UNIVERSITÀ DEGLI STUDI DI MILANO DOTTORATO DI RICERCA IN SCIENZE DELLA TERRA Ciclo XXXIII DIPARTIMENTO DI SCIENZE DELLA TERRA CONTROLLING FACTORS ON THE DEPOSITIONAL ARCHITECTURE OF CARBONATE SYSTEMS: SEDIMENTOLOGY, FACIES, GEOMETRY, DIAGENESIS AND GEOCHEMISTRY OF EASTERN SARDINIA JURASSIC CARBONATES GEO/02 PhD Thesis NEMBRINI MATTIA ID: R11949 TUTOR Prof. GIOVANNA DELLA PORTA Prof. FABRIZIO BERRA COORDINATORE DEL DOTTORATO Prof. FERNANDO CAMARA ARTIGAS Index Abstract ............................................................................................................................................... 6 Chapter 1 Introduction ...................................................................................................................... 9 1.1 Jurassic carbonate depositional systems and reefs ..................................................................... 9 1.2 Aims of this research ................................................................................................................ 10 1.3 Outline of the thesis .................................................................................................................. 12 Chapter 2 Upper Jurassic carbonate systems and reefs: a literature review ............................. 14 2.1 Jurassic time ............................................................................................................................. 14 2.1.1 Geodynamic setting ........................................................................................................... 14 2.1.2 Jurassic monster plate shift ................................................................................................ 16 2.1.3 Jurassic climate .................................................................................................................. 19 2.1.4 Trends in carbonate mineralogy ........................................................................................ 23 2.1.5 Eustatic sea-level changes ................................................................................................. 25 2.2 Jurassic reef components .......................................................................................................... 27 2.2.1 Major biotic changes .......................................................................................................... 27 2.2.2 Microbialites ...................................................................................................................... 30 2.2.3 Microencrusters ................................................................................................................. 34 2.3 Jurassic reef types and carbonate systems ................................................................................ 36 2.3.1 Controlling factors on Jurassic reefs .................................................................................. 36 2.3.2 Early Jurassic ..................................................................................................................... 37 2.3.3 Middle Jurassic .................................................................................................................. 39 2.3.4 Evolution of Upper Jurassic carbonate platforms .............................................................. 41 Chapter 3 Geological setting ........................................................................................................... 65 3.1 Tectonic and palaeogeography ................................................................................................. 65 3.2 Lithostratigraphy ...................................................................................................................... 67 3.2.1 Genna Selole Fm. ............................................................................................................... 67 3.2.2 Dorgali Fm. ........................................................................................................................ 68 3.2.3 Baunei Fm. ......................................................................................................................... 69 3.2.4 Mt. Tului Fm. ..................................................................................................................... 69 3.2.5 S’Adde Limestone ............................................................................................................. 70 3.2.6 Urzulei Fm. ........................................................................................................................ 71 3.2.7 Pedra Longa Fm. ................................................................................................................ 71 3.2.8 Mt. Bardia Fm. ................................................................................................................... 72 2 3.3 Sedimentary evolution of the Jurassic succession in eastern Sardinia ..................................... 74 3.4 Post-depositional tectonic events ............................................................................................. 77 3.5 Evolution of western Sardinia .................................................................................................. 80 Chapter 4 Materials and methods .................................................................................................. 81 4.1 Facies analysis .......................................................................................................................... 81 4.2 Staining techniques and cathodoluminescence microscopy ..................................................... 86 4.3 Strontium isotopes analysis ...................................................................................................... 87 4.4 Oxygen and Carbon stable isotope analyses ............................................................................ 87 4.5 X-ray powder diffraction (XRD) .............................................................................................. 88 4.6 Scanning electron microscope (SEM) ...................................................................................... 88 Chapter 5 Development of coral-sponge-microbialite reefs in a coated grain dominated carbonate ramp ................................................................................................................................ 89 5.1 Abstract .................................................................................................................................... 89 5.2 Introduction .............................................................................................................................. 90 5.3 Geological setting ..................................................................................................................... 91 5.4 Results ...................................................................................................................................... 92 5.4.1 Facies types ........................................................................................................................ 92 5.4.2 Dolomitized facies ........................................................................................................... 102 5.4.3 Facies spatial distribution and build-up types ................................................................. 103 5.5 Interpretation .......................................................................................................................... 106 5.5.1 Depositional model .......................................................................................................... 106 5.6 Discussion .............................................................................................................................. 112 5.6.1 Global controls on Jurassic reefs ..................................................................................... 112 5.6.2 Comparison of eastern Sardinia build-ups with coeval reefs .......................................... 113 5.6.3 Controls on eastern Sardinia reef growth ........................................................................ 116 5.7 Conclusions......................................................................................................................... 117 Chapter 6 Geometry and carbonate factory changes across a Jurassic carbonate ramp ....... 119 6.1 Abstract .................................................................................................................................. 119 6.2 Introduction ............................................................................................................................ 120 6.3 Geological setting ................................................................................................................... 121 6.4 Results .................................................................................................................................... 123 6.4.1 Facies characterization ..................................................................................................... 123 6.4.2 Biostratigraphic data ........................................................................................................ 150 6.4.3 Strontium isotopes ........................................................................................................... 153 6.5 Interpretation .......................................................................................................................... 153 6.5.1 Age of the stratigraphic succession