Why MD always overlying Alluvium

[sango]

Dear Members,

I am an asistant geotechnical engineer in hong kong.

I currently carry out ground investigation study in a reclamation area. It is reavelaed that Marine Deposit (MD), which in general composes of soft, greenish gray, CLAY, overlies Alluvium.

Any reasons behind for this phenomenon?

 

[gandersen]

Sango:

I would imagine that the question that you are posing is highly dependent upon the local conditions and geology. In particular, if there is a marine clay that is overlying an alluvial deposit, it may have been caused by changes in the flow regime(s) of the river(s) that are feeding the nearshore environment that you are studying. At some point in time, the river(s) may have been depositing granular soils and then perhaps changed course and marine clays were deposited in a more sedentary environment. Another possibility may be a submarine slide where the clayey soils flowed on top of some of the alluvial soils. I imagine there are other possibilities. I would speak to a geologist and/or a marine geologist that is local and who would most likely know the actual events that caused the stratigraphy that you are observing.

Good Luck

 

[DBNodurf]

fluctuations in sea level can also cause such a vertical profile

D. Bruce Nothdurft, MSCE, PE, PG, M.ASCE, etc, etc,...
Principal Engineer/Geologist
Atlantic Geoscience & Engineering
Charlotte, NC