Once upon a time, not so long ago, we walked from Pooles to 1080. “Around three headlands, through two pebbly coves, over one long-grass rock bypass, past five large orange dykes, between untidy masses of black lava long since solidified, and onto parallel ridges … Rockface laminated in wavy lines.” That’s how I described it then, with a few vague technical geological terms, dyke and lava, thrown in.
Since then, we’ve been tutored, under the auspices of U3A Bermagui, by Bruce Leaver, a passionate geologist. He gave us an early morning insight into deep time, explaining the origins of all the landmarks we could see. Not only that, but he had rocks on the table which he named and explained. J scrutinised them intently; read and reread Leaver’s lucid notes; and collected and classified pebbles from nearby Hayward’s Beach. Then we were ready to revisit the track from 1080 to Pooles, armed with a bit of knowledge, a geological hammer and a collecting bag.
What were we looking for? The wavy lines that indicate hornfels; the solidified lava; the dykes of intruded rhyolite.
Hornfels first. It’s the result of a meeting between a clay-rich rock and a hot igneous body: a connection that, like all relationships, alters the original rock. ID is still slightly tentative: none of the Google images I found looked anything like this.
Then lava, easily recognised – deep black, sometimes pitted, sometimes with flow marks still visible, sometimes smooth like black marble. It derives from the Cretaceous period, somewhere between 135 and 65 million years ago, and there it is still, squatting or flowing solidly, unmistakably black and unmistakably lava.
Finally, and more doubtfully, rhyolite (is it?) forming dykes, in one place “a vertically oriented sheet of light-coloured igneous material sitting starkly in the old shale rocks” as described by Leaver. Dykes are intruders, pushing their way through other rock and marching in a straightish line across the rockscape.
That’s some sort of progress towards geological understanding. At least we’re on the way to mastering the naming of parts. J has a bag of samples to split, and an urge to master the measuring of specific gravity, which, done precisely, gives a precise rock ID.
But for me there’s more to the beaches than geological understanding . There’s the moody sky with faint wave-splash and reflections in the passage of tide.
There’s jetsam, sometimes easily recognisable, sometimes a mystery, at least to this landlubber.
There are rock patterns (possibly hornfels, definitely aesthetically pleasing); the residue of retreating waves; rock-clingers; and a cuttlefish with a touch of pink dawn.
Behind all this Mother Gulaga lounges – Mother Gulaga, or, speaking geologically, a 98 million year old intrusion into the side of a massive strato volcano, a volcano so immense it was visible from as far away as Wollongong and spread over Cobargo, Tanja and Narooma.
For Aboriginal oral histories of connection to this part of country, see here.