May 20, 2020
On daily walks in Stromness I travel further than you might think. Underfoot I notice the Lake Orcadie landscapes imprinted within each flagstone.
– Rebecca Marr, Photographer, Stromness, Orkney, Scotland
A walk through time / Postcards from Lake Orcadie
Dr Antonia Thomas, Archaeologist
These stones are solid now, but they started their journey around 400 million years ago in a deep freshwater lake. Now known as Lake Orcadie, this rare body of fresh water sat within a mid-continental desert near the equator and its depths teemed with marine animals and plants. Over hundreds of millions of years, the sedimentation of the lake’s silts and muds have created Orkney’s particular geology: a layercake of flagstones, mudstones and sandstones.
Visible in the strata today are abstract patterns, flashbacks to the ancient climatic conditions of Lake Orcadie. They are impossibly old, yet in these meteorological graffiti you can get a sense of specific seasons, or even days. Violent rain showers, which may have lasted a few hours at most, have left their mark after all these years in the pitted flags. Mud-filled sun-cracks that hint at long dry spells of weather are preserved like crazy paving, and ripple-marked stones form an archive of paleozoic ebb and flow. Eroded residues of crystals, which once grew in the lake’s damp sands, now survive as a fretwork skin on the top of paving slabs.
The fish and plants have long gone, but if you look hard enough, you might find one of their ghosts: a fossil, trapped forever in stone.
By Rebecca Marr