Head Office: Università degli Studi di Padova Department of Geosciences Ph.D. COURSE IN: EARTH SCIENCES SERIES XXXI THE CARNIAN (LATE TRIASSIC) EXTREME CLIMATE EVENT: COMPARISON OF THE ITALIAN TETHYS AND SOUTH CHINA GEOLOGICAL RECORDS Thesis written with the financial contribution of China Scholarship Council (grant number 201508510096) Coordinator: Ch. mo Prof. Claudia Agnini Supervisor: Ch. mo Prof. Nereo Preto Co-Supervisor: Ch. mo Prof. Piero Gianolla Ph.D. student: Xin Jin I II CONTENTS ACKNOWLEDGMENTS ................................................................................................................ IX ABSTRACT ....................................................................................................................................... XI RIASSUNTO .................................................................................................................................... XII INTRODUCTION ................................................................................................................................ 1 CHAPTER 1 - What is the Carnian Pluvial Episode (CPE)? .......................................................... 4 1. The terminology and age of CPE ................................................................................................. 4 2. Carnian regression and paleokarst ............................................................................................. 5 3. Carbonate crisis and coarse terrigenous and freshwater input in CPE .................................. 5 4. Humid weather during the CPE inferred from mineral composition and quantitative palynological studies .......................................................................................................................... 6 5. Carbon and oxygen isotopic perturbations in CPE ................................................................... 7 6. Anoxic and black shales in CPE .................................................................................................. 8 7. Biological extinction and occurrence in CPE ............................................................................. 8 8. What caused the CPE? ................................................................................................................. 9 CHAPTER 2 - Carbonate platform crisis in the Carnian (Late Triassic) of Hanwang (Sichuan Basin, South China): insights from conodonts and stable isotope data ........................................ 10 Abstract ............................................................................................................................................. 10 1. Introduction ................................................................................................................................. 11 2. Geological setting ........................................................................................................................ 12 3. Carnian/Norian Stratigraphy of Hanwang area in Sichuan Basin ........................................ 14 4. Methods ........................................................................................................................................ 15 4.1. Sample preparation ................................................................................................................. 15 III 4.2. SEM imaging and cathodoluminescence ................................................................................ 17 4.3. Conodonts ............................................................................................................................... 17 4.4. Stable isotope analyses ............................................................................................................ 17 4.5. Facies analysis methods .......................................................................................................... 18 5. Results .......................................................................................................................................... 18 5.1. Sedimentological and facies description of the HWQ section ................................................ 18 5.1.1. Unit 1: oolitic limestone unit ........................................................................................... 18 5.1.2. Unit 2: bioclastic limestone unit ...................................................................................... 19 5.1.3. Unit 3: inter-reef unit ....................................................................................................... 19 5.1.4. Unit 4: Terrigenous clastic unit ....................................................................................... 20 5.2. Biostratigraphy ........................................................................................................................ 24 5.3. Optical, SEM and CL microscopy for the assessment of diagenesis ...................................... 25 5.3.1. Brachiopods ..................................................................................................................... 25 5.3.2. Other sedimentary components and cements ................................................................... 28 5.4. Carbon and oxygen isotopes ................................................................................................... 32 6. Discussions ................................................................................................................................... 34 6.1. Facies interpretation and depositional profile ......................................................................... 34 6.2. Biostratigraphic age ................................................................................................................ 37 6.3. Alteration of carbonate δ13C and δ18O in punctated brachiopods ........................................... 37 13 18 6.4. Carbonate diagenesis records in δ Ccarb and δ Ocarb ............................................................. 39 6.5. Negative δ13C perturbation in the Qingyan Gou section ........................................................ 41 6.6. Carbonate platform crisis of upper Carnian in South China ................................................... 42 7. Conclusions .................................................................................................................................. 43 Acknowledgements ........................................................................................................................... 44 IV CHAPTER 3 - The aftermath of the CPE and the Carnian/Norian transition in northwestern Sichuan Basin, South China .............................................................................................................. 45 Abstract ............................................................................................................................................. 45 1. Introduction ................................................................................................................................. 46 2. Geological setting ........................................................................................................................ 47 2.1. The Middle Triassic in the northwestern Sichuan Basin ........................................................ 49 2.2. The Upper Triassic (Carnian and Norian) in the northwestern Sichuan Basin ....................... 49 2.3. Magnetostratigraphy in the HWQ section, Hanwang area ..................................................... 51 3. Methods ........................................................................................................................................ 52 3.1. Ammonoids, bivalves and conodonts ..................................................................................... 52 3.2. Palynology .............................................................................................................................. 52 3.3. Organic carbon isotopes .......................................................................................................... 52 4. Results .......................................................................................................................................... 54 4.1. Biostratigraphy ........................................................................................................................ 54 4.1.1. Conodonts ........................................................................................................................ 54 4.1.2. Ammonoids ....................................................................................................................... 55 4.1.3. Bivalves ............................................................................................................................ 58 4.1.4. Spores and Pollen ............................................................................................................ 59 4.2. δ13C of bulk organic matter from woods and bulk rock .......................................................... 62 5. Discussions ................................................................................................................................... 63 5.1. The Carnian - Norian boundary interval in northwestern Sichuan Basin ............................... 63 5.2. The amended age of stromatolitic beds of the uppermost Tianjingshan Formation ............... 64 5.3. A revised magnetostratigraphic correlation of the HWQ section ..........................................