Marble Bar started out on the wrong foot when the bar that crosses the Coongan River was mistaken for marble by the pastoralists of the area and they called it Marble Bar. Once the township started up it was also called Marble Bar but it was later discovered that the bar was not marble but Jasper, so it should have been Jasper Bar.
Then in 1923/4 it obtained and still holds the dubious honour of being Australia’s Hottest Town.
Where the temperature reached a temerature of 37.8° on 160 consecutive days from 31st October 1923 to 7thApril 1924, the temperatures did not drop below 30°C during that time
Geology.
Marble is a rock resulting from metamorphism of sedimentary carbonate rocks, most commonly limestone or dolomite rock. Metamorphism causes variable recrystallization of the original carbonate mineral grains. The resulting marble rock is typically composed of an interlocking mosaic of carbonate crystals.
Jasper, is an aggregate of micro granular quartz and/or chalcedony and other minerals it is an opaque impure variety of silica, usually yellow, red, brown or green in colour; and rarely blue. Since Jaspers are mainly silicon dioxide quartz, the colouring agents end up in the chalcedony by inclusion and infusion. Scientists have shown that in Agates chalcedony, despite its hardness, is slightly porous. Because of this porosity, solutions containing several forms of manganese oxides and iron oxides-and in rare cases uranium oxides and other metal salts-can seep into an agate. Jasper has a tighter structure, so the impurities do not accumulate in it to the same extent as in agate. This accounts for the less vibrant colours in jasper. The original silica may also contain impurities. These impurities are the secret to Jaspers many colours.
Manganese oxides produce violets and blacks.
Iron oxides cause the reds and yellows.
Uranium imparts yellow.
Copper results in red, green and blue.
Nickel salts colours the chalcedony green.
The white layers are pure silica.
Chert is also sedimentary material that also forms in extensive bedded deposits, it is also an opaque variety of chalcedony that can be called a "Jasper."
The "Bar" is part of a Sedimentary deposit that can be traced for over 100km along strike.
The predominant layering you see is sedimentary bedding in rocks that were laid down on the sea floor about 3460 million years ago (see figure A). You will notice that the layering now dips steeply, this is the effect of the long geological history of this area.
The once flat laying rocks have been tilted up on edge and moderately overturned as a result of uplifting and doming of the Mt Edgar granite complex east of Marble Bar (see Picture B)
The Bar is much harder than the surrounding rocks and is exceedingly difficult to erode hence if forms a predominant ridge in the area.
Please READ. Very Important!
If you take some water with you or a container to scoop some out of the river and pour it on the rock face it will enhance the colours.
At GZ you should be standing in the middle of some rocks, with your back to the largest one, looking toward the water you will see a rock with different coloured sedimentary layers running through it.
To Claim this cache you just have to answer a few questions about this particular rock and send your answers to us.
1/.. The name of this Earth cache.
2/.. Feel the texture of the rock in front of you and then feel the texture of one of the rocks above the water line and tell us what the difference is and why.
3/.. What are the most predominant colours of the rock in front of you, and what do you think caused this.
4/.. At what angle and direction are the sediment layers running and why is it different from the rest of the rocks in this area?
References.
Marble Bar Shire and Information centre.
Discovery Trails to early earth :- Martin Van Kranendonk &Jean Johnston.
Wikipedia.
Geology :- James Geikie