ADDIS ABABA UNIVERSITY SCHOOL OF EARTH SCIENCE FACIES AND PALEOENVIRONMENT OF THE CARBONATE UNIT IN THE MERTULE MARIAM SECTION: EAST GOJJAM, CENTRAL ETHIOPIA By Mahider Mulugeta Thesis Submitted to the School of Earth Science, Addis Ababa University in partial fulfillment of the requirement for the Degree Master of Science (Paleontology and Paleoenvironment Stream) September, 2020 Addis Ababa, Ethiopia ADDIS ABABA UNIVERSITY SCHOOL OF EARTH SCIENCE FACIES AND PALEOENVIRONMENT OF THE CARBONATE UNIT IN THE MERTULE MARIAM SECTION: EAST GOJJAM, CENTRAL ETHIOPIA By Mahider Mulugeta Advisor: Balemwal Atnafu (Phd) Thesis Submitted to the School of Earth Science, Addis Ababa University in partial fulfillment of the requirement for the Degree Master of Science (Paleontology and Paleoenvironment Stream) September, 2020 Addis Ababa, Ethiopia ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES SCHOOL OF EARTH SCIENCE FACIES AND PALEOENVIRONMENT OF THE CARBONATE UNIT IN THE MERTULE MARIAM SECTION, EAST GOJAM, CENTRAL ETHIOPIA BY MAHIDER MULUGETA APPROVED BY EXAMINATION BOARD AND DEPARTMENT CHAIRMAN Name Signature Date Dr. Balemwal Atnafu (Head, School of Earth Science) Dr. Balemwal Atnafu (Advisor) Dr. Worash Getaneh (Examiner 1) Prof. Bekele Abebe (Examiner 2) September, 2020 Addis Ababa, Ethiopia DECLARATION I hereby declare that the thesis entitled as “facies and paleoenvironment of the carbonate unit in the Mertule Mariam section: east Gojjam, central Ethiopia” submitted to the School of Earth Science ,Addis Ababa university, is a record of an original work done by me under the guidance of Dr.Balemwal Atnafu. I further declare that the results embodied in this work have not been submitted in any other university or institute for the award of any degree. All sources and materials used for this thesis work have been well referenced. ABSTRACT A detailed study on the facies and paleoenvironment of the 330m thick carbonate unit of the Mertule Mariam section has been conducted. Field work and laboratory analysis were implemented inorder to accomplish the main objectives of this study. A total of 34 rocks and 17 dry marl samples are collected from the study area and have been examined under petrographic and binocular microscopes respectively. Lithostratigraphically, the carbonate unit of the section is characterized by bedded and bioturbated limestone, fossiliferous limestone, mudstone, oolitic limestone and marl unit. Based on field investigations and based on paleontological and petrographical studies, 11 microfacies types have been recognized and are grouped into four microfacies associations related to paleoenvironments of tidal flats, lagoon, high energy shoal and open marine. Consequently, the carbonate units of the study area represent a shallow marine setting depositional system. Based on paleontological studies various macro and micro fossis are identified including foraminifera and ostracod microfossils; and Bivalve, Brachiopod and gastropod. Additionally algal fossils also recognized The age of the carbonate unit is indicated as Callovian to early Kimmerdigian due to the presence of the following index fossils: pfenderina sp., Kurnubia palastiniensis and Alveosepta jaccardi. The present carbonate unit is correlated with different measured sections in the Blue Nile basin and regionally with the Antalo limestone of the Mekele basin and Urandab Formation of the Ogaden basin depending on biostratigraphy and lithostratigraphy. Key words: Carbonate unit, Paleoenvironment, Microfacies, Blue Nile basin, Microfacies association, Microfossil i ACKNOWLEDGMENTS First and foremost, I would like to express my deepest thanks to my god who helped me in finishing this work. I wish to express my special appreciation and sincerest thanks to my Advisor, Dr.Balemwal Atnafu to his support during field work and constructive comments. I would also want to thank my friends and colleagues, Elias wubet, wubamlak Ngussie, Abebe Mihret, Yoseph Muhabaw and Esubalew yehualaw for their advice and encouragement. Finally, I would like to express my deepest gratitude to all my family who supported and encouraged me during my study. ii Table of Contents ABSTRACT ................................................................................................................................................... i ACKNOWLEDGMENTS ............................................................................................................................ ii List of figures ................................................................................................................................................ ii List of Appendix .......................................................................................................................................... iii List of plates ................................................................................................................................................. iii LIST OF ACRONYMS ............................................................................................................................... iv CHAPTER ONE ........................................................................................................................................... 1 1. INTRODUCTION .................................................................................................................................... 1 1.1. BACKGROUND ............................................................................................................................... 1 1.2. Description of the study area ............................................................................................................. 2 1. 2.1 Location and accessibility ........................................................................................................... 2 1.2.2. Climate ........................................................................................................................................ 3 1.2.3. Physiography and Drainage ........................................................................................................ 5 1.2.4. Vegetation coverage .................................................................................................................... 6 1.2.5. Population settlement .................................................................................................................. 6 1.3. Previous Works .................................................................................................................................. 7 1. 4. Problem Statement ............................................................................................................................ 8 1.5. Objectives .............................................................................................................................................. 8 1.5.1 General objective ............................................................................................................................. 8 1.5.2. Specific objective ............................................................................................................................ 8 1.6. MATERIALS AND METHODS ....................................................................................................... 9 1.6.1. Materials ..................................................................................................................................... 9 1.6.2. Methods ..................................................................................................................................... 11 1 .7. Significance of the study ................................................................................................................. 14 1.8. Limitation of the study ..................................................................................................................... 14 1. 9. Structure of the thesis ...................................................................................................................... 14 CHAPTER TWO ........................................................................................................................................ 15 2. REGIONAL GEOLOGY AND BASIN EVOLUTION ......................................................................... 15 2.1 Regional Geology ............................................................................................................................. 15 2.1.1. Basement Rocks ........................................................................................................................ 15 iii 2.1.2. Pre-Adigrat Sandstone .............................................................................................................. 15 2.1.3. Adigrat Sandstone Unit ............................................................................................................. 16 2.1.4. Gohatsion Formation................................................................................................................. 16 2.1.5. Antalo Limestone Unit .............................................................................................................. 17 2.1.6. Mugher Mudstone Unit ............................................................................................................. 17 2.1.7. The Debre Libanose sandstone ................................................................................................. 18 2.1.8. Tertiary and Quaternary Volcanoes .........................................................................................