Representatives of the ammonoid genera Perrinites and Peritrochia are described from south of Chiocomuselo, Chiapas. It is concluded that the containing beds belong in the Leonard series

Furnish, W. M.

Miller, A. K.

English

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Permian Ammonoids from Southernmost Mexico

University of Northern Iowa

Proceedings of the Iowa Academy of ScienceVolume 47 | Annual Issue Article 591940Permian Ammonoids from Southernmost MexicoA. K. MillerState University of IowaW. M. FurnishState University of IowaCopyright © Copyright 1940 by the Iowa Academy of Science, Inc.Follow this and additional works at: https://scholarworks.uni.edu/piasThis Research is brought to you for free and open access by UNI ScholarWorks. It has been accepted for inclusion in Proceedings of the Iowa Academyof Science by an authorized editor of UNI ScholarWorks. For more information, please contact scholarworks@uni.edu.Recommended CitationMiller, A. K. and Furnish, W. M. (1940) "Permian Ammonoids from Southernmost Mexico," Proceedings of the Iowa Academy ofScience: Vol. 47: No. 1 , Article 59.Available at: https://scholarworks.uni.edu/pias/vol47/iss1/59268 IOWA ACADEMY OF SCIENCE [VoL. XLVII 1/20 mm. diameter and thus suited for examination under the binoculer microscope, and the other consisting of fine silts and clays. The percentages of each portion as well as the nature of the residues were used in correlation. Chert is the most diagnostic residue. Its color, texture, and fossil content vary with different horizons. Coals and coal smuts are relatively thin and quite persistent over long distances. Scat-tered through a large percentage of the sediments are varying amounts of pyrite and glauconite. However, their abundance in a single sample and their crystal or grain form may be quite diagnostic. Fine sand, black fissile shale, and red beds are common at some horizons and can be traced over wide areas. The most important fossil residues consist of siliceous, pyrite, and iron oxide sponge spicules, foraminiferal tests, glauconitic coral fragments, and internal fusulinid molds. However, these remains reoccur at different horizons, and unless used in conjunction with other cri-teria may lead to faulty correlations. Chalcedony concretions, often in the form of rosettes, are found in most of the limestones and are of almost no diagnostic value. Goethite and limonite frequently have replaced pyrite and may retain the cubes, spines, or oolitic forms of the pyrite. Minor mineral constitutents not widespread enough to be of any great correlative value include almandine, fluorite, muscovite, bi-otite, authigenic quartz, barite, selenite, and gypsum. Among the minor fossil fragments found are silicified ostracodes, bryozoans, fusulinids, brachiopods, gastropods, crinoid stem segments and carbonaceous fragments. DEPARTMENT OF GEOLOGY, STATE UNIVERSI'l'Y oF IowA, lowA CITY, lowA. PERMIAN AMMONOIDS FROM SOUTHERNMOST MEXICO A. K. MILLER AND w. M. FURNISH Representatives of the ammonoid genera Perrinites and Peritro-chia are described from south of Chiocomuselo, Chiapas. It is concluded that the containing beds belong in the Leonard series. DEPARTMENT OF GEOLOGY, STATE UNIVERSITY OF lowA, low A CITY, low A. 1Miller and Furnish: Permian Ammonoids from Southernmost MexicoPublished by UNI ScholarWorks, 1940

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Permian Ammonoids from Southernmost Mexico

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University of Northern Iowa