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Latest archaeology news, archaeological discoveries from across the globe
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Oldest biodiversity found in Gabonese marine ecosystem

Sun, 2014-07-06 20:37
Researchers have discovered, in clay sediments from Gabon, fossils of the oldest multicellular organisms ever found. In total, more than 400 fossils dating back 2.1 billion years have been collected, including dozens of new types.

The detailed analysis of these finds, published on June 25, 2014 in Plos One, reveals a broad biodiversity composed of micro and macroscopic organisms of highly varied size and shape that evolved in a marine ecosystem.

The discovery in 2010 of 250 fossils of complex multicellular organisms dating back 2.1 billion years in a sedimentary bed close to Franceville, in Gabon, drastically changed the scenario of the history of life on Earth. Until then, the oldest known fossils of complex organisms were 600 million years old (Vendobionta from Ediacara in Australia) and it was commonly accepted that, before that period, life on our planet was exclusively made up of unicellular organisms (bacteria, unicellular algae, etc.). With the Franceville discovery, complex life forms made a leap of 1.5 billion years back in time.

The excavations carried out since 2008 by the team of Professor Abderrazak El Albani, geologist at the Institut de chimie des milieux et matériaux in Poitiers (CNRS/Université de Poitiers), have uncovered 400 fossils. The organic origin (biogenicity) of the samples was confirmed using an ion probe to measure the different sulfur isotopes, while X-ray microtomography revealed their internal and external structures. The rapid fossilization of these individuals by the pyritization phenomenon (replacement of their organic matter by pyrite, brought about by bacterial action) conserved their original forms very well.

Several new morphotypes, e.g. circular, elongated, lobed, etc. have been catalogued by the researchers, each including individuals of different size. Their analyses reveal organisms with radial texture and soft gelatinous bodies. Their forms can be smooth or folded, their texture uniform or knobby and their material in one whole piece or partitioned. The highly organized structure and varied sizes of the macroscopic specimens (up to 17 centimeters) suggest an extremely sophisticated means of growth for the period. This complete marine ecosystem was therefore composed of micro and macroscopic organisms, extremely varied in shape and form, living in a shallow marine environment.

Like the biota [1] of Ediacara in Australia, whose emergence coincided with a sudden increase in oxygen levels in the atmosphere 800 million years ago, the appearance and diversity of the biota in Gabon corresponds to the first peak in oxygen observed between – 2.3 and – 2 billion years ago. This biodiversity apparently died out after this oxygen level suddenly fell [2]. This Gabonese biota raises questions about the history of the biosphere at a planetary scale. The diversity and highly organized structure of the specimens studied suggest that they were already evolved. It is also possible that other forms of life just as old may exist elsewhere on the planet

CNRS (Délégation Paris Michel-Ange)

Categories: General

Rewriting the history of volcanic forcing during the past 2,000 years

Sun, 2014-07-06 19:44
A year-by-year record of volcanic eruptions from a comprehensive Antarctic ice core array

A team of scientists led by Michael Sigl and Joe McConnell of Nevada’s Desert Research Institute (DRI) has completed the most accurate and precise reconstruction to date of historic volcanic sulfate emissions in the Southern Hemisphere.

The new record, described in a manuscript published today in the online edition of Nature Climate Change, is derived from a large number of individual ice cores collected at various locations across Antarctica and is the first annually resolved record extending through the Common Era (the last 2,000 years of human history).

“This record provides the basis for a dramatic improvement in existing reconstructions of volcanic emissions during recent centuries and millennia,” said the report’s lead author Michael Sigl, a postdoctoral fellow and specialist in DRI’s unique ultra-trace ice core analytical laboratory, located on the Institute’s campus in Reno, Nevada.

These reconstructions are critical to accurate model simulations used to assess past natural and anthropogenic climate forcing. Such model simulations underpin environmental policy decisions including those aimed at regulating greenhouse gas and aerosol emissions to mitigate projected global warming.

Powerful volcanic eruptions are one of the most significant causes of climate variability in the past because of the large amounts of sulfur dioxide they emit, leading to formation of microscopic particles known as volcanic sulfate aerosols. These aerosols reflect more of the sun’s radiation back to space, cooling the Earth. Past volcanic events are measured through sulfate deposition records found in ice cores and have been linked to short-term global and regional cooling.

This effort brought together the most extensive array of ice core sulfate data in the world, including the West Antarctic Ice Sheet (WAIS) Divide ice core – arguably the most detailed record of volcanic sulfate in the Southern Hemisphere. In total, the study incorporated 26 precisely synchronized ice core records collected in an array of 19 sites from across Antarctica.

“This work is the culmination of more than a decade of collaborative ice core collection and analysis in our lab here at DRI,” said Joe McConnell, a DRI research professor who developed the continuous-flow analysis system used to analyze the ice cores.

McConnell, a member of several research teams that collected the cores (including the 2007-2009 Norwegian-American Scientific Traverse of East Antarctica and the WAIS Divide project that reached a depth of 3,405 meters in 2011), added, “The new record identifies 116 individual volcanic events during the last 2000 years.”

“Our new record completes the period from years 1 to 500 AD, for which there were no reconstructions previously, and significantly improves the record for years 500 to 1500 AD,” Sigl added. This new record also builds on DRI’s previous work as part of the international Past Global Changes (PAGES) effort to help reconstruct an accurate 2,000-year-long global temperature for individual continents.

This study involved collaborating researchers from the United States, Japan, Germany, Norway, Australia, and Italy. International collaborators contributed ice core samples for analysis at DRI as well as ice core measurements and climate modeling.

According to Yuko Motizuki from RIKEN (Japan’s largest comprehensive research institution), “The collaboration between DRI, National Institute of Polar Research (NIPR), and RIKEN just started in the last year, and we were very happy to be able to use the two newly obtained ice core records taken from Dome Fuji, where the volcanic signals are clearly visible. This is because precipitation on the site mainly contains stratospheric components.” Dr. Motizuki analyzed the samples collected by the Japanese Antarctic Research Expedition.

Simulations of volcanic sulfate transport performed with a coupled aerosol-climate model were compared to the ice core observations and used to investigate spatial patterns of sulfate deposition to Antarctica.

“Both observations and model results show that not all eruptions lead to the same spatial pattern of sulfate deposition,” said Matthew Toohey from the German institute GEOMAR Helmholtz Centre for Ocean Research Kiel. He added, “Spatial variability in sulfate deposition means that the accuracy of volcanic sulfate reconstructions depends strongly on having a sufficient number of ice core records from as many different regions of Antarctica as possible.”

With such an accurately synchronized and robust array, Sigl and his colleagues were able to revise reconstructions of past volcanic aerosol loading that are widely used today in climate model simulations. Most notably, the research found that the two largest volcanic eruptions in recent Earth history (Samalas in 1257 and Kuwae in 1458) deposited 30 to 35 percent less sulfate in Antarctica, suggesting that these events had a weaker cooling effect on global climate than previously thought.

Desert Research Institute – Header Image : WikiPedia

Categories: General

New archaeological find could shed light on late-Roman Britain

Sun, 2014-07-06 19:32
A unique archaeological find uncovered near the site of a Roman villa in Dorset could help to shed light on the rural elite of late-Roman Britain

The skeletal remains are thought to be unique as they are buried near the site of a Roman villa, making it likely that the five skeletons belonged to the owners and occupants of the villa – the first time in Britain that the graves of villa owners have been found in such close proximity to the villa itself.

Five skeletons were found; two adult males, two adult females and an elderly female – with researchers postulating that they could be the remains of three generations of the same family, who all owned the villa.  The bones are thought to date from the mid-4th Century (around 350 AD).

A unique archaeological find uncovered near the site of a Roman villa in Dorset could help to shed light on the rural elite of late-Roman Britain : Bournemouth University

Miles Russell, a Senior Lecturer in Archaeology at Bournemouth University and one of the archaeologists leading the dig, said, “The discovery is of great significance as it is the only time where evidence of a villa and the villa’s occupants have been found in the same location in Britain. This could provide us with significant information, never retrieved before, about the state of health of the villa owners, their ancestry and where they came from.”

Miles continued, “One of the big questions in South West is whether the villas in the South West were owned by Britons who have become Roman or owned by people from another part of the Empire who have come to exploit an under-developed rural area. All villas in this region in the South West are late-Roman – and our findings should tell us more about what life was like in this period of history. This is what what can be assessed when the bones are analysed.”

The discovery was made by staff and students from Bournemouth University, who are working on the Durotriges Big Dig project in North Dorset.

The villa itself was excavated last year by students working on the project, and the latest find is the final step in excavating this particular area of rich archaeological significance.

Paul Cheetham, Senior Lecturer in Archaeological Sciences and co-director of the project, added, “We are looking at the rural elite of late-Roman Britain, living through the economic collapse that took place during this period. These remains will shed light on the final stages of the golden age of Roman Britain.”

Bournemouth University

Categories: General