DIY - soil improvement project

Ah. that's complex. You have there the weald, which is sandstone and 'heath-ey', then tere is a clay vale, then a greensand ridge, then another clay vale, and then a chalk escarpment.

THAT clay is I think far far older than the last ice age, and has had chalk laid over it. So its some sort of seabed clay I think.

I THINK the geology of the bit if england south of London is not post glacial at all. Its far older and is some sort of ancient shallow sea and delta with sand gravel and clay mud, with a load of chalk from smashed up sea creatures on top.

Tim, if you search for bore hole data near you, you will get a full written description of the sections of the ground through which they have bored:

Andrew

That's incredibly interesting - thank you!

"Ashdown beds, sands and silts with subordinate clays - 140m"

Bugger me - that is a resource I didn't know existed - thanks Andrew.

Here's one just up the road:

Sounds like hand augering time :)

And a few yards away it could be different. All large building project have a test hole dug to ascertain whats below. Improving clay soil for horticulture is well documented and it doesn't include "hand augering".

In message , Andrew Mawson writes

Interesting. Thanks. The local water co. bored a large well on our land in 2005.

The detailed register shows no information although I can tell the world it was sandy chalk down as far as they went. I hope the residents of Welwyn/Hatfield are suitably grateful:-)

In message , The Natural Philosopher writes

Fair bit of Herts. came from Norway hence the lumps of pudding stone I'm told.

In message , Chris Hogg writes

Mine are glacial erratics:-)

You may also find this version interesting

Bookmarked - thank you - that is the best overview. Really interesting, looking at my hometown of Banstead in Surrey - that's got several different types all in the space of 500 yards.

I can beat that. Back in 1939 they put one in my garden!

It says

Boulder Clay ) ? UCk ) ... ... 70 70

Which is not what I'd call a full written description.

UCk is apparently

(Obsolete, but I presumably not back then)

Does this mean it was clay all the way, or there was a little bit then the chalk?

There is a big of galvanised _something_ under one of the shrubs. I wonder if that could be it? I keep meaning to dig it up...

Andy

AIUI: UC = Upper Cretaceous, i.e. upper chalk deposits K or k is the conventional abbreviation, from the German kreidezeit, literally meaning 'chalk time' (as in K-T boundary, the division between the Cretaceous and Tertiary geologic periods).

Boulder clay is deposited from melting glaciers ice-sheets etc. As TNP said earlier in this thread, it's ground up rock (but not all clay is simply that). It's basically a surface deposit covering the underlying rocks. Thicknesses can vary widely from a few feet to many tens, even hundreds of feet.

We have a 'galvanised something' in our garden buried under a couple of inches of soil. It's a corrugated sheet that is partly concreted over and covers a 5ft cubed soak-away taking rainwater off the roof.

So it's chalk based clay? Fits. There is the odd flint in it.

The galvanised thingy

There's something in it

that feels as if it's stuck in rubber. Probably not a soakaway... might be the well cap. There was one somewhere once.

Andy

Possibly, although boulder clay contains a right mixture of rock grindings from all over and would be on top of the chalk proper. No reason why there shouldn't be some chalk in it though. Any clue as to what the 70 70 means? Are they depths or thicknesses for example?

Oh _that_ galvanised thingy! You've posted it here before IIRC. I did wonder if it was the top end of a simple lift pump, the thing in the middle being the pump rod that goes up and down, operated by a lever now long gone, rather like this

Umm.. Could it be a well (bore hole)? The one here looked a bit larger in diameter. The central shaft could be the plunger for the pump body located at the bottom of the well. Ours had a wooden shaft and a small electric motor to drive it up and down.

I think the pump seal is cup shaped so it allows water by on the down stroke but seals on the up.

In message , Chris Hogg writes

Snap:-)

Possibly to stop small children shoving things down it:-)

If it is a well-head (or what's left of one) then it's probably drilled down as far as the chalk, as boulder clay isn't going to be very permeable and not a good source of water, whereas chalk is the opposite on both counts. That means the chalk can't be that far down, but whether it can be reached with a hand auger is another matter.

if you want it 'rotavated'.

Or plant spuds everywhere. Double bonus.