Cave volume computed on the behaviour of a blowing well (Tournai basin, W. Belgium)

It is difficult to measure karst volume but important to do so to assess risk of sinkhole formation. Measurements of airflow and atmospheric pressure pattern on a water well in buried karst of the overexploited Tournai hydrogeological basin (Belgium) show that inflow and outflow are highly correlated to atmospheric pressure and the differences of external and internal air densities. The volume of natural voids in connection with the well within the vadose zone can best be estimated by a calculation based on outflow under constant atmospheric pressure, which suggests a possible cavity volume of 700 000 m³ indicating likelihood of sinkhole formation.     

Sensitivity of the Eastern Mediterranean geomorphic system towards environmental change during the Late Holocene: a chronological perspective

Alluvial and colluvial sediment deposition provide a vital record of environmental change during the Holocene. Firm chronological control on these archives is necessary to enable us to relate sediment dynamics to human activity and climate variability. In the Eastern Mediterranean, such relationships are hard to establish due to the lack of spatially well‐distributed sediment archives with good chronological control. This scarcity is problematic with respect to regional‐scale reconstructions of the temporal variation of sediment dynamics. Here, we present a radiocarbon database (n = 178) of geomorphological activity collected from multiple distinct sediment archives within the territory of Sagalassos in south‐western Turkey. The data were grouped according to their sedimentary facies for analysis using cumulative probability distributions (CPDs) and sedimentation rate (SR) modelling. Two small‐scale colluvial valleys, where chronological information was abundant, were investigated in more detail. Results show that sedimentation chronology differs between individual, nearby cores, as it depends strongly on the local geomorphic situation. A generalizing approach combining multiple core results yields more widely valid conclusions. High sedimentation rates coincided with the initial major anthropogenic disturbance of the landscape and decreased afterwards, probably due to hillslope soil depletion. CPD and SR analysis indicates that in general colluvial sedimentation rates did not change much from 2000 BC onwards. River floodplain sedimentation, in contrast, increased markedly during the first millennium BC and during recent times, and a significant time lag in enhanced sediment deposition between the upper and lower reaches of the river valleys was observed. Copyright © 2012 John Wiley & Sons, Ltd.     

Burial history and thermal evolution of Westphalian coal-bearing strata in the Campine Basin (NE Belgium)

A 1D-modelling program has been applied to reconstruct the burial and thermal histories of two exploration boreholes, KB172 and KB174, located in the Campine Basin. The results show differences in geological histories. The coalification of the Westphalian A and B strata in KB174 (0.66–0.98% R_o) was pre-Permian. Calculated maximum temperatures, based on borehole data and vitrinite reflectance, regional thicknesses and a heat flow of 84 mW/m² during the Late Westphalian, range from 110 °C at the top to 175 °C at the bottom of the Westphalian cored in this borehole. The high coalification (0.85–1.30% R_o) of the Westphalian C and D strata in KB172 could be the result of the deposition of 2500 m of Upper Permian to Middle Jurassic sediments in combination with elevated heat flows (71–80 mW/m²). Two coalification periods, i.e. Late Westphalian and Middle Jurassic, are suggested for this borehole. The simulated maximum temperatures range from 130 °C at the top to 175 °C at the bottom of the investigated Westphalian C and D. The differences in the burial and thermal histories of both boreholes can be related to the activity of the transversal Donderslag Fault, a major structural element in the Campine coalfield, and the Roer Valley Graben.