Ioannis Panagiotopoulos

Vertical displacement trends in the Aegean coastal zone (NE Mediterranean) during the Holocene assessed by geo-archaeological data

Trends in the vertical displacement (i.e. uplift or subsidence) of the Aegean Sea coastal zone have been assessed by comparing observational data with those derived from the predictive glacio-hydro-isostatic model of Lambeck and Purcell (2005) for a period spanning from the Mesolithic to the late Roman times. The data base comprises published studies that use both geomorphological (with associated biological material) and archaeological sea level indicators/markers. Localities demonstrating uplift of high amplitude were detected in front of the Hellenic Arc (Antikythira, Crete, Rhodes, Nisyros) and in the northeast Aegean region (Thrace), whilst areas experiencing tectonic subsidence were mainly observed in the central Aegean region which is characterized by an extensional tectonic domain. However, regional-scale tectonic particularities have caused uplift in parts of the west and east coast of central Aegean. Tectonically ‘stable’ sites can be found in the Cyclades Plateau, however, this is due to a balance between uplifting and subsiding movements. Sediment compaction and sediment loading may have affected districts with high sedimentation rates such as the Thessaloniki Plain-Thermaikos Gulf (NW Aegean). Finally, tectonic fragmentation of the coastal area in Minor Asia is responsible for localised uplifting and subsiding events.

A multi-criteria approach for the dumping of dredged material in the Thermaikos Gulf, Northern Greece

A multi-criteria approach was applied for the disposal into the sea of ∼1,100,000 m(3) of sediment, dredged from a coastal area in the northeastern part of the Thermaikos Gulf. This sediment (classified as muddy) is distributed vertically into two distinct Layers (A and B) with the thickness of the surficial sedimentary unit ranging from 7 to 54 cm. Its geochemistry reveals increased Cr and Ni concentrations, which may be attributed to natural enrichment through the erosion of the adjacent igneous and metamorphic rocks. In addition, a low to moderate contamination from urban-originated heavy metals, like Cu, Pb and Zn as well as from aliphatic and polycyclic hydrocarbons was identified for the upper Layer A. However, the limited proportion (5.5%) of the polluted Layer A in the total volume of the dredged material could not affect the good quality (assessed by the Sediment Quality Guidelines) of the bulk sediment. The identification of the optimum marine dumping site was based on (a) the physicochemical similarity (detected by the application of a cluster analysis) of the dredged material with the surficial deposits of potential dumping sites in the Outer Thermaikos Gulf, and (b) the consideration, based on previous studies, of various criteria related to the disposal area such as deep-water circulation, influence on living resources, impact on economical (aquaculture, fishing, navigation), recreational (fishing) and military activities.

Paleoenvironmental and paleoclimatic implications of enhanced Holocene discharge from the Mississippi River Based on the sedimentology and geochemistry of a deep core (JPC-26) from the Gulf Of Mexico

ABSTRACT Several meltwater floods initiated by the Laurentide Ice Sheet (LIS) drained to the Gulf of Mexico (GOM) through the Mississippi River during the last deglaciation (10–21 cal ka [calibrated kiloannum]). Such floods have been efficiently captured in the geochemical record of the Jumbo Piston Core 26 (JPC-26) from the northwestern GOM as distinct peaks in the content distribution of Si, Al, and Fe due to their common occurrence throughout North America. On the other hand, peaks in the content distribution of Ti, K, Zr, and V adequately describe the sediment source of each flooding event due to their clustered areal distribution in North America. The presence of three distinct peaks in the distribution of Si, Al, and Fe at 8.5, 5.2–7.6, and 2.9–3.5 cal ka indicates that events of enhanced Mississippi River discharge (EMRD) occurred during the Holocene as well. The geochemical signature of these flooding events suggests that their origin and sediment source is variable, depending on the retreating state of the LIS and the prevailing precipitation patterns in North America during these time periods. A comparison of the 8.5 and 2.9–3.5 cal ka EMRD events with the oxygen isotope and gas (CH4) records of the Greenland Ice Sheet Project 2 (GISP-2) ice core denotes that these events might be linked to short global warming episodes associated with periods of increased solar irradiance. The 5.2–7.6 cal ka EMRD event is associated with the Holocene Thermal Maximum, which resulted in the intensification of the North American monsoonal circulation.

Impact of dredged urban river sediment on a Saronikos Gulf dumping site (Eastern Mediterranean): sediment toxicity, contaminant levels, and biomarkers in caged mussels

Impacts of chemical contaminants associated with dumping of dredged urban river sediments at a coastal disposal area in Saronikos Gulf (Eastern Mediterranean) were investigated through a combined approach of sediment toxicity testing and active biomonitoring with caged mussels. Chemical analyses of aliphatic hydrocarbons (AHs), polycyclic aromatic hydrocarbons (PAHs), Cu, and Zn in combination with the solid phase Microtox® test were performed on sediments. Concentrations of PAHs, AHs, Cu, and Zn as well as multiple biomarkers of contaminant exposure and/or effects were measured in caged mussels. Sediments in the disposal and neighboring area showed elevated PAHs and AHs concentrations and were characterized as toxic by the solid-phase Microtox® test during and after dumping operations. Biomarker results in the caged mussels indicated sublethal effects mainly during dumping operations, concomitantly with high concentrations of PAHs and AHs in the caged mussel tissues. Cu and Zn concentrations in sediments and caged mussels were generally not elevated except for sediments at the site in the disposal area that received the major amount of dredges. High PAHs and AHs levels as well as sublethal effects in the caged mussels were not persistent after termination of operations. The combined bioassay–biomarker approach proved useful for detecting toxicological impacts of dredged river sediment disposal in sediments and the water column. Nevertheless, further research is needed to evaluate whether sediment toxicity will have long-term effects on benthic communities of the disposal area.

Africa-Arabia Connections and Geo-Archaeological Exploration in the Southern Red Sea: Preliminary Results and Wider Significance

We report on a preliminary exploration of the submerged landscapes in the Saudi Arabian sector of the southern Red Sea aboard the Hellenic Centre for Marine Research (HCMR) Research Vessel, AEGAEO, in May–June 2013. The survey sampled areas of the continental shelf down to the shelf margin at ~130 m depth in the vicinity of the Farasan Islands and combined high resolution acoustic techniques with sediment coring to reconstruct features of the now-submerged landscape of potential archaeological significance, including geological structure, topography, palaeoenvironment, and sea-level change. The region is currently of wide interest and significance: to archaeologists because it is currently regarded as one of the primary pathways of dispersal for early human populations expanding out of Africa during the Pleistocene, in which the extensive but now-submerged shelf region may have played a key role; and to marine geoscientists because the Red Sea offers unusual opportunities as a ‘laboratory’ for investigating Pleistocene sea-level change. Preliminary results indicate that the submerged landscape was characterised by a complex topography with fault-bounded valleys and deep basins, some of which may have hosted, at least intermittently, fresh water during periods of lowered sea level.