The North West Shelf of Australia is an extensive tropical carbonate ramp and forms an important template for the interpretation of similar systems in the sedimentary record. Yet, little is known about the development of the distally steepened ramp from the middle to late Quaternary, a period of high frequency glacioeustatic changes in sea level and climate. This research describes core and seismic-reflection data from a mid- to outer ramp transect at the Northwest Shelf. P-wave velocity of core material was utilized for the creation of an acoustic impedance log as well as to determine its relationship to sedimentary facies. At the studied site, observed p-wave velocities are strongly controlled by grain-size. Mud poor sections display high velocities whereas low velocities characterize sediments rich in carbonate mud. Correspondingly, we observe the occurrence of strong acoustic impedance contrasts and seismic reflections wherever facies changes.

P-wave velocity was measured on shipboard during IODP Expedition 356. The measurement was performed with a Whole-Round Multisensor Logger (WRMSL), which simultaneously measures a multitude of petrophysical properties on the encased whole core. The sonic velocity is defined by the traveltime of 500 kHz ultrasonic waves across the core.