Mesozoic radiolarian faunas from the Antarctic Peninsula: age, tectonic and palaeoceanographic significance

New assemblages of Radiolaria, including some of the few occurrences of high southern latitude Jurassic and Cretaceous radiolarian faunas, show that several localities in the LeMay Group of Alexander Island range in age from latest Jurassic–earliest Cretaceous to at least Albian. By demonstrating that sedimentation and deformation in the LeMay Group was diachronous, younging oceanwards to the northwest, these new age assessments support the model of the LeMay Group as an accretionary complex. The polarity of subduction beneath Alexander Island was not affected by arc collisions from at least the Lower Jurassic to the Oligocene, and such a long period of continuous accretion appears to be unusual. Deposition of the LeMay Group spans the Kimmeridgian to Albian sedimentation in the Fossil Bluff Group fore-arc basin, thus making the earlier concept of the LeMay Group as pre-Jurassic ‘basement’ untenable. Allochthonous latest Jurassic–earliest Cretaceous radiolarian assemblages with some supposed Tethyan affinities are present in the LeMay Group. In contrast, an in situ latest Jurassic assemblage from the Nordenskjöld Formation of the back-arc basin and a further Jurassic assemblage from a probable trench-slope basin have characteristics believed diagnostic of high latitudes. The biogeographic affinities of radiolarians from cherts in the LeMay Group accretionary complex suggest that both these cherts, and associated basalts, are far-travelled slices of the Phoenix plate. Rocks from the probable trench-slope basin, formerly assigned to the younger Fossil Bluff Group fore-arc basin sequence, now appear to be part of a new, previously unrecognized formation

The potential of metal oxalates as novel flame retardants and synergists for engineering polymers

Based on their known decomposition to carbon dioxide, carbon monoxide and the respective oxide, six metal (calcium, manganese (II), iron (II), copper (II), tin (II) and zinc) were synthesised and assessed for their potential flame retardant activity in the absence and presence of selected flame retardants. Initially they were assessed when impregnated on cotton as a screening process and then selectively compounded with polyamide 6.6 (PA66), as a typical engineering polymer. Only manganese (II) and iron (II) oxalates alone reduced the burning rate of cotton, whereas together with ammonium bromide, calcium and iron (II) oxalates showed an apparent additional burning rate reducing effect. Derived synergistic effectivity (Es) values fall within the limits 0<Es<1 indicating a less than additive interaction. TGA/DTA analysis of oxalate/PA66 blends suggested that only zinc oxalate (ZnOx) offers both possible flame retardant activity in terms of enhanced residue formation ≥500oC, coupled with acceptable stability in molten PA66. When compounded with PA66, in the presence and absence of either aluminium diethyl phosphinate (AlPi)-based or selected polymeric bromine-containing flame retardants, LOI values increased in most PA66/ZnOx/flame retardant blends but UL94 test ratings were disappointingly low and more likely than not, “fails”. PA66/ZnOx blends with AlPi and AlPi/MPP gave poor plaques suggesting that thermal interactions were occurring during compounding. The bromine-containing blends had better processibility and both TGA and cone calorimetric studies showed that the PA66/poly(bromopentabromobenzyl acrylate)/ZnOx sample not only yielded the highest residues in air and nitrogen at 500 and 580oC, but also the lowest peak heat release rate value of 398 compared with 1276 kW/m2 for pure PA66. The derived Es value for this blend is 1.17 suggesting a small level of synergy between the zinc oxalate and poly(pentabromobenzyl acrylate) flame retardant. The possible role of zinc bromide is discussed