Some Basalts from the North Kimberley, AV'estern Australia. 
81 
Fitzgerald oxamiiied tlio country along tlie ]\lay, Loiiiiard, Barker, Ad- 
cock, Throsscll, Upper Fitzroy, Hami, Barnett, Isdell, Sprigg, Lower Charn- 
and Lower Calder Rivers. 
Tlie localities from which the vS])ecim(>ns wen' obtained are shown in Figure 
2, wliich is copied from Easton's (1922) geological map of the region, as re- 
printed, to accompany Jutson's Physiography of \V^‘storn Australia ” (Jut- 
son, 1934). No information is a,\ ailable as to tlie iield occurrences of most 
of the specimens, and, as will b(‘ indicat(>d, this is a matter to which any future 
expedition might give attention. 
The collection is the ]iroperty f»f the (leological Survey of Western Aus- 
tralia, and my thanks are due to Mr. H. A. Ellis, wlio was Acting Govern- 
ment Geologist in 1939, and who, at the instance of J^rofossor E. de G. Clarke, 
not only gave me perjnissiou to examine it, but wint, personally, to much 
trouble to put it in order and to collect all tlie lit>ld notes regarding the speci- 
mens which could be found in the otficial records. Mr. Ellis also allowed 
me to make use of a manuscript report on thes(' and other rocks from the 
North Kimberley, which w'as written many yeai‘S ago by H. A, Fai'ijuharson. 
The present study lias been carri('d out in the (hnilogy Department, University 
of ^lelbourne, by kind p('rmission of Pi-oh'.ssor E, W. Skeats. 
(JENE]L\L GEOLOGY. 
The North Kimberley District of VW'storn Austi-alia lies between longi- 
tudes 124° and 128° and bc-tween latitudes 14° and 18° (Fig. 1), and is an 
inaccessible, and therefore little knowTi, part of x-\ustralia. Our knowledge 
of its geology is based chiefly on the accounts and collections of the parties 
led by the surveyors Hardman (1S85), Brockman and Crossland (1901), Fitz- 
gerald (1907] and Easton (1922). 
Over the greater portion of this rc^gion the outcropping rocks consist of lava 
flows interb(’dded whth massive sandstones of Nullagino age, which arc either 
horizontally bedded, or only gently folded. The sandstones appear to overlie 
the lava flows to a largo extent, but Maitland (1902) indicates tJiat some of 
the igneous rocks occur as sills. He n*fors to tlnun ]>ri(>fly as "a series of 
b(‘dded and intrusive igiu'oiis rocks, the pre^'ailing types being andesite, 
<lolorit('>, and rliabaso,’’ sometiuK'S a(;companied l)y beds of \'olcanic ash and 
breccias. In plaf;es ho rc^ports that “tlie sandstones are sometimes altta-ed 
into hard compact (juartzite, portions of which hav(^ been caught up in the 
body of igneous rock,'’ while some sections “intlicate (juite clearly that the 
igneous rocks have (in these localities) found an easy passage along the V->od- 
ding planes of the sedinamtary bi'ds and .... occur in tlu^ form of sills. 
According to Jutson (1934), the North Kimberley is an extensive plateau 
whicli is undergoing rapid dissection by a nnml^er of str(‘ams. These streams 
are arranged radially about Mount Hann (2,800 feet), which lies near tho 
centre of the plateau, and rises about 800 feet above it. Th(.i “ranges” 
marked on most maps of tins I'lgion ar<’^ really tlu^ ritlges or jilatean rem- 
nants forming the interfluves betweim the deep narrow gorg(‘s tieeupied by 
those streams. In their lower tracts the river \*alleys broaden, but they 
retain their steep w^alls througliout their courses. The coastal region has 
undergone subiufagence, giving rise to an extnanely broken coastline of tho 
rias typt', the harbour.s being flanked by precipitous cliffs, often several hun- 
dreds of feet high. 
