South-East Freshwater Biogeographic Province

South-East Freshwater Biogeographic Province – Geology and topography

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Geology

The majority of the FBP consists of the South East Queensland vegetation bioregion, which is characterised by a variety of geology types.  The Australian Natural Resources Atlas[1] has more detailed geological descriptions about the various vegetation bioregions composing the SEQ FBP:

• The South East Queensland vegetation bioregion is characterised by metamorphic and acid to basic volcanic hills and ranges (Beenleigh, D'Aguilar, Gympie, Yarraman Blocks), sediments of the Moreton, Nambour and Maryborough Basins, extensive alluvial valleys and Quaternary coastal deposits including high dunes on the sand islands such as Fraser Island.
• Brigalow Belt South consists of predominantly Jurassic and younger deposits of the Great Artesian Basin and Tertiary deposits with elevated basalt flows.  Sandstone ranges and landscapes of the Barakula and Inglewood sandstones.

Terrain

Relief ratio values for the South-East FBP range from low to high, with a mean of 0.03. Low relief values are confined to small patches within the FBP, particularly the coastal and north-western sections of the FBP. The South-East FBP has steep relief in the southern sections of the FBP (foothills of the Great Dividing Range), and to the west of the coast (D’Aguilar, Blackall and Connondale ranges). Stream segment slope values throughout the FBP also range from low to high, with higher values corresponding to areas with higher relief ratio values.

The FBP is strongly dominated by erosional flatness index class. Only a small proportion of the FBP contains valley bottom flat areas (in the areas with low relief ratio), and ridge top flat is almost absent.  This is likely to result in dominance of coarse bed material in South-East streams and implies a dominance of aquatic assemblages preferring coarser substrate types at the FBP scale. Any biota preferring depositional areas are likely to be restricted in this FBP. The limited extent of valley bottom flats suggests floodplains and the processes associated with floodplain inundation are not likely to be important to the ecology of South-East rivers. The scarcity of depositional areas in the South-East FBP is likely to be associated with the relatively low turbidity of the area and subsequently the widespread distribution of submerged macrophytes.

In some sections of the South-East FBP relief is steep and stream slopes are high. In steeper catchments, run-off is generally faster, producing more peaked discharges and greater erosive power[2]. This contributes to high disturbance intensity of spates in these steeper sections of the FBP. In other sections of the FBP, relief is generally shallow and stream slopes are low, contributing to low disturbance intensity of spates in these sections.

Information about terrain

Information about methods

FBP Terrain Map   State Terrain Map

References

1. ^ ANRA (2002), Australian Natural Resources Atlas. [online], ANRA. Available at: https://data.gov.au/data/dataset/australian-natural-resources-atlas-anra.
2. ^ Thorne, CR (2004), 'Basin', Microsoft Encarta Online Encyclopedia, Microsoft.

Last updated: 22 March 2013