This is an EarthCache and has special requirements for logging it. You cannot log a Found It without responding to the logging requirements set out below.
Only one find claim per Message. Each Geocacher claiming a find must submit an individual response. One team can not lodge a response on behalf of a group of people.
Rock formation uncovered by a man-made pathway.
From 370 to 290 million years ago, thick layers of sediment accumulated in a deep ocean off the geologically unstable eastern edge of Australia. These were subsequently crumpled and uplifted, and now form the Neranleigh-Fernvale beds, Bunya Phyllite, Rocksberg Greenstone, and the Kurwongbah beds. They consist of varying proportions of hardened and slightly recrystallised sedimentary rocks, chert, jasper, slate, greenstone (recrystallised basaltic volcanic rocks), pillow lava and conglomerate. They crop out throughout the South-East Queensland area.
The area surrounding Mt Petrie consists of two of those main geological formations: the Neranleigh-Fernvale Beds and the Bunya Phyllite Formation.
The Neranleigh-Fernvale Beds consist prodominantly of Mudstone, shale, arenite, chert, jasper, basic metavolcanics, pillow lava, conglomerate, metamorphosed to greenschist facies
The Bunya Phyllite Formation has Lithotypes of Phyllite, minor arenite, basic volcanics, metamorphosed to greenschist facies
Nearby Mt. Gravatt, the source of Mimosa Creek, is a hill composed almost entirely of Neranleigh-Fernvale quartzite, a rock type created from the re-crystallization of chert. One phase in the construction of Mt Gravatt Lookout Drive formed a cutting which reveals tightly folded bands of the quartzite, hinting at the magnitude of the enormous forces which once raised the rock unit from the ocean depths to the heights of an ancient mountain range sometime between 350 and 250 million years ago.
We guess that what is called Mt Petrie happened about the same time.
Elements of the Neranleigh-Fernvale geological stratum include rock types already mentioned, such as
- quartzite - a nonfoliated (meaning they do not have a layered or banded appearance) metamorphic rock composed almost entirely of quartz. It forms when a quartz-rich sandstone is altered by the heat, pressure, and chemical activity of metamorphism. These conditions recrystallize the sand grains and the silica cement that binds them together.
- chert - a chemical sedimentary rock consisting almost entirely of silica (SiO2). It usually forms as nodules in limestone.
- shale - a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Mudstones and shales are made of silt- and clay-sized particles that are too small to see. The only difference between mudstone and shale is that mudstones break into blocky pieces whereas shales break into thin chips with roughly parallel tops and bottoms. Both are made of ancient mud.
- greywacke - a sedimentary rock that is made up mostly of sand-size grains, volcanic rock fragments, as well as silt and clay than most sandstone. It is therefore also known as “dirty sandstone.”
- slate - a fine-grained, foliated metamorphic rock that is created by the alteration of shale or mudstone by low-grade regional metamorphism.
which were the prime raw materials of many Aboriginal implements. Such rock types have generated soils which have proved to be highly erodible.
Such is the case near GZ. You will find the rock formation ON THE PATHWAY - it kind-of stands out!
Based upon the above informtion, your task, to log a find, is to
1. decide what type of rock is here
2. desribe the phystical features of the rock that aided your decision
3. describe its colour and texture
4. take of photo of yourself OR your GPS to show a view of GZ. Include it in your message, but please do not post it in your log, it might give too much away.
When you have your response to the above, please, if possible, MESSAGE us, using the link at the top of the page underneath the name of the Cache. We prefer the MESSAGE method, as apparently we don't respond to emails very well, but messages we do. We will contact you by MESSAGE once your MESSAGE has been received. But you can log your find in the meantime, and just say that you have MESSAGED your answers to the COs.
As a footnote, we came across a great article discussing the geology of the Legacy Way Tunnel. Have a read to get an inkling of how geology plays a part in such huge engineering undertakings.