Chillagoe Karst (North Queensland)

Background

The Chillagoe and Mitchell-Palmer karst areas in north Queensland share features of other tropical karst areas of the North Australian Karst Province with those of the East Australian Province. The climate is tropical humid monsoon, with an annual rainfall of about 840mm and a marked winter dry season.

The Chillagoe area shares its surface outcrop character with the rest of the North Australian Province: it shows upstanding limestone outcrops (towers in this case) with large, deep karren sculpturing. On the other hand, its structural setting is that of the East Australian Province in that the limestones are steep dipping and form as narrow linear outcrops.

Landsat 7 image of Chillagoe area (bands 1,2,3).
The grey areas are the limestone towers,
Click on the image to see a larger version..
Landsat.jpg

The steep-sided towers (known locally as "bluffs") can reach up to 90 m high, though most are less than 50 m, and are from 100 m to over a kilometre long. Their surfaces are deeply dissected by deep grikes, and have strongly developed vertical flutes and runnels. Many are surrounded by a limestone pediment or alluvium, but others rise immediately beside the contact with the surrounding (volcanic or sedimentary) rocks.

The towers are riddled with caves which are mainly mazes of phreatic chambers and vertical fissures (which may reach to the surfaces to make giant grikes). The fissures follow either joints or the vertical bedding. The cave floors are more-or-less horizontal and run at or just above the level of the surrounding pediment. A few rifts extend down as much as 15m beneath the level of the plain and these can hold permanent or seasonal lakes. During the wet season some caves are extensively flooded for several weeks at a time.

Speleothems are common. Cave coral is the most common form, but there are also some odd-looking stalactitic shapes (see photos below).


Cross-section showing steep-dipping rocks, the formation of marble near granitic intrusions, the different tower types (rounded on marble, steep on limestone) and a cave within a tower. The wet season flood levels, and the permanent water table are also shown.

Further reading

MARKER, ME., 1976: A geomorphological assessment of the Chillagoe Karst Belt, Queensland. Helictite 14(1): 31_49.
FORD, T.D., 1978: Chillagoe - a tower karst in decay. Trans British Cave Research Assoc. 5: 61-84.
ROBINSON, TR., 1978: A Question of Age. Tower Karst (Chillagoe Caving Club, occasional paper) 2: 18-36.
JENNINGS, JN., 1982: Karst of northeastern Queensland reconsidered. Tower Karst (Chillagoe Caving Club, occasional paper) 4: 13-52.

See also

Karren at Chillagoe: For more photos of the karren, and micro-karren, on the towers and pediments.

Selected photographs and diagrams

To view full size images, click on the displayed image.
A typical limestone tower at Chillagoe, with long deep runnels on the vertical faces.
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Tower of London Bluff, from the air.
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Royal Arch Bluff, which contains the main tourist cave in the area.
IMG00227.jpg
Stereopair showing flat limestone pediment surface with a low tower in the background (Mungana area).
View stereopair cross-eyed. IMG00229.jpg, IMG00230.jpg
A tower surface showing the strong karren sculpture.
IMG00222.jpg
Another view of the sculptured tower surfaces.
IMG00223.jpg
Map of Royal Arch Cave (from an SSS survey, 1969)

"The Groping Hand", an unusual stalactitic formation in Queenslander Cave.
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"Sucker Pads" in Queenslander Cave.
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Cave Pearls and an encrusted snail shell.
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