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Geophysicists uncover new evidence for an alternative style of plate tectonics

When renowned University of Toronto (U of T) geophysicist J. Tuzo Wilson cemented concepts in the emerging field of plate tectonics in the 1960s, he revolutionized the study of Earth’s physical characteristics and behaviours.

Decades later, successor researchers at U of T and Istanbul Technical University have determined that a series of volcanoes and a mountain plateau across central Turkey formed not solely by the collision of tectonic plates, but instead by a massive drip and then detachment of the lower tectonic plate beneath Earth’s surface.

The researchers propose that the reason the Central Anatolian (Turkish) Plateau has risen by as much as one kilometre over the past 10 million years is because the planet’s crust and upper mantle – the lithosphere – has thickened and dripped below the region. As the lithosphere sank into the lower mantle, it first formed a basin at the surface, which later sprang up when the weight below broke off and sank further into the deeper depths of the mantle.

“It seems the heavy base of the tectonic plate has ‘dripped’ off into the mantle, leaving a massive gap in the plate beneath Central Anatolia. Essentially, by dropping this dense lithospheric anchor, there has been an upward bobbing of the entire land mass across hundreds of kilometres,” said Professor Oğuz H. Göğüş of the Eurasia Institute of Earth Sciences at Istanbul Technical University (ITU), lead author of a study reporting the findings published in Nature Communications this month.

Time slices of the computational geodynamic model showing dripping continental root and eventual surface uplift over a 4.5 million year period across Turkey’s Central Anatolian Plateau. CREDIT : University of Toronto handout

It’s a new idea where plate shortening initially squeezed and folded a mountain belt, triggering the thickening and dripping of the deep lithosphere, and then increasing the elevation of most of central Turkey. Puzzled by the presence of such a process at a significant distance away from regular plate tectonic boundaries, the research team set about identifying why, in an area of high heating and high elevation, is the lithosphere below completely gone – something that was recently discovered from seismology.

They tested high-performance computational models against known geological and geophysical observations of the Central Anatolian Plateau, and demonstrated that a drip of lithospheric material below the surface can account for the measured elevation changes across the region.

“It’s a new variation on the fundamental concepts of plate tectonics,” said Professor Russell Pysklywec, chair of the Department of Earth Sciences at U of T and one of the study’s coauthors. “It gives us some insight into the connection between the slow circulation of near-solid rock in Earth’s mantle caused by convection currents carrying heat upwards from the planet’s interior, and observed active plate tectonics at the surface.

“This is part of the holy grail of plate tectonics – linking the two processes to understand how the crust responds to the mantle thermal engine of the planet.”

Pysklywec carried out the study with Göğüş, who received his PhD from U of T in 2010, and fellow researchers at ITU including Professor A. M. C. Şengör, and Erkan Gün of the Eurasia Institute of Earth Sciences at Istanbul Technical Institute. Gün is also now a current graduate student at U of T, supervised by Pysklywec. The research adds to decades of groundbreaking work in plate tectonics at U of T, and builds on Wilson’s seminal work.

“Tuzo Wilson is a towering figure in geophysics internationally and the person most responsible for pioneering the ideas of plate tectonics in the 1960s,” said Pysklywec. “I am pleased that we are continuing his legacy in geophysics with our work.”

While Pysklywec notes there are many locations on Earth missing its lithosphere below, he is quick to reassure that no place is in imminent danger of sinking into the mantle or boosting upwards overnight. “Our results show that the Central Anatolian Plateau rose over a period of millions of years. We’re talking about mantle fluid motions and uplift at the pace at which fingernails grow.”

Göğüş highlights the links of the tectonics with human history saying, “The findings are exciting also because of the link with the remarkable historical human activity of Central Anatolia where some of the earliest known civilizations have existed. For example, Central Anatolia is described as an elevated, dry, cold plain of Lycaonia in Strabo’s Geographika in 7 BC, and even cave paintings in the region dating to approximately 7000 BC record active volcanic eruptions on the plateau.”

UNIVERSITY OF TORONTO

3000-year-old graves found under new E6 highway in central Norway

Bronze Age graves have been unearthed ahead of planned road construction in Melhus municipality in mid-Norway. These are some of the oldest burial sites ever discovered in the region.

Bronze Age graves are rare in Norway. Now 3000-year-old graves in good condition have been discovered in Trøndelag county.

Archaeologists from the Norwegian University of Science and Technology’s (NTNU) University Museum made the gravesite discovery at Sandbrauta in Melhus municipality. They’re working on the site in connection with the planned construction of the new E6 highway between the towns of Melhus and Ulsberg.

“We don’t often make a find like this,” says Project Manager Merete Moe Henriksen at the NTNU University Museum.

Numerous graves

Three smaller stone chambers typical of the period lie to the side of a larger stone ring. The stone ring is part of a burial mound that contains numerous graves.

Local conditions have preserved the site remarkably well. Up to two metres of clay from a landslide covered the area. This mass of earth provides traces of a mudslide that may have taken place already in prehistoric times, perhaps just after people were laid in the graves.

Landowner had no clue

The clay settled like a lid over the graves, sealing the site and keeping it in good condition. This is a good farmland, but the ploughing activity hasn’t gone deep enough to disturb anything.

That 3000-year-old objects could be buried in his fields came as a big surprise to landower Oddvar Narve Langørgen. “I had no clue that anything like this was here. I couldn’t have dreamt it up, either,” he said.

Langørgen says there is good topsoil in the area, which might have offered good growing conditions for people who might have lived here at that time.

Found bones and charcoal

According to the museum, the find represents an invaluable source of knowledge of the Bronze Age’s burial traditions in central Norway.

“We found charcoal and burned bones in the graves,” says project manager Henriksen.

The custom seems to have been to burn the dead before they were laid in the graves. The remains may have been placed in some material that decomposed over the course of the 3000 years.

Archaeologists have known that there could be exciting discoveries here since 2014, when they conducted a pre-roadwork investigation in conjunction with the county’s cultural heritage council. They found signs of human activity from earlier times.

The mould on the right was found at Sandbrauta. On the left is an example of an axe that might have been made in this kind of mould. Photo: Julie Gloppe Solem, NTNU

Site mapping

“It’s incredibly exciting,” said Anne-Lise Bratsberg, who is an advisor and project manager for Nye Veier AS (New Roads Ltd), which is responsible for planning, construction, operation and maintenance of major highways in Norway.

She says she feels awestruck by the find of graves that no one has seen in 3000 years.

Museum Director Reidar Andersen praises Nye Veier and commends the cooperation between the builders and the museum. Andersen hopes that some of the discoveries from the site will be exhibited at a later date. He believes the potential is great for an exhibit.

However, the area will become inexorably changed with the planned roadwork.

“Archaeology is a destructive science, after all. We have to dig to make discoveries,” Hanne Bryn says. She is the field leader for the excavations at Sandbrauta.

The way Bryn sees it is that no one has known about this place for the past 3000 years. Now they can at least map a site that contains valuable scientific finds.

Exciting rock slab

Close to the big burial mound, the museum found part of a rock slab with indented figures, shaped like bowl depressions and a foot. These are motifs that have been found on other rock carvings from this time, but the foot figure is distinct because, unlike most others, it is portrayed with toes rather than as a foot with a shoe on.

The archaeologists believe that the slab may have been part of a burial chamber in the mound.

So far, no finds have been made that would confirm the presence of a settlement at the site. Postholes could indicate this, but might also have been part of a structure connected to the graveyard.

Casting moulds

A casting mould for bronze axe heads was found on the same site. The mould might have been deposited as grave goods, but might also show that casting of bronze objects took place in the region.

The mould may have been used to cast axe heads of the same type as were discovered at Hegra in Stjørdal municipality earlier this year. It’s conceivable that contact between Stjørdal and Melhus – 40 kilometres apart as the crow flies – might have existed in prehistoric times.

Both the carvings on the rock and on the mould suggest that the gravesite was probably used in the Late Nordic Bronze Age, between 1100 and 500 BCE.

This dating makes it the oldest burial site discovered to date in Melhus municipality, and also one of the oldest in central Norway. Several other interesting finds have been made nearby.

The information from the dig, combined with previous finds, allows archaeologists to form a picture of a region where people lived, worked and died over a long period of time.

The Norwegian University of Science and Technology (NTNU)

Archaeologists Discover Three Roman shipwrecks

Archaeologists in Egypt have announced the discovery of three underwater shipwrecks that date from the Roman Era in Abu Qir Bay, Alexandria.

The three wrecks were uncovered during a research project in collaboration between the European Institute of Underwater Archaeology and the Supreme Council of Antiquities.

In a press statement, Dr. Mostafa Waziri added that the project also uncovered a Roman head carved in crystal that may belong to the commander of the Roman armies of “Antonio”, in addition to three gold coins dating back to the Emperor “Octavius”.

Dr. Osama Alnahas – Head of the Central Department of the Underwater Antiquities said that the initial excavations have also indicated that a fourth shipwreck remains to be unearthed, as the project discovered Large wooden planks, as well as archaeological remains of pottery vessels that may represent the ships hull and cargo.

Dr. Ayman Ashmawy, Head of the Ancient Egyptian Antiquities Sector said that the archaeological mission began its excavations last September.

Underwater research by both projects have included a survey of the soil in both the eastern port and the Abu Qir Bay, underwater excavations at the Heraklion sunken city in Abu Qir Bay which includes the discovery of a votive bark of the god Osiris,as well as the completion of the conservation and documentation works.

Third Roman temple discovery in Silchester may have been part of emperor’s vanity project

A Roman temple uncovered in a Hampshire farmyard by University of Reading archaeologists may be the first building of its kind in Britain to be dated back to the reign of Emperor Nero.

The temple remains were found within the grounds of The Old Manor House in the Roman town at Silchester, along with rare tiles stamped with the name of the emperor, who ruled AD54-68.

The temple joined two others to make a group of three when it was investigated in Silchester in autumn 2017, and is the first to be identified in the town for more than 100 years. The three temples are located in a walled sanctuary, numbered Insula XXX by Victorian archaeologists. It would have been a striking gateway to the city for travellers from London.

Four fragments of tiles stamped in Nero’s name were found in a ritual pit within the temple site – the largest concentration ever found in the town – along with another three at the kiln site which made the tiles in nearby Little London. These provide further evidence that the temples could all have been part of a Nero-sponsored building project in Silchester.

Professor Mike Fulford at the University of Reading, who is leading the Silchester archaeology team, said: “These findings are a crucial piece of the jigsaw as we look to solve the mystery of Nero’s links to Silchester. This is something that has puzzled archaeologists for more than a century.

“Only a handful of Nero-stamped tiles have ever been found in the UK, so to unearth this many was very exciting. It adds to the evidence that Nero saw Silchester as a pet project where he could construct extravagant buildings like those seen in Rome, to inspire awe among his subjects in the UK.”

The three temples are the earliest known masonry constructions in Silchester, the city of Calleva in Roman times. They would therefore have been the most prominent buildings in the city, being erected decades before others, like the great complex of the forum basilica in the centre of the town, were rebuilt in masonry. They were aligned north to south at the eastern end of the Roman town.

The remains of the first two temples on the Insula XXX site were first found during grave-digging in St Mary’s churchyard in 1890, with evidence of the third building unearthed in 1902. However, its identity as another temple was overlooked until now.

Ground-penetrating radar, and a follow-up excavation this autumn, have confirmed three temples once stood on the site. They had a typical ‘double-square’ plan – a central cella (shrine) surrounded by a walkway. This design originated in the late Iron Age, and is rare in Britain but more common in France and Germany.

The foundations suggest the temples could have been up to 15m high. The dimensions of the third temple, 15m by 17.5m, are similar to those of the southernmost Insula XXX temple but smaller than the central one, which still remains the largest known of its type in Roman Britain.

Although the religious purpose of the temples remains a mystery, evidence uncovered at the latest temple site suggests it was built in the 50s or 60s of the first century AD – within Nero’s short reign. Similarities in the layout within the three temples suggest all three were conceived and built at a similar time, although further excavations by the team will test this theory.

Nero’s reign is associated with brutality and extravagance. He was known for the persecution of Christians as well as his grand building plans, some of which were constructed after Rome’s great fire, before his suicide. Nero’s buildings were made in high-quality stone, as well as ceramic brick and tile, but only the tiles found at Silchester are stamped in his name.

The existence of one of his buildings in Roman Britain, as well as evidence he might have visited, has always remained elusive. However, the find of the seven tiles, adding to only 14 previously found in the UK, only at Silchester and Little London, validates the theory that Nero was keen to sponsor a building project in Silchester.

Another Nero tile found close to the public baths in Insula XXXIIIA in the south-east of the Roman town suggests the baths were built early in the town’s development. Excavation to test this will take place in the summer of 2018.

University of Reading

An international group of scientists reveals the mystery about the origin of gold

An international group of scientists, with the participation of the University of Granada (UGR), has shed new light on the origin of gold, one of the most intriguing mysteries for Mankind since ancient times and which even today doesn’t have an answer that convinces the scientific community.

Their work, which has been recently published in the renowned Nature Communications journal, has established that the gold came to the Earth’s surface from the deepest regions of our planet. Thus, the Earth’s set of internal movements would have favored the ascent and concentration of the precious metal.

The researchers have found evidence of said process in the Argentinean Patagonia, which in addition represents the first register of gold found under the South American continent, specifically at a depth of 70 kilometers.

The researchers belong to various universities from Chile, Australia and France, and among them there’s also José María González Jiménez, a Ramón y Cajal researcher from the Department of Mineralogy and Petrology at the University of Granada.

The UGR researcher reminds that the interior of the Earth is divided into three large layers: crust, mantle and core. “The minerals we extract and which support our economy are located in the crust. And, although we are experts in taking advantage of them, we still know very little about their true origin. The search for gold has motivated migrations, expeditions and even wars, but its origin is one of the main questions in the field of mineral deposits genesis”.

The mantle is the layer separating the nucleus from the crust in which we all live, and its upper limit is located at about 17 kilometers under the oceans and 70 kilometers under the continents. “This distance is unreachable for Mankind, since we don’t possess the means for reaching the mantle and thus knowing more about it in a direct way yet”, the UGR researcher notes.

Nevertheless, the mantle can reach us thanks to volcanic eruptions, which bring with them small fragments, or ‘xenoliths’, from the mantle under the continents to the surface.

Those rare xenoliths are the ones that have been studied in this research. In them, the researchers have found tiny native gold particles, whose thickness is that of a human hair and whose origin is the deep mantle.

Research at the Deseado Massif

The focus of the research has been the region of the Deseado Massif at the Argentinean Patagonia, one of the largest auriferous provinces in the whole planet and whose gold mines are still being exploited.

Since the concentration of gold at that spot in the crust is very high the researchers have been able to figure out why mineral deposits are limited to some specific regions of the planet. Their hypothesis is that the mantle under that region is unique: it has a tendency to generate gold deposits on the surface due to its history.

“Said history dates back 200 million years, when Africa and South America were part of the same continent -González Jiménez says-. Their separation was caused, among other factors, by the ascent of a ‘mantle plume’ from the deep mantle, which broke the crust (much thiner and fragile) and caused the separation of the two continents. The ascent of said deep mantle plume generated a true chemical factory that enriched the mantle with metals, which would later generate the conditions for the creation of gold deposits. This time the process was caused by the movement of a tectonic plate under another, allowing the circulation of metal-rich fluids through the cracks, which precipitated the metals and concentrated them near the surface”.

The findings of the research team shed new light on the formation of mineral deposits, which are generally attributed to an origin in the crust itself, without taking into account the role of a deeper root from the mantle.

This new scientific evidence could contribute to a more advanced exploration of deposits that takes into account not only surface images or ‘radiographies’ of the crust for their search, but also studies the depths of the mantle, a region where the origin of one of the metals that has allured our species the most could be traced to.

UNIVERSITY OF GRANADA

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