by e. c. andrews. 173 



Deductions from foregoing Observations with References 

 TO Geograpiiv of the Cordillera. 



It is well known that coast lines of the regular or smooth type 

 indicate (except in cases of riverless foreshores) a verj^ advanced 

 stage of marine erosion either in the present cycle or in one 

 immediately preceding recent elevation, the tendency of marine 

 erosion being to reduce irregularities, whereas the recession of the 

 coast line from the edge of the continental shelf, combined with 

 highly indented coast lines and numerous outlying islands, evi- 

 dences the effect of recent subsidence. 



The general trend of a coast line is due to earth movements, a 

 very subsidiary part being plaj^ed by the agencies of marine 

 erosion, no inlets* or fiords arising as the result of such action, 

 these being attributable to the subsidence of deeply eroded 

 plateaux of accumulation or erosion. 



Sedimentation also plays an important j^art in the genesis of 

 coastal topograph}'-, the w^aste resulting from subaerial denudation 

 being arranged to form deltas, coastal plains, shoals and spits. 

 Marine erosion also helps in a lesser degree, but always in the 

 way of forming a regular coast, viz., by attacking the headlands, 

 the waste thus derived being formed into bars, or being swept 

 into sheltered spots. 



In forming an}' theory as to the origin of the present aspect of 

 the Queensland and New South Wales coastal areas we may 

 rememl^er that : — 



(1) The outer edge of the Great Barrier Reef appears to follow 

 the general trend of the coast. 



(2) The seaward edge of the Great Barrier Reef is not the only 

 portion of the continental shelf-margin removed to a considerable 

 distance from the coast line, since that part lying between Lady 

 Elliot Isle (where temperature places a limit on the southward 



* Under " inlets" are not included those small irregularities in a coast such 

 as exist between Port Jackson and Botany Bay Heads, but indentations like 

 the above-mentioned ports themselves. 



