Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Monday, November 21, 2011

Stingray Swamp - a vain search for the Giant Dragonfly

This is a report of our excursion to Stingray Swamp, near Penrose, on an educational excursion organised by Geoff O'Connor of the Moss Vale office of the HNCMA.
Despite the fat that we didn't find any Giant Dragonflies,
it was a very interesting and informative day..

 This is the Giant Dragonfly which we had hoped to find.
Petalura gigantea (The Giant Dragonfly) - Photo: HNCMA video
The Hawkesbury Nepean Catchment Management Authority has produced a video on Hanging Swamps. Ian Baird was one of the specialist speakers who talked with us yesterday.

The Video seems to be a bit slow to download, but let it load for a little while before you try to play it right through, and its OK. I have shown a "still image" from their video to show the Giant Dragonfly (Petalura gigantea). It is about 6 to 9 inches both in length and wing-span. Seriously large.

The assumption is that Swamps are mucky, but the peat was not at all "smelly", and the water which ran out from the swamps was reddish from the Button Grass vegetation, but that's the same kind of peaty water which the Scots use to flavour their Whisky (and Irish use for their Whiskey).
A core sample (after the top left layer of vegetation was removed).

The samples are analysed in 25 mm depth parcels. Typically such samples are aged to 16000 years.

Some of our group. Eucalyptus aquatica in the background is an endangered species.
This shows the depth of the Button Grass.

 The bright "Yellow Eye" or "False Flag"
It looks in general form like an Iris
but it is in fact related to the grasses (Poaceae)
"Yellow Eye" - Xyris sp. (possibly X. operculata)
Click to enlarge image to see flower structure in detail.
The length and shape of the "style" of the flower is diagnostic.
Xyris flower detail. Most likely Xyris operculata
We left the first open area of swamp and drove to another arm of the swamp.
This are was close to a rocky outcrop, 
which showed us something of the complex geology of the area.

Rock ledge showing different geological formations
Closer view of the same complex geology,
with coarse aggregates and quartz pebbles.
The lower level rock is evidently different 
from the much finer sandstone layers above.
Aggregate found in the lower level rock formation (under Sandstone).
In the stream bed below the rock ledge (shown above)
there was a line of Leptospermum shrubs and "Coral Fern".
Below these was a soft bed of Sphagnum Moss.
You can see the bright green moss below Ian's feet.
With Ian's metal spike he could demonstrate that 
the soft bed of organic matter was at least 1500 mm deep
and he speculated that it might be far deeper than that.
Ian standing on Sphagnum Moss in creek bed

We left without having collected any Leeches (for which I was greatly relieved).


mick said...

You have some very interesting habitat down your way. Is there a reason for it being called 'Stingray Swamp'?

Denis Wilson said...

There was some questioning about the name, Stingray Swamp. But no clear answer was provided.
Possibly the shape, when view in "plan view" (as on a map).
But even that is not clear, as it has two branches, so it would have to have been a double tailed Stingray.
Certainly no Stingrays around this area (recently) as it is at 600 metres.