University of Gondar College of Natural and Computational Sciences Department of Geology MSc program in Paleontology and Paleoenvironment MSc thesis Entitled Upper Jurassic Bivalves of Dejen - Gohatsion Section, Blue Nile Basin, Central Ethiopia by WORKU BIRHAN Advisor: - Dawit lebene (PHD.) September,2020 Gondar, Ethiopia College of Natural and Computational Sciences Department of Geology MSc program in Paleontology and Paleoenvironment MSc thesis Entitled Upper Jurassic Bivalves of Dejen - Gohatsion Section, Blue Nile Basin, Central Ethiopia by WORKU BIRHAN Approved by Wuletaw mulualem __________ _________ Head, Department of geology signature Date Dr. Dawit Lebenie __________ _________ Advisor Signature Date Dr. Balemwal Atnafu __________ ________ External Examiner Signature Date Wuletaw Mulualem _________ ________ Assistant Prof Internal Examiner Signature Date Zerihun Dawit _________ ________ Assistant Prof Cherman Signature Date Declaration I declare that this thesis is my original master degree work and has not been submitted to any university or institution in the past for the award of any degree or diploma at any other university. All sources and materials used for this thesis work have been well referenced and duly acknowledged. Worku Birhan __________ __________ Student Signature Date Approved by Dr. Dawit Lebene __________ __________ (Advisor) Signature Date ABSTRACT The study area has excellent exposures of upper Jurassic sedimentary rock which is situated in north western Ethiopian plateau. This research is focused on detail field investigation, description and systematics of upper Jurassic bivalves for the reconstruction of depositional environment and ecology. Different scientific methods were followed in order to achieve and accomplish the stated research problem and the objectives of the study with three main methods. These are pre-field work, detail main fieldwork and post field work. Totally six hundred fifty-two specimens of fossil bivalves have been collected and fifty-four representative samples were prepared for systematic paleontology by identifying down to species level where possible from the Antalo limestone formations in the Blue Nile Basin from three sections with two associations. The sections from which the specimens have been collected include Filikilik section (31%), Demibeza section (48%) and Geligele section (21%). Twenty-one bivalve species have been identified and described systematically and they are belonging to two superfamily, nineteen family, three subfamily, eighteen genera, four subgenera. From the twenty one species, 16 species belong to Demibeza section (Pholadomya socialis, Bucardiomya somaliensis, Pholadomya hemicardia, Pholadomya lirata, Pholadomya aubryi, Pholadomya murchisoni, Pholadomya beamontensis, Palaeonucula lateralis, Paleonucula cuneiformis, Pterotrigonia scabra, Liostrea acuminate, Eligmus asiaticus, Actinostrean gregareum, Nanogyra nana, Nanogyra fourtaui and Ilmatogyra africana), six species were identified from Filikilik (Modiolus bipartitus, Modiolus imbricatus, Paleonucula cuneiformis, Pholadomya murchisoni, paleonucula lateralis and Nanogyra nana ) and six species from Geligele (Nanogyra fourtaui ,Ilmatogyra africana, Nanogyra nana and Liostrea acuminate, Graphaea balli and Exogyra fourtaui) are described systematically. Bivalves in the study area represent mainly Basinal environments and deep shelf. No endemic species were recorded from the studied sections. Keywords: - Upper Jurassic, Systematic Paleontology, Paleoecology, Depositional Environment, Blue Nile Basin, Bivalves. i ACKNOWLEDGEMENT My welfare is only in God, who has been bestowed upon me during this research project, and throughout my life. First of all, and for being a tremendous mentor for me, I would like to express my special appreciation and thanks to my advisor and instructor Associate professor Dr. Dawit lebene. I would like to thank him for guidance, advice, encouragement and introducing me to the scientific the research work. His thorough work on the thesis is most gratefully acknowledged. Secondly, I am deeply grateful my Mom, Dad and family members; your prayer for me was what sustained me thus far. I am highly indebted to them for their blessing, guidance, advice, encouragement and support. My gratitude goes to all of my friends and relatives who directly or indirectly helped me to complete this thesis. Thirdly, I would like to give my sincere gratitude to University of Gondar, department of geology and staff members. ii TABLE OF CONTENTS ABSTRACT ................................................................................................................................ i ACKNOWLEDGEMENT ....................................................................................................... ii TABLE OF CONTENTS ...................................................................................................... iii LIST OF PLATES .................................................................................................................. ix CHAPTER ONE ...................................................................................................................... 1 1 INTRODUCTION ............................................................................................................ 1 Background ............................................................................................................................. 1 Description of the study area.................................................................................................. 3 1.2.1 Location of the study area .................................................................................... 3 1.2.2 Accessibility of the study area ............................................................................. 3 1.2.3 Climate and vegetation of the study area ............................................................. 4 1.2.3.1 Climate ............................................................................................................. 4 1.2.3.2 Vegetation ........................................................................................................ 4 1.2.4 Physiography of the study area ............................................................................ 4 1.2.5 Drainage pattern of the study area ....................................................................... 5 1.2.6 Population settlement ........................................................................................... 5 Statement of the problem ...................................................................................................... 6 Limitation of the study ............................................................................................................ 6 Previous works ........................................................................................................................ 7 Objectives................................................................................................................................ 8 1.6.1 General objectives ................................................................................................ 8 1.6.2 Specific objectives ............................................................................................... 8 Significance of the research .................................................................................................... 8 Thesis Outline .......................................................................................................................... 9 CHAPTER TWO ................................................................................................................... 10 2 REGIONAL GEOLOGY ............................................................................................... 10 Introduction .......................................................................................................................... 10 Geodynamic setting and sedimentation in Ethiopian sedimentary basin ............................ 10 Jurassic Limestone formation in Ethiopian Sedimentary Basin ............................................ 13 Stratigraphy of Blue Nile Basin ............................................................................................. 14 2.4.1 Basement rock .................................................................................................... 14 2.4.2 Paleozoic and Mesozoic Sedimentary Successions ........................................... 15 iii 2.4.2.1 Pre-Adigrat I ................................................................................................... 15 2.4.2.2 Pre-Adigrat II ................................................................................................. 15 2.4.2.3 Pre-Adigrat III ................................................................................................ 16 2.4.2.4 Adigrat Sandstone .......................................................................................... 16 2.4.2.5 Gohatsion Formation ...................................................................................... 17 2.4.2.6 Antalo Limestone ........................................................................................... 17 2.4.2.7 Mugger Mudstone .......................................................................................... 19 2.4.2.8 Debre Libanos Sandstone ............................................................................... 19 2.4.3 Tertiary volcanic ...............................................................................................