The Bullock Creek Fossil site is one of three known vertebrate

Vertebrate

Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

 fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 sites in the Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

's Northern Territory

Northern Territory

The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...

, along with the Alcoota

Alcoota

The Alcoota Fossil Beds are an important paleontological site located on Alcoota Station in Central Australia, 200km north-east of Alice Springs. It is notable for the occurrence of well-preserved, rare, Tertiary vertebrate fossils, which provide evidence of the evolution of the Northern...

 Fossil Beds on Alcoota Station and the Kangaroo Well site on Deep Well Station. It is located about 550km south-southeast of Darwin

Darwin, Northern Territory

Darwin is the capital city of the Northern Territory, Australia. Situated on the Timor Sea, Darwin has a population of 127,500, making it by far the largest and most populated city in the sparsely populated Northern Territory, but the least populous of all Australia's capital cities...

, on Camfield Station.

The Bullock Creek Fossil Site is part of the Camfield Fossil Beds which outcrop in a narrow belt about 50km long. The Bullock Creek local fauna are approximately dated to the mid Miocene

Miocene

The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

 (about 12 million years ago). The Camfield Fossil Beds which contain the Bullock Creek local fauna consist of light coloured calcareous sandstone

Sandstone

Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

, siltstone

Siltstone

Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...

 and limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

. Ferruginous mottling is found at the base and chalcedonic silification at the top. The presentation of fossils at the site ranges from poorly-sorted fragmentary lags to associations with partial skeletons which includes complete crania (skulls) with intact delicate structures.

The Bullock Creek Fossil Site is of natural significance in providing evidence for the evolution of the Northern Territory's fauna and climate.

The Bullock Creek Fossil site is part of the Camfield Fossil Beds which are one of only a few Australian localities where rare fossil marsupials are well preserved. Among the fossils at the Bullock Creek site have been found complete marsupial crania with delicate structures intact. New significant taxa identified from the Bullock Creek mid Miocene include a new genus of crocodile, Baru

Baru

Baru was an extinct genus of Australian mekosuchine crocodilian. It was semi-aquatic, around 4 m in length. Being semi-aquatic its habitat was around fresh pools of water in wet forests, ambushing their prey, much like modern species...

(Baru darrowi), a primitive true kangaroo, Nambaroo

Nambaroo

Nambaroo is an extinct genus of macropod marsupial from the late Oligocene some 25 million years ago of Australia.-Sources:* at National Geographic...

, with high-crowned lophodont teeth; and a new species of giant horned tortoise, Meiolania

Meiolania

Meiolania is an extinct genus of cryptodire turtle from the Oligocene to Holocene, with the last relict populations at New Caledonia which survived until 2,000 years ago....

. New marsupial lion

Marsupial lion

Thylacoleo is an extinct genus of carnivorous marsupials that lived in Australia from the late Pliocene to the late Pleistocene...

, thylacine

Thylacine

The thylacine or ,also ;binomial name: Thylacinus cynocephalus, Greek for "dog-headed pouched one") was the largest known carnivorous marsupial of modern times. It is commonly known as the Tasmanian tiger or the Tasmanian wolf...

, and dasyurid material has also been recovered. The extensive collection of Neohelos

Neohelos

Neohelos is an extinct sheep-sized marsupial from the late Oligocene to middle-Miocene aged deposits of Bullock Creek in the Northern Territory, Lake Ngapakaldi South Australia and riversleigh of Queensland. There are four species in this genera, N. tirarensis from Bullock Creek and the...

(large browsing marsupial) remains from the Camfield beds has initiated a review of the mid Miocene zygomaturine diprotodontids.

Together with the fossil assemblage in the Alcoota Fossil Beds to the north-east of Alice Springs, the Bullock Creek fossil fauna demonstrates systematic and community structural continuity from the mid to late Miocene in northern Australia.

The Bullock Creek assemblage contains biological evidence of seasonality (trapping of small fish in drying backwaters), while lithostratigraphic evidence (interbedded evaporites) suggests longer periods of low precipitation and probably high ambient temperatures. The assemblage provides evidence that aridification

Aridification

Aridification is the process of a region becoming increasingly dry. It refers to long term change rather than seasonal variation.It is often measured as the reduction of average soil moisture content....

was in progress in northern Australia during the Miocene.