What microscopic fossilized shells tell us about ancient climate change

At the end of the Paleocene and beginning of the Eocene epochs, between 59 to 51 million years ago, Earth experienced dramatic warming periods, both gradual periods stretching millions of years and sudden warming events known as hyperthermals.

Driving this planetary heat up were massive emissions of carbon dioxide (CO2) and other greenhouse gases, but other factors like tectonic activity may have also been at play.

New research led by University of Utah geoscientists pairs sea surface temperatures with levels of atmospheric CO2 during this period, showing the two were closely linked. The findings also provide case studies to test carbon cycle feedback mechanisms and sensitivities critical for predicting anthropogenic climate change as we continue pouring greenhouse gases into the atmosphere on an unprecedented scale in the planet's history.

"The main reason we are interested in these global carbon release events is because they can provide analogs for future change," said lead author Dustin Harper, a postdoctoral researcher in the Department of Geology & Geophysics. "We really don't have a perfect analog event with the exact same background conditions and rate of carbon release."

But the study published Monday in the Proceedings of the National Academy of Sciences, or PNAS, suggests emissions during two ancient "thermal maxima" are similar enough with today's anthropogenic climate change to help scientists forecast its consequences.

The research team analyzed microscopic fossils -- recovered in drilling cores taken from an undersea plateau in the Pacific -- to characterize surface ocean chemistry at the time the shelled creatures were alive. Using a sophisticated statistical model, they reconstructed sea surface temperatures and atmospheric CO2 levels over a 6-million-year period that covered two hyperthermals, the Paleocene-Eocene Thermal Maximum, or PETM, 56 million years ago and Eocene Thermal Maximum 2, ETM-2, 54 million years ago.

The findings indicate that as atmospheric levels of CO2 rose, so too did global temperatures.

"We have multiple ways that our planet, that our atmosphere is being influenced by CO2 additions, but in each case, regardless of the source of CO2, we're seeing similar impacts on the climate system," said co-author Gabriel Bowen, a U professor of geology & geophysics.

"We're interested in how sensitive the climate system was to these changes in CO2. And what we see in this study is that there's some variation, maybe a little lower sensitivity, a lower warming associated with a given amount of CO2 change when we look at these very long-term shifts. But that overall, we see a common range of climate sensitivities."

Today, human activities associated with fossil fuels are releasing carbon 4 to 10 times more rapidly than occurred during these ancient hyperthermal events. However, the total amount of carbon released during the ancient events is similar to the range projected for human emissions, potentially giving researchers a glimpse of what could be in store for us and future generations.

First scientists must determine what happened to the climate and oceans during these episodes of planetary heating more than 50 million years ago.

"These events might represent a mid- to worst-case scenario kind of case study," Harper said. "We can investigate them to answer what's the environmental change that happens due to this carbon release?"

Earth was very warm during the PETM. No ice sheets covered the poles and ocean temperatures in the mid-90s degrees Fahrenheit.

To determine oceanic CO2 levels the researchers turned to fossilized remains of foraminifera, a shelled single-cell organism akin to plankton. The research team based the study on cores previously extracted by the International Ocean Discovery Program at two locations in Pacific.

The foram shells accumulate small amounts of boron, the isotopes of which are a proxy reflecting CO2 concentrations in the ocean at the time the shells formed, according to Harper.

"We measured the boron chemistry of the shells, and we're able to translate those values using modern observations to past seawater conditions. We can get at seawater CO2 and translate that into atmospheric CO2," Harper said. "The goal of the target study interval was to establish some new CO2 and temperature records for the PETM and ETM-2, which represent two of the best analogs in terms of modern change, and also provide a longer-term background assessment of the climate system to better contextualize those events."

The cores Harper studied were extracted from Shatsky Rise in the subtropical North Pacific, which is an ideal location for recovering ocean-bottom sediments that reflect conditions in the ancient past.

Carbonate shells dissolve if they settle into deep ocean, so scientists must look to underwater plateaus like Shatsky Rise, where the water depths are relatively shallow. While their inhabitants were living millions of years ago, the foraminifera shells record the sea surface conditions.

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Rock solid evidence: Angola geology reveals prehistoric split between South America and Africa

An SMU-led research team has found that ancient rocks and fossils from long-extinct marine reptiles in Angola clearly show a key part of Earth's past -- the splitting of South America and Africa and the subsequent formation of the South Atlantic Ocean.

With their easily visualized "jigsaw-puzzle fit," it has long been known that the western coast of Africa and the eastern coast of South America once nestled together in the supercontinent Gondwana -- which broke off from the larger landmass of Pangea.

The research team says the southern coast of Angola, where they dug up the samples, arguably provides the most complete geological record ever recorded on land of the two continents moving apart and the opening of the South Atlantic Ocean. Rocks and fossils found date back from 130 million years ago to 71 million years.

"There are places that you can go to in South America, for instance, where you can see this part of the split or that part of it, but in Angola, it's all laid out in one place," said Louis L. Jacobs, SMU professor emeritus of Earth Sciences and president of ISEM. Jacobs is the lead author of a study published in The Geological Society, London, Special Publications.

"Before this, there was not a place known to go and see the rocks on the surface that really reflected the opening of the South Atlantic Ocean, because they're now in the ocean or eroded away," Jacobs said.

Angola rocks and fossils tell the whole story

Africa and South America started to split around 140 million years ago, causing gashes in Earth's crust called rifts to open up along pre-existing weaknesses. As the tectonic plates beneath South America and Africa moved apart, magma from the Earth's mantle rose to the surface, creating a new oceanic crust and pushing the continents away from each other. And eventually, the South Atlantic Ocean filled the void between these two newly-formed continents.

Scientists have previously found evidence of these events through geophysics and well cores drilled through the ocean floor.

But these tell-tale signs have never been found in one place, or been so clearly visible for anyone to see, said study co-author Michael J. Polcyn, research associate in the Huffington Department of Earth Sciences and senior research fellow, ISEM at SMU.

"It's one thing for a geophysicist to be able to look at seismic data and make inferences from that," he said. "It's quite another thing to be able to take a school field trip out to the rock formations, or outcrops, and say this is when the lava was spreading from eastern South America. Or this was when it was a continuous land."

Essentially, Angola presents the opportunity for someone to easily walk through each phase of this geologically significant chapter in Earth's history.

"That gives Angola major bragging rights," Jacobs said.

Jacobs, Polcyn and Diana P. Vineyard -- who is a research associate at SMU -- worked with an international team of paleontologists, geologists and others to analyze both the rock formations they found in eight different locations on the coast and the fossils within them.

Fieldwork in Angola's Namibe Province began in 2005. At that time, the research team recognized particular types of sediments, which gave them a good indication of what the western coast of Africa had been like at various stages millions of years ago. For instance, fields of lava revealed volcanic outpourings, and faults or breaks showed where the continents were being rifted apart. Sediments and salt deposits showed ocean flooding and evaporation, while overlying oceanic sediments and marine reptiles showed completion of the South Atlantic Ocean.

Paleontologists, meanwhile, discovered fossils in Angola from large marine reptiles that had lived late during the Cretaceous Period, right after the Atlantic Ocean was completed and while it grew wider.

By bringing together experts from a wide range of fields, "we were able to document when there was no ocean at all, to when there was a fresh enough ocean for those reptiles to thrive and have enough to eat," Vineyard said.

Many of the ancient fossils are currently on display at the Smithsonian's National Museum of Natural History "Sea Monsters Unearthed: Life in Angola's Ancient Seas" exhibit, which was co-produced with SMU -- a nationally-ranked Dallas-based private university.

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Diverse ancient volcanoes on Mars discovered by planetary scientist may hold clues to pre-plate tectonic activity on Earth

Volcanoes are a common feature on the surfaces of solid planets within the solar system, resulting from magmatic activity occurring within the planetary crust. On Earth, volcanism is driven primarily by heat and crustal recycling associated with plate tectonics, but Mars lacks plate tectonics and the driver of volcanism is not well understood.

Recent research by Professor Joseph MICHALSKI, a geologist in the Department of Earth Sciences at The University of Hong Kong (HKU), has revealed intriguing insights into the volcanic activity on Mars.

He proposes that Mars has significantly more diverse volcanism than previously realised, driven by an early form of crust recycling called vertical tectonics.

The findings, recently published in Nature Astronomy, shed light on the ancient crust of Mars and its potential implications for understanding early crustal recycling on both Mars and Earth.

Traditionally, Mars has been known to have large shield volcanoes similar to those in Hawaii.

However, it was not known that Mars also possessed the diverse, explosive volcanoes that form on Earth due to crustal recycling.

The recent research conducted by Professor Michalski and his international team discover a vast number of diverse volcanoes in the ancient crust of Mars.

'We have known for decades that Mars has volcanoes, but most of the recognised volcanoes correspond to large basaltic shield volcanoes similar to the ones that make up Hawaii,' he explains.

'In this work, we show that the ancient crust has many other types of volcanoes such as lava domes, stratovolcanoes, calderas and large shields of ash, not lava.

Further, most scientists see Mars as a planet composed of basalt, which has low silica content and represents little crustal evolution, but these volcanoes have high silica content which means they formed from a complex process of magma evolution not known before.'

The paper suggests that intense volcanism occurred on ancient Mars, causing the crust to collapse into the mantle, where the rocks re-melted, resulting in magmas that have high silica.

This tectonic process, called vertical tectonics, is hypothesised to have occurred on the ancient Earth, but rocks on Earth from that period (the Archean, more than 3 billion years ago) are highly modified by later geological activity, so we cannot see evidence for this process clearly on this planet.

Therefore, exploring other planets like Mars, which has volcanism but no plate tectonics, can help reveal the mysteries of early crustal recycling on both the Red Planet, and by analogy, on early Earth.

Professor Michalski concluded, 'Mars contains critical geological puzzle pieces that help us understand not only that planet, but the Earth as well.

Martian volcanism is much more complex and diverse than has been previously thought.'

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Geologists challenge conventional view of Earth's continental history, stability with new study

The seemingly stable regions of the Earth's continental plates -- the so-called stable cratons -- have suffered repetitive deformation below their crust since their formation in the remote past, according to new research from the University of Illinois Urbana-Champaign. This hypothesis defies decades of conventional plate tectonics theory and begs to answer why most cratons have remained structurally stable while their underbellies have experienced significant change.

In a study led by Illinois geology professor Lijun Liu, researchers used previously collected density data from the Earth's uppermost rigid layers of crust and mantle -- known as the lithosphere -- to examine the relationship between craton surface topography and the thickness of their underlying lithosphere layer.

The results of the study are published in the journal Nature Geosciences.

The lack of deformation within the cratons since their formation makes them the longest-lived tectonic units on Earth -- surviving supercontinent cycles like the formation and breakup of the supercontinent Pangea, as well as the lesser-known and more ancient supercontinent Rodina, the study reports.

"It is generally accepted that the cratons are protected by their thick underlying mantle roots, or keels, which are believed to be buoyant and strong and thus stable over time," Lui said.

Several recent papers from Liu's research group directly challenge this wisdom by showing that these mantle keels are actually quite dense.

In a 2022 study, the team demonstrated that the traditional view of buoyant craton keels implies that most of the Earth's cratons would be sitting about 3 kilometers above the sea surface, while in reality, their elevation is only a few 100 meters. This requires the lithospheric mantle below the crust to be of high enough density to pull the surface down by about 2 kilometers, Liu said.

In another study, the team used gravity field measurements to pinpoint the density structure of the craton keels to find that the lower portion of the mantle keel is most likely where the high-density material resides, implying a depth-increasing density profile below the cratons.

In the new paper, the team shows that the lower portion of the mantle keel that has a high density and tends to repeatedly peel away from the lithosphere above when mantle upwellings, called plumes, initiate supercontinent breakup. The peeled-off -- or delaminated -- keels could return to the base of the lithosphere after they warm up inside the hot mantle.

"The whole process is like what happens in a lava lamp, where the cool material near the surface sinks and the warm material near the bottom rises," Liu said.

This deformation history is expressed in some of the more puzzling geophysical properties observed in the lithosphere, the study reports.

"For example, the repetitive vertical deformation of the lower half of the mantle keel allows the seismic waves that vibrate the rock vertically to travel faster, compared to the upper half of the keel, which experienced less vertical deformation," Liu said.

The team also determined that mantle delamination will cause the craton surface to rise, leading to erosion.

"This is reflected in the strong dependence of crustal thickness on lithospheric thickness, an observation never made before this study," Liu said. "In particular, there are two major uplift and erosion events in the past, when supercontinents Rodinia and Pangea each separated, the former causing what is known as the Great Unconformity -- a feature in the Earth's rock record shows no evidence of new deposition, only deep craton erosion. This is the reason why we see pieces of ancient lower crust exposed at the craton's surface today."

With the help of numerical simulations, the team said that this episodic deformation style of the lower craton keels is how the craton crusts survived the long geological history.

"We believe this newly hypothesized lifestyle of cratons will significantly change people's view on how continents evolve and how plate tectonics operate on Earth," Liu said.

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South Africa, India and Australia shared similar volcanic activity 3.5 billion years ago

Cratons are pieces of ancient continents that formed several billions of years ago. Their study provides a window as to how processes within and on the surface of Earth operated in the past. Cratons preserve relics of our young Earth as they host a variety of rock assemblages such as greenstones and granites. Greenstones are rock assemblages that primarily comprise of sub-marine volcanic rocks with minor sedimentary rocks. They are the best archives to study early Earth surface processes. A new study published in Precambrian Research by a team of researchers, led by Dr Jaganmoy Jodder of the University of the Witwatersrand's Evolutionary Studies Institute shows that the Singhbhum Craton in India hosts remarkably well preserved volcanic and sedimentary rocks as old as 3.5 billion years, and that it has similar geologic history to parts of South Africa and Australia.

The team that included researchers from the University of the Witwatersrand (Wits University), University of Johannesburg (UJ) and Chinese Academy of Sciences, Beijing, examined volcanic and sedimentary rocks from the Daitari greenstone belt in the Singhbhum Craton of India that were formed approximately 3.5 billion years ago. Jodder and his co-workers conducted detailed field-based studies and precise Uranium-Lead (U-Pb) radiometric-age dating to evaluate the geology of the ancient greenstone rocks. Based on their study, the researchers established key geological timelines that illustrate the tectonic evolution of the Daitari greenstones.

"The Daitari greenstone belt shares a similar geologic make-up when compared to the greenstones exposed in the Barberton and Nondweni areas of South Africa and those from the Pilbara Craton of north-western Australia," says Jodder.

Sub-marine volcanic eruptions were common between 3.5 and 3.3 billion-years-ago, which are largely preserved as pillowed lava within the greenstones of the Singhbhum, Kaapvaal and Pilbara cratons. More importantly the style of volcanism decoded from the silicic rocks provide evidence for explosive sub-marine to sub-aerial settings.

"Following silicic volcanism, sedimentary rocks that comprise sub-marine turbidity current deposits formed upon drowning of the volcanic vent. This provided us with an age estimate for the sub-marine sedimentary rocks that got deposited approximately 3.5 billion years ago, which was based on precise detrital U-Pb zircon data."

Studies of ancient greenstones are important not only to understand the diverse volcanic processes but well-preserved greenstones preserve minor sedimentary rocks that formed under sub-marine settings.

"These volcano-sedimentary rocks provide clues related to habitable environments on the young Earth and can be regarded as time capsules to help us better understand the evolutionary tale of the planet in its early stages," says Jodder.

Jodder and the team of researchers propose that these ancient continents may have been subjected to geologically similar processes 3.5 billion years ago.

"However, we are not certain about their palaeo-geographic positioning. And thus, cannot validate that they once formed part of a supercontinent," says Jodder.

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Ground beneath Thwaites Glacier mapped

The ground beneath Antarctica's most vulnerable glacier has been mapped for the first time, helping scientists to better understand how it is being affected by climate change. Analysis of the geology below the Thwaites Glacier in West Antarctica shows there is less sedimentary rock than expected -- a finding that could affect how the ice slides and melts in the coming decades.

"Sediments allow faster flow, like sliding on mud," says Dr Tom Jordan, a geophysicist with the British Antarctic Survey (BAS), who led the study. "Now we have a map of where the slippery sediments are, we can better predict how the glacier will behave in future as it retreats."

The distribution of sedimentary rocks beneath the Thwaites glacier is included in a new map of the geology of the region produced by the BAS researchers and published in the journal Science Advances. The findings are important because the glacier, which is the size of Great Britain or the US state of Florida, is one of the fastest changing ice-ocean systems in Antarctica.

The Thwaites glacier's grounding zone -- the point where it meets the seafloor -- has retreated 14 km since the late 1990s. Much of the ice sheet is below sea level and susceptible to rapid, irreversible ice loss that could raise global sea-level by over half a metre within centuries.

The new analysis is based on airborne surveys using aircraft equipped with radar which can see through the ice to the rocks below, as well as sensors which can map minute variations in gravity and magnetism hundreds to thousands of metres below the ground and seabed on which the glacier rests.

The researchers then use these multiple data sources to compile a 3D picture of features, including the type and extent of different rocks.

Jordan says: "The integrated nature of the airborne surveys was one of the keys to this research. Each sensor on the aircraft provided an important but incomplete part of the picture, but by bringing them all together we could provide the detailed map of the underlying geology."

In doing so, the study effectively turns back the geological clock to examine what happened when New Zealand was ripped away from Antarctica about 100 million years ago -- long before the Thwaites glacier was formed.

Because the base of Thwaites Glacier lies far below sea level, researchers had expected that thick sediments would have been deposited there over the subsequent millions of years Similar analysis has been done on some other Antarctic glaciers, showing that these other systems were predominantly underlain by thick sediments.

But the aircraft data suggests that only about a fifth of the ground below the glacier is sedimentary rock. These lie in a series of basins between 80 and 200 km long and about 30 km wide.

The rest is made up of other types of geological bodies, including granite peaks and other hard rocks. The scientists think that these sedimentary basins were once much larger, but they have been ground down to the bedrock by movement of the glacier.

It's not yet clear how this new knowledge of the subglacial geology will affect estimates of ice flow and loss from Thwaites and other glaciers. The study does show that the geological landscape has a direct control on the basal shear stress, which influences how fast ice can flow into the ocean. Members of the research team will now carry out more detailed studies of these processes. Modellers may also be able to use the new data to make more reliable projections of future ice loss.

Jordan says: "We hope that by showing the detailed geology, and how it correlates with the basal friction, future models of glacial retreat will have lower uncertainty, as the controls of the basal processes will be better understood."

He adds: "No single scientific study could ever match she scale and challenge of climate change. But it is the incremental building of all the individual scientific studies like this that allows us to understand and tackle that challenge."

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Ecosystem evolution in Africa

Ohio University's Nancy J. Stevens Ph.D., distinguished professor in the Department of Biomedical Sciences in the Heritage College of Osteopathic Medicine, is coauthor on a paper published in the journal Science and funded by the National Science Foundation that documents the evolution of grassland ecosystems on continental Africa.

Collaborating with an extensive team of geologists and paleoanthropologists from universities around the world, led by researchers from Baylor University and the University of Minnesota, the team synthesized data from nine Early Miocene fossil localities in the East African Rift of Kenya and Uganda to determine that the expansion of grassy biomes dominated by grasses with the C4 photosynthetic pathway in Eastern Africa occurred more than 10 million years earlier.

According to the paper, previous reconstructions of early Miocene ecosystems, 15-20 million years ago, have suggested that equatorial Africa was covered by a semi-continuous forest, with open habitats dominated by warm-season, or C4, grasses that were uncommon until 8-10 million years ago. C4 refers to the different pathways that plants use to capture carbon dioxide during photosynthesis. C4 plants produce a four-carbon molecule and are more adapted to warm or hot season condition under moist or dry environments.

As the researchers gathered expertise about geological features, isotopes and fossils found at the sites, the paradigm of a continuous forest blanketing equatorial Africa during the early Miocene shifted to a more complex mosaic of habitats that already included open environments with C4 grasses.

The result of this research pushes back the oldest evidence of C4 grass-dominated habitats in Africa -- and globally -- by more than 10 million years, with important implications for primate evolution and the origins of tropical C4 grasslands and savanna ecosystems across the African continent and around the world.

"We suspected that we would find C4 plants at some sites, but we didn't expect to find them at as many sites as we did, and in such high abundance," Daniel Peppe, lead author and associate professor at Baylor University, said.

A critical aspect of this work was that the team combined many different lines of evidence together: geology, fossil soils, isotopes and phytoliths (plant silica microfossils) to reach their conclusions.

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Where did Earth's water come from? Not melted meteorites, according to scientists

Water makes up 71% of Earth's surface, but no one knows how or when such massive quantities of water arrived on Earth.

A new study published in the journal Nature brings scientists one step closer to answering that question. Led by University of Maryland Assistant Professor of Geology Megan Newcombe, researchers analyzed melted meteorites that had been floating around in space since the solar system's formation 4 1/2 billion years ago. They found that these meteorites had extremely low water content -- in fact, they were among the driest extraterrestrial materials ever measured.

These results, which let researchers rule them out as the primary source of Earth's water, could have important implications for the search for water -- and life -- on other planets. It also helps researchers understand the unlikely conditions that aligned to make Earth a habitable planet.

"We wanted to understand how our planet managed to get water because it's not completely obvious," Newcombe said. "Getting water and having surface oceans on a planet that is small and relatively near the sun is a challenge."

The team of researchers analyzed seven melted, or achondrite, meteorites that crashed into Earth billions of years after splintering from at least five planetesimals -- objects that collided to form the planets in our solar system. In a process known as melting, many of these planetesimals were heated up by the decay of radioactive elements in the early solar system's history, causing them to separate into layers with a crust, mantle and core.

Because these meteorites fell to Earth only recently, this experiment was the first time anyone had ever measured their volatiles. UMD geology graduate student Liam Peterson used an electron microprobe to measure their levels of magnesium, iron, calcium and silicon, then joined Newcombe at the Carnegie Institution for Science's Earth and Planets Laboratory to measure their water contents with a secondary ion mass spectrometry instrument.

"The challenge of analyzing water in extremely dry materials is that any terrestrial water on the sample's surface or inside the measuring instrument can easily be detected, tainting the results," said study co-author Conel Alexander, a scientist at the Carnegie Institution for Science.

To reduce contamination, researchers first baked their samples in a low-temperature vacuum oven to remove any surface water. Before the samples could be analyzed in the secondary ion mass spectrometer, the samples had to be dried out once again.

"I had to leave the samples under a turbo pump -- a really high-quality vacuum -- for more than a month to draw down the terrestrial water enough," Newcombe said.

Some of their meteorite samples came from the inner solar system, where Earth is located and where conditions are generally assumed to have been warm and dry. Other rarer samples came from the colder, icier outer reaches of our planetary system. While it was generally thought that water came to Earth from the outer solar system, it has yet to be determined what types of objects could have carried that water across the solar system.

"We knew that plenty of outer solar system objects were differentiated, but it was sort of implicitly assumed that because they were from the outer solar system, they must also contain a lot of water," said Sune Nielsen, a study co-author and geologist at the Woods Hole Oceanographic Institution. "Our paper shows this is definitely not the case. As soon as meteorites melt, there is no remaining water."

After analyzing the achondrite meteorite samples, researchers discovered that water comprised less than two millionths of their mass. For comparison, the wettest meteorites -- a group called carbonaceous chondrites -- contain up to about 20% of water by weight, or 100,000 times more than the meteorite samples studied by Newcombe and her co-authors.

This means that the heating and melting of planetesimals leads to near-total water loss, regardless of where these planetesimals originated in the solar system and how much water they started out with. Newcombe and her co-authors discovered that, contrary to popular belief, not all outer solar system objects are rich in water. This led them to conclude that water was likely delivered to Earth via unmelted, or chondritic, meteorites.

Newcombe said their findings have applications beyond geology. Scientists of many disciplines -- and especially exoplanet researchers -- are interested in the origin of Earth's water because of its deep connections with life.

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Major North American oil source yields clues to one of earth's deadliest mass extinctions

The Bakken Shale Formation -- a 200,000-square-mile shale deposit below parts of Canada and North Dakota -- has supplied billions of barrels of oil and natural gas to North America for 70 years. A new discovery reveals that the rocks also open a uniquely informative window into Earth's complicated geological history.

A research team, which included geologists from the University of Maryland, George Mason University and the Norwegian oil and gas company Equinor, developed a new framework for analyzing paleontological and biogeochemical data extracted from the formation's rock. Using this technique, the team pinpointed a major trigger of several closely spaced biotic crises during the late Devonian Period almost 350 million years ago: euxinia, or the depletion of oxygen and expansion of hydrogen sulfide in large bodies of water. Published in the journal Nature on March 8, 2023, the team's findings demonstrate links between sea level, climate, ocean chemistry and biotic disruption.

"For the first time, we can point to a specific kill mechanism responsible for a series of significant biotic disruptions during the late Devonian Period," said UMD Geology Professor Alan Jay Kaufman, a senior author of the paper. "There have been other mass extinctions presumably caused by expansions of hydrogen sulfide before, but no one has ever studied the effects of this kill mechanism so thoroughly during such a critical period of Earth's history."

According to Kaufman, the late Devonian Period was a "perfect storm" of factors that played a large role in how Earth is today. Vascular plants and trees were especially crucial to the process; as they expanded on land, plants stabilized soil structure, helped spread nutrients to the ocean, and added oxygen and water vapor to the atmosphere while pulling carbon dioxide out of it.

"The introduction of terrestrial plants capable of photosynthesis and transpiration stimulated the hydrological cycle, which kick-started the Earth's capacity for more complex life as we know it today," Kaufman said.

The Devonian Period ended around the same time the Bakken sediments accumulated, allowing the layers of organic-rich shale to 'record' the environmental conditions that occurred there. Because the Earth's continents were flooded during that time, various sediments including black shale gradually accumulated in inland seas that formed within geological depressions like the Williston Basin, the preserved the Bakken formation.

Undergraduate laboratory assistant Tytrice Faison (B.S. '22, geology) -- who joined Kaufman's lab after taking a course with him through the Carillon Communities living-learning program -- prepared and analyzed more than 100 shale and carbonate samples taken from the formation. After analyzing the samples, Kaufman, Faison and the rest of the Bakken team deciphered clear layers of sediment representing three key biotic crises known as the Annulata, Dasberg and Hangenberg events, with the last crisis associated with one of the greatest mass extinctions in Earth history.

"We could see anoxic events distinctly marked by black shale and other geochemical deposits, which are likely linked to a series of rapid rises in sea level," Kaufman explained. "We suspect that sea levels may have risen during the pulsed events due to the melting ice sheets around the South Pole at this time."

Higher sea levels would have resulted in the flooding of interior continental margins, or the transitional region between oceanic and continental crusts. In these settings, high levels of nutrients, such as phosphorus and nitrogen, could have triggered algal blooms which create low oxygen zones in large bodies of water. These zones in turn would have increased toxic hydrogen sulfide right where most marine animals would have lived. Under those conditions, animals in the oceans and on land around the shoreline would have died during these late Devonian events.

The team's research is not exclusive to global biotic disruptions from hundreds of millions of years ago. Kaufman suggests that their findings are not just applicable to the shallow inland seas of the Devonian Period, but perhaps also to the oceans of today affected by global warming. He compared the ocean's circulatory system to a "conveyor belt" carrying nutrients, oxygen and microorganisms from place to place.

"Cold, salty water develops in the North Atlantic region before it sinks and eventually makes its way to the Indian and Pacific Oceans, cycling around the globe. This oceanic jet stream helps to spread life-sustaining oxygen through the oceans," Kaufman explained. "If that conveyor belt were to be slowed down due to global warming, parts of the ocean might be deprived of oxygen and potentially become euxinic."

The collateral damage caused by global warming might then promote animal migration out of dead zones or put Earth on a path to decreased diversity and increased rates of extinction, he added.

Read more at Science Daily

Magma on Mars likely

Since 2018, when the NASA InSight Mission deployed the SEIS seismometer on the surface of Mars, seismologists and geophysicists at ETH Zurich have been listening to the seismic pings of more than 1,300 marsquakes. Again and again, the researchers registered smaller and larger Mars quakes. A detailed analysis of the quakes' location and spectral character brought a surprise. With epicentres originating in the vicinity of the Cerberus Fossae -- a region consisting of a series of rifts or graben -- these quakes tell a new story. A story that suggests vulcanism still plays an active role in shaping the Martian surface.

Mars shows signs of life and youth

An international team of researchers, led by ETH Zurich, analysed a cluster of more than 20 recent marsquakes that originated in the Cerberus Fossae graben system. From the seismic data, scientists concluded that the low-frequency quakes indicate a potentially warm source that could be explained by present day molten lava, i.e., magma at that depth, and volcanic activity on Mars. Specifically, they found that the quakes are located mostly in the innermost part of Cerberus Fossae.

When they compared seismic data with observational images of the same area, they also discovered darker deposits of dust not only in the dominant direction of the wind, but in multiple directions surrounding the Cerebus Fossae Mantling Unit. "The darker shade of the dust signifies geological evidence of more recent volcanic activity -- perhaps within the past 50,000 years -- relatively young, in geological terms," explains Simon Staehler, the lead author of the paper, which has now been published in the journal Nature. Staehler is a Senior Scientist working in the Seismology and Geodynamics group led by Professor Domenico Giardini at the Institute of Geophysics, ETH Zurich.

Why study the terrestrial neighbour?

Exploring Earth's planetary neighbours is no easy task. Mars is the only planet, other than Earth, in which scientists have ground-based rovers, landers, and now even drones that transmit data. All other planetary exploration, so far, has relied on orbital imagery. "InSight's SEIS is the most sensitive seismometer ever installed on another planet," says Domenico Giardini. "It affords geophysicists and seismologists an opportunity to work with current data showing what is happening on Mars today -- both at the surface and in its interior." The seismic data, along with orbital images, ensures a greater degree of confidence for scientific inferences.

One of our nearest terrestrial neighbours, Mars is important for understanding similar geological processes on Earth. The red planet is the only one we know of, so far, that has a core composition of iron, nickel, and sulphur that might have once supported a magnetic field. Topographical evidence also indicates that Mars once held vast expanses of water and possibly a denser atmosphere. Even today, scientists have learned that frozen water, although possibly mostly dry ice, still exists on its polar caps. "While there is much more to learn, the evidence of potential magma on Mars is intriguing," Anna Mittelholz, Postdoctoral Fellow at ETH Zurich and Harvard University.

Last remnants of geophysical life

Looking at images of the vast dry, dusty Martian landscape it is difficult to imagine that about 3.6 billion years ago Mars was very much alive, at least in a geophysical sense. It spewed volcanic debris for a long enough time to give rise to Tharsis Montes region, the largest volcanic system in our solar system and the Olympus Mons -- a volcano nearly three times the elevation of Mount Everest. The quakes coming from the nearby Cerberus Fossae -- named for a creature from Greek mythology known as the "hell-hound of Hades" that guards the underworld -- suggest that Mars is not quite dead yet. Here the weight of the volcanic region is sinking and forming parallel graben (or rifts) that pull the crust of Mars apart, much like the cracks that appear on the top of a cake while its baking. According to, Staehler "it is possible that what we are seeing are the last remnants of this once active volcanic region or that the magma is right now moving eastward to the next location of eruption."

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Laying geological groundwork for life on Earth

New research analyzing pieces of the most ancient rocks on the planet adds some of the sharpest evidence yet that Earth's crust was pushing and pulling in a manner similar to modern plate tectonics at least 3.25 billion years ago. The study also provides the earliest proof of when the planet's magnetic north and south poles swapped places.

The two results offer clues into how such geological changes may have resulted in an environment more conducive to the development of life on the planet.

The work, described in PNAS and led by Harvard geologists Alec Brenner and Roger Fu, focused on a portion of the Pilbara Craton in western Australia, one of the oldest and most stable pieces of the Earth's crust. Using novel techniques and equipment, the researchers show that some of the Earth's earliest surface was moving at a rate of 6.1 centimeters per year and 0.55 degrees every million years.

That speed more than doubles the rate the ancient crust was shown to be moving in a previous study by the same researchers. Both the speed and direction of this latitudinal drift leaves plate tectonics as the most logical and strongest explanations for it.

"There's a lot of work that seems to suggest that early in Earth's history plate tectonics wasn't actually the dominant way in which the planet's internal heat gets released as it is today through the shifting of plates," said Brenner, a Ph.D. candidate in the Graduate School of Arts and Sciences and member of Harvard's Paleomagnetics Lab. "This evidence lets us much more confidently rule out explanations that don't involve plate tectonics."

For example, the researchers can now argue against phenomena called "true polar wander" and "stagnant lid tectonics," which can both cause the Earth's surface to shift but aren't part of modern-style plate tectonics. The results lean more toward plate tectonic motion because the newly discovered higher rate of speed is inconsistent with aspects of the other two processes.

In the paper, the scientists also describe what's believed to be the oldest evidence of when Earth reversed its geomagnetic fields, meaning the magnetic North and South Pole flipped locations. This type of flip-flop is a common occurrence in Earth's geologic history with the pole's reversing 183 times in the last 83 million years and perhaps several hundred times in the past 160 million years, according to NASA.

The reversal tells a great deal about the planet's magnetic field 3.2 billion years ago. Key among these implications is that the magnetic field was likely stable and strong enough to keep solar winds from eroding the atmosphere. This insight, combined with the results on plate tectonics, offers clues to the conditions under which the earliest forms of life developed.

"It paints this picture of an early earth that was already really geodynamically mature," Brenner said. "It had a lot of the same sorts of dynamic processes that result in an Earth that has essentially more stable environmental and surface conditions, making it more feasible for life to evolve and develop."

Today, the Earth's outer shell consists of about 15 shifting blocks of crust, or plates, which hold the planet's continents and oceans. Over eons the plates drifted into each other and apart, forming new continents and mountains and exposing new rocks to the atmosphere, which led to chemical reactions that stabilized Earth's surface temperature over billions of years.

Evidence of when plate tectonics started is hard to come by because the oldest pieces of crust are thrust into the interior mantle, never to resurface. Only 5 percent of all rocks on Earth are older than 2.5 billion years old, and no rock is older than about 4 billion years.

Overall, the study adds to growing research that tectonic movement occurred relatively early in Earth's 4.5-billion-year history and that early forms of life came about in a more moderate environment. Members of the project revisited the Pilbara Craton in 2018, which stretches about 300 miles across. They drilled into the primordial and thick slab of crust there to collect samples that, back in Cambridge, were analyzed for their magnetic history.

Using magnetometers, demagnetizing equipment, and the Quantum Diamond Microscope -- which images the magnetic fields of a sample and precisely identifies the nature of the magnetized particles -- the researchers created a suite of new techniques for determining the age and way the samples became magnetized. This allows the researchers to determine how, when, and which direction the crust shifted as well as the magnetic influence coming from Earth's geomagnetic poles.

The Quantum Diamond Microscope was developed in a collaboration between Harvard researchers in the Departments of Earth and Planetary Sciences (EPS) and of Physics.

For future studies, Fu and Brenner plan keep their focus on the Pilbara Craton while also looking beyond it to other ancient crusts around the world. They hope to find older evidence of modern-like plate motion and when the Earth's magnetic poles flipped.

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Geologist proposes the number of ancient Martian lakes might have been dramatically underestimated by scientists

Lakes are bodies of water fed by rainfall, snowmelt, rivers and groundwater, through which, Earth is teeming with life. Lakes also contain critical geologic records of past climates. Though Mars is a frozen desert today, scientists have shown that Mars contains evidence of ancient lakes that existed billions of years ago, which could contain evidence for ancient life and climate conditions on the red planet. Through a meta-analysis of years of satellite data that shows evidence for lakes on Mars, Dr Joseph Michalski, a geologist in the Department of Earth Sciences, The University of Hong Kong (HKU) proposed that scientists might have dramatically underestimated the number of ancient Martian lakes that once existed.

Michalski and the international team recently published their results in Nature Astronomy, which describe a global analysis of ancient Martian lakes. "We know of approximately 500 ancient lakes deposited on Mars, but nearly all the lakes we know about are larger than 100 km2," explains Michalski. "But on Earth, 70% of the lakes are smaller than this size, occurring in cold environments where glaciers have retreated. These small-sized lakes are difficult to identify on Mars by satellite remote sensing, but many small lakes probably did exist. It is likely that at least 70% of Martian lakes have yet to be discovered." Scientists monitor these small lakes on Earth in order to understand climate change. The missing small lakes on Mars might also contain critical information about past climates.

The recent paper also reports that most known Martian lakes date to a period 3,500 to 4,000 million years ago, but each of the lakes might have lasted only a geologically short time (10,000 to 100,000 years) during this time span. This means that ancient Mars was probably mostly cold and dry as well, but it warmed episodically for short periods of time. Michalski adds, "Because of the lower gravity on Mars and the pervasive, fine-grained soil, lakes on Mars would have been very murky and might not have allowed light to penetrate very deeply, which could present a challenge to photosynthetic life, if it existed."

Lakes contain water, nutrients and energy sources for possible microbial life, including light for photosynthesis. Therefore, lakes are the top targets for astrobiological exploration by Mars Rovers such as NASA's Perseverance rover now on Mars. But Michalski warns, "Not all lakes are created equal. In other words, some Martian lakes would be more interesting for microbial life than others because some of the lakes were large, deep, long-lived and had a wide range of environments such as hydrothermal systems that could have been conducive to the formation of simple life." From this point of view, it might make sense to target large, ancient, environmentally diverse lakes for future exploration.

"Earth is host to many environments that can serve as analogs to other planets. From the harsh terrain of Svalbard to the depths of Mono Lake -- we can determine how to design tools for detecting life elsewhere right here at home. Most of those tools are aimed at detecting the remains and residues of microbial life," said Dr David BAKER, an ecologist at HKU School of Biological Sciences who is well-informed about the Earth's microbial systems in lakes.

China successfully landed its first lander, Zhurong, on Mars in May this year. Zhurong is currently roving the plains of Utopia Planitia, exploring mineralogical and chemical clues to recent climate change. China is also planning a sample return mission likely to occur at the end of this decade, which could target one of the interesting lake deposits.

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Breaking in a new planet

The harder you hit something -- a ball, a walnut, a geode -- the more likely it is to break open. Or, if not break open, at least lose a little bit of its structural integrity, the way baseball players pummel new gloves to make them softer and more flexible. Cracks, massive or tiny, form and bear a silent, permanent witness to the impact.

Studying how those impacts affect planetary bodies, asteroids, moons and other rocks in space helps planetary scientists including Brandon Johnson, associate professor, and Sean Wiggins, postdoctoral researcher, in the College of Science's Department of Earth, Atmospheric, and Planetary Sciences at Purdue University, understand extraplanetary geology, especially where to look for precious matter including water, ice and even, potentially, microbial life.

Every solid body in the solar system is constantly pummeled by impacts, both large and small. Even on Earth, every single spot has been affected by at least three big impacts. Using the moon as a test subject, Johnson, Wiggins and their team set out to quantify the relationship between impacts and a planet's porosity.

The researchers used extensive lunar gravity data and detailed modeling and found that when large objects hit the moon or any other planetary body, that impact can affect surfaces and structures, even very far away from the point of impact and deep into the planet or moon itself. This finding, detailed in their new study published in the journal Nature Communications, explains existing data on the moon that had puzzled scientists. The research was partially funded by funded by NASA's Lunar Data Analysis Program.

"NASA's GRAIL (Gravity Recovery and Interior Laboratory) mission measured the gravity of the moon and showed that the moon crust is very porous to very great depths," Johnson said. "We didn't have a description of how the moon would get so porous. This is the first work that really shows that large impacts are capable of fracturing the moon's crust and introducing this porosity."

Understanding where planets and moons have fractured, and why, can help direct space exploration and tell scientists where the best place to look for life might be. Anywhere that rock, water and air meet and interact, there is a potential for life.

"There's a lot to be excited about," Wiggins said. "Our data explains a mystery. This research has implications for the early Earth and for Mars. If life existed back then, there were these intermittently big impacts that would sterilize the planet and boil off the oceans. But if you had life that could survive in pores and interstices a few hundred feet or even a few miles down, it could have survived. They could have provided these refuges where life could hide out from these kinds of impacts.

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Modeling reveals how dwarf planet Ceres powers unexpected geologic activity

For a long time, our view of Ceres was fuzzy, said Scott King, a geoscientist in the Virginia Tech College of Science. A dwarf planet and the largest body found in the asteroid belt -- the region between Jupiter and Mars speckled with hundreds of thousands of asteroids -- Ceres had no distinguishable surface features in existing telescopic observations from Earth.

Then, in 2015, the hazy orb that was Ceres came into view. That view was stunning to scientists such as King. Data and images collected by NASA's Dawn mission gave a clearer picture of the surface, including its composition and structures, which revealed unexpected geologic activity.

Scientists had seen the general size of Ceres in earlier observations. It was so small it was assumed to be inactive. Instead, Dawn discovered a large plateau on one side of Ceres that covered a fraction of the dwarf planet, similar to what a continent might take up on Earth. Surrounding it were fractures in rocks clustered in one location. And there were visible traces of an ocean world: deposits all over the surface where minerals had condensed as water evaporated -- the mark of a freezing ocean.

A professor in the Department of Geosciences, King, who mostly studies larger bodies such as planets, wanted to know how a body as small as Ceres could generate the heat needed to power that kind of geological activity and account for the surface features picked up by Dawn.

Through modeling, he and a team of scientists from multiple universities as well as the United States Geological Survey and the Planetary Science Institute found that the decay of radioactive elements within Ceres's interior could keep it active. Their findings were recently published in American Geophysical Union Advances.

King's study of big planets such as Earth, Venus, and Mars had always shown him that planets start out hot. The collision between objects that form a planet creates that initial heat. Ceres, by contrast, never got big enough to become a planet and generate heat the same way, King said. To learn how it could still generate enough heat to power geologic activity, he used theories and computational tools previously applied to bigger planets to study Ceres's interior, and he looked for evidence that could support his models in data returned by the Dawn mission.

The team's model of the dwarf planet's interior showed a unique sequence: Ceres started out cold and heated up because of the decay of radioactive elements such as uranium and thorium -- which was alone enough to power its activity -- until the interior became unstable.

"What I would see in the model is, all of a sudden, one part of the interior would start heating up and would be moving upward and then the other part would be moving downward," King said.

That instability could explain some of the surface features that had formed on Ceres, as revealed by the Dawn mission. The large plateau had formed on only one side of Ceres with nothing on the other side, and the fractures were clustered in a single location around it. The concentration of features in one hemisphere signaled to King that instability had occurred and had left a visible impact.

"It turned out that you could show in the model that where one hemisphere had this instability that was rising up, it would cause extension at the surface, and it was consistent with these patterns of fractures," King said.

Based on the team's model, Ceres didn't follow a planet's typical pattern of hot first and cool second, with its own pattern of cool, hot, and cool again. "What we've shown in this paper is that radiogenic heating all on its own is enough to create interesting geology," King said.

He sees similarities to Ceres in the moons of Uranus, which a study commissioned by NASA and the National Science Foundation recently deemed high priority for a major robotic mission. With additional improvements to the model, he looks forward to exploring their interiors as well.

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What a Martian meteorite can teach us about Earth's origins

What do Mars and Iceland have in common?

These days, not so much. But more than 4.5 billion years ago, it's possible the Red Planet had a crust comparable to Iceland today. This discovery, hidden in the oldest martian fragments found on Earth, could provide information about our planet that was lost over billions of years of geological movement and could help explain why the Earth developed into a planet that sustains a broad diversity of life and Mars did not.

These insights into Earth's past came out of a new study, published today in Nature Communications, by an international team that includes an NAU researcher. The study details how they found the likely martian origin of the 4.48-billion-year-old meteorite, informally named Black Beauty. Its origin is one of the oldest regions of Mars.

"This meteorite recorded the first stage of the evolution of Mars and, by extension, of all terrestrial planets, including the Earth," said Valerie Payré, a postdoctoral researcher in the Department of Astronomy and Planetary Science. "As the Earth lost its old surface mainly due to plate tectonics, observing such settings in extremely ancient terrains on Mars is a rare window into the ancient Earth surface that we lost a long time ago."

What Mars can tell us about Earth

The team, led by Anthony Lagain from Curtin University in Australia, searched for the location of origin of a martian meteorite (officially named NWA -- Northwest Africa -- 7034 for where it was found on Earth). This meteorite, the chemistry of which indicates that Mars had volcanic activity to that found on Earth, recorded the first stage of Mars' evolution. Although it was ejected from the surface of Mars five to 10 million years ago after an asteroid impact, its source region and geological context has remained a mystery.

This team studied chemical and physical properties of Black Beauty to pinpoint where it came from; they determined it was from Terra Cimmeria-Sirenum, one of the most ancient regions of Mars. It may have a surface similar to Earth's continents. Planetary bodies like Mars have impacts craters all over their surface, so finding the right one is challenging. In a previous study, Lagain's team developed a crater detection algorithm that uses high-resolution images of the surface of Mars to identify small impact craters, finding about 90 million as small as 50 meters in diameter. In this study, they were able to isolate the most plausible ejection site -- the Karratha crater that excavated ejecta of an older crater named Khujirt.

"For the first time, we know the geological context of the only brecciated Martian sample available on Earth, 10 years before the NASA's Mars Sample Return mission is set to send back samples collected by the Perseverance rover currently exploring the Jezero crater," said Lagain, a research fellow in the School of Earth and Planetary Sciences at Curtin. "This research paved the way to locate the ejection site of other Martian meteorites, in order to create the most exhaustive view of the Red Planet's geological history."

Payré studies the nature and formation of Mars' crust to determine if Earth and Mars share a common past that include both a continent-like and ocean-like crust. She uses orbital observations captured in this region to investigate whether traces of volcanism similar to Iceland exist on Mars.

"As of today, Mars' crust complexity is not understood, and knowing about the origin of these amazing ancient fragments could lead future rover and spatial missions to explore the Terra Sirenum-Cimmeria region that hides the truth of Mars' evolution, and perhaps the Earth's," she said. "This work paves the road to locate the ejection site of other martian meteorites that will provide the most exhaustive view of the geological history of Mars and will answer one of the most intriguing questions: why Mars, now dry and cold, evolved so differently from Earth, a flourishing planet for life?"

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Hidden in caves: Mineral overgrowths reveal 'unprecedented' sea level rise

The early 1900s were an exciting time across the world, with rapid advances in the steel, electric and automobile industries. The industrial changes also mark an inflection point in our climate. According to an international team of researchers led by the University of South Florida (USF), the sea level has risen 18 centimeters since the start of the 20th century.

The study, featured on the cover of the July 1 issue of Science Advances, works to identify preindustrial sea levels and examines the impact of modern greenhouse warming on sea-level rise.

The team, which includes USF graduate students, traveled to Mallorca, Spain -- home to more than 1,000 cave systems, some of which have deposits that formed millions of years ago. For this study, they focused on analyzing deposits from 4,000 years ago to present day.

The team found evidence of a previously unknown 20 centimeter sea-level rise that occurred nearly 3,200 years ago when ice caps melted naturally over the course of 400 years at a rate of 0.5 millimeters per year. Otherwise, despite major climatic events like Medieval Warm Period and the Little Ice Age, the sea level remained exceptionally stable until 1900.

"The results reported in our study are alarming," said lead author Bogdan P. Onac, geology professor at USF. "The sea-level rise since the 1900s is unprecedented when compared to the natural change in ice volumes over the last 4,000 years. This implies that if global temperatures continue to rise, sea levels could eventually reach higher levels than scientists previously estimated."

To create the timeline, the team gathered 13 samples from eight caves along the coastline of the Mediterranean Sea. The deposits are rare -- only forming near the coastline in cave passages that were repeatedly flooded by sea water, making them accurate markers of sea-level changes overtime. Each deposit holds valuable insight into both the past and future, helping researchers determine how quickly the sea level will rise in the coming decades and centuries.

The samples were taken to the University of New Mexico and University of Bern in Switzerland, where special instruments were used to determine their age by uranium-series method. Over time, uranium decays into other elements such as thorium and lead, allowing researchers to create a timeline of the sea level documented in each deposit.

A complex software at Harvard University helped generate predictions using various ice models and Earth's parameters to showcase an accurate history of the sea level. These predictions are essential because they allow researchers to estimate past global mean sea level, which is key in addressing future sea-level rise.

"If humans continue to be the main driver and the temperature increases 1.5 degrees in the near future, there will be irreversible damage," Onac said. "There will be no turning back from that point on."

Based on ice mass loss from the Antarctic and Greenland, the average sea-level rise since 2008 is 1.43 millimeters per year.

Permanent flooding from the rising sea level won't happen overnight, but Onac says it will be seen more and more during storm surges and hurricanes. With nearly 40 percent of the world's population living within 62 miles of a coast, the rising sea level could be catastrophic with substantial societal and economic impacts.

"Even if we stop right now, sea level will continue to rise for at least a couple of decades, if not centuries, simply because the system is warmed up."

In June, Onac received a new research grant from the National Science Foundation to continue his research to predict future sea-level rise due to global warming. The grant will allow Onac to expand the research further into history by 130,000 years and create a better understanding of sea level globally. Starting in September, Onac and his team will begin analyzing cave deposits from around the globe, including Italy, Greece, Mexico and Cuba.

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Fossils in the 'Cradle of Humankind' may be more than a million years older than previously thought

The earth doesn't give up its secrets easily -- not even in the "Cradle of Humankind" in South Africa, where a wealth of fossils relating to human evolution have been found.

For decades, scientists have studied these fossils of early human ancestors and their long-lost relatives. Now, a dating method developed by a Purdue University geologist just pushed the age of some of these fossils found at the site of Sterkfontein Caves back more than a million years. This would make them older than Dinkinesh, also called Lucy, the world's most famous Australopithecus fossil.

The "Cradle of Humankind" is a UNESCO World Heritage Site in South Africa that comprises a variety of fossil-bearing cave deposits, including at Sterkfontein Caves. Sterkfontein was made famous by the discovery of the first adult Australopithecus, an ancient hominin, in 1936. Hominins includes humans and our ancestral relatives, but not the other great apes. Since then, hundreds of Australopithecus fossils have been found there, including the well-known Mrs. Ples, and the nearly complete skeleton known as Little Foot. Paleoanthropologists and other scientists have studied Sterkfontein and other cave sites in the Cradle of Humankind for decades to shed light on human and environmental evolution over the past 4 million years.

Darryl Granger, a professor of earth, atmospheric, and planetary sciences in Purdue University's College of Science, is one of those scientists, working as part of an international team. Granger specializes in dating geologic deposits, including those in caves. As a doctoral student, he devised a method for dating buried cave sediments that is now used by researchers all over the world. His previous work at Sterkfontein dated the Little Foot skeleton to about 3.7 million years old, but scientists are still debating the age of other fossils at the site.

In a study published in the Proceedings of the National Academy of Sciences, Granger and a team of scientists including researchers from the University of the Witwatersrand in Johannesburg, South Africa and the University Toulouse Jean Jaurès in France, have discovered that not only Little Foot, but all of the Australopithecus-bearing cave sediments date from about 3.4 to 3.7 million years old, rather than 2-2.5 million years old as scientists previously theorized. That age places these fossils toward the beginning of the Australopithecus era, rather than near the end. Dinkinesh, who hails from Ethiopia, is 3.2 million years old, and her species, Australopithecus africanus, hails back to about 3.9 million years old.

Sterkfontein is a deep and complex cave system that preserves a long history of hominin occupation of the area. Understanding the dates of the fossils here can be tricky, as rocks and bones tumbled to the bottom of a deep hole in the ground, and there are few ways to date cave sediments.

In East Africa, where many hominin fossils have been found, the Great Rift Valley volcanoes lay down layers of ash that can be dated. Researchers use those layers to estimate how old a fossil is. In South Africa -- especially in a cave -- the scientists don't have that luxury. They typically use other animal fossils found around the bones to estimate their age or calcite flowstone deposited in the cave. But bones can shift in the cave, and young flowstone can be deposited in old sediment, making those methods potentially incorrect. A more accurate method is to date the actual rocks in which the fossils were found. The concrete-like matrix that embeds the fossil, called breccia, is the material Granger and his team analyze.

"Sterkfontein has more Australopithecus fossils than anywhere else in the world," Granger said. "But it's hard to get a good date on them. People have looked at the animal fossils found near them and compared the ages of cave features like flowstones and gotten a range of different dates. What our data does is resolve these controversies. It shows that these fossils are old -- much older than we originally thought."

Granger and the team used accelerator mass spectrometry to measure radioactive nuclides in the rocks, as well as geologic mapping and an intimate understanding of how cave sediments accumulate to determine the age of the Australopithecus-bearing sediments at Sterkfontein,

Granger and the research group at the Purdue Rare Isotope Measurement Laboratory (PRIME Lab) study so-called cosmogenic nuclides and what they can reveal about the history of fossils, geological features and rock. Cosmogenic nuclides are extremely rare isotopes produced by cosmic rays -- high-energy particles that constantly bombard the earth. These incoming cosmic rays have enough energy to cause nuclear reactions inside rocks at the ground surface, creating new, radioactive isotopes within the mineral crystals. An example is aluminum-26: aluminum that is missing a neutron and slowly decays to turn into magnesium over a period of millions of years. Since aluminum-26 is formed when a rock is exposed at the surface, but not after it has been deeply buried in a cave, PRIME lab researchers can date cave sediments (and the fossils within them) by measuring levels of aluminum-26 in tandem with another cosmogenic nuclide, beryllium-10.

In addition to the new dates at Sterkfontein based on cosmogenic nuclides, the research team made careful maps of the cave deposits and showed how animal fossils of different ages would have been mixed together during excavations in the 1930s and 1940s, leading to decades of confusion with the previous ages. "What I hope is that this convinces people that this dating method gives reliable results," Granger said. "Using this method, we can more accurately place ancient humans and their relatives in the correct time periods, in Africa, and elsewhere across the world."

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Research shows how Gulf of Mexico escaped ancient mass extinction

An ancient bout of global warming 56 million years ago that acidified oceans and wiped-out marine life had a milder effect in the Gulf of Mexico, where life was sheltered by the basin's unique geology -- according to research by the University of Texas Institute for Geophysics (UTIG).

Published in the journal Marine and Petroleum Geology, the findings not only shed light on an ancient mass extinction, but could also help scientists determine how current climate change will affect marine life and aid in efforts to find deposits of oil and gas.

And although the Gulf of Mexico is very different today, UTIG geochemist Bob Cunningham, who led the research, said that valuable lessons can be drawn about climate change today from how the Gulf was impacted in the past.

"This event known as the Paleocene-Eocene Thermal Maximum or PETM is very important to understand because it's pointing towards a very powerful, albeit brief, injection of carbon into the atmosphere that's akin to what's happening now," he said.

Cunningham and his collaborators investigated the ancient period of global warming and its impact on marine life and chemistry by studying a group of mud, sand, and limestone deposits found across the Gulf.

They sifted through rock chips brought up during oil and gas drilling and found an abundance of microfossils from radiolarians -- a type of plankton -- that had surprisingly thrived in the Gulf during the ancient global warming. They concluded that a steady supply of river sediments and circulating ocean waters had helped radiolarians and other microorganisms survive even while Earth's warming climate became more hostile to life.

"In a lot of places, the ocean was absolutely uninhabitable for anything," said UTIG biostratigrapher Marcie Purkey Phillips. "But we just don't seem to see as severe an effect in the Gulf of Mexico as has been seen elsewhere."

The reasons for that go back to geologic forces reshaping North America at the time. About 20 million years before the ancient global warming, the rise of the Rocky Mountains had redirected rivers into the northwest Gulf of Mexico -- a tectonic shift known as the Laramide uplift -- sending much of the continent's rivers through what is now Texas and Louisiana into the Gulf's deeper waters.

When global warming hit and North America became hotter and wetter, the rain-filled rivers fire-hosed nutrients and sediments into the basin, providing plenty of nutrients for phytoplankton and other food sources for the radiolarians.

The findings also confirm that the Gulf of Mexico remained connected to the Atlantic Ocean and the salinity of its waters never reached extremes -- a question that until now had remained open. According to Phillips, the presence of radiolarians alone -- which only thrive in nutrient-rich water that's no saltier than seawater today -- confirmed that the Gulf's waters did not become too salty. Cunningham added that the organic content of sediments decreased farther from the coast, a sign that deep currents driven by the Atlantic Ocean were sweeping the basin floor.

The research accurately dates closely related geologic layers in the Wilcox Group (a set of rock layers that house an important petroleum system), a feat that can aid in efforts to find undiscovered oil and gas reserves in formations that are the same age. At the same time, the findings are important for researchers investigating the effects of today's global warming because they show how the water and ecology of the Gulf changed during a very similar period of climate change long ago.

The study compiled geologic samples from 36 industry wells dotted across the Gulf of Mexico, plus a handful of scientific drilling expeditions including the 2016 UT Austin-led investigation of the Chicxulub asteroid impact, which led to the extinction of non-avian dinosaurs.

For John Snedden, a study coauthor and senior research scientist at UTIG, the study is a perfect example of industry data being used to address important scientific questions.

"The Gulf of Mexico is a tremendous natural archive of geologic history that's also very closely surveyed," he said. "We've used this very robust database to examine one of the highest thermal events in the geologic record, and I think it's given us a very nuanced view of a very important time in Earth's history."

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Large, long-lived, and entirely molten magma chambers once existed in Earth’s crust

An international group of researchers led by geologists from Wits University in Johannesburg have come up with multiple lines of evidence indicating that the Bushveld Complex in South Africa functioned as a "big magma tank" in the ancient Earth's crust. This research was published as a paper in Scientific Reports.

Professor Rais Latypov from the School of Geosciences at Wits University says "While re-examining thin-sections of Bushveld chromitites, we noticed a very puzzling observation: chromite often occurs as individual grains that seemingly 'suspended' within matrix minerals. This observation leads us to a critical question: why have the chromite grains failed to sink towards the chamber floor despite being much denser than the host melt?"

To answer this question, the researchers have studied chromitite in three-dimensions (3D) using high-resolution X-ray computed tomography and revealed that nearly all chromite grains are closely interconnected to form a single continuous 3D framework. "This gave us an answer to the above question: chromite grains are not able to settle freely towards the chamber floor simply because they are all bound together in self-supporting 3D frameworks attached to the chamber floor," says Dr Sofya Chistyakova from the School of Geosciences at Wits University.

There is only one process that may result in the formation of such 3D frameworks of chromite crystals. This is an in situ self-nucleation and growth of chromite grains, for example, when all new chromite grains nucleate and grow on pre-existing chromite grains directly at the chamber floor. This happens from the parental melt that is saturated in chromite as the only crystallising phase.

"This logically brought us to a long-known Cr mass balance issue -- normal basaltic melts contain only a very small amount of Cr so that the formation of thick chromitite layer requires extraction of Cr from a very large volume of liquid that must be present as a thick melt layer in the chamber. Simple mass balance calculations indicate that a 1 metre thick layer of chromitite will require a magma column of 2km to 4km thick," says Latypov.

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Mystery solved about the origin of the 30,000-year-old Venus of Willendorf

The almost 11 cm high figurine from Willendorf is one of the most important examples of early art in Europe. It is made of a rock called "oolite" which is not found in or around Willendorf. A research team led by the anthropologist Gerhard Weber from the University of Vienna and the two geologists Alexander Lukeneder and Mathias Harzhauser as well as the prehistorian Walpurga Antl-Weiser from the Natural History Museum Vienna have now found out with the help of high-resolution tomographic images that the material from which the Venus was carved likely comes from northern Italy. This sheds new light on the remarkable mobility of the first modern humans south and north of the Alps. The results currently appear in Scientific Reports.

The Venus von Willendorf is not only special in terms of its design, but also in terms of its material. While other Venus figures are usually made of ivory or bone, sometimes also of different stones, oolite was used for the Lower Austrian Venus, which is unique for such cult objects. The figurine found in the Wachau in 1908 and on display in the Natural History Museum in Vienna has so far only been examined from the outside. Now, more than a 100 years later, anthropologist Gerhard Weber from the University of Vienna has used a new method to examine its interior: micro-computed tomography. During several passes, the scientists obtained images with a resolution of up to 11.5 micrometres -- a quality that is otherwise only seen under a microscope. The first insight gained is: "Venus does not look uniform at all on the inside. A special property that could be used to determine its origin," says the anthropologist.

Along with the two geologists Alexander Lukeneder and Mathias Harzhauser from the Natural History Museum in Vienna, who had previously worked with oolites, the team procured comparative samples from Austria and Europe and evaluated them. A complex project: Rock samples from France to eastern Ukraine, from Germany to Sicily were obtained, sawn up and examined under a microscope. The team was supported by the state of Lower Austria, which provided funds for the time-consuming analyses.

The inside also gives information about the outside

The tomographic data from the Venus showed that the sediments were deposited in the rocks in different densities and sizes. In between there were also small remnants of shells and six very dense, larger grains, so-called limonites. The latter explains the previously mysterious hemispherical cavities on the surface of Venus with the same diameter: "The hard limonites probably broke out when the creator of the Venus was carving it," explains Weber: "In the case of the Venus navel, he then apparently made it a virtue out of necessity."

Another finding: The Venus oolite is porous because the cores of the millions of globules (ooides) of which it is comprised had dissolved. This is a great explanation for why the resourceful sculptor chose this material 30,000 years ago: It is much easier to work with. The scientists also identified a tiny shell remnant, just 2.5 millimetres long, and dated it to the Jurassic period. This ruled out all other potential deposits of the rock from the much later Miocene geological era, such as those in the nearby Vienna Basin.

A long way for that time

The research team also analysed the grain sizes of the other samples. Hundreds, sometimes even thousands of grains were marked and measured with image processing programs or even manually. None of the samples within a 200-kilometer radius of Willendorf even remotely matched. The analysis finally showed that the samples from the Venus were statistically indistinguishable from samples from a location in northern Italy near Lake Garda. This is remarkable because it means that the Venus (or at least its material) started a journey from south of the Alps to the Danube north of the Alps.

"People in the Gravettian -- the tool culture of the time -- looked for and inhabited favourable locations. When the climate or the prey situation changed, they moved on, preferably along rivers," explains Gerhard Weber. Such a journey could have taken generations.

One of the two possible routes from the south to the north would lead around the Alps and into the Pannonian Plain and was described in simulations by other researchers a few years ago. The other way to get from Lake Garda to the Wachau would be via the Alps. Whether this was possible more than 30,000 years ago is unclear due to the climate deterioration that began at that time. This would be a rather improbable variant if there had already been continuous glaciers at that time. However, the 730 km long path along the Etsch, the Inn and the Danube had always been below 1,000 meters above sea level, with the exception of 35 kilometres at Lake Reschen.

Possible, but less likely, connection to eastern Ukraine

The statistics clearly point to northern Italy as the origin of the Venus oolite. Nevertheless, there is another interesting place for the origin of the rock. It is in eastern Ukraine, more than 1,600 kilometres linear distance from Willendorf. The samples there do not fit as clearly as those from Italy, but better than all the rest of the sample. An interesting connection here: Venus figures were found in nearby southern Russia, which are somewhat younger, but look very similar to the Venus found in Austria. Genetic results also show that people in Central and Eastern Europe were connected to one another at this time.

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