Reading ancient climate from plankton shells

This is a CT reconstruction of a foram measured at the Diamond Light Source. -  Oscar Branson, University of Cambridge
This is a CT reconstruction of a foram measured at the Diamond Light Source. – Oscar Branson, University of Cambridge

Climate changes from millions of years ago are recorded at daily rate in ancient sea shells, new research shows.

A huge X-ray microscope has revealed growth bands in plankton shells that show how shell chemistry records the sea temperature.

The results could allow scientists to chart short timescale changes in ocean temperatures hundreds of millions of years ago.

Plankton shells show features like tree rings, recording historical climate.

It’s important to understand current climate change in the light of how climate has varied in the geological past. One way to do this, for the last few thousand years, is to analyse ice from the poles. The planet’s temperature and atmosphere are recorded by bubbles of ancient air trapped in polar ice cores. The oldest Antarctic ice core records date back to around 800,000 years ago.

Results just published in the journal Earth and Planetary Sciences Letters reveal how ancient climate change, pushing back hundreds of millions of years ago into deep time, is recorded by the shells of oceanic plankton.

As microbial plankton grow in ocean waters, their shells, made of the mineral calcite, trap trace amounts of chemical impurities, maybe only a few atoms in a million getting replaced by impurity atoms. Scientists have noticed that plankton growing in warmer waters contain more impurities, but it has not been clear how and why this “proxy” for temperature works.

When the plankton die, they fall to the muddy ocean floor, and can be recovered today from that muddy ocean floor sediments, which preserve the shells as they are buried. The amount of impurity, measured in fossil plankton shells, provides a record of past ocean temperature, dating back more than 100 million years ago.

Now, researchers from the Department of Earth Sciences at the University of Cambridge have measured traces of magnesium in the shells of plankton using an X-ray microscope in Berkeley, California, at the “Advanced Light Source” synchrotron – a huge particle accelerator that generates X-rays to study matter in minuscule detail.

The powerful X-ray microscope has revealed narrow nanoscale bands in the plankton shell where the amount of magnesium is very slightly higher, at length scales as small as one hundredth that of a human hair. They are growth bands, rather like tree rings, but in plankton the bands occur daily or so, rather than yearly.

“These growth bands in plankton show the day by day variations in magnesium in the shell at a 30 nanometre length scale. For slow-growing plankton it opens the way to seeing seasonal variations in ocean temperatures or plankton growth in samples dating back tens to hundreds of millions of years”, says Professor Simon Redfern, one of the experimenters on the project.

“Our X-ray data show that the trace magnesium sits inside the crystalline mineral structure of the plankton shell. That’s important because it validates previous assumptions about using magnesium contents as a measure of past ocean temperature.”

The chemical environment of the trace elements in the plankton shell, revealed in the new measurements, shows that the magnesium sits in calcite crystal replacing calcium, rather than in microbial membranes in their impurities in the shell. This helps explain why temperature affects the chemistry of plankton shells – warmer waters favour increased magnesium in calcite.

The group are now using the UK’s “Diamond” synchrotron X-ray facility to measure how plankton shells grow and whether they change at all in the ocean floor sediments. Their latest results could allow scientists to establish climate variability in Earth’s far distant past, as well as providing new routes to measure ocean acidification and salinity in past oceans.

Reading ancient climate from plankton shells

This is a CT reconstruction of a foram measured at the Diamond Light Source. -  Oscar Branson, University of Cambridge
This is a CT reconstruction of a foram measured at the Diamond Light Source. – Oscar Branson, University of Cambridge

Climate changes from millions of years ago are recorded at daily rate in ancient sea shells, new research shows.

A huge X-ray microscope has revealed growth bands in plankton shells that show how shell chemistry records the sea temperature.

The results could allow scientists to chart short timescale changes in ocean temperatures hundreds of millions of years ago.

Plankton shells show features like tree rings, recording historical climate.

It’s important to understand current climate change in the light of how climate has varied in the geological past. One way to do this, for the last few thousand years, is to analyse ice from the poles. The planet’s temperature and atmosphere are recorded by bubbles of ancient air trapped in polar ice cores. The oldest Antarctic ice core records date back to around 800,000 years ago.

Results just published in the journal Earth and Planetary Sciences Letters reveal how ancient climate change, pushing back hundreds of millions of years ago into deep time, is recorded by the shells of oceanic plankton.

As microbial plankton grow in ocean waters, their shells, made of the mineral calcite, trap trace amounts of chemical impurities, maybe only a few atoms in a million getting replaced by impurity atoms. Scientists have noticed that plankton growing in warmer waters contain more impurities, but it has not been clear how and why this “proxy” for temperature works.

When the plankton die, they fall to the muddy ocean floor, and can be recovered today from that muddy ocean floor sediments, which preserve the shells as they are buried. The amount of impurity, measured in fossil plankton shells, provides a record of past ocean temperature, dating back more than 100 million years ago.

Now, researchers from the Department of Earth Sciences at the University of Cambridge have measured traces of magnesium in the shells of plankton using an X-ray microscope in Berkeley, California, at the “Advanced Light Source” synchrotron – a huge particle accelerator that generates X-rays to study matter in minuscule detail.

The powerful X-ray microscope has revealed narrow nanoscale bands in the plankton shell where the amount of magnesium is very slightly higher, at length scales as small as one hundredth that of a human hair. They are growth bands, rather like tree rings, but in plankton the bands occur daily or so, rather than yearly.

“These growth bands in plankton show the day by day variations in magnesium in the shell at a 30 nanometre length scale. For slow-growing plankton it opens the way to seeing seasonal variations in ocean temperatures or plankton growth in samples dating back tens to hundreds of millions of years”, says Professor Simon Redfern, one of the experimenters on the project.

“Our X-ray data show that the trace magnesium sits inside the crystalline mineral structure of the plankton shell. That’s important because it validates previous assumptions about using magnesium contents as a measure of past ocean temperature.”

The chemical environment of the trace elements in the plankton shell, revealed in the new measurements, shows that the magnesium sits in calcite crystal replacing calcium, rather than in microbial membranes in their impurities in the shell. This helps explain why temperature affects the chemistry of plankton shells – warmer waters favour increased magnesium in calcite.

The group are now using the UK’s “Diamond” synchrotron X-ray facility to measure how plankton shells grow and whether they change at all in the ocean floor sediments. Their latest results could allow scientists to establish climate variability in Earth’s far distant past, as well as providing new routes to measure ocean acidification and salinity in past oceans.

What do we know — and not know — about fracking?

Fracking is in the headlines a lot these days, and everyone has an opinion about it. But how much do we really know for certain about the oil and gas extraction technique and its health effects? And how do we find out the truth among all the shouted opinions? To help cut through the static, several scientists have put together a multidisciplinary session on fracking and health at the meeting of The Geological Society of America (GSA) in Denver on Sunday.

“There is so much perceived information on fracking in the media, with so little of it based on real science and actual data,” says Thomas Darrah, a medical geologist at Ohio State University and one of the conveners of the GSA Pardee Keynote Session, “Energy and Health: The Emergence of Medical Geology in Response to the Shale Gas Boom.”

“Fracking has moved so quickly, and the research community is playing catch up on water, air, and health issues,” said Robert Jackson, an environmental scientist at Duke University who will present his research this Sunday. “The goal is to present a state of the science for researchers and the public.”

The afternoon keynote session is designed to cover a lot of ground. It will start with the geologists, hydrologists, and air-quality experts who are studying the chemistry and the physical properties of fracking in the ground, water, and air. Then the session veers into territory not often covered at a geological meeting, with talks by toxicologists, researchers in occupational medicine, and epidemiologists.

“This session includes people who would normally not be anywhere near a GSA conference,” said Darrah. “The idea is that we end the session by having the geoscience community interact with a group of people who are looking at health data sets: epidemiologists. That way we can put people working on the other end of the equation in the same room.” Included in the eleven scheduled presentations, and at the medical end of the equation, is a talk titled “Public Health Implications of Hydraulic Fracturing,” by David O. Carpenter of the University of Albany’s School of Public Health, and another, “Energy and Health: The Emergence of Medical Geology in Response to the Shale Gas Boom: An Occupational and Environmental Medicine Perspective,” to be delivered by Theodore F. Them of Guthrie Clinic Ltd.

For his part, Darrah will be presenting a talk about his work, “Understanding In-House Exposures to Natural Gas and Metal-Rich Aerosols from Groundwater within an Unconventional Energy Basin.”

There are two additional presentations on the air-quality issues of fracking, which is perhaps the topic the public knows the least about. Gabrielle Petron of the University of Colorado and NOAA will be talking about outdoor air emissions from hydraulic fracturing activities, and public health researcher Lisa M. Mackenzie of the University of Colorado will talk about work evaluating specific health risks from exposure to natural gas drilling in Garfield County, Colorado.

What do we know — and not know — about fracking?

Fracking is in the headlines a lot these days, and everyone has an opinion about it. But how much do we really know for certain about the oil and gas extraction technique and its health effects? And how do we find out the truth among all the shouted opinions? To help cut through the static, several scientists have put together a multidisciplinary session on fracking and health at the meeting of The Geological Society of America (GSA) in Denver on Sunday.

“There is so much perceived information on fracking in the media, with so little of it based on real science and actual data,” says Thomas Darrah, a medical geologist at Ohio State University and one of the conveners of the GSA Pardee Keynote Session, “Energy and Health: The Emergence of Medical Geology in Response to the Shale Gas Boom.”

“Fracking has moved so quickly, and the research community is playing catch up on water, air, and health issues,” said Robert Jackson, an environmental scientist at Duke University who will present his research this Sunday. “The goal is to present a state of the science for researchers and the public.”

The afternoon keynote session is designed to cover a lot of ground. It will start with the geologists, hydrologists, and air-quality experts who are studying the chemistry and the physical properties of fracking in the ground, water, and air. Then the session veers into territory not often covered at a geological meeting, with talks by toxicologists, researchers in occupational medicine, and epidemiologists.

“This session includes people who would normally not be anywhere near a GSA conference,” said Darrah. “The idea is that we end the session by having the geoscience community interact with a group of people who are looking at health data sets: epidemiologists. That way we can put people working on the other end of the equation in the same room.” Included in the eleven scheduled presentations, and at the medical end of the equation, is a talk titled “Public Health Implications of Hydraulic Fracturing,” by David O. Carpenter of the University of Albany’s School of Public Health, and another, “Energy and Health: The Emergence of Medical Geology in Response to the Shale Gas Boom: An Occupational and Environmental Medicine Perspective,” to be delivered by Theodore F. Them of Guthrie Clinic Ltd.

For his part, Darrah will be presenting a talk about his work, “Understanding In-House Exposures to Natural Gas and Metal-Rich Aerosols from Groundwater within an Unconventional Energy Basin.”

There are two additional presentations on the air-quality issues of fracking, which is perhaps the topic the public knows the least about. Gabrielle Petron of the University of Colorado and NOAA will be talking about outdoor air emissions from hydraulic fracturing activities, and public health researcher Lisa M. Mackenzie of the University of Colorado will talk about work evaluating specific health risks from exposure to natural gas drilling in Garfield County, Colorado.

Radioactive waste: Where to put it?

As the U.S. makes new plans for disposing of spent nuclear fuel and other high-level radioactive waste deep underground, geologists are key to identifying safe burial sites and techniques. Scientists at The Geological Society of America (GSA) meeting in Denver will describe the potential of shale formations; challenges of deep borehole disposal; and their progress in building a computer model to help improve understanding of the geologic processes that are important for safe disposal of high-level waste.

In the United States, about 70,000 metric tons of spent commercial nuclear fuel are located at more than 70 sites in 35 states. Shales and other clay-rich (argillaceous) rocks have never been seriously considered for holding America’s spent nuclear fuel, but it is different overseas. France, Switzerland, and Belgium are planning to put waste in tunnels mined out of shale formations, and Canada, Japan, and the United Kingdom are evaluating the idea.

At the GSA meeting, U.S. Geological Survey hydrogeology expert C.E. Neuzil of Reston, Virginia, will report that some shales are so impermeable that there is little risk of radioactivity from buried nuclear waste reaching ground or surface water.

“This is usually difficult to demonstrate,” Neuzil says, “but some shales have natural groundwater pressure anomalies that can be analyzed — as if they were permeability tests — on a very large scale.” This capability was shown recently at the Bruce Nuclear Site, explains Neuzil, a proposed low/intermediate waste repository 1,200 feet underground in Ontario, Canada. Argillaceous rocks have additional attractive qualities, Neuzil says: They are common, voluminous, and tend to be tectonically quiet — meaning no earthquakes to crack the walls of a fuel-rod burial chamber.

Another disposal option for nuclear waste is deep boreholes. The 2012 presidential Blue Ribbon Commission on America’s Nuclear Future recommended more research, and the U.S. Department of Energy is now developing an R&D plan. However, the U.S. Nuclear Waste Technical Review Board (NWTRB) has statutory responsibility for evaluating the technical validity of DOE’s nuclear waste activities, and is on the record with the position that deep boreholes present many technical challenges and studying them “should not delay higher priority research on a mined geologic repository.”

At next week’s GSA meeting, Review Board senior staff professional Bret W. Leslie and Stanford University geophysicist Mary Lou Zoback, an NWTRB member, will present the board’s assessment of:

  • the technical feasibility of drilling a borehole of the proposed depth (3 miles) and width (about 20 inches), which has never been done;

  • the exposure risk for workers, who would have to repackage waste currently stored in canisters that are wider than the width of the proposed boreholes;
  • the reliability of existing sealing technology; and
  • the large number of deep boreholes that would be required — nearly 700.

Whether nuclear waste winds up in tunnels, boreholes or both, the planning will be helped by new analytical tools. One is a new computer model that will evaluate the behavior of various forms of nuclear waste, and waste containers and barriers, if stored in various rocks. The model is being developed under the auspices of the Center for Nuclear Waste Regulatory Analyses (CNWRA), the NRC’s federally funded research and development center, and will be described at the GSA meeting by NRC performance analyst Jin-Ping Gwo.

Radioactive waste: Where to put it?

As the U.S. makes new plans for disposing of spent nuclear fuel and other high-level radioactive waste deep underground, geologists are key to identifying safe burial sites and techniques. Scientists at The Geological Society of America (GSA) meeting in Denver will describe the potential of shale formations; challenges of deep borehole disposal; and their progress in building a computer model to help improve understanding of the geologic processes that are important for safe disposal of high-level waste.

In the United States, about 70,000 metric tons of spent commercial nuclear fuel are located at more than 70 sites in 35 states. Shales and other clay-rich (argillaceous) rocks have never been seriously considered for holding America’s spent nuclear fuel, but it is different overseas. France, Switzerland, and Belgium are planning to put waste in tunnels mined out of shale formations, and Canada, Japan, and the United Kingdom are evaluating the idea.

At the GSA meeting, U.S. Geological Survey hydrogeology expert C.E. Neuzil of Reston, Virginia, will report that some shales are so impermeable that there is little risk of radioactivity from buried nuclear waste reaching ground or surface water.

“This is usually difficult to demonstrate,” Neuzil says, “but some shales have natural groundwater pressure anomalies that can be analyzed — as if they were permeability tests — on a very large scale.” This capability was shown recently at the Bruce Nuclear Site, explains Neuzil, a proposed low/intermediate waste repository 1,200 feet underground in Ontario, Canada. Argillaceous rocks have additional attractive qualities, Neuzil says: They are common, voluminous, and tend to be tectonically quiet — meaning no earthquakes to crack the walls of a fuel-rod burial chamber.

Another disposal option for nuclear waste is deep boreholes. The 2012 presidential Blue Ribbon Commission on America’s Nuclear Future recommended more research, and the U.S. Department of Energy is now developing an R&D plan. However, the U.S. Nuclear Waste Technical Review Board (NWTRB) has statutory responsibility for evaluating the technical validity of DOE’s nuclear waste activities, and is on the record with the position that deep boreholes present many technical challenges and studying them “should not delay higher priority research on a mined geologic repository.”

At next week’s GSA meeting, Review Board senior staff professional Bret W. Leslie and Stanford University geophysicist Mary Lou Zoback, an NWTRB member, will present the board’s assessment of:

  • the technical feasibility of drilling a borehole of the proposed depth (3 miles) and width (about 20 inches), which has never been done;

  • the exposure risk for workers, who would have to repackage waste currently stored in canisters that are wider than the width of the proposed boreholes;
  • the reliability of existing sealing technology; and
  • the large number of deep boreholes that would be required — nearly 700.

Whether nuclear waste winds up in tunnels, boreholes or both, the planning will be helped by new analytical tools. One is a new computer model that will evaluate the behavior of various forms of nuclear waste, and waste containers and barriers, if stored in various rocks. The model is being developed under the auspices of the Center for Nuclear Waste Regulatory Analyses (CNWRA), the NRC’s federally funded research and development center, and will be described at the GSA meeting by NRC performance analyst Jin-Ping Gwo.

Could the Colorado River once have flowed into the Labrador Sea?

A figure stands on Esplanade surface opposite Vulcan's Throne volcano, Grand Canyon, USA. Photo by J.W. Sears. -  Photo by James W. Sears
A figure stands on Esplanade surface opposite Vulcan’s Throne volcano, Grand Canyon, USA. Photo by J.W. Sears. – Photo by James W. Sears

In the November issue of GSA Today, James W. Sears of the University of Montana in Missoula advocates a possible Canadian connection for the early Miocene Grand Canyon by arguing for the existence of a “super-river” traceable from headwaters in the southern Colorado Plateau through a proto-Grand Canyon to a delta in the Labrador Sea.

Sears proposes that the river flowed first toward the southwest corner of the Colorado Plateau, and then, in a shift initiated by uplift of the Rio Grande Rift, turned north into Paleogene rifts in the vicinity of Lake Mead. He posits that it then followed northeast-trending grabens across the Idaho and Montana Rockies to the Great Plains and joined the pre-ice age “Bell River” of Canada, which discharged into a massive delta in the Saglek basin of the Labrador Sea.

In this scenario, tectonic faulting beginning 16 million years ago dammed the Miocene Grand Canyon, creating a large lake that existed up to six million years ago. Then volcanism, including the action of the Yellowstone hotspot, cut the river off in Idaho about six million years ago, leading to the eventual capture of the Colorado River by the Gulf of California.

Could the Colorado River once have flowed into the Labrador Sea?

A figure stands on Esplanade surface opposite Vulcan's Throne volcano, Grand Canyon, USA. Photo by J.W. Sears. -  Photo by James W. Sears
A figure stands on Esplanade surface opposite Vulcan’s Throne volcano, Grand Canyon, USA. Photo by J.W. Sears. – Photo by James W. Sears

In the November issue of GSA Today, James W. Sears of the University of Montana in Missoula advocates a possible Canadian connection for the early Miocene Grand Canyon by arguing for the existence of a “super-river” traceable from headwaters in the southern Colorado Plateau through a proto-Grand Canyon to a delta in the Labrador Sea.

Sears proposes that the river flowed first toward the southwest corner of the Colorado Plateau, and then, in a shift initiated by uplift of the Rio Grande Rift, turned north into Paleogene rifts in the vicinity of Lake Mead. He posits that it then followed northeast-trending grabens across the Idaho and Montana Rockies to the Great Plains and joined the pre-ice age “Bell River” of Canada, which discharged into a massive delta in the Saglek basin of the Labrador Sea.

In this scenario, tectonic faulting beginning 16 million years ago dammed the Miocene Grand Canyon, creating a large lake that existed up to six million years ago. Then volcanism, including the action of the Yellowstone hotspot, cut the river off in Idaho about six million years ago, leading to the eventual capture of the Colorado River by the Gulf of California.

There’s gold in them thar trees

This is a eucalyptus leaf showing traces of gold. -  CSIRO
This is a eucalyptus leaf showing traces of gold. – CSIRO

Eucalyptus trees – or gum trees as they are know – are drawing up gold particles from the earth via their root system and depositing it their leaves and branches.

Scientists from CSIRO made the discovery and have published their findings in the journal Nature Communications.

“The eucalypt acts as a hydraulic pump – its roots extend tens of metres into the ground and draw up water containing the gold. As the gold is likely to be toxic to the plant, it’s moved to the leaves and branches where it can be released or shed to the ground,” CSIRO geochemist Dr Mel Lintern said.

The discovery is unlikely to start an old-time gold rush – the “nuggets” are about one-fifth the diameter of a human hair. However, it could provide a golden opportunity for mineral exploration, as the leaves or soil underneath the trees could indicate gold ore deposits buried up to tens of metres underground and under sediments that are up to 60 million years old.

“The leaves could be used in combination with other tools as a more cost effective and environmentally friendly exploration technique,” Dr Lintern said.

“By sampling and analysing vegetation for traces of minerals, we may get an idea of what’s happening below the surface without the need to drill. It’s a more targeted way of searching for minerals that reduces costs and impact on the environment.

“Eucalyptus trees are so common that this technique could be widely applied across Australia. It could also be used to find other metals such as zinc and copper.”

Using CSIRO’s Maia detector for x-ray elemental imaging at the Australian Synchrotron, the research team was able to locate and see the gold in the leaves. The Synchrotron produced images depicting the gold, which would otherwise have been untraceable.

“Our advanced x-ray imaging enabled the researchers to examine the leaves and produce clear images of the traces of gold and other metals, nestled within their structure,” principal scientist at the Australian Synchrotron Dr David Paterson said.

“Before enthusiasts rush to prospect this gold from the trees or even the leaf litter, you need to know that these are tiny nuggets, which are about one-fifth the diameter of a human hair and generally invisible by other techniques and equipment.”

CSIRO research using natural materials, such as calcrete and laterite in soils, for mineral exploration has led to many successful ore deposit discoveries in regional Australia. The outcomes of the research provide a direct boost to the national economy.

There’s gold in them thar trees

This is a eucalyptus leaf showing traces of gold. -  CSIRO
This is a eucalyptus leaf showing traces of gold. – CSIRO

Eucalyptus trees – or gum trees as they are know – are drawing up gold particles from the earth via their root system and depositing it their leaves and branches.

Scientists from CSIRO made the discovery and have published their findings in the journal Nature Communications.

“The eucalypt acts as a hydraulic pump – its roots extend tens of metres into the ground and draw up water containing the gold. As the gold is likely to be toxic to the plant, it’s moved to the leaves and branches where it can be released or shed to the ground,” CSIRO geochemist Dr Mel Lintern said.

The discovery is unlikely to start an old-time gold rush – the “nuggets” are about one-fifth the diameter of a human hair. However, it could provide a golden opportunity for mineral exploration, as the leaves or soil underneath the trees could indicate gold ore deposits buried up to tens of metres underground and under sediments that are up to 60 million years old.

“The leaves could be used in combination with other tools as a more cost effective and environmentally friendly exploration technique,” Dr Lintern said.

“By sampling and analysing vegetation for traces of minerals, we may get an idea of what’s happening below the surface without the need to drill. It’s a more targeted way of searching for minerals that reduces costs and impact on the environment.

“Eucalyptus trees are so common that this technique could be widely applied across Australia. It could also be used to find other metals such as zinc and copper.”

Using CSIRO’s Maia detector for x-ray elemental imaging at the Australian Synchrotron, the research team was able to locate and see the gold in the leaves. The Synchrotron produced images depicting the gold, which would otherwise have been untraceable.

“Our advanced x-ray imaging enabled the researchers to examine the leaves and produce clear images of the traces of gold and other metals, nestled within their structure,” principal scientist at the Australian Synchrotron Dr David Paterson said.

“Before enthusiasts rush to prospect this gold from the trees or even the leaf litter, you need to know that these are tiny nuggets, which are about one-fifth the diameter of a human hair and generally invisible by other techniques and equipment.”

CSIRO research using natural materials, such as calcrete and laterite in soils, for mineral exploration has led to many successful ore deposit discoveries in regional Australia. The outcomes of the research provide a direct boost to the national economy.