Search This Blog

Monday, 21 October 2013

South Coast trip, part 2

Now for some serious geology.

The area we were working along contains rocks as old as 510 million years, and it is a coastline that developed 90 to 70 million years ago, at a time when there were still dinosaurs around.  That was when the Lord Howe Island Rise came away from the Australian mainland and set off out into the Pacific.

Mind you, the actual coastline is even newer, because in the past few million years, sea levels have gone up and down, due to assorted ice ages taking water out of the oceans.  This is good, though, because it exposes fresh rocks at regular intervals.

We have faulted, folded mudstones, cherts, basalt intrusions and blocks of granite as well, all mixed in together.  As I indicated in Part 1, I am no geologist., just a rock watcher, so none of my comments should be taken as gospel, though they are reasonable commonsense in most cases.
Mimosa Rocks
 The Mimosa Rocks National Park lies between Bermagui and Tathra, and takes its name from a paddle steamer that was wrecked near there in 1863.  Most references seem to suggest that she was wrecked on the rocks, but the captain of Mimosa reported striking a "detached rock", a mile off shore.

Still, the pyramid form that you reach by heading north from the Aragunnu Beach car-park is worthy of note for the rhyolite capping which shows columnar jointing which is more visible here, where I zoomed in:

 There was more fun to be had down on the shore, where there were some cliffs worth looking at: to my eye (note the qualifier!!), these appear to be faulted and folded varved shales.

Then there were the pebble beaches:

 And in the distance, a strange white rock:

 A closer look solved the mystery, it was covered with seabird by-products. I should have known!

 We then headed north into the Tilba Valley, stopping at Central Tilba for shopping, Devonshire tea and this shot of a rather impressive granite dome, which is actually on the other side of the highway:
Then we headed north, looking for 1080 Beach (pronounced ten-eighty). The name 1080 is used for a rabbit poison which is actually sodium fluoroacetate, but I have no knowledge of the origin of the beach's name.

The beach is little known in the area, so here are instructions:

Drive to Mystery Bay, about 10 km south of Narooma.  Follow the tar until you see the sea, go right into Lamont Young Drive on a good road, looking out for a National Parks road with cryptic signage on the left.  Find that road and drive carefully (it's narrow, with many blind corners: I used my horn quite a bit) along to the end, where there is a car park. Find your way down to the beach.

It's worth it for this dyke:

Incidentally, on the way in and out, watch out for locals:

Next time: Camel Rock and Mystery Bay.

See also 

* Rhyolite-Basalt-Soft Sediment Relationships at Bunga Beds, Aragunnu, Mimosa Rocks, Southern NSW, Australia;

* The Story of Granite and Bega Cheese.

Links to the other four parts:

Part 1

Part 3
Part 4
Part 5

No comments:

Post a Comment