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May 13, 2016

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Delta bravo!

Kylie’s Beach in Crowdy Bay National Park

It’s lucky that travelling in reverse is just as easy as going forwards in Egg, my decrepit wooden kayak (currently held together with duct tape), because lately my paddles seem to be taking me back in time. Back to old haunts and old holiday snaps, but also really really far back into the geological past.

When I took this photo of beautiful Kylie’s Beach in Crowdy Bay National Park in 2011, for instance, I wasn’t thinking “My, what a fine example of a barrier dune system in a wave dominated estuary!”

Diamond Head and Watson Taylor Lake

And this snap from North Brother Mountain, taken on the same trip five years ago, demonstrates that I wasn’t paying enough attention to geomorphology at the time. It’s not a bad shot of the 100,000 year old Pleistocene sand barriers that protect Watson Taylor Lake from the crashing waves of the Pacific. But, in retrospect, I should have given the picturesque tree on the right the flick, and made sure I squeezed in a view of the mouth of the Camden Haven River.

Because, for the New South Wales anyway, this is a pretty special place. As you can see in the pic below by a more geologically literate photographer, enfolded in the lake is a classic river delta – a rare sight in this part of the world. It’s a mini-Mississippi, sloughing off its sediment as it flows into stiller waters, leaving muddy banks along the way and a cluster of little islands at river’s end.

Watson Taylor Lake. Bias, Gene. watsontaylorlake.jpg Pics4learning July 2004. 9 May 2016 <http://pics.tech4learning.com>.

Sad to say, I didn’t notice all this deposition and composition as I paddled down Camden Haven Inlet at dawn, skimming over the seagrass and the sand. Even when I got stuck in the mud – sorry, fluvial sediment – right in the middle of the lake. At high tide. Next to a bunch of knee deep swans. Sometimes I reckon I’m not the sharpest knife in the knifeblock.

Black swans smirking while I try to get afloat after running aground in the middle of the lake

It was only back at camp at Kylie’s, over a first reviving brew-up, when I stumbled on Rod’s Northern Rivers Geology blog with its intriguing story of the missing coastal deltas of New South Wales that I figured out what I’d seen.

South Brother Mountain in dawn light

Up a shallow side creek towards the lake

South and Middle Brother from the northern shore of the lake

A side view of the levees beside the Camden Haven River

Paddling dead casual-like towards the river mouth

Thinking back, I realised I’d been somewhere very similar just a few weeks ago, in another one of the New South Wales’ magical coastal lagoons. Where Dora Creek – home of freakish panda-snakes – empties into Lake Macquarie, the very same levees march, both sides of the river, far out into the open water.

Dora Creek doesn’t have mangrove topped islands at its mouth, like the Camden Haven. Perhaps their beginnings were washed away by the waves that scoot across five kilometres of open water to scare the hell out of unwary kayakers. In the same way storms, waves and the East Australian Current sluice river sand and sediment out into the Pacific or up the coast, leaving barrier beaches in place of river deltas all along the Eastern seaboard.

Island in the delta

But in the sheltered estuary of Watson Taylor Lake I got to enjoy all the rare pleasures of a river delta. Mosquitoes, for instance. More than I’ve encountered anywhere, even my backyard, locally famous for its blood buffet and chubby and contented microbats. With the mozzies come the mozzie eaters.

“Clumping” white-breasted woodswallows

Woodswallows peeping

Woodswallow grooming

I stopped to take pictures of the wood swallows, but in fact, this little beach, at the very end of the Camden Haven’s levees, had almost as many birds as it had bugs. Honey-eaters in an array of colours: brown, striped and yellow-faced. Noisy friarbirds, mobs of them, bursting from the casuarinas to wheel and chatter. Wagtails and fantails. Crested terns chilling out away from the surf. A drongo (I’m not being insulting – it’s a gorgeous bird). Not to mention a special treat – the rarely sighted fungus-faced thornbill.

Egg on “bird watching beach” near the mouth of the Camden Haven River

Spangled drongo

The rarely sighted fungus faced thornbill

Crested terns sticking their tongues out at me.

And, as I wended my way through the maze of islands with the help of the handy map in my Paddlers Guide to NSW, an unflappable young sea eagle, rising majestically above the cloud of biters. It takes a genuine love of raptors to continue taking snaps while half a dozen mosquitos are sucking on your eyelids.

White bellied sea eagle in a river-side casuarina

Juvenile white bellied sea eagle

But as RB just reminded me, if Australia’s eastern coast is wanting for river deltas now, it’s not always been so. It was an enormous braided river delta, like the Amazon or the Ganges that laid down the golden Hawkesbury sandstone, a couple of hundred metres thick, right across the Sydney Basin, 230 million years ago.

Perhaps this is an approach to marketing I can put to the NSW Tourist Board. “Volcanos! Dangerous megafauna! Epic braided river deltas! Go back far enough in time, and New South Wales has it all!!”

Reflections of North Brother Mountain on my way back to the put in at Camden Inlet

More adventures on New South Wales’ coastal lagoons

Geomorphology and dawn reflections on a midwinter lagoon at Myall and Narrabeen Lakes

A paddle across scary Lake Macquarie to see the snake-pandas of Dora Creek

Encounters with eagles on Budgewoi Lake

Moonlit night on Kylie’s Beach

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February 19, 2016

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Alhambra on the Hawkesbury

The last few times I passed by Bujwa Bay, on my way downriver from Berowra Waters, it was shrouded in mist.

On the way to Bujwa Bay

Mist blowing out of Bujwa Bay

A misty morning on Berowra Creek

But last Sunday, in the golden light of late afternoon, there was a revelation.

I’m familiar with the Hawkesbury’s sculpture parks and sandstone art galleries. But the fact that Berowra Creek had well preserved fragments of an ancient Moorish fortress – well, that was news to me.

The “sculpture park” on the northern shore of Long Island, the Hawkesbury

River rainbow, in Berowra Creek

Honeycomb formations in a cave above Bujwa Bay

Sandstone art gallery in Smith’s Creek

When I went home and told RB I’d seen something very like the famous stucco inscriptions of the Alhambra on a estuarine cliffside at the end of Berowra Waters Road, his comment was “You’re barking!”. And he’s probably right.

Honeycomb weathering in sandstone on Bujwa Bay

After all, the Alhambra is an artistic jewel, a masterwork of European Islam, preserved over the centuries after the Moors themselves were driven first into the mountains and then out of Spain altogether. Its delicate carved plasterwork miraculously survived Christian conquerors, dodgy architectural restorers, squatters and tourists. And the sandstone of Bujwa Bay is just, you know, rock.

“The sea” in the Alhambra

Stucco inscriptions

The Alhambra from a distance

Stucco and tile in the Alhambra

Stucco inscription at the Alhambra

But I’ve been reading about “thing power” and it’s given me a whole new angle on inanimate objects. “Thing Power!” – sounds like a killer bathroom cleaner that will sort out all the disturbing life-forms, named and unnameable, in your shower cubicle.

But according to Jane Bennett, its “a creative not-quite-human force capable of producing the new [that] buzzes within the history of the term ‘nature’ ” (2010, 118). Electrons, microbes, minerals, waste, all busily making and shaping things, inside, around, through, against and despite humans and their fancy-pants plans. She reckons things and people rub along or against each other in a pattern that’s “not random or unstructured, but conforms to the strange logic of vortices, spirals and eddies” (2010, 118).

Alveoli weathering in sandstone

Stone lacework on Bujwa Bay

Kooky as it sounds, this is not a bad description of how the Bujwa Bay Alhambra came into the world, according to a paper coauthored, in a way that pleases my penchant for magical thinking, by a geologist from Granada, home of the famous palace.

Honeycomb weathering like this happens in all sorts of porous rocks, around the world – from Antarctica to Jordan – and maybe even on the surface of Mars. It might seem like hollows would form in weaknesses in the rock, but it’s not necessarily so. Blistering heat, frost, chemical weathering and rain are all in the frame – with maybe a little help from the odd patch of algae or lichen. But mostly it’s about salt and wind.

Salty water – in this case from seaspray – seeps into the rock and crystallises, making tiny fractures. If there’s plenty of water, salt crystals forms on the outside surface to form efflorescence, a mineral flowers blooming on a cliffside or a cellar wall or a garden fence. But the real damage is done deep in the rock.

According to Rodriguez and friends, once a depression is formed in the rockface, wind eddies and swirls inside the concave parts of the stone. Faster breezes mean more evaporation and a super-saturated salt solution, meaning more salt crystals and more fretted stone. Eventually the rockface becomes lacework, without any intervention by a rock lacemaker.

Alhambra rocks 1 crop long

The other name for honeycombed rock is alveoli. It’s stone with lungs. Made of mineral flowers. Not alive (or mostly not alive – sorry algae) but doing complicated and beautiful things.

Not immortal, invisible, unfathomable. In fact, as fathomable as the waters of Bujwa Bay at low tide, that is, knee deep to a heron. Just exceedingly hard to grasp.

And that’s not just me banging my head against a corroding brick wall of “Salt weathering: a selective review” – the geologists are still bickering over exactly how it works. In Bennett’s (possibly slightly loopy) words, it’s vital matter, “hard to discern… and, once discerned, hard to keep focused on. It is too close and too fugitive, as much wind as thing” (119). Or perhaps, in this instance, both wind and thing.

A crab wondering what I’m on about, on a beach near Bujwa Bay

References

Jane Bennett 2010 Vibrant Matter, Duke University Press

Eric Doehne (2002) “Salt Weathering: a selective review” from Natural Stone, Weathering Phenomena, Conservation Strategies and Case Studies. Vol 205, 51-64, Geological Society Special Publication

Carlos Rodriguez-Navarro, Eric Doehne,Eduardo Sebastian (1999) Origins of honeycomb weathering: The role of salts and wind, GSA Bulletin; August 1999; v. 111, no. 8; p. 1250–1255

Huinink, H. Pel, L, Kopinga, K. 2004 “Simulating the growth of tafoni” Earth Surface Processes and Landforms 29 1225-33

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November 12, 2015

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Backyard birds, estuaries, Geology, kayaking, national parks, Native birds, waterways

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Old hands

I know I live on, walk on, paddle through, someone else’s country. Guringgai country, and sometimes Darug lands, since Berowra Creek, or so I read, is a boundary line between people of the coast and river people. Sometimes, I venture north of the Hawkesbury – Deerubbin – into Darkinjung country. I try hard to remember that I’m an uninvited guest in this land, and that I know next to nothing about it. Because it’s important to know what you don’t know, if you know what I mean.

But sometimes what you don’t know jumps out and smacks you in the eye. It happened out on the water, on Smith’s Creek, a couple of weeks ago.

I love the “road signs” of the waterways

Smith. It’s a joke name, isn’t it? The sort of name you use to check into a hotel for a dirty weekend with a person who isn’t the one you’re married to. A name white guys use to be anonymous. “Yes, I’m John Smith and so is my wife”.

I’m sure Smith’s Creek is named after a really very important Smith. After all, at one time at the turn of the twentieth century, Kuring-gai Chase – specifically the bit of bushland between Smith’s Creek and Cowan Creek – was considered a possible location for the capital of the new Commonwealth. Magnificent scenery and handy for getting back to Sydney, what? You have to wonder whether the sandstone escarpments of Kuring-gai National Park would have been quite such an amenable environment for roundabouts as Canberra. All in all, I’m very glad it didn’t happen. Aside from everything else, I don’t think I could handle a close encounter with Cory Barnardi at the crack of dawn on a Saturday morning.

So, as I say, there I was in “Smith’s” Creek, blessedly free of conservative crusaders and, indeed, showing little sign of human life at all. In Apple Tree and Stingray Bay, the power boats were moored silently in rows like roosting birds. Nothing stirred.

Silent boats at dawn in Apple Tree Bay

Dawn stillness on Cowan Creek

Fog on the hillside

Looking back towards Berowra

Boat and water

Tree on sandstone

As I slipped with the tide towards Deerubbin, not a jetboat in sight, a wave of love passed over me for the sport of rugby. More specifically, a feeling of warmth for the thrilling final of the 2015 Rugby World Cup, broadcast to the sports fans of Australia at 2am the night before. What a fine influence sport is on the nation! How it improves the tone of the place! All those worn out rugby fans, tucked up in their beds, or snuggled down in their bunks, dreaming of triumph or of despair, but more to the point, not, as yet, starting up outboard motors.

Looking north towards the Hawkesbury

While the rugby fans were sleeping I paddled, more or less, back to Berowra, swaddled in fog that rolled down the valleys, smudging the pictures of my weekly sea eagle (curse it). They slumbered on as I turned the corner into Smith’s Creek following the great big signs on the shoreline, papped some peeved looking cormorants, tried and failed to see any sign of rays in the sands of Stingray Bay. In the stillness, I felt as if I was in a dream myself as I passed along sandstone cliffwalls, rippled and rainbowed, that slide down and down into the bottle green water, and beneath the smooth-barked gums that butt their way into solid rock a metre or two above a tideline line of oystershells.

Peeved pied cormorants

“Smith’s” creek on the day after the rugby final

The sports lovers were still sleeping when I had my magic moment – the one you wait for every trip – when moon and raptor met in the bright morning light. So for all their shiny cruisers and thrumming engines, the rugby fans would have been no good to me at all if Egg the ancient kayak had drifted away, as it very nearly did, while I tried to find that damn whistling kite in what seems, through a zoom lens, like a very very big sky. That would have been me, stranded in sparkling knee-deep water, with a ten k swim through the bobbing jellyfish, all the way home.

Whistling kite and moon

Having a rest in the shallows of Smith’s Creek

Jellyfish and photographer

It wasn’t until I got back and uploaded my photos that I saw, in the corner of a picture, the ochre hand prints on the golden rock. Who put them there and when? I really don’t know. Maybe someone not so long ago – the indigenous rangers of Guringgai take loads of school kids out to see the hundreds of carvings and paintings that are all over the park. I bet a bit of print making happens here and there. Could it be one of the people of West Head slain by smallpox – no accident it seems – just a few years after the convicts arrived? Surely not. Someone in the time in-between, making their mark on country. Still here, though many people were forced far away, as far as Yorta Yorta country, on the borders of Victoria.

I just don’t know. Those hands told me, at least, to remember that I don’t.

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June 23, 2015

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anthropocene, Geology, History, national parks, natural history, Seasons, Soil

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Midwinter lagoon

Bombah Broadwater in the gloaming

It’s past the shortest day of the year, but, in spite of her scrapes and dings, Egg the elderly wooden kayak doesn’t seem to be ready for drydock yet. Perhaps it’s that last unseasonable whirl of autumnal warmth, caught alongside the coast in the East Australian Current, that’s keeping the sea a balmy 20 degrees. Or perhaps it’s just the lure of still, winter water all around.

Since Egg was first laid in our driveway a year ago, I’ve been seeing Sydney differently. Those long roundabout routes from A to B via M and Q and P, punctuated somewhere along the way by a bridge or two, suddenly make sense. The city of roads and buildings retreats and, I feel, just out of sight on every side, the presence of water.

The Hawkesbury estuary

Upper reaches of Berowra Creek, a hop skip and jump from the Hornsby Westfield

This is our backyard, encircled by the salty embrace of the Hawkesbury estuary. But it doesn’t end here, with the secretive topography of flooded river valleys. All the way up (and down) the New South Wales coast, the shoreline is flanked by coastal lagoons. I’m not complaining, even the tiniest little bit, about all these sheltered waters. But I’ve started to wonder what geographic accident has given a timid canoeist so much to feel grateful for.

Along with marshes and flats, coastal lagoons make up maybe 10% of the world’s seaboards, and in NSW lots of us live by them, many more than by the ocean itself. Lagoons (or wave-dominated estuaries – there are ongoing hissy-fits around these definitions) appear where low-lying plains, rather than dramatic cliffs, meet a shallow gently sloping seabed. Usually, they are found on shores shaped mainly by waves rather than big tides, with underlying rock that crumbles nicely into beach sand not finer, silty sediment.

The more sand the better – perhaps our generous continental shelf harbours this bounty from a time when the Sydney Basin was a enormous braided river delta, like the Ganges today. But you don’t want too much rain – lagoons are usually fed by an underwhelming little creek or even just groundwater – that doesn’t (or doesn’t often) burst through the land between waterway and ocean.

Dawn breaks over the barrier between Bombah Broadwater and the open sea

To make a lagoon*, you need a barrier to the open sea. In the nineteenth and first part of the twentieth century, coastal geomorphologists duked it out over just how these barriers were born. Did breaking waves make for ever-rising off-shore sand bars? Did encroaching seas submerge coastal dunes? And then there’s the third, attractively named “spit accretion theory” (Davis and Fitzgerald, 2004). Not, as it might sound, a creation myth where bunyips drool into puddles between the dunes; just sand clinging to rocky headlands as it is carried along the coast by the (delightfully piratical) longshore drift.

It turns out that everyone was right, at least some of the time. Which is nice. It’s hard to keep the heat in a scientific controversy when lots of the evidence, hidden beneath the surface of the sea in the first place, has been washed away or covered over during the last few millenia by terrestrial silt or aeolian sand. Who could be angry with such mellifluous and frankly otherworldly-sounding geomorphologies in play?

Pelican landing on Bombah Broadwater

Most lagoons have only been around for a little while, geologically speaking, formed after sea levels began to rise as glaciers melted 18,000 years ago or thereabouts. Many, like Narrabeen Lake, which we whizzed round on our bikes in the company of half the population of the North Beaches a few weeks ago, are even younger, not seven thousand years old. A blink of the eye for people who were here 50,000 years before.

Strangely, lagoons move. Today’s surfers walk across the relics of yesterday’s drowned lakes. Barrier beaches migrated landward, emerging from the ocean just as “marine transgressions” (that’s advancing oceans, not the naughtiness of waves) slowed. Shaped in stable times, coastal lakes still don’t hang around for long. This shouldn’t surprise me – I know that, despite appearances, beaches are really rivers of sand.

If the tides were higher, if the rivers was faster or siltier, if Australia wasn’t so seismically serene, the lagoons would fill up and dry out or be washed away, and the cormorants would have to hunt elsewhere. In fact, for all our dredging and draining, it’s happening right now. Like life itself, coastal lagoons are a transitory phenomenon, a passing pleasure.

Surfers floating over the relics of yesterday’s lagoon

Narrabeen Lake

Black swans in Narrabeen Lagoon

(Little?) Black cormorants

Intermediate egret in Narrabeen Lagoon

And then there’s the gyttja, something so very special it’s found nowhere else in Australia, and helps qualify Myall Lakes as a unique protected wetland. What is it? Well, rotting pondweed. No, I’m underselling it: it’s up to 70cm of “a highly mobile and organic mud that has a gelatinous appearance”, a “flocculent green–brown material” (Drew et al 2008), “an uncompacted, anoxic and sulphurous ‘ooze'” made from “the decomposition of charophytes, macrophytes, cyanobacteria and algae”. Strangely, not so much about the ooze in the National Parks brochures. But it’s an ooze that’s been there for, perhaps, a thousand years.

Dusk on Bombah Broadwater

Looking west at dawn on Bombah Broadwater

Canoeists in the gloaming

Eric the Egret on the Bombah Point Ferry

Glorious Angophora

Reflections on the tea-brown waters of Myall Lakes

Still morning on Two Mile Lake

I’ve been thinking about lies beneath the surface of the water and the windblown sand. But paddling through the Broadwater two weeks back, in a startling moment I found myself not gliding above the mysteries of quiet waterways, but surrounded, right amongst it. A huge flock, a murmuration almost, of little black cormorants, perhaps returning from a fishing trip, passed above and on one side and on the other without a single cry but with a sound I’ve never heard before: the white noise of hundreds and hundreds of moving wings.

The sound of the midwinter lagoon, all around me.

Little black cormorants murmurating

* Be warned: there’s a chance my account of the origins of coastal lagoons is completely wrong. After all, the New South Wales coast “has provoked many questions and various degrees of controversy” (Thom, 2010, 1238). And perhaps it’s “premature to attempt a comprehensive analysis of coastal lagoon evolution and dynamics when so many lagoons have been so little studied” (Bird, 1994, 13). In case you want to check my workings:

References

Bird, Erik (1994) “Physically setting and geomorphology of Coastal lagoons” in Kjerfve, B. (ed) Coastal Lagoon Processes, Elsevier
Davis, R. and Fitzgerald, D. (2004) Beaches and Coasts, Blackwell Science
Drew, Simon Iona Flett, Joanne Wilson,Henk Heijnis, C. Gregory Skilbeck (2008) “The trophic history Myall Lakes, NSW, Australia” Hydrobiologia 608
Eyre, Bradley and Damien Maher “Structure and Function of warm temperate east Australian lagoons: implications for natural and anthropogenic changes” Coastal Lagoons: Critical Habitats of Environmental Change, dited by Michael J. Kennish, Hans W. Paerl
Martin, Louis and Jose Maria Landim Dominguez (1994) “Geological history of coastal lagoons” Kjerfve, B. (ed) Coastal Lagoon Processes, Elsevier
Masselink, Gerhard and Hughes, Michael (2003) Introduction to Coastal processes and geomorphology, New York, Oxford University Press
Thom, Bruce, Hesp, Patrick, Bryant, Edward (1994) “Last glacial ‘coastal’ dunes in Eastern Australia and implications for landscape stability during the Last Glacial Maximum” Palaeogeography, Palaeoclimatology, Palaeoecology 111 (3-4)
Thom, Bruce (2010) “New South Wales” Eric Bird (ed) Encyclopaedia of the World’s Coastal Landforms, Springer

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February 19, 2015

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What’s at the bottom of the garden?

Where does our backyard end? The unwary burglar or, more plausibly, brush turkey fetishist leaping over the back fence and finding themselves falling off the small but perfectly formed cliff between our place and our downhill neighbours might think the answer obvious. But clearly, property boundaries don’t mean a lot to the brush turkeys or the bowerbirds. As far as they’re concerned, our backyard is just a part of Berowra Valley National Park with better snacks.

And since our yard is, in essence, a part-time storm drain, you could say that this is where our backyard ends:

Waterfall into Berowra creek after rain

Dusty Hole marina, Berowra Creek

Sometimes the view from the deck seems like a theatre backdrop, an artful two dimensional screen behind our suburban dramas. Every evening, the cockies, wheeling and screeching, burst through the scenic backcloth. Last weekend, a bit more quietly (bar the kayak-onto-roofrack related cursing) I did the same, plunging into the dawn mist towards the very bottom of the garden, the watery end point of our backyard.

Sam’s Creek in the mist

In the 1990s, Berowra Creek was not a good place to be a fish. Sewage outflows from waterside communities at Dusty Hole and Berowra Waters and the landlubber suburbs to the south meant algal blooms, brick red water and floating fish. As the cheery Hornsby Shire Biodiversity Plan ten years back noted “Some parts of the tributary creeks in the Berowra Creek catchment feature weed invasion, garden plants and waste, streambed siltation, rubbish and gross pollutants from stormwater drains, bank erosion, undercutting, tree death and poor water quality” (2006, 28). It’s enough to make a gardener think long and hard about what might wash down the hill in the next heavy rain.

Thankfully there’s a whole lot less nitrogen going into the creek these days largely thanks to better poo processing. I don’t have a lot of interest in fish. I don’t eat them, they make rubbish cuddly pets and they lay very tiny eggs far too infrequently. But even to my disinterested eye, the backwaters and mangrove flats of the estuary look like fish paradise. Okay, fish paradise probably doesn’t feature stingrays, cormorants or osprey, but you get my point.

Fishermen (I use that term advisedly) out well before the birds

Welcome swallow still in fluffy slippers and bathrobe

Male and female Chestnut Teal completing their morning ablutions

Fishermen get up earlier than kingfishers, it seems. People who say they’re “up with the birds” or even, in that eloquent Australianism “up before sparrow fart”, are clearly lying through their teeth. The welcome swallows were barely out of the fluffy slippers and the ducks were still brushing their hair and cleaning their teeth, but the fishermen of the Hawkesbury were already out on the water, lurking in quiet bays or drifting mid-channel like tinny Mary Celestes.

The feathered fisherfolk only seemed to appear after the mist began to rise. I’m not sure whether I can attribute that to poor avian night vision or my water spattered multifocals. You’ve got to assume the rufous night heron can see in the dark, but I only saw it scoop up a take-away in a kind of disgruntled way, after some annoying canoeist with an inadequate zoom lens made a nap in the mangroves untenable, and that was long after sunrise.

Mist rising over Berowra Valley National Park

Very patient and faintly curious juvenile white faced heron

Into Joe Craft Bay

Mist rising

White faced heron fishing

Rufous night heron trying to get some shut eye

Miffed night heron, off for a take-away on the way homee

For all the wildlife in these parts, that sharp edged snap of an azure kingfisher sparkling in flight is as much beyond me as a decent crop of salad potatoes, it seems. But I’m not going to complain. Over the last few weeks I’ve seen plenty of boats with girls’ names, but I haven’t seen too many Rubys, Calistas or Beverleys actually messing about in boats. There may be fairies at the bottom of the garden and there are certainly plenty of fish, but there don’t seem to be quite as many fishwives. Seems like it’s a rare privilege to be Her Outdoors.

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January 6, 2015

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In other sandstone country

Ganguddy – a less misleading name than Dunn’s Swamp

Wiradjuri country that is, or Dabee country to be precise: Ganguddy, on the Cudgegong River, that flows west off the Great Dividing Range, not into the Pacific but into the Murray-Darling. Not far from Berowra as the Australian Raven flies – straight across the Wollemi National Park – but a fair trek in the excessively laden ancient vehicle.

Still sandstone though – the older, niftier sandstone of the Narrabeen Group, as it resurfaces at the very edge of the Sydney Basin, with the even older coal measures being mined perilously close by. Layers of ironstone make for fabulous rock formations (if slightly less way out than the famous pagodas of the nearby Gardens of Stone National Park). And of course exceedingly soggy tent groundsheets when big rain sluices off the rocks faster than even sandy soil can soak it up.

Ganguddy

Rock formations

Pagoda

Pagoda lookout

When even sandstone soils can’t absorb the rain

Lakeside sandstone rock formations

Same old sandstone geology, plenty of still water, just like the Hawkesbury estuary down our way, but the critters are different. The feathered food thief at Ganguddy isn’t a brush turkey, it’s the purple swamp hen.

Purple swamp hen posing

Purple swamp hen unperturbed by a flotilla of canoes

Purple swamp hen justifying its name by hanging out in a swamp

Purple swamp hens enjoying the puddles after rain

The “house bird” is a cheeky superb blue wren, not a wattlebird. Rainbow lorikeets – not a one. And none of those aggressive urban generalists, the noisy minors or the magpies, either. Instead crimson rosellas – a rarity in the northern suburbs of Sydney – lurk in implausible locations like the queue for the drop dunny for instance, or the reeds by the river bank.

The ubiquitous but largely invisible bird here isn’t a koel or a channel billed cuckoo but the aptly named clamorous reed warbler. I was at times tempted to nip to the Rylstone Guns and Ammo for a small flame thrower so I could finally get that photograph, but then I reflected that a perfectly focussed snap of a tiny blackened corpse clinging in its rictus to a reed probably wasn’t in the spirit of the thing.

The “house bird”: a male superb blue wren

Crimson rosella waiting impatiently for the drop dunny

The invisible but ubiquitous clamorous reed warbler

Crimson rosella doing unlikely things in the reeds

Little black cormorants watching cricket.

A whiptail wallaby (or “pretty faced” wallaby as fellow kangaroo mafioso prefer to refer to it)

A musk duck. No, it doesn’t have a goitre. It’s meant to look that way.

Eastern water dragon enjoying the attentions of the papperazzi.

Paper daisies.

Thysanotus tuberosus. Another one that’s all over the place.

A teenaged darter hanging out in the local equivalent of a bus stop.

Not just charismatic megafauna. A Botany Bay Weevil.

Lace monitor. Okay, we see these at home too.

Eurasian coots in the mist. Not a good movie title.

A fabulous place. It’s tempting, what with proximity to World Heritage listed Wollemi National Park and all, to think of it as a wilderness. But no. Its gorgeous waterways are the product of a 1920s dam built to to supply a cement works, its teeming fish the introduced gambusia affinis – the “plague minnow” – that outcompetes the locals, though it does seems to keep the mosquito population down. As a camper it’s hard to argue with that, although we didn’t see a single bat, micro, macro or meso, during our five day stay.

There’s something to be said for human intervention, as Tim Low says. In the absence of railway station eves or even a well put together shed, the welcome swallows in desperation had to resort to nesting on the natural stone outcrops. But the local water dragons and turtles seemed to relish the fetid smelling pond downstream from the dam.

A water dragon – is it a grotty eastern or is it something exotic?

Gambezi fish – mosquito killers or just killers?

Welcome swallows making do with a natural rock outcrop rather than the eves of a railway station or public toilet

A tranquil place with a violent past. A “natural” place shaped for a very long time by people in ways that you see and ways that you (or at least I) don’t know enough to notice. A familiar story, on sandstone and otherwise.

Posted by

mccnmatt

Posted on

December 31, 2014

Posted under

Backyard chickens, compost, Gardening, Geology, History, natural history, Soil

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Happy International Year of Soils!

1967 photo of the cuttings for the freeway at Brooklyn on the Hawkesbury. http://www.ozroads.com.au/NSW/Freeways/F3/ConstructionInfo.htm

I’m not kidding. The UN has declared 2015 the International Year of Soils. And not before time. Everyone should be preoccupied with dirt. I know I am. What is going in down there, under the ground? Are my veggies growing in podzol or mycelium? Hang on, that’s soil profiles in Minecraft, not in Berowra.

The CSIRO’s recently released Soil and Landscape Grid with its 3 dimensional digital soil attribute maps could resolve most Australian gardeners’ soil questions. In case you were wondering how these maps were developed, let me put you out of your misery:

“The spatial modeling was performed using decision trees with piecewise linear models and kriging of residuals. Fifty environmental covariates that represent climate, biota, terrain, and soil and parent material were used in the modeling. Uncertainty was derived using a bootstrap (Monte Carlo-type) approach to derive for each pixel a probability density function (pdf), from which we derived 90% confidence limits”

More kriging of residuals, I say!

Gags aside, this free online resource shows why Australia needs publicly funded science and why sacking researchers in the CSIRO to bankroll Gina Rinehart’s tax breaks is a major error (if you need more persuading, CSIRO scientists also invented WiFi, Aerogard, the permanent pleat, and the word petrichor, which describes the lovely smell of damp earth after rain).

After reading about the rocks in our neck of the woods, however, I’m not sure we are best placed to fully exploit the sophisticated visualising technologies of the Soil and Landscape Grid. The geology around here is pretty danged boring. Other than the odd lens of shale, mostly on the ridge-tops (that is, under roads and houses) it’s Hawkesbury sandstone all the way down, 40 million years and 270 metres of it. Or at least, all the way down to Berowra Creek where there’s an outcrop of more fertile Narrabeen Group of shales, sandstone and clays here and there.

Cutting through sandstone at Mooney Mooney

The humungous cuttings between Berowra and the freeway, showing millions of years of sandstone deposition

More ridiculously huge cuttings on the freeway

Of course, we’re not alone in our preposterously deep beds of sandstone. They’re on display in the Blue Mountains too, though with a few more layers clay and basalt intrusions to break up the tedium.

Huge sandstone cliffs at Wentworth Falls

Layers of clay amidst the sandstone near Wentworth Falls in the Blue Mountains

The humungous quantities of sandstone across a swathe of the Sydney Basin makes my sentimentality about the disappearing rock faces along the new railway cuttings of the Northern Line even more absurd. After reading about the good exposures of Ashfield Shale between Hornsbury and Beecroft, I’ve become a tiny bit obsessed with capturing the freshly exposed slices of Sydney Basin geology as they are revealed by the diggers and before they’re covered with nasty grey concrete. Wordsworth was mortified by the ugliness of railway cuttings slashing their way through the nineteenth century British countryside. Here am I mourning for disappearing railway cuttings, a slice of geological time revealed and then lost again.

Sandstone profile

A slice of sandstone

The sadness of disappearing sandstone

Busy workers covering it all up

Perhaps I should stop grieving the lost glories of the Pennant Hills trackwork and spend more time worrying about what my garden might be doing to the “quartz rich, nutrient poor” soils of Berowra.

My snake beans are kinda sallow – I reckon they need a side serve of well-rotted chicken manure. But even as I contemplate emptying the compost tumbler, I can’t help but fret about where my vegetable garden sits, perched above the national park with its “rich and distinctive assemblage of species that thrive on poor soils” , “60-80 different plant species growing together on an area half the size of an average house block” (Benson, Howell, McDougall, 1996, 24-5). Benson and Howell in their fascinating Taken for Granted: the bushland of Sydney and its suburbs (Kangaroo Press/Royal Botanic Gardens, 1990) mourn:

“much of Hornsby’s rugged sandstone terrain remained undisturbed until after World War III when the increasing availability of the car and improved building technology made steeper, more remote sites available for housing. As a result, bushland on ridge-tops and upper slopes has been totally destroyed, the bush remaining only where it is virtually impossible to built, and along steep gullies which have become drainage lines. Virtually very catchment system includes some suburban development, stormwater run-off from which contains silt and nutrients. These promote weed invasion of sandstone gullies… in newer areas such at Mt Colah and Berowra [the] invasion is beginning, and the consequences appear inevitable” (108)

And that’s us, in our mid-century twentieth century house, teetering on a steep slope in a fold of the hillside you might otherwise call a creek bed. My painstakingly-made hot compost, my organic sugarcane mulch, the poo from my beloved chickens, all building nitrogen, carbon, phosphorus rich earth – garden alchemy. I’m creating an anthroposol – a human made soil – and I’m not entirely sure that’s a good thing.

Yellow podzol? or anthroposol?

Run-off from the garden… sorry, creekbed.

As a homage to the UN’s declaration, I’ve stared in a incomprehending way at a schematic cross-section of Hawkesbury soils, I’ve thought long and hard about our B horizon (by staring even longer at this quite marvellous online introduction to soil classification – thanks again, CSIRO) and I’ve double-checked Minecraft’s definition of “podzolic” with the kids but I’m not sure how far it’s got me.

Maybe this is the chthonic thinking – thinking about the soil and the communities, plant and animal that grow from it – that my friend Kate urges us all to do in her fab blog about the Armidale Community Garden, but it’s not so much grounded me as taken me directly to Hades via the Field of Punishment. This is a special special place of suffering for people who long to understand rocks and dirt but can never remember whether the Devonian comes before or after the Carboniferous, no matter how many times they read David Johnson’s splendid Geology of Australia. And that’s without wrestling with the geopolitics of topsoil loss or the impact of international agribusiness on pesticide residues or the links between soil, country and indigenous chlthonic law…

The only solution to this torment, I feel, is another variant of subterranean thinking: that sense of mindfulness I get sitting in a darkened vehicle with a swag of empty shopping bags, gazing tranquilly at the carefully preserved, sandstone rock exposures in the underground car park of Berowra Coles.

Happy International Year of Soils everyone!