Smaller Foraminifera from Eniwetok Drill Holes
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Smaller Foraminifera From Eniwetok Drill Holes BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-X Smaller Foraminifera From Eniwetok Drill Holes By RUTH TODD and DORIS LOW BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS GEOLOGICAL SURVEY PROFESSIONAL PAPER 260-X Smaller Foraminifera were studied as loose specimens from 2 deep holes^ about 22 miles apart^ drilled to the basement rock underlying Eniwetok Atoll UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1960 UNITED STATES DEPARTMENT OF THE INTERIOR FRED A. SEATON, Secretary GEOLOGICAL SURVEY Thomas B. Nolan, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington 25, D.C. CONTENTS Page Systematic descriptions—Continued Page Abstract. ______________________________________ 799 Family Nonionidae_ ____________________________ 828 Introduction _-_------_--_-____________.________ 799 Family Camerinidae_ ____________.____-_-------- 829 Analysis of the faunas. __________________________ 800 Family Peneroplidae____________________________ 829 Correlation between Eniwetok and BikinL _____ 801 Family Heterohelicidae____-__-_-___-___-__--__-- 831 Drillhole E-l_. ____-___-_______--------____ 802 Family Buliminidae_-_--____-_-__-___---__-_____ 831 Drill hole F-l____----_____--___-_--__---___ 805 Family Spirillinidae-____________________________ 835 Comparison of conclusions based on smaller and Family Discorbidae. ____________________________ 836 larger Foraminifera _______________________ 807 Family Rotaliidae. ____-._-___-_--__-__---_--___ 841 Miocene. __________________________________ 808 Family Pegidiidae. ___-_-_____-___--__-__---____ 843 Oligocene- _-------___.._____________________ 808 Family Amphisteginidae_________________________ 843 812 Family Calcarinidae-_-__-_-----_-----_-------__- 845 Paleoecologic interpretation, _ 812 Family Elphidiidae_ ____________________________ 845 Corrections of taxonomy _____ 815 Family Cassidulinidae-._________-___-___---__.__ 846 Systematic descriptions..- ___ 816 Family Cymbaloporidae.-_____--____--------__-_ 847 Family Hyperamminidae 816 Family Globigerinidae.__________________________ 847 Family Textulariidae-_-_ 817 Family Hantkeninidae______-__--_-_------_--___- 850 Family Verneuilinidae___ 818 Family Globorotaliidae.__________.______-_--__-_ 850 Family Valvulinidae _ ___ 819 Family Anomalinidae_ ______________-_------____ 850 Family Miliolidae __ _-_ 820 Family Planorbulinidae-_____________-_--______-. 853 Family Ophthalmidiidae_ 826 Family Rupertiidae___---____------------------- 854 Family Placopsilinidae __ 827 Family Homotremidae_________-__-___-_-_-_____ 854 Family Lagenidae_-___ -_ 827 References cited._________________--------------____ 854 Family Polymorphinidae_ 828 Index.-_-___-------_------__--_----_------------- 857 ILLUSTRATIONS [Plates 255-264 follow index] PLATE 255. Upper Eocene smaller Foraminifera from Eniwetok—Families Textulariidae to Buliminidae. 256. Upper Eocene smaller Foraminifera from Eniwetok—Families Discorbidae and Rotaliidae. 257. Upper Eocene smaller Foraminifera from Eniwetok—Families Amphisteginidae to Anomalinidae. 258. Upper Eocene smaller Foraminifera from Eniwetok—Families Anomalinidae and Planorbulinidae. 259. Upper Eocene Foraminifera, mostly planktonic, from cores in Eniwetok drill hole F-l. 260. Smaller Foraminifera from the section in Eniwetok drill hole E-l presumed to be lower Oligocene. 261. Miocene smaller Foraminifera from Eniwetok—Families Valvulinidae to Peneroplidae. 262. Miocene smaller Foraminifera from Eniwetok—Families Heterohelicidae to Planorbulinidae. 263. Miscellaneous smaller Foraminifera of Miocene to late Eocene age from Eniwetok. 264. Comparison of age of beds and tops of occurrence of certain significant smaller Foraminifera in Eniwetok drill holes F-l and E-l and the Bikini drill holes. Page FIGURE 256. Map showing location of drill holes on Eniwetok Atoll-_-_-______-__-------------_---------------------- 801 257. Composite range chart of diagnostic smaller Foraminifera in the Eniwetok drill holes___ --------------- 803 258. Alternative interpretations of correlation of age between Eniwetok drill holes F-l and E-l and Bikini drill holes 2A and 2B in the questionable interval below unquestioned Miocene and above unquestioned Eocene__ 809 259. Interpretation of relations between strata penetrated by drill holes F-l and E—!--____--------------------- 814 IV CONTENTS TABLES Page TABLE 1. Approximate tentative correlation points between the Bikini drillings and the two holes on Eniwetok-____ ___ 800 2. Distribution and abundance of smaller Foraminifera in the cuttings and cores of drill hole E-l and in the Eocene cores of drill hole F-l_ _________________________________________________________________ In pocket 3. Distribution of smaller Foraminifera in cuttings from drill hole F-l-_-_-_---_____---_____-------_---_- In pocket 4. Significant species in the Miocene section and their age and occurrences elsewhere.-________________________ 810 5. Significant species in the Oligocene section and their age and occurrences elsewhere.________________________ 811 6. Significant species in the Eocene section and their age and occurrences elsewhere_________-.__-_-____-__-____ 813 7. New identifications for specimens called Rotalia calcar (d'Orbigny) in the Bikini drill holes__________________ 817 BIKINI AND NEARBY ATOLLS, MARSHALL ISLANDS SMALLER FORAMINIFERA FROM ENIWETOK DRILL HOLES By RUTH TODD and DORIS Low ABSTRACT indeterminate because of lack of adequate material for identifi Smaller Foraminifera were studied as loose specimens from cation or description. 2 deep holes, about 22 miles apart, drilled to the basement INTRODUCTION rock underlying Eniwetok Atoll: hole E-l about 4,200 feet deep on the southeastern part of the atoll and hole F-l about 4,600 The present study covers the smaller Foraminifera feet deep on the northwestern part of the atoll near where it from two deep holes drilled on two islands of Eniwetok adjoins a guyot. Atoll. Unlike the holes drilled on Bikini Atoll (Todd In both holes, Miocene and upper Eocene sediments were and Post, 1954), these holes penetrated the entire recognized and in hole E-l a 590-foot sequence of beds is tentatively placed in the lower Oligocene. Tentative corre sedimentary sequence and reached the basement rock lation is made between a 350-foot sequence of upper Eocene thus providing a unique opportunity for studying the faunas from the uppermost occurrence of Eocene beds in hole age and ecology of the sediments immediately overlying E-l to the lowermost rocks in hole F-l. A thick sequence of the basaltic foundation of a coral atoll. Eocene GloMgerina limestone represents the uppermost occur The holes on Bikini Atoll were adjacent and were rence of Eocene beds in hole F-l and signifies open-sea deposi tion. Globigerinids and deepwater forms in association with therefore studied as one hole. As shown in figure 256, other species occur in the lower part of the section in hole F-l those on Eniwetok Atoll were drilled on islands in dif and signify moderately deepwater deposition, probably on an ferent parts of the atoll, about 22 miles apart. Despite outer slope of the atoll. No evidence on the deposition of the this geographic distance and the fact that the recovery sediments found in the middle part of this hole can be based of cores and cuttings differed in the holes, several points on smaller Foraminifera. The Miocene sediments in the upper part of the hole indicate shallow but possibly outer slope of correlation can be recognized from hole to hole as well deposition. as in the previously studied deep hole some 190 miles to Throughout the part of hole E-l from which cuttings were the eastward on Bikini Atoll. obtained, the smaller Foraminifera indicate shallow-water Some of these correlation points are approximated deposition, with the possibility of two disconformities or diastems in the lower part. No smaller Foraminifera are in table 1. available from the lowest 1,100 feet of this hole. The smaller Foraminifera thus support the indica Comparison with the deep holes drilled on Bikini shows tion of the larger Foraminifera (Cole, 1957, table 3) close conformity, particularly with hole E-l, in which deposi that the stratigraphic breaks are at slightly shallower tion is of the same type as in the Bikini holes. Correlation of depths in the two Eniwetok holes than they are in the several tops of occurrences, however, shows that levels are slightly shallower at Eniwetok, as much as 250 feet. Bikini holes. Paleontologic affinities of the species seem to be about equally Throughout hole E-l the smaller Foraminifera divided between the Eastern and Western Hemispheres. In recovered are of types indicating deposition under rela the Eocene, notable ties are recognizable to the southeastern tively shallow-water conditions. No smaller Foramini United States and the West Indies as well as to central fera were obtained from deeper than 3,130 feet in the Europe and the Near East. A few correlations can be made hole, and thus only the uppermost 360 feet of the Eocene with the described East Indian faunas of smaller Foraminifera. In the lower Oligocene the major ties are to the Southeastern section were recovered from this drilling. United States. In the Miocene, paleontologic affinities are In hole F-l, on the contrary, nine cores (Nos. 7-15 noted mainly with Australia, New Zealand, Fiji, and other inclusive) were obtained over an interval of 1,500 feet Pacific islands,