Some photo-micrographs are given (by way of illustration) which were taken of some slides of glauconite. No. 1 is taken from material from a greensand pocket in the Redbank, and is intended to show glauconite grains highly altered. No. 2 is taken from the clay ironstone of the Navesink, and shows fresh glauconite grains. The dark spaces between the grains show the ground-mass of limonite and clay. No. 3 is also taken from the clay ironstone of the Navesink, and is to show fibrous glauconite. No. 4 is taken from a sample of Hazlet Sand from near Cliffwood, N. J. It shows fibrous glauconite, and also the size and shape of some of the glauconite grains. mm The diameter of the field of the microscope, when these photomicrographs were taken, was 2.55mm. In the slide from which No. 2 was taken two grains of glauconite were measured, one of which was 1.3m long and 0.65mm wide; and the other was round and 0.2mm in diameter. Some grains are smaller than this, down to 0.1mm or less, but they are not so common, and the average grain is much larger than 0.2mm. Outline of the Mesozoic and related history. 1 This study was made as research assistant of the Carnegie Institution of Wash IGNEOUS AND METAMORPHIC ROCKS. Associated with the Dillard series. General characters. The basic series. The greenstones The feldspathic granular rocks The ultrabasic rocks. The docite-andesite group. Glaucophane and associated schists. Relations to the Myrtle group. General relations. General comparison with the Dillard. The Myrtle conglomerates. Summary. ECONOMIC RELATIONS. Purpose of the discussion. The Myrtle group. The Dillard series. General contrast. Quartz veins. Effects of structure. Copper. Nickel. Chrome iron. Platinum. Limestone. Sandstone and cherts. AREAL DISTRIBUTION IN THE REGION STUDIED. General method of determination. The interior quadrangles. General distribution in Roseburg quadrangle. The Dillard area. The Myrtle Creek area. Smaller areas between the Dillard and Myrtle Creek areas. Contrast between close-lying areas of Dillard and Myrtle. The coastal quadrangles. The Coos Bay quadrangle. The Port Orford quadrangle. THE DISCONTINUITY OF THE DILLARD AND THE MYRTLE. COMPARISON WITH THE STANDARD CALIFORNIA TYPE FORMATIONS. The Myrtle group. Identity with the Shasta. The Dillard series. General characteristics of the Franciscan. The Whitsett limestone fossils. EXTENSION OF THE FRANCISCAN. THE SHASTA (LOWER CRETACEOUS) SEA. THE BOUNDARY OF THE KLAMATH MOUNTAINS. NOMENCLATURE. SUMMARY OF RESULTS. INTRODUCTION During the summer of 1904 the writer, in the course of an investigation of the glaucophane schists of California, made a trip into southern Oregon for the purpose of comparing the geological relations of the schists reported as occurring there with those of similar rocks in California. In particular, the Oregon schists were said to occur in a formation corresponding to the Knoxville and Horsetown of California, and were considered as contact products of irruptives which were intruded into the formation, and were therefore considered at least post-Horsetown in age. In California, on the other hand, similar schists are found in the Franciscan, a thick and important series of formations which underlies the Knoxville unconformably, and the greater part of whose basic intrusives, if not all, are preKnoxville in age. No schists have yet been found in the California Knoxville or later rocks. It would be of considerable interest, then, to the student of petrographical provinces, if such rocks, which are apparently due to rather uncommon conditions, and which in the United States are, so far as known, limited to this coastal (California and Oregon) region, had been developed in different parts of this territory in formations which differ both in age and in lithologic characters, and in relation to igneous rocks of apparently different ages of intrusion. The study of the field relations of the Oregon schists, however, have led to the conclusion that they were developed in formations of the same age and lithologic characters, and have the same associations and relationships, as the corresponding schists in California. At the same time, certain important features of the Mesozoic stratig raphy and history of the region were recognized, and a closer correlation between the geological conditions and sequence in southwestern Oregon, and those of the California Coast Ranges, made possible. To set forth these general results is the purpose of the present paper. HISTORICAL The region under discussion lies in southwestern Oregon, and is included from east to west between the western foothills of the Cascade Range (long. 123° west), and the Pacific Ocean (about 124° 20' to 124° 30' west); and from north to south between the latitude of Roseburg or the head of Coos Bay (about lat. 43° 15′ north), and the Klamath Mountains (about 42° 30′ north). This field has been studied by few geologists. Dana and later Newberry, in their exploration work in the early days, saw but little of the country, and were hardly in position to arrive at any definite conclusions as to even the major events in the geological history of the region. Mr. G. F. Becker, about 1890, studied some of this country in the vicinity of Riddles in conjunction with Mr. W. Q. Brown, and arrived at certain conclusions that were important in extending the knowledge of the Pacific coast Cretaceous. It is to Mr. J. S. Diller, however, that we owe by far the greater part of our present knowledge of southwestern Oregon. He has spent a number of years in the investigation and mapping of considerable areas, and his studies have covered all parts of the region outlined above. His general results are presented most systematically and with the greatest detail in the texts accompanying the Roseburg, Coos Bay, and Port Orford folios3 of the Geologic Atlas of the United States, although certain features are more particularly treated in various memoirs, a number of which will be referred to in the body of this paper. AREAS STUDIED The index map, page 518, shows the relative positions of the three geologically mapped quadrangles of southwestern Oregon— the Coos Bay and Port Orford lying in contact on the coast, and 1 For use of this term see p. 552. 2 Bulletin of the Geological Society of America, Vol. II (1891), pp. 201-6. 3 U. S. Geological Survey, Geologic Atlas of the United States, Folios Nos. 49 (1898), 73 (1901), and 89 (1903). |