Landscape

WORK IN PROGRESS

Hills and creeks – the bones and veins of our country – rock types and creek flows

To understand our country we have to think of its bones – its geology. The geology determines the direction and flow of creeks and from the rocks the soils are derived. Our plants largely depend on soil type (as well as depth, aspect, rainfall) and of course, which animals live with us or visit depends on the plants.

There are four main geological groups in our valley. The oldest cannot actually be seen here but are the metamorphic basement on which all rests. On these, sediments accumulated to form the Kangaroo Creek Sandstones which rise as hills to the south and west.  Then the volcanic rocks – the basalts and rhyolites – and finally the most recent alluviums along the valley floors. Long periods of erosion continued between mountain building events. You can read more about the bones here.

• Views of our hills: We’ll start this journey from the top looking to the west and then to the east. We will see that different vegetation communities are influenced by the rocks which lie below their roots. (Brief description of each road)
  • To the West
    • Mountain Top Road
    • Lodge Road -> Davis Road
    • Jacobson Road
    • Oakey Creek road/Gwynne Road
      • McLennan Road
      • Billen Road
      • Lane Road
      • Mitchell Road
      • Abbey Road
    • Warby Road
      • Bertoli Road
    • Clark Road
    • Stead Road
  • To the East
    • Lodge Road /Davis Road
    • Portessu Road

The rich red soils of Mountain Top are where Jiggi Creek begins – it was the actions of this creek and its tributaries which formed the valley. The creek and its tributaries cut through the lavas of the Lismore Basalt and eventually cut through the Kangaroo Creek Sandstone. In some places, as you walk up the creek, you can see where basalt has flown down valleys previously cut in the Kangaroo Creek sandstones. jiggi Creek merges with Goolmangar Creek at Goolmangar.

Billen Creek flows from Mount Billen along McLennan Road where it is joined by Georgica Creek whose headwaters are north-east of Billen Road. They continue along McLennan Road then flow next to Oakey Creek Road to join Jiggi Creek at Jiggi Road.

Many of the smaller tributaries don’t have names – they are sometimes ephemeral. These include the creek which drains the Warby and Bertoli Road area, the one which runs alongside Davis Road or that alongside and to the west of Mountain Top Road? Can anyone give me names for them?

• Views of our creeks – droughts and floods
  • Jiggi Creek
    • Georgica Creek
      • Billen Creek