Alluvial Fan Depositional Environments & Stratigraphy | GEO GIRL

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: https://amzn.to/3kutTso
Facies models 4: https://amzn.to/3Fp5v3B
http://archives.datapages.com/data/se...
https://doi.org/10.1177%2F03091333770...
http://archives.datapages.com/data/sp...
http://www.eurogeographyjournal.eu/ar...

GEO GIRL Website: https://www.geogirlscience.com/ (visit my website to see all my courses, shop merch, learn more about me, and donate to support the channel if you'd like!)

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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Image sources:
https://www.saddleback.edu/faculty/dw...
https://www.slideshare.net/wwlittle/a...
https://www.chegg.com/flashcards/fluv...
http://archives.datapages.com/data/se...
https://www.researchgate.net/figure/S...
https://commons.wikimedia.org/wiki/Fi...
https://www.flickr.com/photos/zeessto...
https://www.researchgate.net/figure/D...
https://azgs.arizona.edu/photo/cut-fi...
https://www.azgs.arizona.edu/sites/de...
https://en.wikipedia.org/wiki/Graded_...
https://are-review.blogspot.com/2011/...
https://www.researchgate.net/figure/S...
https://www.researchgate.net/figure/D...
http://www.uwosh.edu/faculty_staff/hi...
https://www.researchgate.net/publicat...
https://www.sciencedirect.com/science...
https://www.bsrg.org.uk/photo_archive...

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