X-Ray Analysis of the Gingin Upper Greensand. 
229 
No. 17.~X-RAY ANALYSIS (BY THE POWDER METHOD) 
AND MICROSCOPIC EXAMINATION OP THE 
PRODUCTS OF WEATHERING OF THE 
GINGIN UPPER GREENSAND. 
By W. F. Cole. 
Read 10th June, 1941 ; Published I7th August, 1942. 
INTRODUCTION. 
Available geological literature has reveah'd to the author a scarcity of 
published data on the weathering products of glauconite or glauconitic green- 
sand. It was first proposed by Glinka (1) that with the loss of lime, potash, 
magnesia and ferric iron, glauconite was replaced by ferruginous clay. Cay- 
oux (2) was however of th(‘ opinion that it alters to limonite. In recent years 
Denison, Fry and Gile (3) have shown that muscovite and biotite when under- 
going weathering in the soil, pass by (continuous variations from true micas 
through stages corresponding to glauconite and illite in composition. The 
weathering of the micas was accomj)anied by an iiunvase in water content, 
<lecrease in K, and increase in Al at Hie oxpenst* of Fe and Mg. (diemical 
analyses showed that the final product of alteration of both micas was of about 
the composition of kaolinite. 
In the present study an att(mipt has bcTHi madc^ to identify, by means of 
the X-ray diffraction method of powder analysis, the weathering [noducts of 
the upper gi*eensand of Gretaceous age at Gingin, Western Australia (latitude 
31° 2F S., longitude 1 15° 54*^ F.). This method of analysis is briefly described 
in an earlier paper (4). The microscopic examination w^as undertaluHi with the 
object of determining to what extent the optical properties were consistent 
with the X-ray conclusions. Tins work is pi-eliminary to an investigation of 
the clay content and derivation of copptn deficient soils of the Gingin district. 
MATERIALS. 
Location . — -At Gingin, the Gretaceous rocks have the following sequence in 
descending order 
1. The Upper Greensand or glauconitic sandstone which contains jihos- 
phatic nodules at its base. 
2. The Chalk. 
3. Tlie Lomtw Greensand or glauconitic sandstone. 
The distribution of these rock types is shown in Fig. 1 (5). The beds are 
practically horizontal. It is believed that the intermediate chalk is in the 
form of a lens which thins out to the north and south. 
The topography of the country around Gingin is strongly undulating with 
a number of prominent hills rising above the level of Gingin Brook which im- 
mediately west of the town is about 270 feet above sea level. The heights of 
these hills are : Poison Hill, 724 h^et ; Moorgup, 667 feet ; Ginginup, 666 feet ; 
One Tree Hill, 515 feet and Molecap, 510 foot (6). 
Combining the geology and topography it is ap[)arent that the upper 
greensand will outcrop on the highest liills and the lower hills will be formed 
from the underlying chalk and lower greensand. Hence in order to obtain 
specimens of the upper greimsand and its overlying soil, a number of localities 
j 329/42 
