Science in Christian Perspective
Real World Stratigraphy and the Noachian Flood
William F. Tanner*
Geology Department, Florida State University
Tallahassee, FL 32306-3026
From: PSCF 48 (March 19996): 44-47.
Many people have assumed that all the rocks at the surface of the earth were deposited during the flood associated with the name of Noah (Gen. 6-8). This position, if it were to be substantiated, would eliminate all of geological history. It would nullify all the observational procedures that thousands of experienced geologists have used over many years of field work to record and understand the stratigraphic sequence. It would also destroy the geological principle, "The present is the key to the past."
One early version of "Noachian stratigraphy" was limited to the moraines and till sheets of Europe and North America: the widespread ice-age deposits which have now been shown to have had a glacial origin. Their very great extent led a few early observers to attribute them to a global flood. However, very little attention was paid to the fact that they are not present across three entire continents (Africa, Australia, and South America) and large parts of other continents (much of Siberia, China, India, the southern half of the United States, and Mexico). Therefore, they cannot represent a global marine phenomenon.
A more inclusive version attributes all strata, wherever they may be found, to the Noachian deluge. Neither interpretation has been based on geological field work, but on what might be said to have been an armchair exercise, without much data.
Because many metamorphic rock bodies were once sedimentary rocks (prior to long, slow alteration), this approach crams almost all of geological history into a few monthsócontrary to the facts. The very slow solid-Earth processes that move sediments downward to great depths within the Earth, where they are converted by pressure and heat to metamorphic rocks before they are moved slowly upward again, would have had to occur in a few months.
This approach also denies the obvious fact that the products of erosion of older mountain ranges are incorporated, almost simultaneously, into thick sedimentary sequences which will not be converted into mountain systems until much later. That is, at any given momentóincluding nowówe can note (1) the uplift and erosion of major mountain ranges, such as the Himalayas, and (2) the accumulation of thick stratigraphic sequences which will be folded, uplifted, and eroded at a much later date, such as the 18-km-thick (60,000-ft-thick) pile measured underneath southern Louisiana today. This is a mechanism that requires simultaneous subaerial (but not subaqueous) erosion, on the one hand, and subaqueous deposition on the other. The latter, in the global picture, is an almost synchronous result of the former. This thoroughly-documented and well-understood process cannot operate under a global flood.
Geological field work has produced something quite different from the supposed global, but short-term, catastrophe that many people wish to infer from the Genesis record. For purposes of explanation of the critical differences, a simple model can be presented. In this model, one notes that sedimentary materials accumulate largely in relatively long, narrow beltsósometimes up to some hundreds of kilometers wide, and perhaps as much as a few thousand kilometers long. This is the geosynclinal model, and the facts summarized in the model have not been swept away by the advent of plate tectonics. Sediments deposited in the geosyncline were generally laid down, by more-or-less ordinary processes, on a slowly-subsiding floor in rather shallow water. In due time the sediments locally reached a thickness of 15-25 km, then were folded and squeezed into long, narrow mountain chains. In the overall process, part of the rock sequence was altered by pressure and heat to form a different category of materials (metamorphic rocks). This compression (lateral squeezing) was in effect a "sweeping-to-one-side" operation, which left wide areas without significant sedimentary cover.
The Appalachian Mountain system of eastern North America is such a mountain chain. A very thick sequence of sedimentary layers later was squeezed and folded into a mountain range, which has been eroding slowly to form the mountains that we can see today. These mountains are still being uplifted slowly, and the products of their erosion are being deposited now in depositional areas not too far away: primarily in the states of Virginia, North Carolina, and Louisiana. The agencies of transport that connect the erosion areas and the deposition areas include some well-known freight-carrying lines, including the Ohio and Mississippi Rivers.
The Himalayan Mountains are currently being squeezed and thrust upward at roughly one centimeter per year, and in the process, the thick sequence of sedimentary rocks which had been deposited previously is being folded. Therefore, it is becoming narrower in the map sense. The products of erosion now are being deposited not too far away, especially to the south: on the north shores of the Indian Ocean and to the northeast.
It is not necessary to think of only one geosyncline, or only one mountain range, at any one time. Two or more geosynclines might be accumulating sediments simultaneously, and two or more mountain systems might be under construction (and undergoing erosion) simultaneously. Furthermore, it is not necessary to avoid overlap between (a) filling of one or more geosynclines, and (b) folding and uplifting of one or more mountain systems. But it is necessary to recognize that very slow uplift and subaerial erosion of any given mountain chain is accompanied, essentially simultaneously, with very slow submarine deposition of the products of that erosion. Two examples were given above, but there are others today where the pertinent processes have been studied.
The field geologist who works on stratified (sedimentary) rocks, typically describes those rocks and measures (not guesses) their thicknesses with reasonable precision. This requires careful and detailed work, from older layers to younger, foot by foot and inch by inch (centimeter by centimeter). At the conclusion of his assignment, the geologist can say that he has measured (and described) a certain stratigraphic thickness of rock. I have worked on several such projects. To cite only one example, the Pennsylvanian (age) strata in western Arkansas are at least 12,000 meters thick, and they represent a very small part of geological time. "At least" refers to the fact that the upper limit is a fault; the original sequence was thicker before faulting, but how much thicker is not known. However, our incomplete knowledge today does not reduce the 12,000 meters.
A "composite stratigraphic section" can be made by matching measurements and descriptions from adjacent areas or regions, setting duplications (which are mostly easy to recognize) to one side, and then adding up the remaining thicknesses to find out what the total might be. Sediments in the folded mountain systemóthe Penokean Mountains, long ago worn down to a nearly flat surface on which Chicago is builtódo not overlap the sedimentary sequence in the Himalayan Mountains. Therefore, both total thicknesses must be included in the final grand total.
The value of a "grand total" should be of great interest to us. It can only be estimated, because suitable field work has not yet been carried out in all places. However, this kind of estimate carries with it the corollary that a more nearly correct versionóto be learned at some date in the futureówill be numerically larger than the present value. That is, our errors due to incomplete field work are errors of omission, not of addition. We will increase the numerical total as we fill in the gaps, but measuring additional thicknesses cannot possibly make the sum any smaller.
A general estimate of the combined (non-overlapping) thicknesses, for Cambrian time and later (that is, for Phanerozoic time), is 300 km of deposits, plus-or-minus 100 km. The high value is more likely than the low value, because it is almost impossible to find (or to have access to) the thickest part of the stratigraphic section while doing geological field work. The geologist ordinarily must settle for some high result, but not necessarily the highest.
If we accept (as being roughly correct) a radiometric age for the beginning of Cambrian time as 600 million years ago, we get a long-term average rate of accumulation of half a millimeter every year. This is a reasonable figure in terms of measured modern processes (excluding highly localized events). If, on the other hand, we think that this entire pile of deposits accumulated in the five months assigned to Noah's flood, we must assume 2,000 meters of deposition per day, or 83 meters of additional thickness every hour, coming from some large subaerial landmass, which in some mysterious way was not drowned by the flood. The key figure here is not the rate that can be calculated, but the total thickness: about 300 km of sediment. This figure does not include any part of the probably thicker Precambrian stratigraphic sequence, and therefore, it is a very low value.
Besides this unrealistically low result (300 km thick), we have an equally important problem of a different kind. The deposits of the past were not laid down in uniform sheets like a giant layer cake, or, for the earth as a whole, like a giant onion. Rather, they were concentrated in a few regions, here and there, as indicated above. A single stratigraphic section, covering a small slice of geological time (cited above), is more than 12,000 meters thick. One important aspect of this field result is that nothing has been added to this one stratigraphic sequence since it was squeezed and crumpled into the Ouachita Mountains, which in turn took place before an equally thick section was developed to the west, in Oklahoma. That is, after a relatively long time, deposition shifted from one site to another, some distance away. This kind of long-term history is what the geologist actually finds, but it is far from what we should expect for a very short global flood.
A third, serious problem rests on the fact that mountain systems are not uplifted instantaneously. At a more-or-less realistic (but high) rate of one centimeter of uplift per year, a mountain like Mt. Everest requires more than 900,000 years to reach its present height, provided erosion of the rock surface is somehow prevented during its uplift. If erosion is taken into account, this figure should be much larger. Such episodes of folding and uplift must be fitted between observable depositional sequences.
Finally, there is the problem of erosion of the mountains. Many field geologists have had to contend with the time gap that must be inferred along the more-or-less horizontal plane which separates younger, as yet not folded, rock layers (above) from highly contorted layers (below). The latter, where extensive, suggest a long history of mountain-making and concomitant folding. But these mountains must have been eroding greatly to produce a more-or-less flat surface, and this erosion (removal) requires that millions of years of history are missing locally along this plane. Nevertheless, all of this missing time must be integrated into the stratigraphic sequence at that site.
No "Layer Cake"
The picture obtained by the field geologist is definitely not a uniform series of coats, like the paint that an artisan might put on an expensive piece of cabinet work. In fact, "layer cake stratigraphy" is commonly a term of derision. A better picture, although still not complete, is as follows: first, a sequence of layers is deposited here at this one locality, then there is a lateral compression and folding of these layers; second, a set of layers is deposited over yonder, followed by squeezing of this second set of layers; third, a set of layers is deposited elsewhere, again followed by deformation; and so forth, up into fairly high numbers. There is nothing global about any part of the checkerboard pattern in this depositional history.
The radiometric dates that are now availableómore than 1,000,000 of themóagree with the "checkerboard deposition" scheme outlined above, but are directly contrary to the layer-cake interpretation that must follow any effort to use the Noachian deluge as the model for stratigraphic history. The time-mosaic of deposition, reviewed here, does not arise from the radiometric dates, but instead is a necessary result of the geological field work. The mosaic was established first, many decades ago; the radiometric dates were added later. After the mosaic had been established firmly, by means of field work, it became possible to examine radiometric dates and to note that they are consistent with the mosaic model. However, the mosaic pattern and the great amount of time required are necessary results from the field work. The radiometric dates do not create nor alter the framework. They provide only some additional detail.
The basic stratigraphic model was established long before any dates were available from radioactive materials. It was known even then that the time intervals had to be very great. Various other methods of dating ó not as accurate as radiometric procedures ó were available to help estimate the amount of elapsed time. The results were startlingly large. Radiometric dating has added some precision that was lacking previously and an increase in the total time involved.
The long slow processes of folding and uplift, erosion, transport and depositionóvisible and measurable todayórequire that the business of emplacing the surface rocks on our planet has had an extremely long and complicated history. The physical characteristics of sedimentary rocks indicate that deposition was particularly slow. The tremendous thickness of the composite stratigraphic column similarly shows that this history cannot be explained in terms of one or two catastrophic events. Instead, as the experienced field geologist well knows, there have been many catastrophes, and they were not global.
For further reading on rates of various processes:
Fairbridge, R.W. (ed.), 1968. Encyclopedia of Geomorphology. Reinhold Book Co., New York; pp. 47, 169-172, 205, 224, 262-268.
@BODY TXT 0 9P =Garrels, R.M., and F.T. Mackenzie, 1971. Evolution of Sedimentary Rocks. W.W. Norton and Co., New York; pp. 121-124, 199, 267-270.