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Showing posts with label Archeology and Paleontology. Show all posts
Showing posts with label Archeology and Paleontology. Show all posts

Monday, 6 April 2020

Tooth be told: Earless seals existed in ancient Australia


A fossilised seal tooth found on a Victorian beach could hold the key to uncovering the history and geography of earless seals that graced Australia's shores three million years ago.

This prehistoric specimen is only the second earless seal fossil ever discovered in Australia, and proves the country's local fur seals and sea lions were preceded by a group of sea mammals, known as monachines, now long extinct in Australia.

The study also highlights the current dangers of climate change to Earth's existing wildlife, with falling sea levels likely to have played a role in the extinction of these ancient seals.

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The history of this rare specimen was published today (Friday 3 April) in the Journal of Vertebrate Paleontology by a team of scientists from Monash University's School of Biological Sciences and Department of Anatomy and Developmental Biology, and Museums Victoria, led by PhD candidate James Rule.

"This tooth, roughly three million years old, tells a story similar to what occurred in South Africa and South America in the past. Earless monachine seals used to dominate southern beaches and waters, and then suddenly disappeared, with eared seals replacing them," Mr Rule said.

"Since seal fossils are rare globally, this discovery makes a vital contribution to our understanding of this iconic group of sea mammals."



An Australian citizen scientist and amateur fossil collector discovered the tooth while strolling along the beach at Portland, western Victoria.

But it wasn't until he donated the fossil to Museums Victoria many years later that it was found to have been a tooth from an extinct group of earless seals.

The research team compared the tooth to other pinnipeds -- a group that includes earless seals, fur seals, sea lions and the walrus.

They found the tooth possessed characteristics of monachines and shed light on how these seals lived and what they ate.

"This seal lived in shallow waters close to the shore, likely hunting fish and squid. As monachines cannot use their limbs to walk on land, it would have required flat, sandy beaches when it came ashore to rest," Mr Rule said.

Researchers believe drastic changes in the Earth's climate fundamentally altered Australia's environment by eliminating the beaches used by earless seals to rest.

"These changes in the past have led to the extinction of Australia's ancient earless seals," Dr David Hocking, co-author and Research Fellow in Monash University's School of Biological Sciences, said.



"Our living fur seals and sea lions will likely face similar challenges as the Earth continues to warm, with melting polar ice leading to rising sea levels.

"Over time, this may lead to the eventual loss of islands that these species currently rely upon to rest and raise their young."


Bibliography:

James P. Rule, David P. Hocking, Erich M. G. Fitzgerald.

Pliocene monachine seal (Pinnipedia: Phocidae) from Australia constrains timing of pinniped turnover in the Southern Hemisphere.

Journal of Vertebrate Paleontology, 2020; e1734015

DOI: 10.1080/02724634.2019.1734015

Tuesday, 24 March 2020

Ancestor of all animals identified in Australian fossils


A team led by UC Riverside geologists has discovered the first ancestor on the family tree that contains most familiar animals today, including humans.

The tiny, wormlike creature, named Ikaria wariootia, is the earliest bilaterian, or organism with a front and back, two symmetrical sides, and openings at either end connected by a gut. The paper is published today in Proceedings of the National Academy of Sciences.

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The earliest multicellular organisms, such as sponges and algal mats, had variable shapes. Collectively known as the Ediacaran Biota, this group contains the oldest fossils of complex, multicellular organisms. However, most of these are not directly related to animals around today, including lily pad-shaped creatures known as Dickinsonia that lack basic features of most animals, such as a mouth or gut.

The development of bilateral symmetry was a critical step in the evolution of animal life, giving organisms the ability to move purposefully and a common, yet successful way to organize their bodies. A multitude of animals, from worms to insects to dinosaurs to humans, are organized around this same basic bilaterian body plan.



Evolutionary biologists studying the genetics of modern animals predicted the oldest ancestor of all bilaterians would have been simple and small, with rudimentary sensory organs. Preserving and identifying the fossilized remains of such an animal was thought to be difficult, if not impossible.

For 15 years, scientists agreed that fossilized burrows found in 555 million-year-old Ediacaran Period deposits in Nilpena, South Australia, were made by bilaterians. But there was no sign of the creature that made the burrows, leaving scientists with nothing but speculation.

Scott Evans, a recent doctoral graduate from UC Riverside; and Mary Droser, a professor of geology, noticed miniscule, oval impressions near some of these burrows. With funding from a NASA exobiology grant, they used a three-dimensional laser scanner that revealed the regular, consistent shape of a cylindrical body with a distinct head and tail and faintly grooved musculature. The animal ranged between 2-7 millimeters long and about 1-2.5 millimeters wide, with the largest the size and shape of a grain of rice -- just the right size to have made the burrows.

"We thought these animals should have existed during this interval, but always understood they would be difficult to recognize," Evans said. "Once we had the 3D scans, we knew that we had made an important discovery."

A 3D laser scan of an Ikaria wariootia impression. (Droser Lab/UCR)


The researchers, who include Ian Hughes of UC San Diego and James Gehling of the South Australia Museum, describe Ikaria wariootia, named to acknowledge the original custodians of the land. The genus name comes from Ikara, which means "meeting place" in the Adnyamathanha language. It's the Adnyamathanha name for a grouping of mountains known in English as Wilpena Pound. The species name comes from Warioota Creek, which runs from the Flinders Ranges to Nilpena Station.

"Burrows of Ikaria occur lower than anything else. It's the oldest fossil we get with this type of complexity," Droser said. "Dickinsonia and other big things were probably evolutionary dead ends. We knew that we also had lots of little things and thought these might have been the early bilaterians that we were looking for."

In spite of its relatively simple shape, Ikaria was complex compared to other fossils from this period. It burrowed in thin layers of well-oxygenated sand on the ocean floor in search of organic matter, indicating rudimentary sensory abilities. The depth and curvature of Ikaria represent clearly distinct front and rear ends, supporting the directed movement found in the burrows.



The burrows also preserve crosswise, "V"-shaped ridges, suggesting Ikaria moved by contracting muscles across its body like a worm, known as peristaltic locomotion. Evidence of sediment displacement in the burrows and signs the organism fed on buried organic matter reveal Ikaria probably had a mouth, anus, and gut.

"This is what evolutionary biologists predicted," Droser said. "It's really exciting that what we have found lines up so neatly with their prediction."


Bibliography:

Scott D. Evans, Ian V. Hughes, James G. Gehling, and Mary L. Droser.

Discovery of the oldest bilaterian from the Ediacaran of South Australia.

PNAS, March 23, 2020

DOI: 10.1073/pnas.2001045117

Monday, 2 March 2020

Discovery of a billion-year-old green algae, the ancestor of all plants


Virginia Tech paleontologists have made a remarkable discovery in China: 1 billion-year-old micro-fossils of green seaweeds that could be related to the ancestor of the earliest land plants and trees that first developed 450 million years ago.

The oldest green seaweed on record, the ancestor of all land plants, lived about 1 billion years ago, a new study finds.

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Scientists have discovered the fossils of what may be the oldest green algae ever known. The newfound seaweed — called Proterocladus antiquus — lived about a billion years ago. And even though it was tiny, about 0.07 inches (2 millimeters) in length, the algae had a big role: It could produce oxygen through photosynthesis.

"Its discovery indicates that green plants we see today can be traced back to at least 1 billion years ago, and they started in the ocean before they expanded their territory to the land," study lead researcher Qing Tang, a postdoctoral fellow in the Department of Geosciences at Virginia Tech, have told Live Science in an email.



Proterocladus antiquus : it confirms that green algae already lived a billion years ago

Until now, researchers didn't have hard proof that green algae lived that long ago. Rather, computer models, including those based on molecular clocks, indicated that photosynthesizing plants arose between the Paleoproterozoic era (2.5 billion to 1.6 billion years ago) and the Cryogenian period (720 million to 635 million years ago).

Now that researchers have a fossil, they can confidently say that photosynthesizing plants, a group known as Viridiplantae, lived at least 1 billion years ago, and that they were multicellular, Tang said.

Fossil of green alga P. antiquus . Credits: Qing Tang et al. 2020


"Previously, the oldest widely accepted fossilized green algae was about 800 million years old," said Timothy Gibson, a postdoctoral fellow in the Department of Earth Sciences at Dartmouth College in New Hampshire and the Department of Geology and Geophysics at Yale University, who was not involved with the study. "This work confirms what many have expected based on the existing, though sparse fossil record, which is that green algae likely existed about a billion years ago."

Green algae: they played an important role in maintaining primitive ecosystems

Tang and his colleagues discovered the fossils near Dalian City in Liaoning province of northern China. They had heard there was "a thick pile of well-exposed sedimentary rocks" from the Nanfen Formation dating to about a billion years ago. So, Tang took some of these ancient rocks, mostly mudstone and shale, back to the lab at Virginia Tech.

Tang was "really excited" when he saw the algae fossil under the microscope. In all, he identified 1,028 specimens. "I showed it to my supervisor [Shuhai Xiao, a professor in the Department of Geosciences at Virginia Tech], and we immediately agreed that this was going to be a very interesting discovery," he said.

Like modern algae, P. antiquus has a branched structure and a root system. Credits: Qing Tang et al. 2020

Life on Earth is dependent on photosynthesizing plants and algae for food, yet land plants did not evolve until about 450 million years ago, Tang said. "The new fossil suggests that green seaweeds were important players in the ocean long before their descendants, land plants, took control," he said.

Better understand the appearance and evolution of plants

These fossils came from an ancient ocean, but there is still a debate about where green algae originated. "Not everyone agrees with us; some scientists think that green plants started in rivers and lakes, and then conquered the ocean and land later," Xiao said in a statement.



Moreover, green algae isn't the oldest algae on record. "There is strong fossil evidence that red algae existed over a billion years ago, and we know the red and green algae diverged from a common ancestor," Gibson told Live Science in an email. "So, although this doesn't fundamentally change the way I'll think about the evolution of life, the discovery of this green algal fossil helps fill an important gap and strengthens an emerging timeline for the evolution of early, complex life."


Bibliography:

A one-billion-year-old multicellular chlorophyte

Tang, Q., Pang, K., Yuan, X

Nat Ecol Evol, 2020

DOI: 10.1038/s41559-020-1122-9

Sunday, 23 February 2020

Walls made of human bones found under the Saint Bavo Cathedral in Ghent, Belgium


By excavating places considered conventional, archaeologists can sometimes make unexpected finds. This is the case of a team of Belgian archaeologists who, excavating the underground areas of the Gothic Saint Bavo church, discovered several walls constructed with human bones - only bones of the lower limbs and skulls. A specificity that questions researchers.

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Archaeologists recently discovered walls constructed from human bones, including broken skulls, during the excavation of the grounds of Saint Bavo's Cathedral in Ghent, Belgium. At the end of the excavation, archaeologists had discovered nine walls, built mainly with adult femurs and shins. The intermediate areas were filled with skulls, many of which were fragmented, according to Ruben Willaert.

Bones from the cleaning of an old cemetery

These horrific structures were probably the work of people who, hundreds of years ago, cleaned up an old cemetery to make room for new bodies or the renovation of a church, says archaeologist Janiek De Gryse, Ruben Willaert staff member and excavation project manager.



“When cleaning up a cemetery, the skeletons cannot just be thrown away. Since the faithful believed in a resurrection of the body, the bones were considered the most important part," adds Gryse. Safeguarding human remains was so important that sometimes stone houses were built against the walls of city cemeteries to house skulls and long bones in what is called an ossuary.

The bony walls were discovered on the north side of Saint-Bavon cathedral, formerly known as Saint-Jean-Baptiste or Saint-Jan church. Radiocarbon dating of the bones suggests that they date from the second half of the 15th century, but the walls were probably built later, in the 17th or early 18th century. Historical documents support these dates. A source notes that the church cemetery was cleaned during the first half of the 16th century and again, after 1784, when he stopped accepting new bodies.

Smaller bones like the vertebrae, the bones of the hands or feet were not used for the construction of the walls. Credit: Ruben Willaert

Walls made entirely of lower limb bones and skulls

Whatever the date, these walls are a unique find. Most historic cemeteries are made up of large pits or layers filled with human bones. “We have no comparison in Belgium. We have never seen structures, like walls, intentionally constructed with human bones,” says de Gryse.

Those who built these walls had to be in a hurry, because they did not bother to pick up small or fragile bones, such as vertebrae, ribs or bones of the hands or feet. Curiously, archaeologists also did not find a humerus or radius (main arm bones).



“The walls are made up only of bones of the lower limbs. Is it only a practical thing (stacking bones very compactly) or is there also a religious / spiritual dimension? Asks Gryse. Although there are bones of adult men and women, the bones of children appear to be missing from the walls, which conflicts with the known life expectancy of this period, when children often died of disease.

Source

Wednesday, 12 February 2020

Discovery of a new Tyrannosaurus dinosaur in Canada


Julius Csotonyi / The University of Calgary and Ro

About 80 million years ago, a formidable Saurian predator from the T. rex family roamed the plains of present-day Canada, meticulously tracking down its prey with spectacular efficiency. This dinosaur, discovered by a team of Canadian paleontologists, received the name of "reaper of death". This important discovery will allow paleontologists to reconstruct the Tyrannosaurus lineage in more detail.

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Canadian paleontologists have announced the discovery of a new species of dinosaur closely related to Tyrannosaurus rex , which roamed the plain of North America about 80 million years ago. Thanatotheristes degrootorum (from the Greek for "death harvester") is the oldest member of the T. rex family discovered to date in northern North America and has reached a length of about 8 meters. T. degrootorum is the tenth tyrannosaurid species identified in North America.

“We have chosen a name that embodies what this tyrannosaurus was: the only known large predator of its time in Canada, the reaper of death. The nickname has become Thanatos,” said Darla Zelenitsky, study co-author and professor of dinosaur paleobiology at the University of Canada.



While T. rex - the most famous of all dinosaur species - tracked its prey about 66 million years ago, Thanatos dates back at least 79 million years. The specimen is the first new tyrannosaurus species found in Canada in 50 years.

Artist's impression of the new dinosaur. Credits: Julius Csotonyi / The University of Calgary and Ro

“There are very few species of tyrannosaurids. Due to the nature of the food chain, these large top predators were rare compared to herbivorous or herbivorous dinosaurs," said Zelenitsky in an article published in the journal Cretaceous Research .

The study found that Thanatos had a long, deep snout, similar to that of the more primitive tyrannosaurs that lived in the southern United States. The researchers suggested that the difference in skull shape of the tyrannosaurs between regions could have been due to differences in diet and also in prey available at the time.




Bibliography:

A new tyrannosaurine (Theropoda:Tyrannosauridae) from the Campanian Foremost Formation of Alberta, Canada, provides insight into the evolution and biogeography of tyrannosaurids

Authors: Jared T.Vorisa, Caleb M.Brown ....

Cretaceous Research

https://doi.org/10.1016/j.cretres.2020.104388

Tuesday, 17 December 2019

New clues clarify symbolism of Easter Island statues


For hundreds of years, around 1000 monoliths have stood on Easter Island (Rapa Nui). Called moai (or moai) , the objective of these statues has always been a mystery for anthropologists. Several hypotheses suggest that they are linked to fertility, renewal and abundance. Recently, a team of archaeologists has uncovered evidence confirming this link.

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More than 90% of the moai statues were carved in a quarry called Rano Raraku: a volcanic crater which, at its base, represents less than 1% of the total area of ​​the island, but nevertheless served as a unique source of stone used to make the statues of the island. However, Rano Raraku is not limited to cut stone, according to the researchers, based on an analysis of soil samples taken in the region.



According to the research team, it was an industrial site used to temporarily produce and store the moai before it was removed and transported to other places on the island. However, almost 400 of the monoliths remain in the quarry, and some are buried in the ground with the support of fortified rock structures which suggest that the placement is not temporary. The reason would be the soil rich in calcium and phosphorus, nutrients necessary for the growth of plants and crops.

Several hundred moai are still present in the quarry used to make them. Credit: Easter Island Statue Project

In addition to evidence of soil fertility, researchers also found traces of ancient crops in the samples, including bananas, taro, sweet potatoes, and Chinese mulberry.

These signs show, according to the researchers, that in addition to using the quarry for producing the moai, the Rapa Nui company also used the space as a place to grow the food they needed, taking advantage of the rich soils. and plowed Rano Raraku, which would have produced higher yields with lower labor costs

Why were the moai also erected in the crater, in the middle of the earth from which they themselves were produced? It has long been theorized that the ceremonial purpose of monoliths was associated with fertility rituals, and researchers say their field work provides chemical evidence for this link - not to mention the discovery of carved pits, suggesting that the moai were probably erected to stand and “watch indefinitely” on this fertile ground.




Bibliography:

New excavations in Easter Island's statue quarry: Soil fertility, site formation and chronology

Authors: Sarah C.SherwoodaJ  AnneVan Tilburg Casey R.Barrier MarkHorrocks Richard K.DunnfJosรฉ MiguelRamรญrez-Aliaga

Journal of Archaeological Science
Volume 111, November 2019, 104994

https://doi.org/10.1016/j.jas.2019.104994

Saturday, 14 December 2019

Grave of Celtic warrior reveals "most important British Celtic art object of the millennium"



Although it has been studied for a long time by archaeologists, Celtic culture still holds many mysteries. The funeral practices of the Celts are known to be complex, the living bringing all possible help to the deceased to continue their life in the afterlife. The tomb of a 2,200-year-old Celtic warrior recently discovered in the United Kingdom, containing various objects including a particularly ornate shield, confirms these ancestral practices.

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Among the finds in the tomb is an ornate shield described as "the most important British Celtic art object of the millennium" by archaeologist Melanie Giles of the University of Manchester.

Made in an ancient Celtic art style known as La Tรจne, the shield has an unusual scalloped edge and a triple spiral design called a triskele. The shield also shows organic shapes such as mollusc shells, as well as repair marks.



“ Popular belief is that elaborate metal-faced shields were purely ceremonial, reflecting status, but not used in battle. Our investigation disputes this with evidence of a puncture break in the shield, typical of a sword. Repair marks can also be seen, suggesting that the shield was not only old but also likely to have been used, "said archaeologist Paula Ware of the MAP Archaeological Practice.

Accompanying the deceased in the afterlife

Measuring 75 centimeters in diameter, the shield was made by hammering a bronze sheet from below. All of the leather and wooden accessories that once existed on the defensive weapon have since rotten. Besides the shield, the tomb also features what appears to be a chariot, with horses - although it is unclear whether the horses were sacrificed for burial or had already died before.

Shield found in the Celtic tomb. Credits: MAP Archaeological Practice

Seeing all these weapons, a means of transport and provisions piled up in the tomb indicates how seriously the Celtic tribes of the time envisaged the passage into the afterlife. The society in which this warrior would have lived would have wanted to help him as much as possible in everything that was to follow.

Remains of horses exhumed in the grave. Credits: MAP Archaeological Practice

The possibility of natural death
It is believed that the man himself was in his late forties or more when he died, around 320-174 BCE. Nothing like this type of burial has ever been seen in the UK before, although another grave with chariot and horse was discovered in Bulgaria in 2013.

These latest findings have not yet been published in a peer-reviewed journal, but come from a funeral site originally discovered in 2018, near the town of Pocklington, Yorkshire. A red glass brooch and pig remains (another potential animal sacrifice) were also discovered in the same grave.

“ We don't know how the man died. There is blunt trauma but they would not have killed him. I don't think he died in combat; it is very likely that he died in "old age" "concludes Ware.




Bibliography:

Article: Iron Age shield found in Pocklington is "one of most important ancient finds this millennium"

Source

Wednesday, 20 November 2019

More than 140 new Nazca geoglyphs have been discovered


In 1927, archaeologists discovered for the first time from the air stylized representations of humans, animals and objects of various sizes (between a few tens of meters and several kilometers) drawn in the soil of the Nazca desert in southern Peru. Called the Nazca Geoglyphs, the purpose in which they were traced by the Nazca civilization is still unknown. Recently, a team of archaeologists discovered 143 new geoglyphs, including one thanks to artificial intelligence . This discovery could help to better understand the functions of these representations.

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Scientists have discovered more than 140 new geoglyphs, known as Nazca Geoglyphs (or Nazca Lines): an ancient and mysterious group of giant characters engraved in the desert of southern Peru. These massive and sprawling representations of human beings, animals and objects can be as old as 2500 years old and so impressive that many of them can only be identified from the air.

Archaeologists at the Japanese University of Yamagata report that a long-term study conducted since 2004 has uncovered 143 previously unknown Nazca geoglyphs, including a figure who escaped human detection and discovered by artificial intelligence.

Humanoid geoglyph (about 10 meters long). Credits: Yamagata University

Geoglyphs with still unexplained objectives

The newly identified geoglyphs would have been created between at least 100 BCE and 300 EC. Although the purpose of these great motifs inspired by the ancient culture of Nazca remains controversial, the way they were made is known to archaeologists. " All these figures were created by removing the black stones that cover the earth, exposing the white sand underneath, " says the research team.

Geoglyph representing a bird (about 100 meters long). Credits: Yamagata University

Previous assumptions have suggested that the Nazca people have shaped the giant geoglyphs - some of which are hundreds of meters long - to be seen by deities in the sky or to serve astronomical purposes.

In the new research, led by anthropologist and archaeologist Masato Sakai, the team analyzed the high-resolution satellite imagery of the Nazca region, also conducted fieldwork and identified two main types of geoglyphs.

Two types of geoglyphs with potentially distinct functions

The oldest geoglyphs (100 AECs), called type B, are generally less than 50 meters, while the slightly more recent ones (100 and 300 EC), called type A, extend over 50 meters, with the largest geoglyph discovered by the team measuring more than 100 meters.

Researchers believe that type A geoglyphs, larger, often shaped like animals, were ritual places where people organized ceremonies involving the destruction of various pottery vases.

Geoglyph representing a two-headed serpent (about 30 meters long). Credits: Yamagata University

On the other hand, the smaller Type B patterns were located along trails and could have served as a relay to guide travelers - possibly to a larger Type A ritual space where people would gather. Some of these Type B designs are really tiny, the smallest of new discoveries measuring less than 5 meters, making it difficult to find this type of line.

The help of artificial intelligence in the discovery of geoglyphs

To this end, as part of a recent experimental collaboration that began in 2018 with IBM researchers, the team used a company-developed Deep Learning artificial intelligence that runs on a geospatial analysis system. called IBM PAIRS geoscope.

Humanoid geoglyph discovered by IBM's artificial intelligence (about 4 meters long). Credits: Yamagata University

The Learning Network - IBM Watson Machine Learning Accelerator (WMLA) - has screened huge volumes of images of drones and satellites to see if it can spot hidden marks related to the Nazca lines.

The system found a match: the faded outline of a small humanoid type B, resting on two feet. Although the symbolic meaning of this strange and ancient character is not yet clear, the researchers point out that the geoglyph was located near a path, which makes it perhaps one of the supposed beacons.

Source

Sunday, 27 October 2019

Discovery of the oldest known pearl on an island in the Persian Gulf


Pearls are white or iridescent limestone structures made by some bivalve molluscs. They are the subject of an important trade in the field of luxury jewelry in modern society, but this trade could have roots much older than previously estimated. This is suggested by the discovery of an 8000-year-old pearl on a Neolithic site on Marawah Island, off Abu Dhabi, making it one of the oldest known pearls in the world.

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Archaeologists have discovered what they claim to be the world's oldest natural pearl on the island of Marawah, off the coast of Abu Dhabi. The pearl is dated 8000 years old and was formed during the Neolithic period - the last stage of the Stone Age. Nicknamed the "Pearl of Abu Dhabi", it is pale pink in color and is approximately 0.3 centimeters long. It was found in a layer located on a Neolithic site dating from between 5800 BC. and 5600 BC AD

Before the discovery of the pearl of Abu Dhabi, the oldest known pearl of the United Arab Emirates was found on a Neolithic site in Umm al-Quwain. Ancient pearls from the same period were also discovered in a neolithic cemetery near Djebel Buhais in the emirate of Sharjah. Carbon dating indicates that the pearl of Abu Dhabi is older than these two discoveries.

Abu Dhabi: an important pearl center in Neolithic times

" The presence of pearls on archaeological sites is proof that the pearl trade has existed since at least the Neolithic period, " said Abdulla Khalfan Al-Kaabi, director of the Archaeological Investigations Unit of the Department of Culture and Tourism. Abu Dhabi.

Found at a Neolithic site on the island of Marawah, the pearl testifies to the central pearling activity of the Abu Dhabi region. Credits: Abu Dhabi Department of Culture

Indeed, " if we look at historical sources, we find more than one indication that Abu Dhabi was considered one of the main pearl centers ." According to the statement, the pearls could have been worn as jewelry or exchanged for goods of other civilizations, such as ceramics of Mesopotamia.

This Neolithic site, composed of collapsed stone structures, was first discovered in 1992 and many artefacts have been found, including flint arrowheads, pearls and ceramics. Moreover, as this site is located on an island, many of the objects found, such as fish bones, turtles, dolphins, dugongs and oysters, relate to the sea.

" The inhabitants of this period knew the sea very well and considered it an essential part of everyday life, " explains Al-Kaabi. Even centuries later, pearl diving remained an important activity in the region and was an important engine of the economy of the United Arab Emirates until the 1930s.


Source

Thursday, 24 October 2019

Cretaceous-Paleogene Extinction: The impact of an asteroid has been the main cause of extinction


66 million years ago, dinosaurs and many other species disappeared during mass extinction known as Cretaceous-Paleogene (K-Pg) extinction. The main hypothesis used to explain this event is the combination of intense volcanism and the impact of an asteroid. However, so far, there is no empirical evidence as to which of the two had contributed most to this extinction. But recently, a team of geologists has shown that the impact of the asteroid has caused a brutal acidification of the oceans with massive disruption of the carbon cycle, making this impact the main cause of K-Pg extinction.

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The fossil remains of tiny calcareous algae not only provide information about the end of the dinosaurs, but also show how the oceans have recovered from the impact of the asteroid. Experts agree that a collision with an asteroid has caused mass extinction on our planet, but some hypotheses have been made that ecosystems were already under pressure from increasing volcanism.

Our data shows a gradual deterioration of environmental conditions 66 million years ago, " says Michael Henehan of GFZ's German Geoscience Research Center. With colleagues from Yale University, he published in PNAS a study describing ocean acidification during this period.


Massive acidification of the oceans due to the impact of the asteroid
Henehan has studied boron isotopes in the calcareous shells of plankton (foraminifera). According to the findings, there was a sudden impact that led to massive acidification of the oceans. The oceans have taken millions of years to recover from this acidification. " Before the event, we could not detect any increasing acidification of the oceans, " explains Henehan.

The impact of a celestial body left traces: the Chicxulub crater in the Gulf of Mexico and tiny amounts of iridium in the sediments. Up to 75% of all animal species disappeared at the time. The impact marks the boundary of two geological epochs - the Cretaceous and the Paleogene (formerly known as the Cretaceous-Tertiary boundary).

The study of fossilized oceanic foraminifera (in color on the graph) revealed a rapid acidification of the oceans during the extinction K-Pg (red vertical line), caused by the impact of an asteroid. Credits: Michael J. Henehan et al. 2019

Henehan and his team at Yale University reconstructed environmental conditions in the oceans, using fossils from deep-sea drill cores and rocks formed at that time.

After the impact, the oceans became so acidic that the organisms that made their calcium carbonate shell could no longer survive. As a result, as life forms in the upper oceans have disappeared, carbon uptake by photosynthesis in the oceans has been reduced by half.

The collapse of the carbon cycle and the slow recovery of ecosystems

This state lasted several tens of thousands of years before the spread of calcareous algae. However, it took millions of years for the flora and fauna to recover and for the carbon cycle to reach a new equilibrium. The researchers found decisive data on this subject during an excursion to the Netherlands, where a particularly thick layer of rock from the Cretaceous-Paleogene boundary is conserved in a cave.

The Cretaceous-Paleogene geological boundary is clearly visible in this cave of Geulhemmerberg (Netherlands), where the samples of the study were taken. Credits: Michael Henehan

In this cave, a particularly thick layer of clay accumulated immediately after the impact, which is really quite rare, " says Henehan. In most cases, sediments accumulate so slowly that such a rapid event, such as an asteroid impact, is difficult to identify during rock analysis. " Because so much sediment was deposited at a time, we were able to extract enough fossils to analyze, which allowed us to isolate the transition.

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