Paleoclimatology


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paleoclimatology The End Permian Mass Extinction

Introduction
Think of a world which existed 290 million years ago. As you look out over the terane in front of you, you think that you are on an alien planet. You see volcanoes spewing ash and lava. Beside them is the ocean which is swarming with many different species of echinoderms, bryozoans and brachiopods. As you look down onto the sea floor you are amazed at the countless number of starfish and urchins. Some animals leave you can't even describe and you have no idea even what phylum they belong to. This is a world at its height in diversity of oceanic species. Millions of wonderous species existed at this time in the ocean and most of them will never appear again in earth's history. In the geologic time scale, a million years means nothing but this time things are different. In the blink of an eye things now look vastly different. The world once again looks alien but it looks worse than before. The sky is dark. Oceans are no longer teaming with life. The stench of rotting flesh and plants hangs in the air. The ground trembles under your feet. You feel an intense heat burning you face. You look up and see one of the greatest show of force mother nature has ever shown. Whole mountains are being thrown in the air. Lava and debris are everywhere. You ask yourself, what has happened? Will life ever exist on earth again?

The above paragraph is a primative example of what the end of the Permian period could have looked like. Marine life was devastated, with a 57% reduction in the number of families (Sepkoski, 1986) and an estimated 96% extinction at the species level (Raup, 1979). Oceanic life suffered the most but terrestrial life forms were also greatly affected. There was a 77% reduction in the number of tetrapod families (Maxwell and Benton, 1987). All major groups of oceanic organisms were affected with the crinozoans (98%), anthozoans (96%), brachiopods (80%) and bryozoans (79%) suffering the greatest extinction (McKinney, 1987). The end of the Permian and beginning of the Triassic periods marked the single greatest extinction event the world has ever faced.

Timing of the Extinction
There are many questions regarding the timing of the extinction at the end of the Permian. One of the main questions was the even a catastrophy or gradual. There is evidence for both senarios. Some of the evidence supports an ectraterrestrial even such as a metior. Other evidence supports the theory of the ocean and terrestrial environments slowly changing.

Geochemical evidence
The research done by Xu Dao-Yi and Yan Zheng (1993)gives evidence for an extraterristrial event. They made a table which showed the distribution of carbon 13, iridium, and microspherules across the P/T (Permian and Triassic) border. The section was over a thickness of 35 cm. They found a sudden depletion in C-13 falling from a value near zero to a minimum of less than -6% in some samples. Similar patterns of C-13 have been observed in more than five P/T sections in China. Some other scientists like Baud et al (1989) argue that what could have caused this anomaly is the result of a depositional hiatus or erosional disconformity. Xu and Yan argue that there is no evidence for a significant hiatus and that Baud et al. Even made a mistake in the timing of their rock layers. "If the PTB [Permian Triassic boundary] is considered a catastropic event, a short-time hiatus should be expected and is in fact a reasonable consequence of a catastrophic event" (by Xu Dao-Yi and Yan Zheng, 1993). But what is the significance of C-13 being associated with catastrophic events? Hsu et al. (1982) said that they suggested that carbon isotope anomalies are related to microplankton productivity. We will touch again on this later in the paper. Therefore, the sudden C-13 change may indicate the exact stratigraphic position of the mass killing event at the PTB. Analysis of iridium (Xu Dao-Yi and Yan Zheng, 1993)in the layer reveild some interesting results. High Ir values only occurs in the uppermost part of the layers. This means that the layer is close to the PTB. The concentration of Ir was at ... more

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Radio Carbon Dating




When we think of history, we think of important people, places, cultures, events, and much more.  The backbone of history rests on its chronology.  It gives us the "when" of basic analysis.  It gives us a frame of reference, the order of things. Before having an "absolute" way of determining dates, history was based in guesses and assumptions.  Many attempts were made to organize the dates of the past. Some of these attempts were made by geologist.  Geologist used the idea of "stratigraphic succession" (Renfrew, 1973) which is based on the "principle that when successive layers or strata are observed in position, the underlying ones are the earliest." (Pg. 23 Renfrew, 1973) By setting the layers in chronological order, it only gave a sequence not a real date.  Another method that geologist used in order to date, was the measuring of sediment deposit. They measured the rate at which sediment forms at the bottom of lakes; nevertheless, this method was unsuccessful because it relied in the assumption that the rate of sediment deposit is a constant. It is not. (Renfrew, 1973)
The most famous ways to date has been the Three Age System, which divides prehistory in the three ages that we have come to know as the stone, bronze and iron ages.  Eventhough this method is still used today, it only gives approximations, no absolute dates. (Renfrew, 1973)  There were other attempts to absolute date, but they all were still based in approximation, no real dates.   This made the past seem like a fog of facts and assumptions. Willard F. Libby, and a team of scientist from the University of Chicago, developed a method of dating to clear up the "fog" that made up our history. Libbys method was Radiocarbon dating. (Bowman, 1990)
In 1949, Libby announced the fist radiocarbon dates in a conference in New York.  This changed history forever.  While it created controversy, due to some peoples attachments to the old ways of dating and doubts in this revolutionary method, it proved to be the closest method to have an accurate chronology of history.  In 1955, to prove the accuracy or radiocarbon, Libby published a graph that showed the comparison of the results of radiocarbon dating of specimens from Egypt. These specimens had already an absolute known date.  The graph proved the accuracy of Libbys radiocarbon dating. Figure 1 (Renfrew, 1973)
Libby developed the method of radiocarbon dating though his observation of how cosmic rays create radiocarbon.  From outer space cosmic rays infiltrate earths atmosphere. In the upper atmosphere, these rays hit nitrogen and oxygen atoms in the air. (Renfrew, 1973).  When the neutrons of these highenergy particles (mostly protons) hit nitrogen atoms, Carbon 14 (C-14) is created. The nitrogen atom (atomic number 7) has an atomic mass of 14 (with 7 protons and 7 neutrons). When the nucleus of the nitrogen is hit by the cosmic rays neutrons, the atomic number of the atom decreases by one. The make-up of its atomic mass changes, a proton is emitted and the neutrons are increased by one; therefore, the atomic mass number stays the same. Because the atomic number has changed, a new element, carbon 14, with atomic number 6, has an atomic mass of 14 (with 6 protons and 8 neutrons). (Bowman, 1990) The reaction is 14N + n = 14c + p (where n is a neutron and p is a proton). The newly formed carbon 14 combines with the airs oxygen creating carbon dioxide; this is quickly assimilated into the carbon cycle. (Libby, 1955)
This C-14 is one of the three isotopes of carbon. The other isotopes are carbons 12 and 13.  C-14 is different from the other two isotopes because it is unstable or radioactive, hence the name radiocarbon. is absorbed in a nearly constant ratio in all living organisms. Because C-14 is continually created at a constant rate in the upper atmosphere, and distributed throughout the carbon cycle, the ratio of carbon 14 to carbon 12 is remarkably constant in both the atmosphere and living organisms. (Renfrew, 1973)  
Through the death of an organism, the spontaneous decay of C-14 takes place. Through Beta Radiation, a beta particle or electron, is emitted form the C-14 atom, ... more

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  • P: The End Permian Mass Extinction P: The End Permian Mass Extinction The End Permian Mass Extinction Introduction Think of a world which existed 290 million years ago. As you look out over the terane in front of you, you think that you are on an alien planet. You see volcanoes spewing ash and lava. Beside them is the ocean which is swarming with many different species of echinoderms, bryozoans and brachiopods. As you look down onto the sea floor you are amazed at the countless number of starfish and urchins. Some animals leave you can\'t even describe and you hav...
  • A: The End Permian Mass Extinction A: The End Permian Mass Extinction The End Permian Mass Extinction IntroductionThink of a world which existed 290 million years ago. As you look out over the terane in front of you, you think that you are on an alien planet. You see volcanoes spewing ash and lava. Beside them is the ocean which is swarming with many different species of echinoderms, bryozoans and brachiopods. As you look down onto the sea floor you are amazed at the countless number of starfish and urchins. Some animals leave you can't even describe and you have ...
  • L: Radio Carbon Dating L: Radio Carbon Dating Radio Carbon Dating When we think of history, we think of important people, places, cultures, events, and much more. The backbone of history rests on its chronology. It gives us the when of basic analysis. It gives us a frame of reference, the order of things. Before having an absolute way of determining dates, history was based in guesses and assumptions. Many attempts were made to organize the dates of the past. Some of these attempts were made by geologist. Geologist used the idea of str...
  • E: The End Permian Mass Extinction E: The End Permian Mass Extinction The End Permian Mass Extinction IntroductionThink of a world which existed 290 million years ago. As you look out over the terane in front of you, you think that you are on an alien planet. You see volcanoes spewing ash and lava. Beside them is the ocean which is swarming with many different species of echinoderms, bryozoans and brachiopods. As you look down onto the sea floor you are amazed at the countless number of starfish and urchins. Some animals leave you can\'t even describe and you have...
  • O: The End Permian Mass Extinction O: The End Permian Mass Extinction The End Permian Mass Extinction Introduction Think of a world which existed 290 million years ago. As you look out over the terane in front of you, you think that you are on an alien planet. You see volcanoes spewing ash and lava. Beside them is the ocean which is swarming with many different species of echinoderms, bryozoans and brachiopods. As you look down onto the sea floor you are amazed at the countless number of starfish and urchins. Some animals leave you can\'t even describe and you hav...
  • C: The End Permian Mass Extinction C: The End Permian Mass Extinction The End Permian Mass Extinction IntroductionThink of a world which existed 290 million years ago. As you look out over the terane in front of you, you think that you are on an alien planet. You see volcanoes spewing ash and lava. Beside them is the ocean which is swarming with many different species of echinoderms, bryozoans and brachiopods. As you look down onto the sea floor you are amazed at the countless number of starfish and urchins. Some animals leave you can't even describe and you have ...
  • L: Radio Carbon Dating L: Radio Carbon Dating Radio Carbon Dating When we think of history, we think of important people, places, cultures, events, and much more. The backbone of history rests on its chronology. It gives us the when of basic analysis. It gives us a frame of reference, the order of things. Before having an absolute way of determining dates, history was based in guesses and assumptions. Many attempts were made to organize the dates of the past. Some of these attempts were made by geologist. Geologist used the idea of str...
  • I: The End Permian Mass Extinction I: The End Permian Mass Extinction The End Permian Mass Extinction IntroductionThink of a world which existed 290 million years ago. As you look out over the terane in front of you, you think that you are on an alien planet. You see volcanoes spewing ash and lava. Beside them is the ocean which is swarming with many different species of echinoderms, bryozoans and brachiopods. As you look down onto the sea floor you are amazed at the countless number of starfish and urchins. Some animals leave you can\'t even describe and you have...