We have known for over 150 years that the shelly till contains fossils derived from erosion of rocks on the bed of the Moray Firth and North Sea. We have descriptions of petrified wood from the Jurassic, flints from the Cretaceous chalk and even, at Leavad, what may be Miocene foraminifera. Yet it was only recently that Jim Riding of the British Geological Survey was able to extract pollen and spores from the mud matrix of the shelly till. This was a big step forward in establishing which rocks had been eroded during the ice flows that deposited the shelly till and the direction of travel for the till materials. As the map shows, the shelly till in Caithness carries high concentrations of microfossils reworked from Jurassic and Lower Cretaceous mudstones and sandstones in the Moray Firth. Along the Pentland Firth shore, we start to see an input of Late Cretaceous and Palaeogene materials, suggesting a more easterly component to ice flow. In eastern Orkney, there is a significant component of Permian pollen, eroded from red mudstones and sandstones of this age on the seabed south-east of Orkney. And even Carboniferous spores, possible from a previously suspected small outlier of this age lying against the Wick Fault. The Jurassic and Lower Cretaceous is less well represented on Orkney but, when combined with fossil finds, it’s clear that during the last glaciation the ice that crossed Caithness and Orkney also crossed the bed of the inner Moray Firth.

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