Hydrogeology of the Leederville Aquifer, central Perth Basin, Western Australia

[Truncated abstract] Detailed sedimentological, petrophysical, and hydrogeological studies have provided insight into the groundwater ow patterns and the depositional and structural his- tory of the Leederville Aquifer across the Gnangara Mound. The Gnangara Mound is located in the onshore central Perth Basin, Western Australia, and is one of Aus- tralia's largest and most utilised groundwater resources. The Leederville Aquifer is hosted by the Leederville Formation of the Lower Cretaceous Warnbro Group which was deposited following the break-up of Gondwana. Facies analysis of 300m of drill core was used to identify nineteen facies and seven facies associations in the Leederville Formation. Sedimentological and ichno- logical features indicate deposition in a uvial channel and oodplain (FA1, FA2), in a tidally in uenced channel (FA5), on tidal ats (FA6, FA7) and tidal bars (FA4) and on a shoreface (FA3). An overall tidally in uenced deltaic system is proposed. Five Warnbro Group stratal packages have been recognised in 158 downhole gamma-ray logs across the Gnangara Mound. Gamma-ray character was interpreted using facies associations from drill core. The Gage, South Perth Shale and Mari- giniup stratal packages are absent in the northeast due to a structural high that existed during deposition. The South Perth Shale package was deposited in lower shoreface to o shore conditions during transgression, and the Mariginiup package is composed of prograding delta front tidal bars. These mud-rich packages form the aquiclude at the base of the Leederville Aquifer. The overlying Wanneroo stratal package is composed of delta top deposits that host the Leederville Aquifer. Tidal associations, with well connected sand bodies and high sand percentage, are well developed across most of the Gnangara Mound. Fluvial associations, with poorly connected sand layers and low sand percentage, are restricted to the northeast. The uppermost Pinjar stratal package is composed