What Is the Use of the History of Geology to a Practicing Geologist? the Propaedeutical Case of Stratigraphy
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What Is the Use of the History of Geology to a Practicing Geologist? The Propaedeutical Case of Stratigraphy A. M. Celâl Şengör* İstanbul Teknik Üniversitesi (İTÜ) Maden Fakültesi ve Avrasya Yerbilimleri Enstitüsü, Ayazağa 34810, Istanbul, Turkey ABSTRACT A practicing geologist can benefit from the history of geology professionally in two main ways: by learning about past mistakes so as not to repeat them and by finding out about different ways to discovery. In this article, I discuss some aspects of the history of stratigraphy and point out that the concept of a stratum has shoehorned geologists into thinking time and rock equivalent, which has led to some serious misinterpretations of geological phenomena, such as the timing of orogenic events and the charting of sea level changes. I call this the “tyranny of strata.” The very name of stratigraphy comes from strata, but what it does is simply deduce temporal relations from spatial relations of rock bodies, including fossils, by making certain assumptions about processes, that is, invoking inevitably a hypo- thetical step. What we have learned from looking at the history of geology is that empirical stratal correlation, even when well controlled by index fossils, can never yield perfect temporal correlation, and any assumption that it does is doomed to failure. Geology progresses in a direction that it may soon be possible to date every package of rock in a way to know what process is being dated and where exactly. We can correlate only processes in time hypothetically, not rock bodies empirically. This is the most important lesson a stratigrapher ought to have learned from the history of his or her subject. For such lessons to be usable by professional geologists, they must be narrated by those who are familiar with geological practice as scientists. Online enhancements: appendix. To the memory of my dear friend, the great historian of geology, David Roger Oldroyd (1936–2014) Introduction One can have an interest in the knowledge of the only one way: by analysing them instead of past for its own sake, as part of one’sgeneral merely describing them, and showing how they knowledge: learning about history is entertaining have been built up in the historical development and makes one appreciate one’s own environment. of thought. (Collingwood 1946, p. 230) But this is not only why a geologist needs to know I am in agreement with this statement. Colling- about the past of his science. He needs it to ap- wood saw the job of the historian both as a phi- preciate what he is doing now and to learn how to losopher and as an antiquary. This is a viewpoint do it better. The great English philosopher and ar- that is unfortunately no longer in fashion with chaeologist Robin Collingwood wrote in his most most historians of our days. They seem to be fol- famous philosophical work, The Idea of History: lowers of the great romantic German historian But a mere inventory of our intellectual pos- Leopold von Ranke, who stated that the job of the sessions at the present time can never show by historian was simply to state “how it really was” what right we enjoy them. To do this there is (Ranke 1824, p. VI; wie es eigentlich gewesen). Ranke wrote this against those who considered Manuscript received March 14, 2016; accepted July 11, 2016; judging the past and forecasting the future as among electronically published November 2, 2016. the tasks of history (see his p. V and VI). Michael * E-mail: [email protected]. Grant pointed out that Ranke’s statement was [The Journal of Geology, 2016, volume 124, p. 643–698] q 2016 by The University of Chicago. All rights reserved. 0022-1376/2016/12406-0001$15.00. DOI: 10.1086/688609 643 This content downloaded from 128.135.181.068 on November 29, 2016 10:37:56 AM All use subject to University of Chicago Press Terms and Conditions (http://www.journals.uchicago.edu/t-and-c). 644 A. M. C. Ş ENGÖR probably inspired by the parallel statement “to say corroborated Suess’s model plus the subduction; exactly how things happened” by the “Syrian” see Şengör 2009a). Thus, a model as an attempt to satirist and novelist Lucian of Samosata (now Sam- capture the past is nothing more than the com- sat, southeastern Turkey; ca. AD 120–180) in his pletion in mind of the incomplete data we can How to Write History (Grant 1995, p. 94). That this gather on past objects and past processes, regard- is an unrealizable ideal had been appreciated al- less of how it is done, as long as it is internally ready during the Enlightenment, however; Wilhelm consistent and remains testable by further data. von Humboldt had famously written that This is what the great German geologist Leopold von Buch, Baron of Gelmersdorf, said in his inau- The job of the historiographer is the description gural speech in the Royal Prussian Academy of of what happened. But what happened is Sciences on April 17, 1806, concerning the nature available to our senses only in part. The rest of geology: must be felt, deduced, guessed. What does ap- pear of it is dispersed, torn up, isolated. What When geology manages to cast this great prog- joins up these pieces, what illuminates the in- ress from a shapeless drop to the sovereignty of dividual piece in the right light, gives the whole man into certain laws, then it would be worthy a shape, is hidden from direct observation. of being admitted into the community of the sci- That is why nothing is so rare as an absolutely ences, which, by supporting each other, attempt truenarrative.(vonHumboldt[1821]1959,p.153; to finish the work that nature had begun. (von see also Şengör 2009b) Buch [1808] 1870, p. 16) Humboldt’s thoughts are very familiar in spirit to The job of geological models is thus the “comple- every geologist, who in any introductory course tion” of the work of nature in the minds of the hears that the geological record is woefully incom- geologists, the construction of an intelligible pic- plete. To approximate what the past was like, we ture from the incomplete store of information avail- thus need to build models. As the Nobel laureate able to them. physicist Richard Feynman once said, we do not re- But the geologist never begins from scratch. create the past in our models, but we try to reenact There is and there has always been preexisting it as part of our attempt to re-create the cosmos in models of whatever object or whatever process he our minds. or she is trying to understand. The earliest my- The geologist tries to obtain a knowledge of the thologies of humankind are nothing but cosmolog- past of the geological processes he is interested in, ical (Jensen 1890; Gaerte 1914; Kirfel 1920; Hen- and in doing so he needs to create models in his ning 1947–1948; von Engelhardt 1979), geographical mind. The word “model” is commonly misunder- (Vater 1845a,1845b; Buchholz [1871] 1970; Lang stood by geologists who come from backgrounds 1905; Delage 1930; Rousseau-Liessens 1961, 1962, such as physics and chemistry. They think that a 1963, 1964; Wolf and Wolf 1983; Richer 1994), me- model must be a quantitative description of the teorological (Gilbert 1907; Engelhardt 1919), geo- process one is interested in. They do not seem to logical (Vitaliano 1973; Greene 1992; Şengör 2002; appreciate the fact that Charles Darwin’sandAl- Piccardi and Masse 2007; this book has two articles fred Russel Wallace’s hypothesis of the cause of on mythology-paleontology relationships; the en- biological evolution, natural selection, for exam- tire book was critically reviewed by Oldroyd 2008), ple, was a model that had no quantitative aspect and biological (Abel 1937, 1939; Edwards 1967; whatever (Darwin and Wallace 1857; Darwin 1859). Rudwick 1976; Riedl-Dorn 1989; Thenius and Vávra It was inspired by Thomas Robert Malthus’svery 1996; Mayor 2000, 2005; Gregorová 2006) models crudely quantitative model of the relation between (for a general and very scholarly overview of this a growing population and the augmentation of its entire subject from the viewpoint of a natural sci- food source (Malthus 1798, chaps. 1, 2), but Dar- entist—namely, both a chemist and a physicist— win’s and Wallace’s own model was entirely quali- who had a religiosity not dissimilar to that of Al- tative. Time has shown what a useful model it is. bert Einstein, see Schweigger 1836; also see von Eduard Suess’s model of orogeny was based on a Humboldt 1847). For the mythological views of crude analogy with a wound on a hand that tore the the Jews on scientific questions such as anatomy, skin, folded it on one side, and let blood well up on physiology, pathology, zoology, chemistry, geology, the other (Suess 1875, p. 28; 1878, p. 5), yet it proved physics, and astronomy, see Bergel (1880). Because to be a more accurate description of how orogeny of that ever-present preexistent “knowledge,” every happens than any quantitative model that was of- increment of knowledge added to geology builds fered until the rise of plate tectonics (which largely on, and is conditioned by, previous observations This content downloaded from 128.135.181.068 on November 29, 2016 10:37:56 AM All use subject to University of Chicago Press Terms and Conditions (http://www.journals.uchicago.edu/t-and-c). Journal of Geology HISTORY OF GEOLOGY AND THE PRACTICING GEOLOGIST 645 and hypotheses. However, no hypothesis can be graphic concepts, see Grabau (1921, p.