18 GYPSUM FORMATION ALONG DELAWARE CREEK.—OF NOVA SCOTIA, AND ITALY. 
Estacado as far as the Pecos river, belong to the Jurassic epoch. Ido not find in the collection 
any specimens or fossils which present evidence of the existence of these formations, and I do 
not know the foundation for Mr. Marcou's assertion. 
The collection which Captain Pope made along the banks of Delaware creek is entirely 
different in character from that made on the Llano. The color of the sandstones is not light buff 
and grey, but is red; and the frequent occurrence of the specimens of opaque and transparent 
gypsum shows clearly that the creek has worn its way downwards in the great gypsum forma- 
tion. This is also true of the Pecos, for it is indicated by the specimens; and Captain Pope 
has described a great bed of gypsum, which appears along its banks, and is fifty feet thick.! 
This is said to be translucent, and sufficiently so to be used by the people of New Mexico 
instead of glass. Captain Pope also states, in addition, that ‘‘ numerous caves of pure gypsum, 
of dazzling whiteness within, are found in this entire gypsum formation." This indicates 
that a large part, if not the greater portion of this great bed, is the opaque amorphous variety. 
This is truly an enormous bed, and exceedingly interesting in many points of view. Much 
thicker deposites are, however, found in South America, along the western slope of the Andes, 
where, according to Mr. Darwin, beds of gypsum alternate with red sandstone and shales, 
and, in some instances, are not less than six thousand feet thick.? "Thick beds are also found 
in the Carboniferous formation of Iowa, where, according to Dr. Owen, the beds are from 
twenty to thirty feet thick.* The enormous deposites of gypsum in Nova Scotia are well 
known as the sources of the vast quantities used in agriculture and the arts in the United 
States. These deposites occur among the shales and sandstones of the Carboniferous period, 
and are well described in a recent volume by Mr. Dawson.* The gypsum is found there in 
many varieties, in thin seams of selenite, in reddish and fibrous veins, and in opaque and 
amorphous masses ; often containing anhydrite in seams and crystalline nodules. In the dis- 
trict of Colchester, on the Shubenacadie, there is an immense mass of gypsum, named White’s 
or the Big Plaster rock, which once presented a ‘‘snowy front of gypsum, nearly 100 feet in 
height;’’ but which has been greatly reduced by the operations of the quarry-men, who bring 
down enormous quantities by blasting.’ The great deposite at Plaister Cove, Cape Breton, 
contains a bed which Mr. Dawson estimates at fifty yards in thickness.® 
Extensive deposites of gypsum are also found in the Preston Salt valley of Virginia, where, 
according to Prof. H. D. Rogers,’ it occupies an extensive fault or break in the Umbral or Car- 
boniferous strata of that region. 
According to W. J. Hamilton, esq.,? the great gypsum beds of Italy, which furnish the 
masses of beautiful alabaster used for various ornamental purposes, are found in the Tertiary 
strata of Tuscany, associated with a blue marl. Fossils of the genera Dentalium, Cardium, 
Venus, Cerithium, Pleurotoma, Turritella, and a large Ostrea, occur in the formation. The 
gypsum occurs in detached, irregular masses of great size, and also in continuous beds. Regu- 
lar strata are found near Castellina, where it is mined extensively. The beds have a slight 
inclination, and consist of regularly-alternating strata of blue clay and grey gypsum; the 
latter containing nodules or spheroidal blocks of the pure white alabaster. He states: ‘‘In the 
1 Report of Captain Pope, p. 28. ? Darwin's Voyage of the Beagle. 
? With respect to these beds, Dr. Owen makes the following statement: ‘‘For thickness and extent, this is by far the 
most important bed of plaster-stone known west of the Apalachian chain, if not in the United States. It is seen at 
intervals for three miles, exposed, on both sides of the Des Moines, in mural faces of from eighteen to twenty-five feet, 
always overlying pink shales, from beneath which copious springs of excellent water issue. It has been traced in the 
ravines, back from the river, for nearly three-quarters of a mile, where it is finally lost under the deep alluvion of the vast 
plains that stretch away to the west. "There is every reason to believe that it occupies an area of from two to three miles 
square, retaining an average thickness of Taa, sed perhaps double that thickness at certain points.'" [Report of a 
Geological Survey of Iowa, Wisconsin, and Minne By Dr. D. D. Owen: Phil., 1852, p. 126.] 
* Acadian Geology. By J. W. Sri: Marra 1855 5 Ibid, p. 232. 6 Ibid, p. 279. 
Soe gare on the Salt and Gypsum of the Preston Salt Valley « of Virginia. By Prof. H. D. Rogers: Boston, 1854. 
* Quarterly Journal of the Geol. Soc. Lond., vol. i, p. 273. 
