How about a maritime puzzle to lighten up the Forum? What is it?

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tillergirl

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I 'did' the Little Sunk survey with Gladys in 2019. That was the time of the Sandwich Terns.

Terns by Roger Gaspar, on Flickr

I used Excel to create a profile of the Little Sunk, i.e. a slice across from the Barrow Deep to Black Deep from the NW to SE in a sort of straight line.

Run 1 by Roger Gaspar, on Flickr

On the left, the edge of the Barrow Deep, one the right the Black Deep. The 'teeth' on the sands moving from right to left are (I think) sand waves. There is some more evidence of that available. But that isn't the question. What is that flat area left of centre. No wrecks marked on charts in that area.

I backtracked through the Excel data and I think that flat area is located where the black arrow points on the image below:

Drawing1 by Roger Gaspar, on Flickr

This is my chartlet of course so this is amateur stuff. There is no sign of anything on UKHO charts but in fairness the contour selection wouldn't bring it out. I can adjust the contours from our data so as I had used more contours I would suggest there is an obvious anomaly. Where the black arrow is pointed is approx. where the anomaly on the Excel trace is located. I will backtrack the data again in the morning but I think the centre of where I went over was 51.41.200N 001.23,003E. So there is a sort of...... well I'll call it a small plateau.

I would suggest it is manmade (y) or (n)?
I would make the opening wager by say that sort of round or rectangular area of 4.5m depth isn't right for a wreck: too large, wrong shape. (y) or (n)?
So is it foundation? Nothing on the old stuff to suggest an old lighthouse, or a military thing like a Maunsell Fort. Or did they plan one but it didn't work.

What do you all think?

In the morning I can dig out the chart software manual (all 1463 pages!) and I can do a slice using that software but I don't think it will show much more. I can dig out the video of the Fishfinder trace of the bottom in the morning as well but I wasn't great of getting the best out of that kit at that time.
 
Here is the trace of the seabottom. I think that is evidence that there is 'summat'. I had thought that the Profile created by Excel might be distorting the shape. Excel is just plotting a graph so it has no sense of distance twixt left and right. But the trace of the bottom here confirms (I think) that there is 'summat' (the top line is the bottom, the next line is the echo 'bounce'. Odd it enhances the shape. I best I did out that manual as well)

Image14 by Roger Gaspar, on Flickr

The 'platform' is as hard as the sand either side. I ought to be able to estimate the width of that somehow :unsure:. I am now trying to learn how to create a 'slice' through the sand with the charting software. It is gonna take a while :eek:

Edit: Fishfinder manual: "Second Sonar Return - when the sonar signal bounces between the bottom and the surface of the water and back again. Use the appearance of the second return to determine bottom hardness. Hard bottoms will show a strong second return, while soft bottoms will show a very weak one or none at all" Note the second return on the sand on the Barrow Deep side. Pretty weak. I need to look if there is a similarity to the right.
 
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Can it be a wreck of some sort, covered over by the shifting sands then at times uncoverd, poss a WW2 or WW1 wreck poss a submarine; if i understand it correctly its usuall for some wrecks to shift about a bit and get covered /uncovered ?

rubbish or unfounded thoughts ?
 
It could be part of a wreck that has been 'swept' to remove higher standing structures. When I've dived some wrecks, they are only a bunch of hull plates scattered around the seabed.
 
Could be any of the suggestions. On the basis of the information available I quite like the idea of a foundation for an AA site that never got finished. But didn't the Maunsel Forts just (!) dig piles into the seabed. Ship's hatch are nice and regular. Wrecks have been swept well in the area; there are three on the Sunk Sand in the area and plenty around the Barrow No 2. So one tends to think they should have found that one. Note how easy it was to find the wrecks on the Sunk Sand:

P1070557 by Roger Gaspar, on Flickr

Unfortunately side scan wasn't working well on that day (I hope next season I will have better kit to do that).

But I don't think one can discount it as a wreck just because it hasn't been found. I am tempted to ask the UKHO but don't want to annoy them. I am sure they have enough to do.

Did any of the Mulberry Port sections get built/moved in the Estuary? I guess there might have been some practising sinking a caisson?
 
Applying Occam's razor and your observation that the feature is as hard as the sand surroundng it I'd suggest it is likely to be no more than a plateau of sand...
 
I would counter: why would a distinctive different plateau of sand occur there when beyond there is a uniform graded slope? It is well clear of the Middle Sunk knoll.

The nice thing about this thread is that nobody could be right and nobody could be wrong........
 
Speaking as a lapsed geologist, I have to say that I can't imagine any plausible natural mechanism to create such a feature. Natural features are flow structures, and are either waves (like the sand waves you suspect further along the profile), dunes or streamlined shapes (the overall shape of the bank is such a shape).

I'd suspec a buried wreck or other structure that has disturbed the depositional patterns in its immediate vicinity. It could easily be a previously unknown wreck; the Thames has been a shipping highway for longer than we've bothered to record shipwrecks!
 
According to the software, the plateau is 236 metres and at the left hand side the drop is 2.4metres. Quite big. As a point of reference the SS Richard Montgomery is/was 135m oa. I will try to see if I confirm the measurement via lat/long.

Like AP I can't see it as natural.
 
tillergirl said:
According to the software, the plateau is 236 metres and at the left hand side the drop is 2.4metres. Quite big. As a point of reference the SS Richard Montgomery is/was 135m oa. I will try to see if I confirm the measurement via lat/long.

Like AP I can't see it as natural.
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Given the size and that if it is a wreck, it obviously isn't a recent one, perhaps it's a place where two or three older wrecks have come together? Your research seems to have eliminated everything from WW2 and onwards, and if it was a wreck later than (say) the 15th century, it would be known.
 
AntarcticPilot said:
Speaking as a lapsed geologist, I have to say that I can't imagine any plausible natural mechanism to create such a feature. Natural features are flow structures, and are either waves (like the sand waves you suspect further along the profile), dunes or streamlined shapes (the overall shape of the bank is such a shape).

I'd suspec a buried wreck or other structure that has disturbed the depositional patterns in its immediate vicinity. It could easily be a previously unknown wreck; the Thames has been a shipping highway for longer than we've bothered to record shipwrecks!
Click to expand...
How about a glacial erratic or ledge deposit of mudstone/clay. The beds at Walton may be making a reappearance? Do you have a magnetometer? :)
 
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