Theory of Meteoritic Agglomeration and the Ultimate Source of the Ores

At the present time unusual interest is taken by mining men in the subject of the origin of the deposits of the metallic ores, the extent of the world\u27s supply, and the means of conserving them, for alarming as it may seem the end is already in sight

Depositional Equivalent of Hiatus at Base of Our Coal Measures; and the Arkansan Series, a New Terrane of the Carboniferous in the Western Interior Basin

For a long time it has been known that in Iowa and the neighboring states to the south a break in sedimentation exists at the base of the coal measures. It has been noted in various places in the reports of the Iowa geological survey and reference has been made to it in various other publications. Of its real significance no hint has ever been given

Geological Structure of the Jornada del Muerto and Adjoining Bolson Plains

The recent visits of a number of the members of the Academy to the Tulerosa district and contiguous plains in New Mexico makes it seem worthwhile to call attention to some of the major geologic structures of the region

Eolian Origin of Certain Lake Basins of the Mexican Tableland

The arid region of western United States and northern Mexico is a vast expanse of plain out of which abruptly rise a multitude of lofty mountains. The landscape has been aptly likened to a sea bedecked with volcanic isles. Of the entire area the desert-plains occupy about four-fifths; the mountains one-fifth. Between the different mountain ranges the plains-surface is usually slightly inclined towards the middle. These intermont plains are commonly designated as valleys

Dakota Sandstone as a Basinal Basilium

Meek and Hayden\u27s type-section of the Cretaceous Dakota sandstone is directly across the Missouri River from Sergeant Bluff, below Sioux City. Neither this outcrop, nor the fine exposure at Sergeant Bluff, which latter is commonly considered as Iowa\u27s best section of the formation, are complete to top or to bottom. Drill-core records have shown the Dakota sandstone to extend nearly 200 feet below the base of the exposed section named; and erosion has removed perhaps as many more feet from the top

Genesis of Certain Cherts

As regards origin, the cherts which occur so abundantly throughout the limestones of the lower carboniferous of the Mississippi valley have been the subject of much speculation. The same problem has received attention from every quarter of the globe. While the explanations offered differ very much from one another they in general agree in that they are regarded as formed contemporaneously with the geological formations in which they occur. The writings of Prestwich, Irving, Van Hise, Hull, Benard, Hinde, Hardman, Hovey, and many others corroborate this statement

Evidences of Recent Uprisings of the Shores of the Black Sea

The photographs which I have to show you are to illustrate some remarkably clear examples of very recent changes in elevation of the earth\u27s crust. Most of the pictures were taken in the neighborhood of Sudak, in the Crimea. The southern coast of this peninsula is very rugged. It rises abruptly out of the water to a height of 3,000 to 5,000 feet. The waves are constantly eating back so that in many places the coast land is almost a sheer precipice hundreds of feet high

Physiographic Significance of the Mesa de Maya

The Mesa de Maya is a small elevated tableland lying on the borders of Colorado and New Mexico, between Trinidad and Raton. It has an elevation of over 9,000 feet above sea-level and about 3,600 feet above the valleys on either side