Layered lava flows of the Deccan Traps east of Mumbai, India. Credit: Mark Richards, UC Berkeley
While there is general consensus that a massive asteroid colliding with Earth 66 million years ago contributed to the ensuing mass extinction, including that of dinosaurs, new evidence suggests that this impact triggered more intense volcanic activity, further compounding the extermination.
The new measurements of volcanic activity, which may be the most precise to date, indicate a dramatic increase in the rate of eruption of the Deccan volcanos within 50,000 years of the impact. To gain an understanding of activity at this volcanic range in India, Paul Renne et al. used high-resolution argon dating of local igneous minerals.
This data, combined with the layering of rock, reveals that some subsections of this volcanic region were already active before the asteroid hit. Following the collision, the team notes that the mean eruption frequency of a particular subsection decreased dramatically, but the lava volume (per single eruptive event) increased, causing the mean magma eruption rate to roughly double.
The transition from high-frequency, low-volume eruptions to low-frequency, high-volume eruptions suggests a fundamental change in the magma plumbing system, the authors say. This large volume of magma continued for approximately 500,000 years after the mass extinction, which is similar to the timescale between extinction and the initial recovery of marine ecosystems.
Therefore the authors suggest that the Cretaceous extinction may have resulted from the combined effects of both the asteroid collision and increased volcanic activity.
Reference:
“State shift in Deccan volcanism at the Cretaceous-Paleogene boundary, possibly induced by impact,” by P.R. Renne; C.J. Sprain at Berkeley Geochronology Center in Berkeley, CA; P.R. Renne; C.J. Sprain; M.A. Richards; S. Self at University of California, Berkeley in Berkeley, CA; L. Vanderkluysen at Drexel University in Philadelphia, PA; K. Pande at Indian Institute of Technology Bombay in Mumbai, India. DOI: 10.1126/science.aac7549
Petrographic thin section made from core sample is shown. This 30 micron thin slice of rock allows a view of the types of features thought to be microbial. Here, the blue layers are an epoxy added in to see void-space in the rock and the grey is sediment. The morphology of the orangey-brown layers are suggestive of microbial activity, such as they way they roll over themselves in the bottom left and smoothly drape over the triangular feature. This type of deposition demonstrates that the sediment had to have a degree of cohesive stickiness, such as that provided by the presence of microbial mats. Credit: USGS Core Research Center
The search for life beyond Earth is one of the grandest endeavors in the history of humankind — a quest that could transform our understanding of our universe both scientifically and spiritually.
With news coming this week that NASA has confirmed the presence of flowing saltwater on the surface of Mars, the hunt for life on the Red Planet has new momentum.
“One of the many reasons this is exciting is that life as we currently know it requires water,” said Alison Olcott-Marshall, assistant professor of geology at the University of Kansas. “So the fact that it’s present at Mars means that the most basic and universal requirement for life was fulfilled.”
In the journal Astrobiology, Olcott-Marshall recently has published an analysis of Eocene rocks found in the Green River Formation, a lake system extending over parts of Colorado, Utah and Wyoming.
Marshall and co-author Nicholas A. Cestari, a masters student in her lab, found these Green River rocks have features that visually indicate the presence of life, and they argue that probes to Mars should identify similar indicators on that planet and double-check them through chemical analysis.
“Once something is launched into space, it becomes much harder to do tweaks — not impossible, but much, much harder,” Olcott-Marshall said. “Scientists are still debating the results of some of the life-detection experiments that flew to Mars on the Viking Missions in the late ’70s, in a large part because of how the experiments were designed. Looking at Earth-based analogs lets us get some of these bumps smoothed out here on Earth, when we can revise, replicate and re-run experiments easily.”
The researchers examined cored samples of rock from 50 million years ago that included sections of “microbial mats.”
“Microbial mats are essentially the microbial world’s version of apartment buildings — they are layered communities of microbes, and each layer represents a different metabolic strategy,” Olcott-Marshall said. “Generally, the photosynthetic microbes are at the top, and then every successive layer makes use of the waste products of the level above. Thus, not only does a microbial mat contain a great deal of biology, but a great number of chemicals, pigments and metabolic products are made, which means lots of potential biosignatures.”
At times during the Eocene, the Green River Formation’s water chemistry purged fish and other organisms from the lake, providing room for these microbes to thrive.
“During these times, ‘microbialites’ formed — these are rocks thought to be made by microbial processes, essentially the preserved remnants of microbial mats. The Green River Formation has a wide variety of these structures, and these features are why we went looking in these rocks, as microbialites are one life-detection target on Mars.”
First, the researchers visually inspected the cored samples for signs of biology by identifying geological signs associated with microbialites — such as “stromatolites.”
“These are things like finely laminated sediments, where each lamination follows the ones below, or signs of cohesive sediment, things like layers that roll over onto themselves or are at an angle steeper than what gravity would allow,” Olcott-Marshall said. “These are all thought to be signs that microbes are helping hold sediment together.”
If visual examination pointed to the presence of biology in sections of the rock cores, the researchers looked to confirm the presence of life. They powdered those rock samples in a ball mill, and then used hot organic solvents like methanol to remove any organic carbons that might have been preserved in the rocks. That solvent was then concentrated and analyzed with gas chromatography/mass spectroscopy.
“GC/MS allows an identification of compounds, including organic molecules, preserved in a rock,” Olcott-Marshall said. “Viking was the first time that a GC/MS was sent to Mars, and there is one up there right now on Curiosity collecting data.”
Through GC/MS, the researchers determined that rock structures appearing to be biological indeed hosted living organisms millions of years ago: analysis showed the presence of lipid biomarkers.
“A lipid biomarker is the preserved remnant of a lipid, or a fat, once synthesized by an organism,” Olcott-Marshall said. “These can be simple or very complex. Different organisms make different lipids, so identifying the biomarker can often allow a deeper understanding of the biota or the environment present when a rock was formed. These are a type of biosignature.”
The researchers said their results could be a powerful guide for sample selection on Mars.
“There is a GC/MS on Curiosity right now, but there are only nine sample cups dedicated for looking for biomarkers like these,” Olcott-Marshall said. “It’s crucial those nine samples are ones most likely to guarantee success.
Additionally, one of the goals of the planned 2020 rover mission is to identify samples for caching for eventual return to Earth. The amount of sample that can be returned is likely very small, thus, once again, doing our best to guarantee success is very important. What this shows is that we can use visual inspection to help us screen for these samples that are likely to be successful for further biosignature analysis.”
She said microbial and non-microbial rocks are found in similar environments, with identical preservation histories for millions of years, and many of the same chemical parameters, such as amounts of organic carbon preserved in the rocks.
“The only difference is that one rock is shaped in a way people have associated with biology, and sure enough, those rocks are the ones that seem to preserve the biosignatures, at least in the Green River,” she said.
Petrographic thin section made from core sample is shown. This 30 micron thin slice of rock allows a view of the types of features thought to be microbial, such as the layers that fold over themselves in the middle of the sample marked 2534.8′. This demonstrates that the sediment had to have a degree of cohesive stickiness, such as that provided by the presence of microbial mats. Credit: USGS Core Research Center
Reference:
Olcott Marshall Alison and Cestari Nicholas A.. Astrobiology. Biomarker Analysis of Samples Visually Identified as Microbial in the Eocene Green River Formation: An Analogue for Mars. September 2015, 15(9): 770-775. DOI:10.1089/ast.2015.1339
The Surprise Glacier in Alaska. Credit: U.S. Geological Survey/Flickr
Climate change is causing more than just warmer oceans and erratic weather. According to scientists, it also has the capacity to alter the shape of the planet.
In a five-year study published today in Nature, lead author Michele Koppes, assistant professor in the Department of Geography at the University of British Columbia, compared glaciers in Patagonia and in the Antarctic Peninsula. She and her team found that glaciers in warmer Patagonia moved faster and caused more erosion than those in Antarctica, as warmer temperatures and melting ice helped lubricate the bed of the glaciers.
“We found that glaciers erode 100 to 1,000 times faster in Patagonia than they do in Antarctica,” said Koppes. “Antarctica is warming up, and as it moves to temperatures above 0 degrees Celsius, the glaciers are all going to start moving faster. We are already seeing that the ice sheets are starting to move faster and should become more erosive, digging deeper valleys and shedding more sediment into the oceans.”
The repercussions of this erosion add to the already complex effects of climate change in the polar regions. Faster moving glaciers deposit more sediment in downstream basins and on the continental shelves, potentially impacting fisheries, dams and access to clean freshwater in mountain communities. “The polar continental margins in particular are hotspots of biodiversity,” notes Koppes. “If you’re pumping out that much more sediment into the water, you’re changing the aquatic habitat.”
The Canadian Arctic, one of the most rapidly warming regions of the world, will feel these effects acutely. With more than four degrees Celsius of warming over the last 50 years, the glaciers are on the brink of a major shift that will see them flowing up to 100 times faster if the climate shifts above zero degrees Celsius.
The findings by Koppes and coauthors also settle a scientific debate about when glaciers have the greatest impact on shaping landscapes and creating relief, suggesting that they do the most erosive work near the end of each cycle of glaciation, rather than at the peak of ice cover. The last major glacial cycles in the Vancouver region ended approximately 12,500 years ago.
Reference:
Michéle Koppes, Bernard Hallet, Eric Rignot, Jérémie Mouginot, Julia Smith Wellner & Katherine Boldt. Observed latitudinal variations in erosion as a function of glacier dynamics. DOI:10.1038/nature15385
This flea preserved about 20 million years ago in amber may carry evidence of an ancestral strain of the bubonic plague. Credit: Photo by George Poinar, Jr., courtesy of Oregon State University
About 20 million years ago a single flea became entombed in amber with tiny bacteria attached to it, providing what researchers believe may be the oldest evidence on Earth of a dreaded and historic killer — an ancient strain of the bubonic plague.
If indeed the fossil bacteria are related to plague bacteria, Yersinia pestis, the discovery would show that this scourge, which killed more than half the population of Europe in the 14th century, actually had been around for millions of years before that, traveled around much of the world, and predates the human race.
Findings on this extraordinary amber fossil have been published in the Journal of Medical Entomology by George Poinar, Jr., an entomology researcher in the College of Science at Oregon State University, and a leading expert on plant and animal life forms found preserved in this semi-precious stone.
It can’t be determined with certainty that these bacteria, which were attached to the flea’s proboscis in a dried droplet and compacted in its rectum, are related to Yersinia pestis, scientists say. But their size, shape and characteristics are consistent with modern forms of those bacteria. They are a coccobacillus bacteria; they are seen in both rod and nearly spherical shapes; and are similar to those of Yersinia pestis. Of the pathogenic bacteria transmitted by fleas today, only Yersinia has such shapes.
“Aside from physical characteristics of the fossil bacteria that are similar to plague bacteria, their location in the rectum of the flea is known to occur in modern plague bacteria,” Poinar said. “And in this fossil, the presence of similar bacteria in a dried droplet on the proboscis of the flea is consistent with the method of transmission of plague bacteria by modern fleas.”
These findings are in conflict with modern genomic studies indicating that the flea-plague-vertebrate cycle evolved only in the past 20,000 years, rather than 20 million. However, today there are several strains of Yersinia pestis, and there is evidence that past outbreaks of this disease were caused by still different strains, some of which are extinct today.
While human strains of Yersinia could well have evolved some 10,000 to 20,000 years ago, Poinar said, ancient Yersinia strains that evolved as rodent parasites could have appeared long before humans existed. These ancient strains would certainly be extinct by now, he said.
The complex mode of transmission of plague is also reflected in the flea seen in this fossil.
When a flea feeds on a plague-infected animal, the Yersinia pestis bacteria taken up with the blood often form a viscous mass in the flea’s proventriculus, located between the stomach and esophagus. When this happens, the fleas can’t obtain enough blood, and as they attempt to feed again, bacteria are often forced back out through the proboscis and into the wound.
This blockage is in part what makes them effective vectors of the plague, and the dried droplets on the proboscis of the fossil flea could represent a sample of the sticky bacterial mass that was regurgitated.
“If this is an ancient strain of Yersinia, it would be extraordinary,” Poinar said. “It would show that plague is actually an ancient disease that no doubt was infecting and possibly causing some extinction of animals long before any humans existed. Plague may have played a larger role in the past than we imagined.”
The fossil flea originated from amber mines in what is now the Dominican Republic, between Puerto Plata and Santiago. Millions of years ago the area was a tropical moist forest.
Very few fleas of any type have been found preserved in amber, Poinar said, and none have been reported with associated microorganisms, as in this case. This specimen had some other unique morphological features that indicate it’s a species that long ago went extinct.
But it was the associated bacteria that fascinated the researchers.
“Since the dried droplet with bacteria is still attached to the tip of the proboscis, the flea may have become entrapped in resin shortly after it had fed on an infected animal,” Poinar said. “This might have been one of the rodents that occurred in the Dominican amber forest. Rodent hair has been recovered from that amber source.”
Flea-like creatures found in conventional stone fossils date back to the time of the dinosaurs, Poinar said, and the role of insects in general, and as carriers of disease, may have played a role in the demise of the ancient reptiles.
In 2008, Poinar and his wife, Roberta Poinar, wrote a book “What Bugged the Dinosaurs? Insects, Disease and Death in the Cretaceous.” It explored the evolutionary rise of insects around the same time that dinosaurs went extinct. The thesis developed in the book added insect-borne diseases as a likely component, that, along with other biotic and abiotic factors such as climate change, asteroid impacts and volcanic eruptions, led to the extinction of the dinosaurs. Some modern diseases such as leishmaniasis and malaria clearly date to those times.
Bubonic plague in modern times can infect and kill a wide range of animals, in addition to humans. It is still endemic in many countries, including the United States where it’s been found in prairie dogs and some other animals. Even though today it is treatable with antibiotics, in the U.S. four people have died from plague so far this year.
During the Middle Ages, however, three phases of the disease — bubonic, septicemic and pneumonic plague — earned a feared reputation. Periodic waves of what was called the Black Death, for the gruesome condition in which it left its victims, swept through Europe and Asia, altogether killing an estimated 75 to 200 million people.
Scholars say that religious, social and economic changes caused by the plague altered the course of world history.
Reference:
George Poinar. A New Genus of Fleas with Associated Microorganisms in Dominican Amber. Journal of Medical Entomology, 2015; tjv134 DOI: 10.1093/jme/tjv134
Scientists were able to determine the reddish brown color of a bat species known as Palaeochiropteryx from fossils found in Messel, Germany. The fossil is estimated to about 49 million years old. Photo Credit: Jakob Vinther/University of Bristol
Scientists from Virginia Tech and the University of Bristol have revealed how pigment can be detected in mammal fossils, a discovery that may end the guesswork in determining the colors of extinct species.
The researchers discovered the reddish brown color of two extinct species of bat from fossils dating back about 50 million years, marking the first time the colors of extinct mammals have been described through fossil analysis.
The techniques can be used to determine color from well-preserved animal fossils that are up to 300 million years old, researchers said.
“We have now studied the tissues from fish, frogs, and tadpoles, hair from mammals, feathers from birds, and ink from octopus and squids,” said Caitlin Colleary, a doctoral student of geosciences in the College of Science at Virginia Tech and lead author of the study. “They all preserve melanin, so it’s safe to say that melanin is really all over the place in the fossil record. Now we can confidently fill in some of the original color patterns of these ancient animals.”
The research involved scientists from the U.S., the United Kingdom, Germany, Ethiopia, and Denmark. It is being published this week (Sept. 28) in the Proceedings of the National Academy of Sciences.
The researchers said microscopic structures traditionally believed to be fossilized bacteria are in fact melanosomes — organelles within cells that contain melanin, the pigment that gives colors to hair, feathers, skin, and eyes.
Fossil melanosomes were first described in a fossil feather in 2008 by Jakob Vinther, a molecular paleobiologist at the University of Bristol and the senior author of the current study.
Since then, the shapes of melanosomes have been used to look at how marine reptiles are related and identify colors in dinosaurs and, now, mammals.
“Very importantly, we see that the different melanins are found in organelles of different shapes: reddish melanosomes are shaped like little meatballs, while black melanosomes are shaped like little sausages and we can see that this trend is also present in the fossils,” Vinther said. “This means that this correlation of melanin color to shape is an ancient invention, which we can use to easily tell color from fossils by simply looking at the melanosomes shape.”
In addition to shape, melanosomes are chemically distinct.
Using an instrument called a time-of-flight secondary ion mass spectrometer, scientists identified the molecular makeup of the fossil melanosomes to compare with modern melanosomes.
In addition, researchers replicated the conditions under which the fossils formed to identify the chemical alteration of melanin, subjecting modern feathers to high temperatures and pressures to better understand how chemical signatures changed during millions of years of burial.
“By incorporating these experiments, we were able to see how melanin chemically changes over millions of years, establishing a really exciting new way of unlocking information previously inaccessible in fossils, Colleary said.
The work was carried out at the University of Bristol, where Colleary was a master’s student working with Vinther, and the University of Texas at Austin. It was supported by funds from UT Austin, National Geographic, and the University of Bristol.
“It was important to bring microchemistry into the debate, because discussion has been going on for years over whether these structures were just fossilized bacteria or specific bodies where melanin is concentrated,” said Roger Summons, the Schlumberger Professor of Earth Science at the Massachusetts Institute of Technology, who was not involved in the research. “These two things have very different chemical compositions.”
Summons, who was part of a research team that studied fossils of squid to show that ink from the Jurassic period was chemically indistinguishable from modern cuttlefish ink, said the study further helps demonstrate how all living things on Earth have evolved in concert.
“How color is imparted and how we characterize it in fossils are important, because they inform us about a very specific aspect of the history of life on our planet,” Summons said. “For complex animal life, color is a factor in how individuals recognize and respond to others, determine friend or foe, and find mates. This research provides another thread to understand how ancient life evolved. Color recognition was an important part of that process, and it goes far back in the history of animals.”
Reference:
Caitlin Colleary, Andrei Dolocan, James Gardner, Suresh Singh, Michael Wuttke, Renate Rabenstein, Jörg Habersetzer, Stephan Schaal, Mulugeta Feseha, Matthew Clemens, Bonnie F. Jacobs, Ellen D. Currano, Louis L. Jacobs, Rene Lyng Sylvestersen, Sarah E. Gabbott, and Jakob Vinther. Chemical, experimental, and morphological evidence for diagenetically altered melanin in exceptionally preserved fossils. PNAS, September 28, 2015 DOI: 10.1073/pnas.1509831112
This is figure 6 from Hodges and Stanley: Paleogeographical map of Pangea (gray) showing reefs of the Late Triassic (blue boxes) and the Early Jurassic (red circles). The star represents Ferguson Hill Member corals. Data derived from the Palaeoreef database. Map modified from Lathuilière and Marchal, 2009. Credit: Hodges and Stanley, 2015, GSA Today, and Lathuilière and Marchal, 2009.
Mass extinction events punctuate the evolution of marine environments, and recovery biotas paved the way for major biotic changes. Understanding the responses of marine organisms in the post-extinction recovery phase is paramount to gaining insight into the dynamics of these changes, many of which brought sweeping biotic reorganizations.
In the October issue of GSA Today, Montana Hodges and George Stanley Jr. of the University of Montana Paleontology Center report on coral recovery after the end-Triassic mass extinction event at the Triassic-Jurassic (T/J) mass extinction boundary. The authors examined Jurassic corals in a continuous depositional section of the Gabbs and Sunrise Formations near New York Canyon in west-central Nevada, USA.
Because Early Jurassic corals from North America are so rare, newly discovered occurrences are vital to understanding biotic responses in the post-mass extinction interval. In this paper, Hodges and Stanley make a preliminary report of the earliest Jurassic corals from the U.S., which are also some of the earliest in North America. These examples occur at New York Canyon in west-central Nevada’s Sunrise Formation.
This site has attracted international attention because it is among the best-documented T/J sections in North America. The coral occurrences in this section are near the T/J boundary, making the Nevada site ideal for understanding the dynamics of coral recovery and comparing them with the Tethys.
The authors write that these New York Canyon corals offer additional information on recovery in eastern Panthalassa along the craton of North America. “Paleogeographically, the New York Canyon corals show a strong connection with the Tethys, but in contrast are exclusively solitary and exclusively stylophyllid taxa. Hettangian corals are unknown from North America, so for the present, the New York Canyon site may be the earliest North American Jurassic example.”
According to Hodges and Stanley, analysis of these corals fills a neglected but important part of the T/J recovery phase in North America, while lending support for an earlier opening of the Hispanic Corridor.
Reference:
North American coral recovery after the end-Triassic mass extinction, New York Canyon, Nevada, Montana S. Hodges and George D. Stanley Jr., University of Montana Paleontology Center, 32 Campus Drive, Missoula, Montana 59812, USA. Pages 4–9; DOI: 10.1130/GSATG249A.1
Sketch and corresponding photomicrographs illustrating the micromechanical deformation of thin layer of Carbopol (Ultrez 10, 2 wt%). “Carbopol can be described as a two-phase material: in the optical photomicrographs (right), the tightly coiled microgels or ‘grains’ define darker areas; more aqueous viscous material defines the brighter areas. Gel is stationary while a glass plate (black area) is moved, leading to shear localization close to the glass plate boundary. a, Undeformed Carbopol. b, At low shear strain the viscous material starts to connect, forming a ‘weak’ zone. c, Break-up of microgel grains close to the shear zone. Total shear strain γ = 1.”
Researchers have for the first time been able to measure a material’s resistance to fracturing from various types of tectonic motions in Earth’s middle crust, a discovery that may lead to better understanding of how large earthquakes and slower moving events interact.
The University of Texas Institute for Geophysics (UTIG), research unit of the Jackson School of Geosciences, spearheaded the discovery. The study was published in the September edition of Nature Geoscience.
Scientists conducted the research using Carbopol, a gel-like substance that can simulate the characteristics of rock formations in Earth’s middle crust because it is simultaneously brittle and malleable.
Researchers performed shear tests on the Carbopol, where a portion of the material is pulled one direction and a portion is pulled in the opposite direction. This is similar to what happens to rock formations in the middle crust during earthquakes or slow-slip events, a type of tectonic movement that resembles an earthquake but happens over a much longer period of time.
Previously, nearly all research into such movements of Earth’s crusts was done by measuring tectonic movement using GPS readings and linking these findings with friction laws. Those observations did not address how rock behaves when it softens under heat and pressure.
“It is not really clear how slow-slip events interact with earthquakes, whether they can trigger earthquakes or it’s the other way around — that earthquakes trigger slow-slip events,” said Jacqueline Reber, the study’s lead author who performed this research as postdoctoral fellow at UTIG, and who is now an assistant professor at Iowa State University.
The research also adds insight into middle crust strain transients, temporary stress on surrounding rock that’s caused by tectonic motion.
“By understanding the mechanics of strain transients a little bit better, we eventually hope to get better insight into how they relate to big, catastrophic earthquakes.”
Unlike slow slips events, earthquakes — or stick-slip events — occur when surfaces quickly alternate between sticking to each other and sliding over each other.
“While earlier studies focused mostly on frictional behavior as an explanation for strain transients we focus in our work on the impact of rheology (how a material flows under stress), especially when it is semi-brittle,” said Reber.
The semi-brittle middle crust can be compared to a candy bar made of nuts and caramel. The nuts represent the brittle rock. The caramel represents the ductile rock.
Researchers exposed Carbopol, in which the ratio between brittle and ductile parts determines how much stress it can take before being permanently deformed or breaking, to forces created by a simple spring-powered shearing apparatus. Lower yield stress induced the Carbonol to imitate hotter, more viscous rock from deeper in Earth’s crust by making it more ductile; at higher yield stress it imitated cooler, more brittle rock.
The tests showed viscous deformation and constant creep movement at lower yield stress and slip-stick behavior at higher yield stress. This highlights the importance of a material’s often complex properties for determining the manner and speed it will respond to stress.
Reference:
Jacqueline E. Reber, Luc L. Lavier, Nicholas W. Hayman. Experimental demonstration of a semi-brittle origin for crustal strain transients. Nature Geoscience, 2015; 8 (9): 712 DOI: 10.1038/ngeo2496
Figure 5 from A. Roark et al. (A) Orientation of the sampling transects through specimen MID2 for stable isotopes (outer image; sample billet) and trace elements (inset image; thin section). (B) The resulting isotopic and trace-element data for specimen MID2. Credit: A. Roark et al. and GSA Bulletin
Does assembling a mega-continent necessarily lead to a mega-monsoon? Can you tell by looking at seashells?
This study by Andy Roark and colleagues tested predictions that the supercontinent Pangea underwent strong monsoons, or massive seasonal changes in wind direction, during times of high sea level (i.e., interglacial) by analyzing the chemistry of fossil brachiopod shells. The shells were deposited in a shallow sea in present-day West Virginia and Ohio in the latest Pennsylvanian (~300 million years ago).
By carefully micro-sampling each shell along its direction of growth and analyzing for stable carbon and oxygen isotopes and trace elements, the team reconstructed a record of seasonal variation during the lifetimes of the organisms. The data showed that the region experienced minimal seasonal variation in temperature and rainfall; in other words, at most a very weak monsoon.
These results may help resolve a paleoclimate debate about the relationship between monsoonality and sea level and provide a glimpse of changing seasons on an ancient mega-continent.
Reference:
Low seasonality in central equatorial Pangea during a late Carboniferous highstand based on high-resolution isotopic records of brachiopod shells
A. Roark et al., Dept. of Geology and Geophysics, Texas A&M University, MS 3115, College Station, Texas 77843, USA. This article is online at DOI: 10.1130/B31330.1
Dark, narrow streaks on Martian slopes such as these at Hale Crater are inferred to have been formed by seasonal flow of water on contemporary Mars. Detection of hydrated salts at the streaks supports that interpretation. The features are called “recurring slope lineae.” Credit: NASA/JPL-Caltech/Univ. of Arizona
New findings from NASA’s Mars Reconnaissance Orbiter (MRO) provide the strongest evidence yet that liquid water flows intermittently on present-day Mars.
Using an imaging spectrometer on MRO, researchers detected signatures of hydrated minerals on slopes where mysterious streaks are seen on the Red Planet. These darkish streaks appear to ebb and flow over time. They darken and appear to flow down steep slopes during warm seasons, and then fade in cooler seasons. They appear in several locations on Mars when temperatures are above minus 10 degrees Fahrenheit (minus 23 Celsius), and disappear at colder times.
“Our quest on Mars has been to ‘follow the water,’ in our search for life in the universe, and now we have convincing science that validates what we’ve long suspected,” said John Grunsfeld, astronaut and associate administrator of NASA’s Science Mission Directorate in Washington. “This is a significant development, as it appears to confirm that water — albeit briny — is flowing today on the surface of Mars.”
These downhill flows, known as recurring slope lineae (RSL), often have been described as possibly related to liquid water. The new findings of hydrated salts on the slopes point to what that relationship may be to these dark features. The hydrated salts would lower the freezing point of a liquid brine, just as salt on roads here on Earth causes ice and snow to melt more rapidly. Scientists say it’s likely a shallow subsurface flow, with enough water wicking to the surface to explain the darkening.
“We found the hydrated salts only when the seasonal features were widest, which suggests that either the dark streaks themselves or a process that forms them is the source of the hydration. In either case, the detection of hydrated salts on these slopes means that water plays a vital role in the formation of these streaks,” said Lujendra Ojha of the Georgia Institute of Technology (Georgia Tech) in Atlanta, lead author of a report on these findings published Sept. 28 by Nature Geoscience.
Ojha first noticed these puzzling features as a University of Arizona undergraduate student in 2010, using images from the MRO’s High Resolution Imaging Science Experiment (HiRISE). HiRISE observations now have documented RSL at dozens of sites on Mars. The new study pairs HiRISE observations with mineral mapping by MRO’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).
The spectrometer observations show signatures of hydrated salts at multiple RSL locations, but only when the dark features were relatively wide. When the researchers looked at the same locations and RSL weren’t as extensive, they detected no hydrated salt.
Ojha and his co-authors interpret the spectral signatures as caused by hydrated minerals called perchlorates. The hydrated salts most consistent with the chemical signatures are likely a mixture of magnesium perchlorate, magnesium chlorate and sodium perchlorate. Some perchlorates have been shown to keep liquids from freezing even when conditions are as cold as minus 94 degrees Fahrenheit (minus 70 Celsius). On Earth, naturally produced perchlorates are concentrated in deserts, and some types of perchlorates can be used as rocket propellant.
Perchlorates have previously been seen on Mars. NASA’s Phoenix lander and Curiosity rover both found them in the planet’s soil, and some scientists believe that the Viking missions in the 1970s measured signatures of these salts. However, this study of RSL detected perchlorates, now in hydrated form, in different areas than those explored by the landers. This also is the first time perchlorates have been identified from orbit.
MRO has been examining Mars since 2006 with its six science instruments.
“The ability of MRO to observe for multiple Mars years with a payload able to see the fine detail of these features has enabled findings such as these: first identifying the puzzling seasonal streaks and now making a big step towards explaining what they are,” said Rich Zurek, MRO project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California.
For Ojha, the new findings are more proof that the mysterious lines he first saw darkening Martian slopes five years ago are, indeed, present-day water.
“When most people talk about water on Mars, they’re usually talking about ancient water or frozen water,” he said. “Now we know there’s more to the story. This is the first spectral detection that unambiguously supports our liquid water-formation hypotheses for RSL.”
The discovery is the latest of many breakthroughs by NASA’s Mars missions.
“It took multiple spacecraft over several years to solve this mystery, and now we know there is liquid water on the surface of this cold, desert planet,” said Michael Meyer, lead scientist for NASA’s Mars Exploration Program at the agency’s headquarters in Washington. “It seems that the more we study Mars, the more we learn how life could be supported and where there are resources to support life in the future.”
There are eight co-authors of the Nature Geoscience paper, including Mary Beth Wilhelm at NASA’s Ames Research Center in Moffett Field, California and Georgia Tech; CRISM Principal Investigator Scott Murchie of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland; and HiRISE Principal Investigator Alfred McEwen of the University of Arizona Lunar and Planetary Laboratory in Tucson, Arizona. Others are at Georgia Tech, the Southwest Research Institute in Boulder, Colorado, and Laboratoire de Plan?tologie et G?odynamique in Nantes, France.
The agency’s Jet Propulsion Laboratory in Pasadena, California, a division of the California Institute of Technology, manages the Mars Reconnaissance Orbiter Project for NASA’s Science Mission Directorate, Washington. Lockheed Martin built the orbiter and collaborates with JPL to operate it.
This animation simulates a fly-around look at one of the places on Mars where dark streaks advance down slopes during warm seasons, possibly involving liquid water. This site is within Hale Crater. The streaks are roughly the length of a football field.
Reference:
Lujendra Ojha, Mary Beth Wilhelm, Scott L. Murchie, Alfred S. McEwen, James J. Wray, Jennifer Hanley, Marion Massé & Matt Chojnacki. Spectral evidence for hydrated salts in recurring slope lineae on Mars AOP. Nature Geoscience, 2015; DOI: 10.1038/ngeo2546
Vent chimnety at the Von Damm vent site. Credit: Image courtesy of National Oceanography Centre
A crucial process has been identified to explain the reason why dissolved organic carbon (DOC) levels in the deep oceans are constant despite a continuous supply from the surface ocean. This research has been published today in the journal Nature Geoscience and was conducted by scientists from the National Oceanography Centre (NOC) and The University of Southampton.
Dr Jeff Hawkes, the lead author of this study, from the NOC said: “There has been a long outstanding question about whether hydrothermal vents are a source or sink of organic carbon to the oceans. We have shown that hydrothermal vent fluids contain almost none of the organic carbon which accumulates in the oceans, which means that vents are a sink for this unreactive ‘stored’ carbon.”
The pool of dissolved organic carbon (DOC) in the oceans is as large as all of the carbon in the atmosphere. Phytoplankton, which remove CO2 from the atmosphere and convert it into more complex carbon compounds, are the primary source of DOC in the ocean. Deep ocean DOC concentrations are almost constant throughout the world’s oceans and are thought to be resistant to biological breakdown. However, with the continuous DOC supply from the surface oceans, concentrations in the deep sea are not increasing.
Co-author, Dr Doug Connelly from the NOC, said: “This work finally gives us a mechanism for the deep ocean carbon cycle, addressing the long standing problem of why the DOC in the world’s oceans is not increasing.”
This study highlights the importance of deep ocean water circulation through hot hydrothermal systems as one of the main removal processes in this environment balancing the supply. The vent systems convert the biological resistant long-lived carbon into more readily available carbon, which organisms can then use.
This research was partly based on seafloor sampling at hydrothermal vent sites using the NOC maintained robotic vehicle Isis, which was launched over the side of the RRS James Cook. These vent sites where situated in the Caribbean and Antarctica, and included the Von Damm and Beebe sites.
Eight academic institutions world-wide contributed data from other vent sites to this study. The field work was complemented with high-temperature high-pressure experiments in the laboratory to replicate the hydrothermal observations and to suggest mechanisms for the processes.
Co-author Professor Eric Achterberg, from the University of Southampton, said: “The beauty of this approach is that with both field and laboratory experiments we were able to prove how the mechanisms operate for the removal of organic carbon in the deep ocean.”
This research was funded by the Natural Environmental Research Council (NERC) and forms part of the NOC’s ongoing research into deep sea processes.
Reference:
Jeffrey A. Hawkes, Pamela E. Rossel, Aron Stubbins, David Butterfield, Douglas P. Connelly, Eric P. Achterberg, Andrea Koschinsky, Valérie Chavagnac, Christian T. Hansen, Wolfgang Bach, Thorsten Dittmar. Efficient removal of recalcitrant deep-ocean dissolved organic matter during hydrothermal circulation. Nature Geoscience, 2015; DOI: 10.1038/ngeo2543
How long is the interval between the trigger for a volcanic eruption and the eruption itself? A new study by LMU volcanologists indicates that compositional variations in erupted Magmas can answer this question.
In the lithosphere beneath an active volcano the magma is never at rest. When melts with different chemical compositions come into contact, the result is often an explosive mixture: the molten rock begins to bubble, and an eruption becomes inevitable. A research team led by Professor Donald Dingwell, Director of the Department of Earth and Environmental Sciences at LMU, and Professor Diego Perugini of the University of Perugia (Italy) has now developed a model which, for the first time, allows one to estimate the time that has elapsed between the initial mixing event and the subsequent eruption. The technique has obvious application to ongoing efforts to enhance the forecasting of volcanic eruptions, as the authors demonstrate in their paper, which appears in “Nature Scientific Reports”.
The ‘foaming’ phenomenon is due to the oversaturation of the magma mixture with gases that are released as a result of the mixing process itself. These gases in turn provide the buoyancy that causes the magma to rise. “We know that, very often, the time that elapses from the first encounter between compositionally distinct melts and the ensuing eruption is insufficient to allow complete homogenization of the mixture to occur,” says Dingwell. “So the material that is ultimately extruded is still quite heterogeneous. Here, we use this heterogeneity to model the temporal pattern of the mixing process.”
Simulating eruptions in the laboratory
With its unique combination of instrumentation, Dingwell’s laboratory is ideally equipped to experimentally simulate the conditions of high temperature and high pressure that prevail in the interior of an active volcano. In their latest experiments they used two kinds of samples of erupted material collected in the Campi Flegrei near Naples, one of the most volcanically active areas in Europe, and compared their chemical compositions and mixing ratios. Their results showed that different chemical fractions of the component melts mixed with each other at different rates: Water, for instance, becomes uniformly distributed in mixtures very rapidly, but other substances take much longer to mix thoroughly. “On the basis of the variations in mixing ratios of particular components of the rock between the two samples of erupted material, we can estimate the duration of the period between the initiation of the mixing process and the eruption”, Dingwell explains.
Little advance warning
The results indicates that, in the Campi Flegrei, the interval between the onset of magma mixing and eruption is less than an hour – astonishingly short by comparison with previous estimates of several days. “The more studies of this kind are carried out on other volcanic systems, the sooner we should be in a position to estimate the duration of the run-up phase prior to an eruption using the variance of concentration ratios as a volcanic chronometer,” says Dingwell.
The new method can also contribute to improving the monitoring of active volcanos: Once it is known from studies of erupted material how much time elapsed between initial magma mixing and a given eruption, one can retrospectively identify those events in the monitoring record that represent true precursors of the eruption. “In future, this approach could make it easier to filter the really crucial signals out of the plethora of information picked up by the monitoring system,” says Dingwell. “So our model could help us to provide a realistic estimate of the lead time prior to an eruption – a parameter which is essential for the design of appropriate and practical measures to protect the public.”
Reference:
“Concentration variance decay during magma mixing: a volcanic chronometer.” Scientific Reports 5, Article number: 14225 (2015) DOI: 10.1038/srep14225
Lateral view of the Paranthropus robustus skull SK 46 from the site of Swartkrans, South Africa showing the 3D virtual reconstruction of the ear and the hearing results for the early hominins. Credit: Rolf Quam
Research into human fossils dating back to approximately two million years ago reveals that the hearing pattern resembles chimpanzees, but with some slight differences in the direction of humans.
Rolf Quam, assistant professor of anthropology at Binghamton University, led an international research team in reconstructing an aspect of sensory perception in several fossil hominin individuals from the sites of Sterkfontein and Swartkrans in South Africa. The study relied on the use of CT scans and virtual computer reconstructions to study the internal anatomy of the ear. The results suggest that the early hominin species Australopithecus africanus and Paranthropus robustus, both of which lived around 2 million years ago, had hearing abilities similar to a chimpanzee, but with some slight differences in the direction of humans.
Humans are distinct from most other primates, including chimpanzees, in having better hearing across a wider range of frequencies, generally between 1.0-6.0 kHz. Within this same frequency range, which encompasses many of the sounds emitted during spoken language, chimpanzees and most other primates lose sensitivity compared to humans.
“We know that the hearing patterns, or audiograms, in chimpanzees and humans are distinct because their hearing abilities have been measured in the laboratory in living subjects,” said Quam. “So we were interested in finding out when this human-like hearing pattern first emerged during our evolutionary history.”
Previously, Quam and colleagues studied the hearing abilities in several fossil hominin individuals from the site of the Sima de los Huesos (Pit of the Bones) in northern Spain. These fossils are about 430,000 years old and are considered to represent ancestors of the later Neandertals. The hearing abilities in the Sima hominins were nearly identical to living humans. In contrast, the much earlier South African specimens had a hearing pattern that was much more similar to a chimpanzee.
In the South African fossils, the region of maximum hearing sensitivity was shifted towards slightly higher frequencies compared with chimpanzees, and the early hominins showed better hearing than either chimpanzees or humans from about 1.0-3.0 kHz. It turns out that this auditory pattern may have been particularly favorable for living on the savanna. In more open environments, sound waves don’t travel as far as in the rainforest canopy, so short range communication is favored on the savanna.
“We know these species regularly occupied the savanna since their diet included up to 50 percent of resources found in open environments” said Quam. The researchers argue that this combination of auditory features may have favored short-range communication in open environments.
That sounds a lot like language. Does this mean these early hominins had language? “No,” said Quam. “We’re not arguing that. They certainly could communicate vocally. All primates do, but we’re not saying they had fully developed human language, which implies a symbolic content.”
The emergence of language is one of the most hotly debated questions in paleoanthropology, the branch of anthropology that studies human origins, since the capacity for spoken language is often held to be a defining human feature. There is a general consensus among anthropologists that the small brain size and ape-like cranial anatomy and vocal tract in these early hominins indicates they likely did not have the capacity for language.
“We feel our research line does have considerable potential to provide new insights into when the human hearing pattern emerged and, by extension, when we developed language,” said Quam.
Ignacio Martinez, a collaborator on the study, said, “We’re pretty confident about our results and our interpretation. In particular, it’s very gratifying when several independent lines of evidence converge on a consistent interpretation.”
How do these results compare with the discovery of a new hominin species, Homo naledi, announced just two weeks ago from a different site in South Africa?
“It would be really interesting to study the hearing pattern in this new species,” said Quam. “Stay tuned.”
The study was published on Sept. 25 in the journal Science Advances.
Video
Reference:
Rolf Quam et al. Early hominin auditory capacities. Science Advances, September 2015 DOI: 10.1126/sciadv.1500355
Map showing variability in predicted Sr isotope ratios across the contiguous United States and representatives of the five materials used in this study (Local Water Model predictions from Bataille and Bowen 2012, “Chemical Geology” 304-305:39-52).
University of Cincinnati scientists are reporting a significant finding that could open up entirely new explorations in the fields of ecology and paleoecology. A mathematical analytical tool that was designed to predict a common elemental signal in surface water — resulting in significant savings compared with traditional field surveys — also is effective at predicting values for a wide range of materials, and is in fact most successful when applied to the bones and teeth of mammals. The research by Brooke Crowley and Joshua Miller, assistant professors of geology at UC, and Clément Bataille, an earth scientist at the Chevron Corporation, is published online for an upcoming issue of the research journal, Biological Reviews.
Strontium ratios in rocks vary depending on the type of rock and the rock’s age. The continental-scale water model previously developed by Bataille and Gabriel J. Bowen, an associate professor of geology and geophysics at the University of Utah, uses U.S. bedrock geology and all major river systems and drainages to predict strontium isotope ratios (the ratio of strontium 87 to strontium 86) in surface waters.
The research, led by the University of Cincinnati, used the water model to compare predicted strontium isotope ratios in surface water, soil, vegetation, fish and mammal skeletal tissues from a massive collection of data led by Crowley across the U.S., excluding Alaska and Hawaii.
“Because the ratio of strontium 87 to strontium 86 in water, soil, vegetation and animal tissues predominantly reflect local geology, they can be used to distinguish geologically distinct regions as well as identify highly mobile populations,” says Crowley. “We tested how accurate the model was at predicting strontium ratios not just in water, but in additional materials relevant to ecological and paleoecological research.”
The tool worked for all materials but appeared to be most successful in predicting strontium ratios in mammals. “There’s every indication that mammals are better predicted using this model than other materials,” says Miller.
“We think the model’s success at predicting strontium ratios for mammals is related to how the landscape is sampled by this analytical tool,” adds Crowley. “The predictions for the larger mammals were better than the smaller mammals. This is likely because the amount of area covered by a larger mammal more closely resembles the space that the model understands.”
Tracking strontium isotope ratios is a valuable tool beyond the science at top research institutions like UC. Strontium is a heavy earth metal that can be found in most organic substances such as bones, teeth, soils and plant tissues. As a result, strontium isotope ratios are used in fields including forensics research, animal poaching investigations, and even tracking where marijuana plants came from in drug busts.
Although strontium isotope analysis related to biological research is on the rise, the expense in terms of ground mapping has been prohibitive.
“It’s a really powerful system, but in order to get an idea of where elephant tusks confiscated in Kenya came from, for example, investigators would have to track the strontium signals throughout the country or potentially all over East Africa,” explains Miller. “Models like the one we tested could make it possible to quickly get a good idea of where that animal was originally from.”
The researchers say the water model provides a readily available source of background data for predicting strontium ratios for biologically relevant materials in regions where empirical data are lacking. “The availability of increasingly high-quality modeled strontium data will dramatically expand the accessibility of this geochemical tool to ecological applications,” says Crowley.
Reference:
Brooke E. Crowley, Joshua H. Miller, Clément P. Bataille. Strontium isotopes (87Sr/86Sr) in terrestrial ecological and palaeoecological research: empirical efforts and recent advances in continental-scale models. Biological Reviews, 2015; DOI: 10.1111/brv.12217
Note: The above post is reprinted from materials provided by University of Cincinnati. The original item was written by Dawn Fuller.
Plumes of smoke and flames rise from an eruption at Bárðarbunga volcano, Iceland, in 2014. The amount of sulphur dioxide emitted in the six-month eruption was treble that given off by all of Europe’s industry. Credit: Dr. John Stevenson
A huge volcanic eruption in Iceland emitted on average three times as much of a toxic gas as all European industry combined, a study has revealed.
Discharge of lava from the eruption at Bárðarbunga volcano released a huge mass — up to 120,000 tonnes per day — of sulphur dioxide gas, which can cause acid rain and respiratory problems.
The eruption last year was the biggest in Iceland for more than 200 years. It released a river of lava across northern Iceland, and lasted for six months.
Researchers hope that their study will aid understanding of how such eruptions can affect air quality in the UK.
A team of European scientists, including from the Universities of Leeds and Edinburgh and the Met Office, used data from satellite sensors to map sulphur dioxide pollution from the eruption. These were reproduced by computer simulations of the spreading gas cloud.
As well as being given off by volcanoes, sulphur dioxide is also produced by burning fossil fuels and industrial processes such as smelting. Human-made sulphur dioxide production has been falling since 1990, and was recorded at 12,000 tonnes per day in 2010.
The study, published in the Journal of Geophysical Research, was supported by The Natural Environment Research Council and the Royal Society of Edinburgh, amongst others.
Dr John Stevenson, of the University of Edinburgh’s School of GeoSciences, who took part in the study, said: “This eruption produced lava instead of ash, and so it didn’t impact on flights — but it did affect air quality. These results help scientists predict where pollution from future eruptions will spread.”
Dr Anja Schmidt from the School of Earth and Environment at the University of Leeds, who led the study, said: “The eruption discharged lava at a rate of more than 200 cubic metres per second, which is equivalent to filling five Olympic-sized swimming pools in a minute. Six months later, when the eruption ended, it had produced enough lava to cover an area the size of Manhattan. In the study, we were concerned with the quantity of sulphur dioxide emissions, with numbers that are equally astonishing: In the beginning, the eruption emitted about eight times more sulphur dioxide per day than is emitted from all human-made sources in Europe per day.”
Reference:
Anja Schmidt, Susan Leadbetter, Nicolas Theys, Elisa Carboni, Claire S. Witham, John A. Stevenson, Cathryn E. Birch, Thorvaldur Thordarson, Steven Turnock, Sara Barsotti, Lin Delaney, Wuhu Feng, Roy G. Grainger, Matthew C. Hort, Ármann Höskuldsson, Iolanda Ialongo, Evgenia Ilyinskaya, Thorsteinn Jóhannsson, Patrick Kenny, Tamsin A. Mather, Nigel A. D. Richards, Janet Shepherd. Satellite detection, long-range transport, and air quality impacts of volcanic sulfur dioxide from the 2014-2015 flood lava eruption at Bárðarbunga (Iceland). Journal of Geophysical Research: Atmospheres, 2015; DOI: 10.1002/2015JD023638
The living Komodo dragon and illustration showing how the osteoderm bone reinforces the scales and acts like body armor. Credit: Photo of the Komodo dragon by Bryan Fry, inset by Gilbert Price
As if life wasn’t hard enough during the last Ice Age, research led by the University of Queensland has found Australia’s first human inhabitants had to contend with giant killer lizards.
UQ vertebrate palaeoecologist Dr Gilbert Price said researchers working in Central Queensland were amazed when they unearthed the first evidence that Australia’s early human inhabitants and giant apex predator lizards had overlapped.
“Our jaws dropped when we found a tiny fossil from a giant lizard during a two metre deep excavation in one of the Capricorn Caves, near Rockhampton,” Dr Price said.
“The one-centimetre bone, an osteoderm, came from under the lizard’s skin and is the youngest record of a giant lizard on the entire continent.”
Dr Price and his colleagues used radiocarbon and uranium thorium techniques to date the bone as about 50,000 years old, coinciding with the arrival of Australia’s Aboriginal inhabitants.
“We can’t tell if the bone is from a Komodo dragon — which once roamed Australia — or an even bigger species like the extinct Megalania monitor lizard, which weighed about 500kg and grew up to six metres long,” Dr Price said.
“The find is pretty significant, especially for the timeframe that it dates.”
The largest living lizard in Australia today is the perentie, which can grow up to two metres long.
Dr Price, from UQ’s School of Earth Sciences, said massive lizards and even nine-metre long inland crocodiles roamed Australia during the last Ice Age in the Pleistocene geological period.
“It’s been long-debated whether or not humans or climate change knocked off the giant lizards, alongside the rest of the megafauna,” he said.
“Humans can only now be considered as potential drivers of their extinction.”
The bone was found in what could be Australia’s most fossil-rich site, with the Capricorn Caves housing millions of bones of many species.
Dr Price said scientists could only hypothesise how the giant lizard bone made its way inside the cave, which contains bones of many rodents regurgitated by owls.
He said a crew of volunteer citizen scientists helped with the research by sorting and sieving specimens.
Capricorn Caves manager Ann Augusteyn said the find highlighted her team’s “huge responsibility” to care for the caves.
“This study also begs the question — what else is entombed in our caves and what else can we learn?”
The research, in collaboration with the Australian National University, the Queensland Museum and Southern Cross University, was supported by the Capricorn Caves, the Australian Research Council, the Australian Institute for Nuclear Science and Energy and community organisations such as the Ian Potter Foundation.
The research is published in Quaternary Science Reviews.
Reference:
Gilbert J. Price, Julien Louys, Jonathan Cramb, Yue-xing Feng, Jian-xin Zhao, Scott A. Hocknull, Gregory E. Webb, Ai Duc Nguyen, Renaud Joannes-Boyau. Temporal overlap of humans and giant lizards (Varanidae; Squamata) in Pleistocene Australia. Quaternary Science Reviews, 2015; 125: 98 DOI: 10.1016/j.quascirev.2015.08.013
Image of the giant Sarcosuchus, an extinct crocodilian. Credit: Imperial College London and Robert Nicholls (Paleocreations)
Fluctuating sea levels and global cooling caused a significant decline in the number of crocodylian species over millions of years, according to new research.
Crocodylians include present-day species of crocodiles, alligators, caimans and gavials and their extinct ancestors. Crocodylians first appeared in the Late Cretaceous period, approximately 85 million years ago, and the 250 million year fossil record of their extinct relatives reveals a diverse evolutionary history.
Extinct crocodylians and their relatives came in all shapes and sizes, including giant land-based creatures such as Sarcosuchus, which reached around 12 metres in length and weighed up to eight metric tonnes. Crocodylians also roamed the ocean — for example, thalattosuchians were equipped with flippers and shark-like tails to make them more agile in the sea.
Many crocodylians survived the mass extinction that wiped out almost all of the dinosaurs 66 million years ago, but only 23 species survive today, six of which are classified by the International Union for Conservation of Nature as critically endangered and a further four classified as either endangered or vulnerable.
In a new study published in Nature Communications, researchers from Imperial College London, the University of Oxford, the Smithsonian Institution and the University of Birmingham compiled a dataset of the entire known fossil record of crocodylians and their extinct relatives and analysed data about Earth’s ancient climate. They wanted to explore how the group responded to past shifts in climate, to better understand how the reptiles may cope in the future.
Crocodylians are ectotherms, meaning they rely on external heat sources from the environment such as the Sun. The researchers conclude that at higher latitudes in areas we now know as Europe and America, declining temperatures had a major impact on crocodylians and their relatives.
At lower latitudes the decline of crocodylians was caused by areas on many continents becoming increasingly arid. For example, in Africa around ten million years ago, the Sahara desert was forming, replacing the vast lush wetlands in which crocodylians thrived. In South America, the rise of the Andes Mountains led to the loss of a proto-Amazonian mega wetland habitat that crocodylians lived in around five million years ago.
Marine species of crocodylians were once widespread across the oceans. The team found that fluctuations in sea levels exerted the main control over the diversity of these creatures. For example, at times when the sea level was higher it created greater diversity because it increased the size of the continental shelf, providing the right conditions near the coast for them and their prey to thrive.
Interestingly, the Cretaceous-Paleogene mass extinction event, which wiped out many other creatures on Earth nearly 66 million years ago including nearly all of the dinosaurs, had positive outcomes for the crocodylians and their extinct relatives. The team found that while several groups did go extinct, the surviving groups rapidly radiated out of their usual habitats to take advantage of territories that were now uninhabited.
In the future, the team suggest that a warming world caused by global climate change may favour crocodylian diversification again, but human activity will continue to have a major impact on their habitats.
Dr Philip Mannion, joint lead author from the Department of Earth Science and Engineering at Imperial College London, said: “Crocodylians are known by some as living fossils because they’ve been around since the time of the dinosaurs. Millions of years ago these creatures and their now extinct relatives thrived in a range of environments that ranged from the tropics, to northern latitudes and even deep in the ocean. However, all this changed because of changes in the climate, and crocodylians retreated to the warmer parts of the world. While they have a fearsome reputation, these creatures are vulnerable and looking back in time we’ve been able to determine what environmental factors had the greatest impact on them. This may help us to determine how they will cope with future changes.”
The next step for the researchers will be for them to look at similar patterns in other fossil groups with long histories, such as mammals and birds to determine how past climate influenced them.
Reference:
Philip D. Mannion, Roger B. J. Benson, Matthew T. Carrano, Jonathan P. Tennant, Jack Judd, Richard J. Butler. Climate constrains the evolutionary history and biodiversity of crocodylians. Nature Communications, 2015; 6: 8438 DOI: 10.1038/ncomms9438
Image of a deep sea coral garden from a kilometre below the sea floor on Carter Seamount the Atlantic Ocean. The Image was taken using a remotely operated vehicle on a seven week expedition from Tenerife to Trinidad Credit: University of Bristol
In a paper published today in Science, researchers from the University of Bristol describe how they used radiocarbon measured in deep-sea fossil corals to shed light on carbon dioxide (CO2) levels during the Earth’s last deglaciation.
Around 18,000-11,000 years ago, the Earth’s climate system experienced a dramatic shift: a period known to paleoclimate scientists as the last deglaciation. During this period, atmospheric CO2 concentration increased by ~80 parts per million (ppm), accompanied by sea level rise of almost 120 metres due to ice sheet melting and global warming.
Recent high-resolution ice core CO2 records have revealed that there were three abrupt centennial-scale atmospheric CO2 increases of ~10 ppm superimposed on the more gradual millennial-scale deglacial CO2 rise. The second and third of these events also coincided with abrupt warming of the high latitude North Atlantic region.
The rate of Atlantic Meridional Overturning Circulation – that is, the deep water formation in the high latitudes and associated upwelling – is closely related to the temperature of the North Atlantic region and thus might also be related to these CO2 releasing events. However it has been remarkably hard to find marine archives that can show how deep oceans behave on rapid timescales.
Researchers from the University of Bristol, University of St Andrews and University of California Irvine tackled this problem using radiocarbon measured in deep-sea fossil corals. The corals were recovered by scientific research expeditions to the Equatorial Atlantic and Southern Ocean, funded by the European Research Council and the US National Science Foundation.
Fossil corals have the unique advantage that they can be precisely dated by radiometric uranium-series dating, giving an age scale that can be directly compared to the ice core records. Radiocarbon is introduced into the ocean at the surface and penetrates to deeper layers through deep water formation. During this process radiocarbon decays away, so that deep-sea radiocarbon – and, therefore, the reconstructed fossil coral radiocarbon – can provide information on the past strength of deep ocean circulation.
The measurements revealed two massive transient events where the water becomes homogenized and enriched in radiocarbon in the mid-depth equatorial Atlantic and the Drake Passage, in phase with the second two abrupt increases of the atmosphere CO2 concentration during the last deglaciation.
Lead author, Dr Tianyu Chen of Bristol’s School of Earth Sciences said: “Our radiocarbon data are consistent with two transient and enhanced deep Atlantic overturning events which flushed out respired carbon in the deep water, causing a rapid rise of atmosphere CO2 concentration and abrupt warming of the high latitude North Atlantic.”
Video
Reference:
‘Synchronous Centennial Abrupt Events in the Ocean and Atmosphere during the Last Deglaciation’ by Tianyu Chen, Laura F. Robinson, Andrea Burke, John Southon, Peter Spooner, Paul J. Morris and Hong Chin Ng in Science: DOI: 10.1126/science.aac6159
This artist rendering handout by the CNRS on Wednesday September 23, 2015 shows “Collision of a rock body with the early Earth, causing pulverization of terrestrial crust”
In its early life, Earth suffered a meteorite pummelling that lasted 100 million years and may have changed its chemical makeup forever, researchers said Wednesday.
The steady stream of Earth-shattering collisions shortly after the birth of our solar system, ripped up the planet’s surface and altered the very composition of the rock we call home.
At the same time, those ancient meteorites called chondrites were adding to the Earth’s bulk, which like all planets form through a process of accretion—where material is pulled in by gravity, according to the study published in the journal Nature Communications.
While the Earth lost chunks as the meteorites crashed into it, it nevertheless experienced a net gain in mass during this violent period.
The finding is the latest in a long scientific quest to resolve a puzzle over the makeup of meteorites—building blocks of early Earth—and the chemical signature of our present-day planet.
Embryonic Earth some 4.7 billion years ago, the new research suggests, did in fact have the same chemical mix as at least one type of chondrite (called enstatite).
But the extended bombardment changed the chemical signature of the planet itself.
“Repeated episodes of production and erosion of the terrestrial crust removed large quantities of silicon, leaving the relative excess of magnesium we observe today,” the researchers concluded.
The crust is the outermost layer of Earth, a thin layer over the mantle, which itself covers the planet’s outer and inner core.
If scientists could extract samples from its deep layers, they might have a better idea of what a proto-Earth was made of.
But they have no choice but to rely on other evidence—including meteorites.
For the study, Asmaa Boujibar and colleagues at France’s National Centre for Scientific Research (CNRS) used lab experiments and modelling to test their theory.
They reproduced the conditions under which Earth’s primitive crust accumulated, by melting chondrites under various pressures.
The results, the study concludes, explains the makeup of the molten rock that eventually cooled into Earth’s crust.
Note: The above post is reprinted from materials provided by AFP.
This model shows planetesimals (objects formed from dust, rock and other materials that can be anywhere in size from several meters to hundreds of kilometers) accreting to a growing Earth 4.56 billion years ago. The cutaway reveals the simultaneous formation of the Earth’s core as dense, iron-rich metallic material descending through a planetary magma ocean. Credit: Antoine Pitrou/Institut de Physique du Globe de Parise Physique
There is more oxygen in the core of Earth than originally thought. Lawrence Livermore geologist Rick Ryerson and international colleagues discovered some new findings about Earth’s core and mantle by considering their geophysical and geochemical signatures together. This research provides insight into the origins of Earth’s formation.
Based on the higher oxygen concentration of the core, Ryerson’s team concludes that Earth must have accreted material that is more oxidized than the present-day mantle, similar to that of planetesimals such as asteroidal bodies. A planetesimal is an object formed from dust, rock and other materials and can be can be anywhere in size from several meters to hundreds of kilometers.
Earth formed about 4.56 billion years ago over a period of several tens of millions of years through the accretion of planetary embryos and planetesimals. The energy delivered by progressively larger impacts maintained Earth’s outer layer and an extensively molten magma ocean. Gravitational separation of metal and silicate within the magma ocean results in the planet characterized by a metallic core and a silicate mantle.
The formation of Earth’s core left behind geophysical and geochemical signatures in the core and mantle that remain to this day. In the past, core formation models have only attempted to address the evolution of core and mantel compositional signatures separately rather than looking for a joint solution.
By combining experimental petrology, geochemistry, mineral physics and seismology, the team found that core formation occurred in a hot (liquid) moderately deep magma ocean not exceeding 1,800-kilometer depth, under conditions more oxidized than present-day Earth.
“This new model is at odds with the current belief that core formation occurred under reduction conditions,” Ryerson said. “Instead we found that Earth’s magma ocean started out oxidized and has become reduced through time by oxygen incorporation into the core.”
They found the oxygen concentrations in the core are higher than previously thought and silicon concentrations are lower than previous estimates.
Reference:
James Badro, John P. Brodholt, Hélène Piet, Julien Siebert, Frederick J. Ryerson. Core formation and core composition from coupled geochemical and geophysical constraints. Proceedings of the National Academy of Sciences, 2015; 201505672 DOI: 10.1073/pnas.1505672112
An artist’s depiction of what researchers believe the dinosaur looked like. Credit: James Havens
A Florida State University and University of Alaska Fairbanks research team has uncovered a new species of duck-billed dinosaur, a 30-footlong herbivore that endured months of winter darkness and probably experienced snow.
The skeletal remains of the dinosaurs were found in a remote part of Alaska. These dinosaurs were the northernmost dinosaurs known to have ever lived.
“The finding of dinosaurs this far north challenges everything we thought about a dinosaur’s physiology,” said FSU Professor of Biological Science Greg Erickson. “It creates this natural question. How did they survive up here?”
The dinosaur is named Ugrunaaluk kuukpikensis, which means ancient grazer of the Colville River. The remains were found along the Colville River in a geological formation in northern Alaska known as the Prince Creek Formation.
The discovery is detailed in the Tuesday issue of the paleontology journal Acta Palaeontologica Polonica.
“This new study names and brings to life what is now the most completely known species of dinosaur from the Polar Regions,” said Patrick Druckenmiller, earth sciences curator of the University of Alaska Museum of the North and associate professor of geology at the University of Alaska Fairbanks.
The dig site — the Prince Creek Formation — is a unit of rock that was deposited on an arctic, coastal flood plain about 69 million years ago.
At the time the Prince Creek Formation was deposited, it was located well above the paleo-arctic circle, about 80 degrees north latitude. So, the dinosaurs found there lived as far north as land is known to have existed during this time period.
At the time they lived, Arctic Alaska was covered in trees because Earth’s climate was much warmer as a whole. But, because it was so far north, the dinosaurs likely contended with months of winter darkness, even if it wasn’t as cold as a modern-day winter. They lived in a world where the average temperature was about 43 degrees Fahrenheit, and they probably saw snow.
“What we’re finding is basically this lost world of dinosaurs with many new forms completely new to science,” Erickson said.
Since the 1980s scientists from the University of Alaska Museum of the North, and other collaborative institutions, including Florida State University, have collected more than 9,000 bones from various animals as part of the excavation of the Prince Creek Formation.
The majority of the bones of the Ugrunaaluk kuukpikensis were collected from a single layer of rock called the Liscomb Bonebed. The layer, about 2 to 3 feet thick, contains thousands of bones of primarily this one species of dinosaur.
In this particular area, most of the skeletons were from younger or juvenile dinosaurs, about 9 feet long and three feet tall at the hip.
Researchers believe a herd of juveniles was killed suddenly to create this deposit of remains.
Hirotsugu Mori, a former graduate student at UAF, completed a detailed analysis of the bone structure as part of his doctoral dissertation alongside Druckenmiller and Erickson.
Their work revealed that the Ugrunaaluk kuukpikensis is most closely related to Edmontosaurus, another type of duck-billed dinosaur that lived roughly 70 million years ago in Alberta, Montana and South Dakota.
But, the combination of features found in these skeletons were not present in Edmontosaurus or in any other species of duck-billed dinosaurs.
In particular, researchers observed that the Ugrunaaluk kuukpikensis had very unique skeletal structures in the area of the skull, especially around the mouth.
“Because many of the bones from our Alaskan species were from younger individuals, a challenge of this study was figuring out if the differences with other hadrosaurs was just because they were young, or if they were really a different species,” Druckenmiller said. “Fortunately, we also had bones from older animals that helped us realize Ugrunaaluk was a totally new animal.”
Druckenmiller worked with an instructor of the Iñupiaq language at the Alaska Native Language Center at University of Alaska Fairbanks to develop a name for the new species that was culturally, anatomically and geographically correct. They wanted to pay tribute to the local tribes who live near the research site.
Erickson and Druckenmiller will continue to mine the Prince Creek Formation for additional skeletons. However, accessing the field site is extremely difficult. Besides the frigid weather, they have to use bush planes that are capable of landing on gravel bars and inflatable boats to access the sites, and often have to repel down the side of a cliff to do the digging.
The area is rich with animal skeletons, and they estimate there are at least 13 different species of dinosaur present based on teeth and other remains, plus birds, small mammals and some fish.
They will also delve deeper into how these animals lived and functioned in conditions not typically thought to be amenable to occupation by reptilian dinosaurs.
“Alaska is basically the last frontier,” said Erickson, who is originally from Alaska. “It’s virtually unexplored in terms of vertebrate paleontology. So, we think we’re going to find a lot of new species.”
Three full skeletons of Ugrunaaluk kuukpikensis will be on display at the University of Alaska Museum of the North as well as a new painting of the species by Alaskan artist James Havens.
This research was supported by the National Science Foundation and the Department of Interior’s Bureau of Land Management. The research is also the primary subject of the doctoral thesis completed by Druckenmiller’s former graduate student Hirotsugu Mori, who is now a curator for the Saikai City Board of Education in Japan.
Video
A collaborative team between Florida State University and the University of Alaska Fairbanks has spent the last five years digging in a remote bone-bed of dinosaur remains in the remote Prince Creek Formation in Alaska. FSU Professor Gregory Erickson is excited for the new species of duck-billed dinosaurs uncovered in the dig and believes it opens up a lost province of arctic adapted dinosaurs. The new dino, Ugrunaaluk kuukpikensis, is closely related to Edmontosauras, another duck-billed dinosaur found further south near Alberta, Montana, and South Dakota, but several structural differences in adult skeletons helped Erickson and Pat Druckenmiller of the University of Alaska Fairbanks determine it is in fact a different species.
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Reference:
Hirotsugu Mori, Patrick Druckenmiller, Gregory Erickson. A new Arctic hadrosaurid (Dinosauria: Hadrosauridae) from the Prince Creek Formation (lower Maastrichtian) of northern Alaska. Acta Palaeontologica Polonica, 2016; 61 DOI: 10.4202/app.00152.2015
