A GENERAL GEOLOGICAL REPORT
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Now, how are these indispensable "meteorological conditions" to be obtained? The progress and developments made on both sides of the Atlantic during the past and present century, in the science of Forestry in connection with Meteorology, have shown that there is but one very plain and easy way, and that is by covering one-fourth to one-third of the Plains' surface with forests. Every section of 640 acres on the Plains and Prairies of Texas should have upon it from 150 to 200 acres of well-timbered woodland. Procure the seed or scions of the right kinds of growths, suited to the soil and climate, such as Catalpa speciosa (the most durable of all known growths and best suited for railroad cross-ties), China Aster, Hickory, Maple, Black Locust, Walnut, Chestnut; White, Post, and Live Oak; Ash, Bois d'Arc, etc., etc., and respectable forests could be grown in 30 years or less time; and enough of the same from the necessary thinning out, beginning the fourth or fifth year, could be sold in the meantime to pay all expenses. Experience in Germany and other parts of Europe proves this, and it proves, too, that by or before the end of 30 years the desired "meteorological conditions" may become such all over the Plains and Prairie country and adjacent regions, that destructive summer drouths and devastating freshets would be reduced to the minimum; countless perennial fountains would bubble up from the generous bosom of Mother Earth, and all of these streams great and small would run reasonably full the year round; and much of the Texas prairie country, the "black hog-wallow lands," for example, already productive enough, even under present drouthy " conditions, to make them equal the best lands in Eastern States, would, with the increased and equalized rainfall sure to follow foresting and reforesting, become unsurpassed in fertility.

Of course, farmers on the Plains or Prairies of the West, or those having lands there that they may wish to colonize, ought to begin by boring Artesian wells for immediate purposes. These would also assist materially in bringing about the desired change in meteorological

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conditions; in restoring and equalizing the rainfall; and, in the meantime, judging by what has happened in some other States, might be utilized, to some extent, for irrigating purposes.

Unquestionably, much of the future greatness of Texas will depend upon the success of her people, in producing, by comprehensive management and concerted action, "the requisite meteorological conditions" referred to by Prof. G. G. Shumard, over all that region of the State lying West of the 98th Meridian of West longitude. Produce those conditions over all that immense territory of prairie and plain, lake, river, and mountain, stretching from Austin, Palo Pinto, and Wichita to the Rio Grande, and, as a matter of course, it will have a healthy and beneficial effect on every other part of the State.

In consideration of the importance of the subject to the whole people of Texas, I take the liberty of publishing an Abstract of a Geological Report made by Prof. B. F. Shumard, State Geologist, and by him submitted to the Legislature at its Eighth Session. This Abstract gives a brief, but very comprehensive and compendious statement of the progress of the Geological Survey of the State up to August 1st, 1860. It embodies a great many important facts in reference to the agricultural and mineral wealth of Texas-especially the latter- which are as yet but little known to the public at large. When it is remembered that this Report was never officially published by the State, or if it was, that like the journals and other documents of the Legislature to which it was submitted, were burned in the fire which destroyed the Capitol, thus leaving no copy extant-- nothing, except this Abstract which is copied from the "Texas Almanac" for 1861-it will be admitted that it is in the line of the public good to reprint it now. (See Appendix.)

In the Abstract of Prof. Shumard's Report, it will be seen that as early as 1860 he, as State Geologist, had ascertained that in addition to incalculable quantities of Lignite, Texas also possessed enough Coal of superior quality to supply the demands of her people for centuries to come. Further, it may be stated, that a lack of information as to the existence of valuable and even immense deposits of such Minerals as Copper, Lead, Silver, etc., widely prevails

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which are clearly if not fully reported upon in the accompanying papers.

Dr. George Gettz Shumard, whose geological survey of a portion of the State of Texas is now for the first time published, was a graduate of the Medical School of Louisville, where he combined the study of Geology with that of Medicine.

In the year 1850 a Military Expedition was organized by the War Department to explore the sources of the Red River of Louisiana. Captain R. B. Marcy was appointed to command, with Capt. G. B. McClellan as assistant, and the following year another Expedition was organized to explore the sources of the Brazos and the Big Wichita Rivers of Texas. In both of these Expeditions Dr. Shumard served in the double capacity of Surgeon and Geologist. One of the most important objects of these Expeditions was to gain a better knowledge of the geology of the country adjacent to these rivers, and the selection of Dr. Shumard as Geologist was a high recognition of his eminent ability.

On the termination of the surveys, complete and exhaustive reports showing the results of the Expeditions were made by the General Government.

In March, 1852, another Expedition was ordered by the War Department, "To make an examination of the Red River of Louisiana, and the country bordering upon it." This was also under command of Capt. R. B. Marcy and Geo. B. McClellan, Dr. Shumard again accompanying them as Geologist, Paleontologist, as well as Surgeon of the Expedition. In 1853 a report of this survey was published by the War Department. A large collection of fossils and other specimens, collected by Dr. Shumard on this Expedition, were forwarded, with his notes, to Edward- Hitchcock, then president of Amherst College, for his examination, and the result was a joint report published in 1853 of "The Expedition of 1852," a work comprising several volumes.

In the year 1855, Dr. Shumard was appointed Geologist and Surgeon to the Expedition ordered by the War Department, under command of Capt. John Pope, of the Corps of Topographical Engineers of the United States Army, who was directed to explore a

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large portion of the plains of Texas and New Mexico, with the purpose of testing "in those distant regions the practicability of obtaining water by means of Artesian wells."

To ascertain the practicability of building the Southern Pacific Rail Road was also an especial object of this Expedition.

Dr. Shumard was engaged in this work about three years, when in 1858 his brother, Dr. B. F. Shumard, President of the Academy of Science, St. Louis, was appointed State Geologist of Texas, and he Assistant Geologist.

The surveys for which the above appointments were made were carried on with vigor for more than two years, until the war between the States coming on they were discontinued, and Dr. Shumard left the State, arriving at Cincinnati, Ohio, on the 5th of April, 1861, and on the 8th of the same month was appointed Surgeon General of the State of Ohio.

During his connection with the Geological Department of Texas Dr. Shumard, from time to time, made various reports which are well known. Scientists will remember his discovery of an American substitute for gum arabic.

Dr. Shumard's public career, as a geologist, closed with his leaving Texas. He, however, in private, continued his studies, and contributed largely, by correspondence, to various scientific societies, of which the following are the most prominent:

• The Geological Society of London and of France,
• the Imperial Geological Society of Vienna,
• the Geological Society of Hermstadt,
• and the Academies of Science of Philadelphia, California, Cincinnati, New Orleans, and others of repute.

H. P. BEE, Commissioner of Insurance, Statistics, and History.

ERRATA.

• Frontispiece, third column, for "Lower Siliceous," read Lower Silurian.
• Page 13, first line, for "subforsiformis," read subfusiformis.
• Page 13, tenth line, for "loevinsculd," read loeviuscula.
• Page 13, fourteenth line, for "oepuoreus" read oequoreus.
• Page 22, last line, for "unheaved," read upheaved.
• Page 28, twenty-seventh line, for "Hemitite," read Hematite.
• Page 28, third line from bottom, for "tatiniferous," read titaniferous.

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The region of country the geology of which forms the subject of the present report lays to the west and southwest of the State of Arkansas, and is comprised principally within the limits of the 29th and 35th degrees of latitude and the 94th and 108th degrees of longitude. It extends, on the one hand, from a line drawn from Indianola, on the Gulf of Mexico, by way of San Antonio de Bexar, Fort Inge, and Fort Clark, to Fort Davis, north to within a short distance of the Canadian River; and, on the other hand, from the western borders of the State of Arkansas and the district immediately south as far west as the Mimbres Mountains, situated sixty miles west of the Rio Grande.

Confined as my observations have been merely to detached portions of the region here indicated, and often compelled to conduct examinations hastily, I cannot hope to do more than present a general outline of its leading geological features. I shall, however, avail myself freely of notes taken during my former expeditions to the sources of the Brazos, Big and Little Wichita, and Red Rivers, and also refer to the observations of such other explorers as have had opportunities of visiting portions of the same field that I have not been able to examine myself.

The accompanying vertical section [Frontispiece] is intended to represent approximately the general character, thickness, and relative order of the different stratified formations encountered by myself in the district under consideration. It has been compiled from more than two hundred local sections taken in the course of my explorations in the Expedition under your charge and during former expeditions under Capt. R. B. Marcy. I trust it will he found as correct as could be expected from the necessarily rapid manner in which many of the examinations were conducted.

The first and second columns of the section contain the numbers and names of the several Geological Systems; the third, the subdivisions of the Systems into Formations; the fourth, their estimated thickness; the fifth, the colors employed to represent then; and the sixth, their general lithological character.

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It will be seen that all the stratified rocks of this region may be referred to five of the principal systems of geologists, as follows:

• Quaternary,
• Tertiary,
• Cretaceous,
• Carboniferous,
• and Lower Silurian.

The Quaternary System comprises all the deposits of later date than the Tertiary, and in descending order includes:

• 1st, Alluvium;
• 2d, Bluff Formation or Loess;
• and. 3d, Drift or Boulder Formation.

This formation comprises:

• 1st, Soils;
• 2d, Sand and Pebbles;
• 3d, Clays;
• 4th, Stalactites;
• and, 5th, Calcareous Tufa.

When we consider the extent of surface and variable geological composition of this district, it is not surprising that we should find within its limits a great variety of soils. These, it is well known, derive their character mainly from the mineralogical composition of the underlying strata; and in proportion as these abound in materials favorable or unfavorable for the nutrition of plants, will the soil, other things being equal, be productive or unproductive.

Many of the soils encountered upon the Plains are found to possess in an eminent degree all the necessary elements of nutrition for plants, and if this region were accompanied with the requisite meteorological conditions it would possess a character for fertility unsurpassed by any portion of the North American continent.

Marly Clay Soil.-The most extensive and under favoring circumstances the most productive variety of soil is that derived from the Marly Clay Formation, which is spread over thousands of square miles of surface. It is for the most part of a deep red or brown color, and contains silica, carbonate and sulphate of lime, allumina, magnesia, and oxide of iron, in variable proportions. Could any means be adopted for transporting it to market it would be highly valuable as a manure. Along the streams and in other moist situations it is generally thickly covered with vegetation.

Gypsum Soils.-Gypsum enters largely into the composition of many of the soils of the Plains, and often in such quantities as to constitute their most abundant ingredient. These soils are sometimes white, but more frequently of a light grey, bluish, or red color. They are usually very light,

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and may generally be easily recognized, even at a distance, by the deeper color of the grass growing upon them. These soils are also remarkably well adapted as fertilizers, for which purpose they will doubtless hereafter be extensively employed.

Calcareous Soils.-The soils overlying the limestone of the Upper Cretaceous group usually contain a very large proportion of carbonate of lime, which, indeed, is sometimes present to such a degree as to render the land entirely unproductive. When mixed, however, as is usually the case, with a fair proportion of other ingredients, a highly productive marl is formed.

Soils of the Paleozoic Period.- Although generally less favorably constituted than any of the preceding, many of the soils derived from the decomposition of the Paleozoic rocks are, owing to the more favorable meteorological conditions of the regions in which they occur, far more productive. These do not present a great deal of difference in general mineralogical composition, but vary considerably in the amount of vegetable matter they contain. They consist chiefly of lime and silica in different proportions, with an admixture of alumina, iron, and vegetable matter.

Soils of Igneous Rocks.-Few of the soils derived directly from the igneous rocks have been found of much value. They are generally loose, of a deep red or brown color, and are composed mainly of quartz and felspar in coarse and fine particles. - When they contain small quantities of clay, lime, or gypsum, as is sometimes the case along the streams, they become highly productive and are clothed with rich vegetation.

Water-worn pebbles are of frequent occurrence in the beds of the different streams of Texas and New Mexico. They are derived mainly from the Boulder Formation and older rocks, and exhibit almost every variety of composition. In the beds of the Upper Brazos, Big Witchita, and Red Rivers, they are sometimes accumulated to the depth of four or five feet.

Various metallic ores, as copper, iron, and manganese, have been found in connection with these deposits. In Otter Creek, a small affluent of Red River, having its source in the Witchita Mountains, two small specimens of bluish-yellow quartz, containing gold in small quantities, were found.

To the Alluvial Period we must refer those accumulations of loose sand which occur in the beds of nearly all the streams of Texas, New Mexico, and the adjacent Indian Territories, and which are also occasionally met with in situations remote from existing water-courses. The latter sometimes cover many square miles of surface, and appear to be continually shifting their position. Examples of these shifting sands are to be met with near

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the headwaters of Red River, in the, Sand Hills" of the Llano Estacado, and immediately west of the southern extremity of the Guadalupe Mountains.

In the beds of the larger streams of Texas, accumulations of sand occur many feet in thickness. These often absorb a large quantity of water; and hence it not unfrequently happens, particularly near the sources of these water-courses, that while the beds appear perfectly dry at the surface, by digging down a few feet plentiful supplies of water maybe obtained.

Clays, derived principally from the destruction of the cretaceous strata, are frequently met with along many of the streams. They are usually of a deep red color, and contain lime and gypsum in variable proportions. Many of the principal rivers of Texas, as the Canadian, Red, Colorado, Witchita, Brazos, and Pecos, either have their sources in or flow for a part of their course through the marly clays of the Cretaceous System. These clays mingling with the water impart to the streams their highly characteristic red hue, and are thus transported hundreds of miles. During freshets these materials are deposited in the form of fine sediment upon the adjacent lowlands, and to this circumstance is due the surprising fertility of many of the valleys bordering the lower portions of the streams of Texas.

Are abundant in various portions of Texas and the adjacent Territories In the caverns of the Sacramento Mountains specimens of rare beauty occur. They are generally composed of carbonate of lime, and most frequently occur in districts where the Paleozoic rocks prevail.

In a single locality, viz., in the vicinity of San Antonio, Texas, I have found a deposit of calcareous tufa. It is here light, porous, and chalky, and contains impressions of leaves and stems of recent plants. The rock is sufficiently firm to be employed as a building stone.

The formation to which the term "Bluff" has been applied by Prof. Swallow, State Geologist of Missouri, and which, in the United States, is usually regarded as the equivalent of the Loess of the Rhine, we have recognized at a number of localities in Texas. As in the State of Missouri and other portions of the West, it is here found reposing upon the Boulder

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Formation, and usually consists of thick beds of indurated ash colored loam, containing more or less calcareous matter and abounding in existing species of terrestial and fluviatile shells.

Near Preston, on Red River, a good section of this formation is exposed in a range of vertical bluffs, which extend up and down the river for the distance of several miles. It is here seen resting directly upon soft bluish sandstone of the Cretaceous Period. Fossils are very abundant in this locality, and usually they are in a good state of preservation. They belong chiefly to the genera Lymnea, Physa, Planorbis, Pupa, Helix, and Helicina, and many of the species are identical with those occurring in the loam of New Harmony. Indiana, and elsewhere in the Mississippi Valley, which Sir Charles Lyell, during his visit to the United States, regarded as being the equivalent of the Loess of the Rhine.

The following is a section [No. II.] of the Loess Bluffs near Preston, on Red River. The entire thickness of the formation in this vicinity is about twenty-five feet.

On Loess Creek, a small tributary of the North Branch of Red River, this formation is again well exposed. It here exhibits a thickness of from thirty to forty feet, and is crowded with fossils of the same species of terrestial and fluviatile shells as characterize the formation farther east.

Although there are deposits which very closely resemble the Bluff Formation at several. points along the route from Indianola to El Paso, I have not as yet been able to recognize it with certainty south of the 33d parallel of latitude.

On the Rio Frio and Nueces sections of indurated calcareous loam, sixty to seventy feet thick, are exposed, resting on a deposit of water-worn fragments of hard limestone. (Vide Journal) We are inclined to refer this loam to the age of the Bluff. and should this opinion be found correct, it would give to this formation a geographical range in Texas of not less than four hundred miles.

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During my journey to the sources of Red River, in company with Capt. R. B. Marcy's Expedition, heavy deposits of loose materials, consisting of quartz, greenstone, granite, porphyry, and water-worn shells of the Cretaceous Group, were frequently encountered, resting upon the stratified rocks of the Secondary Period. As the materials forming these deposits were totally different from the rocks occurring in situ anywhere in the neighborhood, and apparently had been transported from a distance, we ventured in our notes on the general geology of that region to refer them to the age of the Drift or Boulder Formation. Since then we have examined deposits of a similar character in other parts of Texas, and have not only had that opinion fully confirmed, but have succeeded in tracing them south and west over a very large district of country.

The Boulder Formation of the region we are noticing varies considerably in character and thickness. In some places it is composed almost entirely of pebbles and small boulders of eruptive and metamorphic rocks, while in others it consists altogether of angular or rounded fragments of Paleozoic and Cretaceous rocks. In Southern Texas it is almost exclusively made up of limestone, sandstone, and silicious nodules, but as we travel north the deposit consists mainly of eruptive and metamorphic rocks. The formation in various parts of the district is often cemented into a conglomerate by means of calcareous or ferruginous matter. As a general rule it is much thicker and coarser as we travel westward. In Western Texas and New Mexico it sometimes attains a thickness of several hundred feet, and contains blocks of sedimentary and eruptive rocks two or three feet in diameter.

Near the headwaters of Red River the Boulder Formation occurs in gently rounded hills from a hundred to a hundred and fifty feet in height. It is here composed of well-rounded pebbles and small boulders of igneous and metamorphic rocks, with occasional beds of coarse silicious sand interstratified, and often contains water-worn fossil shells of the Cretaceous Era, and fragments of silicified monocotyledonous and dicotyledonous wood, weighing occasionally several hundred pounds. Specimens of this fossil wood were submitted to Prof. Hitchcock, who pronounces it to be analogous to that obtained from the Tertiary Deposits of Antigua and the desert near Cairo in Egypt.

This formation may be also traced from near the sources of Red River, almost continuously, but greatly diminished in thickness, as far east as the mouth of Cache Creek, and even east of that point. Farther south, on the Big Witchita and Upper Brazos Rivers, it is again met with, but here is constituted mainly of water-worn fragments of Cretaceous Limestone, replete "

Red River of Louisiana, by Capt. R. B. Marcy.

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with characteristic fossils of that formation, and for the most part firmly cemented with a calcareous paste. Its average thickness here we have estimated at about fifty feet.

In Eastern Texas, Dr. F. Roemer encountered thick beds of loose sand and silex, which he refers to the Diluvial Period. These, he states, form a broad belt of "bad land," extending from north to south across a very considerable portion of the State.

This belt was crossed by the Expedition tinder your charge on the route from Indianola to San Antonio de Bexar, and was found extending in that direction from the Guadalupe River, in the vicinity of Victoria, W. N. W. to a point a few miles beyond Yorktown, occasionally interrupted, however, by several broad districts of fertile country. (Vide Journal) Over this district it consists chiefly of coarse silicious sand, with pebbles and small boulders of silex and other rocks disseminated through it, the whole reposing on the Cretaceous marls and clays.

Between San Antonio and the Guadalupe Mountains, deposits apparently of the same geological age are of frequent occurrence. At several points west of the Rio Pecos they present a thickness of more than a hundred feet, and are to be traced almost uninterruptedly from near the Horsehead Crossing of that stream to the Guadalupe Mountains, a distance of nearly a hundred and fifty miles.

Source.-As has already been remarked, these deposits become thicker and the materials coarser in proportion as we travel from east to west. There can, therefore, hardly be a doubt as to the direction whence they were derived. Indeed in several instances we have succeeded in tracing them for hundreds of miles to their original beds. Thus heavy accumulations of rolled fragments of white limestone and sandstone, agreeing precisely in lithological and paleontological characters with. the Upper Carboniferous limestone and sandstone of the Guadalupe Mountains, are found overlying the clays and sandstones of the Cretaceous System far to the east of that range, and no deposits of the same kind have been encountered west of it. (Vide Journal.)

Accumulations of rolled fragments of red porphyry and granite, presenting the same character as those of the Witchita Mountains, and which, as far as our own observations extend, are peculiar to that range, occur many miles to the eastward, but at no point west of these mountains have we succeeded in detecting any traces of them.

We have thus far spoken of the Boulder Formation only as it occurs east of the Rocky Mountains. We have, however, strong evidence of its existence much farther west. To the same geological period we would refer those extensive accumulations of loose materials which constitute the basins between the Guadalupe and Mimbres mountains. They consist chiefly of sands, clays, and coarse gravel, which have evidently been derived from the rocks, both stratified and unstratified, of the neighboring mountains. In

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some of these valleys their thickness cannot fall far short of four or five hundred feet. At the Artesian Well, a few miles west of Fort Fillmore, they were penetrated to the depth of two hundred and fifty-eight feet without reaching their base, and a little farther north, at the San Diego Mountain, vertical sections are exposed to the height of near five hundred feet. (Vide Report on the Jornada del Muerto.)

Economic Uses.-Should it ever become necessary to construct macadamized roads over any portion of the region in which the boulder formation occurs, it would furnish excellent materials for that purpose. The limestone boulders would also form a good quicklime, and the sand would be well adapted for mortar.

We have been able to detect strata of the Tertiary Period only in two localities throughout the entire district under examination, and even in these the formation is developed upon comparatively an insignificant scale, extending over very limited areas, and attaining a vertical thickness of merely a few feet. Both localities where we have recognized it are in Southern Texas. One is situated thirty-five miles southeast of San Antonio, and was crossed by the Expedition on the 9th and 10th of April, 1855. (Vide Journal.) The Tertiary Strata present here a thickness of about twenty feet, and repose unconformably partly upon the sandstones and grits of the Coal Measures and partly upon the marls of the Cretaceous System. The rock is a dirty ferruginous limestone of a deep yellow color, and varies much in compactness, some of the layers being quite soft and crumbling, and others hard and breaking with an uneven fracture. It contains fossils in great abundance ; but they are usually casts, and so badly preserved as not to permit us to determine accurately their specific characters. They belong mostly to the genera Tellina, Arca, Infundibulum, Fusus, and Natica.

The next locality at which Tertiary Strata were observed is on Leon Creek, a few miles west of San Antonio. Here it consists of light gray earthy limestone, which is scattered at several points over the surface.

Although we have not seen Tertiary Strata in other localities than those just mentioned, there is reason to believe that they are of extensive occurrence in Eastern and Northeastern Texas. Dr. F. Roemer mentions the occurrence of this formation on the Brazos River near the town of Caldwell, and also in the vicinity of Nacogdoches. Assuming this last point as the extreme northeastern limit, it would give to this formation in Texas a northeast and southwest range of about three hundred miles. Nevertheless, as extensive as are these limits, we are of opinion that they include only a portion of the Tertiary area of this region, and that more extended research will develop its existence as far south as the Rio Grande.

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The next formation that we meet, in descending order, in the district under consideration, is the Cretaceous System, which, on account of its great development upon the Western Plains, is far more important than any we have described. The strata of this system here exhibit the enormous thickness of three thousand six hundred feet, and occupy an area of many thousand square miles. With some local exceptions, they cover nearly the whole of the rectangular space included between the 29th and 39th degrees of latitude and the 99th and 105th degrees of longitude, extending southeast into the States of Louisiana, Mississippi, and Alabama, and north into the Territories of Kansas and Nebraska.

In the southern part of the district we have traced them almost continuously from near Victoria on the Guadalupe River in a course nearly W. N. W. to within a few miles of the southern extremity of the Guadalupe Mountains, and thence southward along the base of the Limpea Mountains. Farther north we have encountered them at Fort Towson, Fort Washita, Preston, the Cross Timbers of Texas, and throughout the entire country watered by the Big and Little Witchita, and the upper portions of the Trinity, Brazos, and Red Rivers. Along the Canadian River they have been met with by Mr. Marcon, and north of that stream by Maj. Emory, Lieut. Simpson, Lieut. Abert, Capt. Stansbury, and other explorers.

In the Horse Mountains, and at several other points west of the Guadalupe Mountains, the Cretaceous rocks have likewise been encountered, but we have met with no proofs of the existence of deposits of this age in any portion of the region explored by ourself west of the Rio Grande. North of this, however, along the 35th parallel of latitude, they have been observed by Mr. Jules Marcon, and from the explorations of others we have abundant evidence of their existence in detached basins as far west as the Pacific coast. Dr. John Evans, U. S. Geologist, has recognized well marked Cretaceous strata at a number of points in Oregon and as far west as Vancouvers Island.

The Cretaceous Formation of our district may be separated by well marked lithological characters into two principal groups, viz.:

• 1. Tipper Cretaceous or Calcareous Group.
• 2. Lower Cretaceous or Marly Clay Group.

These rocks have been described by Mr. Jules Marcon as belonging mostly to the Triassic and Jurassic Systems, but evidence of their Cretaceous age will be presented farther on.

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This division of the Cretaceous System consists chiefly of limestone and sandstone, of which the former is much the most abundant and varies much in character. It presents every degree of compactness, from soft chalk to hard subcrystalline limestone. It is, however, generally compact, of a dull earthy appearance, and varies in color from pure white through shades of light gray, yellow, blue, and brown. In many localities it contains a good deal of silex, or sometimes passes into pure silicious sandstone; in others it exhibits a more or less argillaceous character, though beds of clay are rarely observed in it.

The strata are sometimes cherty, and often, especially in the southern extension of the formation, they are crowded with light gray, blue, and dark nodules of flint from one to six inches in diameter. These are sometimes arranged in nearly parallel bands, but more frequently scattered promiscuously through the strata, now and then occurring so abundantly as to form a kind of conglomerate. As we travel north, the Cretaceous strata assume a much more arenaceous character, so that near the headwaters of Red River they are composed almost exclusively of silicious sandstone. But generally the sandstone alternates with the limestone in bands of from twenty to one hundred feet in thickness. It is usually highly ferruginous, and often contains spherical concretions of iron. Its color varies from light gray to deep red and brown. In some localities it is quite hard, durable, and possesses all the requisites of a good building material, but it is often soft and yields readily to the action of the weather.

This division of the Cretaceous System has heretofore been regarded as occupying a comparatively limited portion of the region under consideration. From our own observations, however, taken in connexion with those of other explorers, we are convinced that its real importance in this respect has been greatly underrated, and that instead of being confined merely to isolated and distant points, it really constitutes the prevailing formation over a very large portion of the Plains.

Commencing in the southeast, these rocks occur at a number of points along the route traveled by your Expedition between Victoria and San Antonio. They do not, however, present here a vertical thickness of more than twenty or thirty feet, and are confined to limited areas.

In the vicinity of San Antonio the Upper Cretaceous strata occur in

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gently-rounded hills and bold escarpments about two hundred feet in height, but as we travel westward from this place they increase rapidly in thickness, and at the San Pedro or Devils River, as well as at other points, they show a vertical development of upwards of a thousand feet, and constitute the prevailing surface formation until we arrive within a few miles of the Horsehead Crossing of the Rio Pecos. West of this point they are observed at frequent intervals as far as the sources of Delaware Creek, twenty-one miles east of the Guadalupe Mountains, and in this vicinity exhibit a thickness of five or six hundred feet. (Vide Journal) Farther south their development is equally well marked along the base of the Limpea Mountains, as well as at several intermediate points.

On our return route from the Rio Pecos by way of Fort McKavett, Fort Mason, and Fredericksburg, they are the prevailing rocks as far as San Antonio, being interrupted occasionally by igneous protrusions, upheaved strata of the Paleozoic Period, and bands of red marls of the Lower Cretaceous Group. At several localities along this route the thickness of the Upper Cretaceous strata was estimated at about eleven hundred feet.

North of this route we find these rocks also well developed. From Fort Towson to Fort Washita, and thence in a southwest direction, they are traced almost uninterruptedly as far as the Upper Cross Timbers of Texas. In the vicinity of Fort Washita, and at several localities between that point and the Cross Timbers, they exhibit a vertical thickness of three or four hundred feet, though in this part of the district their usually observed thickness is from one to two hundred feet.

Along the Big and Little Witchita Rivers these rocks form abrupt and gently-rounded hills from four to five hundred feet high. On the Upper Brazos River they occur in elevated plateaus, and near the head of that stream appear in nearly perpendicular escarpments six or seven hundred feet high, forming here those high table lands that stretch away for many miles to the north, south, and west.

Again, these rocks are equally well developed in the region watered by the Upper Red River. Near the source of the Ke-che-ah-que-ho-no, or main branch of Red River, they exhibit a thickness of about six hundred feet, and form the bold escarpments which there characterize the eastern borders of the Llano Estacado.

Finally, other observers have shown the existence of the rocks of this division of the Cretaceous System along the Canadian River, and at a number of points north of that stream.

In the vicinity of Fort Washita the Upper Cretaceous Limestone is usually hard, fine textured, and sometimes more or less crystalline. Its color varies from light gray to blue, yellow, and brown, and not unfrequently it is pure white.

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Near the town of Preston, and at a number of localities between that place and the Upper Cross Timbers of Texas, it is soft, highly argillaceous, and crumbles rapidly on exposure to the weather.

On the Big and Little Witchita and Upper Brazos Rivers, it is hard, thin bedded, and of a dull light gray color, while along the Upper Red River it becomes more or less arenaceous, often passing into pure sandstone, which not unfrequently contains numerous nodular concretions of iron.

Farther south, along the route traveled by our Expedition between Victoria and San Antonio, and at various points west of the first crossing of the Rio Pecos, it is dull white, soft, and resembles pulverized chalk. At San Antonio, Fort Inge, and Fort Clarke, it is white or light gray, earthy in texture, and quite soft when first taken from the quarry, but possesses the valuable property of hardening upon being exposed for a short time to the action of the weather.

On the Rio Seco it is a dull white, soft, and cannot be distinguished from chalk. On the Arroyo Pedro it is of a light fawn color, compact, and breaks with a conchoidal fracture.

At several localities between San Antonio and San Pedro or Devils River it is a buff, compact calcareo-magnesian limestone. Between the San Pedro and Pecos Rivers it, is sometimes hard, ferruginous, and contains a great abundance of flints, while in other localities it is more or less arenaceous, and at times passes into a pure sandstone.

Near the mouth of Delaware Creek it is a hard limestone, full of small, rounded cavities, and of a light cream color; but towards the sources of that stream the strata are thin bedded, of a light gray color, and appear to be undergoing rapid disintegration. South of this stream they are both compact and porous and sometimes crystalline.

Many of the organic remains such as collected by your Expedition from the upper division of the Cretaceous System have been described by Dr. Ferd. Roemer in his excellent and finely illustrated work on the Cretaceous Strata of Texas. We are able, however, to considerably augment the list by the addition of a number of new and interesting forms, which have been placed in the hands of a paleontologist for examination and description. We will, therefore, at present merely enumerate some of those species which have been found most characteristic of the mass.

The following species have been found to range from the top to the base of the formation:

• Gryphoea Pitcheri (Morton),
• Exogyra arietina (Roemer),
• Janira Texana (Roemer sp.),
• Janira quadricostata (Sowerby),
• and Terebratula Wacoensis (Roemer).

In the upper part of the formation we find most commonly the following, and as far as our observations extend they are peculiar to it:

In the inferior strata the most characteristic forms are:

• Ammonites vespertinus (Morton),
• Ammonites Popeanus (B. F. Shumard),
• Turrilites Brazoensis (Roemer),
• Baculites asper (Morton),
• Exogyra costata (Say),
• Exogyra arietina (Roemer),
• Exogyra loevinsculd (Roemer),
• Ostrea vesicularis (Lamarck),
• Gryphoea Pitcheri (Morton),
• Pecten (sp. undt. ),
• Janira quadricostata (Sowerby),
• Inoceramus Cripsii (Mantell),
• Inoceramus mytiloides (Mantell),
• Inoceramus (sp. undt.),
• Pholadomya elegantula (D'Orb),
• Cardium elegantulum (Roemer),
• Cassidulus oepuoreus (Roemer),
• Terebratula Choctawensis (B. F. Shumard),
• Nerinea Texana (Roemer),
• and Trigonia (nor. sp.).

It will be seen from the above list of species that with some few exceptions the fossils of the superior and inferior portions of the Upper Cretaceous strata of Texas and New Mexico are quite distinct. Nevertheless, as we cannot draw a well marked horizon by lithological characters, we have thought proper to make no separation of the strata.

This formation more than any other of the Plains is characterized by lofty and rough precipices and deep and fearful canyons. The elevated plateaus, which sometimes attain an altitude of seven or eight hundred feet, and often are seen stretching across extensive districts of country, present everywhere rough and precipitous cliffs, with sometimes nearly vertical faces, showing almost at a single glance the entire thickness of the formation.

Section No. III, taken from near the headwaters of the Ke-che-ah-que-ho-no, or main fork of Red River, presents a remarkable example of the kind. Here the elevated plateau known as the Llano Estacado terminates abruptly in a line of escarpments from six to eight hundred feet in height. These are for the most part nearly vertical, and extend north and south for a distance of over thirty miles. From their bases there is a descent of about four hundred feet by a succession of abrupt terraces of gypsum, red marly clay, and sandstone, so that we have here in a single locality an exposure of eleven hundred feet of Cretaceous strata.

Section No. IV was taken from near the sources of the main branch of the Brazos River, and exhibits another marked example of the kind. The table land of which this escarpment forms the abrupt boundary has an elevation above the bed of the river of about eight hundred feet, and presents a smooth and nearly flat surface on the top, covered with short yellow moss- like grass and a scattering growth of Mezquite trees. These cliffs are

15

nearly vertical, and form a continuous line thirty or forty miles in length, and throughout nearly the whole of this distance the edges of the limestone strata are finely exhibited, resting on the red marly clay and its intercalated sandstones. The lower plains extending east of this line of cliffs, say for fifty or sixty miles, are marked with small plateaus and truncated conical hills of the same strata as compose the main table land, with which doubtless they were at one time continuous.

The cliffs near the Rio Pecos, known as the "Castle Mountains," and the succession of abrupt terraces encountered on the route of the Expedition between San Antonio and the San Pedro River, and described in the Journal of this report, afford other examples similar to those presented by Sections III and IV. The -Castle Mountains," which are over sixty miles in length, are nothing more than the precipitous borders of an elevated plateau, which stretches thence in an easterly and southeasterly direction for many miles.

Canyons.-Another very important characteristic of this formation is its numerous and remarkable canyons. The most extensive of these with which we are acquainted are those of the San Pedro and Red Rivers. Both of these, as well as others so frequently met with in this region, have been hollowed out of the solid strata of the table lands by the erosive action of water so as to exhibit on either side abrupt and often perpendicular walls seven or eight hundred feet high.

The Canyon of San Pedro River is about sixty-five miles long, and varies from a few hundred yards to several miles in width. The walls of this immense chasm are often deeply fissured, and composed of variously colored limestone in nearly horizontal beds. The river, which winds its way through the canyon, is now comparatively a very insignificant stream, usually not exceeding fifteen or twenty yards in width, with a depth of three or four feet.

The canyon in which the Ke-che-ah-que-ho-no, or main trunk of Red River, takes its rise, has been already graphically described by Capt. Marcy. It is scarcely less extensive than the Devils River Canyon, being about sixty miles in length. On either side are nearly vertical walls of limestone, sandstone, gypsum, and red marly clay, from five to eight hundred feet high. The strata are in nearly horizontal beds, often traversed by deep fissures, and the main chasm is intersected at various points by tributary canyons, some of them several miles long. This gigantic canyon has been produced by the erosive action of the river, which winds through its entire length and finally emerges into the open plain, whence it flows for many miles along the base of the escarpment which forms a portion of the eastern boundary of the Llano Estacado.

Other canyons scarcely less extensive are described in the Journal of this "

Report on Red River of Louisiana.

16

report. These are often exceedingly rugged, and though generally very tortuous, all of them appear to have a general east and west direction; hence they would afford no very serious obstacle to the construction of a railroad to the Pacific.

Denudation.-Besides its numerous escarpments and canyons there are other phenomena in the region we are considering showing the great extent to which the strata of this formation have been removed by denuding agencies. There can be no doubt that the Upper Cretaceous strata at one period occupied almost the entire space included between the western borders of the settlements and the Rocky Mountains. Some of the facts upon which this opinion is based are given in detail in the accompanying Journal, and others equally conclusive are abundantly exhibited along the Colorado, Big Witchita, Upper Brazos, and Red Rivers, and at many points north of these streams. The isolated, truncated, conical hills we have so frequently encountered, and which are described by travelers as constituting one of the most characteristic features of a very considerable portion of the Plains, are nothing more than the remains of a once continuous plateau that has gradually been removed by erosion. These are often six or seven hundred feet high, and in many instances almost wholly composed of nearly horizontal strata of the Upper Cretaceous Group. They are often widely separated from each other, and as already instanced on the Brazos River, sometimes fifty or sixty miles distant from the table lands which they once formed a part. Sections .... and .... of the Journal exhibit the character of some of these hills.

Disturbance.-As will have been gathered from the foregoing remarks, the Upper Cretaceous formation exhibits generally but little evidence of violent disturbance in the district we are noticing. The strata are usually spread out in smooth parallel layers, which usually conform to the general slope of the country. The only localities in which we have observed them violently dislocated or contorted are in the southern extension of the formation; as along the base of the Limpea Mountains; near the mouth of Delaware Creek; a few miles west -of Castroville; on the San Saba and Frio Rivers; and in the vicinity of Forts Inge, Clarke. and Mason. Of these the most important is that near the Limpea Mountains, where the strata are seen contorted, fractured, and inclined against eruptive rocks at angles of from 30 to 50 degrees. The next in point of importance are the disturbed districts of Fort Mason and the San Saba River, which appear to occupy extensive areas. These are elsewhere described in this report.

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Many of the beds of the Upper Cretaceous Group afford excellent materials for construction, for which purpose they are already largely employed in the settled portions of Texas. They are usually very easily wrought, and often combine firmness, beauty, and great durability; hence they are exceedingly valuable for the construction of public works. Some of the most useful varieties have been indicated in the Journal. The rock quarried near San Antonio, Fort Inge, and Fort Clarke, is, on account of its beauty and property of acquiring hardness upon exposure to the atmosphere, peculiarly valuable.

Quicklime.-By burning, an excellent quality of quicklime for mortar can almost always be obtained from the limestone of this formation.

For the construction of macadamized roads upon the Plains this formation will furnish materials in great abundance. In making selections the hard cherty varieties of limestone should always be preferred when they can be readily obtained.

Chalk. -This important article exists in great abundance on the Rio Seco, and is also believed to occur in the neighborhood of Fort Clarke. It is generally much less pure than the foreign article, but may be made to answer many of the purposes for which the latter is employed.

Lithographic Limestone of very fair quality occurs on the Arroyo Pedro. Some examples obtained from that locality are hard, compact, and susceptible of a very good polish, but contain minute veins and crystals of calcite, which would interfere very materially with the usefulness of the rock for lithographic purposes. Others, however, are perfectly homogeneous in texture, possess a light uniform color, and present all the requisites of a good lithographic stone.

Calcareous Marl. - This valuable fertilizer occurs in the greatest abundance throughout almost the entire region occupied by the Upper Cretaceous strata. In many instances it is composed of nearly pure carbonate of lime, existing sometimes in beds thirty or forty feet in thickness. Could means be devised for transporting it to market, it would prove of inestimable value.

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The only ores of this formation of sufficient importance to require notice are those of iron. This metal is disseminated through the different layers, principally in the form of oxides and the bisulphuret or iron pyrites.

Oxides of Iron.-The coloring matter of most of the limestones and sandstones is due to the oxides of iron, which also exist in the form of spherical concretions, which are sometimes so abundant as to impart to the rock a highly mottled appearance. Brown Hematite of very fair quality is found in beds of considerable thickness in connexion with these rocks along the Upper Brazos River.

Bisulphuret of Iron (Iron Pyrites), in cylindrical and globular masses, often studded with beautiful crystals, are of frequent occurrence in the limestone.

By far the largest portion of the rich agricultural district of Texas is comprised within the limits of this formation. Whenever favorably situated for natural irrigation the soil derived from these rocks is usually highly productive and well adapted-for the growth of the great staples, corn, cotton, wheat, tobacco, and almost every product suited to the climate. But as we have already spoken of this subject in detail in connexion with the quaternary deposits and in the Journal, it is unnecessary to pursue it any farther at present.

Although not generally so abundant as we might be led to suppose from the character of the rocks, springs are nevertheless of frequent occurrence in various portions of the region occupied by this formation. Indeed in some instances they furnish almost the only supply of water over districts of country hundreds of miles in extent. They are sometimes unusually large, and generally much more abundant near the base than towards the summit of the formation. The springs in the vicinity of San Antonio and Fort Washita issue from near the junction of the limestone with the underlying marly clay, and afford streams of considerable magnitude. The San Antonio, Guadalupe, Frio, Seco, Medina, San Pedro, Concho, San Saba, False Washita, Brazos, and Red Rivers all originate from springs that gush from the Upper Cretaceous strata.

Subterranean Rivers are known to occur in connexion with these rocks in several parts of Texas. The most remarkable one known to us was discovered near the northern base of the Limpea Mountains by Mr. Thompson, a member of your Expedition. This stream emerges from a triangular

19

opening in the strata, and after flowing about a hundred yards through a basin-shaped depression in the prairie, again disappears beneath massive strata of limestone. Near the point of emergence it is about fifty feet wide, ten feet deep, and flows with a rapid current, but contracts somewhat in width a little lower down. It abounds in fish of the same species as are usually found in the streams of Texas.

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The inferior division of the Cretaceous System is composed chiefly of marly clay, sandstone, and gypsum. The clay and sandstone occur in alternating beds of variable thickness, and constitute the chief mass of the formation; the gypsum usually occurs towards the top, and is either found upon the surface or interstratified with the clay in nearly horizontal bands.

The Marly Clay varies considerably in lithological character, and, as the name implies, it is composed mainly of clay and carbonate of lime combined in different proportions, with which there is frequently a large admixture of sand and gypsum. The prevailing color is a deep venetian red, often elegantly variegated with various shades of blue, brown, and yellow. It is for the most part highly indurated, and sometimes exhibits a schistose structure not unlike the shales of the Coal Measures. In some localities, particularly towards the western boundary, it abounds in small rounded pebbles of granite, porphyry, quartz, and other eruptive rocks. Near the upper part the layers are often beautifully reticulated with gypsum.

The Sandstone passes from a fine-grained variety to coarse gritstone, and its colors are dark purple, red, brown, yellow, gray, and white. In many instances it is thickly marked with small circular light yellow and greenish spots, which are distributed through all the beds. The layers are often finely laminated, and sometimes contain rounded pebbles of eruptive rocks and nodular concretions of iron. The sandstone often contains a good deal of calcareous matter, and sometimes passes gradually into limestone. Usually it is quite soft, being in many instances but little more than slightly coherent sand, which crumbles more or less rapidly when exposed to the weather.

The Gypsum is mostly white, amorphous, and occurs in layers, sometimes of enormous thickness. This rock will be more particularly described under the head of useful minerals.

The Marly Clay Group attains a vertical development of several thousand feet, and as far as our observations have extended, forms, with a few local exceptions, the prevailing formation of all that portion of the Plains east of the Rocky Mountains not included within the limits of the superior division of the Cretaceous Group. It is exposed at various points subordinate to

21

the last, and is well ascertained to occur as far east as Fort Washita, in the Chickasaw Territory.

Beginning in the southern part of the district under notice, we find this formation well developed along the route traveled by your Expedition between Victoria and San Antonio, Texas, where it is frequently exposed in natural sections from fifty to a hundred feet high. Near San Antonio it has been artificially excavated in one place to the depth of a hundred and ten and in another to a hundred and fifty feet without reaching the base. Immediately west of this it disappears beneath the rocks of the Upper Cretaceous Group, and does not again show itself in that direction, save at a few isolated points, until we arrive at the abrupt escarpments known as the Castle Mountains," near the base of which it is seen reposing in nearly horizontal layers (vide Journal), thence westward it forms, with the exceptions pointed out in the preceding chapter, the only rocks to be seen until we approach the sources of Delaware Creek, where it is succeeded by the Paleozoic rocks.

West of the Guadalupe Mountains we again observe the Marly Clay Group, but here it is developed upon a very limited scale, being only a few feet in thickness, and confined to a strip of country not exceeding fifteen or twenty miles in width. West of this we have not been able to recognize positively its existence over any portion of the region explored by ourselves, but from the examinations of others it is highly probable that it appears in detached basins over a large portion of the region comprising the Western or Pacific Slope of our continent.

Farther north we have ascertained its existence at Fort Washita, at several points between there and the Upper Cross Timbers of Texas, and throughout the greater portion of the region watered by the Big and Little Witchita, Upper Brazos, and Red Rivers, and still farther north it has been encountered by Capt. Marcy, Lieut. Simpson, Mr. Marcon, Col. Long, and numerous other explorers.

Thickness.-As deep natural sections are very rarely observed in this formation, we can merely estimate its thickness approximately. As already stated, it has been artificially excavated in the vicinity of San Antonio to the depth of a hundred and fifty feet without reaching the base. Near Fort Washita it is exposed in natural sections sixty or seventy feet high. At the first Artesian Well, located upon the Llano Estacado, about fourteen miles east of the Rio Pecos, the Marly Clay formation was penetrated to the depth of six hundred and forty-one feet, and at the second one, located a few miles farther south, the borings were carried to the depth of eight hundred and fifty-eight feet, and in neither instance was the base of the formation reached. On the Big and Little Witchita and Brazos Rivers it forms bluffs from two to five hundred feet high, while. along the Upper Red River its general thickness, estimated after an examination of numerous sections, cannot be less than two thousand five hundred feet. This is

22

the thickness which we have accordingly given it in the general vertical section; nevertheless it is proper to state that at no point on Red River were we able to see the base of the formation, so that even this enormous thickness may prove to be an underestimate.

The principal distinguishing features of the district occupied by this formation are a gently undulating surface, low ridges often with precipitous sides, and abrupt truncated conical hills. The surface of the country is usually of a deep red color, and the hills and ridges, being composed chiefly of clay and sandstone in alternating and nearly horizontal bands, exhibit a remarkably striated appearance. Owing to the general softness of the strata composing this formation, the beds of the principal rivers are generally broad and deeply sunk below the general level of the country, and the clay mixing with their waters in the form of sediment tinges them their characteristic red hue.

This division of the Cretaceous System, like the preceding, exhibits evidence of denudation on a grand scale. The different hills and ridges, which form such a striking feature in the otherwise monotonous scenery, are the remains of once continuous strata which have been gradually eroded. Many of these hills are four or five hundred feet high. They are, as already remarked, usually isolated and rise abruptly from the surface of the prairie in the form of truncated cones, their summits being usually smooth, flat, and covered with short grass. The accompanying section (No. V) exhibits the geological character of these hills as they occur along the Big Witchita River.

In addition to the above phenomena, there are others of a less general character that serve occasionally to relieve the dull uniformity of the region occupied by this formation. The sandstone and clay, being of unequal hardness, weather unevenly, and the former is sometimes seen projecting in a series of shelves several feet from the face of the bluffs. At other points we observe detached layers of sandstone ten or fifteen feet in diameter supported several feet from the ground on slender pedestals of clay, as exhibited in the following section [No. VI] taken from near the source of the Little Witchita River.

Caverns and deep pits are of frequent occurrence in the gypsum, the former sometimes extending many feet. The pits are usually quite smooth and funnel-shaped.

Dip.-These strata exhibit little evidence of violent disturbance, and are usually found dipping at very slight angles E. S. E. In a few instances they are undulated and unheaved, but these are mere local exceptions.

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The materials composing the larger portion of the Marly Clay formation have been deposited in the bottom of the ocean in the condition of fine sediment, which appears to have been derived chiefly from the destruction of the granites and porphyries that we find towards the western slope of our continent. These are generally of a deep red color, and their disintegration produces materials similar to those constituting the larger part of the Marly Clay formation. The great thickness and extent of this group, covering, as it does, many thousands of square miles, seems to preclude the idea of its having been derived from the destruction of the rocks of the Plains east of the Rocky Mountains, since granites and porphyries that would produce such a deposit are there of uncommon occurrence. Moreover, we find in the marly clay and sandstone, pebbles identical in composition and appearance with the granites and porphyries that form the eruptive ranges towards the western side of the Continent. These pebbles also increase in size and number as we advance in that direction, and the formation itself is greatly increased in thickness. At Fort Washita it is probably not more than a hundred feet thick, while farther westward it is estimated to be not less than twenty-five hundred feet thick.

This formation has been described by Mr. Marcon as belonging partly to the Jurassic and partly to the Triassic Systems. Under the Jurassic he includes a large proportion of the strata described in the preceding chapter, while the Triassic is made to occupy, with a few local exceptions, not only all that portion of the Plains east of the Rocky Mountains not included within the limits of his Jurassic, but also a very extensive area in other parts of the United States.

The data for these conclusions appear to have been derived mainly from the region along the Canadian River, explored by Lieut. Whipple's party, of which Mr. Marcon was a member. Our observations on the geology of the Upper Red River country have also been brought forward in support of these views. Inasmuch, however, as we cannot agree with this geologist in his opinions respecting the parallelism of these strata, we shall proceed to consider a portion of the evidence that has led us to refer the Marly Clay formation of this and other portions of the Plains to the Cretaceous Period.

In the first place we would premise, that with the exception of the gypsum, which is confined to the superior part of the mass, we have not been able to detect any permanent characters that will warrant us in separating the Marly Clay formation into distinct groups. Nearly all the main features mentioned by Mr. Marcon as characterizing the divisions proposed by

25

him, we have found to occur indiscriminately throughout the entire thickness of the formation.

While engaged in the exploration of Upper Red River under Capt. R. B. Marcy, fossil shells, principally Gryphœa Pitcheri, and fragments of silicified monocotyledonous and dicotyledonous fossil wood, were, upon several occasions, observed in the upper part of the Many Clay formation; but as these appeared to be worn by attrition, and were also abundantly distributed through the overlying Quaternary drift, little attention was at that time paid to them. During the same journey we also found in the clay, considerably below the surface, a fossil coral, which Prof. Hitchcock refers to the genus Scyphia, and which lie regards as being closely allied to species that are characteristic of the Cretaceous rocks in other parts of the world.

Subsequently, while exploring near the sources of the Brazos and Big and Little Witchita Rivers, we again found the same shells in the Marly Clay formation, many feet below the top, associated with Ostrea and other forms that we have since detected in the Upper Cretaceous limestone farther southward.

The fossil wood mentioned by Mr. Marcon as occurring so abundantly along the Canadian, and which, we presume, is the same as we have obtained on Red River, only a few miles farther south, cannot be relied upon as evidence of the Triassic age of the Marly Clay formation, since fossil wood occurs abundantly in the Cretaceous rocks of Texas, as will be seen by referring to the Journal of this report, where it is mentioned that specimens were encountered at frequent intervals along our route from Indianola to El Paso. On the Frio and Nueces Rivers fragments of the trunks of trees, some of them several feet in length and weighing over five hundred pounds, were observed. After a careful comparison of some of these specimens with those obtained from the Brazos and Red River country, we are unable to detect any difference whatever. Fossil wood is also mentioned by Roemer and other explorers as occurring abundantly in the Cretaceous strata of Texas. The evidence derivable from fossil wood is therefore altogether in favor of the Cretaceous age of the Marly Clay formation of the Canadian and Red Rivers.

At Fort Washita the layers of the inferior part of the Cretaceous Group contain Ammonites, chiefly A. vespertinus, in a good state of preservation. These are confined principally to the clay, the included layers of sandstone being almost entirely destitute of organic remains.

The shell figured by Mr. Marcon as Ostrea Marshii, and regarded by him as characteristic of the American Jurassic, we have found in the Upper Limestone of Fort Washita, in the same beds with Gryphœa Pitcheri, Hemiaster elegans, Holaster simplex, and Ammonites vespertinus. This shell was described under the name of Ostrea subovata, by Dr. B. F. Shumard, in Capt. Marcy's Report of the Red River of Louisiana (p. 205, pl. 5, fig. 2), who regards it as being quite distinct from 0. Marshii, though it is doubtless a closely allied

26

species. At the same locality we have found in the clay and overlying limestone examples of Gryphæa, which present no specific differences from those figured by Mr. Marcon as G. dilatata (G. Tucumcari ), which this author considers peculiar to the so-called American Jurassic. These difficulties can hardly be reconciled unless we refer the upper rocks of Fort Washita, with their rich array of well-marked cretaceous fossils, also to the Jurassic.

That the clays and sandstones of Fort Washita are really of the same geological age as those farther west, can, we think, hardly admit of a doubt. They are found reposing beneath the same limestone and rest immediately upon the Coal Measures, while their lithological characters are very similar, the only difference being in the color of the clay, which, at Fort Washita, is blue instead of red; but, as will be seen by referring to the Journal, this color also prevails to some extent towards the south and southwest.

Near San Antonio de Bexar well marked specimens of Exogyra costata and Inoceramus crispii, both of them highly characteristic fossils of the Cretaceous formation of Texas and various other portions of the United States, were obtained from near the bottom of the well, which was sunk in the many clay to the depth of a hundred and fifty feet. (Vide Journal.) Specimens of Exogyra costata were also abundantly met with in the same formation a few miles west of San Antonio.

With the exception of that at Fort Washita, the best locality for fossils of the Marly Clay occurs near the Rio Pecos, and is mentioned in the notes of May 17, 1855. (Vide Journal.) Here the Marly Clay is well exposed, subordinate to thick strata of limestone, and is crowded with Gryphœa, identical with those figured by Mr. Marcon as Gryphæa Pitcheri, and which is admitted by him to be a cretaceous species. The same shell is well known to occur at many localities in the upper limestone of the Cretaceous Group throughout Texas.

In looking over the journals of other explorers we find still farther confirmation of the cretaceous age of this formation. Specimens of Inoceramus, and other fossils considered characteristic of the Cretaceous formation, were obtained by Lieut. Abert from near the Raton Pass, latitude 70 degrees 41 minutes, longitude 104 degrees 07 minutes, and at Pablozon, on the Rio Puerco. From the published notes of that officer we judge that one, and probably both, of these localities occur in the Marly Clay formation. Well marked specimens of Inoceramus of the Cretaceous System have also been obtained by Wislizenus and Lieut. Simpson along the valley of the Canadian River, only a short distance from Pyramid Mount, where the Gryphœa Tucumcari and Ostrea Marshii, mentioned by Mr. Marcon, were obtained. On the False Washita, near the Canadian River, Gryphœa Pitcheri has been observed in great abundance in the vicinity of extensive gypsum deposits. Cretaceous fossils were also procured by yourself from the vicinity of the Sulphur Springs of the Colorado. These last, however, as well as those procured by you from the neighborhood of the Sand Hills

27

of the Llano Estacado, may have been obtained from the rocks of the Upper Cretaceous Group.

Finally, among the host of fossils obtained from the Secondary Strata of Texas, New Mexico, and the adjacent Indian Territory, we are not aware that a single one has been found that is positively identical with either Triassic or Jurassic species of Europe. The Ostrea subovata (0. Marshii, Marcon) and Gryphœa Tucumcarii, mentioned by Mr. Maroon as occurring along the Canadian, were probably obtained from the Upper Cretaceous, as they occupy this position in other parts of this region.

The mere lithological character of these strata, so much relied upon by that author, cannot be taken as evidence of their being the equivalents of the Triassic and Jurassic Systems of Europe, though it is true they somewhat resemble the latter in mineralogical composition; but from the same kind of evidence we might, with equal propriety, regard them as being parallel with the Permian of Russia, the Tertiary of Auvergne, or the Carboniferous of Nova Scotia.

As a general rule the rocks of this formation possess very little firmness or durability, and are, therefore, but poorly adapted for building purposes or works of internal improvement. In some localities, however, the sandstone is moderately firm and resisting, and might, in the absence of better materials, be used for construction.

This mineral, on account of its economical value and enormous development upon the Plains, is of far more importance than any rocks we have considered. The Gypsum Field of the West, the great extent of which was published in 1852, shortly after the return to the States of the Red River Expedition, is believed to be the largest in the world, and will hereafter prove an inexhaustible source of wealth to the State of Texas and adjacent Territories.

The exact limits of the gypsum cannot at present be very accurately determined. It is well known to occur in great abundance at several points north of the Arkansas River, and on that stream it is mentioned by Col. Long and others. Thence southward it has been traced through the regions watered by the Canadian, Red, Big and Little Witchita, Brazos, and Pecos Rivers to within a few miles of the northern base of the Limpea "

Reports of Capt. R. B. Marcy, Lieut Simpson, and Mr. Marcon.

28

Mountains, with an average width east of the Rocky Mountains of perhaps not less than two hundred and fifty miles.

West of the Rio Grande gypsum is also met with in great abundance, and towards the south we have abundant evidence that it extends through various portions of Mexico. As already remarked, it occurs chiefly towards the summit of the Marly Clay formation, and is found either upon the surface or interstratified with the clay in successive and nearly horizontal layers of variable thickness. It usually occurs amorphous and pure white, more or less granular, and sometimes its texture is subcrystalline, resembling loaf sugar. Not unfrequently it passes into selenite, fibrous gypsum, or compact alabaster. In some localities it is much discolored with oxide of iron, in others it is variegated with various shades of green and blue by oxides and carbonates of copper. Between the beds the clay is often thickly reticulated with thin veins of selenite and fibrous gypsum.

The thickness of the different beds is sometimes enormous. On Red River they vary from a few inches to twenty-five or thirty feet. On Delaware Creek, a few miles below its source, bluffs of pure white gypsum are exposed to the thickness of about sixty feet, while between the Big Witchita and Brazos Rivers hills composed entirely of gypsum were encountered, whose heights were estimated by myself, as well as by several others of the party, at about seven hundred feet.

We have detected in this formation ores of Iron, Copper, and Manganese. Of these the most abundantly distributed are those of iron, which, in the form of oxides, furnish the principal portion of the coloring matter in the clays and sandstones.

Brown Iron Ore (Brown Hemitite) occurs in workable quantities in several localities along the Big Witchita River. It sometimes contains a large admixture of clay. In the form of Yellow Ocher, it is often used by the Indians as a paint.

Bisulphuret of Iron (Iron Pyrites) occurs in small crystals and spheroidal masses, occasionally disseminated through the clay. The spheroidal form is often beautifully studded with minute shining crystals, and when broken usually exhibits a fibrous radiated structure.

Ferruginous Sands of remarkable purity occur in great abundance on Cache Creek, an affluent of Red River. Specimens which we collected from this locality were submitted to Prof. C. U. Shephard for examination, and found to be-composed of about equal proportions of tatiniferous and magnetic oxide of iron. These sands have doubtless been derived from the Witchita Mountains.

Marcy's Report of Red River of Louisiana.

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Chloride of Copper (Marcylite). -Specimens of a dark colored compact mineral, very closely resembling black oxide of copper, were collected by myself from the Marly Clay formation on Red River, not far from the Witchita Mountains. Prof. Shephard, to whom they were submitted for examination, has pronounced them to belong to a new ore of copper, which he has named Marcylite, in honor of my friend Capt. R. B. Marcy. The following is the result of his analysis of the ore:

This ore, if obtained in sufficient quantity, would, on account of its richness, prove highly valuable. Only a few small specimens of it, however, were met with.

Oxides and Carbonates of Copper.-Small rounded masses of oxide and carbonate of copper of remarkable purity were observed abundantly distributed upon the surface near the sources of the Big Witchita and Brazos Rivers. We were unable to trace them to their source. Specimens of impure oxide and carbonate of copper have also been found in connection with the gypsum near the sources of the North Branch of Red River.

Several other varieties of copper ore have been met with in this formation along the Brazos and Red Rivers, but on account of their great impurity they do not possess much value.

Manganese.-Impure ores of this metal have been met with in two localities- one on the Witchita River, near its source, and the other on Copper Creek, an affluent of Red River. Specimens from the latter were examined by Prof. Shephard, and found to consist of Manganese in the state of binoxide with a very large percentage of silica and some peroxide of iron.

The only deposits of this character met with by myself occur in the southern part of the district, and are described in the Journal. From the observations of other explorers, however, I am inclined to believe that this valuable substance is of extensive occurrence in the country north of Red River. Mr. Marcon mentions thick deposits of rock salt in the Marly Clay formation along the Canadian, and it is known to occur in the greatest abundance N. W. of Fort Gibson, near the great bend of the Arkansas River.

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One of the principal difficulties experienced by travelers upon that portion of the Plains embraced within the limits of the Marly Clay formation, is the great scarcity of water. This arises principally from three causes: first, the great deficiency in the annual amount of rain; second, the impermeable character of the clay, which allows most of the water that falls to be conducted off, either by surface drainage or by evaporation; and, third, the general absence of extensive faults or breaks in the strata, from which cause the water, after having once entered them, is often made to flow long distances through subterranean channels before finding an outlet.

Most of the springs examined by ourselves in this formation issue from near the top of the strata, and are consequently not of a very permanent character, usually drying up soon after the close of the rainy seasons. In some few instances, however, they were found to issue from much greater depths beneath the surface, and then they are larger and yield a more constant supply of water. Wherever the gypsum prevails the water usually possesses a nauseous and bitter taste. This appears to be owing mainly to the presence of salts of lime, magnesia, and soda. It is while flowing through the gypsum formation of the Plains that the waters of many of the larger rivers of Texas, such as the Red, Brazos, and Witchita, acquire their bitter taste.

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Lying unconformably beneath the rocks of the Cretaceous System, we have an assemblage of strata belonging to the Paleozoic Period, and composed, for the most part, of hard gray, blue, and white limestone; heavy bedded quartzose sandstone, conglomerate; millstone grit, and dark shales. Collectively they exhibit a thickness of between six and seven thousand feet, and are observed cropping out extensively both upon the eastern and western side of the Plains. On the east they are well exposed along the western borders of Iowa, Missouri, and Arkansas, and through various portions of the adjacent Indian Territories, and are observed extending southward through Texas as far as Fort McIntosh, on the Rio Grande. West of these they constitute the great floor or trough upon which are deposited the newer formations of the Plains, and after disappearing beneath the latter, are not again met with, save at a few isolated points, until we approach wi