Citation

Brown, C.M. & Stephenson, A.E., 1991. B235 Geology of the Murray Basin, Southeastern Australia. Scale 1:500000. Bulletin  235. Bureau of Mineral Resources, Geology and Geophysics, Canberra.

Abstract

The Murray Basin extends over 300 000 km of inland southeastern Australia, is flanked by subdued mountain ranges, and forms a low-lying saucer-shaped basin with thin flat-lying Cainozoic sediments. Over the past 100 years, the Murray Basin has become one of the most important agricultural regions in Australia. Unfortunately it is also a closed groundwater basin, which consists of a thin sequence of sediments containing a number of aquifer systems, with little capacity to absorb additional recharge. Irrigation and clearing of natural vegetation have increased recharge to these aquifer systems. Resultant rising groundwater levels and discharge of saline water into the landscapes and river systems of the basin, have created salinity problems that threaten to have an increasingly adverse impact on both the regional economy and natural environments. Many of the reasons for salinisation lie in the subsurface geology, and can be related to the development of the structural and stratigraphic framework of the basin over the past 60 Ma. Knowledge of these is a prerequisite to understanding hydrogeological systems and processes contributing to the salinity problem. This document summarises the geology of the Murray Basin. Beneath the Murray Basin, geophysical and borehole evidence indicates that folded and partly metamorphosed Proterozoic and Lower Palaeozoic basement is block-faulted, and that the Cainozoic sequence is locally underlain by poorly defined infrabasins preserved in graben-like troughs. These contain thick sequences of Devonian to Lower Carboniferous sedimentary rock and discontinuous, erosional remnants of Upper Carboniferous, Permian, Triassic and Cretaceous platform-cover sediments. The Cainozoic succession of the Murray Basin forms an extensive blanket of sediment, with a maximum thickness of about 600 m preserved in the deeper, central-western parts of the basin. A subsidiary depocentre with over 400 m of sediment underlies the central-west Riverine Plain, but in most northern, eastern, and southern parts of the basin the sediment succession is generally less than 200-300 m thick, and could be more accurately described as forming a thin platform-cover succession rather than a true basinal sequence. Within the Tertiary succession at least three major depositional sequences (Paleocene Eocene to Lower Oligocene, Oligocene Middle Miocene, and Upper Miocene Pliocene) have been identified. Each sequence consists of a package of genetically related formations separated by disconformities. Poorly consolidated, non-marine sand, silt, clay, and carbonaceous sedimentary rocks predominate in the east and north, but each of the depositional sequences includes weakly lithified marine sedimentary rocks in central and southwestern areas. The stratigraphy translates into a number of regional aquifer systems, confining layers and permeability barriers to groundwater flow, each with distinctive characteristics. In the Mallee region of the west, the Tertiary sediments of the Murray Basin are almost entirely concealed beneath a mainly fossil' arid and semi-arid landscape of Quaternary aeolian dunefields, with minor fluvial and lacustrine morphostratigraphic units. Farther east, where the basin and adjacent highlands are drained by the Murray, Murrumbidgee and Lachlan Rivers, the Tertiary sequence underlies flat-lying fluvio-lacustrine and minor aeolian sediments of the semi-arid landscape of the Riverine Plain. Within the Mallee and Riverine Plain landscapes, active and fossiV (currently inactive) groundwater discharge lake complexes can be identified by characteristic assemblages of Upper Quaternary sediments forming stranded lake floors, gypsum flats, salinas, gypsum and clay pellet dunes and lunettes. These have developed within low-lying areas during the past 0.5 Ma. Their extent indicates the presence of widespread salinisation under 'natural9 conditions at times in the recent geologic past. The main emphasis of the study is on impro
Google map showing geographic bounding box with values North bound -32.0 East bound 147.0 West bound 139.0 South bound -37.0
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Product Type/Sub Type

dataset - GA Publication - Bulletin

Constraints

license
Creative Commons Attribution 3.0 Australia Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

1991

Product Type

dataset

Topic Category

geoscientificInformation

Keywords

GA Publication
Bulletin
geology
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound
-32.0
East bound
147.0
West bound
139.0
South bound
-37.0

Lineage

Unknown

Digital Transfer Options

onLine

DISTRIBUTION Format

pdf

Distributor

Role
distributor
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address

Metadata File Identifier

a05f7892-fda1-7506-e044-00144fdd4fa6

Metadata Standard Name

ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

Metadata Standard Version

1.1

Metadata Date Stamp

1996-10-29

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

Role
pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
Downloads
For information on acquiring this product,
please contact the Geoscience Australia Sales Centre via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).

Please note that support hours are 9 am to 5 pm weekdays