The inner inner core of the Earth: Texturing of iron crystals from three-dimensional seismic anisotropy. 2008. X. Sun and X. Song. Earth and Planetary Science Letters. Available online 19 February, 2008.
From the press release:
Scientists have confirmed the discovery of Earth’s inner, innermost core, and have created a three-dimensional model that describes the seismic anisotropy and texturing of iron crystals within the inner core.
Using both newly acquired data and legacy data collected around the world, Song and postdoctoral research associate Xinlei Sun painstakingly probed the shape of Earth’s core.
Composed mainly of iron, Earth’s core consists of a solid inner core about 2,400 kilometers in diameter and a fluid outer core about 7,000 kilometers in diameter. The inner core plays an important role in the geodynamo that generates Earth’s magnetic field.
The solid inner core is elastically anisotropic; that is, seismic waves have different speeds along different directions. The anisotropy has been found to change with hemisphere and with radius. What they found was a distinct change in the inner core anisotropy, clearly marking the presence of an inner inner core with a diameter of about 1,180 kilometers, slightly less than half the diameter of the inner core.
The layering of the core is interpreted as different texturing, or crystalline phase, of iron in the inner core, the researchers say.
Monday, March 10, 2008
Thomas Jefferson on Megaloynx
From Today In Science History:
On this day in 1797, Thomas Jefferson (1743-1826) presented a paper on Megalonyx to the American Philosophical Society. It was published as "A Memoir on the Discovery of Certain Bones of a Quadruped of the Clawed Kind in the Western Parts of Virginia,"
Transactions of American Philosophical Society 4:255-256, along with an account by Caspar Wistar (1761-1818). In 1822, this huge extinct sloth was named Megalonyx jeffersoni by a French naturalist.
The species name Megalonyx is derived from the Greek language and refers to the large claw on the third digit of each of the sloths hind feet. It was a bear-sized ground sloth, over 2 meters tall, widespread in North America during the last Ice Age. Image from HERE
On this day in 1797, Thomas Jefferson (1743-1826) presented a paper on Megalonyx to the American Philosophical Society. It was published as "A Memoir on the Discovery of Certain Bones of a Quadruped of the Clawed Kind in the Western Parts of Virginia,"
Transactions of American Philosophical Society 4:255-256, along with an account by Caspar Wistar (1761-1818). In 1822, this huge extinct sloth was named Megalonyx jeffersoni by a French naturalist. The species name Megalonyx is derived from the Greek language and refers to the large claw on the third digit of each of the sloths hind feet. It was a bear-sized ground sloth, over 2 meters tall, widespread in North America during the last Ice Age. Image from HERE
Sunday, March 09, 2008
Ancient Bats from Cairo
Ancient bat god from Egypt.
Six new species of ancient bat dating back 35 million years have been discovered in Egypt, researchers say will be described in an upcoming issue of the Journal of Vertebrate Paleontology.
The new species were found by experts who analyzed 33 fossils—including teeth and jawbones—that had been unearthed over a period of decades in El Faiyum, an oasis region 50 miles southwest of Cairo.
Illustration by Bonnie Miljour
The experts were also surprised to find that the new species were similar to some modern-day microbats, a group of bats that uses sonar waves to navigate and hunt in a process called echolocation.From the 33 fragments, experts determined that at least six distinct species could be parsed out.
(Nothing beats parsing data!)
Died This Day: Mary Anning
From Today in Science History:
Mary Anning (May, 21 1799 - March 9, 1847)
English fossil collector who made her first significant discovery at the age of 11 or 12 (sources differ on the details), when she found a complete skeleton of an Ichthyosaurus, from the Jurassic period. The ten-meter (30 feet) long skeleton created a sensation and made her famous. Anning's determination and keen scientific interest in fossils derived from her father's interest in fossil hunting, and a need for the income derived from them to support her family after his death in 1810.
She sold large fossils to noted paleontologists of the day, and smaller ones to the tourist trade. In 1823, Anning made another great discovery, found the first complete Plesiosaurus. Later in her life, the Geological Society of London granted Anning an honorary membership.
Mary Anning (May, 21 1799 - March 9, 1847)
English fossil collector who made her first significant discovery at the age of 11 or 12 (sources differ on the details), when she found a complete skeleton of an Ichthyosaurus, from the Jurassic period. The ten-meter (30 feet) long skeleton created a sensation and made her famous. Anning's determination and keen scientific interest in fossils derived from her father's interest in fossil hunting, and a need for the income derived from them to support her family after his death in 1810. She sold large fossils to noted paleontologists of the day, and smaller ones to the tourist trade. In 1823, Anning made another great discovery, found the first complete Plesiosaurus. Later in her life, the Geological Society of London granted Anning an honorary membership.
Friday, March 07, 2008
The Amazing Missing Links
CLICK TO ENLARGE
Born This Day: Stanley Lloyd Miller
From Today in Science History:
Miller (b.1930) is an American chemist who made a series of
famous experiments beginning in 1953, to determine the possible origin of life from inorganic chemicals on the primeval earth. He passed electrical discharges (simulating thunderstorms) through mixtures of reducing gases, such as hydrogen, ammonia, methane and water, 
that were believed to have formed the earliest atmosphere.
An analysis days later showed that the resulting chemicals included glycine and alanine, the simplest amino acids & the basic building blocks of proteins. Other compounds included urea, aldehydes and carboxylic acids. Thus, a "primeval soup" is the currently accepted most plausible explanation, though incomplete, of the origin of the complex organic molecules of life.
Miller (b.1930) is an American chemist who made a series of
famous experiments beginning in 1953, to determine the possible origin of life from inorganic chemicals on the primeval earth. He passed electrical discharges (simulating thunderstorms) through mixtures of reducing gases, such as hydrogen, ammonia, methane and water, 
that were believed to have formed the earliest atmosphere. An analysis days later showed that the resulting chemicals included glycine and alanine, the simplest amino acids & the basic building blocks of proteins. Other compounds included urea, aldehydes and carboxylic acids. Thus, a "primeval soup" is the currently accepted most plausible explanation, though incomplete, of the origin of the complex organic molecules of life.
Thursday, March 06, 2008
New Light on The Tree of Life
Broad phylogenomic sampling improves resolution of the animal tree of life. 2008. C. W. Dunn et al. Nature, early
on-line publication.
From the press release:
The most comprehensive animal phylogenomic research project to date, involving 40 million base pairs of new DNA data taken from 29 animal species, settles some long-standing debates about the relationships between major groups of animals and offers up a few surprises.
The big shocker: Comb jellyfish – common and extremely fragile jellies with well-developed tissues – appear to have diverged from other animals even before the lowly sponge, which has no tissue to speak of. This finding calls into question the very root of the animal tree of life, which traditionally placed sponges at the base.
“This finding suggests either that comb jellies evolved their complexity independently from other animals, or that sponges have become greatly simplified through the course of evolution. If corroborated by other types of evidence, this would significantly change the way we think about the earliest multicellular animals,” said Dunn.
Charles Darwin introduced the idea of a “tree of life” in his seminal book Origin of Species. A sketch of the tree was the book’s only illustration. Nearly 150 years after its publication, many relationships between animal groups are still unclear. While enormous strides have been made in genomics, offering up a species’ entire genome for comparison, there are millions of animal species on the planet. There simply isn’t the time to sequence all these genomes.
The research also:
•unambiguously confirmed certain animal relationships, including the existence of a group that includes invertebrates that shed their skin, such as arthropods and nematodes;
•convincingly resolved conflicting evidence surrounding other relationships, such as the close relationship of millipedes and centipedes to spiders rather than insects;
•established new animal relationships, such as the close ties between nemerteans, or ribbon worms, and brachiopods, or two-shelled invertebrates.
on-line publication.
From the press release:
The most comprehensive animal phylogenomic research project to date, involving 40 million base pairs of new DNA data taken from 29 animal species, settles some long-standing debates about the relationships between major groups of animals and offers up a few surprises.
The big shocker: Comb jellyfish – common and extremely fragile jellies with well-developed tissues – appear to have diverged from other animals even before the lowly sponge, which has no tissue to speak of. This finding calls into question the very root of the animal tree of life, which traditionally placed sponges at the base.
“This finding suggests either that comb jellies evolved their complexity independently from other animals, or that sponges have become greatly simplified through the course of evolution. If corroborated by other types of evidence, this would significantly change the way we think about the earliest multicellular animals,” said Dunn.
Charles Darwin introduced the idea of a “tree of life” in his seminal book Origin of Species. A sketch of the tree was the book’s only illustration. Nearly 150 years after its publication, many relationships between animal groups are still unclear. While enormous strides have been made in genomics, offering up a species’ entire genome for comparison, there are millions of animal species on the planet. There simply isn’t the time to sequence all these genomes.
The research also:
•unambiguously confirmed certain animal relationships, including the existence of a group that includes invertebrates that shed their skin, such as arthropods and nematodes;
•convincingly resolved conflicting evidence surrounding other relationships, such as the close relationship of millipedes and centipedes to spiders rather than insects;
•established new animal relationships, such as the close ties between nemerteans, or ribbon worms, and brachiopods, or two-shelled invertebrates.
Tuesday, March 04, 2008
The Oldest North American Primate
The oldest North American primate and mammalian biogeography during the Paleocene–Eocene Thermal Maximum. 2008. K. C. Beard. PNAS, published online on March 3, 2008.
Teilhardina magnoliana image courtesy of PNAS/National Academy of Sciences
Consistent with its antiquity, a phylogenetic analysis of dental characters recognizes Teilhardina magnoliana, sp. nov., as the most basal member of this genus currently known from either North America or Europe. Its stratigraphic provenance demonstrates that primates originally colonized North America near the base of the Paleocene–Eocene Thermal Maximum (PETM), but before an important fall in eustatic sea level. Correlation based on carbon isotope stratigraphy and sequence stratigraphy indicates that the earliest North American primates inhabited coastal regions of the continent for thousands of years before they were able to colonize the Rocky Mountain Interior.
The transient provincialism displayed by early North American primates corresponds to similar biogeographic patterns noted among fossil plants. Decreased precipitation in the Rocky Mountain Interior during the early part of the PETM may have been an important factor in maintaining biotic provincialism within North America at this time. These results underscore the need to obtain multiple, geographically dispersed records bearing on significant macroevolutionary events such as the PETM.
The tiny, 55-million-year-old creature raises the controversial possibility that primates arrived in the Americas thousands of years before they reached EuropeAbstract: Undoubted primates first appear almost synchronously in the fossil records of Asia, Europe, and North America. This temporal pattern has complicated efforts to reconstruct the early dispersal history of primates in relation to global climate change and eustatic fluctuations in sea level. Here, I describe fossils from the Tuscahoma Formation on the Gulf Coastal Plain of Mississippi documenting an anatomically primitive species of Teilhardina that is older than other North American and European primates.
Teilhardina magnoliana image courtesy of PNAS/National Academy of Sciences
Consistent with its antiquity, a phylogenetic analysis of dental characters recognizes Teilhardina magnoliana, sp. nov., as the most basal member of this genus currently known from either North America or Europe. Its stratigraphic provenance demonstrates that primates originally colonized North America near the base of the Paleocene–Eocene Thermal Maximum (PETM), but before an important fall in eustatic sea level. Correlation based on carbon isotope stratigraphy and sequence stratigraphy indicates that the earliest North American primates inhabited coastal regions of the continent for thousands of years before they were able to colonize the Rocky Mountain Interior.
The transient provincialism displayed by early North American primates corresponds to similar biogeographic patterns noted among fossil plants. Decreased precipitation in the Rocky Mountain Interior during the early part of the PETM may have been an important factor in maintaining biotic provincialism within North America at this time. These results underscore the need to obtain multiple, geographically dispersed records bearing on significant macroevolutionary events such as the PETM.
Sunday, March 02, 2008
75 Years Ago Today King Kong Was Unleashed On NYC
The movie King Kong was one of the most successful films released in 1933. It went on to inspire many young fans (both in its initial release, numerous re-releases, and on television) to take up the professions of either film-making or paleontology. The field of dinosaur paleobiology would be very different today if King Kong had never met Fay Wray on Skull Island "way west of Sumatra" and been taken to the concrete jungle of New York.
In a remarkable coincidence the artist, Willis O'Brien, who created and brought Kong to life, celebrated his 47th birthday on the day the movie debuted in New York City.
Thanks to Tim Cole for the head's up on this date.
Born This Day: Father of King Kong
A tip of the fedora to the late, great Willis O'Brien who breathed life into the fur and armature that become King Kong, the Seventh Wonder of the World!
His biography from Leonard Maltin's Movie Encyclopedia:
Willis O'Brien (March 2, 1886 - November 8, 1962)
In 1950 O'Brien received (finally!) a special Oscar for his work on Mighty Joe Young which was the first such award ever given for special effects. This film also launched the career of the next great stop-motion animator, Ray Harryhausen.
His biography from Leonard Maltin's Movie Encyclopedia:
Willis O'Brien (March 2, 1886 - November 8, 1962)
Special effects wizard best known to the world as the man who
created King Kong. O'Brien was a sculptor and cartoonist for the San Francisco "Daily News" before he first dabbled in the medium of film during the 'teens. His work caught the attention of the Edison company, for whom he produced several short subjects with a prehistoric them. Titles include The Dinosaur and the Missing Link, RFD 10,000 B.C and Prehistoric Poultry. His method of animating small rubber figures, carefully molded over metal skeletons with movable joints, by moving them a fraction of an inch for each frame of film exposed, became the standard process of live-action animation.
In 1918 he made his most ambitious film yet, The Ghost of Slumber Mountain paving the way for The Lost World (1925), a major Hollywood feature which told of a search for prehistoric creatures. O'Brien's dinosaurs were his most realistic yet, and still impress today, even in the wake of Jurassic Park Still, Obie (as he was known) kept experimenting.When producer Merian C. Cooper saw his work, he hired O'Brien to animate King Kong (which, up to that point, was to have been shot with an actor in a gorilla suit). The extraordinary success of King Kong (1933) spawned an immediate sequel, The Son of Kong (also 1933), and made O'Brien a hero to several generations of fantasy filmmakers to come. O'Brien won his only Oscar for his effects in Mighty Joe Young (1949), another giant-monkey movie, on which his protégé (and successor) Ray Harryhausen worked.
O'Brien worked on other giant-monster movies (including 1957's The Black Scorpion his last) before dying in 1962. Today, O'Brien would be kingpin of his own studio, but even in the wake of King Kong he had trouble launching other film projects, and many promising ideas languished on studio drawing boards for decades to follow. One of the RKO staff with whom he'd worked in the 1930s, Linwood Dunn, gave O'Brien his final employment, doing stop-motion figures for It's a Mad Mad Mad Mad World (1963).
In 1950 O'Brien received (finally!) a special Oscar for his work on Mighty Joe Young which was the first such award ever given for special effects. This film also launched the career of the next great stop-motion animator, Ray Harryhausen.
Saturday, March 01, 2008
Rapid Evolution in Tuatara
Rapid molecular evolution in a living fossil. 2008. J. M. Hay et al. Trends in Genetics 24: 106-109.
From the press release:
In a study of New Zealand’s “living dinosaur” the tuatara has recovered DNA sequences from the bones of ancient tuatara up to 8000 years old. They found that although tuatara, have remained largely physically unchanged over very long periods of evolution, they are evolving - at a DNA level - faster than any other animal yet examined.
The tuatara, Sphendon punctatus, is found only in New Zealand and is the only surviving member of a distinct reptilian order, Sphehodontia, that lived alongside early dinosaurs and separated from other reptiles 200 million years ago in the Upper Triassic period.
“What we found is that the tuatara has the highest molecular evolutionary rate that anyone has measured,” Professor Lambert says.
“Of course we would have expected that the tuatara, which does everything slowly – they grow slowly, reproduce slowly and have a very slow metabolism – would have evolved slowly. In fact, at the DNA level, they evolve extremely quickly, which supports a hypothesis proposed by the evolutionary biologist Allan Wilson, who suggested that the rate of molecular evolution was uncoupled from the rate of morphological evolution.”
“We want to go on and measure the rate of molecular evolution for humans, as well as doing more work with moa and Antarctic fish, to see if rates of DNA change are uncoupled in these species. There are human mummies in the Andes and some very good samples in Siberia where we have some collaborators, so we are hopeful we will be able to measure the rate of human evolution in these too.”
In a study of New Zealand’s “living dinosaur” the tuatara has recovered DNA sequences from the bones of ancient tuatara up to 8000 years old. They found that although tuatara, have remained largely physically unchanged over very long periods of evolution, they are evolving - at a DNA level - faster than any other animal yet examined.
The tuatara, Sphendon punctatus, is found only in New Zealand and is the only surviving member of a distinct reptilian order, Sphehodontia, that lived alongside early dinosaurs and separated from other reptiles 200 million years ago in the Upper Triassic period.
“What we found is that the tuatara has the highest molecular evolutionary rate that anyone has measured,” Professor Lambert says.
“We want to go on and measure the rate of molecular evolution for humans, as well as doing more work with moa and Antarctic fish, to see if rates of DNA change are uncoupled in these species. There are human mummies in the Andes and some very good samples in Siberia where we have some collaborators, so we are hopeful we will be able to measure the rate of human evolution in these too.”
Friday, February 29, 2008
The Early Evolution of Feathers
The early evolution of feathers: fossil evidence from Cretaceous amber of France. 2008. Vincent Perrichot et al. Proceedings of the Royal Society B. Tuesday, February 19, 2008.
Art © Luis Rey
Abstract: The developmental stages of feathers are of major importance in the evolution of body covering and the origin of avian flight. Until now, there were significant gaps in knowledge of early morphologies in theoretical stages of feathers as well as in palaeontological material. Here we report fossil evidence of an intermediate and critical stage in the incremental evolution of feathers which has been predicted by developmental theories but hitherto undocumented by evidence from both the recent and the fossil records.
Seven feathers have been found in an Early Cretaceous (Late Albian, ca 100Myr) amber of western France, which display a flattened shaft composed by the still distinct and incompletely fused bases of the barbs forming two irregular vanes. Considering their remarkably primitive features, and since recent discoveries have yielded feathers of modern type in some derived theropod dinosaurs, the Albian feathers from France might have been derived either from an early bird or from a non-avian dinosaur.
Watch the animated three-dimensional virtual reconstruction of one fossil feather from Early Cretaceous French amber in phase contrast microtomography showing vanes resulting from the opposed but irregular insertion of barbs on the flattened rachis HERE.
Art © Luis Rey
Seven feathers have been found in an Early Cretaceous (Late Albian, ca 100Myr) amber of western France, which display a flattened shaft composed by the still distinct and incompletely fused bases of the barbs forming two irregular vanes. Considering their remarkably primitive features, and since recent discoveries have yielded feathers of modern type in some derived theropod dinosaurs, the Albian feathers from France might have been derived either from an early bird or from a non-avian dinosaur.
Watch the animated three-dimensional virtual reconstruction of one fossil feather from Early Cretaceous French amber in phase contrast microtomography showing vanes resulting from the opposed but irregular insertion of barbs on the flattened rachis HERE.
Duelity: Creationism/Darwinism
"Imagine the story of creation shown thru the cold lens of Science, and evolution told as a biblical tale. It’s a head-spinningly complex splitscreen experience and demands repeat viewing."
"Duelity is a split screen animation that tells both sides of the story of Earth's origins in a dizzying and provocative journey through the history and language that marks human thought." The film has been directed by Boca AKA Marcos Ceravolo and Ryan Uhrich, two students of the Vancouver Film School, and written by Lee Henderson. Sound design: James Boatman and Chris Ray. Voice over: Mariem Henaine and Rob Wood.
"If thou shalt believe the Book of Darwin, t'is billion years after the Big Bang that we behold what the cosmos hath begat: the magma, the terra firma, the creeping beasts and the mankind, whose dolorous and chaotic evolution begat the gift of consciousness."
"If thou shalt believe the Book of Darwin, t'is billion years after the Big Bang that we behold what the cosmos hath begat: the magma, the terra firma, the creeping beasts and the mankind, whose dolorous and chaotic evolution begat the gift of consciousness."
Watch Duelity: Darwinism
"According to the records of the General Organization of Development (GOD) it took a mere six days to manufacture a fully operational universe, complete with day, night, flora and fauna, and installing Adam as its manager to oversee daily functions on Earth."Watch Duelity: Creationism
Thanks to NoFatClips
Born This Day: Karl Ernst von Baer
Feb 29, 1792 - Nov 28, 1876
Von Baer was a Prussian-Estonian embryologist who discovered the mammalian egg (1827) and the notochord. He established the new science of comparative embryology alongside comparative anatomy with the publication of two landmark volumes (in 1828 and 1837) covering the range of existing knowledge of the prebirth developments of vertebrates.
He showed that mammalian eggs were not the follicles of the ovary but microscopic particles inside the follicles. He described the development of the embryo from layers of tissue, which he called germ layers, and demonstrated similarities in the embryos of different species of vertebrates.
From Today In Science History
Von Baer was a Prussian-Estonian embryologist who discovered the mammalian egg (1827) and the notochord. He established the new science of comparative embryology alongside comparative anatomy with the publication of two landmark volumes (in 1828 and 1837) covering the range of existing knowledge of the prebirth developments of vertebrates.
From Today In Science History
Thursday, February 28, 2008
Died This Day: Prof. Thurgood Elson
August 22, 1893 – February 28, 1973
Or at least the actor, Cecil Kellaway, who played him in “The Beast From 20,000 Fathoms” passed away this day in 1973.
For those of you who seen the film, Elson was the palaeontologist who went down in the diving bell looking for the beast, but who did not make it back up.
It’s from Atlas' Crazy #2, 1954 with artwork is by Joe Maneely, a great cartoonist who seemed to work almost exclusively for Atlas before his accidental death.
Or at least the actor, Cecil Kellaway, who played him in “The Beast From 20,000 Fathoms” passed away this day in 1973.
For those of you who seen the film, Elson was the palaeontologist who went down in the diving bell looking for the beast, but who did not make it back up.
CLICK TO ENLARGE
It’s from Atlas' Crazy #2, 1954 with artwork is by Joe Maneely, a great cartoonist who seemed to work almost exclusively for Atlas before his accidental death.
Tuesday, February 26, 2008
When Life Took Its First Breath
Pulsed oxidation and biological evolution in the Ediacaran Doushantuo Formation. 2008. K. A. McFadden et al. PNAS 105: 3197-3202 (the article is not up yet as of this posting)
To test the interaction between biological evolution and environmental change, an international team examined changes in the geochemistry and fossil distribution of 635- to 551-million-year old sediments preserved in the Doushantuo Formation in the Yangtze Gorges area of South China.
The stratigraphic pattern of carbon isotope abundances suggested to these researchers that the ocean, which largely lacked oxygen before animals arrived on the scene, was aerated by two discrete pulses of oxygen.
“The first pulse apparently had little impact on a large organic carbon reservoir in the deep ocean, but did spark changes in microscopic life forms,” McFadden said. The second event, which occurred around 550 million years ago, however, resulted in the reduction of the organic carbon reservoir, indicating that the ocean became fully oxidizing just before the evolution and diversification of many of Earth’s earliest animals,” she said.
Following this second oxidation event, between 550 and 542 million years ago, there was a worldwide increase of Ediacara organisms, complex macroscopic life forms, an event recently dubbed as the Avalon Explosion. “This was when we see the first burrowing animals and the first animals to form external skeletons, or shells.
The triggers for the oxidation events remain elusive, however. “These events recorded in the ocean were probably related to oxygen in the atmosphere reacting with sediments on land,” McFadden said. “Weathering of rocks and soils on the continents would result in the release of certain dissolved ions, such as sulfate, into rivers. These would then be transported to the sea where they might be used by bacteria to oxidize the organic carbon pool in the deep oceans,” she said.
The photo (field of view about 0.15 millimeter in width) is of an exceptionally preserved eukaryotic fossil from the Doushantuo Fm (635–551 million years old) in South China. Photo: Shuhai Xiao
From the press release:The rise of oxygen and the oxidation of deep oceans between 635 and 551 million years ago may have had an impact on the increase and spread of the earliest complex life, including animals.The atmosphere had almost no oxygen until 2.5 billion years ago, and it was not until about 600 million years ago when the atmospheric oxygen level rose to a fraction of modern levels. For a long time, geologists and evolutionary biologists have speculated that the rise of the breathing gas and subsequent oxygenation of the deep oceans are intimately tied to the evolution of modern biological systems.
To test the interaction between biological evolution and environmental change, an international team examined changes in the geochemistry and fossil distribution of 635- to 551-million-year old sediments preserved in the Doushantuo Formation in the Yangtze Gorges area of South China.
The stratigraphic pattern of carbon isotope abundances suggested to these researchers that the ocean, which largely lacked oxygen before animals arrived on the scene, was aerated by two discrete pulses of oxygen.
“The first pulse apparently had little impact on a large organic carbon reservoir in the deep ocean, but did spark changes in microscopic life forms,” McFadden said. The second event, which occurred around 550 million years ago, however, resulted in the reduction of the organic carbon reservoir, indicating that the ocean became fully oxidizing just before the evolution and diversification of many of Earth’s earliest animals,” she said.
Following this second oxidation event, between 550 and 542 million years ago, there was a worldwide increase of Ediacara organisms, complex macroscopic life forms, an event recently dubbed as the Avalon Explosion. “This was when we see the first burrowing animals and the first animals to form external skeletons, or shells.
The triggers for the oxidation events remain elusive, however. “These events recorded in the ocean were probably related to oxygen in the atmosphere reacting with sediments on land,” McFadden said. “Weathering of rocks and soils on the continents would result in the release of certain dissolved ions, such as sulfate, into rivers. These would then be transported to the sea where they might be used by bacteria to oxidize the organic carbon pool in the deep oceans,” she said.
Monday, February 25, 2008
The Organic Nature of Stromatolites
Microbially influenced formation of 2,724- million- year-old stromatolites. 2008. K. Lepot et al. Nature Geoscience 1: 118-121
Abstract: Laminated accretionary carbonate structures known as stromatolites are a prominent feature of the sedimentary record over the past 3,500 Myr. The macroscopic similarity to modern microbial structures has led to the inference that these structures represent evidence of ancient life. However, as Archaean stromatolites only rarely contain microfossils, the possibility of abiogenic origins has been raised.
Here, we present the results of nanoscale studies of the 2,724-Myr-old stromatolites from the Tumbiana Formation (Fortescue Group, Australia) showing organic globule clusters within the thin layers of the stromatolites. Aragonite nanocrystals are also closely associated with the organic globules, a combination that is remarkably similar to the organo-mineral building blocks of modern stromatolites. Our results support microbial mediation for the formation of the Tumbiana stromatolites, and extend the geologic record of primary aragonite by more than 2,300 Myr.
Abstract: Laminated accretionary carbonate structures known as stromatolites are a prominent feature of the sedimentary record over the past 3,500 Myr. The macroscopic similarity to modern microbial structures has led to the inference that these structures represent evidence of ancient life. However, as Archaean stromatolites only rarely contain microfossils, the possibility of abiogenic origins has been raised.
Here, we present the results of nanoscale studies of the 2,724-Myr-old stromatolites from the Tumbiana Formation (Fortescue Group, Australia) showing organic globule clusters within the thin layers of the stromatolites. Aragonite nanocrystals are also closely associated with the organic globules, a combination that is remarkably similar to the organo-mineral building blocks of modern stromatolites. Our results support microbial mediation for the formation of the Tumbiana stromatolites, and extend the geologic record of primary aragonite by more than 2,300 Myr.
When The Ice Levee Breaks
The subglacial origin of the Lake Agassiz–Ojibway final outburst flood. 2008. P. Lajeunesse and G. St-Onge. Nature Geoscience, published online 24 February.
From Physorg.com:
During the last ice age, the Laurentide Ice Sheet once covered most of Canada and parts of the northern United States with a frozen crust that in some places was three kilometres (two miles) thick. As the temperature gradually rose some 10,000 years ago, the ice receded, gouging out the hollows that would be called the Great Lakes.
Beneath the ice's thinning surface, an extraordinary mass of water built up -- the glacial lake Agassiz-Ojibway, a body so vast that it
covered parts of Manitoba, Saskatchewan, North Dakota, Ontario and Minnesota.
And then, around 8,200 years ago, Agassiz-Ojibway massively drained, sending a flow of water into the Hudson Strait and into the Labrador Sea that was 15 times greater than the present discharge of the Amazon River.
The influx of freshwater into the North Atlantic reduced ocean salinity so much that this braked the transport of heat flowing from the tropics to temperate regions. Temperatures dropped by more than three degrees Celsius in Western Europe for 200-400 years -- a mini-Ice Age in itself.
Abstarct: Deglaciation of North America resulted in the development of the ice-dammed lake Agassiz–Ojibway along the southern margin of the Laurentide Ice Sheet and its catastrophic northward drainage 8.47 kyr ago. This sudden outburst of fresh water may have weakened the Atlantic ocean overturning circulation and triggered the cold event that occurred 8.2 kyr ago.
Geological evidence of this flood has been documented in a red sedimentary bed in cores collected in Hudson Strait and by submarine features in Hudson Bay. However, there have been few constraints on the manner in which the lake drained: for example, by flow over the ice sheet or beneath it, in one or several pulses and where the flood routes were located.
Here we present seafloor images obtained using multibeam sonar, which reveal that the outburst flood displaced icebergs to produce arcuate (arc-shaped) scours on the seafloor with a dominant east-northeast–west-southwest orientation. The flood also produced sandwaves in areas unaffected by the arcuate scours, indicating they were protected from iceberg scouring by overlying ice during the event. We suggest that these sandwaves, along with submarine channels inferred from the data, indicate that Laurentide ice was lifted buoyantly, enabling the flood to traverse southern Hudson Bay under the ice sheet.
From Physorg.com:
During the last ice age, the Laurentide Ice Sheet once covered most of Canada and parts of the northern United States with a frozen crust that in some places was three kilometres (two miles) thick. As the temperature gradually rose some 10,000 years ago, the ice receded, gouging out the hollows that would be called the Great Lakes.
Beneath the ice's thinning surface, an extraordinary mass of water built up -- the glacial lake Agassiz-Ojibway, a body so vast that it
covered parts of Manitoba, Saskatchewan, North Dakota, Ontario and Minnesota. And then, around 8,200 years ago, Agassiz-Ojibway massively drained, sending a flow of water into the Hudson Strait and into the Labrador Sea that was 15 times greater than the present discharge of the Amazon River.
The influx of freshwater into the North Atlantic reduced ocean salinity so much that this braked the transport of heat flowing from the tropics to temperate regions. Temperatures dropped by more than three degrees Celsius in Western Europe for 200-400 years -- a mini-Ice Age in itself.
Abstarct: Deglaciation of North America resulted in the development of the ice-dammed lake Agassiz–Ojibway along the southern margin of the Laurentide Ice Sheet and its catastrophic northward drainage 8.47 kyr ago. This sudden outburst of fresh water may have weakened the Atlantic ocean overturning circulation and triggered the cold event that occurred 8.2 kyr ago.
Geological evidence of this flood has been documented in a red sedimentary bed in cores collected in Hudson Strait and by submarine features in Hudson Bay. However, there have been few constraints on the manner in which the lake drained: for example, by flow over the ice sheet or beneath it, in one or several pulses and where the flood routes were located.
Here we present seafloor images obtained using multibeam sonar, which reveal that the outburst flood displaced icebergs to produce arcuate (arc-shaped) scours on the seafloor with a dominant east-northeast–west-southwest orientation. The flood also produced sandwaves in areas unaffected by the arcuate scours, indicating they were protected from iceberg scouring by overlying ice during the event. We suggest that these sandwaves, along with submarine channels inferred from the data, indicate that Laurentide ice was lifted buoyantly, enabling the flood to traverse southern Hudson Bay under the ice sheet.
Sunday, February 24, 2008
Saturday, February 23, 2008
New Fossil Sea Birds From New Zealand
Photo courtesy Jeffrey D. Stilwell
The oldest known bird fossils from New Zealand were recently unearthed along a remote stretch of beach on the Chatham Islands, researchers announced. The fossils represent possibly four new species of seabirds dating back to the late Cretaceous period, around 65 million years ago.
Other remains from the same blocks of fossil-laden sandstone suggest that the birds co-existed with marine and terrestrial dinosaurs. "This is New Zealand's oldest fossil aviary, and it has implications for the origin of modern seabirds," said excavation leader Jeffrey Stilwell of Monash University in Australia.
Stilwell found the fossil trove along a 1.2-mile (2-kilometer) stretch of rugged shoreline on the main Chatham Island, which sits more than 500 miles (800 kilometers) east of Christchurch. Storms had washed sand away from a rocky platform on Maunganui Beach, revealing a wealth of bones from the Cretaceous.
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