|SECOND GEOLOGICAL SURVEY OF PENNSYLVANIA - REPORT OF PROGRESS
P. DESCRIPTION OF THE COAL FLORA OF PENNSYLVANIA
AND OF THE
CARBONIFEROUS FORMATION THROUGHOUT THE UNITED STATES
BY LEO LESQUEREUX; ©1879
|Tables of Contents:
|All Four Volumes:
Scans and Webpage
©George Langford III, 2011
|On the Geographical and Stratigraphical distribution of
the plants of Carboniferous age.
Edited by J.P.L. [J.P. Lesley, State Geologist of Pennsylvania - GL,III,ed.]
The uniformity of temperature, and of other circumstances of climate in
Carboniferous times being taken for granted, as described in the
foregoing chapter, a general uniformity of vegetation over the whole
expanse of land surface becomes a probable inference.
But that the flora was nevertheless greatly diversified in species is well proven by the fossil remains already known to us. And very naturally; for a diversity of characters in plants is the certain result of a diversity of local circumstances: some species thriving at the surface of water; others under the shade of trees; others in open land, and so forth.
The general uniformity of Coal vegetation, then, must be understood as including such local and circumstantial diversities; the same kinds of plants prevailing in all places of the region where their peculiar dispositions were favored. In other words, each species had its habitat, not in any one special restricted part of the region, but in a greater or less number of suitable localities scattered over the whole.
The geographical distribution of the Coal flora is expressed then, by referring the various species growing at any given date or stage of the Coal era to the various localities in which they grew.
§ 23. One would naturally admit a priore that the characters of the vegetation changed in the lapse of time, so that the same plant forms should not be found in the higher strata which are found in the lower.
The Carboniferous age must have been a very long one, judging by the thickness of the coal beds, and the great variety and size of the sandstone, shale and limestone strata which are interposed between them. During so long a time the coal flora must have gone through many modifications; whether by the alteration of types; or by the disappearance of some species and the introduction of others.
The Stratigraphical distribution of the Coal Flora, then, is revealed by a study of the various species proper to the different coal beds in their relations to one another as upper and lower beds, newer and older beds. It is that which appears up and down the pile of Coal Measures, during the entire length of time occupied in their deposit.
The geographical distribution is that which existed over a horizontal surface at some one given time.
The study of this vertical distribution is the more important one, because it may afford data for distinguishing each individual coal bed, and for tracing such a bed from place to place, and identifying it at distant localities. This is its practical value.
Its scientific utility is evident; for it must needs furnish significant materials for solving the problem of organic development, by showing the succession of vegetable types in the course of time.
It is clearly impossible, however, to ascertain what changes took place in the flora of successive coal beds unless the entire flora of each bed in its whole extent be well known. It is not enough to know the various species of each bed in one locality, comparing them with the species of superior and inferior beds in that locality; seeing that the circumstances of growth may have changed or oscillated from time to time at that spot, and the character of the flora of course with the character of the circumstances.
The remains of the plants are only found in the roof shales of a coal bed. Its flora is now known only from these remains. But the species found in the roof shales of a bed in a given place must not be taken as a complete inventory of all the species growing in that bed at one time over the whole expanse of that bed. It will be only a local inventory of such of them as were then growing in that particular part of the bed. Many other species were growing at the same time elsewhere. Circumstances varied with every locality.
Consequently, if a species be found in the roof shales of bed A, and not in those of bed B above it, it does not follow that the species had become extinct. It may have been growing in bed B elsewhere; and by the time bed C came into growth, the same species having returned to its old locality, by force of favorable circumstances, may have left its remains in the roof shales of bed C.
Only after a careful study of the whole extent of all three beds, and upon finding a species in one or more places in bed A, and not anywhere in beds B and C, can the probability of its extinction (or modification into another species) be even provisionally adopted.
Nothing can more plainly show how difficult a study this of the vertical distribution of plants is. A long time must yet pass, and extensive re-searches are still to be pursued, before sufficient data are collected for the elucidation of the problem. The coal fields are of immense extent ; exposures are comparatively few and wide apart, and the roof shales of a very small number of mines have been examined.
§ 24. The area of the coal deposits of Carboniferous age, in the United States, is generally estimated at about 190,000 square miles, divided into six sub-areas or coal-fields as follows, beginning at the east:
§ 25. The term Carboniferous is usually employed properly to designate the coal measures superior to the Pottsville conglomerate or Millstone grit of England, and their coal beds were formerly distinguished as bed A, bed B, etc., beginning at the top of the Conglomerate and lettering upwards. Local geographical names have been substituted for this lettering in Pennsylvania.
The term Sub-Carboniferous has been and is still used to designate all the workable coal beds subsequently discovered to exist either in the body of the Conglomerate or within a few hundred feet beneath it.
The term Inter-conglomerate coals is now frequently used for the beds in the body of the Conglomerate itself, since the discovery of the fact that the Conglomerate is not a solid mass, but divisible into a series of separate deposits of gravel, sand and clay.
Beneath the Pottsville Conglomerate in descending order lie the following formations: Mauch Chunk red shale (No. XI); Pocono sandstone (No. X); Catskill red sandstone (No. IX); Chemung, Portage, Marcellus, Hamilton, Genessee, Upper Helderberg (No. VIII), and Oriskany sandstone (No. VII), which last is adopted as the bottom formation of the Devonian system.
In several of these formations deposits of coal have been discovered much older than the true Carboniferous or Sub-carboniferous, but furnishing no coal beds of practical value except in one or two instances. In a work like this, however, it is important to consider these earlier formations of coal, on account of the peculiar vegetable forms which they contain; and this will now be done as preliminary to a statement of the true coal beds, and beginning with the lowest formation in which coal has been observed.
§ 26. It is needless to speak of the small concretionary pieces of coal which have been found in many places in the Hudson River formation (No. III) near the bottom of the Silurian system; because they are not in the form of coal beds; and have yielded no plants.
The earliest real coal beds have been observed in the Marcellus, near the base of the Portage; but-only in one locality, the region of the lower Juniata river in middle Pennsylvania. As yet no record of the plants which enter into their composition has been got, and therefore no account can be taken in this work of the botany of these Lower Devonian coal measures.
§ 27. From the Catskill group of rocks the only vegetable remains obtained by the explorations of the Pennsylvania Survey represent one species alone, Archaeopteris minor, communicated in numerous specimens by Mr. A. Sherwood from northern Pennsylvania. At a lower stage in the formation Mr. Sherwood found also numerous fragments of Dictyophytum; but the affinity of this plant is as yet uncertain, and its distribution in the column of rocks is generally ascribed not to the Catskill but to the Chemung.*
§ 28. For various reasons not necessary here to give in detail, the base of the Sub-carboniferous, and therefore the base of the entire system of Coal Measures, has been fixed at the dividing line between the top of the Catskill and the bottom of the Pocono formations; although in point of fact no such dividing line can be drawn with precision, because, in the absence of fossils for several hundred feet, no distinction can be made between the two formations except such as is founded on differences of lithological composition. For it so happens that there are alternations of these lithological characters in the beds belonging to the top of the one formation and the bottom of the other. Therefore, in the absence of any non-conformability, and in view of the evident continuation of the deposits, while it may be said that the Chemung formation graduates by alternations upwards into the Catskill, it is nevertheless true that taken as a whole the Chemung formation is perfectly distinguishable from the Catskill formation above it.
Another fact which makes the determination of the base of the Carboniferous at the base of the Pocono purely empirical is this, viz: The first coal beds met with (going up) are not at the base of the Pocono, but about two thirds of the way upwards towards the top. At this stage in the Pocono occurs the first important formation of coal.
There are, nevertheless, certain coarse conglomerate strata at the bottom of the Pocono, formed of large pebbles, which may be considered, perhaps, as the practical base of that formation, and over these are softer sandstone and shale deposits in which no kind of organic remains have yet been discovered.
§ 29. The Pocono (Vespertine) formation (No. X) is a group of rocks best described at one locality in Huntingdon county, Middle Pennsylvania, from data obtained hi the gap of Sideling hill and in the railroad tunnel through that mountain at a higher level. This description will be found in Report F of the publications of the Second Geological Survey, pages 206 to 208.
The lower division of the Pocono is here a series of alternating shales, and massive and sometimes conglomeritic sandstones, with layers of red shale and of carbonaceous shale.
The middle division of the Pocono here contains numerous very thin coal beds, 19 of which are recorded by Mr. Ashburner in his section; but no one of these beds is more than about one foot thick.
In Perry county, Pennsylvania, at the junction of the Juniata and Susquehanna rivers, a coal bed has been opened in the Pocono sandstone (hundreds of feet beneath the Mauch Chunk red shale) which, with its roof shales, measures 4'. Probably other beds of less size accompany it.
On the borders of Virginia. and West Virginia, at the Lewis tunnel of the Chesapeake and Ohio railway through the Allegheny mountain, near the White Sulphur springs, Prof. W. M. Fontaine found what seems to be the Pocono coal measures, 410 feet exposed, holding four or five coal beds, none of them a foot thick. The upper 135' has a local coal bed resting on coarse sandstones. The next 215' contains four coal beds, and rests upon a 60' mass of white, pebbly sandstone. Under these come 500 feet of flags and shales; and these the red marls and shales of the Catskill, No. IX.*
In southern Virginia, on the New river in Montgomery county, and near Augusta, in Augusta county, Prof. W. B. Rogers, the State Geologist of Va., reported, in 1836, workable coal beds far below the Conglomerate. In 1858 Prof. J. P. Lesley described in the Proceedings of the American Philosophical Society, two beds of coal on Tom's creek, Montgomery county, 4' and 8' thick, respectively, in a shale formation overlying the Pocono sandstone, and underlying 1000' of Mauch Chunk red shales; and in the Peak mountain of Wythe county a dozen small coal beds enclosed in the Pocono sandstones.—In 1877, Prof. W. M. Fontaine described in Silliman's Journal a section made at the Lewis tunnel, on the Chesapeake and Ohio railroad, through the Allegheny mountain, where four coal beds, all less than 1' thick, inhabit 215' of measures enclosed between a top conglomerate of 95' and a bottom conglomerate of 60', under which lie 500' of flaggy sandstones and shales; these again lying on Catskill red marls and sandstones.
In the coal measures of the west, the Pocono formation has not been recognized; or, if it exists, is composed merely of limestone strata. Thus in Illinois the Kinderhook group, about 100 feet thick, and mostly limestone, is probably referable to the Pocono; although some geologists consider it Chemung.
§ 30. The Mauch Chunk (Umbral) red shale formation No. XI, lies upon the Pocono, and under the Pottsville Conglomerate. It varies greatly in thickness and composition, exhibiting several thousand feet of red shale in Eastern Pennsylvania, fining down to almost nothing in Western Pennsylvania, and becoming a great limestone formation in the southern and western States. I use the term Sub-conglomerate to designate the forms found in this formation.
In Middle Pennsylvania the section given by Mr. Ash-burner, in Report F, represents it as 1,100 feet thick, divisible into three members: 1, The upper, composed of shales and sandstone, 910 feet thick; 2, The middle (Mountain limestone,) 49 feet thick; and, 3, The lower, composed of shales and sandstone, 141 feet thick, without coal beds in either of the divisions.
In Maryland the red shale is not only repeated and the limestone also, but the whole formation compares in total thickness to that of its normal exhibition on the Schuylkill and Lehigh rivers in eastern Pennsylvania. According to Mr. Howard G. Jones' section (1874 to 1880) it consists (at the top) of 200' of gray shales, 375' of red shale, 360' of limestones, 2000' of red shales, 475' of limestones, and (at the bottom) 300' of gray shales (holding iron ores) immediately above the top of the Pocono, which consists of 100' of very massive white sandrock. The total thickness of Mauch Chunk here is either 3410' or 3710'. Both the limestone divisions are very fossiliferous in their higher layers.
In West Virginia, Professor Fontaine combines in his section of 1,197 feet of rock the Mauch Chunk, with the Conglomerate above it,*
In Alabama, the Warrior Coal basin of Jefferson county exhibits a section which seems to correspond with that of Professor Fontaine, in West Virginia.
At the base lies 100 feet of silicious sandstone, resting on shales, limestone with Pentremites and sandstones, in all 210 feet thick; at the top of the section is a conglomerate 16 to 20 feet thick. The interval of 729 feet between these two conglomerates is filled up with alternations of coal, shale, clay, and sandstone, and in this interval (of 729 feet) lie 13 coal beds, varying in thickness from 1 to 3 feet, and: measuring altogether 25 feet of coal.
In Tennessee, the Sub-Conglomerate measures resting on Mountain limestone, are divided into two parts. The lower, 228 feet thick, contains three thin coal beds (one four feet thick)**
Whether the whole section represents Sub-conglomerate measures, is the question which will be examined in considering the character of the plants found with these coal beds.
In Arkansas, all the Coal measures underlie a conglomerate formation, which varies in thickness from 40 to more than 1000 feet. The Wilmoth coal seam, in Johnson county, is overlaid by 1100 feet of measures, dark yellow-reddish shale, thin-bedded flaggy sandstone, passing upwards into a massive sandstone (sub-divided into three members) from 500 to 600 feet thick. The Spadra coal, also in Johnson county, is a semi-anthracite coal, remarkably rich in fixed carbon (86 per cent.) and like the Wilmoth coal, is covered by 90 feet of black shale under a conglomerate.
In Missouri, the Sub-conglomerate measures, as also the conglomerate strata, are not distinctly defined from the underlying Mountain limestone (Chester, Saint Louis) group. The only remark I find of this formation, is in the Geological Report of Missouri, 1872, p. 279, where, in the description of Lincoln county, is noticed the occurrence of a coal bed of limited area, or coal in isolated masses, lying in depressions, or previously excavated holes, in the sub-carboniferous limestone.
No fossil plants have been received from the Sub-conglomerate strata of Missouri. In Henry county, Taonurus Colletti abounds in the drab shaly sandstone indicated in the report as Lower Carboniferous.
In the Northern coal areas, the Sub-conglomerate coal measures are distinctly and definitely separated from the underlying formations, and generally hold workable coal beds.
The lower division consists, usually, of heavy beds of limestone and sandstone. The Chester and St. Louis (Archimedes, Pentremites, Mountain) limestone groups of Illinois, Indiana, and Kentucky, come in here. The sandstones, which in many places alternate with the limestones and shales in the lower part of the formation, constitute in Kentucky the Knob sandstone series,**** (Pocono, No. X. ?)
The upper division, between the Chester limestone and the Conglomerate, consists of shale beds holding workable coal beds.
In western Kentucky, the lower division, 200 to 500 feet thick, supports shales with one or two workable coal beds. In Breckenridge county two thin coal beds (six to ten inches) are intercalated between the Archimedes limestones. (Geol. Rep. Ky., II, p. 88, and III, p. 328.)
In eastern Kentucky, the lower division consists of from 5 to 50 feet of Knob-stone, and from 70 to 400 feet of limestone ; above which, in the upper (shale) division, come from one to five coal beds, varying from one to five feet in thickness. (Geol. Rt. Ky., IV, p. 451.)
In Illinois, the lower division is mostly limestone, the Chester and St. Louis groups together being nearly 1000 feet thick. The upper shale division holds sometimes one coal bed, three or four feet thick, close under the Conglomerate. There is also a thin coal bed underneath the Chester and above the St. Louis group.
In Indiana, the sub-carboniferous is a diversified formation of 1, a soft black shale; 2, an upper limestone ( Kaskaskia); 3, black shale ; 4, Chester limestone (sometimes sandstone), and 5, St. Louis limestone (200 to 400 feet thick) lying at the bottom of the group.
Here, as in Illinois, a coal bed usually appears with the first black shale just under the Conglomerate; and another between the Chester and the St. Louis groups.
From these sub-conglomerate measures in Indiana and Illinois we have no vegetable remains; but a number of fine plants are described from a clay bed underlying the. Chester group in Illinois; and also from the whetstone beds which in Indiana replace the Chester limestone beds of Illinois.
In southern Ohio the Waverly group, 350 feet thick, and in northern Ohio the Cuyahoga shale and Berea grit 400 to 500 feet thick, have some fossil characters which would identify them with the sub-conglomerate series in Indiana; and their geological horizons have been followed through north-western Pennsylvania.
§ 31. The Pottsville Conglomerate group (No. XII) is a term adopted in Pennsylvania to designate a thousand feet of coarse sand deposits, the mountain outcrop of which marks the southern limit of the First Anthracite coal field. It is analogous to the English term Millstone grit.
This deposit, underlying the so-called Lower Productive Coal measures, and outcropping with steep dips around all the separate basins of the great Anthracite Coal area, diminishes in thickness rapidly in a north-west and west direction from Pottsville; becoming only 250 feet thick at the west end of the Shamokin basin; less than 200 feet thick about Wilkes-Barre, Scranton and. Carbondale; and not thicker in middle Pennsylvania around the Broad Top semi-bituminous coal basin, and in Maryland around the Cumberland semi-bituminous coal basin.
This progressive diminution in the thickness of the formation was supposed, until recently, to go on northward and westward throughout the bituminous coal area spreading west of the Allegheny mountain; for it seems to be less than one hundred feet thick at Towanda and Blossburg, and in western Pennsylvania.
But it is now known that this impression was erroneous. What was taken for the whole formation is in fact only the lower division of it. The whole mass is now subdivided into three great sandrocks,* separated by shales holding carbonaceous slates and coal beds.
Even around the Pottsville anthracite field large and important coal beds have been opened in the body of the Conglomerate; and at Shamokin, where the whole is 250 feet thick, four coal beds are intercalated between five conglomerate sandrock subdivisions of it.
The thickness of the Conglomerate series (No. XII is now known to be maintained beneath the whole Bituminous Coal area of western Pennsylvania, at an average of 250 or 300 feet; and the apparently great local variations in the thickness is due to the great sudden, local variations in the composition of its three (or more) sand divisions.
What has been said in preceding pages respecting the sub-conglomerate rocks of the western and southern States, must be understood to be provisional, inasmuch as no sufficiently close and thorough connection has yet been possible between the definitely limited series in Pennsylvania, and in those States. It is as yet impossible to say with certainty that any individual sandrock beneath the Coal Measures proper in W. Virginia, southern Ohio or Kentucky, is the precise analogue of tne top, middle or bottom members of the Pottsville group in Pennsylvania; even if it may not prove on examination to be lower than any of them in the series ; that is, perhaps an intercalated sand deposit of Mauch Chunk (XI) age.
As the greater number of fossil plants described in this report have come from the mines of Pennsylvania, the uncertainties just alluded to will affect but little the botanical conclusions arrived at as to the vertical distribution of forms. ******
In Western Maryland Mr. Howard Grant Jones' section *******
In the west, as in the south, our knowledge of the constitution and contents of any series of massive sandstones which may be proved hereafter to be strictly cotemporaneous with the Appalachian Conglomerate (XII) is very insufficient. The so-called Conglomerate is variable and rarely described with sufficient minuteness, or traced continuously from one distant locality to another.
In parts of Illinois, especially Morris, Colchester, Murphysborough, etc., on the northern boundary of the field, the Conglomerate is reduced to a single bed scarcely 6 feet thick; but on outlying patches further north it frequently occurs from 20 to 110 feet thick.
In Indiana, also, the Conglomerate is said to vary in thickness from 20 to 100 feet.
In Western Kentucky the Conglomerate is found divided into two members. Under the main mass of conglomerate, and separated from it by a few feet of shales, is a lower stratum of the same composition; and in the interval between the two occurs a bed of coal, as on the Ohio river near Caseyville, (see description of the Battery Rock coal, in the Kentucky reports.)
In Eastern Kentucky, as in Ohio and Pennsylvania, the Conglomerate is still more varied in composition, and undergoes, locally, great changes of thickness; but it is generally in two beds of different characters, both of them variable; so that it is still questionable whether coal beds like the Jackson coal and the Cuyahoga coal of Ohio, should be considered Sub-conglomerate or Inter-conglomerate coals. A. similar question, respecting the Sharon coal of Pennsylvania, has been recently settled with some certainty by the surveys of that State, and that coal bed placed systematically in the Conglomerate, and not under it.
The only coal beds evidently within the body of the Conglomerate which I have myself seen are the Battery Rock bed in Illinois, above mentioned, and a bed on Mill creek above St. Clair, in the Anthracite basin of Pottsville ; but from these beds I have not obtained any valuable materials to represent their flora.
On the North Branch of the Susquehanna, however, in Eastern Pennsylvania, a bed of shale, without coal, but rich in fossil vegetable remains, occurs at Campbell's Ledge above Pittston, between two massive plates of the Conglomerate, the interval being only from 6 to 8 feet.
Whether or not some of the coal strata called Sub-conglomerate, in this report, and from which fossil plants have been obtained, be, or may be Inter-conglomerate coal beds, is a question which shall be examined on the basis of data exhibited in the table of distribution further on.
§ 32. The Carboniferous proper or Productive Coal Measures, are represented in the Anthracite Fields of Pennsylvania, by about 1,400 feet of strata containing (where the coal beds have been most mined) from 12 to 14 coal beds, variable in thickness individually, but averaging at least 100 feet of combustible material.
The section at Scranton, in the Third Anthracite Coal Field, given in Lesley's Coal Manual of 1856, shows 14 coal beds in about 800 feet of measures.
A generalised section published by Messrs. Daddow and Bannan, (Coal, Iron and Oil, p. 247,) gives 14 coal beds, with thicknesses varying from 2 to 15 feet, and footing up 110 feet of coal, in 1,530 feet of measures, measured from the top of the Conglomerate upwards.
The same number of beds and about the same amount of coal (107 feet) is given by Mr. P. W. Sheafer in his memoir, "On the Anthracite Coal Fields of Pennsylvania, and their exhaustion."
A section derived from a boring on Judge Woodward's lands, in Upper Plymouth, Luzerne county, Pennsylvania, shows 949 feet of measures, enclosing 7 coal beds from 5 to 29 feet thick, with 91 feet of coal. This section lacks the higher measures.
§ 33. The plants known through the Anthracite region are numerous enough. But except for the Pittston section few positive data have been obtained relative to the horizons at which the vegetable remains have been obtained. The Mammoth vein, about the fourth above the Conglomerate, and the Salem or Gate vein high up in the mensures are exceptions.
The numerous plants from the Anthracite of Rhode Island are interesting in regard to the geographical distribution of the forms ; but as yet the horizon of the Rhode Island coals is not positively made out.
§ 34. The Bituminous coal measures of Pennsylvania are sub-divided thus:
§ 35. The Permo-carboniferous formation of south-western Pennsylvania and West Virginia.
The recent discoveries by Profs. Fontaine and White of numerous Permian plant-forms in the Upper Barren Measures have been published in Report of Progress PP. (See especially page 117.)
It becomes probable that the Waynesburg sandstone is the analogue of the conglomerate base of the Permian system in other parts of the world; that the red shales higher up represent the red measures of the Permian; and that the numerous beds of limestone in the Green county and Washington county groups represent to an uncertain extent the Zechstein of Europe.
§ 36. In southern Virginia Prof. J. J. Stevenson finds in a total thickness of 1751' -80' = 1671' above the top of the Conglomerate 18 coal beds, varying from 4 inches to 15 feet in thickness. The aggregate thickness of coal in the upper seven beds is only 6' 5"; in the lower ten beds 47' 3".******** The 15' bed is the fifth from the bottom.
He supposes it possible that the lower 883' of this section may correspond to the Lower Productive coal measures of Pennsylvania, since this division increases southward through West Virginia, from about 350' on the Pennsylvania state line to more than 700' on the Baltimore and Ohio railway, and to more than 1200' on the Great Kanawha river,*********
In Tennessee, west of Knoxville, Prof. Lesley's unpublished sections, from the lowest coal bed at the mouth of Coal run (on a level with the lowest drainage of the country, to the tops of the highest mountains, capped with Conglomerate sand rocks, amounted to more than 3000 feet.
§ 37. In Ohio the distribution of plant-forms throughout the Productive Coal Measures is very much the same as in Pennsylvania, with the same amount of local variations.
A generalized section of 1100 feet of Coal Measures, given by Dr. Newberry in the Geol. of Ohio, Vol. II, p. 81, extends from the top of the Conglomerate to 350 feet above the Pittsburgh coal bed, and contains 13 well defined coal beds, five of which above the Pittsburgh bed are scarcely thick enough to be considered workable.
Few plant remains have been obtained or described from the Ohio Coal Measures except those described by Dr. Newberry from the Conglomerate coal of Cuyahoga and the coal of Youngstown on the Ohio river near the Pennsylvania state line; and those described by Prof. E. B. Andrews from a shale of the Sub-carboniferous Waverly group. We have only a few species from the Pittsburgh bed at Pomeroy on the Ohio river, and from St. Clairsville.
Over eastern Kentucky extend the Ohio coal measures, with a similar distribution and variation of plant forms, very few of which, however, are known.
In Illinois the Coal Measures proper are about 1000 feet thick, and include 16 coal beds, the lower seven of which are locally variable in thickness from 2 to 7 feet. The higher beds vary in thickness from 6 inches to 2 feet. (See Geol. Rept. Illinois, 1875, Vol. VI, pp. 2 to 5.)
The lowest (Morris) coal of Illinois, lying generally close above the Conglomerate, is the one worked and exposed at the borders of the field; and the largest number of plant-forms known in that region have been collected from its roof shales. Many of them have been found in calcareous concretions enclosed in these roof shales, on Mazon Creek, at Murpheysborough, and elsewhere.
In western Kentucky, the coal measures of which are an extension of the Illinois field southward across the Ohio river, and similarly constituted, the plants are little known.
In Indiana, the Coal Measures proper, forming the eastern border of the Illinois field, are described in a general section, in the Report to the State Board of Agriculture for 1876. Here 650 feet of measures contain 12 beds of coal, from none of which have we received any plants, with the exception of some fruits from the Conglomerate itself. The vegetable remains mentioned in this report come from the Sub-carboniferous whetstone rocks.**********
In Missouri, Professor J. C. Brodhead, in his Geological Report for 1879, vol. 2, p. 53, gives a condensed vertical section of the coal measures thus sub-divided:
Most of the plants obtained from the Missouri field were got near the roof shales of the Clinton coal, the third from the bottom.
From Michigan, no fossil plants worth mentioning have been obtained. The numerous specimens sent in by the State Geologist, Dr. Roeminger, all represent the omnipresent Stigmaria ficoides, of the under clays.