Spearwood Dune System
Blackwall Reach Reserve is situated on the western edge of the Spearwood Dune System. The Swan Coastal Plain consists of a series of coastal dunes, running roughly parallel to the coastline. The Spearwood Dune System is bound to the east by the Bassendean Dune System and to the west by the Quindalup Dune System. Each system has a distinctive geology, vegetation, topography, drainage pattern and soil characteristics.
In the Spearwood Dune System, leaching has occurred causing the carbonate to precipitate below to form hard compact limestone. At Blackwall Reach this limestone is exposed at the surface.
One of the most prominent features of the Blackwall Reach Reserve is the limestone cliffs, a sedimentary rock formation that rise more than 8metres out of the Swan River. The cliffs have been formed by the eroding processes of the river, which flows from the wide expanse of Mosman Bay into the narrow gap of Blackwall Reach. Rainfall has caused the limestone to be deeply attacked physically and chemically producing frequently sharp points and ledges.
A number of interesting features are developed within exposed limestone across the Perth Region. These include rhizoliths, calcreted surfaces (beach rock), karstic features (e.g. sinkholes, caves), raised beaches, and elevated shoreline platforms. When free from impurities limestones are white, but they generally contain small quantities of other minerals which affect their colour. Many limestones are yellowish or creamy, especially those which contain a little iron oxide, iron carbonate or clay.
Please email me the answers to the following questions:-
1. What kind of rock form is Limestone? (Igneous/Sedimentary/Metamorphic)
2. Study the limestone formations along the edge of the carpark here. What are their primary colours? Why are they this colour
3. Within the rocks, can you see any fossilisation? If so, what are they?
4. Take a picture of yourself on or near the jetty and upload it with your found log.
In accordance with the guidelines, the procedure for logging an Earthcache is:
- Send me the answers.
- Log your visit. "People do not need to wait for permission to log your EarthCache."
Please note : If answers have not been received within 10 days, you will risk having your found log removed.