Blinking Billy to Hinsby Beach – Part 10 – Conclusion

Sleuthing Around Taroona

Pebbles make a foot

 

‘There is much heaving related to water conditions and light structures are moved with the changes’ ~ David Leaman (1999)

I was on such a high after completing that walk that I couldn’t return to those beaches fast enough. The very next day I was back, sleuthing around behind the beaches, particularly the Grange end of Dixons Beach as well as Crayfish Point.

There, in the shade of the canopy behind the boat sheds at Grange Avenue, was the bed the rivulet had made for itself and heading south was a clifftop track.

I bumped into two locals who’ve live behind the beach (Grange, or Grange end of Dixons, take your pick) for decades. I knew the one – she’d taught my daughter. The man and I soon discovered a common connection, this being Hobart. They were happy to share their knowledge about what to expect from the nearby tracks, set me right about the location of Cartwright’s Point but could not identify Beck’s and Retreat Beaches. ‘My dear, I have not been down to the beach for years,’ she said.

The dogs and I pondered the rivulet and the bed it has made for itself then wandered along the cliff top track – and, just for the record, we’ve been back many times since then, accessing it most often from Uitekah Crescent on the southern side of the rivulet. The cliffs are unstable (which is why, for some years, it was closed to the public) and to avoid broken limbs and worse, there’s a wire fence along the edge. There’s also the option, further along the walk, of taking the steep steps down to the shore (where Dixon’s Reef lies wide and exposed on a spring tide) or continuing through a lane, along roads and through bushland down to the beaches at Taroona High School. On this section from Grange there are beautiful views of the estuary through the fringe of casurinas on the cliff edge. On the other side of the path are gardens and the sounds of the suburb.

Clifftop bridge

Sue Mount’s article on bushwalking tracks in Taroona explains that there’s been a path running along the foreshore a long time before the Apex Club upgraded it in 1972 and I like the idea that this was Mouheenener made. I haven’t found anything to suggest that it was but there’s a human tendency to take the path of least resistance and so there would have been a big attraction to following in earlier footsteps. This might seem a long way from Taroona, but in his book Lost trails of the Transvaal (1965), T.V Bulpin says the ox wagon trails of the Voortrekkers often followed already existing tribal pathways through Southern Africa.

Sue Mount also writes in such a way that makes it sound as though the track continues along the Alum Cliffs to the south. I was intrigued – did a path linked with the Taroona beaches run all the way to Kingston or did she mean that you walk along the rocks to Taronga Road and clamber uphill to join the Alum Cliffs track there? This blog heads there next. I made a note to self: find out!

The view from Taroona

I so wanted to show the geo my new discoveries but when, late one evening, I finally got him to walk the garden path with me down to the beach at Grange, malicious little waves were hammering at the steps and the cliffs.

‘It’s gone!’ I gasped, my disappointment profound. You would not have known a beach had been there. For a moment he looked unimpressed but then he turned to watch the wave action on the cliff with growing interest. ‘It’s being undercut,’ he said and we turned and walked back to the car talking beach erosion. And so, perhaps, I took him there in what were for him, ideal conditions after all, but I felt that I had lost my friend, the beach.  (Later, on more long walks, I was to realise that just like Lord’s Beach in Sandy Bay, this beach expands into long and impressive proportions along which there are many instances of beach art.)

The dogs came with me to explore Cartwright Creek too. We followed it from the base of Mount Nelson, across the road and down the grassy bank to the reef below. We visited on high tides and low tides, the expanse of reef exposed and one fine day, with my cycling friend, we walked from Lamberts Rivulet to Cartwright Creek. The creek does have friends. The Friends of Truganini group apparently attempts to make headway against the riot of weeds beneath which it is largely hidden and at this point it does not look as though they are winning the war, at all.

The Sandy Bay beaches inspired me to look into history to make sense of their current shape and appearance but Taroona, with the cone of its volcano beneath the Alexander Battery (Leaman, 1999)  and the squiggles in the roads indications of multiple repairs, lured me into burying beneath the surface to try to understand the variable geology of the beaches

zen

Going along for the ride

The land here is unstable, the soils expansive. The schools and many Taroona streets and houses are travelling on the back of a slow moving landslip down towards the river, and yes, on some cliff tops, their tenure could be precarious! Cracks in walls, roads and soils, hummocky earth and gutters, contorted trees and sudden shifts in slope angle are some of the clues as to what’s lying beneath, as are the inclinometers that track it’s incremental journey.

For those with a short attention span for matters geological, I promise  I’ll be brief!

Simon Stephens is a geologist who has focused his attention on Taroona and he writes that it is ‘a complete microcosm of the geology of the Derwent Valley’, pointing out that the geology determined the way settlement and construction happened in this area. But long before the explorer’s ships anchored, long before the Mouheenener attuned themselves to this land, and at that point in time when the Permain and Triassic rocks had laid themselves down, Tasmania was a part of Gondwanaland, and was a large basin of accumulating sediments, at other times a shallow sea or lowland flats with icebergs visible offshore. Transformed again, a slow river meandered across ‘a vast riverine plain’ (Stephens). I forget dates fast, so I’m not noting the chronological dimensions of eons here – I’m more interested in the different climates and landscapes that have taken a ride through Taroona.

Today, for instance, there are hard, older rocks on the hills and softer rocks, somewhat younger, on what Stephens refers to as the ‘coastal apron.’ The oldest rock is the Grange Mudstone (Permian) and Fern Tree mudstone also occurs here, sometimes with drop stones in it, as well as worm castings. It smells of sulphur if you strike it – but I haven’t, and I’m not going to run through all the different rock formations either, as there are lots, so instead I’ve linked to relevant resources. Also, because my little project has led to geological conversations at home, I’ll put up the geo’s take on the Derwent and D’Entrecasteaux too, I think perhaps after Pierson’s Point where the view to starboard is of the channel, the view to port the river and Storm Bay.

There are glacial scratches on some rocks that I found along this shore and those stones that have dropped into the mudstone (when it was still mud) have probably dropped out of icebergs and I think that is amazing!  It’s actually no wonder that these kaleidoscopic landscapes have led to such a confusing shoreline.

In short, according to Stephens, the climates in which the rocks were laid down varied from Northern Siberian conditions to the sweltering heat of the African Rift Valley. Taroona, (and okay, the island) has had long drawn out climactic moods.  But we’ve had our impact too.  Here’s a conglomerate of ‘anthropocite’!

Anthropocite conglomerate

Clinging to the cliff
After Blinking Billy 3

Taroona’s fault

There are many fault lines in Tasmania and Taroona has it’s very own (although Sandy Bay has more.)  It’s about 60 million years old and when the land subsided and formed the Derwent Valley this fault started opening up, quite possibly as a result of Australia breaking apart from Gondwanaland. Stephens says it runs from close to the Grange quarry (Truganini Reserve), across the Channel Highway and south to the top of Taroona Crescent where it turns and travels out to sea near the southern end of Hinsby Beach and not far from Alum Cliffs. That steep gully I thought so pretty as I came down the wooden steps on to Hinsby Beach? It’s an exposed part of this fault.

Just Past Blinking Billy beach 1
After Blinking Billy 3

Tropical Taroona

Sometimes Taroona exposes its more tropical self in the form of clay soils and fresh water sediments from when it basked beneath a torrid sun. Stephens says that in the area around Karingal Court ‘the sediments are much finer with clay layers which sometimes contain impressions of leaves and other plant matter.’   A friend of mine recently spent time in Coffs Harbour and couldn’t get over all the turtles she saw swimming around in a lagoon. If we could time travel back to when Taroona was (sub)tropical, we could sip on gin and tonics while watching the turtles, rather similar to the Murray River turtles, swimming around our feet in Taroona. It’s true; there’s evidence in those sub-tropical chapters of the rocks.

 

BLACK SAND AND ZIRCONS

After the last glacial period the sea rose to today’s level. Dolerite from the hill tops weathered and fell into the sea, releasing heavy minerals like magnetite. There is black sand on Taroona beach and well as magnetite you can find zircons here.

So that’s all I’ll say about reading rocks to discover Taroona’s hidden personality and life experience, but the geo has assured me of the need to look at the big picture and not just the local details and so I tasked him with scoping the Derwent River Valley and the D’Entrecasteaux.  I think Pierson’s Point is the right place to point that particular telescope starboard up the channel and port side to Storms Bay and the Derwent River valley and in the meantime there more places to go and people to see.

Bibliography

Leaman, D. (1999). Walk into history in southern Tasmania. Hobart, Tas: Leaman Geophysics.

Mount, S. ([n.d.]). More walking tracks. [Hobart], Tasmania: Dept of Sport and Recreation.

Stephens, S. (n,d,). Introduction and early history. [Hobart].

the face


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