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Alluvial Fan Depositional Environments & Stratigraphy | GEO GIRL
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- Опубликовано: 7 авг 2024
- Alluvial depositional environments are those where sediment is deposited in a fan shape adjacent to a mountain where debris or eroded material from the mountain often falls as debris flows to the bottom of it. But how can we identify alluvial fan deposits in ancient rocks? In this video, I go over the dominant processes, deposition, sedimentary structures, and stratigraphy in alluvial fan systems. I start by going over the differences in alluvial fan shapes and what the shape of an alluvial fan can tell us about it's deposition. Then we move on to how alluvial fans are deposited, such as debris flow deposits and water-laid deposits (including sheetflood deposits, stream channels, & sieve deposits), and how to recognize each type of deposit in the rock record. Adjacent facies or depositional environments can help us determine what environment we are looking at in ancient rock strata. The last thing I cover in the video is the typical stratigraphy of alluvial fan deposits so you can reocognize alluvial fans in the rock record, and also what part of the alluvial fan you are looking at, such as the fan apex or head vs the mid-fan and the distal fan sediment.
Alluvial fans are the first depositional environment of many that we will cover in this channel playlist, so please come back to learn more about the geology in other environments!
References:
Depositional Sedimentary Environments: amzn.to/3kutTso
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www.eurogeographyjournal.eu/ar...
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0:00 Where & what are alluvial fans?
0:50 Alluvial fan shape
1:10 What causes alluvial fan deposition?
1:43 Alluvial fan body parts
3:30 Debris flow vs water-laid deposits
3:45 Debris flow vs sheet flood deposits
6:55 Stream channel & sieve deposits
9:07 Adjacent sedimentary facies
9:57 Stratigraphy of alluvial fans
11:26 How to recognize alluvial fans in rocks
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Rachel, Fascinating video 🎬. Thank you. After reading a little more I think the balanced boulders 🪨 in Arizona are not from a glacial moraine 🏔️ or an alluvial fan deposit 🌊 but rather millions of years of erosion of pre-existing bedrock. You probably already knew this 😘.
I am a student from Taiwan, your videos are very easy to know and suitable for us. Thank you and keep doing that.
I am so glad you find the videos helpful! If there are any topics you'd like to see in future videos, let me know :D
I am a student from Nepal. Your video is very useful to me.
WoW! A beautiful lady talking about lenticular deposits and alluvial fan stratigraphy. I can hardly contain myself. I'm a geo nerd and this should be X rated! !laughing! This was great! Thank you!!
Hi Rachel,
Thank you for your video. It was fantastic.
I’ve been trying to find the term for what looks like several miles of alluvial fan systems, namely the mountainsides with canyons. It almost looks like a miles-long series of braided mountainsides. Can you think of what that might be?
Thanks for the information
You're welcome, glad you found it helpful :)
Absolutely awesome presentation materials, but delivery is way too fast for me. But full marks for doing this, well done!
Thanks! I agree I used to talk and edit the videos to the point they were way too fast! I hope my more recent stuff is a bit easier to follow ;)
Wow…Respect from….geology is not a popular subject here..so thank you!! One question though…In video you keep mentioning…..’we discussed this behaviour’…where can find those videos…? Thanks again!
Which book would be good for Depositional enviroment for detail study ?
Hlo maam, with due respect I had a question regarding planar bedding. In sedimentary structures lecture you told that this will form below the wave base then how plannar bedding is forming in the aluvial fans which indicates the shallow environment. Can you please give any clarification on this?
Thanks for the very informative video. I do have one suggestion though, I believe the quality of your video would benefit from you using an external mic. The one from your recording device picked up too much echo from the room making it at times hard to understand what you were saying. I would also second 'Francis Winton's comment about 2 presentations consisting of 12-15 min each. But regardless, still a top-notch video.
Thanks for the support and suggestions! This is certainly an early video of mine, and hope that I have improved at least a few of these things since then, but I will continue to work on it, thanks again! ;D
much thanks😊
You are very welcome, glad you found it helpful ;D
Hi how are you thanks for this video .. may I ask what is the survival percentage chance if some one swim and by mistake stuck into fan like this ? 🤔
Haha, well I don't think anybody goes swimming on top of mountains right? But in theory, if someone were to fall down off a mountain in a mass wasting event I would say that their survival chance depends on the scale of the mountain and the wasting event (is it a small mountain with small pebbles being deposited, or is it larger with boulders tumbling down).
@@GEOGIRL 😃..GEO GIRL 😃..noooo hahaha I mean I was swimming in the sea on the UAE border in Ras Al Khaimah close to the mountains about one kilometer away, and I got stuck in an alluvial fan for a few hours
@@worldgames8355 Wait, in water? Hmm, then I think it's not an alluvial fan at that point, it's a submarine fan (I have a video about those too btw :))
But yes, that would also be difficult to survival rate becuase it really depends on the magnitude of the event and your proximity to the mountains because they drop their largest rocks/boulders first/closest to their base, and smaller grains with distance from source.
But in any case, that is crazy! I am very glad you are ok! ;)
Thanks
Of course :)
PERFECT
Thanks so much, glad you enjoyed it ;D
@@GEOGIRL of course I would like to see another videos but please can you slow your rate with talking, because sometimes I can't follow your fast explain 😅
@@mohamedashrafelsherif6458 Haha, yes, in my more recent videos I try to speak slower. Watch one of my more recent ones and let me know if it is slow enough or still too fast, thanks!
@@GEOGIRL can you give me your email please, I'm studying Geology in Italy and I would like to ask you about some details?
@@mohamedashrafelsherif6458 of course, my email is listed on the about page of my channel. ;)
Hello Alluvial fans are found only in mountains ranges ??
Yep, typically only near (at the base of) mountain ranges.
@@GEOGIRL oh ok I see sort of like a depository stream
Plenty of content but presentation much too fast. Would have been better if the talk had been split into 2 presentations each 12-15 minutes each.
Thanks for the suggestion! I have begun doing that with some of my more recent lectures because I try to include as much info as I can and feel that sometimes I should break them up into two parts. I appreciate the input :)
hi, your video will be good and perfect if your write using pens according to what u said ;)
Cotton Planting
I quoted you on Farcebook.