Carbonate Petrography

Carbonate petrography is the study of limestones, dolomites and associated deposits under optical or electron microscopes greatly enhances field studies or core observations and can provide a frame of reference for geochemical studies.

25 strangest Geologic Formations on Earth

The strangest formations on Earth.

What causes Earthquake?

Of these various reasons, faulting related to plate movements is by far the most significant. In other words, most earthquakes are due to slip on faults.

The Geologic Column

As stated earlier, no one locality on Earth provides a complete record of our planet’s history, because stratigraphic columns can contain unconformities. But by correlating rocks from locality to locality at millions of places around the world, geologists have pieced together a composite stratigraphic column, called the geologic column, that represents the entirety of Earth history.

Folds and Foliations

Geometry of Folds Imagine a carpet lying flat on the floor. Push on one end of the carpet, and it will wrinkle or contort into a series of wavelike curves. Stresses developed during mountain building can similarly warp or bend bedding and foliation (or other planar features) in rock. The result a curve in the shape of a rock layer is called a fold.

Showing posts with label discovery. Show all posts
Showing posts with label discovery. Show all posts

The Messinian Salinity Crisis


You will have heard of The Messinian Salinity Crisis no doubt. From learned articles, geology textbooks, probably lectures at your college or University. Or possibly not. This was not always the hot topic it is now. In fact, the very idea of this happening, was for a while, challenged, even ridiculed. It seemed too incredible that this could happen as it did and Dessication/Flood theories took time to gain traction. But, if you had heard about it, you would remember that The Messinian Salinity Crisis, was a time when the Mediterranean Sea, very much as we know it today, evaporated – dried out, almost completely.



You will have heard of the rates of desiccation, influx and yet more desiccation, repeated in endless cycles over tens, even hundreds of thousands of years. On a human temporal scale, this would have been a long drawn out affair, covering a time hundreds of generations deep, more than the span of Homo sapiens existence. In Geologic terms however, it was a string of sudden events. Of incredibly hot and arid periods followed by rapid ingress of waters, either via spillways through what is now modern day Morocco and the southern Iberian peninsular, or headlong through a breach in the sill between the Pillars of Heracles, the modern day Straights of Gibraltar.


There were prolonged periods of dessication, of desolate landscapes beyond anything seen today in Death Valley or The Afar Triangle. These landscapes were repeatedly transgressed by brackish waters from storm seasons far into the African and Eurasian interiors, or the Atlantic, and these in turn dried out. Again and again this happened. It had to be so because the vast deposits of rock salt, gypsum and anhydrites could not have been emplaced in a single evaporite event. The salt deposits in and around the Mediteranean today represent fifty times the current capacity of this great inland sea. You may have heard too of the variety of salts production, as agglomerating crystals fell from the descending surface to the sea floor, or as vast interconnected hypersaline lakes left crystalline residues at their diminishing margins, as forsaken remnant sabkhas, cut off from the larger basins, left behind acrid dry muds of potassium carbonates – the final arid mineral residue of the vanished waters.


Just under six million years ago, Geologic processes isolated what was left of the ancient Tethys ocean, the sea we know as the Mediterranean, home to historic human conflicts and marine crusades of Carthage, Rome, Athens and Alexandria, a Sea fringed by modern day Benidorm, Cyprus, Malta and Monaco. At a time 5.96 million years ago – evaporation outpaced replenishment. Indeed, just as it does today, but without the connecting seaway to replenish losses. Inexorable tectonic activity first diverted channels, then – sealed them. Cut off from the Atlantic in the West, water levels fell, rose briefly and fell again, and again. The mighty Nile - a very different geophysical feature of a greater capacity than today, and the rivers of Europe cut down great canyons hundreds and thousands of metres below present Eustatic sea and land surface levels, as seismic cross sections show in staggering detail. The cores taken at depth in the Mediterranean, show Aeolian sands above layers of salt, fossiliferous strata beneath those same salts, all indicating changing environments. The periods of blackened unshifting desert varnished floors and bleached playas, decades and centuries long, were punctuated often by catastrophic episodes, with eroded non conformable surfaces of winnowed desert pavement, toppled ventifracts, scours and rip up clasts. Species of fossilised terrestrial plant life, scraping an arid existence have been found, thousands of meters down, in the strata of the Mediterranean sea floor.
 


There is much evidence too, in the uplifted margins of Spain, France, and Sicily, of those hostile millennia when the sea disappeared. Incontrovertible evidence, painstakingly gathered, analysed and peer reviewed, demonstrates via the resources of statistical analysis, calculus and geophysical data that the Messinian Salinity Crisis was a period during the Miocene wherein the geology records a uniquely arid period of repeated partial and very nearly complete desiccation of the Mediterranean Sea over a period of approximately 630,000 years. But for the Geologist, the story doesn’t end there. The Geologists panoptic, all seeing third eye, sees incredible vistas and vast panoramas. Of a descent from the Alpine Foreland to the modern day enclave of Monaco, gazing out southwards from a barren, uninhabited and abandoned raised coast to deep dry abyssal plains, punctuated by exposed chasms, seamounts and ridges, swirling and shifting so slowly in a distant heat haze. A heat haze produced by temperatures far above any recorded by modern man and his preoccupation with Global Warming. An unimaginable heat sink would produce temperatures of 70 to 80 degrees Celsius at 4000M depth within the basins. 




Looking down upon this Venusian landscape, the sun might glint on remaining lakes and salt flats so very far away and so very much farther below. Hills and valleys, once submerged, would be observed high and dry – from above, as would the interconnecting rivers of bitter waters hot enough to slowly broil any organism larger than extremophile foraminifer. All this, constantly shimmering in the relentless heat. Only the imagination of the geologist could see the vast, hellish, yet breathtaking landscape conjured up by the data and the rock record. And finally, the Geologist would visualise a phenomenon far greater in scope and magnitude than any Biblical flood – The Zanclean Event.
Also known as The Zanclean Deluge, when the drought lasting over half a million years was finally ended as the Atlantic Ocean breached the sill/land bridge between Gibraltar and North West Africa. Slowly perhaps at first until a flow a thousand times greater than the volumetric output of the Amazon cascaded down the slopes to the parched basins. Proximal to the breach, there would be a deafening thunderous roar and the ground would tremor constantly, initially triggering great avalanches above and below the Eustatic sea level as the far reaching and continuous concussion roared and rumbled on, and on, and on. For centuries great cataracts and torrents of marine waters fell thousands of metres below and flowed thousands of kilometers across to the East. Across to the abyssal plains off the Balearics, to the deeps of the Tyrrhenian and Ionian seas, into the trenches south of the Greek Islands and finally up to the rising shores of The Lebanon. The newly proximal waters to the final coastal reaches and mountains that became islands, must have had a climatological effect around the margins of the rejuvenated Mediterranean. Flora and Fauna both marine and terrestrial will have recolonised quickly. Species may have developed differently, post Zanclean, on the Islands. And in such a short period, there must surely have been earthquakes and complex regional depression and emergence. Isostacy compensated for the trillions of cubic meters of transgression waters that now occupied the great basins between the African and Eurasian plates, moving the land, reactivating ancient faults and within and marginal to the great inland sea, a region long active with convergent movements of a very different mechanism.

Hollywood and Pinewood have yet to match the imagination of the Earth Scientist, of the many chapters of Earths dynamic history held as fully tangible concepts to the men and women who study the rocks and the stories they tell. The movies played out in the mind of the geologist are epic indeed and – as we rightly consider the spectre of Global Warming, consider too the fate of future populations (of whatever evolved species) at the margins of the Mediterranean and the domino regions beyond, when inexorable geologic processes again isolate that benign, sunny holiday sea. Fortunately, not in our lifetime, but that of our far off descendants who will look and hopefully behave very differently from Homo Sapiens.


Note: This blog is written and contributed by Paul Goodrich. You can also contribute your blog or article on our website. See guidelines here.

Banded-iron formations (BIFs) - Evidence of Oxygen in Early Atmosphere

Our knowledge about the rise of oxygen gas in Earth’s atmosphere comes from multiple lines of evidence in the rock record, including the age and distribution of banded iron formations, the presence of microfossils in oceanic rocks, and the isotopes of sulfur.
However, this article is just focus on Banded Iron Formation.

BIF (polished) from Hamersley Iron Formation, West Australia, Australia

Summary: Banded-iron formations (BIFs) are sedimentary mineral deposits consisting of alternating beds of iron-rich minerals (mostly hematite) and silica-rich layers (chert or quartz) formed about 3.0 to 1.8 billion years ago. Theory suggests BIFs are associated with the capture of oxygen released by photosynthetic processes by iron dissolved in ancient ocean water. Once nearly all the free iron was consumed in seawater, oxygen could gradually accumulate in the atmosphere, allowing an ozone layer to form. BIF deposits are extensive in many locations, occurring as deposits, hundreds to thousands of feet thick. During Precambrian time, BIF deposits probably extensively covered large parts of the global ocean basins. The BIFs we see today are only remnants of what were probably every extensive deposits. BIFs are the major source of the world's iron ore and are found preserved on all major continental shield regions. 

Banded-iron formation (BIF)
is 
consists of layers of iron oxides (typically either magnetite or hematite) separated by layers of chert (silica-rich sedimentary rock). Each layer is usually narrow (millimeters to few centimeters). The rock has a distinctively banded appearance because of differently colored lighter silica- and darker iron-rich layers. In some cases BIFs may contain siderite (carbonate iron-bearing mineral) or pyrite (sulfide) in place of iron oxides and instead of chert the rock may contain carbonaceous (rich in organic matter) shale.

It is a chemogenic sedimentary rock (material is believed to be chemically precipitated on the seafloor). Because of old age BIFs generally have been metamorphosed to a various degrees (especially older types), but the rock has largely retained its original appearance because its constituent minerals are fairly stable at higher temperatures and pressures. These rocks can be described as metasedimentary chemogenic rocks.



                     Jaspilite banded iron formation (Soudan Iron-Formation, Soudan, Minnesota, USA
Image Credits: James St. John



In the 1960s, Preston Cloud, a geology professor at the University of California, Santa Barbara, became interested in a particular kind of rock known as a Banded Iron Formation (or BIF). They provide an important source of iron for making automobiles, and provide evidence for the lack of oxygen gas on the early Earth.

Cloud realized that the widespread occurrence of BIFs meant that
the conditions needed to form them must have been common on the ancient Earth, and not common after 1.8 billion years ago. Shale and chert often form in ocean environments today, where sediments and silica-shelled microorganisms accumulate gradually on the seafloor and eventually turn into rock. But iron is less common in younger oceanic sedimentary rocks. This is partly because there are only a few sources of iron available to the ocean: isolated volcanic vents in the deep ocean and material weathered from continental rocks and carried to sea by rivers.


Banded iron-formation (10 cm), Northern Cape, South Africa.
Specimen and photograph: A. Fraser
Most importantly, it is difficult to transport iron very far from these sources today because when iron reacts with oxygen gas, it becomes insoluble (it cannot be dissolved in water) and forms a solidparticle. Cloud understood that for large deposits of iron to exist all over the world’s oceans, the iron must have existed in a dissolved form. This way, it could be transported long distances in seawater from its sources to the locations where BIFs formed. This would be possible only if there were little or no oxygen gas in the atmosphere and ocean at the time the BIFs were being deposited. Cloud recognized that since BIFs could not form in the presence of oxygen, the end of BIF deposition probably marked the first occurrence of abundant oxygen gas on Earth (Cloud, 1968).
Cloud further reasoned that, for dissolved iron to finally precipitate and be deposited, the iron would have had to react with small amounts of oxygen near the deposits. Small amounts of oxygen could have been produced by the first photosynthetic bacteria living in the open ocean. When the dissolved iron encountered the oxygen produced by the photosynthesizing bacteria, the iron would have precipitated out of seawater in the form of minerals that make up the iron-rich layers of BIFs: hematite (Fe2O3) and magnetite (Fe3O4), according to the following reactions:
4Fe3 + 2O2 → 2Fe2O3
6Fe2 + 4O2 → 2Fe3O4
The picture that emerged from Cloud’s studies of BIFs was that small amounts of oxygen gas, produced by photosynthesis, allowed BIFs to begin forming more than 3 billion years ago. The abrupt disappearance of BIFs around 1.8 billion years ago probably marked the time when oxygen gas became too abundant to allow dissolved iron to be transported in the oceans.
Banded Iron Formation
Source is unknown

It is interesting to note that BIFs reappeared briefly in a few places around 700 millionyears ago,during a period of extreme glaciation when evidence suggests that Earth’s oceans were entirely covered with sea ice. This would have essentially prevented the oceans from interacting with the atmosphere, limiting the supply of oxygen gas in the water and again allowing dissolved iron to be transported throughout the oceans. When the sea ice melted, the presence of oxygen would have again allowed the iron to precipitate.

References:

1. Misra, K. (1999). Understanding Mineral Deposits Springer.
2. 
Cloud, P. E. (1968). Atmospheric and hydrospheric evolution on the primitive Earth both secular accretion and biological and geochemical processes have affected Earth’s volatile envelope. Science, 160(3829), 729–736.
3. 
James,H.L. (1983). Distribution of banded iron-formation in space and time. Developments in Precambrian Geology, 6, 471–490.

Siccar Point - the world's most important geological site and the birthplace of modern geology


Siccar Point is world-famous as the most important unconformity described by James Hutton (1726-1797) in support of his world-changing ideas on the origin and age of the Earth.

James Hutton unconformity with annotations - Siccar Point 



In 1788, James Hutton first discovered Siccar Point, and understood its significance. It is by far the most spectacular of several unconformities that he discovered in Scotland, and very important in helping Hutton to explain his ideas about the processes of the Earth.At Siccar Point, gently sloping strata of 370-million-year-old Famennian Late Devonian Old Red Sandstone and a basal layer of conglomerate overlie near vertical layers of 435-million-year-old lower Silurian Llandovery Epoch greywacke, with an interval of around 65 million years.
Standing on the angular unconformity at Siccar Point (click to enlarge). Photo: Chris Rowan, 2009
As above, with annotations. Photo: Chris Rowan, 2009





Hutton used Siccar Point to demonstrate the cycle of deposition, folding, erosion and further deposition that the unconformity represents. He understood the implication of unconformities in the evidence that they provided for the enormity of geological time and the antiquity of planet Earth, in contrast to the biblical teaching of the creation of the Earth. 

   
How the unconformity at Siccar Point formed.



At this range, it is easy to spot that the contact between the two units is sharp, but it is not completely flat. Furthermore, the lowest part of the overlying Old Red Sandstone contains fragments of rock that are considerably larger than sand; some are at least as large as your fist, and many of the fragments in this basal conglomerate are bits of the underlying Silurian greywacke. These are all signs that the greywackes were exposed at the surface, being eroded, for a considerable period of time before the Old Red Sandstone was laid down on top of them.
The irregular topography and basal conglomerate show that this is an erosional contact. Photo: Chris Rowan, 2009

The Siccar Point which is a rocky promontory in the county of Berwickshire on the east coast of Scotland.

Ancient Fossil Forests Discovered in the Arctic

Ancient Fossil Forests Discovered in the Arctic



What did a portion of the main trees on Earth resemble? Earth researchers from Cardiff University diving around in Arctic Norway are surrounding an answer. Furthermore, that answer is: oddly well known. 

UK scientists have uncovered antiquated fossil forest, thought to be somewhat in charge of a stand out amongst the most dramatic moments in the Earth's atmosphere in the previous 400 million years. 

The fossil forest, with tree stumps saved set up, were found in Svalbard, a Norwegian archipelago arranged in the Arctic Ocean. They were recognized and portrayed by Dr Chris Berry of the School of Earth and Ocean Sciences. 

Prof John Marshall, of Southampton University, has precisely dated the forest to 380 million years. 

The forest became close to the equator amid the late Devonian period, and could give an understanding into the reason for a 15-fold diminishment in levels of carbon dioxide (CO2) in the air around that time. 

Current speculations propose that amid the Devonian period (420-360 million years back) there was an immense drop in the level of CO2 in the air, thought to be to a great extent created by an adjustment in vegetation from humble plants to the main substantial woods trees. 

Woods hauled CO2 out of the air through photosynthesis, the procedure by which plants make sustenance and tissues – and the arrangement of soils. 

Albeit at first the presence of extensive trees retained a greater amount of the sun's radiation, in the end temperatures on Earth additionally dropped drastically to levels fundamentally the same to those accomplished today due to the diminishment in barometrical CO2. 

In light of the high temperatures and vast measure of precipitation on the equator, it is likely that central forests contributed most to the draw down of CO2. Svalbard was situated on the equator around this time, before the tectonic plate floated north by around 80° to its flow position in the Arctic Ocean. 

"These fossil forests demonstrates to us what the vegetation and scene resembled on the equator 380 million years prior, as the main trees were starting to show up on the Earth," said Dr Berry. 

The group found that the woodlands in Svalbard were framed predominantly of lycopod trees, better known for developing a huge number of years after the fact in coal overwhelms that in the long run transformed into coal stores, for example, those in South Wales. They likewise found that the woodlands were to a great degree thick, with little crevices, around 20cm between each of the trees, which presumably came to around 4m high. 

"Amid the Devonian Period, it is broadly trusted that there was a colossal drop in the level of carbon dioxide in the climate, from 15 times the present add up to something drawing nearer current levels. 

"The development of tree-sized vegetation is the doubtlessly reason for this emotional drop in carbon dioxide in light of the fact that the plants were retaining carbon dioxide through photosynthesis to assemble their tissues, furthermore through the procedure of shaping soils."

Saturn's Crisscrossed Rings Hide Tiny Moon

Saturn's Criss-crossed Rings Hide Tiny Moon




It seems that whenever we look at a new picture of Saturn by NASA’s Cassini mission, there’s always something unique. And often, there’s hidden gem.

Captured on Feb. 11, this observation, at first, doesn't make a whole lot of sense. We already know that Saturn sports hundreds of distinct rings, but they all occupy the same plane. How did Cassini see rings that are criss-crossed?

Actually, this observation only shows one ring plane, but behind are the shadows of each ring being cast on Saturn’s upper atmosphere, creating the illusion there are 2 sets of rings.


At first glance, Saturn's rings appear to be intersecting themselves in an impossible way. In actuality, this view from NASA's Cassini spacecraft shows the rings in front of the planet, upon which the shadow of the rings is cast. And because rings like the A ring and Cassini Division, which appear in the foreground, are not entirely opaque, the disk of Saturn and those ring shadows can be seen directly through the rings themselves.


But while you digest the scene and work out which lines are rings and which are shadows, you’re probably overlooking tiny moon Pan, a 17 mile (or 28 kilometre) wide satellite occupying a gap in the rings (just below the middle of the photo).

Many of the gaps in Saturn’s rings possess small moons whose gravity keeps these rings clear of debris as they orbit. Pan occupies the famous Encke Gap, for example. Many other gaps, however, don’t appear to have moons, so their nature is a little more mysterious. Some theories on ring dynamics suggest some of these gaps may have formed through resonances with Saturn’s larger moons.


The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.



Regardless of how they were formed, Cassini continues to capture their beauty, constantly reaffirming Saturn as the jewel of the solar system.

One of Titan's Strange Seas is Pure Methane

One of Titan's Strange Seas is Pure Methane

This image, taken by the Cassini spacecraft, shows the first flash of sunlight reflected off a hydrocarbon lake on Saturn’s moon Titan. The July 2009 image confirmed the presence of liquid in the moon’s northern hemisphere.

A new study of eight years of radar data collected by the Saturn-orbiting Cassini spacecraft shows that the planet’s largest moon, Titan, the only other body in the solar system besides Earth where liquids pool on the surface has a sea of pure methane.



Before Cassini, scientists had expected Titan’s seas to be dominated by ethane, since sunlight breaks apart methane and converts it into the more complex ethane hydrocarbon.

Instead, Alice Le Gall, a Cassini scientist at France’s LATMOS research laboratory, and colleagues discovered that Ligeia Mare, Titan’s second-largest sea, is almost pure methane.

Scientists suspect that methane rain may be regularly filling the sea, or that ethane is locked in the sea’s crust, or flowing into the adjacent sea, according to a press release about the study, which was published in the March 11 issue of Journal of Geophysical Research Planets.

The findings are based on radar observations made by Cassini between 2007 and 2015. Those measurements of heat given off by Ligeia Mare were combined with results of a 2013 experiment that bounced radar waves off the seafloor, which allowed scientists to estimate the sea’s depth.

Ligeia Mare, which turns out to be as deep as 525 feet, also likely sports a layer of organic-rich sludge on its floor, the scientists said.

“It’s a marvelous feat of exploration that we’re doing extraterrestrial oceanography on an alien moon,” Cassini scientist Steve Wall, with NASA’s Jet Propulsion Laboratory in Pasadena, Calif., noted in the press release.

Cassini, which has been studying the Saturn system for almost 12 years, has revealed that almost 2 percent of Titan’s 620,000 square miles of real estate are covered in liquid.

The moon has three large seas, all located in the northern polar region, that are surrounded by small lakes. So far, just one large lake has been found in Titan’s southern hemisphere.

Pregnant T. rex Found, May Contain DNA

Pregnant T. rex Found, May Contain DNA

This illustration shows a pregnant T. rex next to another female.
A pregnant Tyrannosaurus rex has been found, shedding light on the evolution of egg-laying as well as on gender differences in the dinosaur. The remains also could contain the holy grail of all dinosaur fossils: DNA.
"Yes, it's possible," Lindsay Zanno told Discovery News, referring to genetic material that may be present in this as well as similar dinosaur finds. "We have some evidence that fragments of DNA may be preserved in dinosaur fossils, but this remains to be tested further."
What has been confirmed so far is that the T. rex, which was found in Montana and dates to 68 million years ago, retained medullary bone that reveals the individual was pregnant. Medullary bone is only present in female living dinosaurs, i.e. birds, just before and during egg laying. It's this type of bone that could retain preserved DNA.
Zanno is an assistant research professor of biological sciences at North Carolina State University, where she is also head of the North Carolina Museum of Natural Sciences' Paleontology Research Lab and is curator of paleontology. She explained that medullary bone lines the marrow cavity of the long bones of birds.
"It's a special tissue that is built up as easily mobilized calcium storage just before egg laying," she said. "The outcome is that birds do not have to pull calcium from the main part of their bones in order to shell eggs, weakening their bones the way crocodiles do."
Crocodiles, she said, are the closest living relatives of dinosaurs.
"Medullary bone is thus present just before and during egg laying, but is entirely gone after the female has finished laying eggs," she said.
Early on, Mary Schweitzer suspected that medullary bone was present in the tyrannosaur remains, and was able to confirm her suspicions after she, Zanno and their team conducted a chemical analysis of the T. rex's femur.
The material, found to be consistent with known medullary tissues from ostriches and chickens, contained karatan sulfate, a substance not present in any other bone types.
"This analysis allows us to determine the gender of this fossil, and gives us a window into the evolution of egg laying in modern birds," Schweitzer said.
Credits: Discovery news

Homo naledi, new specie of Homo

Homo naledi, new specie of the genus Homo from the Dinaledi Chamber, South Africa

Dinaledi skeletal specimens.
A team of scientists have discovered Homo naledi which is a new specie of extinct homonin within Dinaledi chamber of the rising star cave system, Cradle of human kind, South Africa. The Dinaledi chamber is located approximately 30 meters underground, within the Rising Star cave system at about 26°1′13′′ S; 27°42′43′′ E. The system lies within the Malmani dolomites, approximately 800 meters southwest of the well-known site of Swartkrans in the Cradle of Humankind World Heritage Site, Gauteng Province, South Africa. Modern humans, or Homo sapiens, are now the only living species in their genus. But as recently as 100,000 years ago, there were several other species that belonged to the genus Homo. Together with modern humans, these extinct human species, our immediate ancestors and their close relatives, are collectively referred to as ‘hominins’. 
Fossil hominins were first recognized in the Dinaledi Chamber in the Rising Star cave system in October 2013. During a relatively short excavation, our team recovered an extensive collection of 1550 hominin specimens, representing nearly every element of the skeleton multiple times, including many complete elements and morphologically informative fragments, some in articulation, as well as smaller fragments many of which could be refit into more complete elements. The collection is a morphologically homogeneous sample that can be attributed to no previously-known hominin species. Here we describe this new species, Homo naledi. We have not defined H. naledi narrowly based on a single jaw or skull because the entire body of material has informed our understanding of its biology.
Now Berger et al. report the recent discovery of an extinct species from the genus Homo that was unearthed from deep underground in what has been named the Dinaledi Chamber, in the Rising Star cave system in South Africa. The species was named Homo naledi; ‘naledi’ means ‘star’ in Sotho (also called Sesotho), which is one of the languages spoken in South Africa.
The unearthed fossils were from at least 15 individuals and include multiple examples of most of the bones in the skeleton. Based on this wide range of specimens from a single site, Berger et al. describe Homo naledi as being similar in size and weight to a small modern human, with human-like hands and feet. Furthermore, while the skull had several unique features, it had a small braincase that was most similar in size to other early hominin species that lived between four million and two million years ago. Homo naledi's ribcage, shoulders and pelvis also more closely resembled those of earlier hominin species than those of modern humans.
The Homo naledi fossils are the largest collection of a single species of hominin that has been discovered in Africa so far and, in a related study, Dirks et al. describe the setting and context for these fossils. However, since the age of the fossils remains unclear, one of the next challenges will be to date the remains to provide more information about the early evolution of humans and their close relatives.