500 GREAT SERPENTINE BELT OF NEW SOUTH WALES, i., 



trale has been found in these rocks. The thickness of this Series 

 is unknown. A thickness of 1,300 feet has been observed in the 

 Baldwin Mountain, and 3,000 feet in Cobbadah Creek Gorge, but 

 even here, the basal beds have not been seen. The especial feature 

 of these beds, physiographically, is their great resistance to ero- 

 sion, and consequent high relief. 



No certainty has yet been arrived at, with regard to the manner 

 in which these beds rest on the underlying Tamworth Series. The 

 only junctions between them, studied so far, are those near Tam- 

 worth. These have been claimed by Professor David and Mr. Pitt- 

 man(3) to show an unconformity of a very marked character, 

 but the observations of the writer, on two of the three junctions, 

 show that it is exceedingly difficulty to obtain a true angle of dip 

 for the agglomerates (so much are they jointed), unless a pebble- 

 band is present; and where this is seen, its dip is parallel to that 

 of the Tamworth Beds directly below it. But, as the Tamworth 

 Beds warp rather rapidly in this region, considerable care must be 

 taken in examining them. The observations will be detailed later. 

 The third area described as an unconformity, the writer unfortu- 

 nately did not visit, but the evidence of the first two, throws some 

 doubt on this last determination. 



The apparently marked, lithological unconformity between the 

 Baldwin Series and the underlying Tamworth radiolarian beds, 

 calls for some remark. An unconformity is brought about by the 

 intervention, between the deposition of two series, of a consider- 

 able length of time, during which the conditions have more or less 

 completely altered. The character of the overlying beds has thus 

 no necessary relation to that of the lower beds. Should the deposi- 

 tion, however, have continued while the change of conditions was 

 in progress, and this change have been oscillatory, certain zones 

 interstratified in one series will show indications of the conditions 

 that will be predominant in a higher series, or, conversely, will 

 recall the dominant conditions of lower series. There will be no 

 absolute and sharply defined final break in the character of the 

 sedimentation. Now the Baldwin Agglomerates differ merely in 

 coarseness of grain, from the breccias of the Tamworth Series. The 



