Seismic Hazards Implications of Uplifted Pleistocene Coral Terraces in the Gulf of Aqaba.

The Gulf of Aqaba transform plate boundary is a source of destructive teleseismic earthquakes. Seismicity is concentrated in the central sub-basin and decreases to both the north and south. Although principally a strike-slip plate boundary, the faulted margins of the Gulf display largely dip-slip extensional movement and accompanying footwall uplift. We have constrained rates of this uplift by measurements of elevated Pleistocene coral terraces. In particular the terrace that formed during the last interglacial (~125 ka) is found discontinuously along the length of the Gulf at elevations of 3 to 26 m. Global sea level was ~7 m higher than today at 125 ka indicating net maximum tectonic uplift of ~19 m with an average rate of ~0.015 cm/yr. Uplift has been greatest adjacent to the central sub-basin and like the seismicity decreases to the north and south. We suggest that the present pattern of a seismically active central region linked to more aseismic areas in the north and south has therefore persisted for at least the past 125 kyr. Consequently the potential for future destructive earthquakes in the central Gulf is greater than in the sub-basins to the north and south.

Desalination impacts on the coastal environment: Ash Shuqayq, Saudi Arabia.

Ash Shuqayq (Saudi Red Sea coast) is approximately 28km long and characterised by narrow rocky headlands with intermittent pocket beaches. Fifty-two sediment samples from six different environments (beach, dune, sabkha, tidal/lagoon, offshore and wadi) were analysed. Testing showed that beach and dune sands are mainly medium to fine grained, with some very coarse sand (MZ=-0.59ø). Both beach and dune sands are moderately well to moderately sorted, although some are poorly sorted due to an influx of wadi sediments. Sediment source together with littoral reworking contributed to grain size variation. Carbonate content varied between 1.5% and 23%, whilst the organic content varied between 1.1% and 13%. Spatial analysis showed increasing southward carbonate and organic content, with both correlated (r=0.57). Sabkha sediments had significantly higher carbonate percentages (t=2.898; df=18; p<0.01) and results suggested origins are similar for both UAE Arabian Sea and Saudi Arabian Red Sea coasts. X-ray diffractions show beach and dune sediments are mainly composed of detrital quartz and plagioclase feldspar with uncommon amounts of chlorites. Analysis of sediment characteristics, composition and shoreline distribution alongside coastal processes, indicate that high chlorite levels are probably caused by desalination processes. Due to human and ecosystem health consequences and the likely increased demand for desalination plants, similar analyses should be undertaken elsewhere, e.g. the Mediterranean.

Preliminary phytochemical screening of four common plants of family caesalpiniaceae.

Preliminary phytochemical screening of Bauhinia variegata, Cassia fistula, Cassia tora and Tamarindus indica did not reveal alkaloids and unbound anthraquinones while glycosides as well as flavonoids were present in all the four species of the family caesalpiniaceae. Cardiac glycosides were absent only in C. tora and saponins were present only in T. indica, B. variegata and T. indica were devoid of bound anthraquinones while bound anthraquinones were present in C. fistula and C. tora. Paper chromatography revealed 6 spots in solvent system I, and 5 spots in solvent system 2, showing different Rf values. The per cent yield of crude glycosides was 3.18 in B. variegata, 4.03 in C. fistula, 4.45 in C. tora and 4.14 in T. indica.