Jurassic Coast

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Cliffs at Swanage beach

 

While visiting England this month, I took a quick trip with my mum down to Bournemouth and from there across the chain ferry at Poole to Swanage, the beginning of the Jurassic Coast.  This 95-mile section of coastline along the south-west edge of England is designated a World Heritage site–right along with Stonehenge, The Sphinx, and the Taj Mahal.  The coast is special because in this area the exposed rock cliffs date to the Mesozoic Era, including the Jurassic, and are loaded with fossils of the time.  A leisurely beachcombing walk can yield a treasure of stones containing the fossilized remains of plants and animals that lived 250-65 million years ago.

The cliffs at Swanage Beach date mostly to the Cretaceous Period, 125-90 million years ago, the end of the Mesozoic.  The oldest rocks, from the Triassic in the 250 million year old range, are found at the far west end of the Jurassic Coast in Devon.  The land feature is unusual because the layers of earth were tilted in this area of England, lifting and exposing very old rock that is usually hidden far below the surface.

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Four small stones containing fossils, found on the Swanage beach. The largest is about 4″ across.

I strolled the long, yellow sand beach at Swanage for two hours and hunted near the cliffs for fossils, with some luck.  The cliffs of the Jurassic Coast are quite unstable and tend to collapse, especially after big storms cause erosion.  This can make for unsafe conditions.  The day I visited was sunny and dry, with no large amounts of water running off the cliffs and the tide was at the lowest ebb.  I felt fairly safe getting a close-up view.  All the erosion causes stones from the cliffs to be broken apart, pulled onto the beach and smoothed by the waves to produce fine small specimens.

The best fossil remains are reported to be at the far north end of the beach in the chalk cliffs.  The chalk also represents the youngest rock formations.  I wanted older fossils so I searched farther south.  I found several very interesting small rocks and an area where larger sandstone boulders had fallen to the sand, revealing the fossilized seabed trapped within the rock.16567205450_ceac282587_o

Some of the fossils I collected include what seem to me to be small members of the coral family, echinoids, possibly gastropods and mollusks, and perhaps crinoids.  I am no fossil expert.  16568319569_6222dd4c52_o16753374182_53d0629f0b_o

The large sandstone boulders that have broken open appear to contain crinoid fossils, the long tubes could have been the stems of the animals.  The small pale yellow sandstone rock specimen, in the bottom left of the photo of four stones above, could be the fossilized remains of the feathery tops of crinoids.  16728761966_47cecc0441_oThe tube-shaped creature in the hard blue-gray stone I found washing in the surf zone is a common form of fossil that I have seen in the UK and on the US west coast.  I am not certain what this life form was and prefer not to speculate for fear of being mistaken.

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Preserved tree, possible soft jet, the longest piece about 6″.

Another rare find were bits of wood that the waves had broken from a small tree buried in the cliffs.  If this placement is to be believed, the tree became entombed millions of years ago.  Yet, the fragments appear nearly wood-like with the grain still visible.

The specimens seem to be a type of soft jet, wood that was preserved under severe pressure and not turned to stone, or petrified.  The wood is inundated by veins of harder sandstone mixed with pyrite.  The pyrite is so bright and shiny that is is easy to see why it is called fool’s gold.  16134753673_bf7243d670_oIf the location of this ancient log (encased in hard sandstone at the base of a fifty foot tall cliff) is any indication, then the wood is millions of years old.  The color is a brownish-black and the texture is fragile, easily crumbled.

This perfectly preserved wood may be my favorite find of the excursion.

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