Palaeoenvironments and palaeoecology of the Middle and Upper Jurassic succession of Gebel Maghara (Sinai) Der Naturwissenschaftlichen Fakultät der Friedrich-Alexander-Universität Erlangen-Nürnberg zur Erlangung des Doktorgrades Dr. rer. nat. vorgelegt von Ahmed Awad Abdelhady M.Sc. 2007 Aus El Minia, Ägypten 2014 Als Dissertation genehmigt von der Naturwissenschaftlichen Fakultät der Friedrich-Alexander-Universität Erlangen-Nürnberg Tag der mündlichen Prüfung: 25.07.2014 Vorsitzende des Promotionsorgans: Prof. Dr. Johannes Barth Gutachter: Prof. Dr. Dr. Franz T. Fürsich Prof. Dr. Martin Aberhan ACKNOWLEDGEMENTS My welfare is only in Allah, 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 supervisor ‘Doktorvater’ Professor Dr. Franz Theodor Fürsich (Geozentrum Nordbayern der Universität Erlangen). I would like to thank him for his numerous comments and suggestions. I appreciate his company during many field excursions. Thank you for encouraging me in my research and for allowing me to grow as a scientist. His advice on both research as well as on my career has been priceless and words cannot express how grateful I am. Special thanks to Dr. Martin Aberhan (Museum für Naturkunde, Berlin) for providing recommendation letters, required by the DAAD committee every year. I would like to thank also Prof. Dr. Senowbari-Daryan (GeoZentrum Nordbayern, Erlangen) for identification of some sponges, Dr. Dhirendra K. PANDEY (University of Rajasthan, Jaipur) for aid in identification of some ammonites, and Dr. Debahuti Mukherjee (Geological Survey of India, Kalkutta) for identification of some brachiopods. For providing facilities through the phases of my stay in Egypt and for help to overcome the old routine and bureaucracy, I am grateful to both Prof. Dr. Awad Farghal Ahmed, Dean of the Faculty of Science, Minia University, Egypt and Prof. Dr. Esam El Sayed, Head of the Geology Department. Similarly, I would like to acknowledge all staff members of the Egyptian Desert Research Center (DRC), North Sinai, for providing valuable help during the fieldwork and for granting hospitality. I would like to commemorate all members of GeoZentrum Nordbayern, especially the Flügel-Course team, for their moral support and for being helpful during my work on this thesis. They provided answers, suggestions, and solutions for any scientific or non-scientific problem. I would especially like to thank Mrs. Birgit Leipner-Mata, for preparation of the thin sections. I also want to thank the DAAD and the Egyptian Mission, Ministry of Higher Education, Egypt, for their financial support through the German-Egyptian Research long- term Scholarship ‘GERLS’. Finally, I am deeply grateful to my Mother and my wife Esraa; your prayer for me was what sustained me thus far. Ahmed Awad Abdelhady Abstract The Jurassic succession of Gebel Maghara North Sinai, Egypt, represents a mixed carbonate- siliciclastic sedimentary succession. Combining information from both fossils and rocks collected from four sections has allowed a plausible reconstruction of the palaeoenvironments and benthic communities of the area. As age-diagnostic fossils are rare, and in order to ensure maximal stratigraphic resolution, chronostratigraphic boundaries were determined based on quantitative biostratigraphy (Unitary Associations method). The proposed zones were found to be valid chronological markers and permitted correlation with the Tethyan ammonite zones. The Jurassic succession of G. Maghara was deposited on ramp, and the architecture of the ramp facies was strongly controlled not only by eustatic sea-level changes but also by the extensional tectonics in connection with rifting of the Tethys north of Gondwana. Seven tectonically enhanced third-order sequences (DS1 to DS7) have been recognized. The first three sequences, ranging from the Toarcian to the Bajocian, record the invasion of the sea (intertidal to shallow subtidal conditions) across an intracratonic area resulting from eustatic sea-level changes during a quiescent rift stage. The remaining sequences reflect open marine mid to outer ramp settings. During an active extensional stage, horsts, which acted as barriers separating the G. Maghara sub-basin from the main ocean, subsided. Subsequent rejuvenation and reactivation of faults transformed the homoclinal into a distally steepened ramp topography during the Early Bathonian. As a result, a 200-m-thick deltaic wedge was created and, during the Early Kimmeridgian, a calcirudite and calcarenite dominated slope environment. The macrobenthic palaeocommunities were investigated to identify relationships with environmental parameters and to trace the palaeoecological changes associated with sea-level fluctuations through time. The quantitative analysis of a data matrix comprising 198 macrobenthic taxa in 142 samples identified nine associations and three assemblages, interpreted to be representative of their original environment. Non-Metric Multidimensional Scaling (NMDS) delineated the same degree of habitat partitioning as hierarchical clusters with very little overlap. Detrended Correspondence Analysis (DCA) identified water depth as the primary environmental gradient controlling the distribution of the fauna, while Axis 2 has ordered the taxa according to differences in life habit, which is also related to substrate consistency. Based on diversities, the associations and assemblages were divided into two major groups, (1) low-stress polyspecific associations, (2) high-stress paucispecific associations. The structure of the palaeocommunities is related to the various ramp environments and the sequence stratigraphic framework. The diversity of the macrofauna of G. Maghara exhibits a cyclic pattern that coincid es with the 3rd order sea-level fluctuations and also with the Axis 1 scores of the DCA, which is a well-known bathymetric indicator. Hydrodynamic conditions were most likely the main factor controlling the benthic communities. Hydrodynamic conditions influenced the substrate type, redistributed nutrients, and were responsible for stratified water masses and hypoxia. Middle ramp settings during middle to late TST times were found to provide the best conditions for macrobenthos. During Bajocian times, G. Maghara and the Levant margin were connected but at the same time isolated from the main ocean by islands and shallows (intracratonic setting). These barriers may have limited the dispersal potential of the macrofauna and prevented faunal exchange with even nearby areas. Although these barriers had disappeared by the Bathonian, the same biogeographic patterns prevailed, which may be related to the global sea-level lowstand. By the Callovian, a time of global sea-level highstand, in contrast, the fauna of the study area became very similar to that of northeastern Africa. Similarly, diversity and extinction rates increased from the Middle Bathonian onward, which may reflect immigration of cosmopolitan taxa due to the newly established open marine setting and the global sea-level highstand during the Callovian. Towards the Oxfordian, lowering of temperature may have limited the dispersal within the Ethiopian Province. As a result, a southeastern subprovince including Tanzania, Madagascar, and India became established. Although the geographic pattern of the different faunal groups exhibits some similarity, a positive correlation was found between the life habit of the taxa and their dispersal potential. The dispersal potential was highest for ammonites, followed by that of bivalves and then corals. Brachiopods had the lowest dispersal potential. Keywords: Palaeoenvironments, Quantitative biostratigraphy, Sequence stratigraphy, Macrobenthos, Palaeocommunity analysis, Jurassic, Gebel Maghara, Egypt. Contents 1 Introduction 1.1 Overview .............................................................................................................................. 1 1.2 Palaeogeography and palaeoclimate ..................................................................................... 3 1.3 Geologic and tectonic setting ............................................................................................... 4 1.4 Stratigraphic framework ....................................................................................................... 6 1.5 Data and methods ................................................................................................................. 8 1.5.1 Field work ....................................................................................................................................... 8 1.5.2 Laboratory work .............................................................................................................................. 9 1.5.3 Notes on diversity.......................................................................................................................... 10 1.5.4 Quantitative Biostratigraphy (Unitary Associations) .................................................................... 11 1.5.5 Microfacies analysis ...................................................................................................................... 11 1.5.6 Community analysis ...................................................................................................................... 12 1.5.7 Palaebiogeographic analysis ...........................................................................................