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.
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.
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.
I found this is the back yard early in the morning after rain the previous day. I guessed it was some type of fungus, turns out to be a species of plasmodial slime mold called Fuligo septica, commonly known as scrambled egg slime or dogs vomit slime mold!
It really was odd looking, bright yellow, soft and spongy to the touch and underneath it’s really slimy, like a slugs belly.
Slime molds are bizarre and fascinating things, they were initially classified as a type of fungus but this was found to be incorrect. They are now thought of as sitting under the Amoebozoa taxonomic group, a sister group of fungi and animals.
Slime moulds often exist as single cells, but in times of food scarcity they clump together to become a visible gelatinous mass. In this form they can move about as one and are even seen to change shape and function as well as exhibit sensitivities to environmental hazards and food sources. One scientist John Tyler Bonner, observed that they are “no more than a bag of amoebae encased in a thin slime sheath, yet they manage to have various behaviours that are equal to those of animals who possess muscles and nerves with ganglia – that is, simple brains.”
The sea level, rainfall and temperature climate pages have been updated with the latest data from the BOM. As per usual temperature and rainfall are almost up to date but sea level is more than a year behind with the latest reading from December 2013. Why is this?
Always interesting to see how the most recent weather extremes stack up against the last century or so of readings. This most recent summer that felt so hot was nothing special if you look back only 15 years or so, but the longer term trend is clear for sea level and temperature. But not rainfall.
ABC radio has some really good shows, including a whole bunch of science shows. They offer an awesome podcast feed that combines all their science programs plus any scientific segments from other shows into one. ABC hides this feed really well, whenever I have to reload my podcasting app (with my luck with phones, way to often!) it takes ages to locate the feed again.
Well I finally found it, so here it is for the next time I need it, and for anyone else that may enjoy this gem that the ABC hides so well.