Thessaly Plain Research Articles

Site formation processes in Theopetra Cave: A record of climatic change during the Late Pleistocene and Early Holocene in Thessaly, Greece

AbstractTheopetra Cave preserves a 6.4‐m‐thick sedimentary sequence characterized by alternating, mostly water‐lain sediments, and multisequence burnt layers. Eighteen principal radiocarbon ages provide temporal control for this sequence. The sediments of the cave were examined using micromorphological techniques, which involves the study of petrographic thin sections produced from resin‐impregnated, undisturbed blocks of sediment. Several distinct cold periods are recorded in the sediments. The earliest of these represents a major cooling, and it is tentatively assigned to Oxygen Isotope Stage 4 on the basis of the sedimentation rate and the associated sequence of events. A brief cold event affected the uppermost part of a burnt layer dated to ca. 46 kyr B.P., but its effect ended well before 40 kyr B.P. The second major cold phase spans the period between around 33 kyr B.P. and the end of Last Glacial Maximum (16 kyr B.P.). However, there is ample evidence for a milder interval around 25 kyr B.P. It is argued that a distinctive, albeit weaker and brief cold peak, at about 11 kyr B.P., provides the strongest evidence so far obtained in Greece for the Younger Dryas event. Both major cold phases are characterized by a sequence of events that started with alternating freeze–thaw activity and phosphate cementation and ended with erosion. The return to milder conditions is accompanied by natural aggradation inside the cave. The aggradation accelerated throughout much of the glacial phase and ended soon after the Last Glacial Maximum. In addition, two other major erosional events are recorded in the cave. The first may be correlated with an early Holocene arid interval at around 7.5 kyr B.P. The second is tentatively assigned to the end of Neolithic, although it is not clear if it was triggered by a climatic change or by human disturbance of the landscape. The general sedimentation pattern at Theopetra is comparable with the trend of the alluviation history in the Plain of Thessaly. Moreover, the observed correlation with major climatic variations, such as the Heinrich events in the Northern Atlantic, could represent the influence of northern latitude climatic forcing on the late Pleistocene climate in central Greece. © 2001 John Wiley & Sons, Inc.

Factors affecting aggregate instability of Greek agricultural soils

The aggregate stability of several surface soils from Thessaly plain, Central Greece, was studied using an instability index which classified the soils according to the stability of their aggregates to water. This index was correlated to the basic soil properties influencing aggregate stability. It was found that soil aggregate stability was positively correlated with clay content, total specific surface area, cation exchange capacity, base saturation, and free silicon oxides content. Silt, very fine and fine sand, and the ratio (sand+silt)/clay influenced negatively the aggregate stability. Organic matter content and sesquioxides have no effect on aggregate stability. It was also observed that the fraction of carbonates with silt dimension influenced negatively the aggregate stability. From the results of this study it was concluded that the factors affecting water aggregate stability were specific surface area and cation exchange capacity of the soils.

First palaeoseismological results from Greece

This is a brief account of our approach to trends in palaeoseismological research that are currently emerging in Greece, with the application of modern investigative methods practised world-wide in active tectonic zones. These techniques include fault stratigraphy in trenches, and dating recent fault reactivations in order to understand and distinguish palaeoseismic events along specific segments of active faults, named Gerakarou (Mygdonia Basin, Thessaloniki area), Palaeochori Fault (Kozani-Grevena, Western Macedonia), Souli (Petousi, Epirus), and Volos-Larissa (Thessaly plain). Four palaeoearthquakes were investigated on the Gerakarou fault segment, with a uniform slip rate and return period around 7000 years. In Western Macedonia "aseismic areas" the Servia-Palaeochori recently activated fault shows a -3500 year quiescence. Three coseismic events on the Souli Fault pre- and post-date to 26000 year deposits.