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General section of the cretaceous rocks of Nebraska.

Divisions and subdivisions,

Localities.

Thickness.

Fox Hill beds-forma

tion No. 5.

Gray ferruginous and yellowish sandstone and Fox hills, near Moreau river,
arevaceous clayy, containing Belemnitella Bulbo near Long lake, above Fort
sa, Nautilus Dekayi, Ammonites placenta, A. lo- Pierre, along base of Big Horn
batus, Scaphites conradi, S. Nicollet, Baculites mountains, and on North and
grandis, Busycon Bairdi, Fusus Culbertsoni, F. South Platte rivers.
Newberryi, Aporrhais americana, Pseudo-bucci.
num Nebrascensis, Mactra Warrenana, Cardium
subquadrarum, and a great number of other mol.
luscous fossils, together with bones of Mosasaurus
Missouriensis.

500 feet.

[blocks in formation]

Dark gray and bluish plastic clays, containing Sage creek, Cheyenne river, near the upper part Nautilus Dekayi, Ammonites and on White river, above the placenta, Baculites ovatus, B. compressus, Sca Mauvaises Terres, Fort Pierre, phites nodosus, Dentalium gracile, Crascatella and out to Bad Lands, down Evansi, Cucullæa Nebrascensis, Inoceramus Sa the Missouri, on the high coungensis, I. Nebrascensis, I. Vanuxemi, bones of try, to Great Bend. Mosasaurus Missouriensis, &c.

Middle zone nearly barren of fossils.

Lower fossiliferous zone containing Ammonites Great bend of the Missouri,
complexus, Baculites ovatus, B. compressus, Heli-below Fort Pierre.
coceras mortoni, H. tortum, H. umbilicatum, H.
cochleatum, Ptychoceras mortoni, Fusus vinculum,
Anisomyon borealis, Amauropsis paludiniformis,
Inoceramus subulatus, I. tenuilineatus, bones of
Mosasaurus Missouriensis, &c.

Dark bed of very fine unctuous clay, containing Near Bijou Hill, on the Mis-
much carbonaceous matter, with veins and seams souri.
of gypsum masses, sulphuret of iron, and numerous
small scales of fishes, local, filling depressions in
the bed below.

Eq. Upper or white chalk and Maestricht beds. (Senonien, D'Orbigny.)

700 feet.

Niobrara division

formation No 3.

Lead gray calcareous marl, weathering to a yel. Bluffs along the Missouri.
lowish or whitish chalky appearance above,contain above the Great Bend, to the
ing large scales and other remains of fishes, and vicinity of the Big Sioux river;
numerous species of Ostreg congesta attached to also below there, and on the
fragments of Inoceramus, passing down into light tops of the hills.
yellowish and whitish limestone, containing great
numbers of Inoceramus problematicus, I. psuedo-
mytiloides I aviculoides, and Ostrea congesta, fish
scales, &c.

200 feet.

LOWER SERIES.

Dark gray laminated clays, sometimes alter Extensively developed near
nating near the upper part with seams and layers Fort Benton, on the Upper Mis-
of soft gray and light-colored limestones, Inoceramus souri; also along the latter from
problematicus, I. tenuirostratus, I. latus! I. fragilis, ten miles above James river
Ostrea congesta, Venilia mortoni, Pholadomia pa to Big Sioux river, and along
pyracea, Ammonites mullani, A. percarinatus, A. the castern slope of the Rocky
vespertinus, Scaphites Warreni, 8. larvaeformis

, mountains, as well as at the
S. ventricosus, s. vermiformis, Nautilus elegans, Black Hills.
&c.

800 feet.

formation No. 2. Dakota group-for-Fort Benton group

mation Nol.

Eq. Lower or gray chalk (and upper G. sand) of British geolo

(Turonien and cenomanien of D'Orbigny.)

Yellowish, reddish, and occasionally white sand Hills back of the town of Da-
stone, with, at places, alternations of various col. kota; also extensively devel-
ored elays, and beds and seams of impure lignite; oped in the surrounding coun-
also silicified wood, and great numbers of leaves try in Dakota county, below
of the higher types of dicotyledonous trees, with the mouth of Big Sioux river,
casts of Pharella ? Dakotensis, Axinea Siouxensis, thence extending southward in.
and Cyprina Arenarea.

to northeastern Kansas, and
beyond.

400 feet.

gists.

DAKOTA GROUP.

Although we have hitherto regarded this as a distinct group of cretaceous rocks, with a strong physical line of separation from the group above, I now think the evidence is clear that it passes imperceptibly in its lithological relations up into the Fort Benton group, without any break in time.

In the hills back of Dakota City there are repeated exposures which show the transition layers between the two sandstones of the one and the dark plastic clays of the other. The fossils, however, so far as we now know, are distinct, and for the practical purpose of investigating this rock they may be regarded ae distinct groups.

We have referred the rocks of the Dakota group to the cretaceous epoch, from the fact that they have yielded numerous species of dicotyledonous leaves. Among these leaves, Dr. Newberry and Professor Heer have identified those of trees belonging to the genera Populus, (poplar,) Salix, (willow,) Alnus, (alder,) Platanus, (sycamore,) Liriodendron, (tulip,) Ficus, (fig,) and many others. In the history of geology, no dicotyledonous leaves have been found in fossil condition in rocks older than the cretaceous era. As they are found here in beds lying underneath rocks containing well-known cretaceous fossils, their age is beyond a doubt.

The discovery of these vegetable impressions in sandstones of the cretaceous period at this locality has afforded to geologists an instructive lesson. A geologist of high character, and one of the best botanists in Europe, Professor Heer, declared these plants to be of tertiary age, and even identified some of them with plants already known in the Old World in tertiary rocks.

In 1863, Professor Capellini, of the University of Bologna, Italy, and Professor Marcou, of Switzerland, made a journey up the Missouri river to study these rocks, and to settle this vexed question.

The results of their labors were published in the French and Swiss geological journals. The article of Professor Capellini was first translated by me in this country for Silliman's Journal.

Professor Capellini, in a short but very interesting article, confines his observations mostly to the rocks of the Dakota group, and remarks that he does not hesitate to regard the observations of American geologists as entirely just; the following remarks close the article of Professor C:

“ After all we have observed in relation to the environs of Sioux City, it is easily seen that a stratigraphic series, so complete, throws a clear light upon the isolated facts first noticed at Tekamah and Blackbird Hill, and indicates the exact position of the rocks with dicotyledonous leaves, analogous to the tertiary leaves of Europe, but belonging in reality to the chalk.

“ It may be estimated that the thickness of these cretaceous strata in the environs of Sioux City is about forty metres. They may be divided into two distinct parts, one rich in leaves, a fresh water formation; the other truly chalky, with fishes and inoceramus of marine origin. Both are probably not older than the chalk of Maestricht.

“ This has been my opinion from the time I admitted that the dicotyledonous leaves of the Big Sioux and Tekamah were cretaceous.

“ Once the age of the Mollasse with leaves established by the aid of the stratigraphy and the animal fossils, it would be interesting if it were possible to arrive at the same results by the vegetable remains. On this account Professor Heer came to my aid and investigated the specimens 1 collected in my explorations. More than a dozen species were recognized among the leaves from Tekamah, Blackbird Hill and Big Sioux, but it was especially the first locality which furnished the best specimens.

“We are couvinced that when observations are exact and determinations

made from careful examination of specimens, there is never any disagreement between stratigraphical and paleontological laws."

The remarks of Professor Heer, which preface bis descriptions of the fossil plants by Professor Capellini, are so interesting and important that we copy them entire.

“ The collection of Mr. Capellini contains sixteen species ; four are badly preserved, twelve are determinable; nevertheless, of the latter several are but fragments, so that their determination is difficult and not sufficiently positive. This is especially the case with Phyllites, which I have referred to the genera Platanus and Andromeda.

It is certain that all the leaves found by Mr. Capellini are dicotyledonous, and with great probability one may be referred to the genus Ficus, one to Salix, one to Diospyrus, two to Populus, and two to Magnolia, although there are no accompanying fruits or other parts to confirm these determinations. These genera are yet 'living, and they are also found in the tertiary formations.

If we compare these plants of Nebraska with the cretaceous plants of Europe, we find no identical species among them. I sent drawings of them to Dr. Debey, of Aix-la-Chapelle, who discovered in that locality a cretaceous flora. He has written to me that he has not found one species identical. Even the greater part of the genera are different. There is but one Cissite, (.C aceroides, Debey,) which recalls slightly the C. insignis. (Plate 4, Fig. 5.) The cretaceous plants of Henant, Belgium, those of Blankenburg and Quedlinburg, are also very different.

Professor Schenck has recently sent to me a collection of plants of Quedlinburg for determination. Besides conifers and fern characteristic of the chalk, it contains dicotyledonous leaves, but no forms like those of Nebraska. The cretaceous flora of Moletein, Moravia, which I have lately studied, exhibits more resemblance. It contains two species of Ficus, which much resemble the Ficus of Nebraska, two superb species of Magnolia, one with a fruit cone.

There is a relationship between the flora of Nebraska and that of the upper chalk of Europe, although identical species are wanting. But to the present time no characteristic genus of the cretaceous flora of Europe has been found in Nebraska.

If we compare the plants of Nebraska with the tertiary plants we find no identical species, but seven genera (Populus, Salix, Ficus, Platanus, Andromeda, Diospyrus, and Magnolia) are miocene, and likewise living. .

It then appears that the Nebraska flora is related more to the tertiary than to the cretaceous flora of Europe, a fact which struck me when I first saw drawings of the former. But it should be remarked that we know but a very small number of American species, and on the other hand the European cretaceous flora has more relationship with tertiary flora than I at first supposed. I have found in the cretaceous flora of Moletein, Moravia, species of Ficus and Magnolia which resemble tertiary species ; a Myrtacea, which is a near neighbor to the Ucalyhtus rhododendroides, (Mass.) of Mt. Bolca, a Juglans and a Laurinea, which also have their analogues in the tertiary flora; a Pinus and two other conifers. which belong to the genus Sequoia, which was extensively distributed in Europe and America in the miocene epoch, and which is now only found in California.

As the cretaceous fishes are more nearly related to the tertiary than to the jurassic fishes, the upper cretaceous flora is also entirely different from the jurassic and more nearly allied to the tertiary floras, and it appears that in: America the relation between the tertiary and cretaceous flora is yet more intimate than in Europe.

It is remarkable that the plants of Nebraska (as Magnolia and Liriodendron) present relations with the existing flora of America, whilst the cretaceous* flora of Europe has more of an Indo-Australian character. It thus appears that since

the cretaceous epoch the American flora has not undergone a change so great as the European flora. While the cretaceous flora of Europe is entirely different from the existing European flora, that of Nebraska contains eight genera yet found in America, and it is the more remarkable that the greater part are yet found in a country under the same latitude.”

Professor Heer describes the following species of plants from this group in this memoir:

Populus litigiosa, (?) Debeyana, Salix nervillosa, Betulites denticulata, Ficus primordialis, Platanus, (?) Newberryana, Proteoides grevillea formis, P. daphnegenoides, P. acuta, Aristolochites dentata, Andromeda parlatorii

, Diospyrus primaevus, Cissites insignis, Magnolia alternans, M. Capellini, Liriodendron meekie, Phyllites vanone.

One instructive lesson is derived from the mistakes of these eminent men, that in the progress of geolugical development, America was almost or quite one epoch ahead of Europe--that the fauna and flora of the cretaceous period in this country was really more nearly allied to those of the tertiary period in Europe, and that, geologically speaking, America should be called the Old World and Europe the New. This point will be again alluded to in our remarks on the tertiary rocks.

Again, there is evident simplicity in the form and ornamentation of these leaves, which marks the dawn of the appearance on this planet of trees like our forest, fruit, and ornamental trees.

The beauty of foliage in our present dicotyledonous trees is largely due to the serrations and various forms and patterns which they present, but, so far as my observations have extended, the reverse is the case with this cretaceous vegetation for the most part-thus slowly progressing through the tertiary period from simplicity up to greater complexity and beauty.

The question would arise naturally, have any remains of land animals been found in this group mingled with these vegetable impressions ? None have yet been observed along the Missouri at this locality, and as they have now been studied with considerable care, we may never find any. That land animals did exist we cansot doubt, for the forests which furnished these leaves could not have existed far away.

The leaves are so perfect that they could not have been transported to a great distance before they were imbedded in the sand. On the eastern slope of the Big Horn mountains there are a series of beds which hold a position between the jurassic beds and the Fort Benton group, which I have referred to the

Here occur beds of impure earthy lignite, large quantities of silicified wood and uncharacteristic bones, which Dr. Leidy thinks belonged to some huge saurian. No remains of strictly land animals have ever been found.

The geographical extension of this group of rocks outside of this State has been found to be very extensive. The best of country occupied by them in Nebraska runs nearly southeast and northwest, and is from 60 to 80 miles wide, extending far south into New Mexico, and possibly further and northward into Iowa and Minnesota, and probably far up into British America. It is believed also to occur all along the Rocky mountains, although as yet no positive proof from fossils has been obtained.

There are a series of beds between well-known cretaceous and jurassic rocks in those regions, which have been regarded as belonging to the Dakota group; also, near the sources of the Missouri are a series of beds differing from any other yet described, containing many species of shells and a bed of lignite, which seems to belong to this group. These latter beds need more careful study before the position can be positively fixed in this section.

Along the Atlantic coast, especially in New Jersey, the lower cretaceous beds seem to be lithologically similar, in containing numerous dicotyledonous leaves, so that it is now regarded as the equivalent of the Dakota group of the west.

Dakota group

It is, therefore, evident that this formation is very widely distributed, perhape even east and west from one ocean to the other.

FORT BENTON GROUP. This group bears the above name from the fact that it is largely developed in the vicinity of Fort Benton, near the sources of the Missouri river. In ascending the Missouri, it is first seen in thin outliers below the mouth of Big Sioux river, and on the Big Sioux six miles above its mouth. It is characterized as a dark leaden gray plastic clay, but when saturated with water it is of a black color.

icus, Ostrea congesta, Ammonites, Serpula, &c. Near the mouth of Iowa creek there is the best exposure of this group, as well as groups above and below.

3. Gray and light yellow calcareous marl or chalky limestone, with great numbers of Inoceramus problematicus, Ostrea congesta, and remains of fishes. Niobrara division, 40 to 50 feet.

2. Dark plastic clay, with abundant remains of fishes, I. problematicus, 0.congesta, Ammonites peracutus, Serpula tenuicarinata, and a species of oyster, like O. congesta. Fort Benton group, 30 to 40 feet.

1. Variegated sands and clays of Dakota group, 15 to 20 feet above water's edge; impressions of leaves of willow, laurel, and many crystals of sulphuret of iron.

The beds of the Fort Benton group are widely distributed throughout the west, but in no portion has it revealed any useful minerals or economical rocks of any kind, to my knowledge. The black plastic clays may be rendered useful at some period, but it is quite doubtful. They are everywhere filled with sulphuret of iron.

At the locality where the above section was taken I obtained some of the finest specimens of crystallized sulphuret of iron I have ever seen. There were also many species of selenite. So far as I know, this formation does not exert any favorable influence on the country.

The beds of impure coal near the mouth of Iowa creek are very interesting in a geological point of view. At no other locality do I know of the existence of any seams of carbonaceous matter. This coal is too impure and contains too much sulphuret of iron ever to be made available.

NIOBRARA DIVISION. In many respects this is the most interesting and inost valuable group of the cretaceous rocks in the west. Its principal character is a gray or light yellow chalky limestone; much of it is so pure as to make good chalk for commercial purposes.

It would also be useful, doubtless, as a fertilizer. In ascending the Missouri it is first seen in thin outliers on Pilgrim's Hill, a portion of the Omaha reserve. It then grows gradually thicker as we ascend, and south of Dakota City, in the hills, it becomes ten to twenty feet thick. At Ponka City, St. Helena, and mouth of the Niobrara it is exposed fifty to two hundred feet in thickness, exhibiting a great variety of color and texture.

All along the Missouri this rock is much used for the construction of buildings with success. The fact that so large an area of country exists below the first appearance of this formation destitute of any rock for lime must render this group of much economical importance to the settlers. Its soft, yielding nature gives rise to long ranges of precipitous bluffs along the river.

It is easily cut into innumerable ravines by the temporary streams, and these bluffs often present the appearance of a series of cones.

This formation extends up the river to the foot of the great bend, where it passes beneath the water level. The fossils in this group are few in the number

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