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Smilodon family tree

Mike Thorn (UK) In his book, “Architects of Eternity: The New Science of Fossils”, Richard Corfield coins the term “reluctant palaeontologists”. He has in mind those chemists, biochemists and biologists who use the techniques and skills from their own disciplines to shed new light on our ideas about evolution. Ross Barnett, of the Department of Zoology at Oxford, might well be considered to be in this category. A biochemist by training, he has recently co-authored a paper on the DNA of three extinct cats which has helped to lay to rest some of the arguments about the feline family tree. Fig. 1. Smilodon skeleton. Ross came to Oxford in October 2002, to work on a PhD, after completing his biochemistry degree at Edinburgh. His supervisor, Professor Alan Cooper, was interested in cat genetics and had managed to raise funds to carry out research into the relationships of several extinct cats. In particular, there were questions about where the sabre-toothed cats, such as Smilodon and Homotherium, fitted in. Fig. 2. Ross Barnett in his office. As Ross explained: “There has been a lot of study done on these animals. For example, there is a huge collection of thousands of individuals of Smilodon from Rancho Le Brea in Los Angeles, so they’ve been really well characterised from their morphology. “What the palaeontologists had concluded from this was that there was a split at the base of the cat family tree between the group that goes on to form the sabre- tooths – … Read More

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Alluvial gold: A geological model (Part 2)

Philip Dunkerly (UK) In A geological model for the alluvial gold environment (Part 1), the first part of this article, I discussed how alluvial gold is found and suggested a geological model for alluvial gold deposits. (Readers are recommended to have another look at that part to remind them of the model.) In this second part, I now turn to the nature of the gold itself. Fig. 1. Gold bullion bars of 400 troy oz. Fig. 2. Sites from around the world. Gulch gold Gulch gold is the coarsest that exists in any part of a river system. If nuggets (pieces of gold weighing more than 0.1g) are present, they will mostly be found in gulches (narrow ravines), provided suitable traps are present, such as irregular bedrock. In gulch alluvium, the vast majority of the gold will be found on, or in crevices within, the bedrock. Gulch gold is often coarse and angular and may contain silicate debris, especially quartz. As examples, gold from Victoria Gulch on the Klondike was described as “sharply angular”. In the Ballarat gullies, some enormous nuggets were found and Canadian Gully yielded nuggets of 50.4, 34.7 and 31.4kg. At Bendigo, White Horse Gully, a 17.8kg nugget (including some quartz) was found. (Interestingly, of a list of 92 Victorian nuggets, 34 came from localities specifically named “gullies”.) Finally, in the Sierra Nevada of California, most of the gold is from gulches or minor streams close to croppings. Fig. 3. Old hydraulicking operation of terrace gravels, note … Read More

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Alluvial gold: A geological model (Part 1)

Philip Dunkerly (UK) Mankind almost certainly first found gold when a yellow, glint from the bottom of a stream bed attracted the attention of one of our ancestors in pre- historic Africa. Ever since, the allure of gold – its colour, improbable density, malleability and scarceness – meant it has been prized, and great efforts have been made to accumulate it. Most ancient peoples venerated and coveted gold and used it for decoration, and empires used gold as a store of value and a medium of exchange. The Egyptians are known to have used gold as early as about 5000 BC, followed by many others, including the Romans, the Incas, the Spaniards and, of course, the Anglo-Saxon invaders of North America, Africa, Australia and New Zealand. Fig. 1. Spectacular Roman paleogravel workings at Las Medulas, NW Spain, now a World Heritage site. The mouth of one of the tunnels through which water was released from a header tank is visible in the shadow. Fig. 2. Panoramic view of Las Medulas, worked by sluicing using water brought through canals up to 60km long. Though gold was won from hard-rock deposits in ancient times, most gold until perhaps 1900 was won from riverbeds, and was traditionally called alluvial or placer gold. Prospecting for alluvial gold required relatively little equipment and always attracted hardy pioneers willing to forego the comforts of society in the hope of ‘getting rich quick’. The gold they found – if they were lucky – could almost instantly be … Read More

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From the wet clays of Peterborough to the sunny Caatinga of Brazil

David M Martill (UK) After several gruelling years of working in the sticky wet Jurassic clay pits of the Peterborough district for their gigantic marine reptiles and even more massive fishes, it was a refreshing change to fly south and investigate the sun-baked Caatinga of South America. The Chapada do Araripe, on the borders of the Brazilian states of Ceará, Pernambuco and Piaui, had always fascinated me (Fig. 1). Fig. 1a (left). A map showing the location of the Chapada do Araripe in the northeast of Brazil. Fig. 1b (above). Detail of the Chapada do Araripe. This is one of the most important sites in the world for Cretaceous Gondwanan fossil fauna and flora. I had seen specimens of the fabulous fossil fishes (I hope you like the alliteration) in limestone concretions (Fig. 2) that kept turning up in European fossil shops, but what had really caught my eye was a short letter to the scientific journal Nature that described fossil ostracods from those very same concretion horizons. Fig. 2. A typical concretion from the Santana Formation, with a not so typical fish. This is one of the rare fossil rays. I am not an aficionado of ostracods: who is? They mostly look like small baked beans, and it is so tedious trying to mount them on stubs so that you can see them under the electron microscope. No, it was the remarkable quality of their preservation that caught my eye. The specimens in question were described by Ray Bate, … Read More

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Geology of the Falkland Islands

Phil Stone (UK) Plate tectonics have produced some surprising juxtapositions, as the earth’s continental fragments have drifted and jostled over the eons. Microplates seem to have enjoyed most freedom of movement and none more so than that supporting the Falkland Islands. Though this archipelago is situated in the south-west corner of the South Atlantic Ocean, about 650km east from Tierra del Fuego and the Strait of Magellan, its geology tells of an African heritage. Charles Darwin provided the first evidence for that – although he didn’t appreciate it at the time. Fig. 1. A reconstruction of the Gondwana supercontinent at about 300mya. (© BGS/NERC.) HMS Beagle visited the Falkland Islands twice, in 1833 and 1834, and during the first visit Darwin discovered fossil shells, mostly brachiopods. His first impression had been unfavourable, but, after that discovery, he noted in his diary: “The whole aspect of the Falkland Islands were however changed to my eyes … for I found a rock abounding with shells; and these of the most interesting age.” Darwin published his account of Falklands’ geology in 1846. The “interesting age” proved to be Devonian and, as more data were acquired, a close and surprising similarity was established with the fauna of equivalent age in South Africa. This similarity was soon extended to other aspects of the Falklands rock succession, while the geology of neighbouring Patagonia proved to be quite different. These relationships were not readily explicable without recourse to continental drift, so were largely ignored for many years, … Read More

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Meat-eating dinosaur from Argentina with a bird-like breathing system

Steve Koppes (USA) Mendoza, Argentina. The remains of a new ten-meter-long predatory dinosaur discovered along the banks of Argentina’s Rio Colorado are helping to unravel how birds evolved their unusual breathing system. In September 2008, palaeontologists, led by the University of Chicago’s Paul Sereno, a National Geographic Explorer-in-Residence, have published an article about their discovery in the online journal Public Library of Science ONE. Joining Sereno to announce the discovery at a news conference in Mendoza, Argentina, held on 29 September 2008, were Ricardo Martinez and Oscar Alcober, both of the Universidad Nacional de San Juan, Argentina. The discovery of this dinosaur builds on decades of paleontological research indicating that birds evolved from dinosaurs. Fig. 1. Flesh rendering of the predator Aerosteon with the body wall removed to show a reconstruction of the lungs (red) and air sacs (other colours) as they might have been in life. (Drawing: Todd Marshall c 2008, courtesy of Project Exploration) “Among land animals, birds have a unique way of breathing. The lungs actually don’t expand,” Sereno said. Instead, birds have developed a system of bellows, or air sacs, which help pump air through the lungs. This is the reason birds can fly higher and faster than bats, which, like all mammals, expand their lungs in a less efficient breathing process. Discovered by Sereno and his colleagues in 1996, the new dinosaur is named Aerosteon riocoloradensis (meaning “air bones from the Rio Colorado”). Sereno explained that “Aerosteon, found in rocks dating to the Cretaceous period … Read More

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Mining in Brazil’s ‘Garden of Gold’

Graham Roberts (UK) There is an old maxim in the mining industry that says, “Mines are where you find them”. To put it another way, you cannot change the location of geological deposits. This is frequently unfortunate for all involved and, almost inevitably, takes exploration and mining companies to wherever the best economic mineral deposits can be found, whatever the challenge. Such a quest has recently taken London-listed Serabi Mining plc (Serabi Mining) to the Tapajos region of northern Brazil. The Tapajos was the location of a major artisanal mining gold rush from the early 1970s to the late 1990s. During this time, it has been estimated that up to 30 million ounces of gold may have been extracted, making it one of the largest gold regions in the world. However, despite these figures, this exciting area has been poorly explored to date. Fig. 1. Garimpeiros working gold-rich, weathered bedrock with monitor hoses. The Tapajos region is situated in the Central Amazonian Province, within the Amazon Craton, and is mainly of Proterozoic age. The gold deposits have various geological settings but, amongst these, a dominant NW-SE fracture zone some 100s of kilometres long and about 50km wide is particularly important. Serabi Mining has secured an extensive land position and identified a number of targets along 70km of this zone, in addition to other Tapajos projects. Geological potential also exists for very large, low-grade gold and copper deposits of the porphyry and IOCG (Iron Oxide Copper Gold) types. Fig. 2. Location … Read More

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New predator ‘Dawn runner’ discovered in early dinosaur graveyard

Steve Koppes (USA) A lanky predator roamed South America in search of prey as the age of the dinosaurs began, approximately 230Ma. This dinosaur, named Eodromaeus (the “dawn runner”), sported a long neck and tail, and weighed only 4.5kg to 6.8kg. A team of palaeontologists and geologists from Argentina and the USA announced the discovery of dawn runner in January 2011. Fig. 1. Reconstruction of Eodromaeus, by Todd Marshall. “It really is the earliest look we have at the long line of meat eaters that would ultimately culminate in Tyrannosaurus rex near the end of the dinosaur era,” said Paul Sereno, University of Chicago palaeontologist and National Geographic Explorer-in-Residence. “Who could foretell what evolution had in store for the descendants of this pint-sized, fleet-footed predator?” Sereno and his colleagues described a near-complete skeleton of the new species, based on the rare discovery of two individuals found side-by-side, in the 14 January 2011 issue of the journal Science. The paper presents a new snapshot of the dawn of the dinosaur era – a key period that has garnered less attention than the dinosaurs’ demise. “It’s more complex than some had supposed,” Sereno said. Fig. 2. Dr Paul Sereno. (Photo by Mike Hettwer.) Set in picturesque foothills of the Andes, the site of the discovery is known as the “Valley of the Moon,” said the report’s lead author, Ricardo Martinez of Argentina’s National University of San Juan. For dinosaur palaeontologists, it is like no other. “Two generations of field work have generated … Read More

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Book review: Early Miocene Paleobiology in Patagonia: High-Latitude Paleocommunities of the Santa Cruz Formation, by Sergio F Vizcaino, Richard F Kay and M Susan Bargo

Patagonia has not always been the cold, arid and dry place it is today. About 17mya – because the Andes were much lower allowing humid winds from the west to reach the area – it consisted of substantial forests and grasslands. It was also inhabited by strange and wonderful animals, many of which are now extinct, such as glyptodonts, huge snakes and the giant, tapir-like astrapotheres.