|List||National Heritage List|
|Legal Status||Listed place (20/07/2004)|
|Place File No||4/08/224/0005|
|Summary Statement of Significance|
Approximately 98 million years ago during the early Late
Cretaceous, a shallow and retreating inland sea covered much of what is now
central Queensland. The landscape received high rainfall and ferns, conifers,
early angiosperms, cycads and ginkgos grew in abundance. By around 95 million
years ago the inland sea had retreated to the north. The resultant flat
landscape was dominated by lake and river shoreline environments that contained
broad but shallow drainage channels, sand bars as well as plastic, muddy flats.
It was in such a setting that an extraordinary stampede event is thought to have occurred, an event that has been recorded in the sediment layers within the Lark Quarry Conservation Park. A fossilized record of what was perhaps a 10 to 30 second sequence of events has been captured within between 170 and 200 individual dinosaur trackways made up of nearly 4000 footprints. These trackways contain the most concentrated known set of dinosaur footprints in the world.
Australia contains some of the best dinosaur trackways in the world and those within the Lark Quarry Conservation Park currently the best known and most informative in Australia. They are nationally significant as they contain an abundance of trackways that are preserved within an interpreted palaeo-landscape and behavioural context. They record the paths of a mixed herd of small, two-legged dinosaurs that ran in a single direction across a muddy shoreline area in an apparent attempt to flee a much larger carnivorous dinosaur that stood in their path. This unusual behaviour is consistent with and has been interpreted as a dinosaur stampede event. No other known dinosaur trackway site in the world shows stampede behaviour such as this.
The dinosaur trackways within the Lark Quarry Conservation Park are among the best preserved in the world. They were preserved by burial in a fortuitous flood event soon after they were formed and hence retain an excellent level of preservation. Sediments continued to build up in the mid Cretaceous and have compressed over time to form the sedimentary rocks of the Winton Formation. These interbedded layers of sandstones and claystones also provide important information regarding the nature and extent of the local Late Cretaceous environment. The interpretation of this palaeoenvironment provides evidence of a former, much wetter climate in an area of Queensland that is currently arid.
The primary research conducted on the dinosaur trackways within the Lark Quarry Conservation Park is commonly cited as the benchmark for study into dinosaur footprints and behaviour. As the place preserves nearly all of the world’s dinosaur trackways made by running dinosaurs, it is also an important information source for locomotion studies and performance analysis for the types for both ornithopods (small herbivorous dinosaurs) and coelurosaurs (‘hollow boned’ two legged dinosaurs).
Glen Seymour, a local station manager first discovered
dinosaur trackways in what in now the Lark Quarry Conservation Park in the
1960s. His discovery was made whilst fossicking for opal at the base of a small
hill in an area of what was then Cork Station. This area was later named
Seymour Quarry in recognition of his remarkable find. In 1971 visiting
palaeontologists from the Queensland Museum and the British Museum of Natural
History traced the sediment layer in which the original tracks were discovered
to find more dinosaur tracks in a nearby hillside (Winton Shire Council 2004
and Molnar 1982 p213). |
In 1976 and 1977 a team of volunteers led by palaeontologists from the University of Queensland and the Queensland Museum excavated this hillside over an 18 month period to expose an area of bedding plane approximately 210 m2. This area contains the majority of the known trackways and was later named Lark Quarry in acknowledgement of the man who moved the most rock off the site during the excavation. Dinosaur trackways have since been found within several horizons of the Winton Formation within the Lark Quarry Conservation Park (Thulborn and Wade 1989 p41).
The most significant set of trackways, partially excavated at both Lark and Seymour Quarries, are interpreted as recording the same stampede event. Although Lark and Seymour Quarries are more than 90m apart, the trackways are similar in diversity, abundance, morphology and orientation (Thulborn and Wade 1984 p414). As a result, it is commonly accepted that Seymour Quarry contains an extension of the Lark Quarry trackways (Wade 1984 p381) and that they record the path of the stampeding dinosaurs over a 95m section of palaeo-lake shoreline.
The main trackway areas at Lark and Seymour Quarries were once part of a broad drainage channel that flowed in a southwesterly direction into a lake or waterhole. At the time the trackways were formed, a fine-grained mud covered the area. As the mud was neither water-logged nor tacky, it didn’t slump or collapse whilst the tracks were being created and rarely adhered to the feet of the dinosaurs. The substrate was an ideal medium for preserving footprints, which is reflected in the excellent preservation of the trackways that is still apparent now.
Furthermore, the geological boundary between the footprints and the overlying sandstone constitutes a thin layer of iron oxide rich ironstone that fortuitously allows for relatively easy mechanical separation between the footprint layer and the adjacent overburden. This distinct ironstone barrier contributes to the excellent level of preservation characteristic of the trackways (Cook 2004).
A complex behavioural picture of a large group of dinosaurs over a short period of time has been interpreted from the trackways within the Conservation Park. The study of trackways (the successive steps of one animal) can provide insights into characteristics of extinct animals that are hard to investigate in other ways (Molnar 1991 p659 and Rich and Vickers-Rich 2003 p69). Trackways are studied to provide information on the dimensions, agility and speed of the track makers as well as the environment in which they lived. Speed can in turn be used to investigate physiological attributes such as metabolic rates.
The trackways that record the stampede event are preserved within a near to horizontal sedimentary layer. They show that a large carnivorous theropod (a type of dinosaur from the suborder theropoda) approached the shoreline of a lake or waterhole from the north. From the size of its footprints and the length of its stride, palaeontologists have determined that the theropod was walking at a speed of between 8 and 9 km per hour (Wade and Molnar 2000 p1, Thulborn and Wade 1984 p436 and Long 1998 p128) and that it was probably around 9 to 10 m in length.
Due to the difficulty in attributing dinosaur footprints to known dinosaur taxa, ichnotaxa are often given to the track forms themselves (Kuban 1994 p8). The taxa identified at Lark Quarry are only known from their footprints not fossils of body parts, and as such their names end in ‘opus’ meaning ‘foot of’. The large theropod was placed in the taxa cf. Tyrannosauropus in the super-family Carnosauria.
It is not possible to determine if the Tyrannosauropus was drawn to the shoreline for water or, if it had detected prey in the area. What the trackways do show is that the Tyrannosauropus’ 11 large prints are overlain by a vast number of prints made by smaller dinosaurs moving in the opposite direction. As these smaller tracks are imprinted onto the undried films of mud remaining in the large theropod tracks, palaeontologists believe the smaller dinosaurs ran as a group across the mud whilst the Tyrannosauropus prints were still fresh (Thulborn and Wade 1984 p417 Wade and Molnar 2000 p2). These superimposed footprints are equally well preserved and are thought to have been formed during the same sequence of events (Thulborn and Wade 1984 p418).
There is no evidence that any of the dinosaurs approached the waterbody by crossing the same area of mudflat before the arrival of the large theropod. This suggests that there had been another route to their congregation area that the Tyrannosauropus may have blocked by its presence (Molnar 1991 p662). Apparently trapped by the Tyrannosauropus, a mixed group of small carnivorous coelurosaurs (‘hollow boned’ two legged dinosaurs from the super-family Coelurosaurina) and medium sized herbivorous ornithopods (‘bird like’ two legged dinosaurs from sub-order Ornithopoda), are thought to have stampeded past the Tyrannosauropus in an attempt to flee their apparent entrapment. This flight sequence has much in common with contemporary stampede behaviour, lending weight to the interpretation of the trackways as such.
Between 170 and 200 dinosaurs were involved in the stampede. The true number cannot be calculated as the stream edge has eroded away (Wade and Thulborn 2000 p2). The medium sized ornithopods (bantam to emu sized, between 12 cm and 1.6 m at the hip), represented by well over 1000 footprints have been named Wintonopus latimorum. The small coelurosaurs (about the size of large chickens, between 13 and 22 cm at the hip) are known as Skartopus australis. The holotypes for both these ichnotaxa are from Lark Quarry (Thulborn and Wade 1984 p421 and p427).
Study of the trackways within the Lark Quarry Conservation Park provides for interesting comparisons about the movements of dinosaurs (Thulborn 1990 p260). A comparison of well-researched dinosaur trackways from around the world has shown that dinosaurs moved at average speeds between 2 and 12 km per hr (Kuban 1994 p11). In contrast, the Lark and Seymour Quarry trackways indicate that S. australis was moving at a mean speed of 13 km per hour (Long 1998 p129) whilst W. latimorum was moving at a mean speed of between 12 and 20 km per hour (Long 1998 p130). The apparent speed of these dinosaurs supports the ‘stampede event’ interpretation as triggered by the large carnosaur.
Further evidence that the smaller dinosaurs were running is reflected in that almost all of the Lark and Seymour Quarry footprints show the imprints of toes only, and there are no impressions caused by tail drags or front limbs. For example, of the approximately 2000 prints of W. latimorum identified, only 20 of them show the heel as well as the 3 toes (Rich and Vickers-Rich 2003 p79). In addition, the relative stride length of trackways at Lark Quarry is almost 3 times that of bipedal dinosaur trackways found elsewhere in the world (Thulborn 1990 p324).
The third site known to contain dinosaur trackways within the Lark Quarry Conservation Park is at New Quarry on the side of a hill, approximately 100 m to the south of Lark Quarry. Although there is an eroded gap between New Quarry and Lark Quarry, both sites contain tracks at equivalent stratigraphic levels (Thulborn and Wade 1984 p416) and it is probable that New Quarry is a lateral extension of the trackways at Lark Quarry (Cook 2004). New Quarry contains two distinct claystone layers, both of which have yielded dinosaur tracks (Wade 1984 p381). In a stratigraphic layer similar to that displaying the stampede event, a trackway of a single theropod, possibly W. latimorum has been found (Thulborn and Wade 1984 p416 and p423). In a lower layer of claystone, thoroughly trampled tracks showing no dominant orientation have been discovered on the edge of what was once a watering hole.
In stark contrast to its early Late Cretaceous environment, the Lark Quarry Conservation Park now lies in a spectacular setting of dissected, residual hills and mesas on the edge of the Tully Range southwest of Winton. The Winton Formation, created between 93 and 98 million years ago not only contains the dinosaur trackways within the Lark Quarry Conservation Park, but also other dinosaur and plant fossil sites in central western Queensland. In some areas the Winton Formation is up to 400 m thick indicating the huge amounts of sediment that was once carried and deposited by the inland water systems of the Late Cretaceous.
The steep flat-topped hills, created by erosion over the millennia, now support lancewood Acacia shirleyi shrubland on the plateaus and upper slopes whilst spinifex Triodia longiceps open hummock grassland with scattered Canthium latifolia and Eremophila latrobei grows on the gravelly mid and slower slopes. Eucalyptus normantonensis is found along the drainage lines.
The harsh environment experienced at Lark Quarry Conservation Park means that very few fauna species are noticeable during the daytime when most people visit the Park. The most conspicuous species of fauna are the wallaroos and echidnas that use the escarpment country as shelter during the extreme heat of the day. Knob-tailed geckos and netted dragons as well as over 90 bird species have also been recorded in the Conservation Park.
Off-site interpretation of the Lark Quarry story is available at the Lark Quarry diorama display in the Corfield and Fitzmaurice Building in Winton as well as at the Queensland Museum in Brisbane where a fibreglass cast of the Lark Quarry trackways makes an impressive display.
|Condition and Integrity|
Since the dinosaur
trackways were initially excavated in the late 1970s the site has undergone a
series of developments designed to protect the trackways from exposure and
visitor damage. New and Seymour Quarries have been reburied and are no longer
After the 1976-77 excavation of the Lark Quarry trackways was completed, the site was temporarily reburied under bales of hay and plastic sheeting in anticipation of a more permanent shelter being constructed in the future. By 1979 a flat roofed shelter had been built over the trackways and the hay and plastic was removed. Even at this early stage of their discovery and analysis it was evident that the trackways were being damaged through exposure to the extreme temperate conditions experienced on the site as well as local wildlife that was being attracted to the shelter by the shade it provided.
In 1982 an elevated walkway and interpretive signs were installed and 374 hectares of land surrounding the dinosaur trackways was declared an Environmental Park under Queensland state legislation. Shade cloth and fencing was added to the shelter to stop wildlife accessing the trackways. In the years that followed several restoration, cleaning and maintenance programs were carried out on the trackways to slow their deterioration. In 1983 significant conservation work on the trackways surface was undertaken to stabilize and buttress the exposed trackway area.
In 1994 the Lark Quarry Conservation Park was dedicated under the Queensland Nature Conservation Act 1992, and is managed under the provisions of this Act. The Queensland Parks and Wildlife Service share management responsibilities with the Winton Shire Council whilst the Queensland Museum provides ongoing scientific advice.
During 2001, a new building was constructed over the Lark Quarry trackways to provide better security and a more stable environment for them. After successful lobbying by the Winton Shire Council, the Queensland Heritage Trails Network provided much of the funding for the new building as a Centenary of Federation project.
The building was designed around ecologically sustainable design elements and ensures that further damage to the trackways is minimized by stabilizing temperature and humidity fluctuations, stopping water running over the trackways and by keeping people and wildlife off the trackways. The building uses the thermal mass properties of its rammed earth walls to keep environmental conditions within the building relatively stable. The trackways are also protected from dust and harsh light by being fully enclosed.
As part of the construction process, Dr Alex Cook from the Queensland Museum undertook a programme of preventative maintenance on the surface of the trackways. Following the completion of the building in June 2002, the collapse of a large, rammed earth wall necessitated further corrective and preventative maintenance work to the trackways. As a result, although the surface of the trackways is fragile, it is climatically and chemically stable.
Access to the trackways is restricted and visitors to the trackways must participate in a guided tour. These tours are run 3 times daily and are provided by an operator under license to the Winton Shire Council.
About 374ha, 95km south-west of Winton, comprising Lark
Quarry Conservation Park.|
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Report Produced Sat Apr 19 19:06:18 2014