An ancient river

  The wollondilly Gorge is twenty miles  from thirlmere and the descent into the valley commences at the highest point of the route known as "the Mountains" or in the Aboriginal  language as Queahgong.  This point is approx 1,900 feet above sea-level and the river itself is about one hundred and fifty  fee aboe the sea, this allows of a fall on the road of at least 1,700 feet.

Queahgong, as the crow flies, is only one and a quarter miles from the Nattaai junction

Tectonic activity continued as Gondwana finally split completely apart, and India collided with the Eurasian plate. South America was connected to North America toward the end of the Tertiary. Antarctica — which was already separate — drifted to its current position over the South Pole. Widespread volcanic activity was prevalent.

Climate

Climates during the Tertiary slowly cooled, starting off in the Paleocene with tropical-to-moderate worldwide temperatures and ending before the first extensive glaciation at the start of the Quaternary.

 
In structural geology, an anticline is a fold that is convex up and has its oldest beds at its core.
After the streams in an area have reached "base level", lateral erosion is dominant as the higher areas between the streams are eroded. Finally, the upland is almost gone: the stream floodplains merge in an area of very low to no topographic relief. The resulting flat plain is the ultimate stage in the cycle of erosion or geographical cycle.

The streams within a peneplained region show extensive meandering and braiding. If the area is subsequently uplifted due to adjacent orogenic processes, without internal deformation within the peneplain, the streams will again begin downward erosion - creating incised meanders, water gaps, and other unique geomorphic features.

 
 

The Hawkesbury River has its origin at the confluence of the Nepean River and the Grose River, to the north of Penrith. Both these two tributaries are substantial rivers by the time they join to form the Hawkesbury River.

The headwaters of the Hawkesbury River, the Avon River, the Cataract River, and the Cordeaux River, rise only a few miles from the sea, about 80 kilometres (50 mi) south of Sydney. These streams start on the inland-facing slopes of the plateau which forms the escarpment behind Wollongong. Flowing north-west, away from the sea, these streams combine to form the Nepean River, and flow north past the towns of Camden and Penrith. Near Penrith, the Warragamba River emerges from its canyon through the Blue Mountains and joins the Nepean. The Warragamba, formed by the joining of the Wollondilly River, the Nattai River, the Kowmung River and Coxs River drains a broad region of New South Wales on the eastern side of the Great Dividing Range. The other principal component of the upper Hawkesbury river system, the Grose River, rises in the area of Mount Victoria in the Blue Mountains.

Once formed, the Hawkesbury River proper flows generally northwards, albeit with a significant number of meanders. Initially the river passes the towns of Richmond and Windsor, which are the largest settlements on the river. As it flows north, it enters a more rural area, with only small settlements on the river. On this stretch it passes Sackville and Lower Portland, where it is joined by the Colo River. The Colo River and its tributaries drain the northern section of the Blue Mountains.

The Wollondilly River is a perennial river in New South Wales, Australia. It was originally a tributary of the Warragamba River, and hence of the Nepean and Hawkesbury Rivers. Today it flows into Lake Burragorang, created by construction of the Warragamba Dam across the Warragamba River, which is the major water supply for the Sydney region.[1]

The Wollondilly River river rises about 7 kilometres (4.3 mi) east of Crookwell and initially flows south to a point near Pomeroy. It then flows south-east and then east through Goulburn, where it is joined by the Mulwaree River. At Towrang the river turns north-east to a point near Bullio, where it is joined by the Wingecarribee River. From here the Wollondilly River takes a wide detour to the north-west to Barrallier, where it turn east before eventually regaining its north-easterly course into Lake Burragorang. It has a total length of approximately 156 kilometres (97 mi).[1]

The Kowmung River is a river of the state of New South Wales in Australia.[1] The Tuglow and Hollanders Rivers, and Browns Creek are tributaries.[2] It is 80 km (50 mi) long, and [flows into the Cox's River which] drains into Sydney's water supply, Lake Burragorang.[3] 70% of the river's catchment lies within National Park boundaries, namely the Blue Mountains and Kanangra-Boyd National Parks.[2

Alluvium (from the Latin, alluvius, from alluere, "to wash against") is loose, unconsolidated (not cemented together into a solid rock) soil or sediments, which has been eroded, reshaped by water in some form, and redeposited in a non-marine setting.[1][2] Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel. When this loose alluvial material is deposited or cemented into a lithological unit, or lithified, it would be called an alluvial deposit.

 

In geomorphology, a drainage system is the pattern formed by the streams, rivers, and lakes in a particular drainage basin.

Geomorphologists and hydrologists often view streams as being part of drainage basins. A drainage basin is the topographic region from which a stream receives runoff, throughflow, and groundwater flow. Drainage basins are divided from each other by topographic barriers called a watershed. A watershed represents all of the stream tributaries that flow to some location along the stream channel.

Deranged drainage system

A deranged drainage system is a drainage system in drainage basins where there is no coherent pattern to the rivers and lakes. It happens in areas where there has been much geological disruption.  During the last ice age, the topsoil was scraped off, leaving mostly bare rock. The melting of the glaciers left land with many irregularities of elevation, and a great deal of water to collect in the low points, explaining the large number of lakes which are found in Canada. The watersheds are young and are still sorting themselves out. Eventually the system will stabilize.[1]

Lower Tertiary he global climate during the Paleogene departed from the hot and humid conditions of the late Mesozoic era and began a cooling and drying trend which, although having been periodically disrupted by warm periods such as the Paleocene–Eocene Thermal Maximum, persists today. The trend was partly caused by the formation of the Antarctic Circumpolar Current, which significantly cooled oceanic water temperatures.

 

Mammals began a rapid diversification during this period. After the Cretaceous–Paleogene extinction event, which saw the demise of the dinosaurs, they transformed from a few small and generalized forms and began to evolve into most of the modern varieties we see today. Some of these mammals would evolve into large forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial, and airborne environments. Some mammals took to the oceans and became modern cetaceans, while others took to the trees and became primates, the group to which humans belong. Birds, which were already well established by the end of the Cretaceous, also experienced an adaptive radiation as they took over the skies left empty by the now extinct Pterosaurs. Most other branches of life remained relatively unchanged in comparison to birds and mammals during this period.

As the Earth began to cool, tropical plants were less numerous and were now restricted to equatorial regions. Deciduous plants became more common, which could survive through the seasonal climate the world was now experiencing. One of the most notable floral developments during this period was the evolution of the first grass species. This new plant type expanded and formed new ecological environments we know today as savannas and prairies. These grasslands also began to replace many forests because they could survive better in the drier climate typical in many regions of the world during this period.