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LAP Brochure


Last modified:
Tuesday 16th August 2016

Crop Irrigation Map

LAP Brochure


A report by Brown and Stephenson (1991) contains a comprehensive description of the age, nature, depositional environments and stratigraphic relationships of the sedimentary layers in the Basin.

A summary of the geological sequence in the Mid Murray LAP Region has been extracted from the aforementioned report and is depicted below in Table 1. The surface geology of the Region is mapped in A Study to Underpin a Land & Water Management Plan (AWE, Figure 1.8, page 26) and is available from the Mid Murray LAP Association upon request.


Summary of the geological sequence

Unit

Age

Description

Thickness

Comment

Coonambidgal
Formation (Qa)
Late Pleistocene to Holocene Grey sandy silt and clay Present over surface of floodplain Aquitard
Monomam
Formation (Qa)
Late Pleistocene to Holocene Grey to brown sand and gravel Alluvial deposits in the River valley Alluvial aquifer
Woorinen Formation (Qdw) Late Pleistocene to Holocene Red brown silty sand to sandy clay Extensive, variable thickness but usually 2-3m Forms Mallee sand dunes
Bakara Calcrete (Qca) Early Pleistocene to Holocene Calcrete rubble or massive sheets Extensive, usually less than 2m thick Very low permeability, causes perched water tables
Blanchetown Clay (Qph) Late Pliocene to Early Pleistocene Grey-green or red- brown sandy clay, gypsiferous Extensive, up to 20m thick Defines ancient course of River Murray
Norwest Bend Formation (Tpn Late Pliocene Oyster beds and sandy limestone Generally less than 5m thick, restricted to narrow north-south zone along the River Elevated above the water table
Loxton-Parilla Sands (Tps) Late Miocene to Pliocene Yellow-brown to red silty sand and gravel Thickest in south eastern portion, thin or absent to west of River Major regional unconfined aquifer
Murray Group Limestone (Tml) Oligocene to Middle Miocene Pale grey to yellow fossiliferous limestone Extensive, up to 100m plus thick Regional aquitard
Ettrick Formation (Toe) Oligocene to Early Miocene Grey to green calcareous clay Continuous, 20-30m thick Regional confined aquifer
Lower Renmark Group Eocene to Mid Miocene Cabonaceous and pyritic sand and clay Forms continuous blanket over basement, variable thickness up to several hundred metres Generally forms low permeability base to sedimentary system
Basement Cambrian- Precambrian Folded and metamorphosed sediments Continuous, underlies sedimentary sequence

Hydrogeology

The River valley in the Mid Murray LAP Region is generally incised into the semi-confined regional Murray Group aquifer. Ground water flow discharges from the aquifer into the River valley from east and west.

From deepest to shallowest (oldest to youngest), these aquifers include the:

  • Renmark Group;
  • Murray Group; and
  • Loxton-Parilla Sand aquifers.

The figure below shows:

  • a regional water table aquifer occurring within the Murray Group aquifer;
  • potentially) a localised water table aquifer formed within the Loxton-Parilla Sand beneath irrigated areas, underlain by a semi-confined Murray Group aquifer; and
  • a regional confined aquifer formed within the Renmark Group.


hydrology profile



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