Universidade Fernando Pessoa
Porto, Portugal
Sequence Stratigraphy studies the stratigraphic cycles labeled “sequence”. They are deposited during sea level cycles of 3rd order (time duration ranging between 0.5 and 3.0 My)1. The term “sequence” adopted by Vail1, in 1977, was initially proposed by Sloss2 to define the stratigraphic intervals bounded by major tectonic discontinuities in American cratonic basins. What some geologists call, nowadays, “sequence” or “sequence cycle”3 does not correspond to the Sloss' original definition. They often use the term sequence to coin sedimentary cycles with different hierarchical levels. In the same way, “sequence stratigraphy” is very often applied to describe the analytic study of all stratigraphic cycles and not only those associated with eustatic cycles of 3rd order. Such practices introduce a lot of confusions on (i) the hierarchy of the stratigraphic events, (ii) the lithological predictions and (iii) the scientific approach used in the stratigraphic studies. Etymologically, sequence stratigraphy, is just the study of a part of a larger whole. The whole is Stratigraphy (1), which can only be understood by a holistic or systemic approach. In this notes, we will approach stratigraphy globally. We will study the succession and the interconnections between all stratigraphic cycles, using field, subsurface and seismic data. The term “Systemic Stratigraphy” will be used in place of sequence stratigraphy because it emphasizes better the global thinking and the interlinking between the different geological parameters affecting stratigraphy.
Several geologists have proposed “Cyclostratigraphy”. However, the term cyclostratigraphy is already used to dub the study of the sedimentary intervals deposited in association with the orbital Milankovitch cycles4. In fact, young sediments can be classified on the basis of oxygen isotopes fluctuations to express the Earth's paleothermometry5, i.e. the relative changes of the cryosphere (the zone of the Earth where ice and frozen ground are formed6) in response to Milutin Milankovitch cycles (2). We will not break geological complex phenomena, such as stratigraphy, into pieces to understand the behavior of the whole from the properties of its parts7. On the contrary, will approach stratigraphy, in terms of systems thinking, avoiding the conventional analytic method proposed by Descartes, in which scientific descriptions are believed to be objective, i.e. independent of the human observer and the process of knowing. Actually, the majority of scientists less and less accept the conventional Cartesian approach. In fact, we are going try to progress from general to particular, i.e. from the whole to its parts, assuming that:
(i) Nature and characteristics of Stratigraphy are always different from the mere sum of its parts8.
(ii) Theoretical knowledge precedes stratigraphic observation9.
(iii) What is observed depends not only upon what there is to be seen, but also upon what the observer has seen before10.
Explorationists, and particularly seismic interpreters cannot recognize on seismic profiles deltaic progradations if they do not know what is a progradation, or if they do not know what is a delta. It is superfluous try to understand the infilling of a sedimentary basin in isolation, i.e. independently of:
(i) Global stratigraphy,
(ii) Tectonics,
(iii) Climate and
(iv) Associated biological processes (3).
Earth's problems, and particularly those related with hydrocarbon exploration, in which geological and biological processes are interlinked, cannot be understood in isolation. They are interdependent and interconnected. They are “systemic problems” as dubbed by F. Capra11. The new “systems thinking” paradigm12, which will be followed all along of these notes, takes into account that:
(i) The more we study the major problems of our time (geological, biological, social systems or ecosystems), the more we come to realize that they cannot be understood in isolation.
(ii) The properties of the parts of a system can only be understood from the organization of the system itself13.
________________________________________________________________________________________
Notes (Preface), (see Bibliography):
1-see Vail (1977).
2- see Sloss (1963).
The term sequence used by Sloss is also misleading. In fact, Sloss cut or subdivided the stratigraphy of the american cratonic basins in different building intervals. However, the term sequence used firstly by Sloss comes from the latin word sequere, which means to follow and not to cut. In latin, to cut, is secare (P. Bouisset, oral communication).
3- see Duval (1993).
4- see Dictionary Geology.
5- see Macdougal (1996), pp.
6- see Macdougal (1996).
7- see Capra (1996), pp. 19.
8- see Capra (1996), pp. 29.
9- see Popper (1984 ).
10- see Popper (1981).
11- see Capra (1966).
12- see Soukhotine (1983).
Each paradigm crosses three phases. In a first phase, a large majority of scientists shows against it an implacable hostility, processing its ineptitude, and they refuse to grant it some scientific value. At this phase, it is not yet a paradigm to properly speak, but simply a new promising theory. The second phase is the time of recognition. The majority of scientists integrates it to science. Finally, it becomes to the eyes of everybody the most natural thing of the world, while, already, the most sagacious are wondering if the moment has not come to change it. Soukhotine summarize these phases by three well known french statements.
First phase: “Mais c'est de la folie”. Second phase: ”Tiens, c'est pas si bête”.
Third phase: “Seigneur, mais c'est bête comme tout”.
13- see Capra (1966).
________________________________________________________________________________________
Footnotes (Preface):
(1) The real business of stratigraphy is the correlation of events (Ager, 1984).
(2) “Oxygen has three isotopes, of which 016 is by far the most abundant, making up more than 99%of normal oxygen. However, all oxygen also contains small amounts of both oxygen 17 and oxygen 18. A molecule of water is thus likely to be H2O-16, but it could also be H2O-18. During the process of evaporation, the lighter water molecules - those containing oxygen 16 - have a greater probability of evaporating. The oxygen isotopes in the water are fractionated in the process water vapor being lither (containing a higher percentage of oxygen 16) and the remaining liquid becoming heavier (with a larger fraction of oxygen 17 and oxygen 18) as evaporation proceeds5. Surface and bottom-dwelling creatures preserved in the sediments, particularly those which precipitate their calcium carbonate shells, using the dissolved components of seawater as raw material, can give indications about the temperature difference between the surface and the bottom waters of the ancient oceans, by the relative abundances of oxygen isotopes in the shells. Also, during the glacial times, the changes in the oxygen isotopes of seawater due to the formation of polar glaciers may be as great as those due to temperature fluctuations6.
(3) “There is rarely facts lack, only intellectual lock” 14. ____________________________________________________________________________________________
The majority of geologists performing “Sequence Stratigraphy” uses the analytic, or reductionist approach. They follow the old analytic cartesian paradigm with which western science has been progressing (1) :
“The whole is equal to the sum of its parts” 1
Most of the explorationists still believe that in geological complex system, such as Tectonics, Paleontology, Stratigraphy, etc., the behavior of the whole can be understood entirely from studies of its parts. For instance, they think, that it is possible to understand (not confound with describe) the infilling of a sedimentary basin just by making analytic studies of the stratigraphic building blocks (2) or “sequences”, as coined, in 1977, by P. Vail2. They work by induction and they try to progress from the parts to the whole, rejecting K. Popper's statement3:
“Theory precedes Observation”3
However, one should know that the great shock of the 20th century science, has been that:
“Systems cannot be understood by analysis”4
The holistic or “contextual” scientific approach known as “systemic” and the way of thinking known as “Systems Thinking”, which implies that the properties of the parts of a whole are not intrinsic properties, are undoubtedly finding increasing acceptance in scientific community5. In Systemic Stratigraphy, the properties of the parts can only be understood within the context of the whole, i.e. the cartesian relationship between the parts and the whole has been reversed. In Stratigraphy, as well as Tectonics, etc., it is impossible to describe and understand correctly an outcrop outside of its regional and global geological contexts. In addition, the geological context cannot be approached just by analytic studies of the outcrops. The stratigraphic interpretations of electrical logs, seismic profiles, as well as the study of petroleum systems follow the same methodological principles. Detailed studies of the hydrocarbon parameters, such as source rocks, maturation/migration, reservoir, trapping or retention, when performed outside of the geological context of the petroleum system, do not give a real understanding of potential hydrocarbon accumulations. Shortly, the time when Exploration Managers prevented explorationists, and particularly seismic interpreters, to know the location of seismic profiles, in order to avoid them to make hypothetical-deductive interpretations, is over. Besides, the conjecture of a living earth, formulated in modern scientific language as Gaia hypothesis by J. Lovelock,6 strengthened systems thinking approach and corroborated the hypotheses that:
(i) Geological and biological processes are all interlinked, and
(ii) The Earth is a self-regulating organism.
Earth is nowadays considered by the majority of the géoscientistes as an open system (3) far-from-equilibrium and self organized critically7, i.e. a dissipative structure using Prigogine's terminology8. It receives a continuous flux of matter or energy from the sun which allows it to survive, i.e. to encounter instabilities leading to new forms of order that move it farther and farther away from the equilibrium state, that means, away from death.9 A process of self-regulation is the key to Lovelock's Gaia theory. Lovelock knew, from astrophysics, that the heat of the sun has increased by 25% since life began on Earth. However, in spite of this increasing, Earth's surface temperature has remained more or less constant, at a level comfortable to life during the past four billion years. He explained this self-regulation (4) by a tight interlocking between the planet's living parts (plants, microorganisms, and animals) and its non living parts (rocks, oceans and the atmosphere)10. Such an interlocking does not allows longer to think of rocks, animals and plants as being separated. Capra in Web of Life (1996) gives a nice illustration of the interconnections between living and non living parts of Earth using the carbon dioxide cycle:
“The Earth's volcanoes have spewed out huge amounts of carbon dioxide (CO2) for millions of years. Since CO2 is one of the main greenhouse gases, Gaia needs to pump it out of the atmosphere; otherwise it would get too hot for life. Plants and animals recycle massive amounts of CO2 and oxygen in the processes of photo-synthesis, respiration, and decay. However, these exchanges are always balanced and do not affect the level of CO2 in the atmosphere. According to Gaia theory the excess of carbon dioxide in the atmosphere is removed and recycled by a vast feedback loop which involves rock weathering as a key ingredient. In the process of weathering, rocks combine with rainwater and carbon dioxide to form various chemicals, called carbonates. The CO2 is thus taken out of the atmosphere and bound in liquid solutions. These are purely chemical processes that do not require the participation of life. However, Lovelock and others discovered that the presence of soil bacteria vastly increases the rate of rock weathering. In a sense, these soil bacteria act as catalysts for the process of rock weathering, and the entire carbon dioxide cycle could be viewed as the biological equivalent of the catalytic cycles studied by Manfred Eigen. The carbonates are then washed down into the ocean, where tiny algae, invisible to the naked eye, absorb them and use them to make exquisite shells of chalk (calcium carbonate). So the CO2 that was in the atmosphere has now ended up in the shells of those minute algae. In addition, ocean algae also absorb carbon dioxide directly from the air. When algae die, their shells rain down to the ocean floor, where they form massive sediments of limestone (another form of calcium carbonate). Because of their enormous weight, the limestone melt and may even trigger the movements of tectonic plates. Eventually some of the CO2 contained in the molten rocks is spewed out again by volcanoes and send on another round in the great Gaia Cycle. The entire cycle - linking volcanoes to rock weathering, to soil bacteria, to oceanic algae, to limestone, and back to volcanoes - acts as a giant feedback loop, which contributes to the regulation of the Earth's temperature. As the sun gets hotter, bacterial action in the soil is stimulated, which increases the rate of rock weathering. This in turn pumps more CO2 out of the atmosphere and thus cools the planet”.11
In this perspective, the Wilson's cycles12 are hypercycles of multiple feedback loops. Actually, supercontinents, such as Proto-Pangea or Pangea, were broken into several continents and dispersed by ocean-floor spreading. Then, by consumption and final excision of the ocean-floor by subduction, the continents were gathered to form, again, a new supercontinent. Eventually, this new supercontinent was broken again by new rifting, and so on. The essential properties of Earth, as those of any organism, or living system, are properties of the whole which none of the parts have. They arise from the interactions and relationships among the parts.13 In a geological systemic approach, the description and the understanding of the parts of a system is possible only knowing the organization of the whole, i. e. the regional and global geological contexts. Systems thinking is holistic. It concentrates not on basic building blocks, but on basic principles of organization. Thus, Stratigraphy, which by itself is at the same time a part of a larger whole, i.e. Geology, can not be concentrated in detailed studies of outcroppings, but on basic principles of a network interlinked the different stratigraphical components. This new approach raises an important question. If everything is connected to everything else, or in other words, since all natural geological phenomena are ultimately interconnected, in order to explain any one of them we need to understand all the others, which is obviously impossible.14 Accordingly, any complete and definitive prediction in geology, and particularly in hydrocarbon exploration, is unachievable. Contrary to the Cartesian belief (certainty of scientific knowledge), in the new scientific paradigm “systems thinking” it is recognized that:
(i) Geology cannot be understood completely by analysis.
(ii) Geological concepts and theories are limited and approximate. They can never provide any complete and definitive understanding of geological problems.
(iii) Geological predictions are qualitative and not quantitative.
_________________________________________________________________________________
1- see Capra (1996), pp. 38-39.
2 - see Vail (1977).
3 - see Popper (1984).
4 - see Capra (1996), pp. 38-39.
5 - Ibid., pp. 17.
6 - see Lovelock (1979).
According to different modern physicists, such as Bernal, Schroedinger and Wigner, life is a member of the class of phenomena which are open or continuous systems able to decrease their internal entropy (thereby increase order) at the expense of substances or free energy taken in from the environment and subsequently rejected in degraded form. We can now see that this definition would apply equally well to eddies in a flowing stream; to hurricanes, to flames, or even to refrigerators and many other man-made contrivances.
7 - see Bak (1996).
Self-organized criticality is a new way of viewing nature. The basic picture is one where nature is perpetually out of balance, but organized in a poised state - the critical state - where anything can happen within well-defined statistical laws.
8 - see Prygogine (1967).
9 - adapted from Prygogine (1980).
10 - see Capra (1966), pp. 104, and Lovelock (1991).
11 - Quoted in Capra (104).
12 - see Nance (1988).
Wilson cycle is a tectonic cycle postulate by Tuzo Wilson, involving rifting of a continental plate, the separation of the parts by ocean-floor spreading between them, consumption and final excision of this ocean floor by subduction and formation of an orogene at the suture. New rifting may start the cycle again.
13 - see Capra (1966), pp. 37-41.
14 - Ibid., pp. 41.
15 - see Fischer (1984), pp. 131.
16 - Quoted in Capra (1982), pp. 55.
____________________________________________________________________________
Footnotes (Systems Thinking & Gaia Hypothesis):
(1) In the old cartesian paradigm, physics has been the model, and source of metaphors, for all the sciences. Descartes' statement: “Philosophie est comme un arbre. La racine est la métaphysique, le tronc c'est la physique et les branches sont toutes les autres sciences”, 1 is very significant in this subject.
(2) The cartesian paradigm asserts that the edifice of science must be build on firm foundations (fundamental laws, fundamental principles, basic building blocks, etc.). In the new systems thinking paradigm, the metaphor of knowledge as a building is being replaced by that of the network.4
(3) In an open system entropy or disorder decrease; subsequently, the 2sd law of thermodynamic cannot be applied.
(4) In the Greek mythology, Gaia was the earth's Goddess, wife of Uranus (God of the sky) and the mother of the Titans.
_____________________________________________________________________________
The concept of model varies through an enormous spectrum of meanings. Similar words found in literature of the philosophy of science include: paradigm, homology, simile, analogy, figure, metaphor, explanation, theory, catachresis, artifact, and exemplar1.
Geologists chose to paint a picture of the reality by building a model which is often expressed in the compact language of the mathematics. They try encode experiences of the real world into the symbols and rules of a mathematical formalism and then make use of this formalism to generate predictions2. Similarly, the word observation has its own spectrum of meanings. These range from detached observer totally isolated from the target system, to the diary of a lover:
- the spectrum of participation or involvement3.
Observations and real world facts are the building blocks from which geologists construct the visions of the reality. But each of these views is merely a small slice of the reality, basically a piece in a cosmic jigsaw puzzle. It is the process of putting the pieces together to form ever more accurate pictures that constitutes what in science is called a model4. Observations in every day geological parlance are the memory traces left behind geologists's brains when outside world impresses itself upon them via their sensory channels of sight, sound, touch etc.. In the system approach, observation is done in the ambience of a model, while the model is created in the context of an observation strategy. The rotation of this cycle advances the adequacy of the model and the quality of our observations, and hence our understanding of the world around us. In fact, instead of simply describing all geological and geophysical features by simple cataloging process or “stamp collection”, the models and simulations reveal the general mechanisms.
“Observing details may be entertaining and fascinating, but we learn from generalities”. ... wrote Bak5...
Seismic lines should interpreted under the influence of a sedimentary model. Then, the model can be be modified according to the interpretation of the lines. In this way, we evolve in understanding and the lines may then be reinterpreted according to a new model, and so on. Since, geological hypotheses or models, called paradigm shift, such as Plate Tectonics, Deep Time, Systemic Stratigraphy, etc., have been advanced, they involved representation of physical reality by letters, words or figures. However, all these representations should not be confused with the real things. In stratigraphy, the word sandstone, or turbidite, is not itself a sandstone or a turbidite. In the same way, a stratigraphic model, such as that proposed by P. Vail6, which will be described in the next chapter, should not be mistaken as the reality, but only as an incomplete virtual reality. In this subject, the work of art of the Belgian surrealist René Magritte:
“Ceci n'est pas une pipe”
is very illustrative. Magritte' purpose was to make people aware that an image or model is not to be confused with real thing it represents. “Being” and “Representing” are not the same7. Contrary to the idea that observations in geology are the facts upon which scientific hypotheses are based (1), it must be said that the majority of geological hypotheses were formulated a priori in order to explain problems raised by observations. They have not been built from a collection of detailed geological observations using an inductive approach8. The Plate Tectonics hypothesis (2), which the majority of the geologists adopted, was initially formulated to explain five major geological problems 9:
1) Why the specific gravity of the whole earth is 5.4, whereas the specific gravity of the earth's surface rocks ranges between 2- 3.5?
2) Why the earth's magnetic field had reversed its direction many times during the last millions years?
3) Why earthquakes and volcanoes occur primarily within certain geographic zones, such as the Pacific ocean borders?
4) Why P and S seismic waves are reflected and bent as they travel through the earth?
5) Why west coast of Africa and east coast of South America reveals that the coastline fit together very nicely, and why when fitted together regions of fossilized remains, as well as minerals deposited, on each coast, overlap each other?
Plate Tectonics theory, not only took all these questions into account, but explained the subsequent geological hypothesis:
a) The material below the Earth's surface must be denser than that at the surface.
b) The earth has a magnetic field which can be normal and reversal.
c) The occurrence of earthquakes and volcanoes, and their higher frequency, in certain areas of the globe.
d) The presence of different kind of solids and liquids below the earth's surface.
e) The close fit of the western and eastern coastline of Africa and South America by a better mechanism than that proposed in 1920 by A. Wegner (continental drift).
In the same way, in petroleum geology, for instance, the question very often asked:
Have you all information to evaluate the hydrocarbon potential of this basin?
is not the good question to ask to an explorationist. The real question to ask is:
“What are your ideas to evaluate the hydrocarbon potential of this basin?”
Indeed, observations (seismic, field, subsurface, etc.) are usually presented as the basis of the exploration. However, in reality, explorationists think with ideas and not with observations. Observations do not create ideas. Ideas create observations. Ideas are, in fact, integrated patterns that derive from experience not from observations 10.In other hand, a geological idea will emerge into the consciousness of a group of explorationists somewhat after the group knowledge evolves to the necessary minimum level to support the cognition of that idea 11. In hydrocarbon exploration, as well as in all branches of science, explorationists do not always find what they expect to find. Their predictions do not always work out. The payoff is the understanding that the hypothesis on which the prediction was based needs to be modified. However, sometimes, accidental discovery not sought intentionally result in an even greater payoff. This phenomenon known as Serendipity has an important role in exploration, where a large number of oil discoveries were mere accidents12. The late hydrocarbon discoveries in the cratonic North Sea basin are classical examples of serendipity. Also, several major discoveries in the basement and substratum highs, as well as in volcanic sediments were accidental discoveries, even if the explorationists in charge refuse to admit it. Such a reaction is particularly frequent when the well prognosis is written in a metaphysical way (3). Nevertheless, even in an accidental discovery, one needs the appropriated background to recognize its value. As L. Pasteur (1880) said :
“Dans les champs de l'observation le hasard ne favorise que les esprits préparés” 13.
The importance of serendipity is science was clearly recognized by C. Bernard:
“Ceux qui ont une croyance excessive dans leurs idées ne sont pas bien armés pour faire des découvertes” 14.
Thus, in system thinking approach, geological predictions are limited and approximate. Geology can never provide any complete and definitive understanding of the nature. So, the bigger an exploration domain is and more wildcat are drilled, more chances of finding additional hydrocarbon reserves there are. This conjecture is true particularly when the exploration is based on working teams that test and reformulate the new ideas15 advanced by other explorationists. A working team is a network of communication. It generates feedback loops and acquires the ability to regulate itself 16. A real working team, or real task force maintains an active network of communication and learn from its mistakes. The consequences of a mistake will spread through the network and return to the source along feedback loops. Thus, the working team correct its mistakes, regulates and organizes itself. In other words, a real working team, or a real task force is a self organized critically social structure 17, it is much more than the sum of its components. To end this chapter, one should not forget that, nowadays, geologists view earth history as a matter of evolution in which some changes are unidirectional, others cyclic, and still others are random fluctuations, while the whole is punctuated by smaller or greater catastrophes. The prime tasks of modern historical geology are to separate the local signals from the global ones, to plot the relationships of global patterns both to time and to each other, and to search for the forces that drive these varied processes 18. On the other hand, what geologists judge to be the most likely explanations of geological events perceived around us depend only on the facts as they are presently known. But this is not so, or even not nearly so. A great deal of what geologists currently believe to be true depends not so much on the facts as on the order in which the facts were discovered19. Also, the success of certain geological models is just the result of incessant propaganda and infiltration on educational systems. What is and is not scientific is a time-dependent phenomenon. Also, one should not forget that scientific rules - or “laws” or “models” - are not absolute as a lot of geologists would like to believe20.
___________________________________________________________________
Notes (Geological Models, Reality & Serendipity), (see Bibliography):
1- see Abraham (1994), pp. 18.
2 - see Casti (1995), pp. 3.
3 - see Abraham (1994).
4 - see Casti (1995).
In the scientific method there are three stages: Observation, Hypothesis and Experimentation. Traditionally, it is argued that the scientific process starts with observation but in a field that is already well developed - as Geology, for example - we often start at the hypothesis stage. The term science is more a verb than a noun. Science is something that people do more than a property that distinguish a field of intellectual endeavor from another.
5 - see Bak (1996).
6 - see Vail (1977).
7 - quoted in Wynn (1997), pp.107.
8 - see Popper (1981).
9 - see Wynn (1997), pp. 68-74.
10 - adapted from Roszack (1994).
11- adapted from Abraham (1994), pp. 61.
12 - see Roberts (1988).
13 - quoted in Capra (1996).
14 - see Claude Bernard
15 - see Soukhotine (1983), pp.142.
A new idea points when the fantasize takes it and not at the time that we wish its coming. Waiting for an idea, would be to win the lottery at a fixed moment in advance. In addition, one does not play to the lottery unless to have bought a ticket. In other words, only those who have a good logic device, who have large knowledge and an efficient investigation program, can expect a scientific success.
16 - quoted in Capra (1996).
17 - see Bak (1996).
18 - see Macdougal (1996).
19 - see Hoyle (1993), pp. 71.
20 - adapted from Casti (1993)
A scientific rule should be:
1) Explicit:
No ambiguity in the statement of the rule and it should not require private interpretation to employ the rule for prediction or explanation.
2) Public:
Open to public scrutiny. It should be presented in the open literature and should be tested by anyone who has the time and the desire to do so, an d not only to the “Divinely inspired” (different with several religions' rules).
3) Reliable:
Have stood the test of the time. Generally speaking, the weight of evidence in favor of the rule must be quite overwhelming before we dignify the rule by labeling it scientific.
4) Objective:
Be relatively free of the investigator bias. In other words, the rules are independent of social position, financial status or cultural background of the investigator.
_______________________________________________________________________________________________
(1) M. P. A. Jackson reminded me the famous Nitchze's statement “They are no facts, only interpretations”.
(2) Do not confuse Plate Tectonics theory with the Continental drift hypothesis.
(3) A metaphysical well prognosis is a prognosis that cannot be tested, in the sense pro- posed by K. Popper for demarcation between science and pseudo-science. Indeed, very often, well prognosis are written in such a way that negative and positive well results are predicted. Examples of exploration metaphysical statements taken from internal reports: (i) “there is a trap but the closure is not assured”, (ii) “the source rocks can be mature or not depending on heat flux”, (iii) “reservoirs rocks are present but their petrophysical characteristics are unknown” or “We don't know anything about the source rocks of East Siberian Basin, but they can be oil-prone”. Geologists making such statements are always right. They never make mistakes and their professional career are assured. Un- fortunately, they never make any scientific improvement, since scientific knowledge and experience are direct consequences of our mistakes.
to continue press
next
Send E-mail to carloscramez@gmail.com with questions or comments about this course.
Copyright © 2001 CCramez
Last modification:August, 2014