Since its inception in the 1950's, radiocarbon dating has proved essential to archaeologists and climatic scientists, which rely on the technique to combine organic compounds correctly. But good thing had improved better, as a result of finding two stalagminaids in a Chinese cave that contains a continuous atmospheric record that dates back to Ice Age last.
A seamless record of a high resolution of carbon-12 and carbon-14 atmospheric was found in a pair of stalagks located at Hulu Cave near Nanjing, China, according to new research published today in Science. As this record extends to the last glacial period, for about 54,000 years ago, scientists now have a more accurate standard for radiocarbon calibration.
There is no question that radiocarbon dating has revolutionized archeology. Based on this technique, scientists can date organic compounds, such as bones, hair, wood, seeds and shells. It's further in the time we go, however, the less reliable carbon date comes, as the technique depends on accurate historical measurements of atmospheric carbon, in particular the carbon-12 ratio i carbon-14.
Carbon-14, or C14, is a rare type of carbon, unlike carbon-12 (carbon called "normal"), radioactively. Isotope is a C14 that contains six protons and eight neutrons, and is in permanent decay, including half a life of 5,370 years. As normal carbon, Q14 combines oxygen to create carbon dioxide, absorbed by all living creatures, whether animals or plants. As a result, the ratio of C12 to C14 in each living organism is always the same as the ratio in the atmosphere.
Because atmospheric levels C12 and C14 change over time, the specific ratio in an organic sample (e.g. bones, timber) serves as a deadline for the living creature's death. When an organism dies, it does not acquire new carbon. As the time goes by, the C14 presses as a tick clock, but it will not be replaced. By measuring the amount of radioactive decay, scientists can decide when an earlier living organism has died.
But there are restrictions to this dating method, and it must do with half-life Q14. Only organic objects can be solved only 55,000 to 60,000 years ago, and then C14 in a sample decreases to rigid proportions. What's more, calibration is essential to this technique; Changes in the amount of atmospheric radiocarbon over time mean that radiocarbon dates must be graded against a chronological schedule, or a calendar.
These calendars are easier to build than made. Ideally, scientists would like to have a correct and seamless chronological record of changing atmospheric concentrations C12 and C14 over time. This can be done, for example, by counting tree rings (also known as dendrocrronology), which, as any 8-year-olds will tell you, is a reliable way of deciding the age of a tree. Unfortunately, a few data sets have been calibrated that show a direct sample of atmospheric carbon back in time or the Holocene tree phones record, about 12,600 to 14,000 years ago (obviously , trees do not live to be tens of thousands of years, but in ancient fossils wood can be used using other methods). Therefore, a radiocarbon date has been limited by the ability of specific material to provide an absolute age, while also keeping a record of changing atmospheric conditions.
But now, with the discovery and analysis of two special stalagms in Hulu Cave, scientists have turned on a seamless record of atmospheric carbon dating back to around 54,000 years. Instead of counting tree circles or studying coral rocks (another technique used to collect absolute dates), researchers Hai Cheng of the Global Environmental Change Organization, Xi's and the Jiaotong University, mineral composition inside the stalagms. By dating hundreds of layers within these structures, made using an extremely reliable isotope dating date of the toror-230 dating date, the researchers were able to establish an unprecedented chronological baseline that can be used for radiocarbon dating now .
"So far, different methods for calibrating C14 have their own constraints," said Hai at Gizmodo. "For example, it's still hard [to use] wood rings to galibration C14 atmospheric beyond the current limit of about 14,000 years before the present. Corals are constantly accumulating over thousands of years and are difficult to collect as those in the time range of interest are now undermined. Statistics, which can be excellent choices for torque-230 dating, usually include a significant fraction of carbon resulting from the ultimate limestone bed. "
Geologist UC Berkeley Larry Edwards, co-author of the new study, helped to develop the 230-colored method back in the late 1980's, but could not find ideal cave deposits to perform such a study.
"As well as carbon of the atmosphere, cave deposits contain carbon from limestone around the cave," said Edwards to Gizmodo. "We needed to make correction for the carbon that is derived from limestone. We found that Hulu Cave samples contain very little resulting limestone carbon, and so they are almost ideal for this type of study – so our ability to complete a precise scale of the C-14 timetable, the goal of the scientific community for the last time is almost seven decades. "
In the study, Hai and his colleagues present around 300 carbon-14 and ready-to-dozen carbon dates from the thin collar layers within the Hulu Caves stalagms. The usual seasonal solution between each pair is around 170 years. These specific stalagms, says Hai, are very special, including "dead carbon" that is extremely stable and reliable.
"As such, the Q14 in the Hulu samples are mainly derived from atmospheric sources, which allows us to make a milestone contribution to refine the Q14 calibration curve through C12 / C14 and thromium-230 measurements "said Hai, adding:" The new Hulu record has a lot of uncertainty and it solves a fine scale structure of "" etc. "
As the researchers write in their paper, the new calendar record represents scientists "sacred gravel", offering a high resolution and continuous record of atmospheric C14 that covers the full range of the radiocarbon dating method. For archaeologists, it also means that they can now give organic compounds between 14,000 and 54,000 years with more confidence, especially the older samples.
"For a sample that is actually 40,000 years old, the name C14 age would be approximately 35,000 years, and the age you would be calculated from previous calibration data was around 38,000 years, with great uncertainty, "Edwards explained. "So a difference of 2,000 to 5,000 years, depending on how you choose the calibration of your age, before our work."
Excitingly, this research will be of interest to climate scientists, who can use this data to study atmospheric changes over time.
It is a very cool result of a very cold and unlikely source – the drip slowly drives, drips in a dark cave in eastern China.[Science]