THE BIG PICTURE SPRINGS OF THE MATARANKA AREA 4. THE SWAMP

Timor Sea A cavernous limestone aquifer extends The large swampy area located on the south side of across a large part of the the Roper also owes it’s existence to a and into Queensland. The springs at The Mataranka area is notable for its many springs. geological structure that has caused the aquifer to DARWIN Mataranka are one of several outlet points for become shallower and to thin out towards the Roper the aquifer. Other big springs are found on 295000mE This map shows the location of the main springs and other groundwater discharge features. River (see the cross-section). This has resulted in a the Flora, Katherine and Daly and in broad area underlain by a shallow watertable and Queensland on the Lawn Hill Creek and It explains why the springs are there and describes some of their characteristics. zones of seepage. Extensive tufa deposits formed there because a ridge of bedrock located downstream Daly River Springs KATHERINE Gulf Gregory River. At Mataranka the water of originates from areas to the southeast as far of the seepage zone, ponded the water in a similar Flora River Springs MATARANKA Carpentaria away as the Barkly Tablelands and from the manner to the rock bars in streams as described in 300000mE northwest as far as the King River. Qa1 the note on tufa formation. The ridge formed a base

for tufa to accumulate. Tufa dams merged and grew - Waterhouse Cmt over older ones, eventually forming a continuous sheet of limestone. This occurred in the recent geological past. Tufa is not forming in this 305000mE environment at the present day. Barkly Tablelands River Kl

8355000mN Lawn Hill Springs Kl

Gregory Bare saline soil caused by a shallow brackish watertable. TENNANT CREEK River WHY ARE THE SPRINGS - B

WESTERN Springs Roper Cmt WHERE THEY ARE ? 310000mE

Creek The edge of the limestone aquifer is at its - Cmt Pri- 5. FRESH AND BRACKISH SPRINGS lowest point in the catchment where the Roper River cuts it just east of Mataranka. Qa1 The water from Rainbow Springs, Bitter Springs and Groundwater flows from high areas to low 315000mE Elsey Creek can be classed as fresh. This contrasts areas; thus Mataranka is the natural outlet for with most other springs in the area, which have two the water. The location of individual springs is Qa1 ALICE SPRINGS or three times the amount of dissolved solids (salts) governed by geological structures. Rainbow and which can be termed as brackish. The reason for and Bitter Springs lie along fractures that run this is that the first three springs are sourced directly from northwest to southeast. These provide 2 from the aquifer probably via caverns. No Kl 320000mE weaknesses in the rock where caves can more evaporation takes place prior to the water emerging easily form and allow groundwater to escape QUEENSLAND from the springs and so their water quality is similar to the surface. The Roper Creek has a very to that of the regional groundwater. Beneath the straight course, which coincides with such a SOUTH AUSTRALIA Bitter Spring swampy areas however, the watertable is located fracture. 1 close to ground level. Over thousands of years the swampy vegetation (paperbarks, pandanus and 3 Rainbow Spring and Thermal Pool

8350000mN palms) have tapped the watertable, removing water

but leaving behind the salts. In some cases the THE AQUIFER -

Cmt Cmt- watertable is close enough to the surface to allow direct evaporation and accumulation of salts in the

A layer of rock known as the Tindall Limestone hosts the Mataranka - Botanic Walk Spring soil. The end result is that salt concentrations have

regions main aquifer. The limestone was deposited in a Czk Cmt Pri- increased in the shallow groundwater and in the - Qa1 shallow sea some 500 million years ago. It has been Cmt Fig Tree Spring (at arrow), a brackish spring emerging from cliffs of tufa limestone. Note the bare rock pavements composed of ancient tufa many springs, which drain from it. subjected to weathering over a long period, resulting in a

network of solution cavities ranging from microscopic to the - size of caves. These cavities together with cracks in the Czk Cmt Czk rock comprise the aquifer. A large volume of groundwater is 4 River stored in and flows through the aquifer. 6. TUFA, AN INDICATOR OF PAST AND

5 Fig Tree Spring Roper PRESENT SPRINGS. Qa1 Tufa is a type of limestone commonly associated with springs. It forms when evaporation causes the spring 6 Mataranka Falls water to become super-saturated with calcium carbonate. The mineral then precipitates as a rocky Djilkminggan deposit. It often forms "dams" across streams, Elsey ELSEY NATIONAL PARK Homestead commonly on top of existing rock bars. Evaporation 7 concentrates the minerals in the waterholes upstream of the rock bar. As the water cascades over the bar, STUART

8345000mN turbulence provides the trigger to precipitate the 1. THERMAL SPRINGS Kl calcium carbonate as tufa. The process is

self-sustaining. As the tufa builds up, the water level - Rainbow Spring is commonly referred to as a "thermal" - RN034033 Cmt Czk Cmt behind the dam is raised, more turbulence occurs at the spring. Both Rainbow and Bitter Springs are 33C at their dam, resulting in more tufa formation. Tufa dams have a sources. This is within the range of the ambient Creek characteristic scalloped shape and often form a series temperatures of groundwater in the Top End, indicating that of step like terraces. Only two active tufa dams are they are not true "thermal" springs. The Douglas Hot Springs Elsey present today, Mataranka Falls on the Roper and an

north of Katherine is one of the few thermal springs in the unnamed one, not far away on Salt Creek. Tufa Northern Territory, with a temperature of 50C. - Cmt formation was apparently much more active in the past,

Bitter Springs on the Roper Creek Mataranka Falls - as evidenced by extensive tufa deposits adjacent to the Cmt

HIGHWAY Roper River. Many good examples can be seen along

Creek the walking track that follows the river.

2. MATARANKA SPRINGS

Salt There are many springs just east of 7. "UNDERWATER" STALACTITES Mataranka between the Roper River and Qa2 the . The most prominent RN033679 ROPER A six metre high wall of tufa once damned the Elsey are Rainbow and Bitter Springs, which RN031483 issue directly from caverns in the Creek. It formed at a time when average rainfall was limestone. These have large flows of higher than at present, causing elevated watertables Kl crystal clear water and flow throughout and thus more groundwater discharge. The dam must 8340000mN the year. Less obvious but more HIGHWAY have held back a permanent waterhole many widespread sites of groundwater kilometres long. During the Dry season the water discharge are rivers and swamps. Rivers would have been saturated with calcium carbonate. receive groundwater seepage through Qa2 Pandanus roots extending into the water became encrusted with limestone, forming "stalactite" like their beds and banks. Some of these Pri- streams flow throughout the dry season, Kl features that lined the dam wall. The "stalactites" while others dry up before the wet often have hollow cores where the roots once were.

season begins. Swamps are also Cmt- Czk groundwater discharge sites. Vegetation When the climate dried waterlevels dropped, taps the shallow watertable and water is exposing the dam wall. It would have been subjected to corrosion by the areas slightly acidic rainfall. also directly evaporated through the The Waterhouse River near Rainbow Spring soil. Qa1 Solution cavities developed and the wall was Qa1 eventually breached. It now stands as a relic feature, reflecting a wetter climate. Note that this site is on private property.

3. A LOT OF WATER ! An ancient tufa dam on Elsey Creek showing "stalactites" that grew underwater - around pandanus roots (view looking downstream).

Cmt The combined flow from all the springs - in the area is typically about 1500 litres Kl Cmt per second at the end of the dry season. 8. A GROUNDWATER FED STREAMS This amount has varied between 700 and A 6000 litres per second depending whether rainfall in the preceeding years Some local rivers and creeks receive groundwater inflow through their Qa1 has been above or below average. Bitter beds as well as from springs along the banks. In some cases discrete Spring and Rainbow Spring contribute springs can be seen under the water but often the water probably seeps the most water, with flows averaging 130 8335000mN through wide areas of stream bed. In the case of Elsey Creek a 20 and 300 litres per second respectively. kilometre long waterhole is maintained throughout the Dry season, The volume of groundwater discharged Kl upstream of the Roper Highway. in swamps via vegetation use and evaporation is comparable to that Qa2 discharged in springs.

Elsey Cemetry 8

Kl

The source of Rainbow Spring, a cavern in limestone. - - Cmt Cmt

Qa1 Cmt-

GROUNDWATER FEATURES Cmt- Qa1 GENERAL FEATURES Stream, seasonally groundwater fed

Stream Major road Swamp or marsh 83300000mN 8335000mN 8340000mN 8345000mN 8350000mN 83300000mN Vehicle track Sinkhole Qa2 Cadastral boundary Spring Creek

Geological boundary Bore - Cmt Elsey RN32148 Bore registered number Park boundary

Tufa dam inactive Cmt- Elsey Place name A waterhole on Elsey Creek maintained during the Dry Tufa dam active Qa1 season by groundwater inflow. Gauging station Qa2

A B Line of cross-section Qa2 Groundwater flow

Cmt- LEGEND 295000mE 300000mE 305000mE 310000mE 315000mE 320000mE MAP LOCALITY 0 Silt and clay often with tufa at shallow depths, swampy areas, seasonally groundwater fed, Qa numerous springs

Map compiled by S. Tickell, Qa1 Clay, silt, sand and gravel, alluvial and swamp deposits (active), seasonally groundwater fed A B Geology modified from NT Geological Survey DARWIN Stuart Hwy RN 31483 (Projected) 1:250000 Katherine 53-09 geological map. JABIRU NHULUNBUY 160 RN 33679 Roper Hwy 160 Qa Clay, silt, sand and gravel, alluvial and swamp deposits (inactive) RN 34033 Groundwater discharge area Tindall Cartography by R.Lim, Spatial Data and Mapping, 2 CAINOZOIC Design File : Mataranka_springs Limestone KATHERINE Katherine Barunga ( ) Plot File : Mataranka_springs Limestone and sandy limestone, tufa and calcrete deposits, 140 Cretaceous clay and sandstone Kl RN 34032 140 Beswick Czk Tufa & Alluvium minor cavernous rock aquifer Roper River Cretaceous 65 watertable 120 120 Prepared and produced by the Mataranka 65 Conservation and Natural Resources Group, Kl Clay and sandstone CRETACEOUS Department of Infrastructure, Planning and Environment, 100 100 141 Northern Territory of Australia, August, 2004. TENNANT CREEK MESOZOIC

490 80 Tindall Limestone 80 Groundwater Flow - - Limestone, tindall limestone, minor siltstone, major fractured and Cmt ( Cmt ) For further information contact: Larrimah

cavernous rock aquifer ELEVATION Age (million years) Natural Systems Division, (metres A.H.D.) Proterozoic Sandstone

CAMBRIAN 60 60 ALICE - Conservation and Natural Resources Group, SPRINGS

Cla Basalt (cross-section only), minor fractured rock aquifer Basalt ( Pri- ) Department of Infrastructure, Planning and Environment. 545 PALAEOZOIC - Ph. (08) 8999 3658, Fax. (08) 8999 3667 40 ( Cla ) 40 545 Goyder Centre, Chung Wah Terrace, Palmerston, Northern Territory of Australia. 20 20 This product and all material forming part of it is copyright belonging to the Northern Territory of Australia. You Sinkholes may use this material for your personal, non-commercial use or use it within your organisation 0 0 This map was produced on the Geocentric fornon-commercial purposes, provided that an appropriate acknowledgement is made and the material is not Pri Sandstone, minor siltstone, minor fractured rock aquifer 0 5 10 15 20 - Datum of Australia 1994 (GDA 94) altered in any way. Subject to the fairdealing provisions of the Copyright Act 1968, you must not make Some sections of the limestone aquifer DISTANCE (km) anyother use of this product (including copying or reproducing it or part ofit in any way) unless you have the are so riddled with solution cavities that written permission of the Northern Territory of Australia to do so.

the ground above collapses forming kilometres 0 2 4 6810 Kilometres The Northern Territory of Australia does not warrant that the product or any part of it is correct or complete PALAEOPROTEROZOIC depressions known as sinkholes. Many and will not be liable for any loss damage or injury suffered by any person as a result of its inaccuracy or 1600 of these are filled with water and are incompleteness. Black numbered lines are 5000 metre intervals of the Map Grid of Australia (MGA) Zone 53 probably sites of groundwater discharge. Universal Transverse Mercator Projection Horizontal Datum; Geocentric Datum of Australia (GDA) 1994