|Throw it! THROW IT!|
The rocks to the south of the beach dipped to the left (SW), the ones to the north dipped right (NE), indicating that the rock layers had folded due to compressive forces (like when continents collide). Dave taught us that a convex-upward fold is called an Anticline (like and Arch) and a convex-downward fold is called a Syncline (like a Saucer).
The rocks here were turbiditic sandstones deposited by turbidity currents in deep water, and Dave reminded us of the school experiment we might have done, filling a jam jar with water, mud and rocks, shaking it up and letting it settle. The bigger bits sink to the bottom and the fine mud setlles out slower - leaving a deposit that 'fines upward'.
|A small anticline fold in bedded turbiditic sandstones of the Colonsay Group (deposited about 750 million years ago and folded about 470 million years ago).|
Many thanks to Dave for a fascinating talk/walk, and to all those who came along!