The study has been carried out with data from the four Cluster satellites (Image: ESA)
Space is not empty. A wind of charged particles blows outwards from the Sun, carrying a magnetic field with it. Sometimes this solar wind can break through the Earth’s magnetic field. Researchers at the Swedish Institute of Space Physics (IRF) in Uppsala now have an answer to one of the questions about how this actually occurs.
When two areas with plasma (electrically charged gas) and magnetic fields with different orientations collide, the magnetic fields can be “clipped off” and “reconnected” so that the topology of the magnetic field is changed. This magnetic reconnection can give energy to eruptions on the solar surface, it can change the energy from the solar wind so that it then creates aurora, and it is one of the obstacles to storing energy through processes in fusion reactors.
If two colliding regions of plasma have the same density, temperature and strength (but different orientation) of their magnetic fields, symmetrical reconnection begins. Scientists understand much about this process. But more usual in reality is that two regions of plasma have different characteristics, for example when the solar wind meets the environment round the Earth. Daniel Graham at IRF has recently published a detailed study of this asymmetrical magnetic reconnection in Physical review Review Letters 112, 215004 (2014). The study uses data from the four European Space Agency satellites in the Cluster mission, satellites which fly in formation in the Earth’s magnetic field.
“Especially important were measurements with two satellites only a few tens of kilometres from each other, in the region where the solar wind meets the Earth’s magnetic field,” says Daniel Graham. “We can thus do detailed measurements to understand plasma physics at a height of 60,000 km.”
Heating of electrons parallel to the magnetic field in conjunction with magnetic reconnection is of especial interest.
“We believe that this is an important piece of the puzzle for understanding how magnetic reconnection works, how charged particles are accelerated, and how particles from different regions can be mixed with each other,” says Daniel Graham. “Our detailed measurements in the Earth’s magnetic field can be used to understand the physics even in fusion reactors on Earth, and in far distant regions in space that we can’t reach with satellites.”
Note : The above story is based on materials provided by Institutet för rymdfysik – Swedish Institute of Space Physics (IRF).
How did oxygen levels in the atmosphere expand enough to allow life to evolve? Researchers may have solved one of the biggest puzzles in geochemistry. Credit: Copyright Michele Hogan
Scientists investigating one of the greatest riddles of Earth’s past may have discovered a mechanism to help determine how oxygen levels in the atmosphere expanded to allow life to evolve.
High concentrations of atmospheric oxygen have been essential for the evolution of complex life on Earth. Over the 4.5 billion years of Earth history, oxygen concentration has risen from trace amounts to 21% of the atmosphere today. However, the mechanisms behind this rise are uncertain, and it remains one of the biggest puzzles in geochemistry.
A research group from the University of Exeter has discovered one possible mechanism, relating to the way in which carbon dioxide is removed from the atmosphere over long timescales.
Dr Benjamin Mills, of Geography, said: “On the early Earth, CO2 levels were controlled by hydrothermal processes on the seafloor. As Earth cooled, and the continents grew, chemical processes on the continents took over.”
Using computer models, the group has shown that this switch may explain increasing oxygen concentration over Earth’s middle age (the Proterozoic era), which ultimately led to conditions suitable for complex life. According to the authors, the oxygen rise is caused by a gradual increase in marine limiting nutrients, which are a product of chemical weathering of the continents.
Dr Mills added: “The more CO2 that is sequestered by continental weathering, the larger the phosphate source to the oceans. Phosphate availability controls the long term photosynthetic productivity, which leads to oxygen production.”
“This is not the only reason oxygen rose to high levels, but it seems to be an important piece of the puzzle. Whilst the carbon cycle can function without large continents, it seems that their emergence was critical to our own evolution.”
Note : The above story is based on materials provided by University of Exeter.
Chemical Formula: K2Ca4Al2Be4Si24O60·H2O Locality: Val Milar, Switzerland. Name Origin: Named after its locality.
Milarite is a fairly rare mineral and yet it is one of the two minerals that gives its name to a somewhat large group of silicates, namely the Milarite – Osumilite Group. The group is composed of similar cyclosilicate minerals that are all very rare and very obscure with the exception of milarite, osumilite and sugilite. The primary structural unit of the minerals in the Milarite – Osumilite Group is a most unusual double ring, Si12O30. Normal rings of cyclosilicates are composed of six silicate tetrahedrons; Si6O18. The double rings of the Milarite – Osumilite Group minerals are made of two normal rings linked together by sharing one oxygen in each of the tetrahedrons. The structure is analogous to the dual wheels of a tractor trailer.
Milarite crystals are generally small, but can make excellent micromounted specimens. They are often colored a muted green or yellow and form good prismatic hexagonal crystals. Milarite forms as a primary mineral in granitic pegmatites and syenites, hydrothermal veins and alpine clefts. It has been cut as a gem, but is too rare, small and its general translucency that makes it only suitable to be cut for collectors of rare gemstones. Milarite is named for its locality of first discovery; Val Giuf (Val Milar), Tavetsch, Grischum, Switzerland. Milarite has been known as giufite and giuffite, but milarite is the only accepted name now. Good mineral specimens are available and can be quite attractive, but mostly under magnification.
History
Discovery date : 1870 Town of Origin : VAL GIUV, TAVETSCH, GRISONS Country of Origin : SUISSE
Optical properties
Optical and misc. Properties : Transparent to translucent Refractive Index: from 1,52 to 1,55
Physical Properties
Cleavage: {0001} Imperfect, {1120} Imperfect Color: Colorless, White, Greenish white, Yellowish white. Density: 2.52 Diaphaneity: Transparent to translucent Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 6 – Orthoclase Luminescence: Fluorescent, Short UV=bluish white. Luster: Vitreous (Glassy) Streak: white
The robust teeth of Tyrannosaurus are near circular in cross-section and better adapted to heavy bites than those of almost all other carnivorous dinosaurs. Photograph: Daniel Parks/Flickr
Much of my research looks at reconstructing the behaviour of non-avian dinosaurs: animals that have been extinct for some 66 million years and are represented only by fossils. This statement alone is often enough for people to either ask how on Earth this is possible, or to state quite baldly that it must all be made up. As with many branches of science, certainly there have been (and occasionally still are) some pretty terrible ideas and hypotheses that have been advocated at various times for dinosaur behaviour, but there is a myriad of sources of information and techniques that can be brought to bear on the problem.
The majority of dinosaur remains are of course bones and teeth, but these have a lot to say. Aside from very obvious things like the teeth of carnivores tending towards being sharp, some major anatomical adaptations are strongly linked with certain behaviours. For example, animals that can run quickly and especially those that are efficient over long distances have a short thigh, but long foot, so we can make some reasonable deductions about how they moved from this. Others are still more extreme and clear cut – those animals that dig show a whole suite of adaptations to the claws, fingers, wrist, elbow, shoulder and pelvis and often too the ribs, and joints in the backbone. So when we see all of these features in the tiny alvarezsaurid dinosaurs, we can be very confident that they could dig.
We can even test these kinds of mechanical ideas with computer simulations. The skull of Tyrannosaurus for example has been shown to be exceptionally good at resisting the forces delivered in biting (more so than other carnivores) and this matches the extra-strong teeth they have, the increased areas for muscle attachment to deliver that bite, and even punctures made in the bones of other dinosaurs when tyrannosaurs bit them. Bringing together multiple lines of evidence like this can therefore build an exceptionally strong and coherent picture of certain behaviours.
Bite marks on bones can provide more detail than just how hard animals were biting, but also whole patterns of feeding. Are the teeth driven into the bone, or do they slide across the surface? Actually tyrannosaurs seem to have done both, biting hard on joints, but scraping teeth across the surface to rip meat off a relatively fresh carcass. Often it is hard to match marks from teeth to individual species, but it is possible in some cases.
Better still are stomach contents. Sometimes dinosaur specimens do preserve with the remains of their meals inside (and the reverse is true, dinosaurs were eaten by other animals too). This is more common for carnivores where bones can survive well and from this we know that many carnivorous dinosaurs seem to have preferentially fed on small or juvenile dinosaurs. Others ate a wide variety of other animals, and the tiny gliding Microraptor seems to have been a generalist with various specimens having consumed a fish, a bird, and the foot of an early mammal. Herbivorous dinosaurs are known to have consumed various leaves, ferns and even pine cones. Continuing down the gut, we also occasionally get coprolites – fossil feces – and naturally this can give a pretty clear idea of what the animals were eating.
On oviraptorosaur dinosaur brooding a nest of eggs. Photograph: Ryan Somma/Flickr
Moving on from feeding, we can also reasonably infer that dinosaurs were reproducing, after all, they were around for quite a while and birds (and bees, and even educated fleas) are still doing it. More than that though, we see eggs laid in patterns in nests, as do some modern birds. We also see dinosaurs preserved brooding on those nests, protecting the eggs and perhaps sheltering and insulating them with feathers too. The dinosaur Oviraptor (the “egg thief”) was so named because it was found in association with eggs thought to belong to another dinosaur, but later discoveries of embryos within these eggs, showed in fact that the parents were protecting their unborn offspring. In other dinosaur nests we see babies considerably older than newly hatched individuals and even traces of food. This implies that the adults were looking after these babies long after they hatched, and that some extended parental care may have been involved.
This is something we would predict from their living relatives. Modern birds are literally living dinosaurs, and the crocodilians are their next nearest evolutionary relatives that are still alive today. Both exhibit parental care in nearly all species, looking after both the eggs and the hatchlings, in some cases for a number of years. That this is near universal behaviour for both, and when there is at least some evidence for this in dinosaurs, does imply that it was an ancestral trait for the collective group and thus most dinosaurs likely gave some care to their offspring pre- and post-hatching.
Other patterns of behaviour can also be detected from where fossils are found. For example, specimens of ankylosaurs (those wonderfully squat and armoured dinosaurs) are regularly found in marine deposits, even well out to sea. They were terrestrial animals, but perhaps spent a lot of their time close to the coast or around estuaries and rivers, meaning that they are washed into the sea more often than many others. On the flip side, the pachycephalosaurs and their giant bony heads seem to have favoured upland environments. Fossils of these animals are very rare and most of their remains are only the “skullcaps” of solid bone, but these are rather beaten up. This is exactly the pattern we see when bodies have been transported a long way by rivers with skeletons being broken up, small bones destroyed and only the most robust parts (here, the top of the skull) surviving and the clear conclusion therefore is that they lived in upland areas.
Put all of these lines of evidence together – eggs, nests, anatomical specialisations, coprolites, mechanical tests, bite marks, stomach contents, preservation types – and we can really start to get to grips with these issues. Add into this other studies – such as from footprints and trackways, reconstructing muscle groups, analysis of seasonal temperatures and climatic changes, scans of brains and bones around the ear to give ideas on senses, stress fractures in bones showing where peak forces were delivered, systematic injuries suggesting combat between horned dinosaurs – and you can see how a clear picture can be put together of the otherwise intangible behaviour of long extinct animals.
There are of course limitations here, and plenty is uncertain or unknown, but this is neither impossible to work out nor a work of fiction, but solid researched based on a wealth of data and careful analysis.
Note : The above story is based on materials provided by Dr Dave Hone for theguardian
This is a scanning electron microscope image of ocean plankton. Credit: University of Edinburgh
Rising global temperatures could increase the amount of carbon dioxide naturally released by the world’s oceans, fuelling further climate change, a study suggests.
Fresh insight into how the oceans can affect CO2 levels in the atmosphere shows that rising temperatures can indirectly increase the amount of the greenhouse gas emitted by the oceans.
Scientists studied a 26,000-year-old sediment core taken from the Gulf of California to find out how the ocean’s ability to take up atmospheric CO2 has changed over time.
They tracked the abundance of the key elements silicon and iron in the fossils of tiny marine organisms, known as plankton, in the sediment core. Plankton absorb CO2 from the atmosphere at the ocean surface, and can lock away vast quantities of carbon.
Researchers found that those periods when silicon was least abundant in ocean waters corresponded with relatively warm climates, low levels of atmospheric iron, and reduced CO2 uptake by the oceans’ plankton. Scientists had suspected that iron might have a role in enabling plankton to absorb CO2. However, this latest study shows that a lack of iron at the ocean surface can limit the effect of other key elements in helping plankton take up carbon.
This effect is magnified in the southern ocean and equatorial Pacific and coastal areas, which are known to play a crucial role in influencing levels of CO2 in the global atmosphere.
Researchers from the University of Edinburgh say their findings are the first to pinpoint the complex link between iron and other key marine elements involved in regulating atmospheric CO2 by the oceans. Their findings were verified with a global calculation for all oceans. The study, published in Nature Geoscience, was supported by Scottish Alliance for Geoscience Environment Society and the Natural Environment Research Council.
Dr Laetitia Pichevin, of the University of Edinburgh’s School of GeoSciences, who led the study, said: “Iron is known to be a key nutrient for plankton, but we were surprised by the many ways in which iron affects the CO2 given off by the oceans. If warming climates lower iron levels at the sea surface, as occurred in the past, this is bad news for the environment.”
More information:
Silica burial enhanced by iron limitation in oceanic upwelling margins, Nature Geoscience, DOI: 10.1038/ngeo2181
Note : The above story is based on materials provided by University of Edinburgh
Chemical Formula: (Na,Ca)2Ta2O6(O,OH,F) Locality: Isalnd of Uto, State of Stockholm, Sweden. Name Origin: From the Greek mikros – “small” and lithos – “stone.”
Microlite is a pale-yellow, reddish-brown, or black isometric mineral composed of sodium calcium tantalum oxide with a small amount of fluorine (Na,Ca)2Ta2O6(O,OH,F) . Microlite is a mineral in the pyrochlore group that occurs in pegmatites and constitutes an ore of tantalum. It has a Mohs hardness of 5.5 and a variable specific gravity of 4.2 to 6.4. It occurs as disseminated microscopic subtranslucent to opaque octahedral crystals with a refractive index of 2.0 to 2.2. Microlite is also called djalmaite.
Microlite occurs as a primary mineral in lithium-bearing granite pegmatites, and in miarolitic cavities in granites. Association minerals include: albite, lepidolite, topaz, beryl, tourmaline, spessartine, tantalite and fluorite.
Microlite was first described in 1835 for an occurrence on the Island of Uto, State of Stockholm, Sweden. A type locality is the Clark Ledges pegmatite, Chesterfield, Hampshire County, Massachusetts. The name is from Greek mikros for “small” and lithos for “stone.”
History
Discovery date : 1835 Town of Origin: CHESTERFIELD, HAMPSHIRE CO., MASSACHUSETTS Country of Origin : USA
Optical properties
Optical and misc. Properties: Subtranslucent to opaque Refractive Index: from 1,93 to 2,02
Physical Properties
Cleavage: {111} Indistinct, {111} Indistinct, {111} Indistinct Color: Yellowish brown, Reddish brown, Greenish brown, Green, Gray. Density: 4.2 – 6.4, Average = 5.3 Diaphaneity: Subtranslucent to opaque Fracture: Sub Conchoidal – Fractures developed in brittle materials characterized by semi-curving surfaces. Hardness: 5-5.5 – Apatite-Knife Blade Luminescence: Non-fluorescent. Luster: Vitreous – Resinous Magnetism: Nonmagnetic Streak: light yellow
The moon. A new series of measurements of oxygen isotopes provides increasing evidence that the moon formed from the collision of the Earth with another large, planet-sized astronomical body, around 4.5 billion years ago. Credit: NASA/JPL
A new series of measurements of oxygen isotopes provides increasing evidence that the Moon formed from the collision of Earth with another large, planet-sized astronomical body, around 4.5 billion years ago.
This work will be published in Science on 6th June, and will be presented to the Goldschmidt geochemistry conference in California on 11th June.
Most planetary scientists believe that the Moon formed from an impact between Earth and a planet-sized body, which has been given the name Theia. Efforts to confirm that the impact had taken place had centred on measuring the ratios between the isotopes of oxygen, titanium, silicon and others. These ratios are known to vary throughout the solar system, but their close similarity between Earth and Moon conflicted with theoretical models of the collision that indicated that the Moon would form mostly from Theia, and thus would be expected to be compositionally different from Earth.
Now a group of German researchers, led by Dr. Daniel Herwartz, have used more refined techniques to compare the ratios of 17O/16O in lunar samples, with those from Earth. The team initially used lunar samples which had arrived on Earth via meteorites, but as these samples had exchanged their isotopes with water from Earth, fresher samples were sought. These were provided by NASA from the Apollo 11, 12 and 16 missions; they were found to contain significantly higher levels of 17O/16O than their Earthly counterparts.
Dr Herwartz said “The differences are small and difficult to detect, but they are there. This means two things; firstly we can now be reasonably sure that the Giant collision took place. Secondly, it gives us an idea of the geochemistry of Theia. Theia seems to have been similar to what we call E-type chondrites.If this is true, we can now predict the geochemical and isotopic composition of the Moon, because the present Moon is a mixture of Theia and the early Earth. The next goal is to find out how much material of Theia is in the Moon.”
Most models estimate that the Moon it is composed of around 70% to 90% material from Theia, with the remaining 10% to 30% coming from the early Earth. However, some models argue for as little as 8% Theia in the Moon. Dr Herwartz said that the new data indicate that a 50:50 mixture seems possible, but this needs to be confirmed.
The team used an advanced sample preparation technique before measuring the samples via stable isotope ratio mass spectrometry, which showed a 12 parts per million (± 3 ppm) difference in 17O/16O ratio between Earth and Moon.
Note : The above story is based on materials provided by European Association of Geochemistry.
A newborn ocean. Only few tenths of kilometres separate the massive rift shoulders of the Sinai-Peninsula from the African continent on the far side of the Gulf of Suez. 130 Million years ago, the young South Atlantic ocean has likely looked similar. Credit: Christian Heine, University of Sydney, under Creative Commons
When South America split from Africa 150 to 120 million years ago, the South Atlantic formed and separated Brazil from Angola. The continental margins formed through this separation are surprisingly different. Along offshore Angola 200 km wide, very thin slivers of continental crust have been detected, whereas the Brazilian counterpart margin features an abrupt transition between continental and oceanic crust.
For decades, geoscientists have struggled to explain not only why the amount of thinning and the geometries of opposite rifted continental margin are not symmetric, but also why wide margins are often underlain by highly thinned continental crust. Now geoscientists from the German Research Centre for Geosciences (GFZ), the University of Sydney and the University of London have found an explanation, published in the current issue of Nature Communications. Using high-resolution computer models and geological data from the South Atlantic margins, they discovered that the centre of the rift, where the continental crust gets actively thinned through faulting, does not stay fixed during continental break-up, but migrates laterally.
“We could show that rifts are capable of moving sideways over hundreds of kilometres”, says Dr Sascha Brune of the GFZ. “During rift migration, the crust on one side of the rift is weakened by hot upwelling material in Earth’s mantle, whereas the other side is slightly stronger as the crust there is colder. New faults form only on the warm, weak rift side, while those of the strong side become inactive.” This leads to a sideways motion of the rift system, which is equivalent with conveying crustal material from the South American plate to the African plate. These transferred crustal blocks are strongly extended by the rift and finally constitute the enigmatic thin crustal slivers of the African margin.
Asymmetry of the South Atlantic continental margins. Shown is a model cross section for the South Atlantic, shortly after the separation of Africa and South America 120 million years ago. Credit: Sascha Brune, German Research Centre for Geosciences GFZ
Such a relocation of a rift takes its time: during the formation of the present-day Angolan and Brazilian margins, the rift centre migrated more than 200 km westward. This delayed continental break-up and the generation of oceanic crust by up to 20 million years. The new models reveal that extension velocity plays a crucial role in understanding the widths of South Atlantic margins: faster crustal extension leads to longer rift migration and hence to more pronounced asymmetry of the generated continental margins.
Rifts constitute an important tectonic element of our planet. They are responsible for the shape of today’s continents, and their activity still continues at present.
Illustrating a new aspect of plate tectonic theory, this study shows that during continental break-up, large amounts of material can be conveyed from one side of the plate boundary to the other, a process that has not been yet accounted for. The new models and analyses provide an important stepping-stone toward a comprehensive understanding of rift processes and continental margin formation.
Chemical Formula: KAlSi3O8 Locality: Common world wide occurrences. Name Origin: From the Greek mikron – “little” and klinein – “to stoop.”
Microcline (KAlSi3O8) is an important igneous rock-forming tectosilicate mineral. It is a potassium-rich alkali feldspar. Microcline typically contains minor amounts of sodium. It is common in granite and pegmatites. Microcline forms during slow cooling of orthoclase; it is more stable at lower temperatures than orthoclase. Sanidine is a polymorph of alkali feldspar stable at yet higher temperature. Microcline may be clear, white, pale-yellow, brick-red, or green; it is generally characterized by cross-hatch twinning that forms as a result of the transformation of monoclinic orthoclase into triclinic microcline.
Microcline may be chemically the same as monoclinic orthoclase, but because it belongs to the triclinic crystal system, the prism angle is slightly less than right angles; hence the name “microcline” from the Greek “small slope.” It is a fully ordered triclinic modification of potassium feldspar and is dimorphous with orthoclase. Microcline is identical to orthoclase in many physical properties; it can be distinguished by x-ray or optical examination; viewed under a polarizing microscope, microcline exhibits a minute multiple twinning which forms a grating-like structure that is unmistakable.
History
Discovery date : 1830 Town of Origin : FREDRIKSVARN Country of Origin : NORVEGE
Optical properties
Optical and misc. Properties : Translucent to transparent Refractive Index : from 1,51 to 1,53 Axial angle 2V : 66-103°
Physical Properties
Cleavage: {001} Perfect, {010} Good Color: Bluish green, Green, Gray, Grayish yellow, Yellowish. Density: 2.56 Diaphaneity: Translucent to transparent Fracture: Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern. Hardness: 6 – Orthoclase Luminescence: Fluorescent, Short UV=cherry red. Luster: Vitreous (Glassy) Streak: white
During the Last Glacial Maximum, large lakes (light blue) covered many of the now dry desert basins of Nevada, Oregon and California. Credit: Daniel Ibarra
A new study by Stanford scientists solves a longstanding mystery of how ancient lakes in the western United States grew to such colossal sizes.
The research, published in the journal Geological Society of America Bulletin, found that the lakes were able to grow large – rivaling the Great Lakes – during the peak of the last Ice Age 21,000 years ago, a period known as the “Last Glacial Maximum,” because evaporation rates were significantly lower than today.
“It was previously thought that the lakes grew because there was more rain and snowfall during this period of the Earth’s history,” said Daniel Ibarra, a graduate student in Stanford’s Department of Environmental Earth System Science and the first author of the study.
More quantitative studies of past climate could help refine the computer models used by the Intergovernmental Panel on Climate Change (IPCC) to simulate Earth’s atmospheric conditions under changing atmospheric conditions, said Kate Maher, assistant professor of geological and environmental sciences, who headed the project.
“The IPCC uses climate models to simulate past and future climate, so knowing that some of the models do a better job of simulating past changes gives us more confidence that we understand the physics involved,” Maher said. “That can give us more confidence in the models we use to simulate future climate change.”
During the Last Glacial Maximum (LGM), giant lakes covered large sections of California, Nevada, Oregon and Utah, including where Salt Lake City is today. Earth scientists have long been puzzled by how these ancient lakes, now completely dry, grew so large. The prevailing theory was there was more rain and snowfall during this time period. But recent evidence from paleoecology and climate model simulations indicates that precipitation rates were actually relatively low compared to later periods.
To resolve the discrepancy between computer models and the interpretation of geologic evidence, Ibarra collected more than 80 samples of tufa – a limestone created by the evaporation of mineralized water – from different locations around the edges of Lake Surprise, a moderate-sized fossil lake in Surprise Valley, California.
“The smaller lakes can tell you about the regional climate and can serve as a water gauge for the bigger lakes,” Maher said.
By measuring the decay of radioactive carbon-14 and uranium in tufa samples, the team reconstructed the ancient shorelines of Lake Surprise at different times in the past. Their findings showed that at the height of the LGM, Lake Surprise had a surface area of about 390 square miles, roughly the size of San Francisco Bay.
With support from other laboratories at Stanford, Ibarra also used a mass spectrometer to precisely measure the amounts of two slightly different forms of oxygen in the tufa samples: oxygen-16 and the slightly heavier oxygen-18. Both isotopes of oxygen are present in water, but oxygen-18 water evaporates at a slower rate than oxygen-16 water. By knowing the ratio of oxygen-16 to oxygen-18 in the tufa samples, the scientists were able to calculate Lake Surprise’s water balance through time.
Cooler temperatures
Their analyses revealed that 21,000 years ago, the evaporation rate at Lake Surprise was nearly 40 percent lower than today, with precipitation rates similar to the modern era. These results are consistent with previously run climate simulations that show Earth’s climate was cooler during the LGM.
The cooler global temperatures would have reduced evaporation rates, allowing the lakes to gradually grow over time through inflows from streams and rivers.
“Lake Surprise is located in a closed basin. All streams flow into the lake, but there is no outflow. The only way for water to escape is through evaporation,” Ibarra said.
The team’s dating and isotope measurements also show that precipitation rates in the region increased for a brief period after the LGM. The tufa measurements indicated that Lake Surprise reached its largest size – around 530 square miles – 15,000 years ago.
Thus, the enormous lakes that once dotted the western United States initially grew large during the peak of the LGM due to reduced evaporation, but didn’t reach their maximum sizes until several thousand years later, when rain and snowfall increased.
Knowledge about the past precipitation patterns of the region could be used to test the accuracy of the differing climate models scientists currently use to simulate global climate conditions.
“We can actually rank the models now,” Ibarra said. “Our findings have implications for evaluating the models, and deciding which models successfully reproduced the past precipitation patterns we observe.”
More information:
“Rise and fall of late Pleistocene pluvial lakes in response to reduced evaporation and precipitation: Evidence from Lake Surprise, California,” Geological Society of America Bulletin, B31014.1, first published on June 2, 2014, DOI: 10.1130/B31014.1
Note : The above story is based on materials provided by Stanford University
Upper left to Lower right: This image shows different color morphs, genetically found to be identical, of the chirping giant pill-millipede (Sphaeromimus musicus), and a similar-looking species (lower left) of a different genus (Zoosphaerium blandum). Credit: Wesener 2007
An international team of researchers comprised of Thomas Wesener, Museum Koenig, Bonn, Daniel Le, Field Museum, Chicago and Stephanie Loria, American Museum of Natural History, New York, discovered seven new species of chirping giant pill-millipedes on Madagascar. The study was published in the open access journal ZooKeys.
The species discovered all belong to the genus Sphaeromimus, which is Latin for ‘small ball animal’. However, the designation ‘small’ is not always true for the members of the genus as one of the newly discovered species surprises with a size larger than a ping-pong ball. Another special characteristic of the genus is that its species have the largest chirping organs of any millipede, which are most probably used during mating.
Despite sometimes sharing a habitat with Madagascar’s ‘large’ pill-millipedes, which can reach the size of a baseball, the new species are more closely related to millipedes found in India than their Malagasy neighbours. This relationship dates back more than 80 million years to at least as early as the Cretaceous period, when dinosaurs walked the Earth and India and Madagascar were connected.
One of the new species Sphaeromimus andrahomana offers clues to Madagascar’s ecosystems thousands of years ago. Although the species was found in a cave in Madagascar’s southern dry spiny forest region, genetically, it is a rainforest taxon. The lemur skeletons found inside the same cave are also evidence that a rainforest existed in the now desert-like area until 3000-5000 years ago. The species, sheltered by the humid cave, is probably a living witness to this ancient rainforest.
The discovery is particularly exciting as some of species are microendemics, meaning they are only found in one tiny forest fragment, a few hundred meters long and wide.
S. lavasoa, for example, is restricted to the Lavasoa Mountain, which is covered by an isolated, slightly larger than 100 hectare, rainforest remnant, which is famous for the recent discovery of a large scorpion as well as a dwarf lemur species. This discovery further highlights the importance of the area as a Center of Endemism.
Another new species (S. saintelucei) is probably the most endangered millipede on Madagascar. It was found in a fragment of the Sainte Luce littoral rainforest characterized by its laterite soil that is now so small that no lemur or other large vertebrate species can survive in it.
The nearby Sainte Luce forest fragment with sandy ground harbours a different species (S. splendidus) also believed to be a microendemic. “Despite their close proximity, both species are not even closely related. Both the fragments where they were found are currently threatened by a huge, billion-dollar titanium ore strip mining project. Although there are intentions to designate and manage conservation zones, the plan is to protect only one large fragment may result in the extinction of some of the species if additional conservation measures aren’t undertaken.” explains the lead author Dr. Thomas Wesener from the Research Museum Alexander Koenig in Bonn, Germany.
Original source:
Wesener T, Le DM-T, Loria SF (2014) Integrative revision of the giant pill-millipede genus Sphaeromimus from Madagascar, with the description of seven new species (Diplopoda, Sphaerotheriida, Arthrosphaeridae). ZooKeys 414: 67. doi: 10.3897/zookeys.414.7730
Note : The above story is based on materials provided by Pensoft Publishers
Chemical Formula: AgSbS2 Locality: Braunsdorf, Freiberg, Sachsen (Saxony), Germany. Name Origin: From the Greek, meyon, “smaller” and argyros, “silver.” in allusion to the lessor silver content of the mineral.
Miargyrite is a mineral, a sulfide of silver and antimony with the formula AgSbS2. It is a dimorph of cuboargyrite. Originally discovered in the Freiberg district of Germany in 1824, it has subsequently been found in many places where silver is mined. It usually occurs in low temperature hydrothermal deposits. and forms black metallic crystals which may show a dark red internal reflection. The streak is also red.
Miargyrite is named from the Greek meyon, “smaller” and argyros, “silver,” as its silver content is lower than most silver sulfides.
History
Discovery date : 1829 Town of Origin : BRAUNSDORF, FREIBERG, SAXE Country of Origin : ALLEMAGNE
Optical properties
Optical and misc. Properties : Translucent to Subopaque Reflective Power: 26,3-38,7% (580) Refractive Index : from 2,72 to 2,73
Physical Properties
Cleavage: {010} Imperfect Color: Steel gray, Lead gray, Blackish red, Reddish gray. Density: 5.1 – 5.3, Average = 5.19 Diaphaneity: Translucent to Subopaque Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 2-2.5 – Gypsum-Finger Nail Luminescence: Non-fluorescent. Luster: Sub Metallic Streak: cherry red
The Nyiragongo lava lake at night. Credit: INVOLCAN
Data from the Meteosat satellite 36,000 km from Earth, has been used to measure the temperature of lava at the Nyiragongo lava lake in the Democratic Republic of Congo. An international team compared data from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) on board Meteosat with data collected at the lava lake with thermal cameras. Researchers say the technique could be used to help monitor volcanoes in remote places all over the world, and may help with the difficult task of anticipating eruptions.
Data from the Meteosat satellite has been used to measure the temperature of lava at a remote volcano in Africa.
The scientists compared data from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) on board Meteosat with ground data from a thermal camera, to show the temperature of the lava lake at Nyiragongo, in the Democratic Republic of Congo.
The technique was pioneered in Europe, and the researchers say it could be used to help monitor volcanoes in remote places all over the world.
“I first used the technique during a lava fountain at Mt Etna in August 2011,” says Dr. Gaetana Ganci, who worked on the study with colleagues Letizia Spampinato, Sonia Calvari and Ciro Del Negro from the Istituto Nazionale di Geofisica e Vulcanologia (INGV) in Italy.
“The first time I saw both signals I was really surprised. We found a very similar radiant heat flux curve — that’s the measurement of heat energy being given out — from the ground-based thermal camera placed a few kilometres from Etna and from SEVIRI at 36,000km above the Earth.”
Transferring the technique to Nyiragongo was important — partly because the exposed lava lake can yield data important for modelling shallow volcanic systems in general, but more importantly because advance warning of eruptions is necessary for the rapidly expanding city of Goma nearby.
The research, published in the Journal of Geophysical Research: Solid Earth is the first time in which Nyiragongo’s lake has been studied using ground-based thermal images in addition to satellite data to monitor the volcano’s radiative power record.
Dr. Ganci and her colleagues developed an algorithm they call HOTSAT to detect thermal anomalies in the Earth’s surface temperature linked to volcanoes. They calculate the amount of heat energy being given out in a target area based on analysis of SEVIRI images.
Combining the frequent SEVIRI images with the more detailed but less frequent images from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS), they showed that temperature anomalies could be observed from space before an eruption is underway. They believe that space-based observations can be a significant help in the difficult task of predicting volcanic eruptions, but that providing advance warning will never be easy.
“Satellite data are a precious means to improve the understanding of volcanic processes. There are cases of thermal anomalies being observed in volcanic areas just before an eruption,” says Ganci. “Combining different kinds of data from the ground and from space would be the optimal condition — including infra-red, radar interferometry, seismic measurements etc. But even in well-monitored volcanoes like Mt. Etna, predicting eruptions is not a trivial thing.”
The team developed HOTSAT with a view to making an automatic system for monitoring volcanic activity. They are now developing a new version of HOTSAT. This should allow the processing of all the volcanic areas that can be monitored by SEVIRI in near-real time.Continuing ground-based observations will be needed for validation.
“For remote volcanoes, such as Nyiragongo, providing reliability to satellite data analysis is even more important than in Europe. Thanks to ground-based measurements made by Pedro Hernández, David Calvo, Nemesio Pérez (ITER, INVOLCAN Spain), Dario Tedesco (University of Naples, Italy) and Mathieu Yalire (Goma Volcanological Observatory), we could make a step in this direction,” says Ganci.
“This study shows the range of science that can be done with Meteosat,” says Dr. Marianne Koenig, EUMETSAT’s atmospheric and imagery applications manager for the Meteosat Second Generation satellites, “And opens up the possibility of monitoring isolated volcanoes.”
Note : The above story is based on materials provided by European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT).
This image depicts ecological reconstructions of Hamipterus. Credit: Chuang Zhao
Researchers have discovered the first three-dimensionally preserved pterosaur eggs in China. The eggs were found among dozens, if not hundreds, of pterosaur fossils, representing a new genus and species (Hamipterus tianshanensis). The discovery, described in the Cell Press journal Current Biology on June 5, reveals that the pterosaurs — flying reptiles with wingspans ranging from 25 cm to 12 m — lived together in gregarious colonies.
Xiaolin Wang of the Chinese Academy of Sciences’ Institute of Vertebrate Paleontology and Paleoanthropology says it was most exciting to find many male and female pterosaurs and their eggs preserved together. “Five eggs are three-dimensionally preserved, and some are really complete,” he says.
The fossil record of the pterosaurs has generally been poor, with little information about their populations, the researchers say. Prior to this latest find, only four isolated and flattened pterosaur eggs were known to science.
The resting place of the pterosaurs now described was first uncovered in 2005 in the Turpan-Hami Basin, south of the Tian Shan Mountains in Xinjiang, northwestern China. The fossil-rich area may harbor thousands of bones, including three-dimensional male and female skulls and the first three-dimensional eggs. Wang says that sediments in the area suggest that the pterosaurs died in a large storm about 120 million years ago in the Early Cretaceous period.
The researchers examined the largely intact pterosaur egg specimens to find that they were pliable, with a thin, calcareous eggshell outside and a soft, thick membrane inside, similar to the eggs of some modern-day snakes. The researchers’ observations of 40 male and female individuals suggest differences between the sexes in the size, shape, and robustness of their head crests.
The combination of many pterosaurs and eggs strongly indicates the presence of a nesting site nearby and indicates that this species developed gregarious behavior, the researchers say. Hamipterus most likely buried their eggs in sand along the shore of an ancient lake to prevent them from drying out. While the new fossils shed light on the reproductive strategy, development, and behavior of pterosaurs, there is still plenty left to learn about them.
“Sites like the one reported here provide further evidence regarding the behavior and biology of this amazing group of flying reptiles that has no parallel in modern time,” the researchers write.
Note : The above story is based on materials provided by Cell Press.
Chemical Formula: Cu(UO2)2(PO4)2·8H2O Locality: Schneeberg, Sachsen (Saxony), Germany Name Origin: Named as the lower hydrate of tobernite.
Metatorbernite (or meta-torbernite) is a radioactive phosphate mineral, and is a dehydration pseudomorph of torbernite. Chemically, it is a copper uranyl phosphate and usually occurs in the form of green platy deposits. It can form by direct deposition from a supersaturated solution, which produces true crystalline metatorbernite, with a dark green colour, translucent diaphaneity, and vitreous lustre. However, more commonly, it is formed by the dehydration of torbernite, which causes internal stress and breakage within the crystal lattice, resulting in crystals composed of microscopic powder held together using electrostatic force, and having a lighter green colour, opaque diaphaneity, and a relatively dull lustre. As with torbernite, it is named after the Swedish chemist Tornbern Bergmann. It is especially closely associated with torbernite, but is also found amongside autunite, meta-autunite and uraninite.
History
Discovery date : 1786 Town of Origin: SCHNEEBERG, SAXE Country of Origin : ALLEMAGNE
Optical properties
Optical and misc. Properties : Transparent to Translucent Refractive Index: 1,62
Physical Properties
Cleavage: {001} Perfect Color: Light green, Dark green. Density: 3.7 – 3.8, Average = 3.75 Diaphaneity: Transparent to Translucent Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 2.5 – Finger Nail Luster: Vitreous – Adamantine Streak: light green
McGill field crew collecting fossils as part of a field course in Grasslands National. Credit: Larsson/Bamforth
As far back as the time of the dinosaurs, 66 million years ago, forests recovered from fires in the same manner they do today, according to a team of researchers from McGill University and the Royal Saskatchewan Museum.
During an expedition in southern Saskatchewan, Canada, the team discovered the first fossil-record evidence of forest fire ecology — the regrowth of plants after a fire — revealing a snapshot of the ecology on earth just before the mass extinction of the dinosaurs. The researchers also found evidence that the region’s climate was much warmer and wetter than it is today.
“Excavating plant fossils preserved in rocks deposited during the last days of the dinosaurs, we found some preserved with abundant fossilized charcoal and others without it. From this, we were able to reconstruct what the Cretaceous forests looked like with and without fire disturbance,” says Hans Larsson, Canada Research Chair in Macroevolution at McGill University.
The researchers’ discovery revealed that at the forest fire site, the plants are dominated by flora quite similar to the kind that begin forest recovery after a fire today. Ancient forests recovered much like current ones, with plants like alder, birch, and sassafras present in early stages, and sequoia and ginkgo present in mature forests.
“We were looking at the direct result of a 66-million-year old forest fire, preserved in stone,” says Emily Bamforth, of the Royal Saskatchewan Museum and the study’s first author. “Moreover, we now have evidence that the mean annual temperature in southern Saskatchewan was 10-12 degrees Celsius warmer than today, with almost six times as much precipitation.”
“The abundant plant fossils also allowed us for the first time to estimate climate conditions for the closing period of the dinosaurs in southwestern Canada, and provides one more clue to reveal what the ecology was like just before they went extinct,” says Larsson, who is also an Associate Professor at the Redpath Museum.
Forest fires can affect both plant and animal biodiversity. The team’s finding of ancient ecological recovery from a forest fire will help broaden scientists’ understanding of biodiversity immediately before the mass extinction of dinosaurs. “We won’t be able to fully understand the extinction dynamics until we understand what normal ecological processes were going on in the background.” says Larsson.
Note : The above story is based on materials provided by McGill University.
Dr Mark Cuthbert inspects a speleothem in Wellington Caves. Credit: Martin S. Andersen
Researchers studying the hydrology of Wellington Caves in central NSW have made a discovery that challenges a key assumption used to reconstruct past climates from cave deposits.
Published in Nature’s open access journal Scientific Reports, the research found that there can be a 1.5 degree Celsius difference between the temperature of the air in the cave and the drip water that forms the stalactite.
Stalactites and other cave formations – collectively known as speleothems – form when rainwater drips from the surface into the cave system, picking up minerals along the way that solidify once exposed to the cave air.
Scientists had previously assumed that speleothems formed at a temperature equal to the average temperature outside the cave and used this assumption to construct records of past climate variations, says lead author Dr Mark Cuthbert, holder of a European Community-funded Marie Curie Research Fellowship at UNSW’s Connected Waters Initiative.
“However that assumption had never been tested,” he says. “The 1.5 degree difference is very significant if you’re looking at past climate change. It is similar to the kind of change in temperature that we’ve had in the last 12,000 years naturally during the Holocene.”
The difference in temperature is attributed to evaporative cooling, which occurs as the water moves along the cave wall before reaching the point at which it drips and forms the speleothem.
“If you were looking at a speleothem formed in that environment and didn’t know this process of evaporative cooling was happening, you might jump to the wrong conclusions, in either direction, about what the climate outside the cave was like at the time the speleothem formed,” says co-author Monika Markowska, a Research Scientist at the Institute for Environmental Research at the Australian Nuclear Science and Technology Organisation (ANSTO).
ANSTO researchers have developed expertise in modelling climate change using nuclear techniques such as neutron activation soil analysis and carbon 14 dating.
The research team also includes Professor Andy Baker, Director of the Connected Waters Initiative (CWI) and other CWI researchers.
The same researchers recently found that other important evaporative effects occur between the soil and the cave that also need to be taken into account when interpreting speleothems as records of climate change.
“Further experimental work is underway to investigate the influence of the geometry, orientation, the thermal properties of a particular formation, and the water film thicknesses, on the relative cooling rate,” the researchers say in their paper.
Dr Cuthbert hopes that ongoing research will lead to numerical models that take into account all the different variables in a cave system that might influence climate change calculations.
Speleothem chemistry is one of several methods used to reconstruct past climates alongside other techniques including sediments, ice cores, trees and corals. Caves can yield particularly high-resolution records going back several hundred thousand years.
More information: “Evaporative cooling of speleothem drip water.” M. O. Cuthbert et al. Scientific Reports 4, Article number: 5162. DOI: 10.1038/srep05162. Received 28 March 2014 Accepted 07 May 2014 Published 04 June 2014
Note : The above story is based on materials provided by University of New South Wales
Chemical Formula: Ca(UO2)2(PO4)2· 6-8H2O Locality: Daybreak mine, Mt Spokane, Washington, USA Name Origin: Named as the lower hydrate of autunite.
Meta-autunite is a dehydration product of its close cousin, autunite, hence the name. When the mineral autunite loses water and converts to meta-autunite, it becomes what is known as a pseudomorph. A pseudomorph is generally an atom by atom replacement of one mineral’s chemistry in place of another mineral’s chemistry, while the original crystal’s outward shape remains largely unchanged. The process leaves the crystal shape of the original mineral intact, but the original mineral is no longer there. Pseudomorph translated from latin means false shape (pseudo=false; morph=shape).
The structure of meta-autunite is composed of phosphate tetrahedrons linked to uranium-oxygen groups that form distorted octahedrons. The phosphate and uranium groups form sheets that are weakly held together by water molecules. This structure produces the tabular habit, the one perfect direction of cleavage, and the relative softness. It is an analogous structure to that of the phyllosilicates.
Meta-autunite is a highly fluorescent mineral. It is said to fluoresce with a brightness comparable to some of the brightest fluorescing minerals in the world. The bright green fluorescence of meta-autunite is similar to other green fluorescing minerals such as autunite, adamite, green fluorescing opal and of course the spectacular willemites from Franklin, New Jersey, USA. The uranium is the fluorescent activator in meta-autunite and autunite. Trace amounts of uranium are responsible for the green fluorescence in opal and adamite as well. Remember because of the uranium, meta-autunite is a radioactive mineral and should be stored away from other minerals that are affected by radioactivity and human exposure should always be limited.
History
Discovery date : 1904
Optical properties
Optical and misc. Properties : Translucent to Opaque Refractive Index: from 1,58 to 1,60 Axial angle 2V : 0-20°
Physical Properties
Color: Yellow, Greenish yellow, Yellowish green. Density: 3.45 – 3.55, Average = 3.5 Diaphaneity: Translucent to Opaque Hardness: 1 – Talc Luminescence: Fluorescent, Short UV=pale yellow green, Long UV=pale yellow green. Luster: Pearly
Was it humankind or climate change that caused the extinction of a considerable number of large mammals about the time of the last Ice Age? Researchers at Aarhus University have carried out the first global analysis of the extinction of the large animals, and the conclusion is clear — humans are to blame. A new study unequivocally points to humans as the cause of the mass extinction of large animals all over the world during the course of the last 100,000 years.
“Our results strongly underline the fact that human expansion throughout the world has meant an enormous loss of large animals,” says Postdoctoral Fellow Søren Faurby, Aarhus University.
Was it due to climate change?
For almost 50 years, scientists have been discussing what led to the mass extinction of large animals (also known as megafauna) during and immediately after the last Ice Age.
One of two leading theories states that the large animals became extinct as a result of climate change. There were significant climate changes, especially towards the end of the last Ice Age — just as there had been during previous Ice Ages — and this meant that many species no longer had the potential to find suitable habitats and they died out as a result. However, because the last Ice Age was just one in a long series of Ice Ages, it is puzzling that a corresponding extinction of large animals did not take place during the earlier ones.
Theory of overkill
The other theory concerning the extinction of the animals is ‘overkill’. Modern man spread from Africa to all parts of the world during the course of a little more than the last 100,000 years. In simple terms, the overkill hypothesis states that modern man exterminated many of the large animal species on arrival in the new continents. This was either because their populations could not withstand human hunting, or for indirect reasons such as the loss of their prey, which were also hunted by humans.
First global mapping
In their study, the researchers produced the first global analysis and relatively fine-grained mapping of all the large mammals (with a body weight of at least 10 kg) that existed during the period 132,000-1,000 years ago — the period during which the extinction in question took place. They were thus able to study the geographical variation in the percentage of large species that became extinct on a much finer scale than previously achieved.
The researchers found that a total of 177 species of large mammals disappeared during this period — a massive loss. Africa ‘only’ lost 18 species and Europe 19, while Asia lost 38 species, Australia and the surrounding area 26, North America 43 and South America a total of 62 species of large mammals.
The extinction of the large animals took place in virtually all climate zones and affected cold-adapted species such as woolly mammoths, temperate species such as forest elephants and giant deer, and tropical species such as giant cape buffalo and some giant sloths. It was observed on virtually every continent, although a particularly large number of animals became extinct in North and South America, where species including sabre-toothed cats, mastodons, giant sloths and giant armadillos disappeared, and in Australia, which lost animals such as giant kangaroos, giant wombats and marsupial lions. There were also fairly large losses in Europe and Asia, including a number of elephants, rhinoceroses and giant deer.
Weak climate effect
The results show that the correlation between climate change — i.e. the variation in temperature and precipitation between glacials and interglacials — and the loss of megafauna is weak, and can only be seen in one sub-region, namely Eurasia (Europe and Asia). “The significant loss of megafauna all over the world can therefore not be explained by climate change, even though it has definitely played a role as a driving force in changing the distribution of some species of animals. Reindeer and polar foxes were found in Central Europe during the Ice Age, for example, but they withdrew northwards as the climate became warmer,” says Postdoctoral Fellow Christopher Sandom, Aarhus University.
Extinction linked to humans
On the other hand, the results show a very strong correlation between the extinction and the history of human expansion. “We consistently find very large rates of extinction in areas where there had been no contact between wildlife and primitive human races, and which were suddenly confronted by fully developed modern humans (Homo sapiens). In general, at least 30% of the large species of animals disappeared from all such areas,” says Professor Jens-Christian Svenning, Aarhus University.
The researchers’ geographical analysis thereby points very strongly at humans as the cause of the loss of most of the large animals.
The results also draw a straight line from the prehistoric extinction of large animals via the historical regional or global extermination due to hunting (American bison, European bison, quagga, Eurasian wild horse or tarpan, and many others) to the current critical situation for a considerable number of large animals as a result of poaching and hunting (e.g. the rhino poaching epidemic).
Note : The above story is based on materials provided by Aarhus University.
A geologist studied fossils to confirm that stones used in 19th century Ohio grain mills originated from France. Fossils embedded in these millstones were analyzed to determine that stones known as French buhr were imported from regions near Paris, France, to Ohio in the United States. Dr. Joseph Hannibal, curator of invertebrate paleontology at The Cleveland Museum of Natural History, was lead author on research published in the Society for Sedimentary Geology journal PALAIOS.
The study documents a technique that uses fossils to definitively distinguish French buhr from similar-looking Ohio chert (also known as flint). The most revealing fossil is a one-millimeter wide reproductive structure of a charophyte (a type of algae also known as a stonewort) that occurs in the rocks of the Paris Basin, a geological province centered around Paris, France.
Millstones made of Ohio chert were found to contain typical saltwater marine fossils that are much older than the fossils found in French buhr. These include brachiopods and small oval fossils called fusulinids and brachiopods. These Ohio rocks date from the latter part of the Paleozoic era (about 300 million years ago). Alternatively, the French stone is made from rock derived from freshwater deposits. The fossils found in this stone include freshwater snails and algae. The French stone dates from the Tertiary Period (from 65 to 2.6 million years ago), which is geologically younger than the Ohio stone.
“The story of the importation of this stone from France is not widely known,” said Dr. Joseph Hannibal, curator of invertebrate paleontology at The Cleveland Museum of Natural History. “They are not always correctly identified as being from France. Based on the stones we have examined, it is clear that the French stone was more popular. Examples of millstones made of this stone are widespread in North America and throughout the world. So the use of fossils for their identification is a broadly applicable concept.”
During the late 18th and 19th century, large amounts of stone known as French buhr were imported from France to Ohio and other states in North America for the manufacture of millstones. The French stone was preferred by grain millers over locally found stone because it was considered superior in cutting grain that sifted more easily to produce white flour. The Ohio cities of Cleveland and Cincinnati were major centers for manufacture of millstones made of this French stone. However, local Ohio stone, some of it similar in color and texture to the French stone, was quarried in eastern and southeastern Ohio at localities including the famous locality of Flint Ridge.
“Many millstones have been identified as being made of French stone or Ohio stone,” said Hannibal. “But since the stones used are generally similar in color and other properties, I questioned how these stones had been identified as originating from France or Ohio. When visiting the remains of an old mill in Trumbull County, Ohio, we first noticed that there were charophytes in some millstones. Our study progressed from there.”
The study was done over a period of five years. The research team searched 60 millstone sites, looking at several hundred millstones. A total of 16 millstones containing fossils were included in the study. The research team, which included college students and high school students, analyzed wafer thin samples of rock under microscopes. The team also applied liquid rubber latex to stone surfaces to obtain impressions of fossils such as snails for investigation. Four college students, two from Kent State University, one from Heidelberg University, and one from Oberlin College, are coauthors of this study.
The study is ongoing and is part of a broader research project on the geology of millstones and the trans-Atlantic stone trade. Millstones in about 30 Ohio counties have been studied to date as part of this larger project.
Note : The above story is based on materials provided by Cleveland Museum of Natural History.
