Dig looks at society just before dawn of of urban civilization in the Middle East

Abbas Alizadeh, an archaeologist with the University of Chicago, passes a piece of broken pottery to Gil Stein, Director of the Oriental Institute, University of Chicago (right) and a leader of an excavation in Syria which is uncovering artifacts from a society that flourished just before the formation of urban civilization in the ancient Middle East.
Credit: Oriental Institute, University of ChicagoThirty-one acres in extent, Tell Zeidan is situated where the Balikh River joins the Euphrates River in modern-day Syria. The location was at the crossroads of major trade routes across ancient Mesopotamia that followed the course of the Euphrates River valley.

Stein said Tell Zeidan may have been one of the largest Ubaid temple towns in northern Mesopotamia, and that it was as large or larger than any previously known contemporary Ubaid towns in the southern alluvial lowlands of the Tigris and Euphrates rivers in what is today southern Iraq. However, because the site was not occupied after about 4,000 B.C., the prehistoric strata of Tell Zeidan are immediately accessible beneath the modern-day ground surface instead of being buried beneath layers of deposits from later periods.

Exploring the Stone Age pantry

University of Calgary archaeologist Julio Mercader at work in the Ngalue cave site, Mozambique. Photo: Courtesy of University of CalgaryThe consumption of wild cereals among prehistoric hunters and gatherers appears to be far more ancient than previously thought, according to a University of Calgary archaeologist who has found the oldest example of extensive reliance on cereal and root staples in the diet of early Homo sapiens more than 100,000 years ago.

Julio Mercader, holder of the Canada Research Chair in Tropical Archaeology in the U of C's Department of Archaeology, recovered dozens of stone tools from a deep cave in Mozambique showing that wild sorghum, the ancestor of the chief cereal consumed today in sub-Saharan Africa for flours, breads, porridges and alcoholic beverages, was in Homo sapiens' pantry along with the African wine palm, the false banana, pigeon peas, wild oranges and the African "potato."

Story of 4.5 million-year-old whale unveiled in Huelva

These are vertebra colonised by bivalves. Photo:Esperante et al.In 2006, a team of Spanish and American researchers found the fossil remains of a whale, 4.5 million years old, in Bonares, Huelva. Now they have published, for the first time, the results of the decay and fossilisation process that started with the death of the young cetacean, possibly a baleen whale from the Mysticeti group.

This is not the first discovery of the partial fossil remains of a whale from the Lower Pliocene (five million years ago) in the Huelva Sands sedimentary formation, but it is the first time that the results of the processes of fossilisation and fossil deposition following the death of a whale have been published.

Absence of evidence for a meteorite impact event 13,000 years ago

The woolly mammoth was one of the large mammals that became extinct in North America at the onset of the Younger Dryas approx. 13,000 years ago.An international team of scientists led by researchers at the University of Hawaii at Manoa have found no evidence supporting an extraterrestrial impact event at the onset of the Younger Dryas ~13000 years ago.

The Younger Dryas is an abrupt cooling event in Earth's history. It coincided with the extinction of many large mammals including the woolly mammoth, the saber toothed jaguar and many sloths. This cooling period is generally considered to be the result of the complex global climate system, possibly spurred on by a reduction or slowdown of the thermohaline circulation in North America.

Archaeological study of ostrich eggshell beads collected from SDG site

Ostrich eggshell (OES) beads from SDG site reflect primordial art and a kind of symbolic behaviour of modern humans. Two different manufacturing pathways are usually used in the manufacture of OES beads in Upper Palaeolithic. Pathway 1 is identified from these collections; blanks are drilled prior to being trimmed to rough discs. Based on stratigraphic data and OSL dating, these ostrich eggshell beads are probably in Early Holocene (< 10 ka BP).

Central Africa's tropical Congo Basin was arid, treeless in Late Jurassic

Geochemical analysis of rare ancient soil produces new paleoclimate data

The Congo Basin – with its massive, lush tropical rain forest – was far different 150 million to 200 million years ago. At that time Africa and South America were part of the single continent Gondwana. The Congo Basin was arid, with a small amount of seasonal rainfall, and few bushes or trees populated the landscape, according to a new geochemical analysis of rare ancient soils.

The geochemical analysis provides new data for the Jurassic period, when very little is known about Central Africa's paleoclimate, says Timothy S. Myers, a paleontology doctoral student in the Roy M. Huffington Department of Earth Sciences at Southern Methodist University in Dallas.

"There aren't a whole lot of terrestrial deposits from that time period preserved in Central Africa," Myers says. "Scientists have been looking at Africa's paleoclimate for some time, but data from this time period is unique."

There are several reasons for the scarcity of deposits: Ongoing armed conflict makes it difficult and challenging to retrieve them; and the thick vegetation, a humid climate and continual erosion prevent the preservation of ancient deposits, which would safeguard clues to Africa's paleoclimate.

Myers' research is based on a core sample drilled by a syndicate interested in the oil and mineral deposits in the Congo Basin. Myers accessed the sample – drilled from a depth of more than 2 kilometres – from the Royal Museum for Central Africa in Tervuren, Belgium, where it is housed. With the permission of the museum, he analysed pieces of the core at the SMU Huffington Department of Earth Sciences Isotope Laboratory.

"I would love to look at an outcrop in the Congo," Myers says, "but I was happy to be able to do this."

The Samba borehole, as it's known, was drilled near the centre of the Congo Basin. The Congo Basin today is a closed canopy tropical forest – the world's second largest after the Amazon. It's home to elephants, great apes, many species of birds and mammals, as well as the Congo River. Myers' results are consistent with data from other low paleolatitude, continental, Upper Jurassic deposits in Africa and with regional projections of paleoclimate generated by general circulation models, he says.

"It provides a good context for the vertebrate fossils found in Central Africa," Myers says. "At times, any indications of the paleoclimate are listed as an afterthought, because climate is more abstract. But it's important because it yields data about the ecological conditions. Climate determines the plant communities, and not just how many, but also the diversity of plants."

While there was no evidence of terrestrial vertebrates in the deposits that Myers studied, dinosaurs were present in Africa at the same time. Their fossils appear in places that were once closer to the coast, he says, and probably wetter and more hospitable.

The Belgium samples yielded good evidence of the paleoclimate. Myers found minerals indicative of an extremely arid climate typical of a marshy, saline environment. With the Congo Basin at the centre of Gondwana, humid marine air from the coasts would have lost much of its moisture content by the time it reached the interior of the massive continent.

"There probably wouldn't have been a whole lot of trees; more scrubby kinds of plants," Myers says.

The clay minerals that form in soils have an isotopic composition related to that of the local rainfall and shallow groundwater. The difference in isotopic composition between these waters and the clay minerals is a function of surface temperature, he says. By measuring the oxygen and hydrogen isotopic values of the clays in the soils, researchers can estimate the temperature at which the clays formed.

The last European hadrosaurs lived in the Iberian Peninsula

Photo: Xabier Pereda-Suberbiola et al./ SINCSpanish researchers have studied the fossil record of hadrosaurs, the so-called 'duck-billed' dinosaurs, in the Iberian Peninsula for the purpose of determining that they were the last of their kind to inhabit the European continent before disappearing during the K/T extinction event that occurred 65.5 million years ago. Most notable among these fossils is the discovery of a new hadrosaur, the Arenysaurus ardevoli, found in Huesca, Spain.

A few million years before the catastrophic event that led to the extinction of dinosaurs (with the exception of birds), several species of hadrosaurs coexisted in the Iberian Peninsula. This is what a Spanish team of paleontologists have demonstrated in a research article published in the Journal of Vertebrate Paleontology.

"The Iberian archaeological record is important from an European context due to the quantity and quality of the fossil material discovered," explains Xavier Pereda-Suberbiola, one of the study's authors and a researcher at the University of the Basque Country (UPV / EHU), in an interview with SINC.

The researcher, collaborating with paleontologists from the University of Zaragoza, Valencia, Complutense of Madrid, Autonoma de Barcelona and the Jurassic Museum of Asturias, specifies that the presence of evolved hadrosaurs in Europe could be due to migration from Asia and North America.

"In Europe, primitive hadrosaurs coexist with evolved hadrosaurs, and the persistence of basal members could be due to the insular palaeobiogeography of Europe during the Upper Cretaceous," states the scientist. In addition to the fossils found in the Iberian Peninsula, hadrosaur fossils have been found in the Netherlands, which date back to Late Cretaceous, "although the material is more fragmented than those found in Huesca and Lleida," adds Pereda-Suberbiola.

During that time period, Europe was isolated from other continents and this may have led to the survival of certain lineages. "The European hadrosaur faunas are different from those seen in North America and Asia, which are both dominated by evolved species," explains Pereda-Suberbiola.

Next to the hadrosaurs, identifiable by the fossilised mandibles found in the archaeological sites of La Solana (Valencia) and Fontllonga (Lleida), were a lambeosaurine hadrosaurs yet to be defined, and a newly discovered lambeosaurine, the Arenysaurus ardevoli.
An articulated cranium of great value

The study of the last hadrosaurs that lived in the Iberian Peninsula has been possible thanks to the discovery by the Aragosaurus-IUCA Group of the University of Zaragoza, led by Jose Ignacio Canudo, of the first articulated hadrosaur skull found in southern Europe, from the archaeological sites of Arén, in Huesca, Spain.

The skull belongs to an Arenysaurus ardevoli, a lambeosaurine (hadrosaur with a hollow cranial crest), whose description was recently published in the French journal Comptes Rendus Palevol, and was part of the Spanish fossil record.

According to palaeontologists, the new lambeosaurine lived between 65.5 and 68 million years ago, had a very prominent frontal dome, and its biogeographical relationships suggest a paleo-biogeographical connection between Asia and Europe during the Late Cretaceous.

Researchers have found, in addition to the partially articulated skull, the mandibular remains and postcranial elements such as vertebrae, girdle and limb bones.

The Spanish archaeological record of hadrosaurs is the largest in Europe. Out of the 50 locations where dinosaur remains were discovered since 1984, nearly half have been found in Lleida and Huesca. These archaeological sites stand out for containing fossils pertaining to several species of duck-billed dinosaurs.

Male sabre-toothed cats were pussycats compared to macho lions

Despite their fearsome fangs, male sabre-toothed cats may have been less aggressive than many of their feline cousins, says a new study of male-female size differences in extinct big cats.

Commonly called the sabre-toothed tiger, Smilodon fatalis was a large predatory cat that roamed North and South America about 1.6 million to 10,000 years ago, when there was also a prehistoric cat called the American lion. A study appearing in the November 5 issue of the Journal of Zoology examined size differences between sexes of these fearsome felines using subtle clues from bones and teeth.

The researchers report that while male American lions were considerably larger than females, male and female sabre-toothed cats were indistinguishable in size. The findings suggest that sabre-tooth may have been less aggressive than their fellow felines, researchers say.

In species where males fight for mates, bigger, heavier males have a better chance of winning fights, fending off their rivals and gaining access to females. After generations of male-male competition, the males of some species evolve to be much larger than their mates.

Most big cats have a form of sexual dimorphism where males are bigger than females, said co-author Julie Meachen-Samuels, a biologist at the National Evolutionary Synthesis Centre in Durham, NC. So she and Wendy Binder of Loyola Marymount University in Los Angeles wanted to know if extinct sabre-tooth and American lions showed the same size patterns as big cats living today.

When it comes to fossils, sorting males from females can be tricky. "It's hard to tell who's a male and who's a female in the fossil record," said Blaire Van Valkenburgh, a biologist at UCLA who has studied these animals extensively but was not an author on the paper. "Unless you're lucky enough to get some DNA, or you're working with an animal where males have horns and females don't."

For species that keep growing into adulthood, simply separating the fossils into two groups by size may not do the trick, either. "It's easy to get a younger, smaller male confused with an older, larger female if you're just dividing them by size," Meachen-Samuels said.

The researchers accounted for continued growth using subtle clues from fossilised teeth. "Teeth fill in over time," said Binder. "In young animals the tooth cavity is basically hollow, but as they get older it fills in with dentin. It won't give you an exact age, but it can give you a relative age in terms of young, middle aged or old," Binder added.

Meachen-Samuels and Binder x-rayed the lower teeth and jaws of 13 American lions and 19 sabre-toothed cats recovered from the La Brea Tar Pits in Los Angeles. To account for growth over time, they measured tooth cavity diameter and plotted it against jaw length for each species. Plotted this way, the data for the American lion fell easily into two groups, regardless of age. The researchers concluded that "the little ones were females and the big ones were males," said Van Valkenburgh.

In contrast, sabre-toothed cat sizes seemed to be governed solely by age. It would appear that the males were indistinguishable from their mates. "Even by incorporating a measure of age, you can't distinguish males and females," said Meachen-Samuels.

Size differences between the sexes tend to be more impressive in species where male aggression is more intense, and in the extinct American lion, size differences between the sexes were even more dramatic than in lions living today.

The closest living relative of the American lion, "African lions engage in aggressive takeovers where one to several males will take over an entire pride – the males have battles to the death," said Van Valkenburgh.

"Living lions have huge sexual dimorphism," said Meachen-Samuels.

Based on their findings, the researchers think the American lion probably lived in male-dominated groups, where 1-2 males monopolised and mated with multiple females. "My guess would be that the American lion was similar to African lions, where males guard groups of females," said Meachen-Samuels.

"But we don't see that in the sabre-toothed cat," Binder said. The size similarity in sabre-toothed cats suggests that male sabre-tooth may have been less aggressive than their larger cousins. "Rather than males having harems of females, the males and females in a group might have been more equal," Binder said.

Geologist analyses earliest shell-covered fossil animals

Cambrothyra fossil.Photo: UCSBThe fossil remains of some of the first animals with shells, ocean-dwelling creatures that measure a few centimetres in length and date to about 520 million years ago, provide a window on evolution at this time, according to scientists. Their research indicates that these animals were larger than previously thought.

John Moore, a Ph.D. student in the Department of Earth Science at UC Santa Barbara, and his collaborators, analysed fossils from the epoch called the Early Cambrian. During this important time in the history of the earth, there was a tremendous diversification of animal life in the oceans. Many of the major animal groups that are still alive today appeared at this time, as well as many unusual groups that went extinct.

In particular, the Cambrian marked the first widespread occurrence of animals with shells or other hard parts. Many of these early animals had complex external armours containing dozens to thousands of tiny pieces. When the animals died, the armour fell apart. From the resulting jumbled puzzle pieces, Moore and his research team discerned what the animals were like, and how they are related to other animals.

"In our study, we focused on a strange Cambrian creature, called Cambrothyra," said Moore. He explained that Cambrothyra fossils look like tiny jars or vases, a few tenths of a millimetre long. They have been found in only a few locations in central China. The research team collected rocks from China's Shaanxi Province and brought them back to the lab where they extracted the fossils from the host rocks.

"While some scientists once thought that each little jar-like structure of Cambrothyra was the shell of a tiny single-celled protist, our work instead supports the hypothesis that Cambrothyra was an animal, probably a few centimetres long, that was covered with an armor that was made up of hundreds of separate tiny, jar-shaped pieces," said Moore. "In particular, Cambrothyra seems to be related to another unusual Cambrian animal, the chancelloriids, which were attached to the sea floor and looked a bit like barrel cacti – although they were animals rather than plants which suggests that Cambrothyra may have been a relative."

Cambrothyra also shares similarities with a different Cambrian group, the halkieriids. This animal looked like a slug covered with armour. It travelled around the sea floor and thus may help support the idea that chancelloriids and halkieriids are closely related to each other, despite very different appearances.

Moore presented his findings at the annual meeting of the Geological Society of America in Portland, Ore., today. He completed the work in collaboration with his advisor Susannah Porter, assistant professor in the Department of Earth Science at UCSB; Michael Steiner of the Freie Universität, Berlin; and Guoxiang Li of the Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences.

Ethiopia had higher rainfall, warmer soil in the past

Photo: Southern Methodist UniversityThirty million years ago, before Ethiopia's mountainous highlands split and the Great Rift Valley formed, the tropical zone had warmer soil temperatures, higher rainfall and different atmospheric circulation patterns than it does today, according to new research of fossil soils found in the central African nation.

Neil J. Tabor, associate professor of Earth Sciences at SMU and an expert in sedimentology and isotope geochemistry, calculated past climate using oxygen and hydrogen isotopes in minerals from fossil soils discovered in the highlands of northwest Ethiopia. The highlands represent the bulk of the mountains on the African continent.

Tabor's research supplies a picture of the paleo landscape of Ethiopia that wasn't previously known because the fossil record for the tropics has not been well established. The fossils were discovered in the grass-covered agricultural region known as Chilga, which was a forest in prehistoric times. Tabor's research looked at soil fossils dating from 26.7 million to 32 million years ago.

Fossil plants and vertebrates in the Chilga Beds date from 26.7 million to 28.1 million years ago, Tabor says. From his examination, Tabor determined there was a lower and older layer of coal and underclay that was a poorly drained, swampy landscape dissected by well-drained Oxisol-forming uplands. A younger upper layer of the Chilga Beds consists of mudstones and sandstones in what was an open landscape dominated by braided, meandering fluvial stream systems.

Tabor is part of a multi-disciplinary team combining independent lines of evidence from various fossil and geochemical sources to reconstruct the prehistoric climate, landscape and ecosystems of Ethiopia, as well as Africa.

The project is funded with a three-year, USD322,000 grant from the National Science Foundation. The team includes paleoanthropologists, paleobotanists and vertebrate paleontologists from the University of Texas at Austin, Miami University, Southern Methodist University, the Fort Worth Museum of Science and History, Washington University and the University of Michigan.

Tabor presented the research in a topical session at the Oct. 18-21 annual meeting of the Geological Society of America. The presentation was titled "Paleoenvironments of Upper Oligocene Strata, NW Ethiopian Plateau." His co-researcher is John W. Kappelman, Department of Anthropology, University of Texas.

Author: Margaret Allen

Plant fossils give first real picture of earliest Neotropical rainforests

Photo: WikimediaA team of researchers including a University of Florida palaeontologist has used a rich cache of plant fossils discovered in Colombia to provide the first reliable evidence of how Neotropical rainforests looked 58 million years ago.

Researchers from the Smithsonian Institution and UF, among others, found that many of the dominant plant families existing in today’s Neotropical rainforests – including legumes, palms, avocado and banana – have maintained their ecological dominance despite major changes in South America’s climate and geological structure.

The study, which appears this week in the online edition of the Proceedings of the National Academy of Sciences, examined more than 2,000 megafossil specimens, some nearly 10 feet long, from the Cerrejón Formation in northern Colombia. The fossils are from the Paleocene epoch, which occurred in the 5- to 7-million-year period following the massive extinction event responsible for the demise of the dinosaurs.

“Neotropical rainforests have an almost nonexistent fossil record,” said study co-author Fabiany Herrera, a graduate student at the Florida Museum of Natural History on the UF campus. “These specimens allow us to actually test hypotheses about their origins for the first time ever.”

Herrera said the new specimens, discovered in 2003, also provide information for future studies that promise to provide an even stronger understanding of the plants that formed the earliest Neotropical communities.

Many previous assumptions and hypotheses on the earliest rainforests are based on studies of pollen fossils, which did not provide information about climate, forest structure, leaf morphology or insect herbivory.

The new study provides evidence Neotropical rainforests were warmer and wetter in the late Paleocene than today but were composed of the same plant families that now thrive in rainforests. “We have the fossils to prove this,” Herrera said. “It is also intriguing that while the Cerrejón rainforest shows many of the characteristics of modern equivalents, plant diversity is lower.”

The site, one of the world’s largest open-pit coal mines, also yielded the fossil for the giant snake known as Titanoboa, described by UF scientists earlier this year.

“These new plant fossils show us that the forest during the time of Titanoboa, 58 million years ago, was similar in many ways to that of today,” said Florida Museum vertebrate palaeontologist Jonathan Bloch, who described Titanoboa but was not part of the rainforest study. “Like Titanoboa, which is clearly related to living boas and anacondas, the ancient forest of northern Colombia had similar families of plants as we see today in that ecosystem. The foundations of the Neotropical rainforests were there 58 million years ago.”

Megafossils found at the Cerrejón site made it possible to use leaf structure to identify specimens down to the genus level. This resolution allowed the identification of plant genera that still exist in Neotropical rainforests. With pollen fossils, specimens can be categorised only to the family level.

Researchers were surprised by the relative lack of diversity found in the Paleocene rainforest, Herrera said. Statistical analyses showed that the plant communities found in the Cerrejón Formation were 60 per cent to 80 per cent less diverse than those of modern Neotropical rainforests. Evidence of herbivory also showed a low diversity level among insects.

The study’s authors say the relative lack of diversity indicates either the beginning of rainforest species diversification or the recovery of existing species from the Cretaceous extinction event.

The researchers estimate the Paleocene rainforest received about 126 inches of rainfall annually and had an average annual temperature greater than 86 degrees. The Titanoboa study, which used different methods, estimated an average temperature between 89 and 91 degrees. Today the region’s temperatures average about 81 degrees.

Herrera is now comparing fossils from the Cerrejón site to specimens from other Paleocene sites in Colombia to see how far the early rainforest extended geographically. He is also examining fossils from a Cretaceous site to determine differences in composition before and after the extinction event.

Writer: Bill Kanapaux

World’s oldest submerged town dates back 5,000 years

Archaeologists surveying the world’s oldest submerged town have found ceramics dating back to the Final Neolithic. Their discovery suggests that Pavlopetri, off the southern Laconia coast of Greece, was occupied some 5,000 years ago – at least 1,200 years earlier than originally thought.

These remarkable findings have been made public by the Greek government after the start of a five year collaborative project involving the Ephorate of Underwater Antiquities of the Hellenic Ministry of Culture and The University of Nottingham.

As a Mycenaean town the site offers potential new insights into the workings of Mycenaean society. Pavlopetri has added importance as it was a maritime settlement from which the inhabitants coordinated local and long distance trade.



The Pavlopetri Underwater Archaeology Project aims to establish exactly when the site was occupied, what it was used for and through a systematic study of the geomorphology of the area, how the town became submerged.

This summer the team carried out a detailed digital underwater survey and study of the structural remains, which until this year were thought to belong to the Mycenaean period – around 1600 to 1000 BC. The survey surpassed all their expectations. Their investigations revealed another 9,000 square metres of new buildings as well as ceramics that suggest the site was occupied throughout the Bronze Age – from at least 2800 BC to 1100 BC.

The work is being carried out by a multidisciplinary team led by Mr Elias Spondylis, Ephorate of Underwater Antiquities of the Hellenic Ministry of Culture in Greece and Dr Jon Henderson, an underwater archaeologist from the Department of Archaeology at The University of Nottingham.

Dr Jon Henderson said: “This site is unique in that we have almost the complete town plan, the main streets and domestic buildings, courtyards, rock-cut tombs and what appear to be religious buildings, clearly visible on the seabed. Equally as a harbour settlement, the study of the archaeological material we have recovered will be extremely important in terms of revealing how maritime trade was conducted and managed in the Bronze Age.”

Possibly one of the most important discoveries has been the identification of what could be a megaron – a large rectangular great hall – from the Early Bronze Age period. They have also found over 9,000 square metres of new buildings including what could be the first example of a pillar crypt ever discovered on the Greek mainland. Two new stone built cist graves were also discovered alongside what appears to be a Middle Bronze Age pithos burial.



Mr Spondylis said, “It is a rare find and it is significant because as a submerged site it was never re-occupied and therefore represents a frozen moment of the past.”

The Archaeological Co-ordinator Dr Chrysanthi Gallou a postdoctoral research fellow at The University of Nottingham is an expert in Aegean Prehistory and the archaeology of Laconia.

Dr Gallou said, “The new ceramic finds form a complete and exceptional corpus of pottery covering all sub-phases from the Final Neolithic period (mid 4th millennium BC) to the end of the Late Bronze Age (1100 BC). In addition, the interest from the local community in Laconia has been fantastic. The investigation at Pavlopetri offers a great opportunity for them to be actively involved in the preservation and management of the site, and subsequently for the cultural and touristic development of the wider region.”

The team was joined by Dr Nicholas Flemming, a marine geo-archaeologist from the Institute of Oceanography at the University of Southampton, who discovered the site in 1967 and returned the following year with a team from Cambridge University to carry out the first ever survey of the submerged town. Using just snorkels and tape measures they produced a detail plan of the prehistoric town which consisted of at least 15 separate buildings, courtyards, streets, two chamber tombs and at least 37 cist graves. Despite the potential international importance of Pavlopetri no further work was carried out at the site until this year.

This year, through a British School of Archaeology in Athens permit, The Pavlopetri Underwater Archaeology Project began its five year study of the site with the aim of defining the history and development of Pavlopetri.

Videos: University of Nottingham/Youtube

Banded rocks reveal early Earth conditions, changes

A banded iron formation about 2.5 billion years old near Soudan Underground Mine State Park in Minnesota. Photo: Huifang Xu/UW-MadisonThe strikingly banded rocks scattered across the upper Midwest and elsewhere throughout the world are actually ambassadors from the past, offering clues to the environment of the early Earth more than 2 billion years ago.

Called banded iron formations or BIFs, these ancient rocks formed between 3.8 and 1.7 billion years ago at what was then the bottom of the ocean. The stripes represent alternating layers of silica-rich chert and iron-rich minerals like hematite and magnetite.

First mined as a major iron source for modern industrialisation, BIFs are also a rich source of information about the geochemical conditions that existed on Earth when the rocks were made. However, interpreting their clues requires understanding how the bands formed, a topic that has been controversial for decades, says Huifang Xu, a geology professor at the University of Wisconsin-Madison.
A study appearing as an advance online publication in Nature Geoscience offers a new picture of how these colourful bands developed and what they reveal about the composition of the early ocean floor, seawater, and atmosphere during the evolution of the Earth.
Previous hypotheses about band formation involved seasonal fluctuations, temperature shifts, or periodic blooms of microorganisms, all of which left many open questions about how BIFs dominated the global marine landscape for two billion years and why they abruptly disappeared 1.7 billion years ago.

With Yifeng Wang of Sandia National Laboratories, Enrique Merino of Indiana University and UW-Madison post-doctoral Hiromi Konishi, Xu developed a BIF formation model that offers a more complete picture of the environment at the time, including interactions between rocks, water, and air.

"They are all connected," Xu explains. "The lithosphere affects the hydrosphere, the hydrosphere affects the atmosphere, and all those eventually affect the biosphere on the early Earth."

Their model shows how BIFs could have formed when hydrothermal fluids, from interactions between seawater and hot oceanic crust from deep in the Earth's mantle, mixed with surface seawater. This mixing triggered the oscillating production of iron- and silica-rich minerals, which were deposited in layers on the seafloor.

They used a series of thermodynamic calculations to determine that the source material for BIFs must have come from oceanic rocks with a very low aluminium content, unlike modern oceanic basalts that contain high levels of aluminium.

"The modern-day ocean floor is basalt, common black basalt like the Hawaiian islands. But during that time, there was also a strange kind of rock called komatiites," says Xu. "When ocean water reacts with that kind of rock, it can produce about equal amounts of iron and silica" – a composition ideally suited to making BIFs.

Such a mixture can create distinct alternating layers – which range in thickness from 10 micrometers to about 1 centimetre – due to a constantly shifting state that, like a competition between two well-matched players, resists resolving to a single outcome and instead see-saws between two extremes.

BIFs dominated the global oceans 3.8 to 1.7 billion years ago, a time period known to geologists as the Archaean-Early Proterozoic, and then abruptly disappeared from the geologic record. Their absence in more recent rocks indicates that the geochemical conditions changed around 1.7 billion years ago, Xu says.

This change likely had wide-ranging effects on the physical and biological composition of the Earth. For example, the end of BIF deposition would have starved iron-dependent bacteria and shifted in favour of microbes with sulphur-based metabolisms. In addition, chemical and pH changes in the ocean and rising atmospheric oxygen may have allowed the emergence and spread of oxygen-dependent organisms.

The new study was partly funded by the NASA Astrobiology Institute, and Xu hopes to look for bio-signatures trapped in the rock bands for additional clues to the changes that occurred 1.7 billion years ago and what may have triggered them.

Computers unlock secrets of the mysterious Indus Valley script

Photo: J. M. Kenoyer / harappa.comFour-thousand years ago, an urban civilisation lived and traded on what is now the border between Pakistan and India. During the past century, thousands of artefacts bearing hieroglyphics left by this prehistoric people have been discovered. Today, a team of Indian and American researchers are using mathematics and computer science to try to piece together information about the still-unknown script.

The team led by a University of Washington researcher has used computers to extract patterns in ancient Indus symbols. The study, published this week in the Proceedings of the National Academy of Sciences, shows distinct patterns in the symbols' placement in sequences and creates a statistical model for the unknown language.

"The statistical model provides insights into the underlying grammatical structure of the Indus script," said lead author Rajesh Rao, a UW associate professor of computer science. "Such a model can be valuable for decipherment, because any meaning ascribed to a symbol must make sense in the context of other symbols that precede or follow it."

Co-authors are Nisha Yadav and Mayank Vahia of the Tata Institute of Fundamental Research and Centre for Excellence in Basic Sciences in Mumbai; Hrishikesh Joglekar of Mumbai; R. Adhikari of the Institute of Mathematical Sciences in Chennai; and Iravatham Mahadevan of the Indus Research Centre in Chennai.

Despite dozens of attempts, nobody has yet deciphered the Indus script. The symbols are found on tiny seals, tablets and amulets, left by people inhabiting the Indus Valley from about 2600 to 1900 B.C. Each artefact is inscribed with a sequence that is typically five to six symbols long.

Some people have questioned whether the symbols represent a language at all, or are merely pictograms of political or religious icons.

The new study looks for mathematical patterns in the sequence of symbols.

Calculations show that the order of symbols is meaningful; taking one symbol from a sequence found on an artefact and changing its position produces a new sequence that has a much lower probability of belonging to the hypothetical language. The authors said the presence of such distinct rules for sequencing symbols provides further support for the group's previous findings, reported earlier this year in the journal Science, that the unknown script might represent a language.

"These results give us confidence that there is a clear underlying logic in Indus writing," Vahia said.

Seals with sequences of Indus symbols have been found as far away as West Asia, in the region historically known as Mesopotamia and site of modern-day Iraq. The statistical results showed that the West-Asian sequences are ordered differently from sequences on artefacts found in the Indus valley. This supports earlier theories that the script may have been used by Indus traders in West Asia to represent different information compared to the Indus region.

"The finding that the Indus script may have been versatile enough to represent different subject matter in West Asia is provocative. This finding is hard to reconcile with the claim that the script merely represents religious or political symbols," Rao said.

The researchers used a Markov model, a statistical method that estimates the likelihood of a future event (such as inscribing a particular symbol) based on patterns seen in the past. The method was first developed by Russian mathematician Andrey Markov a century ago and is increasingly used in economics, genetics, speech-recognition and other fields.

"One of the main purposes of our paper is to introduce Markov models, and statistical models in general, as computational tools for investigating ancient scripts," Adhikari said.

One application described in the paper uses the statistical model to fill in missing symbols on damaged archaeological artifacts. Such filled-in texts can increase the pool of data available for deciphering the writings of ancient civilisations, Rao said.