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Bulletin - United States Geological Survey, Utgave 427
Geological Survey (U.S.)
Uten tilgangsbegrensning - 1910
abundant aggregate analysis appear Ascutney associated average basic bionic biotite called characteristic characters Chemung classification column common composition containing continuous correlation County crystals determined Devonian dike distribution dominant dominant species eastern equivalency eruptive essential evidence expressed facts fauna faunules feet feldspar formation fossils Genesee geographical Geol geological granite Hamilton Hamilton formation hornblende important indicate individual intrusive Ithaca Ithaca formation less limestone living localities magma Main measure minerals Mountain nature noted observed occur organisms original particular period phase Portage position present probably quartz range rare recorded regarded region relations relative reported represented rock sandstone schists sediments segregations separate sericite shale shifting species specimens Spirifer statistics strata stratigraphical structure succession Survey syenite Table tion Titanite Trace Tropidoleptus fauna typical unit western whole York zone
Side 49 - After the publication of the classification set forth in the paper of 1886 " a large number of investigations were undertaken, not only in New York, but in other parts of the country, which throw new light upon the questions then raised. But nowhere have the statistics been so well gathered as in New York State. Particularly valuable have been the researches of Prof.
Side 104 - ... of the bottom. If in such case each fauna is kept distinct, the means of tracing the geographic distribution and modification are at hand. If mingled, then the collection, though made at the same locality, will only confuse. Two such faunas meet at Owego, Tioga county, in distinct strata, but in rocks which are of similar lithologic character; one is a remnant of a prevailing western fauna, the other is an eastern and late stage of a new fauna. Fifth. The classification of the rocks may receive...
Side 51 - The microperthite is especially interesting on account of its typical development. The usual intergrowth is that of orthoclase with a plagioclase varying from albite to an acid oligoclase near Ab5An,, but on many cleavage pieces it was easily proved that the triclinic feldspar was intergrown with a monoclinic, itself strongly charged with the soda molecule. Such individuals gave extinctions of 12° and 19° on (010) for the two kinds of...
Side 7 - ... at the base of the hill), is strictly controlled in form by a small elliptical stock of alkaline syenite cutting the softer diorites. Apart from other more general considerations, the fact that these eruptive rocks are more resistant to weather than the surrounding schists is clear from the nature of the slopes and profiles at the contacts. As a rule there is an abrupt steepening of the ascent along the radiating spurs of the main mountain just above the contact between the sedimentary and eruptive...