STOKES INLET is situated about 60 kms West of Esperance on the WA South Coast. With an area of about 14 km2, it is fed by the Lort and Young Rivers, and closed to the Southern Ocean by a sand bar which only opens every few years after significant rainfall. It has a high salt content, mainly as a result of salt rising due to land clearing, but still supports a good fish population, including black bream.
Stokes Inlet was originally a deep valley between the high Pleiocene limestone dunes located along a probable fault structure. During the last 6000 years river sediment has collected in the estuary. The shore rock of the lower estuary appears to have been formed by lime cementation of beach and dune sand as well as rocks washed down by the rivers from further upstream. The Young River, about 120 kms long, and the Lort, about 100 kms long, have both brought granitic compnents from their catchments to the North of the Inlet.
CONGLOMERATE LIMESTONE is seen at GZ of this Earthcache. Limestone is a sedimentary rock composed of a substantial fraction of rounded clasts, mineral particles such as quartz or feldspar as well as igneous rock fragments such as granite and basalt. These are bound together by a matrix of finer grained sediments such as sand, silt or clay. Where there is only one type of rock clasts, the conglomerate is called " monomitic", and where there is more than one rock type, it is termed "polymitic".
EARTHCACHE: Please study the rocks at GZ, and answer the following questions in an email or message. You may log the Earthcache but answers are required in a reasonable time.
1. Describe the colour, shape and size of the "clasts" components you see there and suggest the rock type which has been bound to form the conglomerate limestone.
2. Would you call this conglomerate at GZ, monomitic or polymitic?
3. To prove you were there, please post a photo of the Estuary, with or without your team or GPS, ( but please, no spoiler photo of the rock, this will be deleted)
This Earthcache is at the Day Use area in the Stokes National Park, which is subject to an entry fee at the entrance, unless you have a much recommended National Parks yearly pass. There are picnic tables and gas barbecues there as well as drop toilets. No fires or dogs allowed. Bush camping is also available at the Benwenerup Campground. The access road is gravel with sometimes corrugations, but suitable for most 2WD's.