Ash-flow tuffs: Their origin, geologic relations and identification and zones and zonal variations in welded ash flows / Туфо-лавовые отложения: происхождение, геологические условия и определение, а также зональность строения в потоке

Twenty years have passed since publication of U.S. Geological Survey Professional Papers 366, Ash-flow tuffs: Their origin, geologic relations and identification, by. С S. Ross and R. L. Smith (1961), and 354-F, Zones and zonal variations in ash-flows, by R. L. Smith (I960). As these papers are now being republished, perhaps a few words are appropriate to clarify their historical evolution and to view them in the context of the present time.Clarence Ross and I began an intensive general study of microscopic and field characteristics of "welded tuffs" in 1948, in the hope that such a study would aid our interpretation of the Bandelier Tuff, Jemez Mountains, New Mexico. The study led to a general overview which became Professional Paper 366. Professional Paper 366 was written during the late 1940's and early 1950's. The paper was virtually complete in its present form in 1954 and should have been published in 1955 or 1956. For various reasons the paper with but minor updates to about 1956, did not go to press until 1960, and we feared that it would be obsolete before it was published. Moreover, the first printing of PP366 in 1960 was contracted out by the Government Printing Office and the reproduction of the plates was unacceptable and reprinting was required. This reprinting by GPO delayed the publication date until 1961 after the publication of PP 354-F and my review paper "Ash Flows" (1960). For the specialist in welded tuffs Professional Paper 366 probably was obsolete when published, but fortunately specialists were few and the paper has long been popular and useful to students, teachers and to geologists not specialized in the geology of silicic volcanic rocks <...>