Eustatic and Tectono-Geomorphic Controls on Late Quaternary Sequences in Rift Basins: Alkyonides Gulf, Greece

Rob Gawthorpe¹, Mike Leeder², Richard Collier³, Emma Finch¹, and Lisa McNeil^4
1 University of Manchester, Manchester, United Kingdom
² University of East Anglia, Norwich, United Kingdom
³ University of Leeds, Leeds, United Kingdom
⁴ University of Southampton, Southampton, United Kingdom

The Alkyonides Gulf is bounded by stepped normal faults along its southern margin that control topography/bathymetry and drainage catchments. The faults are segmented and create a steep basin margin separating a sediment-starved hangingwall basin plain (-360 m), from footwall catchments rising to over 1350 m. Late Quaternary sea level and climate changes had a major impact on catchment dynamics and depositional systems, but the stratigraphic expression of these controls is also influenced by along-strike variability in bedrock lithology and basin margin physiography. The magnitude of late Quaternary sea-level falls were moderated by a structural sill at - 70 m, situated over 100 km to the west of the Gulf of Alkyonides. Thus the gulf was nonmarine during glacial periods. Local structural control on shelf width and shelf edge elevation also exerted a major control on basin stratigraphy. The east segment of the Alkyonides Fault is associated with a narrow (<1km) shelf with a shelf break at c. -45 m, whereas the western segment of the fault has a wider shelf (up to c. 2.25 km), and a deeper shelf break (-90 m). As a result, sediment by-pass to the basin floor occurs in the hangingwall of the eastern fault segment, expressed as stacked basin floor fans, whereas the basin floor of the western fault is sediment starved, and lowstand deposition is characterised by shelf-edge deltas. These strike variations in basin floor deposition are also exacerbated by differences in sediment supply from catchments draining different lithologies in the footwall.