Portland Bill - side scan sonar image

[sarabande]

some new composite images have been posted on Google

Here's the .kmz for Google Earth:
http://tinyurl.com/dorismap.


They show the geomorphology of the offshore structures by Portland Bill, and may be hepful in understanding the race.


Here's a GE pic of the Race area:

View attachment 29864

 

[oldbilbo]

Hmmm. What does the panel think of this odd sub-sea structure, south-west of Lulworth? Ancient caldera? Impact crater?

 

[Seajet]

Well if it's an impact crater, maybe the weapons test range right there may be relevant ?!

 

[Moonshining]

Hmmm. What does the panel think of this odd sub-sea structure, south-west of Lulworth? Ancient caldera? Impact crater?

Just dipping sedimentary rocks eroded back to a flat platform as the shoreline has receded.

 

[Dipper]

It's a giant seahorse shoe.

 

[shannon9]

Looks like an old telephone to the right of the horseshoe.

 

[Habebty]

I think these images are fascinating, St Albans ledge looks more telling as well. Try googling images of sidescan images of shipwrecks.

 

[sarabande]

I've just enveigled dtr to look at OBilbo's question re the horseshoe shape.

The dislocated lines to the West of the shoe are oblique faults, possibly in Permian, and the horseshoe is suggested as an eroded salt-dome (the sort of structure associated with oil-bearing strata, and given that the pics are not far away from Wytch Farm Oil Field (the largest onshore oil field in Europe).

All in her humble opinion, of course ( )

 

[benjenbav]

I've just enveigled dtr to look at OBilbo's question re the horseshoe shape.

The dislocated lines to the West of the shoe are oblique faults, possibly in Permian, and the horseshoe is suggested as an eroded salt-dome (the sort of structure associated with oil-bearing strata, and given that the pics are not far away from Wytch Farm Oil Field (the largest onshore oil field in Europe).

All in her humble opinion, of course ( )

I would say it was a glacial valley. I would be wrong of course, as my successive answers to all the photo questions leading up to geography o level were proved to be. Fortunately, I stuck with my guess in the real exam and got an undeserved A grade.

On a more serious note: a very interesting set of pictures.

 

[AntarcticPilot]

I've just enveigled dtr to look at OBilbo's question re the horseshoe shape.

The dislocated lines to the West of the shoe are oblique faults, possibly in Permian, and the horseshoe is suggested as an eroded salt-dome (the sort of structure associated with oil-bearing strata, and given that the pics are not far away from Wytch Farm Oil Field (the largest onshore oil field in Europe).

All in her humble opinion, of course ( )

Agree it is probably an eroded anticline, with faulting perpendicular to the coast. Not sure about the salt-dome bit; if I recall it there are no evaporite sequences in this bit of the world, though there are in the North Sea. I worked on doing seismic exploration in this part of the world in the early 70s, onshore. I may even be a tiny bit responsible for the development (not discovery) of the Wych Farm oilfield! We ran one line along the beach at Studland bay, I think.

 

[oldbilbo]

"....suggested as an eroded salt-dome...."

So no alien spacecraft then....?

 

[LadyInBed]

Lulworth Banks, I used to dive it often. Good for scallops and crabs with the odd flat fish and lobster if you were very lucky.
Nice view of St. Aldhelm's (St. Alban's Head), and the ledge.

 

[michael_w]

Interesting, the waves on The Shambles.