This trace fossil stone from Gemstone Beach (Southland) marks Day Five of New Zealand’s second National Lockdown. Daily Covid-19 case numbers are still climbing, but the positive effects of the Lockdown won’t be felt for at least a couple of days yet. Stone 5 is argillite, a hardened, slightly recrystalised, mudstone formed at the bottom of the sea millions of years ago (probably more than 250 million years for this stone).
Within the stone are captured the movements of small burrowing animals, with maybe a lighter coloured silt filling the burrow as the animal moves on. Or maybe the animal ingests the mud as it goes, excreting it behind itself in a pulsing movement, leaving the shape of an extended worm cast. Sometimes, eddies in the water can cause small ripples on the surface of the mud, and silt can gather in these ripples – and these can also be captured in a stone.
Stone of the Day 6 is here.
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