CnETACEOUS Stratigraphy of Lower Murchison River Area, 35 
Western Australia. 
Scope . — The bnse of the Butte Sandstone is rarely well exposed, though, 
it is sharply detined by the sudden change from the lliin-bedded upper- 
most layers of the Tumblagooda Sandstone. The upper boundary with 
the Thirindine Shales is mostly sharp (text lig. 11), though occasionally 
a more gradual transition can be detected on closer inspection. The 
Text Tig. 11. 
Butte Sandstone and Thirindine Shale in scarp just west of 
emergency landing-ground. The boundary between the two forma- 
tions is marked by A. The top layer of the Butte Sandstone is here 
somewhat ferruginous and, therefore, harder. 
Butte Sandstone thus includes all the strata between the uppermost layer 
of the well-bedded upper part of the Tumblagooda Sandstone and the 
base of the grey, siliceous, and mostly whitish-weathering Thirindine 
Shales. 
Lithologically the Butte Sandstone is rather uniform 
throughout, 1 eing generally a whitish, imbedded, and incoherent deposit 
of quartz grains— in most places, inde(‘d, a ‘‘running sand.” The quartz 
grains have diameters of uj) to 3 mm. Tn the Toolonga section traces 
of cross-bedding can be seen, as well as occasional pebble bands with 
little pebbles not more than about 6 mm. across. Tn the Thirindine Point 
section the base of the Butte Sandstone is a deposit of three feet of 
massive, well cemented, mottled sandstone, with ferruginous patches and 
