Palaeogeographic Evolution of the Sipan – Dubrovnik Area, Croatia, Based on High Resolution Geophysical Data
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UNIVERSITY OF PATRAS FACULTY OF SCIENCE DEPARTMENT OF GEOLOGY Postgraduate Program “Geosciences and Environment” Palaeogeographic evolution of the Sipan – Dubrovnik area, Croatia, based on high resolution geophysical data M.Sc. in Environmental Oceanography Alexandra Tsironi Patra 2017 1 Thesis examining committee: George Papatheodorou, Professor, Department of Geology, University of Patras Maria Geraga, Associate Professor, Department of Geology, University of Patras Slobodan Miko, Head of Department of Mineral Resources in Croatian Geological Survey 2 Page intentionally left blank 3 Acknowledgements With the completion of this thesis my participation in the postgraduate programme “Geosciences and Environment” of the Geology Department of the University of Patras is concluded. From this position, I would like to thank the members of the thesis examining committee; Giorgos Papatheodorou, Professor and supervisor of my thesis, for his encouragement in my wish to follow the direction of Environmental Oceanography, for his trust, his subtle guidance and his support during the process of examining the data. Above all I would like to thank him for his prompt responsiveness to entrust me with the seismic data of a complex geologically area like the study area, giving me this way the opportunity to work with a plethora geological structures and environments. Warmly thank you. Maria Geraga, Associate professor and member of the thesis examining committee, for her guidance and assistance in the chapter of the paleogeographic evolution. Her support and advice eased significantly my acquaintance with the methodology of chronoseismostratigraphic and paleoenvirοnmental implications of the study area. Largely, though, I would like to sincerely thank her for her comforting and reassuring smile every time the dissertation needs led me to her office. Special thanks to Dr. Slobodan Miko, director of the LoLADRIA project, for his participation as a member of the thesis examining committee. Thanks also to the members of the Laboratory of Marine Geology and Physical Oceanography for their assistance during my familiarization with the geophysical software, as well as to my classmates for the numerous hours spending together, for the conversations and exchanges, for the companionship during the two years of our postgraduate studies. Yet, the completion of this long-lasting endeavour, graduate and postgraduate, wouldn’t have been easy or always pleasing without the people that all these years stand by me, supporting and encouraging my efforts; Maria, Xanthi, Alina, Kleio, Giannis, Nikos and Sohel. Nothing would have been feasible without the love, the serenity and the support, moral and financial, from my family; Giannis, Eleni, Kostas and Stefanos. Everything would have been lonely, more difficult and less attractive without Nikos by me side. Thank you dearest for everything; this thesis is dedicated to you all. 4 Abstract The present study focuses its research on the southern part of the eastern Adriatic coast and more specifically on the sea area of the Dubrovnik - Neretva County in southern Croatia. The area is named after the large marine channel running through it, that is the Kolocep Canal, and separates the mainland coast from the southernmost populated Croatian islands, the Elaphiti Islands. The Elaphites form a chain of islands, which extend in a NW-SE direction in the Dubrovnik archipelago and are separated from each other by sea passages through which the channel area is connected to the open sea. Depending on the sea level changes, the Elaphiti Islands functioned as natural barriers causing changes in conditions of sedimentation into the Kolocep canal basin. The Kolocep canal/Elaphiti islands marine geophysical survey is part of an ongoing research project, LoLADRIA - Lost Lake Landscapes of the Eastern Adriatic Shelf, conducted by the Croatian Geological Survey and the Laboratory of Marine Geology and Physical Oceanography of the University of Patras and its principal objective is to recover long paleoenvironmental and palaeoclimate records from either existing coastal or submerged karstic lakes. For the survey, that was carried out from the 21st to the 26th of April 2016, the following geoacoustic systems were used: a high resolution 3.5 kHz ORE Pinger with 4 transducers sub bottom profiler and an EG&G. 272 TD side scan sonar. The present study, whose foremost intentions are to point out the definition of the seismic stratigraphy of the sediment sequence in the Kolocep canal basin, as well as the palaeogeographic evolution of the aforementioned area, primarily processed the data and dealt with the results arising from sub bottom profiler. 5 Table of Contents Acknowledgements ................................................................................................................... 4 Abstract ..................................................................................................................................... 5 1. INTRODUCTION ................................................................................................................. 7 1.1 The karst system ........................................................................................................ 8 1.2 Karst features in Eastern Croatian Coast ................................................................. 10 2. SEA LEVEL CHANGES ........................................................................................................ 12 2.1 Relative Sea level Indicators .................................................................................... 13 2.2 Eastern Adriatic Coast – Sea Level Research ................................................................. 14 2.3 Indicators of SLC in the wider area of Kolocep Canal .................................................... 17 3. STUDY AREA ..................................................................................................................... 18 3.1 Geographical and physiographic characteristics ........................................................... 18 3.2 Geology .......................................................................................................................... 20 3.3 Tectonic regime ............................................................................................................. 21 3.4 Hydrogeological Characteristics .................................................................................... 22 4. FIELD WORK ..................................................................................................................... 24 4.1 Sub – bottom Profiling Survey ....................................................................................... 25 4.2 Geophysical Data Processing ......................................................................................... 28 5. DATA ANALYSIS ................................................................................................................ 29 5.1 The acoustic structure of the study area ....................................................................... 29 5.2 Description of units of seismo-stratigraphic sequences 1-3 ......................................... 34 5.3 Bathymetry of study area .............................................................................................. 37 5.4 Characteristics of seismo-stratigraphic sequences ....................................................... 38 6. PALEOGEOGRAPHIC EVOLUTION OF THE STUDY AREA ................................................... 46 6.1 Interpretation of the acoustic characters of seismic units in study area ...................... 46 6.2 Reconstruction of paleogeographic evolution of the study area .................................. 47 7. CONCLUSIONS – DISCUSSION .......................................................................................... 49 BIBLIOGRAPHY ......................................................................................................................... 52 APPENDIX ................................................................................................................................ 57 6 1. INTRODUCTION Paper Objective As a part of ongoing research program “Lost Lake Landscapes of the Eastern Adriatic Shelf”, LoLADRIA (2014 - 2018), the Croatian Geological Survey, in collaboration with the Laboratory of Marine Geology and Physical Oceanography of the University of Patras, Greece, started in 2014, under the direction of Dr. Slobodan Miko, marine geological investigations in selected positions along the Adriatic Coast to enable the retrieval of long paleoenvironmental and paleoclimate records from either existing coastal or submerged karstic lakes. In order to achieve the above objectives, researchers proceeded in collecting sediment cores (of 5 - 10 m length) from 12 marine and 7 lacustrine positions and then performed high-resolution geophysical surveys in Lošinjski kanal, Kvarnerid, Novigradsko, Karinsko, Pirovafki zaljev and Kolofepski kanal (Miko et al., 2016). The research project is supported by Croatian Science Fund Project LoLADRIA (Project no. 9419) and the EMODnet Geology II project funded by ECDG Mare. In the current thesis, the data collected from the Marine Geophysical Survey conducted in April 2016 at Kolocep Canal have been analyzed and processed and their results are being presented in the chapters to follow. The main objectives are to point out: - The definition of the seismic stratigraphy of the sediment sequence in the Kolocep canal