Bulletin, Issue 675

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U.S. Government Printing Office, 1918 - Geology
 

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Page 59 - ... southwesterly, and its canyon is deep (for this comparatively level country) and tortuous. The upper geological formation is a shelly limestone, that rests upon a light blue or gray sandstone, through which the stream has worn its way to a depth of fifty or sixty feet, forming almost perpendicular bluffs, first on one side of the creek and then on the other. On these bluffs and extending back over small portions of the adjacent level lands and intermingling with our more common forest trees a...
Page 9 - Of this time 17 days were spent in unpacking at the beginning of the season and repacking at its end, in traveling to and from the Chitina, and in visiting the placer camps of Chititu and Dan creeks.
Page v - ADDITIONAL COPIES OF THIS PUBLICATION MAY BE PROCURED FROM THE SUPERINTENDENT OF DOCUMENTS GOVERNMENT PRINTING OFFICE WASHINGTON, DC AT 25 CENTS PER COPY CONTENTS Page...
Page 21 - ... of the deposits, for part of them have been removed by erosion. The coarse sandstone near the top of the series was thought in the field to be a tuff but on further study was found to be a sandstone consisting chiefly of fairly fresh angular grains of feldspar and quartz set in a greenish fine-grained groundmass. It probably represents the material produced by rapid erosion of a neighboring land mass consisting chiefly of igneous rocks like those in the conglomerate. Imperfect plant remains were...
Page 21 - ... are beds of finer conglomerate, associated with sandstone, included between beds of shale. In the following section the thicknesses given are only approximate : Section of Cretaceous conglomerate, arkose, and shale of Young Creek. Sandstone, coarse, green, and gray, interbedded with dark Feet. shales containing imperfect plant remains 700 Shale, brown and gray, with subordinate dark beds 700 Sandstone, greenish or greenish gray 100 Shale, fine grained, brown, gray, or greenish gray 700 Conglomerate...
Page 17 - ... possible that these shales are the most southerly representatives of the Mosasaurus Shales. These hills too are being rapidly undercut and demolished. The distribution of lateritic ironstone on the Rima Group illustrates the importance of parent material, since the sheets are confined to shale bands which form only a small proportion of the total thickness of the group. The Gundumi Group. The Gundumi Group plain is continuous with that of the Rima Group and resembles it — and differs from the...
Page 12 - ... Jurassic sandstones indicate the age of these rocks. A list of the fossils, with locality numbers and descriptions by TW Stanton, is given below : 9484. F 19. Four miles northwest of lower end of Chitina Glacier. Elevation 2,500 feet. Gray sandstone float from top of mountain on the north.
Page 29 - I would assign the collections represented by the list above given to the basal part of the Upper Cretaceous or to near the top of the Lower Cretaceous. If the comparisons are carried to more distant regions the same general results are obtained. Thus the two species of Inoceramus listed are English species and are reported from the Gault and upper Greensand of England. They are also of types not known anywhere in older rocks than the Gault.
Page 8 - River as far west as Canyon Creek. The mapping is of a reconnaissance kind, similar to that done by the United States Geological Survey in many parts of Alaska, and was of much value in the geologic surveys carried on in 1915.
Page 24 - GLACIER. there can be little doubt concerning the propriety of regarding all the lower beds as of the same geologic age. A conflict of opinion has arisen, however, in regard to the interpretation of the fossils, the fauna having been interpreted as indicating a Cretaceous age and the flora a Jurassic age for the same rocks. The. writer, being under the necessity of choosing between these two interpretations, has adopted...

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