Richard Bell's nature sketchbook since 1998
A micro-hike around the arboretum and conifer plantations at Newmillerdam this morning. I got a surprise when I saw a tiny invertebrate trundling by as I focussed on algae on a tree trunk. I couldn’t see it at all with the naked eye but it no doubt ran for cover from the glaring light of the eight LEDs of my mobile microscope.
Natural sandblasting has hollowed out the softer sandstone and left the resistant bands of ironstone standing to give a Swiss cheese effect to this block in an old sandstone wall.
Iron-rich deposits can be precipitated as a scummy layer where a river meets salt water in an estuary. Perhaps that happened 300 million years ago when this sandstone was laid down.
Without knowing exactly what happened, you can still sometimes deduce the sequence of events. Sometimes a rolled pebble – a mini-Swiss roll of ironstone – suggests that a layer of iron had begun to form on a river bed but that it was rolled away by the current before it got covered by the next pulse of sediment.
In other cases, target-shaped nodules conspicuously cut across multiple layers of sandstone, suggesting that the layers came first and that the iron precipitated out as mineral-rich solutions percolated through the sediment.
My dad was in North Africa during World War II, and I remember him telling me that in the desert it dropped so cold during the night that you’d hear rocks exploding: a form of freeze/thaw weathering. I can’t promise exploding rocks in Yorkshire but you can see the effects of the weather on even the toughest of our gritstones and sandstones.
On an old garden wall, I spotted this mushroom-shaped rock that looks like a miniature of one of the Brimham Rocks. Like them it has been sculpted by wind action.
Just another Monday morning in Illingworth Park. This ageing rock star was cobbled together from details of the sandstone walls around the park.
After Robo-Parkie and Elderman, I’m getting familiar with the Photoshop techniques involved. Especially useful is the ‘Select Object’ lasso tool and for finer tuning of the edges having Photoshop on my iPad Pro and being able to draw with an Apple Pencil makes things so much easier.
Sandstone for drystone walls and local buildings was available in blocks and small flagstones from the same small quarry near the small hamlet of Smithy Brook between Middlestown and Thornhill.
At first sight this chevron pattern in the rockface looks as if it might be the result of the layers being folded sharply over, like a half-closed book. The Smithy Brook valley follows a fault-line but the earth movements associated with that wouldn’t have folded the rocks over like that.
What I think happened is something like this:
10.30 a.m.: At first sight this crustose lichen looks like nothing more than a pale stain on the sandstone block at the edge of the raised bed behind the pond. I’m using crayons this morning and the nearest match that I can get is mineral green, applied very lightly with a dash of other colours added. Using watercolours I would have got nearer to the grey in my photograph.
The black oval sporangia* are about a millimetre across.
A neighbouring colony of the same lichen is more densely peppered with sporangia and they appear to me to have a slight brownish cast, like coffee grounds.
I find the details easier to take in on my macro photographs than in real life but peering closely I notice a springtail wandering by. The springtail is a hexapod and it is no longer classified as an insect.
The heavily jointed and irregularly bedded sandstone always looked untrustworthy and a rockfall occurred some twenty-five or thirty years ago. Moss, fern and ash have colonised the jumble of boulders. The patterns of iron staining in one corner of the quarry fascinate me; there’s such a contrast between the iron concretions and the pure white lens of quartz sand. Large pebbles somehow got incorporated into a well-sorted sandbank at the time the sediment was laid down in a river or estuary 300 million years ago.
The graffiti isn’t so ancient.
22°C, 5.50 pm.
THESE PIECES of sandstone at the corner of the pond provide access to the water for birds and perhaps some cover for newts and frogs. They also help disguise the edge of the black plastic pond-liner. The first pond that we dug when we moved here was lined with builder’s damp-proofing plastic – blue polythene sheeting – which wasn’t resistant to ultra-violet light. I covered the edges with turves and
spread garden netting across the bottom of the pond and pressed sub-soil from the hole we’d dug into it. This produced a more natural-looking pond than our present one but it had a tendency to wick water away and the netting wasn’t a good idea; on one occasion I saw a frog that had been drowned when it had gone down into the mud and got caught in it.
I noticed these impressions of fossils shells in the rock on the far right (top). Superficially they look like cockle-shells but these fossil creatures weren’t bivalve molluscs; the Brachiopods (the name is from the Greek meaning ‘arm-foot’) appeared in the Cambrian explosion of life on Earth and have been around for 570 million years. Three thousand fossil species have been described but today only about 100 living species remain. They have suffered from competition with bivalves such as cockles, oysters and mussels.
These fossils are negative impressions of the shells so I pushed a piece of modelling clay into the hole and made this positive cast of the original shell. When this shell was last visible on the surface of the earth it was on the seabed at a time when our part of the Earth’s crust lay close to the equator, some 300 million years ago in the Upper Carboniferous period. As the fossil is in sandstone, I guess these brachiopods must have been living near the mouth of a river.
The ribs on the shell bear this out as they indicate that this species of brachopod was adapted to live in shallow water in a 
strong current. A smooth shells would indicate a species that lives in deeper, calmer waters. That zig-zag line which marks the opening of the shell is known as the commisure (below right); brachiopods developed a folded commisure to increase feeding area while preventing sand particles entering.
Brachiopods stood on a pedicle stalk anchored on the seabed and opened and closed the two valves of their shells to feed. The hole in the shell where the stalk protruded led to them being given the name ‘lamp-shells’, as the larger valve resembles a Roman oil-lamp, with a hole for the wick.