b'Education matters Luke Mahoney, The University ofrelief is produced by both tectonicMuller Range prior to the widespread Melbourne: The structure and evolutioninversion on deep-rooted normaldeposition of the shelfal Darai Limestone. of the northern Australian margin:faults and their linkage to the surfaceIt is suggested that extension along Insights from the Papuan Fold and Thrustvia triangle zones that form within themajor faults beneath the Muller Range Belt, Papua New Guinea. incompetent Mesozoic passive marginaccommodated sedimentation from the sedimentary sequence. Local- andLate Cretaceous to the Eocene, consistent regional-scale heterogeneities within thewith long-lived extensional structures northern Australian continental margin,observed in the foreland across the such as accommodation-zones andStable Platform. The selective removal of transfer structures are now expressed inthis sequence across the Muller Range the fold belt structure as discontinuitiessuggests it was uplifted in the Eocene and cross-cutting structural features thatto Oligocene, possibly in part facilitated are recognised throughout the PFTB. by the inversion of extensional faults in The 2018 Mw 7.5 PNG Highlandsthe Muller Range area. This inversion is earthquake and aftershock sequenceinterpreted to have resulted from the has provided an unprecedentedEocene to Oligocene collision of the opportunity to observe and analyse theexpansive Sepik Terrane to the northwest crustal processes that have ultimatelyof the PNG margin, an interpretation The Papuan Fold and Thrust Belt (PFTB)controlled the evolution of the PFTB.that has significant implications for the in Papua New Guinea (PNG), locatedSeismological, GPS and remote sensingtectonic evolution of PNG and Southeast on the leading edge of the northerndata offer constraint on the complexAsia.Australian continental margin, hasnature and spatiotemporal distributionThe studies presented in this thesis been subject to complex tectonism as aof crustal deformation during the event,provide several key insights that result of its location throughout muchrevealing that the PFTB experienced up tosignificant advance our understanding of the Cenozoic between the obliquely1.2 m of uplift and ground deformationof the geological, structural and tectonic converging Australian and Pacific plates.over 7500 km2. Remarkable spatial andevolution of the PFTB, Papuan Basin The remoteness and inhospitable terrainmorphological similarities exist betweenand northern Australian margin. An characterising the PFTB make it one of thethe distribution of co-seismic groundongoing theme relates to the complex least well-known fold and thrust belts ondeformation associated with the event,interplay between spatial variations Earth. and the less-inverted and un-invertedin the architecture of the margin and The architecture of the northernextensional architecture that is well- spatial and temporal variations in the Australian continental margin hasconstrained in the foreland across thecompressional stress field associated with been affected by both extensional andStable Platform. This suggests that thean evolving tectonic setting between the compressional tectonic forces, which first2018 Highlands earthquake sequenceAustralian and Pacific plates.formed, and subsequently deformed,was related to tectonic inversion along a the Papuan Basin in the period from thepreviously unidentified extensional faultYuwei Li, Australian National University: early Mesozoic through to the present- system beneath the PFTB, indicating theImaging the D structure using waveform day. Defining the geology, structure andnorthern Australian passive margin hasmodelling.evolution of the PFTB and Papuan Basinhad a primary control on the evolution is central to our understanding of theof structural styles observed throughout geological and tectonic evolution of thethe PFTB.northern Australian margin. In this thesis,New low-temperature thermochronology a multidisciplinary approach is used todata from extensive field surveys in investigate the evolution of the PFTB,the Muller Range were combined with Papuan Basin and northern Australianlegacy data in modern thermal history continental margin. modelling tools to investigate the Field mapping and structural analysisthermotectonic evolution of the WFTB within the remote Western Fold andand Papuan Basin. In particular, the Late Thrust Belt (WFTB) provide significantlyCretaceous to Oligocene history of the improved constraints on the geology,region is largely unknown due to the structure and evolution of the fold belt.absence of a continuous stratigraphic New geological constraints acquiredrecord. Thermal history models based onThe D region of the Earth, the lowermost over 100 km of traverses suggest thatthese data suggest two major Cenozoicfew hundred kilometres of the lower the exposed Cenozoic Darai Limestonecooling episodes. The youngest, andmantle, is designated as a thermal has very low shortening between ~ 12- best constrained, is clearly recordedboundary layer and chemically distinct 22% yet structures in the Muller Rangein the stratigraphic record and relateslayer above the core-mantle boundary are elevated up to 7 km above regional.to Neogene collision at the northern(CMB). It plays an important role in Structural work utilising regional-scalemargin of the Australian continent. Anmantle convection, core convection geological observations suggest that theolder episode of comparable or greaterand the resulting geodynamics. inversion of pre-existing rift architecturemagnitude occurred in the Eocene toCharacterising the structure of this region on the northern Australian continentalOligocene and may relate to the removalis crucial to a better understanding of the margin is the primary influence on theof 1500 - 3000 m of Late Cretaceous tomantles thermo-chemical evolution and evolution of the area. The huge structuralEocene stratigraphic section across thethe nature of core-mantle interactions. DECEMBER 2021 PREVIEW 36'