A new estimate for the composition of weathered young upper continental crust from alluvial sediments, Queensland, Australia

We present new major element, trace element and Nd-isotope data for 30 alluvial sediments collected from 25 rivers in Queensland, E Australia. Samples were chosen to represent drainage from the region's most important lithologies, including Tertiary intraplate volcanic rocks, a Cretaceous igneous province (and sedimentary rocks derived thereof) as well as Proterozoic blocks. In most chemical and isotopic aspects, the alluvial sediments represent binary or ternary mixing relationships, with absolute abundances implied to reflect the proportion of lithologies in the catchments. When averaged, the studied sediments differ from other proxies of upper continental crust (UCC) mainly in their relative middle rare earth element enrichment (including an elevated Sm/Nd ratio), higher relative Eu abundance and higher Nb/Ta ratio. These features are inherited from eroded Tertiary intraplate basalts, which commonly form topographic highs in the studied region. Despite the high degree of weathering strong to excellent coherence between similarly incompatible elements is found for all samples. From this coherence, we suggest revisions of the following upper crustal element ratios: Y/Ho = 26.2, Yb/Tm = 6.37, Th/W = 7.14, Th/Tl = 24 and Zr/Hf = 36.9. Lithium, Rb, Cs and Be contents do not seem depleted relative to UCC, which may reflect paucity of K-feldspar in the eroded catchments. Nickel, Cr, Pb, Cu and Zn concentrations are elevated in polluted rivers surrounding the state capital. River sediments in the Proterozoic Georgetown Inlier are elevated in Pb, Cu and Zn but this could be a natural phenomenon reflecting abundant sulphide mineralisation in the area. Except for relative Sr concentrations, which broadly anticorrelate with mean annual rainfall in catchments, there is no obvious relationship between the extent of weathering and climate types, which range from and to tropical. The most likely explanation for this observation is that the weathering profiles in many catchments are several Myr old, established during the much wetter Miocene period. The studied sediment compositions (excluding those from the Proterozoic catchments) are used to propose a new trace element normalisation termed MUQ (MUd from Queensland), which serves as an alternative to UCC proxies derived from sedimentary rocks. Copyright (C) 2005 Elsevier Ltd

A simple practical method for bulk and rapid extraction of free-living nematodes from marine and estuarine sediments

A simple, rapid method is described for the extraction of large numbers of free-living nematodes from estuarine sediments. This method does not physically or chemically alter or damage the nematodes, but instead relies on their downward movement through a filtering layer of double ply tissue paper and into aerated water-filled trays. Seven trials each with 10 trays kept at 25degreesC for an initial period of 24 h yielded 3985 live nematodes l(-1) (+/-511.5 standard deviation) of estuarine sediment, free of sediment and with minimal debris. Time effects were statistically significantly different, with the same 10 trays yielding another 1259 nematodes l(-1) (+/-413.4) when kept for a second period of 24 h at the same temperature. Temperature effects were also significant, and 7 trials each with 10 trays kept for 24 h at 20-21degreesC, produced a lower yield of 2160 nematodes l(-1) (+/-532.7) of sediment. The method is expected to be of use in nematode extractions from both estuarine and marine sediments.