318 C. F. LASERON. 
Wianamatta series. This plateau terminates on its southern 
boundary in high escarpments and deep gorges, which the 
tributaries of the Shoalhaven have in the course of ages 
cut out to a depth of 2,000 feet and more. The most 
familar of these is the valley of the Kangaroo River, which 
can be wellstudied from Bundanoon. This river has eroded 
its channel right through the Triassic, the Upper Coal 
Measures, and well into the Upper Marine Series. From 
its southern edge the plateau follows the northern dip of 
all these strata and slopes gradually until it reaches sea 
level at Sydney. 
The Shoalhaven itself has in its lower courses practically 
reached base level, but the country being broken and 
irregular, it does not cut the deep regular gorges that its 
tributaries do, while the country it drains is exceptionally 
rough. Rich alluvial flats occur on the inside bends of the 
river as far as it was examined, some of considerable area, 
and for some distance above Nowra they are farmed 
successfully. These and the numerous patches of river 
gravel prove that the river has now practically ceased the 
erosion of its bed, and is now depositing material instead. 
River terraces are not uncommon, though they do not 
present the beautiful regularity seen on some rivers. 
Geology.—The items of geological interest of this part of 
the country, and more particularly those which are here 
discussed may be tabulated as follows :— 
(1) Several new and interesting localities for the collec- 
tion of fossils. 
(2) The occurrence at Yalwal Creek of freshwater beds 
containing Glossopteris. 
(3) Theoretical reasons for the supposition of an inlier 
of Devonian rocks between Grassy Gully and Yalwal Creek. 
(4) Beautiful examples of unconformity between the 
Permo-Carboniferous and Devonian formations. 
