Smithsonian Miscellaneous Collections

I SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 152, NUMBER 4 Ciâxitsi B. anb iHarp Vaux Malcott 3Re2(earclj Jf unb LOWER AND MIDDLE CAMBRIAN TRILOBITE FAUNAS FROM THE TACONIC SEQUENCE OF NEW YORK (With 14 Plates) By FRANCO RASETTI Johns Hopkins University, Baltimore, Maryland Honorary Research Associate, Smithsonian Institution (Publication 4710) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION PRESS AUGUST 29, 1967 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOLUME 152, NUMBER 4 Cljarless ©. anb iilarp *âux OTalcott Sêfiearcl) Jf unb LOWER AND MIDDLE CAMBRIAN TRILOBITE FAUNAS FROM THE TACONIC SEQUENCE OF NEW YORK (With 14 Plates) By FRANCO RASETTI Johns Hopkins University, Baltimore, Maryland Honorary Research Associate, Smithsonian Institution (Publication 4710) CITY OF WASHINGTON PUBLISHED BY THE SMITHSONIAN INSTITUTION PRESS AUGUST 29, 1967 PORT CITY PRESS, INC. BALTIMORE, MD., U. S. A. : CONTENTS Page Introduction and Acknowledgments 1 Occurrence of the Fossils 2 Index of Localities 14 Biostratigraphy 15 Lower Cambrian 15 Middle Cambrian 22 Systematic Descriptions Order AGNOSTIDA 26 Family AGNOSTIDAE 26 Family PERONOPSIDAE 31 Family DIPLAGNOSTIDAE 35 Family Undetermined 37 Order EODISCIDA 40 Family EODISCIDAE 40 Family PAGETIIDAE 59 Order OLENELLIDA 68 Family OLENELLIDAE 68 Order Undetermined 73 Superfamily CORYNEXOCHACEA 74 Family CORYNEXOCHIDAE 74 Family DOLICHOMETOPIDAE 76 Family ZACANTHOIDIDAE 80 Family DORYPYGIDAE 82 Family OGYGOPSIDAE 87 Family ORYCTOCEPHALIDAE 87 Family Undetermined 88 Superfamily PARADOXIDACEA 90 Family CENTROPLEURIDAE 90 Superfamily PTYCHOPARIACEA 92 Family CONOCORYPHIDAE 92 Family MENOMONIIDAE 94 Family Undetermined 96 References 108 Plates 112 CfjarlejJ 33. anb iltarp Vaux Wlakott êsêarcl) jFunb LOWER AND MIDDLE CAMBRIAN TRILOBITE FAUNAS FROM THE TACONIC SEQUENCE OF NEW YORK By franco rL\SETTI Johtts Hopkins University, Baltimore, Maryland Honorary Research Associate, Smithsonian Institution (With 14 Plates) INTRODUCTION AND ACKNOWLEDGMENTS In a previous paper (Rasetti, 1966a) the writer described a new faunule of Early Cambrian age discovered in bedded limestone of the Taconic sequence in the East Chatham 75^-minute quadrangle, Colum- bia County, New York. The faunule was exceptional in the large number of new genera and species of the trilobite family Eodiscidae, exceeding the total formerly known for all of North America. This finding stimulated an intensive search for fossils in Cambrian outcrops in northern Columbia County, with highly gratifying results. A greater variety of Early Cambrian faunules than previously known from the Taconic sequence was discovered, and Middle Cambrian trilobites belonging to two faunizones were collected, thereby proving the existence of Cambrian strata of that age, contrary to the general belief held by previous students of that area. For the first time in the study of the Cambrian of the Taconic sequence, it was possible to obtain several faunules in certain stratigraphic order from a single section. Study of the Middle Cambrian faunas allowed a very precise correlation of the strata with those of northern Europe and the western United States. This paper is essentially based on the results of stratigraphic studies and fossil collecting in northern Columbia County. However, com- parisons with strata and fossils in the more northerly parts of the Taconic sequence, in Rensselaer and Washington Counties, are occa- sionally made, even though those areas were by far not as thoroughly SMITHSONIAN MISCEUANEOUS COLLECTIONS, VOL. 152, NO. 4 2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 52 explored by the writer. The early work of Ford, Dale, and Walcott, and the more recent one of Lochman (1956) has given a fairly com- plete description of the Early Cambrian fauna of this area, even though the existence of Early Cambrian faunules not referable to the Elliptocephala asaphoides assemblage had not been recognized (Theokritoff, 1964; Rasetti and Theokritoff, 1967). A paper on the stratigraphy of the Cambrian of Columbia County, describing in detail the sections which supplied the fossils discussed herein, will be published by Bird and Rasetti (in press). The present work was supported by two grants (nos. 3454 and 4028) from the Penrose Fund of the American Philosophical Society, and the writer gratefully acknowledges his indebtedness to the Society. Thanks are also due to several persons who gave valuable help in the course of the field work. Dr. John M. Bird, responsible for the first finding of new Early Cambrian trilobites in Columbia County, continued to cooperate enthusiastically in the discovery and search of new fossiliferous localities and study of the stratigraphy, and accompanied the writer in a number of field excursions. Dr. Donald W. Fisher contributed his knowledge of the area and sug- gested the examination of several potentially fossiliferous exposures, some of which were productive. Dr. A. R. Palmer accompanied the writer on a field excursion and collected valuable fossils. Dr. George Theokritoff also contributed to collecting, and accompanied the writer on an excursion in northern Washington County where he had thoroughly studied and mapped the rocks of the Taconic sequence. To all these persons, and to Dr. E-An Zen, the writer is also indebted for discussions on the stratigraphy and faunas. OCCURRENCE OF THE FOSSILS General statement.—The trilobites described herein, with a few exceptions of specimens from other areas illustrated for comparison, were collected by the writer, aided by the persons mentioned in the acknowledgments, in a limited portion of Columbia County, New York, chiefly either in the East Chatham 75^-minute quadrangle (Kinderhook 15-minute quadrangle) or the Hudson North 7>2- minute quadrangle (Coxsackie 15-minute quadrangle). Almost all the material, excepting a few Lower Cambrian trilobites of the Elliptocephala asaphoides assemblage from shale deposits at Judson Point, was recovered from more or less pure limestone beds or lenses (only in exceptional cases from conglomerate boulders). The specimens are seldom flattened or distorted, and in general preserve NO. 4 TRILOBITES, TACONIC SEQUENCE—RASETTI 3 the test and exhibit the aspect of the outer surface. Further details on the manner of preservation are mentioned in the discussion of the various locaHties. Most of the fossils were collected from outcrops, usually in meas- ured sections, hence in several cases the relative stratigraphic position of various faunules could be established. Some of the specimens illustrated herein, which were recovered from loose limestone blocks in stone walls, belong to faunules that are also known from bedded rocks. Localities, as in the previous paper (Rasetti, 1966a) are designated by the letters cs, followed by a locality number. A list indicating the topographic position of each locality, determined by coordinates on the U. S. Geological Survey maps, is given hereafter. When a collection is from a loose block in a stone wall on or near the Griswold farm (the only area where collections from loose blocks were made), it is labeled by the letters cs followed by the locality number (which may be that of a nearby outcrop, if any), and the letter L or M, to indicate a Lower or Middle Cambrian boulder, respectively, followed by a boulder number. An asterisk preceding the name in fossil lists indicates the type locality for the species. For brevity, author's names are not indicated, since all the listed species are described either in the present paper or the previous one (Rasetti, 1966a). When the collection is sufficiently large, an indication of the fre- quency of species is given by the symbols (rr), very rare, (r), rare, and (c), common. These indications are purely relative; e.g., a species indicated as common may be very rare in an absolute sense, only less so than another designated as rare in the same collection. East Chatham quadrangle : Gristvold farm.—The area is located on a hill about one mile SE. of North Chatham, Columbia County, on the property of Mr. Grafton Griswold, and it supplied a great number of trilobites, belonging to several Lower and Middle Cambrian faunules, both from outcrops and loose blocks. This is the area where unusual Cambrian fossils were first discovered in Columbia County in 1963. A new Lower Cambrian faunule, chiefly characterized by an excep- tionally large number of eodiscid trilobites, was already described (Rasetti, 1966a) from one bed exposed on the Griswold farm (collection cs-4), and conjectures were advanced concerning the relationship of the fossil bed to nearby outcrops. After that paper was written, a trench deep enough to expose bedrock was excavated eastward from : : 4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 52 the fossil locality, revealing a sequence of black shales with several interstratified limestone intervals, some of which did not appear on the surface. All the strata show a uniform dip of 55° E. and unques- tionably represent a sedimentary sequence. The trench was not extended further in either direction, since surface exposures indicate that only green and black shales would have been encountered west- ward and eastward, respectively, for considerable distances. Fossil evidence obtained by comparison with another section ( Maiden Bridge road cut) indicates that the strata are not inverted; i.e., higher beds are exposed eastward. A lens of intraformational limestone conglomerate in green shale is exposed 20 feet stratigraphically below the lowest limestone

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