The Late Devensian arctic marine deposits (Errol Clay Formation) at the Gallowflat Claypit between Perth and Dundee are correlated with the type succession at nearby Inchcoonans, but include an expanded basal glaciomarine unit with rhythms interpreted as symmict varves. Laminated silt–clay couplets are thought to be tidal. Conditions were fully marine by 13.8 ka bp (based on new radiocarbon dates and a 400 a reservoir age). Following recession of the Tay–Forth glacier from its advanced Late Devensian position at the Wee Bankie Terminal Moraine, it is inferred that deglaciation of the middle Tay estuary some 100 km to the west took place between 14.5 and 14 ka bp. The possibility that there was a readvance of ice in the Tay and Forth estuaries during or close to the Heinrich iceberg discharge event H1 is briefly discussed.