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Research at Mines Unearths New Dinosaur Species

Clint Boyd, Ph.D., of the South Dakota School of Mines & Technology, points to a crocodyliform tooth embedded in the femur of a young dinosaur. (Credit: South Dakota School of Mines & Technology)

First fossil evidence shows small crocs fed on baby dinosaursA South Dakota School of Mines & Technology assistant professor and his team have discovered a new species of herbivorous dinosaur and today published the first fossil evidence of prehistoric crocodyliforms feeding on small dinosaurs.
Research by Clint Boyd, Ph.D., provides the first definitive evidence that plant-eating baby ornithopod dinosaurs were a food of choice for the crocodyliform, a now extinct relative of the crocodile family. While conducting their research, the team also discovered that this dinosaur prey was a previously unrecognized species of a small ornithopod dinosaur, which has yet to be named.

The evidence found in what is now known as the Grand Staircase Escalante-National Monument in southern Utah dates back to the late Cretaceous period, toward the end of the age of dinosaurs, and was published today in the online journal PLOS ONE. The complete research findings of Boyd and Stephanie K. Drumheller, of the University of Iowa and the University of Tennessee, and Terry A. Gates, of North Carolina State University and the Natural History Museum of Utah, can be accessed online (see journal reference below).

A large number of mostly tiny bits of dinosaur bones were recovered in groups at four locations within the Utah park — which paleontologists and geologists know as the Upper Cretaceous (Campanian) Kaiparowits Formation — leading paleontologists to believe that crocodyliforms had fed on baby dinosaurs 1-2 meters in total length.

Evidence shows bite marks on bone joints, as well as breakthrough proof of a crocodyliform tooth still embedded in a dinosaur femur.

The findings are significant because historically dinosaurs have been depicted as the dominant species. “The traditional ideas you see in popular literature are that when little baby dinosaurs are either coming out of a nesting grounds or out somewhere on their own, they are normally having to worry about the theropod dinosaurs, the things like raptors or, on bigger scales, the T. rex. So this kind of adds a new dimension,” Boyd said. “You had your dominant riverine carnivores, the crocodyliforms, attacking these herbivores as well, so they kind of had it coming from all sides.”

Based on teeth marks left on bones and the large amounts of fragments left behind, it is believed the crocodyliforms were also diminutive in size, perhaps no more than 2 meters long. A larger species of crocodyliform would have been more likely to gulp down its prey without leaving behind traces of “busted up” bone fragments.

Until now, paleontologists had direct evidence only of “very large crocodyliforms” interacting with “very large dinosaurs.”

“It’s not often that you get events from the fossil record that are action-related,” Boyd explained. “While you generally assume there was probably a lot more interaction going on, we didn’t have any of that preserved in the fossil record yet. This is the first time that we have definitive evidence that you had this kind of partitioning, of your smaller crocodyliforms attacking the smaller herbivorous dinosaurs,” he said, adding that this is only the second published instance of a crocodyliform tooth embedded in any prey animal in the fossil record.

“A lot of times you find material in close association or you can find some feeding marks or traces on the outside of the bone and you can hypothesize that maybe it was a certain animal doing this, but this was only the second time we have really good definitive evidence of a crocodyliform feeding on a prey animal and in this case an ornithischian dinosaur,” Boyd said.

The high concentrations of tiny dinosaur bones led researchers to conclude a type of selection occurred, that crocodyliforms were preferentially feeding on these miniature dinosaurs. “Maybe it was closer to a nesting ground where baby dinosaurs would have been more abundant, and so the smaller crocodyliforms were hanging out there getting a lunch,” Boyd added.

“When we started looking at all the other bones, we starting finding marks that are known to be diagnostic for crocodyliform feeding traces, so all that evidence coming together suddenly started to make sense as to why we were not finding good complete specimens of these little ornithischian dinosaurs,” Boyd explained. “Most of the bites marks are concentrated around the joints, which is where the crocodyliform would tend to bite, and then, when they do their pulling or the death roll that they tend to do, the ends of the bones tend to snap off more often than not in those actions. That’s why we were finding these fragmentary bones.”

In the process of their research, the team discovered through diagnostic cranial material that these baby prey are a new, as yet-to-be-named dinosaur species. Details on this new species will soon be published in another paper.

*Release Date Wednesday, February 27, 2013

Note : The above story is reprinted from materials provided by South Dakota School of Mines and Technology.

Dinosaur Whodunit: Solving A 77-Million-Year-Old Mystery

Reconstruction of the dinosaur nest and the two possible theropod egg layers. Credit: Julius T. Csotonyi

It has all the hallmarks of a Cretaceous melodrama. A dinosaur sits on her nest of a dozen eggs on a sandy river beach. Water levels rise, and the mother is faced with a dilemma: Stay or abandon her unhatched offspring to the flood and scramble to safety?
Seventy-seven million years later, scientific detective work conducted by University of Calgary and Royal Tyrrell Museum researchers used this unique fossil nest and eggs to learn more about how nest building, brooding and eggs evolved. But there is a big unresolved question: Who was the egg-layer?

“Working out who the culprit was in this egg abandonment tragedy is a difficult problem to crack,” says Darla Zelenitsky, U of C paleontologist and the lead author of a paper published today in the journal Palaeontology. “After further investigation, we discovered that this find is rarer than we first thought. It is a one of a kind fossil. In fact, it is the first nest of its kind in the world.”

Zelenitsky says she first saw the nest in a private collection which had been collected in Montana in the 1990s. The nest was labeled as belonging to a hadrosaur (duck-billed) dinosaur, but she soon discovered it was mistakenly identified. In putting all the data together, she realized they had a small theropod (meat-eating) dinosaur nest. “Nests of small theropods are rare in North America and only those of the dinosaur Troodon have been identified previously,” says Zelenitsky. “Based on characteristics of the eggs and nest, we know that the nest belonged to either a caenagnathid or a small raptor, both small meat-eating dinosaurs closely related to birds. Either way, it is the first nest known for these small dinosaurs.”

The nest tells scientists more about the behaviour of the animal as well as some valuable information relating to the characteristics of modern birds. “Our research tells us a lot about the dinosaur that laid the eggs and how it built its nest,” says Francois Therrien, a co-investigator in the study and curator of dinosaur palaeoecology at the Royal Tyrrell Museum in Drumheller, Alta.

The fossil nest is a mound of sand about half a metre across and weighing as much as a small person. The eggs were laid two at a time, on the sloping sides of the mound, and form a ring around its flat top, where the nesting dinosaur would have sat and brooded its clutch.

“Based on features of the nest, we know that the mother dug in freshly deposited sand, possibly the shore of a river, to build a mound against which she laid her eggs and on which she sat to brood the eggs,” says Therrien. “Some characteristics of the nest are shared with birds, and our analysis can tell us how far back in time these features, such as brooding, nest building, and eggs with a pointed end, evolved – partial answers to the old question of which came first, the chicken or the egg.”

Note : The above story is reprinted from materials provided by University of Calgary, via EurekAlert!, a service of AAAS. 

Dinosaur Egg Study Supports Evolutionary Link Between Birds and Dinosaurs

Darla Zelenitsky from the University of Calgary collaborated with David Varricchio at Montana State University to closely examined the shells of fossil eggs from a small meat-eating dinosaur called Troodon. (Credit: Jay Im (University of Calgary))

A small, bird-like North American dinosaur incubated its eggs in a similar way to brooding birds — bolstering the evolutionary link between birds and dinosaurs, researchers at the University of Calgary and Montana State University study have found.

Among the many mysteries paleontologists have tried to uncover is how dinosaurs hatched their young. Was it in eggs completely buried in nest materials, like crocodiles? Or was it in eggs in open or non-covered nests, like brooding birds?

Using egg clutches found in Alberta and Montana, researchers Darla Zelenitsky at the University of Calgary and David Varricchio at Montana State University closely examined the shells of fossil eggs from a small meat-eating dinosaur called Troodon.

In a finding published in the spring issue of Paleobiology, they concluded that this specific dinosaur species, which was known to lay its eggs almost vertically, would have only buried the egg bottoms in mud.

“Based on our calculations, the eggshells of Troodon were very similar to those of brooding birds, which tells us that this dinosaur did not completely bury its eggs in nesting materials like crocodiles do,” says study co-author Zelenitsky, assistant professor of geoscience

“Both the eggs and the surrounding sediments indicate only partial burial; thus an adult would have directly contacted the exposed parts of the eggs during incubation,” says lead author Varricchio, associate professor of paleontology.

Varricchio says while the nesting style for Troodon is unusual, “there are similarities with a peculiar nester among birds called the Egyptian Plover that broods its eggs while they’re partially buried in sandy substrate of the nest.”

Paleontologists have always struggled to answer the question of how dinosaurs incubated their eggs, because of the scarcity of evidence for incubation behaviours.

As dinosaurs’ closest living relatives, crocodiles and birds offer some insights.

Scientists know that crocodiles and birds that completely bury their eggs for hatching have eggs with many pores or holes in the eggshell, to allow for respiration.

This is unlike brooding birds which don’t bury their eggs; consequently, their eggs have far fewer pores.

The researchers counted and measured the pores in the shells of Troodon eggs to assess how water vapour would have been conducted through the shell compared with eggs from contemporary crocodiles, mound-nesting birds and brooding birds.

They are optimistic their methods can be applied to other dinosaur species’ fossil eggs to show how they may have been incubated.

“For now, this particular study helps substantiate that some bird-like nesting behaviors evolved in meat-eating dinosaurs prior to the origin of birds. It also adds to the growing body of evidence that shows a close evolutionary relationship between birds and dinosaurs,” Zelenitsky says.

Note : The above story is reprinted from materials provided by University of Calgary, via EurekAlert!, a service of AAAS.  

Archeologists Explain Mystery Of Ancient ‘Cave Of Death’

Image Credit: panyajampatong / Shutterstock

For over 20 years, archeologists have been recovering an unusually high number of large carnivore fossils from a cave near Madrid, Spain. According to a new report in the open access journal PLOS ONE, the saber-toothed cat, hyena and red panda ancestor remains found at the site are the result of these animals purposely wandering into the cave and then becoming trapped under mysterious conditions between 9 and 10 million years ago.

Fossils at the cave were first discovered in 1991, and archeologists subsequently uncovered over 18,000 fossils between 1991 and 2008 during two major excavations. Many theories have attempted to explain why such a large number of predator remains have been found in one location. These theories have included the animals falling into the cave and dying, carcasses being washed into the cave by water, and entrapment by an apex predator.

Another bizarre aspect of the site is the near absence of any herbivores, as about 98 percent of the fossils recovered are meat-eaters.

To examine potential causes of death, the Spanish and American researchers examined the geologic history of the cave, the age of the cave fossils, and the time frame of the animals’ demises. They started by looking into the fossilization process of over 6,700 preserved bones from different archeological levels in the cave.

By looking at the types of animals recovered, where the fossils were found, and the lack of fractured bones, the researchers concluded that the animals probably decided to enter the cave in search of prey and became unable to make their way out.

The team also suggested that the lack of herbivore remains may be due to the fact that the clearly visible cave opening was simply not attractive to animals in search of vegetation. The lack of herbivore remains was important for the researchers in ruling out the theory that the animal remains were transported to the cave by water.

“Most probably, carnivores got trapped and remained alive for some time,” the authors wrote. “Also, it is possible that carnivores were searching for water during drought periods and not necessarily for food.”

As the millennia passed, layers of sediment poured into the cave – covering up the animal remains and eventually filling in the cave. The researchers said this would explain why the cave’s ‘window of death’ only covers a certain time span.

The team also noted that fossils in this site are well preserved, most likely as a result of their deposition in the isolated and protective environment of the chamber.

In their conclusion, the team advocated further study of both the cave and the fossils that have been found there.

“Further research is needed in order to ascertain the causes of death of carnivorans inside the cavity but exhaustion, hypothermia or poisoning from drinking water or toxic gases are options to consider,” they wrote.

The team, which included Spanish researchers from the Museo Nacional de Ciencias Naturales-Consejo Superior de Investigaciones Científicas in Madrid, was led by M. Soledad Domingo, a paleontologist from the University of Michigan.

Note: This story has been adapted from a news release issued by Brett Smith for redOrbit

Unique Sulfur Isotopes in Plume Lavas Reveal Deep Mantle Storage of Archean Crust

Sulfur isotopes within iron sulfide inclusions in volcanic rocks, like this one from Iceland, demonstrate that sulfur derived from the Earth’s ancient atmosphere was preserved within the mantle for at least 2.54 billion years before coming back to the surface in eruptions at Mangaia volcano, South Pacific Ocean (Rita A. Cabral et al)

An international team of researchers, led by scientists at Boston University’s Department of Earth and Environment, has found evidence that material contained in young oceanic lava flows originated at the Earth’s surface in the Archean (>2.45 billions years ago).

The new finding helps constrain the timing of the initiation of plate tectonics, the origin of some of the chemical heterogeneity in the Earth’s mantle, and may shed light on how the chaotically convecting mantle could preserve such material for so long. The study appears in the April 25 issue of the journal Nature.

Tectonic plates at the Earth’s surface move around and collide at areas called subduction zones. In these areas, one plate is forced beneath the other and is transported into the Earth’s mantle. It has long been suggested that this subducted material must be re-erupted at a later time. However, the residence time of the subducted material in the mantle is uncertain and convincing evidence of its return to the surface has been lacking.

Sulfur isotopes provide the key to the authors’ discovery. According to the researchers, because mass-independently fractionated (MIF) sulfur isotope signatures were generated exclusively through atmospheric photochemical reactions until about 2.5 billion years ago, material containing such isotope signatures must have originated at the Earth’s surface in the Archean. In the new study, the researchers found MIF sulfur-isotope signatures in olivine-hosted sulfides from relatively young (20-million-year-old) ocean island basalts (OIB) from Mangaia, Cook Islands (Polynesia), providing evidence that material once at the Earth’s surface has been recycled through the mantle and re-erupted at a young ocean island.

“The discovery of MIF-S isotope in these young oceanic lavas suggests that sulfur—likely derived from the hydrothermally-altered oceanic crust—was subducted into the mantle more than 2.5 billion years ago and recycled into the mantle source of the Mangaia lavas,” says Rita Cabral, the study’s primary author and a graduate student in BU’s Department of Earth and Environment.

The data also complement evidence for sulfur recycling of ancient sedimentary materials to the subcontinental lithospheric mantle previously identified in diamond inclusions.

Note : The above story is reprinted from materials provided by Boston University College of Arts & Sciences, via Newswise.

Rethinking early atmospheric oxygen

This photo shows researchers doing field sampling of a pyrite-rich black shale outcrop in China. The weathering of such sediments, which contain sulfur originally buried from the ocean, transfers sulfur isotope signals to the ocean to be buried again in marine sediments. – Chu Research Group, Institute of Geology and Geophysics, Chinese Academy of Sciences.

A research team of biogeochemists at the University of California, Riverside has provided a new view on the relationship between the earliest accumulation of oxygen in the atmosphere, arguably the most important biological event in Earth history, and its relationship to the sulfur cycle.

A general consensus exists that appreciable oxygen first accumulated in Earth’s atmosphere around 2.4 to 2.3 billion years ago. Though this paradigm is built upon a wide range of geological and geochemical observations, the famous “smoking gun” for what has come to be known as the “Great Oxidation Event” (GOE) comes from the disappearance of anomalous fractionations in rare sulfur isotopes.

“These isotope fractionations, often referred to as ‘mass-independent fractionations,’ or ‘MIF’ signals, require both the destruction of sulfur dioxide by ultraviolet energy from the sun in an atmosphere without ozone and very low atmospheric oxygen levels in order to be transported and deposited in marine sediments,” said Christopher T. Reinhard, the lead author of the research paper and a former UC Riverside graduate student. “As a result, their presence in ancient rocks is interpreted to reflect vanishingly low atmospheric oxygen levels continuously for the first ~2 billion years of Earth’s history.”

However, diverse types of data are emerging that point to the presence of atmospheric oxygen, and, by inference, the early emergence of oxygenic photosynthesis hundreds of millions of years before these MIF signals disappear from the rock record. These observations motivated Reinhard and colleagues to explore the possible conditions under which inherited MIF signatures may have persisted in the rock record long after oxygen accumulated in the atmosphere.

Using a simple quantitative model describing how sulfur and its isotopes cycle through the Earth’s crust, the researchers discovered that under certain conditions these MIF signatures can persist within the ocean and marine sediments long after O2 increases in the atmosphere. Simply put, the weathering of rocks on the continents can transfer the MIF signal to the oceans and their sediments long after production of this fingerprint has ceased in an oxygenated atmosphere.

“This lag would blur our ability to date the timing of the GOE and would allow for dynamic rising and falling oxygen levels during a protracted transition from an atmosphere without oxygen to one rich in this life-giving gas,” Reinhard said.

Study results appear in Nature‘s advanced online publication on April 24.

Reinhard explained that once MIF signals formed in an oxygen-poor atmosphere are captured in pyrite and other minerals in sedimentary rocks, they are recycled when those rocks are later uplifted as mountain ranges and the pyrite is oxidized.

“Under certain conditions, this will create a sort of ‘memory effect’ of these MIF signatures, providing a decoupling in time between the burial of MIF in sediments and oxygen accumulation at Earth’s surface,” he said.

According to the researchers, the key here is burying a distinct MIF signal in deep sea sediments, which are then subducted and removed from Earth’s surface.

“This would create a complementary signal in minerals that are weathered and delivered to the oceans, something that we actually see evidence of in the rock record,” said Noah Planavsky, the second author of the research paper and a former UC Riverside graduate student now at Caltech. “This signal can then be perpetuated through time without the need to generate it within the atmosphere contemporaneously.”

Reinhard, now a postdoctoral fellow at Caltech and soon to be an assistant professor at Georgia Institute of Technology, explained that although the researchers’ new model provides a plausible mechanism for reconciling recent conflicting data, this can only occur when certain key conditions are met – and these conditions are likely to have changed through time during Earth’s long early history.

“There is obviously much further work to do, but we hope that our model is one step toward a more integrated view of how Earth’s crust, mantle and atmosphere interact in the global sulfur cycle,” he said.

Timothy W. Lyons, a professor of biogeochemistry at UCR and the principal investigator of the research project noted that this is a fundamentally new and potentially very important way of looking at the sulfur isotope record and its relationship to biospheric oxygenation.

“The message is that sulfur isotope records, when viewed through the filter of sedimentary recycling, may challenge efforts to precisely date the GOE and its relationship to early life, while opening the door to the wonderful unknowns we should expect and embrace,” he said.

Note: This story has been adapted from a news release issued by the University of California – Riverside

New Dinosaur Fossil Discovered in China

The meat-eating dinosaur from the Late Jurassic Period was less than a year old. (Credit: Photo courtesy of James Clark, George Washington University)

Fossil remains found by a George Washington University biologist in northwestern China have been identified as a new species of small theropod, or meat-eating, dinosaur.

 

The discovery was made by James Clark, the Ronald B. Weintraub Professor of Biology, in the Department of Biological Sciences of GW’s Columbian College of Arts and Sciences. Dr. Clark, along with his then doctoral student Jonah Choiniere and a team of international researchers, found the dinosaur specimen in a remote region of Xinjiang in China in 2006.
In a research paper published in the Journal of Systematic Palaeontology, Drs. Clark and Choiniere explain recovering the skull, mandible and partial skeleton of the dinosaur. The new theropod was an estimated 1 meter or just over 3 feet long and probably weighed about 3 pounds.

“All that was exposed on the surface was a bit of the leg,” said Dr. Clark. “We were pleasantly surprised to find a skull buried in the rock too.”

The dinosaur is named Aorun zhaoi, after the Dragon King in the Chinese epic tale Journey to the West. It wasn’t necessarily a small dinosaur species, though, because Aorun was still a youngster when it became a fossil.

“We were able to look at microscopic details of Aorun’s bones and they showed that the animal was less than a year old when it died on the banks of a stream,” said Dr. Choiniere.

Dr. Choiniere, now a senior researcher at the Evolutionary Studies Institute at the University of the Witwatersrand in Johannesburg, South Africa, was a doctoral student in Biological Studies at GW when the discovery was made. He was also a Kalbfleisch Fellow and Gerstner Scholar at the American Museum of Natural History.

Aorun lived more than 161 million years ago, in the earliest part of the Late Jurassic Period. Its small, numerous teeth suggest that it would have eaten prey like lizards and small relatives of today’s mammals and crocodilians.

This is the fifth new theropod discovered at the Wucaiwan locality by the team, co-led by Dr. Clark and Dr. Xu Xing of the Chinese Academy of Sciences.

This research was funded by the National Science Foundation Division of Earth Sciences and the Chinese National Natural Science Foundation.

Note : The above story is reprinted from materials provided by George Washington University. 

Lava Erupting On Sea Floor Linked to Deep-Carbon Cycle

Molten magma erupted onto the seafloor freezes to glass that contains clues to its origin in Earth’s deep interior and ancient past (field of view ~1 cm). Volcanic glasses like this one may reveal a link between Earth’s oxidation state and the deep carbon cycle. (Credit: Glenn Macpherson and Tim Gooding)

Scientists from the Smithsonian and the University of Rhode Island have found unsuspected linkages between the oxidation state of iron in volcanic rocks and variations in the chemistry of the deep Earth. Not only do the trends run counter to predictions from recent decades of study, they belie a role for carbon circulating in the deep Earth.

 

The team’s research was published May 2 in Science Express.

Elizabeth Cottrell, lead author and research geologist at the Smithsonian’s National Museum of Natural History, and Katherine Kelley at the University of Rhode Island’s Graduate School of Oceanography measured the oxidation state of iron, which is the amount of iron that has a 3+ versus a 2+ electronic charge, in bits of magma that froze to a glass when they hit the freezing waters and crushing pressures of the sea floor. Due to the high precision afforded by the spectroscopic technique they used, the researchers found very subtle variations in the iron-oxidation state that had been overlooked by previous investigations.

The variations correlate with what Cottrell described as the “fingerprints” of the deep Earth rocks that melted to produce the lavas — but not in the way previous researchers had predicted. The erupted lavas that have lower concentrations of 3+ iron also have higher concentrations of elements such as barium, thorium, rubidium and lanthanum, that concentrate in the lavas, rather than staying in their deep Earth home. More importantly, the oxidation state of iron also correlates with elements that became enriched in lavas long ago, and now, after billions of years, show elevated ratios of radiogenic isotopes. Because radiogenic isotopic ratios cannot be modified during rock melting and eruption, Cottrell called this “a dead ringer for the source of the melt itself.”

Carbon is one of the “geochemical goodies” that tends to become enriched in the lava when rocks melt. “Despite is importance to life on this planet, carbon is a really tricky element to get a handle on in melts from the deep Earth,” said Cottrell. “That is because carbon also volatilizes and is lost to the ocean waters such that it can’t easily be quantified in the lavas themselves. As humans we are very focused on what we see up here on the surface. Most people probably don’t recognize that the vast majority of carbon — the backbone of all life — is located in the deep Earth, below the surface — maybe even 90 percent of it.”

The rocks that the team analyzed that were reduced also showed a greater influence of having melted in the presence of carbon than those that were oxidized. “And this makes sense because for every atom of carbon present at depth it has to steal oxygen away from iron as it ascends toward the surface,” said Cottrell. This is because carbon is not associated with oxygen at depth, it exists on its own, like in the mineral diamond. But by the time carbon erupts in lava, it is surrounded by oxygen. In this way, concludes Cottrell, “carbon provides both a mechanism to reduce the iron and also a reasonable explanation for why these reduced lavas are enriched in ways we might expect from melting a carbon-bearing rock.”

Note : The above story is reprinted from materials provided by Smithsonian, via EurekAlert!, a service of AAAS. 

First Land Animals Kept Fishlike Jaws for Millions of Years

A juvenile Orobates pabsti, a reptile-like four-legged amphibian. Philip Anderson of UMass Amherst and colleagues examined images of 89 fossils of early tetrapods and their fish-like forebears ranging in age from about 400 to 300 million years old. The pictured specimen is from the Museum Der Natur in Gotha, Germany. (Credit: Thomas Martens, Stiftung Schloss Friedenstein Gotha, Germany)

Scientists studying how early land vertebrates evolved from fishes long thought that the animals developed legs for moving around on land well before their feeding systems and dietary habits changed enough to let them eat a land-based diet, but strong evidence was lacking. Now, for the first time fossil jaw measurements by Philip Anderson at the University of Massachusetts Amherst and others have tested and statistically confirmed this lag.

“This pattern had been hypothesized previously, but not really tested. Now we’ve done that,” Anderson says. He and his team found that the mechanical properties of tetrapod jaws did not show significant adaptations to land-based feeding until some 40 to 80 million years after the four-legged creatures initially came out of the water. Until then, tetrapod jaws were still very fish-like, even though their owners had weight-bearing limbs and the ability to walk on land. Anderson says this finding suggests tetrapods may have shown a limited variety of feeding strategies in the early phases of their evolution on land.

“What it took to really initiate evolutionary changes in the jaw system was for these animals to start eating plants,” he says. For the study, published in an early online edition of the journal Integrative and Comparative Biology, Anderson and researchers Matt Friedman of the University of Oxford and Marcello Ruta of the University of Lincoln, U.K., examined images of 89 fossils of early tetrapods and their fish-like forebears. The fossils ranged in age from about 400 to 300 million years old. Anderson and his team were interested in how the jaws of these fossilized animals differed through time.

They used 10 biomechanical metrics to describe jaw differences. One of these, called mechanical advantage, measured how much force an animal can transfer to its bite. Anderson points out that while fossils can’t tell you what an animal actually ate, scientists can infer potential feeding behavior from fossilized evidence of biomechanical tools like jaws. The researchers compared jaw features from the fossil record and calculated the rates at which jaws evolved.

“The basic result was that it took a while for these animals to adapt their jaws for a land-based diet,” Anderson says. “They stayed essentially fish-like for a long time.”

It turns out that just moving into a new environment is not always enough to trigger functional adaptations. In their paper, the authors say the results may be explained by an earlier hypothesis: A shift from gilled to lung breathing in later tetrapod groups was necessary before they could devote their jaw structure to eating plants.

Anderson says the statistical methods they developed for this work could be used in future studies of more subtle biomechanical patterns in fossil animals that may not be initially clear.

Note : The above story is reprinted from materials provided by University of Massachusetts Amherst. 

Climate Change Will Raise the Sea Level in the Gulf of Finland

Map of the Baltic Sea. Created by NormanEinstein, May 25, 2006.

The Finnish Meteorological Institute has updated its estimates concerning the impact of rising sea levels on the Finnish coast. Post-glacial rebound and changes in Earth’s gravity field protect the Finnish coast against rising sea levels, especially in the Gulf of Bothnia. In the Gulf of Finland, the sea level is starting to rise.

The rise in ocean levels varies regionally

Global warming raises ocean levels at an accelerating pace, currently on average about three millimetres per year. The reasons for this are the thermal expansion of sea water and the melting of glaciers. It is estimated that by the end of this century, ocean levels will rise at least about 20 centimetres. The highest estimates are nearly two metres.

There is, however, great regional variation in the rise, for reasons such as the uneven warming of seas, changes in Earth’s gravity field, and changes in the circulation of seas. The Finnish Meteorological Institute has used the latest scientific publications to estimate the impact of these regional factors on the Finnish coast.

As glaciers melt, mass will shift from continents into seas. In consequence, Earth’s gravity field and the height of Earth’s crust will be altered. The mass of continental glaciers will no longer attract sea water as strongly as before. In addition, Earth’s crust will rise under the lighter glacier. For this reason, the rise in the sea level will be minor near the melting glacier, whereas the rise will be felt more acutely further away from the glacier.In consequence, the melting of the continental glacier in Greenland will have a fairly small impact on the Finnish coast. The regional rise in Finland will remain below the global average.

The characteristics of the Baltic Sea affect the Finnish coast

In addition to the regional rise in ocean levels, local events in the Baltic Sea affect the sea level changes on the Finnish coast. In Finland, the uplift of the land after the last glacial period is still 4-10 millimetres per year. Moreover, climate models predict stronger western winds, which will push water into the Baltic Sea through the Danish straits and water will accumulate against the Finnish coast.

So far, post-glacial rebound has offset the rise in sea level in Finland, but the situation is gradually changing on the southern coast. It is estimated that the sea level will start to rise in the Gulf of Finland. In the Gulf of Bothnia, the uplift is still likely to even out the sea level rise in the coming decades.

If the highest projections come to pass, the sea level will rise everywhere on the Finnish coast: by as much as 90 centimetres in the Gulf of Finland by the end of the century, by 65 cm in the Bothnian Sea and by about 30 cm in the Bay of Bothnia.

The current estimate concerns the change in the average sea level in the long term. In addition, the impact of waves and other changes in the short-term variation of the sea level must be taken into account in building and other activities on the coast. In the near future, the Finnish Meteorological Institute will update its estimates of the lowest recommended building heights, where these factors will also be considered.

Note : The above story is reprinted from materials provided by Finnish Meteorological Institute. 

Unique Chemistry Reveals Eruption of Ancient Materials Once at Earth’s Surface

New study supports theory that Earth’s earliest crust was folded back into its mantle and returned to the surface in volcanoes
An international team of researchers, including Scripps Institution of Oceanography, UC San Diego, geochemist James Day, has found new evidence that material contained in oceanic lava flows originated in Earth’s ancient Archean crust. These findings support the theory that much of the Earth’s original crust has been recycled by the process of subduction, helping to explain how the Earth has formed and changed over time.

The Archean geologic eon, Earth’s second oldest, dating from 3.8 to 2.5 billion years ago, is the source of the oldest exposed rock formations on the planet’s surface. (Archean rocks are known from Greenland, the Canadian Shield, the Baltic Shield, Scotland, India, Brazil, western Australia, and southern Africa.) Although the first continents were formed during the Archean eon, rock of this age makes up only around seven percent of the world’s current crust.

“Our new results are important because they provide strong evidence not only to tie materials that were once on Earth’s surface to an entire cycle of subduction, storage in the mantle, and return to the surface as lavas, but they also place a firm time constraint on when plate tectonics began; no later than 2.5 billion years ago,” said Day. “This is because mass independent sulfur signatures have only been shown to occur in the atmosphere during periods of low oxygenation prior to the rise of oxygen-exhaling organisms.”

The new study, which will be published in the April 24 issue of the journal Nature, adds further support to the theory that most of the Archean crust was subducted or folded back into the Earth’s mantle, evidence of which is seen in the presence of specific sulfur isotopes found in some oceanic lava flows.

According to the researchers, because terrestrial independently fractionated (MIF) sulfur-isotope isotope signatures were generated exclusively through atmospheric photochemical reactions until about 2.5 billion years ago, material containing such isotopes must have originated in the Archean crust. In the new study, the researchers found MIF sulfur-isotope signatures in olivine-hosted sulfides from relatively young (20-million-year-old) ocean island basalts (OIB) from Mangaia, Cook Islands (Polynesia), providing evidence that the mantle is the only possible source of the ancient Archean materials found in the Mangaia lavas.

“The discovery of MIF-S isotope in these young oceanic lavas suggests that sulfur—likely derived from the hydrothermally-altered oceanic crust—was subducted into the mantle more than 2.5 billion years ago and recycled into the mantle source of the Mangaia lavas,” said Rita Cabral, the study’s primary author and a graduate student in Boston University’s Department of Earth and Environment.

The data also complement evidence for sulfur recycling of ancient sedimentary materials to the subcontinental lithospheric mantle previously identified in diamond inclusions.

Other study co-authors are Matthew G. Jackson of Boston University; Estelle F. Rose-Koga and Kenneth T. Koga of Université Blaise Pascal in Clermont-Ferrand, France; Martin J. Whitehouse of the Swedish Museum of Natural History and Stockholm University, Stockholm, Sweden; Michael A. Antonelli and James Farquhar of the University of Maryland; and Erik H. Hauri of the Carnegie Institution of Washington in Washington, D.C.

Note : The above story is reprinted from materials provided by University of California

No Redoubt: Volcanic Eruption Forecasting Improved

Redoubt Volcano. (Credit: Courtesy of USGS)

Forecasting volcanic eruptions with success is heavily dependent on recognizing well-established patterns of pre-eruption unrest in the monitoring data. But in order to develop better monitoring procedures, it is also crucial to understand volcanic eruptions that deviate from these patterns.

New research from a team led by Carnegie’s Diana Roman retrospectively documented and analyzed the period immediately preceding the 2009 eruption of the Redoubt volcano in Alaska, which was characterized by an abnormally long period of pre-eruption seismic activity that’s normally associated with short-term warnings of eruption. Their work is published today by Earth and Planetary Science Letters.

Well-established pre-eruption patterns can include a gradual increase in the rate of seismic activity, a progressive alteration in the type of seismic activity, or a change in ratios of gas released. “But there are numerous cases of volcanic activity that in some way violated these common patterns of precursory unrest,” Roman said. “That’s why examining the unusual precursor behavior of the Redoubt eruption is so enlightening.”

About six to seven months before the March 2009 eruption, Redoubt began to experience long-period seismic events, as well as shallow volcanic tremors, which intensified into a sustained tremor over the next several months. Immediately following this last development, shallow, short-period earthquakes were observed at an increased rate below the summit. In the 48 hours prior to eruption both deep and shallow earthquakes were recorded.

This behavior was unusual because precursor observations usually involve a transition from short-period to long-period seismic activity, not the other way around. What’s more, seismic tremor is usually seen as a short-term warning, not something that happens months in advance. However, these same precursors were also observed during the 1989-90 Redoubt eruption, thus indicating that the unusual seismic pattern reflects some unique aspect of the volcano’s magma system.

Advanced analysis of the seismic activity taking place under the volcano allowed Roman and her team to understand the changes taking place before, during, and after eruption. Their results show that the eruption was likely preceded by a protracted period of slow magma ascent, followed by a short period of rapidly increasing pressure beneath Redoubt.

Elucidating the magma processes causing these unusual precursor events could help scientists to hone their seismic forecasting, rather than just relying on the same forecasting tools they’re currently using, ones that are not able to detect anomalies.

For example, using current techniques, the forecasts prior to Redoubt’s 2009 eruption wavered over a period of five months, back and forth between eruption being likely within a few weeks to within a few days. If the analytical techniques used by Roman and her team had been taken into consideration, the early risk escalations might not have been issued.

“Our work shows the importance of clarifying the underlying processes driving anomalous volcanic activity. This will allow us to respond to subtle signals and increase confidence in making our forecasts.” Roman said.

Note : The above story is reprinted from materials provided by Carnegie Institution. 

Canada’s Distinctive Tuya Volcanoes Reveal Glacial, Palaeo-Climate Secrets

Geologists at summit of Kima’Kho volcano look to the east and south across the Kawdy plateau. The plateau hosts at least six other tuyas. (Credit: UBC Science)

Deposits left by the eruption of a subglacial volcano, or tuya, 1.8 million years ago could hold the secret to more accurate palaeo-glacial and climate models, according to new research by University of British Columbia geoscientists.
The detailed mapping and sampling of the partially eroded Kima’ Kho tuya in northern British Columbia, Canada shows that the ancient regional ice sheet through which the volcano erupted was twice as thick as previously estimated.

Subglacial eruptions generate distinctive deposits indicating whether they were deposited below or above the waterline of the englacial lakes–much like the rings left on the inside of a bath tub. The transitions from subaqueous from subaerial deposits are called passage zones and define the high stands of englacial lakes. The depth and volume of water in these ephemeral lakes, in turn, gives researchers an accurate measure of the minimum palaeo-ice thicknesses at the time of eruption.

“At Kima’Kho, we were able to map a passage zone in pyroclastic deposits left by the earliest explosive phase of eruption, allowing for more accurate forensic recovery of paleo-lake levels through time and better estimates of paleo-ice thicknesses,” says UBC volcanologist James K Russell, lead author on the paper published this week in Nature Communications.

“Applying the same technique to other subglacial volcanos will provide new constraints on paleoclimate models that consider the extents and timing of planetary glaciations.”

While relatively rare globally, tuyas are common throughout Iceland, British Columbia, Oregon, and beneath the Antarctic ice-sheets. Kima’Kho tuya forms a high relief structure covering 28 square kilometres rising 1,946 metres above sea level on the Kawdy Plateau near Dease Lake. The plateau hosts six other tuyas.

“We hope our discovery encourages more researchers to seek out pyroclastic passage zones,” says Lucy Porritt, a Marie Curie Research Fellow at UBC and University of Bristol. “With more detailed mapping of glaciovolcanic sequences, and the recognition of the importance of these often abrupt changes in depositional environment, our understanding of glaciovolcanic eruptions and the hazards they pose can only be advanced.”

Note : The above story is reprinted from materials provided by University of British Columbia, via EurekAlert!, a service of AAAS. 

Dinosaur Predecessors Gain Ground in Wake of World’s Biggest Biodiversity Crisis

Ten million years after the mass extinction, members of the archosaur reptiles — such as the 10-foot (3 meter) long Asilisaurus pictured — had more restricted geographic ranges compared to the communities of four-legged animals that existed before the extinction. (Credit: Marlene Donnelly/Field Museum of Natural History)

Many scientists have thought that dinosaur predecessors missed the race to fill habitats emptied when nine out of 10 species disappeared during Earth’s largest mass extinction, approximately 252 million years ago. The thinking was based on fossil records from sites in South Africa and southwest Russia.

It turns out that scientists may have been looking for the starting line in the wrong places.

Newly discovered fossils from 10 million years after the mass extinction reveal a lineage of animals thought to have led to dinosaurs taking hold in Tanzania and Zambia in the mid-Triassic period, many millions of years before dinosaur relatives were seen in the fossil record elsewhere on Earth.

“The fossil record from the Karoo of South Africa remains a good representation of four-legged land animals across southern Pangea before the extinction event. But after the event animals weren’t as uniformly and widely distributed as before. We had to go looking in some fairly unorthodox places,” said Christian Sidor, University of Washington professor of biology. He’s lead author of a paper appearing the week of April 29 in the early edition of the Proceedings of the National Academy of Sciences.

The new insights come from seven fossil-hunting expeditions since 2003 in Tanzania, Zambia and Antarctica, funded by the National Geographic Society and National Science Foundation, along with work combing through existing fossil collections. The researchers created two “snapshots” of four legged-animals about 5 million years before and again about 10 million years after the extinction event at the end of the Permian period.

Prior to the extinction event, for example, the pig-sized Dicynodon — said to resemble a fat lizard with a short tail and turtle’s head — was a dominant plant-eating species across southern Pangea. Pangea is the name given to the landmass when all the world’s continents were joined together. Southern Pangea was made up of what is today Africa, South America, Antarctica, Australia and India. After the mass extinction at the end of the Permian, Dicynodon disappeared and other related species were so greatly decreased that newly emerging herbivores could suddenly compete with them.

“Groups that did well before the extinction didn’t necessarily do well afterward,” Sidor said. “What we call evolutionary incumbency was fundamentally reset.”

The snapshot 10 million years after the extinction event reveals, among other things, that archosaurs were in Tanzanian and Zambian basins, but not distributed across all of southern Pangea as had been the pattern for four-legged animals prior to the extinction. Archosaurs are the group of reptiles that includes crocodiles, dinosaurs, birds and a variety of extinct forms. They are of interest because it is thought they led to animals like Asilisaurus, a dinosaur-like animal, and Nyasasaurus parringtoni, a dog-sized creature with a five-foot tail that scientists in December 2012 announced could be the earliest dinosaur, or else the closest relative found so far.

“Early archosaurs being found mainly in Tanzania is an example of how fragmented communities became after the extinction event,” Sidor said. And the co-authors write: “These findings suggest that . . . archosaur diversification was more intimately related to recovery from the end-Permian mass extinction than previously suspected.”

A new framework for analyzing biogeographic patterns from species distributions, developed by co-author Daril Vilhena, a UW biology graduate student, provided a way to discern the complex recovery, Sidor said.

It revealed that before the extinction event 35 percent of four-legged species were found in two or more of the five areas studied, with some species having ranges that stretched 1,600 miles (2,600 kilometers), encompassing the Tanzanian and South African basins. Ten million years after the extinction event, the authors say there was clear geographic clustering and just 7 percent of species were found in two or more regions.

The techniques — new ways to statistically consider how connected or isolated species are from each other — could be useful for other paleontologists and modern day biogeographers, Sidor said.

In the early 2000s Sidor and some of his co-authors started putting together expeditions to collect fossils from sites in Tanzania that hadn’t been visited since the 1960s and in Zambia where there’d been little work since the ’80s. Two expeditions to Antarctica provided additional materials, as did long-term efforts to examine museum-held fossils that had not been fully documented or named

Other co-authors from the UW are graduate students Adam Huttenlocker and Brandon Peecook, post-doctoral researcher Sterling Nesbitt and research associate Linda Tsuji; Kenneth Angielczyk of the Field Museum of Natural History in Chicago; Roger Smith, of the Iziko South African Museum in Cape Town; and Sébastien Steyer from the National Museum of Natural History in Paris.

Funding was also received from the Evolving Earth Foundation, the Grainger Foundation, the Field Museum/IDP Inc. African Partners Program and the National Research Council of South Africa.

Note : The above story is reprinted from materials provided by University of Washington. The original article was written by Sandra Hines. 

Geoblock

Table of Contents

Introduction

The Geoblock program is integrated software for 2D/3D modeling, computational geometry and visualization of spatial datasets. The program can be used in Earth sciences particularly in such fields as survey, geology and mining modeling, ore reserve estimations and prediction of mineral liberation under grinding and mineral processing operations.

The contents of the Geoblock program are subject to the Mozilla Public License Version 1.1. This software delivers with open source codes as an integrated system for users and developers. You can use it free of charge for non-commercial use.  To order the full installation on CD with the latest stable version and additional documentation

Features

The program supports several spatial dataset types: Drillholes, Points, Polygons, TINs, Solids, Grids and Meshes. Combined datasets can be organized into project collections and displayed inside Map Window of the program as a combination of contours, wireframe or block models simultaneously.
The databases can be stored in various relational formats: Paradox, Interbase, MS Access and Oracle. Spatial data and graphical objects can be exported/imported to DXF (AutoCAD), MIF/MID (MapInfo), GRD (Surfer, ArcInfo) and other formats.

There are a set of routines for grid and mesh generation in 2D and 3D. For example procedures for exploration and processing drillhole data include: 

· Drillhole data analysis and data transformations.
· Compositing drillhole samples inside benches or horizons
· Calculation of sample XYZ coordinates in drillholes and exploration lines
· Mineral liberation and prediction of ore dressing parameters

Interpolation:

· Inverse Distance
· Linear by TINs
· Closest Point

As optional features there are next methods of interpolation:

· Kriging
· Natural Neighbors
· Polynomial Regression

Several spatial models can be visualized simultaneously in Map window using project manager. Constructed grids and block models could be used for open pit optimization and mine planning. Deposit reserves for any ore type or sort can be calculated with different methods using spatial computer models.

  
More Info : Sourceforge 

Fish Was On the Menu for Early Flying Dinosaur

New research reveals that Microraptor, a small flying dinosaur, was a complete hunter — able to swoop down and pick up fish. (Credit: Image courtesy of University of Alberta)

University of Alberta-led research reveals that Microraptor, a small flying dinosaur was a complete hunter, able to swoop down and pickup fish as well as its previously known prey of birds and tree dwelling mammals.U of A paleontology graduate student Scott Persons says new evidence of Microrpator’s hunting ability came from fossilized remains in China. “We were very fortunate that this Microraptor was found in volcanic ash and its stomach content of fish was easily identified.”

Prior to this, paleontologists believed microraptors which were about the size of a modern day hawk, lived in trees where they preyed exclusively on small birds and mammals about the size of squirrels.

“Now we know that Microraptor operated in varied terrain and had a varied diet,” said Persons. “It took advantage of a variety of prey in the wet, forested environment that was China during the early Cretaceous period, 120 million years ago.”

Further analysis of the fossil revealed that its teeth were adapted to catching slippery, wiggling prey like fish. Dinosaur researchers have established that most meat eaters had teeth with serrations on both sides which like a steak knife helped the predator saw through meat.

But the Microraptor’s teeth are serrated on just one side and its teeth are angled forwards.

“Microraptor seems adapted to impale fish on its teeth. With reduced serrations the prey wouldn’t tear itself apart while it struggled,” said Persons. “Microraptor could simply raise its head back, the fish would slip off the teeth and be swallowed whole, no fuss no muss.”

Persons likens the Microraptor’s wing configuration to a bi-plane. “It had long feathers on its forearms, hind legs and tail,” said Persons. “It was capable of short, controlled flights.”

This is the first evidence of a flying raptor, a member of the Dromaeosaur family of dinosaurs to successfully prey on fish.

Note : The above story is reprinted from materials provided by University of Alberta, via EurekAlert!, a service of AAAS.

Earth’s Center Is 1,000 Degrees Hotter Than Previously Thought

This artist’s view depicts the different layers of the Earth and their representative temperatures: crust, upper and lower mantle (brown to red), liquid outer core (orange) and solid inner core (yellow). The pressure at the border between the liquid and the solid core (highlighted) is 3.3 million atmospheres, with a temperature now confirmed as 6000 degrees Celsius. (Credit: ESRF)

Scientists have determined the temperature near the Earth’s centre to be 6000 degrees Celsius, 1000 degrees hotter than in a previous experiment run 20 years ago. These measurements confirm geophysical models that the temperature difference between the solid core and the mantle above, must be at least 1500 degrees to explain why the Earth has a magnetic field. The scientists were even able to establish why the earlier experiment had produced a lower temperature figure.The results are published on 26 April 2013 in Science.

The research team was led by Agnès Dewaele from the French national technological research organization CEA, alongside members of the French National Center for Scientific Research CNRS and the European Synchrotron Radiation Facility ESRF in Grenoble (France).

The Earth’s core consists mainly of a sphere of liquid iron at temperatures above 4000 degrees and pressures of more than 1.3 million atmospheres. Under these conditions, iron is as liquid as the water in the oceans. It is only at the very centre of the Earth, where pressure and temperature rise even higher, that the liquid iron solidifies. Analysis of earthquake-triggered seismic waves passing through the Earth, tells us the thickness of the solid and liquid cores, and even how the pressure in the Earth increases with depth. However these waves do not provide information on temperature, which has an important influence on the movement of material within the liquid core and the solid mantle above. Indeed the temperature difference between the mantle and the core is the main driver of large-scale thermal movements, which together with the Earth’s rotation, act like a dynamo generating the Earth’s magnetic field. The temperature profile through the Earth’s interior also underpins geophysical models that explain the creation and intense activity of hot-spot volcanoes like the Hawaiian Islands or La Réunion.

To generate an accurate picture of the temperature profile within the Earth’s centre, scientists can look at the melting point of iron at different pressures in the laboratory, using a diamond anvil cell to compress speck-sized samples to pressures of several million atmospheres, and powerful laser beams to heat them to 4000 or even 5000 degrees Celsius.”In practice, many experimental challenges have to be met,” explains Agnès Dewaele from CEA, “as the iron sample has to be insulated thermally and also must not be allowed to chemically react with its environment. Even if a sample reaches the extreme temperatures and pressures at the centre of the Earth, it will only do so for a matter of seconds. In this short timeframe it is extremely difficult to determine whether it has started to melt or is still solid.”

This is where X-rays come into play. “We have developed a new technique where an intense beam of X-rays from the synchrotron can probe a sample and deduce whether it is solid, liquid or partially molten within as little as a second, using a process known diffraction,” says Mohamed Mezouar from the ESRF, “and this is short enough to keep temperature and pressure constant, and at the same time avoid any chemical reactions.”

The scientists determined experimentally the melting point of iron up to 4800 degrees Celsius and 2.2 million atmospheres pressure, and then used an extrapolation method to determine that at 3.3 million atmospheres, the pressure at the border between liquid and solid core, the temperature would be 6000 +/- 500 degrees. This extrapolated value could slightly change if iron undergoes an unknown phase transition between the measured and the extrapolated values.

When the scientists scanned across the area of pressures and temperatures, they observed why Reinhard Boehler, then at the MPI for Chemistry in Mainz (Germany), had in 1993 published values about 1000 degrees lower. Starting at 2400 degrees, recrystallization effects appear on the surface of the iron samples, leading to dynamic changes of the solid iron’s crystalline structure. The experiment twenty years ago used an optical technique to determine whether the samples were solid or molten, and it is highly probable that the observation of recrystallization at the surface was interpreted as melting.

“We are of course very satisfied that our experiment validated today’s best theories on heat transfer from the Earth’s core and the generation of the Earth’s magnetic field. I am hopeful that in the not-so-distant future, we can reproduce in our laboratories, and investigate with synchrotron X-rays, every state of matter inside the Earth,” concludes Agnès Dewaele.

Note : The above story is reprinted from materials provided by European Synchrotron Radiation Facility. 

Stromatolites

Stromatolites growing in Hamelin Pool Marine Nature Reserve, Shark Bay in Western Australia. Credit: Paul Harrison

What are Stromatolites?

Stromatolites or stromatoliths are layered accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains by biofilms of microorganisms, especially cyanobacteria (commonly known as blue-green algae). Stromatolites provide some of the most ancient records of life on Earth by fossil remains which date back more than 3.5 billion years ago.

Morphology

A variety of stromatolite morphologies exist including conical, stratiform, branching, domal, and columnar

types. Stromatolites occur widely in the fossil record of the Precambrian, but are rare today. Very few ancient stromatolites contain fossilized microbes. While features of some stromatolites are suggestive of biological activity, others possess features that are more consistent with abiotic (non-organic) precipitation. Finding reliable ways to distinguish between biologically formed and abiotic (non-biological) stromatolites is an active area of research in geology.

Fossil record

Stromatolites were much more abundant on the planet in Precambrian times. While older, Archean fossil

remains are presumed to be colonies of cyanobacteria, younger (that is, Proterozoic) fossils may be primordial forms of the eukaryote chlorophytes (that is, green algae). One genus of stromatolite very common in the geologic record is Collenia. The earliest stromatolite of confirmed microbial origin dates to 2.724 billion years ago. A 2009 discovery provides strong evidence of microbial stromatolites extending as far back as 3.450 billion years ago.

Stromatolites are a major constituent of the fossil record for about the first 3.5 billion years of life on earth, peaking about 1.25 billion years ago. They subsequently declined in abundance and diversity, which by the start of the Cambrian had fallen to 20% of their peak. The most widely supported explanation is that stromatolite builders fell victims to grazing creatures (the Cambrian substrate revolution), implying that sufficiently complex organisms were common over 1 billion years ago.

Stromatolites in the Hoyt Limestone (Cambrian) exposed at Lester Park, near Saratoga Springs, New York.

The connection between grazer and stromatolite abundance is well documented in the younger Ordovician evolutionary radiation; stromatolite abundance also increased after the end-Ordovician and end-Permian extinctions decimated marine animals, falling back to earlier levels as marine animals recovered. Fluctuations in metazoan population and diversity may not have been the only factor in the reduction in stromatolite abundance. Factors such as the chemistry of the environment may have been responsible for changes.

While prokaryotic cyanobacteria themselves reproduce asexually through cell division, they were instrumental in priming the environment for the evolutionary development of more complex eukaryotic organisms. Cyanobacteria (as well as extremophile Gammaproteobacteria) are thought to be largely responsible for increasing the amount of oxygen in the primeval earth’s atmosphere through their continuing photosynthesis. Cyanobacteria use water, carbon dioxide, and sunlight to create their food. A layer of mucus often forms over mats of cyanobacterial cells. In modern microbial mats, debris from the surrounding habitat can become trapped within the mucus, which can be cemented together by the calcium carbonate to grow thin laminations of limestone. These laminations can accrete over time, resulting in the banded pattern common to stromatolites. The domal morphology of biological stromatolites is the result of the vertical growth necessary for the continued infiltration of sunlight to the organisms for photosynthesis. Layered spherical growth structures termed oncolites are similar to stromatolites and are also known from the fossil record. Thrombolites are poorly laminated or non-laminated clotted structures formed by cyanobacteria common in the fossil record and in modern sediments.

The Zebra River Canyon area of the Kubis platform in the deeply dissected Zaris Mountains of south western Namibia provides an extremely well exposed example of the thrombolite-stromatolite-metazoan reefs that developed during the Proterozoic period, the stromatolites here being better developed in updip locations under conditions of higher current velocities and greater sediment influx.

Modern occurrence

Modern stromatolites are mostly found in hypersaline lakes and marine lagoons where extreme conditions due to high saline levels exclude animal grazing. One such location is Hamelin Pool Marine Nature Reserve, Shark Bay in Western Australia where excellent specimens are observed today, and another is Lagoa Salgada, state of Rio Grande do Norte, Brazil, where modern stromatolites can be observed as bioherm

Stromatolites at Lake Thetis, Western Australia

(domal type) and beds. Inland stromatolites can also be found in saline waters in Cuatro Ciénegas, a unique ecosystem in the Mexican desert, and in Lake Alchichica, a maar lake in Mexico’s Oriental Basin. The only open marine environment where modern stromatolites are known to prosper is the Exuma Cays in the Bahamas.

Very recently, the fifth Chlorophyll: Chlorophyll f was discovered by Dr. Min Chen from stromatolites in Shark Bay.

Modern freshwater stromatolites

 Laguna Bacalar in Mexico’s southern Yucatán Peninsula in the state of Quintana Roo, has an extensive formation of living giant microbialites (that is, stromatolites or thrombolites). The microbialite bed is over 10 km (6.2 mi) long with a vertical rise of several meters in some areas. These may be the largest sized living freshwater microbialites, or any organism, on Earth.

A little further to the south, a 1.5 km stretch of reef-forming stromatolites (primarily of the Scytonema genus)

Microbialite towers at Pavilion Lake, British Columbia

occurs in Chetumal Bay in Belize, just south of the mouth of the Rio Hondo and the Mexican border.

Freshwater stromatolites are found in Lake Salda in southern Turkey. The waters are rich in magnesium and the stromatolite structures are made of hydromagnesite.

Another pair of instances of freshwater stromatolites are at Pavilion and Kelly Lakes in British Columbia, Canada. Pavilion Lake has the largest known freshwater stromatolites and has been researched by NASA as part of xenobiology research. NASA, the Canadian Space Agency and numerous universities from around the world are collaborating on a project centered around studying microbialite life in the lakes. Called the “Pavilion Lake Research Project” (PLRP) its aim is to study what conditions on the lakes’ bottoms are most likely to harbor life and develop a better hypothesis on how environmental factors effect microbiolite life. The end goal of the project is to better understand what condition would be more likely to harbor life on other planets. There is a citizen science project online called “MAPPER” where anyone can help sort through thousands of photos of the lake bottoms and tag microbiolites, algae and other lake bed features.

Microbialites have been discovered in an open pit pond at an abandoned asbestos mine near Clinton Creek, Yukon, Canada. These microbialites are extremely young and presumably began forming soon after the mine closed in 1978. The combination of a low sedimentation rate, high calcification rate, and low microbial growth rate appears to result in the formation of these microbialites. Microbialites at an historic mine site demonstrates that an anthropogenically constructed environment can foster microbial carbonate formation. This has implications for creating artificial environments for building modern microbialites including stromatolites.

A very rare type of non-lake dwelling stromatolite lives in the Nettle Cave at Jenolan Caves, NSW, Australia. The cyanobacteria live on the surface of the limestone, and are sustained by the calcium rich dripping water, which allows them to grow toward the two open ends of the cave which provide light.

Note:  The above story is reprinted from materials provided by Wikipedia

Ancient Earth Crust Stored in Deep Mantle

New research demonstrates that oceanic volcanic rocks contain samples of recycled crust dating back to the Archean era 2.5 billion years ago. Credit: © KristijanZontar / Fotolia

Scientists have long believed that lava erupted from certain oceanic volcanoes contains materials from the early Earth’s crust. But decisive evidence for this phenomenon has proven elusive. New research from a team including Carnegie’s Erik Hauri demonstrates that oceanic volcanic rocks contain samples of recycled crust dating back to the Archean era 2.5 billion years ago. Their work is published in Nature.

Oceanic crust sinks into Earth’s mantle at so-called subduction zones, where two plates come together. Much of what happens to the crust during this journey is unknown. Model-dependent studies for how long subducted material can exist in the mantle are uncertain and evidence of very old crust returning to Earth’s surface via upwellings of magma has not been found until now.

The research team studied volcanic rocks from the island of Mangaia in Polynesia’s Cook Islands that contain iron sulfide inclusions within crystals. In-depth analysis of the chemical makeup of these samples yielded interesting results.

The research focused on isotopes of the element sulfur. (Isotopes are atoms of the same element with different numbers of neutrons.) The measurements, conducted by graduate student Rita Cabral, looked at three of the four naturally occurring isotopes of sulfur–isotopic masses 32, 33, and 34. The sulfur-33 isotopes showed evidence of a chemical interaction with UV radiation that stopped occurring in Earth’s atmosphere about 2.45 billion years ago. It stopped after the Great Oxidation Event, a point in time when Earth’s atmospheric oxygen levels skyrocketed as a consequence of oxygen-producing photosynthetic microbes. Prior to the Great Oxidation Event, the atmosphere lacked ozone. But once ozone was introduced, it started to absorb UV and shut down the process.

This indicates that the sulfur comes from a deep mantle reservoir containing crustal material subducted before the Great Oxidation Event and preserved for over half the age of Earth.

“These measurements place the first firm age estimates of recycled material in oceanic hotspots,” Hauri said. “They confirm the cycling of sulfur from the atmosphere and oceans into mantle and ultimately back to the surface,” Hauri said.

Note:  The above story is reprinted from materials provided by Carnegie Institution.

Ice Tubes in Polar Seas “Brinicles” or “Sea Stalactites” Provide Clues to Origin of Life

Life on Earth may have originated not in warm tropical seas, but with weird tubes of ice — sometimes called “sea stalactites” — that grow downward into cold seawater near the Earth’s poles. (Credit: Rob Robbins; image archived by EarthRef.org)

Life on Earth may have originated not in warm tropical seas, but with weird tubes of ice — sometimes called “sea stalactites” — that grow downward into cold seawater near Earth’s poles, scientists are reporting. Their article on these “brinicles” appears in ACS’ journal Langmuir.Bruno Escribano and colleagues explain that scientists know surprisingly little about brinicles, which are hollow tubes of ice that can grow to several yards in length around streamers of cold seawater under pack ice. That’s because brinicles are difficult to study. The scientists set out to gather more information on the topic with an analysis of the growth process of brinicles.

They are shown to be analogous to a “chemical garden,” a standby demonstration in chemistry classes and children’s chemistry sets, in which tubes grow upward from metal salts dropped into silicate solution. But brinicles grow downward from the bottom of the ice pack.

The analysis concluded that brinicles provide an environment that could well have fostered the emergence of life on Earth billions of years ago, and could have done so on other planets. “Beyond Earth, the brinicle formation mechanism may be important in the context of planets and moons with ice-covered oceans,” the report states, citing in particular two moons of Jupiter named Ganymede and Callisto.

Note: The above story is reprinted from materials provided by American Chemical Society. 

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