Bulletin - United States Geological Survey (328) - new book

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: examinations of small areas are unsatisfactory without a general knowledge of the problems presented by the whole province." When this work began practically nothing was known of the geology of northwestern Alaska, and hence the conservative policy was adopted of publishing only such general conclusions as were demanded to elucidate the economic problems. In the present treatment the same policy will be adhered to, though the accumulation of many additional data will make it possible to amplify the previous reports. The discovery of organic remains in some of the terranes has given a key to the stratigraphy that was not available when the earlier reports on the geology were prepared. The surveys of 1900 resulted in the publication of two preliminary geologic maps covering the southern half of the peninsula?one of the southwestern part, or Nome region, by Brooks,6 and the other of the southeastern part, or Norton Bay region, by Mendenhall." Men- denhall, whose journey was rather of the nature of an exploration, did not attempt to differentiate the various groups of metamorphic sediments, but Brooks recognized three terranes, named in ascending order the " Kigluaik series," " Kuzitrin series," and " Nome series."1' The two lower terranes are described by Brooks as rather well defined stratigraphic units, while a great complex of metamorphic rocks which overlie them was thrown together as a cartographic unit under the name " Nome series," since the field work had not gone far enough to indicate any logical basis of subdivision. During the following season the writer extended these subdivisions to the rocks of the northwestern portion of the peninsula, where he was able to differentiate within the Nome a massive limestone member containing fossils which were at that time c...