith generator favored by one particular author over the last 15 years slab failure bob hildebrand so those two names those two phrases need to go together for the rest of today and this is not going to be a bob hildebrand festival for the rest of today or beyond but i've seen enough of bob hildebrand's stuff talking about slab failure and for the first i don't know four or five times i sat down and reading this stuff i'm like i don't even know what slab failure what does he mean i don't even get it well let me show you an animation that i've used for years and i never really thought about slab failure before i got to go find the other laptop hang on would you don't walk into the corner i'm on the old i'm on the old stream there i'm not even going to go cozy fort i think you can maybe see this with a little bit of reflection and i've got this on a loop this is probably tanya atwater i'm not sure who made this thing but tanya atwater made a lot of interesting animations out of santa barbara uh 20 years ago maybe so i've used this for years talking about the creation of the himalayas and of course our this is on a loop uh of course our eyes are drawn to these yellow things and those are continents and depending on how experienced you are with geology you can recognize that this is uh india coming north and colliding with the soft underbelly of asia and creating a continent versus continent collision the himalayas or the himalayas if you've been in school too long and so this collision continues today of course there's absolutely tragic events involving earthquakes in many countries uh along this suture zone between these two continents and i guess i've noticed that when you i don't think i want to pause this or maybe i should hang on can i do this pause oh sorry patrick i can't pause it i'm 58 years old i can't pause this thing so when we start this little animation each time it loops notice that there's an ocean basin we're going to close an ocean basin and just in the first little part i should come on now i got to be able to do this daddy can do this so this is ocean floor that is subducting beneath asia and as this continent gets closer and closer to the this continent we are making this ocean basin get smaller and smaller are we not and this is a slab that's going all the way down to the lower mantle we learned from karen ziglock's lecture but what i want you to notice and it's going to happen so quickly that's why i have it on a loop muffler boy [Music] i want you to notice that as soon as we collide these two pieces of crust up here at the surface i want you to notice that this slab is going to tear away maybe you already noticed it we're going to break this slab that's in the subsurface and we're going to tear it to the point where it breaks free and the only thing that's not on this animation that we want to include here is that there's a stenosphere material this is the model this is the slab failure model there's a stenosphere that's going to surge to the surface through that broken area and whether it's eastward subduction or westward subduction we're going to have this massive magma generator shortly after the main event are you ahead of me you probably are can you play this thing because i can't slab failure right there did you see it let's wait for the next go around it fails right there the slab just failed did you see it it detached the ocean crushed right after the collision detached and a bunch if we want to add to this animation magmas right there and magmas are going to come up and invade the hanging wall or the foot wall or the suture itself but the concept that bob hildebrand is pushing maybe too hard i don't know feels kind of desperate as far as the the regularity and how everything is brought back to slab failure but it's an interesting idea to me and i want to entertain it in this series especially if we're talking about westward subduction instead of eastward subduction those that are ahead of me are already seeing north america [Applause] blindsiding a fixed insular terrain in the pacific and westward subduction as the ocean basin is closed and magmas i'm giving away the rest of the lecture and magmas surging to the surface including mount stewart including the coast range complex coast plutonic complex i always struggle with that including the peninsula range batholith as a direct result of a almost a delayed thing it's a one-two punch collide and then invade collide break off invade collide break off invade with magmas can you see it you don't have to love it i mean you gotta love it you don't have to love it you can do what you want but i'm interested in this idea and i'll be very interested to see if this becomes an idea that is embraced by more than bob now what evidence do we have for that well this guy i mentioned he's incredibly prolific that's an understatement here's a paper from 2013 mesozoic assembly of the northern north american courtyard it's more than 100 pages it's a special paper of 495 and if you just type in roberthildebrand.com i think you can get to a publications page and you can just see all this without i mean i printed it all out i didn't have a stapler big enough i had to go 20 pages at a time and he's got an equally impressive 2017 special paper the tectonic setting and origin of the cretaceous battleless within the northern american courtier he teams up with joseph whalen special paper 532. i mean these are this is like magnum opus or whatever the phrase is part one part two he's got all sorts of other things this is all just in the last decade and what i am attracted to of course are the visuals his maps are so great i don't know enough geochemistry to understand his plots but he approaches it with the way that i like to approach things which is far-reaching it's synthesizing a bunch of individual research camps and trying to put those things together in some sort of coherent uh picture and from experience i know that if you're not a specialist if you're not in one deep research whole with three or four other close buddies if you're not in the hole with them then you're not really part of that you're not really part of the club so i don't know i'm not sure what you're up to but you're not in with us so there's a lot of sociology among geologists like most groups in the world doesn't have to be science and so i think it's fair to say most don't really know what to do with robert they don't really know what to do with all bob's work and as i ask around and talk to a variety of people i don't think they've spent much time reading his stuff i did talk to him for an hour on the phone once a couple years ago and that's one message i remember him saying says that people don't even really read my stuff i mean it's all there well there's a lot there to absorb and i've done my best this week to go through your stuff bob if you eventually see this and i want to pull out a couple things that i'm excited by that are just data one of the things he does now is make these beautiful maps but he synthesizes a bunch of reports and comes up with basic observations on a regional scale which that's really what i like so let's leave this lab break off or the slab failure for a second please don't be fixated on that maybe you're interested in it but let's not get fixated on let's go back to just some data data that i haven't seen put together before quite like this again this is bob hildebrand robert s hildebrand so hang on hang on hang on pantry oh i smell fruitcake so what does bob have for us as far as a little bit more detail about the plutonic rocks the plutons within these three major batholis well he has plenty he's got a whole paper a 50-page paper just on the peninsula ranges basilisk but i found this last night and i found it very interesting and then i slept on it and i wrote i sketched these out about noon today so let me slow down for you so here's two of the three batholis that we're discussing today correct i'm not showing you british columbia yet and i didn't realize this maybe you did that in both of these battle lists there's kind of a split personality so i just grabbed two random colors sorry patrick i didn't you know i don't have declarations for these colors i forget what these are i think this is hot pink actually but can you see these are numbers in millions of years this is the granitic stuff now the plutonic rock in these two batholiths and we according to bob's work again he's just taking all this work by others and kind of putting it together kind of like i do i didn't realize that the western half of these two bathylets have rocks that are older than 100 million years old and the rocks in the eastern half of both of these battleless have rocks that are slightly younger than a hundred million and that depending on who you talk to there's a racing stripe rat down the middle of both of these battle lists that are at about 100 million years now whether that's i don't think that's plutonic material that's 100 million years i think that's evidence of collision whether that's daryl collins pizza boxes and naps on thrust faults whether that's something else structurally whether that's um deformed metamorphic rock i'm not exactly sure to be honest but i've never seen this before that there's a pretty good match with the split personality of this year in nevada batholith and this the split personality of the peninsula rangers baffle like they're the same thing like from this presentation looks like these two guys were connected maybe at one time i'm not saying that right now but i'm just showing you some startling similarities between these two bathulus you okay now i got the same color scheme from our third guy looks a lot bigger because i used a different scale let's go up to british columbia mount stewart is down here there's my front porch washington british columbia vancouver island that's rengelia that's not part of this story but here's this hang on i i feel i need to orient you so we were just looking here correct now we're going way up here right and apparently running right through the middle of the coast plutonic complex is also a racing stripe also this i'm less certain on now from just quickly going through bob's stuff last night is this also 100 million years i'm not sure but notice that we don't have the older stuff in the west and the younger stuff in the east here don't have that what we had in socal or central california i also don't really know and you see my big question mark here i don't think bob did this actually bob hildebrand i don't think he swung this in fact i'm sure he didn't into northern washington but i'm wondering if if we've done so much restoring of the straight creek fault in past episodes if this is truly a split personality thing in the coast range in the coast plutonic complex can we follow it across the straight creek there's question marks all through here i have way more question marks about the bedrock plutonic rock in the coast plutonic complex than i do with these two guys here but that was new to me and maybe new to you let's go back to these two guys that match beautifully according to elder brand and others i gotta say it one more time hildebrand does what i like to do he takes hundreds of individual scientific papers he kind of works through each of them tries to grab a few major concepts a few major dates and maybe he sees those dates change as the technology gets better but he has a way to synthesize things where most of us just get overwhelmed we just read everything in equal weight and we can't pull back and see a bigger story that's what hildebrand is doing and i i like that part of what he's doing now i'm a little confused by people's reaction to him i just saw uppercase it's more technical nick if you mean it's more complicated of course it is okay let's not that pushes a button with me by the way you know personally that pushes a button you didn't mean it that way probably but what i do is trying to do this synthesizing thing as well and when somebody comes back and says well it's way more complicated than that what i hear when you say that to me is you're not as smart as i am i know all the details that you obviously don't get and the reason that's a frustration to me you're probably smarter than i am so that's that's that's no problem but the problem i get into i shouldn't go in this tangent problem i get into is that nobody appreciates science because it's all too complicated for a regular person to understand and then before you know it we got our president drinking clorox on national television because nobody has any idea what's going on in science because it's so complicated all right that's enough of that back to hildebrand so he's finding a couple other interesting parallels on opposite sides so we're back to my little thing here both in the sierras and the peninsula ranges batholith there's a change in silica content from west to east is it truly this major jump from west to east according to him it is i don't know if it truly is or not and now that i say that i think he's showing some of the younger plutons at least in the sierras are eating into this line and invading a little bit more here but there's this interesting change in general from west to east from mafic or darker colored granites to lighter colored granites and sure enough they're invading a bunch of the friends that we had them invading in the north cascades these are familiar rocks to us the green schists and the amphibolites and the enigmatites that's the country rock with many of these places so it's always tough to go a state away or a country away and make convincing cases that you're looking at the same stuff but this weekend we're doing some of that and that's why this continues to be a controversy quote unquote because it's it's tough to find the smoking gun to convince people everybody that you're looking at the same stuff a long way away i'm just throwing out ideas so if we're back to our west our eastward subduction you can get the sense of look at all these plutons each of these little guys each of these little chucker cherries julie is a pluton but their family together muffler man the family together is a batholith in another bath with etc so can you do that with the changing angle of the fairline plate or do you remember what hildebrand likes hildebrand likes slab failure for each of these guys with westward subduction of the ocean floor beneath the insular terrain we're not going to hit that hard today we might uh in show z but just letting you know that the old idea is this is fairlawn plate eastward subduction the new idea from hildebrand and just a couple of others so far is that this is westward subduction beneath the insula the insular comes in and we're getting a bunch of younger plutons with that slab failure tear thing and we're invading from below as a result of that animation that i showed you i can't remember where we started so i don't even know where we are time wise but oh was it now keep going around the block there sir i was in such a great mood and then we had our technology problem and now i'm a little pissy sorry sorry patrick okay we have one more act to go and we visit for the first time a very important scientist merle beck so you're probably not new to me you've seen a bunch of other things that i've been doing over the years and you know that i'm fond of this gentleman merle beck who's i think 87 years old now and living in bellingham washington and just got an email from him yesterday i asked him if he could write up a couple of paragraphs specifically for our show here today and he obliged um and we'll get to his uh specific recollection recollections but here's just a i'll just show them individually here's the original bomb in the marketplace 1972 merle back from western washington it was probably state college at the time and the title anomalous paleo latitudes of cretaceous granitic rocks so we're going to talk about the sierra nevada batholith the coast plutonic complex again and the peninsula ranges complex again but i'm talking about merle so we're going to revisit those three batholiths again but not look at the rock types not look at the light colored versus dark colored etc we're going to look at the paleomagnetism and i can't hold it merle's work is going to show that the coast plutonic complex and the peninsular range batholis are the same stuff paleomagnetically and the sierra is the odd man out remember what we just did the cpc in british columbia was question mark maybe not the same stuff as those other two guys further south merle's saying i've looked at all three of these very very carefully paleomagnetically and the sierras are totally different than the bc and the mexican granite so i've been working with his papers i've been working with the interview i did with him uh in late summer this is according to merle this is the paper in 1976 that was published in the american journal of science that really stirred things up i think he had a different phrase for it we'll talk about discordant paleomagnetic poles in just a second this is my personal favorite of merle's papers because of the way that he laid out some of the data on some very simple maps you know that i'm a simple person so it's mainly these three papers that i've really been enjoying and continue to read and reread uh bernie hausen joined merle in the mid-1990s and so the last major paper that i think exists from merle with bernie is in uh revisiting baja bc 30 years later so for especially those who are brand new to the concept i don't want to spend two hours on this but let me try to give you a very quick version as i understand it and then we'll look at more of my hand-drawn maps using merle's paleomag work and compare them with what we just did with hildebrand's uh synthesis of the bedrock chemistry okay paleomagnetism from a guy who knows very little about it and go this is about volleyball take two this is a volleyball and the volleyball can be our planet planet earth okay and we have a north pole and we have a south pole and perhaps you're aware that our planet is like a giant magnet and there are invisible magnetic field lines that come out of the poles they are parallel to the surface of the earth at the equator and then they intersect the south pole at a 90 degree angle so just look at my hand and the intersection of my hand with the earth's surface in antarctica the magnetic field lines are coming in 90 degrees again at the equator equatorial guinea the field lines are parallel to the surface and then up at santa clause's house the the magnetic field lines invisible are entering the earth at 90 degrees to the earth's surface those are the extremes parallel with the equator vertical magnetic field lines coming in at the poles but if you are at 47 degrees north latitude as uh ellensburg is precisely on 47 degrees north then you have an intersection of these magnetic field lines at a particular angle and the angle as it intersects the earth's surface like intersects your town has a different angle dependent on muffler boy thank you for losing my train of thought jackass sorry patrick so as we get closer and closer to the north pole the intersection of the magnetic field lines with your latitude gets higher and higher that's the general concept so there are rocks like the mount stewart batholith that have magnetite minerals magnetite grange within them there are minerals that are actually magnetic and if this granite or ground let's just call it granite if this granite is 93 million years old and it is and if merle comes and drills a hole in this mount stewart baffleth rock in icicle canyon remember we took a little field trip there and if merle or bernie or some of his students linda merle's original student if they drill into that mountain and they carefully measure the orientation of this core of mount stewart batholith and therefore very carefully measure the inclination of those magnetite grains away from horizontal you can determine where this magma was located when it crystallized 93 million years old you can figure out the paleo latitude of that magma by measuring the orientation of the magnetite grains the magnetite grains are basically a permanent time capsule of the magnetic field of the earth at the time that the magma turned to stone now right off the bat most geologists don't understand paleomagnetism i certainly don't most geologists have never been in a paleomagnetic lab before most geologists don't even really understand how you can take something like this out of a mountain and then do something in a lab and say anything about it like how do you even know the orientation of this thing but that technique has been done more than 50 years that technique of paleomagnetic gathering of data has been done all over the world it's been done in more than granites you can do that same kind of paleo magnetic measurement of magnetite or magnetic grains in sedimentary layers in basaltic lava flows you can be all over the world with different ages not just stuff in the mid cretaceous and the results of all those different kinds of rocks all those different locations around the world and all those different kinds of deposits or settings they're remarkably consistent if you just take the time to look at the data set it seems at this point impossible to just say it's all wrong now there are plenty of people who manage to do that and say it's all wrong but those that are honestly with an open heart and open mind looking at that data and thinking hard about it are seeing that there's value in this paleomagnetic signature especially with the rocks of the insular super terrain but this all started with mount stewart basilisk in 1972 we're coming up on 50 years and we're going to visit with merle in the cozy fort we're going to visit with geologically speaking todd smith from san clemente california in the cozy fort we're gonna have shirley from tahoe city in the cozy fort but before we go to the cozy fort let's do a couple of quick things with merle's work we're starting baja bc early sunday is officially titled baja bc but i'm getting you started right now i didn't i ran out of time but this is some of my notes from five years ago in pencil that i just quickly took a sharpie to and i'm just trying to help you see that it doesn't matter if we have a lava flow or a magma body or even sediment we have different latitudes we have different inclinations this is the these red lines are invisible magnetic field lines intersecting horizontal and therefore using i can't give you the math but in my dummy brain you can go oh we have the 32 degree inclination here that means we were either 32 degrees north or 32 degrees south of the equator at whatever time this lava flow cooled inclination's 81 okay we're close to the poles we're either getting close to the north pole or the south pole north pole or the south pole north pole you get it you can determine latitude from paleomagnetism okay let's go right to merle's papers now merle do i have an uncolored one handy i got to pick up the pace no i don't so these are my colored pencils about five years ago taking one of merle's diagrams from 1982 and merle's saying let me plot for you in his paper this is 10 years after his initial paper by the way here's the cpc here's the peninsula ranges batholith in orange my choice the sierra nevadas and the idaho bathurst so merle says the cpc in the peninsula ranges those guys are identical paleomagnetically and based on the paleomag from these two batholiths we know they had to be closer to the equator when their magmas crystallized let's cut to it i don't give i don't have the details for you yet i will in a second but merle beck's papers in the 1970s and 80s said we have discordant paleomagnetic signatures from the cpc including mount stewart and from the peninsula ranges batholith discordant meaning surprising meaning they show that these two basilisks had their magmas crystallized in the mid-cretaceous much further south than they are now these two guys but the sierra nevada mountains have not moved this is 50 years ago 45 years ago merle beck is saying the sierra nevada batholith has concordant paleomatic details meaning it did not do crazy amounts of northworn movement but these two guys did and they're damn near identical paleomag wise so with that information merle said can i please for you take these two red guys that have low inclinations orientation of magnetite grains that are a lower angle than you would expect given where they are located today and can i restore them we're restoring again but not the fruitcake now we're restoring bathulus back to their original location so this is right out of merle's paper he's keeping the sierras stationary but he's slotting or moving the cpc and the peninsula the pbr the prb further south based on paleo bag let me give you some details there's the same point that i just gave you but a little bit differently i'm drawing a canadian an american and a mexican there's the cpc there's the sierras there's the peninsula ranges baffled the prbc again both of these two guys canadian and mexican are identical as far as the paleomagnetic signature it's the sierras in california that do not show any of that movement north and notice please merle was also noticing a clockwise rotation these batholiths had been rotated clockwise so it's not just moving them north but while they're being moved north they're going to rotate clockwise he can tell that using the paleomagnetic signature now this is about the time in the early 1970s that tonya water is writing an exciting paper about the california geology scene having a san andreas fault and having the entire west coast of california being just a big shear zone where you can i do it backwards for you i'm looking at you but i'm going to try to do it backwards where where stuff in western california is moving north and everything is being rotated in between my two hands a shear zone western california moving farther north than eastern california the san andreas but there are things getting caught in between my two hands i happen to have a volleyball now we don't have planet earth we just have some bedrock can this just be bedrock there's there's the text on the volleyball poorly inflated by the way now what's going to happen to this volleyball if i do that same kind of motion and i move this westernmost part of california further north than eastern california i'm going to rotate the crust caught in between these two guys in a clockwise sense correct merle is seeing this in the paleomagnetic signature of the cpc which is now in british columbia and the peninsula ranges batholith which is in mexico and southern california today but was definitely further south in mexico back then and the cpc moved way farther north than the peninsula ranges back with by the way so discordant paleomag they used to be further south and they have both been rotated similar i'm screaming now but this is so cool many of you love this diagram and i've always thought about ray wells when i put this diagram in your front of your face and bob butler but they were showing uh really in the last 50 million years that this continuous clockwise rotation of california western oregon western washington this works with audiences of all ages they just love the fact that these blocks are moving in a clockwise sense well guess who started the whole thing guess who made the first discoveries of clockwise rotation going back way earlier than 50 million years ago merle freaking back so do i have something a little bit more detailed for you about how much this crust has moved and when sure i do i'm a public servant and then we'll read merle's memory and then it's time to go to the cozy fort he looks at his watch for some reason i don't know why i've already made this point hildebrands plutonic rock ages in chemistry make the sierra nevadas the peninsula ranges match beautifully with the split personalities but i'm now talking about not looking at the age not looking at the minerals in the rock i'm talking about the orientation of the magnetites and in that case the sierras is off not moved north at all not rotated at all these two guys north and rotated clockwise here's merle in the 1970s from his various holes that he drilled into mount stewart batholith and other places in northern washington near his home in british col in uh in bellingham washington it's got to be mid-cretaceous batholis now if you get into far younger batholis there's none of this none of it it's just the mid cretaceous granitic rock that are showing this in the cpc so there's all sorts of checks on this not every grant that he finds in the pacific northwest no but mid-cretaceous part of the cpc you're going to move stuff you can read as well as i we're going to move this block 25 degrees latitude north in 25 million years and emerging at the time again from tony atwater's work is an ocean plate that you'll hear much more about on sunday called the cooler plate and the cooler was an ocean plate that was moving north during this time it's the magic carpet ride as i like to call it to allow this northward movement so i think possibly today will be frustrating for you at the end you'll want to go a lot more detail into this and the mechanics of this and other evidence for baja bc i'm asking if you can wait till sunday for that so maybe the live q a will be kind of me putting you off a little bit i'll try to answer what i can but i'm really trying to separate this into two things all right so those are early numbers i don't know if merle stuck with these numbers and the math with this but this concept of moving that much is still on the table and has been for quite a while so that got the whole idea rolling and ted irving from canada from british columbia hooked up with merle and together they came up with this concept called baja bc where we're doing this crazy amount of northward movement of those is primarily the insular super terrain between 85 and 55 million years ago and you're like wow i've never heard of this why not well most geologists are still not eating it they're still not drinking the kool-aid they're still not 50 years later it's a minority opinion still but some of us feel it's it continues to be interesting and the data continues to come in of various sources that sunday besides just the plutons to back up that this is a thing so it's still a controversy it's still a discussion it's not even 50 50. most geologists don't agree with this but i like it and it impacts areas very close to where i live and so i continue to teach it a little bit from murrell and we go into the cozy fork sent yesterday at noon nick for what they may be worth here are some of my reflections on the state of geo thinking a geotectonic thinking about the western courtier during the 1970s and 80s note that they are my reflections this is merle beck talking to you directly specifically writing this for you these are my reflections and recollections other players such as ted irving and davey jones may have had somewhat different views too bad they're not around to comment well first and foremost i didn't regard the bulk of displaced crystal blocks as in any way exotic without much thought i casually assumed that they had originated as part of north america itself and had been transported relatively north by the north oblique nature of subduction of the farallon plate in fact i spent an inordinate amount of time and energy pondering the circumstances under which this would occur it turns out that theoretically what is needed are a shallow subduction angle a high angle of obliquity and a mysterious factor measuring the stickiness between the interacting plates which i never figured out how to measure i wrote several papers on the subject which you can find very easily the most cited one appeared in the 1991 volume physics of earth and planetary interiors i don't have that one another player in the northward transport game was of course the cooler plate but we didn't know how far south it had ever extended clearly detach a chunk of crust and attach it to the cooler and northward displacement would be very fast but we didn't know how when or even if this might have occurred also in those days i thought of northward displacement as occurring piecemeal along a series of moderately sized strike slip faults and shear zones then ted irving introduced the concept of baja bc which seemed to imply the existence of a san andreas fault type super through going break that really got the geologist stirred up i said earlier that i thought of these alloctanous terrains as originally part of north america not exotic by today's terminology the one universally acknowledged indubitably exotic terrain was of course rengelia which contained rocks that must have originated in the ocean davey jones being a paleontologist may have thought more about along the exotic lines but i don't recall him talking about it the next exotic terrain to be discussed in those early days was i think stacenya but by that time i had departed for the relative simplicity and excellent cuisine of the central andes thank you merle for adding a personal touch to this discussion so through the camera lens i can already feel you wanting to just chew on this and talk more about it or if you have been thinking about baja bc for a long time and you're ready to pounce or whatever i'll do what i can to entertain your questions and comments but um yep so we're going in the cozy fort i don't have a wireless mic but i tried this once in the backyard last spring and it may have actually kind of worked until i got confused there's a chance daddy won't be confused this time so you're gonna have to give me a couple extra seconds here you can notice the uh lights turned off that i have courtesy of oscar oscar's ideas on what to buy so i'm pleased with those oscar i'm curious in the live comments right now if you like me talking without a wireless mic like if you feel like it's louder than uh and video audio that we've had recently i i kind of hoping that's the case for my testing for my testing this week i thought that was maybe the case i'm sure i'm glad you're with us we still have more than 700 i noticed that we have about i think we're hovering about 700 or so that watch live which is great and then i think about i don't know six or seven thousand that watch the replay before the next show i don't have a good sense of people are watching after skipping a bunch like the last one they saw was g and here they are with us now i if people are doing that i i can't imagine it makes a whole lot of sense but maybe it does there's plenty i don't know and we're about to finish the series up i still don't know a bunch of stuff so let's try i don't like the bluetooth and all that i can't rely on anything that's um okay let's let's see if this will work battery 100 battery 100 percent battery 100 battery 100 oh what a clown okay i just realized i gotta turn the laptop around with this thing connected to it i can do it i think so do you know about a guy named todd who lives in san clemente california i think he's mostly active on instagram but his channel is called geologically speaking and todd and his uh whole family i think was watching most of the shows last spring when they were everybody home you know we were all locked down and i've been a big fan of todd's um over the i don't know how long you've been doing it todd but in the last year for sure i've been a fan of what you're doing got a really nice presence and i think you're in real estate you're like a house inspector but you just do this for fun and i saw one that todd posted on the peninsula ranges batholith and i asked him to put it on his youtube channel so if you go to geologically speaking youtube channel uh i think he's posting a little bit there that's where i'm showing you this one but i'm going to i'm going to show the beginning and then this one's 10 minutes long so i'm going to show the beginning and then i'm going to skip to a part that i think is helpful to us todd from san clemente california in orange county between los angeles and san diego okay can i do this definitely not halite oh good morning greetings from southern california usa doing a little dumpster diving this morning near the santa ana mountains you can see them there in the background they're part of the peninsula ranges down in southern california and actually have some of the oldest rocks in orange county i'm going to be looking for two different formations there's the bedford canyon formation which is made up of meta sedimentary rocks from the jurassic period we're talking the age of the dinosaurs late jurassic 100 million years ago and then uh there was some subduction off the coast of california of the farallon plate and it created volcanoes we the most famous ones created by the fairlawn plate are the sierra nevada mountains but the peninsula ranges are actually associated with that same event so not only are we looking for meta-sedimentary rocks from back then but we're also looking for extrusive and intrusive igneous rocks from that fairlawn subduction event where magma was created some of it made it to the surface and some of it didn't so we're dumpster diving in the sense of going up trebuco canyon this is a creek that comes out of the santa ana mountains and what better way to find out what these mountains are made of by coming in to a creek bed where all the erosional debris is being collected so we're just going to trail blaze up the creek and see if we can find something interesting join me uh i'm sorry did you say meta sedimentary rock uh what is that that's right meta sedimentary rock so what is that well let's break it down what's a sedimentary rock this guy's good isn't he you are have such a great presence so i'm going to skip ahead to a little bit of granite stuff towards the end since that's our topic our plutons but i strongly recommend uh watching this whole thing chamber below the santa ana mountain range the age of the dinosaurs you guys mind if i hit some of this intrusive igneous rock with my rock hammer i just got the rock hammer i'd like to use it if you don't mind the reason you want to break open igneous rocks is the outside of it is all weathered so it's kind of dull can't really get the look of what the minerals actually look like you need to expose the minerals from within nick zetner calls them fresh minerals copyright trademark all right let's do this eye protection's on weak come on you can do this [Music] no i do better okay look at that fresh minerals so again this is the intrusive igneous rock the great you do a great job there todd thanks for joining us here today live as you do many times and i hope people can find geologically speaking on instagram and other places we go to merle beck we talked about him in folder number three i visited with merle in his backyard in august this is nick on the fly episode 13. you can find the full interview if you're interested uh here's a section that is appropriate for what we were discussing today a little back story on how merle started in the peninsula rangers baffleth and then started sampling in the uh coast plutonic complex mount stewart what was the context of that paper were you were you adding to somebody's idea already or were you coming out of the blue no i was adding to an idea that i had i had originally originated in my brain some years earlier okay and but i was also basing it on some results that other people had had essentially at that same time okay and the context is when i was at uc riverside i i had already you know i actually had more publications than a lot of the faculty and i had a friend there who wanted to do paleomagnetism and i had a functional lab going in washington dc so he and i studied the paleomagnetism of grenade rocks which we call the southern california batholiths okay now i think they call it the peninsula range basil yeah give us a couple examples where loca where where could you find those rocks that you were near san diego and on the well we didn't go into mexico but okay northern mexico around actually around riverside san bernardino okay wherever there's a grinning crocs exposed in the mountain range that's that's that's that pathway got it and we did a pretty thorough study and ron actually ron went and made the measurements at another guy's lab ron was my student my fellow students sure we got a really nice paleomagnetic direction but it didn't match the reference pole and the way you looked at looked at it and looked like it had been these rocks had originated south of where they are now and had rotated clockwise and so ron and i puzzled over that and at about that same time there was a very seminal paper published in gsa bulletin by tanya atwater of whom you've no doubt heard and she likened western north america when she really got wave in her arms she likened western north america to a huge dexterous shear zone and so rod and i sit there and say well what happens if our little chunk of baffle is stuck in the sheer zone and so the answer of course is with respect to the inter internal part of the continent outside the shooter zone those rocks will have seemed to have been moved north and rotated clockwise but we didn't publish that okay it was too revolutionary as in the mid-1960s maybe that would have been 67 68 okay so then i came up here and i got in my lab and i ratted around trying to find good places to work and with i got a bunch of grad students and one of them was this one very nice and an intelligent woman named linda lawrence later married and became knowsome okay and linda and i worked on the i mean my god what what uh grinning rocks are there around here better than the than the mouse steward bathwork you can drive right through parts of it you go up icicle creek yeah and uh so we went up there and we sampled in a i don't know eight nine ten places and drilled standard paleomagnetic sites six eight ten cores per site brought them down here and she worked in my new lab and she got a beautiful direction and lo and behold it looked like these rocks had moved north with respect to north america and rotated clockwise and i said my god that's what tessera and i found at that point i started thinking there was something really seriously going on here this this kind of application of paleomagnetism to tectonics was pretty much unheard of it was ignored by most geologists but i think the paleomagnetic community took notice uh now a decade earlier the paleo magnetic so that was a real treat to be able to talk to merle directly about this a few years earlier we interviewed him for a very short pbs show i've showed this i think twice already in this live stream series last spring but let me just give you a minute of this and then we'll go to your questions the cascades come on baby but the rock is way too old for the cascade story cascades have only been there for 40 million years only and the rock in mount stewart is 93 million years old a lot of evidence has accrued over the years that major chunks of the western edge of north america didn't form as part of north america it formed out in the pacific someplace and were transported by plate tectonics generally from the south to the north and then they were plastered onto the continent and then sheared up mount stewart was part of an exotic terrain that attached itself to the western edge of north america but where did it come from geologists at western washington university believe the rocks in mount stewart were formed far from here i drove over to western to visit merle beck and bernie housing in their paleomagnetic laboratory merle in particular has spent more than 40 years on this topic collecting samples from mount stewart itself and analyzing that rock for a paleomagnetic signature i got in pretty early i'm not a founding father of paleomagnetism but i'm close you know i'm an elderly nephew sort of thing i got an nsf grant and i worked on rocks in the cascades and there it was mount stewart so we went up there and we drilled in about a little more half a dozen places these granodiorite samples are part of their collection it triggered the whole controversy and it's such a beautiful rock paleomagnetically as well as aesthetically it gives you the nicest directions you've ever seen but those directions came as a shock to the scientific stop okay that's enough and uh both of those programs are online if you just go to youtube into the search bar and uh type in nick zetner baja bc i'm sure you'll find that and more or just baja bc there's probably not a whole lot on youtube just on baja bc there should be more there should be way more of a spotlight on this stuff in my humble opinion and we'll do more with different kinds of data if it was just merle's data then maybe we wouldn't talk about it a whole lot more but there's there's plenty more okay let's try to get the lights back on we're losing the light as promised the lights about to go the sun's about to go behind monash tash ridge behind you there so we're about to get kind of dark anyway but let's close whoo looked into the sun um let's pop the live chat out like a boss and i'll try to answer a few questions here before we quit let me get some wine it's friday afternoon after that after yet another problem so thank you kathy for the uh drink no that's called a glass thank you kathy in brisbane australia for the glass thank you julie from prosser yet another gift horse heaven hills a 2017 merlot and your questions i really appreciate you being here as always oh what just happened i went to another hang on patrick okay so i put so many qualifiers on the on the live q a you're probably not sure what you want to ask now go ahead just go for it saber inside in saguaro national park or whatever is the pluton batholith formation the driving force of the geologic elevator that's an interesting question hildebrand is talking about collision between north america and insular tearing and ultimately failing the slab magmas coming up including the mount stewart granite and then exhalation and uplift happening shortly after that now i'm not sure the timing of that works i definitely know it does not work in the north cascades the north cascades our up our exhibition our geologic up and our exhibition was starting 50. wasn't it i think chelan migmatite was the earliest uh going up and that was like 80 maybe 75 million years ago so that's on my list of things to try to learn more about saber the geologic down and the geologic up with the elevator and the timing of that and what's ultimately causing that so there's going to be plenty of i don't knows but i'll try to comment at least on your good questions marbles collector where are the baja bc faults would you please wait till sunday i will say now i will i'll just give you a little a sneak peek [Applause] i will say now that drawing cartoons like these are maybe not what we want now i was drawing these a few years ago based on daryl cowan's excellent 1997 baja bc revisited crucial tests paper that we will feature on sunday but to draw one major fault similar to today's san andreas is maybe not the best way to go about this because therefore you it feels like if you focus on this with your images and maps and say well are you a boss bc yes or no person then all the interest goes into the actual fault and not the crazy amount of wonderful geologic evidence that will be compiled for you on sunday i feel like the energy and the discussion gets away from the good bedrock evidence and and focuses on is a one monster strike slip fault which probably does not exist if we haven't found it in 50 years it's probably not there it's more likely that instead of one major structure there's a bunch of smaller strike slip faults like we have in the north cascades that together are accommodating this more than 2 000 miles of motion that's my answer but i have more to say and more to share with you on sunday about that thank you for the question marbles collector dino do the ages of the plutons in the cpc get younger or older as you go north that i don't know either there's plenty i don't know it's safe according to what i've read that there's a split personality to the cbc that the western cpc is different than the eastern cpc as you go north i lose confidence i lose basic information and we'll talk about will matthews from calgary on sunday and he's got some interesting things to say about western cpc versus eastern cpc so let's just leave that one there but further north in in yukon and alaska i got nothing to say thanks zig are there any paleo mags from the top and bottom of a pluton or the batholith that's an interesting question i don't know if it matters first of all does it matter if you're at the top or the middle or the bottom of a pluton shouldn't it all be the same paleo mag my first thought is doesn't matter second of all we just have the batholiths we're given at the particular level that we're given so merle went up icicle creek by leavenworth and drilled with his student linda and you go to cpc and you go i mean you're just you're not you're not you know digging five miles down to get a certain sample so interesting never thought about but i'm not sure it matters where we are in the depth of the pluton although maybe i'm missing the message of your question jay could cpc and prb moved then the sierra developed they're all the baffles are all generally the same age you're wondering i think why the sierra nevadas did not i forgot shirley's shirley i'm sorry can you wait till sunday i'm sorry i forgot yours why did i oh yours was a oh and hildebrand hang on hang on okay we're not doing cozy fort but i got two more things to show you it's dark enough i don't think you'll have a big reflection where's the yeah improvisation number 32 today this one's uh my fault actually they're all my fault i'm sure i'm sure they're all my fault am i going to run out of battery here and gary i did the same thing i forgot about the so busy okay so we've got stuff from gary i think i'm gonna cut the live q a short unless i don't know this will work won't it you can see we don't need we don't need sound for gary back country gary a staple for the show i hope this works for you with minimal uh that's not bad is it so you've seen that from the melange belt you've seen that from the melange belt gary's got some pluton shows oh do we need it no we don't uh gary says let's go to a few plutons i mean we've already gone with some other people how about that so in the case of our let's say slab failure plutons if you like that concept black peak batholith that's in the age range we're shortly after uh the 100 million year old main event but the golden horn which is a dominant batholith way too young for our story today golden horn that's why it's called the golden horn says gary gary i'm sorry if this reflection is screwing up with your photos but i just don't want to set up the whole cozy fort again beautiful photos from as always from gary paul in darington washington oh man look at that saddle don't you want to just go right up and over that thing beautiful contact between two plutons black peak twice as old as the golden horn what an amazing gift you are to all of us gary with your work what's this is this more i forget where we are in our show i've shown these haven't they oh no there's three yeah okay these are these are still some of the pluton photos that gary wanted to share the dembele pluton i know nothing about but i certainly want to learn about them now that i've gotten in here up above holden lake the marble mount pluton also equally not very well versed on it so there's plenty to learn remember mike eddy from purdue will be going pluton to pluton so i need to learn way more about these plutons but if there is scene too young for us these guys could not budge that marble mount pluton in whatever year that was okay gary thank you now shirley uh was the one that gave me that beautiful book from the sierra area and she made this video report that's two minutes and 35 seconds long and i need audio for shirley battery battery 100 shirley from tahoe city oh we're not functional hang on hang on i'm not plugged in okay take two here we go shirley hi nick my name is shirley and i manage a construction company in lake tahoe we spend our time at a remote property in the sierra nevada that sits on exotic terrain i wanted to understand the beautiful and unusual rock in the area and fell in love with geology it has been difficult to get information but i found a few sources i truly felt stuck until i came across your video series i thought i would give you a tour of two of these exotic terrains one of which you mentioned in one of your a to z videos here we are at the shoe fly or better known in washington as the alexander formation and possibly the cache creek but we're not in washington we're in the sierra nevada mountains in california near the town of quincy the formations in our area lie on top of each other much like your pizza boxes the area contains several exotic terrains but they start with a shoe fly which may be about ten thousand feet thick folded in containing sandstones slates and shirt the shoe fly is the oldest rock in our part of the sierras here on the quincy laporte road we can find rocks the shoe fly exposed in road cuts i am most familiar with the structure called the sierra buttes formation it is the next youngest and it lies on top of the shoe fly we own 35 acres on the sierra buttes that was once a gold mine the is called the rock green stone the rock is slightly metamorphosed so it's fairly easy to know what the original rock once was the rocks that make up the sierra buttes are daysite volcanic branches tuff chert ash slates quartz and sometimes pretty epidode we have a fossil bed below our property of ammonites this formation was created in the late devonian around 390 million years ago sierra buttes formation is an island arc formed in the deep ocean and shaped by glaciers could the sierra buttes have been formed as an oceanic plateau could the string mean have reached down to my neck of the woods you have taught us how these deep water formations accreted but i have a lot more questions with five additional marine formations plutons erosional and volcanic formations and faults we invite you to the sierra nevadas to help us sort out this hot mess shirley that was excellent thank you you spent a lot of time on that i can tell very much appreciate your time you did a great job with that thank you uh the last thing i have here and uh we got people coming back in the house and who can blame them it's after four o'clock um give me a second i gotta turn on the furnace hildebrand you want to hear him this is a talk that he put online probably for a conference you know in covid time now you can't go to these conferences so you are presenting your talk and you're narrating your slides and then you're putting it online so there's that's one plus you can you can actually get a hold of some of these things so this is a long program i'll just give you the first few slides but he narrates some of his slides and it adds a little bit to what we were doing and add some news things as well that i probably will not expand upon but for a century ago black welder used the term oregonian to refer to the mid cretaceous deformational event in the north american courtier although it is widespread it is generally under appreciated if not unknown by most geologists our work has shown that the orogeny represents to closure at about 100 million years of an oceanic basin that opened after the nevada neurogeny and east of the present-day peninsula ranges in sierra nevada and about 135 million years ago i'm sure that most of you are familiar with this scene okay the peninsula ranges batholith extends from southern california and northern baja southward beneath younger volcanic cover through the baja peninsula and once the gulf of california is closed into the water nejo say what to do well it contains two main magmatic suites a 128 to 105 million year old suite of episode plutons ranging in composition from gabriel to granite with a comagomatic suite of volcanic rocks and associated sediments known as the alacito santiago peak all right moving on this model figure from martini at all shows the overall scheme from opening of a marginal basin in the early cretaceous with sediments derived from both sides of the basin as documented by detailed provenance studies to closure of the basin at about 100 million years note that the ark was on the western plate westward subduction skip all the evidence thus indicates that closure of the bisbee arparos basin at about 100 million years was by westerly seduction all right we found that the two suites were readily differentiated by trace if you go to suite of discrimination diagrams as is well known bob please if you go to robert hildebrand.com i think it is maybe somebody can link to it down below can you find the link where he's got all his publications you can get to that narrated talk as well that's how i found it so there's no shortage of stuff for him to uh share with you if you have interest there's a lot there i still don't totally know what to do with him uh but i sure enjoy looking at the stuff okay i'm back we'll do a few more live q a i still got a little battery lift if you're still with us how many we got we've still got more than 600 sure why not you might have to redo your question because i'm down to real time here i think but i need to pop the chat out like a boss right between the eyes that'll help a little bit i'll go back a couple of minutes but if you've got a burning question go ahead and type it in again if you wouldn't mind if you're still interested in asking a question maybe i'll answer it yeah surely yes shirley did a great job yeah i'm familiar with the burke museum doug that's john figgy that did most of that stuff on that website kyle are you the guy that did the pluton invasion cartoon thank you i think that may have been you kyle asks is there a way to distinguish between plutons created by westward subduction versus eastward subduction hot spots and spreading centers are completely different magmas correct so as i understand it now hildebrandt loves westward subduction mainly because he's finding the plutons here he's liking how can you how can you have this and have the plutons on the opposite side of this suture and most geologists say well what you're saying doesn't match with the bedrock geology that we know in california and nevada and other places and it goes back and forth and back and forth but i think it's a i think his main message is this is eastward for you right he says this is the old this is the model that everybody likes that it's eastward subduction of the farallon and you get your magmas here in the overriding plate but as he views these split personalities of these magmas and other things related to the magmas on either side of the magmas he sees a lot of the magmas or the plutons on the wrong side of the sutures if that makes any sense to you that's about as far as i am dino have you have i seen sig looks automatic scroll reconstruction of western north america on youtube channel earthbite i have not but i'm guessing that's edward clinette's 2020 animation and i'll be using that in show z again but i've already showed it a couple of times patrick h7 you're still with us isn't it your bedtime isn't it supper time patrick patrick age seven is there ever any difference in the paleomagnetic signature within the same batholith patrick i'm not sure i was potty trained when i was age seven i'll have to check with my mom on that but i think i was struggling with that not asking if there's possibly two different paleomagnet signatures in the same batholith good job i don't think so patrick especially if we're in one pluton with one distinct batch of magma that has a pretty narrow age range but if you're asked did you use the word batholith or pluton batholith so if you're thinking of a bath with patrick and you know that there's different ages of plutons within the batholith then that's a really interesting question that's probably what you meant because you're a very interesting person patrick i don't know maybe i'll hear from merle i don't think he knows how to be in the live chat with us but he he's been watching these shows smiling llamas how do you reconcile the discrepancies in data from three embedded pluton bits i don't know what you're talking about i'd be happy to learn if you want to email me what you mean i don't know what three embedded pluton bits means lars how can we tell the difference between post formation tilt and paleomagnetic inclination that's a fair question and one of the main arguments against merle's work you know we're talking more than 90 million years ago that these plutons were liquid and think of all the folding and other kinds of tilting and adjustments that those plutons have experienced it's not like they crystallized a year ago that's more than 90 million years ago how can you possibly say that's the original uh inclination of those grains and all i can say is that there's been decades of follow-up to address that very specific question and i can't give you more than that there's a specific paper out of yale by mark brandon who addresses it specifically with with the mount stewart basilisk another former daryl cowan student i might add but i don't have the background to understand what they did it's still a major argument against the whole thing for sure but again if you look at the breadth of the paleomag work over the decades over the countries with the various rock types and they're all still giving the same story i don't understand i wasn't the bedwetter charlie mr tom how long for a pluton to cool and fully harden good question i don't know there have been some papers that have come out this fall that talk about an amazing amount of magma in a very short amount of time but that's not very helpful to you there's one that just came out i think what was it like i i'll screw it up if i try to say it off the top of my head but it's a basic question i don't have an answer for like are we talking weeks or years or decades or thousand years a million years one more and i think we're done charlie does the 100 million year old line indicate when westward subduction turned into eastward subduction that's a great question let's finish with that i already said we're going to finish with that to me you know most of these live streams are new material and some of it i'm more excited by than others for this show i'm most excited by some of this basic stuff here and the fact that there's a split personality to these battle lists and that there is evidence of a major event a hundred million years ago i love that so charlie's question was if we're going with the slab failure thing and these pinks are coming up as soon as we have north america slam into a fixed insular that's the end of the line for westward subduction right and i think generally that is the answer i hadn't thought about it like that charlie but i stalled for myself there for an extra 30 seconds so i could think about it i think that is the argument it's definitely eastward subduction today is it not pleasure you want to get on camera i think it is today in fact i know it is this is patrick's poster we know that the ocean floor is subducting beneath north america eastward today the question is has it been subducting eastward beneath north america ever since the main event 100 million years and now i'm having trouble because i'm thinking about of a couple inceptions to that rule so let me think more about that on behalf of bijou i would like to do a toast to you and a toast to us you're going to be cut out of the first stream that we did you had good moments there did you know that did you know that you had good moments there i even flipped them around i had you on the on the magnified camera at least your right ear but now you're realizing that you want to be on camera again why would anybody still be watching if all we're doing is looking at a freaking cat all we're doing is looking at you a toast to you here's to your health here's to the health of your parents and your grandparents here's to the health of your children and your grandchildren how'd you go you can squeeze and here's to all the valuable people working at all kinds of jobs trying their best to keep us moving forward in this deeply confusing time that we're all living in on this planet here's to the change of the seasons it's 4 18 p.m and it's almost dark outside here in ellensburg washington latitude 47 degrees north toasting the what that was the plan for today which i never ended up showing you and this is the plan for part two of our discussion so if you had a baja bc question a burning question and because of all my absent-mindedness and technology problems did not get to your question i wholesomely and warmly invite you to join us for this show on sunday morning and i'll try to get to your questions then best i can do that thank you for joining us today i love you i love you and we'll see you sunday morning yep goodbye you

Channel: Nick Zentner

Views: 16,278

Rating: 4.9414635 out of 5

Keywords: Nick Zentner, Myrl Beck, Baja BC, Mount Stuart Batholith, Sierra Nevada Batholith, Peninsular Ranges Batholith

Id: oNKcE-UyFa8

Length: 133min 4sec (7984 seconds)

Published: Fri Dec 04 2020