13°S 143°E Lockhart River – Queensland by Degrees
AT THE POINT
Location: This confluence point is located in the Sir William Thompson Range, 950 m west of the Portland Roads Road. It was accessed by road then on foot and was located accurately by GPS. The nearest settlement is Lockhart River, about 44 km in a direct line to the north east. The point falls within the Lockhart River Shire.
The Landscape: The site is on an outwash area from the low hills of the Sir William Thompson Range at an elevation of 147 m ASL. The site drains to the Wenlock River and the Gulf of Carpentaria. It has a gravelly grey soil derived from the underlying alluvium of Quaternary age (less than 2 million years). Vegetation is a low open savannah of eucalypts and casuarinas. Northern Forest Grass Trees (Xanthorrhea johnsonii) are widespread in the area. There is a sparse groundcover of grasses and sedges. Melaleuca tea-trees were evident in drainage lines near the point. Fauna noted around the point included brumbies, feral pigs, macropods (most common being Northern Nailtail Wallaby and Agile Wallaby). Termite mounds are also common.
Point information and photos: John and Mary Nowill, 2008.
WITHIN THE DEGREE SQUARE
The Country: The topography of this degree square is divided between the series of parallel ranges close to the east coast that reach elevations of 665 m ASL on Mt Carter and 543 m ASL on Mt Tozer. The ranges are very rugged, with many deep gorges and waterfalls. They back a rather narrow coastal plain that is broken in places by the estuaries of east-flowing rivers including the Lockhart and Pascoe. To the west of the ranges the country is undulating to flat, and ranges in elevation from less than 50 m in the west to about 150 m ASL in the east. All of the drainage in this area flows to the Gulf of Carpentaria and includes the Wenlock and Archer River systems.
The ranges have a very complex geology and contain some of the oldest rocks in Queensland. These include slate of Mesoproterozoic age (1600 to 1000 million years) in the Blue Mountains between the Archer River and Geikie Creek, and the schists of Neoproterozoic age (1000 to 545 million years) that include Mt Carter and the Iron Range. The ranges to the east of the Lockhart River are of intruded granite of Silurian age (434 to 410 million years); while Mt Tozer is a classic example of the volcanic rocks of Late Carboniferous (325 to 298 million years).
The lowlands to the west are made up of mudstone of Cretaceous age (141 to 65 million years) while the coastal plain and the major drainage basins are of Quaternary age (less than 2 million years) alluvium. White quartz sands form Chili Beach derived from the coarse granite of the coastal range.
Vegetation across the square is also varied. It ranges from the low open savannah country to the west, to the most extensive areas of lowland rainforest in Australia within the Iron Range National Park. The Iron Range rainforest contains over a thousand identified plant species ranging from tall canopy trees such as Milky Pine (Alstonia scholaris) to epiphytes including the Queensland floral emblem the Cooktown Orchid (Denrobium bigibum). This habitat is home to at least two hundred species of butterfly, and at least two hundred bird species including the Southern Cassowary, Eclectus Parrot, Yellow-billed Kingfisher, Red-bellied Pitta, and Magnificent Riflebird - all of which are more likely to be found in Papua New Guinea than in Australia.
About 200 different types of plants grow in the heathlands at Iron Range. Some of the plants are very unusual and have a distinctive form, which makes them easy to identify. One of the most unusual is the low-lying Pitcher Plant (Nepenthes mirabilis) found in the wetter areas around Tozer's Gap.
The most obvious heathland plants are Sheoaks (Allocasuarina littoralis), Grevilleas such as the orange flowered Fern-leaved Grevillea (Grevillea pteridifolia), and the purple-pink flowering shrub Jacksonia thesioides. Growing close to the ground are orchids and other plants, the most common being a sedge (Schoenus sparteus).
Coconut palms fringe the foreshore at Chili Beach. They are relatively recent intruders in this landscape, and possibly resulted from the increased European activity in the area and the corresponding halt in fire management by the traditional owners. The coastal plants along the foreshore include the Beach Almond (Terminalia catappa) and Beach Callophyllum (Calophyllum inophyllum). In the estuaries of the major rivers there are stands of mangrove forest.
On the western slopes the main vegetation is the low open savannah found at the confluence point. On the better soils, however, the woodland vegetation is taller and the Grass Trees tend to be replaced by Cycads. This is particularly evident in the north-west of the square on Batavia Downs where Bloodwood and Stringybark (Eucalyptus tetrodonta) woodlands are taller and denser. Ground cover is typically grasses such as Spear Grass, the density of which depends on how recently the area has been subject to fire. Cycads, such as the bright green Cycas yorkiana stand out in the landscape after fire as they put out fresh fronds as do the larger Cycas xipholepis with its large pendulous fruit.
Along the rivers riparian forests of eucalypts and paperbarks (such as Melaleuca argentea) are common.
Many species of birds live in the savannah and riparian areas - the Sacred Kingfisher and Sulphur-crested Cockatoo may be seen in the vine thickets and riverine forests. The Palm Cockatoo, a significant totem animal for many local Aboriginal people, may be seen along watercourses, perched high in the canopy. The Australian Bustard, also known as the plains turkey, may be seen searching for food in the cool of the late afternoon. The permanent lagoons, swamps, waterholes and rivers provide refuge and food for many species of waterbirds including Pelicans, Pacific Black Ducks, Radjah Shelducks and Jabirus, Many species of fish, including the popular barramundi, as well as turtles, crocodiles and frogs also inhabit the waterholes and rivers.
The Climate: The climate of the area is classified as tropical savannah. It has a markedly dry winter. The climate station at Lockhart River provides representative statistics.
Lockhart River Airport (site 028008) 1958-2008 (elevation 19 m ASL)
The highest temperature ever recorded in Lockhart River was 40.2°C in November 1990 while the lowest temperature was3.3°C in July 1965. Rainfalls also vary greatly. The highest total of 3298.5 mm was recorded in 1960 and the lowest total of 1136.5 mm in 1961.