Internal Architecture of a carbonate ramp exposed to high amplitude sea-level fluctuations: Evidence from the NW shelf of Australia

The North West Shelf of Australia represents an extensive tropical carbonate ramp and forms an important template for the interpretation of similar systems found within the sedimentary record. Yet, little is known about the development of the distally steepened ramp during the mid-to-late Quaternary, a period during which NW-Australia was subject to high-frequency glacioeustatic changes in sea level and climate. This research presents core and seismic-reflection data from a mid to outer ramp transect at the Northwest Shelf. The investigated interval displays a distinct pattern with alternating changes in core color from dark to light. Dark intervals formed during humid interglacials and are composed of calcitic skeletal carbonates and elevated amounts of fluvial-derived siliciclastic input. Light intervals are predominantly comprised of inorganic precipitated aragonitic carbonates, which formed during arid glacial lowstands. Humid interglacials are characterized by limited sedimentation across the Northwest Shelf of Australia. Yet, substantial amounts of skeletal carbonates were deposited during the Holocene and Marine Isotope Stage 11. The presented results are consequential for the interpretation of seismic and outcrop data found within the rock record, as they emphasize the strong variability of carbonate production in response to glacioeustatic changes in climate, sea level, and antecedent topography. It further highlights a system, which predominantly produces and exports inorganic-derived aragonite during glacial low stands, thereby offering an alternative to the commonly applied platform model of “highstand-shedding”. (Poster)