William J. Miller

Intraformational Corrugated Rocks

CONTENTS INTRODUCTION DIFFERENTIAL MOVEMENT ACCOMPANYING THRUST FAULTING DIFFERENTIAL MOVEMENT ACCOMPANYING NORMAL FAULTING DIFFERENTIAL MOVEMENT ACCOMPANYING REGIONAL FOLDING DIFFERENTIAL SQUEEZING ACCOMPANYING REGIONAL FOLDING DIFFERENTIAL MOVEMENT UNDER THE ACTION OF GRAVITY SUBAQUEOUS GLIDING OR SLUMPING ACTION OF ICE DIFFERENTIAL WEIGHTING CRYSTALLIZATION AND HYDRATION PRESSURE OF INTRUDING MAGMAS ACTION OF MAGMATIC INJECTION MAGMATIC FLOWAGE

Origin of Foliation in the Pre-Cambrian Rocks of Northern New York

Data bearing upon the problem of the origin of foliation in the pre-Cambrian rocks of northern New York have been gathered during the last ten years by the writer while he was engaged in the geological surveys of various quadrangles in the Adirondack Mountain region. In the attempt to explain the origin of the foliated structures of the rocks, examples and analogies from other parts of the world will be introduced, and it is hoped that the conclusions reached may have a wider application than to the Adirondack region alone. This paper is not much concerned with criteria for the determination of original igneous or sedimentary character of the rocks. The conclusions reached are almost wholly based upon observations made upon rocks which have been generally recognized as quite certainly either igneous or sedimentary. Rocks of rather doubtful origin are frequently met in minor quantity, but these may be disregarded in the present discussion. The strata all belong to the very ancient Grenville series, including various gneisses and schists, together with crystalline limestone and quartzite. The chief criteria for the determination of their sedimentary origin are: distinct banded structures, often showing alternating layers of widely different composition sharply separated from each other; presence of extensive bodies of limestone and quartzite interbedded with the gneisses; dissemination of graphite flakes through many of the rocks; and the very common occurrence of garnet in many of the rocks, and the less common occurrence of sillimanite.

Pegmatite, Silexite, and Aplite of Northern New York

During twelve seasons of field work in the Adirondack Mountain region of New York, the writer has made many hundreds of observations on bodies of pegmatite, quartz (silexite), and aplite. Certain of the phenomena long proved to be very puzzling, and more recently it has become evident that some generally accepted interpretations of such phenomena are not satisfactory when applied to many of the occurrences in the Adirondack region. While engaged in the detailed geologic mapping of the Lyon Mountain quadrangle, the writer was soon impressed by the exceptional opportunity for a careful study of the pegmatite, quartz (silexite), and aplite bodies which are there so wonderfully exhibited in countless numbers. Many detailed notes were taken and sketches were made. The North Creek quadrangle, surveyed by the writer some years ago,2 was also revisited for the purpose of making further observations on certain pegmatites there so well exhibited. In this paper the discussions deal almost entirely with the Lyon Mountain and North Creek quadrangles.

Observations on Pseudo-Dikes and Foliated Dikes

Criteria for distinguishing between dikes and pseudo-dikes (or xenoliths), particularly when both are foliated, are discussed in this paper. Consideration is given to time and direction of application of stresses which produced the foliation. Examples are mainly from southern California.

Geology of Deep Spring Valley, California

Deep Spring Valley is one of the most remarkable desert basins in California. Several thousand feet of pre-Cambrian strata and 10,000 feet of Lower Cambrian strata are wonderfully exposed around portions of the valley. A granite-monzonite series, probably of late Jurassic age, intrudes the strata on a large scale. Various conflicting ideas have been expressed in regard to the origin of the valleys of the Basin Range province. Deep Spring Valley very clearly owes its origin to faulting, the whole region being in fact a mosaic of normal fault blocks. Great fault facets are remarkably exhibited. The recency of the dislocation along the main fault is proved by many miles of sharply faulted alluvial cones; the occurrence of river beds on the top of a great fault block; and a field of very fresh lava which has been dislocated 1,500 feet, vertically. In relatively late Quaternary time a deep fresh-water lake occupied the valley.

Glaciation in the San Gabriel Mountains, California

Recently discovered evidence that several glaciers once existed within thirty miles of the site of the business center of Los Angeles is set forth in this paper. The size of the glaciers, the moraines, the amount of ice erosion, a glacial lake-basin, the age of the glaciation, and the factors favorable to the glaciation are all discussed.

Anorthosite in Los Angeles County, California

The purpose of this paper is to describe and attempt to explain the structure and origin of a large occurrence of anorthosite in Los Angeles County, California. Several theories of the origin of anorthosite advocated by petrologists are considered in their application to the occurrence, and comparisons are made with anorthosites of other regions.

Features of a Body of Anorthosite-Gabbro in Northern New York

The body of rock considered in this paper varies from true anorthosite, through anorthosite-gabbro, to true gabbro. It is four and one-third miles long, with a maximum width of one mile. It lies a little west of the central part of the Russell quadrangle in St. Lawrence County, New York (Fig. i). As far as could be determined, the rock immediately surrounding the gabbro is granite which is generally pink in color and carries only moderate amounts of dark minerals. The granite varies from medium grained to coarse grained, and from scarcely foliated to highly foliated. That the granite is younger than the anorthosite-gabbro is proved by the presence of both granite and granite-pegmatite dikes in the gabbro, and by the more or less intimate injection of portions of the borders of the gabbro by the granite. The best and most instructive exposures occur within the northern one-third of the area.

Recognition of Faults in Southern California

In this paper evidence is presented to show that faults are more numerous and geomorphically more important than various geologists believe. Fifteen criteria for the recognition of the faults, especially those in crystalline rocks, are discussed. Many examples are given.

Variations of Certain Adirondack Basic Intrusives

The basic intrusives-gabbros and diabases-discussed in this paper are wholly confined to the North Creek (Warren Co.) New York quadrangle, a detailed geologic map of which will soon appear as a publication of the New York State Museum. The region, though well within the Adirondack area, has afforded an unusual opportunity for detailed field work because of the numerous roads and trails and the large number of excellent exposures as compared with the Adirondacks in general. The gabbros occur almost always as small stocks or bosses, while the diabase always occurs as true dikes. In all, 61 gabbro masses and Ii diabase dikes have been mapped within the quadrangle. Among the gabbros there are many remarkable variations of primary and secondary origin. It is the chief purpose of this paper to describe and attempt to explain the primary variations, though certain secondary features will also be briefly discussed. The writer is greatly indebted to Professors J. F. Kemp, H. P. Cushing, and C. H. Smyth for their able papers dealing with Adirondack basic intrusives, but, so far as the writer is aware, little or no attention has been given to an explanation of the primary variations of the gabbro.