PESA SA/NT GEOLOGY OF WINE FIELD TRIP – SEPTEMBER 2019

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Being kept in the dark in the Maxwell mushroom cave. Picture: Alex Ross

By Dr. Simon Brealey
As is becoming traditional, stalwart devotees of the terroir of the McLaren Vale Wine Region (yes, it’s a bona fide appellation) gathered under a darkening sky in late September to receive the wisdom and tasting notes of Professor Alan Collins of Adelaide University.

Picking up stragglers as we headed south on the 40-minute drive we examined the beautifully-produced geological maps kindly provided by the Dept. Mines (or whatever they were called last week) and met old friends and new.

First stop was on Chapel Hill Road to examine the staggeringly profound unconformity between the Umberatana Group (circa 650 million years old) and the Pleistocene Pirramimma Sandstone of the Seaford Formation (born yesterday).

Despite having pledged to “gee folk along” so that we wouldn’t be late for the pub, the good Professor had to be knocked-out with a geological hammer (see if you can spot it in our picture) and bodily carried onto the bus.

The rain held off and we meandered our way eventually to Maxwell’s Winery, sitting on the intensely fossiliferous Eocene Blanch Point Formation (calcareous, glauconitic siltstones and limestones), with the Tortachilla Limestone at its base and overlain by the Pleistocene

Christies Beach Formation (alluvial fans). Inside the famous “cave” (Figure 2) we were able to get a three-dimensional insight into the construction of a muddy reef system (many thanks Lewis Maxwell). At the same time we were treated to a tasting of a dozen of the finest wines this unique terroir produces, including the aptly-named “Eocene” shiraz.

Feeling somewhat better about the universe, we followed the Blanch Point Formation and its fossils to Maslin’s Beach, Australia’s first official nudist beach, (oh, and listed as a geological heritage site by the Geological Society of South Australia).

Fortunately, it was a bit nippy by this stage and we had the exposure to ourselves (sorry). The breeze was picking up but Prof. Alan had a final treat in store and as the rain became torrential, we despairingly drove past the Victory Hotel to Cactus Canyon, for a view of Willunga Fault Zone to bring the day together.

An intrepid few ventured out into the maelstrom and were rewarded with views of the inside of a waterspout, from what I could tell, but nevertheless, tired (and wet) but happy, we retired to the glorious Victory Hotel for a fabulous lunch in the private wine cellar.

The sun came out and as the wine became a constant torrent, the conversation became a torrid constant. Thank you, Alan for a completely brilliant job and to all attendees for a great day. See you next year, when we may actually discover whether the terroir affects the taste of the wine. Or we may not.

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