FACIES DISTRIBUTION, SEQUENCE STRATIGRAPHY, CHEMOSTRATIGRAPHY, AND DIAGENESIS OF THE MIDDLE-LATE TRIASSIC AL AZIZIYAH FORMATION, JIFARAH BASIN, NW LIBYA A Dissertation by MOHAMED SALEM HAMADI MOUSTAFA Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Chair of Committee, Michael Pope Committee Members, Ethan Grossman Yuefeng Sun Walter Ayers Head of Department, Rick Giardino May 2015 Major Subject: Geology Copyright 2015 Mohamed Salem Hamadi Moustafa ABSTRACT This study presents the depositional facies, sequence stratigraphy, chemostratigraphy and diagenetic evolution of the Middle-Late Triassic Al Aziziyah Formation, Jifarah Basin northwest Libya. Eight measured sections were sampled and analyzed. High- resolution stable carbon isotope data were integrated with an outcrop-based sequence stratigraphic framework, to build the stratigraphic correlation, and to provide better age control of the Al Aziziyah Formation using thin section petrography, cathodoluminescence (CL) microscopy, stable isotope, and trace element analyses. The Al Aziziyah Formation was deposited on a gently sloping carbonate ramp and consists of gray limestone, dolomite, and dolomitic limestone interbedded with rare shale. The Al Aziziyah Formation is predominantly a 2nd-order sequence (5-20 m.y. duration), with shallow marine sandstone and peritidal carbonate facies restricted to southernmost sections. Seven 3rd-order sequences were identified (S1-S7) within the type section. North of the Ghryan Dome section are three mainly subtidal sequences (S8- th th S10) that do not correlate to the south. Shallowing upward trends define 4 -5 order parasequences, but correlating these parasequences between sections is difficult due to unconformities. The carbon isotope correlation between the Ghryan Dome and Kaf Bates sections indicates five units of δ13C depletion and enrichment (sequences 3-7). The enrichment of δ13C values in certain intervals most likely reflects local withdrawal of 12C from the ii ocean due to increased productivity, as indicated by the deposition of organic-rich sediment, and/or whole rock sediment composed of calcite admixed with aragonite. The depletion of δ13C is clearly associated with exposure surfaces and with shallow carbonate facies. Heavier δ18O values are related to evaporetic enrichment of 18O, whereas depletion of δ18O is related to diagenesis due to freshwater input. Al Aziziyah Formation diagenetic events indicate: 1) initial meteoric and shallow burial; 2) three types of dolomite D1, D2 and D3 were most likely formed by microbial, seepage reflux and burial processes, respectively; and 3) diagenetic cements cannot be related to the arid, mega-monsoonal climate of the Triassic and most likely formed subsequently in a humid, meteoric setting. iii DEDICATION This dissertation is dedicated to my father and mother for their encouragement, to my wife and children for their support and patience. iv ACKNOWLEDGEMENTS I thank Allah for endless help, guidance and blessings. I would like to thank my committee chair, Dr. Michael Pope, and my committee members, Dr. Ethan Grossman, Dr. Yuefeng Sun and Dr. Walter Ayers for their guidance and support throughout the course of this research. I also want to extend my gratitude to Dr. Ibrahim Mriheel for providing this proposal and for his guidance and support throughout the course of this research. Thanks also go the Libyan Government (Libya) and Texas A&M University, College Station, Texas for the financial support for this research. I wish to thank Mylod Antat for his field assistance, John Robbins for running the isotope data and Petrobrars International Braspetro B.V., the Libyan and Turkish Branches, and Department of Geology at Sebha University for their field support. I also want to extend my gratitude to my friends and colleagues and the department faculty and staff for making my time at Texas A&M University a great experience Finally, thanks to my father, mother, brothers and sisters for their encouragement and to my wife and children their support and patience. v TABLE OF CONTENTS Page ABSTRACT ..................................................................................................................... ii DEDICATION ................................................................................................................ iv ACKNOWLEDGEMENTS ............................................................................................ v TABLE OF CONTENTS ................................................................................................ vi LIST OF FIGURES ......................................................................................................... ix LIST OF TABLES ........................................................................................................ xvi CHAPTER I INTRODUCTION .......................................................................................... 1 II FACIES ANALYSIS AND SEQUENCE STRATIGRAPHY OF THE MIDDLE–LATE TRIASSIC AL AZIZIYAH FORMATION, NORTHWEST LIBYA .................................................................................. 4 II.1 Overview ........................................................................................ 4 II.1.1 Introduction .......................................................................... 5 II.1.2 Previous studies ..................................................................... 8 II.1.3 Geological setting ................................................................. 9 II.1.4 Methods ............................................................................... 12 II.1.5 Facies analysis and deposition processes ........................... 12 II.1.5.1 Tidal sandstone .......................................................... 13 II.1.5.2 Peritidal carbonate ...................................................... 13 II.1.5.3 Ramp crest facies ........................................................ 17 II.1.5.4 Shallow subtidal carbonate ........................................ 17 II.1.5.5 Deep subtidal facies .................................................... 19 II.1.5.6 Basinal facies .............................................................. 19 II.1.6 Significate surface ............................................................... 21 II.1.7 Sequence stratigraphy .......................................................... 23 II.1.8 Parasequence ....................................................................... 36 vi CHAPTER II.1.9 Discussion ............................................................................ 38 II.1.9.1 Tectonic ...................................................................... 38 II.1.9.2 Al Aziziyah depositional environments ..................... 39 II.1.9.3 Carbonate factory and source of carbonate mud ........ 40 II.1.9.4 Al Aziziyah composite sequence duration ................. 41 II.1.9.5 Climate and paleogeography ...................................... 41 II.1.9.6 Sequence interpretation .............................................. 43 II.1.9.7 Eustatic controls ......................................................... 45 II.1.9.8 Carbon isotope data and sequence stratigraphy .......... 46 II.1.10 Conclusion ......................................................................... 48 III CARBON AND OXYGEN ISOTOPE VARIATIONS ON AN ANCIENT CARBONATE PLATFORM: A CASE STUDY FROM THE MIDDLE–LATE TRIASSIC AL AZIZIYAH FORMATION, NORTHWEST LIBYA ................................................................................ 50 III.1 Overview ..................................................................................... 50 III.1.1 Introduction ........................................................................ 51 III.1.2 Previous studies .................................................................. 55 III.1.3 Geological setting ............................................................... 58 III.1.4 Methods .............................................................................. 60 III.1.5 Stratigraphic framework ..................................................... 61 III.1.5.1 Al Aziziyah facies distribution .................................. 61 III.1.6 Sequence stratigraphy ........................................................ 72 III.1.7 Carbon and oxygen Isotopes .............................................. 73 III.1.7.1 Carbon isotope record ............................................... 73 III.1.7.2 Oxygen isotope record............................................... 74 III.1.7.3 Carbon and oxygen isotope covariance ..................... 75 III.1.8 Discussion .......................................................................... 78 III.1.8.1 Ramp geometry ......................................................... 78 III.1.8.2 Climate ..................................................................... 78 III.1.8.3 Stable isotope patterns and interpretations ............... 79 III.1.8.4 Carbon isotope correlation and relative sea-level change ...................................................................................... 85 III.1.9 Conclusions ........................................................................ 93 IV DIAGENESIS OF THE MIDDLE-LATE TRIASSIC AL AZIZIYAH FORMATION, JIFARAH BASIN, NORTHWEST LIBYA ....................... 95 vii CHAPTER IV.1 Overview ..................................................................................... 95 IV.1.1