First record from Australia of the Cretaceous fern genus Tempskya and the description of a new species, T judithae

Silicified fragments of false-trunks of the fern, Tempskya judithae sp. nov., are described from lower Cretaceous (latest Albian) sediments near Winton, central-western Queensland. The species is characterised by a three-layered sclerenchymatous cortex and a two-layered pith of sclerenchyma cells. In possessing these characters, T judithae is more similar to T readii than to other species of Tempskya. However, the Australian species differs from T readii in the abaxial shape of the petiole xylem trace (concave in T judithae, convex in T readii) and in symmetry attributes of the leaf-bases within the false-trunk (random in T judithae and radially symmetrical in T readii). T judithae is the first record of Tempskya from Australia and the second from Gondwana; the known distribution range of the genus embraces a broad area in mid-high latitudinal regions of Laurasia and the Gondwana record now comprises Australia and Argentina. Ecological signals of plant fossil assemblages recorded from the Australian sediments are in accord with flood plain habitats and a temperate climatic regime. (c) 2004 Elsevier B.V. All rights reserved.

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