till sheet

glacial erratics

glacial stratigraphy

"We returned to the city in time to be present at a most interesting lecture by Hugh Miller on the Boulder Clay. He illustrated it by some scratched boulders which he had collected in the neighbourhood of Edinburgh. He brought the subject before his audience in his own clear and admirable viva voce style. The Duke of Argyll was in the chair, and a very animated discussion took place on this novel and difficult subject. It was humorously brought to a conclusion by the Rev. Dr. Fleming, a shrewd and learned geologist. Like many others, he had encountered great difficulties in arriving at definite conclusions on this mysterious subject. He concluded his remarks upon it by describing the influence it had in preventing his sleeping at night. He was so restless on one occasion that his wife became seriously alarmed. "What's the matter wi' ye, John? are ye ill?" "On no," replied the doctor, "it's only that confounded Bounder Clay!" This domestic anecdote brought down the house, and the meeting terminated in a loud and hearty laugh."

James Nasmyth: Engineer, An Autobiography

Till

Definition: accumulations of unsorted, unstratified mixtures of clay, silt, sand, gravel, and boulders

"Few localities are better fitted at once to interest and perplex a geologist than a cliff of boulder clay" Archibald Geikie (1887, p364)

Till occurs widely on the lower ground of East Lothian but there are few permanent sections. Till is often revealed in foundation work on buildings or in road cuts but stream and coastal sections, together with open-cast mines offer the only long-term exposures.

Till is important because its content and structure provides evidence of the mode of formation of associated glacial landforms. Till also occurs within sequences of other sediments where it provides evidence of glacial conditions within the regional Ice Age stratigraphy. Perhaps most importantly, the fabric and erratic content of till give information of former directions of ice flow.

The dominance of locally-derived debris in the till means that its character, and that of the soil derived from it, varies with the geology across East Lothian. On the Coal Measures, the till is a stiff, dark, mud-rich deposit, with mainly small stones of sandstone, shale and coal. On the Old Red Sandstone, the till is a reddish brown sandy deposit with large blocks. On and adjacent to the greywackes of the Southern Uplands the till is often stony.