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Continental shelves are the most morphologically variable element within the source-to-sink system owing to the numerous processes that influence their formation. A recent multivariate analysis of a global compilation of modern continental shelf data showed that much of the variability is related to tectonic setting, the degree to which the shelf has been glaciated, and carbonate production. While these factors play firstorder roles in determining the morphology of shelves, other controlling mechanisms such as siliciclastic sediment supply, wave and tidal energy, bedrock lithology, and sealevel fluctuations are not as well understood. Here, we report findings from a detailed investigation of the southeast Australian shelf that explored how sediment distribution, wave energy, and bedrock lithology influence shelf morphology. The high-resolution analysis suggests that the southeast Australian shelf has 11 distinct shelf types. No strong relationships exist between the shelf attributes or shelf type with their onshore catchments. However, a substantial section boundary correlates with a bedrock contact between the Sydney Basin in the south and the New England Orogen to the north. South of this boundary, we propose that the shelf morphology reflects transgression with low sediment supply, whereas to the north, the morphology reflects transgression with higher sediment input. Although several factors contributed to this difference in shelf morphology, we suggest that sediment distribution and retention due to the active wave climate during the most recent transgression likely played a vital role. [ABSTRACT FROM AUTHOR]

The circa 1.60 Ga Isan Orogeny in NE Australia has been ascribed to the collision of Australia and Laurentia (North America), marking the final assembly of the Proterozoic supercontinent Nuna. However, details regarding the tectonic evolution of the orogen remain poorly constrained. To investigate the late orogenic to postorogenic thermal evolution and exhumation history, 40Ar/39Ar dating on hornblende, muscovite, and biotite was conducted in the Mount Isa Inlier, NE Australia, where intense crustal imbrication occurred during the Proterozoic continental collision. Published thermochronological results were recalculated using the current decay constant. Petrological examination and calculation of sample‐specific 40Ar/39Ar closure temperatures and cooling rates were used to reconstruct the pressure‐temperature evolution of individual structural domains. Diachronous cooling histories are revealed between western, central, and eastern belts through ~525–330°C, mainly between 1.53 and 1.48 Ga. Contrasting cooling across postmetamorphic fault zones records the reactivation of inherited normal (i.e., early basinal) and reverse (i.e., orogenic) faults. Estimated exhumation rates are generally low (< ~0.5 mm yr−1), pointing to a modest local relief of < ~1,000 m which is comparable to modern analogs, and suggest a "soft" collision with limited crust thickening. Exhumation shortly following orogenesis was contemporaneous with felsic magmatism (1.55–1.48 Ga) in the eastern belt. Magmatism transitioning from trondhjemitic to A‐type granitoids over this period suggests progressive heating of the orogen base, ascribed to lower crust delamination. Thus, thermochronological data reveal a regionally heterogeneous exhumation history controlled by orogenic collapse‐related extensional faulting following the final assembly of the supercontinent Nuna. Key Points: Supercontinent Nuna was finally assembled via a "soft collision" between Australia and Laurentia at circa 1.60 GaSubsequent to the collision, the Mount Isa Inlier experienced slow exhumation (< ~0.5 mm yr−1), mainly between circa 1.55 and 1.45 GaLate Mesoproterozoic (ca. 1.55 Ga) postorogenic exhumation in the Mount Isa Inlier may have been associated with orogenic collapse [ABSTRACT FROM AUTHOR]

This investigation presents an outcrop‐based integrated study of sedimentological analysis and sequence stratigraphy applied to the Lower Permian sedimentary succession in the southern Sydney Basin, Australia. This succession accumulated in several depositional environments and sub‐environments that range from non‐marine (fluvial) to marine (outer shelf), representing the fill of a sedimentary basin that resembles a fault‐bounded, rift basin. The stratigraphic analysis indicates a deepening‐upward trend, and the sequence stratigraphic approach has established that these sediments can be attributed to the lowstand, transgressive, and highstand systems tracts. Lowstand sediments can be defined by fluvial facies that are located between the subaerial unconformity and the maximum regressive surface. Transgressive facies correspond to estuarine, upper and lower shoreface, and inner and outer shelf depositional environments and are located between the maximum regressive and the maximum flooding surfaces. Highstand bottomset sediments are accumulated above the maximum flooding surface and are represented by outer shelf facies. The stratigraphic architecture indicates the development of an almost complete depositional sequence, mainly developed under the control of tectonically induced subsidence, but also influenced by the high sedimentation rates and the high gradient of the inherited topography. Eustatic sea‐level fluctuations were of minor importance during the deposition of the examined sediments. [ABSTRACT FROM AUTHOR]

The Australia-Laurentia connection in the Paleoproterozoic to Mesoproterozoic supercontinent Nuna is thought to have initiated by ca. 1.6 Ga when both continents were locked in a proto-SWEAT (southwestern U.S.-East Antarctic) configuration. However, the longevity of that configuration is poorly constrained. Here, we present a new high-quality paleomagnetic pole from the ca. 1.3 Ga Derim Derim sills of northern Australia that suggests Australia and Laurentia were in the same configuration at that time. This new paleopole also supports a connection between Australia and North China and, in conjunction with previously reported data from all continents, indicates that the breakup of Nuna largely occurred between ca. 1.3 and 1.2 Ga. [ABSTRACT FROM AUTHOR]