NEOGENE CALCAREOUS NANNOFOSSILS FROM THE MAKRAN REGION OF PAKISTAN AND THE INDIAN OCEAN To Christopher Tarquin Teale A thesis submitted for the degree of Doctor of Philosophy of the University of London and for the Diploma of membership of Imperial College. Jeremy Young BA MSc DUC Geology Department September 1987 Royal School of Mines Imperial College London SW7 ABSTRACT A biostratigraphical study has been made of Neogene calcareous nannofossils from the Makran accretionary terrane of South West Pakistan. They are used to help reconstruct the stratigraphy and geological evolution of the region. Comparative material from Deep Sea Drilling Project Sites in the Indian Ocean (Legs 23-26), has also been examined. In particular Reticulofenestra size variation patterns in the Miocene are documented; a Late Miocene (NN10) "small Reticulofenestra interval” is identified; assemblages from above and below it are differentiated; and the biostratigraphic, biological and taxonomic implications of the trends are discussed; the biostratigraphic results are applied in the Makran study. In addition the biological literature on nannoplankton has been comprehensively reviewed, and is used as the basis for analysis of: nannoplankton functional morphology; structural development; and intraspecific variation. The analysis of structural development has produced a predictive model of heterococcolith morphology. This model is applied and tested via: detailed investigation of reticulofenestrid structure, and biometric variation; discussion of the structure of other nannofossils; and development of a computer program for drawing elliptical coccoliths. Analysis of intraspecific variation in living nannoplankton, and evolution in calcareous nannofossils, has lead to significant reassessment of species concepts. It is recommended that more use is made of infraspecific taxa, and in particular varieties, in nannofossil taxonomy. These principles are applied in the systematics section (where most Neogene nannofossil taxa are discussed and illustrated). Forty recombinations of species as varieties are recommended. The taxonomic revisions do not involve any radical name changes, but result in a system that describes nannofossil variation more accurately than the current system. It is also more flexible, and should be easier to learn. Furthermore since it is more closely related to biological species concepts it should form a sounder base for studies of nannofossil evolution, diversity variation, and palaeoecology. 1 C.QN.TSNXS. Abstract 1 Contents and List o£ Figures 2 1. INTRODUCTION 8 1.1 Background to and development o£the project. 8 1.2 Structure and content of the thesis. 9 1.3 Acknowledgements. 11 PART A - PALABOBIOLOGY 2. INTRODUCTION TO NANNOPLANKTQN BIOLOGY 2.1 INTRODUCTION 13 2.2 HIGHER CLASSIFICATION, THE NATURE OF COCCOLITHOPHORES 14 2.3 HAPTOPHYTE LIFE-CYCLES, AND REPRODUCTION 17 2.4 CELL-WALL COMPONENTS AND ORGANISATION 19 2.4.1 Plasmalemma and columnar layer. 19 2.4.2 Organic scales. 22 2.4.3 Heterococcoliths. 22 2.4.4 Holococcoliths. 23 2.4.5 Partially calcified coccoliths. 23 2.5 COCCOLITHOGENESIS 24 2.5.1 Intracellular coccolithogenesis. 24 2.5.2 Extracellular calcification. 25 2.6 LITERATURE SOURCES 26 2.7 GLOSSARY OF TERMS USED IN BIOLOGICAL DESCRIPTION OF HAPTOPHYTES 28 3. FUNCTIONAL MORPHOLOGY 3.1 RELATIONSHIP OF COCCOLITHS AND ORGANIC SCALES 31 3.2 PROTECTION 32 3.3 FLOTATION 34 3.4 LIGHT REGULATION 38 3.5 ENVIRONMENTAL BUFFERING 39 3.6 DISCUSSION 40 4. CQCCQLITH STRUCTURE AND DEVELOPMENT 4.1 SOME GEOMETRICAL ASPECTS OF COCCOLITH MORPHOLOGY 42 4.1.1 Rim width, and ellipticity variation. 43 4.1.2 Element orientation. 43 4.1.3 Element spacing. 45 4.1.4 Discussion. 45 4.2 COCCOLITH DEVELOPMENT DURING COCCOLITHOGBNESIS 46 4.3 A BASIC MODEL FOR HETEROCOCCOLITH DEVELOPMENT 48 4.4 RETICULOFENESTRID STRUCTURE 49 4.4.1 Basic structure. 49 2 4.4.2 Effect of proto-coccolith size and ellipticlty. 51 4.4.3 Nucleation related features. 55 4.4.4 Element growth variation. 56 4.5 EXTENSION OF THE MODEL TO OTHER GROUPS 57 4.5.1 Coccolithaceae. 58 4.5.2 Helicosphaeraceae. 58 4.5.3 Pontosphaeraceae. 59 4.5.4 Holococcoliths. 59 4.5.5 Other groups. 59 4.6 SUMMARY 60 5. SPECIES AND INTRASPECIFIC.VARIATION 5.1 INTRODUCTION 61 5.2 SPECIAL TAXONOMIC PROBLEMS OF COCCOLITHOPHORES 62 5.2.1 Polyphase life cycles. 62 5.2.2 Polymorphism. 63 5.2.3 Polyspecific coccospheres. 63 5.2.4 Discussion. 64 5.3 OTHER TYPES OF INTRASPECIFIC VARIATION 65 5.3.1 Structural variation related to element development. 65 5.3.2 Variation in degree of calcification. 66 5.3.3 Aberrant coccoliths. 66 5.3.4 Size variation. 68 5.4 DISCUSSION - INTRASPECIFIC VARIATION AND NANNOFOSSIL TAXONOMY 68 5.4.1 Conventional species concepts. 66 5.4.2 Relationship of species concepts to taxonomic models. 70 5.5 CONCLUSIONS 71 PART B. - BIQ5TRATI0RAEHX 6. NEOGENE NANNOFOSSIL BIQSTRATIGRAPHY 6.1 NANNOFOSSIL ZONATION SCHEMES 74 6.2 CHRONOMETRIC AGE OF NANNOFOSSIL EVENTS 77 6.3 CORRELATION OF BIOSTRATIGRAPHY AND CHRONOSTRATIGRAPHY 78 6.4 FURTHER DEVELOPMENT OF BIOSTRATIGRAPHY 80 7. RETICULQFENESTRID SIZE VARIATION 7.1 METHODOLOGY 82 7.2 DATA PRESENTATION 83 7.3 RESULTS 84 7.3.1 Main results; DSDP Sites 219,223, 232, and 242. 84 7.3.2 Red Sea Sites, 225 and 227. 88 7.3.3 South West Indian Ocean Sites, 249 and 251A. 88 7.4 COMPARABLE STUDIES 88 7.5 DISCUSSION OF THE SIZE VARIATION TRENDS 90 7.5.1 Validity and extent. 90 3 7.5.2 Possible causes. 90 7.5.3 Taxonomic Interpretation. 91 7.5.4 Biostratigraphic use. 94 7.6 PRINCIPAL CONCLUSIONS 94 9 - BIOSTRATIGRAPHY OF INDIAN OCEAN DEEP SEA DRILLING PROJECT MATERIAL 8.1 SITE 219 95 8.2 SITE 223 96 8.3 SITE 231 98 8.4 SITE 242 100 8.5 RED SEA SITES, 225 & 227. 102 8.5.1 Biostratigraphy 103 8.5.2 Nannofloras 104 8.5.3 Discussion 106 8.6 OTHER SAMPLES. 107 9 - APPLIED BIQSTRATIGRAPHY - THE MAKRAN OF PAKISTAN 9.1 REGIONAL GEOLOGY 109 9.1.1 Tectonic setting. 109 9.1.2 Tectonic divisions and History of Research. Ill 9.2 LITHOSTRATIGRAPHY OF THE COASTAL MAKRAN. 113 9.2.1 Panjgur Facies (basin-plain turbidites) 113 9.2.2 Parkini Facies (slope siltstones). 116 9.2.3 Talar Facies (cyclic shelf sediments). 117 9.2.4 Deformation in the Coastal Makran. 117 9.3 NANNOFOSSIL BIOSTRATIGRAPHY 120 9.3.1 Material and methods. 120 9.3.2 Zonation. 120 9.3.3 Reworking. 122 9.3.4 Results. 123 9.4 DISCUSSION 130 9.4.1 Further micropalaeontological work. 130 9.4.2 Reworking. 130 9.4.3 Stratigraphical synthesis. 131 9.4.4 Continuity of processes. 132 Nannofossil distribution tables. 134 PART C - SYSTEMATIC DESCRIPTION OF NEOGENE NANNOFQSSILS. 10. INTRODUCTION TO THE SYSTEMATIC SECTION 10.1 Taxonomic conventions adopted. 143 10.2 Systematic treatment of intraspecific variation. 143 10.2.1 Rationale 143 10.2.3 Formal usage 144 10.2.3 Informal usage 145 10.3 Taxa not included in the systematic chapters. 145 4 11. COCCOLITHACBAE 11.1 Structure and classification. 149 11.2 Biostratigraphy and size variation 150 11.2.1 Coccolithus pelagicus group 150 11.2.2 Calcidiscus leptoporus group 152 11.2.3 Other species 153 11.3 Systematics 153 12. PRINSIACEAE 170 13. HELICOSPHABRACEAE 13.1 Structure of Helicoliths 178 13.2 Taxonomic groups 180 13.3 Biostratigraphical use. 181 13.4 Systematics 182 13.4.1 Helicosphaera carter! group. 182 13.4.2 Helicosphaera obliqua group. 182 14. PONTOSPHAERACEAE 14.1 Structure 189 14.2 Taxonomic subdivision of Scyphosphaera. 191 14.3 Stratigraphical distribution of Scyphosphaera. 192 14.4 Systematics. 193 15. SPHBNOLITHACEAE 15.1 Structure 201 15.2 Biostratigraphical use. 202 15.3 Systematics. 203 16. DISCOASTERACEAE 16.1 Structure. 208 16.2 Subdivision, stratigraphical distribution and evolution. 211 16.3 Systematics. 212 16.3.1 Early Miocene, D.deflandrei group 212 16.3.2 Middle Miocene, D.exilisgroup 213 16.3.3 Late Miocene, D.variabilis group. 216 16.3.4 Other Neogene discoasters. 219 16.3.5 Discoaster aster and other preservational "species" 226 16.3.6 Catinastex. 227 17. CERATOLITHACEAE AND TRIQUBTQRHABDULACEAE 17.1 Structure. 233 17.1.1 Triquetorhabdulaceae 233 17.1.2 Ceratolithaceae 234 17.2 Possible phylogenetic relationships,and biostratigraphical use 235 17.3 Systematics. 236 17.3.1 Family Ceratolithaceae. 236 17.3.2 Family Triquetorhabdulaceae. 241 17.3.3 Possibly related ortholiths. 243 5 18. SUMMARY AND RECOMMENDATIONS 18.1 Summary of principal conclusions, and results. 248 18.2 Suggestions for future research. 249 BIBLIOGRAPHY 250 Initial Reports of the Deep Sea Drilling Program 263 APPENDICES APPENDIX 1 - Nannofossil distribution chartsfor DSDP material. 264 APPENDIX 2 - Computer programs. 270 PLATES. 276 IMIJCES. 286 LIST OF FIGURES PART. A<—PALAEQBIOLQQIt 1 - Higher classification of coccolithophores. 15 2 - Aspects of haptophyte biology. 18 3 - Cell wall types. 20 4 - Coccoliths and organic scales. 21 5 - Haptophyte cytology. 30 6 - Protection and buffering adaptations. 33 7 - Complex haptophyte tests. 37 8 - Functional model for cqccosphere morphology. 41 9 - Coccolith rim geometry. 44 10 - Coccolith development. 47 11 - Reticulofenestrid coccolith element form. 47 12 - Reticulofenestrid coccoliths. 50 13 - Pseudoemiliania lacunosa variation. 53 14 - Ray width variation. 54 15 - Examples of intraspecific variation in livingnannoplankton. 67 16 - Species concepts and evolutionary patterns. 72 PART B. BIOSTRATIGRAPHY 17 - Neogene and Quaternary nannofossil zonations. 75 18 - Nannofossil events. 76 19 - Estimates of the ages of nannofossil datums. 79 20 - Reticulofenestrid size variation, Sites 219 &223. 85 21 - Reticulofenestrid size variation, Sites 231 &242. 86 22 - Reticulofenestrid size variation, Sites 225, 227, 249, & 251A. 87 23 - Taxonomic interpretations of reticulofenestridsize variation. 92 24 - Biostratigraphy of DSDP Site 219. 95 25 - Biostratigraphy of DSDP Site 223. 97 26 - Biostratigraphy of DSDP Site 231.