Re: Scouring/deposition of inter-tidal mud


"N Cook" <diverse@xxxxxxxxx> skrev i en meddelelse
news:dm74tr$npn$1@xxxxxxxxxxxxxxxxxx
> "Carsten Troelsgaard" <carsten.troelsgaard@xxxxxxx> wrote in message
> news:4386e8e9$0$156$edfadb0f@xxxxxxxxxxxxxxxxxxxxxxx
>>
>> "N Cook" <diverse@xxxxxxxxx> skrev i en meddelelse
>> news:dm6h0g$dc0$1@xxxxxxxxxxxxxxxxxx

> Assuming these maps download complete with overlaid red circles
> The area of interest is just to the east of the red circle on
> local map
> http://www.multimap.com/map/browse.cgi?client=public&search_result=&db=pc&ci
> dr_client=none&lang=&pc=SO172HS&advanced=&client=public&addr2=&quicksearch=s
> o172hs&addr3=&addr1=
> or
> http://tinyurl.com/c4xrq
> the main channel is biased well to the south of mid stream.
> There is no local minor tributory at the site.
>
> regional context , Southampton , Hampshire , UK
> http://www.multimap.com/map/browse.cgi?client=public&X=443000&Y=114000&width
> =700&height=400&gride=443316&gridn=113717&srec=0&coordsys=gb&db=pc&addr1=&ad
> dr2=&addr3=&pc=SO172HS&advanced=&local=&localinfosel=&kw=&inmap=&table=&ovty
> pe=&zm=0&scale=25000&out.x=6&out.y=9
> or
> http://tinyurl.com/awl5y
>
> Freshwater is minor input at point marked Woodmill Lane on the regional
> map

Ok, much of what I wrote doesn't seem apply very well to the setting. I'm
afraid that I'll have to leave it for a local geologist with local/regional
knowledge. One of the keys could be weather your region subside or rise from
glacial rebound - it's probably influenced by a minor subsidence on the
peripheral bulge that rose outside the rim of the ice, and now subsides back
in place. This effect has a major influence in southern Denmark, coastal
Germany and Holland in coastal-plain areas ... and your neighbourhood is
not.. a coastal plain? This is my next question - your maps doesn't provide
topographic information, but from memory, you probably live on a rather
solid piece of land bordering the chanel, and the river somewhat cut down in
the subsurface rather than meandering freely across a flat flood-plain? The
meanders are obvious on the map, but the trumpet shaped rivermouth takes me
somewhat out of my habitual thinking of a delta as a place of preferential
deposition.
Anyway, this is becomming free speculation. There is quite a lot of uk
geologists in the group, so they should give it a shot.
If the burial/emergence of the stubs is a reocurring phenomena, you may be
able to evaluate local migrating barres on your own, studying stream
patterns. If the covering sediment is mud, as you say, then it ought to be a
one-way ocurrence .. mud is difficult to erode, once settled. The quiet gain
of land in tidal areas is through the settling of mud at high tide, mediated
by organisms that facilitate aggregation of the colloides in the water into
faecal pellets. The pellets drop out of suspension whereas the colloides
would have gone back to sea.

Carsten


.

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