Port Askaig Formation on Garbh Eileach (IMAGE) University College London Caption Anthony (Tony) Spencer, co-author of the latest study and of a classic 1971 memoir about the rocks, standing in 2023 on glacial till (sediment deposited by a glacier) of the Port Askaig Formation on Garbh Eileach, the largest of the Garvellach islands. Credit Graham Shields. Usage Restrictions Must be used with credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.