The Livingston Formation of the South Boulder Area

The Livingston formation is a thick succession of late Cretaceous lava flows, tuffs, and bedded water-laid volcanic detritus 200 miles long and 100 miles wide lying along the eastern margin of the Rocky Mountains in western Montana from Augusta to Yellowstone Park. It differs markedly within short distances in lithologic character and sequences, and the total thickness may exceed one mile in some places.

Mineralogy and Genesis of the Vermiculite Deposits at Libby, Montana

The problem considered in this report is one of the mineralogy and mode of formation of the extremely pure, large bodies of vermiculite. Mineralogically the ultrabasic intrusive, with which the economic mineral is associated, presents an array of rather unusual minerals. The determination of these minerals, their associations, and the sequence of alteration that lead to the formation of the vermiculite bodies, constitutes the problem.

The Calcite Veins of the Livingston Formation

An interesting group of calcite veins occur near Livingston Montana in a zone about eight miles wide and forty miles long in the edge of the Plains region of Montana in front of the Main ranges. The zone extends from the Boulder River south of Big Timber, through Springdale and Hunters Hot Springs, to Potter's Basin just north of Wilsall in Park County. The group of veins is particularly interesting because they cut relatively flat lying strata, suggest a structural relation­ship to one another, and they are nearly pure calcite. The present investigation was to determine the position of the calcite veins by plotting them on a base map of the district. In addition, it was planned to determine the mineralogy end origin of the veins and their structural and stratigraphical relationship to the rocks of the Livingston formation which they cut.

Siliceous Sponge Spicules of the Quadrant Formation from Montana.

A sponge spicule is a siliceous or calcareous individual or group of rays which form a framework for the sponge. Sponge spicules are very delicate and easily broken. The methods used in obtaining micro-fossils vary considerably with the type of material from which they are to be recovered and the frailness of the fossil obtained.

Fauna of the Three Forks Formation in Montana

The purpose of this paper is to identify and describe the fauna, correlate it with that of the Upper Devonian of other states, to note the geographic distribution, lithologic variations of outcrops, and to compare measured cross sections.

Stratigraphy and Paleontology of the Eagle Formation in Montana and Adjacent Areas

A conspicuous two hundred and fifty foot sandstone of central Montana, known as the Eagle Formation, constitutes part of the some five thousand feet of Cretaceous sediments in the state. It stands out in steep cliffs which stretch for many miles in the outcrop area from Wyoming to Canada.

Insoluble Residues of Five Sections of the Amsden Formation

The term, "insoluble residue," as used in this report is that portion of the original rock sample remaining after the sample has been digested by a mixture of one part hydrocloric acid and two parts water. The remains or insoluble residue from this acid treatment may vary from nothing to I00 percent.

The Fort Union Formation of Montana and Adjacent Areas

The Fort Union formation is one of the most import­ant and best known geologic formations of the northern Great Plains, and is found lying almost horizontal at the surface over large areas in this region.