THE CORINTH BASIN, GREECE Richard
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SEDIMENTARY FACIES EVOLUTION IN CONTINENTAL FAULT-BOUNDED BASINS FORMED BY CRUSTAL EXTENSION: THE CORINTH BASIN, GREECE Richard E.Ll. COLLIER October 1988 Submitted in accordance with the requirements for the degree of Doctor of Philosophy Dept, of Earth Sciences University of Leeds LS2 9JT U.K. 1 Now Xenophanes holds that the earth is recurrently mingled with the sea and then as time passes is freed again of moisture. He puts forth such proofs as these: that shells are found far inland and on mountains; and that in the quarries of Syracuse imprints of a fish and of seaweed have been found, and in Paros the imprint of a small fry deep in the stone, and in Malta flat slabs [bearing the impressions] of all sorts of fish. He says that the imprint, made long ago when everything was covered with mud, then dried in the mud. 1: Xenophanes of Colophon (c.570-475 B.C.) Hippolytus, Refutations of All Heresies I 14.5-6 (Diels, Fragmente der Vorsokratiker I 122) 2 ABSTRACT Characteristic half-graben and graben geometries are generated by extensional tectonics. The sedimentary infill to such basins reflects their structural evolution. The actively extending basins of central Greece have provided an opportunity to study the mechanisms that control sediment distribution and the resultant facies patterns and geometries produced in such environments. The modern and precedent Neogene to Quaternary sediments studied, and their controlling processes, provide predictive templates for the analysis of controls acting upon ancient extensional basin fills. On a basinwide scale, facies patterns are controlled by the geometry of major basin-controlling normal faults and by the structural level of the basin - determining alluvial, lacustrine or marine environments. Increments of movement on normal faults tilt and vertically displace the depositional surface, producing facies responses in terms of fluvial/submarine channel avulsion or preferential migration into topographic lows, lake or sea coastline advance or retreat across the depositional slope, and the progradation of clastic wedges off fault scarps and uplifted areas. The time-averaged product in the stratigraphic record is typically of clinoforms developed preferentially against basin margin faults and axial channel systems concentrated in the structurally constrained depocentre(s). Such gross morphologies are seen in the Lower Pliocene early rift history of the Corinth asymmetric graben; conglomerate-dominated fan deltas and alluvial fans prograded laterally into the basin. The progradation of an ophiolite-derived, fluvio-deltaic system along the basin axis illustrates the competition of sediment supply rates with tectonic subsidence rates in determining facies geometries. A number of other controls on sediment distribution are variously important through time within extensional basins, in addition to structuration and sediment supply rates (itself a function of hinterland litho-type and structural evolution). These include eustatic and climatic variation and compactional subsidence rates. The Corinth Isthmus has been studied with the aim of establishing the interaction of concurrent tectonic and eustatic relative base-level changes. Computer-modelling of the migration of a coastline through theoretical stratigraphic sections illustrates the effects of varying rates of change of sea-level, tectonic subsidence (or uplift) and deposition with time. Incorporation of the global sea-level curve for the Late Quaternary into such models reasonably predicts observed facies geometries in the Late Pleistocene and Holocene of the Isthmus. U-series disequilibrium dating of corals from the Corinth Canal area has constrained transgressive beach sub-sequences as reflecting c. 100,000 year wavelength eustatic cycles. After subtraction of depositional levels constrained in time and space against the sea-level curve, an average net uplift rate is derived for the central Isthmus of more than 0.3m per 1000 years. The areal distribution of Late Pleistocene marine facies in the southern Corinth Basin is principally controlled by the structural form and evolution at time of deposition. Subsequent tilt block faulting in an alluvial environment illustrates how intrabasinal fault block morphologies may generate axial and lateral sediment transport systems analagous to those on a basinwide scale. The competition between process rates is emphasized. Three- dimensional sedimentary facies patterns within evolving syn-rift basins are shown to be dependent upon the interaction of three principal factors: a) the rate of tectonic displacements through time, on both basinwide and local fault block scales, b) the rate of sea-level change through time (or lake-level change, whether determined by tectonic or climatic means), and c) the rate of deposition at any locality, itself a function of hinterland structure and lithology, climate and depositional geometries. 5 ACKNOWLEDGEMENTS Thanks go to Dr Mike Leeder for offering this PhD project in the first place and for a starting point in the form of his paper with Dr Rob Gawthorpe (1987) on tectonic-induced facies patterns in extensional basins. Many discussions in the field, office or over a glass of vino have been vitally stimulating. Grateful thanks to British Petroleum pic for sponsorship of this project. Thanks to Dr Tim Atkinson at the University of East Anglia for U-Th analytical work and constructive discussion on the results. To Dr John Athersuch at the BP Research Centre for micropalaeontological analyses and Dr Dave Rex here in Leeds for K-Ar dating. Thanks to a whole bunch of people for geological discussions: Andy Simms, Alistair Welbon, Dr Rob Knipe, Dr Jan Alexander, and Pete Bentham, Chris Dart and others in Greece. In Greece, thanks are due to I.G.M.E. for permission to work there, and to friends in and around Corinth and the American School of Archaeology in Ancient Corinth for their hospitality. Last but not least, love and thanks to my parents, and Jane McNicholas (hello Roseanne) and Amanda Harrison for continuing friendship and support . Ta. G Title page 1 Quotation 2 Abstract 3 Acknowledgements 6 Contents 7 List of figures 10 List of tables 12 List of plates 13 List of enclosures 13 CHAPTER 1 GENERAL INTRODUCTION 1.1 Aims of resarch 14 1.1.1 Key themes 16J 1.2 Location of field area 17 1.3 Field work 19 1.4 Laboratory techniques 20 1.5 Thesis layout 21 1.6 Literature review - theory 23 l.G.l Extensional basin evolution 23 1.6.2 Structural framework 28 1.6.3 Sedimentary facies - concepts, qualitative models, quantitative simulations 37 CHAPTER 2 REGIONAL GEOLOGICAL SETTING 2.1 Summary 4 6 2.2 The Aegean province 4 7 2.2.1 Pre-Neogene geology 47 2.2.2 Neogene tectonics 50 2.3 The Gulf of Corinth asymmetric graben system 54 2.3.1 Geological setting 54 2.3.2 Piio-Quaternary stratigraphy 58 2.3.3 Gulf of Corinth structure 61 CHAPTER 3 CORINTH BASIN - EARLY SYN-RIFT GEOLOGY 3 .1 Sununa ry 6 5 1 3.2 Introduction 66 3.3 Facies analysis 71 3.4 Facies associations 74 3.4.1 Distal alluvial fan: FA1 74 3.4.2 Fluvial (braided stream): FA2 75 3.4.3 Lacustrine: FA3 76 3.4.4 F1uvia1-dominated delta front: FA4 77 3.4.5 Estuarine: FA5 80 3.4.6 Proximal submarine "fan"/slope apron: FA6 81 3.4.7 Distal submarine "fan": FA7 82 3.5 Strati graphic sequence - descriptions and interpretations 83 3.5.1 Asprak'nomata-Ka lawona Formation 33 3.5.2 Agios Charalampos Conglomerates 92 3.5.3 Mu 11.i -Coloured Series "Marls" 97 3.5.4 Multi-Coloured Series Sands 102 3.5.5 Upper Conglomerates 122 3 . 6 Andesi tes 130 3.6 Spatial variation in facies 132 7 3.7 Structural evolution of the Lower Pliocene Corinth Basin 133/ 3.7.1 Basin form 133; 3.7.2 Structural evolution 138\ 3.8 Discussion: Controls on evolution of facies geometries 147 j 3.9 Conclusions 154 ' CHAPTER 4 CORINTH ISTHMUS - LATE QUATERNARY TECTONIC AND EUSTATIC INTERACTIONS 4.1 Summary 155 . 4.2 Introduction 156 4.3 The Quaternary Corinth Basin 158 4.4 Modelling eustacy-controlled stratigraphic profiles 161 4.4.1 Computer modelling 163 4.5 Sedimentary facies 171 4.5.1 "Corinth Marl" lacustrine to marine transitional sequence 171 4.5.2 1st sub-sequence 176 4.5.3 2nd sub-sequence 178 4.5.4 3rd sub-sequence 179 4.5.5 4th sub-sequence 182 4.5.6 5th sub-sequence; Holocene 182 4.6. Dating of Corinth canal sediments 183 4.6.1 Previous chronostratigraphy 183 4.6.2 U-series disequilibrium dating 184 4.7 Distinction of eustatic and tectonic controls 189 4.7.1 Interpretation of U-series results 189 4.7.2 Structural evolution of the Corinth Isthmus 191 4.8 Quantification of tectonic displacements 192 4.9 Conclusions 194 CHAPTER 5 RECENT EVOLUTION OF THE SOUTHERN CORINTH BASIN 5.1 Summary 19 6 5.2 Introduction 196 5.3 Facies descriptions & interpretations - marine deposits of the southern Corinth Basin 200 5.3.1 Conglomerate facies SI 200 5.3.2 Unidirectional & herringbone cross-bedded facies S2 201 5.3.3 Syinmetri c-rippled sand facies 33 204 5.3.4 Trough cross-bedded facies S4 206 5.3.5 Planar-laminated facies S5 207 5.3.6 Oolitic sand facies So 208 5.3.7 Large-scale planar cross-bedded facies S7 209 5.3.8 Large-scale dune facies S3 210 5.3.9 Sand wave facies S9 211 5.3.10 Longitudinal sand wave facies S10 216 5.4 Facies associations - marine deposits of the southern Corinth Basin 219 5.4.1 Beach facies association SA1 219 5.4.2 Shoreface facies association SA2 221 5.4.3 Shelf facies association SA3 223 5.5 Marine facies distribution and syn-sedimentary structure 227 5.6 Extensional tilt block faulting and syn-tectonic sedimentation post-doposition