Northern Territory - Karst

Introduction

Limestone Karst

In the Northern Territory the karsts are developed on flat-lying to gently folded, Proterozoic dolomites and Palaeozoic limestones & dolomites. These form areally extensive regions, but in some the depth of the carbonate rock is limited to a few tens of metres. In some areas the carbonate rocks are well-exposed, with strongly karstified outcrops; others have extensive covers of Mesozoic and Tertiary sediments and Quaternary soils. There are also lateritic & silcrete capped deep weathering profiles. Chert nodules & beds are common in some of the carbonates and this can influence the degree of karstification.

The Caves are varied in character, but are generally horizontal systems, sometimes at several levels. They include the Bulleta horizontal maze cave system in the Gregory National Park which had 105 km of mapped passage in 2005, and many caves in the Katherine area. Other areas are less well documented.

Silicate Karst

There are also Silicate Karsts of two main types:

Sandstone karsts involve surface "karren" such as giant grikes and ruined citys, several deep and spectacular collapse dolines and also some significant caves.
Laterite Karst results from leaching within old deep weathering profiles. The main features of these areas are numerous broad but shallow pans on the surface. In detail one also sees a variety of small solutional features, such as solutional tubes and vughs. Small caves occur at scarp edges, but are mainly the result of piping and erosion of soft material from beneath the hard duricrusts - i.e. pseudokarst rather than true silicate karst.

Paleokarsts

The Proterozoic dolomites of Northern Territory contain numerous horizons of brecciated dolomite or chert. These are interpreted as paleokarst breccias, the chert being a secondary cement that has replaced the original carbonate.

Links

Surface karst photos Karren and other features in the Katherine area.
Karren and microkarren of the Gregory Karst PDF poster
Spring tufa deposits This page has photos of tufas from several parts of Australia, including the NT.
Cave photos Caves at Katherine.
Gregory Karst area & Bullita Cave
Barkly Karst Region This region extends across the NT & Queensland border.

Selected photographs and diagrams

To view full size images, click on the displayed thumbnail image.

Map of the Northern Territory karst areas.
The main area is the early Palaeozoic limestones of the Daly, Wiso and Barkly karst regions. Limestone crops out around the edge of these basins, but much of it is buried beneath Mesozoic and Cainozoic sediments.
Outside that area the small black dots are isolated areas of Precambrian dolomite karsts.
Purple dots are areas of laterite karst (mainly shallow pans) - there is probably much more of this, but it is poorly documented.

File: NT-karst.png

Sea cliff at Laameroo Beach, Darwin.
This kaolinitic claystone is the pallid zone of a deep weathering (laterite) profile. It is cut by small solution tubes some of which contain nodular material.
The surface is an old landsurface that has broad shallow closed depressions analogous to karst dolines.
This is "laterite karst" - a type of silicate karst.
Stereo pair - view cross-eyed. 10 cm scale bar.
File: C020524.jpg

[Top] [Home] Go to Main Index menu