Latest / El futuro fue ayer con Juan Guillermo Martín / Un punto clave para determinar la antigüedad de eventos del pasado

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Un punto clave para determinar la antigüedad de eventos del pasado · El futuro fue ayer con Juan Guillermo Martín

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The future was yesterday? It' s an archaeology podcast where ghosts, conspiracy
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theories and aliens have no place. I am Juan Guillermo Martín archaeologist and university
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professor and with the hand of different specialists, would be scientifically addressing our fascinating
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past, a past that offers us answers to face in the future. Welcome
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to the podcast The future was yesterday? I am with Guillermo Martín archeol Today
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we are going to address the issue of dating or dating of archaeological contexts,
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that is, the techniques that are used to finish the age of a deposit.
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To talk about the subject, I have an expert guest on the subject.
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This is Glorianes López Gloria welcome Many thanks, Juan Guillermo. It'
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s a pleasure to be here with you for those who don' t know
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her. Glorinies López is a geologist at AFIT, with a master' s
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degree in Geology from the University of Victoria and a PhD in geology from Macmaster
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University in Canada. He has more than fifteen years of professional experience in earth
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sciences and a long career in field work in tropical coastal environments, as well
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as in field and laboratory sampling methodological procedures, in Israel, Canada, the
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Netherlands, Spain, Portugal, ri Lanka, Kenya, Turkey, Greece,
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Ecuador, Chile, Japan, Mexico, the United States and Colombia. Its
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specialties are sedimentology, tsunami geology, geoarchaeology and geochronology specifically optics, as well
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as scientific dissemination glory. We are going to enter into matter and without a
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doubt, because one of the most important aspects of archaeological research is to precisely
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determine the age of human evidence of the past. Surely, those who listen
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to us will immediately think of carbon fourteen. But obviously, there are a
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number of absolute dating techniques more applied in archaeology. De Bo specifies that there
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is the possibility of making relative dating when we have dating of some archaeological sites
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and styles, for example ceramics, that we can compare with other contexts,
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since it allows us to establish that relative chronology. So, then, the
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question is aimed at that, what are the dating techniques that we can now
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apply to archaeological contexts. Juan Guillermo, only a small correction date or dating
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is not absolute, it never has to be numerical or relative absolute. There
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' s nothing in life, because the only absolute thing is that maybe we
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' re going, because we' re going to die and we' re
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born and we die and we' re done. But as far as adaptations
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are concerned, there are two large groups, two other big types that are
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numeric, because they give you a numerical value and the relative ones that,
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as you well said, is a comparison between different materials or different analyses,
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etcetera. To adapt. In archaeology there are and in Quaternary, which is
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a period of geological time, there are forty- four established methods. Already
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that' s a lot of methods of which, unluckyly nothing people only know
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one, as you well said, carbon fourteen, but it' s forty
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- four and they span a temporality, that is, a fairly large space
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of time. Well, first, thank you for the clarification. Of course,
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in archaeology we always talk about absolute dating. I will never say it
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again, and I hope that those who listen to us will do so,
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and perhaps it is equally desirable because it is the most well- known technique,
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that of carbon fourteen. Please explain to us, Gloria, how this
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thing works, how an antiquity can be established from carbon fourteen. Of course
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you do see that the interesting thing about carbon fourteen and the vast majority of
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dating techniques are created from the fact that radioactivity was found. So, if
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the radioactivity hadn' t been discovered, many of these techniques we couldn'
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t be using now. Carbon fourteen measures or gives the date of organic material,
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i e living beings of living matter. In every living matter there are
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twelve carbon, i e two different types of isotopes, twelve carbon and fourteen
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carbon. Carbon fourteen is unstable, it is radioactive, but it is constant
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within the living body or living matter. While it is alive, true,
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when that organism dies it does not assimilate more carbon fourteen, but begins to
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decay or disintegrate. So, like carbon fourteen, because it is radioactive,
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has what we call an average age of five seven hundred and thirty years,
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that is, every five seven hundred and thirty years, half of its atoms
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break down into nitrogen. Then, as we know, every time the five
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seven hundred and thirty years pass, half of its atoms are broken down.
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What is done in the laboratory is to determine the amount of atoms when you
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took the sample from that leaf or that piece of organic matter and compared it
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to the amount of carbon twelve it has, because carbon twelve remains stable when
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that organism dies. So it' s a method of comparing two different isotopes
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of carbon, and that' s done through what' s called a mass
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spectrometer. So it is if it is a perfect comparison and it is clear
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that it can only be made with organic matter with beings that were alive at
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some point, human partner remains, associated remains of wood charred fauna, basically
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it is the one that we will use to make that kind of dating.
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However, it is clear that, obviously, this dating ultimately means the possibility
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of dating elements in an archaeological context. But when we don' t have
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organic elements or when, for example, we have sites or contexts that are
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over sixty zero years old, what techniques should we apply, because carbon fourteen
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would no longer work even for sites that are over sixty zero years old.
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Right, the methodology was invented in the mid- fifties. Carbon fourteen,
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that is, there is one thing, a very present number. Every time
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we read a carbon age fourteen and it' s the year one thousand nine
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hundred and fifty, because with that it' s going to compare how many
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years. That' s the data, zero of all carbon 14 years old.
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So, when more than sixty thousand years pass, carbon fourteen is no
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good, because the curve in which one compares the ages, does not give
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to extend beyond fifty- five thousand or so five thousand years, that is,
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almost sixty thousand years. Right, so, that' s what the
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other forty- three dating methods are for, of which only and I'
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m counting them here in my head, about ten are giving numerical ages.
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There are ten others that are by ring count, for example. So in
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these we can introduce dendrochronology, which is the counting of trees, but also
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the chronology of corals or the chronology of bivalves, also that has like rings,
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let' s say so, that can pass of the sixty thousand years.
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But the longest it covers is paleomagnetism or archeomagnetism, which I know if
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we are talking about you can reach ages of more than ten million years.
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For the most recent and most used today are the luminescence and electronic paramagnetic resonance,
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which both use granites of sand, quartz granites or feldspar granites, which
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are the two most abundant minerals on the face of the earth and are being
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used a lot in archaeological sites especially in prehistoric sites where it is about determining
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human evolution. So, human evolution uses very much the adaptations by the aminescence
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or SL by its acronym SR, which is the electronic paramagnetic, by its
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ciglas in English as well, and paleomagnetism, that is him. Those are
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the three most they are now using in prehistoric archaeology. Well, and there
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I would like to stop, so that already given your experience and knowledge of
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luminescence, you could explain to us, because that has its detail in collecting
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the samples themselves. Then deepen and explain what this issue is about and how
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accurate this correct technique is. The luminescence is very nice, because basically we
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are measuring the amount of energy trapped in grains of sand due to the natural
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environmental radioactivity that exists around each of those grains of sand. The granite sand,
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when it sees the light of day, loses all that energy, that
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is, it bleaches within every sand credit there are some traps inside its crystalline
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latiz. Then their crystalline structure, and then those traps, when the granite
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is buried, begin to trap radioactive electro. And that happens while the granite
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is buried. If granite sees the light of day, uff all those granites
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come out into the light. That' s why it' s called luminescence,
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because they emit little rays of light. So in the lab what we
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do is we measure the amount of electrons, that is, beams of light
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that come out of each of those grains of sand. However, when we
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are going to take the sample in field, there are several requirements that we
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must follow and that is one not to expose the sample to daylight. So,
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in many archaeological sites, for example, what we do is take the
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sample or at night or under a dark tarp, because many times in those
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archaeological sites you cannot bury tubes within the exposed profile, but they are extremely
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precious and rich cins. Then you can only remove a little bit of material
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by digging around the point you want to adapt. But when you can bury
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a tube, because by burying the tube, you can do it in the
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day. So that tube or that little sample bag taken under in the dark,
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is taken to the lab, it' s done a whole chemical processing
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to extract individual quartz and feldspar granites that are then going to be measured in
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a luminescence reader and that' s going to determine the amount of electrons or
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light signal, and so we can determine the age by comparing it to the
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annual dosimetry at that point. So we also have to do a natural radioactivity
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analysis. On site, at the point where the sample was taken is a
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balance of how much activity there is and how many electrons there are. And
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that' s the equation. And that, the longer an older granite is
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buried. It' s that granite, so the value of luminescence is going
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to be greater. So, age is going to be bigger and in terms
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of precision ranges. At this time, luminescence is the most accurate technique in
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the world. For example, it depends a lot on the sample, the
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type of sample, because not everything is perfect in this life. Then a
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perfect sample is those where there is more light, that is, deserts or
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coastal areas, because at the time of burial, granite needs to be cleared
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of all electrons, or those inside it. Then there are certain types of
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sedimentary deposits that are very turbulent and that do not let granite, at the
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time of burial, get rid of all the vestige inside it. Then there
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are some sites that can be dated much more precisely than others. But the
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precision of luminescence is between five and fifteen percent at this time, that of
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carbon fourteen may vary from a Han to ten percent. Let' s say
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ten to twenty- five percent. So it does exceed 14 carbon. Now
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you see her. That' s a much smaller margin, and I think
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it would also be worth telling those who listen to us about those margins of
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error, because normally, when archaeological vents, they' re going to find
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those numerical dates that say more than fifteen, twenty, thirty or fifty.
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That' s the margin of error. That' s exactly what those dates
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have to do with them. It' s right, right, exactly the
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precision. It' s that margin of error, for example, if you
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have a date that I know a hundred plus five, it' s that
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the age of that material can be a hundred, it can be between ninety
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- five and one hundred and five years. That' s the margin of
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error. That' s right. And obviously to us for very old dates,
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because a margin of error of fifty years is very little. But when
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we are, for example, studying historical sites that are two hundred and three
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hundred years old, that margin of error is enormous. It doesn' t
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make much sense, and that' s why we' re applying another set
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of dating strategies because, well, the carbon radius isn' t going,
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it' s not going to bring us anything. There is another thing that
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I am usually asked also when they read archaeological literature, when they see dates
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and it has to do with the nomenclature of adaptation, we will find c
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before Christ' s D C S of Christ ap before the present or if
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they are in English, because they would be vp beford present for some time
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it is used before the common age. You could explain to us what all
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these ways of presenting a numerical date mean and if we are ever going to
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have the possibility to unify them. Excellent question. That' s the eternal
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debate among geochronologists, or good people who work on this thing of giving things
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look that even recently. Recently, I say, about five or seven years
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ago, the world- wide luminescence community wanted to establish a data sheet As
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I told you earlier, the data for carbon fourteen is nine hundred and fifty
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is established worldwide and that is not going to change. Then why, because
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it is much easier to compare ages when they have the same data, that
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is, when compared based on the same before and after. So, when
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they give you a carbon 14 age, it tells you that' s a
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thousand years plus fifty, but that' s the age. You have to
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see if that' s the calibration age or whether that' s the VP
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age or d age or whatever ad it is before ad means Anu Domini in
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Latin, which translated it as after That. After the death of which of
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Jesus Christ, which is the year zero. We the Gregorian calendar is based
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on the year zero, which is from the death of Jesus Christ, so
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all that is ad Ano Domini is from year zero, for here forward and
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all that is Bci is Bob Ford Christ before Christ is from year zero back.
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Then you have to be very careful, because the carbon fourteen ages,
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for example, are going to give them to you based on a datam that
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is nine hundred and fifty. But then, if you' re comparing with
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an age, year one does not. You have to subtract it, that
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' s a thousand nine hundred five or nine hundred for twenty- nine years
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through carbon fourteen to compare all ages AD or BC, as be Ford Press.
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So, about, like, twenty or twenty- five years ago,
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this movement arose from being politically correct, especially in biology. And that'
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s when they started using the acronym BC and so, they form air before
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the common age, that is, the year zero or d and after the
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common age being is that I always get confused what I have to think in
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English because one already has the mind, as well when they refer to VPB
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Ford present or before the present is before one thousand nine hundred and fifty,
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that is the date the date of carbon fourteen. So I know that looks
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like a letter soup or a really horrible sand car. But it is very
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easy when when in a publication or in a book you are given or compared
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many ages of different nomenclatures always, the best thing is to put all nomenclatures
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in the same nomenclature, that is, to compare, that is to say
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you will put them all in present, that is to say based on one
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thousand nine hundred fifty, or you will put them all in zero based on
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the year zero, or are there people who even put them based on today
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or the year two thousand to paraphrases so understand how long ago the event happened
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or how long ago that organism died or how long ago? To stop you
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an example in luminescence, we do not have datam That is one of the
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difficulties of luminescence, because the luminescence, the datum of luminescence, is the
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moment when the sample was measured, that is, a sample can be taken
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three years ago and measured today year two thousand twenty- four, Then your
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age is going to give you an age one thousand or so fifty datum two
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thousand twenty- four, that is, a thousand years ago was that event
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or what you are dating true based on two thousand twenty- four. Why,
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because everything depends on radioactivity Then the machine has a radioactive source and also
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that it also disintegrates. So all the values depend on the moment you gave
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me the sample. So, we better give the moment that the sample was
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measured and not a datum x, like a year x or something. So
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you have to be very careful about that, and it is to demand or
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ask the authors, if they didn' t put it, ask them what
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the datum is or based on what their measurement did, when it is pluminescence
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or sr understand that, that, of course, is somehow regulated and who
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presents the dates of dating in an article, a scientific publication, because it
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seeks homogeneity. Finally, considering that in carbon fourteen we have a datum of
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one thousand nine hundred and fifty, which in these techniques that are being applied
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now, the datum is related to the moment when the measurement is made.
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What a chance we have after making a comparison. We need to use these
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date calibration programs to make all of us work the same. Or how it
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would work to facilitate that comparison, because even already think of the datum of
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one thousand nine hundred and fifty is seventy- four years of difference, that
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is, we are almost going to reach the century of that datum and that
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is already an important amount of years, not clear, not for comparisons with
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carbon XIV. The easiest thing is to remove those seventy- four years at
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the age of BCR' s luminescence and so they are all in the same
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data. That' s the easiest thing to do to make ok perfect already
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with that and you and you what you think. Obviously, the issue also
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of using a nomenclature as after Christ, before Christ, has a religious connotation,
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of course, that some also enter into the politically correct, for some
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colleagues of other practitioners of other religions, because somehow they are upset with having
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that chronological reference. The most opportune thing, the most pertinent thing in science
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will be to use the pre- present and with that we free ourselves from
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so much different nomenclature. Right. Many people are already passing is to use
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the VP bu for present or before the present or even the calibrated age,
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that the calibrated age is already to put in brackets so calibrated with the version
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of the program that they used to calibrate and ready and one already knows what
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it is before one thousand nine hundred fifty point. All right, there'
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s a question, a question that I have related to organic samples and carbon
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dating fourteen and it has to do with a discussion that there is about samples
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coming from marine environments and that some colleagues say that you can' t take
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into account, for example, vivalves recovered from a garbage dump near the coastline
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because the dates are not good. How true that is or whether it has
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been able to limit the margin of error with marine samples with respect to organic
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samples coming from inland. Very good question, Juan Guillermo. No, this
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has already been resolved because it is also established to see. The problem with
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samples coming from marine environments is that they have a reservoir effect of latent carbon
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fourteen, because it exists as an extra carbon fourteen in the sea, then
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accumulating that all marine organisms absorb it. But that is now also standardized.
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There are already some curves that can be used to remove that reservoir effect to
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the samples that will be adapted with the coastal bivalves, which date a lot
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the trick is that the videzgos have to be in position of life. So
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the problem with a lot of people is that they take any bivalve that is,
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let' s say one half of a single conchita of that bivalve and
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they want to date that. Then that' s no use. You have
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to prove that he' s in a position of life the moment you recovered,
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because you showed that vivalvo. But the lab' s already asking you.
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That' s what environment, that' s land, lake, sea,
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etcetera. And you have to fill out the form when you send the
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sample, and they already know how to compare it and what treatment to do
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to remove that reservor effect from the sample calculation. That means that each sample
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has a particular procedure, so let' s say the origin of the sample
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if it comes, I don' t know about the tropical lowland equator.
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The operation in the laboratory is different depending on the coordinates. Let' s
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put it this way, of obtaining the sample, not so much in the
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coordinates, but of the positional environment, that is, if it is Costa
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Laguna. Yes, the positional environment, from which it was extracted then,
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because it is very different. You treat a sample that are a few leaflets
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of environment the cross a few pieces of trunk buried on a beach. They
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' re different and you have to know why. The person who is working
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in the laboratory needs to know where they come from to know what treatment to
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do and not to do it, because all the cleaning treatments of that material
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to be able to extract the pochitic that is extracted to put it into the
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mass spectrometer, because it is tiny the amount of material that is used in
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perfect spectrometer Gloria. To close, I have one last question. There are
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several laboratories in Latin America that are working and that process and date samples of
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archaeological contexts, especially carbon fourteen illuminescence. How far we are, if there
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is not yet to have them in the region duly certified laboratories that allow us
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to advance our own dates, or we will have to continue to depend on
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the European and North American laboratories that you who are involved in the matter in
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which it goes, because I tell you that the Colombian Geological Service in Bogotá,
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in what is the Directorate of Nuclear Affairs, that is where the geochronology
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program is right now, already has facilities to prepare samples for carbon fourteen and
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have an agreement with the Great Carbon Laboratory fourteen of Brazil, and because they
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have a large spectrometer there and that is where they measure the samples. So,
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on that side, we have the services already for carbon fourteen here in
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Colombia, in the Colombian Geological Service, and for luminescence, wanting God and
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crossing our fingers and burning a thousand bellitos, possibly for about a year and
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a year and a half we will have luminescence laboratory, because that' s
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what we' re doing, what I' m doing right now with geological
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service. I am the expert who is building the new laboratory, the first
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and the new luminescence laboratory for swimming in Colombia with the service, because,
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moreover, it must be said that not only serves for archaeological research that other
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applications, has the possibility to advance numerical dates like the one you are mentioning
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us. In geology, lots of applications, almost all sedimentary environments, that
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is, where material accumulates. In geology they can be dated. So it
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' s very important, for example, to determine rates for every flood in
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a basin. Let' s put it this way, then with luminescence you
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can date first, because the geologist identifies the levels of flooding and with that
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you can date all the floods that have had that basin and have to create
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a database of periodicity or recurrence. The same can be done with tsunami deposits
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and hurricanes. In other words, almost all geo- threats can be dated
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with luminescence. And there, in geotechniques of the soils in agronomy a lot.
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It has many applications in luminescence. At the end of the day,
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with that information, you have a baseline for designing predictive models for the future,
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especially as you mention it. And besides, you' re a geo
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- threat specialist like one of them. That' s right, that'
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s the goal, that' s the goal to be able to have in
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Colombia a table that tells me every time there was a megasoname, because here,
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on the Pacific coast or in the Caribbean, let' s hope we
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can get to that too. Gloria. Thank you so much for your time,
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for sharing your knowledge and experience. It' s really been a pleasure
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and an honor to have a conversation with you. We continue to produce scientific
33:30
content on this podcast. The strong future. Thank you very much Juan Guillermo
33:35
And here to order whenever you want