78 E. 0. TeaU: 



.eluded in the Upper Ordovician. A more extended examination, how- 

 ever, has shown that they are distinct lithologically from the black 

 slates; the junction is always a sharp one, and further .the 

 limestone deposits which have yielded definite Cambrian fossils are 

 interbedded with them. Chemically, these rocks are distinct from 

 the adjacent cherty graptolitic slates. Their analysis shows a low 

 silica percentage and relatively high iron, lime and magnesia con- 

 tent. The soil, therefore, derived from their weathering is of a 

 noticeable red colour and clayey character, supporting a richer 

 growth of grass and other vegetation than the rather stony and 

 sterile soil of the slates. The belt is further marked by a rather 

 striking feature of the weathering of some of the fine grained 

 sediments, which petrological examination proves to be tuffaceous. 

 These rocks weather into striking elongate spheroids with a suc- 

 rcession of spheroidal shells similar to the well-known structure of 

 partly decomposed basalt and other igneous rocks. Their field 

 •occurrence and petrological examination, however, leave no doubt 

 as to their sedimentary origin. 



There are two separate occurrences of this series, both of limited 

 extent. The largest and most important is a long narrow belt along 

 the Dolodrook Valley. It starts about a quarter of a mile north- 

 west of Garvey's hut, and extends siouth-easterly on the southern 

 Slide of the Serpentine as far as Roan Horse Gully, a distance of 

 fthree and a half miles. The greatest width is never more than a 

 few chains. The other occurrence is a small outcrop" of highly con- 

 torted basic sediments exposed in the bed of the Wellington River, 

 roughly on the line of strike, about a mile and a quarter north- 

 west from the termination of the first-named inlier. 



At its north-western extremity, the Dolodrook inlier passes out 

 'of sight under the Upper Palaeozoic rocks, but along its soutliern 

 or south-western boundary it is directly in contact with the Upper 

 •Ordovician slates. The character of the sediments varies from 

 ■coarse serpentinous conglomerate through grits to fine greenish 

 diabasic tuffs. Several sections merit special attention. 



Locality A, (Dolodrook River). — This position is shown on the 

 map extending from the junction of the Black-Soil Gully, in a 

 ■south-westerly direction, for about twenty chains. The succession 

 and relationship are represented in Section No. 1. At the junction 

 of Black-Soil Gully mth the Dolodrook, there is a small inlier of 

 ^Serpentine with contorted black cherty slates in contact on the noath 

 'side. The junction appears to be a fault, and obscure but recognis- 

 uhle Upper Ordovician graptolites can be traced in the cherts almost 



