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: [ Ссылка ]
- Noel P. James and Robert W. Dalrymple. (2010). Facies models 4. Toronto: Geological Association of Canada. [ Ссылка ]
- 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. [ Ссылка ]
- Imboden, D. M. & Wüest, A. Physics and Chemistry of Lakes, chap. 4: Mixing Mechanisms in Lakes, 83–138 (Springer- Verlag, 1995). [ Ссылка ]
- Eugster, H.P. and Hardie, L.A., 1978, Saline lakes, in Lerman, A., ed., Lakes: Chemistry, Geology, Physics: Springer, Berlin, p.238-293. [ Ссылка ]
- 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). [ Ссылка ]
- 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. [ Ссылка ]
- L.A. Buatois, M.G. Mángano; Trace fossil analysis of lacustrine facies and basins. Palaeogeogr. Palaeoclimatol. Palaeoecol., 140 (1998), pp. 367-382. [ Ссылка ]00020-0
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