The White Cart tumbles over a hard band of rock, a dolerite (subvolcanic rock equivalent to volcanic basalt or plutonic gabbro) sill, producing the Linn Waterfall.
The falls were formed due to the resistant (Cathcart) sill intruding through the softer sedimentary strata of the Limestone Coal formation. The Cathcart sill is approximately 3 m thick and composed of olivine microgabbro with sub-vertical columnar jointing which formed perpendicular to the cooling surfaces exposed at the top of the waterfall.
Apart from the dolerite sill, the surrounding rocks are middle and lower carboniferous mudstones with some organic carbon deposites. Coal beds would have been above the current level of the park with the limestone at the level of the park. These form part of a series of Clackmannan Cyclotherms (limestone would form in shallow water which would be inundated by mud brought by the river, which would give way to forests, which would in turn be drowned by sea rise and then fall down to produce a layer of what would later become coal. This cycle would be repeated a number of times giving rise to the different layers of rock).
The glacial sediments have been eroded by the river along the gorge resulting in the formation of the waterfall where the sill crops out. A plunge pool has been excavated by river erosion at the base of the waterfall. Depositional features associated with the river can also be seen, gravel bars have been formed on some bends.
In the cliffs further downstream (opposite the waypoint), the layers of sandstone and shale showed crossbedding and layers indicating that the depositional environment has been sand and gravel bars possibly in a delta or across the mouth of the river. The layers dip in the direction of fluid flow at the time when the beds were laid down. The vertical jointing in the rock is what had facilitated the formation of a cliff face on the eastern side of the river.
To log this Earthcache, please message us (using the button at top of cache page) the answers to the following questions. No need to wait for a reply before logging, if there is a problem with your answers we will contact you. ANY LOGS WITHOUT A MESSAGE BEING RECEIVED WILL BE DELETED WITHOUT NOTIFICATION.
1. Estimate the height and width of the Sill (width being from western to eastern bank, not the width of the water).
2. Go to the waypoint. On the opposite bank, the bedding can be clearly seen in the cliff running approximately north to south. The bedding dips to the south. Estimate the angle of this dip.
3. At various points between the Falls and the waypoint you can see the gravel bars. On which type of bend do they form, inner or outer? Can you explain why they form here?
4. Please attach a photo to your log of you, your dog, gps, thumb or something personal to prove you were here. Please do not show any spoilers in your photo.
June 2019 the logging tasks for EC were updated. COs can now insist on a photo as proof of visit.
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Hope you enjoy a wander around this lovely park. The name 'Linn' derives from the old Scots word meaning waterfall.
The cache is placed with the kind permission of Glasgow City Council.
WELL DONE FINLAY ON BEING FTF AND JOKEROO FOR BEING FTL.
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