Geomorphic and tectonic significance of early Cretaceous lavas on the coastal plain, southern New South Wales

The presence of Early Cretaceous lavas near Mt Dromedary on the coastal plain of southern New South Wales places constraints on the accuracy and applicability for this region of recent models of the Late Mesozoic uplift and erosion of the southeastern highlands. These models are based on apatite fission track ages and mean fission track lengths, and propose that uplift of between 1.5–3 km, followed by an equivalent amount of erosion of the coastal edge of the highlands, occurred during the mid‐Late Cretaceous. The lavas within the Mt Dromedary Igneous Complex were metamorphosed during intrusion of the pyroxenite‐gabbro‐monzonite bodies between 98–100 Ma, and therefore pre‐date the suggested time of approximately 90 Ma for initiation of Tasman sea‐floor spreading and uplift of the southeastern highlands. This suggests that, in at least this immediate region, the amount of uplift and denudation of the highlands during the mid‐Late Cretaceous was considerably less than previously thought.

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