Seatown Ammonites

Lots of serious fossil hunters go to Seatown in Dorset to find fossil ammonites that have fallen to the beach from the cliffs. The cliffs for the most part are composed of Green Ammonite Member which is part of the Charmouth Mudstone Formation laid down in the Jurassic Period. The ammonites that are most commonly found in this type of rock are Aegoceras, Androgynoceras, Liparoceras, and Oistoceras. I haven’t found any decent fossils of the type I could pick up and take home, but there are plenty of fossils and ammonite impressions to be seen lying in pieces of rock on the shingle beach where people with hammers have broken them open. These pictures show some of the specimens that I found on my last visit. I am not sure which species they represent but maybe some local geologist may be able to look at these images and tell me what they are.

Embedded Jurassic Coast ammonite fossils

Ammonite fossil embedded in rock on the Jurassic Coast, Dorset, UK - a spiral pattern in nature (1) 

Tantalising glimpses of ammonite fossils, still deeply embedded in rock – rather than the complete, perfect, and separate specimens that you frequently see featured in books and displays – are the types most likely to be encountered by someone simply walking along and enjoying the beaches of the Jurassic Coast. Many characteristics of these ancient cephalopod mollusc shells are preserved and visible in these embedded fossils but the most evident one is the coiled, compartmented, and ornamented shell which invariably describes a natural spiral pattern.

Ammonite fossil embedded in rock on the Jurassic Coast, Dorset, UK - a spiral pattern in nature (2) 

Ammonite fossil (with barnacles attached) embedded in rock on the Jurassic Coast, Dorset, UK, - a spiral pattern in nature (3) 

Ammonite fossil embedded in rock on the Jurassic Coast, Dorset, UK, - a spiral pattern in nature (4) 

Ammonite fossils embedded in rock on the Jurassic Coast, Dorset, UK - spiral patterns in nature (5) 

Ammonite fossil embedded in rock on the Jurassic Coast, Dorset, UK - a spiral pattern in nature (6) 

Ammonite fossil embedded in rock on the Jurassic Coast, Dorset, UK - a spiral pattern in nature (7) 

Ammonite fossil embedded in rock on the Jurassic Coast, Dorset, UK - a spiral pattern in nature (8) 

Revision of a post first published 18 January 2010

COPYRIGHT JESSICA WINDER 2011

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Ammonites at Chapmans Pool

Ammonite fossil: Pavlovia rotunda ammonite fossil in situ in the Rotunda Shales of the Kimmeridge Clay Series of Jurassic rock strata, exposed on the flat beds of rock beneath the shingle at Chapmans Pool. Dorset, UK, on the Jurassic Coast World Heritage Site (1)

There is one type of fossil that you are more likely to find than any other at Chapmans Pool in Dorset, UK – and that is the ammonite – possibly Pavlovia rotunda or maybe even Pavlovia pallasiodes. These are fossil cephalopods dating from the Jurassic Period. The shelly remains of many thousands of these were buried in sediments that were later compressed into rocks – the so called Rotunda Shales – which are part of the series of marls, shales and clays known as the Kimmeridge Clay that was formed during the Upper Jurassic Period over 135 million years ago. 

The fossil shells (which are generally fragile and flakey) occur at the western side of the bay, at the foot of Houns Tout. Most frequently, they are found where they have been squashed between the rock layers or strata. It would be very difficult to remove the fossils from the bedrock – although the ammonite impressions are sometimes found in large pebbles or cobbles. Usually, these ammonites are seen on the surface of the shale rock pavement that extends seawards from the base of the cliff, often temporarily concealed by a layer of gravel or pebbles. They can also be found on large sharp pieces of shale that have fallen down from the cliff in piles of scree. The third place they can be seen is embedded in the vertical cliff face where they are usually visible in cross-section in a distinct sloping band that traverses the lower part of the cliff.

Chapmans Pool ammonite: Pavlovia rotunda ammonite fossil in situ in the Rotunda Shales of the Kimmeridge Clay Series of Jurassic rock strata, exposed on the flat beds of rock beneath the shingle at Chapmans Pool. Dorset, UK, on the Jurassic Coast World Heritage Site (2)

Dorset ammonite: Pavlovia rotunda ammonite fossil in situ in the Rotunda Shales of the Kimmeridge Clay Series of Jurassic rock strata, exposed on the flat beds of rock beneath the shingle at Chapmans Pool. Dorset, UK, on the Jurassic Coast World Heritage Site (3)

Fossil ammonite cross-section: Pavlovia rotunda ammonite fossil in situ in the Rotunda Shales of the Kimmeridge Clay Series of Jurassic rock strata, exposed in cross-section within the vertical cliff-face at Chapmans Pool. Dorset, UK, on the Jurassic Coast World Heritage Site (4)

Ammonite fossil Pavlovia rotunda: Pavlovia rotunda ammonite fossil in situ in the Rotunda Shales of the Kimmeridge Clay Series of Jurassic rock strata, compressed fossil found on a piece of shale in a pile of scree at the base of the cliff, at Chapmans Pool, Dorset, UK, on the Jurassic Coast World Heritage Site (5)

Chapmans Pool fossil: Pavlovia rotunda ammonite fossil in situ in the Rotunda Shales of the Kimmeridge Clay Series of Jurassic rock strata, compressed fossil found on a piece of shale in a pile of scree at the base of the cliff, at Chapmans Pool, Dorset, UK, on the Jurassic Coast World Heritage Site (6)

Small ammonite fossils on the beach at Chapmans Pool: Pavlovia rotunda ammonite fossil in situ in the Rotunda Shales of the Kimmeridge Clay Series of Jurassic rock strata, compressed fossils found on flat bed of shale extending seawards from the base of the cliff, at Chapmans Pool, Dorset, UK, on the Jurassic Coast World Heritage Site (7)

Chapmans Pool ammonite: Compressed fossil ammonite, Pavlovia rotunda, in situ in the Rotunda Shales of the Kimmeridge Clay Series of Jurassic rock strata, found on flat bed of shale extending seawards from the base of the cliff, at Chapmans Pool, Dorset, UK, on the Jurassic Coast World Heritage Site (8)

Compressed fossil ammonite, Pavlovia rotunda, in situ in the Rotunda Shales of the Kimmeridge Clay Series of Jurassic rock strata, found on flat bed of shale extending seawards from the base of the cliff, at Chapmans Pool, Dorset, UK, on the Jurassic Coast World Heritage Site (9)

Ammonite fossil at Chapmans Pool: Compressed fossil ammonite, Pavlovia rotunda, in situ in the Rotunda Shales of the Kimmeridge Clay Series of Jurassic rock strata, found on flat bed of shale extending seawards from the base of the cliff, at Chapmans Pool, Dorset, UK, on the Jurassic Coast World Heritage Site (10)

Jurassic Coast fossil ammonite: Compressed fossil ammonite, Pavlovia rotunda, in situ in the Rotunda Shales of the Kimmeridge Clay Series of Jurassic rock strata, found on flat bed of shale extending seawards from the base of the cliff, at Chapmans Pool, Dorset, UK, on the Jurassic Coast World Heritage Site (11) 

COPYRIGHT JESSICA WINDER 2011

All Rights Reserved