First riser-drilling research operations undertaken

Approximately 58 km southeast of Shingu City, Japan–Deepsea Drilling Vessel CHIKYU has resumed IODP drilling operations in the Nankai Trough Seismogenic Zone off the Kii Peninsula of Japan. The scientific drilling expedition’s first target is located in water depths of 2,054 meters. Following sea floor surveys, the crew began fitting riser pipe and a blow-out prevention (BOP) system into an upper section of the first borehole to be drilled. The riser pipe and BOP (the blow-out preventer) was successfully connected to the wellhead. After testing the circulation of the drilling fluid, the first riser-drilling operations for CHIKYU in the history of scientific ocean drilling began. The British Broadcasting Corporation (BBC) chronicled the lead-in to this historic activity, the first media organization outside Japan to broadcast live from aboard CHIKYU.

The target drilling depth at the first borehole is 1,600 meters below the seafloor. Following drilling operations, vertical seismic profiling (VSP) is expected to begin as part of geophysical logging.

Riser-drilling involves a large marine riser pipe that connects the CHIKYU to the seafloor. The riser pipe guides the drill pipe as it reenters the well. Drilling fluid is pumped up and down between the riser pipe and the drill pipe. Fluid circulation and use of the blow-out preventer (BOP) help to maintain pressure balance within the borehole and prevent it from collapsing, enabling safer and deeper drilling.

CHIKYU is the world’s first scientific drilling vessel capable of riser-drilling deep beneath the ocean floor and in seismogenic (earthquake-producing) zones that have never been reached before.

The Nankai Trough subduction zone, located southwest of Japan, is one of the most active earthquake zones on the planet, with complex geological formations caused by tectonic plate thrusts. The scheduled drill site, the Kumano Basin, is a fore-arc basin of the Nankai Trough under the influence of the strong Kuroshio ocean current. In combination with inclement weather expected, due to passing typhoons, and riser drilling down to depths of more than 2,000 meters below surface, this phase of NanTroSEIZE is considered one of the most challenging tasks in ocean-drilling history.

The average speed of the Kuroshio current in the surveyed area is about 1.0 knots, relatively slow for the current speed usually observed in the Kumano Basin. Yet, fairings are to be mounted onto to a riser pipe to smooth the hydrodynamic flow behind the riser pipe (to reduce riser drag) and suppress the vortex-induced vibration under high current conditions. The motion of the riser also will be monitored for analysis, in order to use the results in future operations.

Subseafloor sediment in South Pacific Gyre

An international oceanographic research expedition to the middle of the South Pacific Gyre – a site that is as far from continents as it is possible to go on Earth’s surface – found so few organisms beneath the seafloor that it may be the least inhabited sediment ever explored for evidence of life.

Yet since half of the world’s ocean is composed of similar gyres, biomass and metabolic activity may be equally low in sediment throughout much of the world.

Those are among the results of a study led by University of Rhode Island oceanographer Steven D’Hondt published in the online edition of the Proceedings of the National Academy of Sciences during the week of June 22. Other URI members of the research team were Marine Reearch Scientist Robert Pockalny and Oceanography Professors Arthur Spivack and David Smith.

“We wanted to know what life is like in subseafloor sediment where you have the least amount of organic matter produced in the overlying water column,” said D’Hondt, a professor at the URI Graduate School of Oceanography. “So we deliberately went where no one ever goes to compare it with sites previously studied.”

Gyres are semi-still areas in the middle of the oceans where there is little wind, little current, and very little upwelling of deep water, so the water is clear and contains few nutrients. The South Pacific Gyre is the largest of Earth’s gyres, encompassing an area twice the size of North America. D’Hondt describes its center as “the deadest spot in the ocean.”

Because the region is so far from terrestrial sources of sediment and so few organisms live in its water, its sediment accumulates extraordinarily slowly – as few as 8 centimeters per million years.

In 2007, the international team of scientists and students collected nearly 100 cores that reached up to 8 meters below the seafloor of the South Pacific Gyre and measured the number of living cells and the amount of respiration in the sediment. Their cell counts were three to four orders of magnitude lower than have been found at similar depths outside of the gyres, and the rate of respiration was one to three orders of magnitude lower.

Equally surprising was their finding that the subseafloor community is aerobic, unlike all other previously explored sites.

“In most places, oxygen is gone just a few centimeters below the seafloor, but we found that oxygen goes many meters below the seafloor at these sites, and possibly all the way through the sediment to the underlying igneous rock,” D’Hondt said.

In addition, D’Hondt said that the burial rate of organic matter was so low in the sediment that the principle food source for the microorganisms living there may be hydrogen released by the radioactive splitting of water due to the natural decay of elements in the sediment.

“As you get deeper, this hydrogen probably becomes a more important food source than buried organic matter,” D’Hondt said. “And when you get deep enough, it might be the only food available. The next step in our research is to test if that is the case.”

Sudden collapse in ancient biodiversity: Was global warming the culprit?

Ancient fossil leaves tell a story of sudden loss of biodiversity that may have future parallels. -  Jennifer C. McElwain, University College Dublin
Ancient fossil leaves tell a story of sudden loss of biodiversity that may have future parallels. – Jennifer C. McElwain, University College Dublin

Scientists have unearthed striking evidence for a sudden ancient collapse in plant biodiversity. A trove of 200 million-year-old fossil leaves collected in East Greenland tells the story, carrying its message across time to us today.

Results of the research appear in this week’s issue of the journal Science.

The researchers were surprised to find that a likely candidate responsible for the loss of plant life was a small rise in the greenhouse gas carbon dioxide, which caused Earth’s temperature to rise.

Global warming has long been considered as the culprit for extinctions–the surprise is that much less carbon dioxide gas in the atmosphere may be needed to drive an ecosystem beyond its tipping point than previously thought.

“Earth’s deep time climate history reveals startling discoveries that shake the foundations of our knowledge and understanding of climate change in modern times,” says H. Richard Lane, program director in the National Science Foundation (NSF)’s Division of Earth Sciences, which partially funded the research.

Jennifer McElwain of University College Dublin, the paper’s lead author, cautions that sulfur dioxide from extensive volcanic emissions may also have played a role in driving the plant extinctions.

“We have no current way of detecting changes in sulfur dioxide in the past, so it’s difficult to evaluate whether sulfur dioxide, in addition to a rise in carbon dioxide, influenced this pattern of extinction,” says McElwain.

The time interval under study, at the boundary of the Triassic and Jurassic periods, has long been known for its plant and animal extinctions.

Until this research, the pace of the extinctions was thought to have been gradual, taking place over millions of years.

It has been notoriously difficult to tease out details about the pace of extinction using fossils, scientists say, because fossils can provide only snap-shots or glimpses of organisms that once lived.

Using a technique developed by scientist Peter Wagner of the Smithsonian Institution National Museum of Natural History in Washington, D.C., the researchers were able to detect, for the first time, very early signs that these ancient ecosystems were already deteriorating–before plants started going extinct.

The method reveals early warning signs that an ecosystem is in trouble in terms of extinction risk.

“The differences in species abundances for the first 20 meters of the cliffs [in East Greenland] from which the fossils were collected,” says Wagner, “are of the sort you expect. “But the final 10 meters show dramatic loses of diversity that far exceed what we can attribute to sampling error: the ecosystems were supporting fewer and fewer species.”

By the year 2100, it’s expected that the level of carbon dioxide in the modern atmosphere may reach as high as two and a half times today’s level.

“This is of course a ‘worst case scenario,'” says McElwain. “But it’s at exactly this level [900 parts per million] at which we detected the ancient biodiversity crash.

“We must take heed of the early warning signs of deterioration in modern ecosystems. We’ve learned from the past that high levels of species extinctions–as high as 80 percent–can occur very suddenly, but they are preceded by long interval of ecological change.”

The majority of modern ecosystems have not yet reached their tipping point in response to climate change, the scientists say, but many have already entered a period of prolonged ecological change.

“The early warning signs of deterioration are blindingly obvious,” says McElwain. “The biggest threats to maintaining current levels of biodiversity are land use change such as deforestation. “But even relatively small changes in carbon dioxide and global temperature can have unexpectedly severe consequences for the health of ecosystems.”

Ice sheets can retreat ‘in a geologic instant,’ study of prehistoric glacier shows

Modern glaciers, such as those making up the Greenland and Antarctic ice sheets, are capable of undergoing periods of rapid shrinkage or retreat, according to new findings by paleoclimatologists at the University at Buffalo.

The paper, published on June 21 in Nature Geoscience, describes fieldwork demonstrating that a prehistoric glacier in the Canadian Arctic rapidly retreated in just a few hundred years.

The proof of such rapid retreat of ice sheets provides one of the few explicit confirmations that this phenomenon occurs.

Should the same conditions recur today, which the UB scientists say is very possible, they would result in sharply rising global sea levels, which would threaten coastal populations.

“A lot of glaciers in Antarctica and Greenland are characteristic of the one we studied in the Canadian Arctic,” said Jason Briner, Ph.D., assistant professor of geology in the UB College of Arts and Sciences and lead author on the paper. “Based on our findings, they, too, could retreat in a geologic instant.”

The new findings will allow scientists to more accurately predict how global warming will affect ice sheets and the potential for rising sea levels in the future, by developing more robust climate and ice sheet models.

Briner said the findings are especially relevant to the Jakobshavn Isbrae, Greenland’s largest and fastest moving tidewater glacier, which is retreating under conditions similar to those he studied in the Canadian Arctic.

Acting like glacial conveyor belts, tidewater glaciers are the primary mechanism for draining ice sheet interiors by delivering icebergs to the ocean.

“These ‘iceberg factories’ exhibit rapid fluctuations in speed and position, but predicting how quickly they will retreat as a result of global warming is very challenging,” said Briner.

That uncertainty prompted the UB team to study the rates of retreat of a prehistoric tidewater glacier, of similar size and geometry to contemporary ones, as way to get a longer-term view of how fast these glaciers can literally disappear.

The researchers used a special dating tool at UB to study rock samples they extracted from a large fjord that drained the ice sheet that covered the North American Arctic during the past Ice Age.

The samples provided the researchers with climate data over a period from 20,000 years ago to about 5,000 years ago, a period when significant warming occurred.

“Even though the ice sheet retreat was ongoing throughout that whole period, the lion’s share of the retreat occurred in a geologic instant — probably within as little as a few hundred years,” said Briner.

The UB research reveals that the period of rapid retreat was triggered once the glacier entered deep ocean waters, nearly a kilometer deep, Briner said.

“The deeper water makes the glacier more buoyant,” he explained.

“Because the rates of retreat were so much higher in the deep fjord, versus earlier when it terminated in more shallow waters or on land, the findings suggest that contemporary tidewater glaciers in Greenland and Antarctica that are retreating into deep waters may begin to experience even faster rates of retreat than are currently being observed,” said Briner.

Right now, Jakobshavn Isbrae is draining into waters that are nearly a kilometer deep, he said, which means that its current rates of retreat — as fast as 10 kilometers in the past decade — could continue for the next hundred years.

“If modern glaciers do this for several decades, this would rapidly raise global sea level, intercepting coastal populations and requiring vast re-engineering of levees and other mitigation systems,” said Briner.

Close relationship between past warming and sea-level rise

In a paper in Nature Geoscience, a team from the National Oceanography Centre, Southampton (NOCS), along with colleagues from Tübingen (Germany) and Bristol presents a novel continuous reconstruction of sea level fluctuations over the last 520 thousand years. Comparison of this record with data on global climate and carbon dioxide (CO2) levels from Antarctic ice cores suggests that even stabilisation at today’s CO2 levels may commit us to sea-level rise over the next couple of millennia, to a level much higher than long-term projections from the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC).

Little is known about the total amount of possible sea-level rise in equilibrium with a given amount of global warming. This is because the melting of ice sheets is slow, even when temperature rises rapidly. As a consequence, current predictions of sea-level rise for the next century consider only the amount of ice sheet melt that will occur until that time. The total amount of ice sheet melting that will occur over millennia, given the current climate trends, remains poorly understood.

The new record reveals a systematic equilibrium relationship between global temperature and CO2 concentrations and sea-level changes over the last five glacial cycles. Projection of this relationship to today’s CO2 concentrations results in a sea-level at 25 (±5) metres above the present. This is in close agreement with independent sea-level data from the Middle Pliocene epoch, 3-3.5 million years ago, when atmospheric CO2 concentrations were similar to the present-day value. This suggests that the identified relationship accurately records the fundamental long-term equilibrium behaviour of the climate system over the last 3.5 Million years.

Lead author Professor Eelco Rohling of the University of Southampton’s School of Ocean and Earth Science based at NOCS, said: “Let’s assume that our observed natural relationship between CO2 and temperature, and sea level, offers a reasonable ‘model’ for a future with sustained global warming. Then our result gives a statistically sound expectation of a potential total long-term sea-level rise. Even if we would curb all CO2 emissions today, and stabilise at the modern level (387 parts per million by volume), then our natural relationship suggests that sea level would continue to rise to about 25 m above the present. That is, it would rise to a level similar to that measured for the Middle Pliocene.”

Project partners Professor Michal Kucera (University of Tübingen) and Dr Mark Siddall (University of Bristol), add: “We emphasise that such equilibration of sea level would take several thousands of years. But one still has to worry about the large difference between the inferred high equilibrium sea level and the level where sea level actually stands today. Recent geological history shows that times with similarly strong disequilibria commonly saw pulses of very rapid sea-level adjustment, at rates of 1-2 metres per century or higher.”

The new study’s projection of long-term sea-level change, based on the natural relationship of the last 0.5 to 3.5 million years, differs considerably from the IPCC’s model-based long-term projection of +7 m. The discrepancy cannot be easily explained, and new work is needed to ensure that the ‘gap is closed’.

The observed relationships from the recent geological past can form a test-bed or reality-check for models, to help them achieve improved future projections.

Ancient drought and rapid cooling drastically altered climate

Kibo Summit of Kilimanjaro
Kibo Summit of Kilimanjaro

Two abrupt and drastic climate events, 700 years apart and more than 45 centuries ago, are teasing scientists who are now trying to use ancient records to predict future world climate.

The events – one, a massive, long-lived drought believed to have dried large portions of Africa and Asia, and the other, a rapid cooling that accelerated the growth of tropical glaciers – left signals in ice cores and other geologic records from around the world.

Lonnie Thompson, University Distinguished Professor of Earth Sciences at Ohio State University, and researcher with the Byrd Polar Research Center there, outlined the puzzle today to colleagues at the Chapman Conference on Abrupt Climate Change. The meeting was sponsored by the American Geophysical Union and the National Science Foundation.

Thompson, who has led more than 50 expeditions to drill cores through ice caps on some the highest and most remote regions of the planet, believes that the records from the tropical zones on Earth are the most revealing and that the last 1,000 years provides the best clues.

“I would argue that the last 1,000 years are most critical from the perspective of looking at the future,” he said

The first of the two tantalizing events is apparent in an ice core drilled in 1993 from an ice field in the Peruvian Andes called Huascaran. Within that core, they found a thick band of dust particles, most smaller than a micron in diameter, the concentration of which was perhaps 150 times greater than anywhere else in the core. That band dated back to 4,500 years ago.

“Dust that small can be transported great distance – the question is where did it come from?” Thompson said. “I believe that record accurately reflects drought conditions in Africa and the Middle East and that the dust was carried out across the Atlantic Ocean by the northeast trade winds, across the Amazon Basin and deposited on the Huascaran ice cap.

Thompson said that other records, including an ice core taken from glaciers atop Tanzania’s Mount Kilimanjaro, also show a dust event dating to a time when there was substantive drying up of lakes in Africa. He said that it is the only such huge event that the ice core records show for the past 17,000 years.

The other mystery surrounds a major cooling event that Thompson believes happened about 700 years earlier. During a 2002 expedition to the Quelccaya ice cap in Peru, the largest tropical ice field in the world, Thompson and colleagues discovered patches of ancient wetland plants that had been exposed as the edge of the ice cap retreated. When carbon-dated, the plants were shown to be 5,200 years old, meaning that they had been covered, and preserved, by the ice for the last 52 centuries.

Since then, recent expeditions have located similar patches of plants revealed by the ice’s retreat. All date back to at least 5,200 years ago and some as much as 7,000 years ago.

“This means that sometime around 5,200 years ago, there was a rapid cooling event in this region and the ice expanded shielding the plants from damage and decay,” Thompson said.

Other records from around the world seem to support the idea of a cooling event at this time. Divers in Lake Tahoe, Nevada, found nearly two dozen ancient tree trunks preserved at the lake’s bottom. Wood samples from the trunks date back 5,200 years and geologic records show the current lake levels have remained steady since that point in time.

Thompson also pointed to the timing of past climate changes in South America and the rise and fall of early cultures in the region.

Evidence from the ice cores from Quelccaya suggest that cultures might have grown during wet periods in the Peruvian Highlands and waned when the climate became drier. Conversely, cultures appeared to grow in the country’s coastal regions when the climate became wetter and were lost as drying increased.

“This suggests that there could have been persistent climate periods that allowed these cultures to flourish under certain conditions and fail under others,” he said.

Thompson leads a new expedition next week to two new sites in the Andes in hopes of drilling cores that will show more detailed records of both events.

The evidence that researchers have, both from ice cores and from the rapid retreat of glaciers, show that high-altitude ice fields reflect similar changes that are currently visible all across the temperate portions of the globe.

“The ice caps are sentinels of the earth’s overall climate,” he said. “And the data shows that at all of these sites, the rate at which the ice is vanishing is accelerating.

“To me, these are indicators that these areas are already being adversely impacted by changes in our current climate.”

When palm trees gave way to spruce trees

New research reveals the demise of an ancient forest. These are dawn redwood stumps on Axel Heiberg Island, Nunavut. -  David Greenwood
New research reveals the demise of an ancient forest. These are dawn redwood stumps on Axel Heiberg Island, Nunavut. – David Greenwood

For climatologists, part of the challenge in predicting the future is figuring out exactly what happened during previous periods of global climate change.

One long-standing climate puzzle relates to a sequence of events 33.5 million years ago in the Late Eocene and Early Oligocene. Profound changes were underway. Globally, carbon dioxide levels were falling and the hothouse warmth of the dinosaur age and Eocene Period was waning. In Antarctica, ice sheets had formed and covered much of the southern polar continent.

But what exactly was happening on land, in northern latitudes? When and how did Northern glaciation begin, and what does this knowledge add to the understanding of the relationship between carbon dioxide levels and today’s climate?

An international team that included Dr. David Greenwood, an NSERC-funded researcher at Brandon University, now provides some of the very first detailed answers, and they come from an unusual source.

“Fossils of land plants are excellent indicators of past climates,” said Dr. Greenwood. “But the fossil plant localities from the Canadian Arctic and Greenland don’t appear to record this major climate change, and pose problems for precisely dating their age, so we needed to look elsewhere.”

The “where” was in marine sediments entombed when the North Atlantic Ocean was beginning to open, and lying now at the bottom of today’s Norwegian-Greenland Sea. Sediment cores taken from there contained a record of ancient spores and pollen blown from the continent to the west.

“These marine sediment cores give us a very precise chronology of the changes in the dominant land plants,” said Dr. Greenwood “and since many of these species have modern relatives, we can assume that the temperatures and environments they lived in were very similar.”

To arrive at a holistic picture of the climate of the transition, the researchers merged the plant data with physical information about the state of the atmosphere and ocean taken from chemical and isotopic information in the same sediments, and compared this to computer modelling of climate in the period.

“We can see that summer temperatures on land remained relatively warm throughout the Eocene/Oligocene transition, but that the period was marked by increasing seasonality,” said Dr. Greenwood.

“Mean temperatures during the coldest month dropped by five degrees Celsius, to just above freezing,” he said.

“This was probably not enough to create much in the way of continental ice on East Greenland,” he said, “but it did wipe out palms and other subtropical trees such as swamp cypress. They were replaced by temperate climate trees such as spruces and hemlock.”

The researcher said that, nonetheless, the middle period of the transition remained fairly warm. “Hickory and walnut were still present, but these became rare in the final stages,” he said.

Although the march to a cooler world was gradual in northern latitudes, it was inevitable according to Dr. Greenwood.

“Changes in the earth’s position in its orbit were leading a much greater seasonal range in radiation for polar regions and, overall, heat was becoming more concentrated in the tropics, largely due to a global drop in carbon dioxide levels in the atmosphere” he said.

Researchers survey earthquake faults through downtown Reno

The minivibe truck, using a relatively light 700-pound reaction weight, will stop every 30 feet, set the shaker on the asphalt and vibrate the ground for a few minutes. Hundreds of monitoring sensors connected by cable transmit the soundings to the recording truck. It's a slow process, with the truck creeping less than one mile a day along the river route. -  Mike Wolterbeek, University of Nevada, Reno
The minivibe truck, using a relatively light 700-pound reaction weight, will stop every 30 feet, set the shaker on the asphalt and vibrate the ground for a few minutes. Hundreds of monitoring sensors connected by cable transmit the soundings to the recording truck. It’s a slow process, with the truck creeping less than one mile a day along the river route. – Mike Wolterbeek, University of Nevada, Reno

The Seismological Lab at the University of Nevada, Reno is finishing the first phase of seismic surveying through downtown as part of a $1 million U.S. Geological Survey study to create an earthquake hazard map in the Reno-Carson City urban corridor.

“There are several suspected faults in the downtown area, and we don’t know much about them,” John Louie, professor of geophysics in the Seismological Lab said. “We finished the Truckee river profile along Riverside Drive with the minivibe truck and will finish the small southwest Reno portion this week.”

“We have really good data,” he said. “We’re confirming the results of a gravity seismic survey we did 10 years ago, and will be able to more precisely map those and any additional faults we may find.”

The gathering of data for this portion of the USGS project will be complete this week and analysis and findings will be completed in the next several months. Louie will work with the USGS to complete abstracts of the research by September to be presented at the American Geophysical Union’s annual Fall meeting in San Francisco this December.

“This will be the first chance to present it, and I look forward to having our colleagues see our interpretations,” he said.

The Seismological Lab’s portion of the project will last 11 days as they do full-scale seismic reflection soundings up to a half-mile deep and for a total of seven miles along the Truckee River and on Reno streets.

“This is a process of discovery,” Louie said. “We’ve looked for the suspected faults, may possibly find faults we don’t know about and will be able to identify the most hazardous faults.”

The truck, using a relatively light 700-pound reaction weight, stops every 30 feet, sets the shaker on the asphalt and vibrates the ground for a few minutes. Hundreds of monitoring sensors connected by cable transmit the soundings to the recording truck. It’s a slow process, with the truck creeping less than one mile a day along the river route.

Louie is the principal investigator on the seismic survey for the University. He will be working with two PIs from the USGS to make thousands of soundings to complete the high-resolution, non-invasive seismic imaging study using industry techniques for oil and gas exploration.

Louie has seven students working in the crew, gaining valuable real-world experience.

“They will have the opportunity to participate in a real, professional survey not just a class exercise,” he said. “They will have a comprehensive view of the whole process, from knocking on doors notifying residents of the work, to placing the ground motion sensors and interpreting the 3D computer results.”

The engineering and geological sciences department has two co-principal investigators collaborating on the project: Dr. Pat Cashman, an expert in structural geology, and Dr. Ilenna Tibuleac, research seismologist and geophysicist.

“This is a rare project for the USGS,” Louie said. “They have little money for these types of projects and we’re pleased they have turned their attention here.”

The survey will be done using the latest tools of the trade: the vibrator truck is made possible through a National Science Foundation grant, and the several-thousand-dollar software used to process and interpret the data is being donated for the project by the Reno-based global geotechnical engineering firm Optim, which provides geophysical software and data services around the world.

Natural deep earth pump fuels earthquakes and ore

A rock sample of less than 1 mm that was deformed in the middle crust of the earth. It's porosity is highlighted in red - Image credit – University of Western Australia Dr Florian Fusseis
A rock sample of less than 1 mm that was deformed in the middle crust of the earth. It’s porosity is highlighted in red – Image credit – University of Western Australia Dr Florian Fusseis

For the first time scientists have discovered the presence of a natural deep earth pump that is a crucial element in the formation of ore deposits and earthquakes.

The process, called creep cavitation, involves fluid being pumped through pores in deformed rock in mid-crustal sheer zones, which are approximately 15 km below the Earth’s surface.

The fluid transfer through the middle crust also plays a key role in tectonic plate movement and mantle degassing.

The discovery was made by examining one millimetre sized cubes of exposed rock in Alice Springs, which was deformed around 320 million years ago during a period of natural mountain formation.

The evidence is described in a paper published in the latest edition of Nature entitled Creep cavitation can establish a dynamic granular fluid pump in ductile shear zones.

One of the paper’s author’s CSIRO Exploration and Mining scientist Dr Rob Hough said that this was the first direct observation of fluids moving through the mid-crustal shear zone.

“We are seeing the direct evidence for one of the processes that got ore forming fluids moving up from the mantle to the shallow crust to form the ore deposits we mine today, it is also one of the mechanisms that can lead to earthquakes in the middle crust,” Dr Hough said.

Research leader Dr Florian Fusseis, from the University of Western Australia, said that the discovery could provide valuable information in understanding how earthquakes are formed.

“While we understand reasonably well why earthquakes happen in general, due to stress build-up caused by motions of tectonic plates, the triggering of earthquakes is much more complex,” Dr Fusseis said.

“To understand the ‘where’ and ‘when’ of earthquakes, the ‘how’ needs to be understood first. We know that earthquakes nucleate by failure on a small part of a shear zone.”

Dr Fusseis said that while their sample did not record an earthquake it gave them an insight into the structures that could be very small and localized precursors of seismic failure planes.

The discovery was made possible through the use of high-resolution Synchrotron X-ray tomographic, scanning electron microscope observations at the nanoscale and advanced visualisation using iVEC in Western Australia.

The authors of the paper propose that the fluid movement, described as the granular fluid pump, is a self sustaining process where pores open and close allowing fluid and gas to be pumped out.

Geologists demonstrate extent of ancient ice age

Geologists at the University of Leicester have shown that an ancient Ice Age, once regarded as a brief ‘blip’, in fact lasted for 30 million years.

They have published their findings and are due to discuss them at a public lecture at the University on Wednesday June 17.

Their research suggests that during this ancient Ice Age, global warming was curbed through the burial of organic carbon that eventually lead to the formation of oil – including the ‘hot shales’ of north Africa and Arabia which constitute the world’s most productive oil source rock.

This ice age has been named ‘the Early Palaeozoic Icehouse’ by Dr Alex Page and his colleagues in a paper published as part of a collaborative Deep Time Climate project between the University of Leicester and British Geological Survey.

The Ice Age occurred in the Ordovician and Silurian Periods of geological time (part of the Early Palaeozoic Era), an interval that witnessed a major diversification of early marine animals including trilobites and primitive fish as well as the emergence of the first land plants.

The Early Palaeozoic climate had long been considered characterised by essentially greenhouse conditions with elevated atmospheric CO2 and warm temperatures extending to high latitudes, and only brief snaps of frigid climate. However, during his doctoral studies in the internationally ¬renowned Palaeobiology Research Group of the University of Leicester, Department of Geology, Alex Page and his colleagues Jan Zalasiewicz and Mark Williams demonstrated how the ice age was probably of much longer duration.

The team demonstrated that the Late Ordovician and Early Silurian Epochs were characterised by widespread ice formation, with changes in the extent of continental glaciation resulting in rapid sea¬ level changes around the globe.

They compared evidence of sea¬ level change from the rock record of ancient coastlines with evidence of sediments being deposited by glacial meltwaters or ice¬rafting at high latitudes, and with chemical indicators of temperature in the strata.

The team showed that although the Early Palaeozoic Icehouse was of similar extent and duration to the modern ice age, the workings of the carbon cycle appeared markedly different to that of the present day. Unlike the modern oceans, the oceans of the Early Palaeozoic were often oxygen-starved ‘dead zones’ leading to the burial of plankton-derived carbon in the sea floor sediments. The strata produced in this way include the ‘hot shales’ of north Africa and Arabia which constitute the world’s most productive oil source rock. In fact, the burial of organic carbon derived from fossil plankton may have served to draw down CO2 from the atmosphere to promote cooling during the Early Palaeozoic Icehouse.

Page commented: “These fossil fuel-¬rich deposits formed during relatively warmer episodes during the Early Palaeozoic Icehouse when the partial melting of ice sheets brought about rapid sea ¬level rise. This melt¬water may have bought a massive influx of nutrients into the surface waters, allowing animals and algae to thrive and bloom in the plankton, but also altered ocean circulation, creating oxygen¬-poor deep waters which facilitated the preservation of fragile, carbonaceous planktonic fossils. The deglacial outwash formed a less dense, low¬ salinity ‘lid’ on the oceans preventing atmospheric oxygen penetrating to the seafloor. The absence of oxygen under such conditions served to shut down decay accounting for the preservation of these fossils.”

Page added that the burial of oil shales in deglacial anoxia “may have been a negative feedback mechanism that prevented runaway warming, meaning that in the Early Palaeozoic Icehouse at least, processes eventually leading to oil formation may have been the solution to the greenhouse effect.”