Kimmeridge Rocks 7-9

Cliff strata at Kimmeridge Bay

The wide bands of hard limestone exposed by the weathering cliffs at Kimmeridge Bay all have special names to distinguish them in their alternating sequence with the softer shales. The layers are inclined to the horizontal and their line can be traced gently sloping from one side of the bay to the other in the stacked strata of the cliff.

I believe this particular layer is called the Washing Ledge Dolostone Bed, which is part of the Aulacostephanus autissiordorensis Zone of the Lower Kimmeridge Clay from the Jurassic Period. It is a ferroan dolomite with a narrow, dark grey, central bituminous shale band (also called a central oil-shale parting). The limestone is stained yellow and red by the oxidation (rusting) of the iron minerals on the exposed surface of the rock. The colour contrasts dramatically with the grey shales around it.

Reference

West, Ian. Kimmeridge Bay, Dorset. Geology of the Wessex Coast of Southern England. An on-line information resource.

Cliff strata at Kimmeridge Bay

Cliff strata at Kimmeridge Bay

COPYRIGHT JESSICA WINDER 2013

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6 thoughts on “Kimmeridge Rocks 7-9

  1. Nice pictures! We went to Chapman’s Pool close to Kimmeridge last year and the kids brought back a couple of fossils in the Kimmeridge Clay there. One got left outside in the rain, and after only a few weeks had all but disappeared. I find it astonishing the cliffs don’t erode faster than they do.

  2. I love Chapman’s Pool, too. I think the erosion of the cliffs is accelerating at the moment. Right now, this whole stretch of Dorset coast is endangered by rock falls and potential landslides. I believe that most of the Coastal Path is closed while surveys and assessments are being made following the much publicised big fall near Durdle Door a few weeks back. The Coastal Path is certainly closed to walkers near Kimmeridge and Lulworth this week.

  3. Yes, I read about Durdle Door. My mother and brothers live down that way and it was a big thing locally. Ruth, another coastal walker I follow, has also had problems further west with landslides and path closures. I read somewhere that the wet weather seeped deep into the cliffs and made them unstable from within. I hope it is all dried out by the time we get there, but that won’t be for a year yet.

  4. I think that the cliffs are likely to remain vulnerable to collapse in many areas and the coastal paths may well need to be re-routed further inland. We will just have to wait and see. It is going to affect a lot of people who enjoy walking along the Jurassic Coast.

  5. There are so many fascinating things to see and learn about in your part of the world! My hope is to come and explore for myself someday.

  6. It is a great place to look for beach treasures, and well worth a visit, but I think you might find it a bit colder here than where you are. We don’t seem to have had a proper spring this year.

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