A. Stefatos

Marine Debris on the Seafloor of the Mediterranean Sea: Examples from Two Enclosed Gulfs in Western Greece

Abstract During two daylong surveys aboard fishing boats, one in Patras Gulf and the other in Echinadhes Gulf, marine debris retained in the trawl nets was examined. The marine debris concentration on the seafloor of Patras and Echinadhes Gulfs is 240 and 89 items/km2, respectively. The most abundant debris is plastic followed by metal. The high percentage of beverage packaging in Echinadhes Gulf is attributed to shipping traffic, whilst the high percentage of general packaging in Patras Gulf suggests that the source of this material may be on land and it is transported into the gulf by rivers and seasonal streams.

Active faulting within the offshore western Gulf of Corinth, Greece: Implications for models of continental rift deformation

Discrimination between different lithospheric extension models focusing on the roles of low-angle vs. high-angle faulting, and how strain is distributed, requires high-fidelity imaging of brittle deformation. High-resolution seismic reflection and multibeam bathymetric data in the western Gulf of Corinth continental rift were collected to establish the contribution of offshore faults to extension. Onshore fault slip here is significantly less than expected from geodetic strain rates. The rift at this location is a half-graben tilted to the north by S-dipping faults within the uppermost crust. A basement horst on the northern margin is uplifted by the North and South Eratini faults, and the axial channel is fault controlled. Subsided lowstand shorelines in the hanging wall of the North Eratini and the well-studied Aigion fault suggest that the faults have similar displacements. Summed extension from the four major faults across this part of the rift (Eliki, Subchannel, South Eratini, North Eratini) is 8–16 mm/yr, thereby reconciling geologic and geodetic data sets. Distributed deformation across isolated multiple faults can model this part of the rift without recourse to, and potentially incompatible with, an underlying low-angle detachment.

Geometry and slip rate of the Aigion fault, a young normal fault system in the western Gulf of Corinth

The Aigion fault is one of the youngest major normal faults in the Gulf of Corinth, Greece, with an immature displacement profile. Based on geometry, slip rate and comparison with regional faults, we estimate the fault system length at ~10 km. We find the slip rate of the fault system is ~3.5 ± 1 mm/yr decreasing to ~2.5 ± 0.7 mm/yr close to its eastern tip. Complex fault geometry and displacement profiles on the shelf east of Aigion are consistent with the latter as the eastern tip location. Analysis of slip on this fault system and the established fault to the south (Western Eliki Fault) suggests that slip was transferred rapidly but not homogeneously between the two faults during the period of contemporaneous activity. Together with a lack of evidence of lateral propagation at the eastern fault tip in the last 10–13 k.y., we suggest that the fault developed and established its current length rapidly, within its 200–300 k.y. history. These results contribute to our understanding of the process of northward fault migration into the rift and the development of new normal faults.

Small Scale Present Day Turbidity Currents in a Tectonically Active Submarine Graben, The Gulf of Corinth (Greece): Their Significance in Dispersing Mine Tailings and Their Relevance to Basin Filling

A detailed marine survey, in Antikyra bay, in the northern margin of the Corinth Gulf graben in Greece, was carried out to examine the distribution and dispersion of bauxite “red-mud” tailings which have been discharged since 1970 on the shelf at a depth of 100 m. The ‘red-mud’ tailings are transported to the basin floor by turbidity currents is a depth of about 800 m and at a distance of up to 17 km from the source. Over a period of 14 years, ten (10) turbidity flow events have occurred. The turbidity flows form small scattered sheet-like deposits. The deposits are usually lobe shaped, between 0.6 and 4 cm thick, and with an aerial coverage from 1-106 to 12.6106 m2. The turbidites overlap each other and cover a total area of 48 km2.

High Frequency Sediment Failures In A Submarine Volcanic Environment: The Santorini (Thera) Basin In The Aegean Sea

Seismic data have been used to evaluate the extent, characteristics and importance of the sediment failures in the Santorini basin. The failures are small but abundant, occupying almost half of the areal extent of the study area, and modify the relief of the basin and the surrounding slopes. The fact that surficial mass flow deposits are the source area of younger sediment failures is evident of the high intensity and frequency of the sediment instabilities. The major factors which are responsible for the observed instabilities are seismic activity and seismicity related to modern volcanic activity, steep slopes and the open sediment structure due to the specific texture of the volcanic material. Sediment failures are believed to compose a big part of the deeper sedimentary column.