Dalhousie Rockpile
Designation:
Australia-SA_Dalhousie_Rockpile
Location:
| Latitude | Longitude |
|---|---|
-26.481217° | 135.464667° |
Locality and ownership:
Witjira National Park.
Access:
7km WSW of Dalhousie Springs on the Pedirka road to salt lakes.
Local contacts:
Nearest services:
Mt. Dare
Risks:
Loose surface that may collapse into old rabbit holes.
Terrain:
salt pans, mesas
General:
Site descriptions:
- Small plateau about 1km wide and 6km long. The plateau is formed by a hard limestone cap over softer clays. Surface covered with loose slabs of mid grey fine-grained, partly silicified limestone showing some surface dissolution. The underlying clays are smectitic and probably gypsiferous.
- The slopes of the mesa are armoured by fragments of limestone and on their lower slopes by a mixture of limestone and the cobbles derived from the shale. The intervening soil is strongly puffy in texture. The slopes are dissected by runoff gullies which lead down to a saline pan. The smectitic clays of the mound spring rest on an eroded and weathered surface of Bulldog shale. This surface is marked by a lag of hard pebbles and cobbles derived from those within the Bulldog shale and feruginous clasts. The weathered Bulldog shale is dark grey and contains abundant smectite and fragmented sheets of gypsum.
- The pan is at the bottom of a south-flowing channel that is fed by both surface runnoff and mound spring discharge. The channel shows streamlined bedforms and is locally deeply mudcracks. The mudcracks were concentrated in the deepest depressions in the channel floor. The channel sediments consist of fine silty sand and are distinctly moist.
Climate:
Flora and fauna:
Salt tolerant flatbush, including Old Man. Phragmytes aquatic reedgrass. Coolebah and Red Mulga trees. Field mice. Various birds. Giant millepedes.
History:
Aboriginal groups, including the Lower Southern Aranda and the Wongknurru people have made use of the springs for at least 15, 000 years.
Analogue value:
Dalhousie Rockpile is the largest and oldest of the fossil mound springs in the Dalhousie area. It is possible that the site is related to the initial discharge of groundwater that carved the outflow channels and thus is a small scale analogue to similar features interpreted on Mars. The limestone cap may prserve the textures and fossils associated with mound spring biota. The friability of the surface might be interesting for tests of surface walking and spacesuit boots. A star pole in loose soil on the slope dug in to a depth of 40cm could easily be pushed over. One individual sank into soft soil which had been undermined by rabbits.
The site is also of biological interest for containing potential extremophile ecosystems in the salt lake beds and on the slopes.
The site is also of considerable value as a visual analogue, consisting of barren, exposed surfaces with little vegetation, a landscape which is primordial in character.
References:
- van Oosterzee, P. A 2000. Field Guide to Central Australia. Marleston, SA: J.B. Books.
Map reference:
Geology
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