Conifers and the Coal Question

Conifers and the Coal Question

Reblogged thanks to: “Article by E.C.Jeffrrey, Harvard Univ in the Journal Science”

Jeffrey’s article covers some interesting information related to the formation of coal. The coal formation question is integral to evaluating the foundations of geological theory regarding the formation of sedimentary rock and coal formations. This article is interesting because it focuses upon the Morwell coal seams in Australia which are of a depth in certain areas exceeding 2-250 meters per seam. This extraordinary depth poses a problem in my mind with the standard explanations of coal seam formation. Such a depth of coal requires a ratio of biomass to coal seam thickness of far greater depths of organic matter, how was this much material compressed in such an area? Why were these coal seams so deep?

Jeffrey’s article raises some questions

Why were trees from an arid environment in this coal?

Why are “prodigious quantities” of large tree trunks whole and uncompressed in the coal?

Why is the Sequoia a mountain tree found in large numbers in this coal?

Why are trees in New Zealand coal not related to bog environments?

Special Articles Conifers and the Coal Question

For over a century and a half a controversy has raged in regard to that all important mineral, coal. On the one hand it has been maintained that its raw materials are the result of transport by water and that consequently coal is essentially of the nature of an aqueous organic sediment. On the other hand, the opinion has been held that coal is in the main the result of vegetable accumulations similar to those in actual circum-polar peat bogs consisting of the subaerial deposits, representing the successive generations of fallen peat plants. The first view of the origin of coal is usually called the allochthonous or transport theory. The second is known as the autochthonous or in-situ hypothesis. European geologists have in the main in recent years held to the latter view and their American colleagues have for the most part followed them in this opinion. It is important to emphasize however that the earlier and even the current views in regard to the origin of coal are for the most part arrived at in complete ignorance of its organization. Except in very recent years figures revealing the organization of coal are conspicuously absent in geological works, even in those which particularly deal with coal. It is apparently not without significance that the French who above all others gave early attention to the actual organization of coal, are supporters of the transport or aquatic hypothesis of the origin of coal. Although new methods and improved old methods now give us real insight into the organization of coal, there is yet unfortunately in general little observable rational improvement in geological theories regarding the formation of coal deposits.

The Tertiary coals as being nearest to our times and consequently representing conditions most easily compared with those of to-day, suggest themselves as most likely to resolve finally existing controversies. In this connection the lignitic remains in a large number of Tertiary coals have been examined in the writers laboratories with results which are apparently highly significant. It has long been the custom in central Europe to compare the Tertiary coals with such formations as occur today for example in the Dismal Swamp. The characteristic Conifer of such swamps is Taxodium distichum and the abundant remains of wood in German coal deposits were referred to this or a similar species under the generic name Taxodioxylon. A notable difficulty in this connection is the fact that the conspicuous “knees” or pneutamophores of Taxodium have never been found even in the often excellent preserved remains of supposed Taxodium stumps, in the central European Brown coals.

Over two decades ago the present writer pointed out that a reliable diagnostic feature of our two living species of Sequoia is their reaction to wounds. In S.washintoniana (the Big Tree) and S.sempvirens (the Redwood) resin canals are formed in the wood of the wound cap. This feature distinguishes the Sequoia from all other genera possessing the Cupressinxylon type of wood and holds also for the Laramic (upper) Cretaceous (the most remote epoch in which true Sequoias have been found). It now turns out that in many cases the supposed Taxodiums of the German tertiary coals are in reality Sequoias. Both our living species of the genus are mountain trees and in no case are they ever found in swamps. As a result of this addition to our knowledge of the most important ligneous remains of the central European coal deposits, a change in view is necessary in regard to the conditions under which they have been accumulated. It is now admitted even by some of our German colleagues that there must have been inundations (Ueberschwemmungen) by means of which the remains of Sequoias, at that time abundent throughout the northern hemisphere, were washed into the coal bogs. Unfortunately this concession does not go far enough, for an examination of Tertiary coals, in the writers laboratories, covering North America, Europe, and Asia, shows not only the presence of Sequoias, but at the same time a general organization typical of the organic sediments found in the depths of modern lakes, lagoons, and tranquil estuaries. Tertiary coals in general, in the Northern Hemisphere, are consequently to be regarded as the result of water transport and aqueous sedimentation. Even so uncompromising an advocate of the autochthonous hypothesis as the late profesor H.Potonie, agreed that accumulations in lakes and ponds werer to be regarded as allochthonous.

Recently, the writer has had the opportunity of studying brown coals of the Southern Hemisphere, in New Zealand and Australia. Here the evidence against the in-situ or peat bog hypothesis of the origin of coal is equally decisive. The coals from a large number of New Zealand mines not only of Tertiary but also of late Cretaceous age shows organization such as is found today only in lacustrine or similar organic mucks. Further the woods of New Zealand coals belong to the Araucarians and Podocarps, Conifers, which are not found growing in bogs at the present time. It is not without significance in this connection, that the official view of the Geological Survey of New Zealand, is that the coals of that country are of sedimentary or transport origin. In Australia the remarkable brown coal deposits near Morwell in the State of Victoria were examined under very favourable conditions, through the kindness of Sir Edgeworth David, of the Department of Geology, of Sydney University, and Sir John Monash, Chancellor of the University of Melbourne. These deposits are in places nearly 800ft thick and in the open workings which are at present being operated are of a depth of nearly 200ft. In one of these are prodigious quantities of generally admirably preserved tree trunks, which in many instances have not undergone even the slightest compression. A microscopic examination of a number of of these has shown that they are either Araucarian Conifers, or Proteaceae. The Araucarians are certainly not bog plants and the only reasonable explanation of their presence in coal deposits is their having been water-borne from some more or less distant site. The most characteristic Proteaceous wood present is that of the so called silky-oak or Grevillea, which is a notable component of the well-known dry mudstone flora, so characteristic of Australia not only of today but as far back as the Eocene. Teh general organization of these coals is lacustrine like those of New Zealand and in places seams of actual ;;;; shale are in the coal.

It appears advisable that more attention be given to the organization of coal, in connection with theories in regard to its origin. Certainly the prevailing views represent habit and prejudice rather than a rational consideration of the rapidly increasing body of new and significant facts. Not long since the writer was exhibiting the colored plates of his recent memoir on coal to two of his geological friends, one of whom remarked apropos of the brilliant hued illustrations, that coal did not look like that. He was advised by his fellow geologist to go and examine come coal sections. This advice may perhaps be of value to a wider circle.

It is clear from the structural study of Tertiary coals and their contained woods that these coals can not have been formed in-situ as is generally assumed, since the woods are those of land and even desert trees. Further the general organization of brown coals closely resembles the aquatic accumulations of vegetable matter in the same regions at the present time and consequently cannot be compared at all with peat. E.C.Jeffrey Harvard University.

Footnotes

E.C.Jeffrey, Science Vol:65, pp.356-357, Jan-June 1927

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North American coal seams

“Dana” dated but still valid observations on coal seams

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