Physical properties and seismic-reflection interpretation of bathyal marine sediments affected by carbonate and silica diagenesis in the Tasman Sea

Diagenesis of calcareous and siliceous sediments in northern Zealandia produces characteristic seismic reflections that are a valuable tool for constraining paleoenvironmental and tectonic history. We correlate Deep Sea Drilling Program (DSDP) borehole lithology changes with seismic reflectivity to characterise distinct diagenetic horizons. An increase in reflectivity in calcareous Paleocene to Miocene age sediments marks the depth that ooze alters to chalk. Predominantly occurring at c. 300 m below the seafloor on the Lord Howe Rise, variations are observed in the New Caledonia Trough, and in the Eocene in the Southern Lord Howe Rise due to changes in sediment composition. Paleocene–Eocene silica-rich sediments undergoing diagenesis produced distinct negative–positive polarity paired reflections from unaltered and altered sediments, respectively. Sediments undergoing diagenesis range in age from Paleocene to Miocene, indicating that overburden thickness and temperature are the main controlling factors for the onset of diagenesis, whereas the diagenetic potential of sediments is controlled by composition and burial conditions.