Cretaceous Stratigraphy of Lower IMurchison River Area, 
Western Australia, 
^5 
It is not possible fi’om the driller’s log- to differentiate clearly between 
the Second (.Tiilly Shale and the Toolonga Chalk and it may be that part 
or all ot the “yellow clay’’ between 40 and 8o feet shoii(ld rather be 
included in the Toolonga Chalk. It is of some interest that there is no 
indication of the occurrence of the Thirindine Shale in these bores. Gee 
Gie Outcamp is about lo miles west of Weerinoogudda Dam where con- 
siderable outcrops of Thirindine Shale are known to oeciu\ and the dis- 
appearance of the shale in a westerly direction is in complete agreement 
with eouditirnis found along the Murchison River where it peters out 
in Second Gully as described already in this paper. 
No further l)ore records are available until Cobourn and Boolagoorda 
Stations are reached, BO to 40 miles farther north, and it is plerhap^ 
inadvisable at this stage to attempt any detailed correlation of the driller’s 
logs in places so far removed from the type section of the Murchisoi^ 
House Series. It is, however, worth recording that all bores here, after 
penetrating a few hundred feet of soft strata, usually marked as ^^clay” 
or “shale," reach sandy layers. In bores on Coboinm Station the first 
sandy beds were struck at depths below the surface varying from 170 
to 373 feet and on Boolagoorda Station at depths between 403 and 450 
feet. These sandy beds are mostly described either as “sand” or ag 
“soft sandstone” and it would seem that they are most likely the northern 
continuation of the Butte Sandstone of tin* IMiirchison House Series. In 
the Shark Bay region the surfaee of these sandstones seems to dip towards 
the north-west, for in tin* eentre of Peron Peninsula n bore was put 
down to a depth of 1780 i'eet without renching nny sandy rocks at all. 
VT. BTBLTOORAPHT. 
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Western Australian Students. Perth xii -j- HOT pp. 
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Hobson, R. A., 1936. Summary of Petroleum E.xploration in Western Australi;'? 
to January, 1935. Ihifl. for 1D3o^ pp. 22-34. 
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GeoL Snrv. IF. A., TIhII. No. 95, xvi -p 366 pp. 
Maitland, A. Gibb, 1898. The (huntry between Northampton and Peak Hill, 
Ann. Profp'. Rep. Geol. Rnrv. W.A. for 75.97, pp. 14-19. 
Maitland, A. Gibb, 1907. Possibility of the Oc^'iirrence of Artesian Water in 
the Northampton and Geraldine Districts. Geol. Snrv. W.A., Bull. No 26 
pp. 7-9. 
Maitland, A. t!il)b, 1919. A Summary of the Geology of Western Australia. 
Minin f/ TTanflhoal\ Geol. Snrr. IJ\A., Mem. No. 1, ])p. 1-.j5. 
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