BY W. G. WOOLNOUGH AND T. G. TAYLOR, 5o3 



capture of another section of the Wollondilly is certain to take 

 place in the very near future, geologically speaking. 



An interesting example of capture on a smaller scale is sug- 

 gested by the head waters of Barber's Creek, just to the east 

 of Twin Trig. Station. The head of Barber's Creek flows in a 

 northerly direction, then suddenly turns almost at right angles 

 and flows westerly. On the northern side of the divide, con- 

 tinuing the northerly trend of the head waters of Barber's 

 Creek, is a marshy tract of country which serves as the head 

 waters of a small creek flowing into the Wollondilly system. 

 An objection to this idea that capture has recently occurred here- 

 is that the divide between the two systems, though only half a 

 mile wide, is fairly high, and is composed of solid Hawkesbury 

 Sandstones. This may possibly be accounted for by supposing a 

 slight buckling of the crust at this point. Of this buckling we 

 have, however, no very positive proof. The water gap of the old 

 river between Shepherd and Marulan Trigs, lies on the same 

 ridge. Its level is 25 feet below the gravels at Digger's Creek, 

 but is nearly 30 feet above those on the railway line near Wool- 

 shed Flat. We believe that this fact indicates that a slight 

 warping has taken place along the course of the old river-channel. 

 It is possible that this warping may have assisted in the diver- 

 sion of the water of the old river, but capture of the type above 

 described, and so imminent near Bnndanoon, is quite competent 

 to account for all the peculiarities in river-structure in the 

 Tallong area. In our opinion, if warping has taken place, it is 

 more recent than the river-capture, and it is to the latter force 

 that we must ascribe the chief features in the very remarkable 

 topography of this interesting region. 



EXPLANATION OF PLATES. 

 Plate xlii. 

 Map of the captured river. The extent of the gravels described in the 

 text is indicated by dots. Large dots show positions where the coarse gravels 

 occur in situ; small dots the areas where they are more or less hidden by 

 recent wash from the hills. 

 41 



