At the end of a wet day, ten members gathered on Beacon Hill, Penrith on a surprisingly fine evening. John Rodgers set the scene by describing the landscape features to the west of Penrith, well seen from this vantage point. The party then proceeded to Cowraik Quarry where Fi Harwood drew attention to the drumlinoid topography in the immediate foreground. The cover for the drilling for water supplies in the 1976 drought was noted and local water supply and sources discussed. Fi then led us up to the first exposure of Penrith Sandstone, and here a deep red very poorly cemented rock. The hematite coated grains were the well rounded and the rock very friable. We then proceeded to the first of two major faces in the disused quarry. The first displayed large scale cross-bedding, typical of barchan sand dunes, though it was difficult to determine just how many dunes could be identified. John Rodgers had nobly carried a bag of sand and treated the party to a practical demonstration of the formation of the dunes. Fi drew our attention to the approximately horizontal mineralized striations on two vertical faces. Considerable discussion ensued as to whether these were the slickensides and precisely how they were formed.
At the second major quarry face the sandstone was more blocky. Graded bedding could be identified within the dunes. More ‘slickensides’ were observed and more discussion, particularly on the formation of the mineralization along these surfaces ensued. The grains from this quarry were particularly well rounded “millet seed” quartz. Discussions of provenance of the grain, deemed to come from the south, and the processes of cementation concluded the evening before the party returned to the cars and thanked Fi and John for a most interesting evening.
