How to make a Silurian sponge

At school, home economics were not my strong point. I once made a fruit salad in which I left the peel on the orange pieces.

Perhaps appropriately to this blog post, I also made rock cakes that I left in the oven too long. When, at the end of the lesson, the teacher ordered me to extract them from the furnace IMMEDIATELY I did so without question. Unfortunately I also did so without oven gloves. The teacher had to boot the baking tray from my hands before it melted my fingers, and the rock cakes were sent flying across the room. Another culinary failure, and a creative one too. I had to spend the next lesson - double art - dashing back and forth to the sink to cool my scalded digits.

Wear these!

So now, geological aeons later, I find myself reading of Silurian death assemblage cupcakes and wondering if I can come up with anything comparable, and edible. There's only one way to find out: I must overcome my fears and enter the Great Geological Society Bake Off!

Having a Ph.D. in Silurian invertebrate palaeontology, I enjoyed the death assemblage idea very much. However, I don't much care for cupcakes, so I decided to make something else.

With the Geo Bake-off scoring system awarding the highest marks to tectonic or dinosaur-based baking, I realized I couldn't win the competition. So the only tenet I followed was this one:

"If you’re going to make a fossil cake it could at least be interesting"

These fossils are interesting. Just ask Charles Lapworth.

Nothing, I decided, would be more interesting than a patch reef cake based on the Wenlock limestones of Wren's Nest, Dudley, the greatest fossil treasure trove in Britain. More than 600 species of fossilized invertebrates have been discovered in the area, all dating back to the mid-Silurian, a time when the West Midlands lay at about the latitude of Fiji.

So, should you wish to follow in my fossiliferous food-steps and immortalize the dead of Dudley, here's how I went about it.

How to make a Silurian sponge

I wanted to keep the cake simple to allow for my dubious baking skills, but then make its structure and decoration a bit more geologically complex. The fail-safe option was to follow the classic sponge cake recipe of my old friend Delia Smith.

I am probably the only person with a Delia cookery book signed by Rachel Riley.

Unfortunately I only had one cake tin, so I had to use a Victoria sponge recipe from the Independent instead.

I gathered the basic ingredients (175g self-raising flour, 1 level teaspoon of baking powder, 175g spreadable butter, 175g golden caster sugar, and 3 large eggs) but as this had to be a Silurian limestone sponge cake, I replaced the vanilla extract with 1 teaspoon of lemon extract and the zest of 1 lime.

I then made an annotated field sketch:

No minstrels were harmed in the making of this cake.

There are three main rock units in the Wenlock limestone succession at Wren's Nest: the Lower Quarried Limestone, the Nodular Beds, and the Upper Quarried Limestone. I decided I would recreate this stratigraphy by making the sponge cake, cutting it in half, and adding a clastic cream filling.

I checked that my cake tin was of suitably Palaeozoic dimensions...

If you want your own geological measuring stick, buy one here.

...and then poured the cake mix into the tin and plonked it in the oven.

As the sugary sediments underwent rapid diagenesis, I began assembling the invertebrate fauna. It was obvious this had to include Cheerios, for, as Catherine Kenny originally noted, they neatly resemble the columnar ossicles of crinoids. I also realized that broken Shreddies look like fragments of fenestrate bryozoans, so I added them to the bioclast pot.


The other key taxa were trilobites and brachiopods, and I couldn't think how to source them. Then my better half pointed out that we had a Pacman ice cube tray. The Pacmen were half-decent brachiopods, and the ghosts made passable trilobite cephalons. Melt some dark chocolate, and...bingo!

The Palaeozoic answer to sugared locusts.

With the cake baked and the fossils found, I left both to cool and began creating the Nodular Beds. Smashed-up Oreo cookies make excellent rock fragments, and when added to a mix of cream cheese and double cream they form a good muddy layer. I used mini Oreos as the nodules themselves.



Now it was time to build the patch reef. As it was #FossilFriday, and as the company that makes them is based in the West Midlands, I used these confectionary items as the reef foundations:

Mmm, crunchy rocks.

I then began adding the patch reef fauna:

My understanding of Silurian reefs is patchy.

Once the reef fauna were in place, they needed to be fossilized, so I mixed up some limy mud...

Icing sugar, lime juice, a dash of melted chocolate, and some blue food colouring.

...and carried out an obrution event!

This is pretty much exactly how the Wenlock reef fauna were fossilized.

Since no Silurian fossil horizon is complete without its Problematica, I tried to create a machaeridian out of piped icing and flaked almonds.

Chocolepas amygdaloides

Finally, the cake was ready to serve.

The finished product.

My family had gathered in eager anticipation (ok, they were in the house anyway as it was Easter) and all were keen to tuck in (ok, one or two of them were keen. Most were pretty sceptical), so I couldn't keep them waiting any longer.

Time slice.

To my immense surprise, after some silent chomping, the verdict was one of universal approval. My dear mother said the cake was delicious, as did my great aunt. Even my dad, who loves desserts and is usually pretty critical, thought the Silurian sponge was good. There were one or two murmurings about the fact that bits of Crunchie covered in lime icing tasted a bit odd, but that was it.

In the blink of a geological eye, only one slice remained.

Silurian sponge: low preservation potential.

So, in conclusion, mid-Palaeozoic stromatoporoid bioherms may not be the future of baking, but they're clearly the past. And while they won't win the geobakeoff, they have at least allowed me to exorcise some domestic demons.

Now, what shall I make next? A Cambrian Substrate Revolution Pie, perhaps?


(P.S. Should you wish to inspect the entire photo gallery, it can be found here)

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