Tag Archives: garigal national park

Unusual Sandstone Formations

There’s no shortage of sandstone in the Sydney area, almost the entire extent of Garigal National Park sits on whats known as the Hawkesbury Sandstone. The Sydney 1:100 000 Geological Sheet classifies it as “Medium to course-grained quartz sandstone, very minor shale and laminite lenses” I wanted to highlight two sandstone formations, both of which are a bit of a mystery as to how they form.

I came across these formations on a trail run on a section of single track in Belrose that runs from the end of Ralston Ave down to the Bare Creek trail next to Bare Creek.

The first formation is called tessellated pavement.

tessellated pavement on the trail down from Ralston Ave to Bare Creek. Shoe for scale

There are a number of different types of tessellated pavement. The type I came across is seen on flat sections of sandstone that have been fractured into 4-6 sided geometric shapes. Some of the blocks are surrounded by deep grooves with rounded edges. It really looks like a man made road or path the way the blocks lock together. It’s not known how this structure forms.

The second formation is even more of a mystery.

Grooves and ridges on the trail. Is it rundkarren in sandstone?
The same formation with shoe for scale

It was on the same section of trail near the tessellated pavement. Found on a gently sloping section of sandstone, it had rows of deep grooves all running in the same direction from the top of the slope to the bottom. They looked like they could have been worn over many years by the trickle of water. Above the trail was a minor gully, there wasn’t any visible creek but it looked damp and swampy. In wetter times perhaps water could have drained slowly over the sandstone. This is all guessing, I couldn’t find any information on this type of formation. The closest I came was rillenkarren or rundkarren which is the weathering of similar channels in limestone by the slight acidity of the water dissolving the rock. Rillenkarren has sharper ridges and is thought to form out in the open while rundkarren is more rounded and thought to form under a superficial covering like sandy till, peat or a layer of plants and lichen.

Wikipedia

British geological survey

Speliogenisis

One Mans Funnies

Sydney Peppermint Gum Blown Over

Eucalyptus piperita

“A small graceful tree to 15m high, but sometimes much taller” NOPS p.38

During the big storms a few weeks ago I was lying in bed at around 11pm just about to ready to go to sleep when a loud and prolonged cracking sound started coming from just outside the bedroom. I knew right away that the large Sydney Peppermint gum in the back yard was falling over! I jumped up and tried to get to the window but it was pitch dark and storming, I couldn’t a thing. As the cracking continued I was terrified it was going to fall on the house, luckily it went the other way and ended up taking out a sizeable swath of bush and other trees as it came down. Phew!

The Sydney Peppermint gum is  a small to medium tree of up to 15m but can be much taller in the right conditions. It’s trunk is covered by rough grey bark that detaches from the tree and hangs in strips as it reaches higher up revealing smooth white upper branches. The leaves have a strong peppermint smell especially when crushed. The Sydney Peppermint was the first Australian plant to be used medicinally by Europeans. It’s oil was found by a surgeon on the first fleet to be “more efficacious in removing all cholicky  complaints than of the English Peppermint”

As the name suggests Sydney Peppermint gum is found in the Sydney basin, it ranges from the extreme south NSW coast up to the central north coast. Flowering time is early summer.

It was a shame to loose the tree, it was a large feature of the back yard. The pair of kookaburras who used to sit in it came and sat on the toppled tree no doubt wondering what had happened.

Fallen Sydney Peppermint Gum. Sneaker for scale.

It look out a few other sizeable trees as it fell

Resources and references

 

Pink Wax Flower

Eriostemon australasius

Easily recognized by it’s large pink flowers and thick grey green foliageNPOS p.118

After having come home from the boys soccer to an empty house without keys there was only one thing to do, get the boys on their bikes and head down the bush! The weather was warm with the first hints of spring, a number of flowers had started to come out too.

I didn’t have my camera with me so I took these photos with my phone, I’m still so impressed at how clearly they come out with such a small lense and sensor.

This plant took me a while to identify, in NPOS it looks similar to Crowea saligna or Crowea exalata, but the flowers are not quite as depicted in the book. In the end I’m pretty sure it’s a Eriostemon australasius also known as the Pink Wax Flower.

Pink Wax Flowers are common in heath and woodlands on sandstone plateaus. They are a small shrub growing to about 1.5m They have leathery leaves that are narrow, 1cm, and long, 8cm or so. The flowers are numerous and striking, large and pink with 5 petals.

Pink Wax Flower flower

Pink Wax Flower. The genus name Eriostemon is Greek: wool stamen, referring to the hairy stamen, the petals look pretty hairy too!

Pink Wax Flower stem and leaves

Resources and references

Scarlet Honeyeater

Myzomela sanguinolenta

Last Sunday the two boys and I walked down to the Cascades to meet Mat and some of his friends who were doing the 100km Oxfam walk. We did the salmon thing and headed against traffic from Bungaroo. We were on the Oxfam course between about midday and 2pm, the people we were passing were at the 75km or so mark and had been walking though the night without sleep, some people really showed it, most seemed pretty happy though.

Will did very well and walked the whole distance, Tom refused to walk and sat in the backpack until he got too uncomfortable then demanded to be carried!

We had lunch and a bit of a play at the cascades, Mat arrived at about 2:30pm, he was fine.

I finished dad! Lunch at the Cascades

Just after leaving the Cascades I spotted this small bird with bright red coloring in the bush just off the fire trail. It was on a Mountain Devil plant flying from flower to flower drinking the nectar. It moved fast and it was difficult to get a good photo, it let me get within a few meters before flying away. Another one I’ll have to return for to try and get a clearer picture.

It turns out to be a male Myzomela sanguinolenta. It’s also known by a number of different common names, Birds in Backyards goes with Scarlet Honeyeater so that’s good enough for me.

The male Scarlet Honeyeater has a bright red head and body, it’s upper wings and tail are dark grey with lighter grey colouring underneath. The females are dull brown with dull white underparts. They are small birds, the adults being 10 – 11cm long.

Male Scarlet Honeyeater on a Mountain Devil plant. Another pretty boy.

Scarlet Honeyeaters are found from Cape York all the way down the east coast of Australia, but are less common south of Sydney where it’s a summer migrant. They’re also found in New Caledonia, Indonesia and surrounding islands.

Sources and more info