Abundance of non-skeletal grains from IODP Site 356-U1461

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. Throughout the studied core section, several sections rich in ooids and peloids occur. Sediment samples were investigated for their abundance of these non-skeletal grains to better understand the timing and condition of their formation. During arid glacial lowstands, sedimentation is characterized by inorganically precipitated carbonates, including ooids and peloids. Ooids developed under shallow-marine conditions on small-scale flat-topped platforms. Seismic and sedimentological evidence indicates that these platforms grew locally on top of the present-day mid ramp and were typically only active during a single glacial period.