Paleonews

Il blog dedicato ai Paleontologi !!!!

2008-08-03 Impronte di dinosauro in Canada

PEACE REGION PALAEONTOLOGY RESEARCH CENTRE SCIENTISTS DOCUMENT IMPORTANT DINOSAUR TRACK SITE
Elk Valley Coal District, Southeastern British Columbia

Wednesday September 03, 2008

 

Southeastern British Columbia is well known as a major region for coal production, something that is shared in common with the Peace Region in the northeastern part of the province. What is not as well known is that the Elk Valley Coal District is home to some of the most significant fossil footprint sites in western Canada. This may not come as a surprise to residents of the Peace Region where dinosaur tracks have been found in proximity to coal seams from as far back as the 1920’s, and right up to recent finds in the Trend Mine near Tumbler Ridge. Dinosaur tracks have been known locally in the southeast part of the province for more than two decades and are found as a bi-product of coal-mining.

The Elk Valley coal comes from a package of rocks known as the Mist Mountain Formation and is the oldest record of terrestrial (non-marine) rocks in western Canada. The Mist Mountain Formation rock layers straddle the Jurassic-Cretaceous boundary and were deposited approximately 135 million years ago along the coastal region of an inland sea that stretched from the Arctic Ocean almost to the Gulf of Mexico.

By comparison, much of the coal that is produced in the Tumbler Ridge area is approximately 100 million years old.

It should be noted that the record of dinosaur bones is quite incomplete in western Canada, with the majority of bones found in rocks between 75-65 million years old. Nearly all of these specimens come from Alberta. The first excavation of B.C. dinosaurs from near Tumbler Ridge took that record back substantially to 93-95 million years. By comparison fossil tracks provide a fairly complete record of terrestrial vertebrates (including dinosaurs) in western Canada between 135-55 million years ago (an 80 million year time span). The tracks then fill significant gaps left by an incomplete skeletal record.
In early August a substantial track site find in the Elk Valley Coal District was reported to the PRPRC simultaneously from the University of Alberta and the Royal Tyrrell Museum in Drumheller. The reports included several photographs showing evidence of several series of footprints from very, very large dinosaurs known as sauropods, also referred to informally as ‘brontosaurs’. Upon receiving word of the new track site and viewing the photographs PRPRC palaeontologist Rich McCrea and assistant Tyler Shaw immediately organized a two week research expedition. There was good reason for such a quick response. Until recently, Canada had not a single record sauropod dinosaurs either from footprints or bones. In fact the absence of sauropod dinosaurs in Canada was something of a mystery that palaeontologists were at a loss to explain. Sauropod bones and tracks are well known in the United States with discoveries as far north as Montana and Wyoming. Where then were the Canadian sauropods? One reason cited for their conspicuous absence included possible geographic barriers (mountains, inland seas, etc.) that prevented sauropods from entering regions that are now a part of Canada. Another explanation was that sauropods preferred habitats that simply did not exist in Canada at the time of their existence.

One of the strengths of science is that previously accepted and in-grained concepts and ideas may change, or evolve, in the face of the weight of new evidence. Such was the case with supposed absence of Canadian sauropods when, in the fall of 2005, Rich McCrea presented a paper at an international palaeontology symposium in Mesa, Arizona detailing the discovery of this major group of dinosaurs from … the Elk Valley Coal District of southeastern British Columbia! The evidence that Rich presented was based on isolated footprint blocks found in talus piles below open coal pits from research he had conducted in that area since 2000, well before his involvement with the Tumbler Ridge museum project. Canadian sauropods were now an accepted reality, but trackways of these animals on intact surfaces were lacking.

The significance of the recent track find from the Elk Valley Coal District is that it provided the first evidence of trackways (long series of prints from one or more individuals) of sauropods from Canada. Palaeontologists can get much more information from trackways than from single footprints, such as: a better idea of the size of the track-maker; how fast the track-maker was traveling; the habitats in which the track-maker lived; whether the track-maker was traveling alone or in a herd; what other animals were present; etc.

Upon the research team’s arrival at the coal mine the mine staff gave a safety orientation and then provided a buggy whip and radio for the palaeontologists’ use when driving on mine property. The generous access to the track site as well as the good will and assistance provided to the PRRPC research team by the mine cannot be understated.

The track site itself was exposed near a mountain top in an exploration area in the coal mine at close to 2300 metres elevation on a vertical face 48 metres long by 15 metres tall. The vertical nature of the track wall necessitated the use of several ropes and climbing gear to gain access to the track surface. Once on the wall it was evident to the research team there were at least three sauropod trackways and three trackways of large meat-eating dinosaurs (theropods), as well as one trackway from a small theropod.

The sauropod tracks were nearly one metre in length and were impressed quite deeply in the track surface. The researchers noted with alarm that the track surface was slowly crumbling to pieces and that the tracks likely would succumb to the forces of erosion within the next one or two years. It was imperative to have a permanent record of at least a portion of this track surface before it was destroyed.

An ambitious replication project was begun in which the palaeontologists used nearly 45 gallons ($5,000 value) of liquid latex to create a replica peel of the most prominent sauropod trackway. This latex peel measured almost 10 metres long by 3 metres wide and required many applications of latex layers to build it up. The application of a single layer of latex took nearly an entire day. When the latex peel was completed it was visible from more than 8.5km away! Once back at the PRPRC the latex peel would be used to create high-fidelity casts for permanent research and display in the PRPRC.

The palaeontologists explored other areas in the vicinity of the main track site while waiting for the latex layers to dry. They were lucky enough to notice a small three-toed footprint on another vertical surface that was located close to the ground. This new track surface was overlain by other thick rock layers, but after several hours of careful work the scientists were able to expose a short trackway of a small theropod (meat-eating dinosaur) with six footprints preserved. This trackway was on a fractured surface near an area of future mining activity.

The palaeontologists decided to attempt to recover the entire trackway for the PRPRC collections. The recovery of the original trackway slab was a painstaking process as the track layer was only a few centimeters thick, but over two metres long, heavy, and potentially unstable. To begin, palaeontologists covered the trackway with a full latex peel. There were two purposes for this. First, if anything went wrong with the removal there would at least be some record of the trackway in its pristine condition as the latex peel could be used to make an exact replica for research and display. Second, the latex peel could hold the track slab together preventing it from falling apart during the removal, and also cushion it for the bumpy 1300km ride to Tumbler Ridge. Once the latex peel was completed it was time to get down to the business of removing the track slab. After several precision cuts with a rocksaw the palaeontologists were able to custom fit a wooden frame over the track slab before undercutting it with chisels to break it away from the rock wall. The track slab was successfully popped off and was carefully flipped over to allow the wooden frame to be completed. The final specimen weighed between 200-250 kilograms.

The final day, August 24th, saw the removal of the large latex peel covering the sauropod trackway which would weigh another 200-250 kilograms. Fortunately the latex peel was able to be rolled up to fit in the truck box with the help of one of the coal mine staff. The palaeontologists took down their ropes and loaded up the rest of their equipment and began the long, careful drive back to Tumbler Ridge, arriving at 1am Tuesday morning after a very successful trip. The specimens were immediately unloaded into the new museum facility (formerly known as Claude Galibois Elementary School) and now are waiting there patiently for some much needed preparation and casting. More work is needed at this track site, including detailed mapping, measuring and photography of the track surface. Since the palaeontologists have been assured of the welcome of their presence in the mine a follow-up trip could be planned for this September, or early in the summer of 2009.

This research trip is one of many planned to various parts of the province to document British Columbia’s diverse palaeontological heritage and recover important palaeontological specimens for research and display. It is the ultimate goal of the Tumbler Ridge Museum Foundation and the Peace Region Palaeontology Research Centre (PRPRC) to become the central repository and display centre for British Columbia vertebrate fossils as well as an international centre of excellence for palaeontological research and education. The Dinosaur Discovery Gallery in Tumbler Ridge is the only museum in Canada that possesses a trackway of Canada’s largest dinosaurs (sauropods). The public will be able to view this unique specimen when the museum reopens at its new location in the early summer of 2009.

http://www.tumblerridgenews.com/story.php?id=202580

settembre 20, 2008 - Posted by | - R. Dinosauri, 1 Cretaceo, America Northern, P - Impronte, P - Ritrovamenti fossili, Paleontology / Paleontologia | , , , , , ,

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