You can support my field videos by clicking on the "Thanks" button just above (right of Like button) or by going here: www.paypal.com/donate/?hosted_button_id=EWUSLG3GBS5W8
LETS TALK????? Hello Prof...I run Mudfossil University on YT and soon to have live classes on Telegram...you are invited my friend......I study rocks as well but they are actually fossils. Some are very large. I would love to discuss my findings with you. Some of my "Rocks" are cat scanned and DNA tested so quite serious. roger@mudfossils.com
I've seen some compelling research coming out that the Grand Canyon was not formed as gradually as we once thought, but looking upslope, there is ample evidence of massive historic Lake that might have drained rapidly, carving deep, similar to what we see in the channels scablands of Eastern Washington.
there are podcasts here on YT of people that go down deep in caves underground. the "action adventure twins" in a great one. in their videos all sorts of amazing geological features and formations they pass along. would be so cool if they had an actual geologist accompany them to explain such amazing layers, processes and formations. Ever go caving, Shawn?
You really know how to get the camera right up to great examples of what you want to show. It makes for very good videos that are easily understandable. Thank you.
Plasticity and lubricated nature of landforms sliding against liquefied bedding over basement rock. Thank you SOOOO much for your much better back and legs that get me the vicarious field work.
Thanks for the views and the video. While in school (to become a geologist) we hiked to the bottom of the GC and saw the contact, but your sites showed a good deal more about the nature of the Tapeats than what we saw. The sandstones, grits, and conglomerates don't look that old, but facts don't lie. Sure, we were impressed by the unconformity, but thinking about it now after a long (but very short in geologic terms) life as a geologist, soon to join the record myself, one begins to understand just how much can be read from the nature and meaning of that contact.
Loved this video. The best one so far as it shows up close the distinctive strata layers back to over a billion years. To see it so close was amazing. I definitely shared another of your videos to Facebook. Would love to see more videos of this trip. If you could zoom in on any marine life fossils would be great. I wonder if the seas here were to shallow for the sharks of the day back over 200 million + years. Finding a tooth to see would be epic. I don't think they can be taken out, but a picture with one on the hand or a hand next to it's embedded site would be really something to see.
Thanks for watching and learning with me. More Grand Canyon videos to come in next few weeks including one that shows some marine invertebrate fossils in Redwall Limestone.
I took a course on the Geology of the Grand Canyon back in my undergraduate Geology days in the early 80’s. Never made it to the bottom of the canyon. Thanks for taking me there in this video.
the greatest threat to geologists who promote atheism is this. not just the "universal claims" argument that presents a unique contradiction for the claim _"there is no god"_ which can never logically consistently be made in the affirmative.
Great video! (My one grand canyon experience was life-changing.) This helped me better understand the Great Unconformity. Just gorgeous, so appreciated, Shawn.
The Great Unconformity is a really amazing thing and I've never heard or seen it explained so well. You must be having an incredible time on this journey! Thank you for giving us a look at what you're seeing.
@@ucanliv4ever Sure does, ucan. Anything that goes against the prevailing current of belief in the world is scorned and ridiculed. . But observed evidence shows the truth of the Holy Bible.
Thanks! ... the clean look of the layers below the sandstone, I immediately think of long ages of ice ? Need to research more on this unconfoming gap ! 👌
In 1995 I was fortunate to be on an environmental impact expedition down the Grand Canyon. Among our number was a geologist from NAU in Flagstaff who led us on a hike of Blacktail Canyon. Your rendition of the Great Nonconformity took me back to that glorious experience. You are a gifted communicator using the web the way it was first imagined. Bravo
Shawn, thanks - watching this video was a moment lost in time. My understanding is these features in the Grand Canyon are accessed through wining impossibly oversubscribed lotteries for the 10-day whitewater trips to the Colorado River section, and, with reaching the Blacktail Canyon, are subject to the likely but not always given scheduling and interests of the specific tour group. Your sharing this expert "hands-on" reveal of the striking Great Unconformity is an understated sharing of a special adventure.
An incredible piece of Geological history! Just awesome. Siccar Point in Scotland is also another extremely rare example of where you can see what is thought to be part of a 'Great Unconformity' (or Huttons Unconformity) along with the Grand Canyon sequence ( Powell's Unconformity) . I visited the Grand Canyon 25 years ago now from the UK and I was just blown away by it. Such an awe inspiring place to visit and get up close to some amazing geology. You have the best job in the world Shawn!
I'm so envious, that you get to study this incredible geology. I'm a first time viewer, but I've known about the Great Unconformity for a while. I'm glad you've given me a deeper understanding. Thankee, friend.
It was left unsaid in the video, but presumably that contact also represents the ground surface at the moment where erosion waned and deposition took over--as this was in a coastal setting, perhaps it looked something like the rocky coasts of CA/OR, with a wave-cut bench of pitted rocks that enclosed tide pools in the upper reaches. I'm always fascinated by those kinds of windows in time where we can almost see exactly what the landscape looked like. Each one of those rocky cobbles at the lowest layer was dislodged from its source somewhere upstream, then came to rest on the Vishnu schist to be buried--frozen in place for us to see 500M years later.
Isn't the mystery of the Great Unconfomity the millions of years misssing that it represents... and considering the amount of missing material we have to wonder about the mechanism responsible? ....
I am just barely grasping the commentary of what this environment might have looked like and the forces involved. I need an animated 3D visualization! Fascinating video. Thank you!
Fascinating! I just visited the Grand Canyon and Bryce Canyon, and was overwhelmed by their size and their beauty, but had sooo many questions! This video answers some of them, thank you!
Loved this video. It took me back to my Grand Canyon rafting trip in 1968 when I was 14. I still have a photo of the “wavy” rocks that had been sheared and the horizontal strata above them. I was fascinated by them then and enjoyed your explanation of them now. Thanks.
Joining from Germany , just found you and these layers interest me extremely for their old age and how they were formed, Great channel, I took an abo of course , thanks a lot !
Is there any speculating as to what rocks had been between the Tapeats sandstone and the older Vishnu Shist rock beneath and what happened to it? Or is there a place where that layer might still be intact somewhat?
Wow. So cool. This is one of the most thought provoking subjects I know. Starkly terrifying in a way. The planet is so old. Our lives are so short. Your hand on that spot in time. Yeah buddy. What a great day!
I’ve been to both N and S rim of Grand Canyon. I had heard of the great unconformity but have never been down in the canyon so it was great to be able to see it in your video.
Thank you for yet another great video allowing me to see up close a geologic wonder I'd never be able to visit. The Great Unconformity is mind boggling, not only for the length of time involved, but for the sheer volume of material that must have been eroded. It would be so interesting to see what that would have looked like prior to and during the erosion process.
Thanks for the sub and welcome aboard. Enjoy perusing the existing videos. Here's one from the bottom of the canyon of the basement rocks at Phantom Ranch. Video from my Rim to Rim hike in Oct 2021. ruclips.net/video/GHHhu8K-cYE/видео.html
Do you think the metamorphic rocks have been leveled off by glaciers? There was enough time for that, and you would expect to see the smaller rubble on top, which is clearly visible in your video. What else would plane off the rock in that straight a line?
Hike down to Hermits Canyon and see the black Vishnu Schist and the pink Zorastor Granite. It's below the William Boucher stone cabin site just upriver from the Colorado River.
I find this stuff fascinating. I saw a picture once of a rock that was billions of years old and the striations curved and turned all over the place. They weren't broken, just bent with the immensely of time.
Thank you for proving to me that I’m not crazy I am at the Western base of Joshua tree national Park and it is phenomenal. What I find in the canyons here.
It never occurred to me that Southern Ontario has anything in common with the Grand Canyon. The pink granite of the Canadian Shield is overlaid by the Great Lakes limestone at the surface near the northern end of Georgian Bay It's a striking example of an unconformity, and one of the most beautiful places to cruise in a boat in N. America.
Love it! Crazy to be looking at and standing on ONE POINT EIGHT BILLION YEAR OLD ROCK! Damn!!!! This is probably even cooler than visiting the K-Pg Boundary. In terms of deep time it sure is!
Great vid Shawn! Great to see the GU so clearly! I dont think we the GU in Western Australia, but there is a small remaining sliver of an massive unconformity near Perth that is between 3.0-2.6 billion year old gneisses and granites of the Yilgarn Craton and a Cambrian (although its not been possible to get an accurate date) transgressive unit of fining upwards conglomerates, sands, silts and mudstones. Sadly the actual contact is hidden by overburden where I have access to where it would be (it's visible in a private quarry nearby apparently) but it's amazing to wonder what happened in that gap, especially as there were probably 2 supercontinent collision and breakup stories that impacted Western Australia in that time period.
Thanks for taking us along. Those are really old rocks After my geology study of the last 18 months i understand so much more than when I went on a ranger walk near the rim of the grand canyon. This video is reminding me ju how young the rocks here in Central Washington are. The scenic views you show are so very stunning. This summer through videos I'm seeing a vast range of rock ages, from 1.8 billion in the grand canyon to a few days old at the Iceland volcano. I can't help but wonder how time of erosion went on before the sandstone began to deposit. I suspect that there is not a way to truly determine what that time was. Thanks.
thank you so much for doing this wonderful podcast. i never knew geology was so interesting until i started watching you and several others here on YT. i wish i would have had this interest sparked 45 years ago. keep up the good work!
You know, as an electrical engineer this is very explainable. Even that great mica crystal vein you found. But usually these are much smaller in the lab :)
What are the bigger clasts in the Tapeats on the contact? Are they made up of the schists and granites below, some other igneous or metamorphic rocks from somewhere else, or are they something else entirely?
You can support my field videos by clicking on the "Thanks" button just above (right of Like button) or by going here: www.paypal.com/donate/?hosted_button_id=EWUSLG3GBS5W8
LETS TALK????? Hello Prof...I run Mudfossil University on YT and soon to have live classes on Telegram...you are invited my friend......I study rocks as well but they are actually fossils. Some are very large. I would love to discuss my findings with you. Some of my "Rocks" are cat scanned and DNA tested so quite serious. roger@mudfossils.com
What camera did you use? Looks like a reframed 360 of some sort.
I've seen some compelling research coming out that the Grand Canyon was not formed as gradually as we once thought, but looking upslope, there is ample evidence of massive historic Lake that might have drained rapidly, carving deep, similar to what we see in the channels scablands of Eastern Washington.
there are podcasts here on YT of people that go down deep in caves underground. the "action adventure twins" in a great one. in their videos all sorts of amazing geological features
and formations they pass along. would be so cool if they had an actual geologist accompany them to explain such amazing layers, processes and formations.
Ever go caving, Shawn?
talk about an Atheist's Nightmare wow
You really know how to get the camera right up to great examples of what you want to show. It makes for very good videos that are easily understandable. Thank you.
He is The Professor afterall.
Plasticity and lubricated nature of landforms sliding against liquefied bedding over basement rock. Thank you SOOOO much for your much better back and legs that get me the vicarious field work.
Amazing stuff Shawn. Please keep posting these educationally fascinating vlogs. You are a wonderful teacher!
Thank you! Will do! Thanks for watching.
Thanks for the views and the video. While in school (to become a geologist) we hiked to the bottom of the GC and saw the contact, but your sites showed a good deal more about the nature of the Tapeats than what we saw. The sandstones, grits, and conglomerates don't look that old, but facts don't lie.
Sure, we were impressed by the unconformity, but thinking about it now after a long (but very short in geologic terms) life as a geologist, soon to join the record myself, one begins to understand just how much can be read from the nature and meaning of that contact.
Thanks ah so nice. Thanks for taking us there!
My pleasure 😊 and thank you!
Thanks for this clear picture and explanation of the great unconformity. What an incredible place. Love seeing the river.
ruclips.net/video/cvYepk4_F7E/видео.htmlfeature=shared
Loved this video. The best one so far as it shows up close the distinctive strata layers back to over a billion years. To see it so close was amazing. I definitely shared another of your videos to Facebook. Would love to see more videos of this trip. If you could zoom in on any marine life fossils would be great. I wonder if the seas here were to shallow for the sharks of the day back over 200 million + years. Finding a tooth to see would be epic. I don't think they can be taken out, but a picture with one on the hand or a hand next to it's embedded site would be really something to see.
Explanation is clear and a nice place to learn .
Thanks for watching and learning with me. More Grand Canyon videos to come in next few weeks including one that shows some marine invertebrate fossils in Redwall Limestone.
ruclips.net/video/cvYepk4_F7E/видео.htmlfeature=shared
Great mystery..really
I took a course on the Geology of the Grand Canyon back in my undergraduate Geology days in the early 80’s. Never made it to the bottom of the canyon. Thanks for taking me there in this video.
the greatest threat to geologists who promote atheism is this. not just the "universal claims" argument that presents a unique contradiction for the claim _"there is no god"_ which can never logically consistently be made in the affirmative.
Your talks are so interesting, I wish you were my professor. I could listen to you all day.
Wow, thank you! Much appreciated.
Great video! (My one grand canyon experience was life-changing.) This helped me better understand the Great Unconformity. Just gorgeous, so appreciated, Shawn.
Glad it was helpful!
ruclips.net/video/cvYepk4_F7E/видео.htmlfeature=shared
So how do you think all those sand particles you mentioned got there?
Noah's Flood
Spectacular site. Awesome.
The Great Unconformity is a really amazing thing and I've never heard or seen it explained so well. You must be having an incredible time on this journey! Thank you for giving us a look at what you're seeing.
The "Great Unconformity" took probably a couple of minutes to form during Noah's worldwide flood.
earlysda, exactly...and belief in Noah gets you kicked out of the phd club
@@ucanliv4ever Sure does, ucan. Anything that goes against the prevailing current of belief in the world is scorned and ridiculed.
.
But observed evidence shows the truth of the Holy Bible.
HOLY SCHIST...what a cool video...much respect from Baltimore
Thanks! ... the clean look of the layers below the sandstone, I immediately think of long ages of ice ? Need to research more on this unconfoming gap ! 👌
In 1995 I was fortunate to be on an environmental impact expedition down the Grand Canyon. Among our number was a geologist from NAU in Flagstaff who led us on a hike of Blacktail Canyon. Your rendition of the Great Nonconformity took me back to that glorious experience. You are a gifted communicator using the web the way it was first imagined. Bravo
Thanks.
I also went to grad school at NAU. Who was your NAU geologist in 1995? I was there 1997-2000.
Very cool seeing it up close and personal.
Thanks!
Your donation is very much appreciated. Thank you!
Shawn, thanks - watching this video was a moment lost in time. My understanding is these features in the Grand Canyon are accessed through wining impossibly oversubscribed lotteries for the 10-day whitewater trips to the Colorado River section, and, with reaching the Blacktail Canyon, are subject to the likely but not always given scheduling and interests of the specific tour group. Your sharing this expert "hands-on" reveal of the striking Great Unconformity is an understated sharing of a special adventure.
An incredible piece of Geological history! Just awesome. Siccar Point in Scotland is also another extremely rare example of where you can see what is thought to be part of a 'Great Unconformity' (or Huttons Unconformity) along with the Grand Canyon sequence ( Powell's Unconformity) . I visited the Grand Canyon 25 years ago now from the UK and I was just blown away by it. Such an awe inspiring place to visit and get up close to some amazing geology.
You have the best job in the world Shawn!
Yes, I've been to Siccar Point and it is awesome to think of Hutton there in the early 1800s piecing together important geologic concepts.
ruclips.net/video/cvYepk4_F7E/видео.htmlfeature=shared
Awesome, in the true sense of the word.
I'm so envious, that you get to study this incredible geology. I'm a first time viewer, but I've known about the Great Unconformity for a while. I'm glad you've given me a deeper understanding. Thankee, friend.
Wow, This Video is Worth Watching Just for the Scenery.
The Knowledge is a Bonus.
Thanks
Much appreciated
Awesome explanation of an amazing place!
Glad you liked it! Thank you!
Thanks
Thank you for your kind donation.
this is the best video I have seen yet on the Great Unconformity- excellent work!
Thank you!
It was left unsaid in the video, but presumably that contact also represents the ground surface at the moment where erosion waned and deposition took over--as this was in a coastal setting, perhaps it looked something like the rocky coasts of CA/OR, with a wave-cut bench of pitted rocks that enclosed tide pools in the upper reaches. I'm always fascinated by those kinds of windows in time where we can almost see exactly what the landscape looked like. Each one of those rocky cobbles at the lowest layer was dislodged from its source somewhere upstream, then came to rest on the Vishnu schist to be buried--frozen in place for us to see 500M years later.
Isn't the mystery of the Great Unconfomity the millions of years misssing that it represents... and considering the amount of missing material we have to wonder about the mechanism responsible? ....
Agreed. What sheered off the Vishnu schist? Where did the upgradient sands erode from to deposit on the schism at the new shoreline?
Fascinating.
@@jonathansmith2323 I think most geologists agree that is was deep ice sheets that eroded that rock away.
I am just barely grasping the commentary of what this environment might have looked like and the forces involved. I need an animated 3D visualization!
Fascinating video. Thank you!
wow it is just so wonderful to see this so plainly above ground. thank you
Wonderful place, mind blowing. Cheers
Fantastic Canyon with a great story! Thx!
Excellent video. Thanks for posting.
Thanks for sharing. Very interesting !
You should interview Dr. Robert (Bob) Gaines out of Pomona College in CA. I have never met a guy more fascinated with the GUn.
More, please!!
Look for more Grand Canyon videos in next few weeks.
Oh fun, love to see the Colorado and the Grand Canyon. Thanks.
Amazing, tks!
Fascinating! I just visited the Grand Canyon and Bryce Canyon, and was overwhelmed by their size and their beauty, but had sooo many questions! This video answers some of them, thank you!
Awesome. I’ve got a video from just outside Bryce that you might like.
ruclips.net/video/5o-Gb2KPcAg/видео.html&feature=sharea
Really awesome video.thank you so much for posting.
Loved this video. It took me back to my Grand Canyon rafting trip in 1968 when I was 14. I still have a photo of the “wavy” rocks that had been sheared and the horizontal strata above them. I was fascinated by them then and enjoyed your explanation of them now. Thanks.
Thanks Shawn, you took me back to my trip down the river.
Truly beautiful and amazing!
So interesting, thank you.
Hi Shawn. Thanks for the great video on the GC GU.
1.2 billion years gone (in the blink of an eye). Hard to wrap my mind around that. Thanks again.
Very informative vid and the scenery is just breathtaking. Thank you!
I wish I could be there one day!
Glad you enjoyed it!
This is so cool. Thank you.
Very interesting!
Nick Zentner at WSU is also an entertaining watch.
Great episode Shawn and remarkable site you picked. GCNP is such a magical place; hope you had a great trip.
It was so awesome. Look for more videos soon from this trip.
I love your channel! So interesting learning about our earth!
Glad you enjoy it!
Thank You for a great video! Very Informative!
chapeau Shawn - great style
Joining from Germany , just found you and these layers interest me extremely for their old age and how they were formed, Great channel, I took an abo of course , thanks a lot !
Welcome aboard! Hope you enjoy the content here as you peruse the existing videos. Danke!
Fascinating 👍 thx
Is there any speculating as to what rocks had been between the Tapeats sandstone and the older Vishnu Shist rock beneath and what happened to it? Or is there a place where that layer might still be intact somewhat?
Wow. So cool. This is one of the most thought provoking subjects I know. Starkly terrifying in a way. The planet is so old. Our lives are so short. Your hand on that spot in time. Yeah buddy. What a great day!
Sure love your work
I’ve been to both N and S rim of Grand Canyon. I had heard of the great unconformity but have never been down in the canyon so it was great to be able to see it in your video.
Thank you!
Thank you for yet another great video allowing me to see up close a geologic wonder I'd never be able to visit. The Great Unconformity is mind boggling, not only for the length of time involved, but for the sheer volume of material that must have been eroded. It would be so interesting to see what that would have looked like prior to and during the erosion process.
Outstanding!
Thank you kindly!
Shawn, on a stereo system it is confusing to have you only in left channel.
mind blowing!
It's pretty crazy when 340 million YA sounds kind of new. What an amazing place. Thank you for showing us this .
I've been to the top of the rim, and wondered what the bottom looked like. Thanks for this video, Mr. Willsey. Subscribed.
Thanks for the sub and welcome aboard. Enjoy perusing the existing videos. Here's one from the bottom of the canyon of the basement rocks at Phantom Ranch. Video from my Rim to Rim hike in Oct 2021.
ruclips.net/video/GHHhu8K-cYE/видео.html
Thanks very interesting. I have trouble walking or driving by a cliff or rock wall and not looking at the various layers.
You and me both!
Great video. The
"Missing" billion years seem hard to accept. Shouldn't there be massive erosion on the Vishnu?
Wow, just wow
Fun trip thanks
That was amazing, thank you!!!
Glad you enjoyed it!
Excellent video, very informative. Seeing unconformaties really gives a sense of the vast age of the planet.
Finally, an actual explanation & detailed images of the GC currently having incredible exposure by media lately….!
Just discovered your channel. It’s terrific! Subscribed with notifications on. 👍
Awesome, thank you! And welcome aboard. Enjoy the existing videos.
This is so friggin cool.
Well that gave me goosebumps ❤️✌️👍
Do you think the metamorphic rocks have been leveled off by glaciers? There was enough time for that, and you would expect to see the smaller rubble on top, which is clearly visible in your video. What else would plane off the rock in that straight a line?
This ris eally fascinating, though i wish these video's were longer 👍
Wish i could visit sites like this. Beyond fascinating.
Hike down to Hermits Canyon and see the black Vishnu Schist and the pink Zorastor Granite. It's below the William Boucher stone cabin site just upriver from the Colorado River.
So cool! 👍🏼
Great video, Shawn. Nice to see that the NASA shirt is still holding together.
I find this stuff fascinating. I saw a picture once of a rock that was billions of years old and the striations curved and turned all over the place. They weren't broken, just bent with the immensely of time.
Very cool!
Cool, where I live everything above the pre-cambrian level was scraped away by the glaciers.
Thank you for proving to me that I’m not crazy
I am at the Western base of Joshua tree national Park and it is phenomenal. What I find in the canyons here.
I am so glad I did something productive with my life!
It never occurred to me that Southern Ontario has anything in common with the Grand Canyon. The pink granite of the Canadian Shield is overlaid by the Great Lakes limestone at the surface near the northern end of Georgian Bay It's a striking example of an unconformity, and one of the most beautiful places to cruise in a boat in N. America.
Oh wow!
10 day trip, always wanted to do it. Only ever walked from the south rim to the north rim.
Love it! Crazy to be looking at and standing on ONE POINT EIGHT BILLION YEAR OLD ROCK! Damn!!!!
This is probably even cooler than visiting the K-Pg Boundary. In terms of deep time it sure is!
Do you have any published lectures?
I'd love to see them.
He has one on the bonnerville flood here on his channel.
Here are lectures: ruclips.net/p/PLOf4plee9UzChn3Mskz-V_pMWeIODsKPK
Great vid Shawn! Great to see the GU so clearly! I dont think we the GU in Western Australia, but there is a small remaining sliver of an massive unconformity near Perth that is between 3.0-2.6 billion year old gneisses and granites of the Yilgarn Craton and a Cambrian (although its not been possible to get an accurate date) transgressive unit of fining upwards conglomerates, sands, silts and mudstones. Sadly the actual contact is hidden by overburden where I have access to where it would be (it's visible in a private quarry nearby apparently) but it's amazing to wonder what happened in that gap, especially as there were probably 2 supercontinent collision and breakup stories that impacted Western Australia in that time period.
Thanks for taking us along. Those are really old rocks After my geology study of the last 18 months i understand so much more than when I went on a ranger walk near the rim of the grand canyon. This video is reminding me ju how young the rocks here in Central Washington are. The scenic views you show are so very stunning. This summer through videos I'm seeing a vast range of rock ages, from 1.8 billion in the grand canyon to a few days old at the Iceland volcano. I can't help but wonder how time of erosion went on before the sandstone began to deposit. I suspect that there is not a way to truly determine what that time was. Thanks.
Anne, you are right, those are really old rocks. Jesus Christ spoke them into existence, along with the sun, moon, and stars, roughly 6,000 years ago.
Wow, some of that looked just like wood, I hope too go there soon.
thank you so much for doing this wonderful podcast.
i never knew geology was so interesting
until i started watching you and several others here on YT.
i wish i would have had this interest sparked 45 years ago.
keep up the good work!
You know, as an electrical engineer this is very explainable. Even that great mica crystal vein you found. But usually these are much smaller in the lab :)
Great Unconformity would be a sick band name
👍👍👍👍
They would definitely ROCK!
I guess I’ll take your word for it.
What are the bigger clasts in the Tapeats on the contact? Are they made up of the schists and granites below, some other igneous or metamorphic rocks from somewhere else, or are they something else entirely?
Ditto to this question. I believe I saw somewhere, that this is common at the contact, and may be indicative of massive glaciation (snowball earth?)
Mostly quartz and feldspar fragments derived from underlying granite and other basement rocks.