is popular with tourists, and there are a number of tourist lookouts. It is also of geological interest, as it exposes a section through the Tumblagooda Sandstone, a geological sequence rich in Ordovician trace fossils. The maximum age for the initiation of major down-cutting of the Murchison Gorge, as a response to regional Quaternary tectonism, is Late Eocene (33.9–38 million years ago). Estuary The final of the Murchison River, from the Murchison House ford to the mouth, are estuarine, and consist of a sequence of long sandbars and shallow pools mostly less than a metre deep. The estuary is permanently open to the sea, so is constantly affected by tides and the inflow of saline sea water. When river flow is low, the estuary accumulates sediment from the ocean, narrowing the river channel; this sediment is evacuated to the ocean during periods of high flow, but high flow also brings sediment into the estuary from upriver. Because of the high sediment load, and continual stirring by wind and river flow, the water is turbid. The mouth of the estuary is a small delta, closed by a sandbar except for a narrow channel. Although this channel is permanently open, it is usually very narrow and shallow, and so is now dredged every year to allow passage by western rock lobster fishing boats. History The Murchison River was named by the explorer George Grey, whose boats were wrecked at its mouth on 1April 1839, during his second disastrous exploratory expedition; the name honours Grey's patron, the Scottish geologist Sir Roderick Murchison. Murchison's advocacy had been essential in securing official support for Grey's Western Australian expeditions. Murchison House Station, one of the oldest stations in Western Australia, was established by Charles Von Bibra on the banks of the river toward the western end in 1858. The estuary and river mouth was used as a holiday destination by families from the Galena mines in the 1920s and 1930s, and a military holiday camp was built there during World WarII. In 1951 the town of Kalbarri was gazetted at the river mouth, and by the end of the 1990s the population was about 2,000. In 1963 the Kalbarri National Park was gazetted, formally protecting the lower reaches of the river, including the gorge. The Galena Bridge, carrying North West Coastal Highway over the river at Galena, was opened by the Main Roads Department in December