Coal Seam - Midwest History cache #3 Traditional Cache
Coal Seam - Midwest History cache #3
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Difficulty:
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Terrain:
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Size: 
(regular)
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If you enjoy West Australian history, geology, nature, camping out, picnicing, wildflowers (if it ever rains again!) then this is the cache for you!!!!!
History.
In 1846, the explorers and brothers A C and F T Gregory were looking for suitable grazing and agricultural lands. They discovered coal exposed within the sedimentary layers of the banks of the Irwin River, which cuts across an ancient basin of Permian sediments to enter the Indian Ocean at Dongara. After reporting their discovery, the area was declared a reserve and a number of shafts were dug, but only narrow seams of poor quality coal were revealed.
The Gregory's exploration of the area made way for the coming of the pastoralists, who developed the sheep and wheat stations that now surround the park. The settlers and new land uses resulted in changes to the lifestyles of the local Amangu, Badimaya and Widi Aboriginal groups and evidence of their occupation of the area has passed with time.
The mine shafts are still present and there is plenty of information provided on the interpretive boards around the area.
Wildflower Country
Coalseam is in the heart of the wildflower country of Western Australia. It lies between the northern sandplain to the west-where a remarkable variety of woody heath plants flower profusely in spring-and the aridlands of the Murchison region to the east-where winter rains can trigger a late winter flowering of colourful annuals.
Coalseam has the best of both worlds. There is kwongan heath on the sands of the plateau country. On the reddish loams of the floodplain of the Irwin River is wattle scrub. In spring, a carpet of -everlastings- transforms the usually sparse understorey of the wattle scrub.
Everlastings are short-lived annual herbs, mostly from the daisy family, that dry out to produce papery petals and seeds that are dispersed by the wind. If it's wildflower season, take a closer look at the flowers you see around you. There are many forms and colours, although not all of them produce papery petals.
Some of the plants you will find in this area includes jam trees, banksias, hakeas, melaleucas and grevilleas.
The Rock Files
The Irwin River usually only flows after heavy winter rains or in association with cyclonic activity. The river has cut its way through the Perth Basin of sedimentary rocks to the west of the extensive 2500-million-year-old -western shield-, the geological foundation of Western Australia.
About 270 million years ago, a continental ice sheet, similar to Antarctica, covered much of the southern super-continent of Gondwana that included this part of Western Australia. The slow break-up of Gondwana and subsequent movements in the Earth-s crust created the Perth Basin.
Between 250 million years and 65 million years ago, the sea intermittently covered this area. Sediments accumulated on the sea floor and from river deposition. Slowly, the Perth Basin filled and compacted. Subsequent lifting of the sea floor created the flat plateau country seen today above the Irwin River. As the river has carved into this sedimentary basin, it has revealed the sedimentary strata.
Within the strata, seams of coal have formed from plants trapped and transformed by heat and pressure beneath the layers of sediments. You can see the coal seams a few hundred metres upstream from the parking area at 'Fossil' and in the opposite river bank just down stream. The plants that formed the coal once were part of the great forest that covered vast tracts of the southern continents. Today, the coal seams and fossilised plants provide evidence of the continents once forming the huge landmass of Gondwana.
Opposite the Fossil parking area, marine creatures have been fossilised in siltstone sediments. If you look for them in the river bank, please leave them as you find them for others to enjoy.
The area is being upgraded at present and there is a really great tent/caravan area with clean long-drop toilets, free gas BBQ's tables and chairs. Even during the current drought there is so much exploring to be done its really worth a stop-over.
The cache is hidden is at a fantastic viewing spot - please if bringing the Geo-kiddies beaware that there is a 40 metre cliff in the area and dont let them cross the barrier!
The cache contains all the reg. items plus other goodies.
Enjoy.
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