Structural evolution of the early Permian Nambucca Block (New England Orogen, eastern Australia) and implications for oroclinal bending

The Paleozoic to early Mesozoic southern New England Orogen of eastern Australia exhibits a remarkable ear-shaped curvature (orocline), but the geodynamic processes responsible for its formation are unclear. Oroclinal bending took place during the early Permian, simultaneously with the deposition of the rift-related Sydney, Gunnedah and Bowen basins, which bound the oroclines to the west. The Nambucca Block is another early Permian rift basin, but it is situated in the core of the oroclinal structure. Here we present new stratigraphic, structural, and geochronological data from the Nambucca Block in an attempt to better understand its tectonic history and relationships to the formation of the oroclines. We recognized four phases of folding and associated structural fabrics (S1-4), with the second phase (S2) dated at 275-265 Ma by 40Ar/39Ar geochronology of muscovite. This age overlaps with independent constraints on the timing of oroclinal bending, suggesting that the earlier two phases of deformation in the Nambucca Block (F1 and F2) were associated with orocline formation. We propose that oroclinal bending involved three major stages. The first stage

The Drosophila IKK-related kinase (Ik2) and Spindle-F proteins are part of a complex that regulates cytoskeleton organization during oogenesis

<p>Abstract</p> <p>Background</p> <p>IkappaB kinases (IKKs) regulate the activity of Rel/NF-kappaB transcription factors by targeting their inhibitory partner proteins, IkappaBs, for degradation. The <it>Drosophila </it>genome encodes two members of the IKK family. Whereas the first is a kinase essential for activation of the NF-kappaB pathway, the latter does not act as IkappaB kinase. Instead, recent findings indicate that Ik2 regulates F-actin assembly by mediating the function of nonapoptotic caspases via degradation of DIAP1. Also, it has been suggested that <it>ik2 </it>regulates interactions between the minus ends of the microtubules and the actin-rich cortex in the oocyte. Since <it>spn-F </it>mutants display oocyte defects similar to those of <it>ik2 </it>mutant, we decided to investigate whether Spn-F could be a direct regulatory target of Ik2.</p> <p>Results</p> <p>We found that Ik2 binds physically to Spn-F, biomolecular interaction analysis of Spn-F and Ik2 demonstrating that both proteins bind directly and form a complex. We showed that Ik2 phosphorylates Spn-F and demonstrated that this phosphorylation does not lead to Spn-F degradation. Ik2 is localized to the anterior ring of the oocyte and to punctate structures in the nurse cells together with Spn-F protein, and both proteins are mutually required for their localization.</p> <p>Conclusion</p> <p>We conclude that Ik2 and Spn-F form a complex, which regulates cytoskeleton organization during <it>Drosophila </it>oogenesis and in which Spn-F is the direct regulatory target for Ik2. Interestingly, Ik2 in this complex does not function as a typical IKK in that it does not direct SpnF for degradation following phosphorylation.</p

Reply to: “Comment on: Orocline-driven transtensional basins: Insights from the Lower Permian Manning Basin (eastern Australia) by White et al. (2016)”

We welcome the discussion and presentation of new data by Offler et al. (2017). In spite of a large number of independent evidence supporting the structure of the Manning Orocline (Cawood et al., 2011; Fielding et al., 2016; Glen &amp; Roberts, 2012; Korsch &amp; Harrington, 1987; Li &amp; Rosenbaum, 2014; Mochales et al., 2014; Rosenbaum, 2012; Rosenbaum et al., 2012; White et al., 2016), Offler et al. (2017) argue that this oroclinal structure does not exist. They have expressed a similar opinion in earlier discussion and comment papers (Lennox et al., 2013; Offler et al., 2015). We studied the Manning Basin because we think that it is situated in the hinge of the Manning Orocline, and as such, its tectonosedimentary evolution may shed light on the oroclinal structure and its possible formation mechanisms. Offler et al. (2017) mainly focus on specific structural complexities within the Manning Basin and fail to acknowledge the overwhelming volume of independent evidence supporting the proposed tectonic model. Here we address specific comments made by Offler et al. (2017) and demonstrate that the new structural mapping data provided by these authors, when examined in a regional context, further support our regional interpretation for the existence and geometry of the Manning Orocline..

Permian rifting and isolation of New Caledonia: evidence from detrital zircon geochronology

The island of New Caledonia is the second largest rock exposure of the continent Zealandia. The New Caledonian basement rocks have been interpreted as representing a late Paleozoic to Mesozoic intra-oceanic arc system that was possibly correlative to contemporaneous terranes in eastern Australia and New Zealand. In order to understand tectonic relationships between the basement rocks of New Caledonia and other eastern Gondwanan terranes, we obtained >2200 new U-Pb ages of detrital zircon grains from New Caledonia. Our new results, combined with a synthesis of previously published geochronological data, show abundant pre-Mesozoic zircon ages, but an absence of Early Permian to Middle Triassic ages characteristic of eastern Gondwana magmatism. The results thus suggest that the detritus of the New Caledonian basement was derived from a local Paleozoic continental fragment that was rifted from the margin of Gondwana, most likely in the Early Permian. The results imply that dispersal of the Gondwanan margins started earlier than the Late Cretaceous opening of the Tasman and Coral seas, consistent with the Mesozoic endemism of both New Caledonia and New Zealand

Detrital zircons as palaeodrainage indicators: insights into southeastern Gondwana from Permian basins in eastern Australia

Radioisotope geochronology of detrital grains coupled with quantitative classification of grain morphology can provide valuable insight into the history of sediment transportation and recycling. Here we present ca. 750 new concordant U-Pb ages from detrital zircon grains from a relatively understudied Permian sedimentary succession in the New England Orogen (eastern Australia), coupled with values of abrasion that provides a proxy for the relative source-to-sink distance. We show that cumulative proportion curves for age groups that correspond to plausible source regions provide insights into the palaeodrainage, even if the basin stratigraphy is relatively poorly constrained. This approach is particularly suitable for investigating complex depositional systems that received inflow from different provenance, such as back-arc and intra-cratonic basins. Using the example from eastern Australia, our results show that during the Early Permian, a large regional fluvial system transported detritus from continental Gondwana across the landscape of the former active continental margin (New England Orogen) and the simultaneously developing East Australian Rift System. In addition, a local drainage system mobilised detritus within the New England Orogen. Our new constraints for the Early Permian palaeogeography support the idea that the Lower Permian successions of the southern New England Orogen were deposited in a back-arc region that was likely linked to a retreating subduction zone

Migrazione, etnogenesi, integrazione nel mondo romano: il caso dei Longobardi, pp. 31-42.

The New England orogen of eastern Australia is characterized by tight orogenic curvatures (oroclines). Oroclinal bending commenced in the Early Permian during a period of extension that involved crustal melting, widespread emplacement of S-type granitoids, high-temperature metamorphism, exhumation of metamorphic complexes, extensional faulting, and development of rift basins. One of these basins is the Early Permian Nambucca block, which is situated in the "core" of the oroclinal structure, but its origin and time of deposition are poorly constrained. Here, we present new U-Pb ages of detrital zircons from the Nambucca block, which include age populations as young as 299 and 285 Ma, confirming the Early Permian deposition of the succession. Additional Devonian–Carboniferous and Precambrian ages indicate that detritus was mainly derived from the New England subduction complex and cratonic Gondwana. The range of ages suggests that the Nambucca Basin received detritus from both arc and continent and that deposition occurred in a back-arc setting. Given the coeval formation of the Nambucca Basin and the New England oroclines, we propose that this back-arc extensional basin was controlled by trench retreat, which resulted in "Mediterranean-style" orogenic curvatures along the plate boundary of eastern Gondwana. The recognition of a genetic link between oroclinal bending and back-arc extension may explain how accretionary orogens, such as the eastern Australian Tasmanides, were able to obtain an anomalous width without a substantial contribution of accreted exotic terranes. A similar mode of tectonism may have played an important role in other accretionary orogens

Detrital fingerprint: the use of early Precambrian zircon age spectra as unique identifiers of Phanerozoic terranes

Archean and Proterozoic zircon grains are commonly found in much younger clastic sedimentary rocks, but the geological significance of these ages is often overlooked. Here we demonstrate that the age spectra of early Precambrian sedimentary recycled and/or magmatic inherited zircon grains form a unique pattern (detrital fingerprint) that can be used to test connectivity or indicate sediment recycling between terranes. Using the island of New Caledonia as a case study, we compiled 212 (published and new) concordant ages that are older than 1400 Ma from samples that represent contemporary sediments (this study), an allochthonous nappe sequence, and Paleozoic–Mesozoic metasedimentary rocks. By comparing these data with an equivalent dataset of Precambrian zircon ages (n>1400 Ma = 2636) from Paleozoic eastern Australia (Tasmanides), we test connectivity and disjunction of New Caledonia with crustal domains within the Tasmanides. Results show that the early Precambrian detrital fingerprint of New Caledonia is similar to the southern Tasmanides (and possibly East Antarctica), but is significantly different than the detrital fingerprint of the northern Tasmanides. The results thus provide an independent constraint on the origin of the late Paleozoic to early Mesozoic New Caledonian continental basement, shedding new light on the tectonic evolution of the southwestern Pacific region, and demonstrate the capabilities of the methodological approach

Martin Abby

Free to read on publisher's website The New England Orogen in eastern Australia exhibits an oroclinal structure, but its geometry and geodynamic evolution are controversial. Here we present new data from the southernmost part of the oroclinal structure, the Manning Orocline, which supposedly developed in the Early Permian, contemporaneously and/or shortly after the deposition of the Lower Permian Manning Basin. New U-Pb detrital zircon data provide a maximum depositional age of ~288 Ma. Structural evidence from rocks of the Manning Basin indicates that both bedding and preoroclinal fold axial planes are approximately oriented parallel to the trace of the Manning Orocline. Brittle deformation was dominated by sinistral strike-slip faulting, particularly along a major fault zone (Peel-Manning Fault System), which is marked by the occurrence of a serpentinitic mélange, and separates tectonostratigraphic units of the New England Orogen. Our revised geological map shows that the Manning Basin is bounded by faults and serpentinites, thus indicating that basin formation was intimately linked to deformation along the Peel-Manning Fault System. The Manning Basin is thus interpreted to be a transtensional pull-apart basin associated with the Peel-Manning Fault System. Age constraints and structural relationships indicate that basin formation likely occurred during the incipient stage of oroclinal bending, with block rotations and fragmentation of the transtensional pull-apart system occurring subsequently. The intimate link between oroclinal bending and basin formation in the New England oroclines indicates that back-arc extension, accompanied by transtensional deformation, could have played an important role in the early stage of orocline development