First Horned Dinosaur from Mexico

First Horned Dinosaur from Mexico: Plant-Eater Had Largest Horns of Any Dinosaur

A new species of horned dinosaur unearthed in Mexico has larger horns that any other species -- up to 4 feet long -- and has given scientists fresh insights into the ancient history of western North America, according to a research team led by paleontologists from the Utah Museum of Natural History at the University of Utah.

"We know very little about the dinosaurs of Mexico, and this find increases immeasurably our knowledge of the dinosaurs living in Mexico during the Late Cretaceous," said Mark Loewen, a paleontologist with the Utah Museum of Natural History and lead author of the study.

The 72-million-year-old rhino-sized creature -- Coahuilaceratops magnacuerna -- was a four- to five-ton plant-eater belonging to a group called horned dinosaurs, or ceratopsids. The name Coahuilaceratops magnacuerna (Koh-WHE-lah-SARA-tops mag-NAH-KWER-na), refers to the Mexican state of Coahuila where it was found, and to the Greek word "ceratops" meaning "horned face." The second part of the name, magnacuerna, is a combination of Latin and Spanish meaning "great horn," in reference to the huge horns above the eyes of this dinosaur.

The study, partially funded by the National Geographic Society, was conducted by Mark Loewen, Scott Sampson, Eric Lund and Mike Getty, paleontologists at the Utah Museum of Natural History. Also involved were Andrew Farke of the Raymond M. Alf Museum in Claremont, Calif.; Martha Aguillón-Martínez, Claudio de Leon and Rubén Rodríguez-de la Rosa from the Museum of the Desert in Saltillo, Mexico; and David Eberth of the Royal Tyrrell Museum of Palaeontology in Alberta, Canada.

The new species is to be announced in the book "New Perspectives on Horned Dinosaurs" to be released next week by Indiana University Press.


A Different World


For most of the Late Cretaceous Period, from 97 million to 65 million years ago, high global sea levels resulted in flooding of the central, low-lying portion of North America. As a result, a warm, shallow sea extended from the Gulf of Mexico to the Arctic Ocean, splitting the continent into eastern and western landmasses.

`Dinosaurs living on the narrow, peninsula-like western landmass -- known as Laramidia -- occupied only a narrow belt of plains that were sandwiched between the seaway to the east and rising mountains to the west. Central America had not formed at the time, which made Mexico the southern tip of this island continent.

In many ways, the Late Cretaceous is the best-understood time during the Age of Dinosaurs, thanks in large part to more than 120 years of dinosaur hunting in Canada, Montana, New Mexico and the Dakotas. Recent work has revealed new dinosaurs living at the same time in Utah, New Mexico and Texas, yet the dinosaurs from Mexico have remained virtually unknown.

"As the southernmost dinosaurs on Laramidia, we are confident that Mexican dinosaurs will be a critical element in unraveling the ancient mystery of this island continent," Sampson said.

Loewen described the arid, desert terrain where the dinosaur was recovered as nothing like Mexico during the Late Cretaceous. About 72 million years ago, the region was a humid estuary with lush vegetation, an area where salt water from the ocean mixed with fresh water from rivers, much like the modern Gulf Coast of the southeastern United States. Many dinosaur bones in the area are covered with fossilized snails and marine clams, indicating that the dinosaurs inhabited environments adjacent to the seashore.

The rocks in which Coahuilaceratops was found also contain large fossil deposits of jumbled duck-bill dinosaur skeletons. These sites appear to represent mass death events, perhaps associated with storms such as hurricanes that occur in the region today.

"Sitting near the southern tip of Laramidia, this region may have been hammered by monstrous storms," Sampson said. "If so, such periodic cataclysms likely devastated miles of coastline, killing off large numbers of dinosaurs."


Recovering a Giant Horned Head

Until recent years, there have been few large-scale paleontological projects in Mexico focused on the Mesozoic Era, from 253 million to 65 million years ago, also known as the Age of Dinosaurs. Indeed Coahuilaceratops is among the first dinosaurs from Mexico to be named.

Sampson spearheaded the paleontological expeditions to Coahuila in 2002 and 2003, securing funds from the University of Utah and National Geographic Society.

Coahuilaceratops comes from a rock unit known as the Cerro del Pueblo Formation, which dates to between 71.5 million and 72.5 million years ago. The skeletons, which de Leon discovered in 2001 near the town of Porvenir de Jalpa, approximately 40 miles west of Saltillo, were excavated in 2003. The fossils then were prepared at the Utah Museum of Natural History, requiring two years of meticulous work by skilled volunteer preparator Jerry Golden.

Based on the bone development of the skull and skeleton, the scientists believe that this animal was an adult at the time of death. Remains of a juvenile animal of the same species were also found at the site.

Coahuilaceratops was about 22 feet long as an adult, 6 feet to 7 feet tall at the shoulder and hips, with a 6-foot-long skull, and likely weighed about four to five tons.

"Being one of the largest herbivores in its ecosystem, adult Coahuilaceratops probably didn't have to worry about large tyrannosaur predators," Farke said.

By far the most obvious characteristic of Coahuilaceratops is its massive pair of horns, one above each eye. While the researchers lack a complete horn, they estimate from fossils they excavated that the horns were 3 feet to 4 feet long, Loewen said.

Although such horns are common features of ceratopsid dinosaurs, those of Coahuilaceratops appear to be the largest known for the group, exceeding the size of eye horns even in Triceratops. Scientists are uncertain of the massive eye horns' purpose, but the most widely accepted idea is that they were related to reproductive success, functioning to attract mates and fight with rivals of the same species.

Loewen explained that Coahuilaceratops represents the first occurrence of an identifiable species of horned dinosaur in southern Mexico. "The horned dinosaurs are an extraordinary example of vertebrate evolution," he said. They evolved and diversified on Laramidia along a thin strip of land that stretched from Alaska to Mexico. "Finding this horned dinosaur so far south in Mexico offers us a different picture of what the ancestors of Triceratops were like."


An Ancient Ecosystem Revealed


In addition to Coahuilaceratops, the research team found remains of two other horned dinosaurs, which are less well understood. "We need more material to figure out what these other horned dinosaurs looked like," Getty said.

The latest expedition also recovered remains of two duck-bill dinosaurs, as well as the remains of carnivores, including large tyrannosaurs (smaller, older relatives of T. rex) and more diminutive Velociraptor-like predators armed with sickle-claws on their feet.

Together with an abundance of fossilized bones, researchers discovered the largest assemblage of dinosaur trackways known from Mexico, an extensive area crisscrossed with the tracks of different kinds of dinosaurs. In all, the emerging picture shows a diverse group of dinosaurian herbivores and carnivores, perhaps representing a previously unknown assemblage of species.

"Rather than focusing only on individual varieties of dinosaurs, we are attempting to reveal what life was like in Mexico 72 million years ago, and understand how the unique ecosystem of Mexico relates to ecosystems to the north at the time," said Loewen.

Few North American dinosaurs from this time period are known outside of the Drumheller region of Alberta. Eberth explained that researchers now have two points of comparison to examine not only different dinosaurs, but also different environments and ecologies.

As might be suspected, paleontologists are excited about the future paleontological potential of this area. "There are definitely more dinosaurs to be discovered in the region," Lund said.

"Dinosaurs from this particular period are important because this is a time that is relatively poorly understood," said Don Brinkman, a researcher at the Royal Tyrrell Museum. He is studying non-dinosaur vertebrates found at the site, including turtles, fish, and lizards. "The locality in Mexico goes a long way to filling in a gap in our knowledge of the record of changes in dinosaur assemblages throughout the Late Cretaceous."


Fact Sheet: Major Points of the Paper -- Coahuilaceratops magnacuerna
Coahuilaceratops is the first horned dinosaur (ceratopsid) and only the fourth dinosaur species from Mexico to be named and described in scientific literature.
Coahuilaceratops represents the southernmost occurrence of a ceratopsid dinosaur.


Relationships

Coahuilaceratops is a chasmosaurine ceratopsid, often called a "ceratopsian" or "horned" dinosaur, and was almost certainly an herbivore.
Coahuilaceratops is closely related to the famous ceratopsid dinosaurs that appeared in Western North America, such as Chasmosaurus, Pentaceratops and Triceratops.


Anatomy
Coahuilaceratops had the largest horns above its eyes of any known ceratopsid dinosaur.
Coahuilaceratops had a very thick nasal bone with a relatively small rounded nose horn that is unlike that of any other ceratopsid dinosaur.
Coahuilaceratops stood on all four legs and was not bipedal.


Age and Geology

Coahuilaceratops is from the Late Cretaceous Period's Campanian Age, which spanned from approximately 84 million to 70 million years ago.
Coahuilaceratops was excavated from the Cerro del Pueblo Formation, the basal formation of the Difunta Group in the Parras Basin within the state of Coahuila, Mexico. These rocks are dated to about 72 million years ago.


The Fossils
Coahuilaceratops specimens are permanently housed in the collections of the Museum of the Desert in Saltillo, Mexico. Casts of the fossils are reposited in the collections of the Utah Museum of Natural History in Salt Lake City.
The skull of Coahuilaceratops will be unveiled at the Museum of the Desert later this year.

Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Utah, via EurekAlert!, a service of AAAS.

Real-Time Quake Detection

Seismologists Use Ultrasounds to Assess Quakes Faster

Using ultrasound imaging, seismologists can now determine the epicenter and magnitude of an earthquake quake within 10 to 20 minutes, precisely imaging which fault ruptured and where the rupture went. The method could help save lives through early earthquake and tsunami warnings. By the end of this year, the U.S.G.S. will be using the method to analyze earthquakes anywhere in the world.

SAN DIEGO--The first few hours following a major earthquake are critical for seismologists, rescuers and people living in the quake zone. Now, researchers can estimate where a quake made its biggest impact within 30 minutes after a big earthquake.

It was a deadly quake that shook the world. Hundreds of thousands of people died. Kris Walker, a seismologist at Scripps Institution of Oceanography at the University of California, San Diego, says, "It actually took days before the true size of that earthquake was determined."

If, in the first minutes, seismologists had known how large the quake was and exactly where it occurred, they'd have recognized a powerful and widespread tsunami would soon follow. "If our technique was used and had there been adequate communication infrastructure in that area, we would have been able to save a lot of lives," Walker says.

Walker and fellow seismologist Peter Shearer have devised a method to rapidly determine how much surface shaking is generated from the epicenter of a large quake. "What we're able to learn within 10 to 20 minutes of when the earthquake started is about which fault ruptured and where the rupture went," Shearer says.

Earthquakes produce seismic waves. The first waves detected by seismic stations are called p-waves. Once the quake is detected, earth scientists can back track to find where the quake started. Shearer says, "You get a prediction like this, in gray, of the area that experienced the greatest surface shaking."

This new, faster method of sizing up earthquakes can buy important time for people in the first hour following a major earthquake.

By the end of this year, the U.S. Geological Survey in Colorado will be using the back-projection method to analyze earthquakes anywhere in the world. It could become part of a worldwide warning system.

BACKGROUND: Scientists at Scripps Institute of Oceanography have devised a method to use ultrasound images to provide key information about earthquake ruptures in near or real time following a large earthquake.

HOW IT WORKS: The new method uses ultrasound imaging, a medical technique that uses high frequency sound waves and their echoes. It's similar to how bats, whales and dolphins pinpoint locations, and to the basis for the SONAR technology used by submarines. Ultrasound waves not only let doctors see inside the body, they can provide information about the inside of an earthquake. The machine sends out high-frequency sound pulses, which bounce off objects and reflect back to a detector, which sends that data to the machine's computer. The computer can calculate the distance between the machine and the objects by knowing the speed of sound through the earth and the time it takes for the echo to return. By measuring how the frequency of the echoes changes, scientists can also determine how fast that object is moving.

WHAT CAUSES QUAKES: An earthquake is a vibration that travels through the earth's crust. It can be caused by any number of things, including meteor impacts, underground explosions (from a nuclear test, for example) or collapsing structures, such as a mine. But most naturally-occurring earthquakes are caused by the movement of the earth's tectonic plates. The earth's surface is made up of large plates that slide over the underlying layer. At the plate boundaries, plates can move apart, push together, or slide against each other.

WHOSE FAULT IS IT ANYWAY: Wherever plates meet, there will be faults at the boundaries: breaks in the earth's crust where the blocks of rock on each side are moving in different directions. There are many different kinds of faults, but in all of them, the various blocks of rock push together tightly and produce a lot of friction. If there is a large enough amount of friction the plates can become locked, increasing the pressure until the plates suddenly give way and snap forward suddenly, sending out a series of seismic waves. These fault lines are the main source of earthquakes.

The American Geophysical Union, the Incorporated Research Institutions for Seismology and the United States Geological Survey contributed to the information contained in the TV portion of this report.

Scientists Detect Huge Carbon 'Burp' That Helped End Last Ice Age

Scientists have found the possible source of a huge carbon dioxide 'burp' that happened some 18,000 years ago and which helped to end the last ice age.

The results provide the first concrete evidence that carbon dioxide (CO2) was more efficiently locked away in the deep ocean during the last ice age, turning the deep sea into a more 'stagnant' carbon repository -- something scientists have long suspected but lacked data to support.

Working on a marine sediment core recovered from the Southern Ocean floor between Antarctica and South Africa, the international team led by Dr Luke Skinner of the University of Cambridge radiocarbon dated shells left behind by tiny marine creatures called foraminifera (forams for short).

By measuring how much carbon-14 (14C) was in the bottom-dwelling forams' shells, and comparing this with the amount of 14C in the atmosphere at the time, they were able to work out how long the CO2 had been locked in the ocean.

By linking their marine core to the Antarctic ice-cores using the temperature signal recorded in both archives, the team were also able compare their results directly with the ice-core record of past atmospheric CO2 variability.

According to Dr Skinner: "Our results show that during the last ice age, around 20,000 years ago, carbon dioxide dissolved in the deep water circulating around Antarctica was locked away for much longer than today. If enough of the deep ocean behaved in the same way, this could help to explain how ocean mixing processes lock up more carbon dioxide during glacial periods."

Throughout the past two million years (the Quaternary), the Earth has alternated between ice ages and warmer interglacials. These changes are mainly driven by alterations in the Earth's orbit around the sun (the Milankovic theory).

But changes in Earth's orbit could only have acted as the 'pace-maker of the ice ages' with help from large, positive feedbacks that turned this solar 'nudge' into a significant global energy imbalance.

Changes in atmospheric CO2 were one of the most important of these positive feedbacks, but what drove these changes in CO2 has remained uncertain.

Because the ocean is a large, dynamic reservoir of carbon, it has long been suspected that changes in ocean circulation must have played a major role in motivating these large changes in CO2. In addition, the Southern Ocean around Antarctica is expected to have been an important centre of action, because this is where deep water can be lifted up to the sea surface and 'exhale' its CO2 to the atmosphere.

Scientists think more CO2 was locked up in the deep ocean during ice ages, and that pulses or 'burps' of CO2 from the deep Southern Ocean helped trigger a global thaw every 100,000 years or so. The size of these pulses was roughly equivalent to the change in CO2 experienced since the start of the industrial revolution.

If this theory is correct, we would expect to see large transfers of carbon from the ocean to the atmosphere at the end of each ice age. This should be most obvious in the relative concentrations of radiocarbon (14C) in the ocean and atmosphere; 14C decays over time and so the longer carbon is locked up in the deep sea, the less 14C it contains.

As well as providing evidence for rapid release of carbon dioxide during deglaciation, the research illustrates how the ocean circulation can change significantly over a relatively short space of time.

"Our findings underline the fact that the ocean is a large and dynamic carbon pool. This has implications for proposals to pump carbon dioxide into the deep sea as a way of tackling climate change, for example. Such carbon dioxide would eventually come back up to the surface, and the question of how long it would take would depend on the state of the ocean circulation, as illustrated by the last deglaciation," says Dr Skinner.

The results are published in Science.

The research was funded by the Royal Society and the Natural Environment Research Council.
Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Cambridge.

Journal Reference:
Skinner, L.C., Fallon, S. Waelbroeck, C., Michel, E. and Barker S. Ventilation of the deep Southern Ocean and deglacial CO2 rise. Science, 2010; 328 (5982): 1147-1151 DOI: 10.1126/science.1183627

Marine algae and whale diversity

Link Between Marine Algae and Whale Diversity Over Last 30 Million Years, Study Finds

A new paper by researchers at George Mason University and the University of Otago in New Zealand shows a strong link between the diversity of organisms at the bottom of the food chain and the diversity of mammals at the top.

Mark D. Uhen, a geologist at Mason, says that throughout the last 30 million years, changes in the diversity of whale species living at any given time period correlates with the evolution and diversification of diatoms, tiny, abundant algae that live in the ocean. In the paper, published in the latest issue of Science, Uhen and co-author Felix G. Mark of Otago show that the more kinds of diatoms living in a time period, the more kinds of whales there are.

Looking at thousands of published accounts of whale fossil records, the researchers assembled the records in a database to analyze and pinpoint the various fossils. The fossil records show a direct link between the productivity of the ocean and the variety of whale fossils. Uhen says they also found a correlation between global changes and fossil variety.

"This study shows that if we look at the bottom of the food chain, it might tell you something about the top," says Uhen. "Diatoms are key primary producers in the modern ocean, and thus help to form the base of the marine food chain. The fossil record clearly shows that diatoms and whales rose and fell in diversity together during the last 30 million years."

Uhen says this is the first time that such a correlation has been shown. Though scientists in the past have tried to answer the question of how the modern diversity of whale and dolphins arise, this question has been difficult to answer. The fossil record might not truly reflect evolutionary history, says Uhen. "Is it possible that the diversity of fossils we find through geological time might really just reflect the amount of preserved sedimentary rock paleontologists can search -- the more rock there is, the more fossils we find? This comprehensive study has shown that the diversity of these fossils is in fact not driven by the sedimentary rock record."

The researchers hope these findings will encourage other specialists to look at other animals with a similar narrow ecology to see if this link translates.

Uhen is a term assistant professor in Mason's Department of Atmospheric, Oceanic and Earth Sciences and is an expert in marine mammal fossils. In the future, he hopes to conduct research on how the body size of whales changes over time, and how whales became the largest living organisms in the world.

Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by George Mason University.

Journal Reference:
Felix G. Marx, Mark D. Uhen. Climate, Critters, and Cetaceans: Cenozoic Drivers of the Evolution of Modern Whales. Science, 2010; 327 (5968): 993 DOI: 10.1126/science.1185581

How Whales Have Changed Over 35 Million Years

Whales are remarkably diverse, with 84 living species of dramatically different sizes and more than 400 other species that have gone extinct, including some that lived partly on land. Why are there so many whale species, with so much diversity in body size?

To answer that, UCLA evolutionary biologists and a colleague used molecular and computational techniques to look back 35 million years, when the ancestor of all living whales appeared, to analyze the evolutionary tempo of modern whale species and probe how fast whales changed their shape and body size. They have provided the first test of an old idea about why whales show such rich diversity.

"Whales represent the most spectacularly successful invasion of oceans by a mammalian lineage," said Michael Alfaro, UCLA assistant professor of ecology and evolutionary biology, and senior author of the new study, which was published this month in the early online edition of Proceedings of the Royal Society B and will appear at a later date in the journal's print edition. "They are often at the top of the food chain and are major players in whatever ecosystem they are in. They are the biggest animals that have ever lived. Cetaceans (which include whales, as well as dolphins and porpoises) are the mammals that can go to the deepest depths in the oceans.

"Biologists have debated whether some key evolutionary feature early in their history allowed whales to rapidly expand in number and form," Alfaro said. "Sonar, large brains, baleen (a structure found in the largest species for filtering small animals from sea water) and complex sociality have all been suggested as triggers for a diversification, or radiation, of this group that has been assumed to be rapid. However, the tempo -- the actual rate of the unfolding of the cetacean radiation -- has never been critically examined before. Our study is the first to test the idea that evolution in early whales was explosively fast."

One explanation for whale diversity is simply that they have been accumulating species and evolving differences in shape as a function of time. The more time that goes by, the more cetacean species one would expect, and the more variation in body size one would expect to see in them.

"Instead, what we found is that very early in their history, whales went their separate ways from the standpoint of size, and probably ecology," Alfaro said. "This pattern provides some support for the explosive radiation hypothesis. It is consistent with the idea that some key traits opened up new ways of being 'whale-like' to the earliest ancestors of modern cetaceans, and that these ancestors evolved to fill them. Once these forms became established, they remained."

Species diversification and variations in body size were established early in the evolution of whales, Alfaro and his colleagues report.

Large whales, small whales and medium-sized whales all appeared early in the history of whales, with the large whales eating mostly plankton, small whales eating fish and medium-sized whales eating squid.

"Those differences were probably in place by 25 million years ago at the latest, and for many millions of years, they have not changed very much," said the study's lead author, Graham Slater, a National Science Foundation-funded UCLA postdoctoral scholar in Alfaro's laboratory. "It's as if whales split things up at the beginning and went their separate ways. The distribution of whale body size and diet still corresponds to these early splits."

"The shape of variation that we see in modern whales today is the result of partitioning of body sizes early on in their history," Alfaro said. "Whatever conditions allowed modern whales to persist allowed them to evolve into unique, disparate modes of life, and those niches largely have been maintained throughout most of their history.

"We could have found that the main whale lineages over time each experimented with being large, small and medium-sized and that all the dietary forms appeared throughout their evolution, or that whales started out medium-sized and the largest and smallest ones appeared more recently -- but the data show none of that. Instead, we find that the differences today were apparent very early on."

Killer whales are an exception, having become larger over the last 10 million years, Alfaro and Slater said. Killer whales are unusual in that they eat mammals, including other whales.

"If we look at rates of body-size evolution throughout the whale family tree, the rate of body-size evolution in the killer whale is the fastest," Slater said. "It came from the size of a dolphin you would see at SeaWorld about 10 million years ago and grew substantially."

Whales range in size from the largest animal known to have ever existed, the blue whale, which is more than 100 feet long, to small species that are about the size of a dog and can get caught in fishermen's nets, Slater said.

Alfaro and Slater do not find evidence for rapid whale diversification, but extinctions may have made it difficult to detect early rapid diversification.

Whales are about 55 million years old, but the first group of whales to take to water is extinct, Alfaro said. Different hypotheses have been proposed to explain the rapid appearance and diversification of modern whales, which coincided with the extinction of the primitive whales.

Before the extinction of the dinosaurs 65 million years ago, there were large marine reptiles in the oceans that went extinct. When the earliest whales first went into the oceans some 55 million years ago, they had essentially no competitors, Alfaro and Slater noted. These primitive whales ranged in size from several feet to 65 feet long and looked similar to land animals, Slater said. They all fed on fish; the earliest whales did not dive deep down to catch squid.

Alfaro's laboratory uses many techniques, including the analysis of DNA sequences, computational techniques and the fossil record to analytically test ideas about when major groups appear and when they become dominant. He and his research team integrate information from the fossil record with novel computational methods of analysis.

"We are interested in understanding the causes of biodiversity," Alfaro said.

"If we really want to understand species diversity, the number of species in any given group and how the variation in body size came to be, this paper points out that we will need to rely on more of a collaboration between paleontologists and molecular biologists to detect possible changes in the rate at which new species came into existence," Slater said.

The analytical tools for integrating the fossil data with the molecular data are just being developed, said Alfaro, whose research is bridging the divide.

Co-authors on the Proceedings of the Royal Society B study are Samantha Price, a postdoctoral scholar at UC Davis, and Francesco Santini, a UCLA postdoctoral scholar in Alfaro's laboratory.

The research is federally funded by the National Science Foundation (NSF) and by the NSF-funded National Evolutionary Synthesis Center.
Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of California - Los Angeles. The original article was written by Stuart Wolpert.

Journal Reference:
G. J. Slater, S. A. Price, F. Santini, M. E. Alfaro. Diversity versus disparity and the radiation of modern cetaceans. Proceedings of the Royal Society B: Biological Sciences, 2010; DOI: 10.1098/rspb.2010.0408

Deep Subduction of the Indian Continental Crust Beneath Asia

The map shows the location of the study area in the Himalayas. Inset: A schematic shows the Indian plate subducting beneath the Asian plate. (Credit: NOC)

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Geological investigations in the Himalayas have revealed evidence that when India and Asia collided some 90 million years ago, the continental crust of the Indian tectonic plate was forced down under the Asian plate, sinking down into the Earth's mantle to a depth of at least 200 km kilometres.

"The subduction of continental crust to this depth has never been reported in the Himalayas and is also extremely rare in the rest of world," said Dr Anju Pandey of the National Oceanography Centre in Southampton, who led the research.

Pandey and her colleagues used sophisticated analytical techniques to demonstrate the occurrence of relict majorite, a variety of mineral garnet, in rocks collected from the Himalayas.

Majorite is stable only under ultra-high pressure conditions, meaning that they must have been formed very deep down in the Earth's crust, before the subducted material was exhumed millions of years later.

"Our findings are significant because researchers have disagreed about the depth of subduction of the Indian plate beneath Asia," said Pandey.

In fact, the previous depth estimates conflicted with estimates based on computer models. The new results suggest that the leading edge of the Indian plate sank to a depth around double that of previous estimates.

"Our results are backed up by computer modelling and will radically improve our understanding of the subduction of the Indian continental crust beneath the Himalayas," said Pandey.

The new discovery is also set to modify several fundamental parameters of Himalayan tectonics, such as the rate of Himalayan uplift, angle, and subduction of the Indian plate.

The new research findings were published this month in the journal Geology.

The study was supported by the UK's Natural Environment research Council.

The researchers are Anju Pandey and Andy Milton of the National Oceanography Centre, Southampton, Mary Leech of San Francisco State university), and Preeti Singh and Pramod Verma of the University of Delhi.
Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by National Oceanography Centre, Southampton (UK), via EurekAlert!, a service of AAAS.

Journal Reference:
A. Pandey, M. Leech, A. Milton, P. Singh, P. K. Verma. Evidence of former majoritic garnet in Himalayan eclogite points to 200-km-deep subduction of Indian continental crust. Geology, 2010; 38 (5): 399 DOI: 10.1130/G30584.1