Newsletter No. 202 Wollemi Pine
The Black Country Geological Society
Now for the good news! Guess what! There is a wine called Wollemi. It is a cabernet shiraz and comes from south-eastern Australia. It is “full of lovely blackcurrant and plum fruit flavours that are complemented by a hint of spice. A smooth medium bodied wine that is a great accompaniment to spaghetti bolognese, or peppered steak.” Alcoholic content is 13.5% by volume. Sainsbury’s 'ave it!
On the label: “The Wollemi Pine (pronounced Woll-em-i), is one of the world’s oldest and rarest trees. Thought to be extinct, it was re- discovered in Australia in 1994.” ■
As we get older we notice how the language we use, both technical and everyday, evolves and changes; I still find myself referring to the radio as the ‘wireless’. Geological terms also change, quite rightly, as knowledge and techniques develop. I learnt my basic geology in the late fifties and early sixties and I first visited the Wren’s Nest in 1961 as part of a University field trip. I wondered what a report on that visit would look like, if I had been asked to write one: Perhaps something like this:- (Words and phrases in italics have now been changed or re-interpreted.)
Visited the Wren’s Nest in Dudley, a classic locality for the Dudley or Wenlock Limestone. This rock of Silurian age sits between the Wenlock Shale below and the Lower Ludlow Shale above. It is a crystalline limestone, unlike the Chalk. When looked at under a microscope we see good calcite crystals in the Dudley Limestone, whereas the Chalk is mostly a fine grained calcite mud with occasional fossils .The limestones in Dudley are world famous for their fossils, particularly trilobites, a type of Crustacean, and Calymene blumenbachi is a symbol of the town, usually called the “Dudley Locust”. Corals are abundant; this was once a coral reef, and my favourite is the big, rugose cup coral, Omphyma. There are also many sea mats, now called Bryozoa.
The beds are folded into a sharp anticline by great earth movements in the Devonian. The mechanism for such great pressures to fold and fault rocks is not entirely clear, although there are some interesting theories developing. One is that as the Earth cooled down it contracted and so the crust has folded, like the wrinkles on the skin of an old apple. Alternatively it may have something to do with continental drift, as the continents slowly move across the ocean floor.
From Dudley we travelled westward to Church Stretton, and to the Long Mynd which is of Pre- Cambrian age. The Cambrian started 600 million years ago, and rocks older than this contain no fossils and are devoid of life, although recently there have been some peculiar marks found in Pre-Cambrian rocks, in particular a leaf like structure found in the rocks of Charnwood forest. From a viewpoint we could look westward, across the Church Stretton Fault and after it the Welsh Basin or Lower Palaeozoic Geosyncline. A geosyncline is a basin of thick sedimentary rocks deposited in deep seas, so they are mostly muds and shales. Graptolites can be found in graptolitic shale. If we travelled further ►