VU Research Portal Lines of Time Kaandorp, R.J.G. 2007 document version Publisher's PDF, also known as Version of record Link to publication in VU Research Portal citation for published version (APA) Kaandorp, R. J. G. (2007). Lines of Time: Seasonality, climate and environments of the Miocene Pebas Formation in western Amazonia derived from chemical records in molluscan growth-bands. 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Sep. 2021 VRIJE UNIVERSITEIT Lines of Time Seasonality, climate and environments of the Miocene Pebas Formation in western Amazonia derived from chemical records in molluscan growth-bands ACADEMISCH PROEFSCHRIFT ter verkrijging van de graad Doctor aan de Vrije Universiteit Amsterdam, op gezag van de rector magnificus prof.dr. L.M. Bouter, in het openbaar te verdedigen ten overstaan van de promotiecommissie van de faculteit der Aard- en Levenswetenschappen op dinsdag 16 oktober 2007 om 15.45 uur in het auditorium van de universiteit, De Boelelaan 1105 door Ronald Johannes Gerardus Kaandorp geboren te Alkmaar promotoren: prof.dr. J.E. van Hinte prof.dr. D. Kroon copromotoren: dr. G.M. Ganssen dr. H.B. Vonhof voor Brad, Soraya, mijn familie ISBN 978-90-9022201-1 Netherlands Research School of Sedimentary Geology (NSG) Publication n ◦: 20071016 Lines of Time — Seasonality, climate and environments of the Miocene Pebas Formation in western Amazonia derived from chemical records in molluscan growth-bands. [Ph.D. thesis, Vrije Universiteit Amsterdam] In Dutch: Tijdslijnen — Seizonaliteit, klimaat en landschappen van de Miocene Pebas Formatie, westelijk Amazonia, uit chemische data in groeibanden van molluskenschelpen. [ac. proefschrift, Vrije Universiteit Amsterdam] Cover photo’s: satellite picture from NASA World Wind, molluscs photographed by Saskia Kars This project was funded by WOTRO, the Netherlands Foundation for the Advancement of Tropical Research, residing under the Netherlands Organization for Scientific Research (NWO). reading committee: prof.dr. G.J. Boekschoten prof.dr. H. Hooghiemstra dr. C. Hoorn prof.dr. M. Räsänen prof.dr. B.R. Schöne Contents Dankwoord xiii Samenvatting xv Resumen xxi 1 Introduction and summary 1 1.1 Aim of the present work . ....................... 1 1.2 The geography of Amazonia . ....................... 2 1.3 Amazonia’s seasonal variation of climate . ............... 6 1.4 Neogene sedimentation history of the Amazon Basin . ........ 8 1.5 Pebas Formation . .............................. 8 1.5.1 Stratigraphy .............................. 8 1.5.2 Environments of Lago Pebas . ................... 12 1.5.3 Marine influences . ....................... 13 1.6 Isotope records from accretionary growth structures . ........ 17 1.6.1 Isotope records from molluscs . ................... 17 1.6.2 MicroMill . .............................. 17 1.6.3 Mass spectrometry . ....................... 18 1.7 Amazonian climate .............................. 20 1.7.1 Present-day climate . ....................... 20 1.7.2 Low latitudes . ....................... 20 1.7.3 Amazonian Miocene climate . ................... 22 1.8 Main conclusions of this work . ....................... 23 1.8.1 The Miocene climate of Amazonia . ............... 23 1.8.2 Ecological implications of molluscan stable geochemical records . 24 1.8.3 Aquatic landscapes in the Miocene of western Amazonia . .... 25 2 Seasonal variation reflected in Amazonian freshwater bivalve A. trapesialis 27 2.1 Introduction .................................. 28 2.2 Experiment, material and methods . ................... 29 2.2.1 Monitoring project . ....................... 29 vii 2.3 Results ..................................... 31 2.3.1 Playa Cocha water .......................... 31 2.3.2 Isotope composition of aragonite shells . .............. 32 2.4 Discussion . ................................. 35 2.4.1 Seasonal stable isotope variation of water .............. 35 2.4.2 Equilibrium precipitation of shell aragonite . ....... 35 2.4.3 A. trapesialis growth rates ...................... 39 2.5 Conclusions . ................................. 39 3 Growth rates and stable isotopes in juvenile Anodontites trapesialis molluscs 41 3.1 Introduction . ................................. 41 3.2 Material and methods . .......................... 42 3.3 Results ..................................... 42 3.3.1 Bottom water temperature record .................. 42 3.3.2 Isotope records . .......................... 43 3.4 Discussion . ................................. 44 3.4.1 Juvenile growth rates . ...................... 44 3.4.2 Extrapolation of the growth in the dry season . ....... 45 3.5 Conclusions . ................................. 46 4 Seasonal Amazonian rainfall variation in the Miocene Climate Optimum 47 4.1 Introduction . ................................. 47 4.2 Methods . ................................. 49 4.3 Discussion . ................................. 52 4.4 Conclusions . ................................. 52 5 Ecological implications of Miocene western Amazonian bivalves 55 5.1 Introduction . ................................. 56 5.1.1 Pebas Formation . .......................... 56 5.1.2 Molluscs . .......................... 57 5.2 Material and methods . .......................... 58 5.3 Results ..................................... 59 5.3.1 Quality of fossil material . ...................... 59 5.3.2 Stable-isotope composition of Pebas Formation bivalves . 59 5.4 Discussion . ................................. 66 5.4.1 Stable oxygen isotope characteristics of Amazonian continental wa- ters . ................................. 70 5.4.2 Variation of carbon isotopes in host water .............. 71 5.4.3 Variation of carbon isotopes in bivalves . .............. 71 5.4.4 Coupled carbon and oxygen isotope cyclicity . ....... 73 5.4.5 Consistency of isotope signals . .................. 74 5.4.6 Trace element variation . ...................... 74 5.5 Conclusions . ................................. 80 5.6 Appendix . .................................. 81 6 Aquatic landscapes in the Miocene of western Amazonia 85 6.1 Introduction .................................. 85 6.2 Material and methods . ....................... 86 6.3 Description of the section and facies interpretation . .... 89 6.4 Molluscan composition and diversity . ................... 92 6.5 Carbon and oxygen isotope geochemistry . ............... 97 6.6 Growth band chemistry . ....................... 98 6.7 Discussion . .................................. 100 6.8 Conclusions.................................. 106 References 109 Appendices 120 Appendix A– Isotope data of modern molluscs 121 Appendix B – Miocene shells: isotope data and minor elements 125 List of Figures 1.1 Geographic setting of Amazonia ....................... 4 1.2 Amazon River and Amazon Basin . ................... 4 1.3 Confluence Nanay and Amazon rivers . ................... 5 1.4 Amazon environments . ....................... 5 1.5 Seasonal ITCZ movement . ....................... 6 1.6 Climate of Iquitos . .............................. 7 1.7 Stratigraphic ranges of Pebas Formation outcrops . ........ 9 1.8 Drawings of typical Pebas molluscs . ................... 9 1.9 Amazon Basin: interpreting the past . ................... 10 1.10 Grainsize distribution Los Chorros . ................... 11 1.11 Overview of sites . .............................. 11 1.12 Distribution of Pebas molluscan faunas . ................... 12 1.13 Inferred distribution of assemblages . ................... 13 1.14 Palaeoenvironmental impression of Lake Pebas ............... 14 1.15 Molluscan Sr isotope ranges . ....................... 16 1.16 MicroMill . .................................. 18 1.17 Milling thin lines with a thick drill . ................... 19 1.18 Finnigan MAT252 Mass spectrometer . ................... 19 1.19 Seasonal change Amazonian rainwater . ................... 20 1.20 Location of the Playa Cocha and Mazán sites . ............... 22 2.1 Location map of sampling site . ....................... 28 2.2 Marking and cutting of shells . ....................... 30 2.3 Playa Cocha water data . ....................... 33 2.4 Stable isotope records of A. trapesialis .................... 34 2.5 Predicted isotope values and growth rates . ............... 37 3.1 Water temperatures and precipitation . ................... 43 3.2 Isotope records vs growth, determining anchor points . ........ 44 3.3 Growth fit, using 3 anchor points....................... 45 3.4 Temperature change reflected in mollusc oxygen isotopes . ........ 46 xi 4.1 Seasonal ITCZ movement .......................... 48 4.2 Isotopic change of rainwater . ...................... 49 4.3 Location map ................................. 50 4.4 Oxygen isotope records . .........................