|
|
|
|
 |
|
|
The Latton quarry mammoths
 The Latton quarry mammoths
Mammoths
Resources
Messing about in the topsoil
The Latton quarry mammoths were an unusual subject for the Big Monster Dig team. Most palaeontologists concentrate on rocks that are millions of year old, so working in gravels that are a mere 10-100,000 years old is known affectionately as 'gardening' – messing about in the topsoil!
A huge quantity of mammoth bones had been found in a gravel pit, which had to be abandoned as it flooded. The team wanted to see if we could make a similar find in the neighbouring quarry, and – more interestingly – work out why the remains of so many of these beasts had ended up in the same place. The initial idea was that this site may have been a mammoth graveyard, similar to those of modern elephants. Alternatively, the mammoths may have been killed by a catastrophic event such as a herd wandering into a swamp or being caught in a flood. It was also possible that the bones had washed down a river and accumulated over time on a gravel bar at a bend in the river's course.
Melting glaciers
The gravels being quarried here were laid down by large braided rivers of the kind that form on plains in front of melting glaciers. These rivers usually carry coarse, gravely sediment and have a multitude of criss-crossing channels with very fast-flowing streams during spring and summer periods of glacial melting and low flow during the colder winter months. This gravel was deposited in the Thames valley as the glaciers that covered the UK retreated at the end of the last ice age around 8-10,000 years ago.
The gravel was laid on top of Jurassic Clays that were deposited on a seabed 140 million years before. The rock record of the intervening time period (140 million up to 10,000 years ago) was missing. These gaps, known as 'record unconformities', are common in geology. Unconformities form when sediment stops being deposited or is removed by later weathering and erosion. While the rocks can tell us a great deal about what a site was like in the past, when there is no rock record it is only possible to speculate. The unconformity in Gloucester probably represents erosion following the uplift of southern England caused by massive plate movements related to the opening up of the Atlantic ocean.
Steppe mammoths
The team's first task was to find some bones. For this they tried to track the ancient course of the river in which the bones had been found. It soon became apparent that most of the bones on this site were not from within the gravel but at the base of it. They had been laid on the surface between the gravel and the underlying Jurassic Clay; this meant that they could be much older than 8,000 years. This was confirmed when Dave Martill looked at the bones and identified them as Mammuthus trogontherii. These were steppe mammoths that lived in relatively warm conditions and were older than the classic woolly mammoth that we always see in ice age reconstructions.
A tree on Sarah's car
The hunt for bones turned up a few bits and pieces, but not the masses that had been hoped for. Conditions were less than ideal, with the worst gales of the century howling across the country, sending the portable toilet flying and bringing a tree down on Sarah Gabbott's car. Despite the conditions, the diggers were eager and keen and turned up some interesting material, including a couple of hand axes and other flint tools. Things were starting to look interesting – did early man play a part in the demise of our giant furry pachyderms?
The absence of large bones meant relying on Sarah to solve the mystery with her expertise in small fossils. She and her team found a collection of fresh water snail shells, which confirmed that the climate in which the mammoths had lived was fairly temperate, so they were a little older than the main gravels.
Flint tools
Meanwhile, Dave Martill enlisted the help of a man called Will. Will is one of Britain's top flint knappers and was able to teach Dave how to replicate the tools that were being found. He was also able to tell the team that our Stone Age ancestors probably weren't hunting the mammoths, but they would not have missed out on the chance of a free meal from any animals that wandered inadvertently into a swamp.
The team concluded that the mammoths had lived on warm, temperate grasslands before the last ice age. They met their end in swamps and may have been transported short distances in some of the glacial rivers. The flint tools would have been used by people who took full advantage of the freely available meals. The climax of the last ice age forced man and beasts alike south, and the subsequent melting of the glaciers covered the whole of southern England in about 10 metres of gravel, burying the mammoths and the Stone Age butchers' tools.
^ Top
|
|
|
