Two Questions About Varves

[Victoria Deakin]

Hello Professor,

In the lecture 2, slide 2 it is mentioned that lacustrine parent material can be varved. If I understood correctly, I believe you mentioned during one of the lectures that a contributing factor to these varves is suspended materials in water bodies and that these are often coarse particles or silt particles.
Do these suspended materials in water bodies occur during spring melts or was there another cause for them?
Also, can varves only occur in lacustrine parent material or would this be possible for fluvial parent material as well?

Thank you,
Victoria Deakin

[Mario Tenuta]

Hello Victoria. Varves are layers of slightly different material deposited in lacustrine environments. Varves can be seasonal. yes, spring time may have a bit coarser suspended material that deposits. Sometimes it can be primary particles coated with humic organic materials that deposits in a particular season. Sometimes varves can be annual changes in size and colour of material deposited. Example it could be a very wet year on whole bringing slightly coarser material into the lake.

[Mario Tenuta]

Varves is usually used for fine primary particles such as clay and silt. Rivers and streams usually deposit coarser materials. If a river really slows down or pools in areas, then fines may be deposited, but when the water speed picks up with increased water flow, the fines are suspended from the river bed. So varves are rare in rivers and streams. take care, Mario

[Victoria Deakin]

Thank you ! It makes sense that there is some variation with precipitation and that varves mainly occur in lakes.

Best wishes,

Victoria

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