102 
The Queensland Naturalist August, 193& 
GEOLOGY OF THE COOLUM AREA 
(By Professor II. C. Richards, D.Sc.) 
GENERAL SUMMARY 
Some thirty-two years ago, Dr. H. I. Jensen, as a 
Linnean MacLeay Fellow, worked on the area and pub- 
lished his results in the Proceedings of that Society for 
1906, Part I, in a paper dealing with the “Geology of 
the Volcanic Area of the East Moreton and Wide Bay 
Districts, Queensland’" (pp. 74-173). 
Apart from occasional visits from geologists since 
that time, the region of Coolum does not appear to have 
been studied especially, although a few years ago Mr. C. 
C. Morton, of the Geological Survey, studied a nearby 
region when reporting on the auriferous deposits of the 
North Arm Goldfield some eight or nine miles to the 
west. 
The basal rocks of the area are sedimentary in 
character and form portion of the Mesozoic fresh-water 
deposits which were so widely deposited in what is now 
South-Eastern Queensland. These in their turn have been 
intruded by a series of igneous masses, which probably 
did not reach the surface until exposed by denudation. 
The igneous rocks are acid to intermediate in 
character, ranging from aplites to diorites, and are seen 
on the cliff faces and shoreline between Coolum Beach 
and Point Arkwright. 
Subsequently volcanic activity took place in the 
area and Mt. Coolum and Peregian or Emu. Mountain 
now remain as volcanic plugs. 
The region is characterised by much low-lying and 
swampy country which, until the last emergence of 
several feet, was in all probability below sea level. At 
that time Mt. Coolum, the Point Arkwright and Eurun- 
gunder mass and Peregian were islands, the coastline 
proper being several miles to the west of its present 
position. 
The accumulation of coastal sand dunes has barred 
the openings to the sea of these swampy areas, and they 
now drain with difficulty. Quite considerable peaty 
accumulations also have taken place, and just to the 
north of the Coolum Beach settlement, dark brown to 
black peaty sandstone of recent age, containing tree 
roots and stumps, outcrops on the foreshore. No doubt 
at the time of its formation the strand line w r as some- 
what more easterly. 
Altogether distinct from this organically formed 
brownish black sandstone are deposits of loosely 
coherent heavy black metallic sands mixed with the 
