The Top End of Australia: Western Australia

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BIOGEOGRAPHICAL PROVINCE - Western Sclerophyll orWestern Mulga
GEOGRAPHICAL LOCATION Situated over 800km north of Perth, on the westernmost point of the coast of Australia, Shark Bay is bounded by the town of Carnarvon to the north, and extends westwards to include the outer chain of Bernier, Dorre and Dirk Hartog islands, then over 200km southwards joining up with Edel Land and extending southwards to Zuytdorp Nature Reserve. The western boundary is three nautical miles off the coast. The eastern boundary is adjacent to the coast south from Carnarvon to Hamelin Pool, then continuing southwards approximately 70-30km inland from the west coast. The township of Denham and the areas around Useless Loop and Useless Inlet, although within the main boundary are specifically excluded from the World Heritage property.

View of the Hamelin Pool stromatolite site at Shark Bay, Western Australia. Click on the image (open this image) to view at full size. The rainbow is grounded right on the stromatolite site. Pale blue-green water under the rainbow is shallow, saline, low nutrient, low sediment load and warm. It is subject to very high evaporation rates, which produces the warm saline biological "desert" water in which relatively few species can survive. The Fragum erugatum clams (tiny white shells by the trillion) become so abundant that they make up the entire beach at Shell Beach. Foreground shrubs are mixed Acacia and occasional Banksia, typical of the Western Mulga vegetation adapted to arid conditions. The semi-arid to arid climate has hot dry summers and mild winters. Summer temperatures average between 20°C and 35°C and winter temperatures between 10°C and 20°C. Average annual precipitation is low, ranging from 200 mm in the east to 400 mm in the far southwest. Annual high evaporation ranges from 2000mm in the west to 3000mm in the east.

BELOW: A recent high resolution satellite photo of the Shark Bay area by NASA. The road we took to the Old Telegraph Station is visible if you click on the image. However, it is big enough to fill your screen, even though it is compressed for the Web browser.

Above is a map (Australia GeoSciences) and an older satellite photo of the Shark Bay area of Western Australia. Click on the images to see at full size. There are some wonderful names on the map (Petit Point and Useless Loop for example).

Getting to Shark Bay is easy: you fly into Monkey Mia Resort airstrip (recently paved) from Perth. From there you take the Hamelin Pool tour which goes to the Old Telegraph Station (some souvenirs and picnic facilities at the Heritage Site). As you can see from the map on the right, Monkey Mia Resort is separated from the stromatolite locale by a long distance, made longer by the presence of bush adders, chiggers and bushflies, not to mention no shopping malls or gas stations! But it is worth all the effort!

However, my nephew and I arrived as the biweekly Stromatolite tour was over and we had to leave before the next tour left! We had not come halfway around the world to see a World Heritage Site and then be flummoxed by a local tour schedule mismatch (our travel agent did not check). The Resort manager helped us find a tour guide who really knew the area and it turned out to be a couple who had lived at the Old Telegraph Station at Hamelin Pool long enough to raise a family. They also had the local sandalwood harvesting contract: really busy and knowledgeable people. And as luck would have it, the lady and her husband wanted to do a natural history video and, her knowing that I was a biologist was a stroke of luck for all of us! We swapped info on the whole tour, which was private so we could stop anywhere we wanted within the time we had. We had a blast!

First, the tour guides had the local trash hauling contract for the Resort, so we went out of Monkey Mia proudly hauling the week's refuse. At Denham, the trash was suitably deposited and the vehicle was refuled, transforming it to the Shark Bay Taxi Transport (phone 099-481-331), or as their business card logo (a shark about to swallow a small fish) states, S.W.A.T. taxi. I was informed by the owners that the acronym could be read two ways --- SouthWestern Australia Taxi or Swindled Without A Thought. We preferred the more colorful translation.

The S.W.A.T. taxi in Denham (LEFT). We were just emerging from a local ice cream parlor suitably stoked on calories. The Eden Project Gate looking south (RIGHT). A solar electric panel is visible midway aong the fence. There is an area of raked fine sand at lower left which has to be checked daily for kitty paw prints because feral cats sneak into the north Perón peninsula park at night to hunt.

Our route took us through the Eden Project Gate, which separates the northern and southern Perón Peninsula. The Project idea is to clear out the non-native animals (sheep, goats, cats, rabbits and foxes) and then keep them out with a solar-powered double fence right out of Jurassic Park. The native species are then supposted to repopulate the area. Things are sort of going according to the plan: sheep and goats are gone, foxes seem about to be gone, rabbits are still present (in spite of myxoma virus and rabbit calicivirus disease) and the feral kitty cats are very smart, cryptic and tough. More about the Eden Project after the Great Stromatolite Tour.

From the Eden Gate we stopped to see sea eagles (where else but at Eagle Point?) and at Shell Beach, where the beach is made of 110 kilometers of shells 10 meters deep (mostly the Cardiid bivalve Fragum erugatum which favors seawater at about double normal salinity). They have been accumulating for about 4000 years and the higher you go on the beach away from the water line, the more they are cemented together. The consolidated beach rocks are mined locally for an attractive decorative wall block. There were some shell block walls at the resort. My nephew and I sampled the shell distributions on the beach as well as taking sample counts from the blocks in the walls at Monkey Mia. We had a project for the day, which was to figure out how many shells there were on a beach 110 km x 10 m deep by about 80 m wide. We also looked at the size distribution of shells from the waterline to the top of the beach. Our data are HERE.

We then went on to the Hamelin Pool Stromatolites, which have a ten thousand year story to tell. Click on the images below to see the technical story full size. These are my journal notes transcribed from some natural history displays at the World Heritage Site. There is a lot to see and the admission to the museum is well worth the price and the long journey. I have made every effort to be accurate.

The diagram on the LEFT summarizes sealevel changes since the last Ice Age. The diagrams on the RIGHT are made on the long axis of Hamelin Pool so they show the sea grass and sand sill at its mouth. The series show what geologists have worked out about its history by discovering and then interpreting its structure.

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