Lacustrine (Lake) Depositional Environments & Stratigraphy | GEO GIRL

Lake depositional environments are those in which sediment is deposited along the margins and on the basin floor of lakes. In this video, I go over lake depositional processes, sedimentary structures, and stratigraphy, with modern as well as ancient rock record examples. The main types of lakes include volcanic lakes, tectonic lakes, glacial lakes, ox-bow lakes, and man-made lakes. Lakes can be temporary or permanent based on stability (whether it is underfilled, balance-filled or overfilled), fresh water or saline based on salt content, oligotrophic, mesotrophic, or eutrophic based on nutrient content. Factors that control lacustrine deposition include climate, geography, tectonics, basin form, hydrology, the composition of the country rock (original rock), and nutrients available. Open vs closed lakes which are typically balance-filled and underfilled, respectively induce distinct mineral deposits due to the difference in depositional processes; open lake deposits are dominated by terrestrial sediment transported to the lake by river input, while closed lake deposits are dominated by evaporites due to the constant evaporation that occurs during periods of dryness and low input flux. This distinction also caused open lakes to be fresh water and closed lakes to be saline. We then go over lake mixing vs lake stratification which can lead to anoxic conditions in the deep water of the lake, meaning it lacks oxygen due to the lack of mixing of meromictic lakes. Shoreline deposition is typically either dominated by silicate minerals or carbonate minerals depending on the regions original chemistry, the climate, and the amount of river input. Lakes can also have deltas and fan deposits, and their morphology depends on whether the input flow is homopycnal, hypopycnal, or hyperpycnal. We then touch on open lake deposition, and close out the with stratigraphy- how to recognize lake deposits in the rock record.
0:00 Major types of lakes
1:07 Controls on lake sedimentation
1:22 Open vs. closed lakes
3:12 Lake mixing (or lack there of)
4:55 Oxygen depletion in stratified lakes
6:06 Lake salinity and mineral precipitation
7:30 Trophic levels in lakes
9:03 Lacustrine depositional facies
10:01 Shoreline deposition & stratigraphy
12:07 Lake deltas & fans (deposition & stratigraphy)
14:02 Open lake deposition, stratigraphy, & fossils
18:15 Saline/playa lakes, mudflats, & pans
19:46 Stratigraphy of over-filled lakes
21:28 Stratigraphy of balance-fill lakes
22:46 Stratigraphy of under-filled lakes
References:
- Depositional Sedimentary Environments: amzn.to/3gZVi3R
- Noel P. James and Robert W. Dalrymple. (2010). Facies models 4. Toronto: Geological Association of Canada. amzn.to/3mGhVxz
- Thorleifson, L. H., 1995 Review of Lake Agassiz. Geological Survey of Canada (p. 55-84).
- Glenn, C., Kelts, K., 1991. Sedimentary Rhythms in Lake Deposits. In: Einsele, G., Ricken, W., Seilacher, A., eds., Cycles and Events in Stratigraphy. Springer, Berlin. 188-221. www.researchgate.net/publicat...
- Imboden, D. M. & Wüest, A. Physics and Chemistry of Lakes, chap. 4: Mixing Mechanisms in Lakes, 83-138 (Springer- Verlag, 1995). link.springer.com/book/10.100...
- Eugster, H.P. and Hardie, L.A., 1978, Saline lakes, in Lerman, A., ed., Lakes: Chemistry, Geology, Physics: Springer, Berlin, p.238-293. www.springer.com/gp/book/9781...
- Rea, D., Moore, J., Anderson, T., Lewis, C., Lewis, C., Dobson, D., Dettman, D., Smith, A., Mayer, L. (1994). Great Lakes paleohydrology: Complex interplay of glacial meltwater, lake levels, and sill depths. Geology, 22(12). pubs.geoscienceworld.org/gsa/...
- Jones, B.F. and Decampo, D.M., 2003. Geochemistry of saline lakes, in Drever, J.I., ed., Surface and Ground Water, Weathering, and Soils: Treatise on Geochemistry, Volume 5, Elsevire, Aamsterdam, p. 393-424. doi.org/10.1016/B0-08-043751-...
- L.A. Buatois, M.G. Mángano; Trace fossil analysis of lacustrine facies and basins. Palaeogeogr. Palaeoclimatol. Palaeoecol., 140 (1998), pp. 367-382. doi.org/10.1016/S0031-0182(98...
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[@suntaekbang1180]

Thank you for your great explanation. It helps a lot to understand lacustrine deposit.

[@JBond-zf4dj]

Love your videos! They cover everything I'm taking in Geology this year, and are laid out much better than how we're being taught in class.

[@GEOGIRL]

So glad you find them helpful! Let me know if you ever have any topic requests! ;D

[@geoscilove6609]

Really informative. Grateful that your channel exists on YT :)

[@GEOGIRL]

Thank you so much, this made my day! ;D

[@whatever3692]

Thanks for providing this material as it was not available anywhere else on youtube

[@GEOGIRL]

Thank YOU! That is my entire goal, to fill the Geoscience gap on YT. So to hear from you that you think I am doing that means a lot, thanks for the comment! ;)

[@nitrowilly82]

This was a great 20 minute review of 8 credit hours of my degree. Holy fuck did you summarize Fluvial Deposition at Lakes well. I salute you! 07!

[@oladimejioreoluwa6507]

This is a nice explanation, I’m in your DM girl

[@oliverweeweepie3132]

This lake video is amazingly informative ❤️

[@GEOGIRL]

Thank you, I worked very hard on this one, so I am glad that comes across!

[@vaibhav3796]

Focus is totally on the top right corner 😂 admiring the beauty wherever you see it

[@adampax]

Thanks for another informative video! I get a bit confused by the definition of overfilled and underfilled lakes. Surely all lakes ultimately have to be balanced (averaged over a sufficient time window), because if there is more input than output then the lake volume would grow indefinitely, while if there was more output than input, then the lake would eventually disappear. Am I missing something in the definition?

[@GEOGIRL]

No you got it, this is actually what happens! In underfilled lakes the lake typically eventually disappears (unless there is a change in its balance), this leads to the formation of salt flats or 'playa lakes' essentially dried up lakes. The opposite for overfilled lakes, they just continue to slow grow and increase their output in runoff :)

[@adampax]

Ah I see. Very clear, thank-you! ❤

[@palandasghodeswar6169]

Thanks for giving very important information about Hydrocarbon ,coal in Lacustrine environment . Is there Phosphates pockets in and around this type environment ,madam ?

[@GEOGIRL]

Phosphate pockets? I am sorry but I have no idea haha. If 'pockets' is just referring to deposits, I am sure nutrient rich (eutrophic) lakes have plenty of phosphate deposits (although, if there is a lot of primary productivity, they may use most of the phosphate up before it can become deposited). I hope that helps :)

[@CMDROldDuck]

Where I live there are also beaver-made lakes, though geologically speaking I guess they’d be classified as ponds ( just don’t tell the locals that, lol).

[@orbaycam4746]

Is there any generalized columnar section for lake depositional environments?

[@geoscilove6609]

Is there any video where you explain about progradation etc?

[@yaaserwaagyan5701]

Can you speak more of Varves in Lacustrines?

[@moosamoosa8214]

i couldn't find the image of Open vs. closed lakes

[@moosamoosa8214]

can you please sand it to me I need it for my presentation):

[@GEOGIRL]

Unfortunately, that's not an image I found online, it's a figure I scanned form the facies models 4 book: amzn.to/3pdsAPY. The closest I could find online is: gsw.silverchair-cdn.com/gsw/Content_public/Journal/geosphere/12/3/10.1130_GES01143.1/3/721f1.jpeg?Expires=2147483647&Signature=p5iJJJoA5ddP3gmUZpRxtEq9CHuiWpw7IR-e5A~cVKVx7TqkhVl5VZw9vuMm2EJ3XsSlWzQyI6kp71-lYnbO8fTrBnavvobdoGDXnkzEF~goSZdtUJ2CNbz5toC2daa7F0zk63JOt2uioBj3VNu3ZWjaVYT37Lp1ymiCCmL1NZR6lsFOW1Uf~8PgZDYGoHdtI~4-pb~fJh7WzdW9IWykzJEASm186PlyBUvrtfGeDtb8U5PGs-POrhZ9O5oTwkCD7cyPu-5QWfNQwsKUXKhrsfPWzCdbhsN3LPMEk-CGOolMwgD-QBKwoMKmfikBtPBsYDiDlKjQ4RfkJVBNR3rxLA__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA. Hope that helps!

[@moosamoosa8214]

@@GEOGIRL Thx (:

[@buithach4084]

Polymictics is not just a lacustrine phase. My gf went through the same thing now she's my ex.