The Park
GEOLOGY OF PARK
Precambrian rocks form a substantial area of the Mount Lofty Ranges. Para Wirra RP lies entirely within an inlier of basement rock that extends southward towards Torrens Gorge. It is part of a more extensive Precambrian rock mass, the oldest in the Mt. Lofty Ranges. As with other inliers in the region, the basement at Para Wirra is exposed as the core of an anticlinal structure, the axis of which trends approximately north south.
The rocks are Lower Proterozoic and believed to have an age in excess of 1,400 million years. As a result of being, subjected to a number of periods of deformation and heating, the original nature of the basement rocks has been obscured. To the north, east and west and within 2km are the sedimentary rocks of the enclosing Precambrian cover, estimated as being at least 800 million years old.
In the extreme west of the park there are undifferentiated, mostly micaceous rocks (Schists), and gneisses. A zone of distinctive layered or banded quartz feldspar rich rocks (gneisses) extends through the central portion of the park, In the extreme east is another conspicuous rock type (augen gneiss) which is distinguished by the presence of "eye" structures (usually of feldspar) up to 2.5 cm in length.
Epidote is a common mineral in the gneisses. Migration and segregation of minerals has produced plagioclase-feldspar and epidote veins, which typically transect the layering of the gneisses. Some of the quartz veins (or "quartz reefs") have been gold bearing and provided the major prospects in the area. The rather sporadic mineralisation, however, made many profitable ventures short lived.
Gravels and sands formed a ferruginous capping over the area in the Cainozoic (probably early Tertiary) and their subsequent dissection left hill top remnants. Two outliers extend into the park, the larger spreading across the northern limits of the park, with a small area of gravels occurring at one locality on the eastern boundary.
These geological structures are fundamental to the geomorphology and soil structures of the region which in turn strongly determine the vegetation characteristics of the area.
Flora
Native
Chrichton, Harvey and Hill (1978) have described a wide variety of vegetation types in Para Wirra Recreation Park. A copy of this document is available in the Para Wirra office. The natives that are included in this survey report are drooping sheoak (Allocasuarina Verticillata), slaty sheoak (Allocasuarina Muelleriana), beaked hakea (Hakea Rostrata), silver banksia (Banksia Marginata), narrow-leaf wax-flower Eritiostemon angustifolius), Mount Lofty bush-pea (Pultenaea Involucrata), silver daisy-bush (Olearia Pannosa), green mint bush (Prostanthera Chloranthera) and pink-lipped spider orchid (Caladenia Behrii).
Introduced
There are a large number of pest plants within Para Wirra at present. Of these the most important to control are boneseed (Chrysanthemoides Monilifera), olive (Olea Europaea), bridal creeper (Myrsiphyllum Asparagoides) blackberry (Rubus Ulmifolius), and African weed orchid (Monadenia Bracteata).
The high number of pest plants found in the park is the result of past activities within and around the park including: grazing, mining, farming and logging. Current problems surround the large populations of kangaroos that prevent the regeneration of native vegetation, particularly grasses (John Choate, 2000). Any weed control programs that are developed for Para Wirra need to take into account surrounding landholders' planting and weed control activities. Likewise, close watch should be kept on watercourses, highly disturbed/cleared areas and along roads and tracks where most of the serious weed invasion tends to occur.
Fauna
Native
The park provides a sanctuary as well as a corridor for an extensive number of birds, small mammals, reptiles and amphibians within the Mount Lofty Ranges. The diversity of animals is due to the various vegetation associations and landforms found in the park, providing a wide range of habitats and niches. The impact of past land use practices along with the introduction of non-native animals has decreased the diversity of fauna in the area. The fauna that remains provides an important source of stock for recolonising areas that are currently being restored by removing pest plants and revegetating with local indigenous plant species.
The mammal population in the park includes the western grey kangaroo (Macropus Fuliginosus), euro (Macropus Robustus), short beaked echidna (Tachyglossus Aculeatus), yellow-footed antechinus (Antechinus Flavipes), common ringtail possum (Pseudocheirus Peregrinus), common brushtail possum (Trichosurus Vulpecula), koala (Phascolarctos Cinereus) and little insectivorous bats (Microchiroptera Spp).
Over one hundred and twenty birds have been recorded in Para Wirra Recreation Park. The emu was introduced in 1967. The vegetation of the park provides a major winter resource for nectar feeding birds. Quail and grass parrots inhabit the grasslands. White throated treecreepers brown treecreepers and white winged choughs can be observed in the woodlands. Where there is dense ground cover, fairy wrens and robins can be seen.
There are approximately thirty-eight species of reptiles and amphibians found in the various habitats provided by the park and of note is the locally uncommon sand goanna (Varanus gouldii) that was sighted during this study.
Introduced
As well as providing diverse habitats for native animals, Para Wirra also provides a home for a number of introduced animals including cats (Felis Cattus), foxes (Vulpes Vulpes), rabbits (Oryctolagus Cuniclus), hare (Lepus Capensis), and deer. There is still some evidence of goat browsing on numerous shrub species that occurred prior to eradication of the goats in the late 1980s.
The control of pest plants should be integrated with pest animal control, as they act as vectors for the dispersal of blackberry, boneseed and olive. Foxes and birds especially emus are considered important vectors of boneseed in the reserve. Populations of rabbits limit the regeneration of native species by feeding on young shoots and there needs to be a program aimed at reducing or eliminating them in order for successful regeneration of the native flora.